MIL-DTL-62478C(AT)
uniformly illuminated target, subtending an angle larger than the field-of-view of the G/VLLD,
shall be positioned in front of the G/VLLD. An optical magnifier shall be placed behind the
eyepiece of the ITA so the exit pupil is brought into sharp focus in the plane of the reticle of the
magnifier. Measure and record the diameter of the exit pupil by using the reticle in the
magnifier. The G/VLLD shall be removed and the uniformly illuminated target shall be
positioned in front of the optical coupler so it covers the field of view of the coupler. Measure
and record the diameter of the ITA exit pupil. Reposition the illuminated target in front of the
night sight objective lens of the ITA and switch the ITA to the night position. Again measure
and record the diameter of the ITA exit pupil. The three exit pupil measurements shall not be
less than 0.22 in. (5.5 mm).
4.6.5 Field of view verification. To determine conformance to 3.3.5, the integrated
system configuration shall be used. The target image shall be placed at one edge of the G/VLLD
optical field and then at the opposite edge. The angular distance thus traversed shall be
measured. The field of view shall not be less than 5 degrees (0.087 radians) in any pupil matched
condition.
4.6.6 Lateral color verification. To determine conformance to 3.3.6, the integrated
system configuration shall be used. A monochromatic target 0.0000192 in. or 0.0000258 in.
(486 nm or 656 nm) shall be positioned in front of the G/VLLD and off-axis more than half the
angular distance from the central optical axis to the edge of the field. A 5 nm diameter aperture
shall then be positioned at the ITA exit pupil. An alignment telescope shall then be positioned
behind the aperture, so the target image is located at the intersection of the telescope reticle
crosshairs. The F and C filters 0.0000192 in. and 0.0000258 in. (486 nm and 656 nm) shall be
alternately positioned to provide alternate monochromatic illumination of the target. The
apparent angular displacement of the target image which is caused by the alternate illumination
shall be measured with the telescope. The lateral color of the integrated system shall be no
greater than 3 minutes of an arc for wavelengths between 0.0000192 in. and 0.0000258 in.
(486 nm and 656 nm).
4.6.7 Visual anomalies verification. To determine conformance to 3.3.7, the integrated
system configuration shall be used. A 100 watt incandescent lamp shall be positioned at various
angular locations outside the G/VLLD field of view but within the G/VLLD forward hemisphere
at a distance of not more than 2 ft (610 mm). The ITA eyepiece apparent field shall be visually
examined for evidence of flare or ghost images. The positioning of the lamp at various angular
locations shall be repeated while the ITA eyepiece is observed for evidence of light emerging
from outside the exit pupil. No visually perceptible defects shall be observed.
4.6.8 Leak resistance verification. To determine conformance to 3.3.8, the optical
coupler shall be placed in a suitable chamber wherein the helium leak rate from the coupler shall
be measured. The internal pressure of the coupler shall be 1 atm (101.325 kPa) which includes
10 ± 1% helium. The chamber shall be pumped to vacuum so the external pressure on the
coupler shall be no greater than 1/1500 atm (67.55 Pa). The helium leak rate shall be measured
and shall not be greater than 0.000025 atm-cubic centimeters per second.
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