Audience Scanning??

[JStewart]

An interesting thread…

I thought I would add a couple of points of fact to the discussion also, as they may be useful for readers to consider.

Carmangary – to answer your question about viewing a 300mW system in a garage, it is difficult to be precise without knowing a few more parameters, but with a short separation distance involved, and I’m assuming no modifications on typical divergence, you could easily be looking at having the whole cross-section of the beam enter a dark adapted pupil.

With a typical tunnel effect spread over 40 degrees you are probably looking at being around 20-30 times over the MPE for an accidental 0.25sec exposure.

Even with a single 10us pulse you are probably looking at being around 15 times the MPE. A 100us pulse increases the exposure to around 45 times the MPE. And a 1ms pulse could put you around 80 times the MPE. These pulses are durations that you could be exposed to, even if an effect is moving constantly.

The key point here in this application is that you do not have the separation distance needed to bring the effect below the MPE. – (Of course though, adding some smoke will help to attenuate the beams in practice.) If you want to try and keep things nearer to the I would think about diverging the beams if you are using the projector in this environment a lot.

2W Laser in a Club doing a flatscan – again just a guess on the parameters and using a 10m separation distance this time. But even so, on main part of the effect you are probably looking at being around 50 times over the MPE for a 0.25sec exposure. On the ends of the effect it could be more if the effect has not been blanked to remove the hotspots as the galvos change direction

As for the comment posted about “all laser light entering the eye being harmful” this is of course not the case. The whole reason internationally recognised and adopted MPEs (Maximum Permissible Exposures) have been developed is to establish and advise on what levels of laser radiation do and don’t cause harm.

I see in the last post there is a slight retraction in the claim about the laser light causing damage. Again this isn’t quite correct. The light from a Class 4 source CAN be made to expose the eye at a level below the MPE, and hence not be the cause of a retinal injury.

Now, in a court of law several facts need to be established; Firstly, that the plaintiff has suffered an injury attributable to an over exposure of laser radiation, and secondly that the injury was caused by the defendants equipment and being in attendance at where the laser was used.

The laser installer/supplier/operator and venue itself would have a hard time on their hands if they couldn’t prove that any beams that they were putting into the audience were below a level that are scientifically proven to cause harm. One of the first things the court will seek to establish is if the levels of radiation exceeded a known metric (in this case it would be the figures that ICNIRP have derived for the international laser safety standards).

If this is unknown and it is likely that the laser projector could have emitted levels of radiation above the MPE then it will be a difficult case to defend if someone is claiming an injury.

However, if full assessment of the scanned effects had taken place and appropriate control measures put in place, and it can be reliably documented that the levels of exposure are below the internationally accepted levels for damage to occur, the plaintiff would have a fight on their hand trying to prove that the laser show caused their injury.

The courts are unlikely to be interested in anecdotal statements such as, “my friend says it should be safe”, or “someone I know says you will get an injury…”. What they will be interested in is hard fact. The MPE is the critical thing that would be considered.

Best regards

James Stewart
Laser Visuals Research Limited

[JimBo]

I wonder how it would be treated in a British court, "innocent until proven guilty", so would the plaintiff have to prove the show was unsafe?
I guess we will never know until there is such a case.

Jim

[JStewart]

Good point Jim…

UK law is based on the principle of “innocent until proven guilty”, as you quite rightly say.

However the “onus of proof” under section 40 of the Health & Safety at Work Act 1974 (HSAWA 1974) does in effect lead to the situation that the accused is effectively guilty until he proves himself innocent.

This apparent reversal of the burden of proof does seem to go against what we all believe to be the norm, and with the advent of the Human Rights Act which also enshrines the “innocent until proven guilty” ethos, an important test case was bought to the Court of Appeal in 2002 (R. v Davies). Davies appealed on the grounds of the reverse burden of proof of the HSAWA not being compatible with the Human Rights Act.

The appeal was dismissed and the judge stated that section 40 is compatible with the Human Rights Act as it is justified.

So, in a Criminal Health and Safety case, the onus does effectively swing round, with the accused having to prove their innocence.

Some of the key things that the laser operator/installer needs to ensure they have got covered are safe and legal kit, safe working procedures, adequately trained staff, and a suitable a sufficient risk assessment for the work being carried out. It is the companies or businesses not having these points documented or are just blasting the public with laser effects without assessing the hazard and risks, which could quite easily find themselves in problems if ever challenged.

…And for anybody interested in learning more about all this, and how to make safe audience scanning effects, and get a certificate our next Laser Safety training day is Monday the 18th February.

Best regards

James Stewart
Laser Visuals Limited

[JimBo]

Hi James,
a little off topic, but, did you ever release Scanguard Lite?

Jim

[JStewart]

Another good question Jim...

The new full version of the Standard Edition of Scanguard is currently being tested with a few of our customers. It presently needs the in-application documentation updated to help people make clear sense of the data it creates. But it is still a neat tool for allowing operators/installers to help assess their shows.

My own workload over the past year with both other laser and safety work has been been very demanding and not left much time for in-house development so I'm afraid the "free" lite version of the software has had to sit on the back burner.

However, with it being a bit of a quiet spell this month, it gives me the time to concentrate on some of the office based work. So stay tuned... and if you've registered on our website, you'll get a notification of the release via email.

Best regards

James Stewart
Laser Visuals Limited

[UV99LASER]

OK beat me with your key boards.
I might have been over zealous with my statement about any laser light entering your eyes causing permanent damage.
Obviously at some point laser radiation is dissipated to a non harmful level.

I think that 7mm dilation and 250ms blink response numbers are bad numbers.
I think they are clinical numbers and are non representative of real world laser show attendees.
Concert goers and rave party attendees tend to indulge in such thing as LSD, Ecstasy, Mushrooms and methamphetamines.
These four illicit drugs cause severe pupil dilation.
Illicit drugs are not the only drugs that can cause pupil dilation.
Many anti-depressant drugs and drugs used to tread ADD also cause pupil dilation.

The normal scotopic(near total darkness) pupil size range is approximately 4 to 9 mm for healthy non-impaired subjects.
You can reference this statement here.
http://www.cjcenter.org/documents/pd...zeRichman2.pdf
This statement is also supported by five studies also listed at the above site.

So if the pupil size range is approximately 4 to 9 mm for healthy non-impaired subjects in near total darkness what is it for impaired subjects?
7mm it is not.

Another point not touched on here is the burning factors of the red blue and green wavelengths.
Red being the widest wavelength and closest to infrared will need the most power to cause injury.
Blue being closer to ultra violet will need the least power to cause injury.
Green being in the middle will obviously need a power level between that of the blue and red to cause injury.

Therefore a "safe" doses of red, green and blue should have different values.
Red being the highest and blue being the lowest.
This is a point that should be seriously considered especially with the proliferation of 457nm and 473nm lasers.
457 lasers are already hard to look at with the beam looking fuzzy.
200mW of 457 burns a lot of stuff FAST.
Nothing I have seen here mentions differences in power levels for different colored effects.
It is as if all wavelengths were created equal. They are not.

Lastly is the .02 second involuntary blink response.
The involuntary blink response can be overcome by intense starring.
I know this from my own personal experience.
Before I was a laserist I attended rave parties every weekend.
The local laser guy Holly Wood Dog would scan the audience at every show.
This was one of my favorite effects and I would position myself to get a face full as much as possible.
I would resist the urge to blink in order to view the effects.
I have been scanned by tunnels fans and even raw beams.

I used to come home with itchy eyes and suffer 3 day headaches with said itchy eyes.
At the time I thought it was bad drugs. Little did I know it was a bad laser guy.
It was not until I was trained by a safety conscious laserist that I learned the symptoms of retinal burning.
Itchy eyes and 3 day headaches.
At the time I did not know that,
1 The effects were being created by a laser.
2 Lasers are harmful to the eyes.
3 Do not stare into laser with remaining good eye.

So I put to you that I believe "safer"(and more ethical) numbers would be 9mm dilation and .5 second blink response.
I do not believe the current numbers of 7mm dilation and 250ms second blink time would apply to the entire audience.
How would the application of these "safer" values affect the viewed outcome of the audience scan?
Would it be too faint to go through all the trouble?
Would the safer values render the audience scan ineffective?

I do not have any vested commercial interest in proving or disproving the safety of audience scanning systems.
There are members here who do have a vested commercial interest in proving the safety of audience scanning systems.
Remember it is on the petitioner to prove the safety of their product to the FDA for approval.
800 million is the number reportedly spent my Merck bringing Vioxx to market.
That is 800 million and thousands of PHDs bringing the failed drug VIOXX to market.

How many millions were spent researching audience scanning. How many PHDs were involved?
Who spent the money to prove audience scanning safe and what do they have to gain from it's approval?

Again I am speaking from over 15 years real world light show experience.
In general I do not do corporate events. I usually only do music based events.
I put it to you that the risk of permantly damaging ONE eyeball is not worth any amount of millions of dollars.
Just because your eye dilates to a maximum of 7mm does not mean that is the maximum for all people.
I think people should look harder at what they are doing and ASK way more pointed questions.

Thanks,
Let the beating begin.
Matthew "Skipp" Raftery

[Tribal Existance Prod.]

As the conversation gets even more interesting.........

[Dr Laser]

I think there shell be a global ban for laser use anywhere.!

Kidding. But what I really believe shell be baned is that cheap ass China laser show projectors. You probably 've seen those toys for under 500$ on ebay. They also called Dj laser show. I didn't pay any attention to those toys but one night we did a party/show in some rural town. (We got over 900 people there) and one Dj brought this thing up. iT'S BLOODY DANGEROUS !! Compare to my laser projectors. I caught a beam in my eye from that thing. It hurts!. Even a scanned one. It hurts! Who is gonna teach people who is using those laser toys safety? Huh?.

[JStewart]

Skip

I’d suggest if you think that the 7mm aperture and aversion response (which is actually 250ms not 2ms) used in both the ANSI and the international laser safety standards are bad figures, then perhaps come along to next International Laser Safety Conference and raise the concerns there. You’ll meet the worlds leading experts in this subject and be able discuss these things with them. Better still, you might want to think about presenting and publishing a paper on the subject at the meeting too.

As far as the comments on the different wavelengths go. Up to 10s exposure the MPE tables consider damage to be uniform across the visible spectrum, which they consider to be 400nm – 700nm. Only on the longer exposures does the visible band get divided to account for what is known as the blue light hazard.

According the to ICNIRP MPE data, 200mW of 475nm for 0.25s will have the same effect as receiving 200mW of 650nm for 0.25s.

If you have reason to believe that you have a valid claim against the person that caused your injury then why not take it up with them or sue them for the damages you believe occurred. It might stop them form causing harm to others.

Dr Laser - I agree these Chinese toys are a problem. I measured some of the scanned effects created by these last year for a paper I was presenting at ILSC, and as you would expect, these little 100mW-200mW+ devices were easily exceeding the MPE levels for how they are intended to be used by the Mobile DJs etc. Regrettably, with the increasing proliferation, falling costs, and increasing powers, I think it is only a matter of time before someone reports an injury from these mobile DJ type setups.

Best regards

James Stewart

[buffo]

I might have been over zealous with my statement about any laser light entering your eyes causing permanent damage. Obviously at some point laser radiation is dissipated to a non harmful level.

I'm glad you agree. This is exactly how the Pangolin variance for audience scanning works. It reduces the exposure to a non-harmful level.

I think that 7mm dilation and .02 blink response numbers are bad numbers.

.02 seconds *is* a bad number. The actual number is .25 seconds, as James Stewart pointed out above, and is based on sound, peer-reviewed science. The fact that you disagree with these "clinical" numbers proves nothing. Unless you have some data to back up your claim that the numbers used are unsafe, you're just making wild accusations without proof. (For example, have you measured the pupil of someone on Ecstasy? Or done any research on how their blink reflex is affected by the drug? And have you published any of this information so it can be peer-reviewed?)

Furthermore, this is all irrelevant to the discussion of Pangolin's variance, because it doesn't rely on the blink reflex for safety. As Bill Benner mentioned in his post above, the variance relies on a combination of factors (including the large aluminum glass lens on the projector) to make the beams intrinsically safe.

Concert goers and rave party attendees tend to indulge in such thing as LSD, Ecstasy, Mushrooms and methamphetamines.

I'm not sure I understand your concern here. Surely the use of these drugs presents a far greater hazard than a properly varianced audience scanning laser show? Yet you seem to be fixated on the laser danger and simultaneously willing to dismiss the far more serious dangers posed by the drug use... I don't get it.

The normal scotopic(near total darkness) pupil size range is approximately 4 to 9 mm for healthy non-impaired subjects.

Would you be happy if the standard pupil diameter was raised from 7 mm to 9 mm? Is that what you're advocating? Because it sounds like you're trying to move the goal posts here. Either audience scanning can be done safely, or it can't. If you say it can, then we can debate about those criteria you feel need to be met to ensure safety.

So if the pupil size range is approximately 4 to 9 mm for healthy non-impaired subjects in near total darkness what is it for impaired subjects? 7mm it is not.

Based on what? Your own intuition? I ask you again, have you actually measured the pupils of ANYONE that is high on Ecstacy? If not, then you have no business making statements like this.

Another point not touched on here is the burning factors of the red blue and green wavelengths.

James explained this quite completely in his post, so I'll be brief. Short duration exposures are not significantly affected by wavelength, so long as we're talking about visible light.

I have been scanned by tunnels fans and even raw beams.

But have you been scanned by tunnels, fans, and raw beams from a projector that was certified under the Pangolin Audience Scanning Variance, with the custom lens and other hardware in place? If not, then your experience with other, possibly unsafe laser shows has no bearing on the discussion of whether audience scanning can be done safely. (Or, to put it another way, just because you've seen it done wrong doesn't mean it can't be done right.)

I used to come home with itchy eyes and suffer 3 day headaches with said itchy eyes. At the time I thought it was bad drugs.

Again, I have to question your judgement here. You are worried about laser exposure when the MPE levels have been set by numerous experts in the field, after exhaustive peer-reviewed research, yet you think nothing about purchasing illicit drugs (and injesting them) with little or no knowledge about the source of those drugs, the quality, or the dose, despite the fact that there is a large body of evidence to support the very real risk that these drugs preset. That just doesn't make sense.

So I put to you that I believe "safer"(and more ethical) numbers would be 9mm dilation and .5 second blink response.

If the Pangolin variance does not rely on the blink response for protection, would that please you? (Because it doesn't. If you read Bill's post above you'll see.)

How would the application of these "safer" values affect the viewed outcome of the audience scan?
Would it be too faint to go through all the trouble?
Would the safer values render the audience scan ineffective?

I don't know, since I haven't actually seen the Pangolin system in operation. I do believe that they would not have spent 2 years trying to get the variance approved unless they felt that the visual effect was impressive enough to justify their efforts. But again, this is a question best answered by Bill.

There are members here who do have a vested commercial interest in proving the safety of audience scanning systems.
Remember it is on the petitioner to prove the safety of their product to the FDA for approval.
800 million is the number reportedly spent my Merck bringing Vioxx to market.

I've already explained my objections to your use of Vioxx as an analogy to the laser show industry in my previous post; I believe it is a failed analogy due to the cover-up that Merck performed and the minimal increased risk of heart attack when compared to other normal activities that greatly increase heart attack risk.

However, with regard to your comment above about "members here who do have a vested commercial interest in proving the safety of audience scanning systems", are you accusing anyone here of distorting the facts in an effort to prove their point? Because if you are, that's libel.

The peer-reviewed research that Pangolin drew upon when they designed their audience scanning system was not performed by people employed by Pangolin. They used the standards that were universally accepted. Research that was performed not by people with a vested interest in scanning audiences, but by people with a vested interest in PROTECTING the public from unsafe exposure to laser radiation from a wide range of products.

In contrast to this approach, in your posts attacking audience scanning you've make statements like "200mW of 457 burns a lot of stuff FAST" and "All my friends are optical engineers and medical laser guys" and "I am speaking from over 15 years real world light show experience" as if those statements somehow qualify you as an expert in the field of optical damage to the eye caused by coherent light exposure. It does not.

Furthermore, there *are* experts in the field that *have* done the research and *have* published their data, and that information *has* been reviewed by *other* experts in the field, and the resulting consensus is totally at odds with your beliefs. So unless you can counter this vast body of evidence with something more than anectodal stories about your experience with a few unsafe laserists, your statements do not hold water.

I am truely sorry that you have suffered a permanent eye injury as a result of an unsafe laser show operator. And I understand that, having suffered such an injury, you are very sensitive to the subject.

I also agree that there are many laser shows performed in this country and abroad that are not done safely. And I share your enthusiasm for preventing this sort of thing from continuing.

Furthermore, I agree that the proliferation of cheap, self-contained laser projectors made in China that have higher power lasers (above class IIIa limits) is contributing to the prevalence of unsafe laser shows in nightclubs. (Largely due to the ignorance of the club owner who probably bought the projector on E-bay, installed it on a truss, and promptly forgot all about it.)

However, I draw the line when you are out to attack ALL laser shows that use audience scanning, particularly when you are unable to back up your claims with hard data. The fact is, it *can* be done safely, and nothing you've posted so far has refuted this.

Adam