🚀 go-pugleaf

"Frank Bemelman" <bemelmanx@euronet.nl.invalid> wrote in message news:<3f747ee2$0$28885$1b62eedf@news.euronet.nl>...
> "Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> schreef in bericht
> news:a64581c0.0309242126.7a4fe4ee@posting.google.com...

> > So I got some Agilent HEDR-8100 detector chips. they have the lenses
> > built in and do all the hard work for you. The only problem is that
> > they're 150 lines per inch, which is more than I can do reliably on a
> > laser printer. So I'm looking for alternatives.

> If you place a transparent filter on top, also printed with 1mm stripes,
> you don't need a very well adjusted sensor. When the rod with the stripes
> move behind the filter, even you can clearly see that it moves. Most
> optical encoders work like that, makes them get away with pretty coarse leds
> and fotodiodes.

> Place two filters with the stripes 90 degrees apart for A & B signals.
> The effect is named after Moire, it's inventor, I think.

Thanks for the ideas. I have a suspicion that the optical devices I'm
using already exploit the Moire effect, since they appear to only work
at 150 lpi. This would indicate that they already have a 150lpi screen
internally.

The optical mouse sensor idea is something I already thought of, but
the specs for some of the modules they use show fairly lousy
repeatability, which I guess amkes sense. I need pretty good (0.5 mm
or so) repeatability.

I have yet to have any success with ink jet printer on transparencies.
The ink is either too think, blobbing up and obscuring the gaps, or
not dark enough to block the reflection. Perhaps I need better
stationary.

In any case, I've ordered the lower resolution (75 lpi) encoders. I've
printed out some 75 lpi stripes, and checked them under a microscope.
They look clear and distinct, so I'm just going to go with that.

thanks for the responses though.

                   Cory