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Fastest DLP refresh with slowest color wheel.

Discussion in 'Projectors' started by smithgi, Oct 19, 2007.

  1. smithgi

    smithgi Member

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    I have a strange requst, I need to get a very fast frame rate for an animation project and am trying to work out the best approach. I know some sharp projectors can do a 200hz vertical refresh, but I'm trying to use a technique that uses red/green/blue to allow me to display 3 frames in one. i.e By encoding 3 frames into 1 using r/g/b and then take advantage of the fact that DLP projects a sequence of RGB, this way I can increase the frame rate to 600.

    However, to do this, i need to find an old DLP projector that has a color wheel that spins only once per frame otherwise each color will be projected more that once per frame and the effect will not work.

    Presumably only the 1st generation DLP projectos would have a single speed color wheel.

    If anybody has any ideas how to get 300+ frame per second from a projector without buying a TI DLP exolorer kit I'd be grateful to know how.

    I know that the human eye can only resolve about 100hz, but thats not important for this project.

    regards

    Gav
  2. cyberheater

    cyberheater Member

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    It won't work because the projector will 'sample' the incoming video at 60 hz, decode it, resize it and then display it using all the colours of the wheel even if they are not used.
  3. smithgi

    smithgi Member

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    That can't be right surely. If a projector has a vertical refresh rate of 200hz, and you output a 200hz vidio signal from a graphics card, then surely, the projector would display all 2 frames, not 60 as you mention.

    As for the color, if you projected a pure red image, then I believe that when the blue and green parts of the color wheel where in front of the light beam, the DLP mirrors would deflect all the light away from the lense and so not project anthing.
  4. pragmatic

    pragmatic Previously gazbarber

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    It all depends on how the electronics inside react to the input signal ...
    An example of this is the 1080P 24Hz judder effect, idealy a projector should be able to take in a signal of this type and just display it on the screen at either 24fps or a multiple of that, some for example a few mitz projectors, accept a 1080P 24Hz signal but then output it as 60Hz and so introduces a judder that shouldn't exist.

    Feeding the projector via a computer/vga port would hopefuly overide some of the video processing but its an entire model/model basis. Is there no chance you could not just have a set of filters on the outside of the projector switch at the required speed (means a custom job and more work though) unless ofcourse you want each coloured frame to be different (and faster than the eye can see?).

    Another thing to take notice of is that most DLP projectors don't have just RGB segments on the colour wheel, but also a white and/or other coloured segments too.
  5. JagoUK

    JagoUK Active Member

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    would you be this gav?

    http://answers.yahoo.com/question/index?qid=20070727202635AAMumhs

    :D

    tbh im not sure if dlps ever had a 1x colour wheel. and tbh i dont think having a 2x or 4x colour wheel would make it any different for your purposes. it would mearly refresh the image again (tho i suppose you may get some kind of judder, but i think it would be too quick for you to notice)

    EDIT: On the other hand you could always buy 3 dlp's and put colour filters infront of each one and feed them with a splitter box :thumbsup:
  6. smithgi

    smithgi Member

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    Yup, thats me.

    I'm pretty sure the first gen DLP projectors have a 1speed color wheel. They were the ones most likely to suffer from rainbow effect.

    2 speed or more is no good for me, as it means that using the RGB trick, the frames would get repeated.

    I believe the sharp xg-nv7xu might be ideal, as it does up to 200hz over VGA and from what I can deduce has a single speed color wheel.

    Anybody have one that they can spare or do some tests for me?

    Gav

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