Alternate-frame Sequencing

Alternate-frame Sequencing

An active shutter 3D system (a.k.a. alternate frame sequencing, alternate image, AI, alternating field, field sequential or eclipse method) is a technique of displaying stereoscopic 3D images. It works by openly presenting the image intended for the left eye while blocking the right eye's view, then presenting the right-eye image while blocking the left eye, and repeating this so rapidly that the interruptions do not interfere with the perceived fusion of the two images into a single 3D image.

An active shutter 3D system generally uses "liquid crystal shutter glasses" (also called "LCS glasses", "LCS 3D glasses", "LC shutter glasses" or "active shutter glasses"). Each eye's glass contains a liquid crystal layer which has the property of becoming dark when voltage is applied, being otherwise transparent. The glasses are controlled by a timing signal that allows the glasses to alternately darken over one eye, and then the other, in synchronization with the refresh rate of the screen. The timing synchronization to the video equipment may be achieved via a wired signal, or wirelessly by either an infrared, radio frequency, Bluetooth or optical transmitter.

Active shutter 3D systems are used to present 3D films in some theaters. It can be used to present 3D images on CRT, plasma, LCD and other types of video displays.