Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!bu-cs!purdue!decwrl!labrea!glacier!jbn
From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: sci.electronics
Subject: Re: Hobby laser show system
Message-ID: <17883@glacier.STANFORD.EDU>
Date: 7 Dec 88 01:22:17 GMT
References: <2110@puff.cs.wisc.edu>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Distribution: na
Organization: Stanford University
Lines: 14


      The low rent approach to this problem is to glue a mirror to the
cone of an old loudspeaker.  You can produce interesting but not meaningful
patterns in this way.  A setup with two mirrors, one for X and one for Y,
allows positioning.  Connection to a pair of D/As with DC-coupled power amps
provides computer control, or connection to an audio system provides 
decorative patterns.  Don't expect much precision.

      The high rent approach is feedback-controlled mirror galvanometers
from General Scanning Corporation.  These have a mirror, a galvanometer 
movement, and a variable capacitor for position feedback.  This is how
the laser-show people do it.

					John Nagle