Subject: Re: Glass scale problem

> >
> Pretty unlikely. Changes in the index of refraction is not a big

deal,

> as there are really
> no focussed optics in the readout scales. Superglue often

produces a

> white hazy film,
> so you really don't want to use that. I haven't seen glass scales

with

> scratches in the
> glass. I have seen some where the mechanism that controls the

spacing

> of the analyzer
> (read head) to the main scale has worn out, and the two chrome

gratings

> have rubbed
> together. When this happens, generally the scales are not

repairable.

>
> But, other alignment and contamination problems are fairly easily

fixed.

> Deterioration
> of the light source is harder to fix, but some of them can be

fixed.

>
> Jon

The interesting thing is for about ten minutes after I wipe the bad
section of the scale with alcohol it is dead on accurate. After
that it starts missing more and more counts until the whole section
(.176") skips. The DRO flips the last number back and fourth but
doesn't count I'm sure the alcohol leaves a film that's changing the
refraction of the light coming through the scale.
I'm going to take a closer look at the head and also investigate
what's available in the lens coating solutions. I think the CD stuff
sounds promising.


Derek