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DLPLCR6500EVM: Two reflected light beams from the DMD screen are not at the same level when I shine a parallel beam vertical to the DMD screen.

Yayao Ma
Prodigy 10 points

Part Number: DLPLCR6500EVM

I shine a parallel light beam to the DMD screen vertical to the DMD screen and expect to get the two reflected light beams at both sides which should be at the same height with the light source. However, it seems that I have to rotate the DMD by around 30 degree to get the two reflected beams at the same level.    

img1 and img2 are correspondent. img3 and img4 are correspondant. I want the two reflected beams at the same level without rotating the DMD. Do I need to set some parameters in the software?

img1 and img3 say how I shine a light onto DMD which is rotated by different angle.    img2 and img4 are the reflected light beam projected onto the wall.

Hope you can help me. Thank you very much.

Yoolee.

              

          img1                                              img2

      

 img3                                                img4

  • 0
    TI__Guru 54320 points

    Hello Yayao,

    First, welcome to the DLP section of the TI-E2E forums.

    If you measure I think you will find that the angle is 45°.  This is expected behavior.  The mirror orientation and tilt axis is detailed in the data sheet:

    http://www.ti.com/lit/gpn/dlp6500fye - Please see § 6.11 starting on page 23.

    Typically illumination is done from 24° (2X the tilt angle) from the vertical and -45° azimuth from the vector toward the top of the DMD (as shown in Figure 12 of the data sheet). This will result in the projected beam for the "on" state being normal to the DMD window (the reverse of your illumination).  

    This means that your illumination will result in the "on" state beam pointing to -45° azimuth and 24° from the vertical.  Similarly, with vertical illumination your "off" state beam will be at 135° azimuth and 24° from the vertical.  

    Therefore in order to have the beams be at the same level relative to your optical table you will need to rotate the DMD 45° as you have done.

    I hope this helps.

    Fizix