MIL-PRF-49170B(CR)
one or more defects preventing or lessening maximum efficiency shall constitute cause for
rejection.
4.5 Methods of inspection. Measurements taken by the contractor during verification
testing of all environmental performance requirements shall be accomplished using test apparatus
such an environmental test chamber, vibration test table, pendulum shock device or similar
equipment which simulate extreme climatic or environmental conditions. For temperature test,
test duration shall be a minimum of three (3) cycles for operation and seven (7) cycles for storage
at 24 hours for each cycle.
4.5.1 Equivalent focal length (EFL). EFL shall be defined in 3.5.1 and as measured in
ANSI PH 3.35, paragraph 4. Measurements falling outside the specified requirements shall be
considered a failure.
4.5.2 f/number. f/number shall be as defined in 3.5.2 and as measured in paragraph 2.6 of
ANSI PH 3.29. Measurements not in accordance with the specified requirements shall be
considered a failure.
4.5.3 Linear distortion. Linear distortion shall be measured. Use of the procedure in
6.2.i(1) is recommended. Distortion outside the requirements of 3.5.3 shall be deemed a
failure.
4.5.4 Modulation transfer function (MTF). Using the requirements of Figure 1 and
Figure 3, the MTF shall be measured either continuously or in 8 discrete steps from 0 to 16
cycles per millimeter (cy/mm). The MTF test shall be run at infinite conjugates. On-axis MTF
shall be measured and shall not be less than the MTF in Figure 1. Off-axis radial MTF shall be
measured in the same plane used for the on-axis image parallel to the plane defined by the
datum A of Figure 2. The off-axis MTF shall be measured at 2 points in the field 90 degrees
apart.
4.5.5 Relative illumination (RI). RI shall be measured. Recommend using the procedure
found in 6.2.i(2). RI outside the requirements of 3.5.5 shall be unacceptable. RI shall be
measured in 2 mutually perpendicular planes with the first plane measured across the greatest
distance of the oval shape of the mirror.
4.5.6 Flange focal distance (FD). FD shall be measured. Recommend using the procedure
found in 6.2.i(3). FD falling out of conformance with 3.5.6 shall be considered as being failed.
FD shall be measured from datum A in Figure 2 to the flat field plane of best MTF.
4.5.7 Field of view (FOV). The FOV of the IMAGER shall conform to 3.5.7 when
measured with optical devices. Recommend using the procedure of 6.2.i(4). FOV falling
outside the specified range shall be unacceptable.
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