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NBSIR 75-939

The National Measurement

System for Radiometry and

Photometry

H. J. Kostkowski

Institute for Basic Standards

National Bureau of Standards

Washington. D C. 20234

November 1977

Final

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5

J.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 75-939

THE NATIONAL MEASUREMENT

SYSTEM FOR RADIOMETRY AND

PHOTOMETRY

H. J. Kostkowski

Institute for Basic Standards

National Bureau of Standards

Washington, D C. 20234

November 1977

Final

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Acting Director

CONTENTS

EXECUTIVE SUMMARY 1 1. INTRODUCTION 3

2. STRUCTURE OF THE MEASUREMENT SYSTEM 3 2.1 Conceptual System 3 2.2 Basic Technical Infrastructure 5 2.2.1 Documentary Specification System 5 2.2.1.1 Standardization Institutions 5 2.2.1.2 Survey of Documentary Standards 6 2.2.2 Instrumentation System 6 2.2.2.1 Measurement Tools and Techniques 6 2.2.2.2 The Instrumentation Industry 7 2.2.3 Reference Data 7 2.2.4 Reference Materials 7 2.2.5 Science and People 7 2.3 Reference Data 8 2.4 Dissemination and Enforcement Network 8 2.4.1 Central Standards Authorities 8 2.4.2 State and Local Office of Weights and Measures 8 2.4.3 Standards and Testing Laboratories and Services 8 2.4.4 Regulatory Agencies 8 2.5 Organizational Input-Output Transactions Matrix 8 2.5.1 Analysis of Suppliers and Users 8 2.5.2 Highlights of Transaction Matrix 9

3. IMPACT, STATUS AND TRENDS OF MEASUREMENT SYSTEM 11 3.1 Impact of Measurements 11 3.1.1 Functional, Technological, and Scientific Applications .... 11 3.1.2 Economic Impacts -- Costs and Benefits 12 3.1.3 Social, Human, Man-on-the-Street Impacts 13

3.2 Status and Trends of the System 14

4. SURVEY OF NBS SERVICES 14 4.1 The Past 14

4.2 The Present -- Scope of NBS Services 15

4.2.1 Description of NBS Services and Program 15

4.2.2 Users of NBS Services 16

4.2.3 Alternate Sources 16

4.2.4 Funding Sources for NBS Services 16

4.2.5 Mechanism for Supplying Services 16

4.3 Impact of NBS Services 17 4.3.1 Economic Impact of Major User Classes 17 4.3.2 Technological Impact of Services 17 4.3.3 Pay-off from Changes in NBS Services 18

4.4 Evaluation of NBS Program 19 4.5 Future 19

5. SUMMARY AND CONCLUSIONS 19 APPENDIX A 20

APPENDIX B 26

APPENDIX C 27

REFERENCES 23

i

THE NATIONAL MEASUREMENT SYSTEM FOR RADIOMETRY AND PHOTOMETRY

Henry J. Kostkowski

Optical Physics Division

November 1977

EXECUTIVE SUMMARY

This National Measurement System Study is on the measurement of light. More specifically it is concerned with the measurement

of the energy or power in ultraviolet,

visible and infrared radiation.

The study was undertaken to determine the

importance of such measurements in the U.S.,

the accuracy and ease with which they could

be made, the adequacy of this capability,

and the nature of the program NBS should

pursue in this measurement area.

In the last ten years, the economic and

social impact of radiometric and photometric

measurements has increased significantly.

Such measurements are required in the man- ufacture of cameras, color TV and copying

machines. Ultraviolet radiation is being

used extensively for the polymerization of

industrial coatings. An attempt is being

made to use radiometry in measuring atmospheric temperatures for the purpose of

forecasting weather. New solid-state lamps

(LEDs) are used in a variety of visual

displays. Phototherapy is used almost

exclusively in the treatment of some diseases

(e.g. jaundice in the newborn). Regulatory

agencies are concerned with the hazardous

effects of UV on the eyes and skin (skin

cancer), particularly in industrial environments. Dentists are now using a commercially

available "UV gun" for curing various new

dental materials. Applications in the lamp

industry are increasing because of our energy problems. Twenty-five percent of the

U.S. electrical power is used for lighting,

and thus, developing lamps that will produce

the same light for less electrical power has

a high priority. Improving the utilization

of solar energy will require better measurements than are now available. All of these

uses and applications of light require

radiometry or photometry. Many of them will

require a state-of-the-art accuracy of a few

per cent in order to achieve their objectives.

Unfortunately, the current radiometric

and photometric measurement system is inadequate for the many uses and applications

described. Radiometric measurements are among the most difficult measurements to make. The radiant power varies with position,

direction, wavelength, polarization and

time, and the responsivity of most radiometers also varies with these and other

parameters, making such measurements a difficult, multi-dimensional problem. In addition, most of the people needing radiometry have not been trained in the field.

There are relatively few experts available.

As a result of these two factors, measurement

accuracy is poor and large differences in

measurement are widespread. Much time and

money is spent trying to resolve these

differences, particularly when mass produced

products require components from various

companies and these components must meet

radiometric or photometric specifications.

The cost of inadequate radiometry and

photometry is very high. The electrooptical industry alone has annual sales

approaching 15 billion dollars per year. A leading instrument manufacturer estimates

that about $200 million is spent each year

in calibrating radiometric systems or resolving discrepancies in radiometric

measurements. If better radiometry can improve long-term weather forecasting as predicted, the economic impact would be

tremendous. It is virtually impossible to estimate the cost of inadequate radiometry

relative to medical and safety applications,

but public health and safety are certainly

given a high priority in this country.

Adequate radiometry today means making

measurements with a few percent accuracy

commonplace. This will require greater

expertise in the system and more accurate,

easy-to-use, and less expensive standards

and techniques.

NBS has addressed itself to solving

these problems. It helped organize the

Council for Optical Radiation Measurement

(CORM), a group largely representing industry

and providing detailed information and a consensus of the needs in the system. It has worked with the Illuminating Engineering

Society (IES), the Commission Internationale

de L'Eclairage (CIE), and the Infrared Information Symposia (IRIS). NBS is developing

more accurate, easy-to-use, less expensive

standards and techniques and is beginning

to monitor the capability of the system by

inter! aboratory comparisons. It has created
specialized publications to insure that all

this information is efficiently disseminated.

Finally, NBS is also starting to produce a Self-Study Manual for Optical Radiation

Measurements. This is expected to significantly upgrade the level of expertise in the

U.S. in this area.

In summary, this study has shown that

radiometry and photometry are having a significant economic and social impact in

the U.S. today and this impact is expected

to increase. The capability of this portion

of the measurement system is inadequate for

today's needs. An accuracy of a few percent

is frequently needed; 10-50 percent is

commonplace. The reason is that radiometric

and photometric measurements are very

difficult to make, and there is too little

expertise to make these difficult measurements.

NBS' program is designed to improve the

situation by (1) making the measurements

easier through simpler, inexpensive standards

and techniques and (2) increasing the expertise

through a Self-Study Manual on the subject.

2
1. INTRODUCTION

Everyone has his own built-in photometer -- the eye. The normal eye can see differences in light intensity and color of

1%. Yet the most sophisticated instruments

available today do not measure the absol ute intensity of light with an accuracy of

better than 1%. Discrepancies of 10" are common and the 1% accuracy is only realized

in a few cases and in the best standards

laboratories of the world.

In spite of this situation, the accuracy

and efficiency with which radiometry and

photometry can be performed affects every- one in this country. Such measurements are important in

- Developing more efficient lamps (onefourth of the electricity used in the

U.S. is for lighting)

- Developing the use of solar energy

- Treating various diseases by phototherapy (e.g. jaundice in over 10,000

infants born in the U.S. each year)

- Specifying and controlling ultraviolet radiation hazards (these can cause eye damage and skin cancer)

- Pollution monitoring

- Weather forecasting

- Automating the production of many

manufactured products such as lamps, cameras, film and television

- Developing and using modern defensive

weapon systems.

As a result, accurate, efficient measurement

of radiant power is an important factor in our energy shortage, our health, our safety, our economy and the defense of the country.

The National Measurement System Study in Radiometry and Photometry was initiated in 1971. Its primary purpose was to determine

what NBS' program should be in this measurement area. A rapidly developing electrooptics industry, utilizing radiometry and

photometry and the many applications of this

technology to problems of public concern, provided the impetus for such a study. The

first result of the study was an NBS Technical note [1] entitled "The Impact of

Radiometry and Photometry and the Role of

NBS". A second NBS Technical Note [2]

called "The Present State of Radiometry and

Photometry" followed. In the meantime, a new organization of industrial, governmental

and university scientists and engineers,

called the Council for Optical Radiation

Measurement (C0RM), was created. C0RM

prepared and submitted to NBS a report

entitled "Pressing Problems and Projected

National Needs in Optical Radiation Measurements: A Consensus of Services Desired of

NBS". In March 1975 an updated version of

this report was completed and submitted to

3

NBS. During and following the preparation

of these reports, a new NBS program in radiometry and photometry evolved.

In general, the approach used in con- ducting this National Measurement System

Study was to try to answer the following

four questions:

1. Why are radiometry and photometry

important in the U.S. today?

2. What is the status of radiometry

and photometry in the U.S.?

3. What is needed?

4. How should NBS respond?

Information was obtained primarily from personal discussions and correspondence with

many concerned individuals in industry and

government. Extensive interaction with

industry and other government agencies is

continuing. Conditions and needs change.

The NBS program in radiometry and photometry

must be updated to take account of these

changes. The current report is a "snapshot",

"taken" in March 1975, of the U.S. National

Measurement System for Radiometry and

Photo-metry. It is a summary of what we have learned about the System and what we

are trying to do to improve it.

2. STRUCTURE OF THE MEASUREMENT SYSTEM

2.1 Conceptual System

2.1.1 Radiometry

In radiometry, the physical quantity

measured is the radiant power incident on

an aperature or a portion of a surface*.

From this measurement and the geometry

involved, various radiant power densities

are calculated. These include the radiant

power incident per unit area (irradiance)

and the radiant power incident or exiting

per unit projected area and unit solid

angle (radiance). In addition, two quantities

that are used to characterize sources of

*In this Radiometry and Photometry Report,

only incoherent radiant power is considered.

The measurement of coherent radiant power

is treated in the Study of the National

Measurement System for Lasers.
radiation are often of interest. These are

the intensity (of a source), which is the

radiant power emitted by a source in a given

direction per unit solid angle, and the total

flux, which is the radiant power emitted by

a source in all directions. Because accurate

measurement of radiant power often requires

knowledge of how the radiation is distributed

relative to wavelength, a, the spectral

concentration of these quantities is also of

great interest. The wavelength unit typically used in radiometry is nanometers.

The names of the major radiometric quantities, their symbols and units and their

relationship to one another are listed below.

Radiant power or flux (<(>) WATT

Irradiance (E) ? WATT (METER)

Radiance (L) ? WATT (METER)" (STERADIAN)

Intensity (I) - WATT (STERADIAN)

Spectral flux (<(>..)

WATT (NANOMETER)

-1

Spectral irradiance (E^)

WATT (METER)"

2 (NANOMETER)" 1

Spectral radiance (L)

WATT (METER)

2 (STERADIAN)" 1 (NANOMETER)

Spectral intensity (I

x

) WATT (STERADIAN)"

1 (NANOMETER)

-1

E = / L cose dfi =

/ A Exd

I = / L cose dA = /

I A dA

<)> = // L cose dfidA = /<j> A dA

where e is the angle between the direction

of L and the surface normal. Thus all the

radiant quantities are derivable from spectral

radiance.

Spectral-radiance standards have been and are still principally derived from blackbodies.

The spectral radiance of the radiation

associated with a blackbody can be calculated

from the Planck radiation equation provided

that the temperature of the blackbody is

known. Much of radiometry is concerned

with spectral radiances corresponding to blackbody temperatures from about 1500 K to 3000 K. The uncertainty of the best thermodynamic temperature measurements in this

region produces an uncertainty in spectral

radiance in the visible spectral range of

about 1/2%. Additional small systematic

errors increase the state-of-the-art un- certainty in current spectral radiance

standards to about 3/4%.

It is also possible to derive radiometric

quantities from electrical measurements

rather than temperature measurements. This

is done by using a so-called absolute or electrically calibrated radiometer. One

tries to design these instruments so that

they respond in the same way to both radiant

heating and electrical heating. Then, if the

electrical signal is adjusted until the

output of the radiometer is the same as that

when the radiant power is incident, the

latter is equal to the power dissipated in

the radiometer by the electrical signal.

Electrical-power measurements can be made

much more accurately than temperature measurements. However, as of March 1975, the

uncertainty of the electrical-radiant equivalence has limited the uncertainty of this

method of realizing a radiometric scale to about the same as a blackbody-temperaturebased scale. Nevertheless, the recent development of pyroelectric electrically calibrated

radiometers make this approach much more

practical than before, and it is being

investigated extensively.

2.1.2 Photometry

In photometry, the physical quantities

determined are similar to those in radiometry

except that they are spectrally weighted by a function that approximates the spectral

response of the human eye. The radiant power

detected by such a "standard eye" is referred

to as luminous flux. The unit of luminous

flux is the lumen. It is defined in terms of

the radiant power emitted by a blackbody at the temperature of melting platinum. More

specifically, a lumen is the luminous flux

emitted per steradian in a perpendicular

direction by 1/600 000 square meters of a blackbody at the temperature of melting

platinum.

The relationship between radiometric and

photometric quantities is given by the

equation

Photometric Quantity =

„ /(SPECTRAL RADIOMETRIC)

\/ \ QUANTITY /

V(A) dA
where V(a) is the standardized spectralresponse function of the eye* and is

the constant relating the lumen to the watt. The value for may be determined by

applying this equation to a platinum-point

blackbody and the defined value of the

lumen. Using the average of two recently

reported values for the melting temperature

of platinum, Km

is equal to 683 lumens per

watt. The common photometric quantities,

their symbols and their units are listed

below.

Luminous flux (a ) LUMEN

v

Illuminance (E ) LUMEN (METER)"

2

Luminance (L ) LUMEN (METER)

-2 (STERADIAN)" 1

Luminous intensity (I ) LUMEN (STERADIAN)"'

The photometric quantities are related to one another in the same way as the radiometric quantities.

Since photometry initially developed

because of needs in the manufacture, selling

and use of lamps, the luminous intensity (of

a source) has been a very important photometric quantity. Because of this and the

importance of the human eye as a detector,

the corresponding unit was included as one of

the six Base Units of the SI system of

units. Its SI definition parallels that

given earlier for the lumen in terms of the

platinum-point blackbody, and the name, candela, has been assigned this SI unit of

luminous intensity (lumen per steradian).

The accuracy of realizing a platinumpoint-blackbody standard of light has not

been any better than about 1%. In addition

such a realization is very tedious and has

led national laboratories to maintain the

candela on groups of lamps. The lamps from

different national laboratories have been

compared every 4 to 8 years at the International Bureau of Weights and Measures. In this way, international agreement of 1%

to 2% has been maintained over a long period

of time with very infrequent use of platinumpoint blackbodies. The uncertainty of

luminous-intensity calibrations performed at NBS has been estimated to be 1.5% relative to the candela maintained by NBS, 2.3% relative

to the world mean, and 4.1% relative to the

SI unit [4].

2.1.3 Reference Standards and Their Adequacy

NBS now issues a variety of tungsten-lamp

reference standards calibrated in terms of

the radiometric and photometric quantities

described in the two previous sections. The

uncertainty of these calibrations relative to absolute SI units varies from about 1% to 5%

and relative to a fixed NBS base from about

1/2% to 2%. These uncertainties are adequate

for many requirements in the Measurement

System. However, the spectral -radiometric

calibrations cost $1000 to $2000 and often

require 3 to 6 months for delivery. Also

there are no spectral-irradiance standards

below 250 nm, no spectral -flux standards, and

no detector standards above 250 nm currently

available. Therefore, NBS is devoting

considerable effort to making the existing

standards less expensive and available in a shorter time and to developing the standards

mentioned above that are not currently

available. In addition NBS is proposing that

the SI standards of light be redefined so that the photometric standards may be derived

from their radiometric analogues using a defined value for K^. This would reduce the

uncertainty of the photometric standards to

1 to 2% and unify the radiometric and photometric systems. These additions and changes

would make NBS radiometric and photometric

standards adequate for most current requirements.

2.2 Basic Technical Infrastructure

2.2.1 Documentary Specification System

2.2.1.1 Standardization Institutions

There are some twenty-two organizations

[2] associated with procedural standards

each of which covers some aspect of radiometry or photometry. The three most active

and their main area of interest are the

Illuminating Engineering Society (IES)

-- photometry

Commission Internationale de L'Eclairage

(CIE) photometry

Infrared Information Symposia (IRIS) -- military infrared radiometry

*This is a roughly bell shaped curve extending from about 400 nm to 700 nm with a peak

at about 555 nm.

5
A brief description of these organizations

and the other nineteen not listed is given

on page 31 of NBS Technical Note 594-6.

2.2.1.2 Survey of Documentary Standards

The major existing documentary standards

for radiometry and photometry are:

IES Lighting Handbook, Fifth Edition,

1972.

Editor, John E. Kaufman

Published by the Illuminating Engineerning Society (IES),

345 East 47th Street,

New York, N.Y. 10017.

Individual reports on photometry published

by the IES Same address as above.

CIE publications on photometry

List available from

Secretary, U.S. National Committee,

CIE

Room B-304, Metrology

National Bureau of Standards

Washington, D.C. 20234.

Handbook of Military Infrared Technology

Editor, William L. Wolfe

1965

Superintendent of Documents

U.S. Government Printing Office

Washington, D.C. 20402.

Various reports on military infrared radiometry

Infrared Information and Analysis

Center

P.O. Box 618

Ann Arbor, Michigan 48107.

In general, these documents are useful for

5% to 10% radiometry and photometry. A special NBS Technical Note Series -- 594-

on Optical Radiation Measurements -- has

been established for providing detailed

information useful for improving this

accuracy. As of March 1975, nine of these

have been published and are available from

the U.S. Government Printing Office or NBS.

2.2.2 Instrumentation System

2.2.2.1 Measurement Tools and Techniques

The scientific base for radiometry has

been and is still largely the Planck radiation law together with the Thermodynamic

Kelvin Temperature Scale. These enable one

to specify the radiation from a blackbody

which is thus the basic standard.

A large number of blackbodies have

been developed for use at temperatures

ranging from 200 K to 3000 K. Many of these

are available commercially. From about 1200

K to 3000 K, graphite tubes or cylinders

heated by passing a high electric current

through them have been used as blackbodies

with precision and stability of better than

1% for times shorter than about one hour.

From 200 K to 1200 K various metal cavities

surrounded by wire heating elements (or

thermoelectric coolers) have been used as blackbodies with a precision and stability

of about 1% for times of about 100 hours.

Though the platinum-point blackbody used in

photometry has rarely been used with a precision of better than 1%, lower-meltingmetal blackbodies are the most stable radiant

sources available. Gold-point (1337 K)

blackbodies have a precision and long-term

stability of 0.01% or better. Copper-point

(1357 K) blackbodies are better than 0.1%

and tin (505 K) and zinc (692 K) appear to

be as good as the gold-point blackbody

but less data and experience are available

for them than for gold. These melting point

blackbodies have been designed and built by

individual researchers in national laboratories.

However, they are now also available commercially

For temperatures above about 1200 K it is more convenient to use tungsten lamps as reference standards. Therefore standards

laboratories usually compare the tungsten

lamps to the blackbodies and issue the lamps

as standards. Uncertainties of lamp standards at NBS vary from about 1% to 10% and a calibration costs from $100 to $2000. The

specific standards available and their

accuracy and cost are itemized in NBS Special

Publication 250. The techniques used in

realizing the standards and in generating

additional standards are covered in the

previously mentioned NBS Technical Note

Series, number 594-.

In order to realize and use the above

standards with 1% precision, the best

commercially available lamps, power supplies,

double monochromators , detectors, amplifiers,

and optical components are required. The

blackbodies used at NBS are generally

developed in-house. Again, descriptions of

much of the apparatus required are given in

the 594- Technical Notes.
The development of stable silicon-diode

detectors during the past 10 years has

initiated a movement toward detector standards as well as source standards. Also, the

recent development of electrically calibrated pyroelectric detectors and the

availability of stable dye lasers is en- couraging the investigation of using such

black detectors instead of black emitters

(blackbodies) as basic standards. These

detectors are becoming available commercially.

2.2.2.2 The Instrumentation Industry

In the past 10 years, there has been a large increase in the number of commerically

available radiometers and photometers. This

has been motivated by the increased application of radiometry and photometry and made

possible by new technological developments

in electronics and in new, more stable,

convenient-to-use, solid-state detectors.

There are about a dozen manufacturers of

such instruments.

Although these instruments generally have

a precision (short term repeatability) of

about 1% and are usually calibrated with

lamp standards that are accurate from 1 to

2%, the accuracy of using them in practical

applications is usually much worse. The

reason is that for broad-wavelength-band

radiometers, which most of these are, it is necessary to know the relative spectral

response of the radiometer and the relative

spectral distribution of the radiation being

measured. Manufacturers are not currently

able to supply the former information for a modest cost, and, often, the relative spectral

distribution of the radiation to be measured

is not known. As a result, the uncertainty

of the measurement is frequently not known.

It can vary from a few percent, when measurements are being made of a source whose

spectral distribution is similar to the

standard used in calibrating the radiometer,

to 100 percent or more for greatly different

spectral distributions.

2.2.3 Reference Data

The major reference data of interest in

radiometry and photometry are the detailed

characteristics of the various sources,

detectors, monochromators , filters and other

apparatus used. Most data of this type that are available come from the manufacturers of

the apparatus. However, these data are rarely accurate or extensive enough for

radiometry and photometry of a few percent

accuracy. Often such data are developed as one is trying to achieve or use a new state-of-the-art capability. Therefore, as

7

more and more people realize or try to achieve

greater accuracy more reference data will be

generated. To encourage the publication of

such data, the CIE recently sent out a source questionnnaire to leaders in radiometry

and photometry throughout the world. The

information obtained is being consolidated

into a report entitled "A Survey of Photon

Sources Used for the Accurate Measurement of

Visible, Near-Infrared and Near-Ultraviolet

Radiation"

.

2.2.4 Reference Materials

There are very few reference materials

used in radiometry and photometry. Mainly,

they are the metals used in melting-point

blackbodies, and these are available commer- cially with a purity of 99.999%. Such a purity appears to be adequate for 0.01%

radiometry; it is not a limiting factor for

the current state of the art of about 1%.

2.2.5 Science and People

The fields of science supporting this

portion of the National Measurement System

are primarily theoretical physics and solidstate physics. Theoretical physics provides

the basis for the Planck radiation law, the

effects of diffraction and coherence, and

the detailed manner in which radiation is propagated. Solid-state physics provides

the basis for new and improved detectors and sources of radiation -- the major tools

used in radiometry and photometry.

The Optical Society of America and the

Illuminating Engineering Society are the

major professional societies concerned with

this field of measurement, but there are a number of others also involved. Technical

papers concerned with radiometry and photometry appear in a wide range of journals

associated with such specialized areas as heat transfer, photobiology , astronomy, and

meteorology.

The bulk of the people working in radiometry and photometry have little or no formal training in the field. This is

because few colleges or universities offer

any courses in radiometry or photometry, and

only the Optical Science Center at the

University of Arizona and the Insititue of

Optics at the University of Rochester offer

graduate programs in radiometry. In addition,

there are very few books on the subjects.

This is the situation that has led NBS to initiate the writing of the Self-Study

Manual on Optical Radiation Measurements.
2.3 Realized Measurement Capabilities

The accuracy realized in radiometric and

photometric calibrations at NBS varies from

1% to 5%. The May 1974 issue of Optical

Radiation News, distributed quarterly by

NBS and included in this report as Appendix

A, gives more specific information on NBS

capabil ities.

Experts in well-equipped laboratories can realize accuracies in similar measurement

situations almost as well as NBS, say \\ to

6%. The slight degradation is the result of

reference-standard instability and the inability outside of the NBS laboratory to recalibrate the reference standard immediately

before and after the measurements of primary

interest.

Most workers in the field realize 5% to 10% accuracy only with great difficuty and

there is much evidence that significantly

larger errors are commonplace.

Most of the optical-radiation-measuring

community would like to realize a 1% accuracy

as stated in the CORM Report [3] . One of

NBS 1 major goals is to help make this a real ity.

2.4 Dissemination and Enforcement Network

2.4.1 Central Standards Authorities

The central standards authority in the

U.S. is the National Bureau of Standards.

Following a radiometry and photometry re- organization in 1971 a coordinated long-term

program was established with a goal to make

1% radiometry and photometry commonplace

in the U.S. Some of the other countries

that have been active in this area are Australia (NML), Canada (NRC), East Germany

(DAMW), France (CNAM), Germany (PTB) , Japan

(ETL), Union of South Africa (NPRL), United

Kingdom (NPL), USSR (IMM).

The International Bureau of Weights and

Measures (BIPM) serves as a central world

laboratory for conducting photometric intercomparisons and supplying calibrations to those countries of the world that have not

realized their own standards. It has been

trying to extend these services to radiometry as well but has not been very suc- cessful due to insufficient resources.

2.4.2 State and Local Office of Weights and

Measures

State and local offices of Weights and

Measures have not been active in radiometry

and photometry. However, there is some evidence that this may begin to change. For example, the California Highway Patrol has

asked NBS questions related to the measurement

8

and specification of various types of automotive lamps and flashing lamps for emer- gency vehicles.

2.4.3 Standards and Testing Laboratories

and Services

There are a number of commercial radiometric and photometric testing and calibration laboratories in the U.S. These

laboratories obtain standards from NBS and

produce and issue their own reference

standards. In addition, they perform specialized measurements or tests for industry

and other government agencies. All such

laboratories that we know of are listed in

Appendix B. Inclusion in the list only

means that NBS is aware of the services

offered by these commercial concerns. To date it has not been NBS policy to certify

or endorse such laboratories or their meas- urement capabilities.

A few governmental agencies other than

NBS (e.g. DOD and NASA) also have radiometric and/or photometric calibration laboratories. These laboratories primarily

provide services for their own agencies or their contractors. Some interact strongly

with NBS and, in an emergency, could provide

some of the radiometric and photometric

services to the public that are normally

provided by NBS.

2.4.4 Regulatory Agencies

The major regulatory agencies concerned

with radiometry and photometry are the

Bureau of Radiological Health (BRH) and the

National Institute for Occupational Safey

and Health (NIOSH), both in the Department

of Health, Education and Welfare, and the

Occupational Safey and Health Administration

(OSHA) in the Department of Labor. The

legislation that created these agencies and

their assigned responsibilities is outlined

on pages 10 and 11 of NBS Technical Note

594-4. NBS assists these agencies in various

ways ranging from general advice and consulation to detailed research projects to help

insure that their standards and measurement

capabilities are satisfactory.

2.5 Organizational Input-Output Transactions

Matrix

2.5.1 Analysis of Suppliers and Users

The Input-Output Transactions Matrix

shown on page 10 contains the following

suppliers and users:

(1) The Knowledge Community -- scientific organizations, academic institutions, professional societies,
technical publishing organizations,

etc.

(2) International and Foreign Metrological Organizations.

(3) Commission Internationale de L' tclairage (CIE).

(4) Other Documentary Specification

Organizations, both international

(e.g., ISO, IEC, OIML) and national

(ANSI, the DOD standardization

agencies, GSA, IEEE standards

committees, etc.).

(5) The Instrumentation Industry.

(6) NBS.

(7) DOD Standards Laboratories.

(8) Commerical Standards and Testing

Laboratories.

(9) Regulatory Agencies (excluding the

Offices of Weights and Measures).

(10) The Department of Defense (excluding

standards laboratories and any

functions already covered above).

(11) Other Federal Government Agencies,

excluding any functions already

covered.

(12) Industrial Trade Associations

(CORM, LTEC, etc.).

(13) The Lamp Industry.

(14) The Photographic and Film Industry.

(15) Industrial, technological, com- merical, or other intermediate

economic users or suppliers of

measurement goods and services.

(16) The General Public.

The numbers in the intersection boxes of

the matrix are estimates of the direct

transactions between the supplier and user defined by that box according to the following code.

A. The number in the center of each

box indicates the magnitude of the

transaction on a semi-quantitative

"volume" basis where

0 = Trivial

1 = Minor

2 = Moderate

3 = Important

4 = Major.

B. The letter or number in the lower

left corner describes the rate of

change of the transaction where

N = Declining value or needs

(N for Negative)

D = Stable

2 = Growing

4 = Explosive growth.

C. The number in the upper left-hand corner indicates the importance of

the transaction where

1 = Purely a matter of con- venience; transaction not

essential, reasonable alternatives readily available.

2 = Economically important;

strongly desirable.

3 = No satisfactory alternate

source; legally required.

4 = Essential; sole source; matters of life and death.

| D. The number in the upper right-hand corner indicates the adequacies of

the transaction goods or services

where

0 = No foreseeable improvements needed or desirable.

1 = Under control, but could

be improved.

2 = Only marginally satisfactory.

3 = Seriously deficient.

4 = Out of control -- thoroughly

unsatisfactory.

In preparing the matrix, the following

guidelines were adhered to.

A. A box was left empty if the volume

of transactions was negligible. If

numbers were entered in one or more

of the corners, then those in that

box that were left blank should be

read as zeros.

B. The NBS-NBS box included all the

internal transactions within NBS.

C. Every user was also entered as a supplier. The transaction, from a user to a supplier, might only be

information regarding measurement

system needs.

2.5.2 Highlights of Transaction Matrix

The average transaction* for radiometry

and photometry in the transaction matrix is

represented by the following intersection box.

2.2 1.0

1.9

1.2

Obtained by adding the numbers in all the

intersection boxes at each location in the

box and dividing by the number of boxes.

9
DIRECT MEASUREMENTS TRANSACTIONS

MATRIX FOR RADIOKETRY + PHOTOMETRY

INPUT-OUTPUT

U

S

ER

S

1 1

Q ft f "In o 5

Dlfl rt

(-»-*.-*. r-§ w -

r* (• — — rr

o

111 3 1

5 no& n ris

3

Instrumentation

Industry

N

B

S

OOO

Standards

Laboratories ill &«

i8 8

||

8S

fepartaent

of

Defense

(Other)

Hi

u

» S.I

? 8-S — r» M 1

s

"*

1 — r Hr» <3

|li

3?S »

If

SUPPLIERS

1 2

m

4 5 6 7 9 10 11 12 13 1* 15 16 ]7 18 19 20 21 22 23 24 25

tnowl edge Community

3 2

3 2

3 2

2

3 2

2

2 2

2

3 3

2

2

3 2

3

2

3 3

2

3 3

2 2

3 3

2

2

2 3

2 2 3

1 2

2 3

1 2

3 3 2

2

3 3 2

2

2 3

1 2

1 3

1

2 International Metrologlcal Organizations3 1 4

2

2 1 4

2

4 1

2

2 2

2

2

2

2 0

3 1 3 2

1

l

l

l

3 Commission Internationale

de L'Eclalrage (CIE)

4 1 4

2

3 1 3 2

3 1

2

3 1 2 22 1

1 2

2 1 2

2 .

3 2

1 2

2 1 3

2 1 22 1

1 2

4 Other Documentary Specification

Organizations

4 3

1 2

4 2

2

3 3

2

3 2

2

3

2 3

1 2

4 2

1 2

3 2

1

2 2

i 2 1 2 1 2 2 3

1 2 2

1 2

2 3

2 f-1

2

2

2 3

1

Inst rumen tit Ion Industry

3 1 2

2

4 1 2

4

2 1

2

2 1 2

2

4 1 3

2

4 1 2 24 1 2 f-T

2

2

4^-T

3

2

4 t 3 4 1 3

3 1 2

2 4H2 2

4 1 2

2

3 2

4

1 2

1

6 NBS

3 1 4

2

3 1 3 22 1

2

2 2

2

2

3 1 3

2

4 1 4

2

4 1 4 4 1 4

2

4 2

2

2

2 1 2 N

3 1 32 1 4

2

3 1 4

2

3 1 4

2

3 1 2

2

3

1 2 uuu otanoaras Laboratories

2 1 3

1

1

1 2 1 22 t 2

3 1 2

3 1 4 11

1

4 1 41 1

1

1 1

1

2 1

1 2 1

i

1 1

1

8 Commerlcal Standards & Testing

1 *hnr»tnr<«

2 1 2

2

1

1

2 1

2

J 1

1 2

2 2 4

2

3

2

2

i

"1

3 2 2

3

2

2' 1 3

2

j- j

4

N

i I

3 2 1 2

2

2 2 2

2

2 2

3

2

2 2

3 2

g Regul a tory Agencies

3 1 3

2

1 1

1

2

2

2 1 1 2

3 1 3 2

3 1 2 12

1 2

J 1 4

1 1 2

2 1 2

2

3 1 2] 1

1

4 2

2

4 3 4

2 ^ Department of Defense (Other)

2 \ 2 2 1 2 21

2 ]

4 1 4

2 1 2 f-T

i 1—

4 T~~t

i, 2 1 2 f-T

1 2 1

1 H2

4 1 4

11 Other Federal Government Aoencles

2 1 2

2

2 1 1

1

2 1

1 2

i 1

2

1 1

1 2 1 1 2

I 1

1 2

1 1 1 J 1

i 2

2 1 2

2

2 1

1 2

2 1

1 2

1 1

1 2

2 1 2

2 12 Industrial Trade Associations

2 1 2

2

I T

1

2 1

2

2 1 3

2

2 1 3

2

3 1 4

2

1 1

1 2 1 2

2

2 1

) 2

1 1

1 2 1 2

2

2 1 4

2

2 4

2

2

4

2

2

3 2

1

1

13 Lamp

Industry

2 2

3 2

2 1

1 2

2

2

2 1 3 24 1 3

2

4 1 3

2

4 1 3 4 1 3 2

4 1 2

2

4 1 2

4 1 3 2

3 1 4

2

4 4

2

4

3

2

4 1 3 2

4 1 4

2

14 Photographic

and Film

Industry

3 2

2

2

2 1

1 2

2

2

Z 1 2

2

2 1 2 24 1 2

2

4 1 2 4 7 2

2

4 1

1 2

4 i 2 i—

2

2

T" 1 4

2

4

2 2 r

4

2

4 1 3

2

t 1 4

2 15 Other

Industrial

3 3 2

2 2V 2

J

| 1 2 2

3 1

1 2 2V 3 11 2V V2

4 1

1 2V V2 2V 2V 3 1 2

2

3 1 3

2 ^ General

Publ ic

3

1 2

2 1

2

2 1 i

2

2

] 2

2

?

17

i 18

19

20

21

22

23

24

25

10
According to the code this means the average

transaction is characterized by

Moderate volume

Growing slowly

Economically important; strongly

desirable

Under control, but could be

improved.

The main value of this average is to "calibrate" the matrix so that large deviations

from the average can be easily detected.

Using it in this manner, we find the following extremes relative to the suppliers.

Significantly greater volume than average:

NBS

Lamp Industry

Significantly less volume than average:

General Public

Documentary Specification Organizations

Other Federal Government Agencies

International Metrological Organizations

Significantly greater growth rate than

average:

Instrumentation Industry

Lamp Industry

Other Industries

Significantly smaller growth rate than

the average:

DOD

DOD Standards Labs

International Metrological Organizations

General Public

Significantly greater importance than

the average:

Lamp Industry

Photographic Industry

Instrument Industry

NBS

Significantly less importance than the

average:

International Metrological Organization

General Public

Adequacy significantly greater than

average:

General Public

International Metrological Organizations

Adequacy significantly less than average:

Knowledge Community

Documentary Specification Organizations.

At first glance, it is surprising to see how minor a role the International

Metrological Organizations and the General

Public appear to play in the total of all

radiometry and photometry transactions.

However, for this field of measurement, the

International Bureau of Weights and Measures

and the various national standards laboratories, though very important, interact

primarily among themselves. Similarly, a number of the suppliers of these goods and

services do not interact directly with the

Pub! ic.

The adequacy of the transactions is obviously a question of great interest. The

estimate that the Documentary Specification

Organizations are supplying a very inadequate

amount of information to users is a situation that requires attention. The estimate

that the Knowledge Community is seriously

deficient in spite of supplying a near average volume is due to the fact that even though the number of publications is not

low, the number of courses and the training

offered by colleges and technical schools

are completely inadequate.

Trying to summarize the transaction

matrix in terms of the users, in a similar manner to that of the suppliers, it is noted

that there are fewer extremes. The reason

for this is not clear. Such an analysis

tells us only that the total transactions to DOD and the DOD Standards Laboratories have

a significantly lower than average growth

rate which is not surprising. It also tells

us that the importance of the transactions

to NBS is significantly greater than the

average. This is due to the fact that a large number of transactions to NBS consist

of information on measurement-system needs;

and in a system that needs significant

improvement, this is of great importance.

3. IMPACT, STATUS AND TRENDS OF

MEASUREMENT SYSTEM

3.1 Impact of Measurements

3.1.1 Functional, Technological, and

Scientific Applications

Radiometric or photometric measurements

are used widely in

(1) The specification, production and

quality control of many products

(2) Public health and safety

(3) Energy development and conservation

(4) Meterology

(5) Remote sensing

(6) Scientific research

11
Brief comments will be made on each of these

areas. For more details, the reader is

referred to pages 10 to 21 of NBS Technical

Note 594-4.

The lamp manufacturers primarily sell

light. Lamps must be specified, developed,

manufactured and sold in competition with

other producers, domestic and foreign. To

do this efficiently and in an orderly manner

requires the manufacturers to make radiometric and photometric measurements that

agree, at least among themselves, to one per

cent.Photographic film and cameras must be

produced so that they are compatible with

one another. Colored pictures and presentday automatic cameras increase the compatibility requirements. Radiometry of a few

per cent or better in each of various production and testing processes is necessary

to efficiently achieve this compatibility.

Blue light is used to treat newborn

children that have jaundice. However,

experts are becoming concerned about the

possibility of using a larger dosage of

light than is necessary or desirable. Un- desirable photochemical reactions can take

place as well as desirable ones. Thus the

amount of light used in phototherapy should

be specified and controlled just as if light were a drug. Efficient and reliable radiometry is required for this purpose.

In developing more efficient lamps (same

light for less electrical power) one-percent photometry is required in order to detect small improvements in efficiency.

This is particularly important because most

improvements in present-day lamps are expected

to come in small steps of a few per cent. Similarly, radiometry will be required for

determining the efficiency of solar heaters

and converters in the development of solar

energy.

More accurate weather forecasting, both

short- and long-term, is considered possible

if more accurate radiometry were available

to determine temperatures throughout the

earth's atmosphere. A 1% accuracy and a 0.1% long-term precision is the goal — both

beyond the present practical state of the

art.Radiometric measurements of the earth's

surface from aircraft or satellites, a primary form of remote sensing, is beginning

to be used and is expected to be expanded

extensively in years to come. It is expected

to provide a tremendous amount of information

in such areas as agriculture, water and air

pollution, forestry, mapping and resource

management.

Much scientific research utilizes radiometry. Radiometric measurements play an important role in experiments designed to

increase our knowledge of atoms, molecules,

solids and liquids. It is being used increasingly in chemistry, in biology, botany,

oceanography and, of course, astronomy where much

of the information we obtain must be from

measurements on the optical radiation that

is emitted and reaches the earth.

The entire universe consists of matter

and various types of radiation including

optical radiation (infrared, visible,

ultraviolet). Because the accurate measurement of optical radiation has always been

so difficult, its use was greatly limited.

As a result of new technological developments

in solid state detectors, sources, optical

apparatus, electronics and computers it

appears as though this may be changing. In addition, the effects that optical radiation

and its measurement are known to have on public safety and health, on problems as- sociated with energy conservation and

utilization, and on our economy mean that

the number and reliability desired of such

measurements are increasing significantly.

3.1.2 Economic Impacts -- Costs and Benefits

The cost of radiometric measurements is

very high. Radiometers and spectroradiometers range in cost from about $1000 to $25,000 and standards to calibrate them

from $500 to $2000. In addition radiometric

measurements are among the most difficult

types of measurements to make. Optical

radiation varies with position in space,

direction, wavelength, polarization and

time. These variations must be taken into

account along with the manner in which a radiometer response varies with these same parameters. When this is not done, errors

of 10% are commonplace and much greater

errors are also possible. Though it would

be desirable to perform 1% measurements

routinely, this is now the best that can be

done under ideal conditions. This means

also that high-level, well-trained engineers be available to make the measurements,

but few such people are available. Few

colleges give courses in radiometry and

photometry, let along offer a complete

program in this area. Additionally, there

are no suitable modern textbooks on the

subject. Expertise, where it exists, has

been developed on the job, by "trial and

error", through years of effort at high

cost. Where it doesn't exist which is more

frequently the case, discrepancies in measurements are large, particularly between

different organizations, especially manufacturers. Resolving these discrepancies

is time consuming and costly.
As an example of how expensive radiometric measurements can be, a major industrial concern has recently required

spectral measurements from about 350 nm to 800 nm on a special low-level source that

they wished to use as a standard for simulating stars. They made measurements

themselves and had several secondary laboratories do the same. These differed by as much as 25% so NBS was requested to make

the measurements also. In order for NBS to perform the measurements to within an un- certainty of about five per cent, a cost of

$7500 in labor was incurred.

It has not been possible for us to determine the total costs or the economic

benefits of radiometric and photometric

measurements made in the Measurement System;

however, there is no question that significant amounts of money are involved.

The lamp manufacturing industry has

about one billion dollars of sales per

year. The lamp companies tell us that if

the light output of the lamps of one or a few of the companies dropped a few per

cent, it would be disastrous to their

sales. Similarly, not being able to determine the light output of some of the newer, more efficient lamps because of their

unusual spectral distributions and large

variations in intensity as a function of

wavelength would seriously impair sales.

On the other hand, an improved measurement

capability would increase the chances of

improving the efficiency of lamps [1] . When one considers that 25% of the electricity used in this country is for lighting,

an improvement in efficiency of even a few

per cent would have a significant impact.

Turning to the U.S. camera and film

industry, the effect on their 5-bill iondollar annual sales could be significant if

much poorer pictures were obtained with

U.S. products than with foreign products.

To avoid this, quality control in production

must be maintained, and this requires

reliable radiometry.

The aconomic benefits of improving the

accuracy of radiometric measurements in meteorology should be very large. If one

per cent measurements were commonplace in meteorology, experts tell us that long-term

weather forecasting would be possible

[1]. The economic benefit to U.S. farmers

alone, if they were able to predict more accurately the best time to plant or to harvest, would be quite large.

It has been reported that the routine

use of remote sensing would save the U.S.

59 billion dollars [1]. Inability to make accurate radiometric measurements is one of the limitations to more extensive

use of remote sensing.

13

Thus, even though one cannot say how much

it would cost the 1 5-bi 11 ion-doll ar-a-year

electro-optics industry if the currently

available radiometry and photometry in this

country did not exist or how much will be

saved in energy by better weather forecasting

or remote sensing when 1% measurements

become commonplace, there is little question

that the amounts will be much greater than

the approximately one million dollars per

year spent at NBS to provide standards,

standard techniques and "know how" to maintain and improve these measurements in the

U.S.

3.1.3 Social or Human Impacts

Radiometric and photometric measurements

that affect the person on the street directly

are those used for health and safety. One

example of this are the ten thousand newborn

infants that are treated for jaundice

(hyperbilirubinemia) each year by illumination with high-intensity light. The only

other treatment for this disease, prevalent

in many premature infants, is a blood ex- change which is more dangerous and for which

many small hospitals do not have the required

facilities. However, even phototherapy can

be dangerous if the intensity of the dosage

isn't under good control. This requires an easy-to-use 10% radiometry which probably

does not exist in any hospital at the

present time [5] but is well within the

current state of the art. Excessive quantities of ultraviolet light

are hazardous, causing skin burn, eye

damage and ultimately skin cancer. At the

same time, ultraviolet is being used more extensively in industry, in photochemistry,

in graphic arts and in photopolymerization

of plastic materials for coatings. Dentists

are beginning to use ultraviolet "guns" for

curing new epoxy materials used in dentistry.

Regulations are now being established by BRH

and NI0SH to protect the public from excessive

ultraviolet light. These regulations will

require reliable measurements by industry

and the regulators.

Another example of the importance of

radiometry to each one of us is the potential effect of supersonic transportation and

other things such as aerosol products, etc.,

on upper-atmosphere chemistry. "Experts"

debate what changes might occur which would

result in a significant increase in the

ultraviolet radiation incident on the

earth's surface, and in turn would have a great effect on life on earth. A National

Academy of Sciences panel, convened to examine the subject, observed that it was extremely
important to obtain base-line data of solar

ultraviolet flux and to monitor this base

1 ine accurately [1 ]

.

3.2 Status and Trends of the System

Radiometric and photometric measurements

are difficult to make, expensive and generally have very poor accuracy. This is due

in part to the nature of the measurements,

but the situation is much worse than nec- essary due to the lack of adequate inexpensive standards and the lack of adequately

trained people to make the measurements. One

strength in the system is that new solidstate detectors, sources, miniature electronics and miniature computers are improving

the instruments available for these measurements. In addition, developments are taking place at NBS which should improve the

overall situation significantly within a few

years. These consist of (1) attempts to train those needing to make radiometric and

photometric measurements by preparing a SelfStudy Manual for this purpose, (2) developing

additional and less expensive standards and

calibration services and (3) developing new- type electrically calibrated radiometers that

will improve certain types of radiometric

measurements.

4. SURVEY OF NBS SERVICES

4.1 The Past

The history of radiometry and photometry

at NBS may be divided into three periods that

we refer to as (1) the Early Period, starting

in the 1920' s and extending to about the mid

1950's, (2) the Transition Period, from about

1955 to 1965, and (3) the Modern Period,

starting in the mid 1960's and extending to the present.

Radiometry in the Early Period was one primarily involved with experiments verifying

the Planck radiation law. However, irradiance

_p (watt-meter ) standards were developed

with uncertainties of about 5%. Extensive

applications for radiometry did not exist;

moreover, the technology required for practical radiometry was not available.

The situation was somewhat different for

photometry. The widespread use of light

bulbs for illumination developed a need for

light measurements, which were required in order to have an orderly marketplace for

"selling light." As a result photometry was quite active, culminating in the 1930' s in the development of the platinum-point blackbody for the standard of light. Following

this, for about twenty years, a variety of

standard lamps and calibration techniques

were developed which were adequate for

illumination purposes. By 1955, these

photometric standards and calibration methods

had a stability and a precision of a few

percent. Accuracy, which was not nearly

as important as consistency and agreement

with others, was given little serious attention and is estimated to have been about 5%.

The Transition Period, between about 1955

and 1965, saw the first practical standards

in spectroradiometry. The U.S. space program

was the motivating factor. Also suitable

detectors and electronics were becoming

available. The accuracy of the spectralradiant standards was between 5 and 10% and

irradiance standards were improved to an accuracy of two or three per cent. The

standard lamps and calibration methods in

photometry that were developed earlier were

now being used routinely. Photometric

comparisons conducted by BIPM showed international agreement within a few per cent. There

was very little interaction between radiometry

and photometry.

For radiometry the Modern Period began in

the mid 1960's. Photoelectric optical pyrometers made it possible to determine blackbody temperatures more accurately. Military

requirements in radiometry were added to those of the space program and provided the

motivation to use this increased temperaturemeasurement capability to develop spectral

radiance standards with an accuracy of 1%.

In addition, the practical application of

electrically calibrated thermopile detectors

was initiated. It produced irradiance

standards with an accuracy of 0.5%.

For photometry the Modern Period didn't

start until about 1970. A rapidly growing

electro-optical industry required better and

additional photometric as well as radiometric

standards and measurement techniques. Also

a tighter coupling between photometry and

radiometry was desired. An extensive re- organization took place at NBS in 1971,

combining the radiometric and photometric

activities and initiating a strong effort to improve and extend standards and calibrations

in this area. By 1975, practical electrically

calibrated pyroelectric detectors had been

developed and with dye lasers are providing

a new, exciting measurement approach with

great potential

.

Also, this period saw the development of

a much stronger interaction between NBS and

industry via a new organization called the

Council for Optical Radiation Measurements.

In addition, more emphasis was being placed

on disseminating details of NBS technical

efforts through the Optical Radiation Measurements Technical Notes and communicating

more rapidly and generally through the

Optical Radiation Newsletter.

The major weakness of the modern program
has been that the resources have not been

sufficient to produce what is needed as early as it is needed.

4.2 The Present -- Scope of NBS Services

4.2.1 Description of NBS Services and

Program

The radiometric and photometric activities

at NBS are primarily situated in the Optical

Radiation Section and Radiometric Physics

Section of the Optical Physics Division of

the Institute for Basic Standards. In FY 1977, the budget associated with these

activities is about 1% million dollars, and

the staff consists of twenty-one technical

people made up of thirteen senior scientists

and engineers and eight junior professionals

or technicians. The radiometric and photometric services are developed around the

following ten-point program.

(1) Maintenance of existing standards

and provision of calibrations based

on these standards.

Approximately 26 calibration

services are offered covering the

major radiometric and photometric

quantities for which significant

interest exists. Uncertainties

in the calibrations vary from 0.5%

to 10%. NBS Special Publication

250 gives the details of these

services. The dollar volume is

about 90 thousand dollars per year.

(2) Reducing the cost and delivery time

of calibrations.

The most expensive single, routinely

offered calibration costs $2400

and has an average delivery time

of about 6 months. An extensive

effort is under way to significantly

reduce costs and delivery times

through automation.

(3) Development of new standards and

cal ibrations.

The new standards and calibrations

currently being developed or rec- ently developed are spectral

response of silicon diode detectors

that are widely needed throughout

the system, ultraviolet D

2 discharge

irradiance standards for calibrations

associated with measurements of

hazardous radiation, and spectral

total (geometrical) flux standards

so the lamp industry can better

characterize and specify their

new, more efficient lamps.

(4) Dissemination of information on measurement techniques and reference

data.

An NBS Technical Note series

entitled OPTICAL RADIATION MEASUREMENTS has been introduced in

order to publish more detailed

information than is possible in the scientific and engineering

journals and to publish progress

reports on long-term efforts.

A newsletter now published four

times a year disseminates information such as notices of meetings,

new calibration services and intercomparisons, and highlights of NBS

research and development.

(5) Providing leadership and assistance

in developing greater expertise in the System.

NBS is producing a SELF-STUDY

MANUAL ON OPTICAL RADIATION MEASUREMENTS which will be directed

at a bachelor 1 s-degree-level professional with no training in

radiometry or photometry. It is

being published in parts as completed. Four chapters have been

published, and two more are undergoing final editorial review

before publication.

(6) Develop and maintain a Measurement

Assurance Proqram to continuously

assess the accuracy and precision of

the System.

Thus far this effort has been

limited to interlaboratory com- parisons involved in transferring

calibrations from NBS standards

to working standards.

(7) Provide leadership and consulation in solving national problems involving

radiometry and photometry.

NBS has organized a workshop on radiometry requirements in solar

energy utilization, has participated

on an NRC-NAS committee concerned

with phototherapy of newborn infants

having jaundice, is helping develop

the radiometry needed for remote

sensing and is assisting the Environmental Protection Agency and the

Bureau of Radiological Health

relative to their radiometric

needs.

(8) Perform research on new techniques

and instruments.

Research on a new set of modern

tools and techniques such as electrically calibratable pyroelectric

detectors and dye lasers is being

15
pursued.

(9) Interact extensively with the System

in order to understand its needs and

priorities.

Users from industry, government and

science have organized into the

Council for Optical Radiation Measurement (CORM). CORM has submitted

to NBS two reports on Pressing

Problems and Projected National

Needs in Optical Radiation Measurements: A Consensus of Services

Desired of NBS.

(10) Interact with the international meas- urement system to insure that our national system is adequately integrated with it.

NBS is actively involved in the

Advisory Committee of Photometry

and Radiometry (CCPR) of the

International Committee of Weights

and Measures and in the Commission

Internationale de L'ficlairage

(CIE). For example NBS in con- junction with the Measurement

Laboratory of Australia has prepared a publication pressing for

the redefinition of the unit of

light. This redefinition ties

photometry directly to spectroradiometry and will enable photometry to better serve modern-day

industrial needs.

4.2.2 Users of NBS Services

The major users of NBS services are those

in the System desiring to make accurate

radiometric or photometric measurements or measurements that are consistent with others

being made in the U.S. or the world. Currently

the major users are the

Lamp Industry

Photographic Industry

Instrument Industry

DOD Standards Laboratories

Commercial Standards Laboratories

Other Federal Government Agencies

(BRH, EPA, GSA, NASA, NOAA)

Other Industries (Aerospace, Electronics, Computing, Copying, etc.)

As an example of the specific companies

involved, Appendix C contains a list of the

last fifty customers requesting photometric

calibrations from NBS. Users of NBS calibration services generally

use the calibration to establish their own

set of working standards. These working

standards are then used in such activities as

(1) calibrating radiometers and photometers,

(2) controlling the quality of production of

items like lamps, film, cameras, or components

of larger radiometric or photometric systems,

(3) establishing intensity or dosage levels

for public safety or health, or (4) performing

research in product development or science.

In addition to physical standards, NBS

also disseminates information via its scientific papers, its Technical Reports and its

Newsletter. These are distributed to members

of CORM and to others that request them.

CORM members now total over 260 and are listed in CORM Report No. 2 [3].

In general, NBS calibration and information

services provide a means for the entire

National Measurement System to be based on the same scale and units and use measurement

techniques that are similar. This significantly

increases the agreement in the results of

radiometric and photometric measurements made

throughout the System.

4.2.3 Alternate Sources

It is conceivable that, eventually,

virtually all of the calibration and testing

services will be obtained from the commercial

secondary standards laboratories. At present,

however, the frequent discrepancies in measurements encourage many users to get calibrations directly from NBS and eliminate the

additional uncertainty of a middleman. It is

expected that this will change as the capability of the entire System Improves.

4.2.4 Funding Sources for NBS Services

About 75% of NBS funding for radiometry

and photometry comes from direct congressional

appropriations. Ten per cent of the funding

comes from direct charges to customers

receiving NBS calibrations and tests, and

fifteen per cent comes from other government

agencies that have requirements for highly

specialized new standards and have contracted

for NBS to perform the necessary research and

to develop these new standards.

4.2.5 Mechanism for Supplying Services

The mechanisms for supplying NBS services

in radiometry and photometry have been

discussed throughout Section 4.2. These, and

a few not previously mentioned, are listed

below.

Cal ibrations

Other Agency Contracts

Publications

Scientific and engineering

journal

NBS Technical Notes

Self-Study Manual

Newsletter

Measurement Assurance Program

16
Organizational Contacts and

Committees (CORM, ASTM, LTEC,

IRIS, CIE)

Personal Contacts (Visits, letters,

phone calls)

.

4.3 Impact of NBS Services

4.3.1 Economic Impact of Major User Classes

Annual sales for the three major users of

NBS radiometric and photometric services are about one billion dollars for the lamp

industry, five billion dollars for the

photographic industry and a half-billion

dollars for the instrument industry [2].

CORM estimates that the annual sales of the

entire electro-optics industry, which depends

heavily on radiometric and photometric

measurements, is 15 billion dollars [3J. An idea of the economic impact of NBS services

on these companies can be obtained from many

letters received in the past few years. For example, a company in the instrumentation

industry wrote

"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."

A company in the lamp industry wrote

"The consequences of not having standards

can be summarized as follows. 1) The

(lamp) industry is unnecessarily penalized

millions of dollars through rejection of

product offerings due to differing meas- urement level ..."

The social impact of NBS services is significant relative to national security,

citizen health and safety, and advances in fundamental research. Many of the antiballistic missle defense systems utilize

radiometric guidance systems which require

calibrations tracable to NBS. Concerning

health and safety, a representative of a leading lamp company wrote NBS a letter

stating

"All germicidal, sun lamps and ozone producinq

lamps come under the jurisdiction of the

U.S. Department of Health, Education

and Welfare, Food and Druq Administration

via the Federal Hazardous Substances Act

Sec. 1Kb) 15 U.S.C. 1270(b) 1274 which

allows their aqents to inspect the product,

its packaqe label inq, its characteristics,

its place of manufacture and its enerqv

emission. In order to accurately define

the latter, UV reference standards are required.

In the area of basic research, many advances

are made possible by new instrumentation. A leading manufacturer of electro-optical

products writes

"The design and application of new electrooptical products is in many cases being

retarded by the relatively inaccurate

optical standards. Voltage, current and

resistance can be routinely measured to within 0.01% by almost any electronics

firm, while 1% optical measurements are very difficult even for NBS or other

national standard laboratories."

Additional examples of the economic impact of

NBS radiometric and photometric services can

be obtained on pages 12 to 21 in NBS Technical

Note 594-4. The role NBS services plays

relative to these impacts is to provide the

basic standards and techniques so that

national and international agreement exists

in measurements, specifications and related

activities associated with the development,

production, marketing and use of electrooptical products.

4.3.2 Technological Impact of Services

A few examples of technologies supported

by NBS radiometric and photometric services

are the

Development of more efficient lamps

Solar energy conversion

Electro-optical instrumentation

Photopolymerization.

Since 25% of the electrical power generated

in the U.S. is used for lighting, the development of lamps that can produce the same light with less electricity will have a tremendous impact. The lamp manufacturers

claim that technological advances in light

sources come in small increments, which if not discernible due to lack of precision and

accuracy in measurement may go unnoticed and

therefore discourage further development

[1].

In order to develop efficiently the

widespread use of solar energy for heating or

for the production of electricity, better

radiometry is required. Efficiencies of

solar energy converters cannot now be measured routinely to better than about 20%.

Standards and techniques being worked on at NBS would play a major role in improving this

situation.

A leading detector manufacturer says

"state-of-the-art advancements in detector

technology necessitate like advancements

in determination and transfer of standards".

Another detector manufacturer adds

"It seems to me that this whole newly emerging

area of electro-optics fundamentally rests

on a basic calibrations and traceability

capability. Without that fundamental

capability, strongly supported by the

National Bureau of Standards, the electrooptic industry is trying to walk on water."
Relative to photopolymerization , a lamp

industry spokesman writes

"The growing application for the use of UV light sources in photochemistry, in

graphic arts or for photopolymerization

of plastic materials for coatings, etc.,

is hampered by lack of accurate measuring

devices. We have had the experience of

purchasing a UV meter, which when com- pared to laboratory standards, had an error in excess of 100%, undoubtedly due

to lack of adequate reference standards."

Again, the role NBS services play in

supporting these technologies is to provide

the standards and the radiometric "know-how"

so that adequate agreement exists in measurements made by different people, in different industries and at different times.

4.3.3 Pay-off from Changes in NBS Services

The CORM report prepared in 1973 [3]

requested that NBS develop calibration

techniques and provide calibrations for light

emitting diodes (LEDs). The report stated

that

"There is more than a 40% disagreement in

specifications assigned to these devices

by the various manufacturers. In order

to provide a fair basis for domestic

competition and improve foreign sales,

these calibrations should be made

available. Without these calibrations,

the development of the associated

technology will be retarded."

NBS was able to respond rapidly to this

request. It worked with industry in developing a suitable standard and then developed a technique for calibrating these standards.

In 1974 seven standard LEDs were calibrated

for several radiometric and photometric

quantities with an uncertainty of between two

and three per cent and purchased by the major

manufacturers and users of LEDs. The calibrations have provided a simple, direct

means of calibrating instruments for the

measurement of similar LEDs and will make

possible more meaningful specifications and more uniform and predictable finished products

using LEDs. The most recent CORM report, prepared in

1975 [3], lists detector standards and

calibrations as the highest priority for new standards required of NBS. A letter from a leading instrument manufacturer written in

1972 states that

"It is estimated that between 5% to 10% of

the effort expended in last year's electrooptical market was spent in calibrating

systems or resolving calibration and

stability problems. This amounts to about

$200 million. A savings of approximately

one-half of this amount could be expected

with the successful design of a new detector standard by NBS."

A small (1% million dollars in annual sales)

manufacturer of silicon photodiodes states,

in its correspondence with NBS,

"We believe that we can continue our growth

rate at 50 to 70% a year, and continue

our overseas export growth rate at 150%

a year only with more fundamental electrooptical calibration and standards support

from the National Bureau of Standards."

Developing such detector standards has a high

priority at NBS. Finally, relative to impact, the question

"Why is Federal participation by NBS appropriate?" might and should be posed. NBS

Technical Note 594-4 answers the question in

great detail on pages 27 to 29. Some of the reasons given for "Why NBS?" include:

(1) Diversified nature of the industry

with only a few of the companies

large enough to fund the complex

research and development required

to provide accurate standards and

cal ibrations.

(2) Need for a centralized focus.

(3) Statutory obligation of NBS.

(4) NBS's role to strengthen and

advance the nation's science and

technology.

(5) Promotion of strength in the

economy and equity for the buyer

and seller.

(6) Provision of standards and test

methods for protection of the

public from specific hazards.

(7) Position of NBS on international

standards committees.

(8) Industry desire for NBS participation.

A very large company which uses photometric

standards extensively, a company which could

afford to set up its own primary standards

laboratory, asked and answered the question

of "Why NBS?" in a letter they wrote us. We

thought it appropriate to end this section

with their reply.

"Why NBS? Theoretically, some other laboratory

could maintain the standards for luminous

flux, keeping this standard in line with

the rest of the world, but anything other

than the U.S. Government would seem something

less than independent and neutral with

respect to setting commerical , industrial,

and consumer standards. In addition, the

U.S. Government is a huge consumer itself

which should justify some means of evaluating the products it purchases."

18
4.4 Evaluation of NBS Program

The NBS program in radiornetry and photometry is strongly supported by CORM and by

the NAS-NAE-NRC Evaluation Panel for the

Optical Physics Division. Eight of the ten

items in the NBS Ten-Point Program cover

specific things requested by U.S. industry.

The remaining two items concern (1) providing

assistance to other government agencies

working on national problems involving

radiornetry and photometry and (2) research on

a new set of modern tools and techniques for

radiornetry and photometry of the future. In fact, these two items interact strongly with

the other eight items specifically requested

by CORM and, in the long run, will be useful

in meeting all the urgent needs of the System.

Progress is being made on each of the ten points in the NBS program. Unfortunately

performing state-of-the-art standards work in the definitive manner required is time

consuming -- more so than is widely realized.

Repeated efforts to increase the staff and

budget to speed up the effort have not been

successful. As a result it is estimated that

another three years (1980) will be required

to meet the major requests made by industry

in CORM Report Nos. 1 and 2 issued in 1972

and 1975 respectively.

4.5 Future

We are at the beginning of a renaissance

in radiornetry and photometry. By 1980, this

renaissance will be well established. NBS

will have made significant progress in its

program of "making a few percent accuracy in radiornetry commonplace". Many new and

improved standards and calibrations, a Measurement Assurance Program, and a Self-Study

Manual will be available. In addition,

commercial instruments will have reached a new level of sophistication and efficiency.

A wide variety of solid state sources and

detectors and electrically calibrated oyroelectric radiometers will be packaged with

appropriate mini-electronics and computers

for "shirt pocket portability". A new definition for the unit of light, more useful

for modern day photometry, will have been

adopted. As a result of all these factors,

quantitative applications of optical radiation will begin to increase substantially.

Remote sensing, solar energy applications,

medical therapy, and industrial processing

will begin to use routinely what is now considered state-of-the-art radiornetry and

photometry.

What significance will this renaissance

have for NBS? First, the day-to-day demands

made on NBS relative to radiornetry and photometry will increase significantly. Second,

as the NBS Measurement Assurance Program

verifies that a few per cent measurements are being made, applications and demands requiring

a few tenths of a per cent will begin to emerge. This will necessitate an extensive

research effort requiring new equipment,

additional space and additional staff. In summary, by 1980 optical radiation measurements could be well on the way to being

recognized as one of the more important "new" measurement areas for modern technology.

5. SUMMARY AND CONCLUSIONS

This National Measurement System study has

revealed an extensive and important need in

this country for an improved capability in

radiornetry and photometry. The current

capability is limited by the lack of sufficiently accurate, readily available standards and calibrations and by the lack of

adequate training to use, efficiently and

correctly, existing standards and calibrations.

NBS is uniquely situated to improve this

condition and has initiated a program to do

so. Those in industry, government and the

universities concerned with this measurement

area have organized the Council for Optical

Radiation Measurement (CORM), which provides

a continuous input to NBS on specific problems,

needs and priorities. Such input resulted in new budget initiatives to expand greatly NBS' effort in this measurement area. Though

these failed, they provided the impetus to bolster the effort through reprogramming and

the attraction of visiting scientists. The

resulting NBS program emphasizes the creation

of new spectral and detector standards, the

development of a new photometric SI unit

based on radiornetry, and the establishment of

a well -documented, efficient calibration

service and Measurement Assurance Program

(MAP). Finally, and possibly of greatest

importance, plans are now being carried out

to produce a Self-Study Manual to provide the

training in basic concepts and laboratory

techniques required in the National Measurement System.

19
APPENDIX A. Optical Radiation

Raws This newsletter is prepared bimonthly by the staff of the Optical Radiation Section of NBS to report on items of interest in optical radiation measurements.

Inquiries may be directed to A.T. Hattenburg, A223 Physics Bldg., NBS, Wash. DC 20234 (301-921-2008).

U.S. DEPARTMENT OF COMMERCE National Bureau of Standards

NO. 3

May 1974

RADIOMETRY AND PHOTOMETRY AT NBS*

Current Capability and FY 74 & 75 Efforts

The current goal in radiometry and photometry at NBS is to make 1% measurements common

place in the United States. Our overall approach has involved:

1. Developing and providing the standards and calibrations required in our National Measurement System.

2. Disseminating the techniques and basic concepts that will be used with

the above standards.

3. Assessing and verifying the capability of the System.

In addition, a small research effort has been directed towards higher accuracy measure

ment problems, and this effort will increase as our 1% goal is approached.

Our current distribution of effort, and that anticipated in FY 75, is shown in Table 1

DISTRIBUTION OF EFFORT

CURRENT FY 75 FY 76 STANDARDS 75% 50% 2 0% lo ?

BASIC CONCEPTS , Q 30 30 lo ' & TECHNIQUES

VERIFICATION 15 15

RESEARCH 5

Table 1.

*This article is an expanded version of the presentation made by H. J. Kostkowski, Chief,

Optical Radiation Section, at the April 22, 1974, CORM meeting at NBS

20
Trends are also given for FY 76. However, reader input and, in particular, the pending

updating of the CORM report, "A Consensus of Services Desired of NBS", will have a significant impact on our FY 76 and longer-term efforts.

This article will summarize our present capability and FY 74 and 75 efforts, in terms

of the calibration, information, and intercomparison services we provide.

Spectral radiance is usually considered the most basic radiometric measurement parameter. Figure 1 depicts the spectral radiance calibrations currently available from NBS.

SPECTRAL RADIANCE CALIBRATIONS

225nm 500nm 2 4//m bOfJm

i •..•>• nm sleradian

2800K TUNG

STRIP LAMP 2% 1% 6%

400-700K

BLACKBODY 1%

200-400K

8LACKB00Y

TRITIUM ACTIVATED *%

SELF LUMINOUS SOURCE

10 4^wam/cm2 /nm/steradian

Fig.

The scale associated with these calibrations extends from 10 1* to 10 -1+ uW/cm2 nm sr and the

uncertainty from 0.6% to 4%. The 200-400 K blackbody calibration facility is not quite

operational on a routine basis. During the coming fiscal year, our major effort in spectral radiance measurements will be directed towards making such calibrations significantly

less expensive and available in a much shorter time. The present costs and delivery times

vary from $1490-$1960 and from six to twelve months, respectively.

Spectral irradiance is probably the most widely used radiation parameter. Figure 2

SPECTRAL IRRADIANCE CALIBRATIONS

10 ATW

sAn

T TM3 sucm^^~

,

% 100Q juNGSTEN-HALOGEN

.* / AT 50 cm

15 WATT LED AT 10 cm

| 10

' S

- 10

J

S 10

5

10 ' /TT

A

2 5*

C0LLIMATED FILTERED 150 WATT

150 WATT TUNGSTEN

200 400 600 800nm 1 Ojjm 12 14 16

Fig. 2

shows that the available calibrations for this parameter also cover 8 orders of magnitude

with an uncertainty varying from 1% at the highest level to 5% at the lowest. Our current

and FY 75 efforts involving spectral irradiance include

21
1. Maintaining the new 1973 NBS Scale and extending it from 1.6 um to 2.4 um.

2. A Technical Note giving a detailed description of the apparatus and techniques used in realizing the new scale.

3. Establishing deuterium lamp standards and calibrations to 200 nm.

4. Reducing the uncertainties for color temperature standards and calibrations

by a factor of approximately five.

Our current capability and available calibrations for the quantity irradiance are

600 yW/cm2 — 2%

3 mW/cm2 — 2%

30 mW/cm2 — 1%

130 mW/cm2 — 0.5%

The 30 and 130 mW/cm2 levels are maintained with a Thermopile Electrically Calibrated

Radiometer. During the past year we developed a prototype for an AC null-balance Pyroelectric Electrically Calibrated Radiometer (PECR) which, when improved, is expected to maintain the two lower levels of irradiance listed above, reduce their uncertainty and

extend our available calibrations to 10 yW/cra2

. In addition, the null-balance PECR should

make possible, for the first time, a radiometer which has all the following characteristics

1. Accurately calibrated by electrical measurements

2. A flat spectral response

3. Fast

4. Sensitive

5. Easy to use.

In the irradiance area, we also plan to improve the delivery time on calibrations and provide a detailed description of our calibration procedures.

Luminous intensity calibrations at about 90, 700 and 1400 candelas with an uncertainty

relative to NBS units of 1.5% and to SI units of 4% have been available for some time. In

the coming year we plan to determine an NBS (lumens/watt) relating the NBS luminous

intensity and spectral irradiance scales. This will improve the long-term stability of the

NBS luminous intensity standards, reducing the above stated 1.5% to about half this value,

and will enable precise photometric calibrations to be derived from NBS spectroradiometric

standards. Moreover, there is an international move under way to adopt a definition for

photometric units that is based on a definition of 1^. When this occurs the SI uncertainty

of 4% should be reduced to about 1%.

Luminous flux (lumens) is a photometric parameter of great interest relative to lighting and improving the efficiency of lamps. This is particularly important now because

about 25% of all of the electrical energy in the United States is used for lighting. This

past year our luminous flux calibrations (5 levels from 10 000 to 270 lumens) have been

extended to cover miniature lamps ranging from 400 to 6 lumens with NBS uncertainties of

3% and SI uncertainties of 5%. We also published a Technical Note on the Theory of Integrating Spheres, devices frequently used in comparing lamps for luminous flux. We will

soon complete the development of a gonioradiometer for a more accurate realization of

luminous flux standards and for the generation of a standard for spectral flux (watts/nm)

.

I believe we will be the first national laboratory to provide calibrations of this parameter. It is required for accurate measurements of modern high pressure and metal additive

lamps

.

22
The advent of silicon photodiode detectors a few years ago has precipitated the com- mercial availability of a variety of high-precision radiometers. For these devices to be

used accurately, knowledge of their spectral response as a function of wavelength is

required. In FY 1974 NBS initiated a program for developing such a capability. Initial

calibrations from 350 to 1200 nm with an uncertainty of about 5% are expected to be available in FY 75. In the longer run, we expect that the continued development of PECR's and

the use of dye lasers with these pyroelectric devices will enable us to significantly

reduce this 5% uncertainty for spectral response calibrations.

Table 2 is a summary of the new calibrations provided during the past fiscal year and

what we expect to make available in the coming year.

SUMMARY OF NEW CALIBRATIONS

FT 74

LUMINOUS FLUX OF MINIATURE LAMPS

|6 - 600 tuoeasl

IMPROVED SPECTRAL

IRRADIANCE |l%]

LEO slF.,, I, II

SLSs [L vl

LOW LEVEL COLLIMATED

FT 75

SPECTRAL RADIANCE I

IRRADIANCE IREDUCEO COST i TIME

LOW TEMP. BLACKBOOIES

COLOR TEMP. [ HIGHER ACCUR.)

LUMINOUS FLUX

(HIGHER ACCUR ] SPECTRAL FLUX SPECTRAL RESPONSE

DEUTERIUM LAMP |E„ 200 -350 nm]

Table 2.

Relative to dissemination of techniques, two years ago we introduced NBS Technical

Note 594, a continuing series of publications on optical radiation measurements. This has

provided a vehicle for describing apparatus, methods, and results in considerably more

detail than is possible in regular scientific and engineering journals. In FY 74 the following four such notes were issued:

594-5, "Stability and Temperature Characteristics of Some Silicon and

Selenium Photodetectors" by K. Mohan, A. R. Schaefer and

E. F. Zalewski.

594-6, "The Present State of Radiometry and Photometry" by Bruce Steiner.

594-7, "Approximate Theory of the Photometric Integrating Sphere" by

W. B. Fussell.

594-8, "Tables of Diffraction Losses" by W. B. Fussell (Available

June 1974)

.

Technical Notes on the following topics are being planned for the next 12 months:

NBS spectral radiance scale and calibrations

Apparatus and techniques used in realizing the NBS 1973 scale

of spectral irradiance

Laboratory intercomparison for luminous intensity and infrared

spectral radiance

Calibration of self-luminous sources

On realizing a scale of spectral flux

23
A facility for low-temperature blackbody calibrations

Radiometric calibration procedures

In FY 1975, we will initiate an extensive effort to produce the Self-Study Manual discussed in the March '74 Optical Radiation News. During FY 1975 the effort will be directed

at the basic concepts and apparatus portion of this manual with sections on radiometric

quantities, sources, detectors and dispersion devices. These will be issued as they become

available in a separate technical note series.

The assessment and verification of the U.S. capability in radiometry and photometry is

being conducted through inter laboratory comparisons. Intercomparisons involving luminous

intensity and infrared spectral radiance have been completed and the associated reports are being written. An intercomparison involving the spectral radiance of tungsten strip lamps

has been initiated and in FY 75 spectral irradiance and spectral response of detectors will

be added. In the long run we expect this Measurement Assurance Program (MAP) , as it is

sometimes called, to include "audit packages" consisting of one or more sources, detectors

and filters and a set of statistically designed self-checking experiments.

We welcome comments and questions on our current capabilities and present and nextyear efforts. Priorities assigned to the various items in our program will be influenced

by demonstrations of specific interest from the technical community, as evidenced by

requests for new calibrations, suggested topics for our self-study manual, or participation

in laboratory intercomparisons.

SPECTRAL IRRADIANCE SCALE CHANGE

On September 1, 1973, the Optical Radiation Section began issuing lamps on a new scale

of spectral irradiance. 1 This 1973 scale superseded the previous (1963) scale. 2 From its

realization until its replacement, the 1963 scale was maintained in banks of type DXW lamps.

Four of the lamps that maintained the 1963 scale have been measured on the 1973 scale. The

ratio of the spectral irradiance measured on the 1973 scale to the spectral irradiance

assigned on the 1963 scale was: 0.90 at 250 nm, 0.95 at 350 nm, 1.00 at 450 nm, 0.98 at 600 nm, 0.94 at 800 nm, 0.93 at 1300 nm and 0.89 at 1600 nm. The four measured lamps

differed among themselves over a range of 2-3% for all wavelengths.

The results of this experiment cannot be used to adjust accurately other lamps from

the 1963 scale to the 1973 scale. Type DXW lamps have exhibited varying drift rates (with

burning time) 3 and at present little is known of the magnitude of any possible "shelf

effect".

The 1973 scale is being maintained by periodic reference to the NBS high accuracy

spectral radiance standard and thus ultimately to a gold-point blackbody. It is expected

that this procedure will eliminate, or at least minimize, the uncertainties associated

with lamp drift in the future maintenance of this scale.

1 Optical Radiation News, No. 1, January 1974.

2 R. Stair, W. E. Schneider and J. K. Jackson, "A New Standard of Spectral Irradiance",

Appl. Opt. 2, p. 1151 (1963).

3 "Lamp Standards of Spectral Irradiance", available on request from the Optical

Radiation News.

24
SPECTRAL IRRADIANCE INTERCOMPARISON

As part of the program to assess and verify measurements made in laboratories other

than NBS, the calibration and dissemination group is planning an intercomparison of spectral

irradiance measurements. This intercomparison will begin early in September 1974. It will

cost the participants about $500 and require approximately one man week of work in the

participating laboratory.

Laboratories interested in participating in this intercomparison may obtain further

details from:

Donald McSparron

« NBS, Optical Radiation Section

Room B-312, Metrology Building

Washington, D.C. 20234

(301) 921-2113

25
APPENDIX B. COMMERCIAL (PUBLIC ISSUANCE) CALIBRATION LABORATORIES*

Radiometric Calibrations

EG&G

Bedford Division

Cosby Drive

Bedford, MA 01730

Eppley Laboratories, Inc. Newport, RI 02840

Optromc Laboratories

7676 Fenton Street

Silver Spring, MD 20910

Photometric Calibrations

Ann Arbor Testing Laboratories

P.O. Box 2078

Ann Arbor, MI 48103

Electrical Testing Laboratories

2 East End Avenue

New York, NY 10021

Gamma Scientific, Inc. 2165 Kurtz Street

San Diego, CA 92110

Hoffman Engineering Corporation

183 R. Sound Beach Avenue

Old Greenwich, CT 06870

Industrial Testing Laboratories

University of California

Room 6, McLaughlin Hall

Berkeley, CA 94720

Lighting Engineers, Inc. 1681 West Broadway

Anaheim, CA 92802

*Placement on this list indicates either or both

of the following: (1) membership in CORM; (2)

a previous request to NBS that their name be

mentioned to people inquiring about the availability of calibration services in the U.S.

Thus this list is in no sense comprehensive.

Further, it should be clearly recognized by

all users of the list that NBS is not certifying,

recommending, or endorsing the laboratories

or their measurement capability.

26
APPENDIX C. TYPICAL CUSTOMERS THAT REQUEST PHOTOMETRIC

CALIBRATIONS FROM NBS

GSA

Arnold Research 0. WAMCO

NASA J.F. Kennedy Center

RCA

Sperry Flight Systems

Hoffman Eng.

Lighting Engineers

Eastman Kodak

Kaelite Corp.

McDonnell Douglas

Hughes Aircraft

Beoing Aerospace

Hughes Aircraft

Gamma Scientific

Kaelite Corp.

Dupree, Inc. McDonnell Douglas

Singer Co.

ITL Tektronix, Inc. Gamma Scientific

Weston Instru. Optronic Labs

TRW Systems

Gassen

Hoffman

Singer Co. RCA

ETL Weston

Eastman

Hughes Aircraft

Weston

Sperry Flight Systems

Gassen

Gaileo Corp.

Hoffman

GE

Sylvania

Weston Inst. United Standards Laboratory

U. of Iowa 3M Company

Naval Avionics Fac. Weston Instruments

Kollmorgen Corp.

Newark AFB Sylvania

27
REFERENCES

[1] Steiner, Bruce, "Optical Radiation Measurements: The Impact of Radiometry

and Photometry and the Role of NBS", NBS Tech Note 594-4, 1973.

[2] Steiner, Bruce, "Optical Radiation Measurements: The Present State of

Radiometry and Photometry", NBS Tech Note 594-6, 1974.

[3] Council for Optical Radiation Measurements, "Optical Radiation Measurements

Pressing Problems and Projected National Needs in Optical Radiation Measurements -- A Consensus of Services Desired of NBS", #l/#2. Jan. 1975, E. Steeb Large Lamp Division, GE Co., Nela Park, Cleveland, OH 44112.

[4] Velma I. Burns and Donald A. McSparron, "Optical Radiation Measurements:

Photometric Calibration Procedures", NBS Tech Note 594-3, 1972.

[5] Committee on Phototherapy in the Newborn, National Research Council,

"Final Report of the Committee", National Academy of Sciences, 1974.

28
NBS-U4A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

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1. PUBLICATION OR REPORT NO. NBSIR75-9392. Gov't Accession

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3. Recipient's Accession No.

4. TITLE AND SUBTITLE The National Measurement System For Radiometry and

Photometry

5. Publication Date November 1977

6. Performing Organization Code

7. AUTHOR(S)

Henrv J. Kostkowski

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NATIONAL BUREAU OF STANDARDS

UtrAK 1 Men 1 Ur LUMMtKLt

WASHINGTON, D.C. 20234

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)

Detectors; National Measurement System; photometry; radiometry; sources; standards; survey.

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