1、Designation: E1709 09Standard Test Method forMeasurement of Retroreflective Signs Using a PortableRetroreflectometer at a 0.2 Degree Observation Angle1This standard is issued under the fixed designation E1709; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case of revision, 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 test method covers measurement of the retroreflec-tive properties of sign
3、materials such as traffic signs andsymbols (vertical surfaces) using a portable retroreflectometerthat can be used in the field. The portable retroreflectometer isa hand-held instrument with a defined standard geometry thatcan be placed in contact with sign material to measure theretroreflection in
4、a standard geometry. The measurements canbe compared to minimum requirements to determine the needfor replacement. Entrance and observation angles specified inthis test method are those used currently in the United Statesand may differ from the angles used elsewhere in the world.1.2 This test method
5、 is intended to be used for the fieldmeasurement of traffic signs but may be used to measure theperformance of materials before placing the sign in the field orbefore placing the sign material on the sign face.1.3 This test method covers measurements at a 0.2 degreeobservation angle. See Test Method
6、 E2540 for measurementsat a 0.5 degree observation angle.1.4 This standard does not purport to address all of thesafety 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 to determine theapplicabil
7、ity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E284 Terminology of AppearanceE808 Practice for Describing RetroreflectionE809 Practice for Measuring Photometric Characteristics ofRetroreflectorsE810 Test Method for Coefficient of Retroreflection ofRetroreflecti
8、ve Sheeting Utilizing the Coplanar GeometryE2540 Test Method for Measurement of RetroreflectiveSigns Using a Portable Retroreflectometer at a 0.5 DegreeObservation Angle3. Terminology3.1 The terminology used in this test method generallyagrees with that used in Terminology E284.3.2 DefinitionsThe de
9、limiting phrase “in retroreflection”applies to each of the following definitions when used outsidethe context of this or other retroreflection standards.3.2.1 annular geometry, nthe portable instrument retrore-flection collection method where an annular area 0.1 degreeswide around the illumination a
10、xis collects the retroreflectedenergy at an angle to the center of the annular area correspond-ing to a specific observation angle.3.2.2 coeffcient of retroreflection, RA, nof a plane retrore-flecting surface, the ratio of the coefficient of luminousintensity (RI) of a plane retroreflecting surface
11、to its area (A),expressed in candelas per lux per square metre (cd lx1m2).3.2.3 datum axis, na designated half-line from the retrore-flector center perpendicular to the retroreflector axis.3.2.4 entrance angle, b, nthe angle between the illumi-nation axis and the retroreflector axis.3.2.5 entrance h
12、alf-plane, nthe half plane that originateson the line of the illumination axis and contains the retrore-flector axis.3.2.6 instrument standard, nworking standard used tocalibrate the portable retroreflectometer.3.2.7 observation angle, a, nthe angle between the illu-mination axis and the observation
13、 axis.3.2.8 observation half-plane, nthe half plane that origi-nates on the line of the illumination axis and contains theobservation axis.3.2.9 orientation angle, vs, nthe angle in a plane perpen-dicular to the retroreflector axis from the entrance half-plane tothe datum axis, measured counter-cloc
14、kwise from the view-point of the source.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 July 1, 2009. Published February 2010. Originallyapproved in 1995. Last
15、previous edition approved in 2008 as E1709 08. DOI:10.1520/E1709-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM w
16、ebsite.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.10 portable retroreflectometer, na hand-held instru-ment that can be used in the field or in the laboratory formeasurement of retroreflectance.3.2.10.1 DiscussionIn this test
17、 method, “portable retrore-flectometer” refers to a hand-held instrument that can be placedin contact with sign material to measure the retroreflection in astandard geometry.3.2.11 presentation angle, g, nthe dihedral angle from theentrance half-plane to the observation half-plane, measuredcounter-c
18、lockwise from the viewpoint of the source.3.2.12 retroreflection, na reflection in which the reflectedrays are returned preferentially in directions close to theopposite of the direction of the incident rays, this propertybeing maintained over wide variations of the direction of theincident rays.3.2
19、.13 rotation angle, , nthe angle in a plane perpen-dicular to the retroreflector axis from the observation half-plane to the datum axis, measured counter-clockwise from theviewpoint of the source.3.3 Definitions of entrance angle components b1and b2,aswell as other geometrical terms undefined in thi
20、s test method,may be found in Practice E808.4. Summary of Test Method4.1 This test method involves the use of commercial por-table retroreflectometers for determining the retroreflectivity ofhighway signing materials.4.2 The entrance angle shall be 4.4.3 The observation angle shall be 0.2.4.4 The po
21、rtable retroreflectometer uses an instrument stan-dard for calibration.4.5 After calibration, the retroreflectometer is placed incontact with the sign to be tested, ensuring that only the desiredportion of the sign is within the measurement area of theinstrument.4.6 The reading displayed by the retr
22、oreflectometer is re-corded. The retroreflectometer is then moved to anotherposition on the sign, and this value is recorded. A minimum offour readings shall be taken and averaged for each retroreflec-tive color or material on the sign to be tested.5. Significance and Use5.1 Measurements made by thi
23、s test method are related tothe night time brightness of retroreflective traffic signs approxi-mately facing the driver of a mid-sized automobile equippedwith tungsten filament headlights at about 200 m distance.5.2 Retroreflective material used on traffic signs degradeswith time and requires period
24、ic measurement to ensure that theperformance of the retroflection provides adequate safety to thedriver.5.3 The quality of the sign as to material used, age, and wearpattern will have an effect on the coefficient of retroreflection.These conditions need to be observed and noted by the user.5.4 This
25、test method is not intended for use for the mea-surement of signs when the instrument entrance and observa-tion angles differ from those specified herein.6. ApparatusNOTE 1Paragraphs 6.1 and 6.2 are primarily addressing field consid-erations, while paragraphs 6.3 through 6.5 address typical lab sett
26、ingconsiderations.6.1 Portable RetroreflectometerThe retroreflectometershall be portable, with the capability of being placed at variouslocations on the signs. The retroreflectometer shall be con-structed so that placement on the sign will preclude stray light(daylight) from entering the measurement
27、 area of the instru-ment and affecting the reading.6.2 Instrument Standard, or standards of desired color(s)and material(s).6.3 Light Source Requirements:6.3.1 The projection optics shall be such that the illumi-nance at any point over the measurement area shall be within10 % of the average illumina
28、nce.6.3.2 The aperture angle of the source as determined fromthe center of the measurement area shall be not greater than0.1.6.4 Receiver Requirements:6.4.1 The receiver shall have sufficient sensitivity and rangeto accommodate coefficient of retroreflection values from 0.1to 1999.9 cd lx1m2.6.4.2 T
29、he combined spectral distribution of the light sourceand the spectral responsivity of the receiver shall match thecombined spectral distribution of CIE Illuminant A and theV(l) spectral luminous efficiency function according to thefollowing criterion: For any choice of plano-parallel coloredabsorpti
30、ve filter mounted in front of a white retroreflectivesample, the ratio of the RAmeasured with the filter to the RAmeasured without the filter shall be within 10 % of theIlluminantAluminous transmittance of an air space pair of twosuch filters.6.4.3 The instrument may be either a “point instrument” o
31、ran “annular instrument,” depending on the shape of thereceiver aperture (see Fig. 1). Point and annular instrumentsmake geometrically different measurements of RA, which mayproduce values differing on the order of 10 %. Both measure-ments are valid for most purposes, but the user should learn thety
32、pe of instrument from its specifications sheet and be aware ofcertain differences in operation and interpretation. For bothinstrument types, the “up” position of the instrument shall beknown. Both types of instruments may make additional mea-surements at observation angles other than the 0.5 degree
33、ofthis specification and combine the measurement at two or moredifferent observation angles if the readings at the differentobservation angles are reported separately.6.4.3.1 The point instrument makes an RAmeasurementvirtually identical to an RAmeasurement made on a rangeinstrument following the pr
34、ocedure of Test Method E810. The4 entrance angle would be set on a range instrument bysetting b1=4; b2=0. This may be called “-4 entranceangle.” The rotation angle () for the point instrument isdetermined by the angular position of the instrument on thesign face. Assuming the retroreflectors datum a
35、xis to beupward, the rotation angle equals 0 when the instrument isupright. Clockwise rotation of the instrument on the sign faceincreases the rotation angle.E1709 0926.4.3.2 For the point instrument the “up” marking shall beopposite the entrance half-plane. It shall be in the observationhalf-plane
36、(see Fig. 2).6.4.3.3 The annular instrument makes an RAmeasurementsimilar to an average of a large number of RAmeasurements ona range instrument with presentation angle (g) varying between180 and +180. For the 4 entrance angle the range instru-ment would include the b1and b2settings indicated in Tab
37、le 1.There is no definite rotation angle () for the annular instru-ment. All values from 180 to +180 are included in themeasurement.6.4.3.4 For the annular instrument the “up” marking shall beopposite the entrance half-plane (see Fig. 2).6.4.3.5 For both instrument types, the orientation angle (vs)i
38、s determined by the angular position of the instrument on thesign face. It is the rotation angle () rather than the orientationangle (vs) which primarily affects retroreflection of signsmeasured at the small 4 entrance angle.6.4.3.6 Rotationally insensitive sheetings, such as glassbead sheetings, ha
39、ve RAvalues that are nearly independent ofthe rotation angle. Accordingly, the point and annular instru-ments will make practically identical measurements of RAforsigns made with such sheetings.6.4.3.7 Most prismatic retroreflectors are rotationally sensi-tive, having RAvalues that vary significantl
40、y with rotationangle (), even at small entrance angles. The difference of RAmeasurements made with the two types of instrument onprismatic signs may become as great as 25 % in extreme cases,but is generally on the order of 10 %. Neither the magnitudenor the direction of difference can be predicted f
41、or unknownsamples. Thus, critical comparison of prismatic sign RAvaluesmeasured by instruments of the two types is not recommended.FIG. 1 Annular and Point Aperture Instrument AnglesNOTE 1For each instrument type, the illumination beam is 4 down-ward For the point instrument, receiver is above sourc
42、e.FIG. 2 Upright Optical SchematicsTABLE 1 Laboratory Emulation of Annular Instrument Geometryab1b20.2 3.86 1.03 1650.2 3.47 2.00 1500.2 2.83 2.83 1350.2 2.00 3.46 1200.2 1.04 3.86 1050.2 0.00 4.00 900.2 1.04 3.86 750.2 2.00 3.46 600.2 2.83 2.83 450.2 3.47 2.00 300.2 3.86 1.03 150.2 4.00 0.00 00.2 3
43、.86 1.03 150.2 3.47 2.00 300.2 2.83 2.83 450.2 2.00 3.46 600.2 1.04 3.86 750.2 0.00 4.00 900.2 1.04 3.86 1050.2 2.00 3.46 1200.2 2.83 2.83 1350.2 3.47 2.00 1500.2 3.86 1.03 1650.2 4.00 0.00 180E1709 0936.4.3.8 Apoint instrument can gage the variation of RAwithrotation angle by placing it with differ
44、ent angular positionsupon the sign face. RAvariation of 5 % for 5 rotation is notunusual. Accordingly, repeatable RAmeasurement of prismaticsigns with a point instrument, requires care in angular posi-tioning.6.4.3.9 An annular instrument cannot gage the variation ofRAwith rotation angle. Accordingl
45、y, repeatable RAmeasure-ment of prismatic signs with an annular instrument does notrequire care in angular positioning. Positioning to within 615is sufficient.6.4.4 The aperture angle of the receiver as determined fromthe measurement area shall be not greater than 0.1. Theaperture angle of the recei
46、ver is measured from inner to outerring limits for annular receivers (see Fig. 1).6.4.5 The combined stability of the output of the lightsource and receiver shall not change more than 61 % after10 s when the retroreflectometer is in contact with the signface.6.4.6 The linearity of the retroreflectom
47、eter photometricscale over the range of readings expected shall be within 2 %.Correction factors may be used to ensure a linear response. Amethod for determining linearity can be found in Annex A2 ofPractice E809.6.5 Measurement Geometry:6.5.1 The geometry used to determine the photometricperformanc
48、e shall be in accordance with Practice E808.6.5.2 The light source and receiver shall be at opticalinfinity (collimated) and possess an observation angle of 0.56 0.01 (6 36 arc seconds) as measured from the center of thesource aperture to the centroid of responsivity of the receiver atall presentati
49、on angles. For annular receivers, the observationangle is taken as the angular distance when area A and area Bare equal (see Fig. 1). There are two independent reasons forthis collimation requirement. The first reason for this collima-tion requirement is to avoid an observation angle error inmeasurements or retroreflective signs consisting of large opti-cal elements as described in 8.1.4.2. The
