KX i"* I v Y

1

1

I
REFERENCE

Inited states Iartment of 1MERCE

IBLICATION ^Y\

NBS TECHNICAL NOTE 593

Wire-Bond Electrical Connections:

Testing, Fabrication

and Degradation

A Bibliography 1957-1971

U.S.

'ARTMENT

OF

OMMERCE —QC—

XJS1G3

m.fV
NATIONAL BUREAU OF STANDARDS

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BROffl OF b I ANIMUS

JAN 1 1972

I1473-

UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 593

ISSUED JANUARY 1972

Nat. Bur. Stand. (U.S.), Tech. Note 593, 58 pages (Jan. 1972)

CODEN: NBTNA

Wire-Bond Electrical Connections:

Testing, Fabrication and DegradationA Bibliography 1957-1971

Harry A. Schafft

Electronic Technology Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

"»fAU Of

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C, 20402.

(Order by SD Catalog No. C 13.46:593). Price 60 cents.

Table of Contents

Page

1. Introduction 1

2. Bibliography Format, In Brief 2

3. Author Index 4

4. Key Word Index Introduction 7

4A Alphabetical Key Word Listing 8

4B Subject Area Key Word Listing 12

5. Bibliography 21

Appendix A. Organization of Bibliography 49

Appendix B. Sources for Bibliography and Abbreviations 49

Appendix C. Availability 49

Appendix D. Key Word Selection and Use 53

List of Tables

Page

1. Sources for Bibliography 50

2. Abbreviations and Journals Searched 51

3. Availability Notes 52

4. Test Methods and Brief Descriptions 54

iii

Wire-Bond Electrical Connections: Testing, Fabrication

and Degradation —A Bibliography 1957-1971

Harry A. Schafft

More than 245 papers relevant to wire-bond type electrical interconnections used in microelectronic and low-power discrete and hybrid

devices are listed together with key words. The bibliographic search

concentrated on compiling papers which appeared in the period from

1965 to 1970, inclusive. The selection of papers was generally limited

to those that were pertinent to wire bonds where the wire diameter is

less than about 50 urn (2 mils) and where the wire is bonded by either

thermocompressive or ultrasonic means. Two indexes are provided:

(1) an Author Index and (2) a Key Word Index. The latter includes a tabulation of the literature citations.

Key Words: bibliography; degradation (wire bond); discrete devices;

electrical interconnection; fabrication (wire bond); failure (wire

bond); hybrid circuits, integrated circuits; microelectronics; re- liability; testing (wire bond); wire bond.

1. Introduction

Small-diameter (< 50 ym) wire is the government reports, U. S. patents, and con- principal means of making electrical connect- ference presentations relevant to wire bonds

ions (1) between the semiconductor die and in these three subject areas of testing, fabthe terminals leading outside the package of rication, and degradation,

microelectronic and low-power discrete and

hybrid devices, and (2) between different The 6 <lLo.cJU.on ofa papeAA is generally

dice on a single device header of hybrid cir- limited to those that are pertinent to wire

cuits. This o£<LcAKiojxl sLYVtQAC.onnzcJU.on. or bonds that have wire diameters of less than

uxuiz-bond,* as it will be referred to here, about 50 urn (2 mils) and are bonded by either

is considered to be the wire between two thermocompressive or ultrasonic means. This

bonded points, the bonds, the bonding sur- is the class of wire bonds that is of most

face films, and the underlying material in interest in microelectronics. An attempt

the immediate vicinity of the bonds. FcUMlAd was made to make the collection of papers on of a wire bond is one of the principal fail- test and evaluation methods complete while

ure modes in these devices. As a result, the collection of articles in the area of

great importance has been attached to the fabrication and degradation is meant to be

following three subject areas: (1) methods representative. Some interesting papers

for testing and evaluating wire bonds, (2) could not be included because of restrictions

optimization of the fabrication processes for on their distribution. It is quite possible

making wire bonds, and (3) mechanisms of deg- that some papers which should have been inradation and failure of wire bonds. eluded were overlooked. The compiler would

appreciate having such omissions called to ( This bibliography is a comp-ltcutlon of his attention.

more than 245 published articles, U. S.

Acknowledgement

The author is pleased to acknowledge the significant contributions made by Elaine C W. Cohen who assisted in collecting much of the material and performed both expeditiously and cheerfully many of the tedious labors that the compilation of such a bibliography requires.

Thanks also go out to Kathryn 0. Leedy, Frank R. Kelly, Terry A. Schultz and especially to Ruth E. Joel for assisting in various stages of the preparation of the bibliography; to Kaye

E. Dodson for typing the final draft with such dispatch; and to W. Murray Bullis, Frank F. Oettinger, and George J. Rogers for their assistance with various aspects of the format.

This work was performed under the Joint Program on Methods of Measurement for Semicon- ductor Materials, Process Control, and Devices and was supported in part by the National

Bureau of Standards, the Defense Nuclear Agency, and the U.S. Navy Strategic Systems Project

Office.

ft Certain words or phrases are printed in script to assist in scanning.
2. Bibliography Format, In Brief

The two entries shown on the next page are used to indicate the various elements of the

format which are encircled and numbered. The numbers refer to the explanatory notes listed

below. A more complete description of the organization and format is given in Appendices A

thru D.

Explanatory Notes :

1. Identification code, for entry. The first

two digits give the year of publication;

the letter is the initial of the first

author's surname; the last digit serves

to distinguish entries which have the same first three alphanumerics . Entries.

are arranged in the bibliography (pp. 21-

48) according to these codes.

2. Author. ( i>

) , editor(s), or organization (if no name(s) are provided). For AathoU In- dex, see page 4.

3. FlSiAt-level key WOh.d for general subject

area. First-level key words are capitalized for identification purposes.

4. VeACviptOKA to identify the kind(s) of

wire bond(s) pertinent to or described

under the subject of the first-level key

word (in this example, DEGRADATION).

5. Second-level, key WOhd to narrow the subject area of the first-level key word

above it (in this example Mechanism modifies DEGRADATION). The first letter of a second-level key word is capitalized.

6. Tklh-d-level key WOKd to modify the

second-level key word at its left (in

this example intermetallics modifies

Mechanism). All the letters are in

lower-case. Some third-level key words

include words in parentheses.

7. Ondeh. of first-level key words for subject area indicates the relative emphasis

or importance given the respective areas

in the entry. In this example, the main

subject is degradation with test and fabrication following in that order.

8

.

VlhAt-level key wold indicating approach

or type of entry. Only one such key word

is used per entry and it is listed last.

9. Reading ptUotvity is suggested by underlining the identification code and the

appropriate key word(s) of those entries

that are of such relative importance in

a particular area that they should be seen first. The codes for these entries

are also underlined in Section 4B (pp. 12

20).

10. Title

11. SouJtce. See Appendix B (p. 49) and Table

1 (p. 50) for sources used. See Table 2 (p. 51) for abbreviations used for journals and conferences

.

12. Availability note refers to an address

listed in the Appendix. If the number is

in brackets the address is one to which

an order may be placed for a copy of the

entry; if it is in parentheses the addres;

is that of the first author's place of

work at the time of publication.

13. AvalStjablLtiiy note. When the report citation is followed by a number preceded by

the letters AD or PB, or by the letter N,

the report is available from the National

Technical Information Service (NTIS),

Sills Building, 5285 Port Royal Road,

Springfield, Virginia 22151 by using this

NTIS accession number when ordering.

14. In some entries, additional guidance is

provided in brackets. For example, ref- erence may be made to the pages in the

paper that are relevant to the subject.

tt

The three levels of key 'x'0A.di indicating subject area are listed in alphabetical order

in Section 4A (pp. 8-11). Page numbers are provided to assist in locating these key

words in Section UB (pp. 12-20) where they are ordered by subject: test, fabrication, and degradation. With each key word in Section 4B is a tabulation of literature citations (using their identification codes). In both Szctioni 4K and 48, each key word that may require additional definition is followed by an dxplanatony pthlaie. -in bHAcJltti . An

exception is made for the test method key words. Key words for the test methods are listed in alphabetical order in Table. 4 (p. 54) with a brief description for each method.

The descriptions are oriented to their function in testing wire bonds. VucAlptoU are listed in Section 4B (pp. 12-20) with a tabulation of literature citations.
Parker, C. D.)

INTEGRATED SILICON DEVICE TECHNOLOGY

VOLUME XV RELIABILITY

Contract No. AF 33(615) -8306

>

May 19 67. CAD 655082) (Tsee pp. 35-

-(DEGRADATION>bond: TC , US K wire: Al, Au;

film: Al, Au, Au/Mopv§ubstrate : FeNiCo,

Si

Stress: process; thermal

Part : bond

-(Mechanism:) contamination; (intermetallics)

Failure Rates

TEST")

Screening Procedures

FABRICATION>bond: TC , US; wire: Au, Al;

film: Ag, Ag/Cr, Al , Au, Au/Mo;

substrate: Si

Evaluation: metal systems; metallization; wir<

Procedure

-(REVIEW)

10

14

13

36, >-

' 68A3 ) Anderson, J. H., Jr. and W. P. Cox

' AGING EFFECTS IN AU-AL AND AL-AL

BONDS USED IN MICROELECTRONICS

Proc . 7th Annual Reliability and

Maintainability Conf . , pp. 533-536

San Francisco, Calif., July 1968

([7], (2lfl

DEGRA DATION/bond: TC, US; wire: Al , Au; filmlj

Al ._—-""*"" Stress; thermal

Part: v;ire; bond

'lechanism: anneal, intermetallics"\

11

12

4

*l'eST! pun; PSSlSTanCe

FABRICATION-bond: TC ; wire: Au; film: Al

Bonding Surface: film thickness

EXPERIMENTAL
Author Index

Adams, A. H. , 68A1 Adams, M. A., 70A1 Anderson, E. E., 70C1 Anderson, Jr., J. H., 68A1, 68A3, 69A2, 70A2, 70C1 Anderson, 0. L., 57A1, 57A2, 61A1 Andreatch, P. , 57A1

Ang, C. Y. , 69A1 Angelucci, T. L. , 66A2, 67R4 Anstead, R. J. , 67A3 Antle, W. K., 64A1, 66A1 Antler, M., 69A3 Antovevich, J. N., 59A1, 59W1, 60W1 Arleth, J. M. , 67A1

Asmus, M. N. , 65M1

ASTM, 70A3, 70A4, 70A5, 70A6, 70A7 Auchterlonie , J., 67S2 Avedissian, M. K. , 67A2, 68A2 Avil, H. J., 65M1

Ayre, R. S., 61A2

Bagrowski, J., 66B1

Baker, D., 65B1, 66B4 Bancroft, D., 59J1, 60J1, 61J1 Barfield, W. M. , 64D2 Baroody, Jr., A. J., 70B7, 70B8 Bayer, R. G. , 67B4 Beadles, R. L., 67B2

Bell, J. L. , 69B1 Bellin, J. L. S., 69B7, 69K4 Bernstein, L. , 61B1

Berry, R. W. , 68B1 Bevington, J. R., 70B1, 71B3 Bikerman, J. J., 66B6 Binelli, W. D., 69B2

Blech, I. A., 66B3, 67B3

Bobo, S. N., 67B1 Bottaro, D. , 68G2

BoyIan, J. R., 71B2 Bowman, R. , 71P2 Bradfield, G., 70B5, 70B6 Brandewie, G. V., 66B7 Brauer, J. B., 70B4

Brinton, J. , 69B3

Brown, A. E. , 69B7 Browning, G. V., 66B2, 66B5, 69B4- Bryan, I. E., 65B1

Budd, J. B., 69B3 Bullis, W. M., 69B5, 69B6, 70B2, 70B3, 70B7, 70B8,

71B1, 71B4

Burke, T. S. , 67B4

Carpenter, M. R., 67M1

Chen, G. K. C. , 67C3

Chiba, K., 68T2 Christensen, H., 57A1, 58C1, 61A1

Circuits Manufacturing, 69C1

Clews, K. J. , 66C2 Cline, J. E. , 67C2, 69C2 Clunie, D. M. , 64C2 Cohen, A., 64C1

Cohen, J. , 65C1

Collins, D. R., 70P1 Colteryahn, L. E., 65C3, 65C4, 66B5 Conti, R. J. , 66C1

Cook, J. P., 70B1, 71B3

Cox, W. P., 68A3, 69A2, 70A2, 70C1 Cummings, D. G. , 65C2, 66B5 Cunningham, J. A., 65C5, 67C1, 67C4

Curran, L., 70C2

Daniels, H. P. C. , 65D1 Davidson, K. W., 64D1

Davis, D., 69P1, 70D2 Demenus, R. D., 67A1

Demer, L. J., 69D2 Department of Defense, 68D2, 69D3, 70D3 DePrisco, C. F., 60J2, 61D1, 62P1, 64D2 Devaney, J. R. , 7 0D1 Dicken, H. K., 70D4 Dudderar, T. D. , 69D1

Dummer, G. W. A. , 68D1

Dushkes, S. Z., 71D1

Eimbinder, J., 66E1 Eisenberg, P. H., 66B7, 69A1

Electronic Design, 68E1, 68E2 Elmore, W. C, 60J2

Fable, G. W., 65J1 Farrell, J. P., 71S1

Fenster, H., 68M3 Fentnor, L. H. , 69D2

Floyd, Jr. , H. L. , 68F1 Francombe, M. H., 68T1

Gaffney, J.,- 68G1, 6 8G2 Gianelle, W. H., 6 6G2 Gill, W. L., 67G1 Glass, R. A. , 71G1

Go, H. T., 66G1 Goetzberger, A., 61G1 Goldfarb, S., 71G2

Grable, R. C, 69G2

Graham, R. A. , 67G2 Greenan, R. E., 69U2

Gurland, J. , 69G1

Haberer, J. R. , 70H2, 71H2

Hagert, F. W., 65M1 Haigler, E. D. , 67H2

Hakim, E. B. , 65H3

Hall, E. C, 64P1, 66P1

Hall, P.M., 68B1

Hamamoto, A. S., 69B7, 69K4 Hammond, V. J., 66H1

Hanley, L. D., 64P1, 66P1

Harman, G. G., 71H1 Harper, J. G., 67C1

Harris, D. H. , 68H1

Harris, M. T. , 68B1

Hart, R. R., 71H3 Hasiguti, R. R., 62M1

Hattori, S., 69K3 Hayser, J. G. , 67C1 Heinen, K. G. , 69H1 Helda, R. W., 68H5 Higbie, T. E., 67H1

Hill, P., 64H1

Hill, W. H., 68H3 Hnatek, E. R., 70H1 Hoeckelman, R. F. , 63M1

Holmes, P. J. , 68H2 Howard, R. E. , 68H4 Howell, J. R., 64H2, 65H1, 65H2, 65S1 Hutchison, R. E. , 67G2

IEC, 6611, 6711, 6811

Ingle, L. V. , 71B3
Jamieson, A. L. , 65J1 Jennings , I . C . , 68H2 Johannesen, F. , 71J1

Johnson, C. A., 68J1

Johnson, W. G., 64J1

Jones, H. C. , 66G1

Jones, J. B., 59J1, 60J1, 60J2, 61J1, 62J1, 65J1, 67J1

Jones, R. , 66B4

Kalvelage, B. F. , 71K1

Kanz, J. W., 65H2

Kapfer, V. C, 69T1, 70B4 Kashiwabara, M. , 69K1, 69K3

Keen, R. S., 67K2, 67S1, 69S2

Kersey, J. F. , 65C4 Kessler, H. K. , 71H2 Khorouzan, M. , 66K1

King, C. M., 71K2 Kirvida, L. , 65M1

Knollman, G. C. , 69B7, 69KU Kobayashi, S., 6902 Koedam, M., 66K2

Kollner, H. , 66K3 Konsowski , Jr., S. G., 66B1

Koshinz, E. F., 67K1, 68K1

Kramer, I. R. , 65K1

Krieg, R. D., 69K2 Kuliche, Jr., F. W. , 66A2, 67R4

Landis, D., 65L2, 66L2

Lane, W. V. , 67L1 Langenecker, B., 66L3

LaPoint, W. E., 68H5 Larrabee, G. B. , 69H1

Larson, R. B., 66L1

Laub, J. L., 69L2

Lauf fenburger, H. A., 69L1

Lawhorne, S., 6 8 LI Lawler, H., 69P1 Leyshon, W. E., 71L1

Little, D. R. , 70B1, 71B3 Loewenstern, L. R., 67K2 Lombardi, J., 66LU

Longo, T. A., 63L1, 64S1

McAfee, N. J., 66G1 McCormick, J. E., 68M1

McDonough, L., 66L4 McHale, P., 68M3

McKaig, H. L., 62P1 McKinnon, M. C, 63M1

Maki, C. E., 65M1

Mann, R. M., 66M1 Mann-Machbar, P., 70M2 Manowczak, J. S., 68A2

Mansour, M. M., 69L2

Maple, T. G., 70A2, 71G1 Maropis, N., 59J1, 60J1, 61J1 Martin, B. D., 70W1 Martin, D. C, 59W1 Matcovich, T. J. , 71M1

Matsui, K., 62M1 Matsuura, E., 62M1

Mattraw, H. C, 69A1

Meyer , R . A . , 6687 MilLer, L. F., 70M1 Miller, W. , 71P1

Monroe, R. E., 59W1, 60W1

Morris, J. M. , 69C2

Munckeryan, H. M., 68M2

Murfin, W. B., 69K2

Myers, D. K. , 64M1

Myers, T. R. , 69L1

Nachbar, W. , 70M2 Nakayama, S., 69 Kl NASA, 71N1, 71N2 Neppiras, E. A. , 65N1

Nippes, E. F., 65J1 Nishikata, M., 6902

Nowakowski, M. F., 70V1

O'Connell, E. P., 6901

Ono, K., 6902 Oswald, Jr., R. B., 6601

Padden, H., 66L4 Pankratz, J. M. , 70P1 Parker, C. D. , 67P1 Partridge, J., 64P1, 66P1 Patzer, H. E. , 69G2 Peterson, J. M. , 62P1 Phillips, A. L., 65P1 Phillips, L. S., 63P1 Philofsky, E., 70P2, 71P1, 71P2, 71R1 Plough, C. , 69P1

Poston, M. H., 68P1

Promisel, N. E., 65J1

Pruden, D. H., 67P2

Ramsey, J. N., 68L1 Rasimenoks, P. , 67R4

Ravi, K. V., 71R1

Reber, R. L. , 67R3

Reich, B., 65H3 Renaut , P . , 59R1 Rhines, F. N., 65J1 Riben, A. R. , 66R1, 67R1, 67R2

•Robertson, J. M., 68D1

Rock, N. H., 64C2 Rodriguis de Miranda, W. R., 68R1

Root, C. D., 68G2 Rosica, G. A., 67S3 Rossiter, T. J. , 70R1 Ruggiero, E. M., 65R1, 65R2, 68R2

Ruth, S. B., 69R1

Sackett, Jr., W. T., 65M1

Sager, R. K. , 65J1

Scarbrough, R. J. D., 67S2

Schile, R. D., 67S3 Schnable, G. L., 67K2, 67S1, 69S2 Schoenthaler, D., 67P2 Schumacker, D. H. , 67SM- Schwartz, S., 67C2, 69C2 Seashore, C. R. , 65M1 Selikson, B., 63L1, 64S1, 67S5, 69S3

Sello, H., 66B3, 67B3 Shaffer, D. D., 65C3

Sherman, S. L. , 66R1, 67R1, 67R2

Shockley, W. L. , 68S1 Shurtleff, W. 0. , 69S4 Slemmons, J. W., 6UH2, 6 5S1, 69S1

Soltau, R. H., 65S2, 69B2 Spectrum, 70S1

Speer, R. D. , 69S5

Spencer, G. D. , 66B1

Straub, R. J., 70S2, 71S1

Strope, D. H., 70W1

Suzuki, M., 69K1

Szasz, P. R. , 65S3
Takei, W. J., 68T1 Tamburrino , A. L. , 69T1, 70B4- Tanaka, S. , 68T2 Tarowsky, N. , 69T2 Thomas, J. G., 59J1, 60J1, 61J1 Thomas, L. , 66K1

Tiffany, P. , 67T1

Univac, 67U1

Uthe, P. M., 68U1, 68U2, 68U3, 68U4, 68U5, 69U1, 69U2

van Lancker , M. , 67V1 Villella, F., 70V1

Wagner, R. , 66W1

Wales, R. D., 71G1

Walker, R. A. , 64W1

Warr, R. E., 71L1 Wasson, R. D. , 65W1

Weare, N. E., 59W1, 60W1 Weedfall, R. W., 68S1 Weiler, P. M., 63W1 Wilson, A. D., 70W1

Wood, W. A. , 7 0W2 Workman, W., 67G1

Worlton, D. C, 64W1

Wrench, G. D., 68H3 Wright, L. G., 69U2

Young, J. G., 66C2
Key Word Index Introduction

The three levels of key words indicating subject area are listed in alphabetical

order in Section 4A with page numbers where

they are located in section UB. In section

4-B these key words and descriptors are listed by the three subject areas: test, fabrication, and degradation. By each key word

and descriptor is a tabulation of identification codes of entries to which this key

word or descriptor was assigned in the bibliography. Key words and descriptors that may require additional definition are followed by

explanatory phrases, in brackets. An exception is made for the test method key words

They are listed in alphabetical order in Table 4 with brief descriptions for each method

To help identify key words of different

level: first-level key words are in uppercase , second-level key words have only the first letter capitalized, and third-level key

words are in lower-case . Descriptors are

also in lower-case and are listed immediately

below the associated first-level key words in section 4B.
4A Alphabetical Key Word Listing

KEY WORD - [DESCRIPTIVE PHRASE] PAGE NUMBER IN SUBJECT AREA LISTING

OF KEY WORDS (Section ~4B) adjustment - [of apparatus] 16

- [of bonding tool] 17 air blast - [description] 12

- [evaluation] 13 anneal - [of wire, responsible for degradation or failure] 19 Apparatus: [bonding machines and accessories] 16 apparatus - [importance of rigidity] 17

- [evaluation of] 16 Application - [information applicable to test method] 12 bond - [affected by stress] 18 bond (adhesion) - [evaluation of] 16 bond monitor - [application] 13

- [correlation] 13

- [description of test method] 12

- [to evaluate fabrication procedures and processes] 17 bond temperature - [test method used to evaluate fabrication procedures and processes]. 17 bond (type) - [evaluation of] 16 Bonding Surface - [information pertinent to the surface film(s) or metal substrate

of bonding area] 17 care - [of wire] 17 centrifuge - [description of test method] 12

- [evaluation] 13

- [correlation] 13

- [to evaluate fabrication procedures and processes] 17

- [to determine degradation or failure] 20

- [to stress wire bond] 19 contamination - [of bonding surface as related to fabrication of wire bond] 17

- [of parts of the wire bond before or after bonding, responsible for degradation or failure] 19

- [of wire as related to fabrication of wire bond] 17 Control - [importance of control of bonding parameters] 17 Correlation - [between test methods] 13 corrosion - [responsible for degradation or failure of wire bond] 19 DEGRADATION - [degradation or failure] 18 description - [of apparatus] 16 Description - [of the test method] 12 design - [of apparatus] 17

- [of bonding tool] 17 device - [affected by stress] 19 electrical - [stress to wire bond] 19 electrical characteristics - [of wire] 17 electrical parameter - [test method to determine degradation or failure] 20 electron microprobe - [test method to determine degradation or failure] 20 electromigration - [responsible for degradation or failure] 20 Evaluation - [of test methods] 13 Evaluation - [as related to fabrication of wire bonds] 16 FABRICATION - [of wire bonds] 13 fabrication - [of wire] 17 Failure Rates - [general reliability data; relative percentage of failure modes]. ... 20 fatigue - [metal fatigue responsible for degradation or failure] 19 film thickness - [of bonding surface] 17 force - [control of in bonding] 17 grain growth - [responsible for degradation or failure] . 20 hardening - [of wire and responsible for degradation or failure] 20 interferometer - [test method to evaluate fabrication procedures and processes] .... 17 intermetallics - [intermetallic compound formation or the Kirkendall effect

responsible for degradation or failure] 20 IR monitor - [description of test method] 12

- [evaluation] 13 mechanical - [stress to wire bond] 19 mechanical shock - [description of test method] 12

- [evaluation] 13

- [application] 13

- [to evaluate fabrication procedures and processes] 17

- [to stress wire bond] 1"
4A Alphabetical Key Word Listing (continued)

KEY WORD - [DESCRIPTIVE PHRASE] PAGE NUMBER IN SUBJECT AREA LISTING

OF KEY WORDS (Section UB

mechanical shock (radiation induced) - [description of test method] 12

- [evaluation] 13

- [correlation] 13

- [application] 13

- [to stress wire- bond] 19 Mechanism - [of failure or degradation] 19 mechanical characteristics - [of bonding surface] 17

- [of wire] IV metal system - [evaluation of, for fabricating wire bonds] 16

- [of bonding surface] 17 metallization - [affected by stress] 19

- [evaluation of, for fabricating wire bonds] 16 metallurgical exam - [description of test method] 12

- [to evaluate fabrication procedures and processes] 17

- [to determine degradation or failure] 20 metal system - [of bonding surface] 15 MIL-STD-883 - [description of test methods] 12

- [evaluation] 13

- [application] 13 MIL-STD-750B - [description of test methods] 12 moisture - [stress to wire bond] 19 noise - [description of test method] 12

- [evaluation] 13 orientation - [of bonding surface] 17

- [with respect to bonding tool] 17 oscillation - [of bonding tool] 17 package - [evaluation of] 16

- [importance of rigidity] 17 Part - [primarily of the wire bond, affected by stress] 19 photoelastic stress analysis - [test method used to evaluate fabrication

procedures and processes] 17 power - [control of, in bonding] 17 Precautions - [in the use of a test method] 13 preparation - [of bonding surface for bonding] 17 Procedure - [for making a wire bond] 16 process - [stress on wire bond] 19 pull - [description of test method] 12

- [evaluation] 13

- [correlation] 13

- [application] 13

- [to evaluate fabrication procedures and processes] 18

- [to determine degradation or failure] 20

- [to stress wire bond] 19 pull (nondestructive) - [description of test method] 12

- [evaluation] 13

- [correlation] 13

- [to evaluate fabrication procedures and processes] 18 radiation - [stress to wire bond] 19 radiotracer - [test method used to evaluate fabrication procedures and

processes] 18 resistance - [description of test method] 12

- [evaluation] 13

- [correlation] 13

- [precautions] 13

- [to evaluate fabrication procedures and processes] 18

- [to determine degradation or failure] 20 Rigidity - f importance of rigidity when fabricating wire bonds] 17 Schedule - [optimization of procedures and processes for making wire bonds] 16 Screening Procedures - [where a series of test methods are used] 13 shear - [description of test method] 12

- [evaluation]

- [to evaluate fabrication procedures and processes] 18

- [to determine degradation or failure] 20 size - [of wire] 17 spallation - [responsible for degradation or failure] 20

9
4A Alphabetical Key Word Listing (continued)

KEY WORD - [DESCRIPTIVE PHRASE] PAGE NUMBER IN SUBJECT AREA LISTING

OF KEY WORDS ( Section ~Ub) Stress - [stresses that produce weakened wire bonds as a result of the

fabrication process or that result in degradation or failure of

already completed wire bonds] 19 substrate - [affected by stress] 19 TC - [effects of process and material variables on making thermocompression

wire bonds] 16

- [evaluation of thermocompression bonding] ' 16

- [failure rates of thermocompression wire bonds] 20

- [procedure for making thermocompression wire bonds] 16

- [schedule for optimizing procedures and processes for making

thermocompression wire bonds] .16

- [theory of thermocompression bonding] 17 temperature - [importance of the control of] 17 temperature control - [evaluation of methods used in making thermocompression

bonds] 16 temperature cycle - [description of the test method] 12

- [evaluation] 13

- [application] 13

- [to evaluate fabrication procedures and processes] 18

- [to determine degradation or failure] 20

- [to stress wire bond] 19 terminal - [importance of rigidity] IV TES T - [test, evaluation, and screening methods for wire bonds] _12 Test - [used to evaluate fabrication procedures and processes] IV Theory - [of thermocompression and ultrasonic bonding] 15 thermal mismatch - [responsible for degradation or failure] 20 thermal shock - [description of test method] 12

- [evaluation] 13

- [application] 13

- [to evaluate fabrication procedures and processes] 18

- [to stress wire bond] 19 thermal - [stress on wire bond] 19 time - [control of, in bonding] IV Tool - [bonding tool, as related to the fabrication of wire bonds] IV tool - [evaluation of] 16 topography - [of bonding surface] IV

- [of wire] IV Trouble Shooting - [methods for locating and correcting deficiencies in wire bond fabricating procedures] 18

US - [effects of process and material variables on making ultrasonic wire bonds] ... 16

- [evaluation of ultrasonic bonding] 16

- [failure rates of ultrasonic wire bonds] 20

- [procedure for making ultrasonic wire bonds] 16

- [schedule for optimizing procedures and processes for making ultrasonic

wire bonds] 16

- [theory of ultrasonic bonding] I 7 US probe - [description of test method] 12

- [to evaluate fabrication procedures and processes] 18

US stress - [description of test method] 12

- [to stress wire bond] 19 Variables - [effects of process and material variables on the quality of

wire bonds] 1° vibration (variable frequency) - [description of test method] 12

- [evaluation] 13

- [application] 13

- [to evaluate fabrication procedures and

processes] 18

- [to determine degradation or failure] 20 vibration (monitored) - [description of test method] 12

- [evaluation] 13 vibration (fatigue) - [description of test method] 12

- [application]. 13

- [to determine degradation or failure] 20 visual inspection - [description of test method]

- [evaluation]

10
4A Alphabetical Key Word Listing (continued)

KEY WORD - [DESCRIPTIVE PHRASE] PAGE NUMBER IN SUBJECT AREA LISTING

OF KEY WORDS (Section i+B)

- [correlation] 13

- [application] 13

- [to evaluate fabrication procedures and processes^ 18

- [to determine degradation or failure] 20 visual inspection (SEM) - [description of test method] 13

- [to evaluate fabrication procedures and processes] 18

- [to determine degradation or failure] 20 wear - [of bonding tool] 17 wire - [affected by stress] 19 wire - [evaluation of, for different wire bonds] 16 Wire - [information pertinent to fabrication of wire bonds] 17 wire bond - [evaluation of] 16 x-ray - [description of test method] 13

- [evaluation] 13

- [to determine degradation of failure] 20

11
M-B Subject Area Key Word Listing

TEST

TEST [test, evaluation, and screening methods for wire bonds]

bond

TC [thermocompression]

64D1, 64H2, 65B1, 65C2, 67A1, 67G1, 67H1,

67SU, 68D2, 68F1, 68P1, 68R1, 69A1, 69K4,

69S1, 70A1, 70B1, 70H2, 71B3, 71H2, 71S1

US [ultrasonic]

59J1, 60J1, 61J1, 62J1, 64C2, 6WL, 66R1,

67P2, 67R1, 67R2, 68D2, 68F1, 68R1, 69B6,

69B7, 69K1, 69K4, 69P1, 70A1, 70B2, 70D2,

71B1, 71B4, 71G1

Al [aluminum hardened with silicon]

64D1, 66R1, 67R1, 67R2, 68D2, 68R1, 69B5,

69B6, 69B7, 69K1, 69K4, 69P1, 70A1, 70B2,

70D2, 71B1, 71B4, 71G1

Al (pure) [pure aluminum]

67R2 Au [gold]

65C2, 67A1, 67G1, 67H1, 68D2, 68L1, 68P1,

69A1, 69B5, 69K4, 69S1, 70A1, 70B1, 70H2,

71B3, 71H2, 71S1 Au/Cu [gold plated copper]

67S4

film [metal or metal film(s) of bonding surface]

Ag [silver]

70B1, 71B3

Al [aluminum]

65C2, 67A1, 67R1, 67R2 , 68D2, 68P1, 69B6,

69B7, 69K1, 69K4, 69P1, 70A1, 70B2, 70D2,

71B1, 71B4, 71G1, 71S1 Au [gold]

67A1, 67H1, 67S4, 68D2, 69P1, 69K4, 70A1,

70B1, 70D2, 71B3, 71S1 Au/Cr [gold on chromium]

66R1, 67R1, 67R2 Au/Mo [gold on molybdenum]

67G1

substrate [material underlying bonding surface

film(s)]

alumina

66R1, 67R1, 67R2 beryllia

66R1, 67R1 ceramic

67S4

sapphire

66R1, 67R1, 67R2

Si [silicon]

67R1, 67R2 silica (96%)

67R1, 67R2

application

plastic devices

70B1, 70C2 , 70H2, 71B3, 71H2 hybrid devices

70S2, 71S1

Description [of the test method]

air blast

68D2 bond monitor

59J1, 60J1, 61J1 , 62J1, 6W1 , 67P2, 69B6, 69B7 , 71B4 centrifuge

63W1, 66IA, 66P1, 68B1, 68D2, 6811, 69B2 , 6901, 69S4, 70B7, 70D3 IR monitor

67B1, 67S4, 68B1 mechanical shock

63W1, 66P1, 6711, 68D2, 69B2 , 69S4, 70D3, 71N2 , 71K1 mechanical shock (radiation-induced)

68F1 • metallurgical exam

68B1

MIL-STD-883

68D2 , 6901 , 70C2, 71N1 MIL-STD-750B

66P1

65M1 pull

63W1, 65W1 , 67H1, 68B1, 68D2, 68P1, 69K1

6901, 69S1, 70A1 , 70B7 , 71N1, 71N2 pull (nondestructive)

65B1, 69S1 resistance

66M1, 68D2, 70B2, 70H2, 71H2, 71N1, 71N2 shear

67A1, 68D2 temperature cycle

66L4, 66P1, 68D2, 6901, 69S4, 70H2, 71H2 thermal shock

63W1, 68D2, 69B2, 69S4, 70D3

US probe

59R1, 67B4- US stress

69K4, 70B7 vibration (fatigue)

6611 , 68D2, 69S4, 70D3 vibration (monitored)

66H+, 68D2, 70D3 vibration (variable frequency)

63W1, 6611, 66P1, 68D2, 69S4, 70D3

12
4B Subject Area Key Word Listing (continued)

TEST - FABRICATION

visual inspection

66P1, 66L4, 68D2, 68R1, 6901, 71N1 visual inspection (SEM)

69S1, 71N1 x-ray

66L4, 68D2, 68L1, 69S1

Evaluation [of the test method]

air blast

69P1

centrifuge

66L*+, 67G1, 68H4, 6901 IR monitor

67S4 mechanical shock

68F1, 68m

mechanical shock (radiation-induced)

68F1 MIL-STD 883 70S2

pull

68B1

67R2, 68H1+, 70B8, 71B1 pull (nondestructive)

64D1 resistance

67R2, 68B1, 70H2 , 71H2 shear

67G1 temperature cycle

66L4, 68H4, 69B1, 70H2 , 71H2 thermal shock

65H3, 68H4, 69B1, 69P1, 70B1, 71B3 vibration (monitored)

66L4 vibration (variable frequency)

69S4

visual inspection

64H2, 66L4, 67G1, 68H4, 69K1 , 6901, 69P1, 69S4 x-ray

66L4, 67G1, 68Ht

Correlation [between methods for the same type

of wire bond]

bond monitor , 69B7 centrifuge

65B1 mechanical shock- (radiation-induced)

69P1, 70D2 pull

pull (nondestructive)

69A1 resistance

66R1, 67R1, 67R2 visual inspection

67B7, 67G1, 69K1 , 69P1, 70D2, 71G1

Application [information relevant to a particular test method]

bond monitor

64C2, 70B7 , 71K2 mechanical shock

61A2 , 69K2 mechanical shock (radiation-induced)

67G2, 70M2 MIL-STD-883

69B8, 69D3, 71N1 pull

67S3, 68A1, 69B5, 69D1, 70A6 , 70B8, 71BU temperature cycle

69K2 , 70P2 , 70V1 thermal shock

69K2 , 70P2

US probe

69D2 vibration (fatigue)

69K2 visual inspection

68H1

Precautions [in the use of a test method]

resistance

65C2, 68E1

Screening Procedures [where a series of tests is used to cull out unsatisfactory wire bonds]

66P1 , 67G1 , 67P1, 68D2 , 69D3, 69U , 70S2,

71N1, 71S1

FABRICATION

bond

TC [thermocompression]

57A1, 57A2, 58C1, 61A1, 62M1, 63M1, 63P1,

63W1, 64A1, 64D1, 64H1, 64H2, 64J1, 64M1,

65B1, 65C1, 65C5, 65H1, 65H2, 65R1, 65S1,

65S3, 66A1, 66A2, 66B1, 66B3, 66B4, 66B6,

66C1, 66E1, 66G2, 66H1, 66K3, 66L1, 67A2,

67B2, 67C1, 67H1, 67K1, 67P1, 67R4, 67S1,

67S5, 68A2, 68A3, 68B1, 68D1, 68G1, 68H3,

68H5, 68J1, 68K1, 68M1, 68M2, 68M3, 68P1,

68R2, 68T2, 69A2, 69B3, 69G2, 6902, 69S1,

69S2, 69S5, 69T2, 70A2, 70DU, 71B2, 71M1,

71P1, 71R1

65B1, 66R1, 67R1, 67R2, 69A1, 69B7 , 69K1 , 69P1, 70D2, 71G1

US [ultrasonic]

59A1, 59J1, 59W1, 60J1, 60J2, 60W1, 61D1,

61J1, 62P1, 63W1, 64D2, 65D1, 65J1, 65N1,

66B1, 66B6, 66E1, 66H1 , 66L3, 66R1, 67B2,

67H2, 67J1, 67L1, 67P1, 67R1, 67R2, 67S1,

67T1, 68B1, 68D1, 68H3, 68K1, 68M1, 68M2,

13
4B Subject Area Key Word Listing (continued)

FABRICATION

68S1, 68T2, 68U1, 68U2, 68U3, 68U4, 68U5,

69B2, 69B3, 69B5, 69B6, 69K1, 69K3, 69L2,

6902, 69P1, 69 Si, 69S2, 69S5, 69T2, 69U1,

69U2, 70B2, 70B3, 70B5, 70B6, 70B7, 70B8,

70C1, 70D2, 70D4, 70P1, 70W1, 71B1, 71B2,

71B4, 71 Dl, 71 Gl, 71 HI, 71 Jl, 71M1, 71P1,

71P2, 71R1 wire

Ag [silver]

57A1, 57A2, 58C1, 61A1, 62M1, 63W1, 64A1,

66A1, 66C1, 66G2 Al [aluminum hardened with silicon]

57A1, 57A2, 58C1, 61A1, 63M1, 63W1, 64A1,

64D1, 64S1, 65B1, 65D1, 65R1, 66A1, 66B4,

66G2, 66R1, 67B2, 67C1, 67K1, 67L1, 67P1,

67R1, 67R2, 67S1, 67S5, 67V1, 68G1, 68H3,

68K1, 68M2, 68R2, 68T2, 68U1, 69B2, 69B3,

69B5, 69B6, 69K1, 69K3, 6902, 69P1, 69S1,

69S2, 69U1, 70B2, 70B3, 70C1, 70D2, 70D4,

7.0P1, 71B1, 71B2, 71G1, 71J1, 71P1, 71P2, 71R1 Al/Mg [aluminum hardened with magnesi

67V1, 68U1, 69U1, 70P1

Al (pure) [pure aluminum]

67R2, 67V1, 6902 Au [gold]

57A1, 57A2, 58C1, 61A1, 62M1, 63M1,

63W1, 64A1, 64C1, 64H1, 64H2 , 64M1,

65B1, 65C5, 65D1, 65H1, 65H2, 65R1,

66A1, 66B3, 66B4, 66C1 , 66G2, 66L1,

67B2, 67C1, 67H1, 67K1, 67P1, 67S1,

67T1, 68A3, 68H3, 68K1, 68M2, 68M3,

68R2, 68S1, 68T2, 68U1, 69A2, 69B3,

69P1, 69S1, 69S2, 69S3, 69U1, 70A2,

70D4, 71B2, 71P1 Au/Ag [gold with silver added]

66W1 Au/Cu [gold plated copper]

61A1, 66C1 Au/CuBeO [gold plated CuBeO]

71D1 Au/Ga [gold with gallium added]

68S1

Au/Ni [gold covered nickel]

64C1 Au/Pt [gold covered platinum]

64C1 Au/W [gold covered tungsten]

64C1

Cu [copper]

57A1, 57A2, 61A1, 62M1, 63M1 Cu/Ni [gold plated nickel]

66C1

Pb [lead]

57A2

PI [palladium]

63W1

um]

63P1,

64S1,

65S1,

66W1,

67S5,

68P1,

69G2,

70A3,

Pt [platinum]

57A2, 63M1, 65C1

Sn [tin]

57A2 Sn/Cu [tinned copper]

61A1

Ti [titanium]

63M1

Zr [zirconium]

63M1

film

Ag [silver]

63W1, 66G2, 67P1 Ag/Al [silver on aluminum]

63W1, 68T2 Ag/Cr [silver on chromium]

63W1, 64S1, 66G2, 67K1, 67P1, 67S5, 68K1

Ag/Cr-Al [silver on chromium-aluminum al- loy]

63WI

Al [aluminum]

62M1, 63M1, 63W1, 64D1, 64H1, 64H2, 64M1,

64S1, 65B1, 65C5, 65H1, 65H2, 65R1, 65R2,

65S1, 66A1, 66B3, 66B4, 66G2, 66H1, 66W1,

67B2, 67C1, 67H1, 67K1, 67L1, 67P1, 67R1,

67R2, 67S1, 67S5, 68A3, 68G1, 68H3, 68K1,

68M2, 68M3, 68P1, 68R2, 68T2, 69A2,~69B2,

69B5, 69B6, 69K1, 6902, 69P1, 69S1, 69S2,

69U1, 70A2, 70B2, 70B3, 70C1, 70D2, 70D4,

71B1, 71G1, 71J1, 71P1, 71P2 Al/Cr [aluminum on chromium]

63P1, 66H1, 67B2, 67R2 Au [gold]

63W1, 64D1, 64S1, 64B1, 65C5, 65R1, 66A1

,

66B4, 66G2, 66H1, 67B2, 67H1, 67K1, 67P1,

67S1, 68H3, 68K1, 68R2, 69A3, 69B2, 69B3,

69K3, 6902, 69P1, 69S1, 69U1, 70D2, 70D4,

71G1, 71J1, 71P1

'

Au/Ag [gold on silver]

65C5 Au/Ag/Cr [gold on silver on chromium]

69S3 Au/Ag/Cr-Al [gold on silver on chromiumaluminum alloy]

63W1 Au/Al [gold on aluminum]

63M1 AuAl2 [gold-aluminum compound]

68T2 Au/Co ['gold on cobalt]

65C5 Au/Cr [gold on chromium]

63P1, 63M1, 65C5, 66H1, 66R1, 67B2, 67L1,

67R1, 68M2, 69S2

14
M-B Subject Area Key Word Listing (continued)

FABRICATION

Au/Cu [gold plated copper]

71D1 Au/Cu/Ti [gold on copper on titanium]

68M2 Au/Cr/Al [gold on chromium on aluminum]

68K1 Au/Mo [gold on molybdenum]

65C6, 66G2, 67C1, 67P1, 67S1, 67S5, 68M2,

6952, 69S3 Au/Mo/Al [gold on molybdenum on aluminum]

67S5, 70A2 Au/Mo/Mn [gold on molybdenum on manganese]

69B3 Au/Mo/Pt [gold on molybdenum on platinum]

67C1, 67K1, 68K1

Au/Ni [gold on nickel]

65C5, 68M2 Au/NiCr [gold on nichrome]

65S1 Au/Pl [gold in palladium]

63W1

Au/Pt/Ti [gold on platinum on titanium]

67S5, 68M2 Au/Pt/Ti/Pt [gold on platinum on titanium

on platinum]

69S3 Au/Ti/Al [gold on titanium on aluminum]

6953, 70A2

Bi [bismuth] 62M1

Cr [chromium]

68H3, 68T2 Cr/Al [chromium on aluminum]

64S1, 67S5, 69S3

,iCr [copper or nichrome]

65S1

Ga [gallium]

62M1

In [indium]

6 2 Ml

Mi [nickel]

66A1 NiCr [nichrome]

63M1

PI [palladium]

64S1

Pt [platinum]

64H2, 64S1

Pt/Ti [platinum on titanium]

68M2

Sb [antimony]

62M1

Ta [tantalui 63M1

Ti [titanium]

63M1

thick film

Ag [silver]

69B3 Ag/Pd [silver-palladium composition]

69B3

Au [gold] 69B3 Au/Pd [gold-palladium composition]

69B3 Au/Pd/Pt [gold-palladium-platinum compo- sition]

69B3 Au/Pt [gold-platinum composition]

69B3 Pd/Ag [palladium-silver composition]

69B3

substrate

Al [aluminum]

66B4 alumina

65R2, 65S1, 66C1, 66R1, 67L1, 67R1, 67R2, 68H3 beryllia

66R1, 67L1, 67R1

BN [boron nitride]

65R2 ceramic

63P1, 66H1 epoxy

71D1 Fe/Ni/Co [iron-nickel-cobalt alloy]

65B1, 66B4, 69K3, 71G1 , 71J1

Ge [germanium]

57A1, 57A2, 57C1, 61A1, 62M1, 65D1 glass

63P1, 65D1, 65H1, 65H2, 65R2 , 66C1, 66H1,

67L1, 68H3 sapphire

66R1, 67L1, 67R2

Si [silicon]

57A1, 57A2, 57C1, 61A1, 62M1, 63M1, 61+A1, 6UH2, 65C1, 65C5, 65D1, 65R2, 65S1, 66A1,

66BU, 67L1, 67P1, 67R2, 68H3, 68T2 silica (96%)

67L1, 67R1, 67R2

application

hybrid devices

67L1, 67R1, 68H3, 68M3, 69T2

Theory [of bond i

i TC [thermocompression]

57A2 , 61A1, 63M1, 6UA1, 66A1, 66B4, 66B6

,

67B2, 68B1, 69S1

15
i+B Subject Area Key Word Listing (continued)

FABRICATION

US [ultrasonic]

59A1 , 59 Jl, 59W1, 60J1, 60J2 , 60W1 , 61Jl , 62PT, 65D1, 65J1, 65N1, 65P1, 66B6 , 67B2,

67 Jl , 68B1, 68U2, 68U3, 68U4, 69P1, 69S1, 69U1 , 70B3 , 70B8 , 71P2

Evaluation [of]

TC [thermocompression bonding]

63P1, 63W1, 66B1, 66C1, 66E1, 67B2 , 67S1, 68H3 , 68K1, 68M1, 69C1, 69S1, 69T2, 70D4,

71B2

US [ultrasonic bonding]

60J2, 61J1, 62P1 , 63W1, 66B1, 66E1, 66R1,

67B2 , 67L1, 67R1 , 67S1, 68H3 , 68K1, 68M1,

69C1, 69S1 , 69T2, 70D4, 71B2 , 71P2 wire bond [wire bonds, in general, and versus other bonding methods]

67L1, 69B2, 69B3 , 69C1 , 69S5 , 70D4, 70M1 , 71B2, 71M1 apparatus (US) [ultrasonic bonding equipment]

61D1

bond (adhesion)

57A2, 63M1 , 63P1 bond (ball)

64M1, 65B1, 65R1, 66B4_, 66E1, 66G2, 66L1, 67B2 , 67C1, 67K1, 68M3, 68R2, 69B6, 69C1 bond (stitch)

65D1, 65R1, 66E1, 66L1, 67B2 , 68M3, 68R2, 69C1 bond (wedge)

65B1, 65R1, 66B4_, 66E1, 66G2, 66L1, 67B2 , 67C1, 67K1, 68R2, 69C1 bond (general)

66C2 metal system [of the wire bond, i.e. wiremetallization-substrate, for]

(TC) [thermocompression bonds]

63W1, 64S1, 65C5 , 65R2, 66G2 , 67K1, 67P1,

67S5, 68M2, 68T2, 70A2

(US) [ultrasonic bonds]

61J1, 67P1, 67R2, 68M2, 68T2 (general) [bond type not specified]

66W1, 69S3 metallization

65C5 , 66H1, 67C1, 67P1, 68T2, 69B3 , 69S2 package

67G1

temperature control [for thermocompression

bonding]

66L1, 67K1, 68H3, 71B2 tool

(TC) [to make thermocompression bonds]

63-W1, 64M1, 65B1, 66B1 , 68H3

(US) [to make ultrasonic bonds]

63W1

(TC) [for thermocompression wire bonds]

65B1, 65R1, 65R2, 66G2, 67P1, 68H3, 68R2, 71R1

(US) [for ultrasonic wire bonds]

63W1, 67P1, 68U1, 69U1 , 70C1, 70P1, 71R1

(ribbon)

65B5, 69B6 (general) 66W1

Procedure [for making a wire bond]

TC [thermocompression]

57A1, 57C1, 60J2, 61A1, 62M1, 6*+H2_, 64M1,

65C1, 65R1, 65S1, 66A2 , 66L1, 67A2, 67B2,

67H1, 67K1, 67P1, 68A2, 68B1, 68H5, 68K1,

68R2, 69G2, 69S1, 71B2 US [ultrasonic]

60J1, 65J1, 65N1, 67B2, 67P1, 67R2, 67T1,

68B1, 68K1, 69K2, 69K3, 69S1

Schedule [optimization of procedures and processes for making wire bonds]

TC [thermocompression]

57A1, 63M1, 63P1, 64A1, 6HH2 , 65B1, 66A1 , 66C1, 67B2, 67H1, 68B1, 68K1

US [ultrasonic]

59A1, 59W1, 60J1, 60W1, 61J1, 63W1 , 65J1,

66R1, 67J1, 67L1, 67R1, 67R2, 68K1, 68U1,

68U4, 69P1, 69U1 , 70B8, 70D2

Variables [effects of process and material variables on quality of wire bond]

TC [thermocompression bond]

57A1, 57C1, 59A1, 61A1, 63M1, 63P1, 64A1, 64H2 , 65H1, 65H2 , 66A1, 66B1, 66C1, 66L1,

67B2, 67H1, 67K1, 68P1, 69B3

US [ultrasonic bond]

59W1, 60J1, 60J2, 60W1, 61J1, 63W1, 65D1,

65J1, 65N1, 66B1, 67J1, 67R1, 69B3, 69P1 , 70D2 , 71J1

Apparatus [of bonding machines and accessories]

adjustment (TC) [of thermocompression bonding apparatus]

67H1 , 63W1 adjustment (US) [of ultrasonic bonding ap- paratus]

64D2, 68U5, 69B6, 69P1 , 69U1 , 70B3 , 70D2 , 71B4, 71H1 description (TC) [of thermocompression bonding apparatus]

68D1, 68H3 description (US) [of ultrasonic bonding ap- paratus]

60J1, 62P1, 63W1, 67B2, 67L1, 67R2, 68D1, 69U1

16
4B Subject Area Key Word Listing (continued)

FABRICATION

design (TC) [of thermocompression bonding

apparatus

63M1, 63W1 , 64J1, 64M1, 65S3, 66A2, 66K3,

67A2, 67R4, 68H5 design (US) [of ultrasonic bonding apparatus]

59A1, 59W1, 60J2, 60W1, 6 3W1 , 65D1, 65J1,

65N1, 67H2, 67J1, 67S1, 68B1, 68U5, 69L2,

69U1, 69U2, 70B2 , 70B3, 70B6, 70D2, 70W1,

71B4", 71J1

Control [importance of control of] force (TC) [applied in making thermocompression bond]

68P1

force (US) [applied in making ultrasonic bond]

68U4, 70C1 power (US) [used in making ultrasonic bond]

68U4, 70C1 temperature (TC) [in making thermocompression bond]

64H2_, 65H1, 65H2, 65S1, 66C1, 66L1, 68B1, 68H3 , 68J1, 68M3, 68P1 temperature (US) [in making ultrasonic bond]

68B1 time (US) [for making ultrasonic bond]

68U4, 70C1

Tool [bonding]

adjustment (US) [for ultrasonic bonding]

69U1 , 70B2 , 70B3, 71H1 , 70D2 design (TC) [for thermocompression bonding]

63W1 , 64H2, 65B1, 65S3, 66B4, 66C1, 67B2,

67R3, 67S1, 68B1, 68H3 , 69G1, 71B2 design (US) [for ultrasonic bonding]

59W1, 60W1, 63W1 , 65D1, 67R1, 67R3, 67S1,

67T1, 68U1, 69G1, 69P1 , 70B2, 70B7, 70D2

71B1, 71D1, 71G1, 71J1 oscillation (US) [of the ultrasonic bonding

tool]

69B6, 70B2 , 70B3, 70D2, 70W1, 71B1, 71D1, 71H1 wear (TC) [of the thermocompression bonding

tool]

68H3 wear (US) [of the ultrasonic bonding tool]

67R1, 71J1

Rigidity [importance of in]

apparatus

67R2, 68U5, 69P1, 69U1, 70B2, 70B3, 70B7 , 70B8, 70D2, 71B1, 71B4, 71J1 terminal [device]

68U5, 69P1, 70D2, 71B2 package

69U1, 70D2, 71J1

Wirecare

contamination

65K1, 70A3, 70B3 electrical characteristics

66R1, 67R1, 6902, 70A7 fabrication

6902, 70S1 mechanical characteristics

63W1 , 64C1 , 65K1, 66L3, 67R2, 67V1, 68G1,

68S1, 68U1, 69D2, 6902 , 69U1, 70A3 , 70A4,

70B3, 70B5, 71B4, 71R1 size

66C1, 66K2, 68B2, 70A3 , 70A4, 70A5 topography [of the surface]

65K1, 6902

Bonding Surface [of film(s) or metal substrate]

contamination

59W1, 60W1, 64H2, 65B1, 66B4, 66C1, 69A3 , 69H1, 69P1, 70D2, 71G1 film thickness

64H1, 65C5, 65H1, 65H2, 66B3, 66G2, 66R1,

67L1, 67R1, 67R2, 68A3, 69A2, 69A3 , 69K1,

69K3, 70D2, 71G1, 71P1 mechanical characteristics

59W1, 60W1, 69A3 , 69P1, 71H3 metal system

67C1, 68T2, 71G1 orientation [with respect to the bonding

tool]

68S1

preparation

59W1, 60W1, 63P1, 64H1, 65H1, 65H2, 65R2,

66H1, 67C1, 67L1, 67R2, 68T2, 69A3 , 69B3,

70A2, 70B3, 71G1 topography

59W1, 60W1, 63P1, 64H2, 65D1, 66R1, 67L1,

67R1, 67R2, 69A3 , 69P1 , 70D2, 70P1, 71J1, 71P2

Test [used to evaluate fabrication procedures

and processes]

bond monitor

59A1, 59W1, 61J1, 65J1, 65P1, 67J1 bond temperature

61J1 centrifuge

63W1, 64M1, 65B1, 65R1, 67K1, 68R2, 69B2 interferometer

70B2, 70W1 mechanical shock

63W1, 64M1, 65R1, 68R2 , 69B2 metallurgical exam

59W1, 60J1, 60J2, 60W1, 61J1, 65H2, 65jl,

66C2, 67J1 photoelastic stress analysis

61J1

64C1, 67B2, 68S1, 70A3

17
4B Subject Area Key Word Listing (continued)

FABRICATION - DEGRADATION

pull

pull

57C1, 59W1, 60W1, 61A1, 63M1, 63P1, 63W1,

64H2, 65B1, 65C5, 65H1, 65H2 , 65J1, 65S1,

66B4, 66C1, 66G2, 66R1, 66W1, 67H1, 67K1,

67L1, 67R2, 68B1, 68U1, 69B3, 6902, 69P1,

69S1, 69U1, 70B3, 70B7, 70B8, 70C1, 70D2,

7lDl, 71G1 (nondestructive

)

65B1, 66B4 radiotracer

61J1, 69H1 resistance

63M1, 63P1, 66G2, 66R1, 67R2, 70C1 shear

61D1, 64A1, 66A1 temperature cycle

63P1, 69B2 thermal shock

63P1, 63W1, 64M1, 66C1, 67R2

US probe

69D2 vibration (variable frequency)

63W1, 64M1, 65R1, 68R2 visual inspection

57A1, 60J1, 61A1, 63M1, 63P1, 67L1, 67R2,

68U1, 69P1, 69U1, 70C1, 70D2, 71G1 visual inspection (SEM)

69C2, 70B7, 70B8

Trouble Shooting [methods for locating and cor- recting deficiencies in fabricating procedures]

69U1, 71H1

DEGRADATION [degradation

bond

TC [thermocompressj

61G1, 64P1, 64S1. 65H1, 65H2, 65R1. 66B4, 66B5, 66G2. 67C1, 67G1, 67K1. 68A3, 68F1, 68G1. 68P1, 68R2, 69A2. 6901, 6902, 69S1. 70D1, 70H2, 70R1. 71P1, 71R1, 71S1

US [ultrasonic]

59W1, 60W1, 66K1. 67P1, 67L1, 67R1,

68M1, 68U1, 69B5. 6902, 69P1, 69U1,

70P1, 70V1, 71B1. 71R1 wire

Al [aluminum hardened with silicon or so implied]

64S1, 64U1, 65C5, 65R1, 66B4 , 66K1, 66R1,

67A3, 67C1, 67L1, 67P1, 67R1, 67R2, 67S1,

67S2, 67S5, 68F1, 68G1, 68G2 , 68M1, 68R2,

or failure]

on]

64U1, 65C3, 65C4, 65C5,

65R2, 65S2, 66B2, 66B3,

66L2, 67A1, 67A3, 67B3,

67K2, 67P1, 67S1, 67S5,

68G2, 68H2, 68M1, 68M2,

69B3, 69B4, 69K4, 69L1,

69T1, 70A1, 70A2, 7 OBI,

70S2, 70V1, 71B3, 71H2,

66L3, 66R1, 67A3, 67C3,

67R2, 67S1, 68A3, 68F1,

69K3, 69K4, 69L1, 6901,

70A1, 70B2, 70B8:, 70C1,

71B4, 71G1, 71G2, 71P1,

68U1, 69B4, 69B5, 69K3, 69K4, 69L1, 6901,

6902, 69P1, 69S3, 69U1, 70A1, 70B2, 70C1,

70P2, 70V1, 71B1, 71B4, 71G2 , 71P1, 71R1 Al (pure) [pure aluminum]

67R2, 70P2 Al/Mg [aluminum hardened with magnesium]

69P1, 70P1

Au [gold]

61G1, 64P1, 64S1, 64U1, 65C3, 65C4, 65C5,

65H1, 65H2, 65R1, 65R2, 65S2, 66B2, 66B3,

66B4, 66B5, 66G2, 66L2, 67A1, 67B3, 67C1,

67C3, 67G1, 67K1, 67K2, 67P1, 67S1, 67S5,

67A3, 68F1, 68G1, 68H2, 68L1, 68M1, 68M2,

68P1, 68R2, 69A2, 69B3, 69B4, 69K4, 69L1,

6901, 69S1, 69S3, 69T1, 70A1, 70A2, 70B1,

70D1, 70H2, 70P2, 70R1, 70V1, 71B3, 71G1,

71H2, 71P1, 71S1

ilmAg [silver]

69T1 Ag/Cr [ silver or chromium ] 67S5

Al [aluminum]

64P1, 64S1, 64U1, 65C3, 65C4, 65C5, 65H1,

65H2, 65R1, 65R2

,

65S2, 66B2, 66B3, 66B5,

66B7, 66G2, 66K1, 67A1, 67B3, 67C1, 67C3,

67K1, 67K2, 67L1, 67P1, 67R1, 67R2, 67S1,

67S5, 67A3, 68G1, 68G2

,

68H2, 68M2 , 68P1,

68R2, 68U1, 69A2, 69B4, 69B5, 69K4, 69L1,

6901, 6902, 69S1, 69S3, 69T1, 70A1, 70A2,

70B2, 70C1, 70D1, 70R1, 70V1, 71B1, 71B4

,

71P1, 71S1 Au [gold]

64S1, 6W1, 65C5, 65R1, 65S2, 67A1, 67P1,

67S1, 68H2, 68M2, 68R2, 69K3, 69K4, 69L1,

6901, 6902, 69S3, 69T1, 70A1, 70B1, 71B3,

71P1, 71S1 Au/Cr [gold on chromium]

66R1, 67L1, 67R1, 67R2 Au/Mo [gold on molybdenum]

65C5, 67C1, 67G1, 67P1, 67S1, 67S5, 69B4 Au/Mo/Al [gold on molybdenum on aluminum]

67S5, 70A2 Au/Mo/Pt [gold on molybdenum on platinum]

67C1

Au/Pt/Ti [gold on platinum on titanium]

67S5 Au/Ti/Al [gold on titanium on aluminum]

70A2 Cr/Al [chromium on aluminum]

67S5

Ni [nickel] 69T1

thick film

Ag/Pd [silver-palladium composition]

69B3

18
4B Subject Area Key Word Listing (continued)

DEGRADATION

Au [gold]

69B3, 71G2

substrate

alumina

65R2, 66R1, 67L1, 67R2 beryllia

66R1, 67L1

BN [boron nitride]

65R2 FeNiCo [iron-nickel-cobalt alloy]

64S1, 66B4, 66K1, 67P1, 69K3 glass

65H1, 65H2, 65R2 sapphire

66R1, 67L1, 67R2

Si [silicon]

61G1, 64S1, 65R2, 65S2, 67L1, 67P1, 67R2, 69U1 silica (95%)

67R2, 67L1 application

plastic device

68L1, 69T1 , 70B1, 70B4, 70H1, 70H2, 71B3,

71H2 hybrid devices

67L1, 70S2, 71L1, 71S1

Stress [that produces a weakened wire bond as a result of the fabrication process or that results in degradation or failure of an already completed wire bond]

electrical

67B3 mechanical

70W2

71H2, 71L1, 71P1,

moisture

66B7, 69T1, process

59W1, 60W1,

66B2, 66B5,

67G1, 67P1,

68H2, 68L1,

70B4, 70B8,

radiation

66L2, 6601

test (centrifuge

64P1, 64U1, test (mechanical

65U1, 71S1 test (mechanical

68F1

test (mechanical

71S1 test (pu

70A1, 70B8

70B4, 70H2, 71H2, 71L1

61G1, 64P1, 64U1,

66G1, 66K1, 66L3,

67L1, 67R1, 67R2,

68M2, 68P1, 68U1,

70C1, 71B1, 71B4,

) 65S2, 67G1, 67S1, shock

)

65R2, 65S2,

67A3, 67C2,

67S1, 67S5,

69L1, 69U1, 71G1

71S1

test (temperature cycle)

66K1, 70B4, 70H1, 70H2,

71S1 test (thermal shock)

64U1, 67G1, 67R2, 69T1, 70B1, 70B4, 70H1,

71B3, 71S1 test (US stress)

69K4 thermal

61B1, 64S1, 6W1, 65C3, 65C4, 65C5, 65H1,

65H2, 65R1, 65R2, 65S2, 66B3, 66B4, 66B5,

66G2, 66K1, 66R1, 67A1, 67B3, 67C1, 67C.3, 67G1, 67K2, 67L1, 67P1, 67R1, 67R2, 67S1,

67S2, 67S5, 67A3, 68G1, 68G2, 68P1, 68R2,

68T1, 69A2, 69B3, 69B4, 69B5, 69K3, 69L1,

6901, 6902, 69P1, 69S1, 69S3, 69T1, 70A1,

70A2, 70B2, 70C1, 70P1, 70P2, 70R1, 70V1,

71G2, 71P1, 71R1

shock (radiation-induced))

shock)

Part [part affected, primarily of the wire bond]

bond

59W1, 60W1, 61B1, 64P1, 64S1, 6W1, 65C3,

65C4, 65C5, 65H1, 65H2, 65R1, 65R2, 65S2,

66B2, 66B3, 66B4, 66B5, 66G1, 66G2 , 66K1,

66L2, 6601, 67A1, 67A3

,

67B3, 67C1, 67C2,

67C3, 67G1, 67K2, 67L1, 67P1, 67R1, 67R2,

6751, 67S5, 68A3, 68F1, 68H2, 68M2 , 68P1,

68T1, 69A2, 69B4, 69K3

,

69K4, 69S1, 69S3,

69T1, 70A2, 70B1, 70B8, 70D1, 70R1, 70H2,

71B3, 71B4, 71G2, 71H2, 71P1, 71S1 metallization

6W1, 65S2, 66B7, 66R1, 67G1, 67L1, 67R1,

67R2, 68M2, 69A2, 70B4, 70H2 , 71H2, 71L1 substrate

61G1, 65S2, 67G1, 68M2, 68U1, 69U1, 70C1 wire

64P1, 64U1, 65H1, 65H2, 65K1, 65S2, 66B2,

66B4, 66G1, 66G2, 66K1, 66L3, 67A3, 67G1,

67L1, 67R2, 67S1, 67S5, 67A3, 68G1, 68G2,

68H2, 68L1, 69B5, 69K4, 6902, 69P1, 69T1,

70A1, 70B1, 70B2, 70B4, 70C1, 70H2, 70V1,

70W2, 71B1, 71B3, 71B4, 71G1, 71G2, 71H2,

71L1, 71P1, 71R1, 71S1 device [the device of which the wire bond is

a part]

6752, 69P1, 70P1

Mechanism

anneal [wire anneal]

66K1, 67S5, 68A3 , 69P1 , 69B5, 69L1, 6901,

6902, 69P1, 70A1, 70B2, 70C1, 71BI4, 71R1 contamination [on or in the parts of the wire

bond before or after bon<! 65S2, 66G1, 66K1 , 67C2, 67G1, 67P1, 67S2 , 68H2, 68M2, 69L1, 69P1, 70D1, 70P1, 71L1 corrosion

65S2, 66B7, 67C1, 69T1, 70BM

,

71L1

Lgue [metal fatigue]

59W1, 60W1, 65K1, 68G1, 68G2, 70BM , 70V1,

70W2, 71 LI, 71P1, 71R1

19
4B Subject Area Key Word Listing (continued)

DEGRADATION

electromigration

67B3 grain growth

66G2, 66K1, 68P1, 6902, 70A1, 71R1 hardening [of the wire]

59W1, 60W1, 66L3 intermetallics [intermetallic compounds

the Kirkendall effect]

61B1, 64P1, 64S1, 64U1, 65C3, 65C4.

and

65C5. 65H1, 65H2, 65R1, 65R2, 65S2, 66B2, 66B3

66B^, 66B5, 66G1, 66G2, 66W1, 67A1, 67A3

67B2, 67B3, 67C1, 67C3, 67CU, 67K1, 67K2

67L1, 67P1, 67R1, 67R2, 67S1, 67S5, 68A3 68H2, 68M2, 68P1, 68R2, 68T1, 69A2, 69B4

69K3, 69L1, 6901, 69S1, 69S3, 70A2, 70P2

70R1, 71L1, 71P1 spallation [separation of a material or in- terface caused by stress-wave in- teractions]

6601, 68F1 thermal mismatch

65S2, 68H2, 69T1, 70B1, 70B4, 70H2, 71B3. 71H2

x-ray

68L1, 70B4

Failure Rates [general reliability data; rela- tive percentages of failure modes]

TC [thermocompression wire bonds]

64U1, 66B2, 67G1, 67P1, 67S1 , 68H2 , 68M1,

68R2, 69B4, 69K4, 69L1 , 6901, 70S2, 70V1

US [ultrasonic wire bonds]

67P1, 67S1, 68M1, 69K4, 69L1, 6901, 70V1 general

68E2, 70B4, 70H1

Test [used to determine degradation or failure]

centrifuge

65C5, 65S2, 66G1, 67G1 electron microprobe

67C2 electrical parameter

67S2, 69P1 metallurgical exam

59W1, 60W1, 65C3, 65C4, 65H1, 65H2, 66B3,

66B5, 69K3, 70P2 pull

59W1, 60W1, 64S1, 65C4, 65C5, 65H1, 65H2,

66B4, 66G2, 66K1, 66R1, 67C3, 67R1 , 67R2

,

67S5, 67A3, 67L1, 68P1, 69B3, 69B5, 69L1,

6901, 6902, 69P1, 70A2, 70B2, 70C1, 70P2,

70R1, 70V1, 71B1+, 71G1, 71R1 resistance

65H2, 65S2, 66B3, 66B5, 66G2, 66R1, 67C3,

67K2, 67L1, 67R1 , 67R2, 67A3, 69K3, 70A2,

70BH, 70C1, 70R1, 71G2

,

71L1 shear

67A1, 67G1, 69L1

temperature cycle

65C5, 66G1 vibration (fatigue)

65C5 vibration (variable frequency)

66G1 visual inspection

65C3, 70C1 visual inspection (SEM)

67A3, 67G1, 68P1, 69S1, 70A1, 70B8, 70D1, 70V1

20
Bibliography

57A1 Anderson, 0. L. , H. Christensen, and

P. Andreatch

TECHNIQUE FOR CONNECTING ELECTRICAL

LEADS TO SEMICONDUCTORS

J. Appl. Phys., vol. 28, p. 923, Aug.

1957.

FABRICATION-bond: TC ; wire: Ag, Al, Au, Cu; substrate: Ge , Si

Procedure

Schedule

Variables

Test: visual inspection

DESCRIPTIVE

57A2 Anderson, 0. L. ADHESION OF SOLIDS: PRINCIPLES AND APPLICATIONS

Bell Lab. Rec, vol. 35, pp. 441-445,

Nov. 1957.

FABRICATION-bond: TC ; wire: Ag, Al, Au, Cu,

Pb, Pt, Sn; substrate: Ge , Si

Theory : TC Evaluation: bond (adhesion)

DESCRIPTIVE

58C1 Christensen, H. ELECTRICAL CONTACT WITH THERMOCOMPRESSION BONDS

Bell Lab. Rec, vol. 36, pp. 127-130,

April 1958.

FABRICATION-bond: TC ; wire: Ag, Al , Au; sub- strate: Ge, Si

Procedure

Variables

Test: pull

DESCRIPTIVE

59A1 Antonevich, J. N. ULTRASONIC WELDING EQUIPMENT

IRE Intern. Conv. Record, vol. 7,

pt. 6, pp. 204-212, 1959.

FABRICATION-bond: US

Theory : US Schedule

Variables

Apparatus: design

Test: bond monitor; pull

DESCRIPTIVE

59 Jl Jones, J. B. , N. Maropis, J. G. Thomas,

and D. Bancroft

FUNDAMENTALS OF ULTRASONIC WELDINGPHASE I Final Rpt. (Dec. 1, 1957 to Dec. 1,

1958), Contract Mo. NOas 58-108c, May

1959. AD 235508 [summarized in 61J1].

FABRICATION-bond: US

Theory: US TEST-bond: US Description: bond monitor

EXPERIMENTAL

59R1 Renaut, P. APPARATUS FOR THE DETERMINATION OF THE EXISTENCE OR NON-EXISTENCE AND THE QUALITY OF A BONDING BETWEEN TWO PARTS

OR MEMBERS

U.S. Patent 2,903,886; Sept. 15, 1959.

TEST

Description: ultrasonic probe

PATENT

59W1 Weare, N. E., J. N. Antonevich, R. E. Monroe, and D. C. Martin

RESEARCH AND DEVELOPMENT OF PROCEDURES

FOR JOINING OF SIMILAR AND DISSIMILAR

HEAT-RESISTING ALLOYS BY ULTRASONIC

WELDING

Rpt. (July 1957 to June 1958), Contract

No. AF 33(616)-5342, Feb. 1959.

AD 208323 [summarized in 60W1].

FABRICATION-bond: US Theory

Schedule

Variables

Apparatus: design

Tool: design

Bonding Surface: contamination; mechanical

characteristics; preparation; topography

Test: bond monitor; metallurgical exam; pull

DEGRADATION-bond: US Stress: process

Part: bond

Mechanism: fatigue; hardening

Test: metallurgical exam; pull

EXPERIMENTAL

60J1 Jones, J. B., N. Maropis, J. G. Thomas,

and D. Bancroft

FUNDAMENTALS OF ULTRASONIC WELDINGPHASE II Final Rpt. (Dec. 1, 1958 to Feb. 1,

1960), Contract No. NOas 59-6070-c,

Dec. 1960. AD 257514.

FABRICATION-bond: US Theory

Procedure

Schedule

Variables

Apparatus: description

Test: metallurgical exam; visual inspection

TEST-bond: US

Description: bond monitor

EXPERIMENTAL

21
60J2 Jones, J. B. , W. C. Elmore and C. F. De Prisco

METHOD AND APPARATUS EMPLOYING VIBRATORY ENERGY FOR BONDING METALS

U.S. Patent 2,946,119; July 26, 1960.

FABRICATION-bond: US

TheoryEvaluation: US

Procedure

Variables

Apparatus: design

Test: metallurgical exam

PATENT

60W1 Weare, N. E. , J. N. Antonevich, and

R. E. Monroe

FUNDAMENTAL STUDIES OF ULTRASONIC WELD- ING Welding J., vol. 39 (supplement), pp. 331S-341S, Aug. 1960. [summary of

59W1]

FABRICATION-bond: US

Theory : US

Schedule

Variables

Apparatus: design

Tool: design

Bonding Surface: contamination; mechanical

characteristics; preparation; topography

Test: metallurgical exam, pull

DEGRADATION-bond: US

Stress : process

Part : bond

Mechaniam: hardening; fatigue

Test: metallurgical exam, pull

EXPERIMENTAL

61A1 Anderson, 0. L. and H. Christensen

THERMO-COMPRESSION BONDING OF METAL TO SEMICONDUCTORS, AND THE LIKE

U.S. Patent 3,006,067; Oct. 31, 1961.

FABRICATION-bond: TC; wire: Ag, Al, Au,

Au/Cu, Cu, Sn/Cu; substrate: Ge, Si

Theory

Procedure

Variables

Test: pull; visual inspection

PATENT

61A2 Ayre, R. S. TRANSIENT RESPONSE TO STEP AND PULSE

FUNCTIONS

Shook and Vibration Handbook, Volume 1 Basic Theory and Measurements

C. M. Harris and C. E. Crede, Eds.,

McGraw-Hill Book Co., Inc., New York,

1961, pp. 8-1 to 8-54.

TEST

Application: mechanical shock

THEORETICAL

61B1 Bernstein, L. GOLD ALLOYING TO GERMANIUM, SILICON AND ALUMINUM-SILICON EUTECTIC SURFACES

PART 2 Semicond. Prod., vol. 4, pp. 35-39,

Aug. 1961.

DEGRADATION

Stress : thermal

Part : bond

Mechanism : intermetallics

EXPERIMENTAL

61D1 De Prisco, C. F. METHOD AND APPARATUS FOR BONDING METALS

U.S. Patent 3,002,270; Oct. 3, 1961.

FABRICATION-bond: US

Evaluation: apparatus

Apparatus: adjustment

Test: shear

PATENT

61G1 Goetzberger, A. INVESTIGATION OF CRYSTAL IMPERFECTIONS

BY MEANS OF AVALANCHE BREAKDOWN PAT- TERNS OF VERY THIN DIFFUSED JUNCTIONS

IN SILICON

International Conf. on Semiconductor

Physicsj Prague, 1960, Academic Press,

New York, 1961, pp. 808-811.

DEGRADATION-bond: TC; wire: Au; substrate: Si

Stress: process

Part: substrate

EXPERIMENTAL

61Jl Jones, J. B., N. Maropis, J. G. Thomas,

and D. Bancroft

PHENOMENOLOGICAL CONSIDERATIONS IN ULTRASONIC WELDING

Welding J., vol. 40 (supplement),

pp. 289S-305S July 1961. [summary of

59J1]

FABRICATION-bond: US

Theory

Evaluation: US; metal system

Schedule

Variables

Test: bond monitor; bond temperature; metallurgical exam; photoelastic stress an- alysis; radiotracer

TEST-bond: US

Description: bond monitor

EXPERIMENTAL

62J1 Jones, J. B. VIBRATORY WELDING PROCESS AND APPARATUS

U.S. Patent 3,056,192; Oct. 2, 1962.

TEST-bond: US

Description: bond monitor

PATENT

22
62M1 Matsuura, E. , K. Matsui, and R. R. Has i gut

i

TECHNIQUE FOR OHMIC CONNECTING LEADS TO

SILICON

J. Appl. Phys., vol. 33, pp. 1610-1611,

April 1962.

FABRICATION-bond: TC; wire: Ag , Au, Cu; film:

Al, Bi, Ga, In, Sb ; substrate: Ge, Si

Procedure

DESCRIPTIVE

62P1 Peterson, J. M. , H. L. McKaig, and

C. F. De Prisco

ULTRASONIC WELDING IN ELECTRONIC DE- VICES

IRE Intern. Conv. Record, vol. 10,

pt. 6, pp. 3-12, 1962.

FABRICATION-bond: US

Ir.^ory

Evaluation : US

Apparatus: description

DESCRIPTIVE

63L1 Longo, T. A. and B. Selikson

ALUMINUM WIRE BONDING OF SILICON TRANSISTORS

Semicond. Prod., vol. 6, pp. 27-31,

Nov. 1963.

DEGRADATION-bond: TC; wire: Al, Au, Ag; film:

Al, Au; substrate: Si, FeNiCo

Stress: process; thermal

Part : bond

Mechanism: intermetallics

ANALYTIC

63M1 McKinnon, M. C. and R. F. Hoeckelman

MECHANICAL AND ELECTRICAL PROPERTIES

OF THERM0C0MPRESSI0N BONDS

IEEE Intern. Conv. Record, vol. 11,

pt. 6, pp. 93-103, March 1963.

FABRICATION-bond: TC , wire: Al, Au, Cu, Pt,

Ti, Zr; film: Al, Au/Al, Au/Cr, NiCr,

Ta, Ti; substrate: Si

Theory

Evaluation : bond (adhesion)

Schedule

Variables

Apparatus: design

Test: pull; resistance; visual inspection

EXPERIMENTAL

63P1 Phillips, L. S. THERM0C0MPRESSI0N BONDING TO THIN FILM MICROCIRCUITS

Brit. Commun. Electron., vol. 10, pp. 456-458, June 1963.

FABRICATION-bond: TC; wire: Au; film: Al/Cr,

Au/Cr; substrate: ceramic, glass

Evaluation: TC; bond (adherence)

Schedule

Variables

Bonding Surface : preparation ; topography

Test: pull; resistance; temperature cycle;

thermal shock; visual inspection

DESCRIPTIVE

63W1 Weiler, P. M., Ed.

PRODUCTION ENGINEERING MEASURE 2N914

AND 2N995

Final Rpt . (May 1, 1962-Oct. 31, 1963),

Contact No. DA-36-039-SC-86726, Oct. 1963. AD 429 920

FABRICATION-bond: TC , US; wire: Ag, Al, Au,

PI; film: Ag, Ag/Al; Ag/Cr, Ag/Cr-Al,

Al, Au, Au/Ag/Cr-Al, Au/Pl

Evaluation: TC ; US; metal system (TC); tool

(TC,US); wire (US)

Schedule: US

Variables: "US

Apparatus: adjustment (TC); description (US);

design (TC, US)

Tool : design (TC, US)

Wire: mechanical characteristics

Test: centrifuge, mechanical shock, pull,

thermal shock, vibration (variable frequency ) TEST

Description: centrifuge; mechanical shock;

pull; thermal shock; vibration (variable frequency)

DESCRIPTIVE

64A1 Antle, W. K. FRICTION TECHNIQUE FOR OPTIMUM THERMOC0MPRESSI0N BONDS

IEEE Trnas. Component Parts, vol. CP-10,

pp. 25-29, Dec. 1964

FABRICATION-bond: TC ; wire: Ag, Al, Au; substrate: Si

Theory

Schedule

Variables

Test: shear

EXPERIMENTAL

64C1 Cohn, A. GOLD BONDING WIRES

Semicond. Prod. Solid State Technol,

vol. 7, pp. 18-20, July 1964.

FABRICATION-wire: Au, Au/Ni, Au/Pt, Au/W

Wire: care; mechanical characteristics

DESCRIPTIVE

64C2 Clunie, D. M. and N. H. Rock

THE LASER FEEDBACK INTERFEROMETER

ici. Instruments, vol. 41, pp. 489- 492, Aug. 1964.

TEST-bond: US

Application: bond monitor

EXPERIMENTAL

23
64D1 Davidson, K. W. RELIABILITY IMPROVEMENT PROCESS EVAL- UATION

Proc. Conf. on Reliability of Semiconductor Devices and Integrated Circuits,

vol. 1, sect. 14, pp. 14. 1-14. 34, June

1964. AD 645221

FABRICATION-bond: TC ; wire: Al; film: Al, Au

Evaluation: bond (stitch)

TEST-bond: TC; wire: Al

Evaluation: pull (nondestructive)

DESCRIPTIVE

64M1 Myers, D. K. SMALL BALL BONDING

Proc. Conf. on Reliability of Semiconductor Devices and Integrated Circuits, vol. 2, sect. 28, pp. 28.1-

28.6, June 1964. AD 645222

FABRICATION-bond: TC ; wire: Au; film: Al

Evaluation: bond (ball); tool

Procedure

Apparatus: design

Test: centrifuge; mechanical shock; thermal

shock; vibration (variable frequency)

DESCRIPTIVE

64D2 De Prisco, C. F. and W. M. Barfield

METHOD AND MEANS FOR OPERATING A GENERATING MEANS COUPLED THROUGH A TRANSDUCER TO A VIBRATORY ENERGY WORK PER- FORMING DEVICE

U.S. Patent 3,158,928; Dec. 1, 1964.

FABRICATION-bond: US Apparatus: adjustment

PATENT

64H1 Hill, P. UNIFORM, METAL EVAPORATION

Proc. Conf. on Reliability of Semiconductor Devices and Integrated Circuits,

vol. 2, sect. 27, pp. 27.1-27.10, June

1964. AD 645222

FABRICATION-bond: TC ; wire: Au; film: Al

Bonding Surface: film thickness; preparation

EXPERIMENTAL

64H2 Howell, J. R. and J. W. Slemmons

EVALUATION OF THERMOCOMPRESSION BONDING PROCESSES

Presented to 9th Welded Electric Packaging Association Symposium, Santa

Monica, California, Feb. 27, 1964;

Autonetics Report No. T4-240/3110,

March 1964. (13)

FABRICATION-bond: TC ; wire:

Si Au; film: Al,

Pt; substrate:

Procedure

Schedule

Variables

Control : temperature

Tool: design

Bonding Surface: contamination; topography

Test: pull

TEST-bond: TC Evaluation: visual inspection

REVIEW

64J1 Johnson, W. G. LEAD BONDING MACHINE

U.S. Patent 3,125,906; March 24, 1964.

FABRICATION-bond: TC Apparatus: design

PATENT 24

64P1 Partridge, J., L. D. Hanley and E. C. Hall

PROGRESS REPORT ON ATTAINABLE RELIA- BILITY OF INTEGRATED CIRCUITS FOR SYSTEMS APPLICATION

Symp . on Microelectronics and Large

Systems, Washington, D. C, cosponsored by ONR and UNI VAC, Nov. 1964.

(12)

DEGRADATION-bond: TC ; wire: Au; film: al

Stress: process; test (centrifuge)

Part : wire ; bond

Mechanism: intermetallics

DESCRIPTIVE

64S1 Selikson, B., and T. A. Longo

A STUDY OF PURPLE PLAGUE AND ITS ROLE

IN INTEGRATED CIRCUITS

Proc. IEEE, vol. 52, pp. 1638-1641,

Dec. 1964.

DEGRADATION-bond: TC ; wire: Al, Au; film:

Al, Au; substrate: FeNiCo , Si

Stress : thermal

Part : bond

Mechanism: intermetallics

Test: pull

FABRICATION-wire: Al , Au; film: Ag/Cr, Al,

Au, Cr/Al, PI, Pt Evaluation: metal system

DESCRIPTIVE

64U1 Univac

FINAL REPORT FOR INTEGRATED CIRCUIT

STUDY

Contract No. NObsr 89 341, Aug. 1964.

AD 605432

DEGRADATION-bond: TC ; wire: Al , Au; film:

Al, Au

Stress: process; test (centrifuge, mechanical shock, thermal shock); thermal

Part: wire; bond; metallization

Mechanism: intermetallics

Failure Rates

EXPERIMENTAL
64W1 Worlton, D. C. and R. A. Walker

METHOD AND DEVICE FOR CONTROLLING

ULTRASONIC WELDING APPARATUS

U.S. Patent 3,153,850; Oct. 27, 1964.

TEST-bond: US Description: bond monitor

PATENT

IEEE WESCON Convention Record, vol. 9,

Session 16B.3, pp. 1-10, July 1965. [2]

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress : thermal

Part: bond

Mechanism: intermetallics

Test: metallurgical exam; pull

EXPERIMENTAL

65B1 Baker, D. and I. E. Bryan

AN IMPROVED FORM OF THERMOCOMPRESSION

BOND

Brit. J. Appl. Phys., vol. 16, pp. 865- 871, June 1965. [similar to 66B4]

FABRICATION-bond: TC; wire: Al, Au; film: Al, Au; substrate: FeNiCo

Evaluation: bond (ball, wedge); tool; wire

Schedule: TC

Tool: design

Bonding Surface: contamination

Test: centrifuge, pull, pull (nondestructive)

TEST-bond: TC Description: pull (nondestructive)

Correlation: centrifuge; pull

DESCRIPTIVE

65C1 Cohen, J. PLATINUM-SILICON THERMO-COMPRESSION

BONDS

Solid State Electron., vol. 8, p. 79, Jan. 1965.

FABRICATION-bond: TC ; wire: Pt ; substrate: Si

Procedure

DESCRIPTIVE

65C2 Cummings, D. G. IDENTIFICATION OF THERMAL COMPRESSION

BOND FAILURES

IEEE WESCON Convention Record, vol. 9,

Session 16B.1, pp. 1-3, July 1965. [2]

TEST-bond: TC; wire: Au; film: Al

Precaution: resistance

DESCRIPTIVE

65C5 Cunningham, J. A. EXPANDED CONTACTS AND INTERCONNEXIONS

TO MONOLITHIC SILICON INTEGRATED CIRCUITS

Solid State Electron, vol. 8, pp. 735-

745, April 1965.

FABRICATION-bond: TC ; wire: Au; film: Al, Au,

Au/Ag, Au/Co, Au/Cr, Au/Mo, Au/Ni

;

substrate: Si

Evaluation : metal system; metallization

Bonding Surface: film thickness

Test: pull

DEGRADATION-bond: TC ; wire: Al , Au; film: Al

,

Au, Au/Mo

Stress : thermal

Part : bond

Mechanism: intermetallics

Test: centrifuge; pull; temperature cycle;

vibration (fatigue)

ANALYTIC

65D1 Daniels, H. P. C. ULTRASONIC WELDING

Ultrasonics, vol. 3, pp. 190-196, Oct .

Dec. 1965

FABRICATION-bond: US; wire: Al, Au; substrate:

Ge , glass, Si

Theory

Variables

Apparatus: design

Tool: design

Bonding Surface; topography

REVIEW

65C3 Colteryahn, L. E. and D. D. Shaffer

CHARACTERIZATION OF FAILURE MODES IN GOLD-ALUMINUM THERMOCOMPRESSION BONDS

IEEE WESCON Convention Record, vol. 9,

Session 16B.2, pp. 1-8, July 1965. [2]

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress: thermal

Part : bond

Mechanism: intermetallics

Test: metallurgical exam; visual inspection

DESCRIPTIVE

65C4 Colteryahn, L. E. and J. F. Kersey

FAILURE MECHANISMS AND KINETICS OF IN- TERMETALLIC FORMATION

65H1 Howell, J. R. INFLUENCE OF BONDING VARIABLES ON AU/AL

TC BOND FAILURE

Proc. Second Physics of Failure Colloquim (CQAP), pp. 71-79, June 4,

1965, presented on March 29, 1965

at North American Aviation, Inc.,

Autonetics, Anaheim, California

92803, [similar to 65H2] (13)

FABRICATION-bond: TC; wire: Au; film: Al

;

substrate: glass

Variables

Control : temperature

Bonding Surface: film thickness; preparation

Test: pull

DEGRADATION-bond: TC; wire: Au; film: Al; sub- strate: glass

25
65H1 (cont.)

Stress: thermal

Part : wire ; bond

Mechanism: intermetallics

Test: metallurgical exam; pull

EXPERIMENTAL

Wire: contamination; mechanical characteristics ; topography

DEGRADATION

Part : wire

Mechanism: fatigue

ANALYTIC

65H2 Howell, J. R. and J. W. Kanz

TIME-TEMPERATURE EFFECTS ON GOLDALUMINUM THERMOCOMPRESSION BONDS

IEEE WESCON Convention Record, vol. 9,

Session 16B.4, pp. 1-19, July 1965. [2]

FABRICATION-bond: TC ; wire: Au, film: Al;

substrate: glass

Variables

Control: temperature

Bonding Surface: film thickness; preparation

Test: pull; metallurgical exam DEGRADATION-bond: TC ; wire: Au; film: Al;

substrate: glass

Stress: thermal

Part: wire; bond

Mechanism: intermetallics

Test: metallurgical exam; pull; resistance

EXPERIMENTAL

65H3 Hakim, E. B. and B. Reich

U.S. ARMY ADVANCEMENT IN TRANSISTOR

RELIABILITY THROUGH MANUFACTURING

PROCESS IMPROVEMENTS

IEEE Trans. Reliability, vol. R-14

,

pp. 94-99, Oct. 1965. [see p. 98]

TEST

Evaluation: thermal shock

DESCRIPTIVE

65J1 Jones, J. B., G. W. Fable, A. L. Jamieson, E. F. Nippes, N. E. Promisel,

F. N. Rhines, and R. K. Sager

ULTRASONIC WELDING

Welding Handbook, A. L. Phillips, Ed.,

American Welding Society, New York,

1965, Chapt. 49, pp. 1-48. [8]

FABRICATION-bond: US

Theory

Procedure

Schedule

Variables

Apparatus: design

Test: bond monitor; metallurgical exam; pull

REVIEW

65K1 Kramer, I. R. EFFECT OF SURFACES ON MECHANICAL

BEHAVIOR OF METALS

Proc. 3rd Symp. on Fundamental Phenomena in the Materials Sciences, Boston,

Mass.; vol. 3, pp. 171-193, Jan. 1965.

FABRICATION

65M1 Maki, C. E., F. W. Hagert , H. J. Avil,

L. Kirvida, M. N. Asmus, W. T. Sackett,

Jr . , C. R. Seashore

DETECTION OF ELECTRICAL FAULTS BY

R. F. TECHNIQUES

Mater. Eval. , vol. 23, pp. 285-291,

June 1965.

TEST

Description: noise

EXPERIMENTAL

65N1 Neppiras, E. A. ULTRASONIC WELDING OF METALS

Ultrasonics, vol. 3. pp. 128-135,

July-Sept. 1965.

FABRICATION-bond: US

Theory

Procedure

Variables

Apparatus: design

DESCRIPTIVE

65R1 Ruggiero, E. M. ALUMINUM BONDING IS KEY TO 40-WATT

MICROCIRCUITS

Electronics, vol. 38, pp. 98-104,

Aug. 23, 1965.

FABRICATION-bond: TC ; wire: Al, Au; film:

Al, Au

Evaluation: bond (ball, stitch, wedge);

wire

Procedure

Test: centrifuge; mechanical shock; vibration

(variable frequency)

DEGRADATION-bond: TC; wire: Al , Au; film:

Al, Au Stress: thermal

Part : bond

Mechanism: intermetallics

DESCRIPTIVE

65R2 Ruggiero, E. M. GOLD-ALUMINUM ADHESION AND REACTION

ON SEMICONDUCTOR SURFACES

Proc. IEEE Annual Microelectronics

Symp., pp. 6B-1 to 6B-4, May 1965.

[2] (14)

DEGRADATION-bond: TC ; wire: Au; film: Al;

substrate: alumina, BN, glass, Si

Stress: process; thermal

Part: bond

Mechanism: intermetallics

26
65R2 (cont.)

FABRICATION- film: .Al; substrate: alumina, BN,

glass , Si

Evaluation: metal system; wire

Bonding Surface : preparation

ANALYTIC

65S1 Slemmons, J. W. and J. R. Howell

BETTER BONDING METHODS INPROVE HYBRID

CIRCUITS

Electronics, vol. 38, pp. 86-92,

March 22, 1965.

FABRICATION-bond: TC; wire: Au; film: Al

,

Au/NiCr, Cu/NiCr; substrate: alumina,

Si

Procedure

Control : temperature

Test: pull

DESCRIPTIVE

Trans. Met. Soc. AIME, vol. 236,

pp. 392-396, March 1966. [similar to 64A1]

FABRICATION-bond: TC; wire: Ag, Al, Au; film:

Al, Au, Ni ; substrate: Si

Theory

Schedule

Variables

Test: shear

EXPERIMENTAL

66A2 Angelucci, T. L. and F. W. Kulicke, Jr. NAIL HEAD BONDING APPARATUS FOR THERMOCOMPRESSIVELY SECURING LEAD WIRE TO SEMI-CONDUCTOR DEVICES

U.S. Patent 3,250,452; May 10, 1966.

FABRICATION-bond: TC Procedure

Apparatus: design

PATENT

65S2 Soltau, R. FAILURE MODES AND MECHANISMS IN MICRO- ELECTRONIC DEVICES

Seminar on Reliability in Space Vehicles, Los Angeles, Calif., April 2,

1965. (15) . .. DEGRADATION-bond: TC; wire: Au; film: Al, Au; substrate: Si

Stress: process; test (centrifuge); thermal

Part: wire; bond; metallization; substrate

Mechanism: contamination; corrosion; intermetallics; thermal mismatch

Test: centrifuge; resistance

DESCRIPTIVE

65S3 Szasz P. R. BIND-BEAK WIRE BONDING INSTRUMENT FOR THERMOCOMPRESSIVELY SECURING LEADS TO SEMICONDUCTOR DEVICES

U.S. Patent 3,216,640; Nov. 9, 1965.

FABRICATION-bond: TC Apparatus: design

Tool: design

PATENT

66B1 Bagrowski , J., S. G. Konsowski , Jr.,

and G. D. Spencer

INTERCONNECTION OF MONOLITHIC INTE- GRATED CIRCUITS THROUGH THE USE OF AD- VANCED MATERIALS AND TECHNIQUES

IEEE Trans. Pts . Materials Packaging,

vol. PMP-2, pp. 90-98, Dec. 1966.

FABRICATION-bond: TC, US Evaluation: TC, US Variables: TC, US

DESCRIPTIVE

66B2 Browning, G. V. FAILURE MECHANISMS IN MICROCIRCUITS

Proc. Second Int. Symp. on Microelectronics, pp. 485-516, Munich, Germany,

Oct. 1966. (13)

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress: process

Part : wire ; bond

Mechanism: intermetallics

Failure Rates

DESCRIPTIVE

65W1 Wasson, R. D. THERMOCOMPRESSION BOND TESTER

Proc. IEEE, vol. 53, pp. 1736-1737,

Nov. 1965.

TEST

Description : pull

DESCRIPTIVE

66A1 Antle, W. DETERMINING THERMOCOMPRESSION BONDING

PARAMETERS BY A FRICTION TECHNIQUE

66B3 Blech, I. A. and H. Sello

SOME NEW ASPECTS OF GOLD-ALUMINUM

BONDS

J. Electrochem. Soc, vol. 113, pp. 1052-1054, Oct. 1966.

DEGRADATION-bond: TC; wire: Au; film: Al

Stress: thermal

Part : bond

Mechanism : intermetallics

Test: metallurgical exam; resistance

FABRICATION-bond: TC; wire: Au; film: Al

Bonding Surface: film thickness

ANALYTIC

27
66B4 Baker, D. and R. Jones

NEW DEVELOPMENTS IN THERMOCOMPRESSION

BONDING

Microelectronics and Reliability, vol.

5, pp. 229-234, Aug. 1966. [similar to 65B1]

FABRICATION-bond: TC; wire: Al, Au; film:

Al, Au; substrate: Al, FeNiCo, Si

Theory

Evaluation: bond (ball, wedge); tool

Tool: design

Bonding Surface: contamination

Test: pull, pull (nondestructive)

DEGRADATION-bond: TC ; wire: Al; film: Au; substrate: FeNiCo

Stress : thermal

Part : wire ; bond

Mechanism: intermetallics

Test: pull

TEST-bond: TC ; wire: Al

Description: pull (nondestructive)

DESCRIPTIVE

66B5 Browning, G. V., L. E. Colteryahn

and D. G. Cummings

FAILURE MECHANISMS ASSOCIATED WITH

THERMOCOMPRESSION BONDS IN INTEGRATED

CIRCUITS

Physios of Failure in Electronics} vol.

4, RADC Series in Reliability, M. E. Goldberg and J. Vaccaro , Eds., 1966,

pp. 428-446. AD 637529

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress: process; thermal

Part : bond

Mechanism: intermetallics

Test: metallurgical exam; resistance

DESCRIPTIVE

pp. 493-521. AD 637529. [see pp. 510-

516]

DEGRADATION-film: Al

Stress: moisture

Part: metallization

Mechanism: corrosion

EXPERIMENTAL

66C1 Conti, R. J. THERMOCOMPRESSION JOINING TECHNIQUES

FOR ELECTRONIC DEVICES AND INTERCONNECTS

Metals Eng. Quart., vol. 6, pp. 29-35,

Feb. 1966.

FABRICATION-bond: TC ; wire: Ag, Au, Au/Cu,

Cu/Ni ; substrate: alumina, glass

Evaluation: TC Schedule

Variables

Control : temperature

Tool: design

Wire: size

Bonding Surface: contamination

Test: pull; thermal shock

DESCRIPTIVE

66C2 Clews, K. J. and J. G. Young'

METALLURGICAL EVALUATION OF 'MICROCIR- CUIT INTERCONNEXIONS MADE BY THE PARALLEL-GAP PROCESS

Microelectronics and Reliability, vol.

5, pp. 207-208, Aug. 1966.

FABRICATION

Evaluation: bond

Test: metallurgical exam DESCRIPTIVE

66B6 Bikerman, J. J. SOLID TO SOLID ADHESION

Symposium on Fundamental Phenomena in

the Materials Sciences, 2nd, Boston,

1964. Surface phenomena. L. J. Bonis

and H. H. Hausner, Ed. "Fundamental

Phenomena in the Materials Sciences,

vol. 2", Plenum Press, New York, 1966,

pp. 165-174.

FABRICATION-bond: TC, US

Theory

DESCRIPTIVE

66B7 Brandewie, G. V., P. H. Eisenberg,

and R. A. Meyer

INVESTIGATION OF SURFACE FAILURE

MECHANISMS IN SEMICONDUCTOR DEVICE BY ENVELOPE AMBIENT STUDIES

Physics of Failure in Electronics_, vol.

4, M. E. Goldberg and J. Vaccaro, Eds..

RADC Series in Reliability, 1966,

66E1 Eimbinder, J. LINEAR INTEGRATED CIRCUITS

EEE, vol. 14, pp. 76-86, Nov. 1966.

FABRICATION-bond: TC , US

Evaluation: TC ; US; bond (ball, stitch,

wedge

)

DESCRIPTIVE

66G1 Go, H. T., N. J. McAfee and H. C. Jones MICROELECTRONICS RELIABILITY FROM A SYSTEM MANUFACTURER'S POINT OF VIEW Second Int. Symp. on Microelectronics;

Munich, Germany, Oct. 1966. (16)

DEGRADATION

Stress: process

Part : wire ; bond

Mechanism: contamination; intermetallics

Test: centrifuge; thermal cycle; vibration

(variable frequency)

DESCRIPTIVE

28

J
66G2 Gianelle, W. H. ANALYSIS OF SEVEN SEMICONDUCTOR METALLURGY SYSTEMS USED ON SILICON PLANAR TRANSISTORS

Physios of Failure in Electronies,

vol. 4, M. E. Goldberg and J. Vaccaro

,

Eds., RADC Series in Reliability, 1966,

pp. 46-57. AD 637529

FABRICATION-bond: TC ; wire: Ag, Al, Au; film:

Ag, Ag/Cr, Al, Au, Au/Mo

Evaluation: bond (ball, wedge); metal system; wire

Bonding Surface : film thickness

Test: pull; resistance

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress: thermal

Part: wire; bond

Mechanism: grain growth; intermetallics

Test: pull; resistance

ANALYTIC

66H1 Hammond, V. J. THIN-FILM PREPARATION IN RELATION TO MICROBONDING

Microelectronics and Reliability, vol.

5, pp. 213-217, Aug. 1966.

FABRICATION-bond: TC, US; film: Al, Al/Cr,

Au, Au/Cr; substrate: ceramic, glass

Evaluation: metallization

Bonding Surface: preparation

DESCRIPTIVE

66K2 Koedam, M. DETERMINATION OF SMALL DIMENSIONS BY DIFFRACTION OF A LASER BEAM

Philips Tech. Rev., vol. 27, pp. 208- 212, Nov. 2, 1966.

FABRICATION

Wire: size

DESCRIPTIVE

66K3 Kollner, H. METHOD AND DEVICE FOR BONDING A CON- TACT WIRE TO A SEMICONDUCTOR MEMBER

U.S. Patent 3,289,452; Dec. 6, 1966.

FABRICATION-bond: TC Apparatus: design

PATENT

66L1 Larson, R. B. MICR0J0INING PROCESSES FOR ELECTRONIC

PACKAGING PART 3 Assembly Engineering, vol. 9, pp. 30-

33, Nov. 1966. (17)

FABRICATION-bond: TC ; wire: Au

Evaluation: bond (ball, stitch, wedge); tem- perature control

Procedure

Variables

Control: temperature

DESCRIPTIVE

6611 IEC BASIC ENVIROMENTAL TESTING PROCEDURES

FOR ELECTRONIC COMPONENTS AND ELECTRONIC EQUIPMENT PART 2: TESTSTEST F: VIBRATION

IEC Recommendation, publication

68-2-6 (1966) and supplements

68-2-6A, 68-2-6B and 68-2-6C;

1966-1969. [3]

TEST

Description : vibration (variable frequency,

fatigue

STANDARD

66K1 Khorouzan, M. and L. Thomas

CONTAMINATION OF ALUMINUM BONDS IN IN- TEGRATED CIRCUITS

Trans. Met. Soc. AIME, vol. 236,

pp. 397-405, March 1966.

DEGRADATION-bond: US; wire: Al; film: Al;

substrate: FeNiCo

Stress: process; test (thermal cycle); thermal

Part: wire; bond

Mechanism : anneal; contamination : grain

growth

Test: pull

ANALYTIC

66L2 Landis, D. CATASTROPHIC FAILURES IN SEMICONDUCTOR

DEVICES EXPOSED TO PULSED RADIATION

IEEE Trans. Nucl. Sci., vol. NS-13,

pp. 591-600, June 1966.

DEGRADATION-bond: TC; wire: Au

Stress: radiation

Part: bond

ANALYTIC

66L3 Langenecker, B. EFFECTS OF ULTRASOUND ON DEFORMATION

CHARACTERISTICS OF METALS

IEEE Trans. Sonics Ultrason., vol. SU-13,

pp. 1-8, March 1966.

FABRICATION-bond: US

Wire: mechanical characteristics

DEGRADATION-bond: US

Stress: process

Part : wire

Mechanism: hardening

REVIEW

29
66L4 Lombardi, J., L. McDonough , H. Padden

HIGH RELIABILITY SCREENING OF SEMICONDUCTOR AND INTEGRATED CIRCUIT

DEVICES

Final Rpt., Contract NAS 5-96 39, Sept.

1966. N67-16772

TEST

Description: centrifuge; temperature cycle;

vibration (monitored, variable frequency); visual inspection; x-ray

Evaluation: centrifuge; temperature cycle;

vibration (monitored, variable frequency); visual inspection; x-ray

DESCRIPTIVE

66M1 Mann, R. M. BAD WELD DETECTOR USES INTEGRATED

CIRCUITS

EDN, vol. 11, pp. 108-112, July 1966.

TEST

Description: resistance

DESCRIPTIVE

6601 Oswald, K. B. , Jr. FRACTURE OF SILICON AND GERMANIUM

INDUCED BY PULSED ELECTRON IRRADIATION

IEEE Trans. Nucl. Sci., vol. NS-13,

pp. 63-69, Dec. 1966.

DEGRADATION

Stress: radiation

Part: substrate

Mechanism: spallation

EXPERIMENTAL

66P1 Partridge, J., E. C. Hall, and L. D. Han ley

THE APPLICATION OF FAILURE ANALYSIS IN PROCURING AND SCREENING OF INTEGRATED

CIRCUITS

Physics of Failure in Electronics,

vol. 4, M. E. Goldberg and J. Vaccaro,

Eds., RADC Series in Reliability, 1966,

pp. 95-139. AD 637529

TEST

Description: centrifuge; vibration (variable

frequency); mechanical shock; Mil-Std750; temperature cycle; visual inspection

Screening Procedures

DESCRIPTIVE

66R1 Riben, A. R. , and S. L. Sherman

MICROBONDS FOR HYBRID MICROCIRCUITS

PROGRESS REPORT

Rpt. 8 (Nov. 1, 1965-Jan. 31, 1966),

Contract No. DA 36-039 AMC-03742 (E),

May 20, 1966. AD 633723 [summarized

in 67L1]

FABRICATION-bond: US; wire: Al, film: Au/Cr;

substrate: alumina, beryllia, sapphire

Evaluation: US

Schedule

Wire: mechanical characteristics

Bonding Surface: film thickness; topography

Test: pull; resistance

DEGRADATION-bond: US; wire: Al; film: Au/Cr;

substrate; alumina, beryllia, sapphire

Stress: thermal

Part: metallization

Test: pull, resistance

TEST-bond: US; wire: Al; film: Au/Cr; substrate: alumina, beryllia, sapphire

Correlation: pull; resistance

EXPERIMENTAL

66W1 Wagner, R. SEMICONDUCTOR DEVICES WITH SILVERGOLD LEAD WIRES ATTACHED TO ALUMINUM

CONTACTS

U.S. Patent 3,271,635, Sept. 6, 1966.

FABRICATION: wire: Au, Au/Ag; film: Al

Evaluation: metal system; wire

Test: pull

DEGRADATION

Mechanism: intermetallics

PATENT

67A1 Arleth,' J. M. and R. D. Demenus

NEW TEST FOR THERM0C0MPRESSI0N MICROBONDS

Electron. Prod., vol. 9, pp. 92, 94,

May 1967.

TEST-bond: TC; wire: Au; film: Al, Au

Description: shear

DEGRADATION-bond: TC ; wire: Au; film: Al , Au

Stress: thermal

Part : bond

Mechanism: intermetallics

Test: shear

DESCRIPTIVE

67A2 Avedissian, M. K. THERM0C0MPRESSI0N BONDING APPARATUS

U.S. Patent 3,313,464, April 11, 1967.

FABRICATION-bond: TC Procedure

Apparatus: design

PATENT

67A3 Anstead, R. J. FAILURE ANALYSIS USING A SCANNING

ELECTRON MICROSCOPE

Proc. 6th Annual Reliability Physics

Symposium, Los Angeles, Calif, pp. 127-137, Nov. 1967. [2]

DEGRADATION-bond: TC, US; wire: Al, Au; film:

Al

Stress: process

Part : wire ; bond

Mechanism: intermetallics

Test: visual inspection (SEM)

DESCRIPTIVE

30
67B1 Bobo, S. N. MYOELECTRIC WELDING - AN APPROACH TO IMPROVED RELIABILITY

Proc . SAE Electronic Packaging Conf.

New York, N. Y. , pp. 6-12, Feb. 1967.

TEST

Description: IR Monitor

DESCRIPTIVE

67B2 Beadles, R. L. INTEGRATED SILICON DEVICE TECHNOLOGY

VOLUME XIV

Rpt. (Jan. 1966-March 1967), Contract

AF 33 (615)-3306, May 1967. AD 654630.

[see pp. 23-48]

FABRICATION-bond: TC, US; wire: Al', Au; film:

Al, Al/Cr, Au, Au/Cr

Theory: TC, US Evaluation : US, TC ; bond (ball, stitch , wedge)

Procedure: TC, US

Schedule: TC Variables: TC Apparatus: description (US)

Tool: design (TC)

Wire : care DEGRADATION

Mechanism: intermetallics

REVIEW

67B3 Blech, I. A., and H. Sello

THE FAILURE OF THIN ALUMINUM CURRENTCARRYING STRIPS ON OXIDIZED SILICON

Physics of Failure in Electronics 3 vol. 5, T. S. Shilliday and J. Vaccaro,

Eds., RADC Series in Reliability, 1967,

pp. 496-505. AD 655397

DEGRADATION-bond: TC; wire: Au; film: Al

Stress: electrical; thermal

Part : bond

Mechanism: electromigration; intermetallics

DESCRIPTIVE

67B4 Bayer, R. G. and T. S. Burke

APPLICATION OF THE ULTRASONIC RESONANCE

TECHNIQUE TO INSPECTION OF MINIATURE

SOLDERED AND WELDED JUNCTIONS

Mater. Eval., vol. 25, pp^ 20-24,

Jan. 1967.

TEST

Description: US probe

DESCRIPTIVE

67C1 Cunningham, J. A. and J. G. Hayser

SEMICONDUCTOR RELIABILITY: FOCUS ON- THE CONTACTS

EE, vol. 26, pp. 74-79, Jan. 1967.

FABRICATION-bond: TC ; wire: Al, Au; film: Al,

Au/Mo, Au/Mo/Pt

Evaluation: metallization; bond (ball, wedge)

Bonding Surface: metal system; preparation

DEGRADATION-bond: TC ; wire: Al, Au; film:

Al, Au/Mo, Au/Mo /Pt

Stress : thermal

Part : bond

Mechanism: corrosion; intermetallics

DESCRIPTIVE

67C2 Cline, J. E. and S. Schwartz

ELECTRON MICROPROBE TECHNIQUES FOR

FAILURE ANALYSIS OF SILICON PLANAR

DEVICES

Proc. 6th Annual Reliability Physics

Symposium, Los Angeles, Calif, pp. 193-200, Nov. 1967. [2]

DEGRADATION

Stress: process

Part : bond

Mechanism: contamination

Test: electron microprobe

DESCRIPTIVE

67C3 Chen, G. K. C. ON THE PHYSICS OF PURPLE PLAGUE FOR- MATION, AND THE OBSERVATION OF PURPLE

PLAGUE IN ULTRASONICALLY JOINED GOLDALUMINUM BOND

IEEE Trans. Pts. Material Packaging,

vol. PMP-3, pp. 149-153, Dec. 1967.

DEGRADATION-bond: US; wire: Au; film: Al

Stress : thermal

Part : bond

Mechanism: intermetallics

Test: pull; resistance

TEST-bond: US; wire: Au; film: Al

Correlation: pull; resistance

ANALYTIC

67C4 Cunningham, J. A. THE PLAGUES IN SEMICONDUCTOR CONTACTS

EE, vol. 26, p. 39, April 1967.

DEGRADATION . Mechanism: intermetallics

REVIEW

67G1 Gill, W. L. and W. Workman

RELIABILITY SCREENING PROCEDURES FOR INTEGRATED CIRCUITS

Physics of Failure in Electronics, vol.

5, RADC Series in Reliability, T. S. Shilliday and J. Vaccaro, Eds., 1967,

pp. 101-141. AD 655397

DEGRADATION-bond: TC; wire: Au; film: Au/Mo

Stress: process; test (centrifuge, thermal

shock); thermal

Part: wire; bond; metallization; substrate

Mechanism: contamination

Test: centrifuge; shear; visual inspection

Failure Rates

TEST-bond: TC ; wire: Au; film: Au/Mo

31
67G1 (cont.)

Evaluation: centrifuge; shear; visual inspection; x-ray

Screening Procedures

FABRICATION

Evaluation: package

DESCRIPTIVE

67G2 Graham, R. A. and R. E. Hutchison

THERMOELASTIC STRESS PULSES RESULTING

FROM PULSED ELECTRON BEAMS

Appl. Phys. Lett., vol. 11, pp. 69-72,

July 15, 1967.

TEST

Application: mechanical shock (radiationinduced)

ANALYTIC

67H1 Higbie, T. E. THERMOCOMPRESSION BONDING OF GOLD WIRE

FOR MICROELECTRONIC CIRCUITS

Report No. NAFI-TR-1108 , Oct. 1967.

AD 671879

FABRICATION-bond: TC ; wire: Au; film: Al, Au Procedure

Schedule

Variables

Apparatus: adjustment

Test: pull

TEST-bond: TC; wire: Au; film: Au

Description: pull

DESCRIPTIVE

67H2 Haigler, E. D. ULTRASONIC SCISSORS BONDING INSTRUMENT

U.S. Patent 3,314,582; April 18, 1967.

FABRICATION-bond: US

Apparatus: design

PATENT

6711 IEC

BASIC ENVIROMENTAL TESTING PROCEDURES

FOR ELECTRONIC COMPONENTS AND ELECTRONIC EOUIPMENT PART 2: TESTS -

TEST EA: SHOCK

IEC Recommendation, publication 68-2-27

and supplement 68-2-27A; 1967-1968. [3]

TEST

Description: mechanical shock

STANDARD

67J1 Jones, J. B. ULTRASONIC WELDING

Proc. CIRP Int. Conf. on Mfg. Technol.,

sponsored by ASTME , pp. 1387-1409,

Sept. 1967. (18)

FABRICATION-bond: US

Theory

Schedule

Variables

Apparatus : design

Test: bond monitor, metallurgical exam REVIEW

67K1 Koshinz, E. F. THERMOCOMPRESSION BONDING -AN OVERVIEW

Proc. 1967 Welding Congress, pp. 86-94,

Stuttgart, Germany, 1967. [In German]

(19)""

FABRICATION-bond: TC ; wire: Al, Au; film:

Ag/Cr, Al, Au, Au/Mo/Pt

Evaluation: bond (ball, wedge); metal system;

temperature control

Procedure

Variables

Test: centrifuge; pull

DEGRADATION-bond: TC; wire: Au; film: Al

Mechanism: intermetallics

REVIEW

67K2 Keen, R. S., L. R. Loewenstern and

G. L. Schnable

MECHANISMS OF CONTACT FAILURES IN SEMICONDUCTOR DEVICES

Proc. 6th Annual Reliability Physics

Symp. Los Angeles, Calif., pp. 216-233,

Nov. 1967. [2]

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress: thermal

Part : bond

Mechanism: intermetallics

Test: resistance

REVIEW

67L1 Lane, W. V. MATERIALS FOR CONDUCTIVE ELEMENTS PART

II -CONNECTIONS TO THIN FILMS IEEE Intern. Conv. Record, vol. 15,

pt. 7, pp. 129-145, 1967. [summary of

66R1, 67R2]

FABRICATION-bond: US; wire: Al; film: Al,

Au/Cr; substrate: alumina, beryllia,

glass, sapphire, Si; silica (96%);

application: hybrid devices

Evaluation: US; wire bond

Schedule

Apparatus: description

Bonding Surface: film thickness; preparation;

topography

Test: pull; visual inspection

DEGRADATION: bond: US; wire: Al ; film: Al,

Au/Cr; substrate: alumina, beryllia,

glass, sapphire, Si; silica (96%);

application: hybrid devices

Stress: process; thermal

Part: bond; metallization; wire

Mechanism: intermetallics

Test: pull; resistance

EXPERIMENTAL

32
67P1 Parker, CD.

INTEGRATED SILICON DEVICE TECHNOLOGY

VOLUME XV RELIABILITY

Rpt. (March 1966-March 1967), Contract

No. AF 33(615)-8306, May 1967. AD 655082 [see pp. 35-65]

DEGRADATION-bond: TC , US; wire: Al, Au; film:

Al, Au, Au/Mo; substrate: FeNiCo, Si

Stress : process ; thermal

Part : bond

Mechanism: contamination; intermetallics

Failure Rates

TEST

Screening Procedures

FABRICATION-bond: TC , US; wire: Al, Au; film:

Ag, Ag/Cr, Al, Au, Au/Mo; substrate:

Si

Evaluation: metal systems, metallization, wire

Procedure

REVIEW

67P2 Pruden, D. H. and D. Schoenthaler

METHODS OF BONDING ELECTRICAL CONDUCTORS TO ELECTRICAL COMPONENTS

U.S. Patent 3,302,277; Feb. 7, 1967.

TEST-bond: US Description: bond monitor

PATENT

67R1 Riben, A. R. and S. L. Sherman

MICROBONDS FOR HYBRID MICROCIRCUITS

Physics of Failure in Electronics

,

vol. 5, RADC Series in Reliability,

T. S. Shilliday and J. Vaccaro, Eds.,

1967, pp. 534-556. AD 655397. [summary of 66R1, 67R2]

FABRICATION-bond: US; wire: Al; film: Al,

Au/Cr; substrate: alumina, beryllia,

silica (96%); application: hybrids

Evaluation : US

Schedule

Variables

Tool: design; wear

Wire: mechanical characteristics

Bonding Surface: film thickness; topography

DEGRADATION-bond: US; wire: Al; film: Al,

Au/Cr

Stress: process; thermal

Part: bond; metallization

Mechanism : intermetallics

Test : pull ; resistance

TEST-bond: US; wire: Al; film: Al, Au/Cr;

substrate: alumina, beryllia, sapphire;

silica (96%)

Correlation: pull; resistance

EXPERIMENTAL

67R2 Riben, A. R. and S. L. Sherman

MICROBONDS FOR HYBRID MICROCIRCUITS

Final Rpt. (Feb. 1, 1964-April 30. 1966)

Contract Number DA 36-039 AMC-03742(E)

,

33

Jan. 1967. AD 647464

FABRICATION-bond: US; wire: Al (pure), Al

;

film: Al, Au/Cr; substrate: alumina,

sapphire, Si, silica (96%)

Evaluation: metal system

Procedure

Schedule

Apparatus: description

Rigidity: apparatus

Wire: mechanical characteristics

Bonding Surface: film thickness; preparation;

topography

Test: pull; resistance; thermal shock; visual

inspection

DEGRADATION-bond: US; wire: Al , Al (pure);

film: Al, Au/Cr; substrate: alumina,

sapphire, Si, silica (96%)

Stress: process; test (thermal shock); thermal

Part: wire; bond; metallization

Mechanism: intermetallics

Test: pull; resistance

TEST-bond: US; wire: Al, Al (pure); film: Al

,

Au/Cr; substrate: alumina, sapphire,

Si, silica (96%)

Evaluation: pull; resistance

Correlation: pull; resistance

EXPERIMENTAL

67R3 Reber, R. L. STEPPED BONDING WEDGE

U.S. Patent 3,347,442; Oct. 17, 1967.

FABRICATION

Tool: design

PATENT

67R4 Rasimenoks, P., T. L. Angelucci, and

F. W. Kulicke, Jr. THERM0C0MPRESSI0N WIRE BONDING APPARATUS

WITH SCISSORS CUT-OFF

Patent 3,307,763; March 7, 1967.

FABRICATION-bond: TC Apparatus: design

PATENT

67S1 Schnable, G. L. and R. S. Keen

METALLIZATION AND BONDS - A REVIEW OF

FAILURE MECHANISMS

Proc. 6th Annual Reliability Physics

Symp., Los Angeles, Calif, pp. 170-192,

Nov. 1967. [2]

DEGRADATION-bond: TC, US; wire: Al , Au; film:

Al, Au, Au/Mo

Stress: process; thermal; test (centrifuge)

Part : wire ; bond

Mechanism : intermetallics

Failure Rates FABRICATION-bond: TC, US; wire: Al, Au; film:

Al, Au, Au/Mo

Evaluation: TC; US Apparatus: design (US)

Tool: design (TC, US)

REVIEW
67S2 Scarbrough, R. J. D. and J. Auchterlonie Procedure

THE ISOLATION OF A FAILURE MODE IN SILICON PLANAR TRANSISTORS CAUSED BY ORGANIC RESIDUES ASSOCIATED WITH

ALUMINUM WIRE

Microelectronics and Reliability, vol.

6, pp. 319-321, Nov. 1967.

DEGRADATION-wire: Al

Stress: thermal

Part: device

Mechanism : contamination

Test: electrical parameter

ANALYTIC

Tool: design

PATENT

67V1 van Lancker, M. METALLURGY OF ALLUMINUM ALLOYS

John Wiley and Sons, Inc., New York

1967.

FABRICATION -wire: Al, Al (pure), Al/Mg

Wire: mechanical characteristics

REVIEW

67S3 Schile, R. D., and G. A. Rosica

SIMPLE TESTER FOR THE RAPID DETERMINA- TION OF THE TENSILE STRENGTH OF FINE FILAMENTS

Rev. Sci. Instr., vol. 38, pp. 1103-

1104, Aug. 1967.

TEST

Application: pull

DESCRIPTIVE

67S4 Schumacher, D. H. MEASURING MICROBOND INTEGRITY WITH AN INFRARED MICRORADIOMETER

Soc. for Nondestructive Testing, Inc.,

Fall Conf. ; Cleveland, Ohio, Oct. 1967

(20)

TEST-bond: TC; wire: Au/Cu; film: Au; substrate: ceramic

Description: IR Monitor

Evaluation: IR Monitor

ANALYTIC

67S5 Selikson, B. FAILURE MECHANISM INTEGRATED CIRCUIT

INTERCONNECT SYSTEMS

Proc. 6th Annual Reliability Physics

Symposium, Los Angeles, Calif.

pp. 201-208, Nov. 1967. [2]

DEGRADATION-bond: TC ; wire: Al, Au; film:

Ag/Cr; Al, Au/Mo, Au/Mo/Al, Au/Pt/Ti,

Cr/Al

Stress: process; thermal

Part: wire: bond

Mechanism: anneal, intermetallics

Test: pull

FABRICATION-bond: TC ; wire: Al , Au; film:

Ag/Cr, Al, Au/Mo, Au/Mo/Al, Au/Pt/Ti,

Cr/Al

Evaluation: metal system

REVIEW

67T1 Tiffany, P. VIBRATORY WELDING TIP AND METHOD OF

WELDING

U.S. Patent 3,357,090; Dec. 12, 1967.

FABRICATION-bond: US; wire: Au

34

68A1 Adams, A. H. and J. H. Anderson, Jr. MEANS FOR GRIPPING FINE WIRES DURING

MECHANICAL TESTS

Rev. Sci. Instr., vol. 39, p. 1768,

Nov. 1968.

TEST

Application: pull

DESCRIPTIVE

68A2 Avedissian, M. K. and J. S. Manowczak

SEQUENTIAL WIRE AND ARTICLE BONDING

METHODS. U.S. Patent 3,397,451; Aug. 20, 1968.

FABRICATION-bond: TC Procedure

PATENT

68A3 Anderson, J. H., Jr. and W. P. Cox

AGING EFFECTS IN AU-AL AND AL-AL

BONDS USED IN MICROELECTRONICS

Proc. 7th Annual Reliability and

Maintainability Conf., pp. 533-536,

San Francisco, Calif., July 1968.

[7], (21)

DEGRADATION-bond: TC , US; wire: Al, Au; film:

Al

Stress : thermal

Part: wire; bond

Mechanism: anneal , intermetallics

Test: pull; resistance

FABRICATION-bond: TC ; wire: Au; film: Al

Bonding Surface: film thickness

EXPERIMENTAL

68B1 Berry, R. W., P. M. Hall, and M. T. Harris

THIN FILM TECHNOLOGY

Van Nostrand Reinhold Co., Princeton,

New Jersey, 1968, pp. 604-632.

FABRICATION-bond: TC, US

Theory: TC, US

Procedure: TC , US

Schedule: TC Apparatus: design (US)

Control: temperature (TC, US)

Tool: design (TC)

Wire: size (TC)
68B1 (cont.)

Test: pull

TEST

Description: centrifuge; IR monitor; metallurgical exam; pull

Evaluation: noise; resistance

REVIEW

Evaluation: mechanical shock; mechanical

shock (radiation-induced)

DEGRADATION-bond: TC, US; wire: Al, Au

Stress: test (mechanical shock (radiationinduced) ) Part : bond

Mechanism: spallation

THEORETICAL

68D1 Dummer, G. W. A, and J. M. Robertson,

Eds.

ELECTRONIC CONNECTION TECHNIQUES AND

EQUIPMENT 1968-1969

Pergamon Press, New York, 1968.

FABRICATION-bond: TC, US

Apparatus : description

DESCRIPTIVE

68D2 Department of Defense

TEST METHODS AND PROCEDURES FOR MICROELECTRONICS

Military Standard 883, May 1, 1968;

Notice 1, May 20, 1968; Notice 2, Nov. 20, 1969. [1]

TEST-bond: TC, US

Description: air blast; centrifuge; mechanical shock, Mil-Std-883 ; pull; resistance, shear; temperature cycle;

thermal shock; vibration (fatigue,

monitored, variable frequency); visual

inspection; x-ray

Screening Procedures

STANDARD

68G1 Gaffney, J. INTERNAL LEAD FATIGUE THROUGH THERMAL

EXPANSION IN SEMICONDUCTOR DEVICES

IEEE Trans. Electron Devices, vol.

ED-15, p. 617, Aug. 1968.

DEGRADATION-bond: TC ; wire: Al , Au; film: Al

Stress: thermal

Part : wire

Mechanism : fatigue

FABRICATION-bond: TC ; wire: Al; film: Al

Wire: mechanical characteristics

DESCRIPTIVE

68G2 Gaffney, J., D. Bottaro and CD. Root

INTERNAL LEAD FATIGUE IN SEMICONDUCTOR

DEVICES THROUGH THERMAL EXPANSION

Presentation abstracts 7th Annual Reliability Physics Symp . , Washington,

D. C. , p. 28, Dec. 1968. [2]

DEGRADATION-bond: TC; wire: Al ; film: Al

Stress: thermal

Part: wire

Mechanism: fatigue

EXPERIMENTAL

68E1 Electronic Design

TEST YOUR IC IQ

Electronic Design, vol. 15, p. 84,

July 18, 1968.

TEST

Precaution: resistance

DESCRIPTIVE

68H1 Harris, D. H. MEASURING THE ACCURACY OF HUMAN IN- SPECTION

Mater. Res. Std., vol. 8, pp. 8-12,

Dec. 1968.

TEST

Application: visual inspection

DESCRIPTIVE

68E2 Electronic Design

TEST YOUR IC IQ

Electronic Design, vol. 2, p. 108, Jan. 18, 1968.

DEGRADATION

Failure Rates

REVIEW

68F1 Floyd, H. L. , Jr.

A TECHNIQUE FOR DETERMINING TRANSISTOR

SPALL THRESHOLDS

Sandia Corp. Rpt. No. SC-M-68-186A,

April 1968. [22]

TEST-bond: US, TC

Description: mechanical shock (radiationinduced)

68H2 Holmes, P. J., and I. C. Jennings

FAILURE ANALYSIS OF PLANAR TRANSISTORS

USED IN THE UK3 SATELLITE PROGRAMME

Microelectronics and Reliability,

vol. 7, pp. 37-44, Feb. 1968.

DEGRADATION-bond: TC; wire: Au; film: Al, Au Stress: process

Part: wire; bond

Mechanism: contamination; intermetallics

;

thermal mismatch

Failure Rates

DESCRIPTIVE

35
68H3 Hill, W. H., and G. D. Wrench

RECENT ADVANCES IN PULSE-HEATED WIRE

BONDING FOR HYBRID MICROELECTRONICS

Proc. NEPCON, June 1968. Also Hughes

Welding Note - Bulletin 109. [4] (23)

FABRICATION-bond: TC, US; wire: Al, Au; film:

Al, Au, Cr; substrate: alumina, glass,

Si; application: hybrid devices

Evaluation : TC ; US ; temperature control ; tool (TC); wire (TC)

Apparatus: description (TC)

Control : temperature ( TC

)

Tool : design (TC); wea~(TC)

DESCRIPTIVE

68H4 Howard, R. E. HOW TO USE IC RELIABILITY SCREENING

TECHNIQUES

Eval. Eng., vol. 7, pp. 22-26, Nov.-

Dec. 1968.

TEST

Evaluation: centrifuge; mechanical shock;

pull; temperature cycle; thermal shock;

visual inspection; x-ray

DESCRIPTIVE

68H5 Helda, R. W. and W. E. LaPoint

METHOD OF BONDING FILAMENTARY MATERIAL

U.S. Patent 3,400,448; Sept. 10, 1968.

FABRICATION-bond: TC Procedure

Apparatus : design

PATENT

6811 IEC

BASIC ENVIROMENTAL TESTING PROCEDURES

FOR ELECTRONIC COMPONENTS AND ELECTRONIC EQUIPMENT PART 2: TESTS -TEST GA: ACCELERATION, STEADY STATE

IEC RECOMMENDATION, PUBLICATION 68-2-7,

1968. [3]

TEST

Description: centrifuge

STANDARD

68J1 Johnson, C. A. HOT GAS THERM0-C0MPRESSI0N BONDING

U.S. Patent 3,409,977; Nov. 12, 196! FABRICATION-bond: TC

Control: temperature

PATENT

68K1 Koshinz, E. F. SEMICONDUCTOR: WIRE BONDING AND

FACE BONDING CONSIDERATIONS AND

COMPARISONS

Proc. SAE Microelectronic Packaging

Conf., Palo Alto, Calif., pp. 94-100,

Nov. 1968. (19)

FABRICATION-bond: TC , US; wire: Al, Au; film:

Ag/Cr, Al, Au, Au/Cr/Al, Au/Mo/Pt

Evaluation: TC , US

Procedure: TC, US Variables: TC, US

REVIEW

68L1 Lawhorne, S., and J. N. Ramsey

SIMPLIFIED X-RAY EXAMINATION OF SOLID

STATE DEVICES

Solid State Technol., vol. 11, pp. 37-

39, Nov. 1968.

TEST-wire: Au

Description: x-ray

DEGRADATION-wire: Au; application: plastic devic

Stress: process

Part : wire

Test: x-ray

DESCRIPTIVE

68M1 McCormick, J. E. ON THE RELIABILITY OF MICR0C0NNECTI0NS

Electron. Packag. Prod., vol. 8, pp. 187-189, June 1968.

DEGRADATION -bond: TC, US; wire: Al, Au

Failure Rates

FABRICATION-bond: TC, US

Evaluation: TC; US

DESCRIPTIVE

68M2 Muncheryan, H. M. HOW TO USE FAILURE ANALYSIS TO IMPROVE

SEMICONDUCTOR RELIABILITY

EE, vol. 27, pp. 49-54, May 1968.

DEGRADATION-bond: TC , wire: Au; film: Al, Au

Stress : process

Part: bond; metallization; substrate

Mechanism: contamination; intermetallics

FABRICATION-bond: TC, US; wire: Al, Au; film:

Al, Au/Cr, Au/Cu/Ti, Au/Mo , Au/Ni,

Au/Pt/Ti, Pt/Ti

Evaluation: metal system

DESCRIPTIVE

68M3 McHale, P. and H. Fenster

INCREASED YIELDS IN HYBRID THICK FILM CIRCUITS BY INDIRECT ACTIVE DEVICE AT- TACHMENT

IEEE Microelectronics Symp . , St . Louis

,

Missouri, pp. D7-1 to D7-6, June 1968.

[2] (24)

FABRICATION-bond: TC ; wire: Au; film: Al;

application: hybrid devices

Evaluation: bond (ball, stitch)

Control: temperature

DESCRIPTIVE

36
68P1 Poston, M. H. TIME-TEMPERATURE EFFECTS ON WIRE BONDS

IEEE Microelectronics Symp., St. Louis,

Missouri, pp. 1-21, June 1968. [2],

(25)

FABRICATION-bond: TC; wire: Au; film: Al

Variables

Control: force; temperature

DEGRADATION: TC ; wire: Au; film: Al

Stress: process; thermal

Part : bond

Mechanism: anneal; grain growth; intermetallics

Test: pull; visual inspection

TEST-bond: TC; wire: Au; film: Al

Description: pull

DESCRIPTIVE

68R1 Rodrigues de Miranda, W. R. VISUAL INSPECTION OF IC'S BOOSTS

RELIABILITY AT LITTLE COST

Electronics, vol. 41, pp. 104-108,

Aug, 19, 1968.

TEST-bond: TC, US; wire: Al, Au

Description: visual inspection

DESCRIPTIVE

68R2 Ruggiero, E. M. ALUMINUM BONDING FOR HIGH-POWER IC'S Microelectronic Packaging} George

Sideris, Ed., McGraw-Hill, New York,

1968, chapt. 7.3, pp. 240-248.

FABRICATION-bond: TC ; wire: Al , Au; film: Al,

Au

Evaluation: bond (ball, stitch, wedge), wire

Procedure

Test: centrifuge, mechanical shock, vibration

(variable frequency)

DEGRADATION: bond: TC ; wire: Al, Au; film:

Al, Au

Stress: thermal

Mechanism: intermetallics

Failure Rates

DESCRIPTIVE

DEGRADATION

Stress : thermal

Part : bond

Mechanism: intermetallics

EXPERIMENTAL

68T2 Tanaka, S. and K. Chiba

SEMICONDUCTOR DEVICE UTILIZING AN AUAL ? LAYER AS A DIFFUSION BARRIER

THAT PREVENTS 'PURPLE PLAGUE'

U.S. Patent 3,401,316; Sept. 10, 1968,

FABRICATION-bond: TC , US; wire: Au, Al;

film: Ag/Al, AuAl , Al , Cr; substrate:

Si

Evaluation: metal system; metallization

Bonding Surface: metal system, preparation

PATENT

68U1 Uthe, P. M. THE WIRE Uthe Technology, Inc. Technical

Newsletter, vol. 1, Sept. 1968.

[summarized in 69U1] (5)

FABRICATION-bond: US; wire: Al, Al/Mg, Au Evaluation: wire

Schedule

Tool: design

Wire: mechanical characteristics

Test: pull; visual inspection

DEGRADATION-bond: US; wire: Al ; film: Al

Stress: process

Part: substrate

DESCRIPTIVE

68U2 Uthe, P. M. THE SOLID STATE WELD

Uthe Technology, Inc. Technical

Newsletter, vol. 1, May 1968.

[summarized in 69U1] (5)

FABRICATION-bond: US Theory

DESCRIPTIVE

68S1 Shockley, W. L. and R. W. Weedfall

ULTRASONIC BONDING

Microelectronic Packaging, George

Sideris, Ed., McGraw-Hill, New York,

1968, chapt. 7.2, pp. 232-240.

[see p. 239]

FABRICATION-bond: US; wire: Au, Au/Ga

Wire: care; mechanical characteristics

Bonding Surface: orientation

DESCRIPTIVE

68T1 Takei, W. J. and M. H. Francombe

MEASUREMENT OF DIFFUSION-INDUCED

STRAINS AT METAL BOND INTERFACES

Solid State Electron., vol. 11, pp. 208, Feb. 1968.

205-

68U3 Uthe, P. M. THE FRICTION OF NON-LUBRICATED METALS

Uthe Technology, Inc. Technical

Newsletter, vol. 1, June 1968.

[summarized in 69U1] (5)

FABRICATION-bond: US Theory

DESCRIPTIVE

68U4 Uthe, P. M. WELDING

Uthe Technology, Inc. Technical

Newsletter, vol. 1, July 1968.

[summarized in 69U1] (5)

FABRICATION-bond: US

37
68U4 (cont.)

Theory

Schedule

Control: force; power; time

DESCRIPTIVE

68U5 Uthe. P. M. A SIMPLE WIRE BONDER

Uthe Technology, Inc. Technical

Newsletter, vol. 1, Aug. 1968.

[summarized in 69U1] C5)

FABRICATION-bond: US

Apparatus: adjustment; design

Rigidity: apparatus; terminal

DESCRIPTIVE

69A1 Ang, C. Y., P. H. Eisenberg and

H. C. Mattraw

PHYSICS OF CONTROL OF ELECTRONIC

DEVICES

Proc. 1969 Annual Symp. on Reliability,

Chicago, 111., pp. 73-85, Jan. 1969.

[see pp. 76, 82] (13)

TEST-bond: TC; wire: Au

Correlation: pull; pull (nondestructive)

DESCRIPTIVE

69A2 Anderson, J. H., Jr. and W. P. Cox

FAILURE MODES IN GOLD-ALUMINUM

THERMOCOMPRESSION BONDS

IEEE Trans. Reliability, vol. R-18

,

pp. 206-207, Nov. 1969.

DEGRADATION-bond: TC ; wire: Au; film: Al

Stress: thermal

Part: bond; metallization

Mechanism: intermetallics

FABRICATION-bond: TC; wire: Au; film: Al

Bonding Surface: film thickness

EXPERIMENTAL

69A3 Antler, M. WHAT DO GOLD PLATING SPECS REALLY MEAN?

Products Finishing, vol. 34, pp. 56-

66, Oct. 1969.

FABRICATION-film: Au

'Bonding Surface: contamination; film thickness; mechanical characteristics; preparation; topography

DESCRIPTIVE

69B1 Bell, J. L. UPGRADING OF MICROELECTRONIC TEST

PROCEDURES FOR MILITARY HI-REL ACHIEVEMENT

Trans. 23rd Annual Technical Conf..

pp. 767-770, Los Angeles, Calif.,

sponsored by American Society for

Quality Control, Ann Arbor, Mich.,

May 1969.

TEST

Evaluation: temperature cycle; thermal

shock

DESCRIPTIVE

69B2 Binelli, W. D., and R. H. Soltau

DEVELOPMENT OF QUALIFICATION TEST

PROGRAM FOR MICROELECTRONIC DEVICES,

Final Rpt. (Nov. 1, 1968 to July 3,

1969), Contract No. NAS1-8714, Sept.

1969. N70-11544

TEST

Description : centrifuge , mechanical shock ; tnermal shock

FABRICATION-bond: US; wire: Al; film: Al, Au

Evaluation: wire bond

Test: centrifuge; mechanical shock; thermal

shock

DESCRIPTIVE

69B3 Budd, J. B. DIE AND WIRE BONDING CAPABILITIES OF

REPRESENTATIVE THICK-FILM CONDUCTORS

Solid-State Technol. vol. 12,

pp. 59-63, June 1969.

FABRICATION-bond: TC , US; wire: Al , Au; film: Au/Mo/Mn; thick film: Ag , Ag/Pd,

Au, Au/Pd, Au/Pd/Pt, Au/Pt, Pd/Ag

Evaluation : wire bond; metallization

Variables

Bonding Surface: preparation

Test: pull

DEGRADATION-bond: TC ; wire: Au; thick film:

Ag/Pd, Au

Stress: thermal

Test: pull

ANALYTIC

69B4 Browning, G. V. MONOLITHIC INTEGRATED CIRCUIT FAILURE

MECHANISMS

Nat. Electron. Conf. Seminar, Designing with Monolithic Integrated Circuits, Nat. Electron, Conf., Chicago,

111., pp. 1-22, Dec. 1969. (26)

DEGRADATION-bond: TC ; wire: Al, Au; film:

Al, Au/Mo

Stress: thermal

Part : bond

Mechanism: 'intermetallics

Failure Rates

REVIEW

69B5 Bullis, W. M. , Ed.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR MATERIALS, PROCESS CONTROL,

AND DEVICES

NBS Technical Note 488, Quarterly Rpt.

(Jan. 1 to March 31, 1969), July 1969.

[see pp. 21-25] [30] (29)

38
69B5 (cont.)

TEST-wire: Al, Au Application: pull

FABRICATION-bond: US; wire: Al ; film: Al

Evaluation: wire (ribbon)

DEGRADATION-bond: US; wire: Al ; film: Al

Stress: thermal

Part: wire

Mechanism: anneal

Test: pull

DESCRIPTIVE

69B6 Bullis, W. M., Ed.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR MATERIALS, PROCESS CONTROL, AND

DEVICES

NBS Technical Note 495, Quarterly Rpt.

(April 1-June 30, 1969), Sept. 1969.

[see pp. 24-31] [30] (29)

FABRICATION-bond: US; wire: Al; film: Al

Evaluation: bond (ball); wire (ribbon)

Apparatus: adjustment

Tool: oscillation

TEST-bond: US; wire: Al; film: Al

Description: bond monitor

DESCRIPTIVE

69B7 Bellin, J. L. S., A. E. Brown, A. S. Hamaraoto, and G. C. Knollman

PIEZOELECTRIC MONITOR OF MICROELECTRONIC WIRE BONDS

Lockheed Rpt. LMSC B-62-69-9, June

1969. (21)

TEST-bond: US; wire: Al; film: Al

Description : bond monitor

Correlation: bond monitor, pull, visual inspection

EXPERIMENTAL

69B8 Brinton, J. MIL STD 883 - A REAL TEST CASE

Electronics, vol. 42, pp. 131-136,

Aug. 18, 1969.

TEST

Application: Mil-Std-883

DESCRIPTIVE

69C1 Circuits Manufacturing

A PACKAGING TECHNIQUE IS NOT A BONDING

METHOD . . . WIRE-LEADS, FLIP-CHIPS,

ULTRASONICS, WHAT'S IT ALL ABOUT?

Circuits Mfg., vol. 9, pp. 8-16,

Dec. 1969.

FABRICATION

Evaluation : TC ; US; wire bond ; bond (ball,

stitch, wc 1 DESCRIPTIVE

39

69C2 Cline, J. E., J. M. Morris, and S. Schwartz

SCANNING ELECTRON MIRROR MICROSCOPY

AND SCANNING ELECTRON MICROSCOPY OF

INTEGRATED CIRCUITS

IEEE Trans. Electron Devices, vol.

ED-16, pp. 371-375, April 1969.

FABRICATION

Test: visual inspection (SEM)

DESCRIPTIVE

69D1 Dudderar, T. D. THE EFFECT OF GRIP STRESSES ON THE OCCURRENCE OF FAILURE IN TENSION TESTS

OF WIRE

Mater. Res. Std., vol. 9, pp. 26-30,

Oct. 1969.

TEST

Application: pull

THEORETICAL

69D2 Demer, L. J. and L. H. Fentnor

LAMB WAVE TECHNIQUES IN NONDESTRUCTIVE

TESTING

Int. J. Nondestructive Testing, vol.

1, pp. 251-283, Oct. 1969.

TEST

Application: US probe

FABRICATION

Wire: mechanical characteristic

Test: US probe

ANALYTIC

69D3 Department of Defense

MILITARY SPECIFICATION MICROCI RCUITS

GENERAL SPECIFICATION FOR -

Mil-M-38510, Nov. 20, 1969. [1]

TEST

Application: Mil-Std-883

Screening Procedures

STANDARD

69G1 Gurland, J. MICROSTRUCTURAL ASPECTS OF THE STRENGTH AND HARDNESS OF CEMENTED

TUNGSTEN CARBIDE

Contract No. SD-86, Dec. 1969. AD 699187

FABRICATION

Tool: design

DESCRIPTIVE

69G2 Grable, R. C. an.: . . Patzer

WIRE BONDING APPARATUS FOR MICROELECTRONIC COMPONENTS

U.S. Patent 3,430,835; March 4, 1969.

FABRICATION-bond: TC; wire: Au Procedure

PATENT
69H1 Heinen, K. G. and G. B. Larrabee

THE DETERMINATION OF RESIDUAL PHOTORESIST ON SILICON USING RADIOTRACER

IODINE-131

Solid State Technol. , vol. 12, pp. 44- 47, April 1969.

FABRICATION

Bonding Surface: contamination

Test: radiotracer

DESCRIPTIVE

69K1 Kashiwabara, M., S. Nakayama and

M. Suzuki

SETTING AND EVALUATION OF ULTRASONIC

BONDING FOR AL WIRE

Rev. Elec. Commun. Lab., vol. 17,

pp. 1014-1021, Sept. 1969.

TEST-bond: US; wire: Al; film: Al

Description: pull

Evaluation: visual inspection

Correlation: pull; visual inspection

FABRICATION-bond: US; wire: Al; film: Al

Procedure

Bonding Surface: film thickness

ANALYSIS

TEST-bond: TC, US; wire: Al, Au; film: Al, Au Description: US stress

DEGRADATION-bond: TC, US; wire: Al , Au; film:

Al, Au

Stress: test (US stress)

Part: bond, wire

Failure Rates

EXPERIMENTAL

69L1 Lauffenburger, H. A. and T. R. Myers

SUMMARY AND INTERPRETATION OF RELIA- BILITY DATA ON VARIOUS MICROCIRCUIT

BONDING TECHNIQUES

Proc . Holm Seminar on Electrical Con61-68, Nov. 1969.

wire: Al, Au; film:

tact Phenomena, pp. [6]

DEGRADATION-bond: TC , US; Al, Au

Stress: process; thermal

Mechanism: anneal; contamination; intermetallics

Test: pull; shear

Failure Rates

TEST

Screening Procedures

REVIEW

69K2 Krieg, R. D. and W. B. Murfin

STRUCTURAL CONSIDERATIONS IN ELECTRONIC MICROCIRCUIT LEAD WIRES

March 1969. PB 183544.

TEST

Application: mechanical shock; temperature

cycle; thermal shock; vibration

THEORETICAL

69L2 Laub, J. L. and M. N. Mansour

WIRE CLAMP

U.S. Patent 3,430,834; March 4, 1969.

FABRICATION-bond: US Apparatus: design

PATENT

69K3 Kashiwabara, M. and S. Hattori

FORMATION OF AL-AU INTERMETALLIC

COMPOUNDS AND RESISTANCE INCREASE FOR ULTRASONIC AL WIRE BONDING

Rev. Elec. Commun. Lab., vol. 17, pp. 1001-1013, Sept. 1969.

DEGRADATION-bond: US; wire: Al; film: Au; substrate: FeNiCo

Stress: thermal

Part : bond

Mechanism: intermetallics

Test: metallurgical exam; resistance

FABRICATION: bond: US; wire: Al; film: Au; substrate: FeNiCo

Procedure

Bonding Surface-film thickness

EXPERIMENTAL

6901 0'Connell, E. P. AN INTRODUCTION TO MIL-STD-883 TEST

METHODS AND PROCEDURES FOR MICROELECTRONICS

Proc. 8th Reliability and Maintainability Conf . , Denver, Colorado, pp. 530-542, July 1969. [10] (27)

TEST

Description : centrifuge; Mjl-Std-883 ; pull;

temperature cycle; visual inspection

Evaluation: centrifuge; visual inspection

DEGRADATION-bond: TC, US; wire: Al, Au;

film: Al, Au Stress: thermal

Mechanism: anneal, intermetallics

Test: pull

Failure Rates

REVIEW

69K4 Knollman, G. C, A. S. Hamamoto, and

J. L. S. Bellin

REPORTS ON ULTRASONIC SCREENING OF

TRANSISTORS AND INTEGRATED CIRCUITS

Lockheed Rpt. LMSC B-62-69-8, June

1969. (21)

6902 Ono, K. , M. Nishihata and S. Kobayashi

FINE ALUMINUM TRANSISTOR LEAD WIRES

Rev. Elec. Commun. Lab., vol. 17,

pp. 974-988, Sept. 1969.

FABRICATION-bond: TC, US; wire: Al , Al (pure);

film: Al, Au

40
6902 (cont.)

•fire : electrical characteristics; fabrication; mechanical characteristics ; to- pography- Test: pull

DEGRADATION-bond: TC, US; wire: Al; film:

Al, Au

Stress: thermal

Part : wire

Mechanism: anneal; grain growth

Test: pull

EXPERIMENTAL

Evaluation: US Procedure : TC , US

Test: pull

TEST-bond: TC ; wire: Au

Description : pull ; pull (nondestructive )

;

visual inspection (SEM); x-ray

DEGRADATION: bond: TC ; wire: Au; film: Al

Stress: thermal

Part : bond

Mechanism: intermetallics

Test: visual inspection (SEM)

REVIEW

69P1 Plough, C, D. Davis, and H. Lawler

HIGH RELIABILITY ALUMINUM WIRE BONDING

Proc. Electronic Components Conf .

,

Washington, D. C. , pp. 157-165, AprilMay 1969. [2] (28)

FABRICATION-bond: US; wire: Al, Au; film:

Al, Au

Theory

Schedule

Variables

Apparatus : adjustment

Tool : design

Rigidity: apparatus; terminal

Bonding Surface : contamination ; mechanical

characteristics ; topography

Test: pull, visual inspection

TEST-bond: US; wire: Al; film: Al, Au

Evaluation: air blast; thermal shock; visual

inspection

Correlation: mechanical shock (radiationinduced); pull; visual inspection

DEGRADATION-bond: US; wire: Al, Al/Mg

Stress: thermal

Part: wire; device

Mechanism: anneal, contamination

Test: electrical parameters; pull

DESCRIPTIVE

69R1 Ruth, S. B. TORTURE TESTS IMPROVE EQUIPMENT RELIA- BILITY

The Electronic Engineer, vol. 28,

pp. 80-87, June 1969.

TEST

Description: centrifuge; mechanical shock;

thermal shock; vibration

DESCRIPTIVE

69S2 Schnable, G. L. and R. S. Keen

ALUMINUM METALLIZATION ADVANTAGES AND LIMITATIONS FOR INTEGRATED CIRCUIT AP- PLICATIONS

Proc. IEEE

Sept. 1969

FABRICATION-bond

Al, Au/Cr,

Evaluation : metallization

REVIEW

vol. 57, pp. 1570-1580,

TC, US; wire: Al, Au; film:

Au/Mo

69S3 Selikson, B. VOID FORMATION FAILURE MECHANISMS IN INTEGRATED CIRCUITS

Proc. IEEE, vol. 57, pp. 1594-1598,

Sept. 1969.

DEGRADATION-wire: Al, Au; film: Al , Au

Stress; thermal

Part : bond

Mechanism: intermetallics

FABRICATION-wire: Au; film: Au/Ag/Cr,

Au/Mo, Au/Ti/Al, Au/Pt/Ti/Pt, Cr/Al

Evaluation: metal system

REVIEW

69S1+ Shurtleff, W. 0. RELIABILITY HANDBOOK FOR SILICON MONOLITHIC MICROCIRCUITS VOLUME 2 - FAILURE

MECHANISMS OF MONOLITHIC MICROCIRCUITS

Contract NAS 8-20639, April 1969.

N69-23226. [see pp. 2-IV-2 to 2-IV-6]

TEST

Description: centrifuge; mechanical shock,

temperature cycle; thermal shock;

vibration (variable frequency, fatigue)

Evaluation: vibration (variable frequency);

visual inspection

DESCRIPTIVE

69S1 Slemmons, J. W. THE MICR0W0RLD OF JOINING TECHNOLOGY

American Welding Society 50th Annual

Meeting and Welding Exposition; Philadelphia, Pa., April-May, 1969. [8] (13)

FABRICATION-bond: TC, US; wire: Al, Au, film:

Al, Au Theory : TC, US_

69S5 Speer, R. D. CHIP BONDING: PROMISES AND PERILS

Electronic Design, vol. 17, pp. 61-79,

Oct. 25, 1969.

FABRICATION-bond: TC, US Evaluation : wire bond

REVIEW

V,
69T1 Tamburrine, A. L. and V. C. Kapfer

FAILURE MECHANISMS IN PLASTIC ENCAPSULATED MICROCIRCUITS

Contract No. AF-5519, May 1969. AD 689224

DEGRADATION-bond: TC; wire: Au; film: Ag, Al,

Au, Ni; application: plastic devices

Stress: moisture; test (thermal shock);

thermal

Part : wire ; bond

Mechanism: corrosion; thermal mismatch

ANALYTIC

69T2 Tarowsky, N. HOW TO ASSEMBLE HYBRID MICROWAVE IC's Microwaves, vol. 8, pp. 52-62, Aug.

1969.

FABRICATION-bond: TC, US; application: hybrids

Evaluation: TC; US

DESCRIPTIVE

69U1 Uthe, P. M. VARIABLES AFFECTING WELD QUALITY IN ULTRASONIC ALUMINUM WIRE BONDING

Solid State Technol.

76, Aug. 1969.

FABRICATION-bond: US; wire:

film: Al, Au

Theory

Evaluation: wire

Schedule

, vol. 12, pp.

Al, Al/Mg, Au;

72-

Apparatus : adjustment; description; design

Tool : adjustment

Rigidity: apparatus ; package

Wire: mechanical characteristics

Test: pull, visual inspection

Trouble Shooting

DEGRADATION-bond: US; wire: Al , substrate: Si

Stress : process

Part : substrate

DESCRIPTIVE

69U2 Uthe, P. M., Jr., L. G. Wright, and

R. E. Greenan

ULTRASONIC FREQUENCY POWER SUPPLY

U.S. Patent 3,445,750; May 20, 1969,

FABRICATION-bond: US

Apparatus: design

PATENT

70A1 Adams, M. A. AN INVESTIGATION OF THE STRENGTH OF ALUMINUM WIRE USED IN INTEGRATED CIR- CUITS

NASA Tech. Brief 70-10275, Aug.

1970. [9]

TEST-bond: TC, US; wire: Al , Au; film: Al,

Au

Description : pull

DEGRADATION-bond: TC, US; wire: Al, Au; film:

Al, Au

Stress: test (pull); thermal

Part : wire

Mechanism: anneal; grain growth

Test: visual inspection (SEM)

DESCRIPTIVE

70A2 Anderson, Jr., J. H., T. G. Maple, and

W. P. Cox

AGING EFFECTS IN GOLD THERMOCOMPRESSIOr

BONDS TO COMPLEX METALLIZATIONS

IEEE Trans. Reliability, vol. R-19,

pp. 32-34, Feb. 1970.

DEGRADATION-bond: TC; wire: Au; film: Al,

Au/Mo/Al, Au/Ti/Al

Stress: thermal

Part: bond

Mechanism: intermetallics

Test: pull; resistance

FABRICATION-bond: TC; wire: Au; film: Al,

Au/Mo/Al; Au/Ti/Al

Evaluation: metal system

Bonding Surface: preparation

EXPERIMENTAL

70A3 ASTM

STANDARD SPECIFICATION FOR GOLD WIRE

FOR SEMICONDUCTOR LEAD-BONDING

(ASTM DESIGNATION: F72-69)

1970 Annual Book of ASTM Standards,

part 8, 1970. [11]

FABRICATION-wire: Au

Wire: care; contamination; mechanical characteristics; size

STANDARD

70A4 ASTM

STANDARD METHODS OF TESTING FINE ROUND

AND FLAT WIRE FOR ELECTRON DEVICE AND

LAMPS (ASTM DESIGNATION: F219-67)

1970 Annual Book of ASTM Standards,

part 8, 1970. [11]

FABRICATION

Wire: mechanical characteristics, size

STANDARD

70A5 ASTM

STANDARD METHOD FOR MEASURING DIAMETER

OF FINE WIRE BY WEIGHING (ASTM DESIGNATION: F205-63)

1970 Annual Book of ASTM Standards,

part 8, 1970. [11]

FABRICATION

Wire: size

STANDARD

M
70A6 ASTM

STANDARD METHODS OF TENSION TESTING

OF METALLIC MATERIALS (ASTM DESIGNATION:

E8-69)

1970 Annual Book of ASTM Standards,

part 31, 1970. [11] Test Application: pull

STANDARD

70A7 ASTM

STANDARD METHOD OF TEST FOR RESISTIVITY

OF ELECTRICAL CONDUCTOR MATERIALS (ASTM

DESIGNATION: B193-65)

1970 Annual Book of ASTM Standards,

part 8, 1970. [ll]

FABRICATION

Wire: electrical characteristics

STANDARD

70B1 Bevington, J. R., J. P. Cook, and

D. R. Little

PLASTIC IC RELIABILITY EVALUATION AND ANALYSIS

8th Annual Proc. Reliability Physics,

IEEE Catalog No. 70C59-PHY, pp. 73-80,

1970. [abbreviated version of 71B3] [2]

TEST-bond: TC; wire: Au; film: Au, Ag; application: plastic devices

Evaluation: thermal shock

DEGRADATION-bond: TC ; wire: Au; film: Au; application: plastic devices

Stress: test (thermal shock)

Part : bond ; wire

Mechanism: thermal mismatch

EXPERIMENTAL

70B2 Bullis, W. M. , Ed.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR

MATERIALS, PROCESS CONTROL, AND DEVICES

NBS Technical Note 520, Quarterly Rpt

.

(July 1-Sept. 30, 1969), March 1970.

[see pp. 32-i+3] [30] (29)

FABRICATION-bond: US; wire: Al; film: Al

Apparatus : design

Tool : adjustment ; design ; oscillation

Rigidity : apparatus

Test: interferometry

DEGRADATION-bond: US; wire: Al; film: Al

Stress: thermal

Part: wire

Mechanism: anneal

Test: pull

TEST-bond: US; wire: Al; film: Al

Description: resistance

EXPERIMENTAL

70B3 Bullis, W. M., Ed.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR

MATERIALS, PROCESS CONTROL, AND DEVICES

NBS Technical Note 527 , .Quarterly Rpt,

(Oct. 1-Dec. 31, 1969), May 1970.

[see pp. 31-47] [30] (29)

FABRICATION-bond: US; wire: Al; film: Al

Theory

Apparatus : adjustment

Tool: adjustment; oscillation

Rigidity: apparatus

Wire: contamination; mechanical characteristics

Bonding Surface: preparation

Test: pull

EXPERIMENTAL

70B4 Brauer, J. B., V. C. Kapfer, and

A. L. Tamburrino

CAN PLASTIC ENCAPSULATED MICROCIRCUITS

PROVIDE RELIABILITY WITH ECONOMY?

8th Annual Proc. Reliability Physics,

IEEE Catalog. No. 70C59-PHY, pp. 61-

72, 1970. [2] (27)

DEGRADATION-application: plastic devices

Stress: moisture, process, test (temperature

cycle)

Part: metallization, wire

Mechanism: corrosion; fatigue; thermal mismatch

Test: resistance, x-ray

Failure Rates : general

DESCRIPTIVE

70B5 Bradfield, G. ULTRASONIC TRANSDUCERS - 1. INTRODUCTION TO ULTRASONIC TRANSDUCERS,

PART A Ultrasonics, vol. 8, pp. 112-123,

April 1970.

FABRICATION-bond: US

Apparatus: design

REVIEW

70B6 Bradfield, G. ULTRASONIC TRANSDUCERS - ]. INTRODUC- TION TO ULTRASONIC TRANSDUCERS,

PART B Ultrasonics, vol. 8, pp. 177-189,

July 1970.

FABRICATION-bond: US Apparatus: design

REVIEW

70B7 Bullis, W. M. and A. J. Baroody, Jr.,

Eds.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR MATERIALS, PROCESS CONTROL, AND DEVICES

NBS Technical Note 555, Quarterly Rpt.

(Jan. 1 to March 31, 1970), Sept. 1970.

[see pp. 27-36] [30] (29)

43
70B7 (cont.)

TEST

Description : centrifuge ; pull ; US stress

Application: bond monitor

FABRICATION-bond: US

Tool: design

Rigidity : apparatus

Test: pull; visual inspection (SEM)

DESCRIPTIVE

70B8 Bullis, W. M. and A. J. Baroody, Jr.,

Eds.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR

MATERIALS, PROCESS CONTROL, AND DEVICES

NBS Technical Note 560, Quarterly Rpt,. (April 1 to June 30, 1970), Nov. 1970.

[see pp. 29-38] [30] (29)

FABRICATION-bond: US -

' Theory : US Schedule

Wire: mechanical characteristics

Rigidity: apparatus

Test : pull; visual inspection (SEM)

TEST

Evaluation: pull

Application: pull

DEGRADATION

Stress: process; test (pull)

Part : bond

Test: visual inspection (SEM)

DESCRIPTIVE

70C1 Cox. W. P., E. E. Anderson, and

J. H. Anderson, Jr. ULTRASONIC ALUMINUM WIRE BONDING FOR MICROELECTRONIC APPLICATIONS

Proc. 1970 Annual Symp . on Reliability,

Los Angeles, Calif., vol. 3, pp. 228-

236, Feb. 1970. (31)

FABRICATION-bond: US; wire: Al; film: Al

Evaluation: wire

Control: force, power, time

Test: pull; resistance; visual inspection

DEGRADATION-bond: US; wire: Al; film: Al

Stress: process, thermal

Part: wire; substrate

Mechanism: anneal

Test: pull, resistance; visual inspection

EXPERIMENTAL

70C2 Curran, L. PLASTIC IC'S GET FOOT IN MILITARY DOOR

Electronics, vol. 43, pp. 127-130,

May 11, 1970.

TEST-application: plastic devices

Description: Mil-Std-883

DESCRIPTIVE

70D1 Devaney, J. R. APPLICATION OF SCANNING ELECTRON

MICROSCOPY TO INTEGRATED CIRCUIT

FAILURE

Solid State Technol., vol. 13, pp. 7 3- 77, March 1970.

DEGRADATION-bond: TC ; wire: Au; film: Al Part: bond

Mechanism: contamination

Test: visual inspection (SEM)

DESCRIPTIVE

70D2 Davis, D. FACTORS IN HIGH RELIABILITY WIRE

BONDING

8th Annual Proc. Reliability Physics,

IEEE Catalog No. 70C59-PHY, pp. 170-

176, 1970. [similar to 69P1] [2] (28)

FABRICATION-bond: US; wire: Al; film: Al, Au

Schedule

Variables

Apparatus : adjustment , design

Tool : adjustment ; design; oscillation

Rigidity: apparatus, terminal, package

Bonding Surface: contamination; thickness;

topography

Test: pull;, visual inspection

TEST-bond: US; wire: Al; film: Al, Au

Correlation: pull; mechanical shock (radiation induced); visual inspection

REVIEW

70D3 Department of Defense

MILITARY STANDARD - TEST METHODS FOR SEMICONDUCTOR DEVICES

Military Standard 750B, Feb. 27, 1970.

[1]

TEST

Description: centrifuge; mechanical shock;

thermal shock; vibration (fatigue,

monitored, variable frequency)

STANDARD

70D4 Dicken, H. K. SURVEYING CHIP INTERCONNECTION TECHNIQUES

Electron. Packag. Prod., vol. 10, sect. 1, pp. 34-45, Oct. 1970.

FABRICATION-bond: TC , US; wire: Al, Au; film: Al, Au

Evaluation: TC, US, wire bond

REVIEW

70H1 Hnatek, E. R. PLASTIC IC'S ENTICE MILITARY

EDN, vol. 15, pp. 43-47, Nov. 15, 1970.

DEGRADATION-application: plastic devices

Stress: test (temperature cycle, thermal

shock

)

Failure Rates

DESCRIPTIVE

. 44
70H2 Haberer, J. R. STRESS INDUCED INTERMITTENT FAILURES

IN ENCAPSULATED MICROCIRCUITS

Report No. RADC-TR-70-213, pp. 1-49,

Oct. 1970. AD 715984 [see also 71H2]

[1] (27)

TEST-bond: TC ; wire: Au; application: plastic

devices

Description: resistance; temperature cycle

Evaluation: resistance; temperature cycle

DEGRADATION -bond: TC; wire: Au; application:

plastic devices

Stress: moisture, test (temperature cycle)

Part: bond; metallization; wire

Mechanism: corrosion; thermal mismatch

EXPERIMENTAL

70M1 Miller, L. F. A CRITIQUE OF CHIP-JOINING TECHNIQUES

Solid State Technol., vol. 13, pp. 50- 62, April 1970.

FABRICATION

Evaluation: wire bond

REVIEW

70M2 Mann-Nachbar, P., and W. Nachbar

THERMAL SHOCK FOLLOWING RAPID UNIFORM

HEATING OF SPHERES AND LONG CYLINDRICAL

RODS

Rpt. (April-August, 1968), Contract No. F04701-69-C-0066, Feb. 1970. AD 702170

TEST

Application: mechanical shock (radiationinduced)

THEORETICAL

70P1 Pankratz, J. M. and D. R. Collins

A COMPARISON OF 1% MG-A1 AND 1% SI-A1 WIRE INTERCONNECTS

8th Annual Proc. Reliability Physics,

IEEE Catalog No. 70C59-PHY, pp. 163-

169, 1970. [also published in IEEE

Trans. Reliability, vol. R-19, pp. 89-

94, Aug. 1970] [2] (32)

FABRICATION-bond: US; wire: Al, Al/Mg

Evaluation: wire

Bonding Surface: topography

.DEGRADATION-bond: US; wire: Al/Mg

Stress: thermal

Part : device

Mechanism: contamination

EXPERIMENTAL

70P2 Philofsky, E. INTERMETALLIC FORMATION IN GOLD-ALUMINUM

SYSTEMS

Solid State Electron., vol. 13, pp. 1391-1399, Oct. 1970. [also 8th Annual

Proc. Reliability Physics Symp., pp. 177-185, 1970]

DEGRADATION-wire: Al , Al (pure), Au

Stress: thermal

Mechanism : intermetallics

Test: metallurgical exam; pull

TEST

Application : temperature cycle; thermal shock

EXPERIMENTAL

70R1 Rossiter, T. J. AMBIENT EFFECTS ON GOLD-ALUMINUM BONDS

8th Annual Proc. Reliability Physics,

IEEE Catalog No. 70C59-PHY, pp. 186-

190, 1970. [2] (27)

DEGRADATION-bond: TC; wire: Au; film: Al

Stress: thermal

Part : bond

Mechanism: intermetallics

Test: pull; resistance

EXPERIMENTAL

70S1 Spectrum

HIGH-PRESSURE PROCESS MAKES WIRE BY SQUEEZING

Spectrum, vol. 7, pp. 21, Aug. 1970.

FABRICATION

Wire: fabrication

DESCRIPTIVE

70S2 Straub, R. J. RELIABILITY OF HYBRID MICROCIRCUITS II USE TODAY

Proc. Electronic Components Conf.,

May 1970. [2] (33)

TEST-application: hybrids

Evaluation : Mil-Std 883

Screening Procedures

DEGRADATION-bond: TC ; application: hybrids

Failure Rates

DESCRIPTIVE

70V1 Villella, F. and M. F. Nowakowski

INVESTIGATION OF FATIGUE PROBLEM IN

1 -MIL DIAMETER THERM0C0MPRESSI0N AND ULTRASONIC BONDING OF ALUMINUM WIRE

NASA Technical Memorandum, NASA

TM X-64566, pp. 1-45, Nov. 30, 1970.

N71-16494

DEGRADATION-bond: TC , US; wire: Al, Au; film: Al

Stress: thermal

Part : wire

Mechanism: fatigue

Test: pull; visual inspection (SEM)

Failure Rates

TEST

Application: temperature cycle

EXPERIMENTAL

45
70W1 Wilson, A. D., B. D. Martin, and

D. H. Strope

HOLOGRAPHIC INTERFEROMETRY APPLIED TO

MOTION STUDIES OF ULTRASONIC BONDERS

IEEE Ultrasonics Symp. , San Francisco,

Calif., Oct. 21-23, 1970. [2] (34)

FABRICATION-bond: US

Apparatus: design

Tool: oscillation

Test: interferometry

DESCRIPTIVE

abbreviated version] [1]

TEST-bond: TC ; wire: Au; film: Ag, Au; application: plastic devices

Evaluation: thermal shock

DEGRADATION-bond: TC; wire: Au; film:

application: plastic devices

Stress: test (thermal shock)

Part: bond; wire

Mechanism: thermal mismatch

EXPERIMENTAL

Au;

70W2 Wood, W. A. FATIGUE CRACK INITIATION AS VIEWED BY SCANNING ELECTRON MICROSCOPY

Contract N-00014-67-A-0214-0011, Rpt .

,

Jan. 1970. AD 704789

DEGRADATION

Stress: mechanical

Part : wire

Mechanism: fatigue

ANALYTIC

71B1 Bullis, W. M. , Ed.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR MATERIALS, PROCESS CONTROL, AND

DEVICES

NBS Technical Note 571, Quarterly Rpt.

(July 1-Sept. 30, 1970), April 1971.

[see pp. 23-32] [30] (29)

FABRICATION-bond: US; wire: Al; film: Al

Tool: design; oscillation

Rigidity: apparatus

TEST-bond: US; wire: Al; film: Al

Evaluation: pull

DEGRADATION-bond: US; wire: Al ; film: Al

Stress: process

Part : wire

EXPERIMENTAL

71B2 Boylan, J. R. THERM0C0MPRESSI0N BONDING

IEEE Intern. Conv. Digest, New York,

Session 7C1, pp. 598-599, March 1971,

[2]

FABRICATION-bond: TC, US; wire: Al, Au

Evaluation: TC, US; wire bond; temperature

control

Procedure : TC Tool: design (TC)

Rigidity: terminal

REVIEW

71B3 Bevington, J. R. , J. P. Cook, D. R. Little, and L. V. Ingle

RELIABILITY EVALUATION OF PLASTIC IN- TEGRATED CIRCUITS

Rpt. (Jan. 9, 1969 to Sept. 9, 1970)

Contract No. F30602-69-C-0154, pp. 1- 154, Jan. 1971. AD 722043 [70B1 is

71B4 Bullis, W. M. , Ed.

METHODS OF MEASUREMENT FOR SEMICONDUCTOR

MATERIALS, PROCESS CONTROL, AND DEVICES

Quarterly Rpt. (Oct. 1-Dec. 31, 1970)

NBS Technical Note 592. [see pp. 34-

45], [30] (29)

TEST-bond: US; wire: Al; film: Al

Description: bond monitor

Application: pull

FABRICATION-bond: US

Apparatus: adjustment (US); design (US)

Rigidity: apparatus

Wire: mechanical characteristics

DEGRADATION: bond: US; wire: Al; film: Al

Stress: process

Part: bond; wire

Mechanism: anneal

Test: pull

DESCRIPTIVE

71D1 Dushkes, S. Z. A DESIGN OF ULTRASONIC BONDING TIPS

IBM J. Res. Develop., vol. 15, pp. 230- 235, May 1971.

FABRICATION-bond: US; wire: Au/CuBeO; film:

Au/Cu; substrate: epoxy

Tool: design; oscillation

Test: pull

EXPERIMENTAL

71G1 Glass, R. A., T. G. Maple, and R. D. Wales

INTERCONNECTION PROBLEM AREAS IN MICROCIRCUITS

IEEE Intern. Conv. Digest, New York,

Session 5B, pp. 248-249, March 1971. [2]

FABRICATION-bond: US; wire: Al ; film: Al, Au; substrate: Fe/Ni/Co

Tool: design

Bonding Surface: contamination; film thickness;

metal system; preparation

Test: pull, visual inspection

DEGRADATION-bond: US Stress: process

Part : wire

TEST-bond: US; wire: Al; film: Al

Correlation: pull, visual inspection

EXPERIMENTAL

46
71G2 Goldfarb, S. WIRE BONDS ON THICK FILM CONDUCTORS

Proc. Electronic Components Conf .

,

Washington, D. C. , pp. 295-302, May

1971. [2] (36)

DEGRADATION-bond: US; wire: Al, Au; thick

film: Au

Stress : thermal

Part: bond; wire

Test: pull; resistance

EXPERIMENTAL

71H1 Harman, G. G. and H. K. Kessler

APPLICATION OF CAPACITOR MICROPHONES

AND MAGNETIC PICKUPS TO TUNING AND TROUBLE SHOOTING OF MICROELECTRONIC

ULTRASONIC BONDING EQUIPMENT

NBS Tech. Note 573, pp. 1-22, May 1971.

[30] (29) • FABRICATION-bond: US Apparatus : adjustment

Tool: adjustment, oscillation

Trouble Shooting

DESCRIPTIVE

71H2 Haberer, J. R. TECHNIQUES FOR DETECTING STRESS INDUCED INTERMITTENT FAILURES IN ENCAPSULATED

DEVICES

IEEE Intern. Conv. Digest, New York,

Session 7CJ, pp. 612-613, March 1971.

[see also 70H2]

TEST-bond: TC; wire: Au; application:

plastic devices

Description: resistance; temperature cycle

Evaluation: resistance; temperature cycle

DEGRADATION-bond: TC ; wire: Au; application:

plastic devices

Stress: moisture, test (temperature cycle)

Part: bond; metallization; wire

Mechanism: corrosion; thermal mismatch

EXPERIMENTAL

71H3 Hart, R. R. A WIRE EXTENSOMETER FOR DETERMINING THE MECHANICAL PROPERTIES OF FINE WIRES

Mater. Res. Std., vol. 11, pp. 26-28,

April 1971.

FABRICATION

Wire: mechanical characteristics

EXPERIMENTAL

71J1 Johannesen, F. ULTRASONIC ALUMINUM WIRE BONDING

IEEE Intern. Conv. Digest, Session 7CI

,

pp. 600-601, March 1971.

FABRICATION-bond: US; wire: Al ; film: Al, Au; substrate: Fe/Ni/Co

Variables

Apparatus : design

Tool: design, wear

Rigidity : apparatus , package

Bonding Surface : topography

REVIEW

71K1 Kalvelage, B. F. A PNEUMATIC SHOCK TESTER FOR ELECTRON

DEVICES

Solid State Technol., vol. 14, pp. 57- 59, March 1971.

TEST

Description : mechanical shock

DESCRIPTIVE

71K2 King, CM.

DYNAMIC SIMULATION OF AN ULTRASONIC

WIRE BONDING TOOL

Raytheon Report ER71-4135, Contracts

N0003070-C0055 and N0003071-C0061

,

Jan. 25, 1971. (35)

TEST

Application: bond monitor

THEORETICAL

71L1 Leyshon, W. E., and R. E. Warr

AN OVERVIEW OF HYBRID INTEGRATED CIRCUIT RELIABILITY PROBLEMS AND SOLUTIONS

IEEE Intern. Conv. Digest, New York,

Session 7CJ, pp. 606-607, March 1971.

DEGRADATION-application: hybrid devices

Stress: moisture; test (temperature cycle)

Part: metallization, wire

Mechanism: contamination; corrosion; fatigue;

interme tallies

Test: resistance

REVIEW

71M1 Matcovich, T. J. INTERCONNECTIONS IN HYBRID CIRCUITS

IEEE Intern. Conv. Digest, New York,

Session 5B, pp. 240-241, March 1971.

FABRICATION-bond: TC, US Evaluation: wire bond

REVIEW

71N1 NASA

LINE CERTIFICATION REQUIREMENTS FOR ' MICROCIRCUITS

NHB 5300.4(30, May 1971. [30]

TEST

Description: Mil-Std-883; pull; resistance;

visual inspection; visual inspection (SEM)

Application: Mil-Std-883

Screening Procedures

STANDARD

47
71N2 NASA

TEST STANDARDS FOR MICROCIRCUITS

NHB 5300. 4(3D), May 1971. [30]

TEST

Description: mechanical shock ; pull; resistance

STANDARD

71P1 Philofsky, E. DESIGN LIMITS WHEN USING GOLD-ALUMINUM

BONDS

9th Annual Proc. Reliability Physics

Symp., Las Vegas, IEEE Catalog No. 71-C-9-PHY, 1971. [2] (37)

FABRICATION-bond: TC', US; wire: Al, Au; film:

Al, Au

Bonding Surface: film thickness

DEGRADATION-bond: TC , US; wire: Al, Au;

film: Al, Au

Stress : test (temperature cycle) ; thermal

Part: bond; wire

Mechanism: fatigue; intermetallics

ANALYTIC

TEST-bond: TC; wire: Au; film: Al, Au; application: hybrid devices

Screening Procedures

DEGRADATION-bond: TC; wire: Au; film: Al , Au application: hybrid devices

Stress: test (centrifuge, mechanical shock,

temperature cycle, thermal shock)

Part: bond, wire

EXPERIMENTAL

71P2 Philofsky, E., R. Bowman, and W. Miller

ALUMINUM ULTRASONIC JOINING IN SPIDER

AND WIRE CONNECTIONS

Proc. Electronic Components Conf .

,

Washington, D. C, pp. 289-294, May

(37) US; wire: Al; film: Al

1971. [2]

FABRICATION-bond

Theory: US Evaluation: US Bonding Surface

REVIEW

topography

71R1 Ravi, K. V. and E. Philofsky

THE STRUCTURE AND MECHANICAL PROPERTIES

OF FINE DIAMETER ALUMINUM - 1 PCT SI WIRE

Metallurgical Transactions, vol. 2, pp. 711-717, March 1971.

FABRICATION-bond: TC, US; wire: Al

Evaluation: wire

Wire: mechanical characteristics

DEGRADATION-bond: TC, US; wire: Al

Stress : thermal

Part : wire

Mechanism: anneal; fatigue; grain growth

Test: pull

EXPERIMENTAL

71S1 Straub, R. J. and J. P. Farrell

THE EFFECTIVITY OF SCREENING HYBRID

MICROCIRCUITS PER MIL-STD-883

Proc. Electronics Components Conf.,

Washignton, D. C, pp. 17-26, May 1971.

[2] (38)

48
Appendix A. Organization of Bibliography

Each entry has been given an Ide.wtifa.lccutlon

code, which consists of a sequence of two digits,

a letter, and another digit. The first two digits

indicate the year of publication and the letter is the initial of the first author's surname. The last digit is used to distinguish those papers

which would otherwise have the same code . No rule

was used in the assignment of the last digit. The

papers in the bibliography are arranged according

to their codes. The codes are grouped first by

year, then in alphabetical order by letter, and then in numerical order by the last digit.

Key WOKdi (or phrases) are listed beneath

each reference in the bibliography to indicate the contents and approach of the paper. Three levels of key words are used to indicate the subject matter of the entries at three levels of detail. These levels and the key words assignments are discussed in Appendix D. A Key Wo fid Index is provided and presented in two parts. The first part

lists the key words in alphabetical order with the page number where the same key word may be found

in the second part of the Index. This second part

lists the key words by subject area. With each

key word is a tabulation of literature citations

(using their identification codes). In both parts

of the Index, key words that may require additional

definition are followed by clarifying notes , in brackets , except for those for the test methods

.

Brief descriptions of the test methods may be found

in Table 4. Here, key words for the test methods

are listed in alphabetical order with a brief de- scription for each. The test methods listed are

not necessarily restricted to testing wire bonds

.

However , the descriptive phrases are directed to

the particular function described in the papers compiled

.

Reading p>vLonJXy is suggested by giving prominence to those papers that are of such scope or relative importance in a particular area that they

should be seen first. These papers are so indicated by underlining the identification code for the paper listed under the appropriate key word in the Key Word Index. They are also indicated by underlining the code of the citation and the appropriate

key word(s) in the bibliography.

Some citations are followed by notes which

refer to additional information intended to assist

in obtaining the referenced work. This and other

information related to (WoJJjxb-ULLty is included in Appendix C.

A complete Author. Index is also provided.

Appendix B. Sources for Bibliography and Abbreviations

The iOU/iceA of the bibliography are listed in Table 1. Emphasis was placed on searching the report and journal literature from 1965 to 1970. Citations to much of the important earlier work

were found in the articles published during this

period . Another source of papers was a number of

restricted bibliographies, containing references

to unrestricted literature, and personal files.

The journal or conference abbreviation* gen- erally follow those of the Chemical kb&tAjxctd . In

order to minimize any possible confusion, those

journals abbreviated are listed in alphabetical

order by their abbreviations in Table 1. Additional abbreviations are included which are used in citations to some conference meetings. Another

purpose of this Table is to indicate those jour- nals which have been scanned completely at least over the period from 1965 to 1970, inclusive.

They are indicated by an asterisk in the left-hand

margin

.

Appendix C. Availability

Some entries in the bibliography have availability notices after the citation to assist in procurement.

The citations to reports available from the National Technical In^onmxtion SeAiM.ce (WHS),

Sills Building, 5285 Port Royal Road, Springfield,

Virginia 22151, are followed by a number preceded

by the letters AD or PB, or the letter M. This is the NTIS Acession number which should be used when

ordering.

A number of other entries, generally to con- ference papers, have the citation followed by a number either in brackets or parentheses. The number refers to an address listed in Table 3. If the number is in brackets the address listed is one

to which an order may be placed for the paper or the conference proceedings. If the number is in parentheses the address is that of the first au- thor's place of work at the time the paper was published.

49
TABLE 1. SOURCES FOR BIBLIOGRAPHY

Bibliographic search by the Defense Documen- 3. U. S. Patent search. Performed May, 1969. tation Center, Cameron Station, Alexandria,

Virginia 22314- . A data bank and a report »+. Scientific and Technical Aerospace Reports for bibliographic search was performed in May, the years 1965-1970. Subject categories were: 1969 and updated in June, 1970. A two level electronics, electronic equipment, and physics,

search strategy was used: level one - 1. integrated circuits, 2. microelectronics; 5. U. S. Government Research and Development Re- level two - 1. circuit interconnections, ports for at least the period from 1969-1970.

2. bonding, 3. bonded joints, 4. ultrasonic Earlier entries would be included in item 1. welding. Subject fields were electronic and electrical

engineering, methods and equipment, and physics.

Bibliographic search by the Reliability Analysis Center, IIT Research Institute, 10 West 6. Journals in Table 2 that are preceded by an as35th Street, Chicago, Illinois 60616. Per- terisk. Issues of these journals published in formed in June 1969. . the period from 1965 to 1970, inclusive, were

examined.

50
TABLE 2. ABBREVIATIONS AND JOURNALS SEARCHED

AIME - American Institute of Mining, Metallurgical and Petroleum Engineers

ASME - American Society of Mechanical Engineers

ASTM - American Society for Testing and Materials

ASTME - American Society of Tool and Manufacturing Engineers

Appl. Phys. Lett. - Applied Physics Letters

*Bell Lab. Rec. - Bell Laboratories Record

"'Bell System Technical Journal

Brit. Commun. Electron. - British Communication and Electronics

Brit. J. Appl. Phys. - British Journal of Applied Physics

Circuits Mfg. - Circuits Manufacturing

Conf. - Conference

"EDN - (formerly Electrical Design News)

*EE - (now, The Electronic Engineer; formerly, Electronic Industries)

*EEE ^Electron. Packag. Prod. - Electronic Packaging and Production

*Electron. Prod. - Electronic Products Magazine

*Electronic Design

*Electronic Engineer - The Electronic Engineer (formerly EE, formerly Electronic Industries)

"Electron. Lett . - Electronics Letters *Electronics

*Electro-technol. - Electro-technology (New York)

Eval. Eng. - Evaluation Engineering

*IBM Journal of Research and Development

IEEE - Institute of Electrical and Electronics Engineers (formerly IRE)

IEEE Intern. Conv. Record - IEEE International Convention Record (formerly IRE . . .) *IEEE Trans. Electron Devices -IEEE Transactions on Electron Devices (formerly IRE '.

. .

)

*IEEE Trans. Nucl. Sci . - IEEE Transactions on Nuclear Science

»'

! IEEE Trans. Pts. Materials Packaging - IEEE Transactions on Parts, Materials and Packaging

''IEEE Trans. Sonics Ultrason. - IEEE Transactions on Sonics and Ultrasonics

^Industrial Research

''•'International Journal of Nondestructive Testing

Int. - International

IEC - International Electrotechnical Commission

IRE - Institute of Radio Engineers

IRE Intern. Conv. Record - IRE International Convention Record

IRE Trans. Electron Devices - IRE Transactions on Electron Devices

J. Appl. Phys. - Journal of Applied Physics

*J. Electrochem. Soc. - Journal of the Electrochemical Society

J. Sci. Instrum. - Journal of Scientific Instruments

Mater. Eval. - Materials Evaluation

*Mater. Res. Std. - Materials Research and Standards

Metals Eng. Quart. - Metals Engineering Quarterly

*Microelectronics and Reliability

Nat. Electron. Conf. - National Electronics Conference

Mfg. - Manufacturing

NEPCON - National Electronic Packaging and Production Conference

Philips Tech. Rev. - Philips Technical Review

Proc. IEEE - Proceedings of the Institute of Electrical and Electronics Engineers

*Prod. Eng. - Product Engineering

*RCA Review

*Rev. Sci. Instr. - The Review of Scientific Instruments

Rev. Elec. Commun. Lab. - Review of the Electrical Communications Laboratory. To'kyo. (Denki Tsushin

Kenkyujo)

SAE - Society of Automotive Engineers

Semicond. Prod. - Semiconductor Products

*Semicond. Prod. Solid State Technol. - Semiconductor Products and Solid State Technology

Soc. - Society

*Solid State Abstracts

*Solid State Electron. - Solid State Electonics

Solid State Technol. - Solid State Technology

Symp. - Symposium

Technol. - Technology

*Trans. Met. Soc. AIME - Transactions of the Metallurgical Society of the AIME

*Ultrasonics

Welding J. - Welding Journal

WESCON - Western Electric Show and Convention

*Journals searched completely for period 1965-1970.

51
TABLE 3. AVAILABILITY NOTES

[1] U. S. Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, Pennsylvania 19120.

[2] Publications Sales Department, The IEEE, 345 East 47th Street, New York, New York 10017.

[3] American National Standards* Institute , Inc., 1430 Broadway, New York, New York 10018.

[4] Industrial and Scientific Conference Management, Inc., 222 West Adams Street, Chicago, Illinois

60606.

(5) Uthe Technology, Inc., 670 Almanor Ave., Sunnyvale, California 94086.

[6] Illinois Institute of Technology, Chicago, Illinois 60606.

[7] ASME Order Dept., 345 47th Street, New York, New York 10017.

[8] American Welding Society, 345 East 47th Street, New York, New York 10017.

[9] Technology Utilization Division, NASA, Code UT, Washington, D. C. 20546.

[10] Gordon and Breach, Science Publishers, Inc., New York, New York 10001.

[11] ASTM, 1916 Race Street, Philadelphia, Pennsylvania 19103.

(12) MIT Instrumentation Laboratories, Cambridge, Massachusetts 02142.

(13) North American Aviation/Autonetics, Anaheim, California 92803.

(14) Norden Division of United Aircraft Corp., Norwalk, Connecticut.

(15) Philco-Ford Corp., Microelectronics Div. , Blue Bell, Pennsylvania 19422.

(16) Westinghouse Electric Corp., Baltimore, Maryland.

(17) Weltek Div., Wells Electronics Inc., South Bend, Indiana.

(18) Aeroprojects Inc., West Chester, Pennsylvania.

(19) Weldmatic Div., Unitek Corp., Monrovia, California.

(20) Martin Marietta Corp., Quality Engineering Dept., Orlando, Florida.

(21) Lockheed Missiles and Space Co., Lockheed Palo Alto Research Laboratories, Palo Alto, California

94304.

[22] Sandia Labs., Albuquerque, New Mexico 87115.

(23) Hughes Aircraft Co., Welder Dept., Oceanside, California 92054.

(24) United Aircraft Corp., Electronic Components Div., Trevose , Pennsylvania.

(25) Westinghouse Defense and Space, Mfg., Research and Development, Baltimore, Maryland.

(26) McDonnell Douglas Astronautics Co., Western Div., Santa Monica, California.

(27) RADC, Griffiss Air Force Base, Rome, New York 13440.

(28) Fairchild Semiconductor, Research and Development Laboratories, Palo Alto, California 94304.

(29) National Bureau of Standards, Washington, D. C. 20234.

[30] Superintendent of Documents, U. S. Government Printing Office, Washington, D. C. 20402.

(31) Lockheed Missiles and Space Co., Sunnyvale, California.

(32) Texas Instruments, Inc., Dallas, Texas 75222.

(33) AC Electrics Div., General Motors Corp., Milwaukee, Wisconsin.

(34) IBM Corp., Endicott , New York 13760.

(35) Raytheon Co., Sudbury, Massachusetts 01776.

(36) RCA, Somerville, New Jersey 08876.

(37) Motorola Inc., Phoenix, Arizona 85008.

(38) Delco Electronics Division, General Motors Corp., Milwaukee, Wisconsin.

52
Appendix D. Key Word Selection and Use

Thn.ee levelis 0)5 key u)0Kdi are used in the bibliography to indicate the subject material in the

works compiled, each successive level being less broad in scope. To help identify key words of different levels , all the letters are capitalized for

first-level key words while only the first letter

of the second-level key words is capitalized. The third-level key words are all in lower-case.

Fiut-level key words are used to indicate

general subject areas discussed; they are TEST,

FABRICATION, and DEGRADATION. One or more of these

key words may be used, depending on the contents of the work. The order of listing is meant to in- dicate the relative emphasis given each area if more than one is listed

.

The kind ofi mine bond* involved in the discussions of a given subject is described by a series

of dei cKiptonM arranged on the same line and fol- lowing the first-level key word describing the subject area. The descriptions that may be used,

depending on what is discussed, are: bond, uii/ie, i-c&n, thick l*Jbn, iubitn.ate, and application. They

refer, respectively, to the bond involved; the wire

material; the metallization film(s) on the bonding

surface or the material on which the wire is bonded if no metallization film is used; the thick-film

(>> 1 vim) conductive composition, if used; the substrate material under the conducting film; and the application or use of the wire bond in hybrid circuits or plastic devices. Following each of these

descriptors are symbols or words to indicate the kinds of bonds, materials, and applications that

are used or discussed. If the comments are of a general nature and no particular wire bond is mentioned in the entry then descriptors are not given.

If a teit method is discussed in the context

of testing or evaluating the wire bond then the first-level key word TEST is listed under the entry

in the bibliography. As appropriate, one or more

of the following second-level key words is listed

below TEST: Vet>cnJiption, Evaluation, ConAelation,

Application, Pnecautioni, and Screening PnoceduneA;

in that order. The key words (third-level) for the

test methods are arranged in alphabetical order

after and on the same line with the appropriate

second-level key words listed above. If the entry

describes a test method in any detail, the key word

for the method will follow Description; if it evaluates the methods the key word will follow Evaluation; if it presents correlation information with

other methods for the same type of wire bond, then

key words for these methods will follow Correlation.

If the material in the entry is or may be applicable to a test method, its key word will follow Application, while if the material deals with pre- cautions in the use of a method its key word will

follow Precautions. Finally, if the material in the entry deals with procedures in which several

tests are performed as a means of culling out weak

wire bonds then Screening Procedures will be listed without an indication of the test methods in- volved.

If material in the entry deals with some aspect of the fabrication of wire bonds then the first-level key word FABRICATION is used. The Second-level key words that have been selected are

as follows: lhcon.ij, Evaluation, Pnocedune, Schedule, Vcuviables, Appanatui, Control, Tool, Rigidity,

WiAC, Bonding SuA&ace, Test, and Tn.ou.blo. Shooting.

Without mentioning the third-level key words in any

detail, the meaning and intent of the above listed

second-level key words will now be indicated. The key word TheoKy relates to the theory of making a bond while Evalu.atA.on relates to the evaluation of

such things as the type of bonding process , the type of bond, the metal systems used, etc. The key word Pnocedune refers to the procedures or steps in making a particular type of wire bond. The key word Schedule refers to the optimization

of the fabrication processes and procedures for

making wire bonds , while the key word Uaniablei

refers to the effects that specific variables have

on the quality or strength of a wire bond. The key word Apparatus refers to the bonding machine

and its accessories; Contnol refers to the importance of controlling specific parameters ; Tool refers to the tool used to press against the wire

while the bond is made; Rigidity refers, generally,

to the importance of mechanical rigidity and po- sitional control in the fabrication of the wire

bond; WiAe refers to the wire used; and Bonding

SuA^ace to the characteristics of the bonding surface pertinent to good bonding. If test methods

are used to evaluate the fabrication procedures

their key words are listed after Teit. Finally,

if the entry discusses hints or methods for locating and correcting deficiencies in the fabricating

procedures , the key word Trouble Shooting will be

used.

If material in the entry deals with some aspect

of the degradation or failure of wire bonds then

the first-level key word DEGRADATION is used. The second-level key words that have been selected are

as follows: Stness, Pant, Mechantim, Teit, and

Failune Ratei. The third-level key words for the first three of these were selected to be more specific in terms of, respectively, (1) the kind

of stress that produces a weakened wire bond as a result of the fabrication process or that results

in degradation or failure of an already completed

wire bond; (2) the part or component, primarily of

the wire bond, that is or has been affected by the stress; and (3) the mechanism, if defined, that is involved in the degradation or failure. If a test method is used to detect or measure this degradation or failure then the key words of the test methods used will follow Test. If general reliability data, such as failure rates of specific

kinds of wire bonds under specific conditions or

stress, are included in the entry then the key

word Failure Rates is used; third-level key words

follow to indicate if the information pertains to thermocompression or ultrasonic wire-bonds, or if the kinds of wire bonds are not indicated.

The fiiAit-level key words used to indicate the approach or the type of the entry are ANALYTIC,

DESCRIPTIVE, EXPERIMENTAL, and THEORETICAL; and

PATENT, REVIEW, and STANDARD. Only one of these

key words is used and it is listed last.

53
TABLE 4. TEST METHODS AND BRIEF DESCRIPTIONS

air blast

A jet of gas, usually air or nitrogen, is directed at the wire

.

bond monitor

Some measure of the mechanical coupling between

the tool, wire, and metal film is monitored

during ultrasonic bonding.

centrifuge

A constant centrifugal force is applied to the

device.

electrical parameter

A device performance test is used to determine

device degradation caused in some way by the

wire bond

.

electron microprobe

An electron microprobe is used to identify con- taminants in the wire bond

.

IR monitor

The infrared radiation from a bond is used to obtain a measure of the thermal resistance of the bond interface and hence the area of con- tact and the quality of the bond of the wire to the bonding surface

.

interferometry

The motion of ultrasonic bonding tools and ve- locity transformers in ultrasonic bonding machines is studied with use of interferometry.

mechanical shock

A large, short-duration deceleration is applied

to the device.

mechanical shock (radiation-induced)

The absorption of a short pulse of high-energy

electrons in a plate fastened to the base of

the device header is used to generate thermallyinduced stress waves which are used to stress the wire bond

.

metallurgical exam

The structure and interface of wire bonds are examined metallurgically

.

Mil-Std-750B

Military standard test methods for discrete

devices

.

Mil-Std-883

Military standard test methods for integrated

circuits.

noise

Electrical noise measurements are used to detect

abnormalities in the wire bond.

photoelastic stress analysis

Stress distributions in the vicinity of the bond are studied. . .

pull (nondestructive)

The wire is pulled by a probe to a predetermined tensile stress.

radiotracer

Radiotracers are used to detect the distribution of contaminants and to study interfacial

displacements

.

resistance

The contact or bond-interface resistance is measured (directly or indirectly).

temperature cycle

The device is exposed alternately between two temperature extremes to test the ability of the wire bond to sustain the mechanical stresses that result from differences in the thermal

coefficients -of -expansion of the constituent

parts

.

thermal shock Same as temperature cycle except that the trans- fer time between temperature extremes is shorter .

US probe

Ultrasonic energy is used to test (probe) the mechanical quality of bonds.

US stress Ultrasonic energy is used to stress wire bonds.

vibration (fatigue)

The device is vibrated at a fixed frequency for long periods of time at a relatively low maxi- mum acceleration level.

vibration (monitored)

The electrical parameters of the device are monitored while it is being vibrated.

vibration (variable frequency)

The device is vibrated thru a frequency range

at a relatively constant, maximum acceleration.

visual inspection

Wire bonds are examined under a microscope to determine if they conform to predetermined

criteria of physical appearance, location, and orientation.

visual inspection (SEM) The same as the visual inspection test except a scanning electron microscope (SEM) is used.

x-ray exam X-rays are used to look for abnormalities in wire

routing and orientation in encapsulated devices.

pullThe wire is pulled by a probe, usually hooklike, until some part of the wire bond ruptures.

54
DRM NBS-114A (1-7!) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS-TN- 593

2, Gov't Accession No.

3. Recipient's Accession No.

TITLE AND SUBTITLE

Wire-Bond Electrical Connections: Testing, Fabrication and

Degradation— A Bibliography 1957 - 1971

5. Publication Date January 1972

6. Performing Organization Code

AUTHOR(S) Harry A. Schafft 8. Performing Organization

10. Project/Task/Work Unit No. A251522

PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

EA071—801

2. Sponsoring Organization Name and Address Dept. of Navy

Strategic Systems Project Office

Washington, D.C. 20360

(cont. below)

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

>. SUPPLEMENTARY NOTES

also supported by:

Defense Nuclear Agency

Washington, D.C. 20305

J. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

More than 2A.5 papers relevant to wire-bond type electrical interconnections used

in microelectronic and low-power discrete and hybrid devices are listed together

with key words. The bibliographic search concentrated on compiling papers which

appeared in the period from 1965 to 1970, inclusive. The selection of papers was

generally limited to those that were pertinent to wire-bonds where the wire

diameter is less than about 50/'m (2 mils) and where the wire is bonded by either

thermocompressive or ultrasonic means. Two indexes are provided: (l) an Author

Index and (2) a Key Word Index. The latter includes a tabulation of the

literature citations.

Keywords (cont.): (wire-bond); wire-bond.

7. key words (Alphabetical order, separated by semicolons) Bibliography; degradation (wire-bond); discrete devices; electrical interconnection; fabrication (wire-bond); failure (wire-bond)

hybrid circuits; integrated circuits; microelectronics; reliability; testing; (cont.)

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FA 1 *W

NBS TECHNICAL NOTE 594-2

Optical Radiation Measurements:

Photometric Instrumentation

and Research (1970 to 1971)
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac

Radiation2 —Nuclear Radiation-—Applied Radiation 2—Quantum Electronics*

Electromagnetics'—Time and Frequency3 —Laboratory Astrophysics3—Cryogenics3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

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aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

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i Headquarters and Nahoratories ;it Gaitherslmre;, Maryland, unless otherwise notcil ; mailing address Washington, I>,c _'irj.".(.

> I'art o£ the Outer for Radiation Research. Located at Boulder, Colorado 80302.

1 I'art of the Center for Building Technology.
.1 --• -W t-'S w »

' rsrt&z

""

Optical Radiation Measurements:

53

Photometric Instrumentation

~ and Research (1970 to 1971]

Edward F. Zalewski, A. Russell Schaefer,

Kshitij Mohan, and Donald A. McSparron

Heat Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

t

^0r c .

i- Q

J

U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary

NATIONAL BUREAU OF STANDARDS, Lawrence M. Kushner, Acting Director,

Issued September 1972
National Bureau of Standards Technical Note 594-2

Nat. Bur. Stand. (U.S.), Tech. Note 594-2, 44 pages (Sept. 1972)

CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. 03.46:594-2). Price 50 cents.
Preface

This is the second issue of a series of Technical Notes entitled OPTICAL RADIATION

MEASUREMENTS. The series will consist primarily of reports of progress in or details of

research conducted in radiometry and photometry in the Optical Radiation Section of the

Heat Division and will appear about every six weeks.

The level of presentation in OPTICAL RADIATION MEASUREMENTS will he directed at a

general technical audience. The equivalent of an undergraduate degree in engineering

or physics plus familiarity with the basic concepts of radiometry and photometry

[e.g., G. Bauer, Measurement of Optical Radiations (Focal Press, London, New York,

1965)] should be sufficient for understanding the vast majority of material in this

series. Occasionally a more specialized background will be required such as for

some of the electronic techniques required in this issue. Even in such instances, a

careful reading of the assumptions, approximations and final conclusions should permit the non-specialist to understand the gist of the argument if not the details.

At times , certain commercial materials and equipment will be identified in this

series in order to adequately specify the experimental procedure. In no case does

such identification imply recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the material or equipment identified is necessarily

the best available for the purpose.

Any suggestions readers may have to improve the utility of this series are welcome.

Henry J. Kostkowski, Chief,

Optical Radiation Section

National Bureau of Standards

iii
TABLE OF CONTENTS

Page

1. Introduction 1

2. Instrumentation 2

2.1 Photodetector Amplifier 2

2.2 Lamp Power Circuitry o.

2.3 Mechanical Instrumentation 13

3. Experimentation 21

3.1 Flux Lamp Stability Tests 21

3.2 Orientational Dependence of Relative Luminous Intensity 22

3.3 Intensity Lamp Stability 33

h. Conclusion 36

5. References 37

LIST OF TABLES

I. Lamp Repeatability Experiments 35

LIST OF FIGURES

Figure No.

1. Balanced photocell circuit 3

2. Basic current to voltage converter circuit 3

3. Current to voltage converter: first version 5

h. Current to voltage converter: second version 8

5. Lamp power circuits 10

6. Lamp power supply circuit, master/slave, constant current, series

configuration using Kepco JQE series power supplies 12

7 • Optical bench 15

8. Radiance lamp mount 16

9. Sliding sphere mount 18

10. Kinematically designed lamp socket 20

11. Total luminous flux output stability of 200 watt flux lamps run at 102 volts . 23

12. Total luminous flux output stability of 200 watt flux lamps run at 95 volts . . 2h

13. Orientational dependence of relative luminous intensity for clear

bulb C-13 filament lamps 26

lU. Relative luminance intensity versus pitch dependence of inside frosted

C-13 filament lamps 27

iv
15- Orientational dependence of relative luminous intensity for

CC-8 filament clear bulb quartz halogen lamps 28

16. Relative luminous intensity versus pitch dependence for special

nonplanar filament clear bulb lamp 30

IT- Contribution of glass envelope striations to relative luminous

intensity versus pitch dependence 31

18. Extreme example of relative luminous intensity variation as a function of pitch rotation 32

Photometric Instrumentation and Research

(1970 to 1971)

Edward F. Zalewski , A. Russell Schaefer,

Kshitij Mohan*, and Donald A. McSparron

This document was written primarily to serve two purposes.

First, some of the basic instrumentation which has recently been

developed for use in photometry at NBS is described. The design

and application of photodetector amplifiers, lamp power circuitry,

and mechanical instrumentation are discussed. Second, three

photometric experiments are described: the stability testing of

some flux lamps and intensity lamps and the determination of the

dependence of relative intensity on orientation. These experiments and their conclusions have proven useful in pointing out areas which need further investigation and in planning the

directions of future work.

Key words: Instrumentation; lamp orientation; lamp power

circuitry; lamp stability; photodetector amplifier; photometry.

1. Introduction

A little over a year ago there was at NBS a merger of several related groups,

including radiometry and photometry, into one managerial unit. This was done in order to

bring the programs of these heretofore independent groups into concert. Before the merger

there already was a move under way in the photometry group to expand the research program

and modernize the instrumentation. This work continued, of course, and evolved into the

research programs presently under way.

Because the instrumentation developed during this period is now used in several of the

present programs, we have decided to describe it in a single document for ease of reference

in future publications. In addition to a description of our instrumentation, we have

described three of the experiments that were either completed or well under way at the time

of the merger. The results of these experiments have proved useful to us in the planning

of further research in photometry.

In keeping with the intention of this series on research in optical radiation measurement, we have tried to be as detailed as possible in the descriptions of our equipment and

procedures. There is a danger that beyond a certain point additional details become trivia.

It is difficult to determine where this point actually lies because it is a function of the

background of the individual reader. We apologize in advance for those sections that the

reader may find boring and welcome any comments or questions that may arise in those

sections he or she finds obscure.

In the description of our instrumentation we discuss the current to voltage converters

that were designed and built at NBS for the amplification of the photodetector output. The

operation of a stable DC lamp power circuit is presented. And finally, we describe the

various pieces of hardware we have constructed to support and align the lamps and to perform various photometric measurements.

Under the heading of photometric research we have included two different sets of

measurements on lamp stability and one set on lamp characterization. The two experiments

on lamp stability are a study of the drift of a specific type of lamp that may be used as

a standard of geometrically total luminous flux and a study of the reproducibility of the

output of a type of lamp that is currently used as a luminous intensity standard. The lamp

characterization experiment deals with the orientational dependence of the output of three

types of lamps that have been used as either luminous intensity or spectral irradiance

standards

.

*National Bureau of Standards Research Associate from the Electrical Testing Laboratories,
2. Instrumentation

2.1 Photodetector Amplifier

Introduction :

One critical aspect of procedures for the measurement of light is the method used for

measuring the rather small electrical currents produced by photosensitive detectors. Two

of the most common types of these detectors, the selenium barrier-layer cell which has been

used for many years in photometry at NBS, and the silicon photodiode now being employed in

experiments here, are essentially current sources. It has been found that they must be

operated into a very low impedance circuit in order to maintain a linear relationship

between the illuminance incident on these detectors and the resultant current output. The

device used to accomplish this task, besides having a very low input impedance, must be

quite stable, must be linear over the range of currents encountered, and must have a low

noise characteristic. In addition it must be sensitive enough to handle the currents

involved, which typically range from a tenth to a hundred microamps.

In the past, two methods were used at NBS to fulfill the above requirements. These were essentially current balancing techniques which created an effective zero impedance

across the photodetectors . One method, described by Barbrow [l] , involves balancing the

current from a photocell against that from a stable source supply. The other method shown

in figure 1 balances the output current of two photocells to achieve a low impedance. Each

photocell viewed a different source and a null was achieved by varying the distance between

the comparison source and the receiver. These techniques are fairly simple and fulfill the

requirements of low input impedance and high sensitivity. However, these circuits are somewhat cumbersome to use, the stability and linearity are open to question, and they are difficult to adapt to an automated data acquisition system.

A simple experiment to compare a commercially available DC current to voltage con- verter-amplifier with these earlier methods indicated that the signal-to-noise ratio and

the stability of the current to voltage converter were at least as good as the current

balance and the photocell balance circuits. Because of this one would expect a notable

improvement in measurement capability by utilizing state-of-the-art operational amplifiers.

It was therefore decided to design and construct a very stable, sensitive, low noise DC

current to voltage converter using an operational amplifier with good stability and noise

specifications

.

Operational amplifier principles :

A few basic principles of operational amplifiers which make them suitable for the

present application will now be discussed. For a detailed treatment and derivation of

some of the following expressions, see e.g. Graeme et al. [2]. Operational amplifiers are simply high gain amplifiers, often having two differential input terminals and a single

output. There are certain useful properties which a so-called perfect or ideal operational

amplifier would possess. These are an infinite input impedance, Z. ; a zero output impedance, Zq ; instantaneous response time, implying infinite bandwidth; infinite internal or open loop gain, A; and output voltage Vq such that

V = A(V2 - V T

) (1)

where V2 and Vj are the two input voltages. The ways in which the device can be used

depend largely on the type of feedback network employed. Figure 2 shows the basic con- figuration in which the operational amplifier (op amp) is used as a current amplifier, or more specifically, a current to voltage converter. In this diagram a typical real photocell of near infinite impedance is represented by an ideal negative current source i with

infinite impedance coupled with a finite impedance R in parallel. The equivalent voltage

source is shown in the insert for ease of analysis. In this case the positive polarity

input is tied to common so that the voltage drop across the op amp inputs can be

1 Figures in brackets indicate the literature references at the end of this paper.
STANDARD OR

TEST LAMP

tt

H Dfixed

COMPARISON

LAMP

<P

'adj.

PC. +

It

IP

PC. -

<D—»

Figure 1. Balanced photocell circuit. This figure depicts a system in which

the output of a comparison photocell (P.C.) is successively balanced

against that of a photocell measuring the illuminance from a standard

lamp and that from a test lamp. Values of D a(^j , the adjustable distance

between the comparison lamp and photocell, for the two balanced conditions yield the intensity of the test lamp:

I D

2 s s

*

Figure 2. Basic current to voltage converter circuit. The dotted insert shows

the equivalent voltage source.
represented by V

g

. This is called an "inverting circuit", since the polarity of the amplified signal will be changed in polarity. The properties mentioned above now imply that

V = -AV as A -+ <*> (2)

and, since all the current i must flow through the feedback network because of infinite

input impedance of the op amp,

e - V V - Vn

1 s = s

u 3) R R ^ s f

From eqs. (2) and {3.

f

and thus the input impedance of this circuit is

V R

z

s = rrfi (5)

s

Hence in the case of infinite or near infinite gain (A -> °°) the impedance is quite low,

practically zero. Equation (5) also implies V is approximately zero for finite signals i Because of this well-known condition in which the signal input is practically at common potential (i.e. V =0, virtual ground) and because the circuit input impedance is very low

this is an excellent device for measuring current sources. Note also that

i = e/R = -V /R for A ->- °° implies the current i is independent of the feedback resistor

s s o f s R . Changing R alters V , but has no effect on i . The closed loop gain of the circuit

which can be expressed as the ratio of the output voltage to the equivalent source voltage

gives a measure of the amplification of unwanted op amp noise voltage and offset voltage.

From eqs. (3) and (U),

V° /e

>s/R f^1+A ) + X

* (6)

:

If R - R , then this ratio is approximately one, for large A, hence this circuit is often

called a unity gain amplifier. Therefore, the voltage noise in this circuit is not very

important unless R becomes greater than the photocell impedance. High frequency current

noise can be a problem at these high impedances. To overcome this a small capacitor can be placed in parallel with R as a filter.

Current to voltage converter — first version:

With this background let us proceed to the design of the first version of a current

to voltage converter. This work was initiated by Dr. Bruce Steiner. The final design and

construction was done by Mr. Louis Marzetta of the Electronic Instrumentation Section at NBS. The schematic diagram is shown in figure 3. The heart of this device is an Analog

Devices Model 310 J varactor bridge operational amplifier. The most important characteristics which this op amp possesses for the present application are its stability (input

offset voltage drift of ±30 yV/°C; ±100 yV/# power supply drift) and its low input noise

characteristic (10 yV p-p voltage noise for 0.01 to 1 Hz and 10 yV rms voltage noise for

1 to 100 Hz; 10-15 A p-p current noise for 0.01 to 1 Hz and 2 x 10~ 15 A rms current noise

for 1 to 100 Hz). Using the highest feedback resistor of 10 megohm and no filtering

capacitance, which is the worst possible case, this means any current noise to be converted

along with the signal is still a factor of 10° smaller than the signals encountered at this

level (about 0.1 microamp). Hence current noise does not pose a problem. Furthermore,

because of the unity gain configuration, voltage noise will only contribute about 10 yV

noise on any given range: this is about 10 1* less than output voltages generally encounterei

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It is important to have very stable feedback resistors in the circuit. For this reason

0.1$ tolerance, low temperature coefficient (50 ppm/°C) metal film resistors were chosen.

These provide 0-10 volt output ranges for input currents from 0.1 to 100 microamps.

Low leakage capacitors were used in all critical circuit locations because of the high

sensitivity of the op amp and to maintain good accuracy in the transfer through it. A

small capacitance is placed in parallel to limit the bandwidth enough to prevent misbehavior due to high frequency current noise.

The second stage Analog Devices Model kh K op amp which also has a low noise voltage

characteristic is used as a noninverting voltage follower which provides a well isolated

low impedance voltage output. Its main purpose, however, is to provide the ability to

select a given RC time constant filter independent of the feedback range selected. Five

selectable capacitors in parallel with a two megohm resistor yield instrument time

constants of 0.1, 0.3, 1, 3, and 10 sec. for averaging of noisy signals. An output voltage

meter switchable to three ranges (0.1, 1.0, and 10 volts full scale) gives an indication of

output, although in most cases data are recorded by reading the voltage output with a digital voltmeter.

Provision was made for bucking out a signal current of either positive or negative

polarity. This is supplied by a divider circuit which introduces ±0 to 0.1, to 1.0, or to 1.5 microamps of current from the power supply into the signal input of the op amp.

An allowance was also made for voltage biasing a photodetector if desired. The

voltage bias, which appears across the signal input leads, can be selected from the power

supply internally, providing plus or minus to 15 volts. Alternatively the bias can be

switched to a rear panel input which allows the use of an external bias source. The

Analog Devices Model U0J is used as a noninverting follower to allow good isolation and

high input impedance for the voltage bias source, yet a very low impedance is maintained

at the signal input leads for the photodetector current source. With the switching used

one can connect the return signal lead to either a positive or negative internal bias, an externally applied bias, common potential, or an open circuit.

There are several more design features of this instrument that are not evident in the

schematic diagram in figure 3. First, the power supply used was a modular unit constructed

to power operational amplifier circuits with good stability and low noise. Second, to

minimize any AC pickup from this supply, the entire unit and its AC power input cord are located in a separate compartment shielded from the rest of the instrument. Third, the common of the circuit has been left floating, with a terminal on the rear panel to allow

a user the option of grounding the common. Finally, all inputs and outputs are on U-pin

plugs which follow this convention: Pin 1 - chassis ground, Pin 2 - common, Pin 3 - low

or return signal lead, Pin h - high or input signal lead.

Current to voltage converter checkout :

After completion this unit was subjected to extensive usage and checkout procedures

which will now be briefly described.

In order to get an approximate value of the voltage noise for this device, its input was open circuited to simulate the high impedance from a current source. The output was monitored with a five digit, dual-slope integrating digital voltmeter (IDVM) sampling with

a 1/10 second gate, which had an average normal mode rejection ratio of about 10 db or

less for the frequencies encountered (except for harmonics of 0.1 second where it is

considerably greater). The voltage noise registered under these conditions for the maxi- mum instrument bandwidth of - 10 Hz was about 10 yV, independent of feedback range.

To determine an approximate level of stability, the input was again open circuited,

and the output read with the IDVM. A constant signal input was generated simply by

introducing a current through the bucking circuit. This served as a test of both the

stability of the operational amplifier and that of its internal power supply. Output was read automatically every 20 minutes with a data acquisition system. The output was found

to vary only a couple of parts per hundred thousand over a period of eighteen hours.

Linearity was checked using the following procedure. A picoammeter source was used
to generate a current, and a Leeds and Northrup Model K-3 potentiometer was employed for

measuring current and voltage. This was done in conjunction with a voltage divider (Leeds

and Northrup volt box, Model 7592) used in the voltage measurements and a 10,000 ohm metal

film resistor of excellent stability characteristics used for the current determinations.

The procedure was to measure a set current from the picoammeter source with the potentiometer, then switch this current into the operational amplifier and record the voltage output

with the potentiometer for each feedback resistor. The process was then repeated for

another current. Three different ranges of input current were tested. They were: 0.1 to 1.0 yia in steps of 0.1 ya, 1.0 to 10.0 ya in steps of 1.0 ya, and 10.0 to 100.0 ya

in steps of 10.0 ya.

Analysis of the linearity data was done by fitting a straight line to voltage out versus current in for each feedback resistor and for each of the three sets of current

values, resulting in thirty curves. The results indicate the device is linear to within a few tenths of a percent for all currents encountered, and if one chooses the feedback

resistor so that a signal of about one volt or more is put out (as is usually done in

actual practice), then linearity is within a few hundredths of a percent. These linearity

results are undoubtedly limited by the experiment, and not the op amp itself, since

experiments elsewhere [3] have shown that operational amplifiers used in this way are linear even over a greater range and to a greater degree than indicated by the results of

this experiment. This work was done primarily to ascertain that there were no malfunctions

which might manifest themselves as a grossly nonlinear output response.

In summary, this current to voltage converter appeared to be quite satsifactory over

the range of precision and accuracy required for intended laboratory use. However, it was

found during actual use that in order to attain the low noise levels expected from the

manufacturer's specification, it is necessary that the op amp common be grounded rather

than floating. When this connection was made the noise decreased by a factor of ten.

Current to voltage converter — second version:

As might be expected it became apparent that several improvements could be made on a second design of a current to voltage converter. First, it was thought desirable to be

able to reverse the input with a switch to accommodate those photodetectors which had been

wired with a reverse polarity. Second, it might be useful at times to have a greater

bandwidth than - 10 Hz. This could be provided by a switch that in one of its positions

places no capacitance across the second stage op amp, thus allowing a much faster time

response (of the order of several microseconds). Third, a more sophisticated filter, such

as a three pole filter giving a higher filtering ratio with a smaller inherent time

constant would be desirable. Fourth, it was found there were times when even more gain

would be desirable: an additional feedback resistor of 30 megohm would give a maximum

useful sensitivity of 0.1 volts output for 0.003 ya input. Also, a switch and resistor

installed in the noninverting second stage feedback network would permit one to switch in a factor of ten voltage gain. This would result in a maximum sensitivity of 0.1 volts out for 0.3 nanoamps in. The final change desired would be to install an input socket to

include the option of introducing a bucking current from an external source. This would

allow use of a bucking current greater than that supplied by the internal bucking circuit.

A second current to voltage converter was constructed which incorporated the above

mentioned modifications. The circuit diagram is shown in figure k. Instead of the

varactor bridge, however, an Analog Devices Model 142K FET operational amplifier was used

because of its even lower input noise specification and smaller size. Testing proceeded

in about the same manner as for the first device. The results are summarized below.

Noise and stability appear to be of about the same level as with the first model, with

one exception. There was initially a slight degradation in voltage noise (to about 20

microvolts) when the time constant was set at zero. It was range independent. The test

was done with the same IDVM as in the previous checkout. Linearity of this instrument

within experimental limits was again found to be the same as that of the previous one. The

extra feedback resistor was useful, but the optional gain of ten on the second stage, since

it also amplifies the noise voltage by a factor of ten, has not been useful as yet. As with the previous instrument, it has been necessary to run the common at ground potential

to reduce noise effects. There initially was a problem with the ^2 K op amp. It became
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unstable and put out maximum voltage with no signal on the input. This was thought to be

due to the extremely high intrinsic impedance and sensitivity of the FET op amps. Initially the protective diodes for the k2 K op amp were mistakenly connected directly from

the negative to the positive input leads. The problem was corrected by connecting the

diodes directly to common instead of first to the positive input and by installing a different k2 K op amp. The new op amp seemed somewhat less susceptible to this anomaly

and also exhibited a lower voltage noise level of less than 10 yV.

In conclusion, both of these instruments have performed very well in their intended

usage. It is anticipated that similar instruments will be constructed for future use in

photometric and radiometric applications at NBS.

2.2 Lamp Power Circuitry

Introduction :

In order to obtain a steady light output from a tungsten filament lamp for use in

deriving standards for radiometry and photometry, a very stable source of electrical power

must be provided for the lamp. It is known empirically that, for a typical gas filled

tungsten lamp, the light flux is approximately proportional to the 3.^+ power of the voltage

and the 6.2 power of current [h] . Thus, if it is desired to hold the flux output to within

0.01$ of a constant value, then the voltage must be held to within about 0.0029% and the

current to within 0.00l6%. These are fairly stringent requirements which must be met by

the power supply and circuitry over the time of the measurement involved. In some cases this may be several hours. The following material discusses a type of supply and circuit

which has been found applicable to the above mentioned requirements.

Lamp current and voltage measurements :

Figure 5 shows a schematic of the circuits which are typically used. If it is

desirable to make measurements of the load voltage and current with a potentiometer, in

order to assure maximum accuracy, then a voltage divider network or "volt box" and current

measuring shunt must be employed. This divider has an impedance which is low enough

(typically 750 ohms /volt) that a significant amount of current will be diverted through it

from the load. Hence some judgement must be exercised in choosing the location of the

current measuring shunt relative to the measurement of the voltage. If the parameter of

greatest interest is the voltage across the load, then the position of the current

measuring shunt should be as shown in part A of figure 5- Only the voltage divider appears

across the load. This is in keeping with good measurement practice since the potentiometer

can be at a low potential in this configuration, thus reducing the chance of measurement

error due to stray leakage. The current actually measured through the shunt can then be

corrected by calculating the amount of current diverted from the load by the voltage

divider.

If, on the other hand, the load current is the parameter of greatest interest, then

the current measuring shunt should be as shown in part B of figure 5. This will allow a true measure of the current passing through the load, and the voltage measured across the

load and current shunt can be corrected by using the known resistance of the current

measuring shunt. The inconvenience caused by having to correct for the presence of the

voltage divider can be eliminated by using instead a high input impedance digital voltmeter.

The impedance of a high accuracy digital voltmeter is typically 10 ' ohms or more; therefore,

it will draw negligible current from the circuit.

Another decision to be considered is whether to regulate the voltage across the circuit or the current through it. There are certain advantages and disadvantages to each

approach. The well regulated power supplies currently available monitor the voltage across

a load impedance using remote error sensing leads. These sensing leads complete a feedback

circuit that controls the current or voltage by supplying a small bucking or boosting output. Taking these facts into account, the easiest way to power the lamp circuit is to

simply connect it to the supply power output with the remote sensing leads connected

directly to this supply output (circuit input) as indicated in part A of figure 5. The error sensing leads were not connected directly across the load, as might at first seem appropriate, because they are active current carrying leads, and connecting them in such
POWER r --^l

SUPPLY i ^ -^

i _

u-;:fl +

CURRENT MEAS.

SHUNT

A/WPOT

DVM

r

JdvmI

v

L

T

B

X

Hpot]

CURRENT

MEASURING

SHUNT

CURRENT

CONTROL —VW—

<

! POWER

Z_ ! SUPPLY

i

~=t=- SHUNT

B

Figure 5- Lamp power circuits: A, voltage controlled; B, current controlled.

The locations of the remote sensing leads from the power supply are indicated. The appropriate positions of the "high" lead of the

digital voltmeter and potentiometer for the measurement of load

parameters are indicated.

10
a way could conceivably cause errors in determining the actual voltage and current parameters of the load itself.

Because of several factors, for instance, shifting contact potentials at the load

terminals due to lamp replacement or load resistance changes (e.g. that of a lamp filament)

that are a function of time, it has often been found desirable to regulate the current

through the load rather than the voltage across it. This is accomplished by sensing and

controlling the voltage drop across a current control shunt which is shown in part B of

figure 5. In this case the remote error sense leads are used to maintain a constant voltage

across the control shunt. This results in a constant current being supplied to the circuit.

More details of this method will be discussed later.

Basically, then, the lamp power circuit consists of a stable power source; a current

controlling shunt used with the supply to regulate the current flowing in the circuit;

another shunt used to measure the current flowing through the load; a relatively high

impedance voltage divider across the load to allow potentiometric measurement of the load

voltage; a potentiometer for precise continuous measurement of load voltage or current;

and a digital voltmeter for digital measurement and output of these parameters. The

location of the electrically "high" measuring leads of the potentiometer and digital voltmeter with respect to ground for measurement of various parameters is indicated in

figure 5-

In addition to the above considerations, several more comments on this circuit are in

order. First, the location of the system ground is significant. For stable high accuracy

and precision measurements, it is desirable to have the potentiometer and peripheral devices

properly guarded. Also one side of the potentiometer, voltage divider, and current shunts

should be at ground potential to minimize stray leakage currents, as mentioned previously.

This is accomplished by the configuration shown in figure 5.

Second, although the power supply used could be operated with both terminals above the

ground potential, in the circuit in figure 5 one side is very near ground potential, since

the current control shunt is normally only a fraction of an ohm. For the supplies

presently used it is preferable to have the positive output rather than the negative one at ground potential, hence the polarity shown was adopted.

Third, the current shunts must be overrated so that they will not heat up and change

resistance values at the current levels used. Low temperature coefficient shunts

(<30 ppm/°C) with a power rating at least ten times that actually required are desirable.

Fourth, a four terminal system with separate leads for voltage measurement should be

used throughout the circuit.

Finally, the potentiometer, voltage divider, and digital voltmeter should be guarded

and of reasonably high quality, capable of precisely measuring at least five significant

digits

.

Stable DC power supplies :

Using the apparatus described above with loads of a size typically encountered in our experimentation, the Kepco Series JQE power supplies were found for our purposes to give

adequate regulation in both the current and voltage modes, and the Hewlett-Packard Harrison

series performed similarly in the voltage mode. In order to maintain some versatility in

the maximum voltage and current output capability, two supplies are used together in

parallel for higher currents and in series for higher voltages. The output of this type of

supply can be remotely programmed with a variable resistance. In order to run two of the

supplies together in the manner referred to above it is preferable to program only one and

have it control the other supply. This is often called the "master/slave" combination.

Some difficulty was initially encountered in determining how best to run these supplies in

the "master/slave" configuration in series and in the current regulating mode, but after

some experimentation the arrangement shown in figure 6 was settled upon. The details of

how these supplies operate can be found in the manufacturer's handbooks and operating

manuals

.

11
LOAD

dCONTROL _ d "SHUNT ~ KS

Figure 6. Lamp power supply circuit, master/slave, constant current, series

configuration using Kepco JQE series power supplies. The bridge

circuits are internal to the power supplies and the numbered

circles represent the external connections on the instrument.

(See the manufacturer's instruction manual for more information.)

12
For the Kepco power supplies used in our experiments, R , the current control shunt, was chosen such that at maximum current about an 0.5 volt drop occurs across it. The

current control, R , a 0-500 ohm potentiometer in our case, should be a high quality, low

temperature coefficient device. The voltage output of the slave supply is equal to that of

the master supply multiplied by the ratio of the slave supply voltage control resistor, R , to the tracking resistance, R . . Since R

vc

is 60 Kfi, R+ was chosen about 30 Kfi, so that

with the R of the slave supply set at about the halfway position, both supplies contribute

equal amounts of power. The power ratio can be altered at will by adjusting Rvc

• It is

apparent that R+ should also be a high quality resistor. Two diodes are placed across the

individual supply outputs to protect them against possible transient reverse potentials.

This provides a harmless bypass for any reverse current. Each diode, of course, must have

a reverse breakdown voltage greater than the maximum voltage output of the power supply.

The diodes should be able to carry the maximum short circuit current that the power supplies

are capable of producing. It is advisable to use not only heavy power leads, but also

heavy shielded sense and control leads to minimize stray noise pickup.

The supplies and circuit described have been used to regulate current through resistive

loads typical of tungsten lamps at maximum supply voltage capability and approximately half

maximum current capability. Under these conditions, the degree of regulation is about one part in 10 5 over a period of about fifteen hours. Performance appears to be degraded some- what at higher current output levels. The system is capable of regulating in the voltage

mode at all levels of output to the order of one part in 10 5 for periods of twelve hours.

The circuit has proven to be stable, versatile, and convenient for automation, particularly

when using the digital voltmeter. The potentiometer is useful to maintain a check on the

digital voltmeter calibration and to provide simultaneous and continuous analog monitoring

of any desired parameter in addition to the digital measurements of the voltmeter.

2.3 Mechanical Instrumentation

Optical bench enclosure and baffles :

Two Ealing Double Rail optical benches are presently in use in photometric research:

one is 3m and the other is 5m long. Each optical bench is mounted on hardwood surfaced

laboratory benches that have been bolted to the floor. The bench tops are covered with

black suedine cloth (manufactured by Vertipile, Inc., type FF8-718U) and the cloth is held

in place around the outside edge of the table by iron strips one inch wide.

Bolted to the table top at each corner is a channel-frame column (such as Unistrut or Globestrut) kO inches high. These four columns support a channel- frame rectangle which

spans the length and width of the table. This structure serves as a support for the baffles

and for the materials which form a light-tight enclosure. The baffles are hung from wheel

assemblies which roll inside the length of the channel. Black suedine covered aluminum

sheets cover the top of the enclosure and several sets of black drapes about 30 inches

wide cover the sides. The drapes are made of a double thickness of the black suedine

material, back to back, with a sheet of black polyethylene between them. Strip magnets

are sewn into the material around the edges of each drape to hold it closed against the

iron strip along the table edge and against thin, suedine covered iron sheets about

8 inches wide hung in the spaces between the drapes.

By housing the optical bench with magnetically secured drapes, each section of the

bench is made independently and rapidly accessible. In addition to being opaque, the

drapery material is of very low reflectance in order to minimize scattered light. The

baffles are made of aluminum sheet cut to fit within the channel-frame enclosure and

covered on both sides with the suedine cloth. The cloth extends about one inch on the

sides of each baffle to meet with the drapes which billow slightly. Several different size

baffles are used and since the baffles clip onto the movable wheel assemblies they can be

easily inserted, changed or moved to new positions.

Optical bench alignment :

The optical benches have been mounted on their respective table tops in a kinematic

manner. The procedures used may be generally useful and will therefore be summarized for one (5m) of the benches.

13
The 5m "bench has eleven supporting posts each having two leveling screws as shown in

figure 7A. Each supporting post rests on an 8" x lV' x h" aluminum supporting plate. One

of the leveling screws in each of the four supporting posts located at the ends and adjacent

to the center of the "bench has a conical tip. These tips rest in three Vee grooves and a round hole in their respective supporting plates as shown in figure 7B. The remaining

leveling screws have round tips or bottoms and rest on flat portions of the supporting

plates

.

The optical bench was aligned relative to the optic axis defined by the beam from a one milliwatt He-Ne laser in the following manner. The laser was mounted on a channelframe platform separate from the structure which encloses the optical bench. It was then

aligned so that the beam would pass through the center of a baffle hung anywhere within the

channel- frame enclosure; the track in which the wheel assemblies rolled having previously

been made horizontal with the aid of a spirit level. The optic axis is approximately

15 inches above the optical bench rails.

The optical bench was then made level along both the long and short horizontal directions using a spirit level. Leveling was started at the center support posts and progressed

out to the ends. This procedure had to be repeated several times to make the optical bench

approximately level along its entire length. All the screws holding the optical bench

together were then loosened and gradually retightened. The bench was allowed to rest in

this new position overnight and releveled the next day.

The optical bench was then brought into position relative to the laser beam with the aid

of two pointed rods mounted in carriers with fixed position stems. The height of the rods was adjusted so that the points were at the center of the laser beam. The optical bench

was then positioned so that these two rods could be moved anywhere along the bench and

still intersect the beam. The optical bench was then fixed in place by bolting the three

supporting plates having grooves and the one having a hole to the table top. This alignment procedure resulted in no discernable twist along one half of the bench and 0.2° to

0.3° twisting between the support posts along the mating half2

. The distance between the

laser beam and the bench rails was constant to within 1 mm.

Lairro orientation mounts:

Three different lamp mounts, based on two different design principles, have been used

for the rotational positioning of the lamps relative to the optic axis. In one design,

rotation is accomplished by pivots that are colinear with the three axes of rotation;

whereas in the other design two curved surfaces sliding against each other provide rotation.

In the first design category, the mount employed was originally used to position

radiance standards. A sketch of this mount is shown in figure 8. It is very similar to a pair of gimbals with one-half of the circle cut away. Two pillars attached to the base

support the outer pivots. This pair of pivots forms a horizontal axis to allow a pitch

rotation; that is, a rotation about an axis perpendicular to the optic axis. The semicircular ring attached to these pivots is held almost horizontal by a section of a 7%-inch

radius worm gear which extends down to engage a worm screw.

The semicircular ring has an inside diameter of 7 3A inches. It contains a third

pivot which allows a rotation around the optic axis (roll rotation). The axis of this

pivot is perpendicular to that of the first two. A platform 7 inches in diameter is

attached 8.75 inches below this pivot by means of a vertical metal strip. The platform is

fixed to the axis of a gear and worm assembly identical to the one used for pitch rotation.

The third rotation around the vertical axis (yaw rotation) is accomplished by a small

turntable, Unislide Model A250UTS, mounted on the platform. The lamp socket is then

mounted on this turntable and the height adjusted so that the three axes of rotation intersect at approximately the center of the lamp filament.

The relative pitch and roll angles could be read to a resolution of one minute of arc

2 The 5m bench was shipped in two sections.

lit
SUPPORTING PLATE

A

SUPPORTING PLATES

MAJOR AXIS OF

OPTICAL BENCH

V-SHAPED GROOVE ROUND HOLE

B

Figure 7. Optical bench: A, optical bench support post with leveling screws

on flat plate; B, schematic diagram of optical bench. Only the

three plates with vee grooves and the one with a hole, all of which

mate with the conical support screws, are shown. The flat plates

with round tipped screws are not shown but are situated between

these four supporting plates.

15
YAW

Figure 8. Radiance Lamp Mount.

16
from scales attached to the worm drives, and the yaw angle could he read to a resolution of

six minutes of arc from a scale on the turntable. This mount performed well in reproducing

the lamp orientation in pitch and roll; however, some care had to he taken in repositioning

the yaw angle because of the lower resolution of this adjustment and the lightweight

character of the turntable. This objection is, however, outweighed by the scattered light

problem posed by the presence of the lamp mount structure around the sides and in back of

the lamp. This is especially critical in an intensity or irradiance measurement since the

entire lamp, and hence part of the lamp mount, is viewed by the detector. This mount has,

however, proved quite useful in studying the variations in lamp intensity as a function of

orientation and in other experiments where only relative measurements are needed. For con- venience, this mount will be referred to as the "radiance lamp mount".

In order to eliminate the problem of scattered light from the lamp mount, two mounts

based on the sliding surfaces principle were designed and constructed. One of the mounts

consisted of a convex spherical section sliding in a mating concave spherical section, the

other was a cylindrical section sliding within a mating section. The axis (or axes) of

rotation is (are) then through the center of the cylinder (sphere). Since only a small

section of the cylinder or sphere is used, there are no mechanical supports around the lamp

to scatter light into the detector.

A cross sectional view of the sliding sphere mount is shown in figure 9. The radius of

the spherical surface was 8 inches and the diameter of the section (platform) was 8 inches.

Four thumbscrews (only one pair is illustrated) are mounted symmetrically on the outside

block; that is, along two perpendicular lines. These screws pushed against the inside

spherical surface along two directions parallel to the spherical tangents. This produced a rotation either around the optic axis (roll) or around an axis perpendicular to the optic

axis (pitch). The screw lengths and positions chosen allowed about a 10° rotation in pitch

and roll. The yaw rotation was accomplished by means of a small turntable as described in

the previous mount. As in the previous mount the socket height was adjusted so that the

center of the lamp filament was at the intersection of the three axes of rotation.

In order to read the pitch and yaw variations on this mount, a small mirror was affixed

to the lamp socket and the beam from a one milliwatt He-Ne laser was reflected from it to a scale on the laboratory wall. The laser beam was approximately four inches below and

parallel to the optic axis. With this device the relative rotations could easily be

determined to a resolution of better than 0.1°. No measurements of roll variation were made

with this mount and, therefore, no provisions were made for the measurement of roll angle.

An optical lever similar to the one used to measure pitch and yaw could have been con- structed for this purpose.

The main advantage in using a sliding sphere mount is the elimination of scattered

light from the lamp mount itself. On the other hand, the main disadvantage is the difficulty encountered in making an adjustment. This is due to the many degrees of motion

possible with a sphere. For example, in the adjustment of pitch, the yaw angle might change

slightly because the motion was not firmly constrained to be only around the pitch axis.

This difficulty in maintaining alignment prompted the design of a third mount based on

a cylinder sliding in a cylinder. The rotation is, of course, constrained to be around a unique axis and all orientation adjustments can be made below the lamp socket. The sliding

cylinder mount has been adopted for use in the luminous intensity calibrations performed at NBS. However, since it was not used in any of the experiments described in this paper and

since it is an obvious modification of the sliding sphere mount, further discussion of its

construction will be omitted.

Lamp alignment :

The lamp mounts were aligned relative to the laser beam on the optic axis. That is,

the roll axis was adjusted to be colinear with the optic axis and the pitch and yaw axes were adjusted to be at right angles to the laser beam: this set the zero position of all

three rotations. In order to locate the axes perpendicular to the optic axis a pentaprism [5] was employed. The pitch and roll axes on the radiance lamp mount were located

by means of small holes through the center of the pivots. In the cases where the pivot

was not on the axis, a solid object was set on the lamp mount to intercept the beam. The

IT
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18
object was then rotated about one of the rotation axes and the mount position adjusted

until the laser spot appeared stationary.

As a slight digression it should be noted that in these several lamp mount designs the

three axes of rotation are not all independently adjustable. For example, in the radiance

lamp mount and in the sliding sphere mount, a variation of the pitch angle away from the

zero position rotates both the roll and yaw axes away from their original orientation.

Furthermore, in the radiance lamp mount rotation of the roll angle does not alter the

direction of the pitch axis, whereas, in the sliding sphere mount it does. Therefore, at some higher level of accuracy it may not only be important to specify the lamp orientation

relative to the optic axis but also the device on which the lamp was oriented in the

process of calibration. Since the experiments described in this paper are only relative

measurements and not absolute calibrations, the transferability of lamp orientation does

not pose a problem at present.

After the lamp mount has been aligned relative to the optic axis, the detectors and

the lamps themselves must be aligned to the same axis. In these experiments no attention

was paid to the precise orientation of the detectors and only their position on or near the

optic axis was noted. On the other hand, the effects of orientation on the lamp output was studied and in this case two methods were used to locate or reference the lamp orientation.

The first method has been employed in photometry for many years: it is a visual

sighting technique which employs a plumb line, fiducial lines etched on the bulb and the

filament supports within the bulb. The shadows of the filament supports and the plumb line

projected on the laboratory wall were made coincident to set the zero of pitch alignment.

(Note that this does not necessarily correspond to the zero of alignment for the lamp

mount.) Next the lamp was rotated to bring the fiducial lines into alignment with the

optic axis. This was done either by sighting through the bulb to the detector or by using

the laser beam. This method is not compatible with frosted bulb lamps or with the radiance

lamp mount

.

The other method involves prealignment of the lamp socket before insertion of the lamp.

In this case the lamp base must be of mechanically sound construction so that it can be

reproducibly reinserted into the socket. The lamp base that satisfactorily fits this

purpose is a medium bipost base. The pins are 1/U inch in diameter, at least 3 A inches

long and are spaced 7/8 inches apart. As will be seen, a kinematically sound and compact

socket can be constructed to reproducibly reposition lamps with these bases.

In this technique the socket is prealigned by using a pair of parallel lA inch

diameter rods which fit in place of the lamp. Fixed parallel to the rods is a mirror to

reflect the laser beam onto the laboratory wall. This yields a measurement of the pitch

and yaw orientation of the socket. Alternatively the socket can be positioned to coincide

with the zero setting of the lamp mount. In addition, the use of a jig to align the socket

allows a precise distance measurement to be made to the plane formed by the two rods

rather than to an inaccessible point within the lamp bulb.

Lamp sockets :

The medium bipost socket used in all the experiments described in this paper consists

of two silver plated 3/8 x l 1/8 x 1 1/k inch blocks mounted on a piece of transite. The

lamp pins fit into holes in the blocks and are held by horizontally placed screws. Electrical connections are made directly to the block by means of separate screws. One of the

metal blocks is mounted on the transite by means of a pivot to allow for bulb expansion.

These sockets are manufactured by the Elastic Stop Nut Corporation, Model 1985-AL.

Because the lamp base pins are held against the walls of a cylinder, this socket

reproducibly maintains the pitch and roll alignment of the lamp. However, the yaw alignment is not maintained since one of the blocks can rotate. The following socket was designed to eliminate this deficiency. Although it was not used in any of the experiments

described in this paper, its design was prompted by the results of some of them. Therefore,

a description of it is included here.

Two views of this socket are shown in figure 10. The lamp pins are held by spring

19
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20
tension against two stainless steel blocks. One of the blocks has a Vee groove terminating

in a flat plate. By holding one of the lamp pins against this groove and flat, the pitch,

roll and lamp height can be maintained when the lamps are replaced in the socket: providing, of course, that the same pin is placed in the groove each time. The other stainless steel block is cut from hexagonal bar stock to form a roof shaped piece. When the

socket is closed the pin is held against the "peak of the roof", thereby fixing the yaw

rotation and still allowing the lamp base to expand.

The lamp pins are held by two gold-plated copper "pistons", and the pistons are held

under tension by coiled springs inside the nylon block. The two outside screws shown

protruding from the nylon block serve to close the socket. The remaining four screws hold

the stainless steel blocks and the copper pistons in place and serve as electrical connections.

The convention that has been adopted in the use of this socket is depicted in the

figure. That is, the Vee block is the positive electrode and the lamps are viewed by the

detector from the side of the socket containing the Vee block. In this direction, that is,

looking at the lamp from the detector position, the Vee block is on the right.

3. Experimentation

3.1 Flux Lamp Stability Tests

Introduction :

In the Fifth International Intercomparison of Photometric Units, lamps of a special

type [6,7] were used to represent the various national laboratory units of luminous flux

at a color temperature of 2788 K (IPTS-1+8). They were full wreath filament clear bulb,

gas filled lamps. This intercomparison showed these lamps to be relatively stable. The

present work was undertaken to evaluate further these lamps as possible standards of

luminous flux.

The 200 watt lamps of this type are designed to operate at 95 volts and have a rated

life of 1,000 hours at this voltage. For the International Intercomparison the lamps were

seasoned for 120 hours at the voltage necessary for 2788 K operation (approximately 95

volts), and had their bases plated with a nickel cadmium alloy. For the present test 2\

uncalibrated lamps were procured from GEC , England. These 2k lamps were received with

unplated brass bases and had been seasoned for 20 hours at 95 volts. Subsequently several

lamp bases were plated with either pure nickel, nickel cadmium, or silver. The measurements then consisted of reading the total luminous flux of the various lamps, set consecu- tively at current and at voltage, every 5 burning hours after an initial seasoning of

U0 or 60 hours (including the 20 hours seasoning performed by the manufacturer).

Experimental techniques and equipment :

The lamps were seasoned on regulated AC: six lamps at 102 volts (approximately CIE source A) and 8 lamps at 95 volts. The luminous flux measurements were made after 10 minutes warm-up with the lamps operated on DC in a 2 meter integrating sphere by a substitution method. A blue glass filter (Corning 5900) was used to reduce the effects of non- uniformities in the sphere wall spectral reflectance. The photometer detector was a Weston selenium barrier-layer photocell equipped by the manufacturer with a filter [8]

which modifies the spectral response to approximately match the CIE luminous efficiency

function [9]- In order to reduce the errors due to self absorption of the lamps, a standard (NBS 8380) of the same type and manufacturer was used. This standard had been

previously calibrated including absorption correction as part of the international comparison. The standard was run at the beginning and end of each set of measurements to check

for drifts in the photometer.

During seasoning the test lamp voltages were set on a moving iron AC voltmeter

(3/h% accuracy class). The 2 meter diameter integrating sphere was coated with Burch

sphere paint. The detector was a hermetically sealed, viscor corrected Weston barrier

layer cell (Model 856, YYLSV). The detector photocurrent was measured with a commercial

operational amplifier. The lamp voltage and the current, and the operational amplifier

21
output were read on a digital voltmeter (.003% accuracy).

Results :

The results of the experiment are shown in figures 11 and 12. For each of the test

lamps the data is normalized to the first measured value of total luminous flux. In each

case for the first reading only, the lamps were set at voltage and readings taken of the

flux and current. Subsequently the lamps were set at both voltage and current, as indicated in the figures and flux measured for each setting. Lamps NBS 9135 and 9136 were not

measured at current until 135 hours of burning. Lamps NBS 9138, 9139, 91^0 and 91^3

suffered a filament failure at 85, 75, 90 and TO hours, respectively.

Conclusions

The figures vividly demonstrate the superiority of setting lamps of this type by

current rather than voltage. All of the lamps set at voltage showed a steady decrease in

flux output. This decrease was typically at the rate of 1% per Uo hours of burning. In contrast the lamps set at current increased slightly or held constant within the precision

of the measurements . Previous experience has shown this equipment to have an overall

precision level of about l/k%. As the figures indicate, this was about the precision level

of the present experiment. Figure 12 indicates that the lamps should be seasoned for at least 50 hours before initial calibration.

In the limited time period covered by this test no particular effect due to base

plating material was noted. In the long run, it would be expected that plating with

materials such as nickel-cadmium would offer more corrosion resistance than plain brass.

The occasional out-of-pattern point present in most of the lamp curves is probably due

to variation in the experimental technique, and no particular significance should be

attached to these points. The distinct shift in the flux values at 170 hours for lamp

NBS 9135 run at current is in a different category. The cause of this shift is not known

at this time and is particularly hard to explain since the shift is not mirrored in the

flux values measured at voltage. It is unlikely that the shift is due to changes in the

sphere or electrical measuring setup since other lamps measured on the same run in the same apparatus do not show a corresponding pattern. Shifts of this kind emphasize the desirability of running more than a single standard at any given time.

The lamp failures noted above present a problem. Three out of the six lamps run at 102 volts failed. Although the lamps were designed to operate at 95 volts, the manufacturer states he knows of no reason why they could not be run at higher voltage with, of

course, a corresponding reduction in life. He further states that this test is the only

one he knows that has shown this effect. In each case the failure was one of filament

breakage. It would appear that some critical parameter has been exceeded and hence high

failure rates can be expected at this voltage. We have decided to use these lamps only at color temperatures of 2788 K or lower.

It should be noted, particularly since the manufacturer states our experience is

unique, that these tests were conducted on a limited sample from a single production run and may not be indicative of the performance of similar lamps from other production lots.

3.2 Orientational Dependence of Relative Luminous Intensity

Introduction :

In the calibration of the intensity or irradiance from a lamp, it is obviously

important that both the direction in which the lamp is viewed and the lamp orientation be

specified. This is necessary simply because a lamp is a nonuniform source [ 10,11]. The

magnitude of the nonuniformity and consequently the extent of the possible error in the

calibration of the lamps used as standards at NBS has not been documented in sufficient

detail. The study that will be reported here was, therefore, carried out in order to get

a more detailed picture of this effect and to identify the cause.

The terms used in this paper to describe the three orientational degrees of freedom

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are the nautical terms: pitch, roll and yaw. They were introduced in the discussion of

the lamp mounts. Results for three different types of lamps will be given here. They

are (l) 500 watt clear T-20 "bulb (2% inch diameter, tubular), medium bipost lamps with

C-13 filaments (single coil with 7 or 9 supports in a monoplaner "W" configuration).

(2) 100, 300, 500 and 1000 watt frosted bulb, medium bipost, C-13 filament lamps. The

100, 300 and 500 watt lamps of this type had T-20 bulbs and the 1000 watt lamp had a T-2U

(3 inch) type bulb. (3) Tungsten-halogen lamps with a CC-8 type filament (coiled-coil

supported only at the ends) and a 3A inch diameter, tubular, clear quartz envelope. Lamps

of type 1 and 2 have been in use at NBS as standards of luminous intensity and type 3 as standards of spectral irradiance.

Equipment :

All the lamps were seasoned for 2% of rated life at rated volts. The photometric and

electronic equipment used were described earlier. However, the detector amplifier for most

of the measurements was a commercial DC current to voltage converter feeding into a five

digit integrating digital voltmeter. For the pitch and yaw measurements of the clear T-20

bulb, C-13 filament lamps the sliding sphere mount was used. For all other measurements,

the radiance lamp mount was used. In both these setups, the angles could be measured with

a resolution of at least 0.1°.

Photopically corrected [8] selenium barrier layer cells and uncorrected silicon photodiodes were used as detectors. The results from both types of detectors were identical

and, therefore, their specific instance of use will not be identified. The source to

receiver distance was typically 2.5 to 3m and the detector diameters ranged from 0.5 to

U cm.

Results and discussion :

Figure 13 shows the variation of the relative intensity with the pitch and yaw angles

for the clear bulb C-13 filament lamps. Four different detectors were used simultaneously.

To obtain these plots a correction was made for the detector position relative to the optic

axis. The most striking feature of this figure is the large variation of the intensity

with the pitch angle: on the steepest part of the slope the intensity changes by as much

as 2% per degree. Over a greater range the curve somewhat resembles a sine wave (see

figure IT). This pitch dependence appeared to be common to all the lamps of this type that were measured. The positions of the maxima varied from lamp to lamp falling approximately

in the range ±2° from the aligned zero position (relative to the plane of the filament

supports). The relative intensity versus yaw angle plot in figure 13 is also typical of

the lamps studied. However, there did not appear to be a correlation of the peak intensity

with the aligned zero position and the curves did not appear to have a pattern over the

range studied. The steepest slope was about 0.5% per degree. On studying the effects of

different roll positions on the luminous intensity for these kinds of lamps, the effect

could not be detected at the 0.2$ level of the noise.

Figure \h shows the pitch versus relative intensity plots for the 100, 300, 500 and

1000 watt inside frosted bulb, C-13 filament medium bipost lamps. The effect follows

approximately a cosine curve, as shown by the solid lines. The total variation of output

is almost 0.5% over the range covered and appears to be independent of the lamp size. At the 0.2% level of the noise there were no discernable effects due to a change in the yaw

or roll angles over a range of ±5°-

The pitch and yaw variation of a typical CC-8 filament lamp is shown in figure 15.

The lamps were operated with the filament in a vertical position, that is, the axis of the

coil was vertical. The results for these lamps very nearly resemble those for the clear

bulb C-13 filament lamps, except that in the region near the peak of the intensity versus

pitch curve for the CC-8 filament lamps there is a slightly greater flat region. The yaw

variation also appears to be smoother in the case of the CC-8 filament lamps. These are subtle differences, however, and a larger number of lamps would have to be examined before

any general conclusions can be drawn.

25
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bulb C-13 filament lamps. The different point symbols indicate

measurements made by four separate detectors of intensity versus pitch dependency at several yaw angles and intensity versus yaw

dependency at several pitch angles.

26
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emitter.

27
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28
The origin of this effect :

Having established the order of magnitude of the orientation effect on the luminous

intensity of these lamps, two experiments were performed to disclose the sources of the

effect. The coiled structure of the lamp filament and possible lens effects due to

striations in the envelope seemed to be the most probable causes of a nonuniform distribution.

In the first experiment a group of three lamps was obtained which had specially

designed filaments. These filaments were essentially C-13 filaments except that they were

not monoplanar. The two horizontal rods which hold the filament support pins were set at about 1*5° instead of being parallel to each other. This filament design was motivated by

the suspicion that the pitch effect in regular C-13 filament lamps is due to the shadowing

of the rear part of the filament by the front part. This kind of shadowing is inevitable

in a coiled filament. If all the segments (lengths between support pins) of the filament

are in the same vertical plane, as they are in regular C-13 filaments, then the extent of

shadowing at any particular pitch angle is almost the same for each segment of the filament.

The contributions of the individual segments of the filament to the pitch dependence therefore add up or, as one could say, "interfere" constructively to give a large pitch dependence for the whole lamp. In the non planar C-13 filament design used in the special lamps,

one would expect the pitch dependences of the different segments of the filament to peak at different pitch angles. These dependences would thus combine in such a way as to yield a more flat pitch dependence curve for the lamp as a whole. Pitch dependence curves were run

for the three lamps of this type. Figure l6 shows a typical pitch dependence curve. Here

the pitch dependence on the steepest part of the curve is less than 1% per degree change in

the angle: approximately half of the slope in the curve of the monoplanar C-13 filament.

This leads to the conclusion that most of the effect is due to the shadowing effect of the

filament coils, and the fact that in a regular C-13 filament the different segments of the

filament are in the same plane.

In the second experiment an attempt was made to obtain an estimate of the contribution

to the pitch effect due to the striations in the glass envelope. Two clear bulb lamps with

C-13 filaments and noticeably striated bulbs were used. The pitch variation of the

intensity was first measured. Then the glass envelope was cut vertically almost to the

base. One half of the envelope was cut away and the remainder was left attached to the

base of the lamp and the filaments were removed. These lamps were placed in front of and

as close as possible to a frosted bulb lamp that had been totally masked except for a small

rectangular area. This area was of approximately the same dimensions and at the same height as the filament in the original clear lamps. The frosted bulb lamp was kept in a fixed vertical orientation and only the sliced glass envelope was moved. A frosted bulb

lamp was used to simulate the filament because of the possible interactions between the

striations of two clear glass envelopes. Figure 17 shows the pitch dependence of the

lamps before they were sacrificed and of their glass envelopes afterward. The variation

due to the envelope is about 1% over a 10° interval.

As a final note, figure 18 depicts one of the more extreme examples of intensity

variation as a function of pitch rotation. The slope is about 10$ per degree at the

steepest points. Such variations were observed on a few of the clear bulb, C-13 filament

lamps studied. It has been suggested that this behavior is due to the planarity and

straightness of the several coils in the filament. If this is true then it is ironic

because of the natural inclination to choose the most symmetric and apparently defect-free

lamps for possible standards.

Conclusions

:

There are two conclusions that may be drawn from these experiments. The first is in

regard to the amount of orientation control necessary in order to reproduce the luminous

intensity output of clear bulb C-13 and CC-8 filament lamps. If no attempt is made to set the lamp at a position of zero gradient in pitch and yaw and if the pathological cases such as the one shown in figure 18 are eliminated, then the greatest pitch gradient one might encounter would be of the order of 2% per degree. Similarly, the greatest yaw

gradient expected would be about 0.5$ per degree. Therefore, in order to reproduce the

intensity or irradiance to about ±0.1$ based on orientational considerations alone, the

29
0.0

PITCH ANGLE (DEGREES)

Figure 16. Relative luminous intensity versus pitch dependence for special

nonplanar filament clear bulb lamp.

30
-5.0 0.0

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5.0

Figure IT. Contribution of glass envelope striations to relative luminous

intensity versus pitch dependence.

31
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32
pitch realignment must be less than ±0.05° and the yaw realignment must be less than ±0.2°.

For the frosted bulb lamp the pitch realignment must be within +0.5°.

The second conclusion is that in clear bulb lamps the major contribution to intensity

variation is due to the coiled structure of the filament. The contribution from bulb

striations is smaller by about a factor of ten.

Taken together, these two conclusions lead to a choice of a frosted bulb lamp as a standard lamp because of the looser restrictions on orientation. Two objections can be

raised against such a choice. First, the realignment requirements quoted above were for

the case of the largest pitch and yaw gradients. The lamps can be oriented to a position

of almost zero gradient in both rotations in order to relax these requirements. Second,

the use of a large source, such as the frosted bulbs, introduces a greater error in the

assumed inverse-square law behavior of intensity standards. The last objection to the use

of frosted bulbs can, of course, be eliminated if the source to receiver distances are large

compared to the size of the source and the detector.

3.3 Intensity Lamp Stability

Scope of the experiment :

This experiment, as originally conceived, had several purposes. The main thrust of

the measurements was to evaluate the reproducibility of six lamps of a type that have been

used as standards of luminous intensity at NBS. The lamps were obtained from two manufacturers. Of the four lamps from manufacturer A, two were selected at the factory for

quality of appearance (e.g. filament centered and vertical, envelope uniform, etc.), and

two were obtained through normal commercial channels. The two lamps from manufacturer B were selected at the factory for quality of appearance.

The lamps were checked for relighting reproducibility in two ways. In one series of

measurements they were relit after a cool-down period but were otherwise undisturbed. In another series the lamps were removed after cool-down and then replaced in the socket before

relighting. In addition to the relighting reproducibility measurements, the lamps were run continuously for sixteen hours to check drift.

Besides monitoring lamp voltage, current, and the output from four different detectors

during each run, the temperature was checked at four positions along the optical bench.

Finally, this experiment served as a "shakedown cruise" for much of the equipment described

earlier.

Equipment and procedures :

The lamps studied were 500 W, clear bulb, medium bipost , C-13 filament, gas filled

lamps. They were seasoned for 2% of rated life at rated voltage (10 hours at 120 V AC).

During each measurement run the voltage was set at 85.OOO V as read on a five digit integrating digital voltmeter. The voltage was maintained by two Hewlett-Packard model 62T^A

DC power supplies set up in a master-slave, constant voltage, series configuration. The

lamps were mounted in the commercial socket described earlier. Although this socket was affixed to the radiance lamp mount, the lamps themselves were not reoriented for each run because of the additional time it would have taken. The reproducibility of orientation

depended, therefore, primarily on the socket.

The digital voltmeter mentioned above had remote programming capability and BCD readout. The voltmeter was controlled by a data acquisition system and its output was recorded

on punched paper tape by this data system. The data system also had the capability of

switching the inputs to the digital voltmeter.

Temperature was monitored with four thermocouples positioned within the optical bench

enclosure. One thermocouple was set about one-half inch away from the back of the lamp

bulb and another was set about twenty inches in front of the lamp and about ten inches

below the optic axis. The thermocouple nearest the lamp was used to indicate the realization of a thermal steady state condition. The thermocouple below the optic axis indicated

the approximate ambient temperature in that section of the enclosure containing the lamp.

33
The other two thermocouples were positioned to read the approximate temperature change of

the detector mount and the approximate ambient temperature near the detector. These thermocouples were switched directly into the digital voltmeter via low-noise (< 5uV) reed

switches in the data acquisition system.

The four detectors were all about the same distance from the lamp and were held

symmetrically around the optic axis in a single mount. Two of the detectors were photopically corrected selenium barrier layer cells and the other two were uncorrected silicon

photodiodes. The detectors were obtained from four different manufacturers. The detector

outputs were switched into the current to voltage converter (first version design) via one

set of switches in the data system and the output of the converter was switched into the

voltmeter via a different switching circuit board in the same system.

About halfway through this experiment one of the selenium barrier layer cells failed

and was replaced with a similar cell. Unfortunately during the process of changing this

detector, the entire mount was moved and could not be returned precisely to its original

position. This meant that the two series of measurements on each lamp could not be com- pared to the same initial detector readout.

Voltage was sensed at the lamp socket and current was measured with a resistor in

series with the lamp. Both of these signals were fed into the voltmeter via the data

system.

In the repeatability measurements , the lamps were run for thirty minutes before

relighting or replacing. All ten measurements described (that is, lamp current and

voltage, four temperatures, and four detector outputs) were taken sequentially by the data

acquisition system once each minute during a run. During the sixteen hour run, the same data readout sequence was initiated every twenty minutes. The readout sequences were initiated by a clock in the data system itself. The time during each sequence was also

recorded on the punched paper tape readout.

Results and discussion :

No significant temperature changes occurred during the short runs except for the

thermocouple nearest the lamp. There was a temperature increase of this thermocouple

which could be correlated with the lamp warm-up measured in terms of either the increase

of the detector output or the filament resistance as a function of time. Temperature

changes recorded during the long runs could not be correlated with the other changes in

the system.

The detector outputs were noisier (±0.1$) than had been expected. It was later found

that this noise was definitely in the current to voltage converter and could be reduced

by connecting the operational amplifier common to ground. This was pointed out earlier in

the discussion of the construction of these current to voltage converters. Because of this

problem it was difficult to compare the relative noise or relative signal differences to

less than ±0.1$ in the output of each detector. Excepting the output of a failing selenium

detector, the relative outputs of the four detectors were identical within the limiting

noise band. That is, any output trend shown by a given detector followed that of the other

three detectors. It was therefore assumed that the observed changes above the noise were

most likely due to the lamps.

Voltage during each run was stable to ±0.002$. Between each run the voltage setting

was reproduced to within ±0.005$.

The lamp output variations are summarized in the table. This table was compiled using

the output of only one of the four detectors, since their outputs were all identical within

the limit of ±0.1$. The "warm-up" is the time required for the detector output variations

as a function of time to decrease to within the noise limit. The columns labeled "repeat"

are the differences between the averages for the first and second 30 minute runs and the

first and third 30 minute runs for each lamp. The averages were taken over the 15 minute

time interval extending from the 10 minute to the 25 minute point of each run. Finally,

the column entitled "average drift over 10 min." is the difference between the output

averaged over the 5 minute intervals between 10 to 15 minutes and 20 to 25 minutes of each

run.

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35
Conclusions :

Several conclusions can be drawn from the table. First, there is definitely a difference in the repeatability of "in-place" and "repositioned" relightings. This was attributed to the lamp socket design because of, first, the inherent inability of this

type of socket to reproduce the lamp orientation and, second, the findings of the lamp

orientation experiments of the last section. The kinematic lamp socket design described

earlier in this paper was shown to be a definite necessity by this experiment.

Second, it appears as if the inherent repeatability of the lamps given by the "inplace" results is of the order of 0.1%. It must be remembered that this is at the level of

the amplifier noise and cannot be entirely attributed to the lamps themselves. The

inherent lamp repeatability remains a quantity to be evaluated by further experimentation.

Third, the average warm-up time for this type of lamp (and voltage) is about ten

minutes and in almost all cases is less than fifteen minutes by a safe margin.

Fourth, there are a disturbing number of large drifts of the output (0.1% or greater) even after the lamp has warmed up (e.g., the second run of lamp 3-70, the first run of

lamp 9160, etc.) indicated in the "Repeat, In Place" column. Again this is close to the

noise limit but appears to be a real effect and merits further study.

Fifth, the tendency of the lamps to drift to higher output at constant voltage is

inconsistent with a simple model of tungsten evaporation leading to higher filament

resistance. This may be taken to mean that the lamps have not been fully seasoned; however, other effects such as thermal etching [12] could account for this tendency. The

data from this experiment are insufficient to determine for these lamps the adequacy of the

"2% of rated life at rated voltage" seasoning schedule typically used in photometry. However, they do point out the need for additional measurements to answer this question.

Finally, there does not appear to be a significant difference between the lamps of

the two different manufacturers or between the "selected" and the "unselected" lamps.

Although this is a very limited sample, it does mean that perhaps one type of lamp (for

example a specific filament or bulb geometry) may be found to be more stable than another

type. It also means that lamps selected for quality of appearance do not necessarily

perform well.

4. Conclusion

The electronic and mechanical instrumentation has performed well thus far and will

probably not be a limiting factor in our experiments in the near future. The problems

that require immediate attention were indicated in the last experiment. They can be classified under two headings: detector characterization and lamp characterization. The

limitations introduced into the calibrations by the lamp and detector reproducibility and

drift need to be determined. Among other things a study of the detector linearity and

spectral response must be undertaken.

The stability and reproducibility of lamps and detectors is presently being studied.

Work on the other problems confronting luminous intensity and geometrically total luminous

flux calibrations is planned. The fact that there is light has been established in the

early literature [13]. The question of how much light there is, however, still remains

with us

.

36
5. References

[l] Barbrow, L. E. , J. Res. Nat. Bur. Stand. (U.S.), 25, 703 (19^0).

[2] Operational Amplifiers, Design and Applications , Ed. J. G. Graeme, G. E. Tobey and

L. P. Huelsman (McGraw-Hill, Inc., New York, N.Y., 1971).

[3] Marzetta, L. A. and Flach, D. R., J. Res. Nat. Bur. Stand. (U.S.), 73C (Eng. and

Instr. ), U7 (1969).

[U] Walsh, J. W. T., Photometry (Dover, Inc., New York, N. Y., 1958), p. 532.

[5] Ditchburn, D. W. , Light (J. Wiley and Sons, Inc., New York, N. Y. , I963), p. 269.

[6] Power, E. B. , G.E.C. Journal, 33, No. 3 (1966).

[7] Recommendation PU, Consultative Committee on Photometry, 6th Session.

[8] Zworykin, V. K. and Ramberg, E. G., Photoelectricity (J. Wiley & Sons, Inc.,

New York, N. Y. , 19^9 ), Chap. 11.

[9] IES Lighting Handbook, Fourth Ed., pp. 1-3, 2-U (1966), Illuminating Engineering

Society, New York, N. Y.

10] Middleton, W. E. K. and Mayo, E. G., J. Opt. Soc. Am., Ul, 513 (19 51).

11] Barbrow, L. E. and Wilson, S. W., Ilium. Engr. 53, 6U5 (1958).

12] Quinn, T. J. , Brit. J. Appl. Phys . , 16, 973 (1965).

[13] Gen. I, 1, 3.

37
form NBS-114A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-594-2

2. Gov't Accession No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

OPTICAL RADIATION MEASUREMENTS:

Photometric Instrumentation and Research

(1970 to 1971)

5. Publication Date September 1972

6. Performing Organization Code

7. author(s) Edward F. Zalewski , A. Russell Schaefer,

Kshiti.j Mohan and Donald A. McSparron

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Task/Work Unit Nc NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same as No. 9.

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15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.)

This document was written primarily to serve two purposes. First, some of

the basic instrumentation which has recently been developed for use in photometry

at NBS is described. The design and application of photodetector amplifiers, lamp

power circuitry, and mechanical instrumentation are discussed. Second, three

photometric experiments are described: the stability testing of some flux lamps

and intensity lamps and the determination of the dependence of relative intensity

on orientation. These experiments and their conclusions have proven useful in

pointing out areas which need further investigation and in planning the directions

of future work.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Instrumentation; lamp orientation; lamp power circuitry; lamp stability; photodetector amplifier; photometry.

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215
REFERENCE

UNITED STATES PARTMENT OF OMMERCE

JBUCATION

'y\

a

^tnton^

NBS TECHNICAL NOTE 594-3

US753

o.5«H-3

U.S.

iPARTMENT

OF

:OMMERCE

National

Bureau

of

Standards

Optical Radiation Measurements:

Photometric Calibration
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3)

a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac

Radiation2—Nuclear Radiation-—Applied Radiation'-'—Quantum Electronics3—

Electromagnetics3—Time and Frequency1 —Laboratory Astrophysics3—Cryogenics3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

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and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

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1 Headquarters and Laboratories at Gaitherslmrg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

* Part Of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

* Part of the Center for Building Technology.
8 1974

°f St3ndards

Y <X<Lt - 'Ref.

c^ Optical Radiation Measurements:

5. Photometric Calibration

Procedures

Velma I. Burns

anc

Donald A. McSparron

Heat Division

Institute for Basic Standards

U- ^< National Bureau of Standards

Washington, D.C. 20234

"lee Wmu cloJ Kicrk no. 594-3

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of

transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary

NATIONAL BUREAU OF STANDARDS, Lawrence M. Kushner, Acting Director,

Issued November 1972
National Bureau of Standards Technical Note 594-3

Nat. Bur. Stand. (U.S.), Tech. Note 594-3, 35 pages (Nov. 1972) CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. 03.46:594-3). Price 60cents.
Preface

This is the third issue of a series of Technical Notes entitled

OPTICAL RADIATION MEASUREMENTS. The series will consist primarily of

reports of progress in or details of research conducted in radiometry

and photometry in the Optical Radiation Section of the Heat Division

and will appear about every six weeks.

The level of presentation in OPTICAL RADIATION MEASUREMENTS will

be directed at a general technical audience. The equivalent of an undergraduate degree in engineering or physics plus familiarity with

the basic concepts of radiometry and photometry [e.g., G. Bauer,

Measurement of Optical Radiations (Focal Press, London, New York,

1965)] should be sufficient for understanding the vast majority of

material in this series. Occasionally a more specialized background

will be required. Even in such instances, however, a careful reading

of the assumptions, approximations and final conclusions should permit

the non-specialist to understand the gist of the argument if not the

details

At times, certain commercial materials and equipment will be

identified in this series in order to adequately specify the experimental procedure. In no case does such identification imply recom- mendation or endorsement by the National Bureau of Standards, nor

does it imply that the material or equipment identified is necessarily

the best available for the purpose.

Any suggestions readers may have to improve the utility of this

series are welcome.

Henry J. Kostkowski , Chief

Optical Radiation Section

National Bureau of Standards

111
1. Introduction

TABLE OF CONTENTS

Page

1

2. Description of Calibration of Inside Frosted

Lamp Standards of Luminous Intensity 2

2.1 Test Lamps 2

2.2 Photometer 3

2.3 Calibration Procedure ]±

2.k Discussion 5 2.5 References o,

3. Color Temperature 10

3.1 Description of Calibration of Incandescent

Lamp Standards of Color Temperature 10

3.1.1 The NBS Color Temperature Scale 10

3.1.2 Test Lamps 11

3.1.3 The NBS Color Temperature Comparator 12

3.1.U Calibration Procedure 13

3.1.5 Uncertainty ±1+

3.1.6 Discussion l£

3.1.7 References 18

3.2 Inside-Frosted Lamp Standards of Color Temperature , p 19

3.2.1 Test Lamps 19

3.2.2 The NBS Color Temperature Scale for

Inside-Frosted Lamps 19

3.2.3 References 20

IV
Page

h. Description of the Calibration of Incandescent

Lamps for Luminous Flux 20

U.l Test Lamps 20

k.2 Sphere Photometer 20

k.3 Standards 21

k.h Calibration of the Test Lamps 22

k.5 Uncertainties 23

k.6 Care and Handling 26

U.7 References 27

Photometric Calibration Procedures

Velma I. Burns and Donald A. McSparron

The National Bureau of Standards supplies calibrations of luminous intensity, luminous flux and color

temperature on a routine basis. The procedures, equipment and techniques used to perform these calibrations

as of October 1972 are described. Details of the

uncertainty information currently available, including

estimates and procedures for determining uncertainties

of the reported values, are also presented.

Key words: Calibration procedures; color temperature;

luminous flux; luminous intensity; photometry; uncertainty.

1. Introduction

The Optical Radiation Section of the National Bureau of Standards

recently announced a new calibration policy for radiometric and photometric standards (NBS Technical News Bulletin, June 1972). Detailed

descriptions of the procedures and equipment used to perform these calibrations are being prepared as rapidly as possible. For the photometric

calibrations of luminous intensity (candela), geometrically total flux

(lumen) and color temperature, new procedural descriptions are now

available and routinely supplied along with the reports of calibration.

This Technical Note has been prepared to bring these descriptions

together in a single document and make them available to people who have

not obtained a recent NBS calibration.

Lamp standards of luminous intensity and lamp standards of color

temperature calibrated in accordance with these calibration procedures

are routinely available as "off the shelf" items from the Optical Radiation Section. Presently such lamps are calibrated twice (three measurements for each calibration) at least six months apart. Prices and

ordering information can be obtained from NBS Special Publication 250.*

Because of the sporadic nature of requests for luminous flux calibrations,

such tests are performed only at infrequent intervals. The calibration

description which appears here applies specifically to a recent luminous

flux test involving some 180 calibrations from 10 laboratories. Requests

for luminous flux calibrations can also be treated on an individual basis

and, for the immediate future, will be performed in a manner very similar

to the present description.

The material presented in this Technical Note has been limited

solely to a description of the methods and procedures presently being

used by NBS. In many cases the presently available uncertainty information is inadequate or incomplete. In the present document the attempt is

*See Measurement Users Bulletin Number h

1
made to present that information which is available and point out its

limitations. Major research efforts in the Optical Radiation Section are now devoted to improving methods and procedures for these measurements

and determining their uncertainties. As improvements are made and as better estimates of uncertainty become available they will be reported in

this Technical Note series and incorporated into the routine calibrations,

2. Description of Calibration of

Inside Frosted Lamp Standards

of Luminous Intensity

Inside frosted lamp standards of luminous intensity are calibrated

at the National Bureau of Standards by a substitution method on a calibrated horizontal bar photometer. The photometer is calibrated at the

time of the measurements in terms of the unit of luminous intensity

(candela) at approximately the color temperature of CIE standard illuminant A (2856 K - IPTS 68) as maintained at NBS.

2.1 Test Lamps

Description

Gas-filled, inside frosted lamp standards of luminous intensity are calibrated by NBS in 100- , 500- , and 1000-watt sizes. The 100- and 500-

watt lamps have T-20 bulbs ; the 1000-watt lamps have T-2U bulbs . They

all have medium-bipost bases and C-13B filaments. The 100-watt and

1000-watt lamps are designed to have approximately 1000 hours life when

operated at 120 volts. The 500-watt lamps are designed to have 500 hours

life at 120 volts.

Preparation

The lamps are seasoned by operating them at 120 volts ac for

approximately 5% of their rated life and an identifying number is etched

on each bulb

.

Orientation

Test lamps are calibrated while burning base down on a horizontal

bar photometer with the identifying number turned away from the detector.

Lamp orientation is accomplished by aligning the lamp socket so that the

lamp posts are held vertically with the plane formed by the axes of the

posts perpendicular to the optical axis of the photometer. The bottom of

the lamp bulb is 10. l6 cm* below, and the lamp pins are equidistant from,

the photometer axis. Source-to-receiver distances are measured from the

*Some of the 500-watt lamps have light center lengths of 7-62 cm

(3 inches). For these a distance of 7.62 cm is used between the photometer axis and the bottom of the lamp bulb. The distance used is stated

in the individual "Report of Calibration" for the lamps.
plane formed by the axes of the hiposts to the sensitive surface of the

detector.

Before calibration the lamps are checked to ascertain that the

luminous intensity varies by less than 0.1$ for (l) a ±1.5° rotation

about a horizontal axis intersecting the photometer axis in the plane

formed by the axes of the posts (pitch) and (2) a ±1.5° rotation about a vertical axis contained in the post plane and intersecting the photometer

axis (yaw)

Operation

All measurements are performed with the lamps operated on dc power.

Electrical measurements are made potentiometrically to an accuracy of

0.02$. After positioning and alignment, the lamps are slowly (15-30

seconds) brought up to the designated electrical operating point and

allowed to stabilize for at least 10 minutes before measurements are made. Normally, the lamp current is set and measurements are made of

the luminous intensity and of the potential drop across the pins of the

bipost base.

2.2 Photometer

Detector and Amplifier

The photometer detector is a selenium barrier-layer photocell [l] 1 equipped with a filter which modifies its spectral response to approximately match the CIE luminous efficiency function [2]. Measurements are usually made at a photocell illumination level of approximately 80 lux.

The entire photosensitive surface is directly illuminated by the entire

test or standard lamp, and no auxiliary optics are used. The photocell

is fully illuminated during the 10-minute stabilization period of the

lamps

The detector photocurrent is measured with an operational amplifier

(current to voltage converter) arranged in a typical closed loop configuration. Thus the photocell is operating into a near "zero-resistance"

circuit (no voltage across the terminals of the photocell) in accordance

with the formula E output = I input x R feedback. A five place digital

voltmeter is used to measure the output of the operational amplifier.

Optical Bench

All measurements are made on a h. 5-meter optical bench. The

optical bench is housed in an enclosure 6l cm wide and 117 cm high. The

enclosure is covered with black "suedine" cloth on all four sides. The

optical axis is 38 cm above the bench and is located approximately 69 cm

figures in brackets indicate the literature references at the end of

each section.
from the bottom, U8 cm from the top, and 30.5 cm from the sides of the

enclosure. Source-to-receiver distances of 1.3 to k.2 meters are typically used. For the 100- and 500-watt lamp sizes, a limiting baffle

with an aperture 7.6 cm wide and 17.8 cm high is placed 25 cm from the

plane of the biposts and centered with respect to the lamp bulb. For

the 1000-watt test lamps, this baffle aperture is 10 cm wide and 23 cm

high. Additional baffles are placed between the source and the detector

to screen the detector from any directly reflected light. Light emitted

by the lamp in the direction away from the receiver is absorbed with a light trap placed Ho cm behind the lamp.

2.3 Calibration Procedure

Photometer Calibration

The photometer is calibrated, at the time of the measurements, in

terms of the illuminance produced at the detector by each of a group of

500-watt lamps of the same type and construction as the test lamps. The

500-watt lamps used to calibrate the photometer are periodically compared

with a group of 10 similar lamps (group NBS 5&12) which represents the

unit of luminous intensity at approximately the color temperature of CIE

standard illuminant A (2856 K - IPTS 68) as maintained at NBS.

An illuminance substitution method is used for the measurements.

500-watt lamps are calibrated at a photometric distance of 3 meters for

both standards and test lamps. This produces approximately 80 lux at

the photocell. When calibrating 100-watt lamps the photometer is calibrated with the 500-watt standards at a photometric distance of 3 meters

(approximately 80 lux) and again with a distance of U.17 meters (approximately U0 lux). The test lamps are then measured at two distances, one distance to produce approximately 80 lux and another distance to produce

approximately kO lux. The 1000-watt lamps are measured at U.17 meters

with the photometer calibrated with the 500-watt standards at a distance

of 2.9 meters (approximately 80 lux).

Measurement Schedule

Test lamps are measured in groups of approximately 18. Normally

8 standards are used to calibrate the photometer. Measurements of the

standards are interspersed before, after and within the group of test

lamps to check for drifts in the detector sensitivity.

Data Reduction

Individual photometer calibration factors (lux per volt output of

the operational amplifier) are computed for each standard lamp. After

checking these factors to ascertain that no significant drift in the

sensitivity of the photometer has taken place during the calibration of

the test lamps, an average photometer calibration factor is computed.

This average factor is used to compute the illuminance produced by the

test lamps. Test lamp intensities are then computed by multiplying the
measured illuminance by the square of the distance between the lamps and

the detector. The entire measurement procedure is repeated at least

three times, each with a different selenium barrier-layer photocell. The

test lamp intensities reported are the averages of these determinations.

2.U Discussion

Uncertainty

In the measurement of a property of a material object, such as the

luminous intensity of an incandescent lamp, an uncertainty statement is an estimate of the possible discrepancy between the reported value and

the physical parameter this value represents, that is, an estimate of

the possible error in the reported value. Such uncertainties are usually based on a statistical treatment of the random variations of the

measurements and on theoretical deductions together with direct measurements of the possible sizes and types of biases that one recognizes may

be present. Of course, any bias not recognized or not measured is not

considered in determining the uncertainty. Therefore, the true error is never known . Its possible value is merely estimated with varying degrees

of sophistication and assurance ranging from that resulting from a few

measurements and an approximate theory to years of investigation and

continued validation using an "exact" theory. No useful way has been

devised to quantify the reliability of the uncertainty. It can be

judged qualitatively only from the extent and sophistication of its

characterization and the degree to which it has been subjected to con- tinuing validation.

Inherent in an uncertainty statement is the concept that it is

unlikely that subsequent determinations of the same invariant physical

parameter for the same material object will deviate from the original

determination by more than the stated uncertainty. Such subsequent

determinations may be in the form of replications (identical theory,

instrumentation and procedures) or complete redeterminations (totally

different theory, instrumentation and procedures) or any combination of

the two.

The totality of the theory, instrumentation, and procedures which

NBS uses in obtaining a given reported value and its uncertainty is

designated the NBS process. Characteristic of a well-developed process

is a complete and sophisticated investigation that led to its establishment. Characteristic of a well-run process is a continuing validation

of the process parameters (precision, checks for possible biases, etc.)

in the form of replications and periodic redeterminations. The greater

the extent and completeness of the fundamental investigations and the

higher the degree of redundancy in the continuing process, the greater

the confidence that the discrepancy between the sought after value and

the value being reported is not larger than the assigned uncertainty.

The photometric chain, which is used by NBS in realizing and maintaining the illuminant A candela, is subject to a number of biases.
These may be considered in terms of the three major steps used in the

generation of the reported values.

A) Platinum point realization. Specific sources of possible biases

include: the effect of impurities on the freezing point of platinum, the

quality of the blackbody cavity and diffraction effects.

B) Photometric transfer to illuminant A. Specific sources of

possible biases are the nonlinearity and spectral response characteristics of the detectors.

C) Substitution calibration of test lamps. Two distinct types of

bias, constant and time dependent, are possible. If the operation of

the working standard lamps does not duplicate in all essential respects

the conditions under which their assigned values were derived or if

these working standards have changed, a constant bias will be introduced

into all measurements. On the other hand, if the photometric apparatus

is sensitive to variations in an uncontrolled parameter, for instance

environmental temperature or humidity, a time dependent (for example,

day-to-day) bias will result.

The different biases will have varying effect on the uncertainty

with respect to the three bases represented by (l) SI candela, (2) the

world mean candela and (3) the NBS candela. For example, biases in the

NBS realization of the platinum blackbody will have a direct effect on the uncertainty with respect to the SI candela, and an indeterminate

effect on the uncertainty with respect to the world mean. The latest

possibility arises because the various national standardizing laboratories have utilized similar equipment and techniques for realizing the

primary standard of light, and thus may all have the same bias. Biases

introduced during the transfer chain will have a direct effect on the

uncertainty with respect to SI and world mean, but no effect on the

uncertainty with respect to the unit as maintained by NBS. Only the

biases of the substitution calibration will affect the uncertainty of a reported value with respect to NBS. The user of a lamp standard of

luminous intensity will usually wish to know his uncertainty with respect

to one or more of these bases. The remainder of this section presents

data and procedures currently used to assign uncertainties to the illuminant A luminous intensity calibrations.

Three biases will affect the uncertainty of a reported value with

respect to the candela as maintained by NBS. These are: (l) constant

biases of the substitution calibration of the test lamps, (2) time

dependent biases of the substitution calibration and, (3) random variation of the measurements. No detailed investigation has yet been made

of the possible constant biases of the substitution calibration. The

uncertainty due to the other two biases was determined in 1970 from a study of 12U measurements on 36, 500-watt lamps and 80 measurements on

20, 100-watt lamps. These data indicate that time dependent biases are present in the process and usually amount to 0.2-0.3% though a few as large as 1% have been observed. These bias percentages include
short-term lamp instabilities. Occasionally, for example, changes of

0.5% have been observed in merely turning a lamp off and then on again.

Assuming that these time dependent biases are due to the random variation of an uncontrolled parameter, a statistical analysis has been made

of the measurements. A pooled estimate of the standard deviation of a single measurement has been calculated to be 0.3%. In assigning a value

to the uncertainty, an allowance of 1.0% is made for the time dependent

bias in the data and an additional allowance of 0.5% is made for the

random variation in the measurements (three times the standard deviation

of the mean of three measurements). The uncertainty assigned to a reported value with respect to the candela as maintained by NBS is the

sum of these two components or 1.5%-

The most recent international intercomparison of the candela at the

color temperature of CIE illuminant A showed a range of 1.7% among the

eight participating national standardizing laboratories including NBS

[3]. Adding the calibration uncertainty of transferring the NBS candela

to a test lamp (l.5%) to one half this range (0.85%) yields our current

uncertainty of 2.3% for a reported value with respect to world mean.

The uncertainty of a reported value with respect to the SI candela

will be subject to several sources of bias in addition to those discussed

above. Although extensive investigations of these additional sources of

bias have not been made, some relevant information exists on which to

base an uncertainty. The same intercomparison referred to earlier [3]

showed that the candela at the color temperature of CIE illuminant A, as realized in the national standardizing laboratories of the world, was inconsistent with the candela realized at the color temperature of

freezing platinum by as much as 3.5% [h] . Also, recent theoretical work

has indicated that previous realizations of the platinum point blackbody

may have been in error by as much as 1.5% [!?]• Thus in our current

process there are six individual biases or sources of bias relative to

the SI candela for which uncertainties have been assigned. These

together with the uncertainties associated with them are listed below:

Biases

Substitution Calibration

A. Time dependent bias

B. Constant bias

C. Random variation

Assigned Uncertainty

1.05

0.0

0.5

II. Transfer Chain

A. International intercomparison

at 2856 K (1/2 range)

B. International intercomparisons

inconsistency in realizing the

candelas at the platinum point

and 2856 K

0.85

3.5

III. Platinum Point Calibration 1.5
It is unlikely that all these individual uncertainties would have the same sign resulting in a total uncertainty of 1.3%. Therefore a combination in quadrature (square root of the sum of the squares) resulting in

k.1% is considered to give the uncertainty of a reported value relative

to the SI candela.

Recently a program was established at NBS for developing improved

luminous intensity standards and methods of transfer and for more

thoroughly characterizing biases and uncertainties. Results of this

work will be published as they become available.

Precautions

Lamps supplied to other laboratories as standards of luminous

intensity represent the unit of luminous intensity (candela) as maintained at the National Bureau of Standards with the best precision now

available. They are expensive laboratory equipment and deserve the

utmost care in handling and use.

In addition to some obvious precautions, such as keeping the lamps

clean and avoiding mechanical shock to the filament, the following are

a few precautions, sometimes overlooked, which should be used with these

standards

.

1. The lamps should be turned on and off slowly (15-30 seconds),

and great care should be taken so that at no time will the current

appreciably exceed the value stated in the report. The lamp should not

be moved while lighted.

2. In order to prolong the useful life of the lamps, it is recom- mended that they be used sparingly and that for general use, working

standards be prepared by calibrating them relative to the lamps supplied

by NBS. When a laboratory procures standard lamps from NBS it is well

to obtain at least three such lamps in order to be able to detect any

changes that may occur.

3. The lamps should be carefully aligned in accordance with the

procedures described above. Photometric measurements should be made

only after the lamp has stabilized (approximately 10 minutes after turn

on) .

h. Stray light must be excluded. One source of stray light that

is sometimes overlooked is the standard lamp itself. The background of

the lamp on the side away from the detector should not reflect light

back along the photometric axis. NBS uses a light trap made of two

pieces of black glass set at approximately 60° to each other and set

behind the lamp. Black cloth positioned h5 to 60 cm behind the lamp is

convenient and usually adequate.

5. Baffle aperture edges should be very thin or beveled so as not

to reflect light to the detector. It is of little use to coat baffle

8
edges "with black paint or black cloth, since most flat surfaces reflect

light reaching them at large angles of incidence regardless of whether

or not they are blackened.

6. It is preferable not to confine the lamp to a small space,

especially with poor ventilation. Excessive noise in the measurements

often results.

7. The variation of luminous intensity of a gas-filled tungsten

lamp is approximately related to the variation in its current by the

formula:

f =6.25 & 1 i

where I is the luminous intensity and i is the lamp current [6,7]- Thus

a current measurement accuracy of at least 0.032% is required if it is

not to affect the luminous intensity to greater than 0.2%.

2.5 References

[l] V. K. Zworykin and E. G. Ramberg, Photoelectricity , Chapter 11,

John Wiley & Sons, Inc., New York, N. Y. (19U9).

[2] IES Lighting Handbook, Fourth Edition, p. 1-3, 2-U (1966),

Illuminating Engineering Society, New York, N. Y.

[3] Comite Consultatif de Photometrie, 5 e Session (1962) p. 8U.

[h] Comite Consultatif de Photometrie, 6

e Session (1965),

Annexe 3, p. P28.

[5] Ibid., Annexe 1, p. PIT.

[6] J. W. T. Walsh, Photometry , p. 532, Dover Publications, Inc.,

180 Varick Street, New York, N. Y. (1965).

[7] A. Kingslake, Applied Optics and Optical Engineering , p. 6l,

Academic Press , New York, N. Y. (1965).
3. Color Temperature

3-1 Description of Calibration of

Incandescent Lamp Standards of Color Temperature

Incandescent lamp standards of color temperature are calibrated at

the National Bureau of Standards by a substitution method on a red-blue

ratio, color temperature comparator. The color temperature comparator

is calibrated at the time of the measurements in terms of the color

temperature scale maintained by NBS.

3.1.1 The NBS Color Temperature Scale

NBS has established and maintains a scale of color temperature.

Careful distinctions should be made between the concept of color temperature and the related concepts of correlated color temperature and

distribution temperature. Color temperature is defined as the "temperature of the full radiator which emits radiation of the same chromaticity

as the radiation considered" [l]. That is, the test source and the full

radiator (i.e. blackbody) have the same appearance to a human observer.

Note particularly that the corresponding relative spectral power distributions are not necessarily identical or even similar. If the test source and the corresponding blackbody have identical relative spectral

power distributions in the spectral region of interest, the correct

designation is distribution temperature [2]. If one wishes to assign a "temperature" to describe a source whose appearance, and hence whose

relative spectral power distribution, is markedly different from a blackbody, such as a fluorescent lamp, the correct designation is correlated

color temperature [3]. Mathematical procedures are available for

determining the correlated color temperature of any source [h] . In

applying the values of color temperature reported by NBS, the user should

bear these distinctions in mind. Particular care should be exercised in

utilizing the widespread practice of treating color temperature values

as synonymous with distribution temperatures

.

The present NBS scale of color temperature was established in 193^

[5] by visual comparison of monoplane, coiled tungsten filament, incandescent lamps with three melting point blackbodies: platinum at 20^5 K,

rhodium at 2236 K, and iridium at 2720 K. The nine lamps thus calibrated

(three at each temperature) were then used to calibrate three working

standard lamps across the color temperature range. An empirical approach

was adopted for interpolating between the three fixed temperature points.

Taking advantage of the cavity effect due to filament coiling, pyrometric

determinations of the radiance temperature* were made at a position on the inside of a single turn of the coiled filament. It was observed that

*Radiance temperature, also called luminance temperature and brightness temperature, is defined as the temperature of a blackbody for which

the spectral radiance at the specified wavelength is the same as that of

the radiator considered.

10
the difference "between the radiance temperatures so determined and the

color temperature of the lamp as a vhole was a smoothly varying function

of the voltage applied to the lamp. Pyrometric determinations of the

radiance temperatures of three different coil turns of the test lamps

yielded consistent color temperature values for the interpolated region.

Further, from this data it was empirically determined that an equation

relating the color temperature (T ) and the applied voltage (V), of the

form:

T

Q = A + B(V) 1 ^ 2

(1J

was adequate to express all of the data within the estimated uncertainties. The 193^ color temperature scale was also extrapolated up to

3200 K and down to 1500 K. Sources with known color temperatures in the

extrapolated regions were produced by modifying incandescent lamp outputs

(assumed to he sources whose distribution temperatures equalled their

color temperatures), with blue and amber filters whose spectral transmittances had been measured. Incandescent lamps and associated equations

of the form of eq. (l) have been used since 193^ to maintain the NBS

color temperature scale. The scale has been adjusted twice, in 19^9 [6]

and in 1970 [T], to take account of changes in the International Practical Temperature Scale.

The present scale of color temperature resides in nine incandescent

working standard lamps. Lamps BS 9021, BS 9022, and NBS 1005 are used

in the range 2000-2600 K; lamps NBS 1923, NBS 192U, and NBS 1925 are used

in the range 2300-2900 K; and lamps NBS 1926, NBS 1927, and NBS 7875 are used in the range 2700-3200 K. These working standard lamps were originally calibrated by visual comparison with the lamps used to establish

the scale in 19 3^. In addition to the calibrations at fixed color temperature points, associated empirical equations of the same form as eq. (l) are used to establish the scale in interpolated and extrapolated

regions. Empirical equations of the form,

i = A + BT

C + CT^ , (2)

relating the color temperature and the current through the lamps , i

,

have also been found to be completely adequate to represent the data

within the associated uncertainties.

3.1.2 Test Lamps

Description

Airway beacon lamps designated 500T20/13, are issued by NBS as lamp

standards of color temperature. They are 500-watt, 120-volt lamps with

clear T-20 bulbs, C-13B filaments and medium bipost bases. They have a rated life of 500 hours at 120 volts.

11
Preparation

Initially, the lamps are seasoned by operating them at 120 volts ac for 20 hours (k% of rated life). An identifying number is then etched

on each bulb.

Orientation

Test lamps are calibrated while burning base down with the etched

identifying number turned away from the comparator. The lamps are aligned so that their planar filaments are centered on and perpendicular

to the optical axis of the entrance aperture of the collecting sphere

of the color temperature comparator. No auxiliary diaphragms are used,

and thus light from essentially the entire test lamp is viewed by the

comparator.

Operation

All measurements are made with the lamps operating on dc power.

Electrical measurements are made with a digital voltmeter to an accuracy

of 0.1$. After positioning and alignment, the lamp is slowly (15-30

seconds) brought up to approximately the required electrical operating

point and allowed to stabilize for at least 10 minutes before measurements are made. Measurements are then made of the current through the

lamp and the potential drop across the pins of the bipost base necessary

to produce a color match to a comparison source.

3.1.3 The NBS Color Temperature Comparator

At present, all routine color temperature measurements at NBS are made on a device which compares the ratios of the "red" portion of the

visible spectrum to the "blue" portion of the visible spectrum for test

and standard sources. Equality of these two red-to-blue ratios is

interpreted to mean equality in color temperature. Since the measurement

involves the inference of a visual property of the test source ( chromaticity match to the standards) from the measurement of a different

physical property , severe requirements are placed on the test and standard sources. Specifically, their relative spectral power distributions

must be identical throughout the entire visible region of the spectrum.

Only test lamps substantially identical to the working color temperature

standard lamps (clear bulbs, monoplane coiled tungsten filaments) are calibrated by this method.

Numerous devices based on the red/blue ratio principle have been

described in the literature [8]. The present NBS instrument has not

been optimized, either in the electronics used for signal sensing or in

the optical components (filters and detector). It has, however, been

shown to possess adequate sensitivity and precision. The standard deviation of a single measurement for repeated measurements of the same color

temperature on the same test lamp is about 2 K. The chief virtues of

the present instrument are precision, speed, and convenience.

12
The figure on page 15 is a "block diagram of the major components of the

comparator. Radiation from the test or standard source is collected in

a BaSO^ coated entrance sphere (20 cm diameter, 7-5 cm entrance aperture).

The sphere is mounted so that it can be rotated about the optical axis of

its exit aperture and thus view a comparison source. (The function and

use of the comparison source will be discussed in Section 3.1. U, Calibration Procedure.) Radiation leaves the entrance sphere through a 3.8 cm diameter exit aperture and passes through an infrared absorbing filter

(Corning No. h600) . This infrared absorbing filter is placed in the

optical chain to alleviate the effects of the temperature sensitivity of

the red filter. The radiation next passes through either the red filter

(Corning No. 3H86) or the blue filter (Corning No. 5562) and is detected

by a photomultiplier (S-ll, EMI 951^S). The red and blue filter are mounted on a rapidly spinning wheel (1U00 rpm) so that radiation passing

through the two filters is alternately presented to the photomultiplier.

Two synchronously driven electronic gates assure that the signal from

radiation passing the red filter, and only radiation passing the red

filter, is diverted to one amplifier-integrator chain while the signal

from radiation passing through the blue filter is diverted to a second

amplifier-integrator chain. After passing the amplifier-integrator

chains, the two signals are compared on the null meter. Suitable adjustments are made to either the lamp electrical parameters or the signal

attenuator and adjustable voltage divider to obtain equality between the

two signals (see Section 3.1.^, Calibration Procedure). Constant loading

of the photomultiplier over the course of a given test run, is assured

by referencing one of the two signals (either the red or the blue) to a stable dc reference source (0.1% stability) servo controlling the photomultiplier high voltage supply. A front panel reversing switch allows

the operator to select which signal passes which amplifier-integrator

chain and hence which signal references the high voltage supply. The

instrument as described is capable of measurements in the range 2U00 K

to 3000 K. For color temperatures outside this range, there is not

sufficient compensation available in the electronics to achieve a null

between the red and blue signals. For measurements in the range 2000 K

to 2^00 K, a blue "accessory filter" (Corning No. 5900) is introduced

immediately after the infrared absorbing filter. A yellow filter (Kodak

Wratten 2A) is similarly used for measurements above 3000 K.

3.1.1+ Calibration Procedure

Color temperature measurements made on the red-to-blue ratio color

temperature comparator are made by a strict substitution procedure. Test

and standard lamps are placed in the same geometrical position with

respect to the comparator, the optical path through the comparator is the

same and finally, at null, the comparator indicates a spectral match

between the sources.

At the beginning of each calibration run the comparator is calibrated against each lamp of the relevant working standard group in turn.

One member of the working standard group is placed in the measuring

position and allowed to operate at the current required for the desired

13
color temperature for 10 minutes. The signal attenuator and adjustable

voltage divider are adjusted to produce an exact equality between the

red and blue signals from the photomultiplier. The entrance aperture of

the collecting sphere is then rotated to view the comparison lamp and

the voltage across the comparison lamp is adjusted to produce the same equality of red and blue signals. This comparison lamp voltage is noted

and the entire procedure is repeated for each member of the standards

group. The average comparison lamp voltage is computed and the comparison lamp set to that voltage. The red and blue signals now obtained when

viewing the comparison lamp are nulled by adjusting the electronic con- trols. During the remainder of the calibration run, the comparison lamp

is periodically viewed to assure that the red-to-blue null condition

still prevails. Thus the calibration of the comparator depends on the

stability of the comparison lamp and not on the stability of the electronics or the photomultiplier. If a drift from null is observed, the electronic controls are again adjusted to restore the null condition. Test

lamps are then placed in turn at the same position previously occupied

by the standard lamps and after warming up for 10 minutes the exact

current required to match the comparison lamp is determined.

Typically nine test lamps are run at one time. The entire calibration procedure, including calibration of the comparator against each

member of the working standard group, is repeated three times on successive half days. In order to check for possible shelf effects (drifts

that occur while the lamp remains unused on the shelf) in the test lamps

,

at least one additional set of three runs is made six months later. Thus

the values reported for a test lamp are the average of at least six runs made over a period of at least six months.

3.1.5 Uncertainty

The color temperature scale presently maintained by NBS is con- sidered to be a "gage" standard, that is, a standard which NBS has not

investigated sufficiently to assign defensible uncertainties relative

to SI units. However, control relative to NBS standards does exist and

provides at least a uniformity in measurements relative to these standards. The present scale has not been checked against absolute standards

since it was established in 193^+. NBS is presently in the final stages

of a program to realize an absolute scale of spectral irradiance. An

early reevaluation of the present color temperature scale in terms of

this new scale of spectral irradiance is planned. Results of this work

will be published as they become available.

Although nothing definite can be said about the uncertainty of the

NBS color temperature scale with respect to SI, information is available

about the precision of the transfer of the NBS scale to the test lamps.

An analysis of three runs of 7 lamps at 2000 K yielded a standard deviation of a single measurement of 1.1 K. A similar analysis of three runs

on twenty lamps at 2856 K yielded a standard deviation of a single

measurement of l.k K. From these data an allowance of 1.9 to 2.k K is

made for the uncertainty of the transfer of the NBS scale to a test lamp

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15
in a set of three closely spaced runs (three times the standard deviation of the mean of three measurements ) . The procedure to check for

shelf effects in test lamps has only recently been instituted, and thus

only preliminary data is available. Two sets of three runs each 18

months apart have been made on a group of nine test lamps calibrated at

2856 K. These lamps exhibited a directional drift averaging 2 K, but in

one case as large as 7 K. Until a more definitive body of data is

obtained on typical shelf effects, an allowance corresponding to the

maximum observed shift of 7 K is made in assigning an uncertainty to the

transfer of the NBS scale to the test lamps. Thus the estimated uncertainty of the reported value with respect to the NBS scale is 9 K

(precision plus the allowance for shelf effects).

One international intercomparison of national scales of color temperature has been conducted [9]. Two methods of making the color temperature comparisons were used at the Bureau International des Poids et

Mesures: red/blue and spectroradiometric. The table below shows the

range (combined for the two methods of comparison) observed among the

7 participating national standardizing laboratories.

Nominal

Color Observed

Temperature* Range

20-1+2 K 9 K

2200 9

2353 11

2600 29

285U 31

3000 147

^Temperature based on IPTS-U8.

The entries in the table are indicative of the range of color temperature measurements that might have been encountered in the world in 1965.

Since only one such intercomparison has been conducted, no information

is available on the stability of the various scales over long periods of

time. Hence, although NBS was quite close to world mean at that time

(maximum difference between NBS and world mean was 10 K at 3000 K) no inferences are drawn about the relationship of the present NBS scale to

world mean.

3.1.6 Discussion

Lamps supplied to other laboratories as standards of color temperature represent the color temperature scale as maintained by NBS. They

are expensive laboratory equipment and deserve the utmost care in handling and use. In addition to some obvious precautions, such as keeping

the lamps clean and avoiding mechanical shock to the filament, the

16
following are a few precautions, sometimes overlooked, which should be

used with these standards.

1. The lamps should be turned on and off slowly (15-30

seconds), and great care should be taken so that at no time will the current appreciably exceed the value

stated in the report. The lamp should not be moved

while lighted.

2. In order to prolong the useful life of the lamps, it

is recommended that they be used sparingly. For

general use, working standards should be prepared

by calibrating them relative to the lamps supplied

by NBS. When a laboratory procures standard lamps

from NBS it is well to obtain at least three such

lamps in order to be able to detect changes that

may occur.

3. Measurements should be made only after the lamp has

stabilized (approximately 10 minutes after turn on)

Stray light should be excluded from the measuring

instruments. This includes light from the standard

which may be reflected from the background or from

instruments being used.

5. Differentiation of equation 2 yields

di = (B + 2CT ) dT

c c (3)

Typical values of the constants A, B, and C in eq. (2) for the airway

beacon lamps of the type 500T20/13 are, A = -.^5, B = 1.0 x 10-3 and

C = l.k x 10 -7. Evaluating eq. (3) in the range 2000 K to 3000 K, shows

that the sensitivity of the current setting ranges from 0.0016 to

0.0018 amps/K. Since these lamps typically draw about k amps at 2856 K, a current setting accuracy of at least 0.1$ is required if the color

temperature of the lamp is not to be affected by more than 2 K.

IT
3.1.7 References

[l] International Lighting Vocabulary , 3rd Edition, CIE Publication,

No. IT, Section U5-05-2T0, p. 2*9 (l9T0).

[2] Ibid, Section 1+5-05-265, p. 29.

[3] Ibid, Section U5-15-260, p. fk.

[h] K. L. Kelly, Lines of Constant Correlated Color Temperature Based

on MacAdam's (U,V) Uniform Chromaticity Transformation of the

CIE Diagram, J. Op. Soc. Am., 53., No. 8, pp. 999-1002,

August 1963.

[5] H. T. Wensel, D. B. Judd, and W. F. Roeser, Establishment of a Scale of Color Temperature, Bur. of Stand. J. Res., 12 , pp. 527-536, May 193k.

[6] D. B. Judd, The 19^9 Scale of Color Temperature, J. Res. Nat.

Bur. Stand., Ui_, January 1950.

[7] Color Temperature, Luminous Efficacy and the International

Practical Temperature Scale of 1968, Nat. Bur. Stand. Technical

News Bulletin, pp. 206-207, 5^, No. 9, September 1970.

[8] See for instance:

J. S. Preston, Phys . Soc, Proc. U_J_, 1935, p. 1012.

H. G. W. Harding, Phys. Soc, Proc 63, 1950, p. 685.

J. Sci. Inst., 29, 1952, p. 1U5.

W. J. Brown, J. Sci. Inst., 31, 195 1*, p. ^69.

[9] Comite" Consultatif de Photome'trie, 6

e Session (1965), Annexe 7,

p. hf.

18
3.2 Inside-Frosted Lamp Standards

of Color Temperature

Inside-frosted incandescent lamp standards of color temperature at

2856 K are calibrated at the National Bureau of Standards "by a substitution method in accord with the procedures described in Section 3.1,

"Description of Calibration of Incandescent Lamp Standards of Color

Temperature". For inside-frosted lamps, the exact procedure used differs

from the previously described procedure only in the type of lamp calibrated and the standards used for the comparison.

3.2.1 Test Lamps

The test lamps and their preparation are described in Section 2.1,

"Description of Calibration of Inside-Frosted Lamp Standards of Luminous

Intensity". The test lamps are calibrated while burning base down with

the identifying number turned away from the comparator. Lamp orientation is accomplished by aligning the lamp socket so that the lamp posts

are held vertically with the plane formed by the axes of the posts perpendicular to the optical axis of the comparator. The light center of

the lamp is on, and the lamp pins are equidistant from the optical axis

of the comparator (see calibration report for specific light center

lengths )

3.2.2 The NBS Color Temperature Scale

for Inside-Frosted Lamps

Three inside-frosted, 500-watt incandescent working lamp standards

of color temperature have been calibrated at 2856 K and are maintained

by NBS. These lamps (NBS 9171, NBS 9172, and NBS 9173) are of the same type as described above. Initial calibration of these lamps was performed spectroradiometrically against the 500-watt, clear-bulb working

standards of color temperature (NBS 1926, NBS 1927, and NBS 7875). The

spectroradiometer used for this calibration [l] determined the ratios of

the spectral radiant powers of the test and standard lamps at every

10 nm from 380 nm to 760 nm with a spectral bandpass of 5 mi. The data

reduction assumed that the relative spectral power distribution of the

clear-bulb standards was the same as the relative power distribution of

a Planckian radiator. The relative spectral power distribution of the

inside- frosted lamps thus determined was used to compute their chromaticity coordinates. The procedure described by Kelly [2] was then used

to compute the correlated color temperature of the inside-frosted lamps.

19
3.2.3 References

[l] D. A. McSparron, K. Mohan, R. C. Raybold, R. D. Saunders, and

E. F. Zalewski , Spectroradiometry and Conventional Photometry

An Interlah oratory Comparison, Nat. Bur. Stand. (U.S.) Tech

Note 559, pp. 5-12, November 1970.

[2] K. L. Kelly, Lines of Constant Correlated Color Temperature

Based on MacAdam's (U,V) Uniform Chromaticity Transformation

of the CIE Diagram, J. Op. Soc. Am., 53., No. 8, pp. 999-1002,

August 1963.

k. Description of the Calibration of

Incandescent Lamps for Luminous Flux

In response to several requests from the users of luminous flux

standards, the National Bureau of Standards has calibrated a group of

general-purpose incandescent lamps. The lamps range in size from

10 watts to 1000 watts and are approximately 120-volt , base-up burning

lamps. They were calibrated in a 2-meter integrating sphere photometer.

k.l Test Lamps

The lamps to be calibrated were submitted by the users and were

stated to have been properly seasoned before submission. Each lamp

bears an identifying number etched on the bulb.

k.2 Sphere Photometer

The lamps were calibrated while burning base up in the center of a 2-meter integrating sphere photometer. The sphere is coated with Burch

sphere paint. A 7.6-centimeter diameter observation port is located in

the sphere wall and is covered with a white diffusing plastic (Plexiglas,

color W2UU7 Rohm and Haas white) flush with the sphere wall. A baffle,

also coated with Burch sphere paint is placed between the lamp and the

window, 0.55 meters from the window. When measuring 10-watt to 500-watt

lamps, the baffle used was a circular disk 17. 5 centimeters in diameter.

When measuring the 750-watt and 1000-watt lamps, the baffle was shaped

roughly like a projection of the lamp and was 15 centimeters by 23 centimeters.

Because of the somewhat selective spectral reflectance of the sphere

coating and transmittance of the window, a blue filter is inserted

adjacent to the window. The blue filter was selected from a set of

filters of graded color temperature altering power, so that the net

spectral effect of the sphere reflectance, window transmittance and the

blue filter is that the spectral distribution of the flux arriving at

the detector is approximately the same as that leaving the lamp. In

order to select the proper filter, a lamp was operated at 2856 K color

20
temperatlore in the sphere. The filter was then selected such that light

from the lamp operating in the sphere and transmitted through the window

and filter had a color temperature of 2856 K. The proper filter was determined just before this test was started (about four months after

the sphere was painted) . The correction at that time was approximately

6h0 K. The correction was determined again after about half of the data

had been taken (three months later) and the correction needed was approximately TOO K ( a change of about 60 K) . At the conclusion of the test

the correction needed was still TOO K.

A selenium barrier layer photocell [l] (Weston model 856) equipped

with a filter to correct its spectral response to approximately match

the CIE luminous efficiency function [2] is placed in a brass tube

fitted to the window. The brass tube is coated on the inside with mat

black paint. The photocell photocurrent is measured with an operational

amplifier (current to voltage converter) arragned in a typical closedloop configuration. Thus the photocell is operating into a near zero resistance circuit (no voltage across the terminals of the photocell)

A five-place digital voltmeter is used to measure the output of the

operational amplifier.

Three selenium photocells were used in this test and the deviation

from linearity of the response of the detection system with each photocell was determined. This determination was made on a horizontal bar

photometer by an inverse square method. The photocell was mounted on the bar at a known distance from a stable monoplane straight-wire filament lamp. The filament was approximately 2 centimeters square. The

photocell was moved along the bar and its response noted at various

distances from the lamp. The deviation of the response from that which

one would expect by applying the inverse square law was attributed to

the nonlinearity of the detection system. Distances used were O.63

meters to H.1T meters. The lamp was operated at two voltages in order

to cover the desired range within these distances. For illuminance at

the detector of 3 lux to 800 lux, maximum deviations from linearity for

two of the detectors were -k.5% and for the third detector the maximum

deviation from linearity was +6.5%-

U.3 Standards

A group of six 300-watt opal bulb lamps (Group NBS 526) operating at a color temperature of approximately 2T20 K serves as the NBS standard

of luminous flux. The lamps were calibrated by measuring their luminous

intensity distributions relative to their luminous intensity in a single

direction. The luminous intensity in the single direction was measured

by comparison with the NBS standard of luminous intensity. The total

luminous flux was then determined by integrating this luminous intensity

with respect to angle of view. This work was done about 30 years ago

and some check measurements were made about lU years ago and about

5 years ago. The lamps are used very infrequently to calibrate NBS

working standards.

21
The NBS working standards were recalibrated at the start of this

test by comparing them in six runs , using four photocells (the three

photocells mentioned above and one silicon photodiode), with the 300-

watt opal-bulb lamps. The NBS working standards are listed in the

following table. Each group of standards consists of six lamps.

Lamp

Group

Designation

NBS 162

NBS 6807

NBS 3158

BS 5^70

Nominal

Wattage

500

200

100

60

Bulb

PS 35 clear gas-filled

PS 30 frosted gas-filled

A-21 frosted gas-filled

S 21 clear vacuum

Approximate

Color

TemperFilament ature Lumens

C-7 2800 K 6hk0

C-9 2900 K 3260

C-9 2900 K 16U1

Squirrel 2U50 K hh6

Cage

Corrections for nonlinearity of the detection system were applied.

These corrections varied between -0.58% and +1.25%. In addition, correc- tions for the difference in the lamp absorption between the opal-bulb

lamps and the working standards were determined and applied. In order

to determine the correction due to lamp absorption, a 200-watt lamp was placed at the bottom of the sphere and held at constant voltage. Light

from the 200-watt lamp was baffled from the sphere window and from

unlighted lamps placed in turn at the center of the sphere. Readings

were made of the detector output when each of the opal-bulb lamps

(unlighted) was in the socket at the center of the sphere and again

when each of the working standards (unlighted) was in the socket at the

center of the sphere. The correction is the ratio of the average reading

taken with each group of working standards to the average reading taken

with the opal-bulb lamps in the sphere. For these lamps the corrections

varied between -0.l6% and -0.32%.

k.h Calibration of the Test Lamps

The test lamps were calibrated in groups of approximately twenty.

Three measurements were made on each lamp in the group, one on each of

three days. Each lamp was placed in the sphere and allowed to operate

at its designated current or voltage for ten minutes before measurements

of voltage, current, and luminous flux were made. The lamps were

measured in the following order: 2 standards, one half of the test

lamps, 2 standards, the other half of the test lamps, and the remaining

two standards. The lamps submitted by any single laboratory were distributed throughout the group and not measured successively. The three

photocells described above were used, one on each of the three days.

Test lamps were compared with standards which were closest to them in

wattage. Corrections for the non-linearity of the photocell were applied.

These corrections were greatest for the 10-watt lamps. For one photocell

the correction was as high as 2.k%. Corrections for the difference in

22
absorption were determined by the same method as described for the calibration of the working standards. Absorption corrections ranged from

+0.66$ to -0.07$.

U.5 Uncertainties

The geometrically total luminous flux output of the prime reference

group (the six 300-watt opal-bulb lamps) was obtained by measuring the

luminous intensity of the lamps in a large number of directions relative

to the intensity in a reference direction (distribution photometry).

Determination of the luminous intensity of the lamp in this reference

direction, together with integration of these relative intensity measurements then allowed computation of the total luminous flux output of the

lamps. Distribution measurements were made three times, twice in 1938

and once in 1958, on three different instruments. No detailed error estimates were made for these measurements. In the absence of more

fundamental error estimates, the maximum observed range among the three

sets of measurements, for any member of the prime reference group, will

be taken as the estimate of the uncertainty of the distribution photometry measurements. This range is 0.7$.*

The uncertainties associated with the direct substitution comparison of the luminous intensities of two identical inside-frosted lamps

have been discussed in section 2.k L3]. For this type of direct substitution transfer the uncertainty assigned is k.1% relative to SI (individual

components combined in quadrature). For the luminous intensity determination on the prime reference flux group, an additional uncertainty

must be allowed because of the difference between the luminous intensity

standard lamps and the flux standard lamps. Specific differences that

will affect the measurements are: (l) the different physical sizes of

the lamps (23 cm long, PS-UO bulbs for the flux lamps versus 17.8 cm long, T-20 bulbs for the luminous intensity standards); (2) different

spectral distributions (2720 K for the flux lamps versus 2856 K for the

luminous intensity standards); and (3) inability to repeat the alignment

of the flux lamps due to inadequate reference positions on the lamps.

Inverse square law considerations lead to an estimate of 0.5$ for the

uncertainty introduced by the differing physical sizes of the lamps.

Spectral differences of the magnitude encountered here have been

observed to produce differences of up to 0.25$ in other similar luminous

intensity measurements. Finally, misalignment, particularly a systematic

difference in alignment between the distribution photometers and the

photometers used for the luminous intensity determinations might produce

an error of 0.25$ (based on a study of the distribution curves and an estimated ability to align the lamps to ±2°). It is unlikely, that these

uncertainties would have the same sign and therefore, they are combined

in quadrature. This results in an uncertainty relative to SI of U.2$.

*The uncertainties being discussed are listed in the table on page 25

23
The uncertainty of transfer from the prime reference flux group to

the NBS working standards may be divided into three parts, those

uncertainties due to: (l) geometric effects; i.e., the presence of

objects, such as the lamp, its support, and the baffle, in the sphere

and their geometrical arrangement; (2) spectral effects, i.e., differences in the spectral distribution of the lamps being compared or a difference between the spectral response of the detector being used and

the CIE spectral luminous efficiency function; and (3) random variations

of the measurements. No detailed analysis of the geometric and spectral

effects have been made. However, regarding the geometric effects, differences as large as 1$ have been observed when using a sphere geometry

described above compared to a very different geometry requiring more

objects in the sphere during the measurements. An allowance of 1$ has

been made for this source of error. Uncertainties due to the spectral

effects have not been extensively evaluated. An allowance of 1$ is the

best guess estimate for these. For random variations, the standard

deviation of a single measurement obtained from a population of lUU

measurements (6 measurements on each of the 6 lamps on each of the h

groups of working standards) was 0.lU$. The uncertainty assigned for

the random variations was three times the standard deviation of the

mean of the 6 measurements on each lamp or 0.2$. These uncertainties

combined in quadrature give an uncertainty of l.U$ relative to the

prime reference group and when combined in quadrature with the SI

uncertainty of the prime reference group yield k.k%.

The uncertainty of the transfer from the NBS working standards to

test lamps supplied to other laboratories depends on the size and

operating color temperature of the test lamps relative to the standard

group used to calibrate them. For the test lamps which are the same

size and color temperature as the standards used, the uncertainty is

estimated from the random variations. This was computed as three times

the standard deviation of the mean of the three measurements made of

each of the test lamps and is . h% . For the uncertainty of the transfer

from NBS working standards to test lamps of other sizes and color temperatures , additional uncertainties as large as 1.0$ for geometric

differences and 1.0$ for spectral differences must be included. Combining these in quadrature results in an uncertainty of 1.5$.

The total uncertainties of the test lamps relative to SI or to the

NBS prime reference group are obtained by combining in quadrature either

the above 0.k% or 1.5$ with the k ,k% or the l.U$ referred to above and

listed in the table. The resulting SI total uncertainty is k .k% to U.7$

and the total uncertainty relative to the prime reference group is 1.5$

to 2.0$. The specific value depends on the relative size and color

temperature of the test lamps and the NBS working standard lamps used to

calibrate them.

2k
TABLE OF UNCERTAINTIES

Uncertainty of the Prime Reference Group

Uncertainty of the distribution measurements 0.7$

Uncertainty of the NBS luminous intensity scale

relative to SI (individual uncertainties

combined in quadrature) U.l$

Additional uncertainty of the luminous intensity

transfer because of:

(1) different physical sizes of the lamps 0.5$

(2) spectral differences .5%

(3) alignment of flux lamps 0.25$

Total uncertainty relative to SI k.2%

Uncertainty of the NBS Working Standards

Uncertainty of the transfer from the prime

reference group because of:

(1) geometric differences 1.0$

(2) spectral differences 1.0$

(3) random variations 0.2$

Total uncertainty relative to the NBS prime

reference group l.k%

Total uncertainty relative to SI h ,k%

Uncertainty of the Test Lamps

Uncertainty of the transfer from the NBS

working standards

(1) for lamps of the same size and color

temperature as the working standards .h%

(2) for lamps of other sizes and color

temperatures 1.5$

Total uncertainty relative to SI k.h% to k.f%*

Total uncertainty relative to the

NBS prime reference group 1.5$ to 2.0$

Total uncertainty relative to the NBS working standards Q.k% to 1.5$

*depending on the relative size and color temperature of the test lamps

and the NBS working standard lamps used to calibrate them.

25
NBS participated in the fifth international intercomparison of

national standards of luminous flux in 19 69. The results of this intercomparison [h] showed the NBS luminous flux standards to be 0.7% above

world mean. However, later investigations have shown that the technique

used for calibrating the lamps for this intercomparison resulted in the

assignment of luminous flux values which were low by 0.6% relative to

the technique used in the present test. Thus the values assigned to the

lamps calibrated at this time are estimated to be higher than world

mean by 1.3$.

The NBS 200-watt group of working standards (group NBS 6807) and

200-watt lamps of the same type which have been submitted for calibration several times appear to be drifting in luminous flux output relative to lamps of other sizes and relative to the NBS prime reference

group (approximately 1% since 1962). Therefore, these lamps should be

checked frequently.

k.6 Care and Handling

Lamps supplied to other laboratories as standards of luminous flux

represent the unit of luminous flux (lumen) as maintained at the

National Bureau of Standards with the best precision now available. They

are expensive laboratory equipment and deserve the utmost care in handling

and use.

In addition to some obvious precautions, such as keeping the lamps

clean and avoiding mechanical shock to the filament, the following are

a few precautions which should be used.

1. The lamps should be turned on and off slowly (15-30 seconds),

and great care should be taken so that at no time will the current

through a lamp appreciably exceed the value stated in the report.

2. In order to prolong the useful life of the lamps as standards,

it is recommended that they be used sparingly and that for general use,

working standards be prepared by calibrating them relative to the lamp

standards supplied by NBS. When a laboratory procures standard lamps

from NBS, it is well to obtain at least three such lamps in order to be

able to detect any changes that may occur.

3. A baffle should be used between the lamp and the observation

window. The baffle should be as small as possible but large enough to

prevent any light from the lamp reaching the window without undergoing

at least one reflection. The baffle surface should be coated with the

same material as the sphere wall.

h. The variation of luminous flux of a tungsten filament lamp is

approximately related to the variation in its current by the formula:

[5,6]

d^ _ K di

<f> "

i

26
where <j> is the luminous flux, i is the lamp current and K is 6.25 for

gas-filled lamps and 6.05 for vacuum lamps. Thus a current measurement

accuracy of at least 0.032% is required if it is not to affect the

luminous flux to greater than 0.2%.

5. Most detectors are not linear in their response. Detectors of

a single type made "by a single manufacturer sometimes differ significantly

in this respect. If lamps of different flux outputs are to be compared,

the response of the detector should "be studied to determine its departure

from linearity.

6. Most sphere coatings are somewhat spectrally selective in

reflectance. Diffusing windows commonly used in spheres also have

spectrally selective transmittances. Corrections should be made when

comparing lamps operating at different color temperatures. In addition

to this, a detector whose spectral response agrees with the CIE luminous

efficiency function should be used.

7. Lamps of different physical size and blackening absorb different

amounts of the flux reflected to them by the sphere wall. The amount of

flux absorbed also varies with the size of sphere being used and with the

reflectance of its coating. Therefore, when lamps of different physical

size, bulb material and blackening are being compared, corrections for

the lamp absorption should be made. The absorption correction should be

determined in the sphere in which the comparison is made.

8. When comparing lamps which are nearly identical in physical

size, absorption, luminous flux, and color temperature, the corrections

listed above in 5, 6, and 7 may not be significant.

h.'J References

[l] V. K. Zworkin and E. G. Ramberg, Photoelectricity , Chapter 11,

John Wiley & Sons , Inc . , New York, N.Y. (19U9)

[2] IES Lighting Handbook, Fourth Edition, pp. 1-3, 2-1+ (1966),

Illuminating Engineering Society, New York, N.Y.

[3] National Bureau of Standards, Technical News Bulletin, p. kh t (February 1972)

[h] Bureau International des Poids et Mesures, Rapport Sur La

Cinquieme Comparaison des Etalons Nationaux D'Intensite et

de Flux Lumineux (1969).

[5] J. W. T. Walsh, Photometry , p. 532, Dover Publications, Inc.,

180 Varick Street, New York, N. Y. (1965).

[6] A. Kingslake, Applied Optics and Optical Engineering , p. 6l,

Academic Press, New York, N. Y. (1965).

27

FORM NBS-114A (1-711 U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-594-32. Gov't Accession No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

OPTICAL RADIATION MEASUREMENTS:

Photometric Calibration Procedures

5. Publication Date November 1972

6. Performing Organization Code

7. AUTHOR(S)

Velma I. Burns and Donald A. McSparron

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Task/ Work Unit No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same as No. 9

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.)

The National Bureau of Standards supplies calibrations of luminous intensity,

luminous flux and color temperature on a routine basis. The procedures, equipment

and techniques used to perform these calibrations as. of October 1972 are described.

Details of the uncertainty information currently available, including estimates

and procedures for determining uncertainties of the reported values, are also

presented.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Calibration procedures; color temperature; luminous flux; luminous intensity;

photometry; uncertainty'

18. AVAILABILITY STATEMENT

1X1 UNLIMITED.

I I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

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215
MUMUMUI LSL |\CICIU. UsstjMu^m teken from lh8 liDiafy. APR 2 1973 Qc /oo NBS TECHNICAL NOTE 594-4

Optical Radiation Measurements:

The Impact of

Radiometry and Photometry

and the Role of NBS

:)MMERCE
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3,

1 901 . The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3)

a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics —

Linac Radiation- — Nuclear Radiation - — Applied Radiation- — Quantum

Electronics :; — Electromagnetics '• — Time and Frequency 3 — Laboratory

Astrophysics :: — Cryogenics 3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—-Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies

upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

bodies. The Institute consists of a Center for Building Technology and the following

divisions and offices: Engineering and Product Standards—Weights and Measures—Invention and

Innovation—Product Evaluation Technology—Electronic Technology—Technical Analysis—Measurement Engineering—Building Standards and Code Services4—Housing Technology4 —Federal Building Technology4—Structures, Materials and Life Safety4—Building Environment4—Technical Evaluation and

Application4 —Fire Technology.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition,

and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

Publications—Library—Office of International Relations.

'Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

4 Part of the Center for Building Technology.
Optical Radiation Measurements:

The Impact of Radiometry and

Photometry and the Role of NBS

Bruce Steiner

Heat Division

Institute for Basic Standards

National Bureau of Standards

Washington, D.C. 20234

%TAU Of

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued March 1973
National Bureau of Standards Technical Note 594-4

Nat. Bur. Stand. (U.S.), Tech. Note 5944, 56 pages (Mar. 1973) CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Price $0.80 domestic postpaid or $0.55G.P.O. Bookstore.
Preface

This is the fourth issue of a series of Technical Notes entitled OPTICAL

RADIATION MEASUREMENTS. The series consists primarily of reports of progress

in or details of research conducted in radiometry and photometry in the Optical

Radiation Section of the Heat Division and appears about every six weeks. The

current issue, however, is an exception. It presents the impact of radiometry

and photometry on a number of problems of national concern and NBS' role in the

measurement aspects of these problems. The document was originally prepared

for internal use. It is being included in this series because of the belief

that it would be of interest and use to a much wider audience.

Henry J. Kostkowski , Chief

Optical Radiation Section

National Bureau of Standards

111
Foreword

Individual scientists and scientific institutions are being asked increasingly to

identify specific long-term effects of their work. This identification is at best

difficult and imprecise. Nevertheless it provides as quantitative a basis as is possible

for establishing specific programs and priorities.

This examination of potential effectiveness has been stimulated by the increased

concern for national problems, such as the energy crisis, pollution, and public safety.

In the development of solutions for these problems, the suitability of technical approaches

must be assessed. The promise of specific experimental and theoretical procedures must be

evaluated. Thus increasingly the relationship of various technical fields to national

goals and problems must be identified.

One technical area of major potential impact on many problems of national concern is

the field of electro-optics. This field has experienced exceptionally rapid growth in

the last five years . Though this growth has strengthened markedly the ability of the

field to provide solutions to certain problems, it has created its own problems in terms

of increased disagreements among measurements. Disagreements in optical radiation measurements of commercial and public significance are now widely evident and are growing in

severity.

Therefore the National Bureau of Standards is now reviewing its traditional concern

for optical radiation measurement accuracy, the new emphasis on national needs, and the

application of sophisticated technical measurement to national problems. Its review of

these national questions, the answers to which depend on progress in optical radiation

measurement, may interest a wider audience than the Department of Commerce, for which

this report was initially prepared.

The study is designed not only to describe present important problems but to con- centrate on those of future impact. It must therefore anticipate the development of

technology and its problems. It must extrapolate. Therefore this review presents only

a cursory summary of many complex issues and some supporting evidence.

Commercial questions are also intimately involved. Any improvement in industrial

technology stems from and in turn will stimulate keen competitive interest. We are indeed extremely grateful to our correspondents in industry, especially those in the

Council for Optical Radiation Measurement, for the insights that they have given us. But because of the commercial impact of technical forecasting in this area, this version

of the NBS study excludes individual reference to particular companies and the exact data

they have given us

.

A comprehensive study of the issues might well be expected to include a detailed

program for action. In Chapter 5 some general comments are made that suggest such a program. Detailed programs have in fact been constructed separately in the various

projects covering areas of this review. A comprehensive, centralized solution has not

been proposed here. Nevertheless one initial component in a new NBS approach to these

problem-studded fields is the present survey of the issues ultimately involved. In an improved measurement system, NBS must make a sensible contribution derived from an understanding of these ultimate issues.

IV
TABLE OF CONTENTS

Page

1. The Problem is Serious Discrepancy 1

2. The Reason is Growth: Working at the State of the Art 2

2.1 Introduction 2

2.2 Rapid Growth 2

a. U.S. Growth 2 b

Foreign Growth 3

2.3 The Rickety Technical Base 3

a. Radiometry 3 h . Photometry 3

c. Recapitulation 5

2.k Wide Diversification of Growth in the Art and in Public Interest 5

a. New Kinds of Technology 5 (1) Light Emitting Diodes 5 (2) Other New Lamp Types 5 (3) New Detectors 5 (k) New Optical Instrumentation 5 b. Broadened Spectral Range and Distribution 6

c

Low Level 6

d. High Level 6

e. Pulsed Measurements 6

f. New Public Interest 6

(1) Transportation 6 (2) Public Safety 8 (3) Governmental Activity 8

g. Other Anticipated Areas of Impact 8

2 . 5 Measurement Impact of Growth 8

a. Increased Necessity for Intercomparability . . 8 b. Relationship of Photometric to Radiometric Measurements 8

c. Generality of the Difficulty 9

3. The Issues 10

3.1 Statutory Obligation 10

a. Direct Responsibility _ 10

(1) Organic Act 10

(2) Specific Photometric Responsibility (Visible Light) 10

b. Indirect Responsibility . 10

(1) New Legislation 10

(2) Secondary Calibration Laboratory Support 12

3.2 Technological Issues 12

a. New Lamps 12

b. New Detectors 12

c. New Instrumentation 13

v
Page

3.3 Public Issues 13

a. Public Health 13

(1) Phototherapy 13

(2) Clinical Analysis 13

b. Public Safety lk

(1) Atmospheric Transmission of Ultraviolet Light lk

(2) Biomedical Engineering lk

(3) Transportation lk

c. The Energy Crisis 15

d. Meteorology 15

e. Pollution Monitoring l6

f

.

Remote Sensing 17

g. Crime Prevention 18

h. Botany l8

3.*+ Economic Issues 18

a. Unit Production Cost 18

b. Quality Control 18

c

.

Product Improvement 19

d. Innovation 19

e. Equity in Trade 19

(1) The Consumer's Concern with Technical Data 19

(2) Government Purchasing 19

(3) An Orderly Market 19

f. The Balance of Payments 20

3.5 Scientific Issues 21

a. An Opportunity 21

b. "One-shot" Experiments 21

c. Atomic Physics 21

Alternate Solutions 22

k.l Technical Factors 22

k.2 Nontechnical Factors 22

k.3 Other Agencies 23

k.k Synopsis 23

The Role of NBS 2k

5.1 What Needs to be Done 2U

a. The Characterization Required: Research 2k

(l) Source Characterization 2k

(a) Realization of Scales 2k

(b) Transfer to Secondary Standards 2k

(i) Characterization of Present Standards 2k

(ii) Improvement of Present Standards 2k

(iii) Description of Procedures for Present Standards .... 25

(c) Extension of Present Standards 25

vi
Page

(2) Detector Characterization 26

(a) Realization of the Scale: Electrically Calibrated

Detectors 26

(b) Thermal, Nonelectric ally Calibrated Detectors 26

(c) Quantum Detectors 26

(3) Characterization of Certain General Problems 26

b. Dissemination and Verification 26

5.2 Why NBS? 27

a. Fractionated Market 27

bAgreement Rather than Accuracy 27

c. NBS Mission 27

d. Past Accomplishment 28

e. Organizational Contacts 28

f. Industrial Desire for NBS Activity 28

g. Future Savings 29

5.3 Present Program 29

5.h Other NBS Resources to be Applied 29

5 . 5 Non-Monetary Support 29

6. Recapitulation 30

7. References 31

8. Appendices 3I+

Appendix A 35 Appendix B 38

Appendix C 39

Appendix D 1+2 Appendix E 1+3 Appendix F 1+5 Appendix G 1^5

LIST OF TABLES

1. Examples of growth in optical radiation industry 2

LIST OF FIGURES

1. Growth of electro-optics industry 1+

LIST OF PLATES

1. Spectral power distribution of an incandescent lamp, a fluorescent lamp,

and a high intensity discharge lamp 7

vi 1

THE IMPACT OF RADIOMETRY AND PHOTOMETRY

AND THE ROLE OF NBS

Bruce Steiner

Serious measurement discrepancies universally plague quantitative

measurement in the electro-optics industry. The impact of the resulting prohlems is reviewed and the role of NBS explored. The measurement

discrepancies arise chiefly through the recent explosive expansion of

this industry. The growth has precipitated a complex development in

the variety and accuracy of measurements required. The impact of

prohlems in optical radiation measurement falls in many areas. One is

the increasing Federal responsibility for public life defined in recent

legislation. Another is the influence of good optical radiation measurement on the technical development of the electro-optics industry.

The impact of these measurements on a number of public issues is

reviewed: public health, public safety, the energy crisis, meteorology,

pollution, agriculture, crime prevention, and surveillance from air and

space. The economic impact of improved measurement both on a fair

domestic market and on the balance of payments operates through unit

production cost, quality control, product improvement, and innovation.

Leadership by NBS has been urged by the industry not only in fulfillment of its legislative responsibility but also to permit the focus of

elaborate and impartial resources on the complex problem of optical

radiation measurement. In keeping with its mission to help improve

industrial technology and the competitiveness of American industry, NBS

has an opportunity of major proportions in the electro-optics industry.

Leaders of this industry are calling for NBS initiatives to resolve many

of the measurement problems now hindering further progress.

Key Words: Agriculture; clinical analysis; economic impact; energy

crisis; meteorology; photometry; phototherapy; pollution, radiometry;

remote sensing.

1. THE PROBLEM IS SERIOUS DISCREPANCY

Quantitative measurements of optical radiation typically disagree seriously with com- parable measurements. Such discrepancies vary in size between several percent and several

hundred percent. They arise both within and among laboratories, nationally and internationally. They occur in all spectral regions, in the ultraviolet, visible, and infrared.

This situation is widely considered to be intolerable. Concern has been expressed in

conversations and in voluminous correspondence with industry, other governmental agencies,

and universities. It has also been expressed by the electro-optics field as a whole through

the organization of the Council for Optical Radiation Measurement. Reports of Working

Groups of this Council furnish the beginning of an industry-wide consensus on the broad

incidence and the great urgency of the problem.

The basic purpose of this study is to examine the issues. These are studied in

Section 3. Alternatives for dealing with them are covered in Section k. The contributions

NBS can make and why it should do so are covered in Section 5. The fundamental question,

however, is the general technical basis for this situation: "How we got here and why?"

This is reviewed in Section 2. It must be examined first, because it bears on the severity

of the problem. This technical basis also suggests the ultimate range of solutions.
2. THE REASON IS GROWTH: WORKING AT THE STATE OF THE ART

2.1 Introduction

Primary responsibility for serious disagreement in optical radiation measurements rests

on technical growth. On the one hand, there is the recent exceptionally rapid growth of

electro-optics technology. Moreover, expansion also in public concern is making new demands

on this technology. Specific issues will be cited and examined in the next chapter. However, both the significance of these issues, and the present ability of NBS to respond to

them, are strongly affected by three factors: l) the rapidity of recent growth, 2) the

present undeveloped nature of radiometry* and photometry*, and 3) the polydimensionality of

recent development. Both commerce and the public interest require measurement frequently

at or beyond the state of the art. The implications of this situation are severe.

2.2 Rapid Growth

a. U.S. Growth

The present rapid expansion of our electro-optics industry is characterized by two

types of growth. In some cases, established companies are expanding rapidly. At the same time, new high-technology companies are proliferating in number.

Large sections of the industry are expanding by a factor of two to four every nine

years (Table l). The lamp (light bulbs) and lighting fixtures industries are doubling every

nine years. The manufacture of television receiving sets triples in nine years. The dollar

value of cathode ray tubes production quadruples after nine years. The manufacture of light

sensitive diodes nearly doubles in four years. The value of equipment for photogrammetry

nearly tripled in the four years between 1963 and 1967. Optical instrument manufacturing

quadruples in nine years. The manufacture of photographic equipment triples in a nine-year

period. Several of these components are now individually multibillion dollar industries.

Table 1. Examples of growth in optical radiation industry

Millions of Dollars

(Source: U.S. Census of Manufacturers)

Industry 1967 1963 1958

Lamps (Bulbs) 756. 5U6. 39^.

Lighting Fixtures 1,5^3. 1,116. 765.

TV Sets 2,260. 1,092. 727.

TV Tubes 766. 2U9. 177.

Light Diodes 19. 11. not separated

Photogrammetry 5-9 2.2 not separated

Optical Instruments U52. 270. 116.

Photographic Equip- 3,138. 1,631. l,06l.

ment and Supplies

Much of this growth has been reflected in the growth of industrial giants such as Eastman Kodak and General Electric. But the electro-optics industry also contains a large

number of small companies. In fact, the most recent Optical Industry and Systems Directory

lists over 1,^00 suppliers, a number of which are small businesses.

*Radiometry: science of quantitative optical radiation measurement

Photometry: eye-response-weighted radiometry
The most rapid growth is now found in non-Federally related activity. By contrast,

the initial impetus had been furnished hy the defense and space efforts. This Federal

activity formerly provided administrative as well as financial focus. But with the slowdown

in these communities, growth is reflected by a change from centralized Federal sponsorship

to diverse Federal and private interests. This change requires an even greater intercomparability of measurements than would have otherwise been the case.

b. Foreign Growth

Other countries have just begun to move into this very promising field [l] . An important indicator of the rate of growth is the number and variety of demands that the whole

industry is presenting to its national laboratories. The severity of the American situation

is yet approached abroad only by NBC in Canada. Figure 1 gives a qualitative picture of the

development of this field with time. In the figure, assistance requested and time are both

normalized in terms of the point at which national expectation of assistance seriously outdistances the capacity of the respective national laboratory to respond. The data is taken

from personal conversations of the author with those responsible for the programs in radiometry and photometry in the various national laboratories . NBS and NBC find themselves in

a position to anticipate problems and provide leadership in a situation that will surely

arise in the other national laboratories: NPL, PTB, ETL, NSL, BNM, and IMM. It is interesting to observe that there is a rough correlation between the severity of their present

optical measurement crisis and proximity to the U.S. We shall return to the important

foreign trade implications of this picture in Section 3.

2.3 The Bickety Technical Base

a. Badiometry

The initial demands of defense and space technology have been met in radiometry by

the establishment of a few basic standards. These of necessity were tied to fundamental

physical measurement, but as often as not only loosely by contemporary standards. Very few

pillars of this radiometric foundation go to bedrock as seen today. And those few that do are available only at an enormous cost in effort by highly trained and painstaking workers.

The utilization of these standards for measurements of immediate practical interest is so challenging that most efforts become research projects in themselves. The level of agreement among measurements is frequently no better than that in exploratory research.

The previously modest commercial requirements in radiometry were met by spin-off. They were accommodated within the focused attention of DOD and NASA in a few basic areas. However, DOD interest in radiometry and photometry is now being curtailed at a time of rapidly

increasing non-defense need for attention. In a similar way, a modest amount of accurate

radiometric measurement of academic long-range interest has also been entertained within

this Federal framework. However, academic requirements are now increasing in severity at the same time that this skeleton framework has ceased to develop.

b . Photometry

Visual evaluation of light preceded the ability of the physicist to measure its spectral power distribution. But the best photometric measurements are still comparable only

to an accuracy of a few percent. Their conversion to and from purely physical quantities,

e.g. watts, is even now possible at best to about 3%. In the absence of a firmer physical

foundation, agreement among photometric measurements has depended heavily on the limited

variety of objects measured and the limited types of measurements made. It has also been

aided by the traditionally modest level of agreement expected.

This system held together tolerably well for incandescent lamps. For a small variety

of film types, it also worked: film and the photographer were relatively "forgiving" of

imprecise exposure. In other more specialized areas of interest, DOD was able to fund the

figures in brackets indicate the literature references at the end of this paper.
GROWTH OF ELECTRO-OPTICS INDUSTRY

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establishment and separate maintenance of special standards, gages that were not tied

closely to "basic physical measurement.

But no longer. Apart from the comparison of similar incandescent lamps and a few

other specialized objects, photometric measurement can now be performed only with unacceptable agreement and even then only with great effort by contemporary standards. Since the

archaic structure has a weak physical basis it cannot be patched or extended.

c. Recapitulation

For differing reasons, then, the structures of photometry and radiometry have been

minimally responsive to relatively undemanding isolated and non-interrelated requirements.

That era has ended. We shall see that the existing small but firm radiometric foundation

achieved by great labor will accommodate neither the quantity, the variety, nor the interrelation of present needs of the electro-optics industry. A major new thrust will be

required for NBS to make substantial progress in meeting the rapidly evolving expectations

of its constituency in radiometry and photometry.

2.k Wide Diversification of Growth in the Art and in Public Interest

A few specific examples of recent growth may provide a useful framework for understanding Section 3.

a. New Kinds of Technology

A dominant feature of the present growth of the electro-optics industry is the development of very new technology. This technology throws into relief the limitations of much of

classical radiometry and photometry [2], For present measurements to be meaningful, they

must be comparable with others. One cannot continue arbitrarily to set up new gages.

(1) Light Emitting Diodes

The newest and most rapidly growing type of source is the light emitting diode (LED).

It has a unique spectral distribution (color) very different from that of the incandescent

lamp. The use of this lamp has developed very rapidly within the past year [3]. It promises ultimately to replace the incandescent lamp at low levels. Measurement of these new lamps is becoming a very serious problem [*+-7; app. A].

(2) Other New Lamp Types

The proper role of NBS with respect to the lamp industry will be examined closely in

Sections h and 5- For the moment we postulate the argument that accurate measurement of

total flux of a variety of lamps is in the national interest and clearly relates to the

mission of the Bureau. The recent rapid development of new lamp technology then places an enormous new burden on the present system [8]. The variety of lamps produced is such that

the few incandescent lamp standards now available are inadequate to the job.

(3) New Detectors

The rapid development of new detectors has led to a new emphasis in an area that formerly received little attention. The stability of new solid state detectors has aroused

serious interest in a detector that might serve as a secondary standard. This is an attractive idea particularly for photometry, a field built conceptually on a natural detector, the eye [7,9] • Furthermore, a need has arisen for characterization of totally new

detectors such as vacuum photomultipliers incorporating III - V compounds. These provide

an unusually flat wavelength response [10].

(k) New Optical Instrumentation

The growth of the entire electro-optics field is leading to the entry of a number of new radiometers and photometers that offer substantially higher reliability than in the

past [2]. Firms already established in other areas are now entering the field [ll]. With

the increasing commercial availability of optical measurement technology and its increasing
precision, the need for both higher accuracy and more reliable verification of measurement

performance is becoming a pressing problem.

b. Broadened Spectral Range and Distribution

The growth in demand for better measurements is particularly keen in the infrared

[6,12-13; app. B] . Measurements in this region promise to be particularly useful in finding

solutions to a number of social problems explored in Section 3 [6].

The growth in ultraviolet requirements is also remarkable. Both spectral radiance and

irradiance are becoming of primary interest to the ultraviolet user [13]. In addition, the

measurement of ultraviolet total flux is important to the manufacturer of equipment, production and replacement part verification, serving photochemistry, graphic arts, and

chemical production [5].

Sources of light with a spectral distribution different from that of current standards

become more important [T] as the distribution of natural daylight is recognized to be of

considerable health and safety significance (Section 3) and as the spectral distribution of

artificial light sources becomes increasingly bizarre (Plate l)

.

c. Low Level

Measurements at low light levels have presented a new set of problems. Commercially

important sources are presenting serious measurement problems at these lower levels [ U—

T

9 lk; app. A].

Looking to the future, the ultimate feasibility of photon counting as a basic measurement tool, whether as a primary realization or a secondary standard, will depend on the

ability to couple single photon techniques with classical power measurement. A far-sighted

program in radiometry will have to include work in this area if NBS is to prepare itself

for future demands of a basic nature. No standards here presently exist.

d. High Level

At the other extreme, the measurement of high level sources is also increasingly

important [T]. High total flux measurements bear on foreign trade as we shall see in

Section 3 [8]. The importance of high irradiance measurement in new safety requirements

[15] for the photographic industry is now recognized by Underwriters Laboratories. NBS

presently has no high level standards in the range of this new concern.

e. Pulsed Measurements

An area of desultory NBS activity that generally has a very low level of reliability,

but one of increasing commercial and technological importance, is the measurement of pulsed

sources. These are used in photography and traffic control; they are of great importance

in growing laser technology [^,7,1*+; app. A].

f

.

New Public Interest

The growth of public concern, as reflected in new and anticipated governmental action,

poses many new measurement problems that require firm, reliable solutions.

(l) Transportation

Recent Federal entry into the regulation of safety in transportation is leading to new

requirements in automobile lighting. Both head lighting and tail lighting [?] are involved.

Newer materials are complicating the measurements and making obsolete most former measurement techniques [l6].

The problem in this as well as related fields are complicated by the lack of recognition that even the barely tolerable level of past agreement is no longer possible. Diversification in the types of sources and materials being measured is further complicated by

new types of instruments now used to measure them [9]. Continued lack of attention to this
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problem will result in much larger future measurement discrepancies. But at the same time,

broad recognition of the influence of lighting on safety is calling for even tighter

tolerances [IT]. The transfer of responsibilities in this area to the Federal Government moreover provides a new focus for concern. This focus will make the poor measurement

situation more visible, and thus more intolerable.

(2) Public Safety

The growth of concern for public safety is illustrated by activity after the ignition

of clothes by lights on a movie set. Underwriters Laboratories are in the process of

propagating for the first time a specification on the radiant heat a given distance from

movie lights [15]. This particular specification calls for measurements not possible with

current NBS standards.

Another example is the increased medical concern about the ultraviolet flux from lamps.

Biological activity in this spectral region is being very widely recognized and will be

covered in more detail in Section 3. Present standards go back 30 to ko years with conse- quently very questionable accuracy [5]. The basis for new Federal administrative action

has already been laid: new legislation will require both new total flux measurements not now possible and more reliable spectral irradiance measurements than are now available.

(3) Governmental Activity

Recent Federal activity in transportation has been noted. Increasing public concern

about the environment has led to greater Federal concern with optical radiation measurement

in the Radiation Health and Safety Act [5]. NBS is in the interesting position of a Federal agency asked by industry to become more actively involved in interaction with private enterprise [h] . The electro-optics industry clearly desires to fulfill its contractual

agreements reliably, not by an unsatisfactory adherence to sparsely available standards [l^].

g. Other Anticipated Areas of Impact

Among the many applications that are, or shortly will be, strongly affected by rapidly

changing technology are: aerospace cockpit lighting [T]; photographic instruments and

associated filters, sources, and detectors [T,l8]; cathode ray tubes; and computers [T].

Graphic arts and television may shortly be greatly affected by a relatively unfamiliar type

of color image production: liquid crystals [19].

2.5 Measurement Impact of Growth

a. Increased Necessity for Intercomparability

The general diversification of types of measurements made with rapidly developing

technology places a severe strain on the use of a relatively static number of standards.

That is, a new measurement will necessarily imply new techniques and new procedures. In general these will differ in a given laboratory from those in another in "geometry,

polarization, and instrument spectral response" [k] .

Although outside agencies have no legal power to commit NBS resources in order to provide "traceability" , industries and other government agencies increasingly rely on NBS via

"traceability" requirements. Our response to this situation will have broad impact on a substantial segment of industry. NBS, as noted above, has a unique opportunity here as well as some serious hazards to be avoided. Industry is looking actively to NBS.

b. Relationship of Photometric to Radiometric Measurements

A most important type of intercomparability now demanded is that between photometric

(eye-response related) and radiometric (physical) quantities. Because photometric measurements preceded the more basic radiometric ones, a separate system arose. It has become

hallowed first by usage, then by enshrinement as a "Base Unit", the candela, and finally,

by a special legal responsibility of the Secretary of Commerce for maintenance of a special

set of photometric standards (Section 3). Nevertheless, the physical separateness of the

photometric system from the more clear radiometric system has become a serious commercial
liability. In areas where "both eye-response and power units are required, two separate not

legally convertible sets of units are no longer economic [6-7,13,18,20]. Although few

people question the advisability of using eye-related units for visually important quantities, the existence of a detached system for this purpose is increasingly a liability.

Growth in both areas of measurement requires firm convertibility.

c. Generality of the Difficulty

The problems that have been described are widespread problems, as the redundancy in

the referenced comments indicates. It is indeed largely the growth in the redundancy of

these problems [6] that calls for a major new effort. Because of the wide number of

measurements made and the interdependence of the results, a comprehensive program for

attention is required. The constraints that this factor places on feasible NBS programs

will be examined in Section k.
3. THE ISSUES

3.1 Statutory Obligation

a. Direct Responsibility

, 1) Organic Act

Direct NBS responsibility for national standards of measurement is defined in 15 U.S.

Code 272, which authorized the Secretary of Commerce to undertake: "the custody, maintenance, and development of the national standards of measurement, and the provision of means and methods for making measurements consistent with those standards, including the

comparison of standards used in scientific investigations, engineering, manufacturing,

commerce, and educational institutions with the standards adopted or recognized by the

Government"

.

Authorization that: "The Bureau shall exercise its functions for the Government of

the United States: for any state or municipal government within the United States; or for

any scientific society, educational institution, firm, corporation, or individual within the

United States engaged in manufacturing or other pursuits requiring the use of standards or standard measuring instruments" has a renewed significance in connection with more recent

legislation described below.

In carrying out these functions, activity for: "(l) the construction of physical

standards; (2) the testing, calibration, and certification of standards and standard

measuring apparatus; (3) the study and improvement of instruments and methods of measurements" is also authorized. Authorization for "(9) the investigation of radiation, radioactive substances, and X rays, their uses, and means of protection of persons from their

harmful effects" is an incredibly broad responsibility with respect to the marked growth

characterizing the electro-optics industry. "Cooperation with other governmental agencies

and with private organizations in the establishment of standard practices, incorporated in

codes and specifications; advisory service to Government agencies on scientific and technical

problems, invention and development of devices to serve special needs of the Government" will

be increasingly demanded as legislation and its authorized Federal activity expands rapidly.

(2) Specific Photometric Responsibility (Visible Light)

In addition to the important but general authorization in the Organic Act, 15 U.S.

Code 22U, Public Law 8l-6lT, goes considerably further with respect to photometric (eyerelated, that is, visible light) units: "It shall be the duty of the Secretary of Commerce

to establish the values of the primary electric and photometric units in absolute measure,

and the legal values for these units shall be those represented by, or derived from,

national reference standards maintained by the Department of Commerce."

The growth described in Section 2 bears directly on the rapidly increasing obligation

of NBS in connection with photometric units. As the variety of the applications of such

measurement grows, the public expectation of NBS performance, with the substantial backing

of the cited legislation, increases apace. This expectation is particularly demanding with

respect to increasing industrial desire for the strong coupling of photometric and radiometric units L 6-7,13, 18, 20]

.

b. Indirect Responsibility

(l) New Legislation

The preceding citations stressing cooperation with other government agencies convey

renewed significance after the recent passage of several pieces of Federal legislation:

"The Federal Hazardous Substances Act", 15 U.S. Code Chapter 30, The Radiation Health and

Safety Act of 1968, Public Law 90-602, and the Occupational Safety and Health Act of 1970,

Public Law 91-596. This significance for optical radiation measurement at NBS follows.

The "hazardous substances" referred to in the U.S. Code include: "any substance or mixture of substances which (i) is toxic, (ii) is corrosive, (iii) is an irritant, (iv) is

10
a strong sensitizer, (v) is flammable or combustible, or (vi) generates pressure through

decomposition, heat, or other means, if such substances or mixture of substances may cause substantial personal injury or substantial illness during or as a proximate result of any

customary or reasonably foreseeable handling or use, including reasonably foreseeable

ingestion by children." This act provides for the removal from commerce of substances

found by the Secretary of HEW to be hazardous. The lamp industry is already concerned about

the compliance of some of its products [5]. As the biological effects of ultraviolet light

become more widely recognized many other conventional lights may be brought shortly under

this legislation. In addition, eye damage produced by flash lamp radiation in the IR, may

also be recognized within the foreseeable future [20]. Laser damage will be of increasing

concern. Provision has already been made for the monitoring of hazardous substances.

The Radiation Control for Health and Safety Act of 1968, Public Law 90-602, also

implies a similar major new thrust of government concern and government action. It covers

"any manufactured . . . product which . . . acts as part of an electric circuit and emits

. . . ionizing or nonionizing electromagnetic . . . radiation". The Secretary of HEW is

authorized to "plan, conduct, coordinate, and support radiation research" ... to minimize

the emission of . . . unnecessary electronic product radiation" and to "consult and maintain

liaison with the Secretary of Commerce ... on techniques, equipment, and programs for

testing". HEW is to monitor "measures to assure consistent and effective control of the

aforementioned health hazards" and to "invite the participation of other . . . agencies

having related responsibilities and interests". "The Secretary of HEW shall by regulation

prescribe performance standards . . . "and shall give consideration to . . . "the adaptability of such standards to the need for uniformity. "In case of actual controversy . . . any person who will be adversely affected . . . may at any time . . . file a petition with

the United States Court of Appeals". Provision is made also for inspection of testing

procedures

With the increasing public concern for biological effects of radiation, both of

visible and of near visible ultraviolet described later, these provisions indicate a substantial growth in radiometric expectation. This will evolve into support service requests

in the next few years

Finally, the Occupational Safety and Health Act of 19 TO, Public Law 91-596 notes that

"occupational health standards present problems often different from those involved in

occupational safety". The Secretary of Labor is responsible for assuring that "no employee

will suffer material impairment of health or functional capacity even if such employee has

regular exposure to the hazard dealt with by such standard for the period of his working

life". Provision is made for complaint by any employee and subsequent investigation by

Labor. "The United States district courts . . . have jurisdiction, upon petition of the

Secretary to restrain any conditions or practices ... If the Secretary arbitrarily or capriciously fails to seek relief under this section, any employee who may be injured by

reason of such failure . . . might bring an action against the Secretary". Initiative is

thus in the hand of the general public as well as in the Federal Government. Penalties are also prescribed.

Action may come more quickly than expected in this growing area of biological interaction with radiation. The Secretary of HEW is empowered here also to "conduct . . . research . . . relating to innovative methods, techniques, and approaches for dealing with

occupational safety and health problems". The National Institute for Occupational Safety

and Health is created by this act "to develop and establish recommended occupational

safety and health standards". The Secretary is empowered to "develop and maintain an effective program of collection compilation, and analysis of occupational safety and

health statistics", a provision which could place very great burden on radiometric capabilities. One initial effect of this legislation is already apparent in requests from NIOSH

for calibration [21].

In addition, WBS as an employer will be expected to "establish and maintain an effective and comprehensive safety and health program".

If the anticipated connection between radiometry and medicine is shown to be as close

as present experiments suggest, the indirect statutory obligation that NBS is acquiring

will strain the present capability for measurement far beyond its design performance.

11
Measurements now made with primary concern for great reliability do not lend themselves

readily to massive, inexpensive repetition and extension.

(2) Secondary Calibration Laboratory Support

The NBS has not been able to meet all or even most requests for calibration and other

technical assistance. Commercial calibration laboratories have been founded to fill the

gap. But the performance of these laboratories has not met the requirements of the marketplace. Discrepancies are common [6]. This whole small industry must depend on NBS not

only to stay in business but to provide more consistent service. Some sort of direct NBS

assistance will be called for. This aid will probably take the form of measurement intercomparison and the dissemination of techniques. NBS will also have to be prepared for a formal request for the establishment of an accreditation procedure [22].

3.2 Technological Issues

Although the recent rapid growth of electro-optics technology was illustrated by a few

examples in Section 2, the specifically technical implications of this development should now be examined in more detail. The public interest and finally the commercial implications

of this technology will then be examined.

a. New Lamps

In the traditional lamp industry two types of lamps are replacing incandescent lamps:

fluorescent lamps for inside use and high intensity discharge lamps for outside use. Fluorescent lamp measurement is not new. Nevertheless, except under special circumstances

that cannot economically be extended, the level of measurement agreement among lamp companies,

5-22%, is presently intolerable [23]. High intensity discharge lamps are so much more difficult that NBS is not in a position to measure them at all.

One source of this difficulty lies in the greatly differing spectral distribution of

discharge lamps both from each other and from incandescent lamps. Typical spectral power

distributions were illustrated in Plate 1. The photometric system had performed barely

satisfactorily for incandescent lamps, whose spectral distribution could be roughly matched

with one another by adjustment of the filament power. This flexibility is no longer possible

for discharge lamps. In addition, differences in shapes and in sensitivity to operating

temperature sensitivity, as well as other factors, also cause fluorescent lamps to strain the

traditional photometric system [8]. The resulting disagreement is an order of magnitude

larger for fluorescent lamps than that for incandescent lamps [23]. High intensity discharge lamps, whose spectra consists largely of spectral lines, now strain the system to the

point that routine measurements have not even been attempted at NBS. The difficulty arises

here primarily because of the dominant spectral lines and high levels. So many different

lamp types are now on the market [8] that a full set of direct substitution standards is no longer feasible.

The higher UV output of these lamps is an additional new factor in their measurement.

Moreover the potential public health influence of this output, as described later, is

expected to lead to increasingly tight Federal regulation, either under the legislation

just described or by new laws.

Light emitting diodes present problems similar in character to those of the high

intensity discharge lamps: spectral distribution and level. The level involved here,

however, is not higher but lower than normal [3-7; app. A]. As noted before, these diodes

promise to replace all low level signal lights, a potentially very great usage.

b. New Detectors

Until recently most light detectors have been so unstable both in spectral sensitivity

and in total response that they could be used only as comparative devices. That is, they

could compare reliably only similar sources. Moreover, measurements had to be made in

rapid succession. With many new types of detectors these limitations are now becoming less

confining however. The spectral sensitivity of new solid state detectors is now sufficiently

12
stable to make worthwhile reliable measurement with accuracy and precision [7,9]- Silicon

diodes are being widely used in the visible and near infrared. A wide variety of new diodes

is being used throughout the infrared, where technology is moving very rapidly. New vacuum

diodes and multipliers with photocathodes of III - V compounds such as galium arsenide are highly sensitive and display a relatively flat spectral response in the visible, an exciting

development [ 10 ]

This new technology presents new demands on NBS for characterization and measurement.

But these developments also provide new opportunities for new technical solutions to

radiometric problems.

c. New Instrumentation

Optical instrumentation is also developing very rapidly. Beyond the obvious problems

associated with the fidelity of color TV as presently produced, for example, new technology

for TV picture reproduction is on the horizon and will require new techniques. Liquid

crystals are one promising approach [19]. Thin film electroluminescent surfaces are another

[2^]. The development of low level imaging tubes has outstripped the ability to measure

their gain accurately. A measurement capability is now desirable; it will become necessary

[25-26]. Recent developments in the film and camera technology are leading to requirements

for 1% measurements [27], and new radiometric standards [2,18,28],

With recent technical advances, then, better standards are indeed required to support

continued technical growth [2]. Recent developments in all of these fields also make

possible new solutions to radiometric problems, but their effective utilization will require

a major new effort.

3.3 Public Issues

a. Public Health

(1) Phototherapy

The relationship of radiometry to health has been noted by George Zissis, Chairman

of the NAS-NRC Radiometry and Photometry Evaluation Panel [29]. A review of a number of

biological effects of lighting has appeared in the MIT Reports on Research for April 1970

[30]. The jaundice that occurs in 10-20% of premature infants [31], if allowed to persist,

can cause permanent neurological brain damage [32]. It is treated now by phototherapy [33].

The herpes virus infections that cause cold sores and the genital area infections that often

precede cancer of the cervix are also responding to such treatment [3^]. Another direct

effect of light is seen in calcium absorption in elderly men. The amount of absorption has

been shown to be a function of the lighting environment [35-36].

Indirect effects are also observed. A number of neuroendocrine functions both by

humans and animals have been shown to be so controlled. For example, the effect of illumination level and duration on gonadal size has been shown [37-39]. The working ability of

school children has been shown to be affected by the spectral distribution of room illumination [i+0].

Wurtman and Neer have editorialized in the New England Journal of Medicine: "perhaps

it is not too early to suggest than an appropriate Federal body give thought to the ultimate

necessity of regulating the spectral composition of commercially available light sources

. . . It seems safe to state that, whether we like it or not, light is another thing that

physicians must worry about" [Ul].

NBS now has no geometrically total flux standards or techniques in the spectral region

probably of greatest importance in biological activity 200-1+00 nm.

(2) Clinical Analysis

A separate medical issue is the increasing interest in spectrofluorescence as a new

tool in clinical analysis. Professor G. A. Crosby stated in a recent symposium at NBS

that he had received over 500 requests for a recent unquantitative article of his on

13
quantum yields in fluorescence. Most of these requests were from hospitals, with which he

had had virtually no previous contact. The development of this promising chemical analysis

field, in contrast to transmittance or reflectance measurements, will depend on accurate

radiometric standards.

The Task Group for Industrial Activity of the National Academy of Engineering feels

that: "Standards for and acceptance of uniform clinical evaluation procedures required for

successful development and marketing of "biomedical products have not been achieved [U2].

b. Public Safety

Three general areas of increasing importance will depend on new capability in radiometry.

(1) Atmospheric Transmission of Ultraviolet Light

"It has been suggested that the emission of oxides of nitrogen and possibly water

vapor [by the SST] may reduce the ozone content of the stratosphere. Since ozone plays a vital role in screening undesirable ultraviolet radiation from the sun, any significant

reduction in ozone is viewed with concern. Indeed, several alarming estimates of increased

skin cancer have already been made public" [U3]. Accurate measurement of this radiation

thus assumes great importance.

(2) Biomedical Engineering

The regulation of germicidal, sun, and ozone-producing lamps under the Federal Hazardous

Substances Act has been noted above. In addition, the Task Group for Industrial Activity

of the National Academy of Engineering has listed a number of questions that imply a strong

probability for future governmental activity involving radiometry. This Group notes that

"the question of medical device safety and efficacy has been repeatedly posed. The high

possibility of device safety legislation being passed in the near future . . . causes industry to be very concerned about this topic. That an appropriate type of governmental

regulation and control is needed is not challenged by responsible industrial leaders . . . The Task Group recognizes these valid concerns of industry. Because of the critical nature

of many products in direct contact with the patient or used in the diagnosis of diseases,

however, there must be greater assurances than that currently available that adequate

protection is given to persons exposed directly or indirectly to biomedical products or services . . . There is an urgent need to develop a rational program that includes procedures for the development of standards" [1+2],

Not only the National Academy of Engineering but, at the operational level, secondary

calibration laboratories are already feeling the pressure of biomedical problems [?]•

(3) Transportation

The increasing public concern for safety in transportation and particularly for highway safety has led to the transfer of safety monitoring from the states to the Federal

Government

.

This transfer is leading to the instigation of new highway lighting research and to new regulation, e.g. for headlights [^]. These will replace the flexible Society of

Automotive Engineers (SAE) agreements. At one research institute research is in progress

on optimum automobile illumination, both for a driver's own car and for those he meets on a highway. These measurements are being taken with a single instrument and without reference

to NBS standards. Thus equipment made to comply with the new Federal regulation based on these experiments may not duplicate the optimum lighting conditions actually found.

This particular issue is an example of a requirement for photometric standardization

that is not recognized as a problem even by those responsible for it. More generally, this

is an important aspect of the increasing Federal activity in regulation. Those with new measurement responsibility do not always recognize the severity and complexity of the

measurement and standardization problems. Without NBS cognizance, new regulations can be

written that bear very little resemblance to the research data on which they are in

lit
principle based. Such regulations could be a danger to public safety, not its protector.

Surely, if the potential hazards were not severe, no regulation would have been required in

the first place.

The shift in responsibility from the SAE to a Federal agency implies two future trends.

It foretells a tightening of the specifications. It also will mean the first monitoring for

conformance of production to specifications. Partially in response to this movement, industry is developing new photometric capability [U5]. This capability will create new demands

for measurement.

As noted in Section 2 photometric problems in transportation have been aggravated not

only by regulation, but also by the new technology itself. One example is the development

of new red plastic signal light covers that differ substantially in character (spectral

transmission) from the former glass covers. This difference makes obsolete the formerly

satisfactory techniques of color monitoring used when only one type was available. To

support this new safety-related technology, far more sophisticated techniques will be

required [l6]

Low level signal lighting measurements are related to other widely recognized safety

problems. One consequence of such problems is the expensive rejection of a major fraction

of signal panels for aircraft cockpits because these parts fail to conform to present

tolerances [U6], tolerances that are believed to cause difficulty in aircraft guidance.

Dark adaption of the pilot must be protected so that he can see external objects; he must

also see the inside panels distinctly.

c. The Energy Crisis

The rapid and increasing growth in the use of energy in this country is now front page

news [H7]. It has also been well documented [U8-5.0]. Our per capita rate of consumption

of energy is increasing at a time when the availability of sources of power is becoming

questionable [5l]. The Chairman of the Atomic Energy Commission has predicted the probable

eventual rationing of electricity [U7]. The efficiency of utilization of available power

is thus now a matter of great importance.

Approximately one quarter of our electricity consumption is used for lighting [51].

It is here that precise light measurement becomes significant. The efficiency of lighting

has increased from 15 lumens per input watt for standard incandescent lamps to 50 lumens per

watt for early fluorescent lamps to 75 lumens per watt for typical modern fluorescent lamps

and more than 100 lumens per watt for the most efficient "high intensity discharge" lamps.

Some of this progress has occurred in steps, with the introduction of new lmap types. But the 50% increase in efficiency of fluorescent lamps and advancement in other lamp types has

occurred in small steps over a long period of time [52-53]. The technical ability to evaluate such improvement depends strongly on the stability of reference standards. Not only

an industrial standard is involved. Stability is required in all standards to which reference is made.

In addition to the necessity to detect reliably small increases in luminous flux, the

absolute total luminous flux of different new types of lamps must now be intercompared on a common basis if the superiority of advanced types is to be demonstrated reliably . This

capability does not now exist. The issue here is not narrowly commercial, although it has

commercial implications that will be examined later. The strong balance of payments implications of improved lighting efficiency will also be explored later.

d. Meteorology

Meteorology [29] is more limited by present radiometric capability than probably any

other technical field. Conversely, it can make proportionally great progress with better

radiometric measurements. Radiometric information with an accuracy of 1%, but with a longterm precision for the detection of changes of 0.1%, is being requested. Both of these

requests are now beyond the state of the art [13] although not beyond achievement within a modest period of time given the appropriate determination to do so.

15
Ten percent discrepancies are apparent, for example, between Japanese and American

atmospheric profile measurements [5*+]. Such discrepancies and the even more serious lack of

global data have caused the World Meteorology Organization to take action [55]. New

international attention through the Global Atmospheric Radiometric Program (GARP) has been

focused on the physical collection of the proper amount and distribution of data now

unavailable.

Even within the U.S. serious discrepancies in data from the pyranometric network remain

[56-58]. The projected requirements can be achieved only by very few institutions such as NBS with a proper variety of technical resources to make the necessary progress.

Three areas of meteorology will be affected by improved radiometric capability. First,

short-term weather forecasting depends on radiometry for atmospheric temperature profiles

and indirectly to check mathematical models of the atmosphere. The validity of a shortterm forecast depends on the sophistication of the mathematical model used and also on the

reliability of the measured temperature profiles of the atmosphere. That is, the more accurately the temperature distribution is measured, the more accurately the local weather

can be predicted [58]- Such measurements were not feasible on a broad enough scale to make

a substantial impact before the advent of weather satellites. But these satellites present

revolutionary opportunities for large scale sophisticated measurements such as the temperature profiles. These measurements in turn will lead to more reliable models. Before this

promise is realized, however, new technical problems will have to be solved. Calibration

in flight will have to be consistent with ground-based observation. Accuracy is involved

here and not mere stability or precision.

In contrast to short-term weather forecasting, long-term weather projection depends on the global heat balance, i.e. the amount of heat incident on, absorbed by, and radiated from

the earth. It is the heat absorbed by the atmosphere that "drives" the weather. Thus

measurements by satellites must be accurately correlated with ground observations to provide

a meaningful measurement. Long-term drifts cannot be tolerated.

An issue closely related to natural long-term heat balance changes is the influence of

pollutants. To detect such an influence, reproducible measurements over a period of years

are required. Time is running out for the initiation of such measurements. This question

is critical at the 0.1% level because of the lead time for effects to become manifest.

Time is required also for controls to be instituted.

NBS has completed the initial phase of work applicable to this goal. However, much

more remains to be done. The value of this work has been noted by Robert White of NOAA [55].

e. Pollution Monitoring

The field of pollution is so large and moreover so rapidly changing that a quantitative

definition of future requirements is much more difficult than in other fields. Nevertheless,

the potential payoff for a development of radiometry here is so great that it is worthwhile

to examine [29,59] •• Although interrelated, air and water pollution may be separated here

for this analysis.

Air pollution at the top of the atmosphere has been indicated to be of significance

because of its potential for long-range climate modification [6o], In addition, pollution

introduced at the bottom of the atmosphere may have a short-range immediate effect, both in

space and in time. Although work in this field is just beginning, crude radiometric and

photometric techniques are already being used [6l]. These will have to be made more precise

and accurate. They will have to be placed on a continuing basis and provision made for

rapid response levels that suddenly become hazardous. Such an evolution is technically

possible. Pollution experiments on aerosol monitoring are already taking place in Boulder

in a joint NOAA-NCAR effort [62].

The influence on the upper atmosphere chemistry of potential supersonic transportation

was examined by Harold Johnston recently [63]. The implications of the changes produced in

transmitted solar energy on life were so great [U3] that a National Academy of Sciences

panel was convened to examine the subject. This panel observed that "the importance of

obtaining base line data [of the solar ultraviolet flux] in advance of any era of

16
substantial pollution needs to be strongly emphasized" [6U]. The technological challenge

to radiometry hoth quantitatively and qualitatively is enormous. Primary work in this area

is now being proposed by NOAA. NBS has been asked to be of assistance: "NBS calibration

assistance is vital to a successful endeavor" [1+3]

Water pollution is another large area of concern. Thermal pollution particularly is

susceptible to radiometric monitoring [6,51,65], but the challenge is increased by relatively high levels of atmospheric humidity. Other types of pollution are also susceptible

to monitoring [66] through their characteristic spectra. The opportunity that space observation offers in this area is large. The corresponding challenges to radiometry will be

great.

f. Remote Sensing

The field of remote sensing is a technological tool applicable to a wide variety of

ultimate social uses. Some of these were covered in the preceding sections on meteorology

and pollution monitoring. Remote sensing involving optical radiation promises to transform

these fields. In addition, however, other uses are also foreseen [29]. These potential

applications are collectively so important that the Panel on Science and Technology held a review of this field in January 1972 before the House Committee on Science and Astronautics.

The paper of Thiel and C. D. Graves prepared for this Congressional review is included here

[67]. Thiel and Graves note that by the most conservative calculation the benefit from

remote sensing will be $59 billion. About half of this will accrue to agriculture in stress

analysis, meaning for example, crop disease, infestation, and meteorological influences on agriculture. The other half is distributed among human disease, agricultrual inventory,

fishing, animal disease, natural disaster, solid waste disposal, resource management,

mapping, tax assessment, search and rescue, geophysics, water pollution, forestry, nautical

charting, ship routing, and air pollution. The savings in the last field at $1 million are the smallest of those mentioned.

Performance specifications of current NASA earth resources observational components

have not been determined by the quality of the data that would be effectively utilized by

these various fields, however. It is limited by the necessary constraints placed by the

state of the art of radiation measurement [68]. This is a case in which the limitations

presented by the state of the art are indeed costing a substantial, but as yet undetermined,

amount

The launching of the first Earth Resources Technology Satellites (ERTS) this spring

will provide the second NASA earth observation system. The data produced by the first

system, the "Michigan Scanner", will then be comparable directly with other NASA data for

the first time [69]. Initial comparison will present an interesting test of the degree of

correlation of remote sensing data produced by equipment that has seen minimal laboratory

calibration.

The specific limitations of this data for use by the Department of Interior and the

Department of Agriculture will probably become evident only after several such platforms

are in operation. Private concerns operating from airplanes over a long period of time are already suffering from the lack of standards and have requested general assistance from

NBS [66].

This field is still in its infancy. Its growth is widely believed to be hindered by

its ability to demonstrate economic accomplishment. This in turn is very likely limited

by the performance of the systems themselves. These in turn are limited by the state of

the art of practical radiation measurement [68].

One of the most promising techniques in much of the accessible spectral region, the

infrared, is Fourier spectroscopy. The application of this technique to remote sensing is

probably only a question of time. Development of this field presents an opportunity for

NBS to work at measurement frontiers of immediate utility.

17
g. Crime Prevention

The issue of crime is relatively straightforward: there seems to be a direct correlation between effect of street lighting and the incidence of crime [TO]. A variety of

statistics indicate that crime has decreased 30-U0% in streets where new more intense street

lights have been installed. The new highly efficient lamps are of a type that NBS is not now able to measure reliably. Inauguration of manufacture of these lamps by several com- panies produces commercial incentives for measurements as well as the social and technical

ones

.

h . Botany

The small, but presently growing interest among botanists in the influence of light

parallels the growing interest of the medical profession and photobiologists [71]. This new interest in the influence of light on plant growth will indirectly create a demand, not

only for new lamps and their measurement, but also for simple but reliable spectroradiometers

and their calibration.

3.^ Economic Issues

The economic issues that derive from optical radiation measurement are first of all

questions of productivity: unit cost, quality control, product improvement, and product

innovation. These, however, in turn bear also on equity in domestic trade in a manner that

affects the consumer's ability to make intelligent choices. Foreign trade and the balance

of payments also will be strongly affected.

a. Unit Production Cost

Unit production cost is a basic industrial concern. Indeed this issue probably more than any other is immediately responsible for the great industrial concern recently for

improved optical radiation measurement. A lamp industry technological forecast notes:

"Growth stimuli in the market will include . . . improved lighting economics" [72]. A

product testing group is currently looking at its own program activity within the framework

of the widely disseminated internal slogan, "Best Buy Our No. 1 Goal" [73]. The lamp industry in fact sells efficiency, as illustrated 22 February 1972 in the Wall Street Journal

[7^+]. Such a marketing approach is demonstrably not in vain. Special 96" fluorescent lamps

with a 10% greater efficiency than normal production for one manufacturer are sold by him

for an approximately 10% higher price than that for his conventional lamps.

Productivity or efficiency, in turn, is greatly affected by present measurement

techniques. In general, insufficient and discrepant measurements may add hours to a given

measurement [h] . The absence of confidence between the lamp industry and other producers

who incorporate lamps into their own products is now so pronounced that a number of these

lamp-buying producers are installing new acceptance testing laboratories at great expense.

This expense is, of course, paid indirectly by the purchaser of the end product [76]. Moreover, this solution has aggravated another problem in efficiency: the maintenance of

several different unit sizes. For example, a Kodak lumen may differ from a Xerox lumen [8].

Both must be maintained by suppliers at added expense. In addition, purchasers of lamps

will pay indirectly for the extra costs of a supplier whose production is rejected by

another purchaser. A similar problem of even greater magnitude is that faced by LED manufacturers in their rapid growth stage [U,6]. The LED problem is part of a more general lowlevel problem [app. C]. Productivity problems traceable to measurement are being faced by

the laser industry as well. Photodetector production costs also depend on measurements

[6,18]. In addition the cost of complete radiometers, a growing industry, is being affected

by current measurement problems [app. A].

b . Quality Control

An issue closely related to unit product cost is quality control. Some of the major

components of the electro-optics industry both individually and together have testified

that present quality control in the industry is being affected by the state of optical

radiation measurement. The photographic industry is being adversely affected [lU,l8;

app. A]. The laser industry is also affected [77].

18
c . Product Improvement

Reference has already "been made in the section on the energy crisis to the fact that

improvement in the efficiency of lamps has come in small steps [52,53]. It was shown in

that section that improved capability in measurement is of great significance here and

hears directly on improvement throughout the industry. Improvement in radiation measurement techniques will also influence photodetector development [lO].

d. Innovation

The rapid growth of the electro-optics industry described in Section 3 is "based primarily on innovation. But in addition to the technical implications of this growth already

discussed, the commercial value of innovation should be noted also. This value determines

commercial consequences of the related measurement problems. The rapid growth and commercial promise in light emitting diodes, for example, has been cited [3-5; app. A], The

influence of measurement on the commercial development of the rapidly innovating infrared

industry has been noted [6], The connection between innovation and measurement precision

in the photographic industry, particularly in connection with camera automation, has been

noted in conversations between NBS and the Physikalisch Technische Bundesanstalt [78]. The

commercial importance of new discharge lamps has been observed [7^] as well as of new

detectors [10]

e . Equity in Trade

Equity in trade, a dominant issue with those who turn to NBS for assistance in optical

radiation measurement, involves three separate factors.

(1) The Consumer's Concern with Technical Data

The consumer can be the "little old lady" comparison-shopping in the supermarket, the

"commercial and industrial" purchaser, or the "original equipment manufacturer" [8]. These

last two groups account for 60% of the market in the lamp industry. They are exceedingly

cost-conscious. The consumer, primarily large but also small, currently has technical

problems of three types derived from measurements . He has problems of equipment compatibility. He has the efficiency problem of dealing with various manufacturers employing discrepant units [8; app. D, app. E], In addition, he sometimes needs to compare a commercially

derived number with a natural or more purely scientific one. An example is a comparison of

artificial illumination with natural light [5]- Commercial optical radiation measurement

must be more firmly based than at present to be comparable with other measurements. Measurement problems are particularly severe in the ultraviolet.

(2) Government Purchasing

GSA purchasing of light bulbs is of importance not only to economy in government.

Government purchasing is substantial enough to affect the lamp industries themselves [52].

The leverage that it exerts affects the entire market, particularly the purchases of other

governmental agencies, state and local governments.

( 3

)

An Orderly Market

The issue of an orderly market in lamps, photodetectors , or other instruments is

different from that in a government regulated market such as gas-flow or electrical-power

meters. With the diversity of the electro-optics industry, an important question is, "are competing values comparable?" Manufacturers both large and small in the lamp industry feel

that they are not [8,52]. Rather than seeing a potential commercial hazard in new measurement capability, the industry is looking to NBS for assistance [app. E]

This remarkable industry interest in greater activity by the NBS in part stems from

actual experience in that the lamp companies have had, in some cases, to derive independently their own luminous flux assignments. The result on the market is deplored by all

concerned.

19
With the development of new high intensity discharge lamps, the absence both of NBS

standards and of accepted procedures necessarily lead to a separate discharge lamp lumen

for each manufacturer.

The thrust of industry concern here is not: U.S. Government, stay away; but rather,

NBS please help! [app. E].

f . The Balance of Payments

The present adverse balance of payments is widely recognized. Secretary Stans pointed

out in his testimony before the Subcommittee on Science on 27 July 1971: "The major element

which we can influence decisively for the long run is the level of technological development.

It may be our only hope of maintaining a future trade position adequate to support our balance of trade payments in years to come" [79].

But the Secretary noted also: "From 1950-1965 our productivity growth rate trailed

Europe by 35% and Japan by G0%. The trend since 1965 shows an even more rapid relative

decline: United States rates trailed Europe by 60% and Japan by 8k%" [79].

The high technology electro-optics industry is growing very rapidly in this country

and abroad [l]. As demonstrated above, American productivity is affected by measurement

capability through unit product cost, quality control, product improvement, and innovation.

The instrumentation industry as a whole is concerned with foreign trade expansion.

"There will certainly be an unfavorable foreign trade impact if electro-optical devices of

U.S. manufacture cannot be relied upon to yield uniform NBS traceable quantities. The cost impact in this area can easily run into millions of dollars" [h] . A working group of the

Council for Optical Radiation Measurement has also noted: "discrepancies on an international basis, which have occurred, result in lost sales and decreased exports" [app. A].

The light detector industry is also involved. "We expect ... to measurably enhance

our position in both domestic and foreign markets. The latter is an area where our com- petitors, largely nondomestic, have made serious inroads . . . Recent developments in the

international monetary scheme are a great assist, also, and your efforts in resolving the

problems outlined above will help solidify our international position of leadership" [10].

A working group of the Council for Optical Radiation Measurement notes "the lack of

standardization of calibration methods and standards among manufacturers and users of light

emitting diodes and displays". It cites as an important concern the "very large market

domestically and internationally" [app. A].

The photographic industry is likewise concerned: "Lamps are calibrated for our associated companies throughout the world" [80]. "International trade depends on the worldwide acceptability of such measurement" [lU].

The working group on total flux measurement of the Council for Optical Radiation

Measurement with representatives of the lamp industry notes that "many purchases are made

on the basis of promised performance. A difference of one or more percentage points in

promised performance will, therefore, determine the business to be done, either domestic

or foreign, by a given manufacturer or even by an industry. This can run into millions of

dollars" [app. E].

"One company in the lamp industry, at least, has run into the fact that their lumen

levels, for some, if not all lamp types, are different by several percent as compared to

this country. Sales of our industry off-shore have been slowed down because the European

lamp manufacturers are talking loudly about the inflated lumen level of the United States

products. Under such conditions, especially in a competitive business, it is very difficult to grow much of a market at least in Europe where a considerable effort has been

expended" [8]. "If we are to export lamps, our foreign customers must again know that

Boston lumens are the same as Paris, London, Tokyo, or Istanbul lumens" [52].

20
The lamp industry is sufficiently concerned enough about international measurement

agreement as it expands its markets ahroad to he sending its measurement people ahroad

after its sales ads [81-82].

3.5 Scientific Issues

a. An Opportunity

The rapid technological development already descrihed leads to scientific opportunities

that did not previously exist. The promise of Fourier spectroscopy, for example, has only

begun to be realized in science as a whole. It has not yet been applied to quantitative

radiometric measurement of scientific interest. It is much faster, more sensitive, and less

noisy than other techniques. It also averages entire spectra simultaneously, a great advantage in drifting and fluctuating systems.

Every object radiates: this is useful information for material characterization,

always about the state of the surface and usually about the internal state of the systems

as well. The opportunity to acquire and evaluate this knowledge rapidly and with much less

noise than previously will permit realization of new opportunities. If it is to be

exploited fully for material characterization it must be evaluated quantitatively. Remote

sensing of the earth is one area of immediate application.

b. "One-shot" Experiments

One area of opportunity to which radiometry is of great importance because few other

tools exist is astronomy. This field has been transformed by the utilization of satellites

outside the earth's atmosphere. But calibration problems have been intensified. Satellite

measurements made by the Smithsonian Observatory differ by a factor of three from those

made by the Naval Research Laboratory [83]. Evaluation of the solar and other stellar

spectra in the UV will be held up until such uncertainties are clarified. Large amounts of

money are already being spent on such programs and the scientific payoff will be far greater,

with relatively little increase in cost, with more sophisticated radiometry.

c. Atomic Physics

In addition to the new spectacular space spectroscopy, cross section data in atomic

physics is still being limited by the accuracy of radiometry [8U]. Relatively large amounts

of time are now being spent on reducing the uncertainties in radiometric measurement to the

level of other limiting parameters in these measurements

Conventional astronomy and earth-bound stellar astrophysics are sufficiently concerned

about the status of radiometry that a recent symposium on astronomy devoted nearly one quarter of its time to a review of recent developments in radiometry [85]- This concern

reflects both the limiting nature of the present state of the art and great interest in its

advancement

21
h. ALTERNATE SOLUTIONS

These are the impact areas of optical radiation measurement and some of its implications. The question now is, "Why not leave the solutions to those who are most affected?"

There are both technical and nontechnical reasons for not doing so.

k.l Technical Factors

Each radiometric measurement is extremely complex. There are in fact, four sets of

parameters to be controlled or evaluated: spectral, spatial, temporal, and polarization.

To understand and control these four parameters the radiometrist must be highly trained in

optics and heat transfer. He must also be experienced in these and other fields. An

exhaustive examination of each of these parameters even by an expert is expensive and

time-consuming. At some point, of course, even the most careful worker must make a com- promise. If this compromise does not occur in the initial measurements then it will reduce

either repetition or the systematic variation of all parameters. But even the simplest

measurement requires intelligent compromise. The technical difficulty is further complicated by the lack of commercial instruments available to evaluate many parameters. Ultimately the development of technology in this area will make a new generation of instruments

possible.

A large investment in time and effort is thus now required in order to make independent

measurements that are reliable and comparable with other independent measurements at the

1-10% level. For example, one must select and characterize his detector for these four

parameters. He must select and characterize his electronics. He must select and characterize his sources and then his optical system. Since generally accepted techniques and highly

accurate commercial equipment is rarely available, he must usually develop or evaluate these

himself. Moreover, he will also have to attenuate either the beam to be measured or that

from a standard; his attenuation techniques will have to be characterized as well.

In short, the independent worker is left to work without any comprehensive assistance

either in equipment or techniques. The independent development of comprehensive expertise

in every laboratory making photometric and radiometric measurements is an impossibility for

most companies in this industry. It is an uneconomic solution even for the large ones.

k.2 Nontechnical Factors

Large companies are not reluctant to spend considerable sums in the optical standards

area. Indeed they are doing so through automation in this field. But they are not making

so much of an investment in technical development. — Why?

Being right is not enough in the highly competitive field of optical radiation measurement. The really important question is, "Does my measurement agree with another institution's?" If I am selling, "Does it agree with that of the purchaser?" If I am buying,

"Does it agree with that of the seller?" If I am being regulated, "Does it agree with that

of the regulatory agency?" In a bilateral situation, agreement based on an adjustment can generally be made. But the typical market and its regulation involves many different

agencies

.

The development of a complex system of bilateral agreements among companies to enable

them to deal with the real market situation has been forced, but it is- uneconomical. It

is uneconomical in terms of the number of measurements required. It is uneconomical in the

maintenance required of separate units of varying size. It is uneconomical in the effort

required for identification of sources of the differences in measurements. The cost even

of rejected purchases is borne by other purchasers who come along later. It is uneconomical in productivity. The international consequences of this reduced productivity are both more evident and more severe than the domestic ones.

There is also the legal question. In all photometry and in all radiometric areas contingent on Federal activity, the basic legal question is not, "Is it right?", but rather,

"Does it agree with NBS?" This necessity for agreement means that norms must be selected

and values adjusted to them. Particularly when a complex system of bilateral arrangements

is illegal, industrial investment in expensive competence will not purchase legality.

22
Thus even the largest companies will not he inclined to make a major investment or expenditure where agreement with the next fellow is paramount

U.3 Other Agencies

The coordination of other Federal Agencies with NBS is really a part of the preceding

consideration — agreeing with others. In photometry, legal measurement must always he

coupled with NBS. But for radiometry in government purchasing and for regulation through

HEW and DOL, an identification with NBS measurement is also highly desirable. In order to

preserve Federal measurement credibility, it is essential that Federal agencies have

coordinated measurement facilities. Without a proper NBS system, a GSA lumen or a DOT

candela will necessarily come into existence.

h.h Synopsis

To recapitulate, therefore, hoth technical complexity of optical radiation measurement

and the need for comparability and interchangeability dictate a unified solution to the

presently severe optical radiation measurement problems.

23
5. THE BOLE OF NBS

5.1 What Needs to "be Done

A nationally centralized competence in optical radiation measurement is highly desirable for two purposes. First it would provide for the most economical solution to problems

in the characterization of complex optical radiation components and systems. Secondly, it

could also provide a framework for the achievement of uniformity in such measurements on a national basis

.

a. The Characterization Required: Research

The research endeavor implicit in the foregoing review of the issues involves three

separate problem areas: l) source characterization, 2) detector characterization, and

3) the characterization of certain general problems in radiometric technique.

The first two problem areas involve the following separate steps:

(a) Realization of a scale

(b) Transfer of the scale to secondary standards

(c) Development of techniques for the extension of

these standards to dissimilar measurement objects.

The output of the first two steps includes both hardware and software. That is, it includes

the derivation and characterization of objects. It also includes the development of techniques. The output of the third step is almost exclusively software. This software is the

description of new techniques associated not with the generation of standards but with their

utilization for other purposes.

The third separate problem area focuses on the optics employed both with sources and

with detectors. It includes general spectral techniques, diffraction, and attenuation.

(l) Source Characterization

(a) Realization of Scales

The realization of scales in both radiometry and photometry is widely recognized as basic to the NBS mission. In addition, new strong industry desire for the rigid coupling

of photometry and radiometry is now evident [6-7,13,18,20].

(b) Transfer to Secondary Standards

(i) Characterization of Present Standards

"Firm uncertainty information is extremely important to us" [ll]. "The necessity

to provide an estimate of the precision/accuracy/uncertainty for both color temperature and

luminous intensity of the individual stages of calibrations as well as an accumulative

value" has been considered to be paramount [80; cf. 13]. Once the size of the present

uncertainties is recognized in these and other areas, requests follow for a reduction in

size.

(ii) Improvement of Present Standards

In the few cases where the uncertainty is already established, the immediate

requirement is for its reduction [10]. "The need is that of more accurate radiance and

irradiance measurements. The need is for one percent or better standards" [l8]. "There is a pressing need for increased accuracy in the N.B.S. maintained (and transferred) standards

of spectral radiance and irradiance" [13]. "A standard of spectral irradiance accurate to

1 percent" is desirable [20].

2U
(iii) Description of Procedures for Present Standards

A recent request of one of the working groups of the Council for Optical Radiation

Measurement states a widely held desire for, "Provision by NBS of detailed, written description of the methods and techniques through which NBS calibrates standards of spectral radiance, spectral irradiance, luminous intensity, color temperature, etc." [app. F; cf. 13, 86].

Such descriptions are now being initiated by UBS where procedures are already established and preparation of the description is straightforward. However, when a change in

standards or procedures is desirable, time spent in preparing detailed descriptions must be

weighed against the benefit to be gained from a more immediate improvement of the standards

instead.

New types of information are being requested explicitly. One is the influence of the

environment on the measurement process [app. B] . A widespread desire [6,8,13,87] for help

in the selection of lamps for calibration is evident. This request is particularly crucial

with the phasing out of industrial standard lamps manufactured by the main U.S. supplier

[7,18].

(c) Extension of Present Standards

The need for a general description of techniques and methods has been recognized:

"Because of differences in methods of measurement, a standards handbook would give the basic

setup for measurement of radiance and irradiance in the UV, visible, and I.R. range . . . A tutorial treatise should complement the handbook" [l8]. Moreover, "NBS should take the

steps necessary to provide easy access to existing written descriptions of techniques and

methods" [app. F].

Extension in level is of great concern. Extension of irradiance to lower levels has

been requested [7,86,88; app. A]. It is stimulated by the advent of light emitting diodes,

the general increase in use of low level devices, and the increasing attraction of photon

counting as an absolute standard. Conversely, higher intensities are increasingly important

as Underwriters Laboratories begins writing specifications for lamps used in photography

[15]. Optical system calibration is presenting similar requirements [20]. As lamps become

more efficient higher total fluxes are also being generated and must be measured reliably by

lamp manufacturers [ 5 ]

Extension to new spectral regions and improved standards at the present extremes have

also been requested. Infrared is one area where progress is being made but new problems are anticipated. One example is "Extension of blackbody sources to operating temperatures down

to 77 K (mainly for the purpose of calibrating detectors employed in the far infrared region)"

[13]. "Many problems will develop that are not now recognized [in the infrared]" [6].

Extension of the range to 25 um has been requested [app. B]

In the other direction, the importance of extending geometrically total flux measurements into the ultraviolet has been noted [5]. This desire will increase as the biological

effects of this radiation become more widely recognized.

In addition to work in relatively uncharted spectral ranges, the measurement of light

with a nonconventional spectral distribution is a rapidly increasing problem [7,20,87].

Sources with a spectrum similar to daylight have been requested by a working group of the

Council for Optical Radiation Measurement [app. A]. Light emitting diode measurement problems are traceable to their new spectral distribution as well as to their low level. High

intensity discharge lamps are breaking a total flux measurement system already strained by

fluorescent lamps [8]. The problem of spectral lines as well as new measurements outside

of the visible are involved. High priority has been requested for the development of

spectroradiometric techniques [89].

In addition to the extension of present measurements in level and spectrum a spatial

problem has arisen in the infrared. Extended sources need to be evaluated both theoretically

and experimentally [app. B; 90].

25
And finally, the development of new source measurements in the time domain is being

requested. Pulsed irradiance and illuminance measurements are required [7,20,87]. Total

flux pulsed measurements are also required [app. A].

(2) Detector Characterization

Detectors can be usefully divided into three subgroups: electrically calibrated,

thermal but nonelectrically calibrated, and quantum.

(a) Realization of the Scale: Electrically Calibrated Detectors

It is recognized that a series of electrically calibrated detectors is basic. Both

because of their self calibration and because of their relative freedom from wavelength

dependence they are essential to a detector characterization program [13; app. B, app. D].

(b

)

Thermal, Nonelectrically Calibrated Detectors

Dependence on many detectors as transfer devices has been hindered by the absence of

reliable characterization techniques. An electrically calibrated detector can in principle

be used not only as an absolute standard, but as a tool to characterize gray detectors for

spectral response. Such a capability is badly needed both for conventional radiometry

[6,11; app. A] and for laser measurement [app. G].

(c) Quantum Detectors

Quantum detectors have not yet reached sufficient development to qualify as absolute

photon counters. In general they are not gray spectrally either. Nevertheless, the recent

development particularly of solid state photodiodes has led to high stability and sensitivity that make them attractive as secondary standards. A new approach to photometric units,

based as the units themselves are conceptually on an "idealized" detector approximating

human visual response, is particularly attractive in principle. Characterization of promising new photometric detectors has been urged [87-88]. Characterization of spectral

response is particularly desirable [7,13, app. D], Temperature sensitivity is another area

for attention [app. D] . The evaluation of linearity and performance at low levels is basic

[app. D]. And finally, the examination of time response and utilization of detectors for

pulsed measurements has been urged [app. D].

(3) Characterization of Certain General Problems

Finally, the evaluation of certain techniques used to make comparative measurements is

highly desired. Attenuation techniques are requested very frequently [6-7; app. A, app. C]

Other optical system components that have become the foci of questions are the use of

diffusers and integrating spheres in general [7].

A special very important area of general concern is the characterization of spectral

techniques not only for spectral irradiance measurements [l8] but particularly for use with

flux measurements [5,89].

b. Dissemination and Verification

Until the standards and techniques developed by the research program have been applied

not only to the internal generation of standards but also to the verification of measurements made in a variety of laboratories, the maximum benefit will not have been realized.

A proper research program will lead to economical measurement. But the full practical

utilization of this research program will become evident only after the compatibility of

measurements has been actually demonstrated among users [ll].

The Radiometric and Photometric Calibration Program has been greatly expanded, and

twenty-five regularly scheduled calibrations are now routinely available to the public.

In addition to the scheduled items, special calibrations are also available to satisfy

special needs.

26
But "of equal importance is standardization of technique for transferring these standards from NBS to the user, regardless of whether an intermediary is used" [10]. Reliable

transfer will involve a "method of supplying and checking secondary laboratories issuing

standards and calibratee sources", in other words, a "method of specifying NBS traceability"

[13]. Such desires almost certainly imply "Determination of suitable intercomparison

techniques at the various laboratories, and evaluation of the issued product", that is,

"Participation of issuing laboratories in intercomparison" [13]. "Another recommendation

would be to periodically have round-robin measurement comparisons between laboratories"

[app. C]. "When NBS is unable to provide full calibration services, they should provide

some method of guaranteeing that commercial standards labs are providing measurements on the NBS scale . . . Small scale, simple interlaboratory intercomparisons utilizing NBS

techniques . . . with NBS acting as referee, would be desirable . . . [app. F] . "Secondarystandards laboratories will build detectors and participate inperiodic round-robin calibration exercises with NBS" [app. D]

5.2 Why NBS?

a. Fractionated Market

Two reasons for a centralized national competence in optical radiation measurement

were stated in the previous section. The first of these was the diversified nature of the

industry involved. Only very few of the companies in this market are large enough to fund

the complex research and development required to make competent measurements in this field.

The Director has suggested that NBS might "explore ways of aggregating the research and

development capabilities of many companies vying for a fractionated market" [91] • Another

aspect of such problems in infrared has been described: "In the component area, the documentation procured during the development contract is frequently inadequate to support the

procurement of spares later" [12].

b. Agreement Rather than Accuracy

The second issue addressed in the previous section is the need for agreement of

measurements in various laboratories. Since being right is less immediately important than

agreeing with the fellow with whom one is doing business, a centralized focus for achieving

this end has been widely requested.

c. NBS Mission

In addition to these issues which point merely to the designation of the single

national laboratory, certain aspects of the Bureau's mission and program lead specifically

to its desirability as the proper national laboratory.

The first of these is the statutory obligation of NBS covered in Section 3. The

specific NBS obligation with respect to photometric units (visible light) was noted as an important addition to the more general mission cited in the Organic Act. Indirect statutory

obligation was also anticipated through increased reliance on optical radiation measurement

by other Federal agencies

In addition, however, other aspects of the general NBS mission, apart from its standards function, are increasingly the focus of attention. The specific impact of strengthening the photon measurement capability on a variety of public issues was covered in

Section 2. Most of these bear directly on the overall NBS goal "to strengthen and advance

the Nation's Science and Technology and to facilitate their effective application for

public benefit" [92].

More specifically, improvement in optical radiation measurement bears directly on the

various subdividions of this goal. The general necessity for "promotion of accurate,

meaningful, and compatible scientific measurement" has been demonstrated by the number of

requests for improvement in the agreement of optical radiation measurements reviewed in

the previous sections and inoluded in virtually every letter in the Appendices. Moreover

"the more effective use of science and technology" has been called for implicitly both in

these letters and in the working group reports of the Council for Optical Radiation Measurement. "The promotion of strength in the economy and equity for the buyer and seller in

27
trade" [92] has been reviewed in detail in Section 3. The impact of such equity on foreign

trade balance was noted specifically. This impact follows directly from several other

factors that bear on domestic trade as well as in the entire electro-optics industry. "The

provision of standards and test methods for protection of the public from specific hazards"

is already important in view of the demonstrated effects of ultraviolet radiation and will

grow in public concern as this field develops.

The "provision of technical information services" not only through the technical

journals but through the new "Optical Radiation News" column of the NBS Technical News

Bulletin has drawn a flood of requests for inclusion on the mailing list.

The growth of problems in optical radiation measurement that act as a "barrier to

effective use of technology" has been cited by most recent industrial respondents. They are concerned with the application of optical technology both to problems of domestic impact

and those of foreign trade. The influence of measurement on this rapidly growing high

technology domestic industry is of recognized importance.

The "[promotion of] economic growth through product improvement and [the promotion of]

equity in the market place" [29] have been cited in Section 3.3.

d. Past Accomplishment

Does NBS have the competence to perform the needed job?

Its accomplishment in this field is widely known. NBS is the only laboratory in the

world that furnishes spectral radiance standards accurate to one percent. It is one of two

laboratories that generates its own spectral irradiance laboratory standards. Indeed, many

other national laboratories are dependent on these standards for their own work. NBS

achievement in the development of electrically calibrated detectors has been widely

recognized also [55]

There is abundant testimony to NBS competence: "the state-of-the-art measurements

accuracies achievably by NBS" have been recognized [77]. "Ideally, highest echelon standard

would be available from a completely objective, impartial source that enjoys the respect of

the entire technical community: i.e. NBS" [88].

In addition to acknowledged radiometric competence, the recognized application of

sophisticated statistical techniques by NBS permits maximum effective utilization of its

technical expertise. "NBS application of sophisticated statistical techniques to the

calibration of standards has been a welcome addition to its endeavors" [52], "the work

reported in NBS Technical Note 559, ' Spectroradiometry and Conventional Photometry, An

Interlaboratory Comparison' [is] a splendid start" [88].

e. Organizational Contacts

The position of NBS on international standards committees places it in the unique

position to work for the solution of international problems that concern American industry

in this technical area. Its reputation for accomplishment places it in a position moreover

to exercise leadership that is very greatly needed internationally.

In addition, the close contact of NBS with DOD technical problems and solutions in

this area puts it in a position to secure the application of relatively unknown work to new problems of nondefense interest. This opportunity will be of great importance in the application of IR technology, developed largely by DOD, to a growing civilian activity.

f. Industrial Desire for NBS Activity

In a period of wide industrial concern about the effect of Federal activity, it is

clearly remarkable that industry is turning actively to NBS for assistance in research and

development in this area: "We look to NBS" [7?]. "A U.S. Government-operated laboratory

is in the best position . . . and it would again seem that NBS has the best facility to do

this work" [52]. "NBS should provide the national focus . . . Industry would much prefer

to get this kind of help from NBS" [lU].

28
The enthusiasm for NBS activity extends particularly to the desire for verification,

the question of "traceability" . NBS has been urged by industry even to inspect its com- mercial facilities periodically [h] . However, this is an area of expansion that will have

to be closely examined before action is taken.

In still another area of its program, NBS has been urged to continue its activity to

anticipate future needs: "It is imperative that NBS work with aerospace, medical, agricultural, and other industries to keep abreast of these problems as they occur" [6].

And finally, industry has "voted" with its feet. On 10 February 1972, sixty representatives of industry and government met at NBS to consult with one another and establish a a position for future action. They formed the Council for Optical Radiation Measurement to

coordinate the definition of needs, to discuss alternative approaches, to coordinate technical projects, to ask NBS for assistance, and to coordinate activity with other organizations [93].

g. Future Savings

Another factor indicating the desirability for NBS to mount a comprehensive program

now in optical radiation measurement is in the influence that this program will have

ultimately on savings both in NBS expenditure and in costs to those served by the program.

If the present partial gage system of interrelated standards were to be expanded to meet

present needs, the impact on future budgets would be increasingly severe. A systematic

approach leading to a general solution of measurement problems in this area by application

of modern technology will ultimately lead to a more economic solution.

5.3 Present Program

In the absence of increased resources, the program at NBS for the next year or two will

be devoted largely to realizing and improving the radiometric and photometric scales

required. Only a few of the extensions and characterizations called for in Section 5-1 will

be possible.

5 .k Other NBS Resources to be Applied

One resource available to NBS in the development of its program in this area not previously cited is the Optical Physics Division effort in the vacuum ultraviolet. Cross

fertilization between these two programs is already taking place. In addition, the presence

of a strong statistics competence has been noted; it is a highly valued additional resource. Without it, in fact, a viable program for traceability could not be effectively built.

5 . 5 Non-Monetary Support

Non-monetary support is present in the form of an industrial research accociate provided by the lamp industry through the Lamp Testing Engineers Conference via the Electrical

Testing Laboratories. With the increased development of an NBS program in this area and

the demonstration of its competence it is entirely possible that other components of the

electro-optics industry will provide similar assistance.

In addition, several companies have already offered to perform parallel experiments

and to check new procedures in their laboratories. The use of major equipment not available at NBS has also been offered.

29
6 . RECAPITULATION

Serious measurement discrepancies universally plague quantitative measurement in the

electro-optics industry.

These problems arise chiefly through the recent explosive expansion of this industry.

It triples in dollar volume in a period of nine years . It now represents substantially

more than $10 billion in annual sales.

This growth has precipitated a complex development in the variety and accuracy of

measurements required. Virtually each measurement is thus a state-of-the-art study. The

distress that the resulting disagreement costs the industry as a whole is growing rapidly.

At the same time growth in public concerns that have a strong technical base in this industry are just beginning to find a focus for expression. Resulting governmental activity is

undergoing a strong expansion.

The impact of these problems falls in many areas. One is the growth of Federal

obligation. The levering on technical development by good measurements here has been

acknowledged and documented. Public issues encompass public health, public safety, the

energy crisis, meteorology, pollution, agriculture, crime prevention, and a variety of

opportunities in connection with aerial surveillance. These latter promise savings of

$59 billion in the most conservative estimate. The economic lever of improved measurement

operates through unit production cost, quality control, product improvement, and innovation

to equity in domestic trade and the balance of payments abroad. Basic scientists have a vocal stake in progress here too.

Leadership by NBS in this area is dictated not only by legal authorization. The

fundamental problems are too complex to be tackled economically outside of a national

laboratory. Moreover, the necessity for measurement agreement requires the assumption of

responsibility by a central agency. The opportunity to lever a large market through

technical advancement falls squarely within recent conception by NBS of its mission. NBS

has the in-house expertise for the job and the required organizational contacts. The

electro-optics industry with one voice is calling for NBS leadership.

30
7 • REFERENCES

1. Notice of European Electro-Optics Markets and Technology Conference and Exhibition,

Optical Spectra, p. 13, April 1972.

2. EG&G Light Instrumentation Application Note No. 580-3A.

3. Bell Telephone ad in IEEE Spectrum, December 1971.

k. Private communication, spokesman for electro-optical instrumentation industry.

5. Private communication, spokesman for lamp industry.

6. Private communication, spokesman for electro-optical instrumentation industry.

7. Private communication, spokesman for commercial electro-optical calibration laboratory.

8. Private communication, spokesman for lamp industry.

9. Private communication, spokesman for commercial electro-optical calibration laboratory.

10. Private communication, spokesman for photodetector industry.

11. Private communication, spokesman for electro-optical instrumentation industry.

12. Arlyn E. Asch, et al. , Philco Ford Report, IE-TR-70-1 (1970).

13. Private communication, spokesman for commercial electro-optical calibration laboratory.

ik. Private communication, spokesman for photographic industry.

15. Memo 122 Underwriters Laboratories, 2k February 1971.

16. Personal communication from Charles Douglas, Head, Illuminating Engineering Group, NBS.

17. Private communication, other Federal agency personnel.

18. Private communication, spokesman for photographic industry.

19. Edwin Stepke, Electro-Optical Systems Design, p. 20, February 1972.

20. Private communication, spokesman for photographic industry.

21. Memo to Dr. Branscomb from David J. Huebener, NIOSH, 2 November 1971.

22. NBS Administrative Bulletin 71-26.

23. D. A. McSparron, et al. , Spectroradiometry and Conventional Photometry, An Interlaboratory Comparison, NBS Technical Note 559 (1970).

2k. "Trends in Optical Technology" from Optical Spectra, p. 33, June 1972.

25. Private communication, spokesman for image intensification industry.

26. Private communication, spokesman for university-based image research.

27. Private communication, spokesman for photographic industry.

28. Private communication, spokesman for photographic industry.

29. Private communication, George Zissis.

30. MIT Reports on Research, ed. W. K. Stuckey, April 1970.

31
31. J. F. Lucey, Hospital Practice, 2, 21 (1967).

32. L. Thorington, L. Cunningham, and J. Paras can dola, Ilium. Eng. p. 2i+0 (1971) .

33. J. F. Lucey, et al. , Pediatrics, Ul, IOU7 (1968).

3*+. Newsweek, p. 8l, 12 July 1971.

35. R. Neer, T. Davis, and L. Thorington, Clinical Res., 18, No. U (1970).

36. R. M. Neer, et al. , Nature, 229, June 22, 1971.

37. R. J. Wurtman and J. Weisel, Endocrinology 8j>_, 1218 (1969).

38. R. J. Wurtman, Ilium. Eng., Proc. Nat. Conf . , Sept. 9-12, 1968.

39- Michael Menaker, Scientific American, 226 , 22 (1972).

U0

.

M. A. Zamkova and E. I. Krivitskaya, Gig. i Sanit . 31, Ul (1966).

Ul. R. J. Wurtman and R. M. Neer, New Eng. J. Medicine 282 , No. 7 (1970).

U2. National Academy of Engineering, Task Group on Industrial Activity, "An Assessment of

Industrial Activity in the Field of Biomedical Engineering" (1971)

U3. Draft proposal by NOAA.

UU. Private communication, other Federal agency personnel.

U5. Private communication, spokesman for lamp industry.

U6. Private communication, spokesman for airplane cockpit panel industry.

U7. Washington Post, front page story, lU April 1972.

U8. National Petroleum Council: U.S. Energy Outlook, 2 Volumes (1971).

U9. National Petroleum Council: Environmental Conservation, 2 Volumes (1971-1972).

50. T. Cordell Moore, United States Petroleum Through 1980, U.S. Department of the

Interior, PB 188 860.

51. Earl Cook, Scientific American, 22U, 135 (1971).

52. Private communication, spokesman for lamp industry.

53. Private communication, spokesman for lamp industry.

5U. Private communication, university meteorologist.

55- Letter to Dr. Lewis M. Branscomb from Robert M. White, NOAA.

56. Private communication, other Federal agency personnel.

57. NOAA: Remote Sensing Workshop, Miami, March 1971.

58. Private communication, other Federal agency personnel.

59- Freeman Hall, Optical Spectra, p. 21, January 1972.

60. Private communication, Michael McClintock, University of Wisconsin.

61. Robert J. Bibbero, IEEE Spectrum, December 1971, p. U7. 32
62. Private communication, Ronald Fegley, NOAA.

63. Harold Johnston, Science, 173 , 517 (1971).

6k. NAS-NRC, Summary Statement of the Ad Hoc Panel on (NO ) and the Ozone Layer,

29 July 1971.

65. Business Week, pp. 5^-55, 27 November 1971.

66. Private communication, spokesman for aerial survey industry.

67. A. K. Thiel and C. D. Graves, Proceedings Before the Committee on Science and

Astronautics, U.S. House of Representatives, 25-27 January 1972 [No. 13], p. 5k.

68. Private communication, other Federal agency personnel.

69. Private communication, other Federal agency personnel.

70. The Evening Star, Friday, June 1970.

71. George A. Elbert, New York Times, p. 33, 13 February 1972.

72. Proprietary Report.

73. Private communication, spokesman for electro-optics industry.

ik. GE advertisement in the Wall Street Journal, 22 February 1972.

75- Private communication, spokesman for the lamp industry.

76. Private communication, spokesman for the lamp industry.

77. Private communication, spokesman for the laser industry.

78. Private communication, PTB personnel.

79- Statement of Secretary Stans before the Subcommittee on Science, Research and

Development, House Committee on Science and Astronautics, 27 July 1971,

NBS Tech. News Bull., p. 270 (1971).

80. Private communication, spokesman for the photographic industry.

81. German language sales ads.

82. Private communication, spokesman for the lamp industry.

83. Symposium on Far Ultraviolet Radiometry, NBS, 9-10 November 1971.

8^. Private communication, Gordon Dunn, JILA.

85. IBS Astronomy Day Program, NBS, 18 February 1972.

86. Private communication, spokesman for commercial electro-optics calibration industry.

87. Private communication, spokesman for lamp industry.

88. Private communication, spokesman for office equipment industry.

89. Private communication, spokesman for lamp industry.

90. Richard F. Leftwich, Standards for Calibration, k November 1969.

91. NBS Press Release, 8 February 1972.

33
92. NBS Memo on FY 1973 Planning, 2 December 1970.

93. NBS Technical News Bulletin, p. 87, 'April 1972

8. APPENDICES

Appendix A. Council for Optical Radiation Measurement: Summary of Comments of the Working

Group on Classical Radiometry (ill), prepared by Michael Mellon, Chairman.

Appendix B. Council for Optical Radiation Measurement: Summary of Comments of the Working

Group on Infrared (IV), prepared by Russell Yokley, Secretary.

Appendix C. Council for Optical Radiation Measurement: Summary of Comments of the Working

Group on Techniques including Spectrophotometry (VI), prepared by Jack Coulter,

Chairman

.

Appendix D. Council for Optical Radiation Measurement: Summary of Comments of the Working

Group on Detectors, prepared by Richard Leftwich, Chairman.

Appendix E. Council for Optical Radiation Measurement: Summary of Comments of the Working

Group on Geometrically Total Flux (i), prepared by Ernest H. Salter, Chairman.

Appendix F. Council for Optical Radiation Measurement: Summary of Comments of the Working

Group on Dissemination (VII), prepared by Donald McSparron, Secretary.

Appendix G. Council for Optical Radiation Measurement: Summary of Comments of the Working'

Group on Laser Measurement (il), prepared by Howard Pinsky, Chairman.

3U
8. Appendices

Appendix A

A. SCOPE OF DISCUSSION

The extent of the subject areas that could possibly be discussed by this Working Group

is obviously extremely broad. For example, variables such as the following are inextricably linked together

a. quantity of interest: irradiance, radiance, intensity, etc.

b. radiometric or photometric calibration standards needed?

c. specific spectral power distribution of source? Monochromatic or broadband?

d. spectral sensitivity of detector used?

e. spectral or total radiation calibration?

f. absolute power levels

g. time- independent or time-dependent (e.g. pulsed) quantity?

h. coherent or non-coherent?

i. accuracy, relative or absolute

j. repeatability (unit-to-unit)

k. methodology: supporting operational techniques /equipment instructions

1. importance and ramifications of work: effects on sales, profits, trade, jobs, etc.

Rather than attempt a full discussion of each of these factors in the very limited amount

of time available for discussion on February 10, it was decided that each participating

member summarize the problems most familiar to him from his own experience. Individual

comments were, of necessity, limited to approximately 20 minutes. Written summaries of

individual's comments on these and other topics were encouraged by NBS.

B. STATEMENT OF PROBLEM: Lack of NBS-traceable standards qf spectral irradiance and

radiance in the 90-250 nM (vacuum UV) spectral region.

PROPOSED SOLUTION: Development of such standards and associated measuring techniques.

Need 5% accuracy and/or 2% relative (spectrally).

JUSTIFICATION/APPLICATION : (1) Radiation level measurements in spacecraft and stellar

investigations. (2) environmental health studies (e.g. eye damage)

COMMITTEE CONTACT ( S) : Howard McDevitt, David Sliney

C. STATEMENT OF PROBLEM: Lack of daylight-spectrum sources, needed for applications in

photographic film, TV and color-matching fields. Need sources with spectral power

distribution matching daylight solar radiation, various CIE defined spectrums , several

cm2 in size and calibrated spectrally at 10 nM intervals from 350 to 700 nM.

PROPOSED SOLUTION: Development of such standards.

JUSTIFICATION/APPLICATION: The economic repercussions of poor quality control for

example, in the above industries are clearly very pronounced, particularly when

involving consumer markets. Estimated potential losses can be provided by committee

contacts.

COMMITTEE CONTACTS: Richard Becherer, Polaroid

William Heaps , Macbeth

D. STATEMENT OF PROBLEM: Lack of availability of current types of lamps for calibration

purposes.

PROPOSED SOLUTION:

COMMITTEE CONTACT: J. Gordon Hoffman

35
E. STATEMENT OF PROBLEM: Better standards and methods of measurement of luminous intensity

(candela) of low color temperature are needed for current applications in, for example,

aircraft visual display systems (cockpit lighting) . Present lack of agreement among

parties involved, users and manufacturers.

PROPOSED SOLUTIONS: Development and implementation of such standards.

JUSTIFICATION/APPLICATION: Safety, linked to readability of displays; consequent

economic repercussions of disagreements.

COMMITTEE CONTACT: J. Gordon Hoffman

F. STATEMENT OF PROBLEM: Lack of adequate methods for very low illuminance (footcandles)

measurement. Needed, for example, in measurements of low reflected power from retroreflectors used for highway markings etc. , which are illuminated by 1 footcandle indident power density and where the reflected radiation is measured at 100 foot ranges

and levels are 10-6 footcandles. Reflected light is filtered (green, amber, red, etc.)

PROPOSED SOLUTION: Investigate and propose method and/or revision of existing standards

of measurement.

JUSTIFICATION: Safety concerned with visibility of highway and other reflectors.

COMMITTEE CONTACT: Pablo Smester

G. STATEMENT OF PROBLEM: Lack of standardization of calibration methods and standards

among manufacturers and users of light-emitting diodes and displays.

PROPOSED SOLUTION: A relatively comprehensive statement was made concerning the need

for and the implementation of a specialized LED calibration system including standard

sources, detectors, procedures, etc. Basic measurement units suggested are radiant

intensity (watts/sr) , irradiance (watts/cm2

) and radiance. Conversion to photometric

units would be performed numerically using spectral radiometric data and photoptic/

scotopric conversions. It was suggested that a re-examination of the CIE Standard

Observer Curves be undertaken. The general statement was said to represent the

consolidated viewpoint of many of the major manufacturers of LED's (perhaps all).

JUSTIFICATION: Typical standardization ramifications. Very large market, domestically

and internationally.

COMMITTEE CONTACT: Joseph Horwath

H. STATEMENT OF PROBLEM: Inadequate methods of spectral/total radiometric and photometric

measurement of pulsed-type sources such as Xenon flash lamps. Spectral output of these

lamps changes as function of duty cycle, percluding extrapolation of CW calibrations.

Extrapolation also difficult due to reciprocity failure of photographic films.

PROPOSED SOLUTION: Development and standardization of method and equipment.

JUSTIFICATION: Highly important to quality determination and control in photographic

film industry. Also highly important to development and testing of visual warning and

identification systems such as stribe lights on aircraft beacons, emergency vehicles,

etc. where visibility and safety are prime concerns.

COMMITTEE CONTACT (S): Pablo Smester

Dick Becherer

William Heaps

I. STATEMENT OF PROBLEM: Difficulty of present situation in reliable calibration of

laboratory radiometers. Generally speaking, it was felt that the radiometric calibration standards and services of NBS (speaking primarily of incandescent lamp standards)

is presently inadequate from several standpoints.

36
First, there is a notable lack of information from NBS available on exactly what standards

are available, precisely what their characteristics are, methods used to calibrate

the standards at NBS and recommended operational procedures for their use.

Second, the estimated uncertainties of these standards are not well established either

within the industry or apparently within NBS itself.

Third, there is a need for calibration standards of spectral irradiance beyond the

present 0.25 to 2.5 micrometer range. In particular, sources other than tungsten-filament

lamps are needed (e.g. low and medium temperature balckbody radiators.)

Fourth, it would be desirable to upgrade the accuracy of the present standards to permit

better instrumentation accuracy in general.

Fifth, there is a specialized but very widespread need for calibration sources which

can be readily used for the calibration of thermal type detectors and radiometers that are equipped with window materials such as fused quartz, KRS-5 etc. The nature of these

devices requires such a window, for operation at low levels. The far IR spectral response

may frequently not be known with any certainty. What is needed then, is a lamp-filter

combination which exhibits a spectral power distribution which is fully included within

the range of the window under consideration. The filter must be arranged to eliminate

self-emission (i.e. at the detector temperature) which is the problem currently encountered

with standards of irradiance, for example. That is, a significant portion of the total

radiation is emitted by the envelope of the lamp and is located spectrally in the mid to far IR where the quartz (for example) window does not transmit. This is an immediate

need.

JUSTIFICATION: Thermal type radiometers are universally used as calibration (transfer)

devices in the field. Improper calibration results in much increased confusion for

the users of such instruments. Discrepancies on an international basis, which have

occured, result in lost sales and decreased exports. Domestic sales have been affected

as well, with consequent effects of employment levels etc. for manufacturers.

COMMITTEE CONTACT: Michael Mellon

J. STATEMENT OF PROBLEM: Need to accurately calibrate "flat" neutral density attenuators

with transmission factors as low as 10~ 6

. Spectral range not specified.

PROPOSED SOLUTION:

JUSTIFICATION:

COMMITTEE CONTACT:

K. STATEMENT OF PROBLEM: Measurement of low power lasers for environmental health studies.

JUSTIFICATION: NBS Boulder Calorimeters do not operate at low enough level.

COMMITTEE CONTACT: Dave Sliney.

37
Appendix B

Recommendations

(1) Expand NBS calibration temperature range downward (e.g. 170 K - 360 K and extend

X range to say 25 pm and uncertainty to 1%)

.

(2) Such calibrations to also include effects of source environment.

(3) Need information on the use of extended sources

(a) goniometric problems (in some cases)

(b) verification of specifications on such sources

(4) Need application of absolute detector to source calibration

(a) evaluate such a detector

(5) Since much interest (and emphasis) is in the lower temperatures, what about the

development of low temperature freezing point standards (e.g. freezing point of

mercury, gallium, etc.).

38
Appendix C

I . SPECTROPHOTOMETRY

A. Problems

There has been difficulty in the past in checking the transmittance accuracy of

conventional spectrophotometers, especially those without integrating spheres. Possible

sources of error are (1) non-linearity of photodetectors and/or the pen slidewire, (2) slight

wavelength errors in measuring highly wavelength selective samples, (3) spectral stray light

and/or geometrically scattered light, (4) beam shift across the non-uniform detector area,

(5) unrecognized polarization of the light beam combined with dichroic samples, (6) spatially

non-uniform samples, and (7) samples whose reflectance and/or transmittance is a strong

function of angle, especially when measured in spectrophotometers of differing F-numbers.

On the whole, T measurements are routinely good to + 0.5%, R measurements of

specular samples good to + 1%, or of diffuse samples +2 to 5%.

B. Impact

Commercial spectrophotometers are employed in an overwhelming majority of analytical

laboratories or in any research program studying the optical properties of materials. In fact, the optical behavior of materials can be most readily characterized by their measured

reflectance (R) and transmittance (T)

In the vast industrial field of optical thin films, reflectance and/or transmittance

are used as the controlling parameters , and in many cases absolute (rather than relative)

values of R and T are required.

In the field of temperature control by the absorptive and emissive properties of

coated and uncoated surfaces , accurate spectral measurements of R and T are critical in

evaluating the various possible materials. In the past intercomparison of the results among

various laboratories has been hindered by a lack of suitable reflectance standards. Some

examples of the uses of thermal coatings are artificial earth satellites, storage tanks of

volatile fluids, and personal dwellings (housepaints)

In addition the lamp industry needs to have good integrating sphere coatings in

order to measure the luminance of their sources

C. Solutions

We need standards of specular transmittance covering the wavelength range 0.20 to 2.5 ym, transmitting 10% to 100% at intervals of ^ 10%, with an accuracy of ^ + 0.1%. These

specifications would probably have reduced accuracy outside those regions where the sphere

coatings used in the measurements are less efficient. These standards should be flat,

spatially uniform, stable and durable, isotropic and preferably neutral. These standards

would also serve as accurate attenuators. Metal films are probably best because they are

most neutral and are more easily controlled during manufacture.

We also need standards of specular reflectance covering the wavelength range 0.2

to 2.5 ym, reflecting about 10%, 50% and 90%, with an accuracy of ^ + 0.2%. These samples

should also be flat, spatially uniform, stable and durable, isotropic and preferably neutral.

Metal films are probably best for higher levels of R and dielectrics at the lower levels.

Again, as an overlap with attenuator requirements, there should be standards of high

density transmittance, say 10

-

^ to 10~ , with an accuracy of 1% relative.

In addition standards of diffuse transmittance and reflectance are desirable. However, it is more difficult to specify their behavior because of the broad ranges of angular

characteristics that can be described.

One solution would be a standard of perfectly diffuse reflectance (a Lambertian

surface) of well-defined total hemispherical reflectance for near-normal incidence, as a

39
function of wavelength, accurate to + 1%. The wavelength range would again be 0.20 to 2.5 um. Finally, we need a well-defined, non-cumbersome procedure for producing integrating sphere

walls of good diffuseness and high reflectance.

II. ATTENUATION

A. Problems

Many of the absolute radiometric and photometric parameters being measured today

differ by orders of magnitude from the nominal values of the standards issued by NBS. Thus

in order to make transfer calibrations of lower radiant or luminous power devices some form of attenuation must be employed. It is obvious that if high accuracy is to be obtained

in calibrating these lower power working standards reliable and accurate techniques of

attenuation must be utilized. The problem of attenuation is one of being able to determine

both the absolute magnitude of the attenuation as well as the spectral perturbations

introduced by the attenuator. A few examples may better illustrate the problem. Consider

first the case of making an illumination calibration. Photometric standards of illumination

are typically 500 watt lamps. At 150 centimeters distance these lamps yield on the order

of 100 ft candles of illumination. Typical lamps which are calibrated from this standard

might be 50 watt, 5 watt lamps etc. having illuminations at 150 centimeters of from .1 to 1 footcandles i.e. 3 orders of magnitude different from the standard. An extreme might be the

calibration of low light level light sources commonly used to evaluate image intensifier

devices. These devices are calibrated to operate as low as 10~ 7 footcandles, a 10 9 order

of magnitude difference between that of the standard! The problem is further complicated

by the requirement that the spectral distribution of the light source be that of a blackbody of a given color temperature (typically 2870 °K) over a spectral region of .4 u to

.9 u.

Another use of attenuators is to determine linearity of precision measuring instruments, principally the detectors and systems that follow the detectors. Many texts, including

Moon and Walsh roughly describe methods of attenuation but it is felt that the Bureau should

take the lead in establishing and standardizingmore definitive techniques in attenuation.

The current situation is one of each investigator or laboratory employing their own methods

and thus giving rise to data correlation difficulties.

B. Impact

The result of not having standardized techniques for attenuation of high light level sources is disagreement in calibration values of low light level sources made by various

secondary standards laboratories. The potential impact of disagreement between secondary

standards laboratories, i.e. laboratories directly traceable to NBS, is tremendous. A

contractor traceable to secondary laboratory A measures the performance of a device

to meet specifications of a contractee. The contractee traceable to say laboratory B does

acceptance testing of the device and finds it below his specifications and rejects the

devices. Many manhours and delay of important developmental programs may be spent to resolve the discrepancy which in the end was found to result from laboratory A employing

an attenuation method different from laboratory B.

The above situation is indeed a reality in many of the U.S. Army procurement programs for low light level intensifying devices and the problem is difficult to solve since

it requires a significant expenditure of technological resources to determine which is the more theoretically valid method of attenuating a standard source. It is felt that this

task more properly falls into the domain of the National Bureau of Standards.

C. Solutions

It is recommended that the Bureau attempt to collect, describe and analyze all

methods of attenuation pertinent to photometry, radiometry, spectrophotometry. The Bureau

should then make recommendations to industry suggesting which methods are pertinent to different areas of this technology. It is also recommended that these discussions from

the Bureau be put in some form that can be distributed to the scientific community. A

special NBS technical note or monograph along with the results of the other working groups

could be made available to the public. Another recommendation would be to have the results

1+0
of these analyses and working group discussions presented to the regular international CIE

meetings and have international discussions of the results which may be also distributed to the public in the form of NBS technical notes or CIE notes or whatever. Another recommendation would be to periodically have round-robin measurement comparisons between laboratories

similar to those which are held for measurements of luminous intensity. For example

measurements of low level sources as opposed to sources which are of the magnitude of NBS

standards may be compared. Another recommendation is to obviate the use of attenuators by

providing to industry standards of luminous intensity and other photometric and radiometric

standards which are themselves orders of magnitude lower than those which are currently

provided. This relates back to the original discussion of this note: the reason that

attenuators are used is that the phenomena being measured are very often different by many

orders of magnitude from those of the standards obtained from the Bureau.

kl
Appendix D

The objective of this group is to define and provide for the establishment of a national

measurement system for relative and absolute spectral detector response measurements. This

will include defining the NBS role in the measurement system and defining the needed accuracy

and minimum detectable spectral irradiance as a function of wavelength.

SPECIFIC RECOMMENDATIONS

1.) Cavity receiver, electrically calibrated thermal detector capable of NEI on the order

of 1 u watt /cm2 for use in relative spectral response calibrations.

2 . ) NBS should maintain a primary standard in the spectral response area coupled with

recommendations for transfer standards and procedures for their use. NBS should

encourage industry to go into the business of supplying these transfer standards with

calibrations and to set up procedures (such as round-robins) to ensure these calibrations,

3.) A quantum detector should be the transfer standard going down to 0.2 u. A transfer

standard is also needed out to at least 25 u. This standard need not be a quantum

detector.

Studies of the linearity of these transfer standards or procedures for calibrating

their linearity.

Studies of the stability of these transfer standards or procedures for calibrating

their stability.

SPECIFIC PROBLEM AREAS

1.) Getting down to low irradiance levels.

2.) Correlation of pulsed and steady state measurements (integrated vs. peak). There are no pulse standards.

3.) Specification definitions are not well enough defined to really help the consumer

Areas not defined well enough for D* or responsivity specifications.

4.) Temperature dependence of silicon cells.

JUSTIFICATION

The lack of adequate detector spectral response standards, procedures, and definitions

contributes to a disorderly marketplace. The user depends on the detector supplier for

spectral response data which too many times is in dispute. Reliable spectral response data

is needed for accurate data reduction of user's results. In the case of broad band detectors

for example, spectral response is used to establish "effective radiance" characteristics

which call for conversion of received radiation to equivalent blackbody temperature. All

too often, without reliable spectral response standards the user is now forced to develop

effective spectral response results by indirect means.

k2
Appendix E

This group first moved to define its scope; namely, Flux (Luminous, Radiant and Spectralradiant) needs in the area of measurements of luminous flux (lumens) and spectral-radiant

flux (watts/nm) covering sources (incandescent, fluorescent, HID, etc.) of UV, visible and

IR radiation.

Without particular discussion it was agreed that it was desirable for the Bureau to continue on programs now in progress, such as, the work now underway with Mrs. Burns on incandescent lamp standards, the fundamental definition of the candela, and the work on establishing and improving the derivation of the lumen from intensity, or even spectral

irradiance standards goniometrically, then learning to transfer flux standards in spheres

and understanding what is happening in spheres. Dr. Schaefer commented that this latter

capability will be necessary in any event in order to measure spectral-radiant flux. He

questioned if there is not, at least for now, still a necessity to be able to make photometric flux measurements directly with a well characterized detector.

Then came the question, are these needs best met by standards for each of the types of sources or by the development of means for attaining this end through the use of only a very

limited number of standards? Up to the present time, photometric laboratories have been

existing through the use of standards of luminous flux from NBS for incandescent and certain

fluorescent lamps, and color standards for another group of fluorescent lamps. Measurements

of luminous flux from lamp types and sizes outside the range of these standards or color

assignments beyond the limited group have been made by each laboratory on the basis of its own methods or its own developed standards, usually without direct traceability to NBS.

The development of standardized procedures for the determination of spectral-radiant

flux, with a limited number of standards for this characteristic available from NBS, would

make it possible for laboratories to determine total luminous or total radiant flux from the

results of the spectral-radiant flux measurements. A laboratory equipped to make this spectral

determination then would be in a position to transfer flux assignments for a given type and

size of lamp to other lamps of this same size and type for' use as secondary standards in

commercial assignments by substitution methods. A laboratory not equipped to make SED

measurements would have to depend on an independent laboratory to supply these needs.

The development and use of the total spectral radiant flux as a means toward total

luminous flux determinations has an added advantage in that color appearance and color

rendering index both are computable from the results of this measurement. Thus, a standardized procedure for the. determination of luminous flux would, at the same time, yield a standardized procedure for color appearance and color rendering index, where standardized

procedures presently are available only for a small part of the lamp types and sizes being

used.

What would be needed in the way of a range of standards? Lamp measurements now cover

the range from 0.01 to 100,000 lumens. The 0.01 lumen is for sub-miniature incandescent

lamps and the 100,000 lumens for some of the HID lamps.

If measurement were to be made by spectral-radiant flux determination, what range would

be required? Bactericidal and ozone producing lamps would require special techniques for

measurements down to 180 nm. It is, therefore, suggested that two sets of equipment and

two measurements procedures be developed, one in the range from 180 to 320 nm and the other

from 250 to 900 nm.

What is the justification for asking NBS to either furnish standards of all types and

sizes or to develop measurements procedures to standardize the determination of spectralradiant flux? Without lamp standards for the characterisitics or without standardized

measurements procedures, determined values may vary from laboratory to laboratory by amounts

up to 10 per cent or more. Further, since published performance data for various lamp types

are based on the results of measurements in the various manufacturers' laboratories, catalog

data will reflect these variations. As a result, there are influences on (a) business;

domestic and foreign, (b) health and safety of the public, (c) legal liabilities, and (d) consumer protection.

H3
In business, many purchases are made on the basis of promised performance. A difference

of the order of one or more percentage points in promised performance will, therefore, determine the business to be done, either domestic or foreign, by a given manufacturer or even by

an industry. This can run into millions of dollars.

In addition, to the unfair competition resulting from such comparative ratings, there

is the influence of such catalog data on purchase specifications by state and local governments, GSA, OEM, DOT, FAA, etc.

People live in a radiation environment, natural or artificial. Just as too much sun- light may be harmful, certain elements in artificial light may be harmful. On the other

hand, other elements may be beneficial. In other words, there is no doubt but that radiation

may have influences on health. BRH no doubt is interested.

Light plays an important part in the safety of our people. Highway and traffic safety

depend on light signals. DOT and FAA both are active in specifying performance.

Consumer protection is considered to be of such importance that an agency is set up in

government in an effort to provide this protection. One facet of this protection is truth

in advertising, facts and not fiction. FTC is interested in this. When a customer replaces

a lamp, he expects a similar performance from the replacement. In other words, lamps

similarly marked should be interchangeable. With all of this, the manufacturer is subject to possible legal action due to nonfulfillment of contract if lamps do not perform in service as the purchaser was led to believe from catalog data.

With the announced policy of NBS to limit the number of types and sizes of standards to be provided, this group strongly recommends that NBS proceed (1) to continue its present

program of calibration of specific lamp types to provide to industry a baseline for these

types, (2) to develop methods of extending the calibration of secondary standards from a limited number of standards for a given lamp type, and (3) to develop standard procedures

for determining spectral-radiant flux for all types and sizes of lamps. This latter development should provide means for handling different lamp geometries — bulb shapes, etc.

kk
Appendix F

The working group listed the following items, in order of priority, as the most pressing

needs in the area.

1) Provision by NBS of detailed, written descriptions of the methods and techniques

through which NBS calibrates standards of spectral radiance, spectral irradiance,

luminous intensity, color temperature, etc. Ideally, these descriptions would

be duplicated in other laboratories with minimum chance of error.

2) When NBS is unable to provide full calibration services, they should provide

some method of guaranteeing that commercial standards labs are providing

measurement services on the NBS scale. Various methods of formal and informal

certification are under discussion (e.g., NBS calibration reports might

include a value predetermined by the customer in addition to the NBS determined

value and uncertainty statement)

3) Small-scale, simple inter laboratory intercomparisons utilizing NBS techniques

(item 1 above), with NBS acting as referee, would be desirable to determine

the level of agreement between interested labs and NBS in selected areas

(luminous intensity, total irradiance, color temperature, etc.).

4) NBS should take the steps necessary to provide easy access to existing written

descriptions of techniques and methods through bibliographies, subscription

information on periodicals, etc.

The committee recognizes a strong need to coordinate closely its future activities with

the working group on techniques (working group VI). For the immediate future, the working

group on dissemination will direct its efforts toward the preparation of a detailed

outline of most useful material to be included in future NBS write ups of techniques and

methods.

U5
Appendix G

I. STATEMENT OF PROBLEM

The basic problem with laser energy and power measurement is the large scale discrepancy

in calibration of the various energy and power meters that are commerically available.

Although manufacturers of these instruments claim traceability to NBS within 5% of

absolute, variations of as much as 30% have been seen on several different types of

instruments.

The specific problems related to standarization and calibration of laser power and energ;

monitors are as follows

1. Lack of standard laser sources stable enough to use as an equivalent to a standard

lamp.

2. Lack of readily available standard thermopiles or calorimeters.

3. Unavailability of secondary standards labs to provide a traceable industry-wide

calibration service for power and energy meters.

4. Lack of detailed information as to procedures and techniques for use of laser

measurement instrumentation.

II. EXISTING STANDARDS AND PROCEDURES

Presently, NBS-Boulder is capable of achieving a 1% accuracy of laser energy measurement

with the C-series calorimeter system. In general this is accurate enough for all

current laser applications such that a new standard is not needed at this time.

Several NBS documents are available which treat some of the applications of power and

energy meters in a standards laboratory setting; however, a generalized descriptive

procedure in the form of a handbook is badly needed.

III. CONSENSUS ON NECESSARY NBS ACTION

By consensus of the Laser Committee, the following measures are listed in order of

priority:

1. Specification of a generalized class of calorimeters or thermopiles which could

be easily calibrated within a 2-3% uncertainty.

2. Appropriate software to support the above chosen class of calorimeters based

on laboratory data and containing a broad based procedure and technique for

accurate use.

3. Detailed applications note concerning the compounding of errors in laser power

and energy measurements to be used as a guide in designing the measurement procedure.

4. Continuation of the calorimeter and thermopile calibration service at NBS with

the possible future certification of secondary standards labs who could provide

fast accurate calibrations.

IV. JUSTIFICATION FOR NBS ACTION

As previously stated, NBS can achieve a 1% accuracy in measurement of laser energy

and power based on the electrical calibration of its C-series calorimeter. The

measurement problem therefore exists in the calibration and use of the commercially

available measurement devices. As much as 30% error may be found in some instruments

due to calibration uncertainty, faulty application techniques and actual instrument

instability

,

1+6
There is a pressing need for increased accuracy by both laser manufacturers and laser

users. Laser manufacturers must have accurate measuring instruments in order to guarantee product capability and performance. They must also be assured that their

customer's power and energy meters are of the same absolute accuracy such that

discrepancies in power level will not be due to the measurement system.

Laser users on the other hand have a significant number of applications which require

highly accurate measuring instrumentation. Some of these applications are:

1. Laser damage threshold measurements.

2. Laser material and laser system research and development.

3. Raman scattering.

4. Laser radars and range finders.

5. Laser monitoring in conjunction with the new laser safety standards.

The laser industry is expanding in influence in a multitude of new produce areas. With

each new development an increased demand is placed on laser power and energy measurements.

We must rely on NBS to develop new standards and insure that all industry can be

supplied with accurate calibrations.

hi
FORM NBS-114A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-594-4

2. Gov't Accession No.3. Recipient's Accession No.

4. TITLE AND SUBTITLE

OPTICAL RADIATION MEASUREMENTS:

The Impact of Radiometry and Photometry and the Role of NBS

5. Publication Date March 1973

6. Performing Organization Code

7. AUTHOR(S)

Bruce Steiner

8. Performing Organization

10. Project/Task/ Work Unit No. 9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same as No. 9

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.) Serious measurement discrepancies universally plague quantitative measurement in

the electro-optics industry. The impact of the resulting problems is reviewed and the

role of NBS explored. The measurement discrepancies arise chiefly through the recent

explosive expansion of this industry. The growth has precipitated a complex development in the variety and accuracy of measurements required. The impact of problems in

optical radiation measurement falls in many areas . One is the increasing Federal

responsibility for public life defined in recent legislation. Another is the influence

of good optical radiation measurement on the technical development of the electrooptics industry. The impact of these measurements on a number of public issues is

reviewed: public health, public safety, the energy crisis, meteorology, pollution,

agriculture, crime prevention, and surveillance from air and space. The economic

impact of improved measurement both on a fair domestic market and on the balance of

payments operates through unit production cost, quality control, product improvement,

and innovation. Leadership by NBS has been urged by the industry not only in fulfillment of its legislative responsibility but also to permit the focus of elaborate and

impartial resources on the complex problem of optical radiation measurement. In keeping with its mission to help improve industrial technology and the competitiveness

of American industry, NBS has an opportunity of major proportions in the electrooptics industry. Leaders of this industry are calling for NBS initiatives to resolve

many of the measurement problems now hindering further progress

.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Agriculture; clinical analysis; economic impact; energy crisis; meteorology; photometry;

phototherapy; pollution; radiometry; remote sensing.

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U.S.MAII
NBS TECHNICAL NOTE 594-5

Optical Radiation Measurements:

Stability and Temperature

Characteristics of Some Silicon

and Selenium Photodetectors
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry,

and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences 2 — Applied Radiation 2 — Quantum Electronics ' — Electromagnetics * — Time

and Frequency 3 — Laboratory Astrophysics 3 — Cryogenics n

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides

advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor

Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote

the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of

technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innovation — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety 4 — Building

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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

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1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

1 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

* Part of the Center for Building Technology.
est O^c - foL

oo Optical Radiation Measurements:

^Stability and Temperature Characteristics

of Some Silicon and Selenium Photodetectors

Kshitij Mohan, A. Russell Schaefer

and Edward F. Zalewski

Heat Division

Institute for Basic Standards

<J ' National Bureau of Standards

Washington, D.C. 20234

fi^l^^tM ~*U*~ t «* - 5^-3

* \

-*< ^&*^ .#

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued June 1973
National Bureau of Standards Technical Note 594-5

Nat. Bur. Stand. (U.S.), Tech. Note 594-5, 16 pages (June 1973) CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.46:594-5). Price $0.35 domestic postpaid or $0.25 G.P.O. Bookstore.
Preface

This is the fifth issue of a series of Technical Notes entitled

OPTICAL RADIATION MEASUREMENTS. The series will consist primarily of

reports of progress in or details of research conducted in radiometry

and photometry in the Optical Radiation Section of the Heat Division

and will appear about every six weeks.

The level of presentation in OPTICAL RADIATION MEASUREMENTS will

be directed at a general technical audience. The equivalent of an undergraduate degree in engineering or physics plus familiarity with

the basic concepts of radiometry and photometry [e.g., G. Bauer,

Measurement of Optical Radiations (Focal Press, London, New York,

1965)] should be sufficient for understanding the vast majority of

material in this series. Occasionally a more specialized background

will be required. Even in such instances, however, a careful reading

of the assumptions, approximations and final conclusions should permit

the non-specialist to understand the gist of the argument if not the

details.

At times, certain commercial materials and equipment will be

identified in this series in order to adequately specify the experimental procedure. In no case does such identification imply recom- mendation or endorsement by the National Bureau of Standards, nor

does it imply that the material or equipment identified is necessarily

the best available for the purpose.

Any suggestions readers may have to improve the utility of this

series are welcome.

Henry J. Kostkowski, Chief

Optical Radiation Section

National Bureau of Standards

111
TABLE OF CONTENTS

Page

1. Introduction 1

2. Experiments and Results 3

2.1 Stability and Fatigue Effects 3

2.2 Temperature Dependence 7

3. Conclusions 7

4. References 10

Appendix A 11

LIST OF TABLES

1. Percent drift in detector output over approximately

twenty hours 5

2. Detector output drift during ten minutes after shuttering

for twenty minutes 6

3. Temperature dependence of detector output in the interval

20 to 30 °C 6

LIST OF FIGURES

1. Initial short term drift in detector output. Output

normalized to initial reading 8

IV
STABILITY AND TEMPERATURE CHARACTERISTICS

OF SOME SILICON AND SELENIUM PHOTODETECTORS

Kshitij Mohan*; A. Russell Sehaefev and Edward F. Zalewski

This paper describes the comparison of some characteristics of selenium barrier layer photocells and silicon

PIN and PN type photodiodes operated in the photovoltaic

or non biased mode. The work was done to study the suitability of these detectors specifically for goniometric

measurements of flux and possibly for other photometric

(or radiometric) measurements. The characteristics studied

were the stability of detector output over approximately

twenty hours, fatigue or light memory effects over short

periods of time, and the temperature dependence of detector

Output.

Key words: Fatigue; light memory; photocells; photodiodes

photometry; radiometry; selenium; silicon; stability;

temperature dependence.

1. Introduction

Since the advent of physical photometry, barrier layer selenium

photovoltaic cells have been used extensively in photometry at NBS. The

selenium cells used were equipped with photopic filters that approximately corrected the response of the detector to match the CIE defined

spectral luminous efficiency in photopic vision.

Selenium cells have been found [1,2,3] 1 to exhibit certain characteristics, such as fatigue, that are undesirable in goniometric measurements

of total flux. In the last decade solid state technology has made

available several new kinds of photodetectors, some of which seem promising for photometric applications. In particular, silicon photodiodes

appear to be a possible replacement for selenium barrier layer photocells.

We have examined and compared certain characteristics of two

selenium detectors and several different types of silicon detectors to

ascertain their suitability for use in our work. The study is by no

means exhaustive or definitive and was initially meant to be an in-house

guide for the selection of a specific detector for a specific purpose.

It is being published because we are unaware of any other comparative

study of these detectors and also because it may give potential photometric users of these devices a feel for the problems involved.

We have tested photodetectors for three characteristics : the

long-term stability over periods of about 20 hours, light memory or fatigue effects over short time periods, and the sensitivity to changes

^National Bureau of Standards research associate from the Electrical

Testing Laboratories (acting on behalf of the Lamp Testing Engineers Conference) . figures in brackets indicate the literature references at the end of

this paper.
in temperature. Not all the detectors were tested for all these characteristics. Appendix A is a list according to the type and manufacturer

of the detectors that were tested. In this report we shall refer to each

detector by the numbers assigned in Appendix A.

Among the silicon detectors, we have studied the PN type of photodiodes and the PIN type of both the Schottky and planar diffuse varieties.

Descriptions of these devices are available in the manufacturers'

literature, but for the sake of completeness and as an introduction we

shall include descriptions of some typical devices here.

The PN type of photovoltaic cell consists essentially of a junction

of two types of material, referred to as p-type and n-type respectively.

The p-type is doped with impurities such that it is a "hole" conductor;

i.e. there is a deficiency of electrons in the material. The n-type

material has been doped to provide a surplus of electrons. At the

interface of these two materials the surplus electrons and holes diffuse

across the junction to combine with each other and form a depleted

"barrier" region which is now free of holes and electrons. The p-type

material near the junction, having lost holes, acquires a negative space

charge and correspondingly the n-type material near the junction, having

lost electrons, acquires a positive space charge. Thus an electric field

is maintained across the depletion barrier. This electric field will

then inhibit further diffusion of the electrons and holes so that a state

of equilibrium is reached. Now, when a photon is incident on the junction

it can excite an electron from the valence band to the conductance band.

This will happen only if the incident photon has an amount of energy

greater than the energy difference between the valence and the conductance

bands. This difference is known as the "energy gap" for the material

and is different for different kinds of material. The excitation of the

electron makes it free to move in the material and a corresponding free

"hole" is also created. The process is known as the creation of a hole-electron pair. Ordinarily, if other free holes or electrons are present there would be a recombination of the holes with the electrons

or the pair could recombine itself. But if the electron-hole pair is

created in the depleted region where there are no other free holes and

electrons present then the electron will be accelerated to the positive

space charge in the n-region and the hole to the negative space charge

in the p-region. If there is a load resistor across the ohmic (external)

contacts on the n-region and the p-region, there will be a flow of

electrons from the n-region through the load to the p-region. Since by

convention a current flow is said to be in the opposite direction of the

electron flow, there will be a current flow from the p-region through the

load to the n-region.

If every photon incident on the detector were to produce an electron-hole pair, and if all these electrons and holes were to migrate

as predicted, the detector would be absolutely linear.

The PIN type of silicon photodiode derives its name from the fact

that it consists of a p-type semiconductor and a n-type semiconductor

with a layer of nearly intrinsic (i.e. almost pure, non-doped) region

of silicon in between. This intrinsic layer acts as an extended depletion
layer which can, under appropriate conditions, improve the linearity and

response time of the photodiode. In the photovoltaic mode these PIN

photodiodes operate in a manner similar to the PN photodiodes described

above. In the photoconductive or biased mode, a voltage is externally

applied across the electrodes such that there is an electric field

completely across the photodiode and the intrinsic region is fully

depleted. When a photon is absorbed in the silicon, an electron-hole

pair is created and propelled by the external field to their respective

electrodes, creating a current through an external load as before.

In the Schottky barrier PIN silicon photodiode, the p- and n-regions

are created by depositing a thin gold layer on one side of a pure silicon

wafer and an aluminum (or other metal) layer on the other side. The

gold layer is transparent and forms the front side of the detector. In

the planar diffuse type of silicon photodiodes, a layer of aluminum

(or other metal) is evaporated on one side of a silicon wafer and on the

other side silicon dioxide is formed. Then through an opening in the

oxide, an impurity is diffused into the silicon to form a p-type layer.

The spectral response of the detector depends not only on the energy

gap of the pure silicon but also on the spectral transmittance of the

material on the front surface of the detector.

All the detectors that we studied were operated in the unbiased

or photovoltaic mode rather than the photoconductive mode. The advantages of the photoconductive mode are an improved linearity and a faster

response time. These arise from the fact that the strong electric field

applied externally to the junction fully depletes the intrinsic region

and creates greater carrier acceleration. However, the application of

an external voltage also leads to a leakage or dark current which is

large compared to the signal being measured. This dark current is not

constant in time and, therefore, makes the photoconductive mode of

operation unsuitable for dc measurements. In the photovoltaic mode the

dark current was usually quite small (less than 0.1% of our measurement

signals)

2. Experiments and Results

2.1 Stability and Fatigue Effects

One important requirement for a detector that is used in goniometric

photometry is that it should be stable; that is, it should maintain its

calibration during the course of a set of measurements which could take

up to several hours to complete. Another requirement is that the detector

should achieve a stable output within seconds after a change of illumination.

We have studied the stability of detector output for periods of

approximately twenty hours. We have also investigated the short term

stability in a 10-15 minute interval by noting any fatigue effects or other kinds of instabilities that might result after a change in

illumination level.

The experimental apparatus consisted of a 120 volt, 750 watt

quartz-halogen EHF type lamp that was mounted on one end of a 3 meter
optical bench. The lamp was operated at a constant current of 4.8300

± 0.0001 amperes and the voltage was approximately 75 volts. Mounted at

the other end of the optical bench was a detector holder that could hold

two test detectors simultaneously. A third detector with an independent

current-to-voltage converting amplifier was placed about 50 cm from the

lamp and to one side of the optical axis. This detector was used to

monitor the output of the lamp in each test.

One may question the stability of the lamp and monitor detector

combination. However, previous work by one of the authors (E.F. Zalewski)

that compared several lamps of the above type using detector No. 1 had

shown this lamp and detector combination to be stable to less than 0.1%.

Of the six runs in table 1 in which this detector and the monitor detector

are compared, only one run shows a disagreement of more than 0.2% (run

No. 3). This run, it should be noted, shows a larger change in the lamp

voltage than was observed during any other run. We believe, therefore,

that any detector drift that differs by more than 0.2% from the monitor

detector is actually a change in detector response and not a change in

lamp output.

When examining detectors which did not have built-in photopic

filters, a set of infrared and ultraviolet cut-off filters was used to

block radiation from all but the visible part of the spectrum. The ambient

temperature near the detector holder was monitored by using thermocouples.

Except in the case of detectors with built-in amplifiers, the outputs of

all detectors were read by using either of the two current-to-voltage

converters described in an earlier paper [4] and a digital voltmeter. Automatic data acquisition equipment was used to collect data.

For the long term stability measurements, the outputs of the test

detectors and the monitoring detectors, the voltage and current of the

lamp, and the temperature of the detector holder were noted at intervals

of 20 minutes over approximately 20 hours. As mentioned earlier, all the

test detectors were operated in the photovoltaic mode.

Table 1 summarizes the results of the long term stability measurements for the different detectors. The detectors are briefly distinguished in the following manner: Si-S , silicon Schottky; Si-D, silicon

diffuse; and Se, selenium. The numbers for the range of noise are the

short term fluctuations above and below a straight line approximation of

the detector drift. The numbers for the amount of drift for individual

detectors have not been adjusted for lamp drift as sensed by the monitor

detector. Each row in table 1 represents a single run so that detector

drifts appearing in the same row indicate that those detectors were used

simultaneously to provide comparisons between them. Where a plus or a minus appears before the number for percent drift, it indicates that the

increase or decrease in detector output was approximately monotonic. The cases where the detector output first drifted up then down or vice versa, are indicated in the table. The temperature of the test detector holder

was monitored in several runs and found to be within ±0.5 °C. Except for

Nos. 2, 4, 5, and 10, the detectors appear to be stable to within 0.02%

per hour—a fact that should meet most photometric requirements for

stability.

All the measurements had been taken after the lamp had been warmed

up for about 20 minutes, during which time the detector was illuminated.

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TABLE 2 DETECTOR OUTPUT DRIFT DURING 10 MINUTES AFTER SHUTTERING FOR 20 MINUTES

DETECTOR

1 (Si-S)

3 (Si-D)

4 (Si-S)

5 (Se)

7 (Si-D)

8 (Si-D)

9 (Si-S)

DRIFT

less than noise

less than noise

less than noise

-0.4%

less than noise

less than noise

less than noise

RANGE OF NOISE

Before After

0.1% 0.1%

0.05 0.05

0.06 0.06

0.06 0.20/2 min

then 0.06

0.1 0.25

0.1 0.3

0.1 0.1

TABLE 3

TEMPERATURE DEPENDENCE OF DETECTOR OUTPUT IN THE INTERVAL 20 TO 30 °C

DETECTOR

1 (Si-S)

2 (Si-S)

3 (Si-D)

4 (Si-S)

5 (Se)

7 (Si-D)

9 (Si-S)

11 (Si-D)

BLOCK

TEMPERATURE DEPENDENCE

-0.06% per °C

-0.02

±0.07*

-0.12

+0.06

±0.07*

±0.08*

+0.12

REMARKS

Minimum near 24 °C

Maximum near 24 °C

Maximum near 24 °C

*These temperature dependences went through a minimum or a maximum.

The numbers represent the slope on the steep part of the temperature

dependence curve.
This was done to avoid any short term fatigue effects. These were

studied separately.

Using the same experimental set-up described above, detectors were

checked for any fatigue or light hysteresis effects by first warming up

the lamp and illuminating the test detector and then shuttering the

detector for a period of about 20 minutes. The shutter was then opened

and the detector output and other parameters were read out at 20 second

intervals for a period of 10 minutes. Table 2 summarizes the drift and

noise that were observed after the shutter was opened. The numbers for

range of noise Before and After refer to the noise ranges observed before

the detector was shuttered for 20 minutes and after it was again illuminated. No drifts above the noise level were observed except for detector

5 which was a selenium photocell. This detector showed the expected

fatigue effect [2,3]. A comparison plot of the output of this detector

and detector 1 is shown in the figure. Detectors 7 and 8 did not show

any drift, but the noise on both showed a large increase in the 10 minutes

after the shutter was opened. It seems that a longer time period is

required for them to achieve equilibrium.

2 . 2 Temperature Dependence

The temperature dependence of a set of detectors was studied over

the range of approximately 20 °C to 30 °C. The experimental apparatus

remained the same as in the stability studies except that the detectors were mounted in a metal block which was cooled or heated by two thermoelectric plates. The detectors were shielded from room temperature

changes by a transparent plastic box surrounding the detector holder.

The temperature of the detector was changed by altering the amount

of current passing through the thermoelectric plates. The current polarity

determined whether the detector was being cooled or heated. Temperature

was measured by two thermocouples , one of which was embedded in the metal

block that held the detectors. The metal detector cases were in good

thermal contact with this block. The other thermocouple measured the

temperature of the air surrounding the detector in the plastic box.

Readings of the detector outputs and other monitoring parameters were taken when both the temperature of the block and the ambient temperature within the box had achieved equilibrium. Table 3 gives the

changes in detector output per °C change of block temperature. Two

detectors, No. 4 which is a Schottky type PIN device and No. 11 which

is a diffuse PIN device, showed temperature dependences slightly greater

than 0.1% per °C. Some of the detectors had a temperature coefficient

which went to zero (minimum or maximum in the response curve) near room temperature. The maximum slope is, therefore indicated in table 3.

3. Conclusions

As mentioned in the introduction, this study was not meant to be a definitive or exhaustive study of all the different kinds of photodetectors

available today, hence we can not draw any general conclusions of the

relative merit of any manufacturer of these detectors. Detectors of the
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same type and manufacturer may at times perform differently as is

evidenced by the differences in the stabilities of detectors 1 and 2;

both were of the same type, were made by the same manufacturer, and had

the same model numbers.

We can, however, draw some conclusions and also get an indication

of where problems may exist. The study also gives us estimates of a part

of the uncertainty that should be taken into account when these detectors

are used in specific applications.

1. In photometric applications (dc measurements) the silicon

detectors of the kinds that we studied should be operated in

the photovoltaic or non-biased mode.

2. Several of the silicon detectors studied proved to be

sufficiently stable for applications in precise photometry:

the instability of output was less than 0.02% per hour.

However, some of the detectors were significantly less

stable. Thus silicon detectors have to be individually

tested and selected for optimum performance.

3. The silicon detectors did not show any identifiable

fatigue or light memory effects, whereas the selenium photocells studied showed the expected fatigue. Some silicon

detectors are very noisy when first illuminated and it

sometimes can take several minutes before the noise decreases

and the cells achieve equilibrium. In goniometric measurement

of flux, effects due to changing levels in illumination are undesirable. One cannot therefore use the selenium detectors

without some sort of arrangement to take account of these

effects. However, there are some silicon detectors that can be used; again, the characterization of the specific detector

is required.

4. All the detectors showed sensitivity to temperature

changes and if they are to be used in photometric work at

the few tenths of a percent level of precision, temperature

control within ±0.5 °C or less is necessary. For precise

photometric work the specific detector chosen should first

be characterized for its temperature sensitivity and then

the required amount of temperature control should be built

into the detector holder.

Detectors 9 and 10 were silicon detectors that had a current-tovoltage converting amplifier built into the detector case. Detector 9

had stability and temperature dependence characteristics that were of

the same order as the other silicon detectors. Detector 10, however,

showed larger drift and noise. Since these detectors are used without

external operational amplifiers, laboratories that do not now have such

amplifiers may consider using them.

For goniometric measurements of flux the detectors should also be

tested for linearity and spectral response. The linearity, however is

more critical than spectral response for our purposes. Some preliminary

linearity tests using the inverse square approximation have shown that

9
silicon cells operated in the photovoltaic mode are linear within 0.1% over two decades. Future studies of these detectors will include more

detailed linearity and spectral response measurements.

4. References

1. Wilkinson, F. J., "Heterochromatic Photometry with Selenium Photovoltaic Cells", NSL (Australia) Tech. Paper No. 23, 15 pages, 1968,

2. Preston, J. S. , Rev. d'Opt. 27, 513 (1948).

3. Preston, J. S. , J. Sci. Instrum. 27_, 135 (1950).

4. Zalewski, E. F. ; Schaefer, A. R. ; Mohan, K. and McSparron, D. A.;

"Optical Radiation Measurements: Photometric Instrumentation and

Research (1970-71)". NBS Tech. Note 594-2, 44 pages, Sept. 1972.

10
Appendix A

List of Detectors Tested with Assigned Numbers

Assigned No. Detector Type Manufacturer

1 Silicon PIN Schottky, photopically A

corrected

2 Silicon PIN Schottky, photopically A

corrected

3 Silicon PIN diffuse A

4 Silicon PIN Schottky A

5 Selenium barrier-layer, photopically B

corrected

6 Selenium barrier-layer, photopically C

corrected

7 Silicon PIN diffuse D

8 Silicon PIN diffuse D

9 Silicon PIN Schottky with built in A

op amp, photopically corrected

10 Silicon PN diffuse with built in D

op amp, UV optimized

11 Silicon PIN diffuse A

* U. S. GOVERNMENT PRINTING OFFICE: 1973 --511-327/277

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form NBS-114A (1-71)

U.5*. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-594-5

2. Gov't Acceasiw

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

OPTICAL RADIATION MEASUREMENTS:

STABILITY AND TEMPERATURE CHARACTERISTICS

OF SOME SILICON AND SELENIUM PHOTODETECTORS

5. Publication Date June 1973

4. Performing Organizati on Code

7. AUTHOR(S)

Kshitij Mohan, A. Russell Sahaefer and Edward F. Zalewski

I. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Taslc/Worlc Unit No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same as No. 9

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14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This paper describes the comparison of some characteristics of selenium

barrier layer photocells and silicon PIN and PN type photodiodes operated in the

photovoltaic or non biased mode. The work was done to study the suitability of

these detectors specifically for goniometric measurements of flux and possibly

for other photometric (or radiometric) measurements. The characteristics studied were the stability of detector output over approximately twenty hours, fatigue

or light memory effects over short periods of time, and the temperature dependence

of detector output.

17. KEY WORDS (Alphabetical order, separated by semicolons) Fatigue; light memory; photocells;

photodiodes; photometry; radiometry; selenium; silicon; stability; temperature

dependence

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REFERENCE

NBS TECHNICAL NOTE 594-6

Optical Radiation Measurements:

The Present State

of Radiometry and Photometry
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards ' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (I) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences - — Applied Radiation " — Quantum Electronics 3 — Electromagnetics :l — Time

and Frequency " — Laboratory Astrophysics :; — Cryogenics n. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides

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Radiation — Physical Chemistry.

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the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of

technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innovation — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety ' — Building

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the executive branch for the development of Federal standards for automatic data processing

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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

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2 Part of the Center for Radiation Research.

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« Part of the Center for Building Technology.
„ . -. „ ,. . I** National Bureau of; Optical * Kadiatwii Measurements: mnn n „M, APR 2 9 1974 The Present State

of Radiometry and Photometry

Bruce Steiner

Heat Division

Institute for Basic Standards

National Bureau of Standards

Washington, D.C. 20234

/ v \ * ^

*

£i*

&

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued March 1974
National Bureau of Standards Technical Note 594-6

Nat. Bur. Stand. (U.S.), Tech. Note 594-6, 56 pages (Mar. 1974) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1Q71

For ><de liy the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SI) Catalog No. CI 3.46:594-6). Price 95 cent.-.
Preface

This is the sixth issue of a series of Technical Notes entitled OPTICAL

RADIATION MEASUREMENTS. The series consists primarily of reports of progress

in or details of research conducted in radiometry and photometry in the Optical

Radiation Section of the Heat Division. The current issue, however, is an

exception. It attempts to characterize and analyze the radiometry and photometry portions of our National Measurement System. A basic knowledge of the

operation of this system is essential in applying the resources of NBS and

the technical community towards improving it. This document is included in

the Optical Radiation Measurements series to further the understanding of the

radiometry and photometry portions of the National Measurement System.

Henry J. Kostkowski

Optical Radiation Section

National Bureau of Standards
FOREWORD

The recent rapid expansion of the electro-optics industry has generated many new

devices and a wide variety of new components. This industrial and scientific activity has

led to the formation of new technical groups and whole new organizations.

This remarkable growth and the resulting size and scope of problems associated with

it have been chronicled both by the technical journals and by popular journalism. A survey

of related serious problems and their consequences has already appeared in this Technical

Note series under the title "The Impact of Radiometry and Photometry and the Role of

NBS" II] . This review dealt with the relation between precise and accurate optical

radiation measurement and areas of national concern. It identified prominent areas of

impact.

By contrast, the present note identifies the origins and the extent of problems

within optical radiation measurement. It focuses on the performance of the measurements

themselves. The preceding Note identified the external motivation for specific levels

of agreement among measurements. The present Note describes the internal state of, and

interrelationships among, optical radiation measurements. It analyzes the components of

the system comprising these measurements in the U.S. It identifies new trends in the flow

of information within the system. And finally, it draws conclusions on the improvement

of agreement among radiation measurements now causing wide concern.

Prominent issues and conclusions are reviewed in an executive summary at the end of

the document.

figures in brackets indicate the literature references at the end of this paper.

iv
"Enormous sums are involved annually in electrical lighting

contracts, lamps of certain candle-power being usually

specified. Disputes between the consumer and the lighting

company are an almost daily occurrence. It is not that the

lighting company seeks to take advantage of suitable standards

but rather that the company, which usually aims to furnish

a satisfactory service, is handicapped by the lack of

authoritative standards."

— Samuel Wesley Stratton in

address advocating the establishment of a National

Standardizing Bureau, 1900.
TABLE OF CONTENTS

PAGE

CHAPTER I. Background ]_ A. MOTIVATION 1 B. THE DICHOTOMY BETWEEN PHOTOMETRY AND RADIOMETRY 1 C. THE CONCEPTUAL MODEL 2 CHAPTER II. Present State of the Art 5 A. EXPLOSIVE GROWTH IN DEMAND 5 B. NATURE OF THE MEASUREMENTS 5

1

.

Five-Fold Parameter Variation 5

a. Level 5 b. Spatial distribution and sensitivity 7 c. Spectral distribution and sensitivity 7 d. Temporal behavior 7 e. Polarization 9

2. Common Measurement Elements 9

3. Uncertainty: A Question of a Point of View 9 4. Factors Associated with Automation 11

5. Conclusion 11

C. TRAINING 11 CHAPTER III. The Present Optical Radiation Measurement System 14

A. THE MODEL 14

B. PHYSICAL STANDARDS (HARDWARE) 14

C. PROCEDURAL STANDARDS (SOFTWARE) 14

D. FUNDING FRAMEWORK 16

E. ROLE OF THE PROFESSIONAL SOCIETY 16

F. THE COUNCIL FOR OPTICAL RADIATION MEASUREMENT 17 CHAPTER IV. Challenges Facing the National Measurement System 18

A. SYSTEMATIC FACTORS 18

1. Flow of Physical Standards 18

2

.

Flow of Procedural Standards 18

3. Flow of Information for the Establishment of Priorities 18

B. TECHNICAL FACTORS 18

C. COMMERCIAL FACTORS 18

1. Cost 18

2. Aggregation of Resources 19

D. BROADENED FEDERAL CONCERN 19

E. CONCLUSIONS 19

1. Coordination of Activities 19

2. Source Characterization 19

3. Detector Characterization 19

4. Technique Building Blocks 19

5. System Performance Evaluation 20

6. Measurement Assurance 20

7. Types of Transfer 20

8. Setting Priorities 20 ACKNOWLEDGEMENTS 21

REFERENCES 22 APPENDICES 25

APPENDIX A. Examples of Recent Requirements for Improved Measurement 25

1. ORIGINS OF DEMAND 25

vi
PAGE

a. New Technology 25

b. New Public Interest 25

2. CHARACTER OF THE GROWTH 26

a. Rapid Pace 26

b. Wide Diversity 26

APPENDIX B. The Flow of Physical Standards " 28

1. NBS AND OTHER NATIONAL LABORATORIES 28

2. PUBLIC ISSUANCE SECONDARY CALIBRATION LABORATORIES 28

3. COMPONENT MANUFACTURERS 28

4. INSTRUMENT MANUFACTURERS 29

5. AREAS OF IMPACT 29 APPENDIX C. Organizations Associated with Procedural Standards . 31

1. AMERICAN INSTITUTE FOR AERONAUTICS AND ASTRONAUTICS (AIAA) 31

2. AMERICAN METEOROLOGICAL SOCIETY (AMS) 31

3. AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI) 31

4. AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) 31

5. COMMISSION INTERNATIONALE DE^L 'ECLAIRAGE (CIE) 31

6. COMITE CONSULTATIF DE PHOTOMETRIE ET RADIOMETRIE (CCPR) 31

7. COUNCIL FOR OPTICAL RADIATION MEASUREMENT (CORM) 32

8. ELECTRONIC INDUSTRIES ASSOCIATION (EIA) 32

9. ILLUMINATING ENGINEERING SOCIETY (IES) 32 10. INFRARED INFORMATION SYMPOSIA (IRIS) 32 11. INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS (IEEE) 32 12. INSTITUTE OF ENVIRONMENTAL SCIENCES (IES) 32 13. INTERSOCIETY COLOR COUNCIL (ISCC) . 32 14. JOINT ELECTRON DEVICES ENGINEERING COUNCIL (JEDEC) 32 15. LAMP TESTING ENGINEERS CONFERENCE (LTEC) 32 16. MANUFACTURERS COUNCIL ON COLOR AND APPEARANCE (MCCA) 33

17. OPTICAL SOCIETY OF AMERICA (OSA) 33

18. SOCIETY OF AUTOMOTIVE ENGINEERS (SAE) 33

19. THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS (SMPTE) 33 20. SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) 33

21. WORLD METEOROLOGICAL ORGANIZATION (WMO) ... 33 22. UNDERWRITERS LABORATORIES (UL) . . . 33 APPENDIX D. Expansion of the Role of Professional Societies 34

APPENDIX E. Methodology of Study 35

1. GENERAL FACTORS 35

a. Size and Complexity 35

b. Desirability of Interaction Apart from NBS 35

c. Necessity for Interaction Between NBS and Other Elements

of the System 35

2. SPECIFIC CHALLENGES REQUIRING CONTINUITY 35

a. Novelty 35

b. Second-Order Interaction ... 35

c. Commercial Factors 35

d. Personal Confidence 36

e. Location of Right People 36

f. Identification of Crucial Questions • 36

g. Phrasing of Right Question 36

h. "Induction Period" 36

i. "Other Guy" Syndrome 36

j . "Emily Post" Syndrome 37

k. "State-of-the-Art" Syndrome 37

1. Efficiency 37
PAGE

3. PERMANENT STRUCTURES 37

a. Professional Societies 37

(1) Technical discussion 37

(2) Difficulties with systematic action 37

b. Council for Optical Radiation Measurement 38

(1) Origin 38

(2) Requirements 38

(a) Leverage on NBS 38

(b) Coordination of otter activities 38

(3) Operation 38

(4) Initial goal 39

(5) Permanent goals . 39

(6) Prospects for the future 39 APPENDIX F. Relation of Improved Optical Radiation Measurement to Broadened

Federal Concern 40

1. PROMOTING ACCURATE, MEANINGFUL, AND COMPATIBLE SCIENTIFIC AND TECHNICAL

MEASUREMENTS -10 2. PROMOTING MORE EFFECTIVE USE OF SCIENCE AND TECHNOLOGY 40

3. PROMOTING STRENGTH IN THE ECONOMY AND EQUITY FOR BUYER AND SELLER

IN TK \P1' 40

4. STANDARDS AND TEST METHODS FOR PROTECTION OF THE PUBLIC FROM

SPECIFIC HAZARDS 40

5. TECHNICAL INFORMATION SERVICE 40

6. EXPERIMENTAL TECHNOLOGY INCENTIVES PROGRAM 40

APPENDIX G. A Comprehensive Approach to the Measurement System 41

1 . THE RESEARCH REQUIRED 41

a. Source Characterization 41

(1) Realization of the scale 41

(2) Transfer of scales to secondary standards ... 41

(a) Characterization of present standards 41

(b) Improvement of present standards 41

(c) Description of procedures for present standards 41

(3) Extension of present standards 42

b. Detector Characterization 42

(1) Realization of scales 42

(2) Transfer of scales to secondary standards 42

(3) Extension of present standards 42

c. Techniques 43

:. SYSTEM COORDINATION 43

a. Coord inat Lon of Information 43

b. Coordination of Measurements 44

EXECUTIVE SUMMARY 45

LIST OF FIGURES

l. Relationship of areas of preceding study II], outer box, to the area of present

study, middle box, and to NBS, the inner box

Growth curves of lamp efficiency for various types of lamps as a function of

time Ol introduction (Source: References 9-11)

3. Commercial spectral response measurements on a silicon photodiode

viii
PAGE

4. Increase in incandescent lamp efficiency as a function of time (Source:

Reference 10) 10

5. Increase in the luminous flux of commercial fluorescent lamps as a function

of year of production 12

6. Physical standard measurement system 15

ix

THE PRESENT STATE OF RADIOMETRY AND PHOTOMETRY

Bruce Steiner

The electro-optics industry and the public that depends on it are part of

an informal but influential system for optical radiation measurement. The growth

of this industry and of public concerns related technically to it have put severe

new strains on this measurement system. The system itself must therefore be

analyzed. The state of the art, on which the measurement system depends, is

surveyed in terms of basic measurement parameters. The measurement system is

analyzed in terms of its three basic components: the flow of physical standards,

the generation of procedural standards, and the funding framework. The roles of

the professional society and of the Council for Optical Radiation Measurement

are reviewed. New requirements of the system are identified. Finally, the

methodology of the study is reviewed in detail.

Key Words : Measurement system; photometry; professional societies; radiometry;

standards.

CHAPTER I Background

A. MOTIVATION

The Stratton quotation from 1900 on page v suggests several problems that industry and

government, once more after seventy years, are again facing. Lack of agreement among light

measurements is again a problem of severe commercial importance. But now the problem has

public and social significance as well.

Moreover, this time not only the lamp industry is involved. The even larger photographic and television industries are concerned. Many new, small, but rapidly growing,

industries involving a wide diversity of technologies are making light measurements that

present difficulty and serious discrepancies. Examples are new solid state light detectors,

image intensifiers, and a wide variety of information displays: light emitting diodes, films,

electrophoretic devices, gas discharges, and liquid crystals [1-3].

One primary source of this resurgence of optical radiation measurement difficulty is

novelty. Completely new and changed products, made possible with new rapidly advancing

electro-optics technology, differ greatly from their predecessors and from one another.

Moreover, the measurements involved are frequently new to those making them. Coupled with

both types of novelty is the inherent complexity of the measurements. These factors interact

to produce surprisingly large disagreements. "Gross errors, perhaps as high as ±30%, are

now known to be occurring, and with disturbingly high frequency, in our particular field of

optical sensing (photo-emissive detectors, visible and near UV/IR) " [4]. The sources of

such problems are the subject of this Note.

B. THE DICHOTOMY BETWEEN PHOTOMETRY AND RADIOMETRY

A fundamental feature of the measurement of light is the existence of two separate,

not-precisely-convertible, systems of quantities.

The physicist working with electromagnetic radiation typically needs to identify the

flux:

* that is the power or photon rate of flow, with which he is working. For radiation transfer

problems and for the spectral-characterization of surfaces such as film or room illumination,

the ratio of flux to area, or iwadvance

E = dcf>/dA is a quantity of primary importance. Optical systems, because they conserve both flux and

the geometrical throughput, cosSdAdfi (where G is the anyle between the normal to the surface

and direction in question and Q is the solid angle involved) , conserve the ratio of flux to
throughput, or radiance : L = d

2 <t>/cos6 dAd£2 This is the radiometric quantity of primary importance in imaging systems.

In principle photometric, that is luminous, quantities could be derived from the

corresponding radiometric quantities by performance of an algorithm. Thus the spectral

radiometric quantity of interest could be integrated with an agreed normalized eye-response

curve, for example that of the CIE photopic observer, Y or V(X) . The resulting integral

could then be multiplied by the constant Km , the ratio of the average eye sensitivity at its

maximum in lumens to radiometric power in watts. For example, luminance Lv could in principle be calculated from spectral radiance,

L = d

3 4>/(cose dAdH dX)

by means of the algorithm:

Lv

= ^ /

V < A ) L

A dA

But in practice, a separate system of photometric quantities was required long before

a complete radiometric foundation had been laid. As the Stratton quotation on page v suggests, the photometric system was already in wide use seventy years ago for the description of visible light sources. Initially there had been oil lamps and candles, which

were not employed with fixtures or other optical systems. The primary interest was therefore

in the comparison or prediction of illumination in a certain direction at various distances

from a source. At distances large compared with the source dimensions, the concept of

intensity, with dimensions of flux per unit solid angle,

Iv

= J*L cos6 dA % d<f>/da permitted such comparison of sources. This quantity, intensity, provided the practical

utility that it could be identified with a source rather than with an arbitrary surface that

must be specified in space at some distance from' the source. Moreover, with the assistance

of certain assumptions, the concept of intensity also facilitated the comparison of two

different sources by means of the extremely important but highly non- linear and non-digital

detector, the human eye. Given additional assumptions, the necessity for independent but

unavailable radiometric data was avoided (or more accurately, obscured)

.

Initially, arbitrary candles were established as national units of luminous intensity.

These units were then compared with, and defined according to, the intensity per unit area

in the aperture of a platinum blackbody. This unit was incorporated into the SI system as

a Base Unit. The present definition then (1) permits independent laboratory realization

of the unit of luminous intensity, and (2) provides a loose coupling to radiometry via

Planck's law and the melting point of platinum. Presently used values of the melting point

of platinum vary from 2040.8 [5] to 2045 K [6]. These values lead to the values for the

coupling constant, K^: 690 lm/W and 673 lm/W respectively. Very recently, Blevin has

shown that consideration of the index of refraction of air raises previously published

measured melting points 0.3 K and lowers the corresponding K,,, by 3 lm/W [7]. The 3% spread

between 687 and 670 is comparable to the 2% spread in photometric measurements made in

national laboratories, as described later in Appendix B. Few measurements are more certain

than this. Most are substantially less certain.

Thus, although in principle photometric quantities could have been derived from

radiometric quantities, in practice the corresponding unit systems have developed along

independent paths. In radiometry the quantities realized are those just noted: spectral

radiance, spectral irradiance, and irradiance. In photometry, the quantities realized are not the corresponding quantities, luminance and illuminance or illumination, but rather

luminous intensity and luminous flux. The difference in the genesis and operation of the

two unit systems reflects the contrasting nature of the measurements actually made in the

two fields. These differences are of much more than academic interest with" the recent

growth of the electro-optics field and the consequent rapidly increasing desire for

convertibility between the two systems of measurement in the characterization of a single

object.

C. THE CONCEPTUAL MODEL

Measurements of optical radiation can be divided into three interrelated but distinct

shells and each of these into radiometric and photometric components (Figure 1) . In areas

of impact the measurements made by a wide variety of industries, and increasingly by

government agencies, are generally motivated by non-measurement considerations. For example,

production, improvement in efficient energy utilization, and concern for public safety and

health are issues of current concern. The specific rationale for improvement in optical

radiation measurement, which is to be found in the outer box in Figure 1, thus comes from

outside the system of measurements itself, the middle and inner boxes of Figure 1. The areas of impact comprising the outer box were reviewed in an earlier NBS Technical Note [1]

.

The optical radiation measurements themselves, the fields of radiometry and photometry,

constitute an exceedingly informal but elaborate system. If this system performed satisfactorily for those who employ it, an analytical examination of this system would be of

only academic, or metrologic, interest. But as the preceding Note indicated, the performance

of the system is widely considered by those in the areas of impact to be severely inadequate

to the demands made on it. If the system is in fact to be made more responsive to new and

growing demands, it must be analyzed. This analysis forms the core of the present Note.

At the center of the informal system of optical radiation measurement in the U.S. is

the National Bureau of Standards. The reasons that it should be involved in the analysis of

the measurement system and in subsequent action to improve the system have been reviewed

previously [1] . Programs designed to address the current problems are presently being

developed by Dr. H. J. Kostkowski, Chief of the Optical Radiation Section, and his staff.

The looseness of the coupling between radiometry and photometry, as currently practiced,

is also symbolized in Figure 1. The problems in the areas of impact that radiometry and

photometry were designed to address also show a corresponding division. The influence of

this historical division is still strong and must be acknowledged. But both parts must now

be analyzed together as components of a larger system. This system is already being unified

at NBS. Elsewhere it is rapidly becoming highly interrelated.
CHAPTER II Present State of the Art

A. EXPLOSIVE GROWTH IN DEMAND

The feasibility of various solutions to the measurement problems will depend on their

origin and extent. One source of desire for vastly improved radiometry and photometry can

be found in two distinct types of growth: (1) rapid movement of the frontiers of electrooptics technology and (2) growing public auareness that technology must solve or ameliorate

large scale problems that have important technical elements. In each of these cases the

growth involved has two aspects. First is a rapid general expansion characteristic of the

middle part of the growth curve for new fields. Second is a broad diversification in the

technology, diversification involving expansion in multiple directions simultaneously.

A survey of the initial development in demand for sophisticated optical radiation

measurement appeared in the preceding Note [1] . Prominent examples both of rapidly moving

technology and of increasing public awareness were described there. Commercial as well as technical concern with the present status was cited in detail.

The rate of growth can perhaps most succinctly be summarized by a Table. It shows

recent and projected dollar volume for several parts of American industry most directly

affected by optical radiation measurement.

TABLE

(Source: Reference 8)

Millions of Dollars

Lamp (bulbs)

Lighting

Fixtures

TV Tubes

Optical Instru- ments

Photographic

Equipment

1967 1968 1969 1970 1971 1972 1975 1980

943 1015 1243 1703

2254 2478 3301 5259

823 680 580 464 500 520

407 458 484 508 535 565 675 995

3665 4009 4317 4403 4667 5040

The parallel increase in diversification of the technology as well as its dramatic

increase in efficiency is illustrated in Figure 2 [9-11] . By incorporating new technology

the efficiency of space illumination increased more than twenty fold between 1905 and 1965.

Even these recent data were rendered obsolete on 3 October 1973, while the current Note was

in press, by the announcement of low pressure sodium lamps generating 183 lumens per

watt [12], an increase in 74% over the highest value in Figure 2. Other specific examples

of recent growth are reviewed in Appendix A.

B. NATURE OF THE MEASUREMENTS

1. Five-Fold Parameter Variation

Optical radiators and detectors typically differ from one another in five different

parameters: the total power or photon flux level or sensitivity; spatial distribution of

(or sensitivity to) this flux; spectral distribution (or sensitivity to) this flux; temporal

distribution (or sensitivity to) , this flux; and polarization.

a. Level

Differing power or photon flux levels are generally unavoidable in optical radiation

measurement. With a gread deal of effort and cleverness, such differences can of course

be minimized in the standards laboratories. But the field of optical radiation measurement

in essence consists of the measurement of differences in level as a function of various

parameters. In general, therefore, these differences are to be measured and not avoided.

5
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1880 1900 1920 1940

YEAR OF INTRODUCTION

I960

Figure 2. Growth curves of lamp efficiency for various types of lamps as a function of time of introduction (Source: Referer ;es 9-11).
If detectors were generally linear, or if standards existed over the twelve decades of

general measurement from one watt to 10~ 12 watts, then the measurement of different levels

would not constitute a problem. But neither of these conditions obtains. Detectors are generally non-linear by unknown amounts, and standards do not exist at more than a few

levels. The further one gets from the level of the standards [13], the lower the level of

agreement. Many approaches to the determination of detector linearity have been used; they were reviewed recently by Sanders [14] . The various techniques provide differing combinations of accuracy, convenience, and freedom from interactions with the other parameters:

directional, spectral, temporal, and polarization dependence. Thus, the choice of an optimum technique may thus be rather complex. Underestimation of this complexity is

frequently associated with large disagreements among measurements.

b. Spatial distribution and sensitivity

With rare exceptions, the spatial distribution of commonly used sources and the spatial

sensitivity of detectors are generally significantly non-uniform. The lack of uniformity

in the flux distribution of lamps, for example, is sufficient to introduce question in the

total flux produced by different types such as incandescent lamps and fluorescent lamps [15]

,

and even among the various types of fluorescent lamps. Agreement among measurements of light

emitting diodes is hindered by unpredictable variation with distance [16] . The orientation

of standard lamps in the measurement of directional properties such as irradiance and intensity has contributed a major source of error [17-18]

Work with detectors frequently involves differences in image size, location, and angle

of incidence. The non-uniformity of response of detectors is thus only rarely insignificant

but is frequently ignored in actual measurements. New solid state detectors promise to be

substantially more uniform than vacuum photodiodes and multipliers, whose response involves

a complex integral of photocathode characteristics and electron optics. The solid state

devices surely offer a simpler approach to some radiometric and photometric problems. But

the extent of improvement in agreement among measurements remains to be determined.

c. Spectral distribution and sensitivity

The spectral distribution of the flux emitted by lamps now in common use varies

widely [1] . Nevertheless, the photometric system has of past necessity been constructed on

the assumption that the spectral distribution of lamps undergoing measurement either is

identical or can be made so at the detector by appropriate filters. Fluorescent lamps

have strained these assumptions to the point that arbitrary adjustments have had to be made

in their comparison with incandescent lamps [19] . The measurement of flux emitted by high

intensity discharge lamps indeed is so uncertain that few intercomparisons have been

undertaken at all.

Similarly, spectral response differs greatly from one detector to another, perhaps

even of the same type. To be sure, some new solid state detectors promise to be similar

enough to each other to permit interchangeable handling for the first time. But such

treatment is still to be performed only with great care [20]

The measurement of detector spectral response, although simple in principle is now performed commercially in the U.S. only with unacceptable levels of agreement, a factor of

two. (Figure 3) . Several representatives of the detector industry have turned to NBS

with requests for assistance [21-22]

d. Temporal behavior

Both in radiometry and photometry the greatest emphasis has been placed on sources

that are relatively stable. Although fluctuations can be observed in any source or detector,

these fluctuations have frequently been of the order of percent or less over a time period

of seconds or minutes. Such instability influences measurement enough that it is not to be

neglected in precise measurement. But in the absence of wide fluctuation of sources, the

frequency response of measurement systems has been a factor of secondary importance in

their analysis.

There is however a considerable and growing number of fluctuating sources of interest.

The most efficient light-producing media are arc discharges. These respond rapidly enough

to 60 hertz alternating current to display considerable ripple in the emitted flux. Thus,

for example, the mercury spectral lines in fluorescent lamp spectra display 60 hertz

modulation, while the fluorescent continua in the same lamps do not. The spectra of high

intensity discharge lamps also display this 60 hertz variation. Moreover, with increasingly

accurate requirements for photography, the measurement of singly and repetitively pulsed
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sources becomes progressively more important. These rapidly varying sources must be

compared at some point with relatively unvarying sources, a comparison that requires new

techniques as well as the re-evaluation of old ones.

e. Polarization

Polarization is an aspect of optical radiation measurement that is frequently ignored.

In some careful work polarization either has been demonstrated to be negligible or has been

reduced by the incorporation of diffusing elements into the optical system. Nevertheless,

polarization is a significant problem in other areas of optical radiation measurement [23-25]

Polarization is becoming more important both because sources are increasingly remote from

blackbodies in character and because optical systems, especially spectrally dispersive

systems, are increasingly complex. Each reflection and dispersion can introduce a substantial

amount of polarization and increase the sensitivity of the transmission of the optical

system to the character of the polarization of the source.

2. Common Measurement Elements

A complete measurement will require not only an evaluation of these parameters, but

also of their fundamental dependence on the environment and its fluctuation. Effects of

variation in temperature, pressure, and humidity, must be determined. The temporal behavior

of standards over an extended period of time must be also be learned. Earth satellite

measurements in particular require an estimate of temporal stability over months or even

years.

The relative importance of these various factors and their environmental dependence

will depend upon the particular measurement being made and the degree of similarity of the

object being measured to the measurement standards involved. In general one starts a measurement with no prior information. He must now characterize his source, detector, and

optical system to the extent necessary for the particular measurement of interest. Since

similar information will be desired for most standards and system components, generally

available information of this type has been requested in order to save substantial duplication of effort. The detailed description of successful techniques would save similar

widespread duplication in development effort by all laboratories making comparable measurements,

3. Uncertainty: A Question of a Point of View

The uncertainty of a measurement,' like its beauty, is in the eye of the beholder. This

is not to say, like beauty, uncertainty cannot be estimated on an objective basis. Rather

the basis itself is a parameter to be assigned in context.

Several uncertainty bases are used in optical radiation measurement, for example, an uncertainty with respect to the International System (SI) will differ in general from that

with respect to units maintained by NBS, or from that with respect to another group of

comparable measurements. That is, uncertainty implies fidelity to a system. This system in

question must be either specified or directly implied before the term "uncertainty" has

meaning.

For measurements designed for severely limited reference, the point of reference must

always be specified. For example, if a given measurement is intended for reference only

to other measurements made in the same manner, the precision of the measurement will

frequently act as a valid predictor of agreement, and might be designated the uncertainty

of the measurement. If the measurement in question is destined for comparison exclusively

with other measurements made in one of only a few different ways, then the precision of the

result from all such measurements conceivably could be taken as a measure of uncertainty,

provided that the results are sufficiently homogeneous. Figure 4 represents data similar

enough to be compared in this manner. The measurement of the luminous flux produced by

incandescent lamps is shown as a function of production year. In such a system incorporating

only a few measurement methods, even heterogeneous data can still be reconciled by correction

factors allowing for systematic differences. The application of such correction factors

de facto defines a reference to which the uncertainty is related by the size of the factors

involved.

In the most general case of assessment of uncertainty, where each potentially important

comparison with other measurements cannot be anticipated, an estimate of the limits of all

systematic effects must be made in order to arrive at an estimate of the overall uncertainty. Figure 2 illustrates data too dissimilar to be compered reliably without taking into

account systematic effects. The spectral differences of differing lamp types are large
960

Figure 4. Increase in incandescent lamp efficiency as a function of time

(Source: Reference 10).

10
compared with the precision of the measurements. Uncertainty here refers implicitly to international units, the SI. This is the uncertainty that conservative estimators will want

to use. Because of the increasingly wide variety of measurement that are to be compared,

it is the uncertainty with respect to SI that increasingly must be used to provide a reliable

predictor of agreement among measurements. There is relatively little of such information

presently for optical radiation measurement.

Certain consequences of the availability of systematic information can be grouped in

the following manner. Progress in any field depends on two types of advance: breakthroughs

provided by a new technology, and gradual but steady improvement in existing technology.

For the former type of progress to take place with assurance, major systematic errors (with

respect to SI) must be avoided so that the comparison of different technologies is not

obscured by systematic errors comparable in size to the effects being observed. Since new technologies are particularly prone to unexamined systematic errors, critical attention must

be paid to the various parts of the system. One example in classical photometry is the

evaluation of the flux emitted in all directions through use of detectors with a photopic

response. Since the spectral distribution of most new lamps differs so greatly from that of

the incandescent lamps with which they are to be compared, the photometric detector employed

in such measurements must correspond much more closely to the defined visibility curve than

must a detector used simply for intercomparing different incandescent lamps of relatively

similar spectral distribution.

Slow gradual progress also becomes exceedingly important in aggregate. Figure 4 shows

such progress in the efficiency of incandescent lamps. The improvement of about 50% in

fluorescent lamp efficiency over the last twenty years has already been cited [1] . Such

gradual progress (Figure 5) will depend both on the precision of the given measurement and

on the stability of a relatively arbitrary "base line". Precision is exceedingly important

here because of the small size of individual increments that accumulate to an impressive

size over an extended period of time.

4. Factors Associated with Automation

The automatic control of measurement presents not only new opportunities but also new requirements for optical radiation measurement. Automation offers the possibility of such

voluminous data collection that much more precise information can now be obtained for a given measurement than was previously possible. To realize the advantage of this complete

information, radiometric measurements must be redesigned with two factors in mind. First,

smaller systematic effects will become more obvious and thus must be included in experimental investigations. The increasing visibility of measurement differences among increasingly precise numbers is leading to great commercial pressure for a better understanding of

these measurements. Second, measurements must therefore be conceived with automation in

mind at the planning stage.

5. Conclusion

Thus for much work in optical radiation measurement, the SI uncertainty is of growing

importance. It is the required information on systematic errors that is most conspicuously

lacking throughout the measurement system. Dramatically increasing precision is making

this void increasingly felt.

C. TRAINING

Radiometry and photometry draw extensively from two relatively independent fields:

optics and radiant heat transfer. Those with experience in one of these areas usually have

little background in the other. Formal training specifically in radiometry and photometry

is not widely available. Many enter from peripheral fields that employ photons as tools,

such as spectroscopy or collision physics, or from the even more distant electrical

engineering.

This lack of a single focus for training has important general consequences. As we

shall see, the field is generally fragmented into many different schools of experience and

thought. Technical papers appear in widely scattered journals. No coherent body of practice

or literature has developed.

Specific technical consequences of these heterogeneous roots also can be identified.

One example is the differing development and position of the concept of intensity in radiometry and photometry [18] . While the concepts of intensity and a point source have been

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central to the development of the photometric unit system, radiometry makes use of these

concepts primarily in engineering applications. In photometry, intensity is used as the

point of departure for other photometric quantities; while in radiometry, the point of

departure is either radiance or flux. The distinction is not merely an academic one. Zalewski has shown that subtleties in the use of intensity can lead to practical difficulty

in the realization of the unit system [18]

Another example of the fragmentation of the field of radiometry is the use of widely

varying types of nomenclature for given concepts. The situation is so serious that indeed

some radiometrists spend a substantial fraction of their time attempting to sort out what

their colleagues are doing on an elementary level. A comprehensive radiometric dictionary

is now under development by one of the most respected radiometrists, Fred Nicodemus. This

dictionary should constitute a major milestone in the field. In an exactly parallel manner, experimentalists are being called upon to identify what precisely has been determined in

various measurements. Only in this way can various results now be intercompared in a satisfactory manner with predictable levels of agreement.

Because it has been neglected so long, training is very badly needed. But before

appropriate training is to become widely available, appropriate materials must be developed.

This material requires in turn the development of a firm systematic data base so that

appropriate generalizations can be drawn.

13
CHAPTER III The Present Optical Radiation Measurement System

THE MODEL

Optical radiation measurements in the United States are not performed within a com- pletely formalized system of measurement. The typical measurement is made by comparison

to one of a variety of standards in a manner dictated by tradition, by .an agreed procedure,

or by reference to the laws of physics as perceived by the experimenter.

Nevertheless, the system is not completely formless. It consists of three distinct

aspects: the flow of physical standards (hardware), the flow of procedural standards

(software) , and the flow of funding (administrative structure) . The structure of each of

these "subsystems" differs from the others, but all are interrelated. The rates of change

of each also differ. These three system components will now be examined. Then the role of

the professional society will be reviewed. Finally, the effort to identify, strengthen,

and extend the structure through the formation of the Council for Optical Radiation Measurement will be described in some detail.

One general feature of the entire system was outlined in Chapter I: the dichotomy

between radiometry and photometry. The division is the natural consequence of the historical

development of each, which was sketched. The periods of greatest activity have taken place

at different times. Separate standards and procedures have been developed. Funding has

been along rather different administrative lines.

Two years ago NBS took the initiative by combining its activity in the two areas into

one administrative unit. Since then, the committees on photometry both of the Comite

Internationale des Poids et Mesures and the Commission Internationale de l'Erlairage have

added "radiometry" to their names. The change in these committees is already more than

nominal. The maintenance of two separate systems is now being actively questioned,

particularly by those entering these fields for the first time. NBS has recognized that

the technical effort to build bridges between the two systems, however, must be based on a firm awareness of the situation as it actually exists at present, as well as on anticipation

of future modifications in the system.

B. PHYSICAL STANDARDS (HARDWARE)

The general flow of physical standards in the U.S. takes place within a framework

shown in Fig. 6. A measurement occurring in any one of the areas indicated is related to other measurements by a series of operations that is referred to as a calibration chain. In general, this chain will have one link in each of the areas indicated; but such a long

chain is not always involved. Another general feature of the flow of standards is a much

more explicit definition near the origin of the national system, close to NBS, than at more distant points. The individual links in this chain are described in Appendix B along with

data on their performance.

C. PROCEDURAL STANDARDS (SOFTWARE)

The complexity and variety of the measurements noted in the previous chapter, coupled

with the existence of relatively few physical standards, has led to uncoirfortably large

disagreement among these measurements. The situation would nevertheless be even worse if

it were not for the development of various formal procedural standards Ly workers in various

fields. Since the systematic errors contributing to a given measurement are not in general

understood quantitatively, the present levels of agreement have been achieved only through

formal concurrence to perform various measurements in given ways. Because of the diversity

of the fields involved, a wide variety of organizations has developed to generate and codify

the required procedural accords in each field. The boundary line between the proceduralstandards organizations and the professional societies is sometimes indistinct. These

groups are listed and described in Appendix C. The dominant impression left by a survey of the various organizations related to optical radiation standards is one of diversity. Various organizations have been

established or utilized to deal with restricted problems. Identification of specific

activity and its coordination are serious problems.

14
AREAS OF IMPACT

Instrument Manufacturers

Component Manufacturers

Public Issuance Secondary

Calibration Laboratories

NBS

Figure 6. Physical standard measurement system.

15
However, an even more immediate problem has been identified by Robert D. Compton,

editor of Electro-Optical Systems Design [26] . He writes "One of the beauties of the

transistor and tube industry is that some semblance of order has resulted through the

standardization of products through the EIA component registration process. What old timer

in the electronic industry has not heard of the 2N174 transistor or the 6L6 tube? By

contrast, it is a very sad commentary on the optoelectronic industry that so few devices

have been registered and that, without exception, only one company makes each of those

devices that have been registered. How can we expect the general usage of the phototransistors, photodiodes, LED's, and other optoelectronic devices to grow when we discourage

usage of these products through the strict use of house numbers to identify products?"

Mr. Compton has certainly identified a serious problem. It is even more serious than its mere statement might suggest. The radiometrist suspects that, in spite of an elaborate

superstructure of standards groups, the agreements called for could not be reliably formulated at this time. If an attempt were made to do so, it would not really ameliorate the

situation. Measurement agreement is not sufficiently precise, not to mention accurate, to support an identification system similar to that of the electronics industry. There is no serious question that a reliable registration procedure would be desirable. But we must

advance in measurement capability to make such a system feasible. At a crucial time in the

development of the new optoelectronic industry, the physical measurement system is so seriously inadequate that the procedural standards groups cannot perform important tasks.

D. FUNDING FRAMEWORK

The nature of NBS funding of work in the areas of radiometry and photometry is related

strongly to the development and the status of each. Radiometry has been funded, both in the

system as a whole and within NBS, substantially by other agencies of the Federal government.

The primary agencies involved have been the Department of Defense and the National

Aeronautics and Space Administration. This funding provided a certain slow but steady and

firm development of basic measurement standards not available anywhere else in" the world.

Recently however, this "other agency" funding has decreased markedly, while at the same

time commercial and public factors have been receiving increased attention.

Photometry, on the other hand, has until recently largely operated on a pay-as-you-go

basis. Research funds have been devoted largely to the subsidization of the replication of

standards and consultation among users rather than to the development of superior standards.

The research base remained correspondingly weak.

The flow of funding in both areas has been far more important than the value of money

involved. In radiometry, the agencies involved provided explicitly a set of priorities and

implicitly a program framework for NBS. In photometry, the lower level of outside research

funding has been paralleled by the absence of an external structure for the establishment

of priorities. The current shift in NBS program emphasis from the relatively well-focused

"other agency" interest to far more diffuse commercial needs and those of less wellestablished government agencies have left the field without its program formulation structure. NBS has responded to this situation by a consolidation of its effort. But how are

the diffuse new needs to be correlated and priorities established apart from NBS? The

sheer number of standards groups in the field seems to preclude their presenting a coherent

approach to this fundamental organization problem. Two approaches present themselves. The

first is coordination by the relatively small group of professional societies; the second

is the establishment of a new organization for the necessary coordination. These two

approaches will now be addressed in turn.

E. ROLE OF THE PROFESSIONAL SOCIETY

Many individual members of the professional societies have certainly been aware of the

growing technical problems in optical radiation measurement. Nevertheless, for several good reasons the attention of the professional societies has been directed elsewhere. It will

prove worthwhile to examine these reasons now before examining alternative approaches.

The primary purpose of a technical society is the advancement of the field, typically

through conferences and journal publications. The professional societies tend to represent the research-oriented, most rapidly moving parts of technology. Lack of agreement

among such workers is not only expected, it is really a way of life. What sets the electrooptics industry apart perhaps from others is that, even after the first wave of rapid

development has passed, agreement has not followed as it has elsewhere. The man at the

16
bench who has had to face severe measurement problems over an extended period of time is

typically not active in the professional societies. He has been more active in the standards

groups. The professional society member has looked at the serious measurement situation as one to which others should address themselves and not one involving the professional

societies

Closely correlated with these underlying factors within the professional societies has

been the lack of a mechanism to provide for action. These societies are typically "presentation" societies and "debating" societies but not "action" societies. Valuable action has

been undertaken on occasion. An example is the Committee on Color of the Optical Society

of America. But a more typical role is represented by other activity of the Optical Society.

Recent experiments are described in Appendix D.

F. THE COUNCIL FOR OPTICAL RADIATION MEASUREMENT

An outstanding characteristic of the present measurement system as defined in the

preceding sections of this chapter is an absence of overall coordination of activity and a focus for cooperative effort. The reasons that NBS alone cannot fulfill this function are discussed in Appendix E. As described in that Appendix, a new cooperative venture was called for and established last year: The Council for Optical Radiation Measurement. By means of a series of meetings, the Council developed the document, "Pressing Problems in

Projected National Needs in Optical Radiation Measurements: A Consensus of Services

Desired of NBS" [21] . More recently, the Council has completed the formulation of a detailed "Program for Action" [27]

The Council has elected to operate as an activity of US TC 1.2 on Photometry and

Radiometry of the CIE. It has done so for several reasons. In the first place, an increase

in the number of independent groups in the field seems to be undesirable if avoidable. More

specifically, the international impact of the technical problems dictates an approach that

provides for ready expansion into international effort. And finally, the existing international CIE technical committee projects already provide a basis for an international

technical effort that it would be unfortunate to duplicate in a parallel organization.

Four types of activity are called for. In the first place, dissemination of useful

information and debate on suitable approaches to specific problems through professional

and quasi-professional meetings seem essential. In the second place, technical activity

through cooperative technical projects such as those already underway within international

TC 1 . 2 provides an essential foundation. In the third place, communication of information

on priorities throughout the field to NBS for its use in the formulation of its program

is an important step to optimum expansion of the availability of physical standards. And

finally, greater coordination of information about and among the procedural standards groups

is a widely recognized area of concern. Separate groups have been established within the

Council for the achievement of each of these four objectives.

17
CHAPTER IV Challenges Facing the National Measurement System

A. SYSTEMATIC FACTORS

1. Flow of Physical Standards

In the preceding chapter the chain of calibration between two typical measurements was shown to consist of a number of links. Both the length of this chain and its weak nature

are causing very serious concern among those making measurements. If the performance of the

entire system is to be improved this measurement chain must be evaluated quantitatively.

Since NBS is located in a calibration chain typically roughly half-way between two measurements,

NBS may be in a position to exert great influence. Already by a recent change in its

calibration policy in order to provide certain standards to anyone who asks, NBS has shortened

some of the chains involved. In many cases a reformation of the individual links may be

called for.

2

.

Flow of Procedural Standards

The flow of procedural standards is much less clearly defined than is the flow of

physical standards. Many different organizations have addressed themselves to agreement on procedures and practices in limited measurement areas. The cooperative industry-NBS role in

the formation of the Council for Optical Radiation Measurement offers some hope for additional coordination in this important area in this country. The job of coordination is an enormous one. It remains to be seen whether the CIE will rise to this challenge.

3. Flow of Information for the Establishment of Priorities

The transfer of responsibility from the Department of Defense and other relatively

centralized Federal agencies to decentralized communities has left an administrative vacuum

and a new and expanding need for leadership and coordination. The Council for Optical

Radiation Measurement and NBS have a challenge in the fulfillment of this role.

B. TECHNICAL FACTORS

The extremely complex nature of optical radiation measurement was reviewed in

Chapter II. The existence of only 25 standards [13] on which to base a wide variety of

measurements is crucial. If the system were more restricted in size and if the technical

nature of the problems were less complex, then perhaps it would be feasible to establish

physical standards similar to every type of object that one wanted ultimately to measure.

But such an approach is not feasible for so complex a system. And even if it were adequate

now, it would not prove viable in the long run for a technology so rapidly advancing.

Thus, in addition to the diversity, there is the rapid growth of the field. If one were "merely" to strive to solve today's problems as completely as possible and as rapidly

as possible, the resulting hasty solutions would very likely be inappropriate to the problem

that actually existed upon completion of such a crash program.

Approaches must be designed to address these two technical characteristics: complexity

and growth. Dr. Kostkowski, Chief of the Optical Radiation Section at NBS has noted "a standard itself .does not solve your measurement problem" [28]. NBS has thus recognized the

necessity for a broad approach to the solution of optical radiation measurement problems.

C. COMMERCIAL FACTORS

1. Cost

The technical constraints just described imply in addition some economic constraints.

First, the complexity of the measurement means that, without substantial outside assistance,

institutions making reliable measurements face very high measurement costs. Not only will

highly trained people be involved, but at present a great deal of time for research will be

required. The exceedingly high costs thus involved are simply not feasible for a large part

of this fragmented industry. It is much cheaper to argue a case of disagreement in court,

if it comes to that, rather than to set up a research laboratory to solve the problems on an individual basis.

Another cost factor involved is the size of the effort in quality control. Thousands

of lamps must be measured by a large number of people in the lamp industry. Large numbers

18
of measurements on film and cameras must be made. If the costs of sufficiently reliable

measurements are to become compatible with production costs, then work must be designed to facilitate convenience, rapidity, and reproducibility. Much more effort in this direction

is required.

2 . Aggregation of Resources

We have seen that a great variety of technical problems must be solved in order to produce one reliable measurement of optical radiation. At the same time, similar problems

must be solved for a wide variety of different measurements. It has just been noted that

it is not economically feasible for most institutions involved in relatively isolated

parts of the entire electro-optics field to solve individually all of the requisite problems.

If the system is to be optimized only in a given plant or laboratory, the solutions will

necessarily be short range solutions not generally applicable. Only by successfully

addressing the entire set of technical problems can one justify a general, across-the-board

approach. One basic role of the national laboratory is to analyze various specific requests

received and to establish a program geared to optimizing the performance of the entire

system, not of a particular segment. When the entire measurement system is brought into

better agreement, intralaboratory performance will also improve dramatically and indicate

to the individual company or agency that more reliable measurements have been achieved.

D. BROADENED FEDERAL CONCERN

In view of the recently increased public concern for technological answers to national

questions, the Federal government is reviewing its role. Optical radiation measurement plays

a part in all of the issues included in one recent outline reviewed in Appendix F.

E. CONCLUSIONS

A measurement system can be based on conclusions drawn implicitly from the various

factors just described. Before defining one such system (Appendix G) , it may prove useful

to draw these conclusions explicitly.

1. Coordination of Activities

The complexity both of the measurement system and the administrative arrangements

related to it imply the need for strong leadership. "NBS is being asked to help—to supply

technical leadership and the know how in this measurement area" [29]. Nevertheless , even with a greatly expanded budget, it is clearly impossible for NBS single handedly either to define the problems comprehensively in detail or to bring about their solution. It was

this observation that led NBS to contribute to the establishment of the Council for Optical

Radiation Measurement. The question of such leadership is explored in Appendix E.

2. Source Characterization

Dr. Kostkowski has already noted that "we plan to characterize radiometric components"

[28] . The necessity for such characterization is thus already recognized as part of the NBS

program. Indeed until the system as a whole can perform such characterization on a broad

basis, it will continue to perform unsatisfactorily. Source characterization is important

not only to the lamp industry but to anyone making radiometric measurements.

3. Detector Characterization

The growing importance and stability of detectors require a parallel effort in

detector characterization [22] . One can indeed anticipate that some of the burden for

standards now carried by sources will be assumed in the foreseeable future by detectors [30]

Some are quite stable and easy to use. Indeed, although photometric units are defined in terms of a source, the photometric system is built in_ principle on a detector, albeit a very

complex one, the human eye. Thus the use of calibrated detectors may now offer both theoretical and practical advantages over the more traditional photometric hardware.

4. Technique Building Blocks

Optical systems typically consist of more than sources and detectors . The intermediate

components must be characterized not only optically but also radiometrically, that is, in

their effect on the transmission of photons. In addition to the characterization of the

physical components, various physical phenomena must be better understood if their influence

is not to disturb serious optical radiation measurement. Examples of such effects are diffraction, polarization, and partial coherence [29]

19
5. System Performance Evaluation

Although some intercomparisons have been performed, as cited, there is a general

paucity of precise information on operational levels of agreement. Where exactly are the

problems, and the real needs? And how severe are they? The quantitative measurement of

system performance by intercomparisons in a substantial variety of areas would facilitate

the establishment of priorities for close attention in the measurement system [27]

.

6. Measurement Assurance

In the long run, the only way to guarantee that measurements in a system will agree to

a desired level is to provide a program for measurement assurance. Such a program can have

a variety of emphases, but it will necessarily involve periodic realistic sampling of the

entire radiometric and photometric measurement system [31]

.

7. Types of Transfer

In addition to providing the capability to make various measurements, the system must

engender communication of this capability to assure the transfer of the new technology as it is developed to the places where it is needed most. A technical paper in the literature

that contains solutions to measurement problems but that goes ignored is clearly not

influential. Indeed, until a system of transfer is perfected there will probably be little

evidence of improvement in the measurement system as a whole.

8. Setting Priorities

That the problems described are urgent is beyond dispute. The measurement system must

be coordinated in such a way that improvement is apparent to participants as early as possible . Early attention must thus be paid to the most serious prob lems . Relative

urgencies must be periodically reassessed. Attention must also be paid to elements that

have a future impact as well as an immediate one. The technical growth of the industry

should be anticipated in such a way that solutions to the most severe problems are generated

by the time the latter become crucial, rather than years afterward. These two priorities

may appear to conflict, but in fact they need not do so. The second factor may define

the elements of the program, whereas the first factor may define the weighting system

attached to the various elements.

20
Acknowledgements

The furnishing of background data by Joseph Fones is gratefully acknowledged. Extensive conversation, cooperation, and advice from all of the Council for Optical Radiation

Measurement participants and especially its leaders on CIE TC 1.2 are also very gratefully

acknowledged. Contributions of the four Council coordinators should be mentioned in

particular: The Council's founder, Robert Watson, the Council's present Secretary,

E. S. Steeb, the Council's Coordinator with NBS , Franc Grum, and the Council's Coordinator

for Technical Projects, Richard Becherer. Extensive conversations with Jon Geist are also

gratefully acknowledged.

21
REFERENCES

1. Steiner, Bruce, "Optical Radiation Measurements: The Impact of Radiometry and Photometry

and the Role of NBS", NBS Tech Note 594-4, 1973.

2. Jurgen, Ronald K. , "What's new in small Displays", IEEE Spectrum 9_, [11], 19 (1972).

3. Gurtler, Richard W. and Maze, Craig, "Liquid Crystal Displays", IEEE Spectrum 9_, [11],

25 (1972).

4. Eberhardt, Edward H. , private communication.

5. Quinn, T. J., Metrologia 7, 132 (1971).

6. Comite International des Poids et Mesures , "The International Practical Temperature

Scale of 1968", Metrologia 5_, 35 (1969).

7. Blevin, W. R. , Metrologia 8_, 146 (1972).

8. U.S. Department of Commerce, Bureau of Domestic Commerce, "U.S. Industrial Outlook

1972 with Projections through 1980", (1972).

9. General Electric Company, Large Lamp Department, "High Intensity Discharge Lamps",

TP109.

10. General Electric Company, Large Lamp Department, "Incandescent Lamps", TP110.

11. General Electric Company, Large Lamp Department, "Fluorescent Lamps", TPlll.

12. Norelco advertisement, Wall Street Journal, p 9, 3 October 1973.

13. U.S. Department of Commerce, NBS Tech. News Bull. 56_, 152, 246 (1972).

14. Sanders, C. L. , J. Res. NBS, 76A , 437 (1972).

15. Martino, Joseph P., IEEE Spectrum 9_, [10], 32 (1972).

16. Horwath, Joseph; private communication.

17. Zalewski, Edward F. ; Schaefer, A. Russell; Mohan, Kshitij ; and McSparron, Donald A.; NBS Tech Note 594-2 (1972)

.

18. Zalewski, Edward F. ; Geist, Jon; and Schaefer, A. Russell; to be published.

19. Lamp Testing Engineers' Conference, proceedings (unpublished).

20. Budde, Wolfgang; private communication.

21. Council for Optical Radiation Measurement, "Pressing Problems and Projected National

Needs in Optical Radiation Measurements: A Consensus of Services Desired of NBS",

(1972)

.

22. Photodetector industry spokesmen; private communication.

23. Grum, Franc and Spooner, David; J. Color App. 2_, 6 (1973) .

24. Grum, Franc, ed., Report on Polarization, CIE TC 2.3 (1973).

25. Robinson, Barrett; private communication.

26. Compton, Robert D. , "An Open Letter to the Optoelectronic Industry", Electro-Optical

System Design 5_, [3] , 23 (1973) . 27. Commission Internationale de l'Eclairage, U.S. Technical Committee 1.2, "Council for

Optical Radiation Measurement: Program for Action" (1973)

.

28. Kostkowski, Henry, "Radiometry and Photometry, An Interview with Henry Kostkowski",

Electro-Optics Systems Design 5_, [1] , 24 (1973) .

29.' Kostkowski, Henry, statement on reorganization of NBS program in Radiometry and

Photometry, (1971).

30. Wendland, Paul; private communication.

31. Cameron, Joseph; private communication.

32. Bell Labs, IEEE Spectrum 8_, [12], 12 (1971).

33. Eisner, David M. , Wall Street Journal, 23 April (1973) p 16.

22
34. Ref. 1, Plate 1.

35. e.g., EG & G Light Instrumentation Application Note No. 580-34.

36. Infrared industry spokesman, private communication.

37. e.g., Honeywell Radiation Center, "Honeywell Skylab Multispectral Scanner" (1973).

38. NASA, Advance Images and Scanners Working Group Report, in press, 1973.

39. U.S. Department of Transportation personnel, private communication.

40. National Traffic and Motor Vehicle Safety Act of 1966, 15 US Code 1381.

41. Public issuance commercial calibration laboratories, private communication.

42. Douglas, C. A., private communication.

43. Underwriters Laboratories, Memo 122, 24 February 1971.

44. Johnston, Harold; Science 173 , 517 (1971).

45. NAS-NRC, Summary Statement of the Ad Hoc Panel on (NOx

) and the Ozone Layer, 29 July 1971.

46. National Academy of Engineering, Task Group on Industrial Engineering, "An Assessment

of Industrial Activity in the Field of Biomedical Engineering", (1971) .

47. National Petroleum Council; U.S. Energy Outlook, 1971.

48. National Petroleum Council; Environmental Conservation, 1971-2.

49. Post, Richard F. , Physics Today, 26, [4], 30 (1973).

50. Optical Spectra 1_, [2-3], 27 (1973).

51. McLellan, Alden; Proc. Electro-Optical Systems Design Conf . , New York, 244 (1972).

52. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, "Proc. of Miami Workshop on Remote Sensing", (1971).

53. Optical Spectra ]_, [2], 17 (1973).

54. Finch, William A., "Earth Resources Technology Satellite-1, Symposium Proceedings

September 29, 1972", Goddard Space Flight Center X-650-73-10, (1973).

55. Hanson, Kirby J., "Limitation of Radiometry to Meteorology and Oceanography" invited

paper presented at the Optical Society of America Annual Meeting, San Francisco,

October 1972.

56. Neer, Robert M. , "Medical Significance of Light", invited paper presented at the

Optical Society of America Annual Meeting, San Francisco, October 1972.

57. Oke, J. B., "Absolute Flux Measurements in Astronomy", invited paper presented at the

Optical Society of America Annual Meeting, San Francisco, October 1972.

58. Betts, D. B., and Gillham, E. J., "An International Intercomparison of Radiometric

Scales", Metrologia 4_, 3 (1968).

59. Hyde, Edward P., "A Comparison of the Unit of Luminous Intensity of the United States

with those of Germany, England, and France", Bull. NBS , 3_, 65 (1907).

60. Bonhoure, J; "Rapport sur la cinquieme comparaison des etalons nationaux d'intensite

et de flux lumineux (1969)", Comite Consultatif de Photometrie 7 e Session - 1971,

p. 86, (1972)

61. Jones, O. C, Statement to the Conference on Photometry and Colorimetry, Zlatni

Piasatsi, Bulgaria (1973)

62. McSparron, D. A., et al., "Spectroradiometry and Conventional Photometry; An Interlaboratory Comparison", NBS Tech Note 559 (1970).

63. Commission Internationale de l'Eclairage, Committee E-1.2, "International Intercomparison of HPMV Lamps", CIE Publication 14A, 44 (1967).

64. Niindel, S., Proceedings, Conference on Photometry and Colorimetry, Zlatni Piasatsi,

Bulgaria (1973)

65. U.S. Department of Commerce, NBS Tech. News Bull. 57_, 148 (1973).

23
66. Geist, Jon; and Blevin, W. R. , Appl. Opt. 12_, 2532 (1973).

67. Blevin, W. R. , Metrologia 6, 39 (1970).

24
APPENDIX A

Examples of Recent Requirements for Improved Measurement

1. ORIGINS OF DEMAND

a. New Technology

Light emitting diodes (LED's) are a visible manifestation of the new electro-optics

technology. As was the case with lasers, much of the activity concerning LED's has

centered around coaxing them to produce light at shorter wavelengths: first in the red,

then down into the green, and ultimately into the ultraviolet. Red diodes are now common [32]

undoubtedly other colors will be appearing shortly in commercial quantities [33]

The entire history of space illumination for the past hundred years shows rapidly

developing successive technologies (Figure 2) [9-11]. The most efficient lamps, both

fluorescent and high intensity discharge lamps, are characterized not by a single spectral

distribution but by a dozen or so that differ greatly from each other [34,9-11] . A diversity

in geometrical shapes of lamps as technology progresses is another prominent feature of this

development which leads to measurement difficulty. In addition, differences in the extent

and type of fluctuating emission among these lamps add to the sophistication required for

comparisons among different types of sources.

A parallel development has taken place in photon detector technology. Selenium solid

state detectors are being replaced by silicon diodes, which have different characteristics.

Relatively slow thermal infrared detectors are being replaced by a variety of quantum

detectors and by a new type of thermal detector, the pyroelectric (capacitor) detector.

Vacuum photodiodes and multipliers have been widely used for some time, but new photoemissive

materials endow them with unfamiliar properties. Thus, the photometric measurement system,

which in the U.S. and elsewhere was built largely on selenium photodiodes, is having to adjust itself to diversification not only in the types of sources measured but also in the

detectors used to make the measurements. The measurement system is thus not only being

improved, but technically modified in unquantified ways (with quantum detectors)

New complex instrumentation, which employs both new detectors and sophisticated low

noise, solid state electronics is undergoing rapid development. New lines of equipment

are either becoming available [35] or are about to be introduced shortly [36] . Established

electronics firms are entering the promising new field of electro-optical measurements,

e.g., Hewlett-Packard and Tektronix.

Another aspect of the growth in instrumentation derives from new applications, for

example the observation of and from space. The field of remote sensing [37] is growing so rapidly that major measurement problems are just beginning to be uncovered and explored

in detail [38]

b. New Public Interest

Increased public concern for safety, health, and the quality of the environment have

led a number of new, surprisingly broad, Federal responsibilities. Since the review last

year [1] of many of these, still others have emerged. Transportation in an area of

Federal activity previously limited to state government [39-41] . In this case, a change

in focus for governmental responsibility is complicated further by the introduction of new technology, entirely new types of lighting materials that render obsolete former measurement

techniques [42] . In still another area of growing interest, safety, new technology in the

form of very intense lights for movie production is leading Underwriters Laboratories to develop new specifications for safer handling of these lamps [43] . No standards exist at, or even close to, the irradiance levels involved.

The hazards of ultraviolet radiation are a rapidly developing field of public concern.

First, the future of the protection of the earth's surface from solar ultraviolet radiation

by the atmosphere is causing wide debate among scientists [44-45] . The ultraviolet output

of lamps has also raised considerable concern in an area of technology where safety has

not been the subject of activity in the past. Technical questions have been raised in this area by the National Academy of Engineering [46] . In addition, several pieces of legislative

action embody new Federal responsibility with implications for all ultraviolet measurement:

The Federal Hazardous Substances Act, the Radiation Safety and Health Act of 1968, and the

Occupational Safety and Health Act of 1970 [1]

25
Public health issues involving optical radiation measurement arise in two clinical

areas [1], phototherapy and clinical analysis. Phototherapy is being studied now by a panel

of National Academy of Sciences and Engineering as a result of the widespread employment of

this treatment, with little control or understanding of the dosages involved. Clinical

analytical procedures operate with a similar, but not such an extreme, lack of information.

Public concern for the environment has led to activity in areas that depend on optical radiation measurement. One of these is the energy crisis, which has many other

causes and implications [47-48] . There is growing public sensitivity both to power conversion and to the efficient utilization of energy. A review article summarized the situation

with respect to energy conversion recently: "Whatever method is being pursued, the electrooptics community is very firmly entrenched in the search for new energy sources. The longand short-term goals discussed in these pages seem destined to keep a great many of us diligently at work for a good many years to come" [49] . With respect to another promising

type of energy conversion, "the laser reaction idea is the newest one on the fusion scene

and the simplest conceptually" [50] . The efficient utilization of power is also receiving

attention. Since lighting takes 25% of the electric power generated, measurement of

efficiency in lighting becomes important to improving the efficiency of power utilization

as a whole [1]

.

Pollution of the environment must be monitored if it is to be controlled in a realistic fashion. Control of pollution at some level is widely considered a desirable

goal. Remote sensing approaches are being explored [51] . Problems in pollution are coupled

with the energy problems through the wide availability of hydrocarbon fuels that contain

relatively large amounts of sulphur, a serious pollutant. Another specific interest in

monitoring attempts to control pollution is connected with substantial changes in the earth's

atmosphere. Serious climatic changes may follow increased pollution as a long term effect.

In the short term, as just noted, the amount of ultraviolet light, which is controlled by ozone in the upper atmosphere, may be affected. Meteorology in fact is providing some of

the tightest requirements in radiometry [52]

.

2. CHARACTER OF THE GROWTH

a. Rapid Pace

The growth rate of dollar volume in key segments of the US electro-optics industry over

the decade 1958-1967 [1] has been generally maintained since then [8] . It is now expected

to continue into the forseeable future, to 1980 [8] . (See Table in main text) But cause

for some U.S. concern can be found in the sudden change in the fraction of world photographic

equipment and supplies represented by U.S. production. This fell from 68% in 1968 to 63%

in 1970. The original U.S. market lead in electro-optics is now being followed quickly by

other countries. For example, "Tokyo Electric Co. (Toshiba), Tokyo, Japan, has announced

plans to open, in June, two plants to produce LED's and power transistors" [53].

The production quantities of the electro-optics industry have increasingly required

the incorporation of automated measurement. This automation in turn has caused a widespread

re-examination of the optical radiation measurements involved with a view toward providing

both increased comparability among different measurements and greater reproducibility of a given type.

b. Wide Diversity

Some of the diversity of the growth in the electro-optics industry has been indicated

in the preceding description of new technology involved in sources, detectors, and general

purpose instruments.

This new technology involves a wide diversity of technical parameters. One example is a variety in the spectral range of new widely used light sources. Differences in spectral

distribution and sensitivity characterize new detectors and lamps. Combined with the

increasing variety of spectral characteristics are widely differing flux levels. For

example, light emitting diodes are characterized both by an unconventional spectral distribution and by a substantially lower flux level than that previously involved in widely

disseminated standards. At the other end of the scale is the measurement of high intensity

discharge lamps, sources not only consisting for the first time primarily of spectral lines

but also much more intense than those traditionally measured in the past. New flashlamps

have both a different spectral distribution and higher intensity than most standards, while

at the same time they furnish a very different temporal behavior from that of the standard?

with which they are compared.

26
Diversity is a characteristic also of new applications. Transportation and satellite

remote sending [54] are examples of rapidly growing areas. Meteorology is a newly prominent

area [55] . Photobiology and astronomy represent more historic areas of interest [56-57]

The varied authority for enforcement of new Federal regulation is increasingly important.

The Departments of Health, Education and Welfare, Labor, and Commerce are involved. The

Environmental Pollution Agency is responsible for an area of rapidly expanding concern.

27
APPENDIX B The Flow of Physical Standards

1. NBS AND OTHER NATIONAL LABORATORIES

The central position in the U.S. of NBS radiometric standards is derived from the

responsibility of the Secretary of Commerce, defined in 15 US Code 272, to undertake "the

custody, maintenance, and development of the national standards of measurement, and the

provision of means and methods for making measurements consistent with those standards,

including the comparison of s tandards used in scientific investigations, engineering,

manufacturing, commerce, and educational institutions with the standards adopted or recognized

by the Government " . Although photometric standards also are covered implicitly by this

legislation, the responsibility of the Secretary of Commerce for photometric standards has

been made even more explicit. 15 US Code 224 identifies as the specific duty of the

Secretary of Commerce "to establish the values of the primary electric and photometric units

in absolute measure, and the legal values for these standards shall be those represented

by, or derived from, national reference standards maintained by the Department of Commerce".

NBS authority is thus far-reaching. In practice however it is not possible for NBS or indeed for the entire Department of Commerce to provide substitution standards for all types

of sources and detectors used in the country. NBS has calibrated a number of incandescent

lamps that are used by public issuance laboratories to calibrate radiometers and photometers.

These instruments are used, in turn, to measure sources and other detectors of direct interest

to industry, other agencies, and universities. However, these latter groups also receive

standards directly from NBS rather than from the public issuance laboratories.

Before beginning to trace the U.S. calibration chain away from NBS, the observer

should note that other countries have systems similar in principle to the one described

here for the U.S. The various national systems in the past have been quite independent.

But as the need for new standards grows, foreign standards will probably impinge increasingly

upon the U.S. measurement system. The seldom employed chain of American standards to foreign standards typically has as an essential link, intercomparisons between NBS and

foreign national laboratories. In radiometry, few of these intercomparisons have in fact

taken place . Indeed the only one within memory involved lamps that were so unstable as to make the results essentially useless [58] . By striking contrast, international photometric

intercomparisons have taken place over many years at remarkable frequency. One of the

earliest on record, in 1907, displayed a spread of approximately 2% in the measurement of

luminous intensity [59] . The most recent international intercomparison, one that took place

in 1969, showed a similar spread of 2% in the measurement of luminous intensity at two

different color temperatures and of luminous flux at a third color temperature [60] . In the intervening years the national laboratories have repeatedly demonstrated the ability

to perform photometric measurements on certain incandescent lamps with an agreement to roughly 2%. Radiometric measurements can probably be performed to a similar level of

precision. Therefore, unless very special circumstances are predicated, agreement among

new measurements in various countries cannot be expected routinely to agree better than

about 2%. If several steps are involved in international measurements, the spread will

undoubtedly be somewhat greater than this [61] .

2. PUBLIC ISSUANCE SECONDARY CALIBRATION LABORATORIES

The American photometrist or radiometrist will get his reference standard typically

not from NBS but from a secondary calibration laboratory. A civilian will approach one of

a number of commercial calibration laboratories, which typically furnish either radiometric

or photometric standards, but usually not both. Defense Department radiometrists or photometrists will generally obtain standards from a designated service laboratory. There

have been few formal intercomparisons performed among any of these publis issuance secondary

calibration laboratories. Customers who have obtained standards from more than one laboratory have reported differences almost routinely of the order of 10% among standards

from various public issuance laboratories.

3. COMPONENT MANUFACTURERS

Until recently most photon detectors were usually found to be less stable than the

most stable lamps. Those that were sufficiently stable were too insensitive to permit the

filtering required for photometers. For this reason, because sources were frequently of

ultimate interest, and because primary reference has been made to blackbody sources,

28
optical radiation measurement has been largely "source-oriented" in this country. Standard

sources have been furnished, but not standard detectors. In other countries, particularly

England, Netherlands, Japan, Germany, and Australia, important radiometric measurements have

been based on electrically calibrated radiometers, that is those for which electrical

heating can be substituted for radiant heating. But even abroad, reference to electrically

calibrated radiometers has been restricted largely to the national laboratories.

One exception to these generalizations, the large photographic meter industry, has

operated relatively independently of the rest of the systems. Complaints about the level

of agreement of such instruments have not been widespread. This is perhaps an example of a sub-system that has operated fairly readily as a gauge system decoupled from other measurements. Film does not typically have a standard CIE sensitivity. When one finds that his

light meter readings are consistently too high or too low, he can allow for this bias in

setting his camera. These meters are typically not recalibrated by NBS after sale.

In contrast to the detector industry, the lamp industry has always depended heavily

on the availability of the standards both from NBS and from the secondary calibration

laboratories. Because of the central position of these measurements to the industry,

informal intercomparisons of luminous flux and closely related quantities have been arranged

through an industry organization, the Lamp Testing Engineers Conference (LTEC) . The results

of only one of these intercomparisons have been published [62] . Through such intercomparisons, because of the availability of incandescent standards, and because of the similarity

of the lamps measured, agreement among incandescent lamp measurements is not presently a serious problem. This agreement is generally comparable to that of the national laboratories

in their intercomparisons: a spread of 2%.

The single most widely selling type of lamp however is the 40 watt "cool white"

fluorescent lamp. This lamp differs sufficiently from other lamps [34,9-11] that an unsatisfactory spread occurs in their measurement: 2.0% when comparing with a similar

fluorescent standard; 3.6% when comparing with a fluorescent standard with a different

spectral distribution; 5.1% when comparing with an incandescent standard utilizing the same photometric detector used in the comparison with fluorescent lamps, and 22.6% when comparing

with an incandescent standard by spectroradiometric techniques [62]

High intensity discharge lamps were compared internationally ten years ago with a spread of 7% [63] . There is the feeling in the industry that different companies may be

using standards differing at least by 6% in establishing advertised values for such

discharge lamps. This situation is considered to be a serious problem.

Light emitting diode manufacturers have found spreads of the order of 40% among

measurements [16]. Such differences are clearly visible and intolerable commercially.

4. INSTRUMENT MANUFACTURERS

With the development of relatively stable and sensitive silicon photodiodes over the

last few years, the development of convenient radiometers and photometers has blossomed.

These instruments are calibrated against standards either from one of the component manufacturers, as suggested by Figure 6, or directly from one of the public issuance secondary

calibration laboratories or NBS as suggested above in Section 1. Instrument manufacturers

have not yet formally intercompared their instruments inasmuch as this is a new and very

rapidly developing field. But those who use these instruments for measurements find

substantial disagreements. The level of agreement is very likely correlated with the fact

that, while the instruments may be calibrated with one type of standard source, the chain

between measurements by users of two different instruments is typically coupled through

NBS by way of a number of links [c.f. 61,64]. Large disagreements among commercial

photometers and radiometers have led the electro-optics industry to express formal concern [1,21]

In the past it has not been unusual for different parts of a large company to be

getting separate sets of optical radiation standards from NBS. This practice has now fortunately been reduced by the designation of centralized responsibility within such

companies. For some time the indirect results of these previous unnecessarily long chains

of calibration may continue to be felt however.

5. AREAS OF IMPACT

The ultimate user falls generally within one of four major categories: industry,

government, the academic community, and the general public. The photographic industry and

29
related enterprises are the single largest component of industrial users: 5 billion

dollars. The lamp industry is comparable in size: 1 billion dollars. The aerospace and

transportation industries are other substantial users. The television, theater, and movie

industries use of lighting is obvious. Increasingly the computer industry and office equipment manufacturers are using new types of light source displays that are leading to new requirements.

The Federal government is rapidly increasing its concern with optical radiation

measurement. Some of the federal agencies involved are: Department of Transportation

Department of Health, Education and Welfare

Department cf Labor

Department of Commerce

Department of Defense

Environmental Pollution Agency

National Aeronautics and Space Administration

General Services Administration

Academic, as well as Federal, science involves measurements of optical radiation in a wide variety of technical areas: plasma physics, atomic physics, solid state physics, and

astronomy, and the science of optics itself.

Because the user community is so diverse, formal intercomparisons of optical radiation

measurements have not been carried out. The existence of substantial disagreement, however,

is shown by the founding and growth of the Council for Optical Radiation Measurement [21,27],

All segments of the user community are represented. Indeed, one of its most active projects

is the inauguration of a series of intercomparisons [27]

.

30
APPENDIX C

Organizations Associated with Procedural Standards

In order to ascertain the role and status of these organizations as seen by participants, a questionnaire was sent to participants in the Council for Optical Radiation Measurement. Most respondents feel that the standards groups fulfill an essential function,

although sometimes with less than desirable efficiency and alacrity.

A cursory review of the various organizations involved directly and indirectly in the

generation of procedural standards follows. This description is based primarily on the

response to the Council questionnaire: approximately 40 questionnaires were returned from

the original mailing of about 200 in January, 1973. In some cases the following accounts

have been modified by official spokesman. But in all cases the brevity permits only a severely limited perspective of the activities of these organizations. The serious reader

will want to get a fuller picture directly from the organizations themselves.

1. AMERICAN INSTITUTE FOR AERONAUTICS AND ASTRONAUTICS (AIAA)

This professional society has concerned itself with heat balance radiometric requirements in air and space science and engineering. Its Thermophysics Committee, ASTM E-21

Committee, and IES jointly sponsor annual space simulation conferences.

2. AMERICAN METEOROLOGICAL SOCIETY (AMS)

This professional society has concerned itself largely with professional seminars.

Its relationship to the generation of procedural standards has been indirect.

3. AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI)

ANSI coordinates the development of national consensus standards by other voluntary

standards organizations. It is perhaps better known for its procedure for formal recognition of these standards once they have been developed by these other organizations.

Committee Z-36 deals with laser safety.

4. AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM)

ASTM has two primary functions: the development of voluntary standards and the

sponsorship of symposia for the exchange of information. Committee F-1.2 deals with lasers.

Committee E-12 deals with the appearance of materials. Committee E-21 deals with space

simulation. The AIAA Thermophysics Committee and IES cooperate and have overlapping

membership with ASTM Committee E-21 (c.f. AIAA).

5. COMMISSION INTERNATIONALE DE L'ECLAIRAGE (CIE)

This is one of the most prominent international organizations dealing with light

measurement. Its Action Committee, whose chairman is currently Sylvester Guth of GE Nela

Park, guides the technical committees. Technical Committee 1.2 on Photometry and Radiometry

prepares both technical studies and procedural recommendations for the measurement of

illumination in its broadest sense. These are sometimes based on intercomparisons organized

by the committee. Technical Committee 1.4 on Photopic, Mesopic, and Scotopic Vision

coordinates the study of, and measurement practice in, these fields. Technical Committee 2.3 on the Photometric Characteristics of Materials is now completing a comprehensive report on these characteristics and their measurement. Other recent reports deal with polarization

and fluorescence.

In this country CIE consists of a U.S. National Committee made up of the U.S.

representatives to the international technical committees, who are also chairmen of the US technical committees, and a number of others. Its Executive Committee appoints the U.S. technical committee chairman and the membership of the technical committee with the advice

of the respective chairman. US TC 1.2 in the last 2 years has broadened the scope of traditional activity by its organization of the Council for Optical Radiation Measurement (q.v.).

6. COMITE CONSULTATIF DE PHOTOMETRIE ET RADIOMETRIE (CCPR)

This committee is advisory to the Comite Internationale des Poids et Mesures (CIPM;

International Committee on Weights and Measures) , the technical body responsible for the

provisions of the Treaty of the Meter, which established the basis for the International

System of Units. Recommendations of the CCPR, after review by the CIPM, are considered

by the Conference Generale des Poids et Mesures (CGPM; General Conference on Weights and

Measures) , which has ultimate responsibility for carrying out the provisions of the Treaty.

31
The CCPR consists of representatives of the national laboratories and a few designated

experts. It provides a forum for discussion of, and ultimately for international agreement

with respect to, the photometric unit system. To provide a quantitative background for its

decisions, it arranges international comparisons of the various national standards among

the national laboratories. Its most recent international intercomparison, in 1968, involved

national standards of the candela, both those at the platinum point and those at CIE

illuminant A (approximately 2856 K on the International Practical Temperature Scale of 1968)

and of the lumen at approximately 2788 K on IPTS 1968. Thus the CCPR provides both general

coordination and evidence of measurement agreement among a few international photometric

standards. The application of these standards to a wider variety of photometric and

radiometric measurements is left to the CIE.

7. COUNCIL FOR OPTICAL RADIATION MEASUREMENT (CORM)

The Council is an activity of US TC 1.2 of CIE. It has been formed to "fill in the

cracks" between the activities of other standards groups and professional societies. It is

described below in Chapter III and in detail in Appendix E.

8. ELECTRONIC INDUSTRIES ASSOCIATION (EIA)

This group represents manufacturers of electronic products. Among many other activities

it provides for registration and standardization of specifications for new products, including

those connected with optical radiation.

9. ILLUMINATING ENGINEERING SOCIETY (IES)

IES (not to be confused with 12 below) has been a primary vehicle for the establishment of agreement on measurement practices and procedures in the lamp and affiliated

industries. Formal IES recommendations are also used as a basis for illumination practice

in fields such as architecture and transportation. Meetings, written reports, and its

journal deal with applications of illumination and technical background, as well as testing

and measurement.

10. INFRARED INFORMATION SYMPOSIA (IRIS)

These annual symposia engage government and industrial representatives in a continuing

information exchange on infrared technology largely for defense applications. Associated

with these symposia are IRIS Specialty Groups. The Infrared Standards Group has provided

a forum for technical review of measurement problems and, in particular, has been a useful

focus for interaction with NBS on physical standards in the infrared.

11. INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS (IEEE)

The Institute acts both as a professional society and as a standards-writing group.

For example, IEEE has become a particularly important professional society for laser

technology. It is also involved in formulating agreement both on nomenclature and on procedural standards for light emitting diodes.

12. INSTITUTE OF ENVIRONMENTAL SCIENCES (IES)

This IES (not to be confused with 9 above) , along with the AIAA Thermophysics Committee

and ASTM Committee E-21, (c.f. AIAA and ASTM) has taken the lead in trying to arrive at agreements on the best value to be used for the solar radiation constant.

13. INTERSOCIETY COLOR COUNCIL (ISCC)

This is a council consisting of delegates from 29 national societies, plus individual

members, with a common interest in color. Its major technical activities include symposia

at annual meetings and special conferences, and the activity of 14 (currently) problems

subcommittees. The ISCC does not issue standards, but occasionally a problems subcommittee

may publish a recommended practice with the endorsement of the Council.

14. JOINT ELECTRON DEVICES ENGINEERING COUNCIL (JEDEC)

This council has provided agreement on standard measurement conditions for characterizing photodetectors. Committee JC-23 on solid state opto-electronics devices is now beginning to establish procedures for measuring light emitting diodes.

15. LAMP TESTING ENGINEERS CONFERENCE (LTEC)

This conference meets twice a year primarily to exchange lamp measurement information

among various companies in the lamp industry. The conference has carried out several

32
intercomparisons , most notably one in cooperation with NBS published as NBS Tech. Note 559

[62] . Within the framework of this Conference, upon occasion the lamp companies have agreed

to base certain measurements on particular standards in order to provide as consistent a set

of nominal luminous flux values as possible throughout the industry.

16. MANUFACTURERS COUNCIL ON COLOR AND APPEARANCE (MCCA)

This is a trade association composed primarily of manufacturers of color and appearance

instrumentation. One of its major objectives is to arrive at agreements on standards and

techniques in order to provide greater uniformity in the measurements made with these

instruments. A Collaborative Reference Program for color and gloss is being carried out on

a continuing basis under the co-sponsorship of the Institute of Applied Technology of NBS.

17. OPTICAL SOCIETY OF AMERICA (OSA)

This professional society, both as a whole and in its Technical Group on Radiometry and

Photometry, has been predominantly occupied with the exchange of technical information. It has published the monograph, "The Science of Color". Its Committee on Colorimetry is

addressing the problem of defining scales of uniform color difference. The Society is represented in many standards organizations. (See Appendix D)

18. SOCIETY OF AUTOMOTIVE ENGINEERS (SAE)

The Society has been the primary organ for the formation of industry agreement on aircraft and spacecraft lighting as well as automobile lighting. The resulting documents

formed the basis for American practice until the recent increase in Federal responsibility

for highway safety standards. The SAE work was not designed for rigid enforcement, but

rather as more flexible, "designed to conform to", specifications. These specifications

therefore require review before Federal adoption as strictly enforced standards.

19. THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS (SMPTE)

This group provides for the coordination of practice in the motion picture and

television industries.

20. SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)

This professional society roughly complements in function the Optical Society of

America. As the name implies, it emphasizes instrumentation and engineering. Its meetings

are primarily professional in nature, frequently topical seminars.

21. WORLD METEOROLOGICAL ORGANIZATION (WMO)

This organization's Committee on Instruments and Methods of Observation (CIMO) concerns itself with the design of physical standards and measurement techniqeus for the determination

of parameters characterizing solar radiation in the vicinity of the earth. The Committee has

held a number of international intercomparisons of pyrheliometers, instruments for measuring

the direct solar irradiance at the surface of the earth. Until very recently these measurements were not directly coupled to national radiometric standards. A general renaissance

in interest in detector radiometry stated in this field before its more general appearance

in this country as a solution to broader radiometric problems.

22. UNDERWRITERS LABORATORIES (UL)

These private laboratories have not been widely known for dealing with optical radiation

standards. However, recently they have displayed interest in establishing limits for

irradiance in close proximity to high intensity movie lights. Provision of contemplated

standards would require measurements at a much higher level than that for which standards

currently exist.

33
APPENDIX D Expansion of the Role of Professional Societies

The professional societies are undergoing a self re-examination of their role.

Experimentation is a part of this process. For example, at a recent Optical Society

meeting, the Technical Group on Radiometry and Photometry held two panel discussions.

The first of these discussions was entitled "New Stringent Meteorological Demands on Radiometry". Experts in the field of meteorology were invited to summarize the meteorological needs for superior radiometry. A quantitative review of some of the most sophisticated

radiometric measurements on satellites was also presented as a measure of present capability.

A substantial gap between needs and performance was identified but described in too cursory

a fashion to be clear to everyone participating in the discussion. Nevertheless, this

discussion will lead to a more ambitious symposium at a future Optical Society meeting.

At this same meeting a second panel discussion was held on a developing fundamental

problem with practical consequences, the looseness in the coupling between radiometry and

photometry. This discussion was entitled "Re -examination of the Photometric Unit System".

A number of weaknesses in the present system were described and proposals for redefinition

examined [65] . This meeting was designed to lead to a formal proposal by a US technical

committee of the CIE to a meeting of the international Technical Committee this past

summer. It is significant that direct action, if it is to occur, will take place outside

of the framework of the Optical Society but perhaps within the framework of the CIE.

34
APPENDIX E Methodology of Study

Because of the novelty of technology assessment in general and in particular of the

analyses carried out in this Technical Note and in the preceding one on the impact of radiometry and photometry [1] , a review both of the critical factors that have been perceived and

of the responses to these factors that have been developed and tools that have evolved may

find application in other areas. But caveat emptor: any transfer of this "technology" to other areas should follow a preliminary investigation to ascertain whether the contemplated

application is indeed suitable or not.

1. GENERAL FACTORS

a. Size and Complexity

The size of the analytical job involved is far more than one person, working full time, can carry out by himself. The time factor will be explored in detail in the next section.

There is the sheer volume of the potential data that must be collected, correlated, and

evaluated. In addition to the enormous quantity and complexity of data, the necessity for

a critical approach is crucial. And this critical approach requires technical expertise

in a wide variety of technical fields. Evaluation of a broad measurement area must

rely on many experts in relatively narrow technical fields.

b. Desirability of Interaction Apart from NBS

A more fundamental reason, also, exists for the desirability for the involvement of

non-NBS people in key roles of the interaction. The structuring of the data collected

involves critical thought and is part of a useful educational process. The organizational

complexity of radiometry and photometry is shown by the number of different organizations

involved. Key members of the community are desirous of achieving a less parochial approach

to these problems, and this requires an interaction apart from NBS. The synthesis performed

on the variety of needs throughout the field will be far more practicable if those who must

live with the results are involved in the synthesis itself. This is not to say that NBS

should not exercise strong leadership; indeed it has been asked to do so. But others must

be involved in key roles as well and must share this leadership with NBS.

c. Necessity for Interaction Between NBS and Other Elements of the System

Just as it is desirable for the analysis of a system to involve participants in that

system, it is also extremely important to have strong interaction between NBS and the rest

of the system. At times NBS leadership may be required, as just noted. At other times,

pressure by the rest of the system on NBS may be involved. But still more generally, a partnership must be established if optimum solutions are to be achieved. Before drawing

conclusions from these background factors, it is useful to review critical requirements for

continuity

2. SPECIFIC CHALLENGES REQUIRING CONTINUITY

a. Novelty

The serious analysis of the national measurement system is new, although the concept of

the system itself is not. A methodology must be evolved, and this takes time. The present

Appendix is one contribution toward evolution of such a methodology. Technology assessment

is indeed nowhere an exact science yet. Until this methodology becomes fully developed, time

will be required for trial and error, re-analysis-, and further trial.

b. Second-Order Interaction

It was noted in the Chapter III that the chain between NBS and the ultimate user typically has a number of links. Thus NBS has not been highly coupled to the ultimate user. Channels of direct communication must be established. This process requires time and

continuity.

c. Commercial Factors

The preceding impact study [1] noted that individual companies were not strongly motivated to solve basic optical radiation measurement problems on their own. This is partly

because consistency with other measurements is a far more important commercial consideration

than is the strength of the tie to absolute truth in itself. Indeed, if a choice must be

35
made, business constraints require a common measurement basis with others, rather than

fidelity to physical truth. To be sure, the only way that wide agreement in a complex

physical field can be achieved is by resort to fundamental physics. Nevertheless, a complex

cooperative effort is required. This cooperation involves time, participation in a multifaceted effort, and continuity. Agreements, either tacit or explicit, must ultimately be

reached among those most directly involved; and these agreements require time and coordination.

d. Personal Confidence

Because of the commercial impact of information in this area, the flow of information

requires the establishment of personal confidence. The development of personal confidence

requires both time and substantial continuity.

e. Location of Right People

Because of the diversity in the field of optical radiation measurement and the variety

of industries involved, substantial time is required to locate the right person in each

institution. Two factors define the right person, his experience and his inquisitiveness.

Those at the top of a corporate structure cannot always be expected to have at their finger

tips, ready for immediate judgement, an analysis of technical factors limiting the performance of their institution. On the other hand the man at the bench in one part of a company

may not have the breadth of experience to speak authoritatively even for his own company,

much less for the industry as a whole. At an early stage of the coordination of analysis,

basis technical factors must be identified and placed within a coherent structure.

Institutional representatives must thus display not only experience but inquisitive minds

and must also be prepared to do some hard work. Imaginative analysis is required of those

involved at the pioneering stage.

f. Identification of Crucial Questions

When the proper person is located in an institution, or indeed even before he is

located, crucial questions must be identified. The nature of these questions of course varies

with the individual field. Questions on foreign trade may be important in one area and

irrelevant in another. The training of staff involved in the laboratory may be a vital

question in one area and relatively unimportant in another. On the one hand, critical

factors in the structure of the field must be identified and their relationship to

measurement problems established; on the other hand, tractable specific questions must be

formulated. The crucial interaction is one of "development" and not "location" of the

right questions.

g. Phrasing the Right Question

Because of the diversity of this field, phraseology itself becomes an important factor.

The propensity of radiometrists and photometrists for developing nomenclature is well known.

But in a deeper sense, the establishment of a suitable background may be required before

questions can be properly interpreted. Without continuity this background must be continually re-established.

h. "Induction Period"

Even with the right question phrased in the proper manner, the answer may nevertheless

not be immediately forthcoming. Because of the novelty of this analysis both to NBS staff

and those with whom they otherwise never deal, answers, although they may already exist, may

not be specifically identified in the minds of the people initially involved. Weeks or months after a question has been raised the answer may well come in an unexpected context to the novice who has been asked. More indirectly, our postulated novice may recognize, long

after the original posing of a question, another person who knows the answer to the question.

This analog of the "induction period" to a chemical reaction is applicable even to those

experienced in such analysis. One finds relevant data in unexpected places, fertilizing

the "prepared mind" . These data that will not come from a crash search at the time a question

is posed later may provide extremely important leads

.

i. "Other Guy" Symdrome

Since the problem in the measurement system is basically one of agreement, and since

scientists and technicians in general are not aware of all systematic effects on measurements

being made, estimates of uncertainties will frequently not provide a reliable prediction of

the level of agreement actually achieved. Because systematic errors are inadvertently

36
ignored, the tendency is to assume that it is the other person who is in error by more than

his stated uncertainty. Because the other fellow is the one presumably in error, the person

making this evaluation will not be strongly motivated to search for the source of the error.

It is only after considerable interaction with one's colleagues, a result of substantial

continuity, that one builds up sufficient confidence in one's colleagues to motivate a serious re-examination of one's own measurement problems.

j. "Emily Post" Syndrome

Another problem, more psychological then technical in nature, but nevertheless severe,

is a general reluctance to discuss measurement errors. Even in a completely objective,

scientific atmosphere, it is the possibilities that receive primary attention, not the

difficulties . Until a sufficiently firm relationship is established, many will not discuss

in detail their measurement difficulties. "It just isn't done".

k. "State-of-the-Art" Syndrome

Even though levels of agreement are typically worse than anticipated because of the

neglect of unknown systematic errors , rough levels of agreement ultimately become established

in a crude fashion and recognized among experienced workers. This "effective-state-of-the-art"

becomes an excuse that is used to justify the absence of better performance. If one doesn 't do any better, then many will assume that one can 't do any better. In established fields

with long traditions such as those of radiometry and photometry, this complacency has become

a barrier recently to rapid movement of the state-of-the-art. With the introduction of new people and new technical constraints such barriers to improvement can be readily removed.

A "new continuity" is required to replace the old.

1. Efficiency

And finally, the determination of an efficient response to serious measurement disagreement here, as in basic research, may await a new synthesis of previously unrelated factors.

Efficiency demands the identification of new techniques for current problems. This

efficiency requires continuity and time for analysis.

3. PERMANENT STRUCTURES

a. Professional Societies

All of the preceding characteristics indicate the desirability of a permanent organizational structure within which appropriate individuals can be identified and their effort

to improve the national measurement system coordinated. Information coordination has occurred

traditionally through the various technical groups in professional societies. The question

is sometimes asked, "Why not strengthen these technical groups to provide the requisite

continuity and coordination?" Such an approach cannot be excluded. Indeed it offers some attractive opportunities that have not been exploited. We shall see later that these

societies very likely do not offer the total answer.

(1) Technical discussion

The strongest feature of the professional societies has been the provision of a forum

for technical discussions and technical papers. These are a sine qua non for progress in

the measurement system. Without a firm technical foundation, agreement can not be achieved

on a widespread scale. Nevertheless, this is only the first step; it must be followed by

analysis, coordination of information, and response to specific proposals. The technical

groups of these societies can indeed be used to provide for keen interaction among people

in addressing specific questions. One example is the recent use of the Standards Specialty

Group of the Infrared Information Symposia, which operate primarily as a technical society,

to provide tentative answers to specific questions posed by NBS in its re-evaluation of needs

for infrared standards and services. Other examples are given in Appendix D.

(2) Difficulties with systematic action

In spite of their great strengths , professional societies face two problems in serving

as the primary progenitors of solutions to measurement system problems. In the first place,

they offer no formal structure for systematic synthesis and the resolution of difficulties.

These are societies for thought, not typically societies for action, although they may be

changing in this respect. Second, participation in the professional societies typically

is not fully international in scope. But the technical problems know no national boundaries

and must be solved on an international scale if international problems such as trade are to

37
be ameliorated. Cooperation, then, with an international organization is essential as a long-term solution to the measurement system analysis problem.

b. Council for Optical Radiation Measurement

(1) Origin

Early in an intensive effort by NBS to determine the status of, and needs for, the

measurement of optical radiation, a parallel restlessness became evident within industry.

Robert Watson, whose professional activity in industry led him to face severe measurement

problems in an area where few answers were available, suggested that a group of industrial

and NBS scientists in this area get together to discuss a coordinated approach to these

measurement problems. Those who were known to share this mutual restlessness with the

situation were invited to a meeting at NBS that took place on 28 October 1971 under the

title "Conference on the Definition of Pressing Problems and Projected National Needs in

Radiometry and Photometry". Representatives from twelve industrial companies, one military

agency, and NBS both in Boulder and Gaithersburg took part. Two themes developed during the

meeting. The first was industrial desire for more vigorous NBS action in this area and

recognition that such an increase in activity would require justification from industry. The

second theme was the recognition that a permanent organization ought to be formed in order to provide industrial and other-agency information for NBS and to coordinate future activity.

Participants agreed as a first step to submit statements of need to NBS and then, as a second step, to gather to consider these statements together.

(2) Requirements

On 10 February 1972 a second conference was held as a follow-up to the first. It agreed to establish itself on a permanent basis as the Council for Optical Radiation Measurement and to operate as an activity of the Commission Internationale de l'Eclairage (CIE)

.

Action was directed to the following ends:

(a) Leverage on NBS

Uppermost in the minds of participants was - the desire for NBS to increase its service

in the field of optical radiation measurement. The bulk of the first Council meeting was dedicated to establishment of working groups to provide a consensus on the detailed requirements and a justification for these requests. This concern with NBS activity has remained

a primary focus of the Council. It resulted in the lengthy formal report to NBS described

below [21]

.

(b) Coordination of other activities

As noted earlier in this Appendix, three types of activity were to be coordinated. In the first place, an exchange of information throughout the electro-optics industry and

government agencies working in the field is vital in order to optimize progress. In the

second place, the coordination of technical activities with those of the CIE is called for.

And finally, the coordination of activity of the many procedural standards groups described

in Appendix C is a problem that must be addressed.

(3) Operation

Because of the magnitude of the work involved and the relatively limited resources of

the new organization, it was clear that effort ought to be employed with maximum efficiency.

It was this consideration that led to incorporation of the activity within the program of the

CIE. This act provided: (1) the coordination with existing technical projects and (2) the

international interface that would be a primary requirement of long term work in the field.

The Council thus has become a full-fledged, indeed the primary, effort of Technical

Committee 1.2 on Photometry and Radiometry of the US National Committee of the CIE. The

most actively interested participants in the Council meetings were invited to join this

US' CIE Technical Committee, which then proceeded to function as the executive committee of

the Council. The following statement of purpose was adopted at a September 1972 meeting of

TC 1.2, and with it, a statement of operation:

The Council for Optical Radiation Measurement (CORM)

is a body of American industrial, governmental, and university scientists and engineers organized to facilitate

the development of reliable standards and procedures

for the measurement of optical radiation.

38
The Council is an activity of Technical Committee 1.2 on Photometry and Radiometry of the United States National

Committee of the CIE (Commission Internationale de l'Eclairage)

(4) Initial goal

The first formal Council meeting, in February 1972, and the following meeting, in

May 1972, were devoted to the preparation of a formal report to NBS "Pressing Problems and

Projected National Needs in Optical Radiation Measurements: A Consensus of Services

Desired of NBS" [21] • Authors for various sections were designated, and the reports of

various working groups were condensed into a common format. Common elements in the requests

were identified and brought together so that a unified series of proposals for new standards

and techniques was developed. Key ideas were extracted for the introduction. The entire

Technical Committee 1.2 met in June 1972 to review the document in detail. The resulting

document was then sent to all CORM participants for comment, which would then be incorporated

by a meeting of the authors into a final document presented to NBS in the fall of 1972.

(5) Permanent goals

With the report published and well received, the US Technical Committee 1.2 met in

September to adopt the preceding statements of operations and purpose and a set of objectives. These were grouped into four sets of goals, as noted, grouped around four distinct

sets of participants.

I. COUNCIL MEETINGS

To establish and maintain a dialogue throughout the

American electro-optics industry on problems of optical

radiation measurement; to use this dialogue to establish

priorities and to investigate alternative solutions.

II. COUNCIL-INTERNATIONAL TC 1 . 2 TECHNICAL PROJECTS

To coordinate study of specific optical radiation

problems and recommend solutions to them in cooperation with

the international effort organized through the CIE.

III. COUNCIL-NBS INTERFACE

To establish and maintain a dialogue with NBS; to use

this dialogue to inform NBS on industrial priorities; and

to suggest feasible approaches to these problems.

IV. COUNCIL-STANDARDS GROUPS INTERFACE

To coordinate the dissemination of commercial standards

and procedures developed by American and international

standards organizations.

Communication throughout the field was to be maintained by a series of general meetings.

Technical activity was to take place via ten specific projects, the first six of which were

already activities of the international Technical Committee 1.2. Information for NBS was

to be coordinated through establishment of a group for this purpose. And finally, the

coordination of information on the various standards groups was to be coordinated by a fourth activity. Detailed programs in each of these areas have just been issued [27]

(6) Prospects for the future

Comparison of the Council program with the factors necessary for a coordinated attack

on measurement problems identified in the preceding section indicates that a mechanism

for continuity has now been established to carry out the various functions analyzed. Since

the industry and its organizational structure are very much in a state of flux, the future

is hard to predict. The degree of cooperation throughout the field achieved already leads

one to be optimistic about future achievement. CORM leaders were invited to an international conference on Photometry and Colorimetry this summer in eastern Europe to describe

this activity. The problems that the Council is addressing are apparently not localized,

and interest is high. Whether or not the challenges are successfully met remains to be

seen.

39
APPENDIX F Relation of Improved Optical Radiation Measurement to Broadened Federal Concern

1. PROMOTING ACCURATE, MEANINGFUL, AND COMPATIBLE SCIENTIFIC AND TECHNICAL MEASUREMENTS

A traditional central role for NBS has been widely recognized to be: "promoting

accurate, meaningful, and compatible scientific and technical measurements". Paralleling

the expanded public interest in coordinated approaches to various public and national

problems, NBS is re-examining its role in cooperating in this endeavor. One example of a broadened view of the NBS role in "promoting" such measurements is the present study.

2. PROMOTING MORE EFFECTIVE USE OF SCIENCE AND TECHNOLOGY

The recent rapid development of photon sources and photon detectors has been described.

Opportunities to use these new tools in a more effective manner have also been noted. Appropriate strengthening of the measurement system will be required if these new tools are to be

utilized to fulfill their promise.

3. PROMOTING STRENGTH IN THE ECONOMY AND EQUITY FOR BUYER AND SELLER IN TRADE

The economic impact of improved measurement technology for optical radiation falls in

two broad areas identified in the earlier Technical Note [1] . Within this country, if the

buyer is to make intelligent decisions, whether he be an individual buyer in a supermarket

or the economically more important large scale commercial purchaser, he requires such data

as the luminous flux provided by various manufacturers. This data must be of sufficient

accuracy for reliable comparison of dissimilar objects designed to meet a given performance

criterion.

Abroad, the growth of international trade in the rapidly growing electro-optics

industry has been widely recognized. "I have travelled through every country that sells our products and talked to each of our representatives, and their story is the same. We

must have improved light measurement traceability to the National Bureau of Standards" [22]

.

And finally, in the development both of domestic and of international agreements,

authoritative participation is highly desirable if the U.S. is to respond to the coordinated

approach displayed by other countries. We are being asked to achieve a higher degree of

coordination than that which has characterized our activity in the past [21,27]

.

4. STANDARDS AND TEST METHODS FOR PROTECTION OF THE PUBLIC FROM SPECIFIC HAZARDS

In the preceding Technical Note [1] , several pieces of relatively new legislation were

cited. Three of these bear directly on hazards. The first is the Federal Hazardous Substances Act, 15 US Code Chapter 30. More recently has come the Radiation Health and Safety

Act of 1968, Public Law 90-602. And finally there is the Occupational Safety and Health

Act of 1970, Public Law 91-596. These establish very broad powers for the Secretary of

Health, Education and Welfare and the Secretary of Labor. Emphasis will naturally be placed

in certain spectral regions and at specific levels. It is in anticipation of increased

activity in these areas that the national measurement system must be designed.

5. TECHNICAL INFORMATION SERVICE

Because of the state-of-the-art nature of most measurements in this area, information

resulting from radiometric research is awaited with keen anticipation throughout the industry.

In areas where commercial factors may influence technical objectivity, users require access

to relatively unbiased information.

6. EXPERIMENTAL TECHNOLOGY INCENTIVES PROGRAM

Because of the technical complexity and vast extent of the effort of required for

improvement in the measurements, symbiotic approaches by government and industry might be

explored. One path is the NBS Experimental Technology Incentives Program. Both because

of the rapid march of technology in electro-optics and because of a heavy defense

orientation in the past, a number of new commercial opportunities exist that have not been

fully realized in this area. The civilian application of highly advanced, and previously

classified, areas of technology presents an opportunity for the solution of national

problems, both social and economic. This challenge may lead to a very new and complex

interaction with industry.

40
APPENDIX G

A Comprehensive Approach to the Measurement System

A reliable measurement system consists of two parts: (1) research and (2) the interaction between this research and routine measurement.

1. THE RESEARCH REQUIRED

Since radiometry and photometry consist of the measurement of electromagnetic radiation

generated, transmitted, and detected by optical system components, the system can readily be

approached in terms of these elementary functions.

a. Source Characterization

The characterization of a source by a system user typically involves three separate

elements: the realization of a scale, its transfer to secondary standards, and the

development of techniques for extension of these standards to the generally dissimilar

object to be measured. For the characterization of a source in the U.S., a second source typically embodies the scale and a third source the secondary standard. But detectors

may well be used increasingly for these purposes.

(1) Realization of the scale

The realization of radiometric scales by sources for the characterization of other

sources has been a widely recognized accomplishment of the NBS program in radiometry. NBS

leadership in source blackbodies is acknowledged. One important area remains to be

developed within the system as a whole however: the characterization of large area blackbodies. Both space and ground requirements have led to a need for the full characterization

of sources with an area of many square centimeters. A number of designs have been proposed

and used under a variety of conditions. A full analysis remains to be performed however.

(2) Transfer of scales to secondary standards

The transfer of blackbody scales to secondary standards is another area where NBS has

already provided acknowledged leadership. Comparable standards of spectral radiance are available nowhere else. A major fraction of the emphasis of the present NBS program is

still in this area. Substantial NBS work is being directed to the transfer of scales to particular standards in a definitive way at the 1-2% level: standards of spectral irradiance,

luminous intensity, and luminous flux. A fundamental question remains to be examined. For important new standards is it

preferable for the system to operate with additional secondary standards, or rather to generate the additional measurement capability by the establishment of reliable techniques

for the extension of present standards. The second approach is considered by many to be

preferable for large systems. Three system elements can be defined in the area of

secondary standards:

(a) Characterization of present standards

Because of the complexity of the measurements, some NBS standards and most others remain

to be fully characterized. More complete characterization of its standards has a high

priority now at NBS. Particularly as other countries develop similar standards it will be

important for NBS standards to receive full, documented quantitative characterization.

(b) Improvement of present standards

The best U.S. secondary standards are spectral radiance standards, to which is ascribed

an uncertainty of between 1 and 3%. Requests are already being received for radiometric

accuracy better than 1%, and planning should start, at least, for the generation of new

standards better by at least by a factor of 2. But in view of the requirements in other areas,

this area probably will not receive high priority at the moment. Areas receiving primary

attention at NBS now are spectral irradiance and luminous flux.

(c) Description of procedures for present standards

The utilization of present standards has been hampered in the field by lack of a complete description of procedures recommended for their use. Such description ideally

consists of two parts. A complete characterization of the standards involves a description

of the variation of the measured output with respect to the various parameters of the lamp.

One example important for some lamps is the variation with orientation. A second set of

41
parameters deals with the influence of the environment, such as temperature and humidity.

Until such descriptions are supplied with the lamps, the user will still be left with an unnecessarily large job to do and one whose performance would be redundant if performed in

a large number of laboratories.

(3) Extension of present standards

The major thesis of Chapter II was that many different types of measurements were to be made. These can be made either by substitution or by extension, as just noted in

Section 2. For example, most source standards are incandescent lamps, whereas a major

fraction of radiometric and photometric measurements are made on non-incandescent sources. One approach would be to generate an enormous series of non-incandescent standards so that

all field measurements can ultimately be made by substitution with similar standards.

Alternatively, one could generate a set of techniques whereby present standards could be

used reliably to calibrate a wide variety of lamps. If the system were relatively small, the

former approach would inevitably be economical. But for a large system with great diversity

of measurements there are probably fewer aspects that need to be characterized than there are different lamp types to be measured. Lamp production is so varied that even a subset, for

example, fluorescent lamps, are probably more economically standardized against incandescent

standards then by direct substitution standards for each type of fluorescent lamp.

This general approach may also be advisable even for smaller systems where work is

destined ultimately for comparison with that on dissimilar objects. Such is increasingly

the case for artificial illumination and its comparison with natural daylight. If two

dissimilar measurements are to be made on a comparable basis then one must understand

in detail the nature of the measurements. With proper attention to design, it is to be ex- pected that measurements providing for extension of given standards to dissimilar areas can be made sufficiently convenient that economic procedures can be developed. Such a system

has the further advantage that it can be extended with minimal effort as the field grows.

The optimum system may involve the establishment of a few additional secondary standards

in areas where a large number of measurements are relatively similar to each other but very

dissimilar from the secondary standards presently available. But such a conclusion must be

drawn with extreme care. Two dominant factors in such an evaluation will be the stability

of the contemplated new standards and their similarity to the various objects that they are

to serve as standards. These questions both arise, for example, with respect to proposed

LED standards

.

b. Detector Characterization

(1) Realization of scales

Work in a number of national laboratories on electrically calibrated radiometers is

demonstrating that this approach to the realization of radiometric scales is perhaps the

most certain, particularly where spectral information is secondary in importance. One

extremely promising approach to absolute detector radiometry arises in the development of

pyroelectric detector technology. Several vigorous programs in the development of this

technology are already underway at NBS [66]

.

(2) Transfer of scales to secondary standards

Several new detectors seem to promise the stability required of secondary standards.

Pyroelectric detectors are already under active investigation. Several solid state quantum

detectors are also extremely promising, primarily silicon in the visible region. Although

experience on the stability of, and environmental effects on, these detectors remains to be

accumulated, preliminary indications are extremely encouraging. The high sensitivity of new detectors is especially important in permitting detailed spectral response information to be

obtained. Both photometry and radiometry can be expected to undergo a revolution through

this new technology.

(3) Extension of present standards

Vacuum diodes and multipliers have traditionally been considered" to be too unstable to act as primary or secondary standards. Their response must be characterized however and

techniques must be developed for doing so reliably. The National Research Council of Canada

has a strong program in this area. There is a renewed interest in photomultipliers now that

photocathodes composed of elements from the third and fifth periods of the periodic table

(III-V compounds) have been shown to display a remarkably flat response throughout the

visible and into the near ultraviolet and infrared spectral regions.

42
c. Techniques

There is wide agreement that the proper generation and use of physical standards

require close attention to specific measurement techniques. Similar attention to the extension

of present standards to dissimilar measurement objects is greatly needed.

One conspicuous example is the detailed characterization of attenuation. In a recent

poll of members of the CIE international Subcommittee on Detectors, for example, the dominant

concern expressed was for linearity [20] . Although a review article has appeared [14] , the

field is so extensive that an even more detailed review of various techniques with high

precision has been requested.

A second general problem, particularly in photometry, is the characterization of

spectral techniques, especially as applied to spectral lines. With increasing interest in

spectral information, small, convenient, and reliable instrumentation is desired. Fourier

interferometric techniques offer a number of attractive advantages for dealing with such

spectral problems. They have been exploited for spectroscopy, where wavelength information

is the quantity of primary interest. Their radiometric suitability remains to be determined.

A third general area is that of pulsed measurement. The measurements are so heavily

dependent on the particular time scale of the pulses in question that a general approach

may not be feasible.

A fourth area of concern is polariation. Interest in this area will probably continue

to be focused on the characterization of specific components, rather than a general approach.

Although some good reviews have been prepared [23-24], the sheer extent of the effect leaves

much still to be done. A fifth general area of optical radiation measurement is spatial distribution. Although

the description of inhomogeneities is of greatest significance with respect to sources and

detectors (q.v.), general techniques for determination of inhomogeneities would be useful

for the system.

Diffraction is a sixth area of concern. Since the quantitative importance of diffraction

can be determined meaningfully only with respect to an entire system, individual components

clearly cannot be so characterized. Their degree of coherence is important though. The

significance of diffraction is beginning to be recognized [67] , and further work will be

appearing. A full understanding of diffraction will be coupled with some basic questions of

coherence in radiometry.

2. SYSTEM COORDINATION

Unless research continues to be based on up-to-date input from the measurement system

on the one hand and, on the other hand, unless the results of the research are effectively

coupled into the system, the research may be remote and its value, questionable. Thus

interaction with the measurement system is of importance comparable to that of the research

itself. Two types of interaction are involved. First, there is conceptual communication,

either oral or written. Equally important is experimental assessment of measurement performance, a measurement assurance program, and dissemination of standards. Both conceptual

and measurement communication are essential to a smoothly functioning system.

a. Coordination of Information

The importance of strong interaction between the NBS program management and the

community that it serves is widely recognized. In addition to individual bilateral interaction, a number of more systematic channels must be employed. The professional societies

provide facilities for communication of the type already described in Chapter III. These

must be utilized. A more structured format providing for the achievement for coordination

of effort is also extremely important. The organization of the Council for Optical Radiation

Measurement for this purpose has been described and is analyzed in detail in Appendix E. There is an additional type of important interaction. This is the normal initiative

taken by those outside of NBS who would like to have various services performed by NBS,

either routine or special. Many call on NBS for specific services. Some continuing

compilation and evaluation of the kinds of service they are asking for would be highly

desirable. Although some of these contacts occur at a non-technical level, attempts

will be made to generate specific information on the use and utility of standards being

requested.

43
b. Coordination of Measurements

The specific coupling of optical radiation measurements to NBS standards is achieved

in one of two ways. Traditionally, calibrated objects have been disseminated by NBS. This

is the simplest and the cheapest form for the provision of this interaction. It also provides

the least information.

Either alternative or complementary to this calibration service is the establishment

of intercomparison programs in which NBS can play a role. If NBS calibrates one of the objects

used in the intercomparison, then this object can fulfill the function of a calibration.

But in addition it can play a more rounded role. If the object is carefully chosen, its

intercomparison can also assist in the determination of the performance of the measurement

system and thereby provide a firmer basis for the prediction of system performance than can

a calibrated object in itself. Such an approach essentially constitutes the performance of

research in a parallel fashion in a number of laboratories. The great effort required must

be balanced on a case-by-case basis against the expected benefits. Because of the extensive

requirement for resources in such a program, critical planning must play a strong role in

this work. Goals must be clearly established and articulated in advance. The intercomparisons must be carefully designed to achieve their goals with close attention to costs both

at NBS and in cooperating laboratories. By means of such intercomparisons, one can both

provide the basis for the measurement system and demonstrate that it is indeed performing

satisfactorily. Moreover, the impact of system improvements can be clearly demonstrated.

The immediate effect both of research and individual services can thus be measured in

quantitative fashion. NBS is developing such an intercomparison program, but because of

budgeting restrictions its realization will be very slow.

44
EXECUTIVE SUMMARY

The ultimate users of the optical radiation measurement system fall into four major

categories: industry, government, the academic community, and the general public. All are facing severe problems.

Light emitting diode manufacturers, for example, have found spreads of the order of 40%

among mee^urements . Such differences are clearly visible and intolerable commercially. But

the complexity of the measurement means that, without outside assistance, companies making

reliable measurements face very high measurement costs. Not only will highly trained people

be involved, but at present a great deal of time for research will be required. The

exceedingly high costs thus involved are simply not feasible for this fragmented industry.

It is currently much cheaper to argue a case of disagreement in court, if it comes to that,

rather than to set up a research laboratory to solve the problems on an individual basis.

The varied authority for enforcement of new Federal regulation ' is increasingly important.

First was the Federal Hazardous Substances Act, 15 U.S. Code Chapter 30. More recently has come the Radiation Health and Safety Act of 1968, Public Law 90-602. And finally there is

the Occupational Safety and Health Act of 1970, Public Law 91-596. The Departments of Health,

Education, and Welfare, Labor, and Commerce are involved. Furthermore, the Environmental

Protection Agency is responsible for an area of rapidly expanding concern.

In the past, the measurement systems of the various countries have been quite independent.

But as international commerce in electro optics grows, foreign standards will probably impinge

increasingly upon the U.S. measurement system.

Public concern for energy has led to activity in areas that depend on optical radiation

measurement. There is growing public sensitivity both to power conversion and to the efficient

utilization of energy. A review article summarized the situation with respect to energy

conversion recently: "Whatever method is being pursued, the electro-optics community is very

firmly entrenched in the search for new energy sources. The long- and short-term goals

discussed in these pages seem destined to keep a great many of us diligently at work for a good many years to come." The efficient utilization of power is also receiving attention.

Since lighting takes 25% of the electric power generated, measurement of efficiency in

lighting becomes important to improving the efficiency of power utilization as a whole.

Pollution of the environment must be monitored if it is to be controlled in a realistic

fashion. Remote sensing approaches are being explored. Problems of pollution are coupled

with energy problems through the wide availability of hydrocarbon fuels that contain

relatively large amounts of sulphur, a serious pollutant. Another specific interest in

-monitoring attempts to control pollution is connected with substantial changes in the earth's

atmosphere. Serious climatic changes may follow increased pollution as a long term effect.

In the short term, the amount of ultraviolet light, which is controlled by ozone in the upper

atmosphere, may be affected. Meteorology in fact is providing some of the tightest requirements in radiometry.

The study of the measurement system leads to a number of conclusions. The first is the

grave need for coordination of activity. What channels for concerted action can be utilized?

In addition to bilateral interaction between NBS and the various other institutions already

involved, a number of more elaborate systematic channels must be employed. The professional

societies provide facilities for communication of a type described. These must be utilized.

A more structured format providing for this coordination of effort is also extremely important. The establishment of the Council for Optical Radiation Measurement for this purpose

has been described and analyzed in detail. Coordination in the dissemination of commercial

standards and procedures developed by American and international standards organizations

remains to be tackled. A number of technical conclusions are also drawn. Source and detector characterization

are called for as well as greater attention to technique building blocks. Monitoring of

the performance of the entire system and of its basic measurements are called for. Improved

methods of transfer of measurement technology must be developed. And last, a mechanism for

the establishment of priorities in the development of an extremely complex technology is

urgently needed.

45
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OK REPORT NO. NBS TN 594-6

2. dov't Accession

No.

4. TITLE AND SUBTITLI: OPTICAL RADIATION MEASUREMENTS:

THE PRESENT STATE OF RADIOMETRY AND PHOTOMETRY

3. Recipient's Accession Nc.

5. Publication Date March I97U

6. Performing Organization ( ode

7. AUTHOR(S)

Bruce Steiner

8. Performing Organ. Report Nc

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project Task 'Work Unit No.

11. Contract/Grant Nc

12. Sponsoring Organization Name and Complete Address (Street, City, State. ZIP)

Same as No. 9.

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less tactual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

The electro-optics industry and the public that depends on it are part of

an informal but influential system for optical radiation measurement. The growth

of this undustry and of public concerns related technically to it have put severe

new strains on this measurement system. The system itself must therefore be

analyzed. The state of the art, on which the measurement system depends, is

surveyed in terms of basic measurement parameters. The measurement system is

analyzed in terms of its three basic components: the flow of physical standards,

the generation of procedural standards, and the funding framework. The roles of

the professional society and of the Council for Optical Radiation Measurement

are reviewed. New requirements of the system are identified. Finally, the

methodology of the study is reviewed in detail.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Measurement system; photometry; professional societies;

radiometry; standards.

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rIBLICATION NBS TECHNICAL NOTE 594-7

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,114-

U.S.

Iartment

OF

DMMERCE

National

Bureau

of

Standards

1

1

^a^^^^^^k^^M^ Optical Radiation Measurements:

Approximate Theory of

the Photometric

Integrating Sphere
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences " — Applied Radiation " — Quantum Electronics * — Electromagnetics n — Time

and Frequency 1 — Laboratory Astrophysics ' — Cryogenics".

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the executive branch for the development of Federal standards for automatic data processing

equipment, techniques, and computer languages. The Institute consists of the following

divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

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1 Headquarters and Laboratories at Gaithersburg. Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Research.

3 Located at Boulder. Colorado 80302.

• Part of the Center for Building Technology.
Optical Radiation Measurements: N*ai Bur8au pf a****

APR 2 9 1974 Approximate Theory of the

Photometric Integrating Sphere

W. B. Fussell

Heat Division

Institute for Basic Standards

National Bureau of Standards

Washington, D.C. 20234

/ v\

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, D/recfor

Issued March 1974
National Bureau of Standards Technical Note 594-7

Nat. Bur. Stand. (U.S.). Tech. Note 594-7, 39 pages (Mar. 1971) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1974

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Preface

This is the seventh issue of a series of Technical Notes entitled

OPTICAL RADIATION MEASUREMENTS. The series will consist primarily of

reports of progress in, or details of, research conducted in radiometry

and photometry in the Optical Radiation Section of the Heat Division.

The level of presentation in OPTICAL RADIATION MEASUREMENTS will be

directed at a general technical audience. The equivalent of an undergraduate degree in engineering or physics, plus familiarity with the basic

concepts of radiometry and photometry [e.g., G. Bauer, Measurement of

Optical Radiations (Focal Press, London, New York, 1965)]» should be

sufficient for understanding the vast majority of material in this series.

Occasionally a more specialized background will be required. Even in

such instances, however, a careful reading of the assumptions, approximations, and final conclusions should permit the non-specialist to understand

the gist of the argument if not the details.

At times, certain commercial materials and equipment will be identified in this series in order to adequately specify the experimental

procedure. In no case does such identification imply recommendation or

endorsement by the National Bureau of Standards, nor does it imply that

the material or equipment identified is necessarily the best available for

the purpose.

Any suggestions readers may have to improve the utility of this series

are welcome.

Henry J. Kostkowski, Chief

Optical Radiation Section

National Bureau of Standards

iii
Contents

Page

1

.

Introduction 1

2. Current NBS Techniques for Comparing the Total Luminous

Fluxes of Lamps with the Integrating Sphere 3

3

.

Elementary Sphere Analysis 6

3.1. Empty Sphere Luminance Distribution 6

3.2. Introduction of the Baffle 10

3.3- Effects of Absorbing Objects 12

4. Analysis: Sphere with Coaxial Disc Baffle 13

4.1. First Order Luminance at the Sphere Window

as a Function of Source Point Coordinates 13

4.2. Lamp Flux Reflected from the Baffle 18

4.3. Extended Source Distributions 18

4.4. Extended Source Distributions : Approximate Model 20

4.5. Optimum Baffle and Lamp Positions to Minimize

the Error in Measuring Total Luminous Flux 23

4.6. Upper Bound on the Fractional Sphere Error 25

4.7. Factors Neglected 27

5

.

Conclusions 30

6 References 31

Figures

Figure 1. Cross section of typical integrating sphere 32

Figure 2. Cross section of empty sphere; viewfactor geometry 33

Figure 3. Integrating sphere geometry 34

IV
Approximate Theory of the Photometric Integrating Sphere

W. B. Fussell

An approximate mathematical theory of the photometric

integrating sphere is developed. The analysis is accurate to

the first order in the ratio of the baffle area to the sphere

wall area. The sphere is assumed to be occupied by a circular

baffle and a spherical lamp; the centers of the baffle and the

lamp lie on a diameter of the sphere. The surfaces of the

sphere and the baffle are assumed to reflect in a uniformly

diffuse manner. The lamp is assumed to absorb a fraction of

the radiation incident upon it, and to transmit (or specularly

reflect) the remainder. The luminance distribution at the

sphere window is derived for a general source input at any

point of the sphere wall. A model lamp illuminance distribution is assumed, and a formula for the fractional error in

comparing the total luminous fluxes of two lamps in the

integrating sphere, is derived. The physical significance of

the formula is described.

Keywords: Illuminance distribution; integrating sphere; lamp

comparisons; photometric accuracy; photometry; total luminous

flux.

1. Introduction

The photometric integrating sphere was invented by R. Ulbricht, who

made the first sphere in 1900 [1J . The usefulness of the integrating

2

sphere for comparing the total luminous fluxes of lamps was quickly

recognized, and many large spheres were soon constructed £33*

In 1915 a large integrating sphere of 2.2-meter (88-inch) diameter

was constructed at NBS by Rosa and Taylor |V]. They compared total

luminous flux values obtained with this sphere for several incandescent

Figures in square brackets are literature references at the end of the

text.

2The nomenclature of this paper is that of the International Lighting

Vocabulary (1970) [2].
lamp-reflector combinations, against corresponding values obtained bydistribution photometry, and found differences ranging from to 1.6$ in

magnitude. These differences are within acceptable limits for NBS values

of total luminous flux, even today. (The current NBS goal is an accuracy

of 2-§# for reported values of total luminous flux, for incandescent

lamps .

)

Integrating spheres are now universally used in photometric laboratories to compare the total luminous fluxes of lamps of all types. NBS

for example, uses at present two 2-meter (79-inch) diameter spheres, one

76-cm (30-inch) sphere, and one 30-cm (12-inch) sphere, to compare the

total luminous fluxes of incandescent lamps emitting from 10,000 lumens

to 6 lumens.

The purpose of the analysis presented in this paper is: (1), to

pinpoint the major sources of error in comparing the total luminous

fluxes of lamps with the integrating sphere; (2), to estimate the magnitude of the errors in the present NBS techniques for comparing the total

luminous fluxes of incandescent lamps with the integrating sphere; (3),

to show how the errors described in (1) and (2) may be minimized.
2. Current NBS Techniques for Comparing the Total

Luminous Fluxes of Lamps with the Integrating Sphere

Figure 1 shows the cross section of a typical integrating sphere

with the baffle and a lamp inside the sphere. The lamp (whose total

luminous flux is to be compared with that of another lamp) is located at

the center of the sphere; the baffle is placed between the sphere window

and the lamp so that it completely screens the lamp from the window.

The baffle is usually placed roughly l/3 the sphere radius from the

lamp, since calculations have shown that this distance will approximately

minimize the error in comparing the total luminous fluxes of two lamps

t^-J. Usually, the substitution technique is employed; that is, if the

total flux of lamp A is to be compared with that of lamp B, the detector

output is measured with only lamp A in the sphere, and then with only

lamp B in the sphere.

The correction for the difference between the absorptances of lamps

A and B is found approximately by Helwig's method |j?D» which uses an

auxiliary lamp placed in the sphere near the wall. Lamps A and B are

successively placed in the sphere with the auxiliary lamp (which is

shielded so that none of its flux strikes either the sphere window, or A

or B, directly). The lamps A and B are unlit , and the correction for

the difference between the absorptances of A and B is approximately the

ratio of the detector outputs produced by the auxiliary lamp when first

A, and then B, is placed in the sphere.

The diameter of the integrating sphere used to measure the total

luminous flux of a lamp, depends upon the magnitude of the lamp's flux

output. As will be shown later, if the sphere is too large, the
detector signal will be too small, if the sphere is too small, the sphere

error will be too large. At NBS, lamps emitting between 270 and 10,000

lumens are measured in a 2-meter diameter sphere; lamps of smaller flux

output are measured in either the 76-cm or the 30-cm sphere.

At present, only tungsten-filament incandescent lamps are calibrated

for total luminous flux on a regular basis at NBS [6]].

The internal surfaces of the NBS integrating spheres (and the surfaces of the baffles) are coated with paints of high reflectance which

reflect in an approximately uniformly diffuse manner. (A surface which

reflects - or emits - in a uniformly diffuse manner is defined as a surface which has the same luminance in all directions.) One 2-meter diameter sphere is painted with a thick coating of barium sulfate; the other

2-meter sphere - and the 76-cm and 30-cm spheres - is coated with Burch

sphere paint (Burch Paint Mfg. Co., 10609 Briggs Road, Cleveland, Ohio

4^111) . The spectral reflectance of Burch sphere paint varies with

wavelength, falling off towards the blue end of the visible spectrum £7]].

(The spectral reflectance of barium sulfate is more uniform over the visible spectrum than that of Burch sphere paint C8j.) The net effect of

this varying spectral reflectance is to reduce the color temperature of

the illumination at the detector from that of the lamp in the sphere, by

a large amount. (For example, the color temperature of the illumination

at the detector, produced by a 2856 K lamp in the sphere, is reduced by

700 K - including the effect of the sphere window [°].)

This reduction in the color temperature of the illumination at the

detector from that of the lamp, due to the decreasing spectral reflectance

of Burch sphere paint towards the blue end of the visible spectrum,
produces an error in comparing the total luminous fluxes of two lamps with

different color temperatures. To compensate for this effect, a blue

filter (Corning 5900 glass; Corning Glass Works, Corning, N.Y. 14830) is

used to make the net spectral transmittance of the sphere (from the lamp

to the detector) approximately independent of wavelength. Calculations

show that the spectral reflectance of an integrating sphere coated with

Burch sphere paint can be neutralized sufficiently by this technique, to

reduce the error due to this cause , in comparing lamps having color

temperatures of 2360 K and 3000 K, to less than 0.2$.
3. Elementary Sphere Analysis

Elementary integrating sphere analysis has been presented in the

literature £lOJ. The first step is to compute the luminance distribution in an empty sphere.

3.1. Empty Sphere Luminance Distribution

Refer to figure 2 and let a be the colatitude angle of a source point

P(a) on the sphere wall; let 9 be the colatitude angle of a detection

point on the sphere wall. (The azimuth angles of the source point and

the detection point are ignored, since the sphere wall reflectance is

assumed to be spatially uniform, and hence the sphere is symmetric about

the polar axis.)

It is assumed throughout this paper that the sphere wall and the

baffle surfaces reflect in a uniformly diffuse manner. This means that

the luminance of an element of surface area is independent of the direction

from which it is viewed.

(The luminance, in a given direction, of an element of surface area,

is defined to be the quotient of the luminous flux leaving the surface

through an element of solid angle in the given direction, divided by the

product of the element of solid angle and the projection of the element

of surface area in the given direction. Symbolically, the luminance L

is defined as

L - lira [(6

20)/(6a»6AcosG)],

6a -K)

6A->0

where 6 is the element of luminous flux leaving the element of surface

area 6A, through the element of solid angle 6o, in a direction inclined

6
at angle 8 to the normal to the element of surface area.)

Let the reflectance of the sphere wall be r, and let the luminance

of the sphere wall at D(6), produced by a 1 lumen source input at P(a)

,

be denoted L(a,9). The 1 lumen source input at P(ct) produces a secondary source of luminous intensity r/n candelas at P(cl); this secondary

source illuminates the wall of the, sphere with a uniform illuminance of

r/(^TTR ) lux (neglecting multiple reflections). To demonstrate that

this illuminance is uniform, refer to figure 2 and consider the chord PD.

The length of PD, denoted Pi), is 2Rsin(p/2) ; the angle between the normal

to the sphere at P(cl) and the chord PD is L = tt/2 - p/2 ; this is also

the angle between the normal to the sphere at D(6) and the chord PD.

Thus the illuminance at D(6) produced by the 1 lumen source input at

P(a) , denoted E(a,0), is given by

E(a,9) «= (r/TT)(PD)"2cos

2

E;

since

PD2

= ZfR2

COS2

2,

the equation for E(a,G) becomes

E(a,9) - rC^TTR

2 )"1

,

and so it is seen that E(a,6) is indpendent of the positions of P(a) and

D(8) , as desired.

Thus the illuminance at any point on the sphere wall, produced by a

source input at any other point on the wall, is independent of the positions of the source point and the detection point, when the reflectance
of the sphere wall is spatially uniform and uniformly diffuse. Stated

in another way, the viewfactor of unit area on the sphere, as viewed from

any point on the sphere, is constant and equal to l/(^TTR ). (The viewfactor of a surface A-., as viewed fran surface A-, is defined as the

fraction of the total flux emitted by A

? which is incident upon A-,, assuming that A

?

radiates in a uniformly diffuse manner. The concept of viewfactor is also useful in radiometry and heat exchange.)

The constant viewfactor of any. area of the sphere, as viewed from

any point of the sphere, is the basic property which makes the empty

sphere, with walls of spatially uniform and uniformly diffuse reflectance,

a perfect flux integrator.

Now it is necessary to consider the interreflections in the sphere.

It is seen that the uniform illuminance over the wall of the sphere , E

(dropping the functional dependence notation), produced by the 1 lumen

source input at P(a), in turn produces a luminance distribution L

1 which

is also uniform. It is clear that

L» = rE/u = r2/(4A2

).

The uniform luminance distribution L

1 in turn produces a uniform

illuminance over the sphere wall, E

1 , which is given by

9 i n 2

E» = ZniUBr)'1

! dG'sine'L'R ;

this reduces to

E

t = r

2 /(^nR2

),

which is equivalent to

8
E« - rE.

Thus it is seen that the uniform illuminance in the sphere produced

byj the n-th reflection from the wall, E , is related to the initial illu- n minance from the source point, E, by the equation,

E = r

1^.

n

Therefore the total illuminance in the sphere, E„

CT , is also uniform

and is given by

E

TCT

= E

n^0r •

which reduces to

E

TQr =E/(l-r).

Consider now instead of a point source input, the input illuminance

distribution E ( ct) . The total input flux, 0* , is

0fjj « 2nR^ da'sina'EIN

(a«).

The total illuminance over the sphere wall produced by E

IN (a) is therefore

( excluding the input illuminance)

TT -1 n?-1

E

TOr

= r(l-r)-x

/ da»sina'E

IW (a')2

In terms of 0$M , it is seen from the preceding two equations that

IN

E

TOT

= ^r/L^-m^l-r)].

This is the basic integrating sphere equation ; it states that the

illuminance inside an empty sphere, with walls whose reflectance is

9
spatially uniform and uniformly diffuse, is proportional to the total

source luminous flux in any region of the sphere which is not directly

illuminated by the source .

Note that in this simple model, E^qt Decomes very large as the wall

reflectance r approaches 1; note also that E^QT decreases rapidly with

increasing sphere radius R.

A necessary condition on Emgj, is that it satisfy flux conservation;

that is, the total flux absorbed at the wall of the sphere, 0XITr

» must

equal the source input flux, 0* . To show that E satisfies flux

conservation, note that

*OUT " V"*2

' 1-1^1- " *h3.2. Introduction of the Baffle

Consider a source point P(a) which is screened from a detection point

D(6') by an infinitesimal baffle. The effect of such a baffle is to

eliminate the initial illuminance due to the source point P(a) at D(0').

Thus the total illuminance distribution in the sphere is no longer uniform,

and it is now a function of 6 as well as a. It is seen that, at a detection point D(6) which is not screened from the source point by the baffle,

the total illuminance (now denoted E(6) since it is a function of 6)

for a 1 lumen source input, is

E(G) TOT

= r/|>R6 (l-r)],

identical to the illuminance equation for the empty sphere given above.

However, for the screened detection point D(9'), it is clear that the

total illuminance, E(0') , for a 1 lumen source input, is

10
E(6') T0T =E(e)

TOT

- r/(W2

),

since the illuminance from the source point which is screened by the

2 baffle from the detection point is r/(4TtR ). Thus one arrives at the

result,

E(e-)

TOT

= r

2

/(>TTR

2 (l-r)].

The basic effect, therefore, of even an infinitesimal baffle is to screen

every point on the sphere from another point on the sphere; if a detection

point is screened from a source point, the total illuminance at the detection point due to the screened source point, is equal to the total

unscreened illuminance due to the source point multiplied by the spherewall reflectance r. Consider now the effect of a baffle of finite size. The baffle

clearly screens an area of the sphere wall from each point on the wall;

the screened area associated with each point is defined by the projection

of the baffle boundary from the point to the sphere wall. For a source

point P(cc) and a detection point D(O') screened by the baffle, the major

effect of the baffle is the screening of the initial i lluminance from

P(a) at D(6'). This effect is termed a "zero-order" effect, since it is

independent of the baffle area. For an accurate "first order" analysis

("first order" as used in this paper means the ratio of the baffle area

to the total sphere-wall area, a quantity assumed to be much less than 1)

,

several other effects must be considered (such as the flux reflected from

baffle surfaces, and the screening of sphere -wall areas which are not

source areas). These effects, however, vary as the baffle area and thus

are excluded from the elementary analysis of this section.

11
3.3. Effects of Absorbing Objects

The effects of introducing absorbing objects into the sphere are of

two types: first, the screening effect which was treated in an elementary

fashion above, and second, the absorption effect. This effect depends

upon the area of the absorbing object, and the absorptance of the object.

An elementary expression for the absorption effect can be derived from the

flux conservation requirement discussed in section 3.1.

Consider a source point P(a) in an empty sphere which generates the

uniform illuminance E

TOT over the wall of the sphere. If an absorbing

object of area A and absorptance X is introduced into the sphere, then the

illuminance in the sphere is no longer uniform, due to the screening effect

of the object. If the object is assumed to be opaque , with reflecting

surfaces of absorptance k (at any angle of incidence) , then the illuminance

at the detection point D(6), denoted E (a,8,X), is given approximately by

[l-(l-r)S(a,9)]

E

TOT

<*' e ^~ E

TOT^^^

where S(a,9) is the screening function of the object. This function is

defined to be 1 if the object intercepts the line connecting the source

point F(a) and the detection point D(6), and otherwise.

If the object is assumed to be transparent, with non-reflecting

surfaces, and to absorb the fraction X of the incident flux which strikes

it from any direction, then the illuminance at the detection point is

given approximately by

[l-A(l-r)S(a,e)]

E (a,e,A) = * -. T0T [l+U/(4T!R2 (l-r))]

12
4. Analysis: Sphere with Coaxial Disc Baffle

4.1. First Order Luminance at the Sphere Window

as a Function of Source Point Coordinates

In figure 3» a is the radius of the disc baffle B; the baffle axis

goes through the centers of the sphere and the lamp L; the plane of the

baffle is a distance h from the center of the sphere; the center of the

lamp is a distance 1 from the center of the sphere (1 is measured in the

opposite sense from h) ; the radius of the lamp is b, and R is the radius

of the sphere. The position of the source point P(a) is defined by the

colatitude angle a; a" is the colatitude angle of the projection on the

sphere wall of the center of the lamp, from P(ot); a is the colatitude

angle of the projection on the sphere wall of the center of the baffle,

from P(a) . The detection point is now taken to be the sphere window W

at the south pole of the sphere (that is, at 0=tt) . The luminance of the

sphere wall at the window, produced by a 1 lumen source input at P(oc) , is

denoted L,(a,TT,X); X is the absorptance of the lamp. The surface of the

baffle visible from the lamp is labeled the "north" surface, and has

reflectance r„. The surface of the baffle visible from the sphere window is labeled the "south" surface, and has reflectance r

s

. The lamp is

assumed to be transparent and non-reflecting, and to absorb the fraction

\ of radiation incident upon it from any direction.

The viewfactor of the baffle from the point P(a) is defined as the

fraction of the luminous flux reflected from P(a) which strikes the

baffle; this viewfactor is denoted F

fip

(a). Similarly, the viewfactor of

the lamp from P(a) is denoted F^a). The viewfactors of the baffle and

the lamp from the detection point at the sphere window, are denoted

13
F

BD

(n) and F^n), respectively.

At this point it is assumed (as suggested by Safwat £llj) that the

baffle radius a is much less than the sphere radius R; it is also assumed

that the radius of the lamp b is sufficiently small to ensure that no

luminous flux from the lamp reaches the sphere window directly (this is

the "screening condition"); thus the lamp radius b is also much less than

the sphere radius R. On the basis of these assumptions, therefore, it

is reasonable to compute the luminance produced at the sphere window by

a 1 lumen source input at P(a) , L-(a,n,X.), to terms of the first order in

the ratio of the area of the baffle to the sphere-wall area, and to neglect

terms of higher order in this ratio. Thus the first order luminance at

the sphere window produced by a 1 lumen source input at P(a) is found to

be ( note that this is the luminance within the sphere at the window)

< a < 26 .

x[l-(l-rs

)FBD(TT)-(l-rN

)FBp(a)-XFLp(a)]; (1)

26 < a < Y ,

Ljte.TT.X) m r^TT^G)"1

X[l-r( l-r

s

) FBD( tt) -r( l-r

N

) F

Bp

( a)

+r(2.r

s-r

N

)a'V1

+rX(b' 2

-F

Lp

(a))]; (2)

14
y < a < tt .

x[l-r(l-r

s

)FBD(n)-r(l-r

s

)FBp(a)

+r(2-r

s-r

N

)a« V1

+rX(b« 2

-FLp(d)

)

44(l-r)r

sF

BD

(TT)F

Bp

(a)a'"

2

]. (3)

In eqs (l)-(3)» the quantity G is

G = [(l-rJ+rU-rg-r^a'V1***^ 2

],

and

a' «= a/R, b' «= b/R;

in addition, referring again to figure 3t it is seen that 6 is the half

angle subtended by the baffle at the sphere window W, while Y is the

colatitude angle of the baffle plane.

The physical significance of the various terras in eqs (l)-(3) is as

follows

a. The term "+rr

N

F

B

p(a)" represents luminous flux from the source

point which strikes the north surface of the baffle, is reflected to the

sphere wall, and then is reflected to the sphere window.

b. The term M -rFRD(Ti)" represents luminous flux from the sphere

wall (excluding the direct flux from the source point) which is screened

from the sphere window by the baffle.

c. The term "-rF (a)" represents luminous flux from the source Br

15
point which is screened from the sphere wall by the baffle, and is thus

screened indirectly from the sphere window. (Note that the terms "a."

and "c." represent positive and negative effects, at the window, of the

same flux; for example, if r

N

«=l, then term "a." cancels term "c.".)

2 -1

d. The term "-r(r

s+rN

)a' k ", together with the same term in the

quantity G in the denominator, represents the luminous flux from the

sphere wall (excluding the direct flux from the source point) which

strikes the north and the south surfaces of the baffle, is reflected to

the sphere wall, and then is reflected to the sphere window.

2 -1

(Note that the net effect of the terms "-r(r

s +rN

)a' 4 " in the

numerator and the denominator is positive . For example, if the quantity

(1-r) is much larger than the magnitude of the remaining terms in G, then

G~ may be written to first order accuracy as

G"1 « (l-r)":L[l-r(2-r

s-r

N )a»V1

(l-r)~1-rXb ,2 (l-r)"1

].

When this expansion of G~" is multiplied the numerator, the term

2 -1

"-r(ro+rN

)a' k " in the numerator combines with the term

2 -1 -1 -1

"+r(r

s +rN

)a l k (1-r) " in the expansion of G

* to yield the net term

2 2 —1 -1

"+r (r

s +rN

)a l kT (1-r) " in the first order expansion of the product.)

2 -1

e. The term "+ra* 2 " , together with the same term in the quantity

G in the denominator, represents the luminous flux from the sphere wall

(excluding the direct flux from the source point) which is screened from

the sphere wall by the baffle, and is thus screened indirectly from the

sphere window.

2

f. The term "+rA,b' ", together with the same terra in the quantity G

in the denominator, represents the luminous flux from the sphere wall

16
(excluding the direct flux from the source point) which is partly

screened (since the lamp absorptance k is less than 1) from the sphere

wall by the lamp, and is thus screened indirectly from the sphere window,

g. The term "-rXF (a)" represents luminous flux from the source """ lor point which is partly screened from the sphere wall by the lamp, and is

thus screened indirectly from the sphere window.

h. The term "+rroFBD

(n)" represents luminous flux from the sphere

wall (excluding the direct flux from the source point) which strikes the

south surface of the baffle, and is reflected directly to the sphere

window.

i. The term "+rr

sFB

p(a)" has the same physical significance as term

"a.", "+rr

N

F

B

p(a)", except that the source point now illuminates the south

surface of the baffle.

j. The term "+iKl-r)rgFBD(^)FBp(a)a , " represents luminous flux

from the source point which strikes the south surface of the baffle, and

then is reflected directly to the sphere window.

Referring again to figure 3t it is convenient to denote the intersections of the baffle axis with the sphere as the "north" and "south"

poles; the north pole is marked N in figure 3t the south pole is marked

W, since the sphere window is located at this point. The photometric

detector D (in the typical photometric integrating sphere) is located at

the sphere window, but is placed outside the sphere; the detector views

the luminous flux transmitted through the translucent (diffusely transmitting and reflecting) window. (Filters required to match the spectral

responsivity of the sphere-detector system to the CLE. photopic luminosity function [l2~\, are placed between the detector and the sphere window.)

17
4.2. Lamp Flux Reflected from the Baffle

In figure 3i it is seen that if 1 lumen is incident upon the north

surface of the baffle, the resulting luminance at the sphere window,

denoted L, R

, is

L

1B

m r

N

2^0d6,Sine,F

BD

(e,)Ll

(e, ' TT ^) ^

, "2-^r

N

F

LBi:i

(0 ' TT »^-

In this equation, F^g is the viewfactor of the lamp as viewed from the

baffle, L^CO^TTjX) is the luminance produced at the sphere window by a 1

lumen source input to the sphere wall at a point whose colatitude angle

is 8

1 , and L,(0,tt,X) is the average luminance produced at the sphere

window, by a 1 lumen source input which illuminates uniformly the area of

the sphere wall defined by the projection of the lamp from the center of

the baffle, onto the sphere wall. (The preceding equation for L^g is

approximate, and valid to first order only. Note that F

LR is of first

2

order in a 1 , and that for an extended source distribution, the fraction

of the total source flux emitted by the baffle can reasonably be assumed

to be also of first order; thus for an extended source distribution, the

term involving F, R becomes of second order and hence may be discarded in

a first order analysis.)

4.3. Extended Source Distributions

If the source illuminance on the sphere wall is denoted E(a) , the

total lamp flux 0£ (lumens) is given by the equation,

0£ - 2TTR^/ de«sine«E(e')-Hlf*B (l-rN

), (4)

where 0* is the lamp flux which strikes the baffle. The luminance L^

18
produced at the sphere window by this lamp flux is therefore

TT L

T » 2TiR'd/ de«sine«E(G')L1

(e , ,TT,X).

It is useful to define the ratio of the luminance at the sphere

window to the lamp flux which produces that luminance; denote this ratio

k t so that

k = I^/0£.

It is seen from the preceding equations that k is given in terms of E(a)

by the equation,

2TTR

2

/ nd9 • sine »E( 6 • )Lt ( 6

« ,n,X)

k = *-# i . (5)

2TTR^/ d9 'sine »E( G ' )-^*

B (i-rN

)

It is convenient now to normalize the lamp flux to 1 lumen, for

comparing lamps of different illuminance distributions. Then eq (5)

becomes

,

k «= 2TTR^/ de»sine»E l (e»)L1(e«,TT,X) f

where E'CG*) is the normalized source illuminance distribution on the

wall of the sphere.

Consider now two different lamps, A and B, whose total luminous flux

ratio is desired. The the fractional error 6k' in the ratio of the

sphere-window luminances, WrA*TM* compared with the true total luminous

flux ratio, ^Tu/^fj,* ^s defined,

6k- - (kg-V/V

19
If the normalized illuminance distribution of lamp A is E ' ( 9

' )

, and

that of lamp B is E*(9')t then it is seen that

/Sde'sinelE^ceML^ce'.TT^j-E^e'^O'.TT,^)]

* 1 & LI _| I 1_ | 1M III , L /Sde'sine'E^e^L-^ce'.TT,^)

6k» = -2 -S S -^-. (6)

k.k. Extended Source Distributions: Approximate Model

To compute the fractional error in the ratio of the sphere-window

luminances of two different lamps, with respect to the ratio of the total

luminous fluxes of the lamps, one may of course use experimental lamp-illuminance distribution data, if these are available. Another approach is

to use a model distribution to approximate the true lamp illuminance distribution. A useful one-parameter model distribution is the cardioid,

E«(6) = (l4g(9)cos9)/(4nR2

);

the parameter g(G) is assumed to be a random variable such that

J"od9'sin0»g(9')cos9' = 0. (7)

If the above cardioid lamp illuminance distribution is substituted

into eq (4) for the total lamp flux 0£, then it is seen that the total

lamp flux is independent of g(9), provided it satisfies eq (7) and that

the lamp flux which strikes the baffle, 0j*g, is also independent of g(9).

Assume now that the two different lamps, A and B, have the following

parameters: lamp A is characterized by X. , b. , and gA

(6); lamp B is characterized by X^, bp, and g (6). Now substitute these values into eq (6)

for 6k 1 , refer to eqs (l)-(3) for L-,(9,n,X), and use the normalization

condition (that is, the total flux from both lamp A and lamp B is 1 lumen)

20
to obtain the approximation,

AC

6k« «G-1[r(xAy

2-xB

b^2 )+(i-r) 2

/ode« S ine'cose'(gA

(e«)-gB(e«))2-1

3, (8)

where

G

B

= [(l-rJ+rCE-rs-r^a'V1^^2

],

and it has been assumed further that lamps A and B have similar illuminance distributions in the sense that the average value of the difference

between their normalized fluxes, over any area of the sphere, is never

larger in magnitude than a first order quantity.

It is helpful to consider the physical significance of the terras in

eq (8) at this point. The first term,

i 2 x hi 2. r<i^-^)A>B

.

represents the difference between the fraction of its total luminous flux

absorbed by lamp A, and the fraction of its total luminous flux absorbed

by lamp B. This is seen from the fact that the flux absorbed by the

sphere wall is proportional to tynR (1-r), the flux absorbed by lamp A is

2 proportional to ^nrX. b. , the flux absorbed by lamp B is proportional to

2

^TTrX^bo, and the flux absorbed by the baffle is proportional to

nra

2 (2-r

s-rN

).

The second term,

(i-r)

/iG-1

/ de'sine«cose'(gA

(e«)-gB (e»))2 \

represents the difference between the fraction of its total luminous flux

absorbed by the screened region of the sphere wall for lamp A, and the

21
fraction of its total luminous flux absorbed by the screened region of

the sphere wall for lamp B.

It should be noted that this analysis of the physical significance of

6k 1 (for sources of similar illuminance distributions) is independent of

the positions of the lamps and the baffles within the sphere, provided

that the first order approximation is valid; that is, the lamps and the

baffles may have any position within the sphere for which the lamps are

screened from the sphere window and from each other, and for which all

the interaction viewfactors (the viewfactors of the baffles and the lamps

as viewed from the sphere wall and from each other) are of the first order.

If these conditions are fulfilled, then the sphere error 6k 1 in comparing

the total luminous fluxes of lamps A and B is given to first order accuracy by the formula,

6k 1 « [(Fractional Flux Absorbed by A)

-(Fractional Flux Absorbed by B)

+( Fractional Screened Flux of A Absorbed)

-(Fractional Screened Flux of B Absorbed)]. (9)

Eq (9) is not valid, of course, if the illuminance distributions of lamps

A and B differ widely.

In most practical cases, the sphere-wall absorptance is much larger

than the lamp and the baffle absorptances ; this means that

(1-r) » [r(2-r

s-rN

)a« V^rXb*2

].

If this inequality holds, then 6k 1 becomes approximately,

OX

ok' m [r(^2-AB

b^

2 )(l-r)-1

-Kl-r)/ de'sine'cose'(g

A

(e , )-gB(e'))2-1

]. (10)

22
Now define an average value of (gA

(6)-gg(6)) over the screened

region of the sphere wall by the formula,

_ _ At

(gA

(0)-gB

(e)) sc

<= (2sin

z6)'1

; de'sine'cose'(gA

(e«)-g

B

(e«)).

Then eq (10) for 6k 1 can be written,

6k' « [r(XA

b|24^2)(l-r)-

1

+(l-r)(g

A

(e)-gB

(e))scsin

2

6];

this formula assumes that the magnitude and the sign of the average value

of (g.(9)-gR (9)) over the screened region of the sphere wall are known;

usually this information is not available, and it is reasonable to consider (gA

(9)-gB

(6)) sc

as a random variable. In this case, the two components of 6k' should be added in quadrature, so that the formula for 6k 1

becomes,

6k' « [(r(4bA

2-^2 )(l-r)-1

) 2+((l-r)(gA

(e)-g

B

(e)) sc

sin

2

6)

2

]. (11)

4.5« Optimum Baffle and Lamp Positions to Minimize

the Error in Measuring Total Luminous Flux

Referring to figure 3 and eq (9) » it is seen that the sphere error

6k' can be reduced by decreasing the magnitude of the fractional screened

fluxes of lamps A and B. It is also clear from figure 3 that the fractional screened flux is a function of the positions of the baffle and the

lamp within the sphere. Note particularly that in the general case,

where a fraction of the lamp flux is directly incident upon the north

surface of the baffle, the fractional screened flux includes that incident upon the baffle. If the lamp illuminance distribution is spherically uniform, then the fractional screened flux is equal to the sum of:

23
(1), the fractional solid angle (that is, the fraction of a complete sphere]

subtended by the projection of the baffle from the sphere window onto the

sphere wall, at the lamp center; plus (2), the fractional solid angle

subtended by the baffle at the lamp center. (A more realistic situation

is a spherically uniform lamp illuminance distribution up to a limiting

colatitude angle which may - or may not - include part of the baffle.)

Thus it is desired to find the baffle and lamp positions which will minimize the sum of (1) and (2) above; this is equivalent to minimizing the

total screened solid angle, as viewed from the lamp center. It can be

shown that this total screened solid angle is approximately equal to

na« 2[(h , +l , )"2-+4(l-h l )"2(l-l«)"2

], where h'«=h/R and l'KL/R.

The positions of the baffle and the lamp which minimize the preceding

expression for the total screened solid angle, viewed from the lamp center,

are found to be

h' - 1« - 0.212.

Thus the optimum positions of the baffle and the lamp when the lamp

illuminance distribution is spherically uniform, are: (1), the baffle

placed 0.212 of the sphere radius from the center of the sphere, and 0.788

of the sphere radius from the sphere window; and (2), the lamp center

placed 0.212 of the sphere radius from the center of the sphere, and 1.212

of the sphere radius from the sphere window; both the baffle and the lamp

are assumed to be coaxial with the sphere axis which passes through the

center of the sphere window.

If the lamp position is fixed, and only the baffle position is varied,

then to every lamp position corresponds a baffle position which minimizes

24
the total screened solid angle; for a spherically uniform lamp illuminance

distribution, the optimum values of h

1 and l

1 are related by the equation,

1 h' ^[(l-l')2 /3^1/3]/^!-!') 2 /^1/^.

If, for example, l'«=0 (the lamp at the center of the sphere), then the

optimum value of h

1 is 0.386.

Now assume that the lamp has a spherically uniform illuminance distribution up to a limiting colatitude angle which excludes the baffle; in

other words, no lamp flux strikes the baffle directly. Then it is found

that the optimum baffle and lamp positions are

h« - l

1 - 0;

that is, the baffle and the lamp should both be located at the center of

the sphere. (Note that the optimum values of h

1 and 1* derived above

for a coaxial baffle and lamp configuration, also hold for baffle and

lamp positions along any chord of the sphere emanating from the sphere

window, except that h

1 and 1* must be replaced by h'cosE and l'cosE,

respectively, and these displacements along the chord are referenced to

the chord center, which is a distance RcosE from the sphere window; here

Z is the angle between the chord and the sphere axis coaxial with the

sphere window.)

^.6. Upper Bound on the Fractional Sphere Error

Eq (11) shows that: (1), if two lamps have the same fractional

absorptance, the dominant term in the error in comparing their total

luminous fluxes in an integrating sphere (if they have similar illuminance

distributions) is the difference in their fractional screened fluxes; (2),

25
if two lamps have the same fractional screened flux, the dominant term in

the error in comparing their total luminous fluxes is the difference in

their fractional absorptances.

It is useful to estimate an upper bound for the fractional sphere

error in present NBS techniques for comparing the total luminous fluxes

of 1000-watt incandescent lamps in a 2-meter integrating sphere f93-

The geometry employed is as follows: the baffle is placed 0.55 meter from

the sphere window and is shaped roughly like a projection of the 1000-watt

lamps; the baffle dimensions are 0.15 meter by 0.23 meter (the equivalent

radius is 0.093 meter, to yield the same area); the lamps are separately

placed at the center of the sphere for total flux measurement (that is,

only one lamp is in the sphere at the time of measurement) ; the radius of

the lamps is roughly 0.08 meter. The reflectance of the sphere wall and

of the baffle surfaces is assumed to be 0.90 £7j. To proceed further,

it is necessary to introduce the following reasonable assumptions: (1),

the difference in the absorptance A. of the lamps is less than 0.05; (2),

the magnitude of the quantity (g.(6)-g^6)) is less than 0.5 (that is,

the fractional screened fluxes of the lamps differ by less than half the

fractional screened flux of a lamp of spherically uniform illuminance

distribution)

.

With the preceding assumptions, eq (11) for the fractional sphere

error 6k' yields 0.29% for the component of the sphere error due to the

difference in fractional lamp absorptance, and 0.13$ for the component of

the sphere error due to the difference in fractional screened flux.

Adding these two components in quadrature, as indicated in eq (11), yield!

an estimated upper bound of 0.32% for the fractional sphere error in

26
present NBS techniques for comparing the total luminous fluxes of

1000-watt incandescent lamps in a 2-meter integrating sphere.

^.7. Factors Neglected

The preceding analysis has neglected several factors and their

effects on the sphere error in comparing the total luminous fluxes of

lamps in the integrating sphere. These factors are: (1), varying spectral reflectance of the sphere and the baffle coatings, (2), varying

spectral absorptance of the lamp, (3)* spatial variations in the spherewall reflectance, (k) , specular component of the sphere-wall reflectance,

(5)» reflectance of the lamp, (6), deviations of the sphere-window transmittance from the cosine law, (7), detector signal-to-noise considerations,

(8), deviations of the sphere wall from perfect sphericity.

Referring to eq (11), it is seen that the effect of increasing the

spectral reflectance of the sphere wall is to increase the fractional

fluxes absorbed by the lamps (whose total luminous fluxes are to be compared) , and to decrease the absorption of the fractional screened fluxes

of the lamps. It is also seen from eq (H) that the effect of increasing

the spectral absorptance s of the lamps is to increase the fractional

fluxes absorbed by the lamps.

Theoretically, if the spectral distributions in the visible are

given of, (1), the spectral reflectance r(X) of the sphere wall (X is the

wavelength), (2), the spectral absorptances k^(k) and X^(X) of the lamps

A and B, (3)» the spectral transmittance t(X) of the sphere window, and

(4-) , the spectral luminous fluxes of the lamps, JK^) and J'(X), normalized to unit luminous flux, then the average sphere error over the visible

27
spectrum, 6k 1 , can be computed.

The approximate formula for 6k 1 is (accurate to first order, and

assuming that lamps A and B have similar spectral luminous flux distributions) :

A.2 6kT « (U^1dk^r(X l )t(X i )(lM^)r\j^ t )-Jl(k l ))f

X.2 ^f/^dX'r^XOtCX^Cl-rCX'))-^^^')^^')^2-^^*)^2

)]

2

+f/x^dX'r(X»)t(X')J|(X')sin2

6(gA

(e)-g

B

(e)) sc]

2

)

- 5

,X2 1 -1

X(/udX'rU')tU«)(l-r(X')) L

) \ (12)

Eq (12) is analogous to eq (11) for 6k* in that the error components are

treated as random variables and hence are added in quadrature to obtain

the total sphere error 6k'; X, and X~ are the limits of the visible spectrum (approximately 0.38-0.78 micrometer Ziz]) ; JiM and «U(X) are normalized so that

X2 X2

/udX«J|(X«) <=/udA'J£(X«) -1.

Spatial variations in the reflectance of the sphere wall may be a

significant source of error. Experimental work is needed to establish

the magnitude of this effect.

The specular component of the sphere-wall reflectance is estimated

to produce a second order sphere error in comparing the total luminous

fluxes of two lamps of similar illuminance distributions; hence this

error can be neglected in a first order analysis. (To ensure the validity of this assumption, the baffle must be of adequate size to make the

28
maximum angle of reflection, from the portions of the sphere wall directly illuminated by the source, to the sphere window, less than the critical angle at which specularity effects become important.)

The effect of luminous flux reflected from the lamp bulb is estimated

to be negligible for extended sources.

The deviations of the sphere window from cosine-law transmittance

(that is, from uniformly diffuse transmittance) are probably a significant

source of error, except where the lamps compared have very similar illuminance distributions. Probably the best procedure (if the illuminance

at the sphere window is high enough to provide an adequate signal-to-noise

ratio at the detector) is to remove the window and replace it with a

small auxiliary integrating sphere; the inner surface of this auxiliary

sphere is then viewed by the detector.

Detector signal-to-noise considerations are important in limiting

the maximum sphere diameter which can be used to compare lamps of a given

flux output. At NBS, for example, the 2-meter diameter integrating

sphere is not used to measure total luminous fluxes of less than 200

lumens [?j. Thus to optimize the accuracy of measurements of total

luminous flux, the sphere diameter should be roughly that which equalizes

the magnitudes of the computed sphere error 6k • , and the measurement error

due to detector noise.

The effect of deviations of the sphere wall from perfect sphericity,

on the sphere error in comparing two lamps of similar illuminance distributions, can be shown to be of second order (and hence negligible) for

deviations which consist of flattened portions of first order area (that

is , the area of each flattened portion is comparable with the baffle area)

29
5. Conclusions

The approximate mathematical theory of the photometric integrating

sphere, developed in section 4, leads to the following conclusions:

For typical sphere parameters, the fractional sphere error in comparing the total luminous fluxes of two incandescent lamps is probably

less than 0.2$ if: (1), the viewfactor of the baffle from the sphere window is less than 0.025; (2), the lamp flux directly incident upon the

baffle is negligible; (3)» the lamps compared have similar illuminance

distributions; (k) , the lamp dimensions are similar; (5)» the lamp absorptances differ by less than 0.02; (6), the total flux of each lamp is measured with only that lamp in the sphere (the screening effect and the

absorptance of the other lamp introduce errors if it is also present in

the sphere).

30
6. References

£l3 Ulbricht, R., Die bestimmung der mittleren raiimlichen lichtintensitat durch nur eine messung, Elektrotechnische Zeit. 21, 595

(1900).

£zj International Lighting Vocabulary (Bureau Central de la CIE, Paris,

1970).

[33 Ulbricht, R., Das Kugelphotometer , pp. 1-12 (R. Oldenbourg, Munich

and Berlin)

[V] Rosa, E. B., and Taylor, A. H., Theory, construction, and use of

the photometric integrating sphere, Sci. Papers Natl. Bur. Stand.

(U.S.) 18, 281 (Aug. 1922).

[53 Keitz, H. A., Light Calculations and Measurements, p. 3^5 (MacMillan

and Co., New York, 1971).

[6] Natl. Bur. Stand. (U.S.), Tech. News Bull. $6, 153 (June 1972).

[7l Private communication from V. I. Burns of the NBS Optical Radiation

Section.

£8^ McSparron, D., Mohan, K., Raybold, R. , Saunders, R., and Zalewski,

E., Spectroradicmetry and Conventional Photometry, an Interlaboratory Comparison, Natl. Bur. Stand. (U.S.), Tech. Note 559, p. 186

(Nov. 1970).

£9} Burns, V. I., and McSparron, D. A., Photometric Calibration Procedures, Natl. Bur. Stand. (U.S.), Tech. Note 59^3, p. 21 (Nov. 1972).

£l03 For a typical presentation see: Walsh, J. W. T., Photometry, chap.

(Dover Publications, Inc., New York, 1958).

£ll3 Safwat, H. H., Effect of centrally located samples in the integrating sphere, J. Opt. Soc. Am. 60, 53^ (April 1970).

£l23 American Institute of Physics Handbook, 3rd ed., chap. 6, p. 18^

(McGraw-Hill Book Co., New York, 1972).

31
Figure 1. Cross section of typical integrating sphere:

B-baffle, D-detector, F-filter, L-lamp f W-window,

32
V

^^

Figure 2. Cross section of empty sphere; viewfactor geometry.

33
D

Figure 3. Integrating sphere geometry: B-baffle, D-detector, L-lamp,

N-north pole, P( a) -source point, R-sphere radius, W-sphere

window; a-baffle radius, b-lamp radius, h-displacement of baffle south of sphere equator, 1-displacement of lamp north of

sphere equator; a-colatitude angle of projection of baffle

center from P(a) to opposite sphere wall, a"-colatitude angle

of projection of lamp center from P(a) to opposite sphere

wall, 6-half angle subtended by baffle at window, Y-colatitude angle of baffle plane intersection with sphere.

3*
FORM NBS-114A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN 594-72. Gov t Accession No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE OPTICAL RADIATION MEASUREMENTS;

Approximate Theory of the Photometric Integrating Sphere

5. Publication Date March 1974

6. Performing Organization Code

7. AUTHOR(S) W. B. Fussell 8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Task/ Work Unit No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same as No. 9

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) An approximate mathematical theory of the photometric integrating sphere is developed. The analysis is accurate to the first order in the ratio of the baffle area to

the sphere wall area. The sphere is assumed to be occupied by a circular baffle and a

spherical lamp; the centers of the baffle and the lamp lie on a diameter of the sphere.

The surfaces of the sphere and the baffle are assumed to reflect in a uniformly diffuse

manner. The lamp is assumed to absorb a fraction of the radiation incident upon it, and

to transmit (or specularly reflect) the remainder. The luminance distribution at the

sphere window is derived for a general source input at any point of the sphere wall.

A model lamp illuminance distribution is assumed, and a formula for the fractional error

in comparing the total luminous fluxes of two lamps in the integrating sphere, is

derived. The physical significance of the formula is described.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Illuminance distribution; integrating sphere; lamp comparisons; photometric

accuracy; photometry; total luminous flux.

18. AVAILABILITY STATEMENT

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*eP.

Tables of Diffraction Losses

W. B. Fussell

Heat Division

Institute for Basic Standards

M . S, National Bureau of Standards

'" Washington, D.C. 20234

TeJiM a \£a$) nofe no. 5^^-g

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

issued June 1974
Library of Congress Catalog Number: 74-600088

National Bureau of Standards Technical Note 594-8

Nat. Bur. Stand. (U.S.), Tech. Note 594-8, 39 pages (June 1974) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1974

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.46:594-8). Price 75 cents.
Preface

This is the eighth issue of a series of Technical Notes entitled

OPTICAL RADIATION MEASUREMENTS. The series will consist primarily of

reports of progress in, or details of, research conducted in radiometry

and photometry in the Optical Radiation Section of the Heat Division.

The level of presentation in OPTICAL RADIATION MEASUREMENTS will be

directed at a general technical audience. The equivalent of an undergraduate degree in engineering or physics, plus familiarity with the

basic concepts of radiometry and photometry [e.g., G. Bauer, Measurement

of Optical Radiations (Focal Press, London, New York, 1965)], should be

sufficient for understanding the vast majority of material in this

series. Occasionally a more specialized background will be required.

Even in such instances, however, a careful reading of the assumptions,

approximations, and final conclusions should permit the non-specialist

to understand the gist of the argument if not the details.

At times, certain commercial materials and equipment will be identified in this series in order to adequately specify the experimental

procedure. In no case does such identification imply recommendation or

endorsement by the National Bureau of Standards, nor does it imply that

the material or equipment identified is necessarily the best available

for the purpose.

Any suggestions readers may have to improve the utility of this

series are welcome.

Henry J. Kostkowski, Chief

Optical Radiation Section

National Bureau of Standards

111
Contents

Page

1. Introduction 1

2. Tables of Diffraction Losses as Functions of

Wavelength and Geometry 3

3. Scaling the Diffraction Loss Tables 22

4. Effective Wavelengths to Use in the

Diffraction Loss Tables 22

5. Sample Diffraction Loss Calculations 23

5.1. Sample Diffraction Loss Calculations

for a Simple Case 2 3

5.2. Sample Diffraction Loss Calculations

for a Complex Case 23

6. Formulas Used for Computing the Diffraction Loss Tables. ... 26

7. Estimated Accuracy of the Diffraction

Loss Tables 29

8. References 30

Figures

Figure 1. Diffraction geometry used in the

diffraction loss tables 31

Figure 2. Diffraction geometry for the sample diffraction

loss calculations: complex case 32

Figure 3. Diffraction geometry used in the general

diffraction loss formulas 33

IV
Tables of Diffraction Losses*

W. B. Fussell

Tables of diffraction losses are given for

a range of typical experimental geometries for

wavelengths from 0.2 to 100 micrometers. The

scaling relationships for the diffraction losses

for varying wavelengths and geometries are also

given, and sample calculations are presented.

General formulas are given for the diffraction

losses; the formulas are derived from the

Kirchhoff scalar paraxial diffraction theory.

The accuracy of the tabulated values is estimated.

Key words: Diffraction; diffraction losses; Fresnel

diffraction; Kirchhoff diffraction theory; photometry; radiometry; scalar diffraction theory.

1. Introduction

With the improved precision and accuracy of radiometric measurements, diffraction losses have become significant. It is useful, therefore, to compute and tabulate diffraction losses for a range of typical

geometries and wavelengths, The Kirchhoff scalar paraxial diffraction

theory is used to calculate these losses. This is an approximate model

which evaluates the phase relationships over the diffracting aperture

(see fig. 1) for each elemental source area, for a given detection point

and wavelength; the resulting complex number is then integrated over the source area and the magnitude of the sum indicates the relative spectral

irradiance at the given detection point, compared with other detection

points on the detector area. The model assumes: a., all source points

radiate independently (that is, incoherent radiation); b., there are no polarization effects (that is, no vector effects); c. , off-axis angles

are small, and hence obliquity effects can be neglected. (Section 6 outlines the derivation of the equations used to compute the tables.)

The mathematical formulas used to compute the diffraction losses are refinements of the basic Fraunhofer on-axis diffraction formula (see

1 Blevin [1]

1 ) . The tabulated on-axis diffraction losses are estimated to

be accurate to within 10% mathematically; the off-axis diffraction losses

are estimated to be accurate to within 20%. (If the physical realities

of an experiment differ from the assumptions of the. Kirchhoff model,

there will be additional errors besides those due tc the mathematical

approximations used to compute the tables; however, it is expected that

*Supported in part by the Calibration Coordination Group of the Department of Defense.

1 Figures in brackets indicate the literature references at the end of

this paper.
most situations in radiometry and photometry will be within the regime

of the Kirchhoff model. Blevin [1], for example, finds excellent

experimental agreement with the Kirchhoff model.) Thus, if it is

desired to calculate the off-axis diffraction loss for a given experiment

to within 0.1% of the spectral irradiance at the detector, then the

geometry of the experiment should be such that the tabulated diffraction

loss is less then 0.5% of the spectral irradiance at the detector, since

an error of 20% of 0.5% is equal to 0.1%.

The geometries and wavelengths selected for the diffraction loss

tables are:

a., wavelengths from 0.2 to 100 micrometers;

b., source (or detector) diameters from 0.5 to 5 cm;

c.

,

source (or detector) -to- aperture distances from 5 to 20 cm;

d.

,

aperture diameters from 0.005 to 0.5 cm.

The geometry and terminology used in the diffraction loss tables is shown

in figure 1.

In general, if the circumference of the circle produced by projecting the aperture from every point on the detector (the geometry in this

report is assumed to be circularly symmetric in all cases) , onto the

plane of the source, lies within the source, then the radiation incident

on the detector is proportional to the source radiance (less diffraction

losses) . On the other hand, if the circumference of the circle produced

by projecting the aperture from every point of the source, onto the plane

of the detector, lies within the detector, then the radiation incident on

the detector is the total source radiation through the aperture (less

diffraction losses) . (The diffraction losses for a given configuration

are identical, whether the source is treated as a detector and the detector as a source, or vice versa; this is sometimes a conceptual advantage

in that it transforms a source radiance measurement into a total aperture

radiation measurement.) In this report, the source radiance geometry

will always be meant unless it is explicitly stated that the total

aperture radiation geometry is under consideration.

For a given geometry, the diffraction loss in the plane of the detector is least on the axis; the diffraction loss increases steadily as the

distance from the axis increases (see sec. 6) . Therefore, the diffraction loss realized with a circular detector increases steadily as the

detector radius increases. The diffraction losses listed in the following tables are for the on-axis case (the "point" detector) , and also for

the case of a detector that sees 90% of the diameter of the source (the

radius of such a detector is designated x ). These diffraction losses,

designated E'. and E' r respectively, bracket the loss for detector

radii between zero ana x to within roughly ±20% for geometries where

the aperture diameter is much less than the source diameter, and more

accurately for ratios of the aperture diameter to the source diameter

2
larger than 0.1 (see the end of sec. 7).

2. Tables of Diffraction Losses as Functions

of Wavelength and Geometry

Terminology

A is the wavelength in micrometers.

d is the source diameter in cm (or the detector diameter, for

a total aperture radiation measurement; see sec. 1)

b_ is the source- aperture distance in cm.

D is the aperture diameter in cm.

v is the dimensionless quantity rrDd(2bA)~ .

E'. is the diffraction loss 1 for a point detector on- axis

whose distance from the aperture is at least 10 times

the source-aperture distance.

E'maxis the diffraction loss 1 averaged over the area of a circular detector of radius x _ (see sec. 1 and fig. 1)

the radius x is defined to De that radius for which

the field of view through the aperture covers the portion of the source disc whose ^diameter is 0.9 the source

diameter; the distance of the detector from the aperture

must be at least 10 times the source- aperture distance.

1 The diffraction losses E'. and E' are given as a percentage of the

irradiance that would be present at the detector in the absence of

diffraction. The mathematical formulas used to compute E". and E' are given in section 6. Upper bounds for the errors in E '.' and E

4 can be computed using the dimensionless quantity v, and formulas for

such computations are given in section 7.
X = Ch_2 (urn)

d = 0.5 (cm)

b

(cm;

D =

(cm)

005 01 .02 • 05 .1 .2 .5

v

(#)E'

mm

max

39-3

1.62

2.59

78.5

0.81

1.27

157

o.4i

0.62

393

0.16

0.24

785

0.08

0.12

1570

.05

.06

3930

10

20

v 19.6 39-3 78.5 196 393 785

E' . 3.2i+

min 1.62 0.81 0.33 0.17 0.10

E' 5-19

max

2.55 1.24 0.U7 0.23 0.13

v 9-82 19.6 39.3 98.2 196 393

E' . 6.49 3.24 1.62 0.66 0.3^ 0.19 mm

it max

<18* 5.09 2.48 0.95 0.47 0.25

I960

982

b

(cm)

d = 1 (cm)

(*)E'

(^)E'

mm

max

78.5

0.81

1.31

157

0.41

0.65

314

0.20

0.32

785

0.08

0.12

1570

o.o4

0.06

3140

0.02

0.03

7850

0.01

0.01

10

V 39.3 78.5 157 393 785 1570 3930

E' . 1.62 0.81 0.1+1 0.16 0.08 0.04 0.02 mm

' 1 max

2.62 1.30 0.61+ 0.25 0.12 0.06 0.03

20

V 19.6 39-3 78.5 196 393 785 I960

E' . 3.24 1.62 0.81 0.33 0.16 0.0b 0.04 mm

E' max

5.24 2.59 1.27 0.49 0.24 0.12 0.06

(Note: These values are upper bounds.)
X = 0^2 (ym)

d = 2 (cm)

b

(cm)

D =

(cm)

.005 01 .02 05 .1 .2 .5

v

(%)E« mm

max

157

0.41

0.66

314

0.20

0.33

628

0.10

0.16

1570

0.0U

0.06

31 40

0.02

6280

0.01

0.03 0.01

15700

0.00

0.01

10 v

E'I*

mm

max

78.5

0.8l

1.32

157

O.Ui

0.66

314

0.20

0.32

785

0.0b

0.13

1570

0.04

31 40

0.02

7850

0.01

0.06 0.03 0.01

20

V 39-3 78.5 157 393 785 1570 3930

E' . 1.62 0.81 0.1+1 0.16 0.08 0.04 0.02 mm

max

2.64 1.31 O.65 0.25 0.12 0.06 0.02

lb (cm)

d = 5 (cm)

v

WE'

mm

max

393

0.16

0.26

785

0.08

0.13

1570

0.04

0.07

3930

0.02

0.03

7850

0.01

15700

0.00

0.01 0.01

39300

0.00

0.00

10 vE' mm

max

196

0.32

0.53

393

0.16

0.26

785

0.08

0.13

I960

0.03

0.05

3930

0.02

7850

0.01

0.03 0.01

19600

0.00

0.00

20 v

E' mm

max

98.2

0.65

1.06

196

0.32

0.53

393

0.16

0.26

982

0.06

0.10

i960

0.03

3930

0.02

0.05 0.02

9820

0.01

0.01
X = 0^ (urn)

d = 0.5 (cm)

b

(cm;

D =

(cm)

v mm

max

005

15-7

4.05

6.1+8

.01

31. 4

2.03

3.18

.02

62.8

1.01

1.55

.05

157

0.1+1

0.59

.1 .2

314 625

0.21 0.12

0.29 0.16

• 5

1570

10

20

V 7.85 15-7 31.^ 78.5 157 311+ E' . _ mm 8.11 4.05 2.03 0.82 0.42 0.2U

E

1 max

^0* 6.37 3.10 1.19 0.59 0.32

V 3.93 7.85 15-7 39.3 78.5 157

E' . _ mm

- 8.U 1+.06 1.64 0.64 0.48

E' max

<20*

d =

6.19

= 1 (cm)

2.37 1.17 0.64

785

393

b

(cm)

10

20

(*)E«

(#)E~

mm

max

v

E*

E' min

max

v

E

T

. _ mm

E' max

31.4

2.03

3.28

15-7

4.05

6.55

7.85

8.11

<20*

62.8

1.01

1.62

31.4

2.03

3.24

15-7

4.05

6.48

126

0.51

0.80

62.8

1.01

1.59

31.4

2.03

3.18

314

0.20

0.31

157

0.41

o.6i

78.5

0.81

1.23

628

0.10

0.15

314

0.20

0.30

157

0.41

0.59

1260

0.05

0.07

628

0.11

0.15

314

0.21

0.29

3140

0.03

0.03

1570

0.05

0.07

785

0.11

0.14

*(Note: These values are upper bounds.)
A = 0.5 (ym)

d = 2 (cm)

b

(cm)

10

20

D = (cm)

v

(50e-

(%)!"•

mm

max

v

E

1

E' mm

max

v

E

1

E' mm

max

.005

62.8

1.01

1.65

31. h

2.03

3.30

15.7

4.05

6.59

.01

126

0.51

0.82

62.8

1.01

1.64

31.4

2.03

3.28

.02

251

0.25

o.4i

126

0.51

0.81

62.8

1.01

1.62

.05

628

0.10

0.16

3l4

0.20

0.32

157

o.4i

0.63

.1 .2 .5

1260 2510 6280

0.05 0.03 0.01

0.08 0.0U

628

0.10

0.15

314

0.20

1260

0.05

628

0.10

0.01

3140

0.02

0.07 0.03

1570

0.04

0.31 0.15 0.06

d = 5 (cm)

b

(cm)

V 157 314 628 1570 3140 6280 15700

5 We' . mm 0.41 0.20 0.10 0.04 0.02 0.01 0.00

(*)e«

max

0.66 0.33 0.16 0.06 0.03 0.02 0.01

V 78.5 157 314 785 1570 3140 7850

10 E' . 0.81 o.4i 0.20 0.08 0.04 0.02 0.01 mm

max

1.32 0.66 0.33 0.13 0.06 0.03 0.01

20

V 39.3 78.5 157 393 785 1570 3930

E' . 1.62 0.81 0.4l 0.16 0.08 0.04 0.02 mm

max

2.65 1.32 0.66 0.26 0.13 0.06 0.02
X = 1 (urn)

d = 0.5 (cm;

b

(cm)

D =

(cm)

.005 01 02 05 .1 .2 • 5

(*)E» min

max

7.85

8.11

<20*

15.

T

1+.05

6.37

31.1+

2.03

3.10

78.5

0.82

1.19

157

0.42

0.59

31U

0.24

0.32

785

10 v

E' mxn

max

3.93 7.85

8.11

<20*

15-7

4.06

6.19

39.3

1.64

2.37

78,5

0.84

1.17

157

0.48

0.64

393

20 vE' _ ]mm

1.96 3.93

max

7.85

8.12

<20*

19-6

3.28

4.74

39.3

1.69

2.34

78.5

0.96

1.27

196

d = 1 cm.

b

(cm)

V 15.7 31.4 62.8 157 314 628 1570

5 (Jt)E' . 4.05 2.03 1.01 0.41 0.20 0.11 0.05

10

20

(*)E

mm

? max

v

E* mm

1 max

v

E' mm

max

6.55

7.85

8.11

<20*

3.93

3.24

15.7

4.05

6.48

7.85

8.11

<20*

1.59

31.4

2.03

3.18

15.7

4.05

6.37

0.61

78.5

0.81

1.23

39.3

1.63

2.45

0,30

157

0.1+1

0.59

78.5

0.82

1.19

0.15

0.29

157

0.42

0.59

0.07

314 785

0.21 0.11

0.14

393

0.22

0.28

*(Note: These values are upper bounds.)
X = 1 (ym)

d = 2 (cm)

b D= .005 -01 .02 .05 .1 .2 .5

(cm) (cm)

v 31.4 62.8 126 314 628 1260 3140

5 (#)E f

. 2.03 1.01 0.51 0.20 0.10 0.05 0.02 _min

($)E' 3.30 1.64 0.81 0.32 0.15 0.07 0.03

max

v 15.31.

52.8 157 314 628 1570

10 E' . 4.05 2.03 1.01 0.4l 0,20 0.10 0.04 mm

E' 6.59 3.28 1.62 0.63 0.31 0.15 0.06

max

v 7.85 15.7 31.4 78.5 157 314 785

20 E' . 8.11 4.05 2.03 0.8l 0.41 0.20 0.09 mm

E' <20* 6.55 3.24 1.26 0.6l 0.30 0.12

max

d = 5 (cm)

b

(cm)

V 78.5 157 314 785 1570 3140 7850

5 (f)E' . mm 0.81 o.4i 0.20 0.08 0.04 0.02 0.01

(OT' max

1.32 0.66 0.33 0.13 0.06 0.03 0.01

V 39.3 78.5 157 393 785 1570 3930

10 E' . mxn1.62 0.81 0.41 0.16 0.08 0.04 0.02

E' max

2.65 1.32 0.66 0.26 0.13 0.06 0.02

V 19.6 39.3 78.5 196 393 785 I960

20 E' . mm 3.24 1.62 0.81 0.32 0.16 0.08 0.03

E' max

5.29 2.64 1.31 0.52 0.25 0.12 0.05

*(Note: These values are upper bounds.)
A_ = 2 (ym)

d = 0_^_ (cm)

b D = .005 .01 .02 .05 .1 .2 .5

(cm) (cm)

v 3.93 7.85 15-7 39-3 78.5 157 393

5 {%)E t

. - 8.11 4.06 1.64 0.84 0.48 _ min

(^)E' - ^0* 6.19 2.37 1.17 0.64

max

v 1.96 3.93 7.85 19.6 39-3 78.5 196

10 E' . - - B.12 3.28 1.69 O.96 _ mm

E* - <20* k.7h 2.34 1.27

max

v 0.982 1.96 3.93 9.82 19.6 39-3 98.2

20 E' . - - - 6.55 3.38 1.93 _ mm

E' - - <LQ* 4.68 2.55

max

d = 1 (cm)

b

(cm)

V 7.85 15.7 31.4 78.5 157 314 785

5 (*)E» . mm 8.11 4.05 2.03 0.81 0.41 0.21 0.11

(%)E«

max

<20* 6.48 3.18 1.23 0.59 0.29 0.14

V 3.93 7.85 15.7 39.3 78.5 157 393

10 E» . _ mm

- 8.11 4.05 1.63 0.82 0.42 0.22

E' max

— <20* 6.37 2.45 1.19 0.59 0.28

V 1.96 3.93 7-85 19-6 39-3 78.5 196

20 E* . _ mm

- - 8.11 3.25 1.64 0.84 0.43

E' - - <20* 4.90 2.37 1.17 0.56

max

*(Note: These values are upper bounds.)

10
A_ = 2 (ym)

d = 2 (cm)

b

(cm)

D =

( cm)

005 .01 .02 • 05 .2 • 5

(Jf)E'

(#)E

mm

max

15.

4.05

6.59

31. U

2.03

3.28

62.8

1.01

1.62

157

0.41

0.63

314

0.20

0.31

628

0.10

0.15

1570

0.04

0.06

10

20

V 7.85 15-7 31.4 78.5 157 314 785

E' . mm a. ii 4,05 2.03 0.81 0.4l 0.20 0.09

E

1 max

<20* 6.55 3.24 1.26 0.6l 0.30 0.12

V 3.93 7-85 15-7 39-3 78.5 157 393

E' . - 8.11 4.05 1.62 0.81 0.4l 0.17 mm

max

<20* 6.48 2.53 1.23 0.59 0.24

b

(cm)

d = 5 ( cm)

(*)E'

(*)E«

mm

max

39.3

1.62

2.65

78.5

o.8i

1.32

157

0.4l

0.66

393

0.16

0.26

785

0.08

0.13

1570

0.04

0.06

3930

0.02

0.02

10 v

E«

E' mm

max

19.6

3.24

5.29

39-3

1.62

2.64

78.5

0.8l

1.31

196

0.32

0.52

393

0.16

0.25

785

0.08

0.12

I960

0.03

0.05

20 vE'E

1 mm

9.82

6.48

<1R*

max

19.6

3.24

5.28

39-3

1.62

2.63

98.2

O.65

1.04

196

0.32

0.51

393 982

0.16 0.07

0.25 0.09

'(Note: These values are upper bounds.)

11
1=5. (pm)

d = CL_5 (cm)

b D = .005 .01 .02 .05 .1 .2 .5

(cm) (cm)

v 1.57 3.14

5 (*)E« . _ min

U)E»

max

v 0.785 1-57 3.14 7.85 15.7 31. 4 78.5

10 E

1

. mm

E' - max

v 0.393 0.785

20 E' . - mm

E

? - - <20* 6.37

max

d = 1 (cm)

6.28

10.1

15.7

4.09

31. 4

2.11

62.8

1.21

<23* 5-93 2.93 1.59

3.14 7.85

8.19

15-7

4.22

31. 4

2.1+1 - <20* 5.85 3.19

1.57 3.93 7.85

8.44

15.7

4.82

b

(cm)

V 3. lit 6.28 12.6 31.4 62.8 126 314

5 U)E' . mm

- 10.1 5.07 2.03 1.02 0.53 0.27

(JOE' max

- <23* 7.96 3.06 1.48 0.73 0.35

V 1.57 3.14 6.28 15.7 31.4 62.8 157

10 E' . mm

- - 10.1 4.0b 2.05 1.06 0.54

E'

max

- - <23* 6.13 2.96 1.46 0.70

V 0.785 1.57 3.14 7.85 15.7 31.4 78.5

20 E' . mm

- - - 8.13 4.09 2.11 1.08

E'

max

- - - ^0* 5.93 2.93 1.39

: (Note: These values are upper bounds.)

12
X= 5. (ym)

d = 2 (cm)

b

(cmj

10

20

D =

(cmj

(*)E- min

l#)E

max

v

E' min

i max

v

E

1 mm

max

.005

6.28

10.1

<23*

3.l4

1.57

.01

12.6

5. 07

8.19

b.28

10.1

<23*

3.14

.02

25-1

2.53

4.05

12.6

5-07

8.11

6.28

10.1

<23*

.05

62.8

1.01

1.58

31.4

2.03

3.16

15.7

4.06

6.32

.1

126

0.51

0.77

52.8

1.02

1.53

31.4

2.03

.2

251

0.26

0.37

126

0.51

0.74

62.8

1.02

3.06 1.48

.5

628

0.11

0.15

314

0.22

0.30

157

0.43

0.59

b

(cm)

d = 5 (cm)

10

20

v

(JOE'

(£JE»

min

max

v

E

T mm

max

v

E'

15.7

4.05

6.61

7.85

8.11

<20*

3.93

mm

max

31.4

2.03

3.30

15-7

4.05

6.60

7-85

8.11

<20*

62.8

1.01

1.64

31.4

2.03

3.2b

15.7

4.05

6.57

157

0.41

0.65

78.5

0.81

1.30

39.3

1.62

2.59

314

0.20

0.32

157

o.4i

0.64

78.5

0.81

1.27

62b

0.10

0.15

314

0.20

0.31

157

0.4l

0.b2

1570

0.04

0.06

785

0.08

0.12

393

0.16

0.24

'(Note : These values are upper bounds.)

13
b

(cm)

D = (cm)

.005

V 0.785

5 (*)E» . min

-

(*)E«

max

-

V 0.393

10 E' . min

-

E

1 max

—

V O.196

20 E' . min

-

E

1 max

-

X = 10 (urn)

d = 0^ (cm)

.01 .02

1.57 3.14

0.785 1.57

.05 .1 .2 .5

7.85

8.19

15.7

4.22

31. k

2.41

78.5

<20* 5-85 3.19 -

3.93 7.85

8.44

15.7

4.82

39.3

<20* 6.37

0.393 O.785 1.96 3.93 7.85 19.6

9.65

'(Note: These values are upper bounds.)

<20*

d = 1 (cm)

b

(cm)

v 1.57 3.14

5 (^)E' . _ mm

max

v 0.785 1-57

10 E' . - mm

E' - max

v 0.393 O.785

20 E' . mm

E' - <20* 5.85 2.78

max

6.28 15-7 31.4 62.8 157

10.1 4.06 2.05 1.06 0.54

<23* 6.13 2.96 1.46 0.70

3.14 7.85 15.7 31.

4

78.5

- 8.13 4.09 2.11 1.08

- <20* 5-93 2.93 1.39

1.57 3.93 7.85 15.7 39-3

- - 8.19 4.22 2.16

14
A_ = 10 (ym)

d = 2 (cm)

b

(cm)

_D = (cm)

.005 .01 .02 .05 .1 .2 • 5

5 (*)E* mm

3.11* 6.28

10.1

12.6

5.07

31. 4

2.03

62.8

1.02

126

0.51

31^

0.22

max

- <23* 8.11 3.16 1.53 0.74 0.30

10

V

E' . 1.57 3.l4 6.28

10.1

15-7

4.06

31.4

2.03

62.8

1.02

157

0.43

_ mm

E' - <23* 6.32 3.06 1.48 0.59 max "

v 0.785 1-57 3.14 7.85 15.7 31.4 78.5

20 E' . - - 8.11 4.06 2.05 0.86 mm

E« - - - ^0* 6.13 2.96 1.18

max

d = 5. (cm)

b

(cm)

v 7.85 15-7 31.4 78.5 157 314 785

5 (%)E' . 8.11 4.05 2.03 0.81 0.41 0.21 0.08 _ mm

(#JE f <20* 6.60 3.28 1.30 0.64 0.31 0.12

max

v 3.93 7.85 15.7 39-3 78.5 157 393

10 E' . - 8.11 4.05 1.62 0.8l 0.4l 0.16 _ mm

E' - <20* 6.57 2.59 1.27 0.62 0.24

max

v 1.96 3.93 7.85 19.6 39-3 78.5 196

20 E' . - 8.11 3.24 1.62 0.81 0.33

_ mm

E' - ^0* 5.19 2.55 1.24 0.47

max

'(Note : These values are upper bounds.)

15
A

= 20 (urn)

d = 0.5 (cm)

b JD = .005 .01 .02 • 05 .1 .2 • 5 (cm) (cm)

V 0.393 0.785 1.57 3.93 7.85 15.7 39.3

5 (*)E« . mm

- - - - 8.UU 4.82 -

(*)E'

max

- - — — <20* 6.37 -

V 0.196 0.393 0.785 1.96 3.93 7.85 19.6

10 E' . mm

- - - - - 9.65 -

E

1 max

— — — - — <20* —

V 0.090 0.196 0.393 O.982 1.96 3.93 9.82

20 E' . _ mm

— — — — — — —

E

1 max

~ TM " " — "*" mm

b

(cm)

d = 1 (cm)

0.785 1-57 3.14 7.85 15.7 31. 4 78.5

(%)E' . - - - 8.13 4.09 2.11 1.08 _ mm

(#)E' - <20* 5.93 2.93 1.39

max

v

v 0.393 0.785 1.57 3.93 7.85 15.7 39.3

10 E' . - - - 8.19 4.22 2.16

_ mm

E' - - <20* 5.85 2.78

max

v O.196 0.393 O.785 1.96 3.93 7.85 19.6

20 E

1

. - - - - 8.41+ 4.32

_ mm

E* - ^0* 5.56

max

*(Note : These values are upper bounds.)

16
X = 20 (um)

d = 2 (cm)

b _D = .005 .01 .02 .05 .1

(cm) (cm)

b

(cm)

v 1.57 3.14

5 (*)E« . _ min

(*)E'

max

v 0.785 1.57

10 E

1

. _ mm

E' - max

v 0.393 0.785

20 E' . mm

v 3.93

5 (^)E' . mm

max

v 1.96

10 E* . mm

E

1 max

v 0.982

20 E' . mm

6.28

10.1

15.7

4.06

31. 4

2.03

62.8

1.02

157

0.1*3

<23* 6.32 3.06 l.U'8 0.59

3.14 7.85

8.11

15.7

4. 06

31.1*

2.05

78.5

0.86

- <c^Q* 6.13 2.96 1.18

1.57 3.93 7.85

8.13

15-7

4.09

39.3

1.73

E

? - ^0* 5-93 2.36

max

d = 5 (cm)

7.85

8.11

15.7

1*.05

39.3

1.62

78.5

0.81

157

0.1*1

393

0.16

^0* 6.57 2.59 1.27 0.62 0.24

3.93 7.85

8.11

19.6

3.24

39.3

1.62

78.5

0.81

196

0.33

- <20* 5.19 2.55 1.24 0.1*7

1.96 3.93 9.82

6.49

19.6

3.2l*

39.3

1.62

98.2

0.66

E' - - <18* 5.09 2.48 0.95

max

'(Note : These values are upper bounds.)

17
b

(cm)

B =

(cm)

.005

V 0.157

5 mm

- U)E'

max

-

V 0.079

10 E

1

. min

-

E'

max

—

V 0.039

20 E' . mm

-

E

1 max

-

b

(cm)

V 0.314

5 (%)E» . mm

- Wemax

—

V 0.157

10 E' . min

-

E' max

*~

V 0.079

20 E' . mm

-

E' max

-

A_= 50 (urn)

d = 0__5_ (cm)

.01 .02 .05 .1 .2 .5

0.314 0.628 1.57 3.14 6.28 15.7

- 12.1

_ <23*

0.157 0.314 0.785 1-57 3.14 7.85

0.079 0.157 0.393 0.785 1-57 3.93

d = 1 (cm)

O.628 1.26 3.14

0.314 0.628 1.57

6.28 12.6 31.4

10.2 5.28 2.70

^3* 7.32 3.48

3.14 6.28 15.7

- 10.6 5.40

^3* 6.95

0.157 0.314 0.785 1.57 3.14 7.85 _____ 10.8

<20*

*(Note : These values are upper bounds.)

18
(cm)

D =

(cm)

.005

V 0.628

5 (*)E« . mm

-

max

-

V 0.314

10 E

1

. mm

-

E' max

—

V 0.157

20 E' . mm

- E

f max

-

b

(cm)

V 1.57

5 mm

-

(^)E'

max

-

V 0.785

10 E' . mm

-

E' max

V 0.393

20 E

f

. mm

-

E' max

-

X = 50 (ym)

d = 2_ (cm)

.01 .02 .05 .1 .2 .5

1.26 2.51

0.628 1.26

0.314 0.628 1.57

d = 5 (cm)

3.1>*

1.57

0.785

'(Note : These values are upper bounds.)

6.28 12.6 25.1 62.8

10.1 5.08 2.56 1.08

<23* 7.66 3.70 1.48

3. lit 6.28 12.6 31. 4 - 10.2 5.12 2.16

- <23* 7.41 2.96

1.57 3.14 6.28 15.7

- - 10.2 4.32

^3* 5.91

6.28

10.1

15.7

4.05

31.4

2.03

62.8

1.01

157

0.41

^3* 6.48 3.18 1.55 0.59

3.14 7.85

8.11

15.7

4.0^

31.4

2.03

78.5

0.82

- <20* 6.37 3.10 1.19

1.57 3.93 7.85

8.11

15.7

4.06

39-3

1.64

<20* 6.19 2.37

19

.
A = 100 (um)

d = 0__5 (cm)

b D = .005 .01 .02 .05 .1 .2 .5

(cm) (cm)

v 0.079 0.157 0.311* 0.785 1.57 3.11* 7.85

5 («E'

m±n

w)E .

- ...... maJC . ...... v 0.039 0.079 0.157 0.393 0.785 1.57 3.93

10 E

1

. -

_ mm

max

v 0.020 0.039 0.079 0.196 0.393 O.785 1.96

20 E' . - _ mm

max

d = 1 (cm)

b

(cmj

v 0.157 0.311* 0.628 1.57 3-lU 6.28 15.7

5 WE

' min ----- 10.6 5.^0

{%)%' - - <23* 6.95

max

v 0.079 0.157 0.314 0.785 1-57 3.11* 7.85

10 E' . - - - - - 10.8

_ mm

E' _____ <20*

max

v 0.039 0.079 0.157 0.393 0.785 1.57 3.93

20 E' . - min

max

*(Note : These values are upper bounds.)

20
A

= 100 (urn)

d = 2 (cm)

b JD = .005 .01 .02 .05 .1 .2 .5

(cm) (cm)

V 0.3l4 0.628 1.26 3.14 6.28 12.6 31.4

5 _ mm

- - - - 10.2 5.12 2.16

max

— — — — <23* <16* 2.96

V 0.157 0.314 0.628 1.57 3.14 6.28 15.7

10 E

1

. mm

- - - - - 10.2 4.32

E' max

— - - — — <23* 5.91

V 0.079 0.157 0.314 0.785 1.57 3.14 7.85

20 E* . mm

- - - - - - 8.65

E' max

- - - - - - <20*

b

(cm)

d = 5 (cm)

v 0.785 1.57 3.14 7. 85 15.7 31.4 78.5

U)E' . - - 8.11 4.05 2.03 0.82 mm

U)E' - <^0* 6.37 3.10 1.19

max

v

10 E' mm

E' max

v

20 E'

0.393 O.785 1.57 3.93

0.196 0.393 0.785 1.96

mm

7.85

8.11

15-7

4.06

39-3

1.64

^0* 6.19 2.37

3.93 7.85

8.12

19.6

3.28

E' - - <20* 4.74

max

*(Note : These values are upper bounds.)

21
3. Scaling the Diffraction Loss Tables

The range of the diffraction loss tables can be extended by using

scaling relationships (provided that the errors in the formulas used to

compute the diffraction losses do not become excessive in the extended

range) . It is clear from the formulas in section 6 for the quantities

E'. and E

1 given in the tables, that the scaling relationships are simple only if the ratio of the aperture diameter to the source diameter,

Dd-1

, is constant . Subject to this condition, the scaling relationships

are as follows:

Quantity Scales as (constant Dd-1

)

E' . , E' A, b, D

-2 (or d" 2

) ; mm max —

Upper Bounds A

- 5

, b

°*5

, D~ 1 (or d

-1

).

(The upper bounds are the quantity denoted E(v,v,0) in sec. 6.)

4. Effective Wavelengths to Use in

the Diffraction Loss Tables

The effective wavelength, A -

, for computing the diffraction loss for

a given experimental geometry with a source of spectral radiance distribution 3-, (A), is defined to be that wavelength which yields the average

spectral diffraction loss when substituted into the approximate Kirchhoff

scalar paraxial model (see sec. 1). Furthermore, if the approximate

formula for the effective diffraction loss for a circular detector, eq

(12) of section 6, is valid (see sec. 7 for a discussion of the mathematical errors in the formulas used in this report) , then the diffraction

loss scales proportionally to the wavelength, and an explicit equation

for A" can be derived in the form,

f^XdXS, (A) _ A 1 A

'xiaxsx

(x) '

where Al and A2 are the short- and longwavelength limits to S. (A)

.

A If S (A) is the Planck blackbody spectral radiance function [2]

,

denoted L (A,T) at temperature T, then A - can be related to the temperature by approximate equation (derived by Blevin[l]),

A~ - 5324/T (micrometers)

,

(1)

if T is in degrees Kelvin. Thus A~ is about 1.84A , the wavelength of

maximum spectral radiance for a blackbody at temperature T.

loss for a source of spectral radiance distribution S (A) , is given by

A

The effective wavelength, A", for computing the luminous diffraction

for a soi

ie equation,

22
/^XdXV(X)S (X)

/^dXV(X)S

x

(X)

where V(X) is the spectral luminous efficiency function for photopic

vision and XI and X2 are the limits of the visible spectrum [3] . If

S.. (X) is the Planck blackbody spectral radiance function, then Blevin

[I] has shown that Xis 0.572 micrometers for a blackbody temperature

of 2856 K (CIE Illuminant A)

5. Sample Diffraction Loss Calculations

5.1. Sample Diffraction Loss Calculations for a Simple Case

A simple example is the following: Compute the average

diffraction loss over the face of a circular detector which views a 500 K

blackbody through a small aperture. The geometry is that of a source

radiance measurement (see fig. 1) . The diameter of the blackbody

aperture (d) is 1 cm; the distance from the blackbody aperture to the

diffracting aperture (b_) is 5 cm; the diameter of the diffracting

aperture (D) is 0.1 cm; the distance from the diffracting aperture to the

detector (a.) is 60 cm; the detector diameter (2x ) is 5 cm. Since the

blackbody temperature is 500 K, eq (1) shows that the effective diffraction wavelength X~ is 10.6 micrometers. Referring to the diffraction

loss tables (sec. 2) , it is seen that the tabulated wavelength closest to

10.6 micrometers is 10; at this wavelength, and at d = 1 cm, b_ = 5 cm,

D = 0.1 cm, the on- axis diffraction loss E' . (for a. at least 10b, a con- dition which is met by this example) is found to be 2.05%; the corres- ponding area-average diffraction loss over the face of a detector of

radius x , E' , is found to be 2.96%. From the formula for X , max max max

x = 0.5[(0.9d-D)ab_1 - D] , (2)

max —

it is found that x is 4.8 cm; the detector radius is given above as 2.5 cm. Denoting the desired average diffraction loss over the face of

the detector by the symbol E

1 , it is reasonable to interpolate between

E' . and E

1 by the following area-weighting formula: min max

E' = E' . +[E' - E' . ] (x /x ) 2. (3) mm max min o max

Thus E

1 is found to be 2.30% at the wavelength of 10_micrometers ; the

scaling table in section 3 shows that both E'. and E' scale proportionally to the wavelength, so the desired value or E' at a wavelength of

10.6 micrometers is therefore obtained by multiplying 2.30% by the ratio

10.6/10 = 1.06 to get 2.44%.

5.2. Sample Diffraction Loss Calculations for a Complex Case

Figure 2 shows the essential geometry of a circularly symmetric

source-radiometer system currently in use at NBS. The source S is a

23

wmim
blackbody whose temperature is roughly 300 K; the source aperture SA

limits the radiating area; the radiometer aperture RA defines the solid

angle in which radiation is received from SA; the radiometer cavity RC

collects the radiation transmitted through RA, It is desired to calculate the diffraction loss for radiation from S transmitted through SA

and RA to RC.

This is really a 2-step diffraction problem; the total diffraction

loss DL is obtained from both:

a. , the diffraction loss for radiation from S transmitted through

SA to RA, denoted DL , and;

cl

b. , the diffraction loss for radiation from SA transmitted through

RA to RC, denoted DL, .

Thus the total diffraction loss, denoted DL, is

DL = DL + DL - DL DL, a r» a V

since the diffraction loss at the detector is given as a percentage of

the irradiance that would be present in the absence of diffraction.

The effective diffraction wavelength X" for this problem is found

from the given temperature of 300 K and eq (1) of section 4 to be 17.7

micrometers. It is clear that the quantity of interest in computing DL

is the effective radiance of SA, compared with the radiance of S. On

the other hand, the quantity of interest in computing DL is the fraction

of the total radiation from SA, transmitted through RA, which is collected by RC. Therefore, in computing DL it is necessary to treat RC as the source and SA as the detector, since (as explained in sec. 1) the

diffraction loss formulas and the tables in this report all refer to the source radiance measurement geometry, and not to the total aperture

radiation measurement geometry.

Referring to figure 2, and using the terminology of the tables, it

is seen that the essential parameters for computing DL and DL are:

DL : X - = 17.7 micrometers, d= 0.2 cm, b = 0.35 cm, D = 0.05 cm,

a

a_ =17.1 cm, x = 0.575 (source radiance measurement, see

fig. 3); °

DL : X~ = 17.7 micrometers, d = 2.0 cm, b_ = 8.0 cm, D = 1.15 cm,

a_ =17.1 cm, x = 0.025 cm (total aperture radiation measurement, see fig. 3).

To compute DL , note that d = 0.2 cm is smaller than 0.5 cm, the

smallest tabulated value for d; therefore it is necessary to multiply d

and D (to keep the ratio Dd-1 constant) by a scaling factor to use the

tables. Let d' = 3d be the scaled d and D' = 3D be the scaled D; if

24
3 = 10, then d' = 2.0 cm and D

1 = 0.5 cm, which are tabulated values.

Furthermore, b = 0.35 cm is much smaller than 5.0 cm, the smallest

tabulated value for b_; therefore it is necessary to multiply b by a scaling factor a to use the tables. Let b

1 = otb_ be the scaled b; if

a = 14.3, then b' = 5.0 cm, a tabulated value.

In addition, the effective wavelength A - = 17.7 micrometers is not

a tabulated wavelength. Therefore A~ is multiplied by a scaling factor

9 to use the tables. Let A~ ' = 6A~ be the scaled X -

; if = 1.13, then

A- ' = 20 micrometers, a tabulated value.

Next compute x from eq (2) of section 5.1 to get x =3.15 cm,

j-u *. / nmaS max

so that x /x =0.18.

o max

Referring to the diffraction loss tables for the values of E'. and

E' for the scaled parameters, A" 1 = 20 micrometers, d

1 = 2.0 cm, ' D* = 0.5 cm, b' = 5.0 cm (note that the condition that a. be at least 10b_

is met for the geometry of DL ) , it is found that E'. = 0.43% and

E' = 0.59% for the scaled parameters. To interpolate between E'. and

E

4 ' to obtain the desired average diffraction loss E' over the radiometer aperture RA, for the scaled parameters, refer to eq (3) of section

5.1 and substitute the preceding values of E ' . , E' , and x /x into

/-,* TM, , -, j? ;; ~ „-m-„ pn , , max , n o max

eq (3). The resulting value of E' = 0.435% for the scaled parameters is

essentially equal to E ' . . mm

The scaling process must now be reversed to obtain DL , the diffraction loss for the original unsealed parameters. Referring to the scaling

table in section 3, it is seen that

DL = E' (scaled)

2 a" 1 0~ 1

, a

or DL = 6. 19E ' (scaled) = 2.69%. This value is very close to that calculated for DL from the more accurate formula, eq (12) of section 6,

2.70%.

a

Unfortunately DL cannot be obtained from the tables in their

present form. The values of E'. and E" in the tables are computed by

. , min , . max . f , assuming that the detector-aperture distance a_ is much greater than the

source-aperture distance b. This clearly does not hold for the geometry

of DL (see fig. 2), since a_ = 17.1 cm (as explained above, since this

is a total aperture radiation measurement, the source is treated as the

detector and vice versa) and b = 8.0 cm, and therefore a_ = 2.14b and the

condition for the validity of the tables that a_ be at least 10b is not

met.

In addition, since Dd_1 = 0.575 for the geometry of DL , the values

of d and D cannot be scaled to fit the tables because Dd" 1 = 0.5 is the

largest value tabulated, and Dd-1 must be held constant in scaling.

In a situation of this kind, it is necessary to return to the

general formula given in section 6, eq (12) , for the average diffraction

25
loss over the detector disc. This formula is not subject to the restriction of the tables, that the aperture- detector distance a_ be at least 10

times the source-aperture distance b. In eq (12) the average diffraction loss over the detector disc is denoted E(u,v,w ) , where u, v, and w are dimensionless functions of the geometry and wavelength given by

eqs (5), (6), and (8), respectively. Substituting the values given above

for DL into eqs (5) , (6) , and (8) , u, v, and w are computed and then

substituted into eq (12) for E(u,v,w ) to get DLn = 0.87%.

o b

Finally, therefore, the total diffraction loss, DL, from the source

S to the radiometer cavity RC, is found to be DL = 3 . 55% .

6. Formulas Used for Computing the Diffraction Loss Tables

The formulas used in computing the diffraction loss tables are derived from the basic Fresnel-Kirchhoff diffraction formula as given,

for example, in Born and Wolf [4].

For a source radiance measurement (as shown in fig. 3) , the diffraction losses increase with increasing detector radius x . It is felt

that a reasonable upper bound for the detector radius, for a source radiance measurement, is defined by the condition that the detector field of

view not extend beyond the inner portion of the source disc whose radius

is 0.9 of the source radius. If this upper bound is denoted x , it is seen from figure 3 that x r is given by eq (2) of section 5.1. The

minimum source diameter, for a source radiance measurement, is that which

makes x =0; thus the minimum source diameter is [D(l + ba~ ) /0 .9] . max —

For a total aperture radiation measurement, the diffraction losses

decrease with increasing detector radius. It is felt that a reasonable

lower bound for the detector radius, for a total aperture radiation

measurement, is defined by the condition that all the source radiation

which passes through the aperture - except for diffraction losses - be

incident upon that portion of the detector disc whose radius is 0.9 of

the detector radius. If this lower bound is denoted x . , it is seen from figure 3 that

x . = 0.5[(d+D) (0.9) _1 ab-1 + D]

.

man —

Following the analysis of Blevin[l], it is found that the on-axis

diffraction loss at the center of the detector, denoted E(u,v,0), for

the source radiance geometry, is approximately

E(u,v,0) = ^[(v-u) -1 + (v+u) -1

], (4)

where u and v are the dimensionless quantities,

u = ttD 2 ^- 1 + b" 1

) (2X)" 1

, (5)

v = TTDd(2bX) -1

. (6)

26
If the aperture-detector distance a. is much greater than the sourceaperture distance b, then u is approximately

u . = TrD 2 (2bA) -1

- vDd-1

; (7) min —

note that u . is independent of a. mm —

Now let E(u,v,w ) denote the diffraction loss at the off-axis point

in the detector plane whose radius is x (see fig. 3) , and define a third

dimensionless quantity,

w = uDx (aA) -1

. (8) o o —

Blevin [1] has shown that E(u,v,w ) is approximately

E(u,v,w ) = TT -2 /^d0[(-u + w cosG + (v2 -w2 sin 2

9) °*5

) -1

+ (u + w cos0 +

o o o o

(v2 -w 2 sin 2

6) '5 )- 1

] , (9) o

and that E(u,v,w ) increases steadily from the minimum value E(u,v,0) as the radius of the off- axis detection point increases from x = (on axis)

out to the radius of the rim of the detector (which is also labeled x in

fig. 3) . °

Referring to eq (4) for E(u,v,0), it is seen that if the aperturedetector distance a^ is much greater than the source-aperture distance b_, then E(u,v,0) is approximately E (u . ,v,0), denoted E'. , and mm mm

E\ - 2(ttv)- 1 (1 - D

2 d~ 2

) -1

. (10) mm

Note that E'. is independent of a_ and that it is the minimum value of

E(u,v,0), considered as a function of a_, since E(u,v,0) decreases steadily to E'. as a increases (assuming the other parameters are held mm —

constant; .

Referring to eq (9) for E(u,v,w ), it is seen that the average

diffraction loss over the surface of a detector of radius x , denoted

E(u,v,w ), is given by the formula,

o E(u,v,w ) = w

-2

/ °2wdwE(u,v,w)

(11) o o Since the off-axis diffraction loss E(u,v,w ) increases steadily as the detection point moves away from the axis, it is clear that the

average diffraction loss over the disc of radius x also increases

steadily as x increases. Thus E(u,v,w ) attains its maximum value,

o o considered as a function of x , for a detector radius of x

o max

If the detector plane is now moved towards the aperture, holding the source diameter d, the source-aperture distance b, and the aperture

27
diameter D constant, then a point will be reached for which x =0.

The value of a at this point is denoted a . (see fig. 3) , and it is

4-u 4. — -mm

seen that

a . = bD(0.9d - D)

-1

. —min —

It can be shown that the maximum value of E(u,v,w ) , the average

diffraction loss over the detector disc of radius x , considered as a function of the aperture-detector distance a, occurs at a . ; it can also

w u o-t. — —nun be shown that

w + u = 0.9v,

max

where w is defined as max

w = ttDx (aA) _1

. max max —

Note that the preceding analysis assumes that the detector radius is x , and that the radius varies with x as the detector is moved

max . ^ max

towards the aperture.

Now consider the behavior of the average diffraction loss over the

disc of radius x as the detector plane is moved away from the

aperture. It is clear that u will approach its minimum value u . asymptotically in this case, and that consequently w will correspondingly approach its maximum value, considered as a function of a_, which

is v(0.9 - Dd-1

) . It can be shown that the average diffraction loss over

the disc of radius x , E(u,v,w ), attains its minimum value, con- sidered as a function of a, when a_ is much larger than b (and hence u is

approximately equal to u . and w is approximately equal to v(0.9 - Dd-1 )). This minimum value of E(u,v,w ) is denoted E

1 and is indemax max pendent of a_.

Steel, De, and Bell_ [5] have derived a very useful and compact

approximate formula for E(u,v,w ), o [(v+w ) 2 - u

2

] E(u,v,w ) = (2ttw ) _1 ln . (12) ° ° r / \ 2 2i

[ (v-w ) z - U

Z

] o

Thus E

1 can be expressed approximately by the formula,

(1.9-2Dd-1

) E' = [2TTv(0.9-Dd-1

) ] _1 ln [19 ]. (13)

(O.l-^Dd" 1

)

28
7. Estimated Accuracy of the

Diffraction Loss Tables

Steel, De, and Bell [5] show that an upper bound for the fractional error in E ' . , as computed from eq (10) of section 6, is (2v)

-1

; thus

E' . is not given in the tables for values of v less than 5, in order to

limit the estimated error in the tabulated values to less than 10% (of

the value)

Similarly, Steel, De, and Bell [5] show that an upper bound for the

fractional error in E' , as computed from eq (13) of section 6, is

0.06 + 1.6V" 1

; thus E* is not given in the tables for values of v less

than 12, in order to limit the estimated error in the tabulated values to

less than 20% (of the value). However, an upper bound for E' is given

for values of v between 6 and 12; this upper bound is the diffraction

loss for the point on the axis at which the rim of the aperture appears

to coincide with the rim of the source; in other words, the field of view

through the aperture from this point coincides with the source disc (in

fig. 3, this point is the distance a from the aperture) . Blevin [1]

shows that the diffraction loss for this point, denoted E(v,v,0), is given

by the approximate formula,

E(v,v,0) = (ttv)" *5

.

Note that the ratio [E 1 /E' . ] depends on Dd-1 only, and varies

,. , ., max mm approximately as follows

E ' /E '

max min

1.64

1.45

1.39

1.35

1.32

1.29.

bracket the diffraction loss, for detector radii

between zero and x , to within ±20% roughly for the worst case,

Dd = 0, and more accurately for larger values of Dd~.

Furthermore, if the Kirchhoff scalar paraxial model does not

accurately represent the physical behavior of the experimental situation,

then the diffraction loss values in the tables will contain an additional

error besides those due to the mathematical approximations used to compute

the tables.

A good criterion for the validity of the Kirchhoff model, as Stratton

[6] points out, is that the diameter of the diffracting aperture must be

much larger than the wavelength. In the terminology of figure 3, if

29

Dd-1

0.0

0.1

0.2

0.3

0.4

0.5

Thus E' and E

1

. 1
D/A > 10,

then the Kirchhoff model is held to be valid; if this condition does not

hold, then the exact vector model may be required.

8. References

[1] Blevin, w. R. , Diffraction Losses in Radiometry and Photometry,

Metrologia 6_, 39 (April 1970) .

[2] See for example: Jamieson, J. A., et. al., Infrared Physios and

Engineering, p. 19 (McGraw-Hill Book Co., New York, 1963).

[3] The photopic spectral luminous efficiency function, V(\), is given

in: American Institute of Physics Handbook, 3rd ed. , chap. 6,

p. 184 (McGraw-Hill Book Co., New York, 1972).

[4] Born, M. , and Wolf, E., Principles of Optics, 2nd ed. , chap. 8,

p. 382 (The MacMillan Co., New York, 1964).

[5] Steel, W. H. , De , M. , and Bell, J. A., Diffraction Corrections in

Radiometry , J. Opt. Soc* Am. 6_2, 1099 (Sept. 1972) .

[6] Stratton, J. A., Electromagnetic Theory, p. 463 (McGraw-Hill Book

Co. , New York, 1941)

.

30
Figure 1. Diffraction geometry used in the diffraction loss tables

31

A^M^^^^H^^M
<

q

cm'

cr

« o

T

o

od

w

hO

Figure 2. Diffraction geometry for the sample diffraction loss calculations; complex case: A-A, optical axis; RA, radiometer aperture; RC, radiometer cavity; S, 300 K blackbody source; SA,

defining aperture for S (distances in cms; aperture diameters

magnified 10 times with respect to distances along the axis)

.

32
\

\

\

\

UJ

tfl

< -z. _i £ Q_

o

X UJ

CO X

• UJ o

UJ

nr ix h- ZD < 2 o

o

T

(j)"73

i / \ \

U_

QQ UJ UJ

* i- x

< < (-

Figure 3. Diffraction geometry used in the general diffraction loss

formulas: A, aperture; B, detector; C, source; d, source

diameter; D, aperture diameter; x , detector radius; xmax i maximum detector radius for a source radiance measurement;

xmin/ minimum detector radius for a total aperture radiation

measurement; a_, aperture-detector distance; amin , minimum

aperture-detector distance; a^, aperture-detector distance for

computing an upper bound for the diffraction loss; b_, source- aperture distance.

33
f*B5-l 14A IREV. 7-73)

U .S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

I. I'l HLK ATION OK Kl-!POK I NO. NBS TN 594-8

2. Oov 't Accession

No.

4. TIT LI- AND SUBTITU- OPTICAL RADIATION MEASUREMENTS:

Tables of Diffraction Losses

3. Recipient's Accession N<

5. Publication Date June 1974

6. Performing Organization ( ode

7. AUTHOR(S)

W. B. Fussell

Performing Organ. Report Nc

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project Task Work Unit N<

11. Contract Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

same as No. 9

13. Type of Report & Period Covered Final

14. Sponsoring Agency Cod

15. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 74-60008!

16. ABSTRACT (A 200-word or less (actual summary ol most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

Tables of diffraction losses are given for a range of typical experimental

geometries for wavelengths from 0.2 to 100 micrometers. The scaling relationships

for the diffraction losses for varying wavelengths and geometries are also given,

and sample calculations are presented. General formulas are given for the

diffraction losses; the formulas are derived from the Kirchhoff scalar paraxial

diffraction theory. The accuracy of the tabulated values is estimated.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Diffraction; diffraction losses; Fresnel diffraction; Kirchhoff diffraction theory,

photometry; radiometry; scalar diffraction theory.

18. AVAILABILITY [x_ Unlimited

~2 For Official Distribution. Do Not Release to NTIS

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