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I'm hardly an engineer and probably would not take the time to test out my concept, but it seemed like a good idea, so I'll throw it out here. Hopefully, this is a good place to discuss such and idea.


I'm thinking it would be possible to design a passive, and active, 3D system for a projector by using something akin to the color wheel of a DLP projector, but instead of colors being on the wheel, the polarizers normally used in passive systems would be on either side. That is, one half of the circle would have a polarizer for one eye, and the other side the other polarizer. The wheel would then be synced with the refresh rate of the projector to show every other frame in one polarization, and the other corresponding frames in the other polarization. With 3D content designed for active shutter-based systems, that showing frames alternatively for each eye, the content may be instead seen with regular polarized glasses by each eye seeing every other frame, as is done with active shutter glasses, by each eye's polarizer blocking every other frame's light.


This seemed like an interesting idea for an alternative to the expensive active shutter solutions we have, which require hundreds of dollars to be spent on glasses. It would only require the purchase of one device to make the same concept apply, while leaving the cost of the glasses insignificant.
 

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I expect that the circular motion of the color wheel will cause the angle of the polarized light to change as each polarizing segment of the wheel rotates through the beam. Thus requiring the audience to constantly bob their heads to the right or left in order to maintain the 3D effect.


I think something like the Dolby 3D system which uses RGB for one eye and a slightly different set of RGB frequencies for the other eye would work better with a color wheel. The 2D stuff could just use the same image for both eyes, maybe with a different calibration.
 

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If you want passive, you can sometimes find the old computer version of the "Z-Screen" for sale on Ebay. The Z screen is what RealD uses to passively polarize the image coming out of the projector, but the technology was first used on high end CRT PC monitors to aid 3D imaging in the healthcare field.


I had one for awhile but eventually decided to go with a conventional active system as it was hard to get a good sync for the Z screen and then I would have had to buy a new screen to reflect back the polarization.


If you're serious about it, there used to be a guy on this forum that was selling new polarization screens to place in front of projectors.
 

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Some company is making a device to do it but all you are really doing is eliminating the need to wear the active glasses. The device swaps polarity based on the IR signal for the active glasses. So you still need a silver screen and you aren't gaining any image brightness. For the price of the device, you would be better off spending the extra money to do a dual projector setup. You could buy 10 to 20 sets of the active glasses for the price of the single projector polarizer unit.
 
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