Re: [CAD_CAM_EDM_DRO] Re: LCDs and UV

Graham Stabler wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@...> wrote:
>
>
>>Also, if you can keep it cool, the DLP can handle a
>>LOT of
>>light -- like a 1000 W Xenon arc lamp focussed on a thumbnail. The
>>trick is the
>>DLP shines the mirror spots on the target, or on a black beam dump.
>>
>>
> >The LCD absorbs the light not wanted. Turn the "screen" black, and
>it >has to absorb the entire 1000 W in the polarizers! Poof!
>
>The question becomes how much power does the hardening of the resin
>require? Assuming the very near UV resin was used as per the paper
>(460nm). A wide field system has the advantage over a scanning on of
>speed so if it requires greater exposure times because of lower power
>it might not be so bad.
>
>DLPs are certaily nice but I had a feeling they were a tad expensive
>to play with. Anyone any ideas?
>
>
>

They are basically unavailable. TI holds an impressive,
all-encompassing US patent
that has, I believe, kept all other makes of similar design off the US
shores. And, they
decide who will be allowed to buy the chips. Essentially every chip
made is a custom
design for the particular projector (or whatever) maker. I had a long
discussion with
Gary Feather, the developer and patent holder of the concept, and now VP
for that
general product line.

So, the only way I know of to get one is to buy a projector and take the
chip(s) out.
They are basically a static RAM with serial access, and they have a
control chip that
rapidly reloads the pattern to pulse-width modulate every pixel. I
suppose you
could just send the thing a monochrome, one-bit VGA image and let the
hardware
do what it is supposed to do.

In the early days (when they were still called MMD (micro-mirror device)
TI had a
$5700 projector development kit, but you had to be an approved OEM to even
be permitted to buy one. New commercial XGA projectors with one DLP
chip and
the spinning color filter are now going for about $1000.

Hg-Xe short-arc lamps put out an incredible amount of light, tens of
Watts in each
of the major visible Hg emission peaks, for a 100 - 200 W lamp!

Jon