MIL-PRF-49052G
3.6.13 Image alignment. A test reticle projected on the photocathode of the
assembly concentric with the optical axis shall produce an image on the screen of
the assembly such that the center of the reticle's image shall fall within an
ellipse of 0.012 inch major axis and 0.006 inch minor axis. The ellipse shall be
concentric with the optical axis of the assembly and the major axis of the
ellipse shall be horizontal when the alignment slot of the assembly is displaced
75 degrees ± 0.5 from the horizontal in a counterclockwise direction, when viewed
from the screen end of the assembly.
3.6.14 Lens interface. The assembly shall show no evidence of intermittent
operation, arcing, flashing, flickering, corona, or bright spots beyond that
allowed in 3.6.19, and the input current of the operating assembly shall not
increase when coupled with an F/1.4 objective lens assembly conforming to drawing
SM-C-657375 and, also, with an F/1.05 objective lens assembly conforming to
drawing A3144480.
3.6.15
Resolution.
3.6.15.1 Center resolution. The center resolution, referenced to the
photocathode, shall not be less than 32 line pairs per millimeter (lp/mm).
Disagreement concerning compliance shall be resolved by performing the modulation
transfer function test in accordance with paragraph 3.6.17.
3.6.15.2 Peripheral resolution. The peripheral resolution, referenced to
the photocathode, shall not be less than 32 lp/mm. This requirement shall be met
at two points separated by 90 degrees spaced on a 14 mm diameter circle
concentric with the optical axis (see 3.12.15).
3.6.16 Peripheral illumination stability. There shall be no flashing,
flickering, or other intermittent operation when the input fiber optic is
illuminated outside the 19.5 mm diameter with 20 fc for a period of 20 minutes. The
input current deviation from the steady state value shall not be greater than ±2.0
mA.
3.6.17 Modulation transfer function (MTF). The MTF values (see 3.12.12) of
the assembly shall not be less than those specified in Table III.
Table III.
Modulation transfer function.
Spatial Frequency1
Orientation
2.5 lp/mm
7.5 lp/mm
15.0 lp/mm
on-axis
86%
58%
20%
1
in units of line pairs per millimeter (lp/mm)
3.6.18 Useful cathode diameter.
The useful cathode diameter shall not be
less than 17.5 mm (see 3.12.20).
8
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