MIL-PRF-38169A
(This section contains information of a general or explanatory nature which may be helpful, but is
not mandatory.)
6.1
Intended use. This specification provides the optical characteristics of visor and goggle
lenses used by flight personnel to protect their eyes from wind blast, sunlight, and electromagnetic
radiation.
6.2
Acquisition requirements. Acquisition documents must specify the following:
a.
Title, number, and date of this specification and class lens being procured.
b.
Issue of the DoDISS to be cited in the solicitation, and if required, the specific
issue of individual documents referenced (see 2.1).
c.
Packaging requirements (see 5.1).
d.
Data required.
e.
When first article test is required (see 3.4).
f.
Visor and lens measurements.
g.
Packaging requirements including protective coverings (see 5.1 and 6.4).
6.3
Definitions.
6.3.1 Prismatic deviation. Prismatic deviation, for the purpose of this specification, includes the
inherent prismatic power resulting from nonparallel surfaces of the material.
6.3.2 Transmittance. Transmittance, T, is the ratio of transmitted to homogeneous radiant flux.
6.3.2.1 Luminous transmittance. Luminous transmittance is defined as the ratio of the luminous
flux transmitted by the visor and goggle lens to the luminous flux incident. It is measured with a
sensor corrected to compare with the photopic sensitivity of the human eye without regard to
specific wave lengths. ASTM D 1003 or a specified modification thereof is a way of determining
luminous transmittance.
6.3.2.2 Spectral transmittance. Spectral transmittance, Tc, is the radiant energy transmitted
evaluated for a specific range of wave lengths of incident energy. It is desirable that it be
measured with an automatic recording spectrophotometer of the required range of sensitivity and
evaluated according to the applicable instructions.
6.3.3 Average spectral transmittance deviation calculation. An example for calculation of
spectral transmittance deviations is shown in table I. The average spectral transmittance deviation
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