ASTM E2153-01(2017)

Standard Practice for Obtaining Bispectral Photometric Data for Evaluation of Fluorescent Color

SIGNIFICANCE AND USE
5.1 The bispectral or two-monochromator method is the definitive method for the determination of the general (illuminant-independent) radiation-transfer properties of fluorescent specimens (2). The Donaldson radiance factor is an instrument- and illuminant-independent photometric property of the specimen, and can be used to calculate its color for any desired illuminant and observer. The advantage of this method is that it provides a comprehensive characterization of the specimen’s radiation-transfer properties, without the inaccuracies associated with source simulation and various methods of approximation.  
5.2 This practice provides a procedure for selecting the operating parameters of bispectrometers used for providing data of the desired precision. It also provides for instrument calibration by means of material standards, and for selection of suitable specimens for obtaining precision in the measurements.
SCOPE
1.1 This practice addresses the instrumental measurement requirements, calibration procedures, and material standards needed for obtaining precise bispectral photometric data for computing the colors of fluorescent specimens.  
1.2 This practice lists the parameters that must be specified when bispectral photometric measurements are required in specific methods, practices, or specifications.  
1.3 This practice applies specifically to bispectrometers, which produce photometrically quantitative bispectral data as output, useful for the characterization of appearance, as opposed to spectrofluorimeters, which produce instrument-dependent bispectral photometric data as output, useful for the purpose of chemical analysis.  
1.4 The scope of this practice is limited to the discussion of object-color measurement under reflection geometries; it does not include provisions for the analogous characterization of specimens under transmission geometries.  
1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Historical
• Publication Date: 31-Oct-2017
• ICS: 35.240.99 - IT applications in other fields
• Technical Committee: E12 - Color and Appearance
• Drafting Committee: E12.05 - Fluorescence

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2153 − 01 (Reapproved 2017)
Standard Practice for
Obtaining Bispectral Photometric Data for Evaluation of
Fluorescent Color
This standard is issued under the fixed designation E2153; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The fundamental procedure for evaluating the color of a fluorescent specimen is to obtain bispectral
photometric data for specified irradiating and viewing geometries, and from these data to compute
tristimulus values based on a CIE (International Commission on Illumination) standard observer and
a CIE standard illuminant. The considerations involved and the procedures used to obtain precise
bispectral photometric data are contained in this practice. Values and procedures for computing CIE
tristimulus values from bispectral photometric data are contained in Practice E2152. General
considerations regarding the selection of appropriate irradiating and viewing geometries are contained
in Guide E179; further specific considerations applicable to fluorescent specimens are contained in this
practice.
1. Scope establish appropriate safety, health, and environmental prac-
tices and determine the applicability of regulatory limitations
1.1 This practice addresses the instrumental measurement
prior to use.
requirements, calibration procedures, and material standards
1.6 This international standard was developed in accor-
needed for obtaining precise bispectral photometric data for
dance with internationally recognized principles on standard-
computing the colors of fluorescent specimens.
ization established in the Decision on Principles for the
1.2 This practice lists the parameters that must be specified
Development of International Standards, Guides and Recom-
when bispectral photometric measurements are required in
mendations issued by the World Trade Organization Technical
specific methods, practices, or specifications.
Barriers to Trade (TBT) Committee.
1.3 This practice applies specifically to bispectrometers,
2. Referenced Documents
which produce photometrically quantitative bispectral data as
output, useful for the characterization of appearance, as op- 2
2.1 ASTM Standards:
posed to spectrofluorimeters, which produce instrument-
E179 Guide for Selection of Geometric Conditions for
dependent bispectral photometric data as output, useful for the
Measurement of Reflection and Transmission Properties
purpose of chemical analysis.
of Materials
1.4 The scope of this practice is limited to the discussion of E284 Terminology of Appearance
E925 Practice for Monitoring the Calibration of Ultraviolet-
object-color measurement under reflection geometries; it does
not include provisions for the analogous characterization of Visible Spectrophotometers whose Spectral Bandwidth
does not Exceed 2 nm
specimens under transmission geometries.
E958 Practice for Estimation of the Spectral Bandwidth of
1.5 This standard may involve hazardous materials,
Ultraviolet-Visible Spectrophotometers
operations, and equipment. This standard does not purport to
E1164 Practice for Obtaining Spectrometric Data for Object-
address all of the safety concerns, if any, associated with its
Color Evaluation
use. It is the responsibility of the user of this standard to
E1341 Practice for Obtaining Spectroradiometric Data from
Radiant Sources for Colorimetry
This practice is under the jurisdiction of ASTM Committee E12 on Color and
Appearance and is the direct responsibility of Subcommittee E12.05 on Fluores-
cence. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2017. Published November 2017. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2001. Last previous edition approved in 2011 as E2153 – 01 (2011). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E2153-01R17. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2153 − 01 (2017)
E2152 Practice for Computing the Colors of Fluorescent 3.2.6 diagonal fluorescence, n—the contribution of fluores-
Objects from Bispectral Photometric Data cence to diagonal values of a bispectral radiance factor matrix,
due to the finite range of actual irradiation and viewing
2.2 NPL Publications:
wavelengths when nominal irradiation and viewing wave-
NPL Report MOM 12 Problems of spectrofluorimetric stan-
lengths are equal (µ = λ).
dards for reflection and colorimetric use
3.2.7 discrete bispectral radiance factor, B(µ,λ), n—the
2.3 CIE Publications:
matrix defined for specified irradiation and viewing bandpass
CIE No. 38-1977 Radiometric and Photometric Characteris-
functions, and viewing-wavelength sampling interval (Δλ) as
tics of Materials and Their Measurement
follows:
CIE 15 Colorimetry
CIE 182:2007: Calibration Methods and Photoluminescent
H
B~µ,λ![b ~µ!·Δλ (2)
λ
Standards for Total Radiance Factor Measurement
where:
2.4 NIST Publications:
¯
NBS No. 260-66 Didymium Glass Filters for Calibrating the b (µ) = the average bispectral radiance factor of the
λ
Wavelength Scale of Spectrophotometers specimen, as weighted by the specified irradiation
and viewing bandpass functions.
3. Terminology
3.2.8 Donaldson radiance factor, D(µ,λ), n—a special case
3.1 Definitions—The definitions contained in Terminology
of the discrete bispectral radiance factor, for which the speci-
E284 are applicable to this practice.
fied irradiation and viewing bandpass functions are perfectly
rectangular, with bandwidth equal to irradiation and viewing-
3.2 Definitions of Terms Specific to This Standard:
wavelength sampling interval.
3.2.1 bispectral fluorescence radiance factor, b (µ), n—the
F
λ
ratio of the spectral radiance at wavelength λ due to fluores-
NOTE 2—The Donaldson radiance factor is approximately equal to the
cence from a point on the specimen when irradiated at ratio of the specimen radiance within the rectangular waveband of width
Δλ centered at λ to the radiance of the perfect reflecting diffuser when each
wavelength µ to the total radiance of the perfectly reflecting
is irradiated over the rectangular waveband of width Δλ centered at µ.
diffuser similarly irradiated and viewed (see NPL Report
3.2.9 fluorescence, n—this standard uses the term “fluores-
MOM 12).
cence” as a general term, including both true fluorescence
3.2.2 bispectral radiance factor, b (µ), n—the ratio of the
λ
-8
(with a luminescent decay time of less than 10 s) and
spectral radiance (radiance per unit waveband) at wavelength λ
phosphorescence with a delay time short enough to be indis-
from a point on a specimen when irradiated at wavelength µ to
tinguishable from fluorescence for the purpose of colorimetry.
the total (integrated spectral) radiance of the perfectly reflect-
3.2.10 near-diagonal element, n—off-diagonal elements of
ing diffuser similarly irradiated and viewed.
an uncorrected bispectral matrix whose values include a
b µ [L µ /L µ (1)
~ ! ~ ! ~ !
λ λ
d
significant reflection component, due to reflection overspill.
3.2.3 bispectral reflection radiance factor, b (µ), n—the
Rλ
For instruments with irradiation and viewing bandpass func-
ratio of the spectral radiance at wavelength λ due to reflection
tions which approximate the recommended trapezoidal or
from a point on the specimen when irradiated at wavelength µ
triangular shape, this should be limited to within two to three
to the total radiance of the perfectly reflecting diffuser similarly
bands of the diagonal.
irradiated and viewed.
3.2.11 off-diagonal element, n—any element of a bispectral
3.2.4 bispectrometer, n—an optical instrument equipped
matrix for which irradiation and viewing wavelengths are not
with a source of irradiation, two monochromators, and a
equal.
detection system, such that a specimen can be measured at
3.2.12 reflection overspill, n—the contribution of reflection
independently-controlled irradiation and viewing wavelengths.
to off-diagonal values of the discrete bispectral radiance factor
The bispectrometer is designed to allow for calibration to
matrix, due to the partial overlap of irradiation and viewing
provide quantitative determination of the bispectral radiation-
wavebands when nominal irradiation and viewing wavelengths
transfer properties of the specimen. (1)
are not equal (µ≠λ).
NOTE 1—Typically, a reference detection system monitors the radiation
3.2.13 spectral effıciency factor, b(µ), n—the ratio of the
incident on the specimen. This reference detection system serves to
total (integrated spectral) radiance from a point on a specimen
compensate for both temporal and spectral variations in the flux incident
upon the specimen, by normalization of readings from the instrument’s
when irradiated at wavelength µ to the total radiance of the
emission detection system.
perfectly reflecting diffuser identically irradiated and viewed.
3.2.5 diagonal elements, n—elements of a bispectral matrix
b~µ![L~µ!/L~µ! (3)
d
for which irradiation and viewing wavelengths are equal.
4. Summary of Practice
4.1 Procedures are given for selecting the types and oper-
Available from National Physical Laboratory, Queens Road, Teddington,
Middlesex, United Kingdom TW11 0LW, http://www.npl.co.uk/.
ating parameters of bispectrometers used to provide data for
Available from CIE (International Commission on Illumination) at
the calculation of CIE tristimulus values and other colorimetric
www.cie.co.at or www.techstreet.com.
5 values to quantify the colors of objects. The important steps in
Available from National Institute of Standards and Technology (NIST), 100
Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov. the calibration of such instruments, and the material standards
E2153 − 01 (2017)
required for these steps, are described. Guidelines are given for 6.1.3 The spectral parameters for both irradiation and
the selection of specimens to obtain the highest measurement viewing, including wavelength range, wavelength measure-
precision. Parameters are identified which must be specified ment interval, and spectral bandpass.
when bispectral photometric measurements are required in 6.1.4 Identification of the material standards used for instru-
specific test methods or other documents. ment calibration.
6.1.5 Special requirements determined by the nature of the
4.2 In this practice, the measuring instrument, a
specimen, such as measurement orientation for anisotropic
bispectrometer, is equipped with two separate monochroma-
specimens.
tors. The first, the irradiation monochromator, irradiates the
specimen with monochromatic light. The second, the viewing
7. Apparatus
monochromator, analyzes the radiation leaving the specimen.
7.1 Bispectrometer—The basic instrumental requirement is
A two-dimensional array of bispectral photometric values is
a bispectrometer designed for measurement of Donaldson
obtained by setting the irradiation monochromator at a series of
radiance factor using one or more of the standard irradiation
fixed wavelengths (µ) in the excitation band of the specimen,
and viewing geometries described in Section 8.
and for each µ, using the viewing monochromator to record
readings for each wavelength (λ) in the specimen’s emission
7.2 Irradiator—The irradiator, which consists of the radia-
range. The resulting array, once properly corrected, is known as
tion source, a dispersive element and related optical
the Donaldson matrix (2), and the value of each element (µ,λ)
components, shall irradiate the specimen with monochromatic
of this array is the Donaldson radiance factor (D(µ,λ)).
radiation of known wavelength bandpass and measurement
interval.
4.3 While recognizing the CIE recommendation (in CIE 15)
7.2.1 The radiation source must be stable with time and
of numerical integration at 1 nm intervals as the basic
have adequate energy output over the wavelength range used
definition, this practice is limited in scope to measurements and
for specimen irradiation.
calculations using spectral intervals greater than or equal to 5
7.2.2 The dispersive element, which provides energy in
nm.
narrow wavelength bands across the UV and visible spectral
range, may be a prism, a grating, or one of various forms of
5. Significance and Use
interference filters or wedges. The element should conform to
5.1 The bispectral or two-monochromator method is the
the following requirements:
definitive method for the determination of the general
7.2.2.1 When highest measurement accuracy is required, the
(illuminant-independent) radiation-transfer properties of fluo-
wavelength range should extend from 300-830 nm; otherwise
rescent specimens (2). The Donaldson radiance factor is an
the range from 300 to 780 nm should suffice. For specimens
instrument- and illuminant-independent photometric property
confirmed to be non-fluorescent or those exhibiting only
of the specimen, and can be used to calculate its color for any
visible-activated fluorescence (negligible excitation below 380
desired illuminant and observer. The advantage of this method
nm), the wavelength range from 380 to 780 can be used. Each
is that it provides a comprehensive characterization of the
user must decide whether the loss of accuracy in the measure-
specimen’s radiation-transfer properties, without the inaccura-
ments is negligibly small for the purpose for which data are
cies associated with source simulation and various methods of
obtained.
approximation.
7.2.2.2 The wavelength interval should be 5 or 10 nm. Use
5.2 This practice provides a procedure for selecting the
of wider wavelength intervals, such as 20 nm, may result in
operating parameters of bispectrometers used for providing
reduced accuracy. Each user must decide whether the loss of
data of the desired precision. It also provides for instrument
accuracy in the measurements is negligibly small for the
calibration by means of material standards, and for selection of purpose for which data are obtained.
suitable specimens for obtaining precision in the measure-
7.2.2.3 The irradiation wavelength interval should equal the
ments. viewing wavelength interval.
7.2.2.4 The spectral bandpass (full-width at half maximum
6. Requirements for Bispectral Photometry power in the band of wavelengths transmitted by the dispersive
element) should, for best results, be equal to the wavelength
6.1 When describing the measurement of specimens by the
in
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2153 − 01 (Reapproved 2011) E2153 − 01 (Reapproved 2017)
Standard Practice for
Obtaining Bispectral Photometric Data for Evaluation of
Fluorescent Color
This standard is issued under the fixed designation E2153; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The fundamental procedure for evaluating the color of a fluorescent specimen is to obtain bispectral
photometric data for specified irradiating and viewing geometries, and from these data to compute
tristimulus values based on a CIE (International Commission on Illumination) standard observer and
a CIE standard illuminant. The considerations involved and the procedures used to obtain precise
bispectral photometric data are contained in this practice. Values and procedures for computing CIE
tristimulus values from bispectral photometric data are contained in Practice E2152. General
considerations regarding the selection of appropriate irradiating and viewing geometries are contained
in Guide E179; further specific considerations applicable to fluorescent specimens are contained in this
practice.
1. Scope
1.1 This practice addresses the instrumental measurement requirements, calibration procedures, and material standards needed
for obtaining precise bispectral photometric data for computing the colors of fluorescent specimens.
1.2 This practice lists the parameters that must be specified when bispectral photometric measurements are required in specific
methods, practices, or specifications.
1.3 This practice applies specifically to bispectrometers, which produce photometrically quantitative bispectral data as output,
useful for the characterization of appearance, as opposed to spectrofluorimeters, which produce instrument-dependent bispectral
photometric data as output, useful for the purpose of chemical analysis.
1.4 The scope of this practice is limited to the discussion of object-color measurement under reflection geometries; it does not
include provisions for the analogous characterization of specimens under transmission geometries.
1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all
of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate
safety safety, health, and healthenvironmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E179 Guide for Selection of Geometric Conditions for Measurement of Reflection and Transmission Properties of Materials
E284 Terminology of Appearance
E925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidth does not
Exceed 2 nm
E958 Practice for Estimation of the Spectral Bandwidth of Ultraviolet-Visible Spectrophotometers
This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.05 on Fluorescence.
Current edition approved Nov. 1, 2011Nov. 1, 2017. Published November 2011November 2017. Originally approved in 2001. Last previous edition approved in 20062011
as E2153 - 01 (2006).E2153 – 01 (2011). DOI: 10.1520/E2153-01R11.10.1520/E2153-01R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2153 − 01 (2017)
E1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation
E1341 Practice for Obtaining Spectroradiometric Data from Radiant Sources for Colorimetry
E2152 Practice for Computing the Colors of Fluorescent Objects from Bispectral Photometric Data
2.2 NPL Publications:
NPL Report MOM 12 Problems of spectrofluorimetric standards for reflection and colorimetric use
2.3 CIE Publications:
CIE No. 3838-1977 Radiometric and Photometric Characteristics of Materials and Their Measurement
CIE No.15.215 Colorimetry, 2nd EditionColorimetry
CIE Report of TC-2.25:182:2007: Calibration Methods and Photoluminescent Standards for Total Radiance Factor Measure-
ment
2.4 NIST Publications:
NBS No. 260-66 Didymium Glass Filters for Calibrating the Wavelength Scale of Spectrophotometers
3. Terminology
3.1 Definitions—The definitions contained in Terminology E284 are applicable to this practice.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 bispectral fluorescence radiance factor, b (μ), n—the ratio of the spectral radiance at wavelength λ due to fluorescence
F
λ
from a point on the specimen when irradiated at wavelength μ to the total radiance of the perfectly reflecting diffuser similarly
irradiated and viewed (see NPL Report MOM 12).
3.2.2 bispectral radiance factor, b (μ), n—the ratio of the spectral radiance (radiance per unit waveband) at wavelength λ from
λ
a point on a specimen when irradiated at wavelength μ to the total (integrated spectral) radiance of the perfectly reflecting diffuser
similarly irradiated and viewed.
b μ [L μ /L μ (1)
~ ! ~ ! ~ !
λ λ
d
3.2.3 bispectral reflection radiance factor, b (μ), n—the ratio of the spectral radiance at wavelength λ due to reflection from
RRλλ
a point on the specimen when irradiated at wavelength μ to the total radiance of the perfectly reflecting diffuser similarly irradiated
and viewed.
3.2.4 bispectrometer, n—an optical instrument equipped with a source of irradiation, two monochromators, and a detection
system, such that a specimen can be measured at independently-controlled irradiation and viewing wavelengths. The
bispectrometer is designed to allow for calibration to provide quantitative determination of the bispectral radiation-transfer
properties of the specimen. (1)
NOTE 1—Typically, a reference detection system monitors the radiation incident on the specimen. This reference detection system serves to compensate
for both temporal and spectral variations in the flux incident upon the specimen, by normalization of readings from the instrument’s emission detection
system.
3.2.5 diagonal elements, n—elements of a bispectral matrix for which irradiation and viewing wavelengths are equal.
3.2.6 diagonal fluorescence, n—the contribution of fluorescence to diagonal values of a bispectral radiance factor matrix, due
to the finite range of actual irradiation and viewing wavelengths when nominal irradiation and viewing wavelengths are equal (μ
= λ).
3.2.7 discrete bispectral radiance factor, B(μ,λ), n—the matrix defined for specified irradiation and viewing bandpass functions,
and viewing-wavelength sampling interval (Δλ) as follows:
H
B μ,λ [b μ ·Δλ (2)
~ ! ~ !
λ
where:
b¯ (μ) = the average bispectral radiance factor of the specimen, as weighted by the specified irradiation and viewing bandpass
λ
functions.
3.2.8 Donaldson radiance factor, D(μ,λ), n—a special case of the discrete bispectral radiance factor, for which the specified
irradiation and viewing bandpass functions are perfectly rectangular, with bandwidth equal to irradiation and viewing-wavelength
sampling interval.
NOTE 2—The Donaldson radiance factor is approximately equal to the ratio of the specimen radiance within the rectangular waveband of width Δλ
centered at λ to the radiance of the perfect reflecting diffuser when each is irradiated over the rectangular waveband of width Δλ centered at μ.
Available from National Physical Laboratory, Queens Road, Teddington, Middlesex, United Kingdom TW11 0LW, http://www.npl.co.uk/.
Available from U.S. National Committee of the CIE (International Commission on Illumination), C/oIllumination) at
Thomas M. Lemons, TLA-Lighting Consultants, Inc., 7 Pond St., Salem, MA 01970, http://www.cie-usnc.org.www.cie.co.at or www.techstreet.com.
Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
E2153 − 01 (2017)
3.2.9 fluorescence, n—this standard uses the term “fluorescence” as a general term, including both true fluorescence (with a
-8
luminescent decay time of less than 10 s) and phosphorescence with a delay time short enough to be indistinguishable from
fluorescence for the purpose of colorimetry.
3.2.10 near-diagonal element, n—off-diagonal elements of an uncorrected bispectral matrix whose values include a significant
reflection component, due to reflection overspill. For instruments with irradiation and viewing bandpass functions which
approximate the recommended trapezoidal or triangular shape, this should be limited to within two to three bands of the diagonal.
3.2.11 off-diagonal element, n—any element of a bispectral matrix for which irradiation and viewing wavelengths are not equal.
3.2.12 reflection overspill, n—the contribution of reflection to off-diagonal values of the discrete bispectral radiance factor
matrix, due to the partial overlap of irradiation and viewing wavebands when nominal irradiation and viewing wavelengths are not
equal (μ≠λ).
3.2.13 spectral effıciency factor, b(μ), n—the ratio of the total (integrated spectral) radiance from a point on a specimen when
irradiated at wavelength μ to the total radiance of the perfectly reflecting diffuser identically irradiated and viewed.
b μ [L μ /L μ (3)
~ ! ~ ! ~ !
d
4. Summary of Practice
4.1 Procedures are given for selecting the types and operating parameters of bispectrometers used to provide data for the
calculation of CIE tristimulus values and other colorimetric values to quantify the colors of objects. The important steps in the
calibration of such instruments, and the material standards required for these steps, are described. Guidelines are given for the
selection of specimens to obtain the highest measurement precision. Parameters are identified which must be specified when
bispectral photometric measurements are required in specific test methods or other documents.
4.2 In this practice, the measuring instrument, a bispectrometer, is equipped with two separate monochromators. The first, the
irradiation monochromator, irradiates the specimen with monochromatic light. The second, the viewing monochromator, analyzes
the radiation leaving the specimen. A two-dimensional array of bispectral photometric values is obtained by setting the irradiation
monochromator at a series of fixed wavelengths (μ) in the excitation band of the specimen, and for each μ, using the viewing
monochromator to record readings for each wavelength (λ) in the specimen’sspecimen’s emission range. The resulting array, once
properly corrected, is known as the Donaldson matrix (2), and the value of each element (μ,λ) of this array is the Donaldson
radiance factor (D(μ,λ)).
4.3 While recognizing the CIE recommendation (in CIE Publication 15.2) 15) of numerical integration at 1 nm intervals as the
basic definition, this practice is limited in scope to measurements and calculations using spectral intervals greater than or equal
to 5 nm.
5. Significance and Use
5.1 The bispectral or two-monochromator method is the definitive method for the determination of the general (illuminant-
independent) radiation-transfer properties of fluorescent specimens (2). The Donaldson radiance factor is an instrument- and
illuminant-independent photometric property of the specimen, and can be used to calculate its color for any desired illuminant and
observer. The advantage of this method is that it provides a comprehensive characterization of the specimen’sspecimen’s
radiation-transfer properties, without the inaccuracies associated with source simulation and various methods of approximation.
5.2 This practice provides a procedure for selecting the operating parameters of bispectrometers used for providing data of the
desired precision. It also provides for instrument calibration by means of material standards, and for selection of suitable specimens
for obtaining precision in the measurements.
6. Requirements for Bispectral Photometry
6.1 When describing the measurement of specimens by the bispectral method, the following must be specified:
6.1.1 The photometric quantity determined, such as Donaldson radiance factor or spectral efficiency factor.
6.1.2 The geometry of irradiation and viewing, including the following:
6.1.2.1 For bi-directional geometry, whether annular, circumferential, or uniplanar measurement conditions are to be used, and
the number and angular distribution of any multiple beams.
6.1.2.2 For hemispherical geometry, whether total or diffuse measurement conditions (specular component of reflectance
included or excluded) are to be used.
6.1.3 The spectral parameters for both irradiation and viewing, including wavelength range, wavelength measurement interval,
and spectral bandpass.
6.1.4 Identification of the material standards used for instrument calibration.
6.1.5 Special requirements determined by the nature of the specimen, such as measurement orientation for anisotropic
specimens.
E2153 − 01 (2017)
7. Apparatus
7.1 Bispectrometer—The basic instrumental requirement is a bispectrometer designed for measurement of Donaldson radiance
factor using one or more of the standard irradiation and viewing geometries described in Section 8.
7.2 Irradiator—The irradiator, which consists of the radiation source, a dispersive element and related optical components, shall
irradiate the specimen with monochromatic radiation of known wavelength bandpass and measurement interval.
7.2.1 The radiation source must be stable with time and have adequate energy output over the wavelength range used for
specimen irradiation.
7.2.2 The dispersive element, which provides energy in narrow wavelength bands across the UV and v
...