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How to test / check for IR Emission?

Traveller

Traveller

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Hi2all!

Like many of you here, I own a 532nm laser which theoretically uses an IR filter. I plan to purchase safety goggles to protect against 532nm wavelengths but such goggles generally do not protect against IR wavelengths.

So clearly I'd like to verify that my laser is indeed equipped with an IR filter. Is there any simple way, without an IR card, to check for (heavy) IR emissions?

FWIW, I have a Sony Cybershot DSC-V1 that has the ability to take shots in IR mode (the camera basically removes the internal IR filter and also emits an IR beam). I figured that if a laser were to emit excessive IR, then it should be considerably brighter when viewed by the camera in Nightshot mode (IR) then when viewed in standard mode... .

What do you think and/or can you recommend a fool-proof test please?

Your $0.02 will be much appreciated  :)
 





Try this:

Get 1 or 2 negitive film cards,then things that come in disposible camera prints along with your pictures.

Cut into 5 prices and gather them up

Then shine your laser through the film negitives.

While doing that take a picture of video with your camera

If you see a purpleish dot their then that means it's leaking IR

Hope that helps!  
 
You don't need to go through all that. Just turn on your laser, & look through the LCD screen while pointing the camera at the laser FROM AN ANGLE. If it's leaking IR, you should see purplish colored rays coming out of the laser ;)
 
The green light is going to swamp out the IR, and most Sony cameras have detectors to switch out of night vision mode if there is too much visible light (to prevent them from seeing through clothing).  You'll need an IR-pass filter to block out the visible light and allow only the IR to pass through.

Even so, these green laser pointers nearly ALL produce noticeable amounts of IR compared to "real" IR-filtered lasers like the PGL-III (Alpha series) lasers, even if "filtered."  When I did some visual tests with my IR camera and an IR-pass filter, even the 5mW laser pointers still produced more IR than the PGL-III I have (~80mW).  Still, that doesn't mean the amount of IR emitted is dangerous; they nearly all leak some.  To test for a definitive amount, you'll need a meter and a way of blocking the green light.  A red-pass filter can work, just make sure it doesn't melt from absorbing the green.

You can always pay more for some broadband 532nm + IR protecting goggles.
 
Thanks to all for the kind support and innovative suggestions :D

Phoenix, I tried your "quicktest" but I can't say that I saw anything...  :-/

Bionic Badger, sounds to me like you've done some IR photography in your time...  ;)

Although I'd still like to try out the other options you've presented, in the meantime I figured out a way to check my own LP for an IR filter & yes, it has one! What I did was to remove the batteries and shine a powerful light source into the back-end of the host and I was able to clearly see the square blue-greenish filter that was glued in place.

As a matter of fact, I even managed to clearly see the KTP holder and the purplish Vanadate crystal (Nd:YVO4) attached to / behind the KTP  :o

But I will still try to run those test(s) because I think it's important to know when a pair of 532nm goggles will be enough or not. Bionic Badger, thanks for the link to the multi-wavelength googles, that would probably be the smartest move & I might even be able to swallow the $160 (+ shipping + 16% customs + 20% VAT - EU taxes...), but I don't want to loose to much visibility by blocking out too much light...  :-/
 
Hallucynogenyc said:
Just use a red plastic (like the one in a 3D glasses)

Google Images

Then just look after the filter with a digital camera (to test if it see IR just push the remote control of your TV and look at the light bulb with the camera).
Click to expand...

Well I did the test, verified that my cell phone will pick up IR light (much better than I expected) and shined the laser through the red lens of a pair of 3D glasses. The majority of the green light was filtered out, so to the naked eye it was just a very small and dim green point. On the camera though, it was a purplish-white light. Much larger than the dim green light, but not nearly as bright as the green laser itself was on camera.
 
Halfy said:
Well I did the test, verified that my cell phone will pick up IR light (much better than I expected) and shined the laser through the red lens of a pair of 3D glasses. The majority of the green light was filtered out, so to the naked eye it was just a very small and dim green point. On the camera though, it was a purplish-white light. Much larger than the dim green light, but not nearly as bright as the green laser itself was on camera.
Click to expand...

That works - although it's not a good measure of how much IR is leaking! You need a power meter for that.

Also - this thread was last posted to in 2009, over 7 years ago. Please avoid bringing back old threads from the dead.

Thanks!
 
Shine the laser through green blocking laser glasses and use a ccd camera to see if any ir is on the other side? Striking a black sheet of paper maybe?

Yes, web cams, security cams, all but photography cameras usually don't have the ir filter.

If you have a power meter you can use an ir filter and see if the output drops.
 
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You can also look for the IR 'dot' or beam width on a nearby wall using the CCD camera. IR, with its much longer wavelength, will have a much larger circle surrounding the 'dot' made by the green wavelength.
 
RedCowboy said:
Shine the laser through green blocking laser glasses and use a ccd camera to see if any ir is on the other side? Striking a black sheet of paper maybe?

Yes, web cams, security cams, all but photography cameras usually don't have the ir filter.

If you have a power meter you can use an ir filter and see if the output drops.
Click to expand...

Drops significantly at least - 532nm output will drop a little bit too with an IR filter.
 
Even cameras that DO have IR filters on them will be able to see near-IR light to some degree. You can easily verify this by pointing the camera at the tv remote and pressing a button. This will usually display flashes of light in some odd color (often purple-ish).

The wavelength of remote controls varies, it can be 850 to 980 nm, but is comparable to the IR light leaked from your typical green DPSS (808 and 1064 nm). The 808 nm pump light usually isn't collimated with the green light though, so at a distance it's not that much of a problem. The 1064 nm light may be more co-collimated, but if it's leaking a lot of that, the laser probably isn't working all that well (most modern dpss use intra-cavity doublers so leakage of 1064 also means loss of 532).
 
I think the best method is using a filter which passes IR but blocks green with a power meter, but without the meter maybe use a security camera without the IR filter to look for the presence of IR after the visual spectrum light has been removed, as an indicator, but of course that won't tell you how much is there in terms of power.

The general consensus is not to bring old threads alive, but my thought is either you add to an old thread, if a reasonable amount of time has been spent searching, or make a duplicate thread all over again making future searches more difficult for the specific question. But.... I suspect some trolls post to old threads on purpose to get a rise out of members who have issue with it. Best not to post to old threads if a new member so as not to be mistaken as one.
 
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As long as it's a sensible continuation or contribution i don't really see any problem with pickup up old threads.

That said, using cameras can verify that there is IR light emitted, and to some degree how well it's collimated with the desired green light. This is never quantitative as the sensitivity of cameras to near-IR light is extremely variable.

One thing that commonly leaks from 532 nm lasers is the 808 nm pump light, but that is rarely collimated with the green, so at a distance poses little danger. With intracavity doubling the amount of 1064 nm leaked is typically very low when the laser is working properly. If it is defective (e.g. due to a failed doubler), however, it might be signficant.
 
My iPhone appears to have a IR filter in it as it isn't very sensitive to that wavelength, but I bought a cheap CCD camera and removed the filter and it is sensitive enough now. I've made some measurements of the IR alone from a cheap 8 dollar 50-100mw 532nm laser pointer from China and found the IR to typically be 20-25 percent of the total power, that is quite a lot, probably far more than better pointers, but they have no IR filter in them, some of the 532nm pointers do.
 
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