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  • TI Thinks Resolved

DLPDLCR4710EVM-G2: Color fringes with projection lens removed

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Replies: 15

Views: 798

Part Number: DLPDLCR4710EVM-G2

Hi! 

Our optical set up requires that we use the projector without its own projection lens. However, we noticed vertical color fringes on the DMD (picture attached). Anyone else has this issue or knows a workaround? It happens even in monochrome- the fringes are then light and dark bands of the same color. 

Thanks!

Cher

  • Hello Cher,

    Did the projection look correct before removing the optics? It will be required to use projection optics in order to obtain a good image.

    Thanks,
    Kyle
  • In reply to Kyle Rakos:

    Hi Kyle, yeah the projection was correct before removing the optics.

  • In reply to Cherlyn Ng:

    Hi Cherlyn,

    Is this an image directly of the DMD? Or are there other optics in front of the DMD as well?

    Thanks,
    Kyle
  • In reply to Kyle Rakos:

    Directly of the DMD. No other optics in front. Thanks Kyle!
  • In reply to Cherlyn Ng:

    Hi Cherlyn,

    Please share the picture of the set-up. We needs to get understanding of what you are looking into.

    Normally there is TIR prism infront of DMD. Please conform are you taking picture without removing Prism.

    In addition , the image should taken with camera focus on ON pupil.

    Thanks,
    Navneet
  • In reply to Navneet Singh:

    Hi Navneet, we did not remove the prism. Here are photos of our set up. Thanks! -cher

    Untitled-1 copy.pdf

  • In reply to Cherlyn Ng:

  • In reply to Cherlyn Ng:

    Hi Cher,
    The artifacts in the image for the following two reasons:

    1. Camera image capture is not in sync with color refresh of the DMD. It is causing color fringes in the image. The DMD mirrors are modulated to create a gray value . Therefore you would notice similar effect in the monochrome image too. In addition, when you focus the camera directly on to DMD, the light intensity is too high and camera reduces exposure time to prevent saturation. Short exposure also makes this effect visible. This will not be true when projection lens is mounted.

    2. The camera is also capturing flat-state and off-sate light. In a projection lens these stray lights are blocked by an aperture.

    I hope this explain the image artifact you are observing.

    regards,
    Vivek
  • In reply to Vivek Thakur:

    Hi Vivek, thanks for replying. 

    1. There were color fringes even when we simply projected onto a white screen and looked with our naked eyes without a camera. 

    2. We could see in full grayscale, so it was't just flat and off states light.

    Besides, we found (with another DMD) that putting a diffuser in the illumination path before the DMD removes the fringes. Is there any way to do the same for this projector? 

    Thanks! -cher

  • In reply to Vivek Thakur:

    1. There were color fringes even when we simply projected onto a white screen and looked with our naked eyes without a camera.

    2. We could see in full grayscale, so it was't just flat and off states light.

    Besides, we found (with another DMD) that putting a diffuser in the illumination path before the DMD removes the fringes. Is there any way to do the same for this projector?

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