Laser safety

[KidRay]

We are thinking about adding a laser to our Tina Turner tribute show, I'm looking at something like the KAM iLink RGY, to be used a couple of times in the show, specifically for a yellow "tunnel" effect during "Goldeneye", and maybe in one or two other songs. I've been reading up on the various H&S issues with lasers, the KAM unit is a class 3B, and is key operated, also I will run the remote interlock to the lighting position so it can be turned off independently of everything else. I was thinking about a physical barrier to prevent problems if the unit should accidentally get moved during a show and the beam drop to somewhere it shouldn't be, and thought that I could position the laser behind our backdrop (pvc banner tied to lighting truss) and make a small hole for it to project through, so if it moved the beam would be cut off by the backdrop. I would certainly consider a training day if anyone can recommend one.

 

I went to see a Floyd tribute recently, who had a laser show, and I was a little concerned with the safety aspect. The video shows what I mean, about 20 seconds in vertical scans are sweeping across the audience. I assumed that they had to be 3m above the audience. Is this an "illegal" use of lasers?

 

http://www.youtube.com/watch?v=1rgXct81rsw

[David Lee]

Some laser controllers can attenuate the Beam at certain positions. At least the one at the last club night could. Sorry I can't be more specific except it was pc based. Will try to get more details of the laser op who was doing the show.

[greenalien]

Although it's a class 3B laser, the KAM unit that you are considering is very low-powered for a single laser light show, certainly much lower power than those in the video appear to be - you should definitely 'try before you buy' as you might find the result disappointing. It's a disco effect and that's about all it's suitable for.

 

As far as safety is concerned, all lasers must be operated in accordance with BS 60825 part 3 - and for any and all discussions about lasers, please refer to the photonlexicon forum where you will find much more detailed information on the subject.

[Dmills]

The show in the video MAY have been acceptable, depends on the laser power level (very hard to tell from a video), and the presence of any required scan failure interlocks.

I was concerned by the scans hitting the mirrorball however, very hard to calculate for eye safe levels with doing that.

 

3B from behind a upstage drape will likely be fine, but you should do the paperwork anyway and check the venue license conditions, they sometimes have things to say about lasers. I doubt that 3b is going to give you the effect you are after however, at least not without a very heavy haze in use.

 

The software you are thinking of is probably from Pangolin who have a "Beam Attenuation Map" feature, but that is probably gross overkill for a cheap 3B rig.

 

Regards, Dan.

[KidRay]

Thanks for the info greenalien, I'll check out your link.

I'm aware that the KAM unit is fairly low powered, it's just an idea for an effect in one song really, not a laser "show" as such. I'm trying to be sensible about purchasing much more in the way of lighting gear, as I'm hoping that next year we will be hiring in for all our shows and our small rig will become redundant.

The effect I'm trying to get is to have our 5 250w halogen scanners with their beams crossing at a point somewhere in front of the backdrop, and the laser "tunnel" appearing from this point. The effect will be on for a couple of seconds at various points in the song, and the scanners and laser will be the only light sources for these few seconds, so it's not got a huge amount to compete against.

[Brian]

If you only need it for one effect you might want to check out Coemar Tunnel Light. They come up on eBay from time to time.

[KidRay]

I'll keep an eye out Brian, thanks.

The idea was mainly for the Goldeneye track, but if I've got an RGY laser I might make use of the red for the moody backlit instrumental intro we do to "We don't need Another Hero". I'm not a big fan of green!

[MrBoomal]

You may find that a s4 with a rosco "lazercone" gobo and a bit of gel is far more effective.

[KidRay]

The show in the video MAY have been acceptable, depends on the laser power level (very hard to tell from a video), and the presence of any required scan failure interlocks.

I was concerned by the scans hitting the mirrorball however, very hard to calculate for eye safe levels with doing that.

 

 

I get your point about the mirrorball, but surely in this case the obvious danger is that the laser is shining directly at the audience at eye level and coming from the direction in which they are looking.

[greenalien]

the obvious danger is that the laser is shining directly at the audience at eye level and coming from the direction in which they are looking.

 

It entirely depends on the laser power at the point at which the beam hits the audience, which is in turn dependent on the output laser power, the beam dimensions, the beam divergence, the distance from source to audience and the amount of fog in the air - it could be safe if the MPE (Maximum Permissible Exposure) limits aren't being exceeded, because it's a scanning beam and thus only hits the eye intermittently. However, it's the responsibility of the operator to demonstrate that the MPE limits aren't being exceeded, and this requires an accurate way to measure beam power amd pulse length and a certain flair for maths. All the details of how to do the calculations are in the BS 60825 standard document mentioned earlier; if you're not prepared to do this, you shouldn't be doing audience scanning with a laser.

 

A non-scanning beam, such as that from a laser pointer, or from a laser projector with a failure in its scanning system, is potentially much more damaging, so a professional laser projector suitable for audience scanning will always be fitted with some sort of scanfail detector that shuts off the beam if a scanner stops working. (Laser scanners, called galvos, move a very small, lightweight mirror very quickly to move the beam in one axis; they are prone to sudden failure without warning, even in the best quality equipment)

[KidRay]

if you're not prepared to do this, you shouldn't be doing audience scanning with a laser.

 

 

Point taken, I'm actually not considering scanning the audience, I intend to keep the beams 3m away from them, I was just curious about the gig I attended.