ZScreen

ZScreen is a push-pull electro-optical liquid crystal modulator that is placed immediately in front of the projector lens or computer screen to alternately polarize the light from each video frame. It circularly polarizes the frames clockwise for the right eye and counterclockwise for the left eye.

The RealD 3D system now showing in theaters is using the ZScreen that was invented by Lenny Lipton.

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Wikipedia