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Old 05-22-2020, 11:03 AM
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Polarizedd light in LEDs


I want to use polarized light for macro photography. LEDs would be ideal because of small size and low power. I have polarizing filters and mounts but need a light source.

How about non-polar LEDs? Are they a potential source?
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Old 05-22-2020, 11:11 AM
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The usual way to get polarized light is to start with any old light source, and shine it through a polarizing filter. Do it the cheap and easy way, and you'll end up throwing away half of the light, though there are ways around this if that's a problem for you.
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Old 05-22-2020, 11:13 AM
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If you pass unpolarized light through a polarizing filter, the output will be polarized. However, it will also reduce the intensity of the light, so you need to take that into account.

ETA never mind, ninjaed

Last edited by DPRK; 05-22-2020 at 11:14 AM.
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Old 05-22-2020, 11:28 AM
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So is there anything special about polarized light and LEDs or is it just sos? And how about non-polar LEDs?
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Old 05-22-2020, 11:44 AM
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Quote:
Originally Posted by Crane View Post
So is there anything special about polarized light and LEDs or is it just sos? And how about non-polar LEDs?
Unless your diode is explicitly labelled as producing polarized light, I would assume the light is unpolarized. However, even the output from polarized LEDs, at least the early ones, is not completely polarized, so you would still need a filter.

What you need to find out is how many watts of light you need and at what wavelength(s), and see what LEDs, polarized or not, are available. The filters also need to be able to handle the power. If it is really low-power, it may not be a problem, but even LEDs producing a few watts or tens of watts get hot and need a heat sink etc.

Last edited by DPRK; 05-22-2020 at 11:44 AM.
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Old 05-22-2020, 12:01 PM
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There's always this, I suppose:

https://www.laserfocusworld.com/lase...-polarized-led

Quote:
LIGHT-EMITTING DIODES: Student develops first polarized LED

Martin Schubert, a doctoral student in electrical, computer, and systems engineering at Rensselaer Polytechnic University (Troy, NY), won the $30,000 Lemelson-Rensselaer Student Prize for his development of the first polarized light-emitting diode (LED), an innovation that could vastly improve liquid-crystal display (LCD) screens, conserve energy, and usher in the next generation of ultra-efficient LEDs.
https://www.nature.com/articles/lsa201222

https://www.spiedigitallibrary.org/c...73.short?SSO=1

I don't see any commercially-available polarized LEDs. But diode lasers ARE polarized, so if you don't want to throw away half your energy (or use some complex combining scheme) you can just buy a polarized laser diode.


Why do you want polarized light? It isn't necessary for macro photography itself. Are you planning to use it to improve contrast, or something?
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Old 05-22-2020, 01:35 PM
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Thanks - Yes I was looking at contrast enhancement.

I'm considering making some specimen holders for micro photography using embedded LEDs. I can pwm drive the LEDs so that they do not overheat the slide. Since there's nothing novel about LEDs and polarization, I'll make a test fixture and get some measurements.

I hesitate to have a laser diode anywhere near a microscope. Call me chicken.
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Old 05-22-2020, 02:26 PM
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Quote:
Originally Posted by Crane View Post
Thanks - Yes I was looking at contrast enhancement.

I'm considering making some specimen holders for micro photography using embedded LEDs. I can pwm drive the LEDs so that they do not overheat the slide. Since there's nothing novel about LEDs and polarization, I'll make a test fixture and get some measurements.

I hesitate to have a laser diode anywhere near a microscope. Call me chicken.
I'll bet you wear a Face Mask, too!
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Old 05-22-2020, 05:05 PM
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Yep, but it's difficult with a beak
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