Three-dimensional displays have made it to televisions and even handheld video game consoles, but there are limitations. One is that the illusion of three dimensions starts to break down if the viewer looks at the image from a range of different angles. Furthermore, 3-D displays can produce headaches and even nausea.
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ZSpace, a California technology company, has designed a large display that preserves the 3-D illusion better than almost anything out there, because it tracks the viewer's head. It still requires glasses, but the glasses have small reflective tabs on them that allow a computer to track the exact spot the user is looking at.
Ordinarily a 3-D display presents two images, each offset a tiny bit from the other, or with different polarizations. The images flicker in such a way that each eye sees a different image - that's where the glasses come in, to help the eye focus on the image it's "supposed" to.
The problem is head movement or standing away from the center of the image. When you move, the image projection is off because in most displays it only goes in one direction, straight out to the middle of the room if it's a 3-D television.