Sandbox 3

3D GLASSES

In order to view any 3D movie using current technologies, a separate a left-eye view and a right-eye view needs to be produced that can only be viewed by the corresponding eye. Polarizing technologies are used in most movie theaters to separate the two images that are projected on the screen. LCD shutter technology uses special glasses that alternately apply a voltage to two liquid crystal lenses to darken the left lens while the right is transparent, and then darken the right lens while the left is transparent. This must happen at high speed in order to avoid strobe effect. Currently, a minimum of a 120 Hz refresh rate is required so that action scenes appear to flow smoothly.

Active LCD shutter glasses is the technology being developed for 3D HDTV at present

There are two categories of 3D glasses technology, active and passive. Active glasses have electronics which interact with a display.

Active

Liquid crystal shutter glasses

LCD shutter glasses Glasses containing liquid crystal that block or pass light through in synchronization with the images on the computer display, using the concept of alternate-frame sequencing. See also Time-division multiplexing.

Display glasses

Head-mounted display A stereoscopic head-mounted display has two small displays, one for each eye, producing a separate perspective, near each eye. It operates without any external screen at a distance to view and is only a shared experience, if more people are wearing them and watching the same media. A set can be small and compact, similar to regular glasses.

Passive

Linearly polarized glasses

Polarized 3D glasses To present a stereoscopic motion picture, two images are projected superimposed onto the same screen through orthogonal polarizing filters. It is best to use a silver screen so that polarization is preserved. The projectors can receive their outputs from a computer with a dual-head graphics card. The viewer wears low-cost eyeglasses which also contain a pair of orthogonal polarizing filters. As each filter only passes light which is similarly polarized and blocks the orthogonally polarized light, each eye only sees one of the images, and the effect is achieved. Linearly polarized glasses require the viewer to keep his head level, as tilting of the viewing filters will cause the images of the left and right channels to bleed over to the opposite channel – therefore, viewers learn very quickly not to tilt their heads. In addition, since no head tracking is involved, several people can view the stereoscopic images at the same time.

Circularly polarized glasses

Polarized 3D glasses To present a stereoscopic motion picture, two images are projected superimposed onto the same screen through circular polarizing filters of opposite handedness. The viewer wears low-cost eyeglasses which contain a pair of analyzing filters (circular polarizers mounted in reverse) of opposite handedness. Light that is left-circularly polarized is extinguished by the right-handed analyzer, while right-circularly polarized light is extinguished by the left-handed analyzer. The result is similar to that of steroscopic viewing using linearly polarized glasses, except the viewer can tilt his or her head and still maintain left/right separation.

The RealD Cinema system uses an electronically driven circular polarizer, mounted in front of the projector and alternating between left- and right- handedness, in sync with the left or right image being displayed by the (digital) movie projector. The audience wears passive circularly polarized glasses.

Infitec glasses

Infitec stands for interference filter technology. Special interference filters in the glasses and in the projector form the main item of technology and have given it this name. The filters divide the visible color spectrum into six narrow bands - two in the red region, two in the green region, and two in the blue region (called R1, R2, G1, G2, B1 and B2 for the purposes of this description). The R1, G1 and B1 bands are used for one eye image, and R2, G2, B2 for the other eye. The human eye is largely insensitive to such fine spectral differences so this technique is able to generate full-color 3D images with only slight colour differences between the two eyes.[7] Sometimes this technique is described as a "super-anaglyph" because it is an advanced form of spectral-multiplexing which is at the heart of the conventional anaglyph technique.

Dolby uses a form of this technology in its Dolby 3D theatres.

Complementary color anaglyphs

Full color Anachrome red (left eye) and cyan (right eye) filters

Anaglyph image

Complementary color anaglyphs employ one of a pair of complementary color filters for each eye. The most common color filters used are red and cyan. Employing tristimulus theory, the eye is sensitive to three primary colors, red, green, and blue. The red filter admits only red, while the cyan filter blocks red, passing blue and green (the combination of blue and green is perceived as cyan). If a paper viewer containing red and cyan filters is folded so that light passes through both, the image will appear black. Another recently introduced form employs blue and yellow filters. (Yellow is the color perceived when both red and green light passes through the filter.)

Anaglyph images have seen a recent resurgence because of the presentation of images on the Internet. Where traditionally, this has been a largely black & white format, recent digital camera and processing advances have brought very acceptable color images to the internet and DVD field. With the online availability of low cost paper glasses with improved red-cyan filters, and plastic framed glasses of increasing quality, the field of 3D imaging is growing quickly. Scientific images, where depth perception is useful, include the presentation of complex multi-dimensional data sets and stereographic images from (for example) the surface of Mars, but, because of the recent release of 3D DVDs, they are more commonly being used for entertainment. Anaglyph images are much easier to view than either parallel sighting or crossed eye stereograms, although these types do offer more bright and accurate color rendering, most particularly in the red component, which is commonly 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. Processing reconfigures the typical anaglyph image to have less parallax to obtain a more useful image when viewed without filters.

Compensating diopter glasses for red-green method

Simple sheet or uncorrected molded glasses do not compensate for the 250 nanometer difference in the wave lengths of the red-cyan filters. With simple glasses, the red filter image can be blurry when viewing a close computer screen or printed image since the retinal focus differs from the cyan filtered image, which dominates the eyes' focusing. Better quality molded plastic glasses employ a compensating differential diopter power to equalize the red filter focus shift relative to the cyan. The direct view focus on computer monitors has been recently improved by manufacturers providing secondary paired lenses fitted and attached inside the red-cyan primary filters of some high end anaglyph glasses. They are used where very high resolution is required, including science, stereo macros, and animation studio applications. They use carefully balanced cyan (blue-green) acrylic lenses, which pass a minute percentage of red to improve skin tone perception. Simple red/blue glasses work well with black and white, but blue filter unsuitable for human skin in color.

ColorCode 3D

Michelle Obama and Barack Obama and their party watch the commercials using ColorCode 3D during Super Bowl XLIII on February 1, 2009 in the White House theatre.

ColorCode 3D is a newer, patented[8] stereo viewing system deployed in the 2000s that uses amber and blue filters. Notably, unlike other anaglyph systems, ColorCode 3D is intended to provide perceived full colour viewing with existing television and paint mediums. One eye (left, amber filter) receives the cross-spectrum colour information and one eye (right, blue filter) sees a monochrome image designed to give the depth effect. The human brain ties both images together.

Images viewed without filters will tend to exhibit light-blue and yellow horizontal fringing. The backwards compatible 2D viewing experience for viewers not wearing glasses is improved, generally being better than previous red and green anaglyph imaging systems, and further improved by the use of digital post-processing to minimise fringing. The displayed hues and intensity can be subtly adjusted to further improve the perceived 2D image, with problems only generally found in the case of extreme blue.

The blue filter is centred around 450 nm and the amber filter lets in light at wavelengths at above 500 nm. Wide spectrum colour is possible because the amber filter lets through light across most wavelengths in spectrum. When presented via RGB color model televisions, the original red and green channels from the left image are combined with a monochrome blue channel formed by averaging the right image with the weights {r:0.15,g:0.15,b:0.7}.

In the United Kingdom, television station Channel 4 commenced broadcasting a series of programmes encoded using the system during the week of 16 November 2009.[9] Previously the system had been used in the United States for an "all 3-D advertisement" during the 2009 Super Bowl for SoBe, Monsters vs. Aliens animated movie and an advertisement for the Chuck television series in which the full episode the following night used the format.

Chromadepth method and glasses

The ChromaDepth procedure of American Paper Optics is based on the fact that with a prism colors are separated by varying degrees. The ChromaDepth eyeglasses contain special view foils, which consist of microscopically small prisms. This causes the image to be translated a certain amount that depends on its color. If one uses a prism foil now with one eye but not on the other eye, then the two seen pictures – depending upon color – are more or less widely separated. The brain produces the spatial impression from this difference. The advantage of this technology consists above all of the fact that one can regard ChromaDepth pictures also without eyeglasses (thus two-dimensional) problem-free (unlike with two-color anaglyph). However the colors are only limitedly selectable, since they contain the depth information of the picture. If one changes the color of an object, then its observed distance will also be changed.[citation needed]

Anachrome "compatible" color anaglyph method

Anachrome optical diopter glasses. A recent variation on the anaglyph technique is called "Anachrome method".[citation needed] This approach is an attempt to provide images that look fairly normal without glasses as 2D images to be "compatible" for posting in conventional websites or magazines. The 3D effect is generally more subtle, as the images are shot with a narrower stereo base, (the distance between the camera lenses). Pains are taken to adjust for a better overlay fit of the two images, which are layered one on top of another. Only a few pixels of non-registration give the depth cues. The range of color is perhaps three times wider in Anachrome due to the deliberate passage of a small amount of the red information through the cyan filter. Warmer tones can be boosted, and this provides warmer skin tones and vividness.

"Red eye" shutterglasses method

The Red Eye Method reduces the ghosting caused by the slow decay of the green and blue P22-type phosphors typically used in conventional CRT monitors. This method relies solely on the red component of the RGB image being displayed, with the green and blue component of the image being suppressed.[citation needed]