Divergence Issues

[Things]

Hey guys, last night I decided to take my laser outside and shine it onto a tree. now I know its only a laser rated for 100mw, but the divergence seems to be wayyyy off, and I know it would be ALOT brighter if the beam was tighter. So I measured the beam, at about 9 metres (Measured by estimation, not exact), and the dot is about 2cm big!Now its more oval shaped than round, so I am guessing there is some mode hopping going on? Its a CNI style laser module, and outta warranty, so I wanna try fix it up as much as I can. I find the divergence also makes alot of the test hard to read, since the beam is so thick. When I bought it, I knew it was gonna have a small line through the beam, but im pretty convinced this isnt caused by the line. Any idea's to what I could do? I'll get a pic of the dot now ..

Or am I just expecting too much, apparently the divergence is like .7mRad. Doesnt look like it @ that distance LOL



Cheers

[Dr Laser]

Refocusing the beam will help.

[Things]

The beam exits at about 1.3mm big. How would you recommend focusing it? Its hard to see how big the dot is, at a large distance.

[buffo]

Put someone downrange with goggles on. Give them a tape measure. Adjust the lens on the output aperture of the laser and have them check the beam diameter. Then adjust the lens some more. Eventually you'll find the point where turning the lens in either direction results in a larger beam. Find that middle point and you're golden.

This is best done with a longer throw. 30 meters or so.

Adam

[Zoof]

The beam exits at about 1.3mm big. How would you recommend focusing it? Its hard to see how big the dot is, at a large distance.

You could use a mirror to be close to the dot and the laser...

But 2m at 9m does not sound bad at all. My suggestion is that you don't get hung up on it. Dpss beams are simply not like gaussian hene beams. Anything you change except the focus is likely to make things worse. Take that from someone who completely rebuilt a lambdapro green dpss just because the beam wasn't aligned perfectly with the case

[Things]

Just seems like a kinda thick beam to me. TBH, I think it may be even less than 9M. I am actually starting to think it may have negative divergence (ie, the beam starts small, gets smaller and smaller, then gets bigger at a distance. I am going to remove my CNI module and play around with the focus abit. Atleast you cant totally screw up your laser with it :P

[Zoof]

Have a look at this applet, it may be of use to understand what is going on and settle on a final setting for your focus.

http://www.ee.buffalo.edu/faculty/ca...ets/index.html