Laser shows

Nisei

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Dec 17, 2006
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OK I read many posts on this forum now and am fully aware of the dangers associated with lasers. I was wondering how this is for laser shows. I mean, they shine their beams into the public and it seems to me these are pretty high spec lasers, not like <5mW pointer beams. How come this isn't dangerous?

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Nisei

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Ah so why are they allowed then? If a 5mW beam can cause permanent damage to your eyes than those beams you see at shows should instantly make you blind. I don't understand.
 

Luap

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I have often wondered about this too..

But I think you'll find that at shows the lasers cant be pointed directly at people, so have to go above head height for the most part.
However, there will be regional regulations which differ from place to place on this.

Secondly, the laser beams are usually moving around pretty fast. Certainly a lot faster than you or I could manage by waving around any laser pointer by hand.. So even if at a show the beam does catch you in the eye, it isn't going to be there for very long at all.

Thirdly.. These lasers might not be as powerful as you think.. Concerts and other events with laser shows nearly always have a lot of smoke/fog. And it doesn't take much fog and smoke at all to vastly exaggerate the visibility of a laser beam.

Keep in mind the illusion that is persistence of vision too.. Where we apparently see more than is actually there.. Again, exaggerating the effect of fast moving lasers.

Put all this together, plus factor in the distances involved, along with hefty divergence of the beams (from my experience) makes for pretty and very vibrant displays. Yet relatively speaking, fairly safe and not as dangerous as it might appear.

Just an educated guess..

Paul
 

Madz

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Those green lasers are only about 60mW or less since the color spectrum is so over powering to our eyes. Also they use beam splitters to multiply the beam which also lowers the power of each beam you see. <5mW beam cannot damage your eye from a quick shot . Someone posted statistics on here once and I think that at 5ft it would take a Class IIIA lasers 25 minutes of direct eye exposure to cause any kind of damage. and at 100mW at 15ft away it would take 1/1250th of a second to cause permanat eye damage. I am not sure how accurate that is but Id say that if it is accurate taking a 40mW beam and splitting it 3-4 times (dropping each instace of the beam to approx 10mW isnt so dangerous. These shows are engineered by some VERY smart people. I doubt they would go shining deathrays at the audience.
 

comozo

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I assume you live in the USA. You can find the answers you seek at the CDRH website. ILDA also follows similar protocals
 

jtice

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Some places thats not even legal.
And yes, it is a bit dangerous, but there are two things that make it slightly less dangerous.
1. you are only exposed to very fast flashes that actually hit your eyes.
2. The beams from alot of the laser shows are a bit wider than the tightly focused beams of laser pointers.

For the most part, it is dangerous, but going to a show every once in a while shouldnt cause PERMINATE damage.
But I wouldnt doubt that you are seeing spots the rest of the night when you get home.

~John
 

liveforphysics

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I think intentional divergence is what makes them 'safe'.

A pointer with a 1mm^2 beam at 5mW will have the same intensity of a 100mW laser with a 2cm^2 beam size. Light quanity isn't what damages your eye, light intensity is what causes damage. I think most of the diode baised laser stuff is setup with pretty large divergence to drop the intensity to safe-ish levels while keeping power levels high.
 
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