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I've posted comments/questions on this in a couple of threads but got no replies, so I'm trying again. :p


I've noticed that in pictures I've seen of various Archimedes or SCR color wheel designs, posted here and at TI's site, they have different spiral patterns. Mark Hunter posted one (back in 2001!) that seems to be a fairly early prototype with essentially 2 spirals, so that for each revolution of the wheel you'd get 2 complete color sequences -- somewhat similar to the current RGBRGB wheels.


However there is a picture in TI's . SCR white paper (see Figure 3) which shows an SCR wheel with a much higher ratio of color sequences per wheel revolution -- looks like about 33 by my count. It would seem that while any SCR wheel is still going to yield only one color at a time for a given group of pixels, this would result in a much smaller grouping with smoother distribution, that changes at a higher frequency than even current 5x color wheels. If the wheel rotational speed is kept at the same 150 Hz (2.5 * 60 Hz) of most HD2 projectors, this might be effectively like an 83x (33 * 2.5) color wheel, not even considering the scrolling effect which breaks each field into different colors. Given that very few people can detect rainbows on the 5x color wheels, and assuming that the 33-spiral wheel is closer to a production Archimedes wheel than the 2-spiral wheel, I think this could be pretty good stuff. Of course the processing and timing would get pretty intense in some of the above so maybe a 60 Hz wheel would be required so the DMD could keep up. I can see why it's taken TI a while to get the kinks worked out
 

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Paul,


The SCR wheel does not spin at the same rotaional speed. It is slower for the very reasons you just listed. All the same, the tighter color sequences do create a better than 5x experience for HT use. Good catch.
 
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