unfocused spot changing shape

[guitarman]

Hi guys

Pretty new to the DIY laser thing.

Recently "built" a 200mw green (basic build - driver and module pre-assembled).

I've noticed if I shine the unfocused spot at a wall, the round spot sometimes wiggles and changes into an oval with two dark lines through it. If I turn it off and back on again that usually makes it turn back to a spot. I know for sure that it's not due to a loose lens or anything, it seems to be something to do with the diode itself. I tried taking a photo but my camera on my phone doesn't show it up properly.

Is what I have described normal or do I have a faulty module?

Cheers.

 

[Wolfman29]

That's actually called mode-hopping. It usually has to do with overheating on the part of the crystal. It's relatively common in lower quality builds. I assume you got the 200mW green module from a cheap Chinese site?

 

[guitarman]

Bingo!

yep, was from a Chinese ebayer - Techhood. Was only $75ish with driver and module, so I'm not too concerned. As long as its not going to die after a few weeks use.

thanks for the info.