RealD: Denotes a 3D projection process that does not require a second projector like some older models. Instead, already existing DLP-Projectors are used that only get an attachment. The spectators need special glasses, the operator needs a silver-coated screen. The technique RealD uses is similar to the traditional method of 3D projection, the linear one polarization uses.
In the traditional method, two linearly polarized images are projected onto the same screen, polarized at +45° and -45° from the horizontal, respectively. The viewer's glasses, which polarize at the same angles, ensure that each eye sees only the correct image. This type of 3D projection requires two projectors and has the disadvantage that ghost images occur when the viewer tilts their head to the side and the angles of the polarization filters on the projector and glasses no longer match exactly.
Disposable glasses RealD methodRealD, however, only requires a single projector that alternately projects the right and left image and uses circularly polarized light. A LCD-Element in front of the projection lens polarizes the light clockwise for one eye and counterclockwise for the other. A combination of a retardation plate and a polarization filter sits in the spectator glasses. The retardation plate converts the circularly polarized light into linearly polarized light. The polarization filter behind it only lets through the light of one polarization direction. Different orientations of the polarization filters in the lenses ensure that each eye only sees its own image, even when the viewer tilts their head. The very high refresh rate of 72 frames per second and eye ensures a flicker-free image. Since the video signal only delivers 24 frames per second, each frame is projected three times in RealD Cinema to avoid a flickering effect.