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ASTM E2175-01(2013)

(Practice)

Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers

Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers

SIGNIFICANCE AND USE
4.1 This practice is for the use of manufacturers and users of instruments to measure the appearance of gonioapparent materials, those writing standard specifications for such instruments, and others who wish to specify precisely the geometric conditions of multiangle spectrophotometry. A prominent example of industrial usage is the routine application of such measurements by material suppliers and automobile manufacturers to measure the colors of metallic paints and plastics.
SCOPE
1.1 This practice provides a way of specifying the angular and spatial conditions of measurement and angular selectivity of a method of measuring the spectral reflectance factors of opaque gonioapparent materials, for a small number of sets of geometric conditions.  
1.2 Measurements to characterize the appearance of retroreflective materials are of such a special nature that they are treated in other ASTM documents and are not included in the scope of this standard.  
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
30-Sep-2013
ICS
17.180.30 - Optical measuring instruments
Technical Committee
E12 - Color and Appearance
Drafting Committee
E12.03 - Geometry
Current Stage
Ref Project

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ASTM E2175-01(2013) - Standard Practice for Specifying the Geometry of Multiangle SpectrophotometersASTM E2175-01(2013) - Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers
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ASTM E2175-01(2013) - Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:E2175 −01 (Reapproved 2013)
Standard Practice for
1
Specifying the Geometry of Multiangle Spectrophotometers
This standard is issued under the fixed designation E2175; 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 appearance of metallic coatings and plastics usually depends on the directions of illumination
and viewing, a phenomenon called “gonioappearance.” This phenomenon is also observed with other
materials, such as lustrous textiles and materials containing pearlescent or interference pigments. The
characteristic appearance of most such materials is accentuated by directional illumination, such as
that provided by the sun on a clear day or a small lamp at night. The variation in color, as a function
of geometry, is usually measured by spectrophotometry with several specified sets of geometric
conditions. Measurement of this kind, at a few selected angles, is called “multiangle
spectrophotometry,” as distinguished from measurement over a broad range of angles, which is called
“goniospectrophotometry.” Spectrophotometric aspects of these measurements, including spectral
resolution and linearity of photometric scales, are treated in other standards, including Practice E308
and Practice E1164. Practice E1767 provides practice for specifying the geometry of measurements.
Retroreflectors exhibit a special kind of gonioappearance, which is treated in otherASTM documents.
The present document provides standard practice for specifying influx and efflux angles, angular
selectivity, spatial distributions of illuminators and receivers, and angular aspects of standardizing the
photometric scale, that are peculiar to multiangle spectrophotometry. Directional illumination
emphasizes the gonioappearance of most materials, but when interference pigments are used, such as
those used in ink to mark paper currency, the effect is observed with diffuse illumination and varying
angles of viewing, so these materials are also measured with diffuse illumination.
1. Scope 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This practice provides a way of specifying the angular
E284 Terminology of Appearance
and spatial conditions of measurement and angular selectivity
E308 PracticeforComputingtheColorsofObjectsbyUsing
of a method of measuring the spectral reflectance factors of
the CIE System
opaque gonioapparent materials, for a small number of sets of
E1164 PracticeforObtainingSpectrometricDataforObject-
geometric conditions.
Color Evaluation
1.2 Measurements to characterize the appearance of retrore-
E1767 Practice for Specifying the Geometries of Observa-
flective materials are of such a special nature that they are
tion and Measurement to Characterize the Appearance of
treated in other ASTM documents and are not included in the
Materials
scope of this standard.
3. Terminology
1.3 This standard does not purport to address all of the
3.1 Fordefinitionsofappearancetermsusedinthispractice,
safety concerns, if any, associated with its use. It is the
refer to Terminology E284.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Significance and Use
bility of regulatory limitations prior to use.
4.1 Thispracticeisfortheuseofmanufacturersandusersof
instruments to measure the appearance of gonioapparent
1
This practice is under the jurisdiction of ASTM Committee E12 on Color and
2
Appearance and is the direct responsibility of Subcommittee E12.03 on Geometry. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2013. Published October 2013. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2001. Last previous edition approved in 2008 as E2175 – 01 (2008). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E2175-01R13. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E2175−01 (2013)
materials, those writing standard specifications for such specular reflection by an ideal plane mirror at the sampling
instruments, and others who wish to specify precisely the aperture.Anglessubtendedattheoriginandmeasuredfromthe
geometric conditions of multiangle spectrophotometry. A specular direction are called“ aspecular angles” and are posi-
prominent example of industrial usage is the routine applica- tive in sign when measured in the direction toward the normal.
...

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5.1 This practice is for the use of manufacturers and users of equipment for visual appraisal or measurement of appearance, those writing standards related to such equipment, and others who wish to specify precisely conditions of viewing or measuring attributes of appearance. The use of this practice makes such specifications concise and unambiguous. The functional notation facilitates direct comparisons of the geometric specifications of viewing situations and measuring instruments.
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1.1 This practice describes the geometry of illuminating and viewing specimens and the corresponding geometry of optical measurements to characterize the appearance of materials. It establishes terms, symbols, a coordinate system, and functional notation to describe the geometric orientation of a specimen, the geometry of the illumination (or optical irradiation) of a specimen, and the geometry of collection of flux reflected or transmitted by the specimen, by a measurement standard, or by the open sampling aperture.  
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Standard Practice for Specifying the Geometry of Multiangle Spectrophotometers

SIGNIFICANCE AND USE
4.1 This practice is for the use of manufacturers and users of instruments to measure the appearance of gonioapparent materials, those writing standard specifications for such instruments, and others who wish to specify precisely the geometric conditions of multiangle spectrophotometry. A prominent example of industrial usage is the routine application of such measurements by material suppliers and automobile manufacturers to measure the colors of metallic paints and plastics.
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4.1 The angular distribution of scatter is a property of surfaces that may have direct consequences on an intermediate or final application of that surface. Scatter defines many visual appearance attributes of materials, and specification of the distribution and wavelength dependence is critical to the marketability of consumer products, such as automobiles, cosmetics, and electronics. Optically diffusive materials are used in information display applications to spread light from display elements to the viewer, and the performance of such displays relies on specification of the distribution of scatter. Stray-light reduction elements, such as baffles and walls, rely on absorbing coatings that have low diffuse reflectances. Scatter from mirrors, lenses, filters, windows, and other components can limit resolution and contrast in optical systems, such as telescopes, ring laser gyros, and microscopes.  
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SCOPE
1.1 This practice describes procedures for determining the amount and angular distribution of optical scatter from a surface. In particular it focuses on measurement of the bidirectional scattering distribution function (BSDF). BSDF is a convenient and well accepted means of expressing optical scatter levels for many purposes. It is often referred to as the bidirectional reflectance distribution function (BRDF) when considering reflective scatter or the bidirectional transmittance distribution function (BTDF) when considering transmissive scatter.  
1.2 The BSDF is a fundamental description of the appearance of a sample, and many other appearance attributes (such as gloss, haze, and color) can be represented in terms of integrals of the BSDF over specific geometric and spectral conditions.  
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5.1 Turbidity is a measure of scattered light that results from the interaction between a beam of light and particulate material in a liquid sample. Particulate material is typically undesirable in water from a health perspective and its removal is often required when the water is intended for consumption. Thus, turbidity has been used as a key indicator for water quality to assess the health and quality of environmental water sources. Higher turbidity values are typically associated with poorer water quality.  
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SCOPE
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SCOPE
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This practice describes the photomultiplier properties that are essential to their judicious selection and use of in emission and absorption spectrometry. The properties covered here include structural features, electrical properties, and characteristics involved in precautions and problems. The structural features covered are envelope configurations, window materials, electrical connections, and housing for the external structure, and the photocathode, dynodes and anode, and rigidness of structural components for the internal structure. Electrical properties, on the other hand, incorporate the following: optical-electronic characteristics of the photocathode including spectral response; current amplification including gain per stage, overall gain, gain control (voltage-divider bridge), linearity of response, and anode saturation; signal nature; dark current including cathode size, internal aperture, and refrigeration effects; noise nature including additivity of noise power, signal-to-noise ratio, equivalent noise input; and photomultiplier properties as a component in an electrical circuit including output impedance, response time, and signal gating and integration possibilities. Finally, the characteristics involved in precautions and problems cover fatigue and hysteresis effects, illumination of photocathode, and gas leakage.
SCOPE
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Section  
Structural Features  
4  
General  
4.1  
External Structure  
4.2  
Internal Structure  
4.3  
Electrical Properties  
5  
General  
5.1  
Optical-Electronic Characteristics of the Photocathode  
5.2  
Current Amplification  
5.3  
Signal Nature  
5.4  
Dark Current  
5.5  
Noise Nature  
5.6  
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5.7  
Precautions and Problems  
6  
General  
6.1  
Fatigue and Hysteresis Effects  
6.2  
Illumination of Photocathode  
6.3  
Gas Leakage  
6.4  
Recommendations on Important Selection Criteria  
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4.1 Generally, Raman spectra measured using grating-based dispersive or Fourier transform Raman spectrometers have not been corrected for the instrumental response (spectral responsivity of the detection system). Raman spectra obtained with different instruments may show significant variations in the measured relative peak intensities of a sample compound. This is mainly as a result of differences in their wavelength-dependent optical transmission and detector efficiencies. These variations can be particularly large when widely different laser excitation wavelengths are used, but can occur when the same laser excitation is used and spectra of the same compound are compared between instruments. This is illustrated in Fig. 1, which shows the uncorrected luminescence spectrum of SRM 2241, acquired upon four different commercially available Raman spectrometers operating with 785 nm laser excitation. Instrumental response variations can also occur on the same instrument after a component change or service work has been performed. Each spectrometer, due to its unique combination of filters, grating, collection optics and detector response, has a very unique spectral response. The spectrometer dependent spectral response will of course also affect the shape of Raman spectra acquired upon these systems. The shape of this response is not to be construed as either “good or bad” but is the result of design considerations by the spectrometer manufacturer. For instance, as shown in Fig. 1, spectral coverage can vary considerably between spectrometer systems. This is typically a deliberate tradeoff in spectrometer design, where spectral coverage is sacrificed for enhanced spectral resolution.
FIG. 1 SRM 2241 Measured on Four Commercial Raman Spectrometers Utilizing 785 nm Excitation  
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SCOPE
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SCOPE
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SCOPE
1.1 This guide covers Raman shift values for common liquid and solid chemicals that can be used for wavenumber calibration of Raman spectrometers. The guide does not include procedures for calibrating Raman instruments. Instead, this guide provides reliable Raman shift values that can be used as a complement to low-pressure arc lamp emission lines which have been established with a high degree of accuracy and precision.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 Some of the chemicals specified in this guide may be hazardous. It is the responsibility of the user of this guide to consult material safety data sheets and other pertinent information to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to their use.  
1.4 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.  
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