How powerful is 10mW?

This thread reminds a great deal of an argument about gun safety.

You have one side yelling all guns are dangerous, and the other yelling people kill people not guns

Bottom line, it depends on the operator, not on the laser output.

Side question: what is the minimum laser power required so beam can be seen at night?

@nikitospav

It depends on other conditions. You can see the beam from even a 5mW green laser if it's very dark, and there is a lot of humidity.

Anything 30mW of higher, you should see a nice clean beam from a 532nm laser.

When camping and semi doing astronomy - showing girls constellations I use a 20mW pen... it's enough in the dark, and doesn't attract as much attention as brighter lasers

nikitospav said:

Side question: what is the minimum laser power required so beam can be seen at night?

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It depends on the frequency of the light.

Since here, we're discussing 532nm greens, even 5mW can be seen in the sky at night.

However, the ANGLE at which you're viewing the beam will have a great effect. Under city or suburban light pollution, or bright moonlight, or fireworks, like in the OP's example, it takes probably 30mW or more to be seen from the side when standing more than 20-30 feet away from the laser.

My experience is much like InfinitusEquitas just above my post here. I have some 30mW greens I was paranoid about sky/star pointing with, until I had a friend point out a star, and I walked up my driveway to watch him from 50 feet away, and I couldn't find the beam at all.

Holding the laser and looking right up the beam, or standing right next to the person and looking up the beam, it's much brighter.

Pitch black countryside, only lit by starlight, it's much easier to see the beam from the side from a greater distance. Even then though, it will require fog, smoke, or a few 100mW's to be really visible from the side at any great distance, like 100's of feet.

^^^Interesting observation. I never actually looked at a laser from any kind of distance... 5 feet maximum. Gonna do an experiment when I have the chance.

The legal limit in the US is 5mW for a reason. A direct hit from anything over 5mW can cause damage to your eye in less time than it takes to blink. A direct hit of 5mW can generally causes damage after time equal to that of the average blink reflex.

So yes, 3mW can cause damage if you have slow reflexes, while 7mW may not if you're quick **come onnnnn**

**disclaimer** not saying it's safe to do this. Just be careful guys..

^^^You also have to consider the question of the amount of damage, and whether it is consequential or not, and permanent or not. Not sure if this is an accurate analogy, but every time you go to the beach and get a tan... you're doing damage to your skin, not much though. Really wish we had an ophthalmologist to chime in right about now.

Our brains are also very very good at essentially hiding a lot of visual problems from us.

So while I definitely advocate laser safety... I think it would be kind of paranoid to wear any goggles for a laser <50mW, and common sense will always serve as better protection than any goggles. Personally I wear goggles with higher powered lasers because of specular (is that the right word?) reflections from not normally reflective surfaces.

I thought this was pretty good clarification-wise. Put into very, very simple terms.

Can a pocket laser damage the eye? : Scientific American

Nice article. I thought this part especially was interesting:

In FDA-regulated pointers, the laser power limit is set at one-tenth the actual threshold of damage.

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If that's the case, it may explain why didn't suffer any damage when I took a direct hit to my right eye from a 50mW green laser... one of my friends was drunk and retarded.

I found the comments to be rather funny... people just get super paranoid I guess.

InfinitusEquitas said:

Nice article. I thought this part especially was interesting:
If that's the case, it may explain why didn't suffer any damage when I took a direct hit to my right eye from a 50mW green laser... one of my friends was drunk and retarded.

I found the comments to be rather funny... people just get super paranoid I guess.

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Well you wouldn't really know if you suffered any damage your brain will fill in blind spots with what it thinks is there so you wouldn't really notice at all with a tiny blind spot.

Laws are laws for a reason! Just be careful and you'll be fine (don't give your 50mW greens to drunk friends )

swimminsurfer256 said:

Well you wouldn't really know if you suffered any damage your brain will fill in blind spots with what it thinks is there so you wouldn't really notice at all with a tiny blind spot.

Laws are laws for a reason! Just be careful and you'll be fine (don't give your 50mW greens to drunk friends )

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That's kind of the point I was trying to make before... the amount of damage and whether it's permanent or not is rather important. Permanent damage is cumulative after all.

Not going to argue about laws... although it's fun

As for my drunk friend, he's not allowed anywhere near my dangerous toys anymore, if he even goes near them... he's warned and I have handcuffs. His GF punished him enough I think... in the same episode he was also retarded enough to shine the laser at her.... didn't catch her in the eye or anything, but she was very pissed off... she kicked him in the crotch enough so that his face looked like this smiley :wtf:

You probably are blind where the laser hit you. You just won't notice because your brain fills in blind spots with what it thinks is there. So you can't see in that spot you just can't notice it.

@laserx323 - Think of it this way... If you have one dead pixel on a 1920x1080 monitor, if it's not dead center, in areas where you aren't always looking... after a while you stop noticing it. Our eyes are quite a bit more "hd"

Same principle applies with your eyes. There are actually many imperfections in our vision... and our brain is very very good at hiding things from us, since we have two eyes the brain is also able to kind of fill in the missing parts.

The only sure way to tell is to actually go see an ophthalmologist and have him take a look at your retina... even than it's not clear cut since it's possible there are natural defects... but at least you will have a starting point for tracking future problems.

InfinitusEquitas said:

Nice article. I thought this part especially was interesting:
If that's the case, it may explain why didn't suffer any damage when I took a direct hit to my right eye from a 50mW green laser... one of my friends was drunk and retarded.

I found the comments to be rather funny... people just get super paranoid I guess.

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Your Not Reading It Right...

Red laser pointers that are "properly labeled" in the 3-5 mW range have not caused eye damage -- no retinal damage has been reported -- but there are very real concerns. One is pointers not manufactured to federal specifications. There are reports that green lasers, improperly imported to the U.S., far exceed safety limits

In FDA-regulated pointers, the laser power limit is set at one-tenth the actual threshold of damage. If a person sees a bright light, they will automatically blink, on the average in less than 0.2 seconds. This is referred to as the blink reflex, and it is considered when the limit is assigned for how much power will cause an eye injury



A close reading of exposure limits indicate that a 5 mW laser could cause eye damage.

Why even worry about 5 mW (5 thousandths of a watt), which is less than one percent of one percent of the power of a 60 Watt incandescent bulb? First, the numbers are used differently. Light bulb wattage measures the power it uses. It only converts about 10 percent of that electrical power into light. In a laser, the power is a measure of the light output.

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So it's saying that FDA regulated pointers that are True 1-5mW Lasers Are sold because they are 1/10 the damage level.

Above 5 and more argumentatively Above 10 mW are then entering into the range where it does do damage faster than you can blink. The Higher the mW the more the damage becomes Worse and long term effects.

And your illustration of the pixels isn't quite right Our Brain Edits the 2 Images into a working picture and this includes filling in blank areas and it a lot more different than a computer screen.

^^^@Krogith the screen analogy was just to get the point across. Whenever possible I try to keep things as simple as possible. The way our vision works is actually quite interesting and complicated. I'm willing to bet many people would freak out if you told them they have laser damage and then showed them their natural blind spot in each eye

Now regarding the safety threshold, and damage- you do have a point there. I kind of assumed - didn't think about it really - that damage would increase in direct proportion to the increase in the output of the laser.

This article could be worded somewhat better.

I Agree he didn't Write that Well.