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Purpose:
This document defines glass
surface quality on optical components per MIL-O-13830.
Definitions:
SCRATCH:
Any marking or tearing of the
glass surface.
SLEEK SCRATCH:
A hairline scratch.
CRUSH or RUB SCRATCH:
A surface scratch or a
series of small scratches.
DIG:
A small rough spot on the
glass surface similar to pits in appearance. A bubble is
considered a dig.
Procedure:
Surface quality is to be
specified by a number such as 60/40. The first digits
relate to the maximum width allowance
of a scratch as measured in microns. The next digits
indicate to maximum diameter allowance for a dig in
hundredths
of a millimeter. Thus, as can be seen from the table
below, a surface quality callout of 60/40 would permit a
scratch
width of .0024 inches and a dig diameter of .0158 inches.
The size of a defect is to be measured through the use
of an optical comparator.
|
Scratch or
Dig Number |
Maximum
Scratch Width |
Maximum Dig
or Bubble Diameter |
Dig or Bubble
Separation Distance |
|
|
mm |
inch |
mm |
inch |
mm |
inch |
|
120 |
0.12 |
0.0047 |
1.20 |
0.0473 |
20 |
0.787 |
|
80 |
0.08 |
0.0031 |
0.80 |
0.0315 |
20 |
0.787 |
|
60 |
0.06 |
0.0024 |
0.60 |
0.0236 |
20 |
0.787 |
|
50 |
0.05 |
0.0020 |
0.50 |
0.0196 |
20 |
0.787 |
|
40 |
0.04 |
0.0016 |
0.40 |
0.0158 |
20 |
0.787 |
|
30 |
0.03 |
0.0012 |
0.30 |
0.0118 |
20 |
0.787 |
|
20 |
0.02 |
0.0008 |
0.20 |
0.0079 |
20 |
0.787 |
|
15 |
0.015 |
0.0006 |
0.15 |
0.0059 |
20 |
0.787 |
|
10 |
0.010 |
0.0004 |
0.10 |
0.0039 |
1 |
0.040 |
|
05 |
0.005 |
0.0002 |
0.05 |
0.0020 |
1 |
0.040 |
|
03 |
0.003 |
0.00012 |
0.03 |
0.0012 |
1 |
0.040 |
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