A three-dimensional (3D) television (TV) is a device that is capable of displaying special video recordings that contain extra visual information. Various techniques are used to create three-dimensional video recordings, each of which corresponds to different 3D TV technology. These special televisions can then use that extra visual information to create a somewhat realistic image that either appears to have depth or seems to project into a three-dimensional space in front of the TV set. Some 3D TV technology is built right into the television, while other TV sets are referred to as "3D ready" since they require additional equipment to render a three-dimensional image.
The concept of 3D imaging has been around since at least the 1890s, when the first patent was filed for a three-dimensional film process. Test reels of 3D footage were produced in the early part of the 20th century, though a different process was used to film the popular 3D movies of the 1950s. Three-dimensional television also dates to the early part of the 20th century, though it wasn't until the 21st century that new technologies and distribution systems were introduced to create the modern 3D TV.
Techniques such as two dimensions (2D) plus depth, multi-image capture, and stereoscopic recording can all be used to create video data that can later be turned into a three-dimensional image. Each technology creates a unique type of video data that will only work with certain televisions due to the processes involved. A 3D TV designed to use 2D plus depth uses a compressed greyscale video image that is included in the video feed to generate an illusion of three dimensions, while other methods rely on two different images to produce a stereoscopic effect.
There are two main categories that each 3D TV can be separated into based on the equipment that the device includes. A 3D-ready television is capable of producing three-dimensional images only if extra equipment is purchased and installed. This often means a 3D signal adapter that can be plugged into the television and one or more sets of active shutter glasses. The adapter is then used to activate the glasses at the proper intervals to display the 3D image. Other televisions do not require this adapter, as they come equipped with the proper hardware to operate the glasses.
Another type of 3D TV technology which is commonly referred to as "autostereoscopic" does not require glasses. This type of 3D TV is designed to automatically send a different image to each eye of a viewer, creating the desired three-dimensional effect. Since there are no glasses used with this type of technology, a viewer typically has to be a certain distance from the television and within a limited viewing angle in order to see the image in 3D.