MIL-PRF-13830B
will not impair the performance of the finished instrument, shall be permissible.
Whether a particular defect shall be permitted will depend on the location of the
element in the finished optical system. Defects in elements not near a focal plane are
not as important as in elements which lie in or near a focal plane. In all instances
primary emphasis shall be placed on the performance of the lens or prism rather than
its appearance unless the latter definitely indicates poor workmanship. The order of
importance is as follows:
a. Most critical surfaces,
Etched surface of reticle
Surface of collective lenses in a focal plane
b. Less critical surfaces,
Surface of ocular field lens nearest the reticle,
Collective lens, center lens or prism surfaces near a focal plane
c. Least critical surfaces,
All other surfaces of windows, objectives, prisms,
erector, and eyelenses
3.8.2.2 Alignment. The optical elements of all optical systems procured
assembled in their instruments shall be aligned so that the exit pupil viewed on the
optical axis shall have a minor diameter not less than 90 percent of its major
diameter. The exit pupil shall be concentric with the exit free aperture within 10
percent of the exit free aperture when viewed from a point on the optical axis at a
distance of approximately two feet from the eyelens.
3.8.2.3 Sealed joints. When specified, moisture preventive sealing compound (see
3.2.4) shall be evenly applied to the optical component to form an unbroken bead.
When injection sealing is utilized, 24 hours shall elapse before collimation of the
instrument.
3.8.2.4 Padding. The use of pads, shims, wedges, or opening under or around
optical elements is prohibited and shall be cause for rejection of the instrument unless
specified by the drawings
3.8.2.5 Performance characteristics.
3.8.2.5.1 Vibration. After being subjected to the vibration test specified in 4.2.10.7
the optical instrument shall show no dirt (dust or lint) in excess of that allowed by the
item specification. In the absence of detail requirements, dirt in any confined space
shall not be in size or amounts larger than the allowable dig specification for the
adjacent surface requiring the best dig quality. The instrument shall show no evidence
of loose or damaged parts subsequent to this test.
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