ASTM E810-03(2013)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E810 −03 (Reapproved 2013)
Standard Test Method for
Coefficient of Retroreflection of Retroreflective Sheeting
Utilizing the Coplanar Geometry
This standard is issued under the fixed designation E810; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E809Practice for Measuring Photometric Characteristics of
Retroreflectors
1.1 This test method describes an instrument measurement
E1709Test Method for Measurement of Retroreflective
of the retroreflective performance of retroreflective sheeting.
Signs Using a Portable Retroreflectometer at a 0.2 Degree
1.2 The user of this test method must specify the entrance
Observation Angle
andobservationanglestobeused,andmayspecifytherotation
2.2 Other Document:
angles.
CIE Publication No 54 Retroreflection—Definition and
Measurement
1.3 This test method is intended as a laboratory test and
requiresafacilitythatcanbedarkenedsufficientlysothatstray
3. Terminology
light does not affect the test results.The testing apparatus must
be able to achieve the coplanar geometry. 3.1 The terms and definitions in Terminology E284 and
Practice E808 apply to this test method.
1.4 Portable and bench retroreflection measuring equipment
maybeusedtodetermine R valuesprovidedthegeometryand 3.2 Definitions:
A
3.2.1 coeffıcient of retroreflection, R —of a plane retrore-
appropriatesubstitutionstandardreferencepanels,measuredin
A
accordance with this test method, are utilized. In this case the flecting surface, the ratio of the coefficient of luminous
intensity (R) to the area (A), expressed in candelas per lux per
methods of Procedure B in Practice E809 apply. Additional
I
−1 −2
information on the use of portable retroreflectometers may be square metre (cd·lx ·m ). R = R/A.
A I
3.2.1.1 Discussion—The equivalent inch–pound units for
found in Test Method E1709.
coefficient of retroreflection are candelas per foot-candle per
1.5 This standard does not purport to address all of the
−1 −2
square foot (cd·fc ·ft ). The SI and inch pound units are
safety concerns, if any, associated with its use. It is the
numerically equal, because the units of R reduce to 1/sr. An
A
responsibility of the user of this standard to establish appro-
equivalenttermusedforcoefficientofretroreflectionisspecific
priate safety and health practices and determine the applica-
intensity per unit area, with symbol SIAor the CIE symbol R'.
bility of regulatory limitations prior to use.
Thetermcoefficientofretroreflectionandthesymbol R along
A
with the SI units of candelas per lux per square meter
2. Referenced Documents
−1 −2
(cd·lx ·m ) are recommended by ASTM.
2.1 ASTM Standards:
3.2.1.2 Discussion—R is a useful engineering quantity for
A
E284Terminology of Appearance
determining the photometric performance of such retroreflec-
E308PracticeforComputingtheColorsofObjectsbyUsing
tive surfaces as highway delineators or warning devices. R
A
the CIE System
may also be used to determine the minimum area of retrore-
E691Practice for Conducting an Interlaboratory Study to
flective sheeting necessary for a desired level of photometric
Determine the Precision of a Test Method
performance. R has been used extensively in the specification
A
E808Practice for Describing Retroreflection
of retroreflective sheeting.
3.2.2 coplanar geometry, n—retroreflection geometry in
whichtheretroreflectoraxis,illuminationaxis,andobservation
This test method is under the jurisdiction of ASTM Committee E12 on Color
and Appearance and is the direct responsibility of Subcommittee E12.10 on axis lie in one plane.
Retroreflection.
3.2.2.1 Discussion—In the coplanar geometry: the second
Current edition approved Jan. 1, 2013. Published January 2013. Originally
entrance angle component, β , is equal to 0°; presentation
approved in 1981. Last previous edition approved in 2008 as E810–03 (2008).
angle, γ, is equal to either 0° or 180°; orientation angle, ω,is
DOI: 10.1520/E0810-03R13.
s
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
equal to either the rotation angle, ε,orto ε + 180° or ε − 180°.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Available from the CIE Webshop at http://www.cie.co.at.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E810−03 (2013)
3.2.3 datum axis, n—adesignatedhalf-linefromtheretrore- axis of symmetry of the retroreflector. For retroreflective
flector center perpendicular to the retroreflector axis. sheetingthenormaltothesurfaceischosenastheretroreflector
axis.
3.2.4 datum mark, n—an indication on the retroreflector, off
the retroreflector axis, that establishes the direction of the
3.2.16 retroreflector center, n—the point on or near a ret-
datum axis.
roreflector that is designated to be the location of the device.
3.2.5 entrance angle, β,n—the angle between the illumina-
3.2.17 rotation angle, ε,n—theangleinaplaneperpendicu-
tion axis and the retroreflector axis.
lar to the retroreflector axis from the observation half-plane to
3.2.5.1 Discussion—The entrance angle is usually no larger
the datum axis, measured counterclockwise from a viewpoint
than 90°, but for completeness its full range is defined as 0° ≤
on the retroreflector axis.
β≤180°.IntheCIE(goniometersystem)βisresolvedintotwo
3.2.17.1 Discussion—Range:−180° <ε≤ 180°. The defini-
componentsβ andβ .Sincebydefinitionβisalwayspositive,
1 2
tion is applicable when entrance angle and viewing angle are
the common practice of referring to the small entrance angles
less than 90°. More generally, rotation angle is the angle from
that direct specular reflections away from the photoreceptor as
the positive part of second axis to the datum axis, measured
anegativevalueisdeprecatedbyASTM.Therecommendation
counterclockwise from a viewpoint on the retroreflector axis.
is to designate such negative values as belonging to β .
3.2.17.2 Discussion—Rotation of the sample about the ret-
3.2.6 goniometer, n—an instrument for measuring or setting
roreflector axis while the source and receiver remain fixed in
angles. space changes the rotation angle (ε) and the orientation angle
(ω ) equally.
3.2.7 illumination axis, n—thehalf-linefromtheretroreflec- s
tor center through the source point.
3.2.18 rotationally uniform, adj—having substantially con-
stant R , when rotated about the retroreflector axis, while the
3.2.8 observation angle, α,n—the angle between the illu-
A
source, receiver, retroreflector center and retroreflector axis all
mination axis and the observation axis.
remain in a fixed spatial relation.
3.2.8.1 Discussion—The observation angle is never nega-
3.2.18.1 Discussion—The degree of rotational uniformity
tive and is almost always less than 10° and usually no more
than 2°. The full range is defined as 0°≤α < 180°. can be specified numerically.
3.2.9 observation axis, n—the half-line from the retroreflec- 3.2.19 source, n—an object that produces light or other
tor center through the observation point. radiant flux.
3.2.10 receiver, n—the portion of a photometric instrument
4. Summary of Test Method
that receives the viewing beam from the specimen, including a
collector such as an integrating sphere, if used, often the
4.1 This test method involves the use of a light projector
monochromator or spectral filters, the detector, and associated
source,areceiver,adevicetopositionthereceiverwithrespect
optics and electronics.
to the source and a test specimen holder in a suitable darkened
3.2.11 retroreflection, n—reflection in which the reflected
area.Thespecimenholderisseparatedfromthelightsourceby
rays are preferentially returned in directions close to the
15 m.
opposite of the direction of the incident rays, this property
4.2 Thegeneralprocedureinvolvedistodeterminetheratio
being maintained over wide variations of the direction of the
of the light retroreflected from the test surface to that incident
B
incident rays. [CIE]
on the test surface.
3.2.12 retroreflective material, n—a material that has a thin
4.3 The photometric quantity, coefficient of retroreflection,
continuous layer of small retroreflective elements on or very
is calculated from these measurements.
near its exposed surface (for example, retroreflective sheeting,
retroreflective fabrics, transfer films, beaded paint, highway
5. Significance and Use
surface signs, or pavement striping).
5.1 Measurements made by this test method are related to
3.2.13 retroreflective sheeting, n—a retroreflective material
visual observations of retroreflective sheeting as seen by the
preassembled as a thin film ready for use.
humaneyewhenilluminatedbytungsten-filamentlightsources
3.2.14 retroreflector, n—a reflecting surface or device from
such as a motor vehicle headlamp.
which, when directionally irradiated, the reflected rays are
preferentiallyreturnedindirectionsclosetotheoppositeofthe 5.2 The values determined relate to the visual effects for a
direction of the incident rays, this property being maintained given geometric configuration as specified by the user of the
over wide variations of the direction of the incident rays. [CIE, testmethod.Thistestmethodhasbeenfoundusefulfortestsat
B
1982] observation angles between 0.1 and 2.0° (observation angles
3.2.15 retroreflector axis, n—adesignatedhalf-linefromthe between 0.1° and 0.2° may be achieved by careful design of
retroreflector center. source and receiver aperture configuration), and at entrance
3.2.15.1 Discussion—Thedirectionoftheretroreflectoraxis angles up to 60°. It has been used to determine coefficient of
−1 −2
is usually chosen centrally among the intended directions of retroreflectionvaluesaslowas0.1cd·lx ·m ,butforvalues
−1 −2
illumination;forexample,thedirectionoftheroadonwhichor less than 1 cd·lx ·m special attention must be given to the
with respect to which the retroreflector is intended to be responsivityofthereceiverandtotheeliminationofverysmall
positioned. The retroreflector axis usually coincides with the amounts of stray light.
E810−03 (2013)
6. Apparatus 6.2.6 The field of view shall be limited by use of light
baffles or a field aperture on the instrument so that the entire
6.1 Light Source—The light source shall be of the projector
testsampleisfullywithinthefieldofview,rejectingstraylight
typeandshallmeetthefollowingrequirements(anilluminance
asmuchaspractical.Abackgroundlightlevel m lessthan5%
b
at the 15 m specimen distance of about 10 lx is commonly
of the smallest m reading is acceptable.
available within these restrictions):
6.2.7 The receiver aperture shall be a standard circular
6.1.1 The spectral energy distribution of the source shall be
aperture as defined in Practice E809. For measurements at
proportional to CIE standard Source A (a correlated color
observation angles (α) of 0.2°≤α≤ 2.0°, the receiver shall be
temperature of 2856 K, see Practice E308). The projection
provided with an entrance aperture 26 mm (62 mm) in
lamp together with the projection optics shall be operated such
diameter.Thiscorrespondsto0.1°angularapertureat15mtest
that it illuminates the test specimen with this spectral power
distance. For measurements at observation angles (α) of 0.1° ≤
distribution.
α < 0.2°, the receiver shall be provided with an entrance
6.1.2 An unpolarizing light source shall be used.
aperture 13 mm (61 mm) in diameter. This corresponds to a
6.1.3 The source aperture shall be a standard circular
0.05° angular aperture at 15 m test distance. The size of the
aperture as defined in Practice E809. For measurements at
entrance aperture stop must be small so that the receiver may
observation angles (α) of 0.2°≤α≤ 2.0°, the exit aperture of
be positioned physically close to the source exit aperture
the source shall be uniformly radiant, circular and 26 mm (62
without shadowing any of the illuminating light beam.
mm) in diameter. This corresponds to 0.1° angular aperture at
15mtestdistance.Formeasurementsatobservationangles(α) 6.3 Test Specimen Goniometer (Test Specimen Holder)—
Thespecimenholdermustholda200mmsquarespecimenand
of 0.1°≤α < 0.2°, the exit aperture of the source shall be
uniformly radiant, circular and 13 mm (61 mm) in diameter. meet the following requirements (see Fig. 1):
This corresponds to 0.05° angular aperture at 15 m test
6.3.1 A means must be provided to rotate the specimen on
distance.
anaxiscontainedintheplaneofthespecimensurfaceifseveral
6.1.4 The illumination at the sample produced by the entrance angles are to be used.
projector shall be such that the test specimen and only a
6.3.1.1 The entrance angle component β is used to set the
minimum of the background is illuminated. This is commonly
goniometer when no specific component is specified (see
accomplished by placing a restrictive aperture in the projector
Practice E808).
slide port.
6.3.2 The specimen surface must be positionable so that the
6.1.5 The source shall be regulated such that the illumi-
entrance angle is accurate to within 0.5% of its complement
nance at the test surface does not change by more than 61%
(that is, for a 30° entrance angle this angle must be accurately
for the duration of the test.
set to 60.005 × 60°= 60.3°). This is obtainable by providing
6.1.6 The illuminance produced on the sample surface shall
an accurate optical means to align the test surface to the “ 0
be uniform within 65% of the average illuminance normal to
degree” entrance angle and then adjusting the angular setting
the source at the distance of 15 m.
(within the required tolerance).
6.2 Receiver—The receiver shall meet the requirements that
−1 −2
follow. (In this test, for 10 lx incident upon a 1 cd·lx ·m
retroreflective sheeting test specimen with area of 0.04 m , the
incident normal illuminance at the receiver will be about
−3
1.8×10 lx).
6.2.1 The responsivity and range of the receiver shall be
sufficient so that readings of both the incident normal illumi-
nance (at the specimen) and the retroreflected light at the
observation position can be measured with a resolution of at
least 1 part in 50 on the readout scale.
6.2.2 The spectral responsivity of the receiver shall match
that of the 1931 CIE Standard Photopic Observer (see Annex
A1 of Practice E809).
6.2.3 The receiver shall be insensitive to the polarization of
light.
6.2.4 The linearity of the photometric scale over the range
of readings to be taken shall be within 61%. Correction
factors may be used to ensure a linear response. Linearity
verification tests m
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