1、Designation: F1316 18Standard Test Method forMeasuring the Transmissivity of Transparent Parts1This standard is issued under the fixed designation F1316; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONTest Method D1003 has received wide acceptance as a test method to measure luminoustransmissivity in transparent materials. However, be
3、cause Test Method D1003 requires criticalalignment of equipment on both sides of the transparency, it is not suited to measuring thetransmissivity of large, curved parts or parts that are installed. In addition, Test Method D1003measures the luminous transmissivity of the material in a direction per
4、pendicular to the surface of thematerial. For the majority of aircraft windscreens, the pilot is not viewing through the transparencyperpendicular to the surface. Since the transmissivity varies as a function of viewing angle the valuesof transmissivity measured perpendicular to the surface do not i
5、ndicate what the pilot will see whenviewing through the windscreen.For the above reasons this test method has been developed to allow the measurement oftransmissivity of a transparent part at any angle. Since the relative alignment of the equipment itemson either side of the transparency is not crit
6、ical, this test method can also be used on large, thick, orcurved parts and parts that are already installed.1. Scope1.1 This test method describes an apparatus and procedurethat is suitable for measuring the transmissivity of large, thick,or curved transparent parts including parts already installe
7、d.This test method is limited to transparencies that are relativelyneutral with respect to wavelength (not highly colored).1.2 Since the transmissivity (transmission coefficient) is aratio of two luminance values, it has no units. The units ofluminance recorded in the intermediate steps of this test
8、method are not critical; any recognized units of luminance (forexample, foot-lamberts or candelas per square metre) areacceptable for use, as long as use is consistent.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of
9、 the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization establi
10、shed in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1003 Test Method for Haze and Luminous Transmittanceof Transpare
11、nt Plastics3. Terminology3.1 Definitions:3.1.1 black referencea light-absorbing, black material,such as black velvet flocking.3.1.2 photometera device that measures luminance asdefined by the spectral sensitivity of the photopic curve.3.1.3 Photopic curvethe photopic curve is the spectralsensitivity
12、 of the eye for daytime conditions as CommitteeInternationale dElairage (CIE) 1931 standard observer.3.1.4 regulated light sourcea light source with electronicfeedback to ensure that its illuminance remains constant overtime.3.1.5 transmission coeffcientsame as transmissivity.1This test method is un
13、der the jurisdiction of ASTM Committee F07 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved June 1, 2018. Published June 2018. Originallyapproved in 1990. Last previous edition approved in 2013 as F1316 -
14、 90(2013).DOI: 10.1520/F1316-18.2For 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 website.Copyright ASTM International,
15、 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 established in the Decision on Principles for theDevelopment of International Standards, Guides an
16、d Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.6 transmissivitythe transmissivity of a transparent me-dium is the ratio of the luminance of an object measuredthrough the medium to the luminance of the object measureddirectly.4. Summary of Te
17、st Method4.1 A regulated light source with a relatively large, diffuselyradiating surface area is placed on one side of a transparent partto be measured. A black, light-absorbing reference surface isplaced next to the light source. A photometer is used tomeasure the luminance of the light source and
18、 black referencedirectly and through the transparency. The light source readingmeasured through the transparency minus the black referencereading through the transparency is divided by the light sourcemeasured directly minus the black reference measured directly(see Eq 1). This ratio is the transmis
19、sion coefficient of thetransparency. The black reference surface is used to correct themeasurement from the effects of light scatter due to haze andfrom reflections.35. Significance and Use5.1 SignificanceThis test method provides a means tomeasure the transmissivity of parts in the field (alreadyin
20、stalled on aircraft) and of large, thick or curved partsphysically difficult to measure using Test Method D1003.5.2 UseThis test method is acceptable for use on anytransparent part. It is primarily intended for use on large,curved, or thick parts either pre- or post-installation (forexample, windscr
21、eens on aircraft).6. Apparatus6.1 Test EnvironmentIt is preferable to carry out this testmethod in a light-controlled environment although this is notabsolutely necessary. To do so, shade the transparency fromdirect sunlight falling on the surface and place a light-absorbing black cloth in the appro
22、priate reflection geometrywith respect to the transparency to reduce reflections.6.2 PhotometerUse any properly calibrated photometerfor this measurement. The photometer is to have a measure-ment field that is smaller than the regulated light source toensure accurate readings. It is recommended that
23、 a small,portable photometer with a 1 measurement field (or less) beused.6.3 Light SourceRegulate the light source to ensure that itdoes not change luminance during the reading period. The lightsource is to have a relatively large, diffusely emitting surfacearea to permit easy measurement when using
24、 the photometer.The spectral distribution of the light source is not critical unlessthe transparency under test has significant spectral peaks orvoids. For daylight measurements it is possible to use a whitereflecting surface illuminated by sunlight instead of a poweredlight source. Care must be tak
25、en that the luminance of thereflective surface does not change during the reading.6.4 Black ReferenceUse a shaded, light-absorbing blackmaterial such as velvet to increase the accuracy of themeasurement. This reference must have about the same area asthe light source or reflective material used for
26、the light readingsince the photometer must also measure the apparent lumi-nance of the black reference.7. Test Specimen7.1 Clean the part to be measured, using any acceptableprocedure, to remove any surface contaminants with thepotential to contribute to the loss of transmissivity. No specialconditi
27、oning other than cleaning is required.8. Calibration and Standardization8.1 The photometer is to have the same spectral sensitivityas the eye but since the measurement involves the division oftwo quantities measured by the photometer it is not necessarythat the photometer be calibrated in absolute l
28、uminance units.9. Procedure9.1 Place the light source (or white-reflective surface) onone side of the transparency such that is can be viewed fromthe other side of the transparency. Place the transparency at thedesired angle for measurement. The distance from the lightsource to the transparency is n
29、ot critical but must be greaterthan 30 cm (11.8 in.) to prevent erroneous readings due to lightscatter and reflections. The distance from the light source to thephotometer is also not critical, but is to be short enough so thatthe photometer measurement field easily falls within theemitting area of
30、the light source. The distance from thetransparency to the photometer is not critical, as the smallestpermitted distance is 0 cm. Place the black reference adjacentto the light source so that it is also visible through thetransparency. Place the light-absorbing cloth next to the trans-parency on the
31、 opposite side from the light source (see Fig. 1).9.2 If the transparency is subject to direct sunlight, use asolar shield to shade the area of the transparency (see Fig. 1).9.3 The photometer is then used to measure the luminanceof the light source and the black reference. These readings aredesigna
32、ted Lsand Lbrespectively. The light source and blackreference are then measured again but this time viewingthrough the transparency. These readings are Lstand Lbtrespectively. Make both the direct measurements and themeasurements through the transparency from about the samedistance and angle from th
33、e light source.10. Calculation10.1 The transmissivity of the transparency is calculatedusing the following equation:t 5Lst2 LbtLs2 Lb(1)3Task, H. L. and Merkel, H. S., A New Method for Measuring the Transmissivityof Aircraft Transparencies. Technical Report AAMRL-TR-89-044, ArmstrongAerospace Medica
34、l Research Laboratory, 1989.F1316 182where:t = the transmission coefficient of the transparency,Ls= the luminance of the light source (white surface),Lst= the luminance of light source measured through thetransparency,Lb= the luminance of the black reference, andLbt= the luminance of black reference
35、 measured throughthe transparency.The transmission coefficient, t, can be converted to percenttransmission, T, by multiplying by 100. In equation form:T 5 100 3 t (2)10.2 The second term in the numerator in Eq 1 removeseffects due to light scatter or reflections from the measurement.Similarly, the s
36、econd term in the denominator removes errorsthat arise from the black reference pattern not being completelyblack. See the Appendix X1 for the derivation of this equation.11. Precision and Bias11.1 Four tests were done on a set of nine samples to obtaininformation on precision and bias.3The first te
37、st was doneusing Test Method D1003 for comparison purposes; the otherthree tests were done using the current procedure. These testswere reproducibility test (using Test Method D1003) at fourlaboratories with a total of six devices, repeatability test usingone photometer and one operator for twelve t
38、rials, reproduc-ibility test using one operator in one laboratory with sevendifferent photometers, and reproducibility using one photom-eter and six operators at four different laboratories.11.2 The nine transparent samples included one laminatedsample (2.22 cm (78 in.) total thickness), three thick
39、 (1.59 cm(58 in.) monolithic samples, and five thin (0.32 cm (18 in.)monolithic samples. The samples ranged from about 90 %transmissive to about 15 % transmissive, that includes most ofthe transmissivities that would be encountered in aircrafttransparencies and helmet visors. There is no reason to e
40、xpectthat thickness of the sample or number of layers would have aneffect on the measurement of transmissivity.11.3 To provide a reference for comparison, the ninesamples were measured following Test Method D1003 at fourlaboratories using a total of six devices, yielding 54 measure-ments. The varian
41、ce and coefficient of variation (standarddeviation divided by the mean transmissivity, with that quo-tient multiplied by 100% to express measurement precision asa percentage of the mean) were calculated for the six measure-ments made on each sample. The variance 2was 0.214 and themean coefficient of
42、 variation was 0.97 %, resulting in a 95 %confidence interval of 61.9 % of the transmissivity reading.Note that the coefficient of variation was not uniform withrespect to transmissivity but tended to be higher for lowertransmissivities.11.4 All nine samples were measured using the proceduredescribe
43、d herein by a single operator at one laboratory using asingle photometer. The procedure was repeated twelve times,yielding 108 measurements. The variance and coefficient ofvariation were calculated for each sample as noted above. Theestimate of the variance e2was 0.0115 and the mean coeffi-cient of
44、variation was 0.18 %. The coefficient of variation wasfairly uniform independent of the transmissivity of the sample.11.5 All nine samples were measured with this procedure bya single operator at one laboratory using seven differentphotometers, yielding 63 measurements. The estimate of thevariance p
45、2was 0.0564 and the mean coefficient of variationwas 0.49 %.11.6 All nine samples were measured with this procedure bya total of six operators at four laboratories using a singlephotometer, yielding 54 measurements. The estimate of thevariance o2was 0.0467 and the mean coefficient of variationwas 0.
46、35 %.11.7 Considering a typical application of the new procedureto involve different operators in different laboratories usingdifferent photometers, an estimation of the confidence intervalresults from the acquired data. The variance of the transmis-sivity measurement, 2, is modeled as:25 o21p21e2(3
47、)where:o2= the variance of the operator,p2= the variance of the photometer, ande2= the variance of the repeatability error.It is assumed there is no operator-photometer interaction.Substituting the appropriate values into Eq 3 yields.25 0.115 (4)The corresponding 95 % confidence interval is then:61.
48、96 3x3100% 561.12% (5)FIG. 1 Geometry of the Transmissivity MeasurementF1316 183where:x = the mean transmissivity of the samples (T = 100xt=59.5, using Eq 2).11.8 The preceding information indicates this new proce-dure is slightly more precise than Test Method D1003 since itresults in a tighter conf
49、idence interval. The confidence intervalof the new procedure is 1.12 %, versus 1.90 % for Test MethodD1003. Thus if the transmissivity were measured to be 0.50(0 %) the 95 % confidence interval would be 0.494 to 0.506(49.4 % to 50.6 %).11.9 This test method has no known inherent bias. However,it is likely slightly different results will be obtained using thistest method than Test Method D1003. When light is incident ona nominally transparent part the transmitted light is composedof both scattered and unscattered components. The scatteredlight is m
