As soon as the merged picture appears, we get the 3D view. So when making the 3D-TV programs, there are two cameras acting as two eyes.
But how to make sure that the single very eye only see the very picture meant for it? Then we need to use 3D glasses in most cases (We will talk about the 3D glasses later).
*More Informations
Anaglyph
Anaglyph images were the earliest method of presenting theatrical 3-D, and the one most commonly associated with stereoscopy by the public at large, mostly because of non theatrical 3D media such as comic books and 3D TV broadcasts, where polarization is not practical. They were made popular because of the ease of their production and exhibition. Though the earliest theatrical presentations were done with this system, most 3D movies from the 50s and 80s were originally shown polarized.
In an anaglyph, the two images are superimposed in an additive light setting through two filters, one red and one cyan. In a subtractive light setting, the two images are printed in the same complementary colors on white paper. Glasses with colored filters in each eye separate the appropriate images by canceling the filter color out and rendering the complementary color black.
Anaglyph images are much easier to view than either parallel sighting or crossed eye stereograms, although the latter types offer bright and accurate color rendering, particularly in the red component, which is muted, or desaturated with even the best color anaglyphs. A compensating technique, commonly known as Anachrome, uses a slightly more transparent cyan filter in the patented glasses associated with the technique. Process reconfigures the typical anaglyph image to have less parallax.
An alternative to the usual red and cyan filter system of anaglyph is ColorCode 3-D, a patented anaglyph system which was invented in order to present an anaglyph image in conjunction with the NTSC television standard, in which the red channel is often compromised. ColorCode uses the complementary colors of yellow and dark blue on-screen, and the colors of the glasses' lenses are amber and dark blue.
The anaglyph 3-D system was the earliest system used in theatrical presentations and requires less specialized hardware.
The polarization 3-D system has been the standard for theatrical presentations since it was used for Bwana Devil in 1952, though early Imax presentations were done using the eclipse system and in the 60s and 70s classic 3D movies were sometimes converted to anaglyph for special presentations. The polarization system has better color fidelity and less ghosting than the anaglyph system.
In the post-'50s era, anaglyph has been used instead of polarization in feature presentations where only part of the movie is in 3D such as in the 3D segment of Freddy's Dead: The Final Nightmare and the 3D segments of Spy Kids 3D.
Anaglyph is also used in printed materials and in 3D TV broadcasts where polarization is not practical. 3D polarized TVs and other displays only became available from several manufacturers in 2008; these generate polarization on the receiving end.
Polarization systems
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,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.
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.
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.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.
Eclipse method
With the eclipse method, a mechanical shutter blocks light from each appropriate eye when the converse eye's image is projected on the screen. The projector alternates between left and right images, and opens and closes the shutters in the glasses or viewer in synchronization with the images on the screen. This was the basis of the Teleview system which was used briefly in 1922.
A variation on the eclipse method is used in LCD shutter glasses. Glasses containing liquid crystal that will let light through in synchronization with the images on the computer display or TV, using the concept of alternate-frame sequencing. This is the method used by nVidia, XpanD 3D, and earlier IMAX systems. A drawback of this method is the need for each person viewing to wear expensive, electronic glasses that must be synchronized with the display system using a wireless signal or attached wire. The shutterglasses are heavier than most polarized glasses though lighter models are no heavier than some sunglasses or deluxe polarized glasses.
Pulfrich
The Pulfrich effect is based on the phenomenon of the human eye processing images more slowly when there is less light, as when looking through a dark lens.
Imagine a camera which starts at position X and moves right to position Y as shown by the arrow. If a viewer watches this segment with a dark lens over the left eye, then when the right eye sees the image recorded when the camera is at Y, the left eye will be a few milliseconds behind and will still be seeing the image recorded at X, thus creating the necessary parallax to generate right and left eye views and 3D perception, much the same as when still pictures are generated by shifting a single camera. The intensity of this effect will depend on how fast the camera is moving relative to the distance to the objects; greater speed creates greater parallax.
A similar effect can be achieved by using a stationary camera and continuously rotating an otherwise stationary object. If the movement stops, the eye looking through the dark lens (which could be either eye depending on the direction the camera is moving) will "catch up" and the effect will disappear. One advantage of this system is that people not wearing the glasses will see a perfectly normal picture.
Of course, incidental movement of objects will create spurious artifacts, and these incidental effects will be seen as artificial depth not related to actual depth in the scene. Unfortunately, many of the applications of pulfrich involve deliberately causing just this sort of effect and this has given the technique a bad reputation. When the only movement is lateral movement of the camera then the effect is as real as any other form of stereoscopy, but this seldom happens except in highly contrived situations.
Though pulfrich has been used often on TV and in computer games, it is rarely if ever used in theatrical presentations.
New systems without glasses
There is increasing emergence of new 3-D viewing systems which do not require the use of special viewing glasses. These systems are referred to as Autostereoscopic displays. They were initially developed by Sharp.
The first Autostereoscopic LCD displays first appeared on the Sharp Actius RD3D notebook and the first LCD monitor was shipped by Sharp in 2004 for the professional market. Both have since been discontinued. The first Autostereoscopic mobile phone was launched by Hitachi in 2009 in Japan and in 2010 China mobile is to launch its version. Manufacturing trials are being run for TV. For the gaming market the first probable commercial application will be handheld gaming devices, such as the Nintendo 3DS. These systems do not yet appear to be applicable to theatrical presentations.
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Relax Time
（Tangled 2011）
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