1. Binocular parallax stereoscopic display
Binocular parallax stereoscopic display technology imitates the principle of human eye observation. When human eyes observe objects, they will get two slightly different images (3D image pairs) because of the different positions of two eyes. Two images with slightly different human brain fusion will produce distance sense, depth perception and three-dimensional sense. Therefore, binocular parallax stereoscopic display technology is used to transmit the left eye / right eye image of the generated 3D image pairs to the left eye / right eye by various means of technology, and the 3D image is obtained through the fusion of human brain to 3D image pair. The dual stereo stereoscopic display technology can be divided into the auxiliary stereoscopic display technology and the free stereoscopic display technology, according to whether the auxiliary devices are needed to obtain the 3D image.
1.1 Auxiliary stereoscopic display technology
The auxiliary stereoscopic display technology usually requires the left eye / right eye images to be sent to the left eye / right eye with the help of 3D glasses or helmet. Among them, 3D glasses can be divided into three types: chromatic aberration, polarized light and shutter. The corresponding display technology is called color difference stereoscopic display technology, polarized stereoscopic display technology and shutter stereoscopic display technology. Color stereo display eye image technology using red and green (or blue and red) two complementary colors displayed at the same time, the color 3D glasses on the left and right filter can absorb light from the opposite image, so that the left eye / 3D images of the right eye images were sent to the left / right eye.
Polarized stereoscopic display technology using polarized light polarization direction perpendicular to the left and right eye images displayed at the same time, polarized 3D glasses on the left and right with the polarization direction of polarizer allows only consistent part of the light through, so that the image of the 3D left / right eye image were sent to the left / right eye. The LCD switch glasses are used in the shutter stereoscopic display technology. When the liquid crystal is pressurized, it can shield the light incident on the glasses. In the display, the display displays the left / right eye images alternately, and synchronizes the right / left eye lenses to apply the voltage, so that the right / left eye lenses are in an opaque state alternately, so that the left eye / right eye can only receive the left eye / right eye image. Helmet mounted stereoscopic display technology uses two small flat panel displays to display 3D image pairs, and magnifies images by optical system, and then produces similar remote effects. Since left eye / right eye images correspond to left eye / right eye, 3D images can be generated through human brain fusion. Although the auxiliary stereoscopic display technology is the first and widely promoted stereoscopic display technology, the discomfort caused by glasses or helmets prevents the further development of the technology, and makes the researchers turn to the research of autostereoscopic display technology.
2. Free stereoscopic display technology
The technology of free stereoscopic display can send the left eye / right eye image to the left eye / right eye without using any auxiliary devices such as glasses or helmet, so it is also called the naked eye 3D display technology.
The traditional free stereoscopic display technology can be divided into parallax baffle type and columnar lens type free stereoscopic display technology.
As shown in Figure 1, a schematic diagram of a parallax baffle free stereoscopic display technology. Display pixels respectively display odd even columns around the eye image, the LCD screen placed in front of a baffle fence, monocular observer saw a column of pixels on the display through a slit only baffle the final odd / even pixel light can only be received by the brain and left / right eye fusion 3D image.
Due to the use of parallax baffles, the luminance and power consumption of the display parts are greatly reduced. Also because the use of odd and even column pixels to display the left and right eye images separately makes the resolution of the 3D image only half the pixel of the display panel when it is displayed in the 2D. In addition, because can only see half of the pixel visual observation, it will produce a fence effect.
Figure 2 shows the schematic diagram of a multi view parallax baffle free stereoscopic display technology. In order to get 3D images at multiple locations (with multiple 3D views), each slit needs to correspond to multiple columns (more than two columns) pixels, so the resolution of 3D images is further reduced.
In addition, the parallax baffle baffle area proportion increased, will cause the display brightness and power consumption further reduced. In order to increase the resolution of the 3D image, it is necessary to further reduce the size of the slit, which will cause the diffraction effect and will lead to the reduction of the image quality. It can be seen that there is a mutual restriction between the resolution and the number of visual angles of the parallax baffle free stereoscopic display.
Figure 3 shows a schematic diagram of a cylindrical lens type free stereoscopic display technology.
As shown in Figure 3, the odd and even column pixels display the left and right eye images on the display screen. The front of the display is coupled with a micro column lens, and the image plane of the LCD panel is located on the focal plane of the lens.
Because of the refraction of the lens unit, the light is guided into a specific observation area, so that the single eye can only see a column of pixels on the display screen through the lens lens.
Finally, the light emitted by the odd / even column pixels can only be received by the left / right eye. Then the 3D image is obtained through the fusion of human brain. Since all light can be received through the eye through the lens, the display of brightness is not affected. However, the alignment of the display screen with the microlens is difficult, and there is still a problem of crosstalk between the left and right eye images. In addition, the columnar lens type stereoscopic display technology is the existence of mutual restriction and trellis effect between the resolution and the number of perspective.