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DLP9000: Origin of light from OFF pixels

Roman Popov
Prodigy 250 points
Part Number: DLP9000
Other Parts Discussed in Thread: DLPC900

When displaying a certain pattern using our DLP projector, we see a dim light in the regions which are not supposed to be illuminated. 

1. I'm trying to understand the origin of this light: Is it due to scattering on the micromirrors even though they are constantly pointing to the 'light sink'? Or is it due to the 'intended' behavior of the micromirrors periodically 'vibrating' to the ON state while the OFF state is prevailing in terms of duration?

2. Could you please advise how can I minimize (better eliminate) the light from the OFF pixels without reducing light from the ON-pixels?

  • 0
    TI__Intellectual 1080 points

    Hi Roman,

    The light that you see in the regions which is not supposed to be illuminated is due to the small amount of light which is not directed towards the sink/not absorbed by the sink

    1. It is definitely not because of the micromirrors periodically switching to the on state. You can verify this by switching the DMDs off and turning on the LEDs projecting the DMDs if you have the control.

     2. To improve the contrast, without affecting the brightness, optics play a major role. The light getting reflected off from the DMD in off state needs to be minimized by placing the optics in such a way that most of the light from off micromirrors goes to the sink or having a better absorbing one. We have algorithms in display applications like Dynamic black for improving the contrast.

    Hope this helps.

    Thanks

    Sachin

  • 0 in reply to Bhatta
    Prodigy 250 points

    Hi Sachin,

    Thanks for your response. Could you please tell a bit more what you meant by 'algorithms ... like Dynamic black'?

    Regards,

    Roman

  • 0 in reply to Roman Popov
    TI__Intellectual 1080 points

    Hi Roman,

    DLPC900 controller doesn't support Dynamic black. We vary LED currents based on the image content to improve contrast.

    These algorithms are supported only for display applications.

    Thanks

    Sachin