From: dstamp@watserv1.waterloo.edu (Dave Stampe-Psy+Eng)
Subject: Re: head tracking
Date: Sun, 8 Dec 1991 04:07:19 GMT
Message-ID: <1991Dec8.040719.12377@watserv1.waterloo.edu>
Organization: University of Waterloo



mike@x.co.uk (Mike Moore) writes:

>Why all this big deal about cameras?  If all you want is motion tracking
>then a simple set of LED's in the ceiling, minute mirrors on the user and
>sensitive Photo Voltaic cells mounted all over the room surface should
>suffice surely?  Another method altogether would be to criss-cross the room
>with (very) low power lasers with as small a gridding (cubing?) as you
>required to measure movement, get the user to wear a mirror suit that had
>specific reflectance qualities for each area of the body you were interested
>in (e.g. colour, intensity) and have some system to recognise which laser
>hit which part of the body and landed where.

Oh, come on now!  Not one of these ideas is cost-effective compared to
what was discussed.  Plus the resolution is low, and the noise level is 
high.  Here's the problems:

1) "Minute mirrors"-- very little light reaches the photosensors.  Any
room background illumination causes HUGE noise effects.  And this system 
won't work geometrically.

2) "Laser grids"-- what-- a laser every 5 mm?  And how do you tell which 
beam you broke?  Better to "scan" the room with lasers, then the timing tells
you the position.  And mirrors don't work well.

3) Color/intensity:  Intensity is right out (distance effects).  Color is
an option, but only useful for camera systems.  It's easier to use 
time-multiplexing than color on a fast-scanned system.  Besides, you
can only disciminate 8 or so colors well without getting "identity noise"
(yechh).

--------------------------------------------------------------------------
| 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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