Got my Opto 40mW, odd faint circle visible around the point

[elsporko]

Just got my 40mW Optotronics greenie, rated at 44mW. So far, I love this thing. The beam is bright, the dot is great, pops balloons, overall it's just awesome (of course, this is in comparison to a <5mW laser I had before... But still! )

The only thing I'm having trouble with is a faintly visible green circle that is around the dot. It isn't visible on certain surfaces, but if you focus you can see it. I'm just wondering if it's normal, or if there could be something wrong with the laser itself, or if it's something small like the lense being smudged or something. Forgive me, this is my first real laser

I tried to take some pictures, but it's very hard to get a good idea of what it looks like with this camera :\

Again, it's hard to see, but I tied to outline in red where I could see the circle I'm talking about. I think it's easiest to see in the third image. It's like there's the normal dot, and then the surrounding light of it being reflected, but then there's a subtle, near perfect circle just around it.

I can live with it, since it's only really noticeable if you look at it closely (which I don't think you should be doing anyways ) but I'd like to know if I can just leave it, or if I should do something about it.

Edit: I just went into a much darker room and tried it on a wall about 4-5 meters away. The green circle is a lot more visible in the dark, and measuring about a foot from the laser point to the edge of the circle.

Another picture:

I put my two fingers just around the beam about a foot away from the laser or so. You can see the beam is about a centimeter away from my bottom finger, but most of that area of my finger is covered in green light. I just tried cleaning it a bit with a q-tip, but that didn't help much.

 

[millirad]

Yes its normal for run of the mill optics. You can get better beam profiles in the higher end products. It really doesn't matter too much though.

 

[Bionic-Badger]

They come often from internal reflections within the laser barrel and the "run-the-mill optics" as millirad said.

You should see rings the "labby" lasers DX sells produce. Now THOSE are awful.

 

[elsporko]

Thanks for the replies.

I'm glad to hear that it's not uncommon. Is this dangerous at all? The circle can get pretty big when you point it far away. If someone were to walk into the area of it, would it be very dangerous? I'm not gonna go around pointing it at people, but if I point it somewhere in the daytime and the ring (which is pretty much invisible during the day) goes over their eyes by accident since I can't see it, could it damage their vision? I'm just curious Better safe than sorry, right?

 

[matrixcs]

so what could be the possible solution for this guys?

 

[Jaseth]

I really don't see that outer ring damaging anyone by accident. Green 532nm is close to the most visible light, which means even very weak light is quite visible. Therefore, if the light is almost invisible, it will not have the power to damage eyes in an instant. In particular when you are far away and the ring is large, the power of it will be more spread out and even weaker.
With other wavelengths you will have to be careful however, as they are less visible but burn just as much. My DIY blu-ray @ 146mW has an almost invisible dot at a 20 foot distance when the sun is out, but if I aimed it into someone's eye they would have their vision seriously damaged.

 

[Bionic-Badger]

so what could be the possible solution for this guys?

You'd need to attach some sort of aperture to the end or modify the one that the beam exits from, so that it absorbs the stray light, or reduces those reflections.

On those diode lasers, the axziz lens is usually round near the end that goes towards the diode to make the output look round. However, this reduces the output because the light is just blocked away. I also worry that the light will reflect back to the diode and reduce its lifespan.

For the greens, if you can get the front aperture off without messing with the optics or something, then maybe you could spray some matte black paint into it so that it doesn't reflect as it goes out.