Well, i made some experiments with
this thing, that i got from DX (just cause now i have a better one from Vivitar
)
It's not cheap as the other similar ones, but this one have the internal tube in metal, and a longer course (for act both as microscope and telescope), so it's practically already a Galileian expander, so i said, why not try ?
IT WORK
You just need to take away the Porro prism assembly (AKA "inversion" prism), that you don't need in a beam expander and that cause some more power loss if left in place ..... for do that, unscrew the eyepiece, then unscrew the blocking disk, drop out the prism assembly (are the 2 parts i circled in red), and screw back the eyepiece ..... no need to place back also the disk, its only use is for keep the prism assembly in place ..... and ofcourse need to build some sort of adapter, taking away the gum paralight from the eyepiece (thing that you have to do also with other systems, anyway
), and, voila', a ready-to-use Galileian beam expander, with glass AR coated lenses.
Lenses have some sort of AR treatments, also if not optimized for lasers, they are a lightly blue tinted, so it will work better for red and green beams, than for blue, probably.
Still need to do decent optic measurements (no time at the moment), but from the first trials, using a simple "cheap" 50mW green module i got times ago from o-like, at 30 meters the dot is around 11mm dia without the expander, and around 5mm with the expander ..... ofcourse, as any other expanders, you have no more "straight" beams, from it, cause it's bigger than before, at the expander output, but after all, the purpose of an expander is to focus to long distance, not to burn at close distance, so i suppose it's not a problem
EDIT: sorry Hak, i just noticed that was a GB feeler, no intentions to ruin it ..... just to share informations :beer: