Analysis on the Revolutionary Road and Technology Classification of 3D Digital Film

The development of 3D technology has a history of more than 60 years. At present, the commercialized 3D projection technologies in cinemas around the world mainly include active stereo and passive stereo. Recently, some companies have introduced spectral stereoscopic projection technology (INFITEC) using RGB color separation technology. 3D imaging is produced by the difference in vision between human eyes. There is usually a distance of about 8 cm between the eyes (pupils) of a person. In order for people to see 3D images, the left eye and right eye must see different images, so that the two images have a certain gap, which is to simulate the situation when viewed by the actual human eye. This is how the three-dimensional sense of 3D comes from. After more than 60 years, 3D technology has not made breakthrough progress, and it has always been focused on improving the recording of stereoscopic images obtained based on the principle of human eye binocular parallax, the performance of binocular reception, and the viewing effect. Up to now, we can only say that the stereoscopic image realization technology based on the principle of human eye binocular parallax is the most mature, but not the best. Obviously, it is most ideal to be able to view the stereoscopic images without glasses, just as we usually perceive the stereoscopic images of the real world to watch the stereoscopic images, that is, naked-eye 3D. In the film era of movies, due to the use of film, the deformed and compressed left and right eye images were recorded separately in the upper and lower parts of a frame. During projection, a deflection prism was used to restore the complete left and right eye images, and then polarization technology was used for left and right images. The separation of the eye frame is correspondingly received by the left and right eyes of the person to form a three-dimensional image. Of course, limited by technology and equipment, the 3D picture quality is not high, and the subjective feeling is not good. After a period of lively, it fell into silence. After 2000, with the promotion of digital film technology and the use of digital technology to regain 3D film technology, the picture quality was improved. Coupled with the success of the 3D blockbuster 'AvatarPopularity, and finally accepted by the audience.　　 Nowadays, stereoscopic image realization technology based on the principle of human eye binocular parallax is still the mainstream 3D technology for movies. Of course, in terms of realizing the separation and synthesis of left and right eye images, according to different processing methods, it can be divided into three methods for separating left and right eye images: spatial domain, time domain, and color domain. Representative manufacturers are Read.D, X.pand and DOLBY. This article gives a brief introduction. 1. Spatial separation 　 This technology mainly uses polarized light of different polarities to separate the left and right eye images in space. It is also called polarized 3D technology or passive 3D technology. Although natural light is scattered in the direction of propagation, it has polarization characteristics, and we can change its polarization polarity through technical methods. If a filter polarizer is installed in front of the projector lens to separate the light of the left and right eye images with different polarities, the audience can separate the left and right eye images projected by the projector in space by wearing polarized glasses, and finally be received by the left and right eyes respectively. A three-dimensional image can be formed.　 According to the polarization characteristics produced, it can be divided into linear polarization and circular polarization. Linear polarization is polarized light that is perpendicular to each other. Circular polarization is polarized light propagating spirally. The principle of separating the left and right images is the same, but each technology has its advantages. Although linear polarization requires the glasses to remain vertical, a slight deviation will reduce the separation ability and produce ghost images, but its resolution is relatively high. This is why IMAX 3D uses linear polarization. Circular polarization does not require the angle of wearing glasses, and the crosstalk between left and right images is small, but the resolution is not as good as linear polarization. 2. Time domain separation This technology mainly uses the projector synchronization signal to open and close the projected left and right eye images and the 'liquid crystal valve' of the glasses synchronously to achieve the purpose of opening the left image, the left lens is open, the right image, and the right lens are opened, respectively. It is received by the left and right eyes of a person to form a three-dimensional image. This method of separating the left and right eye images by opening different liquid crystal lenses in time is called time domain separation, also known as an active 3D system. The time domain separation 3D technology, theoretically the separation of the left and right eye images is higher than that of the airspace separation technology, and the light efficiency is slightly higher. The requirement for the screen is not high. Any screen can be used. The disadvantage is that the glasses use batteries. , Relatively bulky, and the price is higher. 3. Color gamut separation　 This method is to project on the screen by separating the two left and right eye images according to different color components, and then use special technology to be received by the left and right eyes to form a three-dimensional image. 4. The initial red and blue glasses adopted this method. Of course, the red and blue glasses were not adopted by the film due to the serious color cast of the image. They were only used as an experimental experience of color gamut separation. The current upgraded version of DOLBY 3D is a fast-rotating color filter wheel installed in the projector. The red, green and blue are divided into high and low wavelength parts, each containing the left and right eye images, and the three-dimensional image is generated through color filter glasses.　 Since this technology needs to separate the spectrum of the picture, it will have a certain impact on color reproduction. Therefore, it is necessary to add color management software to the projector for color correction in order to obtain good results.　 The above three technologies are relatively mature, and the final effect is also accepted by the audience, so they are all applied in the current 3D projection of digital movies.