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Old 07-07-2010, 04:25 AM #33
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Default Re: Laser Dot Danger

Quote:
Originally Posted by knorkneutel View Post
If I play with my 150mW Jayrob green laser and shining onto mirrorballs and using kaleidoscopic tips on a party I can be dangerous for other people's eyes?
YES.

You have exposed your friends to a risk of vision damage by gross negligence.

And by exposing others to potential harm without informed consent, you demonstrate that you are not responsible enough to handle anything more than a cheap red pointer of 5mW or less. That you would point it at a mirror only serves to underline the fact that you have absolutely no idea of the behavior of light, let alone highly collimated, highly coherent, monochromatic light.

Put away your excellent laser and take a safety course before using it again.

I don't care if you blow a hole in your own retina. Just like I don't care if you shoot yourself in the head with a gun. But I will still insist that you need to understand gun safety to handle a gun, so you don't shoot someone else. And I will similarly insist that you understand the safety concerns associated with a high power laser before you use it, so that you don't harm anyone else with it.

The human eye is excellent at focusing collimated light, such as that from a laser, to a very small spot on a very sensitive part of the retina. The only reason you do not see any damage when it occurs, is that the human brain is even better at hiding blind spots. This is something a driving instructor will no doubt be able to explain and demonstrate very well.

Figures from the army are for military purposes.

They have conducted experiments to see how much laser light they need to be assured of damage, and how much power a laser must have to deliver that amount of light in combat. Just because the army will require 500mW output to be assured of permanently blinding the enemy in combat does not mean you will be anywhere near safe shining a 150mW laser at mirrors or disco balls with unsuspecting guests present.

Mayo Clinic has conducted experiments that are designed to see how much power is safe, and the conclusion is that a green laser of any appreciable power (including 5mW) is a risk, with the level of risk increasing as the power of the laser is increased. Red lasers of 5mW are safe when not combined with focusing optics. Green lasers are unsafe at 5mW, and a lower power level was not tested.

At 5mW, you have time to blink before damage occurs, provided you don't try to stop from blinking. At 150mW, your blink reflex means nada. The figure 30mW is thrown around quite liberally, and probably constitutes acceptable risk for most people if properly IR filtered, but is still not okay to expose anyone to unless they consent with foreknowledge of the risks (which, in turn, requires a fair idea of how laser light behaves).

I wish people like you would stop endangering the future of the hobby, and the eyes of others.


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Old 07-08-2010, 02:29 AM #34
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Default Re: Laser Dot Danger

[QUOTe

Even if the retina is as large as 1cm², the amount of light reaching the retina seems like it would be much less. It would take an error of nearly 1,000,000% before the power goes above the generally accepted "safe"(ish) 5mW.

quote]

Well, you missed the optical gain of the lens and fluid structure of the eye. The cornea forms a weak lens with the fluid and you have the actual lens.
That gain is about 100,000, not quite the 1 million your looking for, but close.

If you give me a few days, I can dig out the proof on that one.


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Old 07-08-2010, 03:08 AM #35
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Default Re: Laser Dot Danger

What about the opticsl effect of the light front you calculated? the amount of light per area is what hits the surface of the eye, then it is focused onto the retina. so if the dispersion is attenuated via a cosine function then that needs to be accounted for and then the focussing of the light by the lens of the needs to be accounted for to figure the energy density of the light at the retina.
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Old 06-09-2013, 02:03 PM #36
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Default Re: Laser Dot Danger

I am new to this thread. I have seen that even for 2-3 meters away, my 5mW green laser(I suspect its actually 15mW) dot on a white wall is uncomfortable to look at.
However, I am curious about red lasers. Suppose I have a red laser and I shine it on a wall 3 meters away which has a matt white paint. can I look at the dot for a short period, or is it too dangerous?
What about cheap green tinted glasses? Sure, they will not protect against direct hit, but what about the dot? Will they protect against dot reflected off a wall?

I am not talking about Class IIIb lasers (200mW). I understand, Class IV, one watt lasers are truly dangerous.
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