1、Designation: E 811 95 (Reapproved 2001)Standard Practice forMeasuring Colorimetric Characteristics of RetroreflectorsUnder Nighttime Conditions1This standard is issued under the fixed designation E 811; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes the instrumental determinationof retroreflected chromaticity
3、coordinates of retroreflectors. 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
4、 specifica-tions are described in Section 7.1.3 The description of the geometry used in the nighttimecolorimetry of retroreflectors is described in Practice E 808 andthe methods for calculation of chromaticity are contained inPractice E 308.1.4 This standard does not purport to address all of thesaf
5、ety concerns, if any, associated 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:E 284 Terminology of Appearance2
6、E 308 Practice for Computing the Colors of Objects byUsing the CIE System2E 808 Practice for Describing Retroreflection2E 809 Practice for Measuring Photometric Characteristicsof Retroreflectors22.2 CIE Documents:CIE Publication No. 15.2 Colorimetry, 2d ed.3CIE Standard S 001/ISO IS 10526, Colorimet
7、ric Illumi-nants3CIE Standard S 002/ISO IS 10527, Colorimetric Observers33. Terminology3.1 The terms and definitions in Terminology E 284 apply tothis practice.3.2 Definitions:3.2.1 chromaticity coordinates, nthe ratios of each of thetristimulus values of a psychophysical color to the sum of thetris
8、timulus 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 by x10, y10, z10.3.2.2 CIE 1931 (x, y)-chromaticity diagramthe chroma-ticity diagram for the CIE 1931 standard observer, in which t
9、heCIE 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 matching functions x(l), y (l), z (l)corresponding to a field of view subtending a 2 angle on theretina; commonly called the “2 standar
10、d observer.” CIEB43.2.3.1 DiscussionThe color matching functions of theCIE 1931 standard observer are tabulated in Practice E 308,CIE Publication 15.2, and CIE Standard S 002.3.2.4 CIE standard illuminant A, ncolorimetric illumi-nant, representing the full radiation at 2855.6 K, defined by theCIE in
11、 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 PracticeE 308, CIE Publication 15.2, and CIE Standard S 001.3.2.5 CIE standard source A, na gas-filled tungsten-filament lamp operated at a c
12、orrelated color temperature of2855.6 K. CIEB3.2.6 entrance angle, b, nin retroreflection, angle be-tween the illumination 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. To completely spe
13、cify the orientation, this angle ischaracterized by two components, b1and b2.1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.10 on Retrore-flection.Current edition approved March 15, 1995. Published May 1995.
14、Originallypublished as E 811 81. Last previous edition E 811 94a.2Annual Book of ASTM Standards, Vol 06.01.3Available from USNC/CIE Publications Office, % TLA Lighting Consultants,Inc., 7 Pond St., Salem, MA 01970.4Stephenson, H. F., “The Colorimetric Measurement of Retroreflective Materi-als. Progr
15、ess Report on International Exchange Tests.” Proceedings of the CIE, 18thSession (London), pp. 595609, 1975.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.7 goniometer, nan instrument for measuring or settingangles.3.2.8 illumin
16、ation 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 and the observed (reflected) beam, (in retrore-flection, a, angle between the illumination axis and theobservation
17、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 reflectedrays are preferentially returned in directions close to theopposite of the direction of the incident rays
18、, 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 retroreflective sheeting, na retroreflective materialpreassembled as a thin film ready for use.3.2.14 retroreflector, na reflecti
19、ng surface or device fromwhich, when directionally irradiated, the reflected rays arepreferentially returned in directions close to the opposite of thedirection of the incident rays, this property being maintainedover wide variations of the direction of the incident rays. CIE,1982B3.2.15 retroreflec
20、tor 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 retroreflector axisis usually chosen centrally among the intended directions ofillumination; for example, the direction of the
21、 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 surface.3.2.16 retroreflector center, na point on or near a retrore-flector that is designated to be the center of the
22、 device for thepurpose of specifying its performance.3.2.17 rotation angle, e, nin retroreflection, angle indicat-ing the orientation of the specimen when it is rotated about theretroreflector axis.3.2.17.1 DiscussionThe rotation angle is the dihedralangle from the half-plane originating on the retr
23、oreflector axisand containing the positive part of the second axis to the halfplane originating on the retroreflector axis and containing thedatum mark. Range: 180 # e # 180.3.2.18 spectroradiometer, nan instrument for measuringthe spectral distribution of radiant energy or power.3.2.19 tristimulus
24、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, and to convertthe relative spectral responsivity of the receiver to the respon-sivi
25、ties 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 speci-mens.3.2.20 viewing angle, v, nin retroreflection, the anglebetween the retrorefle
26、ctor 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 instrument.3.3.2 telespectroradiometer, na spectroradiometerequipped with collection
27、 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 E 809). Procedure A is based on a calibrated lightsource, colored reference filters, a white reference standard anda telecolorimeter equipped
28、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 retroreflectedlight is measured under the test geometry and the correctedrelative tristimulus valu
29、es 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 aredetermined. In both procedures, the chromaticity coordinates x,y are based on the
30、CIE 1931 Standard Color Observer.5. Significance and Use5.1 This practice describes a procedure for measuring thecolor appearance of retroreflectors as seen under nighttimeconditions of illumination and viewing. CIE Standard SourceAhas been chosen to represent a tungsten automobile headlamp.Although
31、 the geometry must be specified by the user of thispractice, it will, in general, correspond to the relationshipbetween the vehicle headlamp, the retroreflector, and thevehicle drivers eyes. Thus, the chromaticity coordinates de-termined by the procedures in this practice describe numeri-cally the n
32、ighttime appearance of the retroreflector.56. Use of the CIE Chromaticity Diagram for theSpecification of Color6.1 Tristimulus Values for a Colored SampleThe spectralnature of the light coming to the eye from a retroreflectordepends upon the spectral distribution of the radiation from thesource, S (
33、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 tristimulus values, x, y, and z, the illuminantpower S (l), and the reflectance quantity R (l) are usedtogether to
34、calculate three numbers, the tristimulus values X, Y,and Z as follows:5Rennilson, J. J., “Chromaticity Measurements of Retroreflective MaterialUnder Nighttime Geometry,” Applied Optics, Vol 45, April 15, 1980.E 811 95 (2001)2X 5 k*380740SAl! Rl! xl!dlY 5 k*380740SAl! Rl! yl!dlZ 5 k*380740SAl! Rl! zl
35、!dlwhere:SA(l) = spectral power distribution 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 f
36、or the correspondingtristimulus value X, 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 o
37、ut in calculating x, y, and z. Thus, x, y, 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 chos
38、en for thispurpose.6.3 CIE 1931 (x, y) Chromaticity DiagramThe chroma-ticity coordinates x and y can be plotted as shown in PracticeE 308, 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
39、of various wave-lengths falls are indicated 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 diag
40、ram. A specification for a specific retroreflec-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 chromaticity
41、coordinates in the specification.6.5 Daytime versus Nightime 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 illumina
42、ting light. Daytime color is viewedunder 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; illuminatio
43、n in the nighttime comes from apoint very 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 t
44、he color area on the 1931 CIE chromaticitydiagram (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
45、 giving the filter glass type andthickness 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” specularrefl
46、ection from entering the receptor. Therefore, instead ofspecifying 0, the entrance angle is usually specified so thatspecular light is reflected away from the receptor.)7.1.5 Rotation angle (e) and the location of the datum mark,if random orientation of the test specimen is not suitable.7.1.6 Observ
47、ation distance (d).7.1.7 Test specimen dimensions and shape.7.1.8 Receptor angular aperture, usually 6 min of arc.7.1.9 Source angular aperture, usually 6 min of arc.7.1.10 Reference center of the retroreflector.7.1.11 Reference axis of the retroreflector. (The referenceaxis is usually perpendicular
48、 to the surface of sheeting. In suchcomplex devices as automobile or bicycle reflectors, thereference axis and reference center may be defined with respectto the viewing direction.)8. Apparatus8.1 The apparatus shall consist of either a spectroradiometerequipped with collection optics or a telecolor
49、imeter, a regu-lated light projector source, a goniometer sample holder, aphotometric range, and calibration standards.FIG. 1 Two Arrangements Suitable for Calibration ofTelecolorimeter or TelespectroradiometerE 811 95 (2001)38.2 TelecolorimeterThe telecolorimeter shall be equippedwith:8.2.1 CIE 1931 tristimulus value filters, consisting of:8.2.1.1 An xredfilter for the long wave portion of the x (l)function.8.2.1.2 An xbluefilter for the short wave portion of the x (l)function.8.2.1.3 A y filte
