Here's a good slide show covering how PICO projectors operate:
http://www.slideshare.net/Funk98/pico-p ... r-12565671
The problem that people are having with getting a PICO projector to work with a 3D printer is that the spectra produced by the three LED's or three lasers used (Red (635nm), Green (530nm) and Blue (460nm) in the PICO projectors are outside the sensitivity range of the resins they are using.
If the PICO projector only emits light in the three sprectra shown in the following graph then only resins sensitive to those same spectra will work.
http://upload.wikimedia.org/wikipedia/c ... pectra.png
One solution is to just use unmodified PICO projectors with resins that cure in the UV through Blue in the visible spectrum.
See this thread for more info: viewtopic.php?f=12&t=84&start=210#p9616
PICO Projectors and Lithography
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