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400 microsecond delay between HDMI frames

Logan Clark
Prodigy 80 points

Hello,

I'm using the lightcrafter in 1 bit 1 color mode over HDMI to project patterns at 1440 Hz. However, I notice that between each frame (i.e. after every 24 patterns) there is a roughly 400 microsecond delay before the next frame starts (measuring the output light with a photodiode). Moreover, it seems that all mirrors turn "off" during this 400 microseconds regardless of the settings in the previous frame.

Is there any way to eliminate this 400 microsecond delay or at least have the lightcrafter continue displaying the previous pattern during the delay?

Thank you!

  • 0
    Prodigy 80 points

    Alternatively, what are the mirrors themselves actually doing during that dark period? Are they turned off or are just the LEDs turned off? In the long term I'm intending to remove the LEDs, and if the mirrors can be made to remain in their previous state during the 400 microsecond delay then that is sufficient.

    Thanks in advance!

  • 0 in reply to Logan Clark
    TI__Mastermind 30875 points

    Hello Logan,

    Welcome to DLP&MEMS forum.

    The mirrors continue to hold the last 1bpp pattern data during the 400uSec dark time. The illuminators alone turned OFF.

    At 60Hz the available time is 16667uSec in which the first 1bpp pattern display (illuminator turned ON) occurs at 225uSec from the VSYNC and the illuminator turned OFF after displaying last pattern at 16541uSec from the VYSNC. So effective time utilized for displaying will be 16541 - 225 = 16316uSec.  This will give about 350uSec of dark time (16667-16316). You may also want to check the external video signal actual timing it may be like 59.9Hz.

    So in short the answer to your question is during this 400uSec dark time the last  1bpp pattern continue be available on the DMD.

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Prodigy 80 points

    Thank you very much Sanjeev! That's exactly what I wanted to hear.

    Logan