When each eye sees very similar, but different versions of an image, the brain thinks it is seeing depth, or three dimensions.

VOA: special.2010.01.26

The Magi here are, again, an image, a kind of visionary symbol, an image available "in the mind's eye" at all times.

这儿，三圣贤又是个意象，一个幻想出的标志，时时存在于大脑中的一个意象。

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So each eye sees a slightly different image, producing the 3-D effect.

VOA: special.2010.01.26

In this case the operator would wear goggles that convert infra-red light into an image that the eye can perceive.

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The cinema systems also don't flicker -- a big complaint about the active lenses, which shutter open and closed very rapidly to try to send a different image to each eye.

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The split-brain research mentioned by Gazzaniga included showing a subject a different image in each eye, meaning the right and left halves of the brain were presented with different stimuli, with neither being aware of the other.

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