I've been thinking just now how something like this could work.
Traditionally they had those red/green filter things didn't they? But they weren't very practical because although it represented depth, you had that horrible red/green colour clash.
So what about polaroid filters? The screen can be made to compose two distinct images out of plane polarised light: the image for the left eye aligns horizontal; the right eye vertical, and then spectators have a pair of polaroid glasses to view it with.
This would mean that you could still watch the picture without the glasses, and still make good sense of it. Plus it means that each eye receives the true colours, not some colour filtered image.
The advantage to lcd/tft technology is that it already has the capability to polarise the light through the liquid crystal.
Say we have a red pixel, and the left eye wants 128 red, the right eye wants 96 red. The the pixel outputs polarised light at an intensity of 160 red (pythagoras) at an polarisation angle of arctan(3/4) (trigonmetry)
That's how I'd try and design it anyway.
