Stereoscopic systems operate by presenting two distinct images to a viewer. Filtering may be utilized to present one image to one eye, and the second image to the other eye. Filtering may employ polarization or spectral-division methods to separate the two images.
One example of a widely-implemented stereoscopic projection system is the ZScreen (manufactured by the assignee, RealD). The ZScreen includes a liquid-crystal based polarization switch located at the output of a projection lens. The ZScreen alternates the polarization state of the outgoing light between two orthogonal polarization states in synchronization with the display of the left and right eye images at the projection panel. Spectacles (or eyewear) pass orthogonal polarization states to each eye and complete the filtering function.