ASTM E2153-01(2023)

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.
Designation: E2153 − 01 (Reapproved 2023)
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-
2.1 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
E284 Terminology of Appearance
1.4 The scope of this practice is limited to the discussion of
object-color measurement under reflection geometries; it does E925 Practice for Monitoring the Calibration of Ultraviolet-
Visible Spectrophotometers whose Spectral Bandwidth
not include provisions for the analogous characterization of
specimens under transmission geometries. does not Exceed 2 nm
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 June 1, 2023. Published July 2023. Originally approved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 2001. Last previous edition approved in 2017 as E2153 – 01 (2017). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2153-01R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2153 − 01 (2023)
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.
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 (2023)
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 nm to 830 nm;
rescent specimens (2). The Donaldson radiance factor is an
otherwise the range from 300 nm to 780 nm should suffice. For
instrument- and illuminant-independent photometric property
specimens confirmed to be non-fluorescent or those exhibiting
of the specimen, and can be used to calculate its color for any
only visible-activated fluorescence (negligible excitation be-
desired illuminant and observer. The advantage of this method
low 380 nm), the wavelength range from 380 to 780 can be
is that it provides a comprehensive characterization of the
used. Each user must decide whether the loss of accuracy in the
specimen’s radiation-transfer properties, without the inaccura-
measurements is negligibly small for the purpose for which
cies associated with source simulation and various methods of
data are obtained.
approximation.
7.2.2.2 The wavelength interval should be 5 nm or 10 nm.
5.2 This practice provides a procedure for selecting the
Use of wider wavelength intervals, such as 20 nm, may result
operating parameters of bispectrometers used for providing
in 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
interval. The spectral bandpass function should be
bispectral method, the following must be specified:
symmetrical, and approximately triangular or trapezoidal.
6.1.1 The photometric quantity determined, such as Donald-
7.2.3 The irradiator should uniformly irradiate the sample.
son radiance factor or spectral efficiency factor.
6.1.2 The geometry of irradiation and viewing, including 7.3 Receiver—The receiver consists of the detector, a dis-
the following: persive element and related optical components.
6.1.2.1 For bi-directional geometry, whether annular, 7.3.1 The detector must be a suitable photodetector such as
circumferential, or uniplanar measurement conditions are to be a photoelectric device or silicon photodiode. The detector must
used, and the number and angular distribution of any multiple be stable with time and have adequate responsivity over the
beams. wavelength range used.
6.1.2.2 For hemispherical geometry, whether total or diffuse 7.3.2 The dispersive element, which provides energy in
measurement conditions (specular component of reflectance narrow wavelength bands across the visible spectral range,
included or excluded) are to be used. may be a prism, a grating, or one of various forms of
E2153 − 01 (2023)
(1) Using a sphere coating which is as spectrally-neutral as possible.
interference filters or wedges. The element should conform to
(2) Using the specular component excluded mode.
the following requirements:
(3) Using the smallest possible sample port area.
7.3.2.1 The receiver’s dispersive element may either be
(4) Increasing the exit and entrance port fractional areas.
coupled with a slit, in order to function as part of a scanning
(5) Lowering the reflectance of the coating to a reflectance factor of
monochromator, or coupled directly to a detection array, in
80 % or less (5).
NOTE 4—Options 4 and 5 will decrease the absolute efficiency of the
order to function as a spectrograph (polychromator) (3).
sphere.
7.3.2.2 When highest measurement accuracy is required, the
wavelength range should extend from 360 nm to 830 nm;
9. Calibration and Material Standards
otherwise the range from 380 nm to 780 nm should suffice.
Each user must decide whether the loss of accuracy in the
9.1 Calibration and its verification are essential steps in
measurements is negligibly small for the purpose for which
ensuring that accurate results are obtained by bispectral pho-
data are obtained.
tometric measurement. Calibration and verification may re-
7.3.2.3 The wavelength interval should be 5 nm or 10 nm.
quire the use of material standards not supplied by the
Use of wider wavelength intervals, such as 20 nm, may result
instrument manufacturer. The instrument user must assume the
in reduced accuracy. Each user must decide whether the loss of
responsibility for obtaining and maintaining the necessary
accuracy in the measurements is negligibly small for the
material standards.
purpose for which data are obtained.
9.2 Photometric Scale:
7.3.2.4 The viewing wavelength interval should equal the
9.2.1 General Requirements for Photometric Calibration—
irradiation wavelength interval.
Specific procedures for photometric calibration of a bispec-
7.3.2.5 The spectral bandpass (full-width at half maximum
trometer are described in Annex A1. General requirements for
power in the band of wavelengths transmitted by the dispersive
such calibration are as follows:
element) should, for best results, be equal to the wavelength
9.2.2 Full-Scale Calibration—For accurate bispectral
interval. The spectral bandpass function should be
measurement, it is necessary to calibrate the bispectrometer so
symmetrical, and approximately triangular or trapezoidal.
that:
7.3.3 The receiver should uniformly view the sample.
9.2.2.1 Absolute Photometric Calibration—For diagonal el-
ements of the Donaldson radiance factor matrix, the values of
8. Irradiating and Viewing Conditions
the perfect reflecting diffuser are assigned the numerical value
8.1 Types and Tolerances—Unless special considerations
1.00 (100 %). For off-diagonal elements, (where irradiation
requiring other tolerances are applicable, the instrument shall
and viewing wavelengths are unequal), the perfect reflecting
conform to the same geometric requirements defined for
diffuser is assigned the numerical value 0 (See 9.2.3).
spectrophotometers in Practice E1164. Types described in
9.2.2.2 Relative Spectral Photometric Calibration—The
Practice E1164 include the following:
relative spectral selectivity of the instrument, due to the
8.1.1 45°/Normal (45/0) and Normal/45° (0/45) Geom-
relative spectral power distribution of the source of irradiation
etries.
or the relative spectral responsivity of the instrument’s detec-
8.1.2 Total/Normal (t/0) or Diffuse/Normal (d/0) and
tion system, or both, is compensated by means of correction
Normal/Total (0/t) or Normal/Diffuse (0/d) Geometries.
factors applied to off-diagonal elements of the bispectral matrix
8.2 Selection of Irradiating and Viewing Conditions—The
of instrument readings.
guidelines provided by Practice E1164 shall generally apply to
9.2.3 Zero Calibration or Verification—When a calibration
the selection of appropriate geometric conditions of irradiation
of the zero point of the photometric scale is required, it may be
and viewing with a bispectrometer. Additional considerations
carried out by any of the methods listed in Practice E1164
pertaining specifically to fluorescent specimens include the
(paragraph 9.2.2), or by the following means:
following:
9.2.3.1 A bispectral baseline matrix may be derived from a
8.2.1 In absence of specific geometrical requirements, a
matrix of readings for a known non-fluorescent specimen by
bi-directional instrument geometry (such as 45/0 or 0/45) is
deleting diagonal and near-diagonal values from this matrix,
normally preferred. For certain applications, however, the use
and replacing them with values derived by interpolation across
of an integrating-sphere instrument geometry may be desirable;
the near-diagonal region. The value of each element of this
for example, in order to produce more repeatable measurement
baseline matrix may then be subtracted from corresponding
of specimens with a structured surface, for historical
elements of the matrix of readings obtained for the specimen.
consistency, or for compatibility with other measurements.
9.2.4 Linearity Verification—After the full-scale and zero-
8.2.2 Use of integrating-sphere instrument geometries (t/0,
scale photometric readings are verified, the linearity of the
d/0, 0/t, 0/d) with fluorescent specimens will introduce certain
scale should be verified by measuring one or more calibrated
systematic errors into the measurement of Donaldson radiance
standards having intermediate radiance factor.
factor (4). It is the responsibility of the user to assess the
significance of such errors for the purpose for which data are 9.3 Wavelength Scale—This section applies to both the
instrument’s irradiation and viewing wavelength scales:
obtained.
9.3.1 Scale Calibration or Verification—The wavelength
NOTE 3—When users choose the use of integrating sphere instrument
scale should be calibrated or verified, or both, for linearity and
geometries, they can reduce the systematic errors due to such instrument
geometries by: offset as follows:
E2153 − 01 (2023)
9.3.1.1 For instruments with a spectral bandpass of about 10 10.5 Measurement data for transparent specimens will de-
nm or less, a line source, or a combination of line sources, such pend upon the thickness of the specimen.
as Mercury or Argon-vapor lamps, should be used, as described
10.6 Special considerations, some of which have been
in Practice E1341. Alternatively, a rare-earth oxide reflectance
noted, apply to the measurement of retroreflective or translu-
standard may be used, following procedures similar to those
cent specimens.
given in NBS SP-260-66.
10.7 Specimens should be handled carefully to avoid con-
9.3.1.2 For instruments with a wider spectral bandpass, the
tamination. Care should be taken not to touch the area to be
method of linear filters should be used (6).
measured except for application of a suitable cleaning proce-
9.3.2 Spectral Bandpass Verification—The approximate
dure. The condition of the specimens before and after mea-
spectral bandpass of the instrument should be verified by using
surement should be noted and reported.
a line source, or a combination of line sources, such as Mercury
or Argon-vapor lamps, as described in Practice E1341.
11. Procedure
Alternatively, a rare-earth oxide reflectance standard may be
11.1 Selection of Measurement Parameters—To the extent
used, following procedures similar to those given in NBS
allowed by the measuring instrument(s) available, select the
SP-260-66, Practice E925 or Practice E958.
following measurement parameters:
9.4 Stray Light—The level of stray light in the instrument
11.1.1 Select the irradiating and viewing geometry; for
should be verified as being adequately low by measuring a
bi-directional geometries, select whether annular,
suitable specimen or specimens with low radiance factor. A
circumferential, or uniplanar conditions will be used, and for
detailed discussion on methods of stray light verification is
hemispherical geometries, select whether total or diffuse quan-
beyond the scope of this standard; see Practices E1164 and
tities will be measured.
E1341.
11.1.2 Select the irradiation and viewing wavelength ranges,
wavelength measurement interval, and spectral bandpass.
NOTE 5—A known non-fluorescent specimen may be used for such
11.1.2.1 General Requirements for Unscreened
verification for off-diagonal elements of the bispectral matrix, in a manner
Specimens—For a specimen of unknown excitation and emis-
similar to that described in 9.2.3.1.
sion properties, the selected irradiation wavelength range
9.5 System Verification—The precision and bias of the entire
should extend at least from 300 nm to 780 nm, and the selected
measurement system, including calculation of CIE tristimulus
viewing wavelength range should extend at least from 380 nm
values, should be determined by periodic measurement of
to 780 nm.
calibrated verification standards, either supplied by the instru-
11.1.2.2 Screening Specimens to Determine Regions of
ment manufacturer or obtained independently. Such standards
Fluorescence—When the bispectral region of fluorescence is
should include both non-fluorescent color standards, such as
known for a particular specimen, it is acceptable to limit the
the BCRA series ceramic color standards (7), and standards
collection of fluorescence data (off-diagonal values) to this
exhibiting fluorescence in the bispectral region of interest.
region.
11.2 Selection of Computational Variables—When the in-
10. Test Specimens
strument incorporates or is interfaced to a computer so that
10.1 Measurement results depend on the quality of the
calculation of CIE tristimulus values and derived color coor-
specimens used. Test specimens should be representative of the
dinates automatically follows measurement, select the vari-
material being tested, and should also conform to the following
ables defining these computations, foll
...