Afocal/Cover Lens Switching (NFOV-WFOV).
Lens switching (Figure 2-10) is accomplished manually by operating
the night sight field-of-view (FOV) handle. Operating the FOV handle
rotates the FOV lens switching housing approximately 90 degrees about
a horizontal axis to bring one lens into operating position and to
stow the other. The external FOV handle is attached directly to the
fork inside the afocal/cover housing.
The fork straddles a pin on
one end of the link assembly.
The link assembly has a pin through
each end and is loaded against the focus frame by a helical spring.
The pin engaged by the fork goes through the link assembly and
attaches to the connecting link.
The other end of the connecting
link is connected to a pin on the lens switching housing. Operating
the FOV handle causes the lens switching housing to rotate
approximately 90 degrees about a horizontal axis to change FOV.
linkage in the FOV lens switching mechanism operates a switch mounted
on the basic sight assembly. The switch contacts are closed in WFOV
and open in NFOV.
The position information generated by the switch
is supplied to the TOW guidance circuitry via the night sight