3D Televisions are starting to appear in the market. They work in conjunction with special glasses to show a different image to each eye. These two images have been constructed to have the same horizontal distance as our eyes have. As a result the viewer's brain perceives depth in the image.

The technology is not new but it has not been put into consumer devices before. The shutter glass technique was popularized in the 80's by Silicon Graphicshttp://techpubs.sgi.com/library/tpl/cgi-bin/listdocs.cgi?coll=hdwr and Crystaleyeshttp://www.sharpertechnology.com/stereographics.html in high end CG workstations. The advent of fast update LCD and Plasma displays has enabled it as well as the advent of Stereo films in the cinemas. The new displays update at 120Hz. That's 60 images per second for each eye and that makes the images much steadier on the eyes than previous systems. Also the resolution of the displays is very high at typically HDTV resolution. These changes make it much more likely that 3DTV will not be a passing fad.

There is another technology in use today for 3D Monitors but it is not currently planned for Television. This is called Auto-stereo. No glasses need to be worn and the displays have a number of zones to accommodate an assembled audience. However pixel resolution is lost as a lenticular lens grid is placed over the display screen to redirect the left and right eye views to see different images. Limitations on the viewing angle also means its less flexible than the glasses version which also has full resolution.

Historically there have been a variety of 3D systems that have attempted to gain acceptance in the market - and the game's not over yet.

The standard is red/blue anaglyphic stereo - where the two views are given these hues and the user must wear glasses with red and blue(cyan) filters one for each eye (usually red is on the left eye). This mechanism works best for black and white imagery as the strong red and blue filters make subtle colors very difficult to determine. However it is also widely used for color imagery. The brain is very good at correcting for color imbalances and after looking through glasses like this for a comparatively short time - the viewer will perceive most colors correctly. The big shock is on removing the glasses - the colors will now appear reversed and it will take some time for the eyes and Brain to readjust. Fundamentally this is what makes this technique unpopular. Red and Blue are typically used but any two complementary colors will work as well.

The simplest 3D which does not require any glasses but works on the Brain's desire to place objects moving at different rates makes use of an effect called Motion parallax and the effect is only possible if there is small motion in the picture. In a stationary scene this is simulated by the camera making small circular movements. This is also what causes the technique to be unpopular. No static shots are possible and we are used to seeing "locked off" cameras when (say) looking at closeups of people talking together.

Another approach which also uses the Brain's desire to define the depth of objects based on their appearance is the Pulfrich effect where darker objects appear to be further away. In this case one of the eyes has a darker lens than the other.There is a sister effect which takes advantage of the brain's tendency to think Blue objects are further away than Red objects.

The display hardware is in place. The other thing needed for 3DTV to prosper is content. The driving market force for this is going to be Sport. The addition of a second lens and/or matched camera is required to capture stereo imagery. ESPNhttp://sports.espn.go.com/espn/news/story?id=4796555 have stated that they will be shooting a significant number of games in 3D stereo. 85 in the first year. Some games in the FIFA world cup are being shot in stereo. ESPN have decided to use a cheaper side by side shooting mechanism which compresses the two stereo images next to each other on the same frame. This lowers their costs as they need only regular cameras with a special lens attachment. But the quality is not as good as shooting with two full resolution images.

Sony, Discovery and Imax are also linking to create a 3D channel in the USA for 2011http://www.reuters.com/article/idUSTRE6043BS20100105