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DLP4500: Striped artifacts in laser light at 670-690nm

Alexander Hill
Prodigy 50 points
Part Number: DLP4500

Hi - 

I'm reflecting 690 nm laser light from a DLP4500 controlled using the Lightcrafter 4500 control board. After propagating some distance I see distinct horizontal striping that seems to always be aligned with the wide axis of the DLP4500 (i.e., if the DLP4500 is rotated about the laser axis, the striping will also be rotated). I have attached a picture for reference. In the picture I've applied a blazed grating, though the effect happens even if I apply a solid field using the Lightcrafter control software. I do not have a good test of this at other wavelengths, but a cursory test with a 520nm handheld laser does not seem to have the same issue. Also, I have reproduced this on two DLP4500 and one DLP4500NIR and all have the same issue to some degree.  Any advice would be appreciated.

Thanks!

  • 0
    TI__Mastermind 28005 points
    Alexander,

    Thanks for your interest in our DLP products.

    You mentioned using a LightCrafter 4500 to control your system. Are you using the LightCrafter 4500 optical engine for your tests, or are you using the LightCrafter 4500 to drive an external optical engine that you have provided? If so, can you provide your setup specifications?

    Best Regards,
    Philippe Dollo
  • 0 in reply to Philippe Dollo
    Prodigy 50 points

    Hi - 

    We use the Lightcrafter 4500 DMD driver board but do not use the light engine. We've taken the LEDs and lenses off completely so all we have is a bare DLP4500 DMD attached to the original driver board. We then bounce a 690-nm laser off the DMD and use the DMD for steering/holography. The laser is a nice Gaussian beam, but after reflecting from the DMD it develops these stripes regardless of the angle of incidence. 

    Initially I thought the DMD might be toggling between different LEDs, and because we aren't using the light engine there are no LEDs to strobe, our reflected beam would look smeared out. However, it still seems to be smeared out even when I manually select only one of the LEDs in the Lightcrafter control GUI.

  • 0 in reply to Alexander Hill
    TI__Mastermind 28005 points
    Alexander,

    I recommend you start by testing the system using the stock light engine with a basic test pattern (such as a white raster or white ramp) to see if there are any blemishes or faults in the display in a standard test case. If this test passes you may have an issue with your optical setup. If this is the case you may want to review your reference design.

    I hope this helps. Let me know if you get stuck or need further assistance.

    Best Regards,
    Philippe Dollo