Do IR LEDs put out visible light?

Any at all?
If not, how can they be tested by a layman?
Is there a range for such things where some might and some might not?
Likewise, is there an UV LED that puts out 0 visible light?

Near-infrared (NIR) LEDs can output a small amount of radiation in the visible portion of the spectrum. This would generally appear as a very dim, deep cherry red glow that can be seen in a dark place after your eyes have adjusted to darkness, and is typically only visible with LEDs that emit NIR light at 900nm or shorter, and with LEDs that are driven at at least their design specifications.

Most video cameras and digital cameras are sensitive to NIR and short IR wavelengths up to about 1,300nm or thereabouts.

To the best of my knowledge, there are no UV or NUV LEDs that do not emit low but highly visible levels of visible radiation.

I've used a bank of 600 IR emitters, somewhere around 920nm, and when the panel is running I can't see the faintest glimmer of visible light. I can see 850nm light, but it fizzles out shortly past that wavelength.

Some people can barely make out the shorter IR wavelengths.

If it is pure IR light it should not be noticeable otherwise I may have missunderstood another useful sideeffect of IR light. /ubbthreads/images/graemlins/grin.gif

To answer your question about testing IR LEDs, and as Craig alluded to, you can view or photograph the IR with a digital camera or cam corder in darkness and you should be able to see it glowing. This works with TV remote controls at any rate.

...

I guess I'm one of those people then. I've never had problems seeing the LEDs, though the level of output they have in the visual range is almost useless beyond a few meters. The human eye just isn't designed to see in those ranges, which means the only way to take advantage of that light is to use a nightvision scope or a camcorder or camera equipped to detect in that range.

I have a first generation night vision scope with an IR illumunator. When turned on, in a dark setting, you can see the deep red light coming from the illuminator - but only if your standing nearby. It's not bright enough to the naked eye to give your position away from a distance.

My understanding is that LEDs emit light in a spectrum something like a bell curve - majority of the light energy centered within a few nm of center, then diminishing rapidly as you look up and down the spectrum from there. However, the curve is wide enough that you probably will find human-detectable amounts of light from just about any currently available LEDs that are UV- or IR-centered.

I am not sure of how deep into IR LEDs are these days, but I know that there are serious issues with UV LEDs that seem to get harder to keep stable as the wavelengths get shorter.

I can see a little RED glow at 850nm, but longer than that is invisible

A normal digital camera will allow you to check your IR LEDs and Radio Shack has a little $5 card with some strange chemical on it that will allow you to check for IR light

You first have to "charge" it with normal white light first

Once upon a time, in a long forgotten land that was covered by darkness, there came a Wizard named Peter. Peter the Wizard brought forth a device, about the size of one's little finger, that brought forth LIGHT upon this dark land. He called it, the ARC AAA. After the land lightened up, Peter the Wizard brought forth the ARC AAA in colors, to bring joy to the people.

It came to be that Peter the Wizard developed a warped since of humor. He brought out a new light for the people to enjoy, and called it the ARC AAA IR. It was pure magic......it would use up the power source (called the battery) and NOT produce any light that the people could see. It came to be that the light produced by this magic ARC AAA IR cold only be seen indirectly. When the people looked at the light through their digital cammeras, lo, they could see the light called IR. Some of the people that came from the a time before digital cameras, had devices called LIGHT Meters. It was found that some of these "Light Meters" could also see this light called IR.

The Great Peter the Wzard still, to this day, gets a giggle when one of the people find one of the magic ARC AAA IR lights and wonders why he can only see a dull red glow coming from the front of the light in a dark room! /ubbthreads/images/graemlins/party.gif

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INRETECH said:
...Radio Shack has a little $5 card with some strange chemical on it that will allow you to check for IR light...

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This card is Radio Shack part number 276-099 if anybody wants to buy one. /ubbthreads/images/graemlins/smile.gif
There is an orange square measuring about 1/2" on each side at the upper left of the card; this is the IR-sensitive region.



Here's a picture of one of these IR sensor cards.

Whats weird about it, is that you first must "charge" the sensor using White light from the sun or other source then the area is sensitive to IR

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INRETECH said:
Whats weird about it, is that you first must "charge" the sensor using White light from the sun or other source then the area is sensitive to IR

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I've used these cards and I've found that after a strong charge they will glow dimly even without a NIR source nearby. I'm guessing that charging the chemical excites some electrons and they somehow get locked into a higher orbit (conduction band), then the presence of NIR light knocks those electrons back down to a lower orbit (ground state), thus releasing (visible) photons...? Anyone know for sure?

BTW, there's a newer version of these cards that emits green light and doesn't require pre-charging. I don't know what the chemical makeup is though.

There seems to be at least two versions of arc AAA IR. I've got both versions. One appears to be twice as bright as the other.

Does the older (dimmer/less visible) arc AAA IR puts out more IR than the newer version?

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PhotonWrangler said:
BTW, there's a newer version of these cards that emits green light and doesn't require pre-charging. I don't know what the chemical makeup is though.

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I'm guessing this IR detector card uses an anti-Stokes phosphor, which does not require charging first.
This is how General Electric SSL-3 and SSL-3F LEDs from the late 1960s work. They have a NIR die at 940nm, with a green-emitting anti-Stokes phosphor over it.
I've never seen one, so I can't tell you how bright they are.

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The_LED_Museum said:
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PhotonWrangler said:
BTW, there's a newer version of these cards that emits green light and doesn't require pre-charging. I don't know what the chemical makeup is though.

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I'm guessing this IR detector card uses an anti-Stokes phosphor, which does not require charging first.
This is how General Electric SSL-3 and SSL-3F LEDs from the late 1960s work. They have a NIR die at 940nm, with a green-emitting anti-Stokes phosphor over them.
I've never seen one, so I can't tell you how bright they are.

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Wow... interesting. So that was probably the first phosphor-coated LED, and it was way back in the 60s! It couldn't have been that terribly bright since it has to "borrow" some of the energy to manage the upconversion process from IR to visible light.

Here is a photograph of a modern IR LED illuminating an anti-Stokes detector, like the original GE SSL-3 LED illuminated its phosphor:



I do not have this detector card; a website fan sent me the photograph, and it was used with permission.
The original GE SSL-3 came in a metal can type case in 1967, which I have not yet seen. It's one of the LEDs I have listed on my LED Museum's entry page as a specimen I'm looking for, so there is still hope of eventually getting one.

I am wanting to get a flash for a camera that I modified for seeing infrared light. Has any one made any progress with infrared led's. I was told that the led array worked good on video cameras but not on flash type. The camera I have is an Olympus D 380.
Can anyone help?