During cinema screening, two projectors are used, and each frame of the movie is simultaneously projected to simulate two images captured by the left and right eyes. The two images are stacked together to create a blurry image.

To achieve the effect of binocular stereo imaging, the key is to make the left and right eyes only see the corresponding images, and then synthesize them into one through the brain. The secret of blurring and stereoscopic transformation is hidden in 3D projectors and 3D glasses.

In 1922, the world's first 3D film was released on glasses usa, and the audience wore the earliest 3D glasses - red and blue light glasses.

This form of a 3D movie, when projected, adds red and blue filters to the left and right projection machines respectively, resulting in two different colored images.

The glasses worn by the audience have a filtering function, with red lenses responsible for filtering blue light and blue lenses filtering out red light, so that the left and right eyes can see monochromatic images separately.

It is low-cost, but colored filters can distort the color of the image, which is fatal for film art that emphasizes color. Currently, polarized 3D glasses are commonly used in commercial cinemas.

Light is a transverse wave with a polarization phenomenon, which means that the direction of vibration and propagation are asymmetric. The natural light we see every day is an irregular collection of countless polarized lights that do not deviate from a certain direction, so it is nonpolarized light.