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1w 445nm without safety glasses?

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apollo248

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I understand there are just about no uses for a 1W laser without safety glasses beside possibly star pointing(checking for planes first of course), but lets say you pointed the laser at a tree 100ft away without glasses, could you still damage your eyes by glancing at the point? Is there a definitive distance were you could be considered relatively safe to point at a none reflective surface(trees, or grase etc.)?:thinking:
 





Pointing a 1W 445 inside your house is the only time you really need goggles. Looking at the spot on a white wall from <10 feet away will leave spots in your eyes. However, pointing the object at anything >20 feet shouldn't require you use safety goggles. Again, these distances are only for white walls. For pointing at grass, trees, etc you shouldn't need goggles when the spot is >10 feet away.
 
At the point, 100ft away? Unlikely. But there are calculators to figure this out such as EasyHaz:

http://laser-professionals.com/resources/easyhazweb.htm

For example, entering 445nm, 1 watt, for a 1 second exposure; beam diameter of 2mm and beam divergence of 1.5mRad we get:

~OD3 eyeware required

Intrabeam NOHD (meaning, a direct hit from the beam - Nominal Ocular Hazard Distance) - the distance you can be from the laser and 'survive' (optically) a direct hit from the beam: 2.51e+2m, or 251m (or about 750 ft) ... (taking into account divergence there, too.)

Now what you're concerned about is Diffuse Reflection NHZ - the distance at which you can stop worrying about reflections damaging your eyes from the laser (worst case), and that shows: 0.133m or 0.4ft; about five inches or so. Now keep in mind, that is *diffuse* reflection, not specular. (This goes up a little for prolonged exposure; but not much. Probably ~7 inches from 5 inches. The direct exposure limits go up by quite a bit, to about 1000ft.)

But, that said, in summary, yes, you'd be fine looking at the dot on a tree from 100ft away. However, I have to underline: mistakes happen, so thats why you wear the goggles. Not for when things 'go as planned', but because sometimes they don't.


EDIT: What Laser_Freak said, but in more words. heh.
 
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Outside you should be fine pointing at stuff over 30 feet away as long as it's not reflective. DON'T point at street signs or parked cars!!!!!!! I once pointed a 140mw green at a stop sign 100 feet away and it was way too bright for comfort...
 
would i nedd to wear glasses outside at night and would i need glasess outside for a 1w 447 ?
 
So in summary if I follow right, glasses are for safety and should always be worn. If, on the other hand, you want to actually see the blue laser you spent more on, you could risk your own safety and take the glasses off. If you don't point the laser at anything reflective, you should be pretty safe as the diffused reflection isn't that high off any kind of realistic pointing distance. If you hit something reflective though, you could end up with a direct hit from the beam which could cause permenent damage.
 
You for sure should have the goggles. If you want to watch, make sure you point to something really dark, or really far away. Or use defocusing add-on lens.
 
lastnight i used my 445 at 850-900ma without goggles. i wanted to see the beam, color, etc. so i target the beam inside a room and i was outside the room avoiding to see the dot... after several minutes of playing with the 445 i won for free a big headache and my eyes are dry and uncomfortable, but still viewing fine (i think so)


1 watt of 445 always can be a menace for indoor, more if your walls was white. Remember accidents happen
 
IMO, and it's just a theory I've pulled out of thin air, but I don't think the human brain/vision system is used to processing single wavelength pure sources. Nothing in nature does this, there's always some frequency/wavelength spread and bleed no matter what the source.

When you look at an incandescent source that's say red, unless it's got some serious lab-grade filtering, there's always some blue or green bleed however minor mixing in. So I think the brain is not evolved or used to having only the red cells in your retina firing with zero signal from the others.

I notice that aside from lasers, that spectrally pure light sources like bright high-flux colored LED's in blue, red, green etc. take some getting used to as well. It just seems "unnatural" and the eye/brain protests a bit.
 
A lot of it depends on focus too, if its way out of focus you can have it closer (still dont want it indoors). Tighten it down and becomes more and more of a hazard. I often terminate mine in to a pine tree in my back yard. Around noon or so you really have to look for the dot to even find it. The danger is in hitting something reflective. It only takes once. There are a lot of reflective surfaces you don't think about. Like my pine tree, imagine if I hit a bit of fresh leaking sap, a water droplet, etc... It wouldn't be a death ray reflection or anything and the chances of it hitting me in the eye are slim, but it could happen. I take my chances and do it anyway ;)
 
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danilow said:
lastnight i used my 445 at 850-900ma without goggles. i wanted to see the beam, color, etc. so i target the beam inside a room and i was outside the room avoiding to see the dot... after several minutes of playing with the 445 i won for free a big headache and my eyes are dry and uncomfortable, but still viewing fine (i think so)


1 watt of 445 always can be a menace for indoor, more if your walls was white. Remember accidents happen
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It's odd that you mention this as I also have an uncomfortable feeling in my eyes when I look at 750mW of 445. I'm only looking at the beam from the side and have had no reflection or direct exposure. I do not think that this is mind over matter. I do notice that my eyes are uncomfortable after just a short amount of viewing the beam. Does anyone else notice this? Bill
 
WRM said:
It's odd that you mention this as I also have an uncomfortable feeling in my eyes when I look at 750mW of 445. I'm only looking at the beam from the side and have had no reflection or direct exposure. I do not think that this is mind over matter. I do notice that my eyes are uncomfortable after just a short amount of viewing the beam. Does anyone else notice this? Bill
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Its more common with 405, bit eyes just don't care for things in that range, especially in pure form. Like when I play with my 405s I get a headache even though they are very weak and I am being safe.
 
IMO you really shouldn't go pointing a Watt of any wavelength outside, although I know people will do it anyway. Be mindful of where it may land. Shiny objects such as the aforementioned street signs and parked cars can reflect it back at you, pedestrians, drivers, or even people in their own home. Depending on where you live, it could be very easy to inadvertently tag someone in the eye through a window of their home. Pointing a class IV laser around is much like pointing a handgun around, overall it's just a dumb idea.
 
I would only shine it outside with no glasses on,
Anything over 40mw and i have my glasses on.
 
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