The principle of stereoscopic film

Three-dimensional movies are composed of two lenses, such as human eyes, shooting scenes from two different directions at the same time. During screening, two groups of films shot by two cameras are simultaneously screened by two projectors, so that two slightly different images overlap on the screen. At this time, if you look straight with your eyes, the picture you see is blurred. If you want to watch stereoscopic movies, you must install a polarizer in front of each movie machine, and the role of the polarizer is to play the role of a polarizer. The light emitted from the two projectors becomes polarized light after passing through the polarizer. The polarization directions of the polarizers in front of the left and right stereoscopic film effect projectors are perpendicular to each other, so the polarization directions of the two polarized lights are also perpendicular to each other. These two beams of polarized light are projected on the screen and then reflected to the audience, and the direction of polarized light remains unchanged. The viewer can only see the corresponding polarized light image with the polarized glasses, that is, the left eye can only see the picture reflected by the left machine, and the right eye can only see the picture reflected by the right machine, thus creating a stereoscopic impression like looking straight. This is the principle of three-dimensional movies.

Principle analysis

People's left and right eyes look at the same object, and the eyes see different angles, so the images formed on the retina are not exactly the same. After the two images are synthesized by the brain, they can distinguish the front and back, the distance and the distance of the object, thus producing stereoscopic vision. The principle of stereoscopic film is that two cameras imitate the visual angle of human eyes and shoot at the same time, and two projectors project on the same screen at the same time for left and right eyes to watch, thus producing stereoscopic effect. When shooting a three-dimensional movie, it is necessary to put two cameras on a special tripod head with adjustable angle, and shoot at a specific included angle according to the principle of the three-dimensional movie. The synchronization of the two cameras is very important, because even a few tenths of a second error will make the left and right eyes feel uncoordinated; So be sure to hit the board when shooting, so that you can find the synchronization point when editing. When showing a three-dimensional movie, two projectors are placed in a certain way, and two pictures are projected on the same screen point-to-point in a completely consistent and synchronous way. A polarizer should be added in front of the lens of each projector, one is a horizontal polarizer and the other is a vertical polarizer (or diagonally crossed), so that the screen will reflect different polarized light into the eyes of the audience. Viewers should also wear polarizers when watching movies, and the polarization direction of the left and right lenses must match the projector, so that the left and right eyes can filter out the unpolarized images and only see the corresponding polarized images, that is, the left eye can only see the images projected by the left machine and the right eye can only see the images projected by the right machine. After these pictures are synthesized by the brain, stereoscopic vision is produced. A film that produces a three-dimensional effect when shown by using the characteristics of human eyes' different viewing angles and convergence function. Ordinary movies or photos are shot from a single perspective, and the images are all on the same plane. People can only produce a sense of space according to their own life experiences (such as proximity, distance, smallness, light and shade). A stereoscopic movie is composed of two pictures with different horizontal viewing angles, which are similar to human eyes. During the screening, the two pictures overlap on the screen to form a double image. Through special glasses or a semi-conical lens grating in front of the screen, the audience's left eye sees the picture taken from the left perspective, and the right eye sees the picture taken from the right perspective. Through the convergence function of the eyes, it is synthesized into a stereoscopic vision image. Some of the images seen by the audience seem to be hidden behind the scenes, while others come out of the box as if they are within reach, giving people an immersive sense of reality. Stereoscopic movies with radial semi-conical lens gratings in front of the screen are strictly limited by the location of the seating area in the audience hall, so the audience's head can't move casually, otherwise the stereoscopic effect will disappear, which makes the audience feel extremely inconvenient. Colored glasses and polarized glasses are widely used in stereoscopic movies watched with glasses. Color glasses method is to print two images taken from left and right perspectives on the same screen in red and cyan (or green) respectively to make film. General projection equipment can be used for projection, but the audience needs to wear a pair of red glasses and another pair of blue (or green) glasses. So that the eyes passing through the red lens can only see the red image, while the eyes passing through the cyan lens can only see the cyan image. The disadvantage of this method is that the audience's eyes are unbalanced and easy to get tired; The advantage is that there is no need to replace the projection equipment. This method is often used in early three-dimensional movies. 1985 Tsukuba International Science and Technology Expo in Japan exhibited a black-and-white film in this way, and the effect was better. Stereoscopic film with polarized glasses has been paid attention to by many countries since 1922. Some countries combine it with movies with large vision to produce color stereoscopic films with higher quality and better effect. When this film is shown, the left and right pictures are projected on a metal screen with a polarization axis of 90 degrees, which will not destroy the polarization direction and become overlapping ghosts. When watching, the audience wears polarized glasses with a polarization axis of 90 degrees and corresponding to the polarized light of the projected picture, so that the ghost can be separated and a stereoscopic effect can be obtained. Due to the different production and projection techniques, polarized stereoscopic movies can be divided into two machines and single machine. 1985 Tsukuba Expo exhibits 70mm large-screen color stereoscopic movies. Since 1960s, China's stereoscopic films have been polarized stereoscopic films. In the 1970s, the Soviet Union experimented with holographic stereoscopic movies, with a wide range of image brightness without glasses. Because the visual adjustment and convergence of the audience's eyes are natural, it will not cause excessive tension and fatigue. As long as the audience turns their heads, they can see the position change like the real thing, which is more profound than ordinary movies, just like the real thing. This kind of film is still in the experimental stage.

Polarization technology

Have you ever seen a three-dimensional movie? Do you know the truth about it? This is an example of polarization with light. When watching a three-dimensional movie, the audience should wear a pair of special glasses, which are polarizers whose vibration transmission directions are perpendicular to each other. In this way, the scene seen from the screen is three-dimensional. If you don't wear this pair of glasses, the image on the screen will be blurred. Why is this? This should start with people looking at things. Observing an object with two eyes at the same time can not only broaden the field of vision, but also judge the distance of the object and produce a three-dimensional sense. This is because when people's eyes observe objects at the same time, the images formed on the retina are not exactly the same. The left eye sees more objects on the left and the right eye sees more objects on the right. These two images can distinguish the distance of objects after being synthesized by the brain, thus producing stereoscopic vision. Three-dimensional movies are composed of two lenses, such as human eyes, shooting scenes from two different directions at the same time. During screening, two groups of films shot by two cameras are simultaneously screened by two projectors, so that two slightly different images overlap on the screen. At this time, if you look directly with your eyes, the picture you see is blurred. To see stereoscopic movies, a polarizer must be installed in front of each movie machine, and the role of the polarizer is to play the role of a polarizer. The light emitted from the two projectors passes through the polarizer and becomes polarized light. The polarization directions of the polarizers in front of the left projector and the right projector are perpendicular to each other, so the polarization directions of the two polarized lights are also perpendicular to each other. These two beams of polarized light are projected on the screen and then reflected to the audience, and the direction of polarized light remains unchanged. When the audience watches with the polarized glasses, each eye can only see the corresponding polarized light image, that is, the left eye can only see the picture reflected by the left machine, and the right eye can only see the picture reflected by the right machine, thus creating a stereoscopic impression like direct viewing. This is the principle of three-dimensional movies. Of course, the actual projection of three-dimensional movies is to use one lens, and two groups of images are alternately printed on the same film, which requires complex devices. It's not involved here.