Focusing an IR beam?

[mliptack]

Hopefully pointing it at the camera didn't fry it... assuming it was at a high enough power density, and also assuming the cam doesn't have the IR filter.

[Aseras]

look for a blueish dot. that's your laser. any camera IR filtered or not should see it unless it's over 1300nm.

[The_Doctor]

Forget the cam. Try a bit of thermal paper, a shopping receipt is likely to provide. Pass it quickly through the beam oriented like a karate blow. If you can get a thin clean black line at the point you want it focussed, you have it set right. Pass it slower if you don't see it the first time. Don't get your eyes too close, and arrange it so the angles are such that it can't reflect strongly at your eyes.

You might need a cam if you're looking for a 5 mW beam, but if you're working with over 20 mW, thermal paper should tell you more, and more accurately too.

[mliptack]

Thats really smart... when you first said thermal paper all I could think of was that 'mood paper' that would change colors from the temp of your hand. That would be interesting as well except for the fact that it was made of a plastic, and would likely melt really fast...