DLP: an ideal display technology for HMDs?
Posted: Sat Jun 09, 2012 8:05 am
You guys have really piqued my interest in VR, and now my OCD wont let me sleep!
I admit, I'm pretty much a noob when it comes to HMDs, and optics in particular, but I know my way around a circuit board and engineering concepts enough to be dangerous. With that said, if I just sound stupid, then let me know - maybe I'll actually be able to fall asleep.
So I decided to do a bit of reading and brain racking on the subject, but repeatedly found that LCDs seem to leave a bit to be desired for various reasons. Then there's OLEDs, which for most intents and purposes are not really any different. That leaves us with a few other exotic technologies, and DLP. I had a vague understanding of how DLP worked, so I decided to read up on it and peek at some of TI's introductions and datasheets, and found that this might actually be a very promising solution. Here are a few reasons why:
1. No individual color elements per pixel. Primary colors are reflected off the mirrors in sequential order at a very high rate (in the KHz). Current tech uses LEDs.
2. Slight pixel blurring due to the physical movement of the mirrors, which eliminates the "screen door effect"
3. Very high refresh rates possible, at the expense of luminance detail.
4. All mirror elements have a corresponding 1-bit frame buffer (my own term for it), and all mirrors refresh simultaneously.
5. Up to 1920x1080 resolutions available
I think it might even be practical to get away with using a single DMD for stereoscopy. When energized, each mirror has two possible states (ignoring the fast transitions): -12/+12 degrees. In TV/projector designs, the on state typically reflects the light into the optics, while the off state reflects it onto a heatsink. But what if the DMD was placed towards the front of the HMD with the light source perpendicular to it? That means depending on the state of the mirrors, the light would be reflected either to the left or the right at a 12 degree angle. Like I said before, I'm a dummy when it comes to optics, but I'd imagine it's quite workable (maybe not much more than a well positioned plano concave lens since even a 1080 DMD is less than 1" diagonal?). Of course, you wouldn't want the light that's being reflected away from one eye to be seen by the other, but that could be resolved by simply having an LC shutter on each side. It should even be possible to use a standard DMD controller IC, the only necessary processing would be that one of the stereo frames would need to be a negative of itself.
I got a few more ideas for it, but I'll just shut up for now.. Let me know what you think!
I admit, I'm pretty much a noob when it comes to HMDs, and optics in particular, but I know my way around a circuit board and engineering concepts enough to be dangerous. With that said, if I just sound stupid, then let me know - maybe I'll actually be able to fall asleep.
![Laughing :lol:](./images/smilies/icon_lol.gif)
So I decided to do a bit of reading and brain racking on the subject, but repeatedly found that LCDs seem to leave a bit to be desired for various reasons. Then there's OLEDs, which for most intents and purposes are not really any different. That leaves us with a few other exotic technologies, and DLP. I had a vague understanding of how DLP worked, so I decided to read up on it and peek at some of TI's introductions and datasheets, and found that this might actually be a very promising solution. Here are a few reasons why:
1. No individual color elements per pixel. Primary colors are reflected off the mirrors in sequential order at a very high rate (in the KHz). Current tech uses LEDs.
2. Slight pixel blurring due to the physical movement of the mirrors, which eliminates the "screen door effect"
3. Very high refresh rates possible, at the expense of luminance detail.
4. All mirror elements have a corresponding 1-bit frame buffer (my own term for it), and all mirrors refresh simultaneously.
5. Up to 1920x1080 resolutions available
I think it might even be practical to get away with using a single DMD for stereoscopy. When energized, each mirror has two possible states (ignoring the fast transitions): -12/+12 degrees. In TV/projector designs, the on state typically reflects the light into the optics, while the off state reflects it onto a heatsink. But what if the DMD was placed towards the front of the HMD with the light source perpendicular to it? That means depending on the state of the mirrors, the light would be reflected either to the left or the right at a 12 degree angle. Like I said before, I'm a dummy when it comes to optics, but I'd imagine it's quite workable (maybe not much more than a well positioned plano concave lens since even a 1080 DMD is less than 1" diagonal?). Of course, you wouldn't want the light that's being reflected away from one eye to be seen by the other, but that could be resolved by simply having an LC shutter on each side. It should even be possible to use a standard DMD controller IC, the only necessary processing would be that one of the stereo frames would need to be a negative of itself.
I got a few more ideas for it, but I'll just shut up for now.. Let me know what you think!