3D glasses - how do they work?
Watching a 3D movie in a cinema is nothing new for most people now, but in fact, it has been around longer than you could think. The illusion that is created while watching a 3D movie is called stereoscopy, which in basic terms means that each of your eyes is seeing a different image and your brain is joining it as a one, 3D looking image. It may sound simple and the stereoscopy itself can be as old as photography, but how do 3D glasses work to give you that effect?
What movie producers switched to seems to be much better and working well with today standards and that is the technology based on polarized light. Here, two images are projected through polarizers of two different orientations, typically 45 and 135 degrees relative to the horizon. This way your right eye cannot see the same image the left eye sees and vice versa.
It may come as a surprise, but the polarized 3D technique was used all the way back in the 1990s, when 3D movies were largely popular. However, with the technological development that has happened since then, the movies are far greater quality now. One of the reasons for that is the use of digital projectors which have eliminated the need of using two projectors that had to be well aligned and perfectly synchronised.
There are still problems with the 3D glasses, one of them being that glasses used to cause headaches. If you wanted to watch a movie in 3D, your head needed to be level with the screen and any head tilt would change the way you see the screen. This has been dealt with by creating circularly polarized 3D glasses that are now used widely in cinemas all around the world.