Laser Safety, Midi, random Q's

[Ninebar]

Hey guys,

So ive managed to get my projectors up and running and gave them there first proper outing in a warehouse style venue. I was blown away by them, they really exceeded my expectations.

Now as a noob, ive spent a lot of time researching and trying to get a understanding of how lasers work etc. Im slowly getting through sams laser guide. But im really worried about audience scanning as they're 2w projectors. So i didnt bother doing any for the last gig all effects where above the head. Now after reading abit of sams guide im aware that a beam has to be greater then 7mm in diameter to become safe (correct me if im wrong people) and that you've to take into account "phase shift?" (the time the beam spends on your eye) and the power behind the beam.

So according to the given specs of my projector:
beam specifications: Color Size at aperature Disvergence
Red 5*8mm <2.5mrad
Green <3mm <1.5mrad
Blue 4*2mm 1.5mrad

Output red >R>1000mw/650nm CNI
Output green>G>200mw/532nm OPT
Output blue >B>800mw/445nm CNI



Am i right in saying.. that at 1 meter from the projector Reds beam size is 14.5mm (5.8x2.5)

Now i did take note that the beams where very wide by the time they had hit the back wall, and that red spilled out when projecting white. Which is normal so i believe. Is it safe for me to be audience scanning with these projectors and if so from what distance??

Finally, recommendation of a cheap midi controller suitable for Quickshow that i can trigger cues via buttons and alter temp via a twisty knob? Did not like using quickshow with keyboard and mouse on my first outing.

Thanks
Dan

EDIT: Im from IRELAND so no variances or licenses needed to audience scan

[White-Light]

Hey guys,

Now after reading abit of sams guide im aware that a beam has to be greater then 7mm in diameter to become safe (correct me if im wrong people) and that you've to take into account "phase shift?" (the time the beam spends on your eye) and the power behind the beam.

No that's only the assumed pupil diameter of the eye. You can't assume that a beam of greater than 7mm is safe as it all depends on the irradiance.

To audience scan safely you need to take power measurements and do calculations to establish the actual irradiance of the pupil by the laser at the closest possible point to the audience in mw/cm 2 and then reference this with the MPE level. The irradiance will be determined by a number of factor including power, divergence, distance from the audience etc.

Its a complex business and you need actual measurements not paper specs which means you need a laser power meter, an oscilloscope with a fast photodiode sensor (there is some argument of the necessity of the latter, but if you're doing commercial shows you'll probably have to demonstrate that you've checked the pulse rate), and the necessary knowledge to use all of the above.

Best option would be to book a safety course with LVR Limited (J Stewart who runs he courses comes on here): http://lvrlimited.com/lasertraining.htm

Other reference documents that might help would be:

http://www.laserist.org/files/Art%20...20Science4.pdf

You'll quickly see its a complex subject.

BTW Ireland as part of the EU is subject to EU regulations and its a Criminal Offence in the EU to expose any employee to a level of exposure exceeding MPE. There may also be specific Heath and Safety Regulations on lasers (don't know the law in the Irish Republic), not to mention the fact that you'll face a whole host of lawsuits if you damage the eyes of your audience. So you don't want to even think about audience scanning until you properly understand the subject and how to calculate MPE correctly and repeatedly, and thus how to do a show safely.

Best way to perform safely is book and undertake a safety course.

[White-Light]

For controller:

Akai APC 40:



from Pangolin or many Akai dealers

or there is now a custom touchscreen option:



from: http://www.pangolin-dealer.com/

[pschlosser]

Red 5*8mm <2.5mrad

Am i right in saying.. that at 1 meter from the projector Reds beam size is 14.5mm (5.8x2.5)

One of the coolest things about milliradians as a measure of angle, is the relationship between distance and expansion. An angle at N mrad expands by N for every meter it travels. Thus, a 1mrad laser beam will expand by 1mm for every meter, and 1m for every km, lol.

Your Red, at 1 meter, has expanded by 2.5mm. Your beam size should be 5+2.5 x 8+2.5 which is 7.5 x 10.5mm. At 10m, your beam size should be 30 x 33 mm.

[Ninebar]

Thanks for the reply guys, im now one step closer to not blinding someone.

Ive found a local laser health and safety course which im going to enrole soon enough. I reckon ill be able to use the equipment there to find out the MPE level as i cant afford a meter myself at the moment.

Here is the course: http://www.nuigalway.ie/ncla/courses.html

Thank you "pschlogger" for clarifying that unit of measurement for me. I now understand

[White-Light]

Thanks for the reply guys, im now one step closer to not blinding someone.

Ive found a local laser health and safety course which im going to enrole soon enough.

Great move provided its a good vendor. J Stewart on here might know more about particular operators as he's in the safety business.

I reckon ill be able to use the equipment there to find out the MPE level as i cant afford a meter myself at the moment.

Unfortunately it doesn't work like that.

I'm sure some of the people on here who do professional shows will advise you but my understanding is that you have to measure the power and pulse repetition before EVERY single event. In the UK I'm pretty sure for one off events as opposed to a licensed club where the laser setup has previously been passed, you have to submit a Health and Safety Assessment for the event with all details including evidence of measured values and set up in that event location. I'm pretty sure in Ireland the regulations will be similar.

Jem on here has written a guide to Health and Safety Assessment procedures in the UK. I'm sure he could link you to it although you'd have to check this against Irish regulations.

Norty, Laser Insanity, Dan, AndyC are all experienced UK commercial operators (apologies to anyone I haven't thought of off the top).

Also, the MPE isn't constant for any given laser. It will be different at every event due to differing distances to the crowd and thus divergence and thus irradiance, lasers also potentially output differing amounts of power every time they are started so you can't just assume that because it was 2.00 Watts on one day, it will be 2.00 Watts the next day as it could for example be 2.50W.

There are no short cuts on safety unfortunately.

Audience scanning is great but it involves a lot of expensive equipment, knowledge and preparation to do it safely and legally, commercially.

I suggest that if some of the above people don't chip in, you hit them up on PM and speak to them about commercial safety procedures as its not a simple game.

[Ninebar]

I've a lot of work ahead of me so. Thanks for the info, I'm staying clear of audience scanning until I know for sure

I do want to do this right, and avoid harming anyone

Are the cheaper homemade meters reliable? Or a second hand meter maybe

[Jem]

Here's a link to the risk assessment. Remember though, you'll need to adapt it to your own situation, but at least it gives you a start...

http://www.pangolin.com/resguide09j.htm

[JStewart]

Hi Dan,

Great post, and great to hear your lasers are looking good. Definitely a wise move to avoid pointing effects at people directly until you’re able to establish what the exposure levels are, and how they relate to the exposure limits (MPE).

“At the moment” simple to use “Laser MPE Meters” are still quite a rarity, but you can establish a lot using a basic laser power meter, as long as you are aware of its limitations. Something like the Coherent Lasercheck power meter available for around 300 euro can be a good starting point for measuring static beams. If you know the power of a static beam at the point of contact with the audience, you can work out the irradiance, and how this relates to the accidental exposure limits (25.4W/m^2 and 10W/m^2). If your projectors don’t have any scan-fail detectors fitted, or you are not sure of their effectiveness, (i.e. the time it takes to detect a fault, what is considered as a fault, and how long it takes to extinguish the output), these limits are generally the ones you should be sticking to.

If you can guarantee the exposure duration will be shorter than that of 0.25s duration beam, the dose of laser light you can illuminate someone with without exceeding the MPE increases. Therefore you can use more light.

Knowing the static beam irradiance of your beam is useful, for even in the absence of more sophisticated instrumentation, you can estimate and set what may be permitted to scan an audience with, if you’re able figure out the pulse durations and number of events during a scanning exposure.

Getting yourself signed up on a laser safety course is a great way to learn about laser hazards and risks, and how to best control them. I’m not aware of the course you’ve indicated, but what you should do is check with (any) provider is that they have some experience in light show applications. I know of some people having spent a small fortune on generic laser safety courses, only to spend the day talking about control measures such as door interlocks, machine guards, staff training and beam isolation techniques, which can all be quite alien to the practicalities of using display lasers to thrill audiences with laser light.

If you are able to get over to Yorkshire in late June (22nd/23rd), forum member Jem (Jeremy) has organised a laserist get together through the ShowLEM. I’ll be there on the Sunday giving a quick 101 and demonstration on assessing audience scanning laser effects. The weekend is open to anyone with an interest in display lasers, so you would be most welcome to pop along.

In any event, good luck with using your lasers, and taking the initiative to want do things properly and not put people’s eyesight at risk. As you’ve probably worked out already, there are a few hurdles to clear in order to scan safely with a level of confidence. But it’s not impossible, and even with a few basic techniques followed, possible to establish how exposures compare with the exposure limits.

In relation to your question about second-hand or homemade meters, it is possible, but they need to be calibrated and the uncertainty of the measurement known, so that you know how close to the indicated value is to the real exposure level.

Hope this helps,

James