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NBS TECHNICAL NOTE 594-4

Optical Radiation Measurements:

The Impact of

Radiometry and Photometry

and the Role of NBS
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 L> — Applied Radiation - — Quantum

Electronics :: — Electromagnetics :i — 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.

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.

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

<f WW \

&.';,

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.
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 b

.

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 lh

(1) Atmospheric Transmission of Ultraviolet Light 14

(2) Biomedical Engineering ll+ (3) Transportation lh

c. The Energy Crisis 15

d. Meteorology 15

e. Pollution Monitoring l6

f. Remote Sensing 17

g. Crime Prevention 18

h. Botany 18

3.4 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

4. Alternate Solutions 22

4.1 Technical Factors 22

4.2 Nontechnical Factors 22

4.3 Other Agencies . . 23

4.4 Synopsis 23

5. The Role of NBS 24

5.1 What Needs to be Done 24

a. The Characterization Required: Research 24

(l) Source Characterization 24

(a) Realization of Scales 24

(b) Transfer to Secondary Standards 24

(i) Characterization of Present Standards 24

(ii) Improvement of Present Standards 24

(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, Nonelectrically 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

b

.

Agreement Rather than Accuracy 27

c. NBS Mission 27

d. Past Accomplishment 28

e. Organizational Contacts 28

f. Industrial Desire for IBS Activity 28

g. Future Savings 29

5.3 Present Program , 29

5.^ Other NBS Resources to be Applied 29

5 . 5 Non-Monetary Support 29

6. Recapitulation 30

7. References 31

8. Appendices 3I4

Appendix A 35 Appendix B 38

Appendix C 39 Appendix D 1^2 Appendix E . . I4.3 Appendix F I4.5 Appendix G l|g

LIST OF TABLES

1. Examples of growth in optical radiation industry 2

LIST OF FIGURES

1. Growth of electro-optics industry I4

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

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 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 h. 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 industryMillions 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 i+52. 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,U00 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 by 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] 1

. 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 . Bowever, 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. Bowever, 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

1 Figures in brackets indicate the literature references at the end of this paper.

3
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 he 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 [U-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 k 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 [7] 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 [h-J t 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 [7]. 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 [U,7,l^+; 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 [7] 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 [17]. 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 Uo 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 [lU]

,

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 [7l; photographic instruments and

associated filters, sources, and detectors [7,l8]; cathode ray tubes; and computers [7].

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

'l) 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 22^, 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]

.

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 1970, 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, NBS 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 [l ,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 [3l], 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 [Uo].

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-^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" [1+3]. 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 [7]-

(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 [hh] . 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

1-1+
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 [U7]. It has also been well documented [U8-50]. 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 [Vf].. 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 [5l]>

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 . Wot 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*0. 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 [60]. 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 [k3] 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" [61+]. The technological challenge

to radiometry hoth quantitatively and qualitatively is enormous. Primary work in this area

is now heing proposed by NOAA. NBS has been asked to he of assistance: "NBS calibration

assistance is vital to a successful endeavor " P+3L

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 [7l]. 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.h 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 [k] . 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

"bears directly on improvement throughout the industry. Improvement in radiation measurement techniques will also influence photodetector development [10],

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 he 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; hut 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 60%. The trend since 1965 shows an even more rapid relative

decline: United States rates trailed Europe by 60% and Japan by Qk%" [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" [k] . 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" [lO].

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" [8o], "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 abroad to be sending its measurement people abroad

after its sales ads [81-82].

3.5 Scientific Issues

a. An Opportunity

The rapid technological development already described 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 [8!+]. 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
k. 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.

U.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.

h.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.

k.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 desirahle. 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.

k.k Synopsis

To recapitulate, therefore, "both 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 ROLE 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 precis ion /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].

2\
(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 NBS 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]. "Secondary

standards 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" [°l]. 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 included 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 standards

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" [77]. "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" [ik] .

28
The enthusiasm for NBS activity extends particularly to the desire for verification,

the question of "traceability" . NBS has "been urged hy industry even to inspect its com- mercial facilities periodically [h] . However, this is an area of expansion that will have

to he 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.U 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. 2U0 (1971)

.

33. J. F. Lucey, et al. , Pediatrics, kl, IOU7 (1968).

3U. Newsweek, p. 8l, 12 July 1971.

35. P. Neer, T. Davis, and L. Thorington, Clinical Res., 18, Wo. k (1970).

36. R. M. Neer, et al. , Nature, 22£, June 22, 1971.

37- R. J. Wurtman and J. Weisel, Endocrinology 85_, 1218 (1969).

38. R. J. Wurtman, Ilium. Eng., Proc. Nat. Conf . , Sept. 9-12, 1968.

39- Michael Menaker, Scientific American, 226, 22 (1972).

kO. M. A. Zamkova and E. I. Krivitskaya, Gig. i Sanit . 31, kl (1966).

kl. R. J. Wurtman and R. M. Neer, New Eng. J. Medicine 282 , No. 7 (1970).

k2. National Academy of Engineering, Task Group on Industrial Activity, "An Assessment of

Industrial Activity in the Field of Biomedical Engineering" (l97l).

k3. Draft proposal hy NOAA.

kk. Private communication, other Federal agency personnel.

U5. Private communication, spokesman for lamp industry.

k6. Private communication, spokesman for airplane cockpit panel industry.

kf. Washington Post, front page story, lk April 1972.

kQ. 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.

5^. 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. *+7. 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.

'jk. 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 (l97l)

•

81

82

83

8U

85

86

87

91

Private communication, spokesman for the photographic industry.

German language sales ads.

Private communication, spokesman for the lamp industry.

Symposium on Far Ultraviolet Radiometry, NBS, 9-10 November 1971.

Private communication, Gordon Dunn, JILA.

IBS Astronomy Day Program, NBS, 18 February 1972.

Private communication, spokesman for commercial electro-optics calibration industry.

Private communication, spokesman for lamp industry.

Private communication, spokesman for office equipment industry.

Private communication, spokesman for lamp industry.

Richard F. Leftwich, Standards for Calibration, k November 1969.

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 (ll), 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_° 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~ 5

. 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 urn. 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 p.

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 standardizing more 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.

in
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 y 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 y. A transfer

standard is also needed out to at least 25 y. 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.

1+2
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.

^3
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 sunlight 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 interlaboratory 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.

^5
Appendix G

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 energy

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.

k6
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.

^7
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

9. PERFORMING ORGANIZATION NAME AND 10. Project/Task/Work Unit No. 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.

18. AVAILABILITY STATEMENT

ITl UNLIMITED.

I | FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

56

22. Price

$.80 Domestic Postpaid

$.55 GPO Bookstore

USCOMM-DC 66244-P71

<r U. S. GOVERNMENT PRINTING OFFICE : 1973 O - 511-324 (198)
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