From: dstamp@watserv1.waterloo.edu (Dave Stampe-Psy+Eng)
Subject: Re: Optical gyroscopes for Head/body trackers
Date: Tue, 31 Dec 1991 14:39:20 GMT
Message-ID: <1991Dec31.143920.20987@watserv1.waterloo.edu>
Organization: University of Waterloo


geoffrey@cosc.canterbury.ac.nz (Geoff Thomas) writes:

>I'm wondering whether anyone has done any work with optical gyroscopes for
>tracking of body/head/fingers etc.?
>
>In the Physics Dept. here the gurus are working on a ring laser (a fancy
>optical gyroscope) about 1 metre square, which can detect the expansion
>on one side of the building caused by heat from the sun.
>
>It ought to be possible (says he with *very* little knowledge of what's
>involved!)
>to put one of these type of optical gyroscopes together on an integrated
>circuit,
>and a 3D version ought to be possible.
>
>[Stuff deleted]
>
>Does anyone know if such devices are available in this form (and if so,
>who markets them), or how difficult it would be to make them?

Optical gyros are not that compact.  What you've seen is an optical
interferometer that measures changes in the length of 2 or more paths
of a light beam.  When a building expands, it will change the length
of the fixed legs and not the reference ones.

Optical gyros work by passing light through several thousand turns of
fiber.  Because the speed of light is constant, rotation of the coil
is detected as differential delays in the passage of light in the
clockwise and counterclockwise directions.  This is detected by 
interfering the beams of light with each other.

Because you need all that fiber, laser diodes, nonlinear mixers
and fast counting logic, I don't think the price will soon drop
to that of mechanical gyros.  But no moving parts is an advantage.
How small they can be made... Probably larger than the GyroMouse.

--------------------------------------------------------------------------
| My life is Hardware,                    |                              | 
| my destiny is Software,                 |         Dave Stampe          |
| my CPU is Wetware...                    |                              | 
| Anybody got a SDB I can borrow?         | dstamp@watserv1.uwaterloo.ca |
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