New Laser MPE Limits published

[mixedgas]

Its all about "You" isn't it? The straw man argument fails.

I just asked you to do a somewhat humor-ized version of some problems what I had to do to pass the industry standard safety course.
Both of the cases stated below had a real world basis. I might have worked at one of them when I was young. I certainly visited the other.


You just declined to do the basic level problems the laser industry (not just shows) would have you do as Safety Course 101. The test was open book.

So much for your credibility in this manor.

For the record, I had been asking for ILDA and others to try to change the process for years, including providing hobbyist level licensing.

10 years ago the accepted and highly developed "toy" I admired had to sell at 3000$ per unit, and you still had to use it at many, many, points in the audience for each effect, because effects have hotspots. In other words it took hours, if not days, to validate all the effects in the show, to the satisfaction of regulators. The R&D, validation, and insurance costs drove the cost up. Plus the sensor was not that simple.

Doing the math speeds the required process over doing the MPE meter. Placing the scan fail system in the projector validates the math and speeds the safety case.

Lots of very skilled people with viable financial interest have invested large amounts of time in this area of laser shows. They opened their data and techniques to the industry. We rest on their shoulders. We have to do what they have worked out, there is not much of a viable option, and the science is pretty much spot on.


Steve

[The_Doctor]

You singled me out and demanded others to stay out till I complied with your demands. You made it 'about me'. I tried to stay with an idea, buy you have made it personal every time you posted. Now sod off. Go find a way to spare people from the minutiae of analysis if you want them to do better. Most people who will buy a scanner these days aren't going to jump through those hoops either, and you're just going to have to find a way to deal with that if it bothers you. I think it IS bothersome, hence trying to put an idea up for consideration. I'm interested in thought from others but I'm about done with yours.

[mixedgas]

Guess what. As laser power increases, more and more regulators will take interest. This is a worry. Lasers are not following Moore's law, but they are starting to rocket up in power and come way down in cost. At some point this will become an issue.

You would not grasp the problem by doing the work. I'm not going to set here and do your design work for you. I would have helped you if you would have worked to understand what was presented to you in that problem. I just set in a room watching people who REALLY wanted to have the cert struggle for two hours to pass the test. They are the future professionals. They wish to be on the edge. They wish to improve things for others and be safe. And most of them paid for the course out of their own pocket.

Post after post, you have posted little but poorly informed opinion lately. You just had the chance to take things to the next step, but you declined.

Steve

[The_Doctor]

Good for them. I'm just some punk with a wide range of interests that include lasers, electronics, and 1970's Doctor Who. I'm not studying to be a professional laser operator.

I do know enough to know that when some drug-addled geezer is climbing some lighting gantry in the middle of the night like a psychedelic spider, the pupils of those eyes might be anywhere from under a mm wide to over a cm. And you're not going to know which, or be able to police it. So your hypothetical Marilyn Monroe is a load of tosh if you think specifying an arbitrary mid-range eye pupil size is useful here to solve a general problem. I'm not a doctor but I can tell you that desire, shock, reaction to some other light, or sound, or smell, can make a pupil vary a great deal over the course of a minute or two in a live show. So you're just going to have to deal with worst case, quantify it as X, then figure out a fast detector for X that will work when some guy setting up a show waves it in front of the test projection from the closest audience position before the show to test whether the beam might be a risk to known worst case conditions. You say it's never that simple, but if there IS a worst case, and if you can quantify it, it IS that simple. If you can't do it, don't expect me to do it or it makes you look like John Cleese as drill instructor urging me to lunge at you with various mixed fruit. If you know that Python sketch you'll know who looks the silliest there.

I'm inferring from one of your earlier posts that you have tried to persuade the big boys for many years that you are serious, and not one of the dangerous loons playing lightsabres for fun and profit. If they have not been convinced by you to change the way they think in all that time, maybe you need to figure out what you did wrong. Berating me isn't going to endear you to them either. If other people aren't challenging you on this, I have to wonder if they're more scared of crossing you than of their lasers. Which would be silly because they should not fear you, and their lasers are scary. Or maybe they're indifferent, in which case you really have a problem, and the sooner you, or someone competent to do it, makes that little safety box, the better.

[mixedgas]

You just basically indirectly told every professional laser safety expert, and the self educated laser safety folks you are an absolute fool.

Ok gents, the Doctor makes his own rules it seems. He does not even want to learn how the different parts of the physics relate. Make darn sure you don't stand down range when he tells you its safe.

Another armchair expert who needs to make friends, get some exercise, and have a life, maybe try out a church?


Writing this post just feeds his need for attention.

Ok, Its a Holiday in the US tomorrow and I don't expect any responses. I'll have time on the airplane on Tuesday to write the cases for publication on Wednesday.

Loosely based on three different actual events, except the Marilyn part, that was added for fun.

Steve

[The_Doctor]

Not personal, eh? Amazing. You;re a troll, a bigger, tree-top gorilla chest-thumping troll, but a troll all the same. Hopefully other people will recognise an attempt to suggest some answer to the problem and look at it from a a more thoughtful perspective. You seem to busy trying to belittle me again and again and again. I don't know what the scientific rationale is for that, but I doubt there is one. Keep slugging, champ. The ring is empty. And fyi, I ran several miles tonight. Can you do that? I've seen a picture of you. I suspect you can't. So don't play smartarse with me about 'getting excercise'. Keep your dumb personal speculations to yourself!

[White-Light]

Doctor your theory is fine, but here's a real life incident - permanent eye damage from 200mw cw pointer at range:

http://www.laserist.org/2009-07_Belgian-incident.htm

Laser safety levels exist for a reason and that reason is laboratory tests have been done on eye balls to see at what levels changes occur in the cells, and then safe levels forumlated from that and other supportinmg inforemation. The levels aren't just plucked out of the air for fun.

[norty303]

Steve, you're being a bit of an ass-hat at this juncture from my perspective.
You are very knowledgeable, granted, but trying to show up the Doctor for the stuff he doesn't know seriously detracts from the thread direction imho. In short, you are being a bully.

From where I'm standing he has it right, but that may be the Atlantic divide.

We cannot hope to run before we can walk, and over here (and I think over there too...) we have a seriously unregulated industry. I've made this point before myself; 'anything' that makes it easier/cheaper for people to do safety, even if they're not doing it fully is 'progress'.

Thats why the safety scan lens is so good. It simply requires the numpty concerned to attach it to the front of the projector. Nothing more. The show is now orders of magnitude safer than it was previously, even without doing any sort of calculations or understanding any maths. It may still no be 'legal' or 'safe' but its a better situation than it might otherwise be.

If you can't do the math, which is simple. le, you wont get the gig past a safety case in the US or UK

Can't speak for the US, but in the UK I could've written a load of nonsense in my safety record for a number of gigs and it wouldn't have made a blind bit of difference to the approval or not.

[mixedgas]

A not so simple set of time tested, peer reviewed, very conservative assumptions are used to make the calculations workable. If you accept them, its not hard to "plug and chug" to solve this equation. The real trick is to keep the units consistent.

7 mm is not a bad value, it is the accepted, peer reviewed value. its there for a reason.

What causes the problem is the way the Laser Safety equation is written and explained. It looks some Alien character set. With Phi and Theta so close together, you might as well toss in an Omega and really confuse people. No one wants to mess with the mathematical gobledegook around it.

Therein lies the problem, getting the word out on what to change to make an effect safe.

Steve

[The_Doctor]

Doctor your theory is fine, but here's a real life incident - permanent eye damage from 200mw cw pointer at range:

http://www.laserist.org/2009-07_Belgian-incident.htm

Laser safety levels exist for a reason and that reason is laboratory tests have been done on eye balls to see at what levels changes occur in the cells, and then safe levels forumlated from that and other supportinmg inforemation. The levels aren't just plucked out of the air for fun.

I didn't have a theory. I understand that empirical tests are done on actual eyeballs. So isn't it possible to find a worst-case, then determine duration and power and wavelength that does it, then build a cheap widget that will detect it to warn people? The idea being that for any wavelength, pupil size, whatever, other than worst case, things will be safer. No doubt this could 'enforce' some very low MPE values, but it wasn't me calling for them to be raised. Nor have I ever made any pronouncement about laser safety either generally or specifically, despite Steve's claims. I stay well out of that talk, for good reason. I only asked here if there could or should be some kind of MPE warining widget because it's now clear that the 'thin blue line' trying to police this stuff is so totally overstretched that it ought to welcome any suggestions that might raise the issue's profile, if nothing else! I even made the suggestion that a photodiode with proportional output can be accelerated by differentiator. It works for power meters, so should be considered in this context.