To present a STEREOSCOPIC MOTION PICTURE, two images are projected superimposed onto the same screen through CIRCULAR POLARIZING FILTERS of opposite handedness.
The viewer wears eyeglasses which contain a pair of analysing filters (circular polarisers mounted in reverse) of opposite handedness. Light that is left-circularly polarised is blocked by the right-handed analyser, while right-circularly polarised light is blocked by the left-handed analyser.
The result is similar to that of stereoscopic viewing using linearly and circular polarised glasses, except the viewer can tilt his or her head and still maintain left/right separation (although stereoscopic image fusion will be lost due to the mismatch between the eye plane and the original camera plane).