50 mw cheap laser hazards

[harry89]

Hi all,

I am new here on this forum because i need some help...
A couple of years ago i ordered a cheap 50 mw green laser from the internet. It was a 50 mw but it couldnt burn or pop anything, I could point it at my skin without even getting warm.


Recently i found this laser pointer again because i read some info about hazards and blindness and stuff. It freaked me out because a couple of years ago i was shining the laser pointer at a few kids on the street (through my double glass bedroom window) and it hit one of the kids in the eyes for a splitt second, it wasnt my purpose to shine at the face but it did happen, because one of the kids yelled "ouch you want me blind or something"? I pointed the laser at the kids because they were throwing Snowballs on my window, and i was pissed of because i couldnt sleep, so i tried to scare them off....

The distance from my house to the kids was about 100 feet... and the window of my bedroom had double glass (i also shined the laser through the window at a big angle... how big is the chance that the kid got any permanent eye damage ? The laser waved past the kids head only for a splitt second.

I never see the kid again but the info on the internet freaked my out, back then i was a bit naïve and i dint know the exact risks of these laser pointers.
I learned my lesson and threw away the piece of junk. I think ill never buy a laser pointer again, if i ever do, then it will be a safe 5 mw pointer with IR filter.

Does the double glass window absorb some of the laser`s power and how does the power weaken over distance?

How much damage can the IR radiation do over distance since i heard its not a straight beam like the green laser ? And whinch laser would be more dangerous for your eyes from a distance (of around 100 feet) (for a splitt second): a real good quality 50 mw laser that can pop balloons and burn stuff etc (with IR filter) or a cheap ass laser that doesnt burn stuff and without IR filter??

I think the more the laser burns , the more damage it can do to the eye when pointed in the eye for a splitt second. Is this true?

I also read that many cheap 50 mw laser pointers only got 10 mw of green light, and 40 mw of IR light. Does IR light burn stuff at the same power of the green light?? so for example 50 mw IR light vs 50 mw greenlaser only (wihout IR) For example: which laser will pop the balloon faster?

I once openend the pointer, and there was no IR filter in it. But when i assume the pointer is 10 mw of green light and 40 mw of IR light, why doesnt it pop balloons and stuff?

Hope the kid`s ok :cryyy: and looking forward for some info....

thanks in advance

 

[laserpyro]

I'm pretty sure if he's blind and you shone it from your house you'd know about it.

I'm almost certain that 50mW from that distance through glass would have very little effect.

Some one smarter than me i'm sure will chime in and explain about the power or IR and 532...

 

[Trevor]

Well, at 100 feet he likely did not take more than 5mW to the eye. I can try and calculate exactly what he did get hit with, if you want.

But... never do that again. Ever.

-Trevor

 

[harry89]

well if you can do that, would be good and interesting....

 

[Trevor]

well if you can do that, would be good and interesting....

Sure. What was the beam divergence?

-Trevor

 

[harry89]

well I have no idea, it was a standard cheap laser pointer from ebay. Im not an expert in lasers... but the info on the laser pointer said: Wavelength 532 nm, Max output <50 mW
Class 3b laser product, danger etc.

The very cheap (probably Chinese ones) in 5-100 mw range. The dot was pretty big I think but to be safe go for an average good quality 50 mW laser pointer. with an average divergence.

 

[Trevor]

Okay. For the sake of argument, we'll say that it had a beam divergence of 1.3mRad (which is good for a crappy Chinese pointer) and an output power of 75mW (a very liberal estimate).

Let's call 100 feet 30 meters for the sake of simplicity.

So your 1mm beam is going to diverge to 40mm over the course of 30m. This means the whole 75mW is distributed across a 1256mm^2 area.

Say the person's eye was completely dilated... let's say to 1cm. That's a 78mm area.

So based on those VERY liberal estimates, they might have seen 4.65mW, give or take a few milliwatts.

If the power were really 50mW and the divergence were 1.5mRad, they would have been exposed to something like 2.3mW.

You most likely did not cause any permanent damage, especially since the exposure was fleeting.

-Trevor

 

[harry89]

Thanks Trevor!

anyone can anwser the rest of my questions?

much appreciated...

 

[Benm]

I think Trevor wrote that up very nicely for you. Something like the window in between could take off another 10% or so if double glazed, but its a relatively small factor.

As for the IR: its usually not that well collimated with the green light, and not that likely to pose a hazard at 100 feet distance from an ordinary pointer. It appears what you did remained within blink-reflex safety limites, but finding that out in retrospect is never a good thing!

 

[mewrox99]

Also from a more practical point perspective like others have said .

If you blind a child from your house, do you really think you will get away with it and no one will hear about it? Of course not.

Don't worry about it, the kid is fine.

At least your a good person to be concerned