Focusing dragon beam expander for minimum divergence

[davidgdg]

I have a Viper 125mw with a beam expander. My question is - how can I determine the correct setting for minimum divergence at infinity? There is nothing on the screw to show the correct setting. Is the only way to try it out or is there a more scientific technique?

Many thanks

David

 

[RA_pierce]

I would just set it at the best divergence over the longest distance you have available and put a dot of white paint on both sides of the expander to mark the best setting... so that when the dots are matched up, you know you have the minimum divergence.
It's easier to set divergence with someone at the other end of the beam to tell you when to stop.
Also, when adjusting, it isn't necessarily the best to set it at the smallest spot size at 'X' meters away, but at the point where the beam spot is the same size as the beam diameter at aperture 'X' meters away. This way, you don't get negative divergence (a converging focal point somewhere in the beam).

For example, with 1cm initial beam diameter from your expander, you want the beam to be close to 1cm at 1 meter away, 10 meters away, 50 meters away, etc.

 

[Laser_Ben]

I have a Viper 125mw with a beam expander. My question is - how can I determine the correct setting for minimum divergence at infinity? There is nothing on the screw to show the correct setting. Is the only way to try it out or is there a more scientific technique?

Many thanks

David

There really isn't a more "scientific" way of doing it rather then trial and error, there are several ways to measure the divergence as you adjust it, however I think the only one which is feasible and affordable for people is to use a long distance and a measuring device.

 

[davidgdg]

Thanks all!