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Is TI looking into better stray light absorption on the DMD level?

Dylan Seeger
Prodigy 80 points

I'm just curious if there's been any development since the inception of the DarkChip 4 DMD almost a decade ago to further reduce light scatter on the DMD level. For several years I've been excited hearing about all the uses that the VantaBlack carbon nano-tube material has brought to optical telescopes and other optical applications.  Now I see that there is a spray on application that closely meets the original VantaBlack material for light absorption. This new Vantablack S-VIS nano-tube compound seems perfectly suited to be used as an extremely dark light absorption material that can be used behind the mirrors and even on the front facing housing to dramatically improve light scatter and improve on/off and ANSI contrast performance. Obviously the DMD chamber would also need to be coated in this material for the best contrast performance, but seeing how this part of the optical engine doesn't typically have a large surface area it could be coated with this material an a relatively cheap level. 

I'm coming at this from a home theater projection perspective. I absolutely love a DLP image, but over the pasts 6 or 7 years the performance gains in contrast with reflective-LCD based technologies from JVC and Sony have increased to the point where DLP simply looks washed out by comparisons because the performance difference in contrast has widened immensely. There haven't been any meaningful increases in potential contrast performance on the DMD level since the DC4 DMD came out. I'm just hoping something like VantaBlack could potentially help. 

Please feel free to comment if I'm mistaken, but couldn't something like VantaBlack help bring DLP closer to LCoS reflective-LCD panels in terms of on/off contrast performance given a manufacturer also used this material when designing the light engine? 

If you're not familiar with VantaBlack, you can read about it here:

www.surreynanosystems.com/vantablack

  • 0
    TI__Prodigy 675 points

    Hi, Dylan.  Thanks for posting.

    There are two types of contrast that are discussed for projector specs - ANSI contrast and full-on/full-off (FOFO) contrast.  FOFO measurements have a tendency to be highly favorable on datasheets when adding in the impact of auto-irises and illumination dimming, but the spec has little correlation to image quality. 

    A metric that is highly correlated to real world image quality is ANSI contrast.  DLP projectors typically outperform the competition in ANSI contrast. With single chip DLP, we don’t have the recombination optics required of 3 panel systems, so we have less potential for light scattering.  Evan Powell, of Projector Central, wrote a helpful article on contrast:

    There are multiple system-level enhancements for contrast (such as auto-irises previously mentioned) that system integrators and projector brands are implementing.  The use of Vantablack inside, say, an optical engine might be such an idea that could be explored by any projector technology.

  • 0 in reply to Raecine Meza
    Prodigy 80 points

    While this may be true in a business type setting where there is no control over ambient light and reflected light, this is not at all true in a well treated darkened theater. And even then, with a well treated theater, you'd be hard pressed to get more than around 400:1 ANSI contrast due to light reflections bouncing back hitting the screen lowering ANSI contrast performance.

    The potential for high ANSI with DLP is there (possibly up to 1000:1 with good optics and a good light engine), but the room and screen ruin any potential for real world ANSI contrast ever getting that high. So what you end up with is a DLP projector with real-world /off the screen ANSI of around 400:1.  Most LCD based projectors are around 325:1 ANSI. So the large difference you're referencing in ideal conditions measured from the lens (not the screen which is where that measurement matters) is actually a lot smaller than you're leading on about.

    The more important contrast number not mentioned yet is intrascene contrast, which takes both ANSI and on/off contrast performance into consideration. I would say this is the most indicaive number to go off off to judge how contrast overall will look between projectors under the same conditions. There is a considerable point of diminished returns with ANSI contrast when the average picture level (APL) of the video content reaches a certain brightness. Below a certain point, on/off contrast matters much, much more to how well the image appears than ANSI contrast and unfortunately the vast majority of Hollywood movie content is at or below this APL level. So I have to disagree with you when you say ANSI contrast is a more indicative number to judge contrast by as the type of content that home theater projector owners normally watch actually favors on/off contrast performance due to the low APL of the content.

    What I've said above reflects perfectly with my real world subjective take on the matter. For Hollywood movies, unfortunately, on/off contrast matters more. This is something easy to see and demonstrate. In fact, I currently own a DC4 DMD projector with excellent optics which has around 700:1 ANSI contrast measured from the lens. My theater is treated well with black velvet on all surfaces near the screen but even still, measured ANSI contrast from the screen is no where near as high as if you were to measure from the lens. The projector is a Runco Q750i. It has roughly 2000:1 native on/off and around 10000:1 dynamic contrast through Dynamic Black. Unfortunately it does not compare favorably to my other projector, the JVC DLA-RS500. The JVC has 325:1 ANSI contrast and 30000:1 native on/off contrast and a orderf of  magnitude more dynamic contrast. Subjectively the Runco's image appears washed out by comparison once the video content gets even a little dark.

    So back to my question which wasn't answered; is TI looking into ways to increase potential contrast performance? Both ANSI and on/off contrast would benefit if there was a way to reduce light reflections inside the optical engine and on the DMD mirror level. I love what DLP does to an image, but unfortunately the on/off contrast performance between even a high priced 3-chip DC4 DMD projector and current reflective-LCD based projectors from JVC, Epson or Sony has widened substantially over the past 7-10 years to the point where the DLP projector's image isn't even remotely competitive anymore in regards to contrast. Unfortunately on/off contrast is extremely important to the overall image. I was hoping to hear TI has acknowledged this and is actively looking into solutions to help bring on/off contrast performance up.

  • 0 in reply to Dylan Seeger
    TI__Prodigy 675 points
    TI is continually investing in new ideas to improve performance at the DMD-level as well as consulting with the rest of the ecosystem and end equipment designers on elements for the rest of the system (optics, electronics, even software algorithms) that impact resolution, contrast, brightness, and color -- some design decisions representing trade-offs among those top care-abouts. Unfortunately I cannot publicly share details on unreleased features or technology road maps. However, do continue to share your perspective with end equipment providers on your key specs for selecting a Pro AV projector, and we will continue to work with end equipment providers on evaluating chip and system-level design options to meet market demands.