Research status of naked-eye 3D

Naked-eye 3D technology can be divided into light shield, cylindrical lens and directional backlight 3D technology. As early as 2009, the multilayer display technology (MLD) developed by PureDepth Company in the United States is naked-eye 3D display technology. The advantage of this technology is that it will not cause adverse reactions such as nausea and dizziness to viewers. At the same time, this technology also broke through the limitation of vision and angle, and further expanded the viewing place. The most personalized point is that using this 3D display technology, you can also add two-dimensional subtitles. Now this technology has been widely used in Las Vegas, USA. Compared with MLD technology, cylindrical lens 3D display technology has no advantage. As the name implies, the cylindrical lens type is to use a cylindrical lens. Install a row of cylindrical lenses in front of the LCD screen, so that the image will appear on the focal plane of the lens. Therefore, each pixel in the image is presented in two eyes of a person through the lens. Once the light of a pixel enters the left and right eyes through different angles, people will superimpose the images received by both eyes in the brain to form a 3D image. Compared with other display technologies, the main advantage of cylindrical lens 3D display technology is that it can meet the brightness requirements of the image, but the image is presented to the audience through a layer of lens, so it is difficult to make a greater breakthrough in the resolution of the image. Moreover, installing the lens in front of the LCD screen requires high manufacturing cost and high maintenance cost, which is not conducive to popularization and use. Grating 3D display technology is a new display technology developed by several engineers in the European R&D department of Sharp Company. This technology adds polarization mode and polymer layer between LCD panel and internal light emitting device. When the image is displayed in front of the audience through the LCD panel, the polarization mode can distinguish the images received by the left and right eyes, thus forming a three-dimensional display screen in the audience's brain. This technology integrates polarization mode and polymer layer in display, which can play a certain role in the widest range and cost control, but it is difficult to improve brightness in image display and 3D display technology. Directional light source 3D technology is basically similar to the above display technology in display principle, except that two background light sources are needed when presenting 3D images. When the left and right eyes of the audience receive the picture at the same time, the background light sources in different directions light up alternately in turn, and the pictures of the left and right eyes are alternately presented to the audience through the 3M reflective film. Because the human eye has a certain visual pause time, alternating pictures can form 3D pictures in the human brain. But the final display effect can not meet the requirements of high definition. The key technologies of naked-eye 3D display mainly include the optical principle of view separation, sub-screen division, presentation of independent views, graphic processing software of stereoscopic display LCD screen, etc. In fact, naked-eye 3D images are presented according to the parallax of human eyes. As long as the left and right eye images can be presented reasonably, a stereoscopic video effect can appear. Sub-screen partition is to divide the naked-eye display into views, and each view has a fixed area. In video display, the images in each sub-picture need to be presented alternately, which forms a stereoscopic video in the audience's mind. At present, the naked-eye 3D display technology is not mature enough, and it is too early to realize the naked-eye 3D display that can be used everywhere in people's lives. However, the huge visual enjoyment that naked-eye 3D display can bring to people still inspires the research enthusiasm of relevant personnel, and its huge market potential also promotes the continuous progress of related technologies to achieve high-definition display effects. So it is not a mature naked eye.

Coding mode of naked-eye 3D display terminal

3D image presentation needs to transmit a large amount of data, so in order to upgrade 3D technology, data compression technology must be quite advanced. Traditional 3D image coding basically takes the left transmission channel as the basic layer of data and the right transmission channel as the auxiliary layer of the left channel. Europe's ATTEST system framework adopts single-channel video data transmission when transmitting 3D image data, and at the same time cooperates with the 3D stereoscopic video format of corresponding depth data. By ultra-light compression of deep video data, the amount of data can be reduced, and video data is mainly transmitted through a single channel. The bit rates of Orbi and Interview for deep coding are 6.2% and 3.5% of their respective single channel bit rates. This coding method of 3D stereoscopic image presentation terminal is suitable for the traditional naked-eye 3D display technology. Their imaging principle is basically that the left and right eyes receive the transmitted image information respectively, and then form a three-dimensional figure in the brain, so only two channels are needed to transmit video data. However, to realize naked-eye 3D video display, the amount of data to be output is larger, and the traditional display terminal coding method is theoretically impossible. However, the most successful method in naked-eye 3D display is the stereoscopic video terminal coding method based on parallax. Its main working principle is: firstly, the image information to be received by the left eye is encoded by H.264 standard, then the encoded left eye received image is compared with the right eye received image, and the corresponding visual difference information is obtained through visual estimation, and then the information is encoded by H.264; The finally generated left-eye data stream and parallax data stream are sent to the decoding end through the transmission channel, and the encoded left-eye view and the encoded parallax view are obtained by decoding operation. According to these information, the right eye view data and the data information of the other six viewpoints are obtained, and finally all the data are integrated and displayed on the naked-eye 3D stereoscopic display. This display terminal coding method has also been applied in some practical displays, but there are still some problems: the screen will flicker, which has always been a problem of the display. Different sizes of screens and different display environments will cause different flicker intensities and frequencies; Because of the periodic motion of the grating in front of DLP screen, it is easy to produce pixels different from the original pixels in a certain area of the audience, which is also commonly known as rainbow effect, and it will also exist in naked-eye 3D displays. It is very difficult to completely eliminate these problems, and the related technologies are still in the research stage. Technically, naked-eye 3D can be divided into three types: light barrier cylindrical lens technology and pointing light source. The biggest advantage of naked-eye 3D technology is to get rid of the shackles of glasses, but there are still many shortcomings in resolution, viewing angle and viewing distance.

When watching, the audience needs to keep a certain position with the display device to see the 3D image (the 3D effect is greatly influenced by the viewing angle), and there is still a certain gap between the 3D image and the common polarized 3D technology and shutter 3D technology. However, liquid crystal panel giant AUO and R&D giant 3M have been actively developing, and it is expected that some naked-eye 3D display devices will be mass-produced this year and next. Optical barrier-Optical barrier 3D technology is also called parallax barrier or parallax barrier technology, and its principle is similar to polarized 3D, which was successfully researched by engineers in Sharp European Laboratory for more than ten years. Photobarrier 3D products are compatible with the existing LCD liquid crystal technology, so they have advantages in mass production and cost, but the image resolution and brightness of products using this technology will decrease. A series of 90-degree vertical stripes are made by using liquid crystal layer and polarizing film. Advantages: It is compatible with the existing LCD technology, so it has advantages in mass production and cost.

Disadvantages: the brightness of the picture is low, and the resolution will decrease inversely with the increase of images played by the monitor at the same time. Cylindrical lens technology is also called lenticular lens or micro-cylindrical lens 3D technology, and its biggest advantage is that its brightness will not be affected. The principle of cylindrical lens 3D technology is to add a layer of cylindrical lens in front of the LCD screen. Advantages: 3D technology has better display effect, and the brightness is not affected.

Disadvantages: The related manufacturing is not compatible with the existing LCD liquid crystal technology, and new equipment and production lines need to be invested to point to the light source-the main company that has invested a lot of energy in the 3D technology of pointing to the light source is 3M Company. With the 3D technology of pointing light source, two groups of light-emitting diodes, and the fast-response LCD panel and driving mode, 3D content can enter the viewer's left and right eyes in order to exchange images to produce parallax, and then people can feel the 3D effect. Not long ago, 3M Company just demonstrated its successfully developed 3D optical film. The interview of this product can display real 3D images on handheld devices such as mobile phones and game consoles without wearing 3D glasses, which greatly enhances the communication and interaction based on mobile devices. Advantages: The resolution and light transmittance can be guaranteed, the existing design architecture will not be affected, and the 3D display effect is excellent.

Disadvantages: the technology is still developing and the products are not mature.