The original 3D experience of movies depended on the viewer wearing stereoscopic green and red glasses. Problem is, it strains the eyes. Another process for 3D uses a special screen and polarized glasses. In this system images for the left and right eye are rapidly alternated, and the glasses pick up the appropriate image for each eye.

Now Sony and Panasonic have introduced an “active shutter” technique for high definition plasma and LCD TVs. The viewer still has to wear polarized glasses, but in this system the glasses have LCD active shutters that are synchronized with signals from the TV. The shutters rapidly block the right and left eye views alternately so each eye receives the correct image.