How does hdtv 3d work

Though the big boys of consumer electronics are not yet betting on this, the method offers the best viewing experience we have seen so far. Take the technology from HDI, a startup that can take two separate full-resolution imagers and integrate it as one projector. For viewers, this means no reduction in image quality, and brightness that is almost as good as what you can get from a traditional LCD TV. Increasingly, movie theaters are offering polarized glasses for 3-D movies.

Meanwhile, LG has said it is working on having a 3-D ready TV next year based with polarized glasses. Pros: Light weight; pictures with amazing level of detail and color. If putting on a pair of glasses all day to watch TV sounds annoying, there's a way to do it without glasses called autostereoscopy. There are two ways to get this right: lenticular lenses or the parallax barrier.

The idea uses cylindrical plastic lenses known as lenticules. The lenticules are placed on a transparent sheet which is fixed on the LCD screen. The lenticules must be perfectly aligned with the image underneath. Each lenticule then acts as a magnifying glass to enlarge and display the portion of the image below it.

The viewer's eye directly perpendicular to the screen sees the portion of the LCD that is directly under each lens. The other eye, observing the screen from a slightly different angle, sees a portion of the LCD that is off-center under each lens.

The brain then combines the two views to create the perception of depth. The idea comes with some real fine print. It requires an optimum viewing distance of 13 feet or 4 meters , and there's no messing around with that. Sit outside that zone and you are likely to see a set of muddled images.

The parallax barrier works on a similar principle. It has a layer of material with some precise slits placed in front of a regular LCD screen. These allow each eye to see a different set of pixels creating the 3-D effect.

For instance, Sharp, which has shown 3-D TVs that don't require glasses, has developed electrically switchable liquid crystals that are aligned with the columns of pixels in the display.

When switched on, the parallax barrier controls the direction at which the light leaves the display and the way it hits your eyes. Even better, the parallax barrier can be switched off for 2-D content. Sharp's 3-D TV technology is unlikely to hit the production line anytime soon. One set of images is for viewers directly in front of the screen. Another is for viewers way to the side of the screen, and additional pairs take care of all the viewers in between.

If you do move from side-to-side, you simply transition from one pair of right-left images to the next. The technology is very challenging. Figure 1. In real life, each eye sees the world from a slightly different angle. Your brain compares the difference between the two perspectives to produce an impression of depth. Figure 2. In a 3D movie theater, the screen displays images shot from two different perspectives, each using light with a different polarization. Polarized glasses filter just one perspective to each eye.

Figure 3. In active shutter glasses, LCDs over each eye alternate between clear and opaque in synch with the TV. You see through only one eye at any given moment, but the alternation happens fast enough that you perceive a single 3D image. Figure 4. Engineers are developing 3D TVs that work without glasses. You can't use a standard television and expect active glasses to work. You must have some way to synchronize the alternating images on the screen with the LCD lenses in the glasses.

That's where the stereoscopic sync signal connector comes in. It's a standardized connector with three pins that plugs in to a special port on a 3-D-ready television or monitor. The other end of the cable plugs into an IR emitter. The emitter sends signals to your active 3-D glasses. This is what synchronizes the LCD lenses with the action on the screen. The connector operates using transistor-transistor logic TTL. One pin on the connector carries low-voltage electricity.

A second pin acts as a ground wire. The third pin carries the stereo sync signal. There are two different types of 3-D active glasses and they aren't compatible with one another. While emitters for both styles work with the stereoscopic sync signal standard, E-D glasses will only work with an E-D emitter. For example, when the E-D emitter sends a signal for the left lens to be transparent, the ELSA glasses will make the left lens opaque and cause the right lens to be clear.

Even if you have a 3-D-ready television, an emitter and a pair of active glasses, not everything on your television will appear to be three dimensional. Content providers must optimize the signal for 3-D first. While it's possible to modify existing footage into 3-D content, some providers prefer to create video with 3-D in mind beforehand. Currently, the easiest way to view 3-D content is to connect a computer to your 3-D-ready television using an HDMI cable, and then stream the 3-D content from your computer to your television.

In the future, we'll probably see more DVD players capable of sending 3-D signals to televisions and perhaps even incorporate 3-D transmissions into cable and satellite services. While 3-D technology is impressive, some people still want a solution that doesn't require them to wear glasses. There have been several attempts at creating a display capable of projecting images into a three-dimensional space.

Some involve lasers , some project images onto a fine mist or onto artificial smoke, but these methods aren't that common or practical.

There's one way to create three-dimensional images that you may see in places like sports arenas or in a hotel during a big conference. This method relies on a display coated with a lenticular film. Lenticules are tiny lenses on the base side of a special film. The screen displays two sets of the same image. The lenses direct the light from the images to your eyes — each eye sees only one image. Your brain puts the images together and you interpret it as a three-dimensional image.

This technology requires content providers to create special images for the effect to work. They must interlace the two sets of images together. If you were to try and view the video feed on a normal screen, you would see a blurry double image.

Another problem with lenticular displays is that it depends upon the audience being in a sweet spot to get the 3-D effect. If you were to move to the left or right from one of these sweet spots, the image on the screen would begin to blur. Once you moved from one sweet spot to another, the image would return to a cohesive picture. Future televisions may include a camera that tracks your position. The television will be able to adjust the image so that you're always in a sweet spot.

Whether this will work for multiple viewers of the same screen remains to be seen. Some people experience a feeling similar to motion sickness after watching a lenticular display for more than a few minutes.

That's probably because your eyes have to do extra work as they deal with the discrepancy between focus and convergence.

But on the other hand, you don't have to worry about losing an expensive pair of active glasses. Will 3-D television become the next big trend or is it destined to be a fad that comes back every couple of decades? It's too early to say right now. But the technology continues to improve. It may not be long before you duck out of the way the next time a baseball player hits a line drive toward the camera.

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