Check out this cool laser tester DIY. Very complicated but good source of information if you are into laser testing equipment.
The laser beam spot is the tool in laser welding cutting. Industrial lasers are really great, but there’s a huge problem when it comes to knowing the state of your tool. I mean, in a normal milling machine the mill bit can visually be examined to see if a part of the edge is chipped off. But how does your beam spot look? How is your beam quality? You might have pretty good idea of how good the beam quality is but the truth is: You don’t know. You can’t just look at the laser beam an tell. First of all trying to look at a laser beam without the right safety measures could seriously harm you. Secondly, if you’ve got these measures in place, theres nothing to see. Here’s a guide on how you can build yourself a laser beam analyzer! Get going! It’s great fun!