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@ AJ Abrams


thanks also for the link; it shows, that the new wheel will become more reality. It was told and rimours about this new color- wheel since a few month - how long, I didn´t know exactly.


then main point of this wheel - as told - shall be less or still no rainboweffects


hb
 

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It is interesting to note that the new colour wheel boosts light output by approximately 40%. That is good news for those who have large screens. I wonder when we can expect the new colour wheel to make its way into commercial products. My guess it that it will be at least another year.
 

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Reducing rainbows is not on the agenda. Rather, they are trying to get all three colors on the DMD at the same time so they can reuse the wavelengths of light that are reflected off each dichroic color segment by reflecting them back so they'll possibly go to a different color. This will increase light efficiency only.


If you look at the design, it appears that each color forms a rectangular horizontal band scrolling vertically on the DMD. This won't help rainbows unless the color changes are more frequent, since so much of the screen is still one color at a time.


Rainbows are reduced when the same color is cycled more often for each 1/60th second field. This makes the rainbow into more and narrower bands, and eventually the brain will perceive the bands as just a trail of a single color in the same way you don't see the shadow mask on a direct-view TV unless you sneeze on it.


The prototype mentioned has 126 color segments rotating at only 660 rpm. This works out to 7.7X, where current wheels are 5X. Not much of an improvement.
 

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@ FlatusM


That´s also arguments sounding very interesting. Hopefully a prototype will be shown at INFOCOMM.


As I understand you,


better color saturation - more likely to a 3 DMD chip unit,

less lamp power necessary - longer lamp life with less cost

calmer and less noise picture


please correct me, because it looks, that you will be an engenier at this project


hb
 

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FlatusM,


7.7 seems like a big jump to me, a little better than a 50% improvement in speed.


Regards,

Glenn
 

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The SCR wheel was shown last year at Infocomm.


Personally, I wouldn't bet on it being in projector models for quite some time. The firmware is going to be very tough.


I think many more subtle artifacts will be introduced with this design. I wouldn't count on it solving the current rainbow "situation".


We will just have to wait and see, but for the most part I think the SCR is going to generate small gains when it is eventually implemented.


I also think Barco's idea of letting the bulb light intenually pulse brighter during the red segment of the color wheel (red is usually very dim) will have a greater benefit than the SCR.


-Mr. Wigggles
 

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I think that the SCR wheel not improve the rainbow effect by itself. When I started off with this post, I was thinking that it *would* improve things... but when I got to the end I realized that I was wrong!


Currently, each field (red, green, blue) is flashed onto the screen. This happens 60 times per second. Systems with higher speed wheels will flash the colors at a higher rate.


Worse case scenario (single speed wheel), there will be 1/180th of a second between when your eye sees the red field and when it sees the green field. When you move your eyes across the screen, the individual fields hit your retina at different positions. This causes you to see a rainbow because the fields are no longer lined up due to your eyes moving. When you keep your eyes perfectly still (which is almost impossible) and don't move your head, you typically don't see rainbow.


Now, take the SCR wheel. Simplifying what it is doing, it scrolls three colors at once up the screen. Worse case scenario (single speed SCR wheel) it will scroll all colors up the screen in 1/60th of a second, or once per refresh frame. Lets also pretend that it divides the screen up into 3 rectangles, one for R, G, and B that it is scrolling. In reality, it will be divided up into some sort of arc shaped pieces instead of rectangles.


Since the wheel is refreshing RGB 60 times per second, and the screen is divided into 3rds, there will still be 1/180th of a second between when your eye sees one color and when it sees the next color for a given pixel.


Therefore, I still see the potential for rainbow. However, it might not be as visible... or maybe it could have worse artifacts :|
 

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It's very interesting the discussions put up by FlatusM, Mr.Wiggles, and Pultzar on the theories of reducing the rainbow artifacts, etc.


I for one am not sensitive to the rainbow artifacts (thank God!?). However, like Mr.Wiggles said, we'll yet to see what will be delivered when the product is put on display.


If the wheel is to spin faster, will it make the noise louder?

I'm more interested in having the design of more cost efficient and at the same time better bulbs, really.
 

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Discussion Starter · #12 ·
I've wondered if the scrolling nature of the new color wheel itself might effect the way our brain perceives the image. Because we have all three primary colors on the screen at the same time at different points. It might be possible that this in itself changes they way we perceive the rainbow effect. I believe that aspect needs investigation.
 

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I agree highly with firmware issues.


This thing has to deal with non linear changes to the DLP in multiple regions. What I mean by this is that the colours are "swirled", in that a horizontal line drawn across the DMD will have different colours at different points. I can just imagine the computations needed for that, and the great potentiontial for inaccuracy and pixels with more than one colour on them....


However, I am against the plan Barco has. Many of the DLPs I have seen, most recently the Seleco HT250, seems to already have issues with strobing, pulsing light. No need to intentionally add to that problem :)
 
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