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Underlying checkerboard pattern on DLP Pico Projector

Giacomo Calmasini
Prodigy 40 points
Other Parts Discussed in Thread: DLPC300

Hello,

I am shining a laser on the mirror array and observing the resulting image on a camera. There is always an underlying checkerboard pattern on the mirrors. If I send an image through dvi signal what I get is the image superimposed to the checkerboard pattern. Someone was working on this before me so I thought they must have loaded one of the internal test patterns but even if I put it in internal test pattern mode and change the pattern the checkerboard still remains. It is visible even if the projector is turned off. Is there a way to get rid of it?

This image is supposed to be a white rectangle on black background but you can see there is a checkerboard pattern in the background.

I hope I posted this in the right forum.

Thanks,

Giacomo

  • 0
    TI__Genius 11275 points
    Hi Giacomo,

    Could you let us know which evaluation module you are using? Is the the LightCrafter based on the DLP3000 and DLPC300?

    Thanks,
    Clinton
  • 0 in reply to Clinton Rodgers
    Prodigy 40 points
    Hi Clinton,
    Thanks for you reply. I am using a DLP Pico Projector Development Kit Version2. I think it has the DLP 0.17 HVGA chipset so DLP1700 and DLPC100.

    Giacomo
  • 0 in reply to Giacomo Calmasini
    TI__Genius 11275 points
    Hi Giacomo,

    This device is no longer available. I would recommend moving to the LightCrafter platform (based on the DLP3000, DLPC300) for development, if it fits your application requirements.

    It appears that the underlying pattern you are seeing was likely displayed by the previous user of your kit for extended periods of time (maybe weeks or months). A suggestion to reverse this issue would be to place the kit in a warm environment and project the inverse pattern for an extended period of time. How long will depend on how long the previous pattern was left projected.

    Since you are using a laser source, there are other design considerations for your system. If you are looking a single order, there is effectively an aperture created in space and variance in the mirror tilt angle can change the intensity of light observed. Please take a look at section 6 (High De-magnification System Considerations) of the application note below as well as figure 6 (Diffraction Orders with Coherent Illumination).

    www.ti.com/.../dlpa052

    If your optical system does not take this into account, you could potentially project a pattern for only a short time(ex. an hour) and then see similar effects as you are seeing now (i.e. that pattern would persist when you display another pattern).

    Thanks,
    Clinton