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From: musgrave-forest@cs.yale.edu (F. Ken Musgrave)
Newsgroups: comp.graphics
Subject: Re: Wall sized video
Keywords: lasers, video
Message-ID: <26025@cs.yale.edu>
Date: 6 Sep 90 12:58:28 GMT
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  I did my undergrad thesis on exactly this topic back in '77; two years ago I
saw such a device in operation at a company around Moffet Field in the Silicon
Valley (can't remember the name).  

  While the resolution was spectacular and the color was theoretically-optimal,
there were three significant problems: first, the interference-speckle charac-
teristic of coherent monochromatic light, second, a problem with interlaced
video and zero-decay time pixels (phosphor-equivalents), third, and strangest
of all, a sort of crawling of the image reminiscent of a heavy dose of psyche-
delic drugs.

  The fist problem is straightforward and well-understood.  There may be a 
phase-randomizing technique to defeat it, but I suspect that it will always
occur with monochromtic light sources - it indeed is caused by phase shifts
in such light.

  The second problem showed up as disappearance of alternate scan lines when
the action moved vertically.  I was mystified by it at the time, but have since
hypothesized that it is a result of intantaneous decay of the image on the
"screen" (whatever that is chosen to be).  This might have the result of the 
image decay being relegated to the optic nerves, which are moving (in image 
space) with the action, thus causing interlaced scanlines to overlap at criti-
cal vertical motion speeds.  On the other hand, it may have been a strange
electronic problem with the system; impossible to tell, since I'm working from
memory.

  The third problem was truly bizarre.  The image appeared to be swimming, 
crawling, billowing, like it was slowly melting.  The company rep said that it
had something to do with the vitreous humor of the eye, but the explanation
didn't fit any physics that I knew at the time.  It was, however, clearly
an effect generated in the human visual system, and therefore perhaps very
difficult to solve.

  The overall effect was quite impressive - a 40 foot wide image with amazing
color and resolution.  But I think that these problems would make it unaccept-
able to the general consumer.  At any rate, the device was for sale, at 
~80,000 dollars per unit.  If anyone really wants, I think I can find the name
of the company...

							Ken
-- 

*===============================================================*
F. Kenton ("Ken") Musgrave	arpanet: musgrave-forest@yale.edu
Yale U Depts of Math and CS	(203) 432-4016