Circular Polarized 3D Glasses vs Linear Polarized 3D Glasses
What is the difference between circular polarized 3D glasses and linear polarized 3D glasses?
Both types of polarized 3D systems create the 3D effect by filtering the intended image to the correct eye using differences in light polarization, or “direction”. Hence, both techniques require a 3D silver screen or 3D silver paint when the 3D content is being projected, to be able to maintain light polarization, as standard white surfaces depolarize the light that hits them and deflected back to the viewer. For 3D polarized projection, each image for each eye should be polarized differently; that way the polarized 3D glasses can filter the corresponding image to each eye and create the 3D effect. The source of the 3D content is divided into left eye video and right eye video and each source/video is filtered differently. This can be done in various ways; for example, in the dual projector 3D projection system each video for each eye is projected using a different projector, so in order to polarize sources/videos differently you should simply place a 3D filter in front of each projector; then the light will pass through the 3D projection filters and will be polarized (obtain a different “direction”).
In a linear polarized 3D system, the 3D filters are made from a differently oriented “Linear polarizer” for each eye, in a circular polarized 3D system there is another layer attached to the “Linear polarizer” which is called a “Quarter Wave Plate”; therefore, on the circular polarized 3D system the light is first polarized linearly and only then gets its “right hand” and “left hand” spins when passing through the Quarter wave plate.
Polarized 3D glasses should be compatible with the projection filters, so if you are using linear filters, you will need linear polarized 3D glasses, and if you are using circular filters, you will need circular polarized 3D glasses.
Advantages and Disadvantages
For the viewer, the main disadvantage of the Linear Polarized 3D Glasses is that you can’t really tilt your head without losing the 3D effect, as the light direction is angle dependent. However, circular polarized 3D glasses allow some tilting of the head which makes them more comfortable when watching extended 3D content, like a 3D movie.
For the 3D cinema itself, the advantages of Linear polarized 3D glasses is that they cost a bit less than circular polarized 3D glasses, and, also, when using them with a dual projector 3D system a special technique can be implemented which will allow more light transmitted through the filters.
The most common type of polarized 3D glasses being used today in the cinemas are the “circular polarized 3D glasses” which is technology being used by brands like RealD, MasterImage, LG, DepthQ and others. The Linear polarized 3D technique is being used mainly by IMAX cinemas and private businesses.