1、Designation: F1863 16Standard Test Method forMeasuring the Night Vision Goggle-Weighted Transmissivityof Transparent Parts1This standard is issued under the fixed designation F1863; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he 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.INTRODUCTIONTest Methods D1003 and F1316 apply to the transmissivity measurement of transparent materials,the former be
3、ing for small flat samples, and the latter for any materials including larger, curved piecessuch as aircraft transparencies. Additionally, in Test Method D1003, the transmissivity is measuredperpendicular to the surface of test sample and both test methods measure only in the visible lightspectral r
4、egion. Night vision goggles (NVGs) are being used in aircraft and other applications (forexample, marine navigation, driving) with increasing frequency. These devices amplify both visibleand near-infrared (NIR) spectral energy. Overall visual performance can be degraded if the observeruses the NVGs
5、while looking through a transparency that has poor transmissivity in the visible andNIR spectral regions. This test method describes both direct and analytical measurement techniquesthat determine the NVG-weighted transmissivity of transparent pieces including ones that are large,curved, or held at
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:3D1003 Test Method for Haze and Luminous Transmittanceof Transparent PlasticsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precis
10、ion of a Test MethodF1316 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 spectrophotometric or spectroradiometricins
11、trumentation. The data are then examined using analyticmethods to determine the NVG-weighted transmissivity of thepart.1This 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 Mater
12、ials.Current edition approved April 1, 2016. Published April 2016. Originallyapproved in 1998. Last previous edition approved in 2010 as F1863 10. DOI:10.1520/F1863-16.2RCA Electro-Optics Handbook, RCA/Solid State Division/Electro Optics andDevices. Technical Series EOH-11. Lancaster, PA; 1974.3For
13、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, 100 Barr Harbor Drive, PO Box C700,
14、West Conshohocken, PA 19428-2959. United States13.1.2 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-weightedtransmissivity of the part is then determined by forming theratio of the NVG o
15、utput luminance 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 sp
16、ectraltransmissivity 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 an NVGas a function of input wavelength.3.1.6 photometer, na device that measures lum
17、inous in-tensity 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 defi
18、nedby the Commission 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 objectm
19、easured directly.4. Summary of Test Method4.1 General Test ConditionsThe test method shall beperformed in 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 sensitiv
20、ity of the NVGs.Afixture holdsthe NVG and its objective lens is aimed at and focused on atarget. The target shall 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
21、 samples carefully so as not to causeany damage. Do not clean them with any solvents. Usepart-specific, prescribed cleaning materials and methods.4.1.1 Direct Test MethodAttached directly to the eyepieceof the NVG is a photodetector. The measured field of view(FOV) shall be smaller than the uniforml
22、y illuminated portionof the target. The target illumination is adjusted so that theoutput of the NVGs is about 1.7 cd/m2(0.5 fL). This ensuresthat the NVG input level is sufficiently low that it does notactivate the NVG automatic gain control (AGC) circuitry. Theluminance output of the NVG is measur
23、ed with no transpar-ency in place and then repeated with the transparent material inplace between the light source and the NVG. The transmissiv-ity is equal to the NVG output luminance with the transparentmaterial in place divided by the NVG output luminancewithout the material (see Eq 1). The resul
24、t is the NVG-weighted transmissivity (TNVG) of the transparent material.4.1.2 Analytical Test MethodWithout 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 spectroradiometer fix
25、-ture. Perform spectral measurements, also from 450 through4Wyszecki, Gunter, and Stiles, WS, Color Science: Concepts and Methods,Quantitative 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 Spe
26、ctral Transmissivity of a TransparentPart Equals the NVG-Weighted Spectral Transmissivity of that Part. Integrating the Curve with Respect to Wavelength Yields the PartsNVG-Weighted Transmissivity (TNVG) ValueF1863 162950 nm in 5-nm incremental steps. Obtain from the NVGmanufacturer the spectral sen
27、sitivity 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 transparency throughwhich NVGs are used at night to v
28、iew outside, nighttimeambient illuminated natural scenes.5.2 UseThis test method may be used on any transparentpart, including sample coupons. It is primarily intended for useon large, curved, or thick parts that may already be installed(for example, windscreens on aircraft).6. Apparatus6.1 Test Env
29、ironmentThis test method shall be performedin light-controlled area (for example, light-tight room, dark-ened 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, te
30、lephone pole lights, status indicator lights onequipment, and so forth) can also interfere with the measure-ment.6.2 White Diffuse TargetThe white target shall be anyuniformly diffusely reflecting or translucent material (forexample, cloth, flat white painted surface, plastic). The targetarea shall
31、be either smaller (see Fig. 2) or larger (see Fig. 3)than the NVG FOV (35 to 60 typical) to minimize potentialalignment errors.6.3 Light SourceThe light source shall be regulated toensure that it does not change luminance during the readingperiod. It shall be a low output, 2856K incandescent light s
32、incethis type emits sufficient energy in both visible and infraredwithout any sharp emission peaks or voids.2Its output must beuniformly distributed over the measurement area of the whitediffuse target. Use of neutral density filters or varying the lampdistance shall be used as needed to achieve suf
33、ficiently lowluminance levels for test, since varying the radiators outputwill shift its color temperature.6.4 Night Vision GogglesAfamily of passive image inten-sifying devices that use visible and near-infrared light andenable the user to see objects that are illuminated by fullmoonlight through s
34、tarlight-only conditions. The goggle that isused for test shall be the same as that intended to be used withthe given transparent material.6.5 PhotometerA calibrated photometer shall be used forthis measurement. The detector must be properly coupled tothe NVG eyepiece, and the FOV over which the lig
35、ht isintegrated must be known.7. Test Specimen7.1 If necessary, clean the part to be measured using theprocedure prescribed for the specific material. Use of nonstan-dard cleaning methods can irrevocably damage the part. Nospecial conditions other than cleaning are required.8. Calibration and Standa
36、rdization8.1 It is not necessary that the photometer be calibrated inabsolute luminance 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
37、ProceduresPerform all measurements in adarkened, light-controlled area. To control the 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
38、 than the measurement light falls on the areabeing tested.9.2 Direct Test MethodThis test method allows analysis oflarge or small transparent parts placed at either normal (per-pendicular to the optical axis) or installed orientations, such asFIG. 2 Direct Test Method Equipment Set Up to Measure the
39、 Night Vision Goggle-Weighted Transmissivity of a Transparent Part Usinga Transilluminated Lightbox that Underfills the NVG FOVF1863 163an aircraft windscreen. Fig. 2 illustrates the use of a small,transilluminated lightbox. Fig. 3 depicts the use of a large,front-illuminated, white, diffusely refle
40、ctive target, illuminatedas uniformly as possible using a regulated white incandescentlight source. The size of the target is dependent upon the testlocation, the obtainable luminance uniformity, and the FOV ofthe photodetector assembly. In the field, a transilluminatedlightbox has been found to be
41、the easiest to set up and use, asit offers the advantage of compact, self-contained portability.Maintain the same target-to-NVG distance during the measure-ments. In a light-tight room, a white, diffusely reflecting,front-illuminated surface may be used. In the field, the NVGshall be held by hand or
42、 mounted in a fixture and underlaboratory conditions, shall be mounted in a fixture. Aim andfocus the NVG on the white target.Attach the photodetector tothe NVG eyepiece. With the transparent material removedfrom the measurement path, adjust the variable white light toproduce an NVG output luminance
43、 of about 1.7 cd/m2(0.5 fL).This ensures that the NVGs input is not saturated; the AGC isnot activated. As a result of the extreme sensitivity of NVGs,neutral density filters shall be placed in front of the light sourceor the NVGs, as needed, to obtain low enough apparent targetluminance.After recor
44、ding the NVGs output luminance, placethe transparent material in the measurement path. If thematerial is a sample, its orientation relative to the measurementpath shall be simply perpendicular or at the installed angle. Ifan aircraft transparency is being tested, the NVG shall belocated at the desig
45、n eye position relative to the transparency,which is mounted in its installed position. Measuring at theinstalled angle is critical since many materials exhibit varia-tions in transmissivity as a function of angle. Record theNVGs output with the test piece in place. To prevent damageto the NVGs, ver
46、ify that they are turned off before the test arealights are turned on.9.2.1 There are numerous classes of NVGs (Generations 2,3; Types A, B, C) that vary in their spectral sensitivity,intensified FOV, resolution, and so forth. It is important toselect the proper NVG type that will be used in a given
47、application. The NVG must also be in good working conditionand meet minimum user performance specifications.9.2.2 The target illumination source shall be an incandes-cent light operating at 2856K, which is the standard colortemperature that is used for many NVG test procedures. Theillumination from
48、this source shall be varied using neutraldensity filters, as necessary, since varying the lights voltagewill cause a corresponding color temperature shift. If the NVGis to be used to view an area through a specific transparentmaterial that is illuminated by a different kind of light source(for examp
49、le, mercury vapor, sodium), then that source must beproperly noted in the test report.9.2.3 The luminance output of the NVG is measured andthen repeated with the transparent 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 aspectrophotometer, the sample is usually limited to about 2- by2-in. sample coupon
