Comments by "Grak70" (@Grak70) on "How Optical MEMS Won an Oscar" video.

  1.  @PaulFisher ere are several sources of flare in DMD. 1) the material below the mirror itself does show through a bit since it has to be exposed for a mirror to be free of its adjacent companions. While this is typically coated in a material selected to be as black as possible over the desired wavelength range, it’s not perfect. So even if 100% of light directed at the mirror is diverted, there will be some reflected light from the substrate. 2) the mirror can only tilt so far. Ideally you’d direct all the light onto a light dump orthogonal to the exit pupil, but the mirrors can’t flex 90 degrees, only about 10-12. So some light will be scattered from the mirror edges and the anchor via structure, letting a little light through even in the static full off position. 3) ideally, your light source would have total spatial coherence (or equivalently, be a point source at infinity). Real light sources are only partially coherent and have finite size, so some photons impinge on the mirror at a small angle. When these are reflected in the off state, some small amount of light will still go through the exit pupil. 4) the light dump material is chosen to be as black as possible and actively cooled from behind. However in practice, a true black body does not exist, so there will be a tiny amount of reflection which will bounce around the DMD cavity. Some of this will escape through the pupil.
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  2.  @curtlundgren6867  sounds about right. Off state black levels are a major reason DLP became obsolete as LC black levels improved and then LED off-current improved. Then came active LED, OLED, and then quantum dots with ever better black levels. There was a lot of room at the bottom for solid state light solutions, but DLP could never quite keep up. MEMS in general are much more finicky and lower yielding to fab, not to mention they face very different challenges to CMOS. TI repurposed a lot of silicon equipment to make DMDs and I think the ROI of using apples to make orange juice was difficult to justify in the long term, especially with such stiff competition from Japan, Korea and later China. Once China started pumping out decent quality LED displays that kicked even the best DLP’s ass, the margins in display evaporated.
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  3.  @PaulFisher  no problem! By the way, notice that cause 1 and cause 2 are in competition! If you tilt the mirror more, you can divert more light, but then you are exposing the substrate even more. So there is a complex trade-off between the torsion material flexibility and lifetime, the substrate reflectivity, and the view factor of the mirror all interacting with a non-ideal source. Still pretty cool it works at all though!
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  4. Awesome! I asked for this topic last year! I’m so glad to see you explored this cool tech.
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  5. They reflect the light from a source. In the on state, the pixel is bright. When the mirror tilts, it turns the pixel off.
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  6. You joke but this WAS a topic that garnered some serious consideration. The problem, as the EUV folks discovered, is almost nothing worth building reflects light well below 100nm wavelength. X-rays and gamma rays would also cause soft errors in the underlying SRAM, if not permanent midband traps. Even making a DMD that can reflect DUV light is difficult from a materials perspective. I always thought it would be cool to replace the reticle in a lithography scanner with a strip of DMD mirrors and then use that as your pattern master. But UV DMDs like to get stuck in one state or the other after getting beat on with ultraviolet light, and so tend to get an unacceptable accumulation of dead pixels over time.
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