Why can I watch 3D movies with red and blue glasses?

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

The reason why human vision can distinguish distance is because of the difference between two eyes. People's eyes are about 5 cm apart, and nothing will have the same angle except aiming straight ahead. Although the gap is very small, it is transmitted to the brain through the retina, and the brain uses this tiny gap to generate the depth of distance, thus creating a three-dimensional sense. Although one eye can see objects, it is not easy to tell the distance between them. According to this principle, if the same scene is made into two images by using the difference between the two eyes, and then each eye sees its own image on one side, the depth of field can be stereoscopic through the retina. Various three-dimensional demonstration technologies also use this principle, which we call "polarization principle".

There are many forms of making 3D movies, among which polarized glasses method is widely used. It uses human eyes to observe the scenery, uses two parallel movie cameras to represent people's left and right eyes respectively, and shoots two movie pictures with tiny horizontal parallax at the same time. 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, the polarization axes of the left and right polarizers are perpendicular to each other and consistent with those in front of the projection lens; The viewer's left eye can only see the left image, and the right eye can only see the right image. The left and right images are superimposed on the retina through binocular convergence function, and the brain nerve produces stereoscopic vision effect. Show a coherent three-dimensional picture, let the audience feel that the scenery is coming, or enter the deep recess of the picture, which can produce a strong sense of "being there".

At present, cinemas mainly show two kinds of 3D movies with different principles:

One is imax large-screen stereoscopic film, which has the best effect, which is the so-called polarized light technology. When playing, two projectors with polarizers are used to display two parallax images at the same time, that is, the images that the left and right eyes want to see respectively. So, if you don't have charged 3d polarized glasses, what you see on the screen is a ghost, and the 3d glasses worn by the audience are two polarized lenses. Through them, our left eye and right eye can see the parallax images of the left eye and right eye projected on the screen respectively, thus creating a stereoscopic effect. The screen of imax cinema is as high as 16 meters, the image is very clear, the 3d effect is strong, and the sound is great, so it is the best in the stereoscopic cinema at present.

There is also a three-dimensional film called red and blue complementary colors, which has been shown in China before. When watching a movie, the cinema will give the audience a pair of left red and right blue filter glasses that can be bought for a few dollars. After wearing, the left eye can see the red shadow image on the screen, and the right eye can see the blue shadow image, thus creating a stereoscopic image. This kind of stereoscopic film is much worse than imax, and the stereoscopic effect is even worse, but the cost is lower, and it can also be shown on ordinary movie screens. More people can experience the visual magic brought by three-dimensional movies. At the same time, because this kind of movie has no restrictions on the screen, we only need to spend a few dollars to buy a pair of red and blue stereoscopic glasses, and we can watch stereoscopic movies on the computer. (Now this kind of movies are no longer shown in theaters, mainly downloaded by DVD BT)

Another commonly used technology is the stereoscopic glasses principle. This kind of stereoscopic glasses turns off the left and right liquid crystal lenses alternately in time sharing, and plays the parallax images of the left and right eyes synchronously and alternately on the screen with the playing software, so that our left and right eyes can see the parallax images respectively. As long as the alternating speed is fast enough, we can see stereoscopic images without flicker. Therefore, the requirements for computer monitors are higher, and CRT monitors are needed, and the refresh frequency is at least above 100hz.