Are collimated LEDs at all useful / interesting / worth exploring?

rhd · May 23, 2011

What does the beam from something like one of these look like:
Thorlabs.com - Collimated LED Light Source

Is there any practical ability to get these beams anywhere near the size of a true laser beam? I didn't even know that the concept of a collimated LED existed.

lasersbee · May 23, 2011

It will look like a collimated flashlight beam by the look
of the optics.. IMO
It would be more of a focused LED...

You will never get a Laser collimated beam from a LED.
You can focus it to a degree but you will never get a
thin Laser like beam...(not today)

Jerry

Wolfman29 · May 23, 2011

What's the difference between a laser and a LED? Isn't it simply that a laser is:
1) Monochromatic
2) In phase

The rest of the characteristics of the beam are all derived strictly from the optics and housing of the diode, right?

Benm · May 24, 2011

The most important one you forgot:

A) emitting surface area

A (power) LED has a emitting area that is several square mm, whereas a (single mode) laser diode has an emitting area of about 1x1 um.

So yes, give the correct optics, you can get a beam with low divergence from a power LED. The problem is that it would probably be a meter in diameter if you wanted to get 1 mrad.

The divergence/diameter tradeoff is inherently limited by the emitting area, and doesnt rely on monochromaticity or phase that much.

Wolfman29 · May 24, 2011

But what if we are talking about your run-of-the-mill LEDs?

rhd · May 24, 2011

Something just popped into my head:

- Regular old digital projectors could turn black every pixel except the middle one, and you'd effectively get a very tiny beam. This would be a silly way to accomplish beam creation, since projectors use LCDs. But the point is that at the very least, a regular light source CAN produce a single very thin beam with the right optics. Still pretty bad divergence, but at least in the close visible range of 30 or 40 feet, it would appear to be a beam.

- Granted, this is hugely inefficient, because you're effectively taking one 480,000th of the actual optical power (1 pixel from 800x600). However, isn't the concept solid? IE, with the right optics, we can create a laser thin (or at least, laser with bad divergence-thin) beam from a regular light source.

Cyparagon · May 24, 2011

Assuming you had a contrast ratio of ∞:1, yes. But that's because the emitting area is now (in a way) the chip that filters the light. And the area of a single pixel on those LCDs is very small. Covering a light source with a black sheet of plastic and poking a pinhole and sticking a lens in front of it would likely have the same effect.

rhd · May 24, 2011

^ And would effectively give you the infinity to 1 contrast ratio you'd need.

laser_freak · May 24, 2011

I remember seeing a demonstration of a LCD projector being used to produce beam shows very similar to those of laser projectors. I cannot find the video, but I remember it was an application specifically designed to create laser-projector looking effects.

BShanahan14rulz · May 24, 2011

emitting area is very tiny for laser diodes, smaller than the diameter of a human hair. Emitting area is huge for LEDs. 1mm^2 was common, now more like 2 or 3mm^2 now. you can't focus an LED like a laser beam. BUT, much like a laser beam, if you expand the diameter of the beam, the divergence is easier to tame. Hence, the larger the lens' diameter that you use, the farther you can get that light to throw.

Benm · Jun 3, 2011

rhd said:
- Granted, this is hugely inefficient, because you're effectively taking one 480,000th of the actual optical power (1 pixel from 800x600). However, isn't the concept solid? IE, with the right optics, we can create a laser thin (or at least, laser with bad divergence-thin) beam from a regular light source.

This reasoning is not that bad - but what you are effectively doing here is creating a sheet with a pinhole over the large emitting area, reducing it by a factor of 640 x 480 in size. This would effectively make the light source similar in size of that found in a laser, and performance would be similar too.

Downside is a factor 300k loss, turning a 300 watt (optical!) projector into a measly 1 mw cat toy.

Helios · Jun 3, 2011

Benm said:
This reasoning is not that bad - but what you are effectively doing here is creating a sheet with a pinhole over the large emitting area, reducing it by a factor of 640 x 480 in size. This would effectively make the light source similar in size of that found in a laser, and performance would be similar too.

Downside is a factor 300k loss, turning a 300 watt (optical!) projector into a measly 1 mw cat toy.

Well you could use a much smaller light source to increase efficiency. It would always be less efficient than a diode BUT you could have a laser that is not only of ANY spectrum you could imagine but also one that you could tune the spectrum of on the fly! :bowdown:

EDIT: What if you were to pierce a pin hole in a sheet of aluminum and mount it right to the face of a high output LED like a smaller Cree and then mount that in a drilled out Aixiz module with lens?

I have a feeling it cant be that easy. And I guess it would not be a "laser" since it wont be a single wavelength.

Wolfman29 · Jun 3, 2011

Wouldn't a sheet of aluminum reflect most of the light back to the LED and then kill it?

rhd · Jun 3, 2011

Yet, perhaps this approach will finally allow us to achieve the "pink/magenta" miraculous wavelength.

Wolfman29 · Jun 3, 2011

We could get that "wavelength" just buy getting an RBG system and significantly boosting the red (or dropping the blue/green).

Helios · Jun 3, 2011

Wolfman29 said:
Wouldn't a sheet of aluminum reflect most of the light back to the LED and then kill it?

Paint it black. I also dont think LEDs are that sensitive if you had it heat sinked well.

Im also not proposing a finial design just a test prototype. I have a sneaking suspicion its not that easy but I cant figure out why it wouldnt work.

Also a thinner material than aluminum sheet might be better suited.

Wouldnt have much power probably since it would need to be a tiny hole but it would be awesome to create a collaminated beam similar to a laser diode but DIY and using different technology.

Are collimated LEDs at all useful / interesting / worth exploring?

rhd

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