Afocal Assembly Optics.
The afocal/cover assembly optics (Figure 2-8) gathers IR energy and
focuses it onto the scan mirror.
The afocal/cover assembly optics
has two interchangeable field-of-view (FOV) telescope lenses, with an
objective lens, made of special IR passive material, common to both
fields of view.
The interchangeable lenses provide 4.5X and 1.5X
magnifications of the fields-of-view. The 4.5X Narrow Field-Of-View
(NFOW) lens set consists of two IR lenses. The 1.5X Wide Field-Of-
View (WFOV) lens is a single IR lens. Both lenses are mounted on the
same frame which is moved longitudinally for focus and laterally,
either vertically or horizontally, for boresight.
The lenses are
mounted so that an approximate 90-degree rotation about a horizontal
axis brings one lens into position and stows the other to accomplish
an FOV change.
Figure 2-8.
Afocal Assembly Optics.
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MM4812
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