3D glasses and polarization, how it works?

In summary, the conversation discusses how 3D glasses work and the differences between passive and active glasses. The speaker also shares their own experiment with a cinema 3D glasses and an LCD monitor. They ask questions about the results and how polarization and perception play a role in creating a 3D image. It is mentioned that passive glasses use circular polarization while active glasses use lcd elements. The speaker also references Nintendo's use of a parallax barrier for 3D effects on their devices. The color shift in images seen through the glasses is explained by the variation in retardance of the quarter-wave plate.
  • #1
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I was thinking about how does the 3D glasses(not the one with red and blue lens) work. My first idea is that the lenses are polaroids with orthogonal polarization. So I got a 3D glasses from a cinema and try to prove it.

I wear the glasses properly(with the arms on my ears) and then look at my LCD monitor. if I rotate my head to about 45 degree, the whole scene becomes bluest. If I rotate 45 degree to the opposite direction, the whole scene becomes yellowest. The same for both eyes.
I also get the same result when I look at a rainbow, which should be polarized.
I do the experiment with LCD monitor again, but I am not wearing the glasses properly this time. I look through the lenses in the reverse direction(with the arms pointing to the screen) and the result is different. For 45 degree anti-clockwise rotation, nearly no light can pass, and for 45 degree clockwise rotation, the brightest image can be seen. The same for both lenses again.

If my idea is right, here is my question:
1. If I wear the glasses properly, I expect the image will be dimmer and brighter as I rotate, but why is it isn't the case and resulting in the change of color?
2. Why isn't the result be the same when I look from different side of the lenses?
3. The images are the same when I look through the left lens and the right lens, that means they have the same polarization, so how could we perceive a 3D image?
 
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  • #2
There are several approaches to 3D movies/tv/etc. AFAIK, 'passive' glasses use circular polarization: the combination of a linear polarizer and quarter-wave plate. This is so you can tilt and swivel your head around and still maintain the 3D effect:

http://en.wikipedia.org/wiki/RealD_Cinema

In order for the projected scene to maintain polarization, a metallized scrim must be placed behind the movie screen.

'Active' glasses have lcd elements that alternate viewing through the left or right eye:

http://en.wikipedia.org/wiki/Liquid_crystal_shutter_glasses

I'm not sure what magic Nintendo invented to do this:
http://www.nintendo.com/3ds/hardware
http://en.wikipedia.org/wiki/Parallax_barrier

Your lcd display produces linearly polarized light- if you turn your glasses around ('backwards') the linear polarizer is in front and this explains your results. Wearing the glasses normally, the color shift occurs (AFAIK) due to the chromatic variation in retardance of the quarter-wave plate.
 

1. How do 3D glasses work?

3D glasses work by using different colored lenses or filters to create the illusion of depth. The glasses separate the images intended for the left and right eye, allowing each eye to see a slightly different image. When the brain combines these two images, it creates the illusion of depth and makes the images appear to be in 3D.

2. What is polarization in 3D glasses?

Polarization in 3D glasses is the process of limiting the light that enters the lenses to only one direction. This creates two distinct images, one for each eye, which the brain then combines to create a 3D effect. The polarization process is achieved by using special lenses that filter out specific light waves.

3. How does polarization affect the 3D viewing experience?

Polarization greatly enhances the 3D viewing experience by creating a more realistic and immersive effect. Without polarization, the images would appear flat and without depth. By filtering out specific light waves, polarization allows the brain to perceive the images as having depth and dimension.

4. Can any type of 3D glasses be used for polarized 3D movies?

No, not all 3D glasses are suitable for polarized 3D movies. Only glasses with polarized lenses are able to filter out specific light waves and create the desired 3D effect. Other types of 3D glasses, such as anaglyph glasses, use different methods to create 3D and are not compatible with polarized 3D movies.

5. Are polarized 3D glasses harmful to the eyes?

No, polarized 3D glasses are not harmful to the eyes. The lenses in these glasses are designed to filter out specific light waves, not to magnify or distort them. As long as the glasses are used correctly and in good condition, they pose no harm to the eyes.

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