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

ANAGLYPH

Anaglyph images are used to provide a stereoscopic 3D effect, when viewed with 2 color glasses (each lens a chromatically opposite color, usually RED and CYAN). Images are made up of two color layers, superimposed, but offset with respect to each other to produce a depth effect. Usually the main subject is in the center, while the foreground and background are shifted laterally in opposite directions. The picture contains two differently filtered colored images, one for each eye. When viewed through the "color coded" "anaglyph glasses", they reveal an integrated stereoscopic image. The visual cortex of the brain fuses this into perception of a three dimensional scene or composition.

Anaglyph images have seen a recent resurgence due to the presentation of images and video on the internet, Blue-ray HD discs, CDs, and even in print. Low cost paper frames or plastic-framed glasses hold accurate color filters that typically, after 2002, make use of all 3 primary colors. The current norm is red and cyan, with red being used for the left channel. The cheaper filter material used in the monochromatic past dictated red and blue for convenience and cost. There is a material improvement of full color images, with the cyan filter, especially for accurate skin tones.Video games, theatrical films, and DVDs can be shown in the anaglyph 3D process. Practical images, for science or design, where depth perception is useful, include the presentation of full scale and microscopic stereographic images. Examples from NASA include Mars Rover imaging, and the solar investigation, called STEREO, which uses two orbital vehicles to obtain the 3D images of the sun. Other applications include geological illustrations by the USGS, and various online museum objects. A recent application is for stereo imaging of the heart using 3D ultra-sound with plastic red/cyan glasses.Anaglyph images are much easier to view than either parallel (diverging) or crossed-view pairs stereograms. However, these side-by-side types offer bright and accurate color rendering, not easily achieved with anaglyphs. Recently, cross-view prismatic glasses with adjustable masking have appeared, that offer a wider image on the new HD video and computer monitors.

The first method to produce anaglyph images was developed 1853 by Wilhelm Rollmann, a German, in Leipzig.

How anaglyph works
Viewing anaglyphs through appropriately colored glasses results in each eye seeing a slightly different picture. In a red-blue anaglyph, for instance, the eye covered by the red filter sees the red parts of the image as "white", and the blue parts as "black" (with the brain providing some adaption for color); the eye covered by the blue filter perceives the opposite effect. True white or true black areas are perceived the same by each eye. The brain blends together the image it receives from each eye, and interprets the differences as being the result of different distances. This creates a normal stereograph image without requiring the viewer to cross his or her eyes.

In comics
3-D Glasses distributed with special Batman comic books between 1953 and 1964 These techniques have been used to produce 3-dimensional comic books, mostly during the early 1950s, using carefully constructed line drawings printed in colors appropriate to the filter glasses provided. The material presented were typically short graphic novels of a war story, horror, or crime/detective nature similar in content to some modern Japanese manga. These genres were largely eliminated in the US by the rise of the Comics Code Authority. Anaglyphed images were of little interest for use in the remaining comics, which emphasized bright and colorful images, unsuited for use with the viewing and production methods available at the time, which were usually red-green rather than red-cyan.

Today, there are more advanced solutions for 3D imaging available, like shutter glasses together with fast monitors. These solutions are already extensively used in science. Still, anaglyph images provide a cheap and comfortable way to view scientific visualizations.