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FrozenGate by Avery

Checking IR output from Green Labby

H

Hodad

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I know this is a much discussed topic. I've read everything I can find on it in the forum. But I'm still not quite sure of the best way to test for it. I have a 200+mW Green Lab laser on the way and I've been promised it has a good IR filter with no leakage. I believe them ;) But call it paranoia, or maybe its just the engineer in me, but of course I'm going to want to prove it.

I saw something Bionic-Badger had posted about using a IR pass filter on a camera. Sounds good, and I've found some cheap ($20) IR pass filters but they only list one wavelength (eg - 700nm, or 850nm, 900nm etc). I don't know if this is their center wavelength or what the rest of the response curve is. So how would I know I'm covering 808nm and 1064nm?

Then there's the IR blocking filter from NOVA: I guess I could put one of those between the aperture and my power meter and see if the power drops. If it doesn't, then that proves there is no IR, right? But how much will the NOVA filter attenuate the 532nm power?

Has anyone concluded what the best method would be? Any thoughts on this will be much appreciated.
 





So the inexpensive ones are generally R72 filters, which means they pass light above 720nm. If you look through them things look like a really dark red, which means some visible light can make it through. I use a B+W #093 filter which allows no visible light through, though the filter cost a bit more (but still a good deal on Amazon. From what I've read, this filter passes only 1% at 808nm and 88% at 900nm. Some low-res response curves can be seen here comparing them. I really ought to do a comparison with the two filters to see if the apparent intensity changes.

Since 532nm is so far past the cutoff of any of those filters, all the 532nm ought to be filtered out anyway. I haven't tried it with any of my filters yet (as in shining a beam through the filter), mostly because I don't have a meter to verify the output.
 
Shine your labby through some coca-cola and look at the other side with a digital camera 8-) You can use other drinks aswell, pepsi may work, red grap juice may work, red wine may work, usually if you shine your laser through it and only a TINY amount of green comes through then that will work :)#

-Adam
 
Thanks guys, for the info. That's right in line with what I needed to know.
 
Exposed film works too I think, it blocks out visible light and passes IR from what I've heard. I think you have to take photos of black first though which I didn't do so haven't tested this yet.
 
Ahhh yes. . . . I do own a prism! [smiley=thumbsup.gif] Sometimes I tend to overlook the obvious. :-[

A prism should separate the green from the infrared, I think? Hmmm, more thinking required...

(and yes, I've always been interested in lasers but I am definately, quickly, becoming a fanatic) ;D
 
I've seen [link=cgi.ebay.com/5-pieces-wholesale-Nd-YAG-IR-1064nm-laser-visualizer_W0QQitemZ220277811606QQihZ012QQcategoryZ109452QQssPageNameZWDVWQQrdZ1QQcmdZViewItem]this[/link] stuff, which I think is incorrectly labeled - I think they mean that the ceramic is coated with KTP, but I'm not sure. Either way, what they are selling is a material that doubles certain frequencies, which has the useful effect of bringing the longer IR wavelengths down into the shorter visible range (just like these materials do in DPSS lasers). Unfortunately they don't tell us what the operable bandwidth is, so I don't know which IR wavelengths are covered.

There are less expensive cards that have a film window that is supposed to glow in the presence of IR. [link=www.rayscience.com/infrared%20viewer%20card.htm]These[/link] have various bandwidths including some broadband ones that cover pretty much the whole IR part of the spectrum.

I haven't used either of these; they're just things I've found while looking around. I'd love it if there was a paint or something that fluoresced in the presence of IR; I'd paint the area around my workbench. In teh meantime I might pick up a couple of those cards.

My digital camera can see every type of IR I am capable of generating, using IR LEDs, remotes, and lasers. One thing that surprised me was a green laser module from DX - it didn't appear to be emitting much IR in the forward direction, but there was a huge amount coming out of the *back* of the module, where the little circuit-board hooks on. I pulled the shrinkwrap away from the hole and picked up the module, and the IR coming out stung my fingers. Ironic, that someone in the path of the laser would be relatively safe but the person holding the laser gets cooked. (I've since mounted that module in a custom heatsink so I don't have to worry about it.) So sometimes it shows up where you least expect it.
 
Thanks Foobario. I have a camera that also does a very good job of seeing IR. I never thought about it possibly coming out the back! I'll have to carefully check mine there and from now on I'm going to have the mindset that IR can be coming from any part of the head - and check for it, or just do what you did so I don't have to worry about it. Thanks again :)
 
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