1、Designation: E1709 161Standard 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 o
2、r, 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.1NOTEParagraph 6.5.2 was editorially corrected in April 2017.1. Scope1.1 This test method
3、covers measurement of the retroreflec-tive properties of sign 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 i
4、n contact with sign material to measure theretroreflection in 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 fr
5、om the angles used elsewhere in the world.1.2 This test method 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
6、measurements at a 0.2 degreeobservation angle. See Test Method 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-pri
7、ate safety and health practices and to determine theapplicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Interna
8、tional Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D4956 Specification for Retroreflective Sheeting for TrafficControlE177 Practice for Use of the Terms Precision and Bias inASTM T
9、est MethodsE284 Terminology of AppearanceE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE808 Practice for Describing RetroreflectionE809 Practice for Measuring Photometric Characteristics ofRetroreflectorsE810 Test Method for Coefficient of Retrorefle
10、ction ofRetroreflective 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.
11、3.2 DefinitionsThe delimiting 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 arou
12、nd the illumination axis 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 retr
13、oreflecting surface to its area (A),expressed in candelas per lux per square metre (cd lx1m2).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, 2016. Publ
14、ished November 2016. Originallyapproved in 1995. Last previous edition approved in 2009 as E1709 09. DOI:10.1520/E1709-16E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,
15、refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization estab
16、lished in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.3 datum axis, na designated half-line from the retrore-flector center perpendicular to the retrorefle
17、ctor axis.3.2.4 entrance angle, ,nthe angle between the illumina-tion axis and the retroreflector axis.3.2.5 entrance half-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 th
18、e portable retroreflectometer.3.2.7 observation angle, ,nthe angle between the illu-mination axis and the observation 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, s,nthe angle in a p
19、lane perpen-dicular to the retroreflector axis from the entrance half-plane tothe datum axis, measured counter-clockwise from the view-point of the source.3.2.10 portable retroreflectometer, na hand-held instru-ment that can be used in the field or in the laboratory formeasurement of retroreflectanc
20、e.3.2.10.1 DiscussionIn this test 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, ,nthe dihedral angle from theentrance half-plane to the observatio
21、n half-plane, measuredcounter-clockwise 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 di
22、rection of theincident rays.3.2.13 rotation angle, ,nthe angle in a plane perpendicu-lar to the retroreflector axis from the observation half-plane tothe datum axis, measured counter-clockwise from the view-point of the source.3.3 Definitions of entrance angle components 1and 2,aswell as other geome
23、trical terms undefined in this 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
24、angle shall be 0.2.4.4 The portable 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
25、reading displayed by the retroreflectometer 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 Us
26、e5.1 Measurements made by this 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 degrades
27、with time and requires periodic 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 an
28、d noted by the user.5.4 This 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 fieldconsiderations, while paragraphs 6.3 through 6
29、.5 address typical labsetting considerations.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) fr
30、om entering the measurement 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 within1
31、0 % of the average illuminance.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.
32、1to 1999.9 cd lx1m2.6.4.2 The combined spectral distribution of the light sourceand the spectral responsivity of the receiver shall match thecombined spectral distribution of CIE Illuminant A and theV() spectral luminous efficiency function according to thefollowing criterion: For any choice of plan
33、o-parallel coloredabsorptive 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 eit
34、her a “point instrument” oran “annular instrument,” depending on the shape of theE1709 1612receiver 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 purpo
35、ses, but the user should learn thetype 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 observati
36、on angles other than the 0.5 degree 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 o
37、n a rangeinstrument following the procedure of Test Method E810. The4 entrance angle would be set on a range instrument bysetting 1=4; 2=0. This may be called “-4 entrance angle.”The rotation angle () for the point instrument is determined bythe angular position of the instrument on the sign face.As
38、suming the retroreflectors datum axis to be upward, therotation angle equals 0 when the instrument is upright.Clockwise rotation of the instrument on the sign face increasesthe rotation angle.6.4.3.2 For the point instrument the “up” marking shall beopposite the entrance half-plane. It shall be in t
39、he observationhalf-plane (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 () varying between180 and +180. For the 4 entrance angle the range instru-ment would include the 1and 2set
40、tings indicated in Table 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 o
41、rientation angle (s)is determined by the angular position of the instrument on thesign face. It is the rotation angle () rather than the orientationangle (s) which primarily affects retroreflection of signsmeasured at the small 4 entrance angle.6.4.3.6 Rotationally insensitive sheetings, such as gla
42、ssbead sheetings, have 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 rotationallysensitive, having RAvalues that
43、 vary significantly 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
44、can be predicted for unknownFIG. 1 Annular and Point Aperture Instrument AnglesNOTE 1For each instrument type, the illumination beam is 4downward For the point instrument, receiver is above source.FIG. 2 Upright Optical SchematicsE1709 1613samples. Thus, critical comparison of prismatic sign RAvalue
45、smeasured by instruments of the two types is not recommended.6.4.3.8 Apoint instrument can gage the variation of RAwithrotation angle by placing it with different angular positionsupon the sign face. RAvariation of 5 % for 5 rotation is notunusual.Accordingly, repeatable RAmeasurement of prismaticsi
46、gns with a point instrument, requires care in angular posi-tioning.6.4.3.9 An annular instrument cannot gage the variation ofRAwith rotation angle. Accordingly, repeatable RAmeasure-ment of prismatic signs with an annular instrument does notrequire care in angular positioning. Positioning to within
47、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 receiver is measured from inner to outerring limits for annular receivers (see Fig. 1).6.4.5 The combined stability of the output of the lightsourc
48、e and receiver shall not change more than 61 % after 10s when the retroreflectometer is in contact with the sign face.6.4.6 The linearity of the retroreflectometer photometricscale over the range of readings expected shall be within 2 %.Correction factors may be used to ensure a linear response. Ame
49、thod for determining linearity can be found in Annex A2 ofPractice E809.6.5 Measurement Geometry:6.5.1 The geometry used to determine the photometricperformance 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 of0.2 6 0.01 (6 36 arc seconds) as measured from the centerof the source aperture to the centroid of responsivity of thereceiver at all presentation angles. For annular receivers, theobservation a
