# Application of Three-Dimensional Vision Technology in Dance
## 2 Three-Dimensional Vision Technology
### Three-Dimensional Vision Technology Types
#### 2.2.2 Traditional Three-Dimensional Vision Technology  
Traditional 3D vision technology is categorized into glasses-type 3D vision technology and naked-eye 3D vision technology according to whether specialized glasses are required [8]. In glasses-type 3D technology, light is processed through special glasses to show different images to the audience's two eyes, utilizing parallax to deceive the human eye and form a 3D effect. Glasses-type 3D technology is the mainstream of the current market due to its simple technology and low cost. The most common glasses-type 3D technology  
Figure 4: Schematic diagram of pseudo-holographic technology application in stage. Figure 3: Three levels of 3D vision technology. includes color-multiplexed stereo imaging technology, time-multiplexed stereo imaging technology, and polarization-multiplexed stereo imaging. In color-multiplexed technology (as known as 3D anaglyph technique), the image is specially processed, and the dominant colors of the left and right images are red and cyan, respectively. The viewers are required to wear special glasses consisting of filters close to complementary colors, such as red and cyan (or blue). As shown in Figure 5a, some colors are reproduced by combining the red component of one eye's view with the green and blue components of the other eye's view. Due to the simple imaging principle and low cost, color-multiplexed stereo imaging was widely used in the early days. However, since the two filters on both sides will filter out the light of other colors, each side of the eye can only feel part of the color, which leads to massive information loss. Moreover, the edges of the picture are prone to color deviation. Hence, compared with other stereo imaging technologies, it has a poor 3D effect and cannot be applied on a large scale [9]. Time-multiplexed stereo imaging technology is based on the ability of the human visual system to merge the components of a stereo pair within 50 ms. This \"memory effect\" is exploited by time-multiplexed displays, in which an LCD shutter, commanded by a synchronization signal, sequentially opens one eye while blocking the other, and the left- and right-eye views are rapidly alternated. The shutter system is typically integrated into a pair of glasses and controlled via an infrared link. Both constituent images are reproduced by a single monitor or projector at full spatial resolution, thus avoiding geometric and color differences. Both shutters switch to transparency when the observer leaves the screen, and the time-multiplexed display is fully compatible with two-dimensional presentations. This technology has good stereoscopic imaging and does not lead to any loss of color or brightness. However, the glasses are more complex in structure, more costly in playback equipment, and require repeated utilization of the brain for information extraction, which tends to fatigue the viewers. Also, high-frequency shutter operation can lead to flickering on the screen [10]. Polarized light stereo imaging technology is based on the mechanism of polarized light to separate the left and right images. It is one of the most popular technologies with an excellent stereoscopic effect and practicality among all the current 3D vision technologies. During production and broadcasting, two devices are needed to mimic how people observe things with their left and right eyes and synchronously shoot and broadcast different images with horizontal parallax. As shown in Figure 5b, when viewing, it is necessary to equip two non-interfering polarizers in front of the two lenses respectively. At the same time, the viewers  
Figure 5: (**a**) Two-color stereoscopic imaging glasses and the schematic diagram of its principle; (**b**) schematic diagram of polarized stereoscopic film. are asked to wear special polarized glasses corresponding to the polarization direction of the lenses so that the viewers receive two images that do not interfere with each other. After the brain processes the image, it will generate 3D stereoscopic visual effects.