1、Designation: E811 09Standard Practice forMeasuring Colorimetric Characteristics of RetroreflectorsUnder Nighttime Conditions1This standard is issued under the fixed designation E811; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes the instrumental determinationof retroreflected chromaticity coordinates of retror
3、eflectors. Itincludes the techniques used in a photometric range to measureretroreflected (nighttime) chromaticity with either a telecolo-rimeter or telespectroradiometer.1.2 This practice covers the general measurement proce-dures. Additional requirements for specific tests and specifica-tions are
4、described in Section 7.1.3 The description of the geometry used in the nighttimecolorimetry of retroreflectors is described in Practice E808 andthe methods for calculation of chromaticity are contained inPractice E308.1.4 This standard does not purport to address all of thesafety concerns, if any, a
5、ssociated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E284 Terminology of AppearanceE308 Practice for Comput
6、ing the Colors of Objects byUsing the CIE SystemE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE808 Practice for Describing RetroreflectionE809 Practice for Measuring Photometric Characteristics ofRetroreflectors2.2 CIE Documents:3CIE Publication No.
7、15.2 Colorimetry, 2d ed.CIE Standard S 001/ISO IS 10526, Colorimetric Illumi-nantsCIE Standard S 002/ISO IS 10527, Colorimetric ObserversCIE Technical Report 54.2 Retroreflection: Definition andMeasurement3. Terminology3.1 The terms and definitions in Terminology E284 apply tothis practice.3.2 Defin
8、itions:3.2.1 chromaticity coordinates, nthe ratios of each of thetristimulus values of a psychophysical color to the sum of thetristimulus values.3.2.1.1 DiscussionChromaticity coordinates in the CIE1931 system of color specification are designated by x, y, z andin the CIE 1964 supplementary system
9、by x10, y10, z10.3.2.2 CIE 1931 (x, y)-chromaticity diagramthe chroma-ticity diagram for the CIE 1931 standard observer, in which theCIE 1931 chromaticity coordinates are plotted with x as theabscissa and y as the ordinate.3.2.3 CIE 1931 standard observer, nideal colorimetricobserver with color matc
10、hing functions x (l), y (l), z (l)corresponding to a field of view subtending a 2 angle on theretina; commonly called the “2 standard observer.” CIEB43.2.3.1 DiscussionThe color matching functions of theCIE 1931 standard observer are tabulated in Practice E308,CIE Publication No. 15.2, and CIE Stand
11、ard S 002.3.2.4 CIE standard illuminant A, ncolorimetric illumi-nant, representing the full radiation at 2855.6 K, defined by theCIE in terms of a relative spectral power distribution. CIEB3.2.4.1 DiscussionThe relative spectral power distribu-tion of CIE standard illuminant A is tabulated in Practi
12、ce E308,CIE Publication No. 15.2, and CIE Standard S 001.3.2.5 CIE standard source A, na gas-filled tungsten-filament lamp operated at a correlated color temperature of2855.6 K. CIEB1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility
13、 of Subcommittee E12.10 on Retrore-flection.Current edition approved Dec. 1, 2009. Published January 2010. Originallyapproved in 1981. Last previous edition approved in 2001 as E811 95 (2001).DOI: 10.1520/E0811-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM C
14、ustomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from U.S. National Committee of the CIE (International Commissionon Illumination), C/o Thomas M. Lemons, TLA-Lighting Consultants, Inc.,
15、 7 PondSt., Salem, MA 01970, http:/www.cie-usnc.org.4Stephenson, H. F., “The Colorimetric Measurement of Retroreflective Materi-als. Progress Report on International Exchange Tests,” Proceedings of the CIE,18th Session (London), pp. 595609, 1975.1Copyright ASTM International, 100 Barr Harbor Drive,
16、PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.6 entrance angle, b, nthe angle between the illumi-nation axis and the retroreflector axis.3.2.6.1 DiscussionThe entrance angle is usually no largerthan 90, but for completeness its full range is defined as 0 #b # 180. In the CIE (goni
17、ometer) system b is resolved intotwo components, b1and b2. Since by definition b is alwayspositive, the common practice of referring to the small entranceangles that direct specular reflections away from the photore-ceptor as negative valued is deprecated by ASTM. Therecommendation is to designate s
18、uch negative values asbelonging to b1.3.2.7 goniometer, nan instrument for measuring or settingangles.3.2.8 illumination axis, nin retroreflection, a line from theeffective center of the source aperture to the retroreflectorcenter.3.2.9 observation angle, nangle between the axes of theincident beam
19、and the observed (reflected) beam, (in retrore-flection, a, angle between the illumination axis and theobservation axis).3.2.10 observation axis, nin retroreflection, a line fromthe effective center of the receiver aperture to the retroreflectorcenter.3.2.11 retroreflection, nreflection in which the
20、 reflectedrays are preferentially returned in directions close to theopposite of the direction of the incident rays, this propertybeing maintained over wide variations of the direction of theincident rays. CIEB3.2.12 retroreflective device, ndeprecated term; use ret-roreflector.3.2.13 retroreflectiv
21、e sheeting, na retroreflective materialpreassembled as a thin film ready for use.3.2.14 retroreflector, na reflecting surface or device fromwhich, when directionally irradiated, the reflected rays arepreferentially returned in directions close to the opposite of thedirection of the incident rays, th
22、is property being maintainedover wide variations of the direction of the incident rays. CIE,1982B3.2.15 retroreflector axis, na designated line segmentfrom the retroreflector center that is used to describe theangular position of the retroreflector.3.2.15.1 DiscussionThe direction of the retroreflec
23、tor axisis usually chosen centrally among the intended directions ofillumination; for example, the direction of the road on which orwith respect to which the retroreflector is intended to bepositioned. In testing horizontal road markings the retroreflec-tor axis is usually the normal to the test sur
24、face.3.2.16 retroreflector center, na point on or near a retrore-flector that is designated to be the center of the device for thepurpose of specifying its performance.3.2.17 rotation angle, , nthe angle in a plane perpen-dicular to the retroreflector axis from the observation halfplaneto the datum
25、axis, measured counter-clockwise from a view-point on the retroreflector axis.3.2.17.1 DiscussionRange: 180#180. The defini-tion is applicable when entrance angle and viewing angle areless than 90. More generally, rotation angle is the angle fromthe positive part of second axis to the datum axis, me
26、asuredcounterclockwise from a viewpoint on the retroreflector axis.3.2.17.2 DiscussionRotation of the sample about the ret-roreflector axis while the source and receiver remain fixed inspace changes the rotation angle () and the orientation angle(vs) equally.3.2.18 spectroradiometer, nan instrument
27、for measuringthe spectral distribution of radiant energy or power.3.2.19 tristimulus colorimeter, ninstrument that measurespsychophysical color, in terms of tristimulus values, by the useof filters to convert the relative spectral power distribution ofthe illuminator to that of a standard illuminant
28、, and to convertthe relative spectral responsivity of the receiver to the respon-sivities prescribed for a standard observer.3.2.19.1 DiscussionIn some instruments, the filters maybe combined into one set placed in the receiver; in such cases,caution should be observed when measuring fluorescent spe
29、ci-mens.3.2.20 viewing angle, v, nin retroreflection, the anglebetween the retroreflector axis and the observation axis.3.3 Definitions of Terms Specific to This Standard:3.3.1 telecolorimeter, na tristimulus colorimeter equippedwith collection optics for viewing a limited area at a distancefrom the
30、 instrument.3.3.2 telespectroradiometer, na spectroradiometerequipped with collection optics for viewing a limited area at adistance from the instrument.4. Summary of Practice4.1 Two procedures are described in this practice (see alsoPractice E809). Procedure A is based on a calibrated lightsource,
31、colored reference filters, a white reference standard anda telecolorimeter equipped with tristimulus filters. In thisprocedure, measurements of the incident light on the whitestandard at the specimen position are made using the coloredfilters and correction factors developed. Then the retroreflected
32、light is measured under the test geometry and the correctedrelative tristimulus values are computed. In Procedure B,spectral measurements are made of the incident light and of theretroreflected light under the test geometry required. Fromthese spectral measurements, the relative tristimulus values a
33、redetermined. In both procedures, the chromaticity coordinates x,y are based on the CIE 1931 Standard Color Observer.5. Significance and Use5.1 This practice describes a procedure for measuring thechromaticity of retroreflectors in a nighttime, that is, retrore-flective, geometry of illumination and
34、 observation. CIE Stan-dard Source A has been chosen to represent a tungstenautomobile headlamp. Although the geometry must be speci-fied by the user of this practice, it will, in general, correspondE811 092to the relationship between the vehicle headlamp, the retrore-flector, and the vehicle driver
35、s eyes. Thus, the chromaticitycoordinates determined by the procedures in this practicedescribe numerically the nighttime appearance of the retrore-flector.56. Use of the CIE Chromaticity Diagram for theSpecification of Color6.1 Tristimulus Values for a Colored SampleThe spectralnature of the light
36、coming to the eye from a retroreflectordepends upon the spectral distribution of the radiation from thesource, S (l), and a quantity proportional to the spectralreflectance of the retroreflector, R (l). For nighttime colori-metric measurements of retroreflectors, S (l) is Illuminant A.The spectral t
37、ristimulus values, x, y, and z, the illuminantpower S (l), and the reflectance quantity R (l) are usedtogether to calculate three numbers, the tristimulus values X, Y,and Z as follows:X 5 k*380740SAl! Rl! xl!dlY 5 k*380740SAl! Rl! yl!dlZ 5 k*380740SAl! Rl! zl!dlwhere:SA(l) = spectral power distribut
38、ion of Illumi-nant A,R(l) = spectral reflectance factor of the sample,andx(l), y(l), z(l) = color matching functions of the CIEstandard observer.100/k 5*380740SAyl!dlIntegration of each curve across the visible region (380 to740 nm) give the numerical value for the correspondingtristimulus value X,
39、Y, or Z.6.2 Chromaticity CoordinatesThe chromaticity coordi-nates x, y, and z are computed from the tristimulus values X, Y,and Z as follows:x 5 X/X 1 Y 1 Z!y 5 Y/X 1 Y 1 Z!z 5 Z/X 1 Y 1 Z!The normalization constant k in the equations for X, Y, andZ cancels out in calculating x, y, and z. Thus, x, y
40、, and z expressthe color of the reflected light without regard to its intensity.Because the sum of x, y, and z is always equal to one, only twoof these quantities are needed to describe the chromaticity of alight. The chromaticity coordinates x and y are chosen for thispurpose.6.3 CIE 1931 (x, y) Ch
41、romaticity DiagramThe chroma-ticity coordinates x and y can be plotted as shown in PracticeE308, Fig. 1. The outline in the figure encloses the entire rangeof combinations of x and y that correspond to real colors. Thepoints at which monochromatic radiation of various wave-lengths falls are indicate
42、d on this boundary, with the morenearly neutral colors being represented by points toward thecenter of the bounded region.6.4 Specifying Color LimitsA color point representing thex and y chromaticity coordinates of a test sample can be locatedon the CIE diagram. A specification for a specific retror
43、eflec-tive color limit would require that the color point for a sampleof this color fall within specified boundaries of the diagram.The area within these boundaries is referred to as a color area,and is defined exactly by specifying four sets of chromaticitycoordinates in the specification.6.5 Dayti
44、me versus Nighttime Color LimitsDifferent colorlimits are required to specify daytime and nighttime color.Nighttime and daytime color limits are different for two majorreasons: the quality of the illuminating light and the geometryor direction of the illuminating light. Daytime color is viewedunder
45、a source of daylight quality, and nighttime color isviewed under Source A (a CIE source corresponding to anincandescent lamp, such as an automobile headlamp). Illumi-nation in the daytime is from skylight, and diffusely reflectedlight is observed; illumination in the nighttime comes from apoint very
46、 near the observer, and retroreflected light is ob-served.7. Requirements to be Stated in Specifications7.1 When stating colorimetric retroreflective requirements,the following requirements shall be given in the specificationfor the material:7.1.1 Limits of the color area on the 1931 CIE chromaticit
47、ydiagram (usually four pairs of chromaticity coordinates (x andy) are required to define an area on the diagram).7.1.2 Chromaticity coordinate limits and spectral transmit-tance limits of the standard filter when Procedure A is used.(These may be specified by giving the filter glass type andthicknes
48、s or the manufacturers part number of the filter.)7.1.3 Observation angle (a).7.1.4 Entrance angle (b) and when required the componentsof the entrance angle b1, and b2. (When specifying entranceangles near 0, care must be taken to prevent “white” specularreflection from entering the receptor. Theref
49、ore, instead ofspecifying 0, the entrance angle is usually specified so thatspecular light is reflected away from the receptor.)7.1.5 Rotation angle () and the location of the datum mark,if random orientation of the test specimen is not suitable.7.1.6 Observation distance (d).7.1.7 Test specimen dimensions and shape.7.1.8 Receptor angular aperture, usually either 6 min or 10min of arc.7.1.9 Source angular aperture, usually either 6 min or 10min of arc.7.1.10 Reference center of the retroreflecto
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