MIL-PRF-49147D(CR)
3.5.2 Resolution. The eyepiece shall have a minimum resolution of 20
lp/mm when measured using a high contrast USAF 1951 Resolution Power Test
Target (clear lines on black background or black lines on a clear background)
and viewed binocularly from a 50 mm eye relief.
3.5.3
Magnification.
The on-axis magnification shall be between 3.75
and 4.0.
3.5.4 Transmission. The transmission of the eyepiece shall be 80
percent minimum for the region of spectral output of a P-20 phosphor.
3.5.5 Field of view.
The field of view of the eyepiece shall be 42.5
degrees minimum.
3.5.6 Field flatness. The field flatness shall deviate no more than
1/4 diopter over a 46 mm format with a 100 mm radius of curvature for the
fiber optic magnifier output.
3.6 Environmental. Verification of conformance after environmental
tests shall be Diopter setting (3.5.1), Resolution (3.5.2) and Transmission
(3.5.4).
3.6.1 Temperature Extremes. The eyepiece shall not be damaged nor
suffer degradation of performance (see 3.10.1 and 3.10.4) after being
subjected to storage at +68°C or -51°C. The eyepiece shall not be damaged nor
suffer degradation of performance (see 3.10.1 and 3.10.4) after being
subjected to repetitive changes between +23°C and +68°C within 5 minutes and
between +23°C and -51°C within 5 minutes. Soak time at each temperature
extreme shall be sufficient for the eyepiece to attain temperature
stabilization. Time for temperature stabilization is defined as the amount of
time required for the most internal part of the unit under test to achieve the
specified temperature.
3.6.2 Immersion. The eyepiece shall not be damaged (see 3.10.1) after
being immersed in fresh water to a depth of not less than 3 feet for a period
of not less than 30 minutes. The eyepiece shall be pre-conditioned by
exposure to a temperature of +45°C ±3°C for a period of 2 hours prior to being
immersed in the fresh water at a temperature of +18°C ±5°C.
3.6.3 Vibration. The eyepiece shall not be damaged nor suffer
degradation of performance (see 3.10.1 and 3.10.4) after being subjected to
vibration equivalent to that encountered in tracked vehicles, during 5000
miles of operation. Vibration shall be limited to one sine sweep from 5.0 to
500 Hertz (Hz.) and back to 5.0 Hz. within 15 minutes in the vertical axis
only. Vibration shall be performed from 5.0 to 5.5 Hz at 1 inch displacement,
5.5 to 30 Hz. at 1.5 g's peak, 30 to 50 Hz. at 0.33 inch displacement and 50
to 500 Hz. at 4.2 g's peak (see 3.10.5).
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