Polarization is another method of displaying 3D content via passive glasses. It works by using lenses that block certain wavelength of visible light. Linear polarized glasses use vertical polarization on one lens and horizontal polarization on the other. In a movie theater two images shot at slightly different angles are shown on the screen with two projectors. Each image is polarized to match one glasses lens and each image is then shown to a separate eye. This produces a 3D effect as long as the users head is kept straight. Tilting the head will break the 3D effect.
Circularly polarized lenses are polarized clockwise for one eye and counter-clockwise for the other. This method of polarization will maintain the 3D effect if the head is tilted and it also only requires a single projector. A circular polarizer is placed in front of the projector and it quickly alternates between the two polarizations to create the 3D effect.
In Dolby 3D Theaters a technology called Infitec is used. Infitec stands for interference filter technology. This method uses colors filters like the previously mentioned glasses but use a much more advanced method. Each color is split into two channels (Red is R1 and R2, Blue is B1 and B2 and Green is G1 and G2). Each lens lets one channel through and full color 3D is produced with only a very slight color difference sent to each eye.