now you will need to focus the laser, screw the lens all the way back into the housing
(if the laser has a focal point then you will have to unscrew the lens and take the spring out from behind it)
with the lens all the way in the beam should start out small and spread pretty quickly.
unscrew the lens a little bit and turn it on again, it should be the same as above but it has a lower divergence.
keep turning it on then undoing the lens a bit until the dot is quite small at a distance (if the beam focuses to a point then diverges you have turned it too far, screw it back in a bit)
you can either leave the laser like this or you can do the following step and try to get a really low divergence.
find somewhere that you can sit the laser somewhere and hang up a peice of paper about 20 or more meters away from it.
i used the neighbors tennis court i put a stool in one end and a peice of paper on the fence at the other end.
now get someone to stand near the paper as you shine the laser on it (put it in bluetack or something to keep it steady)
and slowly adjust the lens and get them to tell you wether it is getting bigger or smaller if it is getting bigger then turn it the opposite way and if it is getting smaller then keep turning (do this at night so the dot is easier to see).
by doing this i managed to get a divergence of 0.1mrad! i think its worth it
.
heres a picture of the paper with the laser shining on it at 34 meters away.
(if the laser has a focal point then you will have to unscrew the lens and take the spring out from behind it)
with the lens all the way in the beam should start out small and spread pretty quickly.
unscrew the lens a little bit and turn it on again, it should be the same as above but it has a lower divergence.
keep turning it on then undoing the lens a bit until the dot is quite small at a distance (if the beam focuses to a point then diverges you have turned it too far, screw it back in a bit)
you can either leave the laser like this or you can do the following step and try to get a really low divergence.
find somewhere that you can sit the laser somewhere and hang up a peice of paper about 20 or more meters away from it.
i used the neighbors tennis court i put a stool in one end and a peice of paper on the fence at the other end.
now get someone to stand near the paper as you shine the laser on it (put it in bluetack or something to keep it steady)
and slowly adjust the lens and get them to tell you wether it is getting bigger or smaller if it is getting bigger then turn it the opposite way and if it is getting smaller then keep turning (do this at night so the dot is easier to see).
by doing this i managed to get a divergence of 0.1mrad! i think its worth it
. heres a picture of the paper with the laser shining on it at 34 meters away.
. 
.
.