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DMD tilt angle

Sheng Xiao
Prodigy 10 points

Hi,

From the DMD manual, both the bias voltage and addressing voltage will determine the mirror state. The bias voltage Vb is the same on both side of the mirror. And the addressing voltage (dual CMOS memory state) is always opposite on two side of the mirror, either (Va, 0) or (0, Va). The next frame will be preloaded into the CMOS memory which changes its state. And the mirror can only switch state when the bias voltage is reset.

But if the bias voltage is applied and the mirror is in some state, it seems that depending on the CMOS memory state (either (Va, 0) or (0, Va)), there should be two voltage situations applied to the mirrors, which are (Vb + Va, Vb) or (Vb, Vb + Va). Will this lead to two different mirror angles in that state? And does it mean that the mirror actually have 4 different stable tilt angles, which depends on the current and next frame transition (Stay ON, Stay OFF, Switch ON, Switch OFF)?  

Thank you! 

  • 0
    TI__Guru 54705 points

    Hello Sheng,

    Welcome to the DLP Advanced Light Control section of the TI-E2E Community. 

    When mirrors are landed, the spring tips primarily determine the tilt angle, but bias voltage and address voltage do affect the tilt angle slightly.

    The effect of the difference between a stay or switch state is quite small - on the order of 1/5°.  In a well designed projection system this variation will not cause any discernible difference in brightness at the screen/target surface. In very small NA systems, it is possible to see the difference.  This variation is not referenced since it is well within the tilt spec of 12° ± 1°.

    Fizix