808nm vs 980nm

Hi, I know that you can see a faint red spot with 808nm lasers, but what about 980nm laser? Also Does one have less divergence or are they both about equally as crappy?

well according to this document on 3d laser scanners that goggle indexed here ( 209(dot)85(dot)229(dot)132/search?q=cache:0pA9d4NTiUAJ:faculty.evc.edu/z.yu/nsf2/Module%25203.doc+laser+divergence+as+a+function+of+wavelength&cd=1&hl=en&ct=clnk&gl=us&client=firefox-a ) sorry for the screwed up link but I can't post real links yet.

"Divergence  is a function of wavelength and initial beam diameter.  Longer wavelength has larger divergence, and bigger initial beam diameter results in smaller divergence. "

so yes the 980nm has worse divergence than the 808nm. although how much worse is dependent on your application and circumstances.

Thanks for the reply. Divergence is crappy on both. How about the spot. I think it would be sweet to have no spot at all rather than a faint red spot.

I'm fairly sure 980nm would be completely invisible to the eye. I had some diodes at one point, but I'm not sure of their exact wavelength, but I couldn't see ANY light while they were running at all. Also, a camera didn't even see anything. yet when I pointed it into a power meter I got 500mW out. Very strange.

Thanks Gooey, that was the answer I was looking for.

POST 473

Yeah if you don't want to see anything you need something out side the range 380 to 750 nm (that's the range the human eye typically sees it can vary quite a bit.). longer wavelengths go towards infrared and shorter is towards ultraviolet. A sufficiently short or long wavelength is completely invisible to the human eye and most camera's without filters.

You can always see an IR spot if you get an IR card

http://www.youtube.com/watch?v=Ey46Qc9RVbQ