ASTM F1863-98(2004)
(Test Method)Standard Test Method for Measuring the Night Vision Goggle-Weighted Transmisivity of Transparent Parts
Standard Test Method for Measuring the Night Vision Goggle-Weighted Transmisivity of Transparent Parts
SIGNIFICANCE AND USE
Significance—This test method provides a means to measure the compatibility of a given transparency through which NVGs are used at night to view outside, nighttime ambient illuminated natural scenes.
Use—This test method may be used on any transparent part, including sample coupons. It is primarily intended for use on large, curved, or thick parts that may already be installed (for example, windscreens on aircraft).
SCOPE
1.1 This test method covers apparatuses and procedures that are suitable for measuring the NVG-weighted transmissivity of transparent parts including those that are large, thick, curved, or already installed. This test method is sensitive to transparencies that vary in transmissivity as a function of wavelength.
1.2 Since the transmissivity (or transmission coefficient) is a ratio of two radiance values, it has no units. The units of radiance recorded in the intermediate steps of this test method are not critical; any recognized units of radiance (for example, watts/m2-str) may be used, as long as it is consistent.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F1863 – 98 (Reapproved 2004)
Standard Test Method for
Measuring the Night Vision Goggle-Weighted Transmissivity
of Transparent Parts
This standard is issued under the fixed designation F1863; 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.
INTRODUCTION
Test Methods D1003 and F1316 apply to the transmissivity measurement of transparent materials,
the former being for small flat samples, and the latter for larger, curved pieces such as aircraft
transparencies. Additionally, in Test Method D1003, the transmissivity is measured perpendicular to
thesurfaceoftestsampleandbothtestmethodsmeasureonlyinthevisiblelightspectralregion.Night
vision goggles (NVGs) are being used in aircraft and other applications (for example, marine
navigation, 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
while looking through a transparency that has poor transmissivity in the visible and NIR spectral
regions.This test method describes both direct and analytical measurement techniques that determine
the NVG-weighted transmissivity of transparent pieces including ones that are large, curved, or held
at the installed position.
1. Scope 2. Referenced Documents
1.1 Thistestmethodcoversapparatusesandproceduresthat 2.1 ASTM Standards:
aresuitableformeasuringtheNVG-weightedtransmissivityof D1003 Test Method for Haze and Luminous Transmittance
transparent parts including those that are large, thick, curved, of Transparent Plastics
or already installed. This test method is sensitive to transpar- E177 Practice for Use of the Terms Precision and Bias in
encies that vary in transmissivity as a function of wavelength. ASTM Test Methods
1.2 Sincethetransmissivity(ortransmissioncoefficient)isa E691 Practice for Conducting an Interlaboratory Study to
ratio of two radiance values, it has no units. The units of Determine the Precision of a Test Method
radiance recorded in the intermediate steps of this test method F1316 Test Method for Measuring the Transmissivity of
are not critical; any recognized units of radiance (for example, Transparent Parts
watts/m -str) may be used, as long as it is consistent.
3. Terminology
1.3 This standard does not purport to address all of the
3.1 Definitions:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.1.1 analytical test method, n—the test method that uses
spectral transmissivity data of a transparent part collected by
priate safety and health practices and determine the applica-
the use of either spectraphotometric or spectraradiometric
bility of regulatory limitations prior to use.
instrumentation. The data are then examined using analytic
methods to determine the NVG-weighted transmissivity of the
part.
3.1.2 direct test method, n—the test method that uses the
actualluminousoutput,asmeasuredbyaphotometer,properly
coupled to the eyepiece of the test NVG. The NVG-weighted
This test method is under the jurisdiction of ASTM Committee F07 on
transmissivity of the part is then determined by forming the
Aerospace andAircraft and is the direct responsibility of Subcommittee F07.08 on
Transparent Enclosures and Materials.
Current edition approved Oct. 1, 2004. Published October 2004. Originally
approved in 1998. Last previous edition approved in 1998 as F1863–98. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/F1863-98R04. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
RCA Electro-Optics Handbook, RCA/Solid State Division/Electro Optics and Standards volume information, refer to the standard’s Document Summary page on
Devices. Technical Series EOH-11. Lancaster, PA; 1974. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1863 – 98 (2004)
ratio of the NVG output luminance with the transparent part in light sources). The ambient illumination must be very low
place to the luminance output without the part. becauseoftheextremesensitivityoftheNVGs.Afixtureholds
3.1.3 NVG-weighted spectral transmissivity, n—thespectral
the NVG and its objective lens is aimed at and focused on a
transmissivity of a transparent part multiplied by the spectral
target. The target can be either an evenly illuminated white,
sensitivity of a given NVG (see Fig. 1).
diffusely reflecting surface or a transilluminated screen (light-
3.1.4 NVG-weighted transmissivity (T ), n—the spectral
NVG box). The illumination is provided by a white, incandescent
transmissivity of a transparent part multiplied by the spectral
light source. Handle the samples carefully as not to cause any
sensitivity of a given NVG integrated with respect to wave-
damage. Do not clean them with any solvents. Use part-
length (see Fig. 1, Eq 1 and Eq 2).
specific, prescribed cleaning materials and methods.
3.1.5 NVG spectral sensitivity, n—the sensitivity of an
4.1.1 Direct Test Method—Attacheddirectlytotheeyepiece
NVG as a function of input wavelength.
of the NVG is a photodetector. It has been found that the
3.1.6 photometer, n—a device that measures luminous in-
measured field of view (FOV) should be smaller than the
tensity or brightness by converting (weighting) the radiant
uniformly illuminated portion of the target. The target illumi-
intensityofanobjectusingtherelativesensitivityofthehuman
2,4 nation is adjusted so that the output of the NVGs is about 1.7
visual system as defined by the photopic curve.
cd/m (0.5 fL). This ensures that the NVG input is not
3.1.7 photopic curve, n—the photopic curve is the spectral
saturated; the automatic gain control (AGC) is not active. The
sensitivity of the human eye for daytime conditions as defined
luminance output of the NVG is measured and then repeated
by the Commission Internationale d’Eclairage (CIE) 1931
2,4
with the transparent material in place. The transmissivity is
standard observer.
equal to the NVG output luminance with the transparent
3.1.8 transmission coeffıcient, n—see transmissivity.
material in place divided by the NVG output luminance
3.1.9 transmissivity, n—the transmissivity of a transparent
without the material (see Eq 1). The result is the NVG-
medium is the ratio of the luminance of an object measured
weighted transmissivity (T ) of the transparent material.
through the medium to the luminance of the same object NVG
measured directly.
4.1.2 Analytical Test Method—Without the sample in place,
measure the light source’s spectral energy distribution from
4. Summary of Test Method
450 through 950 nm in 5-nm incremental steps. Place the
4.1 General Test Conditions—The test method can be
sample into the spectrophotometer or spectraradiometer fix-
performedinanylight-controlledarea(forexample,light-tight
ture. Perform spectral measurements, also from 450 through
room, darkened hangar, or outside at night away from strong
950 nm in 5-nm incremental steps. Obtain from the NVG
manufacturer the spectral sensitivity of the goggle that will be
4 used in conjunction with the part. Perform the analytic method
Wyszecki, Gunter, and Stiles, WS, Color Science: Concepts and Methods,
Quantitative Data and Formulae, 2nd ed., New York, John Wiley and Sons, 1982. as defined in Eq 2 to derive the T .
NVG
FIG. 1 An Example of How the Spectral Sensitivity of a Generation 3 NVG Multiplied by the Spectral Transmissivity of a Transparent
Part Equals the NVG-Weighted Spectral Transmissivity of that Part. Integrating the Curve with Respect to Wavelength Yields the Part’s
NVG-Weighted Transmissivity (T ) Value
NVG
F1863 – 98 (2004)
5. Significance and Use moonlightthroughstarlight-onlyconditions.Thegogglethatis
used for test should be the same as that used with the given
5.1 Significance—This test method provides a means to
transparent material.
measure the compatibility of a given transparency through
6.5 Photometer—Any calibrated photometer may be used
which NVGs are used at night to view outside, nighttime
for this measurement. However, the detector must be properly
ambient illuminated natural scenes.
coupled to the NVG eyepiece, and the FOV over which the
5.2 Use—This test method may be used on any transparent
light is integrated must be known.
part,includingsamplecoupons.Itisprimarilyintendedforuse
on large, curved, or thick parts that may already be installed
7. Test Specimen
(for example, windscreens on aircraft).
7.1 If necessary, clean the part to be measured using the
procedure prescribed for the specific material. Use of non-
6. Apparatus
standard cleaning methods can irrevocably damage the part.
6.1 Test Environment—This test method can be performed
No special conditions other than cleaning are required.
in any light-controlled area (for example, light-tight room,
darkened hangar, or outside at night away from strong light
8. Calibration and Standardization
sources)sincetheNVGsareextremelysensitivetobothvisible
8.1 It is not necessary that the photometer be calibrated in
and near infrared light. Extraneous light sources (for example,
absolute luminance units since the measurement involves the
exit signs, telephone pole lights, status indicator lights on
division of two measured quantities yielding a dimensionless
equipment, and so forth) can also interfere with the measure-
value. A generic photodetector can be substituted for the
ment.
photometer if its FOV is known.
6.2 White Diffuse Target—The white target can be any
uniformly diffusely reflecting or translucent material (for
9. Procedure
example, cloth, flat white painted surface, plastic). The target
area should be either smaller (see Fig. 2) or larger (see Fig. 3) 9.1 General Procedures—Perform all measurements in a
than the NVG FOV (35 to 60° typical) to minimize potential darkened, light-controlled area. To control the effects of
alignment errors. reflection, verify that there are no extraneous light sources that
6.3 Light Source—The light source should be regulated to can produce reflections within the measurement area of the
ensure that it does not change luminance during the reading transparent material. To control the effects of haze, verify that
period. It should be a low output
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