Saftey features/ What is possible

[obsidianjaguar]

I know I am probably going to get told off for asking this ... But I am still new and knowledge thirsty , so I don't mind.. so here goes

I was wanting to know the Upper limits of lasers that can be considered safe to view without safety glasses ... I have understood from reading on here that anything 5mw or over would require safety glasses , And I firmly believe no amount of "WOW" factor would ever be worth risking damage to ones eyes, and this applies indefinitely more so when faced with the possiblity of risking another persons health ... so I'd get nervous even getting near that threshold ... On the other hand I want to share my love of lasers with my friends !
I am guessing green would be easiest to see at lowest Power , so therefore it would be easiest to see as a bright light ,while keeping it in the safe power range? I'd like to have a specific laser that I could carry round casually and show to my friends , to spark their interest , then when they are all drooling , Id invitee them over to my place , bring out glasses for everybody to wear and show them the really cool stuff ...

Also , I am wondering if there is such a thing as some form of filter you can attach to the end of a say 1W or 2W laser , that would reduce the output down to "eye safer" levels .... Im thinking if this is possible , i'd somehow have a key or something that would force this saftey lens to be in unless I unlock it ... if not a lens , is it possible to achieve the same result through the electronics ( I.E a low power/Safety mode .. then some button/switch , that could unlock the High power mode only after entering the correct sequence of button presses ...)

I am basically trying to share my interest in laser with people , and looking out to minimize accidents ...

 

[John Capelo]

Well depends on how you're using it. If there's even a remote chance it'll get in someone's eye, then about 10mW is the max limit, and even that's rather dangerous.
However, if you're simply pointing at things on the wall, floor, etc., without risk of reflections, then up to about 50mW of green is safe (green since it's the most visible wavelength to the human eye). However if you're burning, you'll be too close and specular reflections would be dangerous.
There are lenses that decrease the power output, but I'm not exactly sure where you get them. A prime example is Lazerer's (or WL, not sure) "training" lens, which decreases output to about 20% of the output. You can also have different modes, but that's pretty expensive. This just limits the amount of power fed to the driver/diode IIRC, but those do exist.
Pointing at the night sky is always an option, no risk of reflections or blinding, as long as there aren't planes around. That's IMO the best way to show off, since at night the beam is most visible as well.

 

[obsidianjaguar]

Thank you so much , that is what I was after exactly ... I just wanted to go to the maximum visibility, while being safe in case of reflections ...

btw .. I sometimes see youtube videos where people have got huge laser beams shining at street level in urban areas , and reflecting off stop signs ,metal mailboxes , even office windows ... this seems unsafe to me. Is there a certain distance where reflections from the beam become less dangerous ? like say 20m or is it still unsafe at any distance? I just ask , because it might be tempting to use a refraction filter and make some cool special effects against a brick wall , or on other surfaces , but again , I'd like to have a good saftey margin , but also have maximum coolness in the light show I want to carry in my pocket

 

[John Capelo]

Well depends on the power of the laser. Diffraction (the things that split the beams, I think that was what you were talking about) gratings don't really decrease the beam's power that much, and though I don't know the specifics, seem to have the relatively same amount of power per beam. If you're using, say, a 50mW green, looking at the dots and beam won't harm you, just don't get it into your eyes. However, at around 500+mW or so, IIRC, looking at the dot will be harmful for your eyes, though not sure if they're able to blind you at that level. At more than 1W, looking at the dot will blind you, and safety glasses are a must! Though you seem to be relatively careful, so I don't think it would be a problem. A 50mW greenie would be the best choice for you in my opinion, bright, visible, yet safe to look at without glasses, as long as you're not around reflective surfaces.