Looking at a 1-1.5 W 445

Hello all I know to never look at the spot or beam without protection but I have been seeing people talking about looking at the beam in the sky.
So being the person I am I would rather ask than just assume when is it ok to look at a 1, 1.5 ,2 W laser without goggles?

Looking at the dot and beam are FINE. The only dangerous thing is looking at the dot UP close, from a reflective surface, and directly.

If it is a diffuse reflection, looking at the dot is perfectly alright (provided you are within a reasonable distance for it to spread out), and looking at the beam has never injured anyone.

I've noticed that looking at the 1.1W blue beam indoors has done something to my vision. The white ghosts from when you look at a light bulb, and then look away are now blue. I think I might have blue light damage. So in all honesty I cant recommend looking at the beam, or spot indoors. I dont see outdoors being a problem. Just dont shine it when aircraft are in the skies.

I don't think the *beam* could have caused that damage, right? The beam "emits" very little light (that's not the right word, but whatever). The dot would be the problem, but the beam is only Rayleigh scattering, which is almost nothing compared to what hits the wall.

You dont need high energy to do damage. Its more about the color than the power.

Maybe it's just a fluke than that you got the blue light damage? Because so many people have been playing with these things so often and there have been hardly any reports of the phenomenon that you are reporting.

To be honest I'm not sure, but my vision has definitely changed. The ghosts are bluish now, so I figured I got some damage.

I certainly would not recommend looking at the dot of your 1-1.5 watt blue laser at any close distance. I am experiencing a similar side effect to extensive exposure to bright blue light, as Tech_Junkie. Since 1-1.5 watts of laser power is considered Class 4, a Class in which damage can occur to the retinas by merely looking at the dot, I would strongly recommend avoiding looking at the dot, at any close distance (under 10 feet perhaps), especially at night time and at fluorescent or white surfaces (also reflective surfaces).

Thanks,
Remember, it is better to be safe than sorry. The best protection from eye damage is using your laser with care.

AAlasers

I think we should be a bit realistic here, though - not that I am not advocating laser safety, but think about it: on a diffuse, white surface, which would diffuse close to ALL of the power, gaining distance from the dot reduces power drastically.

My guess is that, at 1cm away from a dot on a white, diffusing surface (like your wall?), you would get a huge portion of that power being reflected back into your eye, even during the day (assuming the dot is well focused).

That means that, at 2cm, you get half of that, because the amount of light is inversely proportional to the distance squared.

So at 2cm, you're getting 250mW, at 5cm you're getting 40mW, at 10cm, you're getting 10mW, at 50cm, you're getting a measly .4mW.

Now, of course, those numbers aren't accurate, they were just a thought experiment, but the point is, even at half a meter, even assuming that my numbers are a tenth of the actual power you would receive, you would still be getting less than the 5mW limit that has been determined to be dangerous before your blink reflex.

And, again, to be honest, I look at the dot from my ~1W 445 from a fairly close distance all the time - no vision loss yet, and I don't have that "blink reflex" when I see it.

I am *not* advocating that you look at it up close or not use safety goggles. Be weary of reflections in doors, too! Those can do as much damage as a direct hit. For God's sake, PROTECT YOUR EYES.

I am just saying that we need to be realistic here, and that looking at the dot from ten feet across the room is, for all intents and purposes, fine.

I am going to get hugely flamed for this, but... meh.

Wolfman29,

You bring up a good point and your thought experiment is interesting, it seems like the risk of damage from looking at the dot from a moderate distance is low. I am considering buying a 1W 445 nm and I have been wondering these same thoughts. They are sweet and are not too expensive, but I am hesitating because it seems so dangerous as a handheld laser, I'll have to make sure no friends or siblings plays with it without knowing how dangerous it is!

But anyway I'm glad this topic came up and I like that you're looking at it scientifically, and I've had a couple thoughts I wanted to add to your experiment, if I may be so bold:

First, the 1/r^2 is a good place to start, but I don't think the light will diffuse out perfectly in a sphere. I think the wall would act like a very rough mirror, with a greater percentage of light being reflected back at the angle of incidence. So it is probably safer in general to position yourself so that your eye is not catching the brunt of the reflected light.

Also, using 5mW as the safe cutoff of light to be reflected from the dot into your eye isn't actually safe. Someone out there determined that having 5mW of laser light on your retina is safe only when combined with the blink reflex, which cuts the time of the exposure to 1/10 of a second. It isn't about whether or not the blink reflex kicks in, its about the amount of time that a single spot on your retina is exposed to the light. Since we look at the dot for many seconds in a row, the safe amount of radiation to have coming into our eyes is probably much less than 5mW.

Finally, I wonder if blue light is more dangerous than other wavelengths just because it has more energy than the other wavelengths. I know it isn't as bright as a green of similar power output which can lul some into a false sense of security, but even that could be controlled for I wonder if it is more damaging to the retina. Haven't been able to find an answer to that yet.

So I probably wouldn't want to look at the dot from a half meter away, but I bet by the time the dot is 3-4 meters away its probably safe, especially if you hit the wall at an oblique angle.

PS I'm not flaming you I'm just thinking this stuff out loud

Thanks for the lack of flaming!

I gotcha on the perfect sphere. Probably *more* would be reflected at the angle of incidence, but I am sure a large majority of it would be reflected in a hemisphere. Further, it may actually be safer if it is reflected at the angle of incidence, assuming you don't aim it nearly perpendicular to the wall - that way it will reflect more away from you.

Finally, you're right. That was just an example, assuming I was off by a massive factor of ten. I am probably more off by a factor of two or so, which leads to .8mW, which is relatively safe. And that's only at half a meter. So at a meter or two, it's going to be a very low power dot.

I must say I'm appalled. He asked if it was ok to look at the beam outside, and you guys tell him its ok to look at the beam/spot indoors? You dont know any aspects of his, or anyone else's interior. Also you cannot predict he will not hit something that will reflect the beam back in his eye. I think its completely irresponsible to recommend looking at a 1.5W lasers spot no matter what. Yeah in a perfect world your math works, but wake up, its not a perfect world. You can have kids reading what you wrote and think its ok to shine the beam around the house.

I'll never understand how some people can be so smart, and complete idiots at the same time.

I said it was okay to look at the beam outside, just so you know.

Further, that's why I had such a huge notice in my first post. And you know what, you're right, I should have included to be weary of reflective surfaces, as well. I am going to edit my post and throw that in there just to be extra safe. But it *is* alright to be reasonable yet still encourage safety.

EDIT: By the way, thanks for the compliment!

Tech_Junkie has a good point. To clarify, I am definitely not advocating flashing this laser around recklessly without glasses. I am just trying to get a sense of what is safe vs. what is dangerous if operating this laser in a very controlled setting. Of course, if you are just shining the thing around the house and it hits a reflective or semi-reflective surface, it can cause permanent eye damage. Even if you're shining it around outside you could hit a neighbor's window, which might be enough to hurt you or someone inside.

So in the real world, the safest thing to do is to not buy hand held class IV lasers. But this is LPF after all, so assuming you already own one or plan to buy one it should only be operated if all people in the vicinity are wearing eye protection. That being said, if a responsible person is shining the laser up into the open sky, I would feel comfortable looking at the beam.

Exactly. I was trying to state something similar - in that, if you are taking extreme precautions, it *could* be alright to use the 445 indoors without glasses. Say, if you are pointing it at a piece of paper from two to three meters away, and both the laser and the paper are being held in place, then there shouldn't be a problem - the power would diffuse rapidly, and the chance of reflection would be nil. However, safety is *always* a first. As many people have said, you only have one pair of eyes.

Problem with 'Blue Light' damage is that you don't realize the damage is done until it starts getting really bad. I gotta side with T_J on this one. Better to err on the side of caution.

But, they are your eyes... if you don't want to take care of them, nothing I'm gonna say will convince you.