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The 3-d televisions currently available use active
The 3-d movies played in cinemas use passive 3D technology. Two images are shown concurrently. Audiences wear polarized glasses which filter the images into left and right eye to produce the 3D effect.
3D televisions using shutter glasses such as Toshiba 55WX800U or Samsung UN55D8000 have active lenses which flicker in sync with the refresh rate so that each eye only sees the frames that are intended for it to view. This is what's called active 3D, or alternate frame sequencing. Typically these televisions have a 120 frames per second refresh rate allowing it to show 60 frames for each eye per second. The glasses they have uses a filter that movies on and off in sync with the television set to generate the proper picture to each eye. Most of the 3-d televisions currently available use this type of technology.
Obviously, ideal home 3D would say goodbye to the special glasses, simply because watching a movie ought to be a group experience. At present you can find a couple of manufacturers who make 3-d displays that are viewable with no glasses. These television sets work with optical elements as part of the screen to generate the 3-d illusion. They're flat panel televisions which use lenticular lenses or parallax barriers to supply different pictures to each eye.
The drawback to most of these technologies is they are built to produce a good 3-d image only at a specific distance and across a narrow range of viewing angles. The lenticular lens system used by LG, for instance, needs an ideal watching distance of exactly 13 feet. Parallax barriers, like those used by Sharp's 3D television sets, may be either liquid crystal formed lenses or hard ones. The liquid crystal style has the benefit of being able to be switched off to allow traditional TV viewing on a single set.
In more recent years there have been alternative types of these displays show up, for instance Integral Imaging that utilizes tiny images which are seen through an array of spherical convex lenses which the human brain then views as a 3D image. It is a hard lens form of the parallax barrier. HoloVizio has come up with a kind of parallax called 'continuous motion' which uses 'voxels.' These are substitutes for pixels that project several beams of light in numerous directions simultaneously.
If these glasses-free types of 3D televisions become popular, people would need to design rooms that were long and narrow to allow for ideal viewing by the most people. In the mean time, the active 3D technology continues to drop in price, enabling more and more people to afford these types of configurations, which also work together with 3-d Blu-ray dvd players and 3D movies online.