How Does 3-D TV Work Without Glasses?

Most people are familiar with 3-D glasses in one of their many guises. Since the earliest days of their introduction, these devices have been the only available means of bringing a 3-D presentation into focus. Although all varieties do succeed in the attempt, many people have found them annoying to wear, and movie theaters do not always appreciate the added expense and hassle of providing them.

The migration of three-dimensional entertainment from movie theater to living room has given rise to an increasingly large group of people who prefer to enjoy the special effects unencumbered by any extraneous accoutrements. Few can blame them.


The Theory Behind the Technology

Anyone with adequate vision will routinely view the world in three-dimensional splendor. That’s because binocular vision forces each eye to view what’s in front of it from a slightly different angle. The brain combines the two offset images into one that offers both dimension and depth.
All living creatures rely upon binocular vision to lend depth to a scene. By the same token, objects viewed through only one eye will look unnaturally flat. This phenomenon often impedes depth perception in individuals who suffer from partial visual impairment,


The Workings of 3-D Entertainment

All forms of 3-D entertainment operate by presenting the viewer with two interlaced, slightly offset views of a scene. The 3-D effect itself relies on the aid of some sort of external filtering device to dictate which portion of the image arrives unimpeded at each of the viewer’s eyes. This assistance has traditionally come in the form of the special glasses that many viewers prefer not to wear.
In the absence of filtration, the viewer will see only a blurred double image. Unless 3-D glasses do the job, the process must take place at the source of the image itself. Enter parallax barrier and lenticular lens technology, two major players that perform their magic directly in front of the television screen.


Parallax Barrier Technology

The parallax barrier consists of a liquid crystal display, or LCD, containing invisible slits. When placed directly in front of the television screen, this barrier blocks certain light rays from view while redirecting the others. In this manner, it presents each of the viewer’s eyes with a distinct set of pixels and a slightly different view of the image. To switch between 3-D and 2D viewing, the viewer need only turn the parallax barrier on or off.


Lenticular Technology

This technology uses a lenticular lens containing interlaced strips placed at different angles to split the image, directing the appropriate portion of it to the eye that is meant to see it. The lenticular method permits a slightly wider viewing angle than that afforded by the parallax barrier technology. It also works as well with CCFL and LED as it does with LCD. However, it is also more difficult and expensive to produce.



As promising as parallax barrier and lenticular technology may be, they share one serious drawback: To receive the full effect, each viewer must sit in a specific position relative to the screen. Any movement out of this range will blur the picture and evaporate the 3-D effect.
For this reason, either variety of eyeglass-free 3-D technology is easier to implement on such single-user devices as cell phones and Nintendo 3-Ds. Any device capable of offering three-dimensional viewing by a number of people in a living room setting will need to accommodate as many as 32 varied viewing angles. That’s where eye-tracking devices can help.


Eye Tracking

The incorporation of special cameras into a lenticular or parallax barrier 3-D system will provide it with the invaluable ability to detect the direction from which a viewer is watching. With this information, the system can adjust the direction of its output to match.
To work correctly, however, the camera will require a continuous frame of reference. Hand-held devices containing gyrometers, accelerometers, compasses and GPS modules enable users to tell the system exactly where they are sitting.


The Future of Glassless 3-D TV

The union of glassless 3-D technology with ultra-high-definition 4K television screens could prove to be the wave of the 3-D future. The hope is strong that this synergy will entice additional viewers, allowing 3-D television to eventually become commonplace in the world’s living rooms while relegating 3-D glasses to the bottomless pit of distant memory.

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