MIL-PRF-13830B
aperture in width. Imperfections beyond the free aperture shall be permitted providing
their characteristics do not impair performance of the instrument.
3.7.11.2 Edge chips. Edge chip limitations shall be evaluated in accordance with
3.7.9.2.
3.7.11.3 Parallelism of flat surfaces. Parallelism of reticle flat surfaces shall be
within the tolerances specified by the drawings. Where no tolerance is given on the
drawing, the tolerance shall be 6 minutes of arc deviation of light path.
3.7.11.4 Markings. Reticle markings shall be viewed through an eyepiece of
essentially the same power under which the reticle will be viewed in the finished
instrument. Letters and numerals (whether in part number or adjacent to
graduations) shall be inspected primarily for legibility. Defects in numbers or letters
shall be acceptable provided each letter of figure is legible beyond doubt. Unless
otherwise specified, any printing style is permitted for letters and numbers, however,
the style selected must be uniform throughout each reticle and must meet with the
approval of the procuring agency. Line breaks one half the width of the line shall be
permitted. For reticles containing more than 15 lines, 1 break per 5 lines or fraction
thereof shall be permitted. All lines shall appear to be of uniform width and depth and
the intersections of lines shall appear to be sharp. Smooth or abrupt variations in line
width along the entire line shall not be in excess of 20 percent of the line width and in
no case shall reticle lines be bowed in excess of 1/2 the reticle line width. The fillet
radius at the intersection of reticle lines shall not exceed the line width. Acid burns
shall be cause for rejection, if visible when the reticle is viewed with the appropriate
eyepiece.
3.7.11.5 Illuminated reticles. If the brightness of a defect is greater than the
brightness of a reticle line when illuminated by the associated instrument light or light
of equal intensity, the defect shall be cause for rejection.
3.7.12 Wedge and window. Wedge and window surface quality shall be in
accordance with 3.7.9.1.
3.8 Optical systems.
3.8.1 Unassembled. Optical systems of specified design procured unassembled
shall be grouped into systems in accordance with the optical diagram pertaining to
the system, and shall be inspected as specified in 4.2.9.
3.8.2 Assembled. Optical systems of specified design procured assembled in their
respective instruments shall be assembled in accordance with the drawing and
specification for the instrument, and shall be inspected as specified in 4.2.10.
3.8.2.1 Defect criteria. Defects not otherwise covered in this specification, which
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