RE: 3D SPEX (and LCS in general)

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Wed, 27 Aug 1997 19:57:13 -0500
>From: P3D Larry Berlin  <lberlin@xxxxxxxxx>
>Subject: RE: 3D SPEX (and LCS in general)

>>Good point, I'd forgotten about DMM.  This is important because this
>>technology will probably replace commercial film projectors.  

>******  All I've read about this method is what's been discussed here in
>P3D. I didn't see anything in what was described that could possibly be used
>for commercial film projecting. How is that possible? Wouldn't they melt
>down in the intense light and heat?

Projection is what they're mainly used for. I don't know what the limits are-
the surface is highly reflective and it's only the absorption you care
about. I would guess that most of the infrared is filtered before it gets
to the "digital micromirror device" in a typical projector, and of course
you can use forced air and other cooling techniques.

>>However,
>>considerable advancement and cost reduction is needed before it can
>>be used for "personal" displays.  These devices already use an enormous
>>amount of bandwidth to modulate intensity via time division - doubling
>>that to provide stereo would undoubtedly cause some TI engineers to
>>pull their hair out in frustration!

>*****  They should be starting with the spec for stereo image work as the
>basis of development. Then not only would it be robust enough for stereo, it
>would have no problem with regular applications either. Doubling a process
>shouldn't be too difficult if you know that you want it. Just design for it
>from the beginning. Too many current difficulties (and associated
>re-engineering costs) in computers for both stereo applications and other
>new developments, are from precisely this same kind of deliberate
>(information is there but ignored) lack of vision. Having run into problems
>with past mistakes should provide a lesson to plan ahead in future
>developments, or face getting bettered by the competition.

As generic advice, I can see plenty of cases where that would work, and
plenty where it wouldn't work. Time to market, competition with other
technologies, the usually incremental refinements punctuated with
occasional breakthroughs, and uncertainty about which way the technology
will develop add to the risk of planning too far ahead, and the labor of
designing in contingencies adds real cost to product development
(basically you're betting a lot of money *now* and slowing down the
introduction of your first product, in the hope that this will be a
better business decision than introducing a fix later). *Sometimes*
it makes sense to design contingencies into your first product, and
sometimes it doesn't. NTSC color encoding is awkward, but it works
reasonably well - would it have made sense to delay the introduction
of television in the US another 10 years in order to standardize the way
color would be implemented some decades later? (Bearing in mind that such
a standard would probably have contained provisions on how to synchronize
the flywheel. :-)

In the specific case of DMD devices, the micromirrors themselves have
considerable potential for frame sequential stereo - their switching
speed is claimed to be on the order of 10 KHz. The control circuitry
to make use of this speed is a challenge to develop (and, I expect,
proprietary), but again I don't see why DMDs in particular would have
bandwidth problems. I've heard at least one speaker from TI make a public
statement at a conference that he believes DMD (as the technology was 
called at the time) would be well suited for stereo applications.

John R


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