MIL-PRF-49173B(CR)
3.5 Performance characteristics.
3.5.1 Effective Focal Length (EFL). The EFL of the Imager in the 7.6 to 11.75 micrometer
spectral region shall be 67.8 mm, ± 0.7 mm at the nominal flange focal distance (see 3.5.6) is
defined by ANSI PH 3.35, paragraph 4.
3.5.2 f/number. The f/number of the Imager shall be f/1.19 or faster, set by the clear
aperture of the first lens element (see Figure 3) as defined by ANSI PH 3.29, paragraph 2.6.
3.5.3 Linear distortion. The linear distortion of the Imager shall be between 0 to -3 percent
at the edge of the field.
3.5.4 Modulation transfer function (MTF). The MTF of the Imager shall not be less than
the MTF given in Figure 1.
3.5.5 Relative Illumination (RI). The RI of the Imager shall not be less than 60 percent at
the edge of the field for a field diameter of 20 millimeters at the image plane.
3.5.6 Flange focal distance (FD). The FD shall be set to a nominal of 17.71 mm, and be
adjustable ± 0.47 mm at ambient temperature (see 6.5.2).
3.5.7 Field of view (FOV). The imager shall have a field of view sufficient to fill a circular
format with a diameter of 20 mm.
3.5.8 Optical transmittance. The optical transmittance of the Imager, measured in the 7.6 -
11.75 micrometer spectral region shall be at least 85% at ambient temperature (see 6.5.2).
3.5.9 Deviation. The optical axis of the imager shall not deviate from 90.0 degrees by more
than ± 0.5 degree.
3.6 Environmental conditions.
3.6.1 Temperature shock. The Imager shall not be damaged by sudden changes in
temperature between -54°C and +95°C (see 6.5.1).
3.6.2 High temperature. The Imager shall not be damaged by storage to +95°C or
operation to +71°C (see 6.5.1).
3.6.3 Low temperature. The Imager shall not be damaged by operation to -54°C or storage
to -62°C (see 6.5.1).
3.6.4 Shock. The Imager shall not be damaged by high intensity shocks of 100 "g's" peak
amplitude with 11 milliseconds duration (see 6.5.1).
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