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Passive 3D televisions are three-dimensional TVs that use passive glasses that rely on different light waves rather than relying on battery power. The glasses used with passive 3D televisions are polarized in a specific way to block different forms of light for each eye, creating the illusion of depth. This stands as an alternative to active 3D televisions, but may present a problem for people who have trouble perceiving depth. Both the passive televisions and passive glasses are cheaper than the active forms, and the glasses are substantially lighter than active 3D glasses, which require batteries.
To create the illusion of depth and achieve a 3D image, each eye has to be presented with a different image. Not only does the eye have to see another image, but it has to see both at once through each eye, causing the brain to combine the images and create a depth illusion. With passive 3D glasses, a special polarizing process similar to that done with sunglasses takes care of the problem. The difference is that sunglasses dim all forms of light, while passive 3D glasses dim different colors and forms of light for each eye, causing each eye to perceive the image differently.
Passive 3D televisions are any that use these passive glasses. There is usually an option to change between two-dimensional (2D) and 3D viewing, because some people may want to limit their exposure to 3D or would prefer to see a particular movie or show in 2D. Unlike active 3D televisions, which have an infrared device that interacts with the glasses, passive 3D televisions do not include this. The passive glasses also can be used with any passive television, regardless of make or model.
There are some problems with passive 3D televisions, particular to the passive technology itself. Sometimes movies and shows will blur or will not appear entirely 3D, because the glasses are made to work in a general way and can misinterpret light. The 3D effect also can only be viewed from certain angles, so users need to sit directly in front of the television to get the full effect. Concentrating on particular spots on the screen also can cause eye irritation, but this goes for both active and passive 3D glasses.
While there are some trade-offs in image quality with passive 3D televisions, there also are advantages. The biggest one is price, because both the television and the glasses are much cheaper than their active counterparts. Glasses do not use batteries, so chargers are not needed. The glasses also are much lighter, which helps users relax when using the glasses.