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Thread: is the light from colored LEDs mostly polorized?

  1. #1
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    Default is the light from colored LEDs mostly polorized?

    I have been told that "light emitted by LEDs usually shows some preferred polarized direction" and "with a polarizer you will only see a small reduction of light". Is this true? And if yes, why is this the case and do we have a general reduction percentage?

  2. #2
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    I know that LCDs are polarized. Not sure about LEDs.

  3. #3
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    Well LCDs are not light emitters, they optionally block light from other light sources via polarizers.

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    Get a polarizer and try rotating it. Just did it the display on my cable box and it did dim a lot but not total. My iPad dims out totally. Btw. If you shine a laser on a phone or iPad it acts like a grating and makes a nice dot pattern on the ceiling.

  5. #5
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    I just checked with a polarizer, apparently leds are NOT polarized and I wonder how the person who said otherwise got his phd.
    OLED and AMOLED screens appear to have polarized light because they have polarizer film applied to increase contrast in cost of brightness.

    But there seems to be a $80 solution to turning led light source polarized by only killing 20% of the source brightness.
    http://www.imagineoptix.com/technolo...ersion-system/

    But then again, what the hell is "etendue"? Even google just gives few results with vague descriptions. Depending on what that is, a 50%-75% increase of it might make this conversion optics pointless. Wish they would respond to customer emails...

  6. #6
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    Lightbulb

    Quote Originally Posted by gilbard View Post
    I just checked with a polarizer, apparently leds are NOT polarized and I wonder how the person who said otherwise got his phd.
    OLED and AMOLED screens appear to have polarized light because they have polarizer film applied to increase contrast in cost of brightness.

    But there seems to be a $80 solution to turning led light source polarized by only killing 20% of the source brightness.
    http://www.imagineoptix.com/technolo...ersion-system/

    But then again, what the hell is "etendue"? Even google just gives few results with vague descriptions. Depending on what that is, a 50%-75% increase of it might make this conversion optics pointless. Wish they would respond to customer emails...
    was just telling you what I saw with my eyes. Maybe the cable box display is not led. Little harse in the response. Drink less coffee.

    i can think of two quick ways to separate the p and q. Cube/plate and polarizer film. You toss half or more of the light away but that will do the trick. The reason you loose half or more is that the source is obviously random polarized. What are you doing that you need this? Maybe my cable box has a polarizing film on it. Not sure why they would do that. Looking closer it might be an lcd screen.

    i also think I remember if you bounce light off water it polarizes too. That’s why you can see into water with sunglasses.

    I really do hope you think before insulting in the future. It serves no point. My intention was to just tell you what I saw as I just happened to have a polarizer sitting on the table next to me for some random reason. Really I should learn to put things away.

    Have a a good day and if in the USA happy thanksgiving.

  7. #7
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    Etendue is the total light flux collected from a uniformly radiating object with respect to the optical invariant. It’s usually used when you’re talking about the radiometey of an optical system. VERY GENERALLY, you can look at it as a property of the optical throughput of a system.

    Edit with a better explanation in context to the link:
    in a perfect optical system, the entendue remains constant from the light source to the aperture. The less it increases, the “better”.
    Last edited by CountFunkula; 11-22-2017 at 06:01. Reason: Added more info

  8. #8
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    kecked, I wasn't refering to you, like I said in my first post someone had told me that "light emitted by LEDs usually shows some preferred polarized direction" and "with a polarizer you will only see a small reduction of light". I'm pretty sure he isn't from this forum.
    Quote Originally Posted by CountFunkula
    Etendue is the total light flux collected from a uniformly radiating object with respect to the optical invariant. It’s usually used when you’re talking about the radiometey of an optical system. VERY GENERALLY, you can look at it as a property of the optical throughput of a system. Edit with a better explanation in context to the link: in a perfect optical system, the entendue remains constant from the light source to the aperture. The less it increases, the “better”.
    I'll try to grasp this, while I'm at it, with an "Only 50-75% Increase in Etendue" between a light source and a laser scanner, a DLP or LCD matrix with this polariser converter sold on that webside ( http://www.imagineoptix.com/technolo...ersion-system/ ), what will happen? Just want to know what 'worse' translates to in terms of visual quality (focus, resolution) in these display systems.

  9. #9
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    Quote Originally Posted by gilbard View Post
    kecked, I wasn't refering to you, like I said in my first post someone had told me that "light emitted by LEDs usually shows some preferred polarized direction" and "with a polarizer you will only see a small reduction of light". I'm pretty sure he isn't from this forum. I'll try to grasp this, while I'm at it, with an "Only 50-75% Increase in Etendue" between a light source and a laser scanner, a DLP or LCD matrix with this polariser converter sold on that webside ( http://www.imagineoptix.com/technolo...ersion-system/ ), what will happen? Just want to know what 'worse' translates to in terms of visual quality (focus, resolution) in these display systems.
    I was wondering......have a good holiday all

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