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point of + and - tilt angles of micromirrors in DMDs

Mike Sh.
Expert 1405 points
Other Parts Discussed in Thread: DLP3010, DLP4710

My guess it is to allow to choose the side to put the illumination source for side illuminated DMDs (eg. DLP3010) and chose between top and bottom for bottom illuminated DMDs (eg DLP470TP). If not I would like to know what or what else it is useful for.

  • 0
    TI__Mastermind 23090 points
    Hi Mike,
    Could you please further elaborate your question? Are you asking why DLP Mirror architecture is bi-stable (on and off) along tilt axis?

    Are choice of illumination direction - side Vs bottom?

    regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Expert 1405 points
    "Are you asking why DLP Mirror architecture is bi-stable (on and off) along tilt axis?"

    Yes
  • 0 in reply to Mike Sh.
    TI__Mastermind 23090 points
    Hi Mike,
    Illumination direction bottom or side (for TRP pixel) is decided by the orientation of the pond of mirrors around active array. Please see table 2 on page 21 of DLP470TP DMD. www.ti.com/.../dlp470tp.pdf

    These pond of mirrors are permanently oriented in one direction and they do not switch. They need to be in off-state for incoming illumination light.

    From pond of mirror perspective, you could interchange between left & right for side illumination; similarly between bottom and top for bottom illuminated DMD. However, the windows and aperture on DMD is optimized in size and placement for once side only. Therefore it is typically either side illuminated from left or bottom illuminated.

    The bi-stable architecture of mirror is key to consistent and uniform operation of million of mirror within a device and across devices. It eliminates any oscillation and facilitated fast switching.

    I hope this explain.

    Regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Expert 1405 points

    What is the actual purpose of Pond Of Micromirrors? Are they justa byproduct of DMD manufacturing?

    And it sounds to me if one wants right side or top side illumination he can simply rotate the DMD 180 degrees?

  • 0 in reply to Mike Sh.
    TI__Mastermind 30875 points
    Hi,
    Pond Of Micormirrors are the mirrors around the active mirror array, the only difference is that these are not addressable and always hold value of '0' in them. Basically black around the active mirror array.
    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Expert 1405 points
    as I asked, What is the actual purpose? Not what are they.
  • 0 in reply to Mike Sh.
    TI__Mastermind 23090 points
    It is part of manufacturing process to ensure uniformity and consistency of mirror characteristics.
    regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Expert 1405 points
    hm, how does it help with uniformity vs just overspilling?
  • 0 in reply to Mike Sh.
    TI__Mastermind 23090 points
    Hi Mike,
    It is manufacturing specific question and beyond scope of the forum.
    regards,
    Vivke
  • 0 in reply to Vivek Thakur
    Expert 1405 points

    Okay. But I still feel like I don't quite understand how the TRP micromirrors work. The docs mention the benefits but not how they acually work. From what I can see in the diagrams the rotation is not only in one axis but both pitch and roll. Is this to have the unused light redurected to a more convenient angle? I'm asking because my optical engineer needs to know where to lace the absorber for the DLP4710 and also how to properly design the RTIR prism.

    There is one diagram (Figure 1) here for the +-12 degree DMDs but only one axis is illustrated for those.

    However in this page illustrating the angles for the +-17deg DMDs the micromirror is rotated in two axis.

  • 0 in reply to Mike Sh.
    TI__Mastermind 23090 points
    Hi Mike,

    The TRP pixel stands for "Tilt and Role Pixel". The mirror first tilts by 12 degree along a diagonal and than roles by 12 degree for on and -off. It is creates a compound 17 degree angle.

    Please refer to the "Optical Engine Reference Design for DLP3010 Digital Micromirror Device" www.ti.com/.../dlpa079.pdf
    The figure 1 in page shows location of ON-state, OFF-state and Flat-state light. The incoming light, ON state and Flat state are in one plane.

    For the side illuminated device the OFF-state is at 45 degree angle and at 48 degree of separation from ON-State.

    For bottom illuminated pixel, it will be just rotate, the OFF-state will in 45 degree to right (upper) with a 48 degree of separation from ON state.

    regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Expert 1405 points
    Thank you. Would be helpful to have that info on the other product pages which use this architecture as well.
  • 0 in reply to Mike Sh.
    TI__Mastermind 23090 points
    Thanks your feedback. I will pass it to our team.
    regards,
    VIvek