3D Polarized Glasses

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Kurushimi
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3D Polarized Glasses

Postby Kurushimi » Tue Jul 27, 2010 12:29 am UTC

So, I have these two 3D polarized glasses. Each lens is polarized oppositely (hence the 3D). When I place the glasses facing each other, but have one upside down and the other right side up, I noticed (as expected) that almost all of the light was blocked out by the lenses. What I didn't expect was that the light that wasn't blocked out was all very blue/purpley. I expected things to get dark but not change color. I think I remember playing with polarized lenses in physics but I don't remember that happening (either that, or I was just really unobservant that day). What do you guys think could be causing things to turn blue? Does it have something to do with the fact that blue is on the end of the visible light spectrum?

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meatyochre
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Re: 3D Polarized Glasses

Postby meatyochre » Tue Jul 27, 2010 12:56 am UTC

Possibly could be related to the way old school 3d glasses are red and blue. Are 3d movies made with red and blue dependence, or is it just line drawings and comics that do that?
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Kurushimi
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Re: 3D Polarized Glasses

Postby Kurushimi » Tue Jul 27, 2010 1:13 am UTC

Well, the problem with that is that i can't get the glasses to show any red, no matter how I orient them. And wikipedia's page on 3D Polarized Glasses explains that they work merely by showing two images which are themselves polarized, but each eye only sees one image. The red-blue thing works on a similar principle, but I don't think they're connected in that way.

Cave Wizard
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Re: 3D Polarized Glasses

Postby Cave Wizard » Tue Jul 27, 2010 1:15 am UTC

My guess is that the glasses only polarize light at readily visible wavelengths, and making them block UV light would be more expensive, so they don't bother

That'd also explain why the ones I've used have those warnings about not using them as sunglasses

I don't know how light gets polarized by materials though, so maybe I'm completely wrong

Spen
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Re: 3D Polarized Glasses

Postby Spen » Tue Jul 27, 2010 6:18 am UTC

Might have something to do with them being circularly polarised? The real3d ones when you take them apart turn out to be 2 polarising lenses back to back different orientations (can't remember how different), might be worth taking one of the pairs apart to take a look at that? (Note: They are a BITCH to get into).

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Charlie!
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Re: 3D Polarized Glasses

Postby Charlie! » Tue Jul 27, 2010 6:43 am UTC

Oh yeah, circularly polarized filters always have that blue color. Probably because the wave plate used only has a specific frequency range where it's actually a quarter-wave plate.
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justaman
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Re: 3D Polarized Glasses

Postby justaman » Tue Jul 27, 2010 9:46 pm UTC

It could also be that blue light is transmitted better by the glasses than other wavelengths, much as blue light is the last to be filtered/scattered out as you descend in depth of water.
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Waylah
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Re: 3D Polarized Glasses

Postby Waylah » Sun Aug 01, 2010 2:13 am UTC

I vote cave wizard is right

Cave Wizard wrote:My guess is that the glasses only polarize light at readily visible wavelengths, and making them block UV light would be more expensive, so they don't bother

That'd also explain why the ones I've used have those warnings about not using them as sunglasses

I don't know how light gets polarized by materials though, so maybe I'm completely wrong

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Charlie!
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Re: 3D Polarized Glasses

Postby Charlie! » Sun Aug 01, 2010 6:31 am UTC

Waylah wrote:I vote cave wizard is right

Cave Wizard wrote:My guess is that the glasses only polarize light at readily visible wavelengths, and making them block UV light would be more expensive, so they don't bother

That'd also explain why the ones I've used have those warnings about not using them as sunglasses

I don't know how light gets polarized by materials though, so maybe I'm completely wrong

Linear polarizing filters tend to work by just being conductive in one direction and not another, with a more than wide enough frequency range. Plus, if they let through blue more already, they would have looked blue, which probably would have been noted.

It sounds much more like a waveplate is at fault.
Last edited by Charlie! on Sun Aug 01, 2010 12:09 pm UTC, edited 1 time in total.
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dainbramage
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Re: 3D Polarized Glasses

Postby dainbramage » Sun Aug 01, 2010 11:43 am UTC

Real3D uses circularly polarized light, then a QWP and linear polarizer in the glasses.


EDIT: This is in response to Charlie!, reinforcing the idea that it's the waveplate at fault.


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