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My question is why do 3d movies have a red and blue"double image" that is basically just a few inches to the right and left of the real image. And how does this help us see the image as "3d". Does it have anything to do with polarized light. And do you need a special computer screen to produce these images because when I use 3d glasses to loot at 3d images on google i still see the see image?

Qmechanic
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random user
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    The red/blue 3D system is different from the modern circular-polarization system. Your post seems to conflate the two. – dmckee --- ex-moderator kitten Oct 31 '15 at 20:38
  • Your brain primarily interprets depth by seeing how much an object shifts position between your two eyes' images: more shifting = closer. Convince yourself of this by alternately winking one or the other eye. All technologies (red/blue filters, polarized filters, interlaced images, separate screens) are based on feeding your two eyes slightly shifted images to trick your brain into seeing depth. –  Nov 01 '15 at 02:31
  • I'm voting to close this question as off-topic because it shows insufficient prior research – John Rennie Nov 01 '15 at 08:08

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red/blue double image is the (very) old technology to see 3D on paints, drawings and ordinary screens. See 'Anaglyph' on wikipedia. It requires red/blue glasses (very cheap on Ebay :-) ).

Polarized display is expensive, and is the one requiring polarized glasses.

Fabrice NEYRET
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  • so polarized displays wold be the movie screens at amc or other big movie theaters. – random user Oct 31 '15 at 20:37
  • yep. and they are 2 kinds : both using polarized glasses, but not the same. ( parallel vs circular polarization). They are also some theaters with the electronic glasses fastly shuttering each eye in alternance (no polarization, then). – Fabrice NEYRET Oct 31 '15 at 20:43
  • Indeed the display is metallic, it's the projectors which are polarized. – Fabrice NEYRET Oct 31 '15 at 20:44
  • The parallel type didn't last long. It causes headache and confusion anytime you snuggle up to your date put your head on his or her shoulder. – dmckee --- ex-moderator kitten Oct 31 '15 at 20:44
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    Yeah, but with the circular if you rotate your head at the frequency of light the stereo won't work any more. Nothing is perfect :-p – Fabrice NEYRET Oct 31 '15 at 20:46
  • @hoodlamic1 : indeed with some training you can use your paint program to draw simple 3D shapes (that you will see 3D in your red-blue glasses). And you can easily programm this, see for example interactive online examples in shadertoy : https://www.shadertoy.com/results?query=anaglyph – Fabrice NEYRET Oct 31 '15 at 20:50
  • Some examples of red-and-blue 3D figures on the site: http://physics.stackexchange.com/a/194688, http://physics.stackexchange.com/a/200611, http://physics.stackexchange.com/a/197239, http://physics.stackexchange.com/a/198171, http://physics.stackexchange.com/a/192583. Alas the user who did those left us. – dmckee --- ex-moderator kitten Oct 31 '15 at 21:43