3D TV. Basic operation
2012-11-11
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Description of the latest technologies used in 3D TV systems
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Any process that allows you to create 3D images is known with the name of stereoscopy, and essentially based on the natural principle of human vision, where each one of our eyes capture in the same moment two images slightly similar, due to its separation from each other. Both images are mixed in our brain, allowing us to see the world in 3D, as we know it. While the 3D TV commercial is relatively new, the stereoscopic visualization techniques are as old as the origins of photography.

When he began to be studied 3D technology, the films were filmed using two cameras separately for obtaining two angles of vision. Later appeared the dual cameras (with dual optical system) getting the same result as using two cameras. To obtain two different images with different angles, we simulate the different perspectives of the left and right eye.


What we are trying to to create a 3D TV or device that reproduces images in 3D display is alternately a camera image to and the other B, something which can be achieved by using various techniques. This means that it is reflected in the screen image of the camera to and then the camera B, all of this, of course a very fast. The tricky part of this process in the TV, is to achieve the exact image for the correct eye. To solve this problem is developed the active 3D goggles.

It should be added that there are two major categories of 3D glasses: the passive systems (or anaglifos) and active systems.

The lenses anaglifos, use color filters (red-blue, red-green or amber-blue), which allow you to display different images in each eye, thus giving a depth effect relatively convincing.

Today are used passive polarized lenses, mainly in cinema 3D. These lenses filter out the wavelengths of light coming from various corners of the screen, allowing each eye separately receive only the image that it is polarized. These lenses were immediately more popular than the anaglifos due to not using color filters that could distort the original color of the image.

On the other hand, are the active glasses, which are used in TV 3D. These glasses have nothing to do with the ones used in the film for the same purpose. The models of glasses used in 3D TV are constructed with "liquid crystal active", and this window is activated through an infrared signal from an infrared transmitter built into the TV. Also, the goggles incorporate an infrared receiver. With this signal from the TV are blocked the crystals of the glasses of alternatively, synchronizing these with the images that are reproduced in the TV. Image to the right eye on the screen, consequently glass of the right eye open and glass of the left eye locked. When playing back the image for the left eye, in the glasses but the opposite happens. As this occurs very quickly, the brain interprets all of this information as a three-dimensional image.

The conventional TV signals may not be able to play in 3D since the video signal is completely different. In a normal TV would be the screen in black or white if we try to play a signal in 3D. You need high-resolution screens and with a refresh rate fairly quick. The 3D movies recorded on Blu-ray have a resolution of 1920x2160 (each eye receives signal in 1080p) and that are received via DVB-T transmissions of 960x1080 (each eye receives signal in 540p).

TV manufacturers have designated two logos to differentiate the TV3D available:

3D - Ready: TV that is capable of reproducing images in 3D and the included infrared transmitter to send orders to the 3D glasses

3D-capable: TV that is capable of reproducing images in 3D but is not supplied the infrared emitter. In order to view images in 3D would require a transmitter module with glasses.

On the other hand we have technologies that do not render necessary the use of glasses to enjoy the TV 3D.

The VUTSI uses the same basic principle for watching TV in 3D, an easy way to watch TV in stereoscopy or pseudoscopia, through the control of the tour of the electromagnetic energy in the space, discovered by the Bolivian military Scientific Ing. Rigoberto Mendizábal Marquez the July 05 2001, a system that takes advantage of the time interval between the current point of the observation of a sequence compared to the prior, where the system causes the system to observe at the same time. It should be noted that while watching the current sequence with one eye, with the other we can see the sequence above, still possible to see in three dimensions real or inverted, depending on the direction of travel of the camcorder or camera movement of the objects that are captured by a single camera. Not getting any results, if the camera or objects are static. Interesting option for all the viewers who do not have the resources to purchase LCD TV or PLASMA 3D, the more specific your lenses, on the basis of the technology they use. This technology has been called VUTSI (Dimensional Universal Viewer Image Sequence), it is possible to use the VUTSI in projections of normal movies in movie theaters, computer games, and home videos, without requiring any edition, it is recommended that the sequences of images should be of high quality for best results.

The television autoestereoscopica is in which more is currently under investigation. The operating principle of this system is based on the use of microlens that allow you to control diffraction beams of light. With this, in addition to represent the information of depth is achieved the arbitrary selection of the point of view and direction within the scene. Thus, a change in the position of the spectator affects the image that this notes. We got the feeling that the scene is rotated by the movement of the observer. This phenomenon is known as Free viewpoint (point of view free) and these are limited to 8 currently by technology issues. Each Free Viewpoint are two images (one for each eye) so we can display at present 9 images at the same time, different in the horizontal plane, which means that the screen will have to take a huge resolution, much greater than HDTV.

A significant advantage is that there may be more of a spectator. Also allow it to maintain the mode of two dimensions.

One of the disadvantages of the use of lenses in front of the screen, is that we can have losses of brightness, contrast and color if you do not applies a rigorous control system.

Philips was a pioneer in presenting to the market the first tv autoestereoscopico, baptized with the name of WOWvx. With a size of 42 inches, has a viewing angle of 160 degrees and a resolution of 3840x2160 pixels. You can represent 9 images at a time. WOWvx is a type of monitor and software tools manufactured by Philips, that offers images in 3D without glasses for several viewers at a time.

The only use that you have been given, has been for advertising, entertainment and display 3D. The WOWvx format uses 3D called ' 2D-plus-depth' that has a depth of a map of grayscale to the side of each table 2D.
Philips suspended sales of this model in March 2009 because the company feels that another format war is counterproductive and disastrous for the market.

Another type of TV autoestereoscopica is the that uses the technology called Multi-view of lenses. Consists of an array of lenses and cylindrical transparent ready on the screen of the TV. This system can influence the contrast and brightness that the TV is capable of providing.

While with one eye we perceive a portion of the screen, with the other one is in another different angle with respect to the screen, see a different part of image directed at this eye in particular. In this system, each pixel is a viewing lens, which in turn is divided into sub-pixels. The 3D effect is achieved when the information of each pixel of this lens is sent in a different direction.

One of the characteristics to take into account in this type of 3D TV is the difference between resolution (pixels) and depth. In a sequence in the 3D pixels are used to display the image depth. For this reason the layout of the lenses is very important, since according to the let lose resolution horizontal or vertical. If we put them in vertical above the screen, the horizontal resolution decreases proportionally to the number of images displayed at the same time. This phenomenon causes an imbalance in the aspect ratio of the pixel. To solve this opts for tilt lenses with a repeating pattern, this decreases the horizontal and vertical resolution by a factor proportional. This creates an effect as if some pixels are repeated horizontally. This system has some shortcomings, because if we change our point of view can be seen images a little incorrect. However, it is impossible to do otherwise by the time not to see areas with gaps.

As always happens with the new systems, these must be compatible with the existing systems. Here we are with 3D TV that also must reproduce images in 2D. This aspect, in the 3D TVS that use 3D glasses is solved easily snatch away the glasses and watching scenes in 2D. The problem we have with the TV systems autoestereoscopica, because the lenses we are going to modify the image.

To solve this problem there are two ways:

1.- by applying a processing to the video signal. Knowing the optical characteristics of the lenses, the content of the signal can be redistributed in the (sub)pixels to cancel the effect of the lenses.

2. -lenses of LC (liquid crystal) lets you disable the effect of the lenses. With lenses of LC in 2D mode, all the pixels contribute in a single high-resolution image. This process has been patented by PHILIPS 3D and is to vary the refractive index of the lens. The layer of lenses is filled with liquid crystal and in this way have a refractive index different mode that allows the 3D. To change the 2D mode, applies an electrical charge on the liquid crystal to alter its index of refraction and the result is that no refracte the light that passes through it.

Now that we have the 3D TV running there is to know what type of players we need to see TV 3D. Mainly to enjoy 3D content must have a Bluray, Play Station or computer with 3D graphics card and content in 3D.

On the other hand we have infrastructure such as cable TV or satellite TV, and even through the DVB-T that they are prepared to issue content 3D. In this respect, the producers have been found with a small problem, because the 3D videos need play twice the number of frames that the 2 dimensions, something that would require having to replace all the decoders of subscribers and therefore, would mean an investment too large.

One of the solutions to tackle the problem in the cable television stations is to compress to half the 2 frames of each eye (left and right) and convergerlos in one only. In this way is sent the same amount of frames that a broadcast 2D conventional, even if we lose image quality. This conversion would sacrifice the issuance to 1080p for about a resolution of 720p and sometimes even less.
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