Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!genrad!decvax!yale-com!leichter 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