extent that they significantly impair the ability
3-7. Inspection of Optical Components
to observe the field-of-view.
Note. Optical instruments will not be rejected for
b. When looking directly through the eye-
conditions which can be detected only by the shading
piece of the body assembly there will be no
or shadowing technique. When viewing through the
eyepiece of the instrument, only those defects which
`evidence of moisture or fungus growth.
are apparent when the instrument is used in a manner
c. Polished optical surface shall show no
simulating field conditions will be cause for rejection.
evidence of grayness or stain.
Shadowing is the technique of looking into the eye-
d. Eyepiece focus shall be set between the
piece or objective of an instrument obliquely so as to
limits of -0.5 and -1.0 diopter.
optical system. With this method the surfaces of len-
e. The image will be sharp and clear at the
ses are dark grey in appearance and all defects, such
center of field.
as condensate, scratches, etc. show up as white par-
3-8. Inspection of Electrical Components
Note. Due to irregularities in the fluorescent screen
a. Inspect switch 10516220 to see that the
of the image converter tubes, hot or cold spots will
knob is tight on the shaft and that the action
appear as dark or light spots. The hot or cold spots are
of the switch is firm. Make sure the
not to be considered dirt. To differentiate between
switch mounting screws are tight and hold
these spots and dirt, decrease the power supply voltage
and the irregularities will change from dark to light
the switch firmly in position.
or light to dark spots, while dirt on the optical surfaces
b. Inspect plug 1290-764-9178 for damage
and to see that it is tight and that a good
electrical connection is made when the 24-volt
a. The presence of dirt, lint, scratches and/
or digs will be cause for rejection only to the
external supply is plugged in.
3-12. Inspection of Optical Components
a. Head Assembly. When looking through
This section sets forth the procedure to be
the head assembly of the periscope there shall
followed by maintenance shops in performing
be no objectionable dirt smears, scratches,
inspection of periscope XM48 when removed
digs, condensate or fungus growth. Chips and
from the end item and turned into the shop
fractures are permitted provided they are ston-
ed or ground and do not extend more than
3-10. Initial Inspection
1/4-inch beyond the clear aperture. In all cases
prime emphasis should be placed on perform-
The general inspection procedures outlined
ance of the periscope rather than the optical
appearance, unless the latter definitely indi-
lowed when periscope XM48 is initially re-
cates poor workmanship.
ceived in the shop.
b. Body Assembly. When looking directly
through the eyepiece of the body assembly,
cement separations extending more than 1/4-
Determine integrity of seals with soap and
inch from the edge of the clear aperture will
water solution as specified in paragraph 5-
not be acceptable.