Re: Fun with encoders

> From: Mike Romine <mromine@...>
>
> I am currently working on a project that uses the relatively new HP HEDR
> encoder module. This is a REFLECTIVE read head, as opposed to the more
> typical TRANSMISSIVE read head. I found all the talk on having linear
> strips made very interesting as I have been getting quotes to do just
> this for the last few weeks. NO, a typical mylar printer cannot do
> these accurately. You need to go to shops that specialize in high
> accuracy lithography. I have several companies lined up to do this
> right now. The actual printing of the strips is fairly cheap. But the
> cheapest setup charge I have found is $600. There is a company out of
> germany call PWB-Rulahtec that will make samples of any resolution you
> want for $250. But that is still out of hobby $ range, isn't it.

No, not if you get several people involved in it. What you really want is
to get somebody to make a glass master pattern (either film emulsion
or chrome evaporated on glass) with whatever pattern you like, on
a piece of glass longer than the biggest scale you would want.
Then, with relatively simple photographic processes, you can crank
out strips of litho film contact printed with the same pattern.
With a little more work, you could get glass strips vacuum deposited
with chrome, then apply photoresist and expose with the master
pattern, and after etching the chrome, get glass scales with chrome
patterns just like professional linear scales. But, you could easily
get direct-reading quadrature scales with resolution of, say,
.000025" (counting all transitions). Once you have the master
pattern, the rest is not so terribly difficult.

Jon