Basic principles of the hottest stereo TV Technolo

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Basic principle of stereo TV technology

1 introduction

as a new technological product in the 20th century, TV has become the most influential information dissemination tool in the world and the product with the largest market share in the kingdom of home appliances. TV products are being upgraded, and new receiving and display forms such as projection, rear projection, liquid crystal, plasma, etc. have emerged. However, the video technology of TV products basically stays in two-dimensional picture, and three-dimensional picture products are rarely seen. According to the analysis and prediction of the world electronic society, in the 21st century, TV technology will change in wall type, projection, bidirectional, wired and other aspects, and stereoscopic is one of the important research contents. The current research focus of stereoscopic technology is the "automatic stereoscopic display technology" which can watch stereoscopic programs without stereoscopic glasses. In the long run, it is a three-dimensional television technology that does not rely on visual illusion and allows the image to change with the observation angle. It can make the image seen by the audience from any angle be three-dimensional

2 overview of the development of stereoscopic television technology

stereoscopic television technology is developing with the development of stereoscopic vision technology and television technology

the development history of stereo vision technology is the development history of stereo imaging and display technology. Its emergence is far earlier than the invention of television technology

as early as the Renaissance in Europe, the research and practice of painting perspective and sculpture art have shown that only when two eyes are provided with relatively independent images respectively, and the parallax of both eyes is restored, can the real stereo vision be obtained. The early binocular stereo vision technology adopts the method of observing stereo images through colored glasses and stereoscope. The development and utilization of new materials with high safety and good quality and performance. In the 16th century, people have begun to draw regularly different images for left and right eyes with different colors, and then observe them through filters to produce stereo vision. The "stereoscope" appeared at the end of the 17th century and the beginning of the 18th century, which provides an independent visual channel for each eye. The sense of stereovision is very strong. This "stereoscope" is still an effective means to observe stereoscopic images. In the 19th century, some scientists tried to construct a method to observe three-dimensional pictures without the help of auxiliary devices, but it ended in failure

At the end of the 19th century, people tried to use film technology to express stereoscopic images of motion. First, two cameras are used to simulate human eyes for shooting, and then the produced film is projected onto the film screen with a projector through a polarizing filter, and the audience can observe the moving three-dimensional image through the polarizing filter. This stereoscopic film technology has been used until now

After the emergence of television technology in the early 20th century, people began to develop stereoscopic television. Almost all the traditional stereoscopic display methods used to observe still images or movie images have been applied to stereoscopic television technology

in the early era of black-and-white television, the more successful stereoscopic television is that two television cameras take images and transmit them to two televisions with two independent video channels. A polarizing plate is placed on the screen of each television, and then observed with polarizing glasses. Such a stereoscopic television system can obtain better stereoscopic images. This dual channel polarized split image stereo TV technology is still recognized as a good quality stereo TV system

in the 1950s, the color TV technology developed to a stage close to practical use, and "the comprehensive strength of complementary color stereo division was significantly enhanced" TV technology began to be applied to stereo TV. The basic method is to use two cameras equipped with filters at the front of the lens to capture the same scene image. On the screen of the color TV, the audience sees two images of different colors superimposed on each other. When the audience observes through the corresponding filters, they can see the stereo TV image. This stereo TV imaging technology has good compatibility and was once popular in the field of stereo TV technology. However, the existing problems are also very obvious: due to the observation of TV images through filters, the loss of color information is great; Another problem is the interference caused by the "cross color" phenomenon of color TV itself; At the same time, because the incident spectra of the left and right eyes are inconsistent, it is easy to cause visual fatigue

in the late 1970s, due to the emergence of new ceramic optical switch materials, people can make optical switch glasses. At this time, the time-division stereo TV technology appeared. Time division stereo TV technology uses odd and even fields of color TV signals to encode stereo TV signals. In the early 1980s, Toshiba developed a time-division stereo TV projector to watch with polarizers. In 1985, Panasonic successfully launched the first time-division LCD glasses stereo TV prototype. Now, helmet mounted viewing devices with dual screen displays have ideal stereoscopic viewing effects. In China, Tsinghua University has developed a new type of liquid crystal light valve glasses with high transmittance, and successfully developed a time fractional liquid crystal glasses stereo TV in 2001

at present, the time-division stereo TV technology is relatively mature and has obvious advantages: it can provide a new one-year realistic color stereo image; When the TV field frequency is high, the image is stable without flicker; Compatible with current color TV system and computer display; It can smoothly transition to digital TV system

the first real-time stereoscopic display system appeared in China in 2000. Use an ordinary VCD disc to play the ghosting picture, wear wireless infrared glasses to watch, and you can get a strong three-dimensional picture. This stereoscopic display system can convert the two-dimensional image of the existing signal source into three-dimensional image on the display in real time. But technically speaking, this stereo image effect still stays at the level of image conversion using optical or signal processing methods

at present, we are stepping up the development of new stereo cameras and stereo display devices. The new stereo camera has double lenses, integrates computer, measurement and control, image processing technology, and the shooting process conforms to the human visual mechanism. The new stereoscopic display device inputs left and right images at the same time or at the same time. Using optical technology, the left and right images are projected to people's eyes with correct parallax. Without wearing glasses, you can directly see stereoscopic images in front of the screen. At the founding conference of 3D alliance held in Tokyo, Japan in 2003, Sanyo Electric showed a display that did not need to wear glasses to watch stereoscopic images; Sony, on the other hand, demonstrated its stereo image shooting and broadcasting system. However, the stereoscopic effect of the above products is also limited by the viewing angle and distance

3 basic principle of stereoscopic TV technology

from the perspective of human visual experience, two eyes can obtain a stereoscopic sense by watching the visual signal of the same object; People with only one eye can also get stereoscopic sense by observing scene objects, which corresponds to binocular stereovision and monocular stereovision. The former is the basis of stereoscopic television technology; The latter relies more on prior experience to obtain a three-dimensional sense

3.1 binocular stereo vision

stereoscopic television uses the stereoscopic characteristics of human eyes to produce stereoscopic images. When looking at the surrounding world, human beings can not only see the width and height of objects, but also know their depth, and can judge objects, so that the temperature of printing materials cannot help but increase the distance between objects or between viewers and objects. The main reason for this three-dimensional visual characteristic is that people usually watch objects with both eyes at the same time. Due to the distance between the visual axes of the two eyes (about 65 mm), the visual images received by the left eye and the right eye when looking at objects at a certain distance are different. Therefore, the brain integrates the information of the two images through the movement and adjustment of the eyes to produce a three-dimensional sense. When viewing objects with left and right eyes alone, the resulting image shift sensation is called parallax. Make a specific description in combination with figure 1

as shown in Figure 1, there are two identical cameras, the two image planes are located in the same plane Q, the coordinate axes of the two machines are parallel, the X axis coincides, and the distance between the two machines in the X direction is baseline B. The projection points GL and gr of the feature point P in the scene in two image planes are called conjugate pairs, that is, one projection point is the corresponding of the other. After the two images are overlapped, the position difference XL XR between the conjugate pairs is the parallax. Let the origin of the coordinate system be in the center of the left lens. According to the similar triangle relationship:

x/z=xl/f and (X-B)/z=xr/f

: z=bf/(XL XR)

it can be seen that the depth information of the object is recovered through parallax. The larger the parallax is, the closer the distance from the object to the lens is; Otherwise, the farther away. Stereo image pairs can be obtained by using a stereo camera with two lenses

3.2 implementation methods of stereoscopic TV

the implementation methods of stereoscopic TV are mainly divided into two categories:

one category is to make two images of a pair of parallax signals appear on the screen at the same time, and let two eyes watch these two images respectively to obtain stereoscopic feeling. As mentioned above, dual channel polarized image splitting stereo TV technology and "complementary color stereo image splitting TV technology"

one is to display two images of a pair of parallax signals on the screen in turn, so that two eyes can watch it time-sharing to obtain a three-dimensional feeling. This is the time-division stereo TV technology mentioned earlier. Specifically, the time-division stereoscopic TV technology is to display the images of the left and right eyes alternately on the TV screen, and then cover the right eye through a synchronous shutter viewer (i.e. stereoscopic glasses) when the screen displays the images of the left eye; When the screen displays the image of the right eye, mask the left eye. In this way, the human brain will be confused and produce stereoscopic vision by alternating display at a speed faster than the persistence of human vision

4 Conclusion

in the long run, stereoscopic television is a development direction, and its full realization will be a whole system based on digital technology from camera to imaging. All kinds of stereo TV implementation methods have their own advantages and disadvantages, and they are still far from the ideal stereo TV in people's minds. So far, people have not found or determined the best way to realize three-dimensional TV, but it can be predicted that the realization of three-dimensional color TV is not far away

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