Safety regulations on laser parcours

Hello,
I am building a laser parcours for a public exhibition. The parcours will have a smoke machine and anyone can try it out (so nobody is wearing eye protection). This parcours will be taking place in the evening, so it will be a bit darker.

I am trying to find the most optimal laser configuration. What I've found out so far is that <5mw is legal and green lasers are the most visible ones.

But I've also found some other installations that use lasers with a higher wattage that turn off whenever someone crosses a beam.

For example: https://www.youtube.com/watch?v=wI7fljQK7Ls

"We set an automatic security system for 200mW lasers that may scratch the eye retina and may burn the skin. Whenever the player touches the lasers, the system turns off automatically, the lights are on and the alarms get activated."

How are these systems with more powerful lasers looked upon?

An other way seems to be to use a >5mw in combination with a beam expander.. From my understanding this makes the beam wider and less harmful. Can I use for example a 20mw laser with a beam expander so that it is eye safe? Does the beam get less visible when expanded?

Thanks!

TVG said:

Hello,
I am building a laser parcours for a public exhibition. The parcours will have a smoke machine and anyone can try it out (so nobody is wearing eye protection). This parcours will be taking place in the evening, so it will be a bit darker.

I am trying to find the most optimal laser configuration. What I've found out so far is that <5mw is legal and green lasers are the most visible ones.

But I've also found some other installations that use lasers with a higher wattage that turn off whenever someone crosses a beam.

For example: https://www.youtube.com/watch?v=wI7fljQK7Ls

"We set an automatic security system for 200mW lasers that may scratch the eye retina and may burn the skin. Whenever the player touches the lasers, the system turns off automatically, the lights are on and the alarms get activated."

How are these systems with more powerful lasers looked upon?

An other way seems to be to use a >5mw in combination with a beam expander.. From my understanding this makes the beam wider and less harmful. Can I use for example a 20mw laser with a beam expander so that it is eye safe? Does the beam get less visible when expanded?

Thanks!

Click to expand...

Sorry to mention safety but 200mW isn't going to just "scratch your eye". That's enough to blind you on the spot!

A beam expander dosen't make the beam wider, it actually does the opposite. It keeps the beam thinner(AFAIK) allowing it to travel farther before spreading out, it also won't reduce the amount of power coming from the laser.

-Alex

If you can design a FOOLPROOF way to shut off the laser as soon as it is blocked, I guess you could do something with photodiodes. Just really really make sure that it shuts down before the laser can deliver a dangerous dose of energy. (Based on 0.25 sec rule at 5mW I'd guess that has to be somewhere within 1ms.)

As for the beam expander, TVG is right and The Greenlander is partially right A beam expander indeed expands the beam, making it wider at the aperture. However, since divergence of a beam is linked to its diameter, the divergence will be less so far away it'll be thinner than the beam that started thinner but diverged faster.
So yeah, a beam expander would make the power density lower, but I have no experience as to what that would do with beam visibility.

Shutdown would have to be under 100 nanoseconds at 200 mW.

Steve

LSRFAQ said:

Shutdown would have to be under 100 nanoseconds at 200 mW.

Steve

Click to expand...

I did write it was a guess, but didn't think I'd be THAT far off. What's wrong with saying "Well, 0.25 sec exposure at 5mW is 'barely safe', so a 40x higher intensity would result in a 40x shorter exposure --> 0.25/40 = 6.25 ms"?

Just curious

Tha Greenlander said:

A beam expander dosen't make the beam wider, it actually does the opposite. It keeps the beam thinner(AFAIK) allowing it to travel farther before spreading out, it also won't reduce the amount of power coming from the laser.

-Alex

Click to expand...

If you don't know, don't answer. You're completely wrong here. Divergence is inversely proportional to beam width. A beam expander increases the beam diameter, which in turn decreases the divergence.