POLARIZED

Polarized 3D glasses create the illusion of three-dimensional images by restricting the light that reaches each eye, an example of stereoscopy which exploits the polarization of light.

To present a stereoscopic motion picture, two images are projected superimposed onto the same screen through different polarizing filters. The viewer wears low-cost eyeglasses which also contain a pair of different polarizing filters. As each filter passes only that light which is similarly polarized and blocks the light polarized in the opposite direction, each eye sees a different image. This is used to produce a three-dimensional effect by projecting the same scene into both eyes, but depicted from slightly different perspectives. Since no head tracking is involved, several people can view the stereoscopic images at the same time.


System construction and examples
Light reflected from a motion picture screen tends to lose a bit of its polarization, but this problem is eliminated if a silver screen or aluminized screen is used. This means that a pair of aligned DLP projectors, some polarizing filters, a silver screen, and a computer with a dual-head graphics card can be used to form a relatively high-cost (over US$10,000 in 2010) system for displaying stereoscopic 3D data simultaneously to a group of people wearing polarized glasses.


On TV and computer screens
Polarizing techniques are most simply used with cathode ray technology, as polarizers are used within ordinary LCD screens for control of pixel presentation — this can interfere with these techniques.

In 2003 Keigo Iizuka discovered an inexpensive implementation of this principle on laptop computer displays using cellophane sheets.


History

Main article: 3-D film
Polarized stereoscopic pictures have been around since 1936, when Edwin H. Land first applied it to motion pictures. The so called "3-D movie craze" in the years 1952 through 1955 was almost entirely offered in theaters using polarizing projection and glasses. Only a minute amount of the total 3D films shown in the period used the anaglyph color filter method.

In the 2000s, computer animation, digital projection, and the use of sophisticated IMAX 70mm film projectors, have created an opportunity for a second wave of polarized 3D films.


Health care
In optometry and ophthalmology, polarized glasses are used for various tests of binocular depth perception