do IR lasers need different focus/lens?

[Mannitu78]

Hello,
is it just me or is focussing a 850nm diode more difficult? None of me lenses i use for my blue lasers really work. I can get a point only on 30 or 40 cm distance maybe. I tried the usual 9mm-stuff, G8 lens, three-element....

 

[Gryphon]

I havent tried anything deeper into the IR than 780nm, but even that focused down fine with plenty of room to spare with stock plastic lenses, G2's and G8's.

 

[RedCowboy]

Hello,
is it just me or is focussing a 850nm diode more difficult? None of me lenses i use for my blue lasers really work. I can get a point only on 30 or 40 cm distance maybe. I tried the usual 9mm-stuff, G8 lens, three-element....

(1) What kind of 850nm laser do you have ?
(2) How about posting a pic of the laser ?
(3) Have you looked at the lasers specs ( emitter size and divergence ) ?
(4) I assume it's multi mode..... is it multi mode ?

 

[Eidetical]

Lenses designed for blue, or lenses corrected for the visible may not work well in the infrared. The problem may also be that the antireflection coatings on a lens made for use with blue light might be reflective at 850nm. Even broadband AR coatings may have that problem.

 

[paul1598419]

I have an 808 nm laser that I was able to focus well using a G2 lens. Can't imagine a small emitter diode at 850 nm being any more difficult to focus than mine.

 

[steve001]

Generally no. Technically yes lenses are made from different materials that have better transmission for IR. Optical coatings are also important. Info.

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