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.
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