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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.physics
Subject: Re: deflecting laser
Message-ID: <290@ssc-vax.UUCP>
Date: Thu, 20-Dec-84 16:02:22 EST
Article-I.D.: ssc-vax.290
Posted: Thu Dec 20 16:02:22 1984
Date-Received: Fri, 21-Dec-84 04:25:09 EST
References: <10800014@uiucdcsb.UUCP>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 29

> 
>   I remember seeing the world map projected onto the silver dome
> in monochrome laser in the EPCOT center, Florida. How did they do that?
> They must have a way of deflecting the laser light to make it 
> does raster scanning. I can imagine only two ways to do this:
> 
> 1) move the laser device mechanically. 
> 2) projects laser through some tansparent medium whose refractivity
>    is electronically controllable.
> 
>   The second one seems to be a more reasonable solution to me. Anyone 
> knowledgeable in the field care to comment on this?
> 
> 
> Kaihu Chen
> uiucdcs!chen

There are additional ways to do it.  One way is to mount a curved
mirror on an audio speaker voice coil.  As the voice coil moves in
and out, the laser beam would strike different parts of the mirror,
and hence would be reflected off in different directions.  Two
such mirrors could provide two axes of motion, with turning the
laser on and off providing pixels.  This is similar in principle
to how CRT and TV tubes operate.  Another method involves a
rapidly spinning wheel with flat mirrors spaced around the rim.
As a single mirror intercepts the beam, the reflection would scan
in an arc.  As you reach the edge between two mirrors, the beam
would suddenly jump to the other side.  This is the type of motion
you want in raster scanning.