3D is one of the fastest-growing areas in the film, television and games industries. But many people don’t know how they work, or why images seem to come out of the movie theater screen. Here are a few basic tips to understanding how 3D, or stereoscopic images are formed.
3D technology is based on the human characteristic of binocular vision. Our eyes are placed about two inches (five centimeters) apart. Therefore, each eye sees the world from a slightly different perspective. The brain uses these different perspectives to calculate distance by correlating the images from each eye into a single picture.
For a quick test of binocular vision, have a friend throw you a ball and try to catch it with one eye closed. You’ll find that it’s markedly harder than with both eyes open and your binocular system in operation. Or pick up an old fashioned View-Master, in which each eye is presented with an image that results from two cameras having photographed the object from slightly different positions. As your brain correlates the stereoscopic images into one picture, you are able to determine depth.
3D Glasses work on this principle. In a movie theatre or with a 3D TV, the screen produces a separate image for each eye. The glasses filter these images, allowing only one image to come through each lens.
Red-Green, Red-Blue and Red-Cyan glasses are commonly used in 3D, although they are being supplanted by polarized lenses and LCD glasses. These dual color lenses are used in systems in which two images are displayed on the screen by separate projectors, one in red and the other in blue or cyan. The filters in the glasses allow only one image to reach each eye, and the brain integrates the two images.
In the theater they use polarized light. All images for the left eye have one light wave and all images for the right eye have a second different light wave. Then the right lens will block the light waves of the left eye images. The left lens does the same. Television can not do polarized light waves so they use the above anaglyph 3d format.
Field sequencial 3d uses shutter glasses and looks just like polarized 3d and is often used for television as a better alternative to anaglyph 3d. The lenses use electricity to open and close. Now one lens will open while the other one closes and they do this back and forth really fast. Now when the image for the left eye flashes on the television screen the left lens will open. Then the right image will flash on the screen and the right lens will open. So each eye again only gets one image. This format requires and special tv, a convertor box, and the shutter glasses.