How do linear polarization filters work?

3D polarization filters

Light is a form of electromagnetic radiation that spreads from a light source. The propagation happens in a relatively disordered manner. If we imagine a line drawn in the propagation direction, the electromagnetic light waves would oscillate along this line. Some waves would move up and down on the imaginary line others from the left to the right.

Polarization filters or polarizers are optical gratings that you can imagine as miniature bars arranged in parallel. If the light waves impinge on the optical grating of the polarization filter, only those waves are able to pass the oscillations of which have the same orientation than the grating. The exiting light is polarized.

If you turn the polarization filter by 90 degrees, the orientation of the grating changes. Light waves that were able to pass before are blocked now. At the same time, other light waves are allowed to pass.

With passive 3D stereo projections, the polarization filters are fitted in front of the projectors in such a manner that their optical gratings are orthogonal to each other. The same applies to the polarizers in 3D glasses.  This is the way, the desired channel separation is achieved, because the right filter only admits the right and the left filter only the left image.

The use of polarization filters always involves a loss of brightness. The underlying principle is: the higher the transmission factor respectively the transmission rate of the filter, the brighter the projection. Therefore, the use of anti-reflection glasses is advantageous. They do not only improve transmission but also help to extend the service life of the projector lamps.

Benefits of linear polarization filters:

  • Inexpensive
  • Excellent channel separation
  • Excellent results when using high quality filters


Drawbacks of linear polarization filters:

  • Ghost images when you tilt your head strongly
  • High light loss when using filters of poor quality
  • A 3D screen maintaining polarization is required


You can find our polarization filters here.


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