College Physics: Why does our teacher say that stereoscopic movies use polarized light principle?

Light waves are shear waves, and three-dimensional movies use the polarization of light.

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 two eyes observe an object at the same time, the images formed on the retina are not exactly the same. The left eye sees the left side of the object more, and the right eye sees the right side of the object more. These two images can be synthesized by the brain to distinguish the front and back, far and near, far and near of the object, 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.