1、Designation: E 1709 00e1Standard Test Method forMeasurement of Retroreflective Signs Using a PortableRetroreflectometer1This standard is issued under the fixed designation E 1709; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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.e1NOTEEditorial changes were made to Fig. 1 and Fig. 2 in October 2001.1. Scope1.1 This test method covers measurement o
3、f 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 in contact with sign
4、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 from the angles used e
5、lsewhere 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 standard does not purport to address al
6、l 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 theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 284 Terminology of
7、 Appearance2E 808 Practice for Describing Retroreflection2E 809 Practice for Measuring Photometric Characteristicsof Retroreflectors2E 810 Test Method for Coefficient of Retroreflection orRetroreflective Sheeting23. Terminology3.1 The terminology used in this test method generallyagrees with that us
8、ed in Terminology E 284.3.2 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 coeffcient of retroreflection, RA, nof a plane retrore-flecting surface, the ratio of the coeffi
9、cient of luminousintensity (RI) of a plane retroreflecting surface to its area (A),expressed in candelas per lux per square metre (cd lx1m2).3.2.2 datum axis, na designated half-line from the retrore-flector center perpendicular to the retroreflector axis.3.2.3 entrance angle, b, nthe angle between
10、the illumi-nation axis and the retroreflector axis.3.2.4 entrance half-plane, nThe half plane that originateson the line of the illumination axis and contains the retrore-flector axis.3.2.5 instrument standard, nworking standard used tostandardize the portable retroreflectometer.3.2.6 observation an
11、gle, a, nthe angle between the illu-mination axis and the observation axis.3.2.7 observation half-plane, nThe half plane that origi-nates on the line of the illumination axis and contains theobservation axis.3.2.8 orientation angle, vs, nthe angle in a plane perpen-dicular to the retroreflector axis
12、 from the entrance half-plane tothe datum axis, measured counter-clockwise from the view-point of the source.3.2.9 portable retroreflectometer, na hand-held instru-ment that can be used in the field or in the laboratory formeasurement of retroreflectance.3.2.9.1 DiscussionIn this test method, “porta
13、ble retrore-flectometer” refers to a hand-held instrument that can be placedin contact with sign material to measure the retroreflection in astandard geometry.3.2.10 presentation angle, g, nthe dihedral angle from theentrance half-plane to the observation half-plane, measuredcounter-clockwise from t
14、he viewpoint of the source.3.2.11 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.3.2.12 rotation an
15、gle, e, 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.1This test method is under the jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibi
16、lity of Subcommittee E12.10 onRetroreflection.Current edition approved July 10, 2000. Published September 2000. Originallypublished as E 1709 95. Last previous edition E 1709 95ae1.2Annual Book of ASTM Standards, Vol 06.01.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, Uni
17、ted States.3.3 Definitions of entrance angle components b1and b2,aswell as other geometrical terms undefined in this test method,may be found in Practice E 808.4. Summary of Test Method4.1 This test method involves the use of commercial por-table retroreflectometers for determining the retroreflecti
18、vity ofhighway signing materials.4.2 The entrance angle shall be nominally 4.4.3 The observation angle shall be 0.2.4.4 The portable retroreflectometer uses a instrument stan-dard for standardization.4.5 After standardization, the retroreflectometer is placed incontact with the sign to be tested, en
19、suring that only the desiredportion of the sign is within the measurement area of theinstrument.4.6 The 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 will be taken a
20、nd averaged for each retroreflec-tive color on the sign to be tested.5. Significance and Use5.1 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 hea
21、dlights at about 200 m distance.5.2 Retroreflective material used on traffic signs degradeswith 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 h
22、ave an effect on the coefficient of retroreflection.These conditions need to be observed and 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. Apparatus6.1 Portable R
23、etroreflectometerThe 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 area of the instru-ment and aff
24、ecting 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 illuminance.6.3.2 The aperture angle of
25、the source as determined fromthe center of the measurement area shall be not greater than0.1.6.4 Receiver Requirements: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 source.FIG. 2 Upr
26、ight Optical SchematicsE 170926.4.1 The receiver shall have sufficient sensitivity and rangeto accommodate coefficient of retroreflection values from 0.1to 1999.9 cd lx1m2.6.4.2 The combined spectral distribution of the light sourceand the spectral responsivity of the receiver shall match thecombine
27、d spectral distribution of CIE Illuminant A and theV(l) spectral luminous efficiency function according to thefollowing criterion: For any choice of plano-parallel coloredabsorptive filter mounted in front of a white retroreflectivesample, the ratio of the RAmeasured with the filter to the RAmeasure
28、d without the filter shall be within 10 % of theIlluminant A luminous transmittance of an air space pair of twosuch filters.6.4.3 The instrument may be either a “point instrument” oran “annular instrument”, depending on the shape of thereceiver aperture (see Fig. 1). Point and annular instrumentsmak
29、e 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 thetype of instrument from its specifications sheet and be aware ofcertain differences in operation and interpretation. For
30、bothinstrument types, the “up” position of the instrument shall beknown.6.4.3.1 The point instrument makes an RAmeasurementvirtually identical to an RAmeasurement made on a rangeinstrument following the procedure of Test Method E 810. Thedenoted 4 entrance angle would be set on a range instrumentby
31、setting b1=4; b2=0. The rotation angle (e) for the pointinstrument is determined by the angular position of theinstrument on the sign face. Assuming the retroreflectorsdatum axis to be upward, the rotation angle equals 0 when theinstrument is upright. Clockwise rotation of the instrument onthe sign
32、face increases the rotation angle.6.4.3.2 For the point instrument the “up” marking shall beopposite the entrance half-plane. It shall be in the observationhalf-plane (see Fig. 2).6.4.3.3 The annular instrument makes an RAmeasurementsimilar to an average of a great number of RAmeasurements ona range
33、 instrument with presentation angle (g) varying between180 and +180. For the denoted 4 entrance angle the rangeinstrument would include the b1and b2settings indicated inTable 1. Table 1 includes the setting b1=4; b2=0, amongothers. There is no definite rotation angle (e) for the annularinstrument. A
34、ll values from 180 to +180 are subsumed inthe measurement.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)is determined by the angular position of the instrument on thesign face. It
35、 is the rotation angle (e) 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, have RAvalues that are nearly independent ofthe rotation angle. Accordingly
36、, 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 significantly with rotationangle (e), even at small entrance angles. The difference o
37、f 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 for unknownsamples. Thus, critical comparison of prismatic sign RAvaluesm
38、easured by instruments of the two types is not recommended.6.4.3.8 A point 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
39、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
40、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
41、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
42、thod for determining linearity can be found in Annex A2 ofPractice E 809.6.5 Measurement Geometry:6.5.1 The geometry used to determine the photometricperformance shall be in accordance with Practice E 808.6.5.2 The light source and receiver shall be at opticalinfinity and possess an observation angl
43、e of 0.2 6 0.01 asmeasured from the center of the source aperture to the centroidTABLE 1 Laboratory Emulation of Annular Instrument Geometryab1b2e0.2 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
44、.47 2.00 300.2 3.86 1.03 150.2 4.00 0.00 00.2 3.86 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 180E 17093of responsivity of the receiver at all presentation a
45、ngles. Forannular receivers, the observation angle is taken as the angulardistance when area A and area B are equal (see Fig. 1).6.5.3 The entrance angle of the light source shall be 461.7. Standardization7.1 The retroreflectometer shall be standardized using aninstrument standard consisting of a se
46、parate panel or disc of amaterial with a known RAvalue. The calibration values shall bemaintained by checking against other standards or by labora-tory recalibration sufficiently often to ensure that no largeuncertainties in the measurement can occur.7.1.1 Instrument standards are generally of glass
47、-beadsheeting construction. The glass-bead sheeting instrumentstandard shall be calibrated in the laboratory range instrumentat a=0.2; b1=4; b2=0; e=0. The glass-bead sheetingstandard must have a datum mark for the calibration laboratory,but this mark is not required for its use with either type ofi
48、nstrument.7.1.2 If prismatic materials will be used as standards, theyshall be calibrated differently for the two types of instrument.7.1.2.1 A prismatic standard for a point instrument shall becalibrated following the procedure of Test Method E 810. Itshall be calibrated in the laboratory range ins
49、trument at a=0.2;b1=4; b2=0; e=0.7.1.2.1.1 The prismatic instrument standard must have adatum mark for the calibration laboratory, and this mark isrequired for its use with the point instrument. The datum markshall align with the “up” direction of the instrument.7.1.2.2 A prismatic standard for an annular instrument shallbe calibrated in the laboratory range instrument at the anglesgiven in
