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From: leichter@yale-com.UUCP
Newsgroups: net.micro
Subject: Re: Question on the mouse, comments abou - (nf)
Message-ID: <1690@yale-com.UUCP>
Date: Thu, 30-Jun-83 09:20:40 EDT
Article-I.D.: yale-com.1690
Posted: Thu Jun 30 09:20:40 1983
Date-Received: Thu, 30-Jun-83 19:50:13 EDT
Lines: 29

About light pens:

First, the good news.  The large radius of the pen tip does NOT make accurate
pointing impossible; you can be clever.  What you do is project a crosshair
pattern just above where the pen is sensed to be.  Other than the pen-control
software, everyone thinks the pen is "at" wherever the CROSS-HAIR is; it can
be controlled quite accurately.  (This isn't my idea, BTW, but I'm afraid I
don't have the reference...)

Now, the bad news:  Light pens have one really unfortunate feature:  You have
to hold them up to a vertical display screen.  This is very tiring after a
fairly short time, as many experiments have shown.  That's the main reason
light pens haven't been that heavily used.

(Of course, if you build the screen into your desktop, you have a different
situation...)

The single best "pointing device" I've ever heard of was developed at Bell
Labs a couple of years back - again, sorry, I don't have the reference.  The
system was called something like "reading through your hand".  You used a
half-silvered mirror to project a "semi-transparent" image of your hand over
an image of the screen.  It turns out that, if you do it right, the image
doesn't interfere at all with your ability to read what is on the screen,
but provides you with all the feedback you need to control your hand.  The
position of the hand is, of course, read by some sort of touch-sensitive
surface.  This hasn't caught on, probably because the size, complexity, and
cost of the necessary equipment.
							-- Jerry
				decvax!yale-comix!leichter leichter@yale