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Author Topic: Understanding Laser Safety - Multi-effects "DJ" fixtures  (Read 1954 times)

Wes Garland

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Understanding Laser Safety - Multi-effects "DJ" fixtures
« on: November 17, 2017, 09:47:17 am »

Can you guys help me understand what I need to understand in order to operate those "DJ"-grade multi-effects lights which include a laser?

My query is specifically with respect to the Microh Monsoon FX GB since that's what the local rental house carries, but I may wind up buying some more lights, so I'd like to understand "what's what".

So, the FX GB has two lasers in it; green 50mW and blue 130mW.  The rental place - basically the Canadian version of Guitar Center - seems to think I can point these anywhere ... and indeed, they do in their showroom.

The instructions for the unit say that it should be 9 feet off the ground and perpendicular to the ground.  The problem with that is that the rest of the lights will be pointing in a useless direction. Additionally, when you study their online videos, the laser beam looks like it is diffracted with a dispersion of around 70 degrees.  This means that even installed by the book, little man in the diagram is going to get some laser in his face.



Also, Microh's own marketing shows the light installed exactly as I used it --



Is my bass player in danger here?



Are these fixtures just a bad idea? Should I just put a piece of gaff tape over the laser?  Or does the dispersion lens make them safe?  (They are constantly-moving, non-flashing effects)

The lighting turned out really nice on this show, though.  The Monsoon FX was used, sparingly, to give life to some of the more intense/psychedelic moments of the show, and mostly not aimed at the audience. I just left my console in programming mode and slid the channel 1 slider to select automatic/sound-activated programs as needed.  Here's a video (Space > Drums > The Other One for you Dead Heads out there): https://www.facebook.com/TheCardMan/videos/10155730822888632/

The Monsoon was installed upstage right on a nine-foot stand. You can see it directly at 7:30.

Thanks for any insight.

Wes
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Lyle Williams

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Re: Understanding Laser Safety - Multi-effects "DJ" fixtures
« Reply #1 on: November 18, 2017, 05:26:41 pm »

I have tiny 1sq inch mirrors held by a magnet that are used to direct the laser upward/outward while the derby effect falls on the floor.
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duane massey

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Re: Understanding Laser Safety - Multi-effects "DJ" fixtures
« Reply #2 on: November 19, 2017, 03:47:58 pm »

Reality is that entertainment lasers are commonly used in illegal fashions. I had a discussion with one of the major manufacturers back when I sold lighting gear, and I complained that their videos showed the beams coming straight at the viewer, yet when you tell the client they can't do this they are upset. His response was pretty insulting, basically don't say anything until they complain.
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Duane Massey
Technician, musician, stubborn old guy
Houston, Texas

Jeff Lelko

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Re: Understanding Laser Safety - Multi-effects "DJ" fixtures
« Reply #3 on: November 21, 2017, 04:31:20 pm »

Hi Wes,

Below is one of the better explanations to your question that I have found:

According to the manufacturer’s user manual, the multiple beams (e.g. after being split from the laser diodes) are each less than 5 milliwatts maximum.

Visible lasers between 1 and 4.95 milliwatts are U.S. FDA Class IIIa (3R). This is the same maximum power as a laser pointer, which in the U.S. must be below 5 mW.

So basically this projector is sending out dozens or hundreds of laser pointer beams.

People can have a brief, accidental exposure to a laser pointer beam but 1) for safety they must not stare into a beam and 2) legally you cannot deliberately aim a laser pointer at them.

The user manual specifically states “According to laser safety regulations, it is not legal to aim Class 3R lasers into areas where people can be exposed, even if the laser is aimed below people’s faces such as at a dance floor.”

This is true. Under U.S. FDA regulations for laser light shows, any laser beam above 1 mW cannot be lower than 3 m (10 ft) from the floor or other surface on which a person could reasonably be expected to stand.

If your ceiling is below 3 meters, you could not legally use the laser projector. If the ceiling is 3 meters or above, you can legally use the laser projector as long as no beams go below the 3 meter legal limit. To do this, you could use sturdy foamcore, black foil or similar materials to mask off the bottom of the beam “star field”. Just be sure no beams are below the 3 meter limit.

You may have been to other events and shows where lasers went directly into an audience. Sometimes this is done legally, with the laser producer having an "audience-scanning variance" from FDA. Such a variance ensures the laser power in the audience is at a level considered safe (below 2.54 mW per sq. cm.).

All too often, however, audience scanning is done illegally — and probably with no knowledge of the actual beam power which is in the audience area. Such shows are definitely illegal and are probably unsafe for eye exposure.


This is from http://www.lasershowsafety.info/faq.html

So...despite the manufacturer telling you not to aim the lasers at a crowd they still build and advertise the units to do so.  Shame on them.  The fact of the matter is though that these lasers are aimed at crowds all the time as well as put to use outdoors by the average consumer (ex. Christmas light decorations) despite the explicit warnings saying not to.  At the end of the day, what you decide to do with your laser is your choice and a choice you'll have to be responsible for.

For what it's worth, similar discussions were had back when Chauvet released their "Fat Beam" technology.

All of that said, I'm not aware of a single case of a 3R laser causing injury when used as intended (i.e. not dismantled or used with the deliberate intention to cause harm).  That goes for legit FDA-compliant devices.  A far more dangerous product that has been turning up in bars/clubs/bowling centers are the Class 3B and Class 4 lasers purchased from ebay.  I've encountered many of these units in the wild, almost always aimed in such a way that direct eye exposure will occur.  Of course you can all but guarantee that they're not used in compliance with the regulations (variance, clearances, etc.) nor are they operated in a manner safe for crowd scanning.  Sadly, as with the sketchy rigging I tend to encounter, nothing will be done until someone gets hurt.  Hope this helps! 
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duane massey

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Re: Understanding Laser Safety - Multi-effects "DJ" fixtures
« Reply #4 on: November 23, 2017, 01:57:26 am »

On a related note, several years ago I received a call from a skating rink, and was contracted to install lights they had purchased online. Everything was ADJ except a Chinese RGB laser with little documentation. I installed everything but the laser, and explained that there was no way to safely use the device without at least knowing the class rating (and it was DEFINITELY a "big boy") The owner was a bit peeved, but he paid me for my work per agreement, which was T/M. Went back 30 days later to tweak some programming and they had installed the laser themselves, aimed straight across the skate rink so the entire area was within the beams. I told the manager that this was potentially dangerous and they could be held liable, etc. His response was typical: "The DJ said it was fine because it was scanning most of the time, and he knew what he was doing because...well, he's a DJ".
They are no longer in business, thankfully NOT because of the laser.
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Duane Massey
Technician, musician, stubborn old guy
Houston, Texas
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