1、Designation: E 808 01Standard Practice forDescribing Retroreflection1This standard is issued under the fixed designation E 808; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indi
2、cates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides terminology, alternative geo-metrical coordinate systems, and procedures for designatingangles in descriptions of retroreflectors, specif
3、ications forretroreflector performance, and measurements of retroreflec-tion.1.2 Terminology defined herein includes terms germane toother ASTM documents on retroreflection.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
4、ty 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 Appearance22.2 Federal Standard:Fed. Std. No. 370 Instrumental Photometric Meas
5、urementsof Retroreflecting Materials and Retroreflecting Devices32.3 CIE Document:CIE Publication No. 54, Retroreflection-Definition andMeasurement43. Terminology3.1 Terms and definitions in Terminology E 284 are appli-cable to this standard.3.1.1 In accordance with the convention appearing in theSi
6、gnificance and Use section of Terminology E 284, thesuperscript B appearing after CIE at the end of a definitionindicates that the given definition is a modification of that citedwith little difference in essential meaning.NOTE 1The terminology given here describes visual observation ofluminance as
7、defined by the CIE V (l) spectral weighting function for thephotopic observer. Analogous terms for other purposes can be defined byusing appropriate spectral weighting.3.2 Definitions: The delimiting phrase “in retroreflection”applies to each of the following definitions when used outsidethe context
8、 of this or other retroreflection standards.3.2.1 coeffcient of line retroreflection, RM, nof a retrore-flecting stripe, the ratio of the coefficient of luminous intensity(RI) to the length (l), expressed in candelas per lux per metre(cdlx1m1). RM= RI/l.3.2.1.1 DiscussionRMdepends on the spectral co
9、mposi-tion of the illumination which is usually CIE illuminant A.3.2.2 coeffcient of luminous intensity, RI, nof a retrore-flector, ratio of the luminous intensity (I) of the retroreflector inthe direction of observation to the illuminance (E)attheretroreflector on a plane perpendicular to the direc
10、tion of theincident light, expressed in candelas per lux (cdlx1). RI=(I/E).3.2.2.1 DiscussionIn a given measurement one obtainsthe average RIover the solid angles of incidence and viewingsubtended by the source and receiver apertures, respectively. Inpractice, I is often determined as the product of
11、 the illuminanceat the observer and the distance squared (I=Erd2). RIdependson the spectral composition of the illumination which is usuallyCIE illuminant A.3.2.2.2 DiscussionAlso called coeffcient of (retrore-flected) luminous intensity. Equivalent commonly used termsare CIL and SI (specific intens
12、ity). CIE Publication 54 uses thesymbol R for RI. The ASTM recommendation is to use thesymbol RI.3.2.3 coeffcient of retroreflected luminance, RL, ntheratio of the luminance, L, in the direction of observation to thenormal illuminance, E, at the surface on a plane normal to theincident light, expres
13、sed in candelas per square metre per lux(cdm2)lx1.RL5 L/E! 5 RI/A cos n! 5 I/EA cos n! 5 RA/ cos n! (1)where:A = surface area of the sample, andn = viewing angle.3.2.3.1 DiscussionThe units millicandela per square me-tre per lux (mcdm2)lx1 are usually used to express the RLvalues of road marking sur
14、faces. This quantity is also referred1This 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 Dec. 10, 2001. Published February 2002. Originallypublished as E 808 81. Las
15、t previous edition E 808 - 99a.2Annual Book of ASTM Standards, Vol 06.01.3Available from Standardization Documents Order Desk, Bldg. 4 Ave., Phila-delphia, PA 19111-5094, Attn: NPODS.4Available from USNC/CIE Publications Office, TLA Lighting Consultants,Inc., 7 Pond St., Salem, MA 01970.1Copyright A
16、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to as specific luminance. Historically the symbol SL was usedfor RL. In some references CRL is used. These are allequivalent, but RLis preferred.3.2.3.2 DiscussionRLdepends on the spectral composi-
17、tion of the illumination which is usually CIE illuminant A.3.2.4 coeffcient of (retroreflected) luminous flux, RF, ntheratio of the luminous flux per unit solid angle, F8/V8, in thedirection of observation to the total flux F incident on theeffective retroreflective surface, expressed in candelas pe
18、rlumen (cdlm1).RF5 F8/V8!/F5I/F5RA/cos b (2)3.2.4.1 DiscussionThe units for this photometric quantity,candelas per lumen, are sometimes abbreviated as CPL.3.2.4.2 DiscussionRFdepends on the spectral composi-tion of the illumination which is usually CIE illuminant A.3.2.5 coeffcient of retroreflectio
19、n, RA, nof a plane retrore-flecting surface, the ratio of the coefficient of luminousintensity (RI) to the area (A), expressed in candelas per lux persquare metre (cdlx1m2). RA= RI/A.3.2.5.1 DiscussionThe equivalent inch-pound units forcoefficient of retroreflection are candelas per foot candle pers
20、quare foot. The SI and inch-pound units are numericallyequal, because the units of RAreduce to 1/sr. An equivalentterm used for coefficient of retroreflection is specific intensityper unit area, with symbol SIA or the CIE symbol R8. The termcoefficient of retroreflection and the symbol RAalong with
21、theSI units of candelas per lux per square metre are recommendedby ASTM.3.2.5.2 DiscussionThe radiometric BRDF is not the ana-logue of RAbut rather of RF.3.2.5.3 DiscussionRAdepends on the spectral composi-tion of the illumination which is usually CIE illuminant A.3.2.6 co-entrance angle, e, nthe co
22、mplement of the anglebetween the retroreflector axis and the illumination axis.3.2.6.1 Discussione=90-b. Range 0e, the receiver over the source, for testing.FIG. 7 RM (Road Marking) SystemE808017sensitive to rotation. ASTM recommends that the conditionsdesired for test be completely specified.8.2 Wh
23、en the entrance angle b alone is specified withoutreference to components, it has been a common practice in theUnited States to consider b2=0 and b1=b. Because the use ofsuch conventions results in misunderstandings and conflictingstandards, ASTM deprecates the use of this convention andrecommends t
24、hat the conditions desired for test be completelyspecified. Note in particular that for sign sheeting b2=0, b1=bis a poor representation of the road scenario and may result inmisapplication of some materials.9. Aperture Description Conventions9.1 Since the efficiencies of retroreflectors are often r
25、apidlyvarying functions of the observation angle a and the rho angler, it is usually important to describe the apertures of the sourceand receiver that are to be used in a measurement. Thefollowing conventions for describing apertures are based on theassumptions that: (1) the luminance of the source
26、 in thedirection of the retroreflector is uniform over the sourceaperture stop, (2) the illumination axis passes through thecenter of the source aperture stop, ( 3) the responsivity of thereceiver in the direction of the retroreflector is uniform over thereceiver aperture stop, and (4) the observati
27、on axis passesthrough the center of the receiver aperture stop.9.1.1 Circular ApertureThe angular size of a circularaperture, either source or receiver, should be described bygiving the angle subtended at the retroreflector center by adiameter of the aperture.9.1.2 Rectangular ApertureIf a rectangul
28、ar aperture, ei-ther source or receiver, has one side parallel to the observationhalf-plane, then its angular size should be described by givingfirst the angle subtended at the retroreflector center by the sideparallel to the observation half-plane and second the anglesubtended at retroreflector cen
29、ter by the side perpendicular tothe observation half-plane. For example, a 0.1 by 0.2rectangular aperture has its short side parallel to the observa-tion half-plane.10. Keywords10.1 Application system; CIE (goniometer) system; en-trance angle; Intrinsic system; observation angle; orientationangle; p
30、resentation angle; retroreflection; rotation angleAPPENDIX(Nonmandatory Information)X1. TRANSFORMATION TABLESX1.1 Equations for transformation from the 1959 BrusselsCIE coordinate system (a, E, V, H) to the CIE (goniometer)system (a, b1, b2, e).NOTE X1.1The symbol E is used to designate the rotation
31、 angle in the1959 Brussels system to avoid confusion.a5acos b5 cos V cos Hsin b152sin Vsin2V 1 cos2V cos2H!1/2cos b15cos V cos Hsin2V 1 cos2V cos2H!1/2sin b252sin H cos Vcos e5cos E cos H 1 sin E sin V sin Hsin2V 1 cos2V cos2H!1/2sin e5cos E sin H sin V sin E cos Hsin2V 1 cos2V cos2H!1/2X1.1.1 Speci
32、al cases: when V =0andH = 6 90then b251290 note sign reversal!b15 0e5 EX1.2 Equations for transformation from CIE (goniometer)system (a, b1, b2, e) to the 1959 Brussels CIE coordinatesystem (a, E, V, H).a5 asin V 5 sin b1cos b2sin H 5 sin b2sin2b21 cos2b1cos2b2!1/2cos H 5cos b1cos b2sin2b21 cos2b1co
33、s2b2!1/2cos E 5sin e sin b1sin b21 cos e cos b1sin2b21 cos2b1cos2b2!1/2sin E 5cos e sin b1sin b2 sin e cos b1sin2b21 cos2b1cos2b2!1/2X1.2.1 Special cases: when b2=0andb1= 6 90then H 5 0V 51290E 5 eX1.3 In the SAE J594f system, the transformations are thesame as in Sections X1.1 and X1.2, with the fo
34、llowingconventions:E808018E = eSAE(eSAEis rotation angle in SAE J594f)b10 =down SAE J594f angleb10 =right SAE J594f angleb20, sgn(x)=+1; sgn(0)=0. This agreeswith most software, but some define sgn(0)=+1.X1.4.1 Equations for transformation from Intrinsic systemto CIE system are as follows:b15tan1tan
35、 b cosg! (X1.1)b25sin1sin b sin g! (X1.2)e5vs tan1tan g cos b! 901 sgncos g! (X1.3)X1.4.2 Equations for transformation from CIE system toIntrinsic system are as follows:b5cos1cosb1 cosb2! (X1.4)vs5e1tan1Ssin b2tan b1D1 90 1 sgnb1! (X1.5)g5tan1Stan b2sin b1D1 90 1 sgnb1! (X1.6)X1.4.2.1 For the specia
36、l case b1=0fib2, makevs= e + 90 sgn(b2).For the special case b1=0=b2, make vs= 0.X1.4.2.2 For the special case b1=0fib2, makeg = 90 sgn(b2).For the special case b1=0=b2, make g =-e.X1.4.3 Equations for transformation from Application sys-tem to CIE system are as follows:b15 sin1sinbcosvs e! (X1.7)b2
37、5 tan1tanb sinvs e! (X1.8)X1.4.4 Equations for transformation from CIE system toApplication system are as follows:b5cos1cosb1 cosb2! (X1.9)vs5e1tan1Ssin b2tan b1D1 901 sgnb1! (X1.10)X1.4.4.1 For the special case b1=0fib2, makevs= e + 90 sgn(b2).For the special case b1=0=b2, make vs= 0.X1.4.5 Equatio
38、n for transformation from Intrinsic system toApplication system is as follows:e5vs tan1tan g cos b! 901 sgncos g! (X1.11)X1.4.5.1 For the special cases where tan g is infinite, makee=vsg.X1.4.6 Equation for transformation from Application sys-tem to Intrinsic system is as follows:g5tan1Stanvs e!cos
39、bD1 901 sgncosvs e! (X1.12)X1.4.6.1 For the special cases where tan(vse) is infinite,make g=vse.X1.4.7 Equations for transformation from RM system toApplication system are as follows:a5cos1sin a sin e cos a cos b cos e! (X1.13)b590 e (X1.14)e5d tan1Stan a sin btan e 1 tan a cos bD1 901 1 sgntan e 1
40、cos a cos b!(X1.15)vs5 d b 1 180 (X1.16)X1.4.8 To transform from RM system to CIE system, firstuse the equations in X1.4.7 to transform to the Applicationsystem, then use the equations in X1.4.3 to transform to theCIE system.X1.4.9 Equations for transformation from CIE system toRM system are as foll
41、ows:a 5 sin1cos b1a!cos b2! (X1.17)b 5 180 1 sgn b2!cos1Ssin2b2cosb1cosb1a! 1 sinb1sinb1a!= 1 cos2b1cos2b2=1 cos2b1a!cos2b2D(X1.18)e 5 sin1cos b1cos b2! (X1.19)d 5vs1 b 180 (X1.20)X1.4.9.1 To use Eq X1.20 requires first using Eq X1.18 toobtain b and equation Eq X1.5 to obtain vs.X1.4.10 Equations fo
42、r transformation between rotationangle and rho angle are as follows:r5 tan1Stanvs e!cos bD1 tan1Stan vscos bD1 90sgncosvs e! sgncos vs! (X1.21)e5vs tan1Stan vscos b tan r cos2bcos b1tan vstan rD 1 Q (X1.22)Make Q=0 or Q=180 so as to produce e in the samequadrant as r.E808019ASTM International takes
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