Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!mcsun!hp4nl!sara5!amccca!jonker
From: jonker@amc.uva.nl
Newsgroups: comp.robotics
Subject: Re: What is the cheapest shaft encoder you know o
Message-ID: <1991Jun20.094757.237@amc.uva.nl>
Date: 20 Jun 91 09:47:57 GMT
Lines: 14

To construct a real tiny shaft encoder (might cause problems with
the optical part of the encoder) reduce a printout (need not be
very small) of a radial wheel by photograping it (on b/w film?),
and directly using the film as a shaft encoder wheel. That's major
resolution. Perhaps you can make an interference pattern with a 
laser diode, and such a wheel. Two optical diodes can detect the
motion of the interference pattern and with that, the direction
of the wheel turning:             #     laser diode
             ----------------------     wheel 
rotation axis           ^         P     two photo diodes
The photodiodes must be on the same radial distance to the axis,
close to eachother, perhaps with a slit on top of them ?
any comments, catches or flaws ?
ard