Autostereoscopy

SOURCE FROM     http://en.wikipedia.org/wiki/Autostereoscopy

Autostereoscopy is any method of displaying stereoscopic images (adding perception of 3D depth) 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 or glasses-less 3D". The technology also includes two broad approaches used in some of them to accommodate motion parallax and wider viewing angles: those that use eye-tracking, and those that display multiple views so that the display does not need to sense where the viewers' eyes are located. Examples of autostereoscopic displays include parallax barrier, lenticular, volumetric, electro-holographic, and light field displays.

Many organizations have developed autostereoscopic 3D displays, ranging from experimental displays in university departments to commercial products, and using a range of different technologies. Currently, most flat-panel solutions employ lenticular lenses or parallax barriers that redirect incoming imagery to several viewing regions at a lower resolution. When the viewer's head is in a certain position, a different image is seen with each eye, giving a convincing illusion of 3D. Such displays can have multiple viewing zones allowing multiple users to view the image at the same time, though they may also exhibit dead zones where only a monoscopic, crosseyed, or no image at all can be seen.

Eye tracking has been used in a variety of systems in order to limit the number of displayed views to just two, or to enlarge the stereoscopic sweet spot. However, as this limits the display to a single viewer, it is not favoured for consumer products.

Parallax barrier

     The principle of the parallax barrier has been invented by Auguste Berthier but was later popularized by the independent invention by Frederick E. Ives. Sharp developed the technology to commercialization, briefly selling two laptops with the world's only 3D LCD screens. These displays are no longer available. Similarly, Hitachi has released the first 3D mobile phone for the Japanese market under distribution by KDDI. In 2009, Fujifilm released the Fujifilm FinePix Real 3D W1 digital camera which featured a built-in autostereoscopic LCD display measuring 2.8" diagonal. Nintendo has also implemented this technology on their latest portable gaming console, the Nintendo 3DS.

 Lenticular lens

The principle of lenticular display is usually attributed to Gabriel Lippmann. Photographers had patented the idea as early as 1915. Pierre Allio produced some of the first patents in lenticular displays in the mid-1980s. Philips solved a significant problem with these displays in the mid-1990s by slanting the lenticular lenses with respect to the underlying pixel grid. Philips produced its WOWvx line, based on this idea, until 2009, running up to a 2160p resolution of 3840×2160 pixel 46 viewing angles. Lenny Lipton's company, StereoGraphics, produced displays based on the same idea, citing a much earlier patent for the slanted lenticulars. Magnetic3d and Zero Creative have also been involved. The hardware overlay for iPhone and iPod touch named 3DeeSlide also adopts this technology to convert the standard screen into an auto 3D display.

 Other

Dimension Technologies released a range of commercially available 2D/3D switchable LCDs in 2002 using a combination of parallax barriers and lenticular lenses.Real Technologies has developed a holographic display based on eye tracking. CubicVue exhibited a color filter pattern autostereoscopic display at the Consumer Electronics Association's i-Stage competition in 2009.

There are a variety of other autostereo systems as well, such as volumetric display, in which the reconstructed light field occupies a true volume of space, and integral imaging which uses a fly's-eye lens array.

The term automultiscopic display has recently been introduced as a shorter synonym for the lengthy "multi-view autostereoscopic 3D display".

Sunny Ocean Studios, located in Singapore, has been credited with developing an automultiscopic screen that can display autostereo 3D images from 64 different reference points.

 Movement Parallax: Single View vs. Multi-View Systems

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.

Many autostereoscopic displays are single-view displays and are thus not capable of reproducing the sense of movement parallax, except for a single viewer, in systems capable of eye tracking.

Some autostereoscopic displays, however, are multi-view displays, and are thus capable of providing the perception of left-right movement parallax. Eight and sixteen views are typical for such displays. While it is theoretically possible to simulate the perception of up-down movement parallax, no current display systems are known to do so, and the up-down effect is widely seen as less important than left-right movement parallax.