Most human beings come equipped with two eyes and an absolutely amazing binocular vision system. For objects up to about 6 to 7 meter away, the binocular vision system lets us easily tell with good accuracy how far away an object is. For example, if there are multiple objects in our field of view, we can automatically tell which ones are further and which are nearer, and how far away they are. If you look at the world with one eye closed, you can still perceive distance, but your accuracy decreases and you have to rely on visual cues or focusing distances, both of which are slower.

The binocular vision system relies on the fact that our two eyes are spaced about 5 cm apart. Therefore, each eye sees the world from a slightly different perspective, and the binocular vision system in your brain uses the difference to calculate distance.

In a movie theater, the reason why you wear 3-D glasses is to feed different images into your eyes. The screen actually displays two images, and the glasses cause one of the images to enter one eye and the other to enter the other eye. There are two common ways for doing this:

  • Polarisation –  If you went to see Avatar at a 3-D venue you would have used polarised lenses because they allow colour viewing. Two synchronized projectors project two views onto the screen, each with a different polarisation. The glasses allow only one of the images into each eye because they contain lenses that are polarised as well.

  • Red/Blue – Polarisation cannot work on an ordinary TV or computer screen, so the anaglyph system is used. Two images are displayed on the screen, one in red and the other in blue (or sometimes green). The filters on the glasses allow only one image to enter each eye, and your brain does the rest. You cannot really have a colour movie when you are using colour to provide the separation, so the image quality is not nearly as good as with the polarised system.



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    Combined

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    Links

    http://robertinventor.com/anaglyphs/index.htm#cube