Polarization systems
Polarization systems
cardboard 3D linear polarized glasses from the 80s similar to those used in the 50s. Though some were plain white, they often had the name of the theatre and/or graphics from the movie
Further information: Polarized 3D glasses
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 polarizing filters oriented differently (clockwise/counterclockwise with circular polarization or at 90 degree angles, usually 45 and 135 degrees,[5] with linear polarization). As each filter passes only that light which is similarly polarized and blocks the light polarized differently, 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, the entire audience can view the stereoscopic images at the same time.
Resembling sunglasses, RealD circular polarized glasses are now the standard for theatrical releases and theme park attractions.
In the case of RealD a circularly polarizing liquid crystal filter which can switch polarity 144 times per second is placed in front of the projector lens. Only one projector is needed, as the left and right eye images are displayed alternately. Sony features a new system called RealD XLS, which shows both circular polarized images simultaneously: a single 4K projector (4096×2160 resolution) displays both 2K images (2048×858 resolution) on top of each other at the same time, a special lens attachment polarizes and projects the images.[6]
Thomson Technicolor has produced a system using a split lens which allows traditional 35mm projectors to be adapted to project in 3D using over/under 35mm film. This is a very cost-effective way to convert a screen as all that is needed is the lens and metallic (silver) screen rather than converting entirely to digital.[7] A metallic screen is necessary for these systems as reflection from non metallic surfaces destroys the polarization of the light.
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 linear polarizing projection and glasses. Only a minute amount of the total 3D films shown in the period used the anaglyph color filter method. Linear polarization was likewise used with consumer level stereo projectors. Polarization was also used during the 3D revival of the 80s.
In the 2000s, computer animation, competition from DVDs and other media, digital projection, and the use of sophisticated IMAX 70mm film projectors, have created an opportunity for a new wave of polarized 3D films.[
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Tags: 3-D film, Circular polarization, Edwin H. Land, Film, Liquid crystal display, Polarizer, RealD Cinema, Stereoscopy