D is the prefix of English Dimension, and 3D refers to three-dimensional space. Internationally, 3D movies are used to represent 3D movies.

In daily life, people observe three-dimensional external scenery with two eyes. 3D movie is a kind of movie that uses binocular stereo vision principle to make the audience get three-dimensional spatial sensory images from the screen. It is different from ordinary movies, which only have a sense of plane when showing.

There are many ways to make 3D movies, such as shooting two movie pictures with slight horizontal parallax with two parallel movie cameras. During screening, two films are respectively loaded into the left and right film projectors, and two polarizers with polarization axes of 90 degrees are respectively installed in front of the projection lens. The two projectors need to run synchronously and project the picture onto the metal screen at the same time to form a double image of the left image and the right image. When the audience wears special polarized glasses, because the polarization axes of the left and right polarizers are perpendicular to each other and consistent with the polarizers in front of the projection lens, the audience can only see the left and right images with their left eyes, and the left and right images are superimposed on the retina through the binocular convergence function, resulting in stereoscopic vision effect with the brain nerve; A camera is equipped with two lenses, and the distance between the lenses is similar to the distance between human eyes, about 2.5 inches, which is convenient for shooting. A projector is enough for projection. The picture is put on the screen as if it were a ghost. At this time, when the audience wears glasses with a red lens and a blue lens, each lens filters out another image, and the human brain fuses the two images together, and the stereoscopic picture pops up.