Help my friends from going blind

[PUFF1N]

Hi, first post, so apologies in advance, but time is short on thus one.

So my DJ friend has a monthly party, which has been growing and we've been adding to the equipment slowly, hence we've entered the last zone. He bought one of the cheap eBay 1W RGB jobs with USB controller and ishow. Of course no warning labels, concrete specs or support. Not a good start I know.

I'm in IT and pretty tech savvy so do all the installs and set ups. A quick read of same faq and a bit of googlefu highlighted my concerns about safety. Unfortunately tomorrow, this is going on if I like it or not, but I do have a chance to mitigate some risk, so some straight forward replies would be much appreciated.

1. How dangerous is thing in reality? Say from 2 meters away if someone cops an eye full. 1 being very low risk and 5 being instant blindness. Assume no one is staring directly into the beam, natural avoidance and blinking.
a. On single beam mode?
b when projecting a multi color beam / tunnel?
c. When projecting a stock cartoon animation?

2. The room is large, but the recommend distances for scanning cant be observed. I've read enough to know that I should keep it moving as quickly as possible and use colors as far away from ir as possible. Any other tips? If someone is familiar with ishow, what would be one of the safest stock images to use?

Sorry if this has all been covered a million times and I will read a lot mire, but just need a ballpark danger reading in this type if gear.

Kind regards
Puff

[edison]

Send Mccarrot a PM. He knows allot about doing safe shows. You have a 1 watt laser so it is dangerous when standing 2 meters away and have it at full power. I don,t have enough knowledge and so i can,t tell you what is best but ask MCcarrot and he can help you out using the projector safely

[gashead]

Puff daddy,

Where are you in the world ?

[norty303]

1. How dangerous is thing in reality? Say from 2 meters away if someone cops an eye full. 1 being very low risk and 5 being instant blindness. Assume no one is staring directly into the beam, natural avoidance and blinking.
a. On single beam mode?
b when projecting a multi color beam / tunnel?
c. When projecting a stock cartoon animation?

Ok, assuming it is making a full 1W, and making some bland assumptions that the beams are all the same spec/shape, and all 3 modules are 'on', but going for a 'typical' set of values across the DPSS and diode based modules...

3mm diamter at aperture
2mrad divergance
1000mW

Assuming no scanfail device, so 0.25s exposure duration worst case (blink reflex, turning away, etc)

Single Beam at 2m = Irradiance 25W/cm^2 which is 1024 times MPE (scary stuff!) This doesn't reach MPE until 112 metres away
Tunnel/Flat Beam = Assuming no fault conditions (without scanfail we should still use 0.25s, but we know that these types of effect typically have <1ms exposure duration) 2.6W/cm^2 or 257 times MPE
Animation should be in the same region as the flat tunnel, but may have more 'hotspots' on corners or small details.

Regardless of how you look at it, at 2m it is WAAAAAY over MPE. Increasing distance to 10m reduces the hazard significantly, but still leaves the single beam 95 times over MPE.

[danielbriggs]

Should you be new to all this:

MPE = Maximum Permissible Exposure.
i.e. the standard definition of the highest power considered safe.

[steve-o]

Safest way: Mount the laser 3 meters above the audience and scan no lower than 3 meters above the higest point that anyone's eyes/ head could be. (overhead show)

[White-Light]

Easy solution mount it so it scans overhead.

1 Watt demands a lot of respect.

Edit Cross posted with Steve

[norty303]

Safest way: Mount the laser 3 meters above the audience and scan no lower than 3 meters above the higest point that anyone's eyes/ head could be. (overhead show)

Actually, it's 3m from the floor, not from the highest point. So this should still be clear of outstretched hands or people sitting on people's shoulders

[Bradfo69]

@Norty - I've gotta hand it to you. I've read a bunch of your replies to people regarding safety recently and you've really digested all that information from your LSO class pretty well. You certainly can crank out the answers and do the math much better than I can! I'm looking forward to taking my LSO course again at the ILDA conference and hope someday I've got as good a handle on the answers and calculations as you seem to have now! (not that I can audience scan in the US anyway but it's great information to know.)

[norty303]

The math is the easy bit - I use James' (LVR) Laser Show Safety App
I can do the math as well now, but why make life difficult. The important thing is in understanding in what scenario you should use what time frames, and that's the stuff the course teaches you, and also where it is reasonable to make certain assumptions, and where it isn't.
The other thing the course showed me was that this forum is actually very rich with safety info, including access to calculators, spreadsheets, etc. By the time I attended, I pretty much knew what I needed to know, but just didn't know that - and James put me right on a few things I was a bit 'squiffy' on.

I will be the first to admit, I used to do shows that were not well evaluated (I know, pot, kettle, etc) , and I guess ignorance is a partial excuse, until someone points out the error of your ways, or you discover them yourself, you simply don't know.

Knowing now how I can relatively easily evaluate a show, make the required changes (power, divergence, distance, etc) and be safe, and show to others/authorities that it is safe, is an enormously empowering feeling.
I can now go out without any of that nagging 'is it going to be ok' feeling, where I kinda knew I was 'mostly' right, but still doubt...

The problem with cheaper lasers is that the cost of a course is then a significant proportion of the outlay on the kit (you can buy lasers cheaper than the course is!) so people simply don't consider it as viable.

I took the decision this year to jump in with both feet - and do it properly, its a one off cost essentially (I hope!)
Since January I've spent about £1500 just on lenses (8 arrived today from Bill, sitting on my desk next to me now), getting and fitting scanfails to all my projectors, making eStops and working through the problems of interlock loops (thanks DZ ). there's one mor part of the development path still to sort, but you'll have to wait for that one...
It is one step to buying the laser kit, but to learn how to do it properly, and then set up your kit appropriately as well, is a whole other undertaking, both in building and financially. But that is where the difference is between the smaller and larger operators. And come the revolution, and any tighter regs enforcement, hopefully I'm not going to be thinking 'Oh sh*t!'

And all this for about 10 gigs a year! Hopefully it'll pick up a bit At least my soldering skills have improved...