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Thread: An interesting post......

  1. #1
    Join Date
    Feb 2008
    East Sussex, England

    Default An interesting post......

    ...from a forum i moderate which got onto lasers and safety.

    Be interesting to read you guys take on it. The thread does go on, but I'll perhaps save some of the responses for later, depending on the feedback

    You DONT NOT need licenses to run a laser systems

    If you want you can as i have go on the LSO ( laser safety officer ) course which was crap and a waste of money if you ask me because the British Standard user’s guide for laser safety, PD IEC TR 60825-14:2004, recommends that a Laser Safety Officer (LSO) is appointed where Class 3B and Class 4 lasers are used.

    The problem with rigging a laser standalone on auto is you also have no control over where it stops if its crowd scanning. I've seen a lot of instances where reasonably powerful lasers leave static patterns in the crowd at close range, something that is generally frowned upon

    ---- as long as the scanners are scanning it will not do any damge to your eyes IF the scanners do fail they are are linked to blanking relay which will turn off the diode with in about 0000.2 sec.

    Dry hiring lasers is getting dodgier and dodgier as without a trained operator or hiring to someone that is you have no way of enforcing even the basics like interlock safety or scanning rates - 500mw is pretty potent too

    ---- WRONG ther's no such thing as a trained operator and 500mw isn't that bright. Ive had my 1.8w laser in clubs that hold 500 people before and guess what no one was hurt and everybody could still see at the end of the night.

    The only thing you shouldn’t really do is targeting with lasers over 800mw becuase IF it hits you in the eye your see green spots for about 5 secs thats all.

  2. #2
    Join Date
    Jan 2006
    Charleston, SC

    Exclamation Unsafe - pure and simple!

    I don't know which forum you pulled that post from (and I really don't want to know!), but the guy is talking out of his ass. 500 mw *is* dangerous. And just because patrons could "see at the end of the show" when he was shooting his 1.8 watt laser around doesn't mean that he didn't cause damage to those people's eyes.

    Eye damage is *very* hard to notice. In fact, we *all* have a blind spot that covers nearly 10% of our total field of vision, yet none of us are aware of it. This is the blind spot where the optic nerve attaches to the retina, and it's right in the middle of our field of vision! But the brain is so good at combining images into a seamless picture that we never even notice this blind spot unless we're taking a special test that is specifically designed to bring it to our attention.

    Likewise, laser-induced blind spots are not immediately apparent. But the damage is cumulative, so that multiple high-energy laser exposures will, over time, increase the "blind" area until one day you're shocked by something appearing out of nowhere in your field of vision. But by then it's too late to do anything about the damage.

    Furthermore, the rest of the points that he makes in the post are equally ridiculous. For example, what the heck is 0000.2 seconds? Does he mean .00002 seconds? If so, then he's got the fastest damn relay I've ever heard of, and I call bullshit. (20 microseconds? Come on!) On the other hand, if he meant .2 seconds, that's a fairly long time, and 1.8 watts can certainly do *lots* of damage in that amount of time.

    As for his claim that "as long as the scanners are scanning it will not do any damge to your eyes" (sic) - well, that's also wrong. There are hot spots in just about any scanned image. Especially in cases where the scanned line makes an abrupt change in angle. So you have points where the beam will dwell in a certain spot for a short period of time. Dwell time = greater exposure.

    Anyone that has had even the most rudimentary training would know about this, and also know how to calculate the exposure to the eye at those points. (Indeed, that's part of the curriculum at the laser safety seminars that James Stewart teaches.)

    Finally, this guy's claim that "ther's no such thing as a trained operator" (sic) is patently false. My guess is that he feels threatened by the other post suggesting that he get certified as an LSO, and rather than admit that he doesn't know all that much about safety, he decided to flame away with no more knowledge that what he has personally experienced. That is a recipe for damaged retinas, my friend.

    Point of clarification: Audience scanning - even with multi-watt lasers - *can* be done safely, even here in the US. (You know - the land of lawyers and restrictive government regulations on laser shows!) However, it is *not* something that should be attempted by unqualified persons. The price of making a mistake is pretty darn serious. So you really need to know what the hell you're doing.

    Even if you live in a country where your government won't go after you for breaking the rules, or in a country where you won't get sued by your patrons, do you really want to be responsible for damaging someone's eyesight? I know I don't.

    The key here is that this guy feels comfortable with his past exposure to lasers, and he thinks that this experience qualifies him as an expert. And while I have to admit that feel fairly comfortable risking my own eyesight by standing inside a scanned image from my low power projector that's operating in my living room, there's no way in hell I'd do that in a nightclub! He doesn't see the difference, and that's dangerous.

    I respect the companies that have got through the effort to get an audience scanning variance approved with the CDRH. And I would trust my eyesight to those companies. But I do *not* respect anyone that simply mounts a 1 watt yag on a post and sends beams flying into the audience. Scanned or not, that's a dangerous situation. And the guy that wrote that post you quoted is playing around with other people's eyesight. I'd avoid him like the plague if I were you.

    My $.02 anyway...


  3. #3
    Join Date
    Aug 2005


    On the assumption that this is in the UK , it is true that you don't need a licence to operate a laser in the UK.( I'm also assuming the double negative is a typo ! )

    However , If you don't follow the recommended guidlines ( HS(G)95 , and you do some damage , you will not be able to defend yourself in court . Nor will you be able to put the show through the required risk assessment needed to operate in a venue with an entertainment licence from the local authorities.

    Almost all local authorities in the UK have a blanket ban on the use of lasers , strobes and pyrotechnics in clubs etc. In order to use these gadgets, you have to do a specific risk assessment proving that the equipment is safe . Most other equipment is included in a genral risk assessment for the entire building , with the lasers, strobes and pyro's coming under the heading of " special conditions " on the entertainment licence.

    In the case of lasers , HS(g)95 is the current guideline along with the more general Health and safety at work act. The local authority still has the right to refuse audience scanning , even if your projector is ultra safe and within MPE levels. The big stick is losing the venues entertainment licence through non compliance to the " special conditions " ie lasers , strobes and pyrotechnics.

    The rest of the post is just as Adam has decribed it.

    Do we know who this chap is?


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  4. #4
    Join Date
    Feb 2008
    East Sussex, England


    I'm not sure I should identify the poster, the thread was more about discussion of the issues rather than to ridicule or berate, although Google can be a fairly effective tool.....

    One of the interesting things he says is about the scan fail devices. Now I'd always thought that i didn't atually have any on my projectors, but his comments seem to suggest that any scanner with feedback is probably set up for this. How true is that? Is it just the way it works these days?

    Here was my response, some things may not read quite right due to paying service to some other posts in between, I'm just hoping i got the gist of it right!

    You DONT NOT need licenses to run a laser systems

    I never said that, however venues have their license granted based on certain activities happening in the venue, 'pyro and special effects' being the coverall that lasers fall into. If they do not have provision for these activities on their license then they are required to apply on an individual basis. If they do have provision for these activities there will usually be some fairly clear specs about what can and cannot happen and how.

    So you as an operator do not have to have a license, but you may be required to work to particular standards, and prove modes of operation when you do go into those venues. As I said, venue managers are often ignorant of these facts, which is why its not as much of an issue as it perhaps should be.

    Since the publication of HSG95 and the Green Book, many local licensing authorities have used the recommendations in those publications as the basis for granting entertainments licenses to venues.

    as long as the scanners are scanning it will not do any damge to your eyes IF the scanners do fail they are are linked to blanking relay which will turn off the diode with in about 0000.2 sec

    Safe crowd scanning is all about safe MPE, and not about whether they are scanning or not, some patterns are safer than others, but as its so difficult to actually measure any particular pattern its very hard to prove what the output is. speed of scan is also less relevant as although it may be moving quicker, it is also passing over the eye more frequently. A static spot or a corner that is 'hot' will carry far higher levels than the middle of a line, so another variable to consider
    Not seen the feedback blanking advertised on too many cheaper chinese lasers, as they often use galvos without feedback option. I agree though, the chinese are really pushing the market on, CNI, Laserwave, Lasever amongst others are all actively engaged in user testing to improve the product.

    The link at the bottom of the page makes special mention of scan fail detection devices, and that if a projector doesn't have one it shouldn't be considered for crowd scanning

    ther's no such thing as a trained operator and 500mw isn't that bright. Ive had my 1.8w laser in clubs that hold 500 people before and guess what no one was hurt and everybody could still see at the end of the night.

    I think that your anecdotal evidence as to injury may be just that. The fact that nobody actually got hurt is not proof that it may still not be a hazardous practise. There is evidence to suggest that people do not notice damage if it is not directly in the centre point of vision, and that the brain tends to 'fill in the gaps' so that damage is not so noticeable anyway (although still very much there)

    I would disagree that 500mW is not that big, its cwertainly big enough to punch holes very quickly through tape at range, and do the whole lighting matches trick.

    Again, there is first hand evidence from people with display laser injuries that happened with lasers of 200mW and under.

    Here's a somewhat dated explanation of some of the facts and myths as represented by Nulight, which explained the a decade ago. It comments on the HSG95 documents and the fact that licensing authorities will be working to the guidelines in the future.

    Also, North Devon's EHO website as an example states the following in relation to laser use: The one in red is often the kicker, if you cannot demonstrate the calculation of safe MPE at every position then the crowd scanning is a no-no
    Class 3B & 4 Laser Products (eg. used for display purposes)
    • The operator of the laser system should provide the proprietor/employer etc. with sufficient information to demonstrate it can be used safely.
    • Minimisation of the emission of invisible and visible radiation.
    • All equipment to be rigidly mounted.
    • Use of non-flammable beam stops.
    • Supervision by competent person.
    • Control against unauthorised use.
    • Demarcation of laser display areas.
    • Secure and appropriate siting of laser control console.
    • Emergency cut-off.
    • Laser radiation exposure levels to be determined in advance at all appropriate positions.
    • Marking of area boundaries.
    • Precautions in setting up and aligning laser systems.
    • Functional checks prior to public operation.
    Last edited by norty303; 04-02-2008 at 11:57.

  5. #5
    Join Date
    Jan 2007
    Sheepsville, Wales, UK


    A closed loop scanner with feedback is not a scan fail system. The feedback signal can be used as part of a safety system with some other hardware that will kill laser output in the event of the input signal to the scanners and the feedback signal from the scanners not matching. A scanner driver card cannot kill the laser output so if the scanner stops working - coil fried - the amp will just keep on trying to move the motor which will never go anywhere and a big fat beam could be literally anywhere in the room.
    I love the bit about as long as its scanning it wont harm you! This guy should not be left in charge of a laser - he clearly needs some further understanding as for being an LSO....(laser stupidity officer?)

    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
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  6. #6
    Join Date
    Dec 2006


    just to save everyone googling !

    Yes the guys attitude is bold to say the least , and all over the country theres hundreds if not thousands on ebay buying in chinese kit for their DJ rigs and happily scanning the crowd at every local party in town !

    At the moment they are all buying 50-250mW units as thats the price market they are in , in a couple of years it will be 500mW-1 Watt units in the sub £500 price ? ( ? ) , and then the shit really hits the fan ........ a couple of headline news stories ..... the goverment will knee jerk to deal with it or talk very sternly about it leaving everyone with the impression ALL LASERS ARE BANNED and then a few years later we will copy the USA legislation where its the projector that has to get licensed !
    and a few years after that everyone will have forgotten about it except us and the cheapchinese imports will continue as normal.

    What effect has the tougher licensing have in the states ... does everyone ignore ?

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  7. #7
    Join Date
    Feb 2008
    East Sussex, England


    What effect has the tougher licensing have in the states ... does everyone ignore ?
    That was question i put to someone from the US who posted some pics of his soundsystem at an event, where the laser was clearly all over the crowd. Unfortunately he couldn't comment as it wasn't his laser.

    The post

    His pics

    See, we like pics of our DIY stuff too

  8. #8
    Join Date
    May 2007
    Milwaukee WI


    as long as the scanners are scanning it will not do any damge to your eyes IF the scanners do fail they are are linked to blanking relay which will turn off the diode with in about 0000.2 sec.
    I love this statement! two tenths of a second....??? what are the first 4 zeros for?!?

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