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TM 9-254
9-6.
Inspecting Optical Components - Continued
Table 9-5. Objective, Erector Lenses and Windows
Estimated
Number of
Scratch
Maximum
Number of pits,
Size of pits,
diameter
scratches
size
length
digs, bubbles
digs, bubbles
up to 1.250
5
60
3/16
4
40
1.251 - 2.000
8
60
1/4
7
40
2.001 - up
10
60
5/16
10
40
Table 9-6. Reticles **
Estimated
Number of
Scratch
Maximum
Number of pits,
Size of pits,
diameter
scratches
size
length
digs, bubbles
digs, bubbles
up to 1.250
3
60
1/8
3
10
1.251 - 2.000
3
80
3/16
3
20
2.001 - up
3
80
1/4
3
40
** No scratches, pits, or lint will be permitted in central reticle pattern (etching) or in central area of field lens where it will be
superimposed on reticle pattern.
Section III. Reclamation of Optical Components
NOTE
In the following processes (decementing, decoating, coating, and cementing of optical
components) all lens halves, after being separated, should be kept together.
9-7.
Decementing (Separating) Optical Components.
a.
Reasons for Decementing. Lenses which are defective because of deterioration of the cement or the coating
must be separated for repair.
b.
Hot Plate Method of Decementing. This method of decementing incorporates the use of a hot plate placed
inside an enclosed containment hood. The purpose of the containment hood is to reduce the amount of cooler room air
coming in contact with the heated lens, causing it to fracture. The procedure for decementing with this method is as
follows:
(1)
Place a fiberglass cloth over the hot plate heating surface, to protect the lens surface from damage, and
preheat the hot plate to 350 to 450 degrees Fahrenheit.
Change 2 9-23
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