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FrozenGate by Avery

Focusing infrared.

agravlin

agravlin

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I've seen a few infrared builds with focus rings.

How exactly do you accurately focus infrared? It's not visible, so you can't exactly see where you're putting the focal point. I suppose you could put your hand in the beam and feel for the point where it is the hottest, but that's just stupid.

I suppose you could look at the beam through a camera, but you don't have three hands, so you'd have to hold the camera with your feet - or your genitals...

So really, what purpose does a focus ring serve on an IR/UV laser if you can't even figure out where the focal point is?
 





so it can be adjusted. once you get an idea of where its focused at you can kinda learn a quarter turn moves the focal point +- 5 feet.

But thats just my 2 cents
 
^It depends on the IR wavelength. You can see it up to about 850nm, past that it's completely invisible.
 
My 2 cents worth would be as follows.
for ir steal the flir camera out of the lockbox and run some focus settings per distance measurements so i could later mark the focus ring and host barrel with some form of corresponding graduations.

2nd experiment would be to try a small pinhole and ir thermometer at the distances in question.
when there was an indication of temperature rise on the target behind the pinhole, i'd have an indication i was focused at the pinhole distance.

cant see ir enough to focus it let alone get the aim down pat?
try photosensitive stock, or maybe a low reflective filter arrangement that would allow the dot to become viewable.

for uv, that's easy, get some flourescent paint off the nearest hippie.
 
agravlin said:
I've seen a few infrared builds with focus rings.

How exactly do you accurately focus infrared? It's not visible, so you can't exactly see where you're putting the focal point. I suppose you could put your hand in the beam and feel for the point where it is the hottest, but that's just stupid.

I suppose you could look at the beam through a camera, but you don't have three hands, so you'd have to hold the camera with your feet - or your genitals...

So really, what purpose does a focus ring serve on an IR/UV laser if you can't even figure out where the focal point is?
Click to expand...

I simply use a digital camera on a tripod, it's really easy. My c-mount is too far in the IR to see anything at all with the naked eye, even at >3watts, so I really don't have many other options and the camera does just fine.
 
You could put a camera on a tripod or you could place the laser in a holder and sit the camera on the ground and lie on the ground and look through the camera, there is also these cards you can buy on CNI lasers that show up infrared I've never used one but they look great, last suggestion, you could wire a video camera to your T.V and do it that way... anyway, just a few ideas.
 
Wow I just logged onto the link for Aixiz in post #9 and got an warning that there are malious threats there from my virious software ?
 
^ I tried the link and it didn't come up malicious for me. Strange. <scratches head> I wonder if the OP found how easily you can find the focal point with a match/IR eyewear quite easily.
 
I just find the smallest spot where it burns into a piece of wood with a majic marker spot on it or where it burns the best is how far I hold it. It will burn white hot it the smallest point. But I cand seem to focus it for distance. Any ideas?
 
High powered IR diodes usually have a terrible beam profile, they don't tend to focus very well over long distances.

Nice thread bump BTW :p
 
blogging?
Anyway, you posted a reply to somebody that posted a questions roughly a year ago. Usually that's not very useful, he'll probably already have his answer or gave up. It brings up threads that are not that relevant anymore, so people try not to post in topics that are very old.

Things gave the right answer of the focussing. Usually the higher the power of the laser diode the worse the beam profile, and that also affect the divergence and spot size in case of a focussed beam.
 
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