1、Designation: E 810 03Standard Test Method forCoefficient of Retroreflection of Retroreflective SheetingUtilizing the Coplanar Geometry1This standard is issued under the fixed designation E 810; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 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 test method describes an instrument measurementof the retroreflective performance of retr
3、oreflective sheeting.1.2 The user of this test method must specify the entranceand observation angles to be used, and may specify the rotationangles.1.3 This test method is intended as a laboratory test andrequires a facility that can be darkened sufficiently so that straylight does not affect the t
4、est results. The testing apparatus mustbe able to achieve the coplanar geometry.1.4 Portable and bench retroreflection measuring equipmentmay be used to determine RAvalues provided the geometry andappropriate substitution standard reference panels, measured inaccordance with this test method, are ut
5、ilized. In this case themethods of Procedure B in Practice E 809 apply. Additionalinformation on the use of portable retroreflectometers may befound in Test Method E 1709.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
6、 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 Appearance2E 308 Practice for Computing the Colors of Objects byUsing the CIE Sys
7、tem2E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3E 808 Practice for Describing Retroreflection2E 809 Practice for Measuring Photometric Characteristicsof Retroreflectors2E 1709 Test Method for Measurement of RetroreflectiveSigns Using a Portable R
8、etroreflectivemeter22.2 Other Document:CIE Publication No 54 RetroreflectionDefinition andMeasurement43. Terminology3.1 The terms and definitions in Terminology E 284 andPractice E 808 apply to this test method.3.2 Definitions:3.2.1 coeffcient of retroreflection, RAof a plane retrore-flecting surfac
9、e, the ratio of the coefficient of luminousintensity (RI) to the area (A), expressed in candelas per lux persquare metre (cdlx1m2). RA= RI/A.3.2.1.1 DiscussionThe equivalent inchpound units forcoefficient of retroreflection are candelas per foot-candle persquare foot (cdfc1ft2). The SI and inch poun
10、d units arenumerically equal, because the units of RAreduce to 1/sr. Anequivalent term used for coefficient of retroreflection is specificintensity per unit area, with symbol SIA or the CIE symbol R8.The term coefficient of retroreflection and the symbol RAalongwith the SI units of candelas per lux
11、per square meter(cdlx1m2) are recommended by ASTM.3.2.1.2 DiscussionRAis a useful engineering quantity fordetermining the photometric performance of such retroreflec-tive surfaces as highway delineators or warning devices. RAmay also be used to determine the minimum area of retrore-flective sheeting
12、 necessary for a desired level of photometricperformance. RAhas been used extensively in the specificationof retroreflective sheeting.3.2.2 coplanar geometry, nretroreflection geometry inwhich the retroreflector axis, illumination axis, and observationaxis lie in one plane.3.2.2.1 DiscussionIn the c
13、oplanar geometry: the secondentrance angle component, b2, is equal to 0; presentationangle, g, is equal to either 0 or 180; orientation angle, vs,isequal to either the rotation angle, e,ortoe + 180 or e 180.3.2.3 datum axis, na designated half-line from the retrore-flector center perpendicular to th
14、e retroreflector axis.1This test method is under the jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibility of Subcommittee E12.10 onRetroreflection.Current edition approved Feb. 10, 2003. Published April 2003. Originallyapproved in 1981. Last previous edition app
15、roved in 2001 as E 810 01.2Annual Book of ASTM Standards, Vol 06.01.3Annual Book of ASTM Standards, Vol 14.02.4Available from USNC/CIE Publications Office, TLALighting Consultants, Inc.77 Pond St., Salem, MA 01970.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
16、PA 19428-2959, United States.3.2.4 datum mark, n an indication on the retroreflector,off the retroreflector axis, that establishes the direction of thedatum axis.3.2.5 entrance angle, b, nthe angle between the illumi-nation axis and the retroreflector axis.3.2.5.1 DiscussionThe entrance angle is usu
17、ally no largerthan 90, but for completeness its full range is defined as 0 #b # 180. In the CIE (goniometer 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 f
18、rom the photore-ceptor as a negative value is deprecated by ASTM. Therecommendation is to designate such negative values asbelonging to b1.3.2.6 goniometer, nan instrument for measuring or settingangles.3.2.7 illumination axis, nthe half-line from the retrore-flector center through the source point.
19、3.2.8 observation angle, a, nthe angle between the illu-mination axis and the observation axis.3.2.8.1 DiscussionThe observation angle is never nega-tive and is almost always less than 10 and usually no morethan 2. The full range is defined as 0 # a 180.3.2.9 observation axis, nthe half-line from th
20、e retroreflec-tor center through the observation point.3.2.10 receiver, n the portion of a photometric instrumentthat receives the viewing beam from the specimen, including acollector such as an integrating sphere, if used, often themonochromator or spectral filters, the detector, and associatedopti
21、cs and electronics.3.2.11 retroreflection, nreflection in which the 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
22、material, na material that has a thincontinuous layer of small retroreflective elements on or verynear its exposed surface (for example, retroreflective sheeting,retroreflective fabrics, transfer films, beaded paint, highwaysurface signs, or pavement striping).3.2.13 retroreflective sheetinga retror
23、eflective 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, this property being mai
24、ntainedover wide variations of the direction of the incident rays. CIE,1982B3.2.15 retroreflector axis, na designated half-line from theretroreflector center.3.2.15.1 DiscussionThe direction of the retroreflector axisis usually chosen centrally among the intended directions ofillumination; for examp
25、le, the direction of the road on which orwith respect to which the retroreflector is intended to bepositioned. The retroreflector axis usually coincides with theaxis of symmetry of the retroreflector. For retroreflectivesheeting the normal to the surface is chosen as the retroreflectoraxis.3.2.16 re
26、troreflector center, nthe point on or near aretroreflector that is designated to be the location of the device.3.2.17 rotation angle, e, nthe angle in a plane perpendicu-lar to the retroreflector axis from the observation half-plane tothe datum axis, measured counterclockwise from a viewpointon the
27、retroreflector axis.3.2.17.1 Discussion Range: 180 e # 180. The defi-nition 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, measuredcounterclockwise from a viewpoint on the retror
28、eflector 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 (e) and the orientation angle(vs) equally.3.2.18 rotationally uniform, adjhaving substantially con-stant RA, when rotated about the ret
29、roreflector axis, while thesource, receiver, retroreflector center and retroreflector axis allremain in a fixed spatial relation.3.2.18.1 DiscussionThe degree of rotational uniformitycan be specified numerically.3.2.19 source, nan object that produces light or otherradiant flux.4. Summary of Test Me
30、thod4.1 This test method involves the use of a light projectorsource, a receiver, a device to position the receiver with respectto the source and a test specimen holder in a suitable darkenedarea. The specimen holder is separated from the light source by15 m.4.2 The general procedure involved is to
31、determine the ratioof the light retroreflected from the test surface to that incidenton the test surface.4.3 The photometric quantity, coefficient of retroreflection,is calculated from these measurements.5. Significance and Use5.1 Measurements made by this test method are related tovisual observatio
32、ns of retroreflective sheeting as seen by thehuman eye when illuminated by tungsten-filament light sourcessuch as a motor vehicle headlamp.5.2 The values determined relate to the visual effects for agiven geometric configuration as specified by the user of thetest method. This test method has been f
33、ound useful for tests atobservation angles between 0.1 and 2.0 (observation anglesbetween 0.1 and 0.2 may be achieved by careful design ofsource and receiver aperture configuration), and at entranceangles up to 60. It has been used to determine coefficient ofretroreflection values as low as 0.1 cdlx
34、1m2, but for valuesless than 1 cdlx1m2special attention must be given to theresponsivity of the receiver and to the elimination of very smallamounts of stray light.6. Apparatus6.1 Light SourceThe light source shall be of the projectortype and shall meet the following requirements (an illuminanceat t
35、he 15 m specimen distance of about 10 lx is commonlyavailable within these restrictions):E8100326.1.1 The spectral energy distribution of the source shall beproportional to CIE standard Source A (a correlated colortemperature of 2856 K, see Practice E 308). The projectionlamp together with the proje
36、ction optics shall be operated suchthat it illuminates the test specimen with this spectral powerdistribution.6.1.2 An unpolarizing light source shall be used.6.1.3 The source aperture shall be a standard circularaperture as defined in Practice E 809. For measurements atobservation angles (a) of 0.2
37、# a #2.0, the exit aperture ofthe source shall be uniformly radiant, circular and 26 mm (62mm) in diameter. This corresponds to 0.1 angular aperture at15 m test distance. For measurements at observation angles (a)of 0.1 # a 0.2, the exit aperture of the source shall beuniformly radiant, circular and
38、 13 mm (61 mm) in diameter.This corresponds to 0.05 angular aperture at 15 m testdistance.6.1.4 The illumination at the sample produced by theprojector shall be such that the test specimen and only aminimum of the background is illuminated. This is commonlyaccomplished by placing a restrictive apert
39、ure in the projectorslide port.6.1.5 The source shall be regulated such that the illumi-nance at the test surface does not change by more than 61%for the duration of the test.6.1.6 The illuminance produced on the sample surface shallbe uniform within 65 % of the average illuminance normal tothe sour
40、ce at the distance of 15 m.6.2 ReceiverThe receiver shall meet the requirements thatfollow. (In this test, for 10 lx incident upon a 1 cdlx1m2retroreflective sheeting test specimen with area of 0.04 m2, theincident normal illuminance at the receiver will be about1.8 3 103lx).6.2.1 The responsivity a
41、nd range of the receiver shall besufficient so that readings of both the incident normal illumi-nance (at the specimen) and the retroreflected light at theobservation position can be measured with a resolution of atleast 1 part in 50 on the readout scale.6.2.2 The spectral responsivity of the receiv
42、er shall matchthat of the 1931 CIE Standard Photopic Observer (see AnnexA1 of Practice E 809).6.2.3 The receiver shall be insensitive to the polarization oflight.6.2.4 The linearity of the photometric scale over the rangeof readings to be taken shall be within 61 %. Correctionfactors may be used to
43、ensure a linear response. Linearityverification tests must be made utilizing the entire receiverreadout device including the detector, load, range selectionsystem and readout display device.6.2.5 The stability of the receiver shall be such that readingsfrom a constant source do not vary any more tha
44、n 1 % for theduration of the test.6.2.6 The field of view shall be limited by use of lightbaffles or a field aperture on the instrument so that the entiretest sample is fully within the field of view, rejecting stray lightas much as practical.Abackground light level mbless than 5 %of the smallest m1
45、reading is acceptable.6.2.7 The receiver aperture shall be a standard circularaperture as defined in Practice E 809. For measurements atobservation angles (a) of 0.2#a#2.0, the receiver shall beprovided with an entrance aperture 26 mm (62 mm) indiameter. This corresponds to 0.1 angular aperture at 1
46、5 m testdistance. For measurements at observation angles (a) of 0.1#a 0.2, the receiver shall be provided with an entranceaperture 13 mm (61 mm) in diameter. This corresponds to a0.05 angular aperture at 15 m test distance. The size of theentrance aperture stop must be small so that the receiver may
47、be positioned physically close to the source exit aperturewithout shadowing any of the illuminating light beam.6.3 Test Specimen Goniometer (Test Specimen Holder)The specimen holder must hold a 200 mm square specimen andmeet the following requirements (see Fig. 1):6.3.1 A means must be provided to r
48、otate the specimen onan axis contained in the plane of the specimen surface if severalentrance angles are to be used.6.3.1.1 The entrance angle component b1is used to set thegoniometer when no specific component is specified (seePractice E 808).6.3.2 The specimen surface must be positionable so that
49、 theentrance angle is accurate to within 0.5 % of its complement(that is, for a 30 entrance angle this angle must be accuratelyset to 6 0.005 3 60 = 60.3). This is obtainable by providingan accurate optical means to align the test surface to the “0degree” entrance angle and then adjusting the angular setting(within the required tolerance).6.3.3 The specimen holder must be provided with a meansof eliminating reflections from the edges of the specimen andthe holder itself must be nonreflect
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