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DMD switching

Brigitte de Haas
Prodigy 20 points

I am working with the DMD for a project and I've read that the position of the mirrors changes synchronously with a micromirror clocking pulse. Does this mean that the mirror switches on and off (from -12 deg to +12 deg) when it is in the 'on' position or does it stay on +12 deg? Is there anyway I can ckeck it?

  • 0
    TI__Genius 9935 points

    Brigitte,

    The memory plane for the DMD must be loaded for every binary frame. The following couple of sentences are a "first order" description, which I will elaborate afterwards. The memory cell under each mirror contains a "0" or a "1". When the "reset" pulse occurs, the mirrors flip to the position ("on" or "off", +12 degrees or -12 degrees tilt) corresponding to the binary bit values under them. If the binary value of the cell has changed from its previous state, the mirror flips to the new position. If the binary value of the cell has not changed, then the mirror does not flip to a new position, but remains in its previous state.

    In reality, though, the mirrors are all released by the reset pulse, then either continue to their new opposite state, or resume their same state. This means that the mirrors which are not changing state do move slightly, before returning to the same state as previous. This can be seen by illuminating the DMD with constant illumination, then changing patterns between binary frames while observing the reflected light. For example, if you put all of the mirrors into the "off" state for several frames, you may be able to observe a momentary increase in reflection at and immediately after the reset pulse. Or, if put all of the mirrors into the "on" state, you may be able to observe a slight dip in the reflected light at and immediately after the reset pulse.

    The visibility of this reset variation in light will be very dependent on the numerical aperture (NA) of the pickup lens. The wider the cone of pickup, the more visible will be the slight variations - and vice versa.

    I hope this helps.

    Best regards,

    Pascal