How do 3D glasses work?
All of them work by displaying a different image to each eye but how they do this varies. The simplest type use red and green lenses and two slightly different images printed on top of each other, one in red and one in green. The eye with the green filter only sees the green image while the other one only sees the red one. Your brain thinks that the two different images are of the same thing and so the differences between them must be due to some bits of the image being nearer or further away. Red and green lenses work well for printed materials, for 3D movies two different projectors with polarizes are used, the lenses in the 3D glasses also contain polarizes and so each eye can only see the picture from one of the two projectors. This has the added advantage that the glasses just look like normal sunglasses. 3D glasses for home computers work by blocking each eye in turn very quickly. The computer then changes the image it is displaying at exactly the same time so that each eye sees
