How Does Double Image Stuff Make Us See in 3D? Part 2

This follows on from the previous post on 'How does Double Image Stuff make us see in 3D. The answer: Active and Passive glasses. Yep, to see these images and movies in 3D means wearing cool (or sometimes not so cool) glasses. Let's look at the 2 types; Passive and Active.

Passive

Passive glasses break down into 2 types, Anaglyph and polarized.

For Anaglyph, think back to the eighties (those who are old enough) and you may remember those strange red and green cardboard glasses that you got in cereal packets to see cool 3D images. Each lens would be a different color (e.g. red and blue). The TV picture/ still picture's 3D picture consists of two identical images in 2 slightly different locations, one with a blue tint and one with a red tint. The red lens absorbs all the red light, effectively blanking out the red-hued images whereas the blue lens cancels the blue light, canceling out the blue-hued images. The eye behind the red lens sees the blue image and the eye behind the blue lens the red image. The brain puts them together which gives you the 3D experience. In the polarized glasses, a similar process takes place but instead of using color filtering, light passes through each lens depending on a particular angle that the light is projected. This method is much more common in modern TV and movie systems and the color is less affected than than the Anaglyph system.

Active

In modern active glasses, the two images are separated by each lens opening and closing alternately (by using LCD technology). Using an infrared connection to the TV or movie system, the two images at different locations are presented alternately every frame and synchronized with the glasses. The result: the switching of images happens so quickly that the eye does not notice and the lenses open and close at the same speed as the alternating TV image, giving the viewer the 3D affect. Which methods become the mainstream remains to be seen, still early days, although suffice to say the old Anaglyph glasses have probably already passed into the realm of Nostalgia!