Received: from watserv1.uwaterloo.ca (watserv1.waterloo.edu) by karazm.math.UH.EDU with SMTP id AA08349 (5.65c/IDA-1.4.4 for ); Fri, 25 Oct 1991 13:51:51 -0500 Received: by watserv1.uwaterloo.ca id ; Fri, 25 Oct 91 14:47:37 -0400 Date: Fri, 25 Oct 91 14:47:37 -0400 From: Dave Stampe-Psy+Eng Message-Id: <9110251847.AA19649@watserv1.uwaterloo.ca> To: glove-list@karazm.math.uh.edu Coyt Watters sent me some mail. I tried to get back to him, but the address didn't work. So I'll post my reply here, as I think it's of general interest: >Been following the thread on Sega LCD glasses. > >Why does 30hz to each eye cause a flicker, when 24hz (Film) does not? > I believe the reason is that the Sega glsses give you 50% duty cycle on the images to each eye, and a movie projector gives over 90%. This results in 5 times the 24 Hz/30Hz flicker (at least). You can see the flicker in movies if you have a fast-moving white object on a dark background-- just look at the edges. > >Would it be possible to use two camcorder viewfinders, mounted at >the sides of the head and projecting onto curved screens before the >eyes? > >The center of vision would not be a problem, but there would be distortion >at the edjes of vision due to the curving screen. This could be overcome >by the lens used to project the image. > >Attempt at picture > __ __ > / \ / \ <-- screen > / | \ not to scale (of course!) > | o^o | > U( )U <-----projector > """ > ^ > User >Provided the screens were made of a tough, lightweight plastic, the unit would >not weigh very much, and the weight of the video units would be centered >of either side of the head, so their weight would balance. > >-Coyt D. Watters (cwatters@magnus.acs.ohio-state.edu) Not that bad an idea. There are a few implementation problems for garage VR, though. First, the mirrors must be a fairly special shape, and making such a mirror is not trivial. You'd have to have some way to turn computer-generated shape data into a form to mold plastic around, then get it coated. Not my field, but someone else might know how. The second, more serious problem has to do with the high mangification. A slight shift of the mirrors on the head will cause motion in the image proportional to the same shift in the progector CRT position. For example, a 1mm motion with a CRT 12mm wide (standard viewfinder CRT) shifts the image by 1/12 of its width. And unless the mirrors were REALLY light, it is difficult to eliminate shifts entirely. Still, I've seen military helmet-mounted displays that use this technique. So perhaps these problems are more easily solved than I think. BTW, sci.virtual-worlds is back up. I guess we should take the eyephone stuff back there (B-{)) -------------------------------------------------------------------------- | 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 | __________________________________________________________________________