1、Designation: F 1863 98 (Reapproved 2004)Standard Test Method forMeasuring the Night Vision Goggle-Weighted Transmissivityof Transparent Parts1This standard is issued under the fixed designation F 1863; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the 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.INTRODUCTIONTest Methods D 1003 and F 1316 apply to the transmissivity measurement of transparent
3、materials,the former being for small flat samples, and the latter for larger, curved pieces such as aircrafttransparencies. Additionally, in Test Method D 1003, the transmissivity is measured perpendicular tothe surface of test sample and both test methods measure only in the visible light spectral
4、region. Nightvision goggles (NVGs) are being used in aircraft and other applications (for example, marinenavigation, driving) with increasing frequency. These devices amplify both visible and near-infrared(NIR) spectral energy. Overall visual performance can be degraded if the observer uses the NVGs
5、while looking through a transparency that has poor transmissivity in the visible and NIR spectralregions. This test method describes both direct and analytical measurement techniques that determinethe NVG-weighted transmissivity of transparent pieces including ones that are large, curved, or heldat
6、the installed position.1. Scope1.1 This test method covers apparatuses and procedures thatare suitable for measuring the NVG-weighted transmissivity oftransparent parts including those that are large, thick, curved,or already installed. This test method is sensitive to transpar-encies that vary in t
7、ransmissivity as a function of wavelength.1.2 Since the transmissivity (or transmission coefficient) is aratio of two radiance values, it has no units. The units ofradiance recorded in the intermediate steps of this test methodare not critical; any recognized units of radiance (for example,watts/m2-
8、str) may be used, as long as it is consistent.21.3 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 determine the applica-bility of regu
9、latory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1003 Test Method for Haze and Luminous Transmittanceof Transparent PlasticsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Pre
10、cision of a Test MethodF 1316 Test Method for Measuring the Transmissivity ofTransparent Parts3. Terminology3.1 Definitions:3.1.1 analytical test method, nthe test method that usesspectral transmissivity data of a transparent part collected bythe use of either spectraphotometric or spectraradiometri
11、cinstrumentation. The data are then examined using analyticmethods to determine the NVG-weighted transmissivity of thepart.3.1.2 direct test method, nthe test method that uses theactual luminous output, as measured by a photometer, properlycoupled to the eyepiece of the test NVG. The NVG-weighted1Th
12、is test method is under 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 Oct. 1, 2004. Published October 2004. Originallyapproved in 1998. Last previous edition appr
13、oved in 1998 as F 1863 98.2RCA Electro-Optics Handbook, RCA/Solid State Division/Electro Optics andDevices. Technical Series EOH-11. Lancaster, PA; 1974.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSt
14、andards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.transmissivity of the part is then determined by forming theratio of the NVG output luminance
15、 with the transparent part inplace to the luminance output without the part.3.1.3 NVG-weighted spectral transmissivity, nthe spectraltransmissivity of a transparent part multiplied by the spectralsensitivity of a given NVG (see Fig. 1).3.1.4 NVG-weighted transmissivity (TNVG), nthe spectraltransmiss
16、ivity of a transparent part multiplied by the spectralsensitivity of a given NVG integrated with respect to wave-length (see Fig. 1, Eq 1 and Eq 2).3.1.5 NVG spectral sensitivity, nthe sensitivity of anNVG as a function of input wavelength.3.1.6 photometer, na device that measures luminous in-tensit
17、y or brightness by converting (weighting) the radiantintensity of an object using the relative sensitivity of the humanvisual system as defined by the photopic curve.2,43.1.7 photopic curve, nthe photopic curve is the spectralsensitivity of the human eye for daytime conditions as definedby the Commi
18、ssion Internationale dEclairage (CIE) 1931standard observer.2,43.1.8 transmission coeffcient, nsee transmissivity.3.1.9 transmissivity, nthe transmissivity of a transparentmedium is the ratio of the luminance of an object measuredthrough the medium to the luminance of the same objectmeasured directl
19、y.4. Summary of Test Method4.1 General Test ConditionsThe test method can beperformed in any light-controlled area (for example, light-tightroom, darkened hangar, or outside at night away from stronglight sources). The ambient illumination must be very lowbecause of the extreme sensitivity of the NV
20、Gs.Afixture holdsthe NVG and its objective lens is aimed at and focused on atarget. The target can be either an evenly illuminated white,diffusely reflecting surface or a transilluminated screen (light-box). The illumination is provided by a white, incandescentlight source. Handle the samples carefu
21、lly as not to cause anydamage. Do not clean them with any solvents. Use part-specific, prescribed cleaning materials and methods.4.1.1 Direct Test MethodAttached directly to the eyepieceof the NVG is a photodetector. It has been found that themeasured field of view (FOV) should be smaller than theun
22、iformly illuminated portion of the target. The target illumi-nation is adjusted so that the output of the NVGs is about 1.7cd/m2(0.5 fL). This ensures that the NVG input is notsaturated; the automatic gain control (AGC) is not active. Theluminance output of the NVG is measured and then repeatedwith
23、the transparent material in place. The transmissivity isequal to the NVG output luminance with the transparentmaterial in place divided by the NVG output luminancewithout the material (see Eq 1). The result is the NVG-weighted transmissivity (TNVG) of the transparent material.4.1.2 Analytical Test M
24、ethodWithout the sample in place,measure the light sources spectral energy distribution from450 through 950 nm in 5-nm incremental steps. Place thesample into the spectrophotometer or spectraradiometer fix-ture. Perform spectral measurements, also from 450 through950 nm in 5-nm incremental steps. Ob
25、tain from the NVGmanufacturer the spectral sensitivity of the goggle that will beused in conjunction with the part. Perform the analytic methodas defined in Eq 2 to derive the TNVG.5. Significance and Use5.1 SignificanceThis test method provides a means tomeasure the compatibility of a given transpa
26、rency throughwhich NVGs are used at night to view outside, nighttimeambient illuminated natural scenes.5.2 UseThis test method may be used on any transparentpart, including sample coupons. It is primarily intended for use4Wyszecki, Gunter, and Stiles, WS, Color Science: Concepts and Methods,Quantita
27、tive Data and Formulae, 2nd ed., New York, John Wiley and Sons, 1982.FIG. 1 An Example of How the Spectral Sensitivity of a Generation 3 NVG Multiplied by the Spectral Transmissivity of a TransparentPart Equals the NVG-Weighted Spectral Transmissivity of that Part. Integrating the Curve with Respect
28、 to Wavelength Yields the PartsNVG-Weighted Transmissivity (TNVG) ValueF 1863 98 (2004)2on large, curved, or thick parts that may already be installed(for example, windscreens on aircraft).6. Apparatus6.1 Test EnvironmentThis test method can be performedin any light-controlled area (for example, lig
29、ht-tight room,darkened hangar, or outside at night away from strong lightsources) since the NVGs are extremely sensitive to both visibleand near infrared light. Extraneous light sources (for example,exit signs, telephone pole lights, status indicator lights onequipment, and so forth) can also interf
30、ere with the measure-ment.6.2 White Diffuse TargetThe white target can be anyuniformly diffusely reflecting or translucent material (forexample, cloth, flat white painted surface, plastic). The targetarea should be either smaller (see Fig. 2) or larger (see Fig. 3)than the NVG FOV (35 to 60 typical)
31、 to minimize potentialalignment errors.6.3 Light SourceThe light source should be regulated toensure that it does not change luminance during the readingperiod. It should be a low output, 2856K incandescent lightsince this type emits sufficient energy in both visible andinfrared without any sharp em
32、ission peaks or voids.2Its outputmust be uniformly distributed over the measurement area of thewhite diffuse target. Use of neutral density filters or varying thelamp distance may be needed to achieve sufficiently lowluminance levels to be obtained for test, since varying theradiators output would s
33、hift its color temperature.6.4 Night Vision GogglesA family of passive imageintensifying devices that use visible and near-infrared light andenable the user to see objects that are illuminated by fullmoonlight through starlight-only conditions. The goggle that isused for test should be the same as t
34、hat used with the giventransparent material.6.5 PhotometerAny calibrated photometer may be usedfor this measurement. However, the detector must be properlycoupled to the NVG eyepiece, and the FOV over which thelight is integrated must be known.7. Test Specimen7.1 If necessary, clean the part to be m
35、easured using theprocedure prescribed for the specific material. Use of non-standard cleaning methods can irrevocably damage the part.No special conditions other than cleaning are required.8. Calibration and Standardization8.1 It is not necessary that the photometer be calibrated inabsolute luminanc
36、e units since the measurement involves thedivision of two measured quantities yielding a dimensionlessvalue. A generic photodetector can be substituted for thephotometer if its FOV is known.9. Procedure9.1 General ProceduresPerform all measurements in adarkened, light-controlled area. To control the
37、 effects ofreflection, verify that there are no extraneous light sources thatcan produce reflections within the measurement area of thetransparent material. To control the effects of haze, verify thatno light other than the measurement light falls on the areabeing tested.9.2 Direct Test MethodThis t
38、est method allows analysisof large or small transparent parts placed at either normal(perpendicular to the optical axis) or installed orientations,such as an aircraft windscreen. Fig. 2 illustrates the use of asmall, transilluminated lightbox. Fig. 3 depicts the use of alarge, front-illuminated, whi
39、te, diffusely reflective target, illu-minated as uniformly as possible using a regulated whiteincandescent light source. The size of the target is dependentupon the test location, the obtainable luminance uniformity,and the FOV of the photodetector assembly. In the field, atransilluminated lightbox
40、is probably the easiest to set up anduse, as it offers the advantage of compact, self-containedportability. Maintain the same target-to-NVG distance duringthe measurements. In a light-tight room, a white, diffuselyreflecting, front-illuminated surface may be used. In the field,the NVG can be held by
41、 hand and under laboratory conditions,can be mounted in a sturdy fixture.Aim and focus the NVG onFIG. 2 Direct Test Method Equipment Set Up to Measure the Night Vision Goggle-Weighted Transmissivity of a Transparent Part Usinga Transilluminated Lightbox that Underfills the NVG FOVF 1863 98 (2004)3th
42、e white target.Attach the photodetector to the NVG eyepiece.With the transparent material removed from the measurementpath, adjust the variable white light to produce an NVG outputluminance of about 1.7 cd/m2(0.5 fL). This ensures that theNVGs input is not saturated; the AGC is not activated. As are
43、sult of the extreme sensitivity of NVGs, neutral density filtersmay need to be placed in front of the light source to obtain lowenough target luminance. After recording the NVGs outputluminance, place the transparent material in the measurementpath. If the material is a sample, its orientation relat
44、ive to themeasurement path can be simply perpendicular or at theinstalled angle. If an aircraft transparency is being tested, theNVG should be located at the design eye position relative tothe transparency which is mounted in its installed position.Measuring at the installed angle is critical since
45、many materialsexhibit variations in transmissivity as a function of angle.Record the NVGs output with the test piece in place. Toprevent damage to the NVGs, verify that they are turned offbefore the test area lights are turned on.9.2.1 There are numerous classes of NVGs (Generations 2,3; Types A, B)
46、 that vary in their spectral sensitivity, intensifiedFOV, resolution, and so forth. It is important to select theproper NVG type that will be used in a given application. TheNVG must also be in good working condition and meetminimum user performance specifications.9.2.2 The target illumination sourc
47、e can be an incandescentoperating at 2856K, which is the standard color temperaturethat is used for many NVG test procedures. The illuminationfrom this source can be varied using neutral density filters,since varying the lights voltage would cause a correspondingcolor temperature shift. If the NVG i
48、s to be used to view anarea through a specific transparent material that is illuminatedby a different kind of light source (for example, mercury vapor,sodium), then that source must be properly noted in the testreport.9.2.3 The luminance output of the NVG is measured andthen repeated with the transp
49、arent material in place. Thetransmissivity is equal to the NVG output luminance with thetransparent material in place divided by the NVG outputluminance without the material (see Eq 1). The result is theNVG-weighted transmissivity (TNVG) of the transparent mate-rial.9.3 Analytical Test MethodWhen using a spectrophotom-eter, the sample is usually limited to about 2- by 2-in. samplecoupons held in a normal position. In general (but dependingon the model), a spectraradiometer can be used to measurelarge or small parts at normal or installed positions. W
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