240mw Green Lasers - How Dangerous are they?!

[GreenMist]

About ten years ago, I bought two green lasers off ebay. I was 18 at the time and thought they were pretty cool, and being in the UK, I couldn't really see any mainstream websites to buy them from, whereas there was an abundance on ebay. So, I did my research, and found a seller that was stocking 50mw, 100mw, 200mw etc green lasers and had very good feedback. I had some back and forth with her about what I had read was a problem in some other green lasers "No IR filter," and she reassured me all the lasers she sold had IR filters. I think the one I bought was 100mw in the end.

Prior to that purchase though, perhaps before doing my research, I had bought a "240mw" green laser off ebay too. It was somewhere in China or Hong Kong. Now don't get me wrong, I was suspicious about the product in general. I came to find out that all 240mw green lasers weren't actually 240mw but more like about 30mw, and they also had no IR filter. Not great.

So, in the last ten years, very irregularly (maybe once a year or so) I have got the lasers out on foggy nights mostly, to have a quick play around. Pretty much every time I've used them, I've never ever had a direct accidental shot into my eye, nor reflection into my eye for that matter, but I have looked at the side of the beam fairly close up. I only use them for a few minutes and put them away, but most of the time after using, I find my eyes have a dull ache for a while which gradually subsides. I just believe this to be because they're very bright. Furthermore, I just bought a new 50inch TV, when setting that up the other week, in a fairly dark room, my eyes started aching after a while as I was probably too close to the TV when watching it.

Regardless, I wanted to know how dangerous these so-called 240mw lasers are. How would they affect you (some people say you can't see the infra-red...?) and what time period after would you notice any changes to eyesight if you did happen to damage something?

Purely reading some of the posts on here made me a little paranoid, although what people specifically meant was unclear. How can these lasers damage your eyes if you don't get a direct shot?

I have looked at the side of the beam many times up pretty close over the years, and never noticed any damage to my eyes. I've never had a direct shot though nor reflection as I've used them pretty carefully.

How does this IR damage work? My Dad said that shining it in fog if it has no infra red filter, it will reflect off fog and come back at you.....really? If so, then surely I'd be screwed right now. I've never had any black spot or anything form in my vision, but as I said, I've never had a direct shot/reflection into my eye.

Also - how can you test if these have an IR filter and what mw they are exactly? If anyone is in the UK and can do this, please get in contact, I'd be interested to find out. Thanks

 

[paul1598419]

So very many problems with what you have assumed or been told. I'm assuming you have DPSS lasers at 532nm. Most don't have IR filters, but the IR content is always far below the visible light. Any reflections off fog are diffused and, as such, are no cause for concern. That includes the much smaller IR component as it is 1064nm and basically follows the same path that the visible beam does. Unless you have a calibrated laser power meter you cannot know what the output power of your lasers are. You might be surprised at how low the output power of that 240 mW laser really is.

 

[GreenMist]

Hi Paul, thanks for responding. I wouldn't know whether it's DPSS or not, but it is 532nm yes I just checked. All I remember is I got it from some dodgy ebay place from China or Hong Kong. And it says <240mW and 532nm on the pointer. Ok that's good to know, RE fog. I mean I have used it over the years in fog and never had a problem. No changes in vision nor black spots, but again, I've never had a direct shot, reflection or not. I think it's still risky though without safety glasses though, and perhaps I'd be better off with some? Be good if there is somewhere in the UK that could test the power output of the lasers, as I'm not buying something I'll barely ever use.

And indeed, people have said the <240mW are more like 20 or 30mW.

 

[paul1598419]

Yes, <240 Mw can be anything for 1 mW up to 229 mW. It is likely much less than 240 mW as you cannot see the beam without fog. I have a lab laser that does 230 mW and it has a very visible beam in a well lit room without fog. You take a chance of specular reflections by not wearing safety goggles, but it is the risk all of us take to see the beams as they aren't visible through goggles. I use my goggles whenever there is a risk of a specular reflection like when setting up cylindrical lenses. Or when setting up a holography table, but just for watching the beams I'm aware of everywhere I can point them with little risk of that happening.

 

[brendon7358]

See how it burns various things, black foam, black plastic, matches, dark balloons. And let us know your results, that will give you a rough idea of the output power. Just don't stare directly at the spot you are burning, look away. Safety goggles would be best but your laser probably isn't over 100mW anyways.