How do circular polarization filters work?

Circular polarization filters work according to the same principle as linear polarizers. Optical gratings let only pass light waves with matching orientation.

Circular polarization filters are composed of two optical components: a linear filter and a so-called lambda/2 film. In a 3D projection, the light first passes through the linear filter. This process provides for a kind of pre-sorting and the light waves are aligned uniformly. Subsequently, the polarized light waves are twisted spirally: the light of the one image channel is twisted clockwise whereas the light of the other is twisted in opposite direction.

In circular 3D glasses, the light first passes through the lambda/2 film and afterwards through a linear polarization filter. The lambda/2 films restore the initial orientation of the light waves; the linear polarizer films realign them once again.

Not every pair of circular 3D glasses complies with all circular 3D filter systems. This is due to the alignment of the linear films. The most common system is 0/0 alignment. This means that the optical gratings of the linear films run parallel in horizontal direction. This system is used by RealD in all RealD cinemas and has established as a standard in the meantime. Circular 3D glasses with 0/0 alignment work very well in Master Image II cinemas and in combination with the most passive 3D TV sets and monitors.

Circular polarization filters with linear 0/0 alignment are excellently suited for passive 3D projections with DLP beamers. They are not compatible with LCD or LCoS beamers, however. In LCD and LCoS beamer systems, the light is pre-polarized. The light waves of the green light range are treated differently than other light waves, however. The use of circular 0/0 polarization filters produces color shifts. Therefore, we always recommend buying DLP projectors. We offer special circular polarization filters for LCD beamers. LCoS is not recommended.

Benefits of circular polarization filters:

  • Excellent channel separation even when you tilt your head
  • Excellent results when using high-quality filters

Drawbacks of circular polarization filters:

  • More costly than linear polarization filters
  • High light loss when using filters of poor quality

You can find our polarization filters here➝

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