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Danger of naked eye exposure to 445nm beam

Spezialemic

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Hey there. I’m experienced with lasers up to 1.5 but have just recently purchased a new laser which is 7w. I bought a couple new pairs of quality absorptive eyewear and as any responsible user, I will never operate the laser unless everyone around it is properly protected. Obviously the most damaging action would be a beam reflection, direct exposure, or looking directly at the dot. That said, I’m personally curious about the risk of naked eye exposure to the beam ONLY. How bad is it for one to look at the beam itself from behind the diode, without looking at the point of light?
 



FuzzyPancake

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There are virtually zero risks associated with looking at beams going into the night's sky. A bug or something could fly into the beam closer to your eyes, but even if you were focused on that bug as it flew into the beam, you would be exposed to the reflected light for such a tiny amount of time that it wouldn't be a considerable safety risk.

That bug could be a shiny beetle or something and the light could be reflected into your eyes and flash blind you, but that's the only circumstance where you could possibly be at risk other than if you or someone else accidentally tripped/stumbled with the laser and pointed it at someone's face which actually is a practical concern and steps should be taken to avoid this.
 
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hwang21

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I disagree with your statement about duration of exposure for a bug flying through the beam - this IS very potentially hazardous to your eyes, especially with Class IV lasers. 5mW is the limit for an *accidental* exposure of laser light to not damage your eyes. In this case, accidental meaning non-intentional - that, if you were exposed, your natural reaction would be to blink and then avert your gaze. Since the average reaction time of a person is ~0.25 seconds, the 5mW limit actually has a duration to it too - 5mW for 0.25 seconds is about all your retina can handle for a direct exposure (assuming a worst case scenario with how your eye's lens, cornea, vitreous humor, etc. absorb and focus light). This is why staring at the sun (which very very roughly approximates a 1mW laser light source) can still permanently damage your eyes

Especially with lasers >500mW, where just looking at the dot too closely can cause eye damage, I would be concerned about a bug flying through the beam. IIRC there was a thread posted about this very thing happening before - luckily, I don't think they suffered any eye damage. Most people are not the worst case scenario - I've had a direct shot of 50mW into my eye before with no injuries. That does not excuse playing with fire though...
 

FuzzyPancake

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I disagree with your statement about duration of exposure for a bug flying through the beam - this IS very potentially hazardous to your eyes, especially with Class IV lasers. 5mW is the limit for an *accidental* exposure of laser light to not damage your eyes. In this case, accidental meaning non-intentional - that, if you were exposed, your natural reaction would be to blink and then avert your gaze. Since the average reaction time of a person is ~0.25 seconds, the 5mW limit actually has a duration to it too - 5mW for 0.25 seconds is about all your retina can handle for a direct exposure (assuming a worst case scenario with how your eye's lens, cornea, vitreous humor, etc. absorb and focus light). This is why staring at the sun (which very very roughly approximates a 1mW laser light source) can still permanently damage your eyes

Especially with lasers >500mW, where just looking at the dot too closely can cause eye damage, I would be concerned about a bug flying through the beam. IIRC there was a thread posted about this very thing happening before - luckily, I don't think they suffered any eye damage. Most people are not the worst case scenario - I've had a direct shot of 50mW into my eye before with no injuries. That does not excuse playing with fire though...
I'm going to stand by what I said. A bug (and it would have to be a big bug) flying in front of a 7W laser beam would be fried and out of the beam faster than even a quarter of a second and the chance of harm is just too minimal for me to tell someone not to do that without protection. Now if a person lives in the Amazon and there are 5 bugs every square foot, then yeah, shooting lasers into the sky without protection probably isn't a good idea. But for people from Ohio like me that don't deal with that many bugs, especially while it's still pretty cold out, I say go for it. Just make damn sure that laser is ONLY shining up.

And on a different note, I am all for minimizing accidents, but I think there is a line you can cross where you scare people away from the hobby and all the learning that is associated with it, and telling people that it's not okay to point high powered lasers in the sky without protection is crossing that line. I bet you'd be very hard pressed to find even a single person on these forums that has not pointed their 1W+ laser into the night sky without protection... have you not? It doesn't make it 100% safe regardless if everyone does it, but if you can't even do that with your class IV laser, then where's the fun?
 
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paul1598419

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Bugs? Really?! If you wear goggles you won't see the beam at all. I assume you want to see the beam. Goggles are meant to keep yours eyes safe from an accidental specular reflection or strike. Diffuse reflections actually decrease in intensity by the square of the distance you are away from it. BTW, those 7 watt lasers produce a broad line as opposed to a dot and the line gets longer the farther away you put the spot on an object.
 

CurtisOliver

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I seriously doubt that a bugs flying inside the beam will emit enough diffused light to damage your eyesight. First time I've even heard this proposed as a possible hazard too. Do your bugs fly around with miniature disco balls where you live?
 

FuzzyPancake

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I just wanted to be thorough. Surely you guys could imagine a worst case scenario where a light seeking June bug flies into and gets caught in front of a lens and diffuses a dangerous amount of light just feet from your eyes, no?

We're really diving into tin foil cone hat levels of paranoia compared to the much more significant risks associated with just stumbling with the laser and hitting a stop sign, car, window, ect, but again I want to cover all my bases.
 

CurtisOliver

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Well, I'll give it to you that you are thinking about alternative safety hazards. But the inherent risk there is small.
 

Snecho

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I agree with the point that bugs are something to consider.

However, the point I'd wanna make is the odds that that would happen...

That there would have to be a bug in your area that also just happens be a bigger bug that is also shiny like a beetle, that also just happens to fly directly in and through the path of about a cm cone of light at just the right angle to reflect a portion of that light directly into your eyes.

It's about the same odds as being attacked by a gorilla at any point of your day.
 

hwang21

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I wasn't really intending to give the message of using laser goggles to observe a laser beam shining into the sky at night, as that would be rather pointless lol. I simply meant to draw attention to the potential of it being a hazard - yes, I know the risk is small, but I'd rather say "you COULD be hurt, be aware/observant of your surroundings and be careful" than say "you WON'T be hurt, shine away". I would think that most laser enthusiasts asking about shining their lasers into the night sky are relatively new to the hobby, and something like a bug flying into the beam might not have even crossed their mind as a potential hazard. I'd much rather they be more cautious than they need to be, than be not cautious and therefore unprepared for an unexpected situation

That being said, yes, I have shined 1W+ lasers into the night sky without eye protection on, and do so pretty regularly. I just feel like the difference between "ehhh there's nothing that could happen shining my laser into the sky" vs. "yes, I recognize that a bug could fly into this beam and create a potential hazard. Yes, I still want to see a laser beam, i.e. no eye protection. Therefore, I shall proceed accordingly" is a big one

Since this has sparked some interesting discussion, I thought I'd poke around and see what I could find, since I know for a fact that this has happened before:





It looks like overall, the chances of this occurring are pretty small, and the risk of eye damage even smaller, but flashblindness is a pretty good warning in my book. My personal experience with this is that one warm August night in Midwestern Illinois, my friend and I were in his backyard stargazing and then later on shining a 3.5W 445nm laser around. We had been in the dark for probably over an hour by that point, so our eyes were pretty dark-adjusted. I happened to be looking away from the laser when what must've been a big white moth flew into the beam - the entire backyard lit up blue briefly. It kinda felt like a bolt of lightning had struck right next to us, but without any thunder (and a bit more blue than white). My friend said he got flashblinded pretty good, he was seeing yellow tint for a good few minutes afterwards. No lasting eye damage luckily, but being flashblinded and seeing the complementary color can't be great for your eyes
 

paul1598419

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I believe the chances of real eye damage from brief diffused reflections are more than just rare. They are actually near nonexistent. I cannot say that they cannot happen as those that do will almost always live to regret saying such things, but you are more likely to get hit by lightning on a clear day than this happening to you.
 

hakzaw1

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''It's about the same odds as being attacked by a gorilla at any point of your day. ''
More people are killed while hanging out or sleeping under a Coconut tree in Florida.( by a coconut)
BEFORE anyone else has an opinion plz read my tutorial on the Laser Safety Officer. (fyi its at the tutorial section (DUH))

It just stands to reason that concerts or laser show could NOT happen if viewing beams where a risk. AND when viewing from behind any laser is also pretty much harmless. Beam-off-bug--- what?
some need to read their post before clicking save or submit and dele them.

More than 100 people attending SELEM have never had any laser problems where we are allowed to go anywhere there we want- DOZENS of very powerful projectors are being operated.

NO Henny Penny the sky is NOT falling.

If you attended a star/constellation gathering you will NOT see any eye protection. Zero chances of hitting a bug/beetle and getting any reflection to your eyes let alone one that would be any problem .

In Moscow more than a dozen attendees at a concert got an eye hit that was serious. The ones setting up the Moscow show were idiots. My (USA) friend got a $2000 fine because one of his 'workers' did not have his eye protection on his person. EVERY laser-show outfit MUST at LEAST, have on payroll, a certified LSO. Once the LSO instructs the 'workers' how to set up the show safely, the LSO does not have to be THERE.

READ my LSO 'tute' and STUDY what you see at LPS.org.
The MORE one knows about laser safety IMO the less dangerous lasers are.
Under regular light our eye's 'opening' is about 7 mm.
In the dark it is bigger and the same for most on some kind of some drugs.
Some drugs make it less than 7mm.
Any power is a risk if the beam hits our own eye's lens--more than 100times brighter (or MORE). We (LPF) have had a very few members who got eye injuries-- READ their threads plz.

Those with less laser safety knowledge should error on the side of MORE/EXTRA safe use.

Steve Roberts (LSRFAQ) is one of the very best experts at LPF/PL (At PL he is 'mixedgas') .. He sat next to me at the LSO class. I will be watching for his posts in this thread.

link









enjoy lasers safely.
hak
 
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