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DLPLCR6500EVM: Performance difference between HDMI and pattern-on-the-fly modes

Douglas Kelly
Prodigy 10 points
Part Number: DLPLCR6500EVM


We have been using the DLP6500 to modulate light in a custom-built microscope. We have found that by changing from pattern-on-the-fly mode to streaming HDMI we see a significant (~4x) decrease in apparent contrast. In the comparison, identical features were projected and all other aspects of the optical set up the same. Effectively we are seeing a "glow" from OFF pixels that decreases the signal-to-noise in comparison with the ON pixels. 

Digging a little deeper, we found that as we increased the frame rate of the camera that we use to record the projected pattern we saw beating in the light from the "OFF" pixels until 60 Hz (~monitor refresh rate), at which point the background remains constant. 

Is there some synchronisation setting for video mode that we have missed? Or any other troubleshooting steps that we could use to bring the (effective) contrast ratio projecting patterns streamed over HDMI up to that of pattern-on-the-fly mode?

  • 0
    TI__Guru 54705 points

    Hello Douglas,

    Welcome to the DLP section of the TI-E2E Community.

    For clarification are you using "Video Mode" (i.e. like a monitor) or are you using Video Pattern Mode?

    If Video Mode, then it is governed by what the video source is putting out.  If it is Video Pattern Mode, you must define how it will treat the input bits, and set exposure time and bit depths.

    You need to synchronize the camera to the video sync of the HDMI in any case, or you will see all sorts of strange effects in the camera image.  The camera should be set to the same frame rate as the video output. 

    If you are using Video Pattern Mode, you will want to set the exposure time of the output to be slightly less than that of the camera. This will ensure that the camera captures all of the light from the EVM.

    Fizix