Re: 5mW 405nM $9 on eBay
I just got mine today and they're the same way. It's not a dud, it seems that is how most of these simple 405's look off of a non-fluorescent surface. I've heard it has mostly to do with how close to UV it is - it's almost as if you can't quite focus your eye's on the 'spot', right?
Kind of. The reason I say this is, when viewing from a distance, 30-35', it appears like I originally stated. If I get closer to the spot on the wall, While leaving the laser at 30-35' away, the smudge/pattern/whatever looks like a fairly clean dot with some difraction rings around it.
The oddest phenomonon is this...
I have vertical astigmatism in my eyes which makes a kind of ghost image of
the dot for other wavelength lasers I own (532nm & 650nm) appear above or below the
REAL dot. It's almost like a vertical line unless I squint my eyes. If I don't squint, I see something that looks like a line with 2 bright spots at either end. I know it's my eyes since rotating the laser does nothing to the displayed image. But, cocking my head from side to side, makes the line effect rotate from vertical to whatever angle my head is cocked to.
OK, with this 405nm laser...
The effect seems reversed. Instead of a vertical distortion, it's horizontal!
If I rotate the laser..no affect...however, if I cock my head, the distortion/line appears vertical.
I'm beginning to wonder if the effect i'm noticing is a combination of my astigmatism and some weird feature based on the 405nm wavelength and my brain is trying to make sense of it.
Very strange effect!
I'll never be a good beam analyser with eyes like this.