3D GLASS FOR 3D LOVERS: 2010-12-19

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

Liquid crystal shutter glasses

Main article: LC 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. There have been many examples of shutter glasses over the past decade, but the Nvidia 3D Vision gaming kit introduced in 2008 introduced this technology to mainstream consumers and PC gamers.

"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.

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

Main article: 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 (dichromatic 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. 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

3D red cyan glasses are recommended to view this image correctly.

: 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, for instance, the presentation of complex multi-dimensional data sets and stereographic images of the surface of Mars. With 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-cyan 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 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 nearly full colour viewing (particularly within the RG color space) 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.^[13] 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.

Anachrome "compatible" color anaglyph method

Anachrome optical diopter glasses.

A recent variation on the anaglyph technique is called "Anachrome method". 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 is claimed to provide warmer skin tones and vividness.

Printable cross eye viewer.

Autostereoscopy

Autostereoscopy is any method of displaying stereoscopic (3D) images without the use of special headgear or glasses on the part of the viewer. Because headgear is not required, it is also called "glasses-free 3D". The technology includes two broad classes of displays: those that use head-tracking to ensure that each of the viewer's two eyes sees a different image on the screen, and those that display multiple views so that the display does not need to know where the viewers' eyes are directed. Examples of autostereoscopic displays include parallax barrier, lenticular, volumetric, electro-holographic, and light field displays.
Some autostereoscopic dispalys are also capable of recreating a perception of movement parallax, which is not possible with any of the active or passive technologies discussed above. "Movement parallax" refers to the fact that the view of a scene changes with movement of the head. Thus, different images of the scene are seen as the head is moved from left to right, and from up to down

Other display methods

It has been suggested that 3D display be merged into this article or section.

Autostereograms

A random dot autostereogram encodes a 3D scene which can be "seen" with proper viewing technique

Main article: autostereogram

More recently, random-dot autostereograms have been created using computers to hide the different images in a field of apparently random noise, so that until viewed by diverging or converging the eyes in a manner similar to naked eye viewing of stereo pairs, the subject of the image remains a mystery. A popular example of this is the Magic Eye series, a collection of stereograms based on distorted colorful and interesting patterns instead of random noise.

Pulfrich effects

Main article: Pulfrich effect

In the classic Pulfrich effect paradigm a subject views, binocularly, a pendulum swinging perpendicular to his line of sight. When a neutral density filter (e.g., a darkened lens -like from a pair of sunglasses) is placed in front of, say, the right eye the pendulum appears to take on an elliptical orbit, being closer as it swings toward the right and farther as it swings toward the left.
The widely accepted explanation of the apparent motion with depth is that a reduction in retinal illumination (relative to the fellow eye) yields a corresponding delay in signal transmission, imparting instantaneous spatial disparity to moving objects. This occurs because the eye, and hence the brain, respond more quickly to brighter objects than to dimmer ones.
So if the brightness of the pendulum is greater in the left eye than in the right, the retinal signals from the left eye will reach the brain slightly ahead of those from the right eye. This makes it seem as if the pendulum seen by the right eye is lagging behind its counterpart in the left eye. This difference in position over time is interpreted by the brain as motion with depth: no motion, no depth.
The ultimate effect of this, with appropriate scene composition, is the illusion of motion with depth. Object motion must be maintained for most conditions and is effective only for very limited "real-world" scenes.

Prismatic & self-masking crossview glasses

"Naked-eye" cross viewing is a skill that must be learned to be used. New prismatic glasses now make cross-viewing as well as over/under-viewing easier, and also mask off the secondary non-3D images, that otherwise show up on either side of the 3D image. The most recent low-cost glasses mask the images down to one per eye using integrated baffles. Images or video frames can be displayed on a new widescreen HD or computer monitor with all available area used for display. HDTV wide format permits excellent color and sharpness. Cross viewing provides true "ghost-free 3D" with maximum clarity, brightness and color range, as does the stereopticon and stereoscope viewer with the parallel approach and the KMQ viewer with the over/under approach. The potential depth and brightness is maximized. A recent cross converged development is a new variant wide format that uses a conjoining of visual information outside of the regular binocular stereo window. This allows an efficient seamless visual presentation in true wide-screen, more closely matching the focal range of the human eyes.

Lenticular prints

Main article: Lenticular printing

Lenticular printing is a technique by which one places an array of lenses, with a texture much like corduroy, over a specially made and carefully aligned print such that different viewing angles will reveal different image slices to each eye, producing the illusion of three dimensions, over a certain limited viewing angle. This can be done cheaply enough that it is sometimes used on stickers, album covers, etc. It is the classic technique for 3D postcards.
A variant of this for portable electronic devices, the parallax barrier, has begun deployment.

Displays with filter arrays

The LCD is covered with an array of prisms that divert the light from in their notebook and desktop computers. These displays usually cost upwards of 1000 dollars and are mainly targeted at science or medical professionals.
Another technique, for example used by the X3D company, is simply to cover the LCD with two layers, the first being closer to the LCD than the second, by some millimeters. The two layers are transparent with black strips, each strip about one millimeter wide. One layer has its strips about ten degrees to the left, the other to the right. This allows seeing different pixels depending on the viewer's position.

Wiggle stereoscopy

This method, possibly the simplest stereogram viewing technique, is to simply alternate between the left and right images of a stereogram. In a web browser, this can easily be accomplished with an animated .gif image, flash applet or a specialized java applet. Most people can get a crude sense of dimensionality from such images, due to parallax
Closing one eye and moving the head from side-to-side when viewing a selection of objects helps one understand how this works. Objects that are closer appear to move more than those further away. This effect may also be observed by a passenger in a vehicle or low-flying aircraft, where distant hills or tall buildings appear in three-dimensional relief, a view not seen by a static observer as the distance is beyond the range of effective binocular vision.
Advantages of the wiggle viewing method include:

No glasses or special hardware required
Most people can "get" the effect much quicker than cross-eyed and parallel viewing techniques
It is the only method of stereoscopic visualization for people with limited or no vision in one eye

Disadvantages of the "wiggle" method:

Does not provide true binocular stereoscopic depth perception
Not suitable for print, limited to displays that can "wiggle" between the two images
Difficult to appreciate details in images that are constantly "wiggling"
Lack of 3D illusion to those who can detect the wiggling too easily.

Most wiggle images use only two images, leading to an annoyingly jerky image. A smoother image, more akin to a motion picture image where the camera is moved back and forth, can be composed by using several intermediate images (perhaps with synthetic motion blur) and longer image residency at the end images to allow inspection of details. Another option is a shorter time between the frames of a wiggle image through the use of an animated .png.
Although the "wiggle" method is an excellent way of previewing stereoscopic images, it cannot actually be considered a true three-dimensional stereoscopic format. To experience binocular depth perception as made possible with true stereoscopic formats, each eyeball must be presented with a different image at the same time – this is not the case with "wiggling" stereo. The apparent "stereo like effect" comes from syncing the timing of the wiggle and the amount of parallax to the processing done by the visual cortex. Three or five images with good parallax produce a much better effect than simple left and right images.
Wiggling works for the same reason that a translational pan (or tracking shot) in a movie provides good depth information: the visual cortex is able to infer distance information from motion parallax, the relative speed of the perceived motion of different objects on the screen. Many small animals bob their heads to create motion parallax (wiggling) so they can better estimate distance prior to jumping.^[18]^[19]^[20] You can see this for yourself in a 3D movie by removing the glasses during a scene where the camera is moving: the glasses have very little additional effect at such a time.

http://en.wikipedia.org/wiki/Stereoscopy#3D_viewers

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Thursday, December 23, 2010

SHUTTER GLASS