I see dead "waves" :)

[sigmounte]

Hello ,

i'm trying to make another illuminator , i have a lab 808nm IR laser ( 150mw) , i can see the beam with my night vision camera , but i have a problem :

i send the laser to a white paper on the wall , film the wall .
I can see a really bright spot in the center , and lot of circlex around this spot , and some kind of waves all around the same spot .

It's clearly unuseable for IR illumination , impossible for me to understand what i'm illuminating .

So my question : what kind of optics do they use to flatten the spot ??

Thanks

 

[WizardG]

I think what you're seeing are diffraction artifacts that most laser diodes will produce. Rather than trying to clean up the laser I'd suggest you use a high power IR LED instead. They're available with several watts of optical output in many wavelengths.