1) Is it legal to do audience scanning everywhere in the world? What are your memories of the evolution of audience scanning?

It is strictly forbidden to do Audience Scanning within Sweden. Basically they restrict any kind of display laser use to being over the heads of the audience (3 meters over the floor), or to the sides of the audience, but in an area where they can not touch (2.5 meters to each side).

Although it is legal to do Audience Scanning in most places of the world, certain governments are taking action to restrict this use. For example, Western Australia has recently taken action to move their laws regarding the use of laser more towards that of the US. This movement has been ongoing since approximately February of 2007. But more recently, after a series of "attacks" on commercial airliners on the part of laser pointer mis-users, the entire country of Australia has recently enacted what may very well be the tightest regulations on lasers yet. They have classified hand-held lasers and laser systems as lethal weapons, and you now need a lethal weapons permit to use any kind of laser, including those for laser display. But this is aside from the regulations on audience scanning.

Regarding my memories of the "evolution", really I guess Audience Scanning started long ago insomuch as people pointing a laser projector toward people and doing audience scanning. In fact, it was Ruediger Mueller, one of the founders of the famous German laser company called Tarm, who claims he started doing audience scanning within Germany. He claims that before him, the German laws restricted it, but the somehow he was able to convince them to change the law. It might be very interesting to talk to him about this. He can be reached at r.mueller@mr-showtechnik.de or +49 (0) 234 53993-0. I am sure he will speak freely about this.

As far as "evolution" I guess we can say that this happened in phases, rather than as a linear evolution. What I mean is this:

We can say that primitive audience scanning happened as a result of uneducated people pointing laser graphic projectors into the audience. This went on for some time -- perhaps a decade.

After that we have the next phase, wherein some studies were performed into the safety of audience scanning. These studies were done independently, by people in different parts of the world, who were largely unaware that others were doing the same thing. I can say that LOBO certainly did studies, and came up with a device that they call the LMS-2 safety measurement system. Greg Makhov and myself also did a series of studies, albeit using a variety of common test equipment. And John O'Hagan and John Tyrer also did studies -- some of which resulted in another specialized measurement instrument. I can say as a result of the studies, all companies (at least publicly) concluded the same thing: That audience scanning could (and should) be done safely, and when it was done safely, it also resulted in a more pleasurable show. So we can call this like a "second step" in the evolution -- maybe an "awareness era".

My opinion is that most recently, we have taken another step recently into additional safety but also into making shows more visually effective. On a personal level, I can say that this is the result of research and development done by Pangolin and by LSDI which led to various new features within the Pangolin software (such as Beam Attenuation Maps, and advanced color palette handling) and also which led to the hardware creation of PASS. Finally, the collection is now embodied into off-the-shelf projector systems which people can buy from LSDI as a standard product. The combination of these allow audience scanning to be done safely, effectively, and easily within the USA.
 

As far as I know, there has not been really an evolution towards audience scanning, as laser shows practically started with audience scanning effects.

At one of the ILSC conferences some years ago, we had several presentations on audience scanning, and the gentleman from Sweden stood up, and declared that audience scanning was a source of man-made radiation and could never be justified for human exposure.

To the best of my knowledge, Sweden does not allow audience scanning at all. I have heard rumors that Thailand has also restricted audience scanning, because of wide spread abuse (like in the UK), but I am not sure if this is enforced.

I am not aware of audience scanning being specifically illegal anywhere, but there may be challenges for those who wish to do it. Sweden is one of the few countries with specific legislation concerning laser safety. In general, there is a requirement to keep exposures below the maximum permissible exposure level.

2) Are the basic restrictions the same everywhere? Is it just a matter that in some countries there are "guidelines" while others have "laws"? And is it that some countries have untrained inspectors and others have trained inspectors?

As for enforcement, there are a few elements of this. Within the USA, it can be said that the laser safety standards themselves have the force of law, and therefore you must comply with the standards (because they are the law). Outside of the USA, for example in Europe, the laser safety standards themselves do not have the force of law (at this time). Instead, they are considered something called "guidance status". However, even though in, for example UK, the laser safety standards themselves do not have the force of law, it could be (and it is) the case that the laser safety standards are enforced by governments -- but only because of a kind of indirect way.

Within the UK it is technically illegal to expose people to light levels above the MPE. The legal basis is the general safety legislation. Firstly, there is the "Health and Safety Work Act of 1974". The basic premise of this is that people at work should have their "health and safety welfare" protected. However, this also applies to people who may be affected by a "work activity" (for example, audience members). There are other regulations within the UK which basically state that there needs to be a "suitable and sufficient risk assessment" done for various activities. This came into play in 1999 and also affects audience scanning.

So this is an illustration of how laws which, in and of themselves, have absolutely nothing to do with the laser safety standards or MPE per se, can wind up being applied and, essentially, forcing people to stay within the MPE.

I am honestly not sure how the laws work in Germany. I think it might very well be a good idea to hear this right from a TUV officer's mouth, rather than hear some filtered version from laserists...

Remember how, above, I wrote how within Europe, the laser safety standards don't have the force of law "at this time"? And remember how, above, I wrote that within the UK, there is no specific legislation covering laser safety itself? Well, theoretically, this will change in April of 2010 when something called the "Artificial Optical Radiation EU Directive" becomes law. This has already become law within the EU itself, and member states have until April of 2010 to enact their own ways of implementing and enforcing it. Basically this directive states that any exposure above the MPE will need to be investigated and that the recipient will be entitled to a medical examination. However, as I have heard, there is a lot of problems with implementing this directive, and it might very well be that this never comes to pass, or is somehow dropped...
 

 There are a few standards that have about the same guidelines and the same exposure levels like ANSI and 80625-x. I think all inspectors have to be trained to become an inspector but I am sure that there will be difference in knowledge and how they perform a test among them.

Most developing nations and underdeveloped nations have little to no regulations. It is the developed nations who perhaps have too much time on their hands and need more things to create jobs.

I believe in informed consent. You can walk into a bar with 12' high ceilings and be blasted with 1200 watts of discharge lamp containing high levels of UV and IR, prop yourself up at a bar and drink alcohol “I mean pickle your liver”, light up a known carcinogen “I mean cigarette” but heaven forbid if you get audience scanned by a laser.

 Whatever happened to informed consent coupled with good ole fashioned liability insurance?

Independent of the valid regulations of the given venue, it makes sense to make any endeavor ensuring safe laser performances, as it is not just a question of applicable laws and regulations at the given country or venue, but finally a question whether people are harmed or not. As we see with the Russian incident, it has a strong impact on the whole industry if audience is harmed in any way by lasers.

Certainly sometimes inspectors have more or less expertise (as in any other field of work).

On the other hand, Germany has an extensive inspection force, and according to my German colleagues, each and every show must be inspected.

Some countries, you may have to search far and wide to find anyone who is even interested in what is being done.

I believe there are questions of understanding and interpretation within countries, as well as between countries. The maximum permissible exposure level is internationally agreed and I understand that legislators believe that the public should not be exposed to laser radiation above these levels. However, we know that the assessment of even quite a simple audience scanning show is complex and time-consuming. My experience has been of inspectors who "trust" the laser company to do the "right thing"; those who have a little knowledge and don't necessarily apply it correctly; those who are over-cautious; and a (very) few who really understand what is going on.

I would suggest that a general approach in Europe is that it is the duty of the laser company to prove that audience scanning is safe, rather than the inspector to prove that it is not. One of my concerns with this approach is that it is quite easy to use an inappropriate detector to show that the exposure levels are "low".

The UK has specific guidance - HSG95. Germany also has guidance - BG-Information 5006 "Laser-Einrichtungen für Show- und Projektionszwecke".

IEC 60825-3 has been internationally adopted, but because it is "only" a Technical Report and not a formal Standard, it is up to each country to specically adopt it or not. It has been adopted in the UK.

3) Are the MPE levels set so low that companies could exceed the MPE by a significant factor (2x, 10x?) and still be safe? I.e. Is there an "orange zone" above the MPE where scanning is still safe - even though it may not be legal?"

It could very well be that, for the practice of audience scanning, some of these assumptions are not valid. For example, I would be willing to bet that with the light levels of environments where audience scanning is commonly taking place, the pupil is closer to 5mm instead of 7mm. Moreover, I would say that, once you are scanned, the pupil further constricts. Because of how the eye works (and the laws of geometry), a 5mm pupil will only allow half the light into the eye when compared with a 7mm pupil. Also, the pulse width is reduced by 30%. Both of these are favorable...

So it could very well be that, for the purpose of audience scanning, the MPE could be exceeded by a factor of 2 or more, and still be just as safe as if there was a human laying on an exam table with pupil fully dilated, person prevented from blinking, and laser beamed into the eye.

It could be... The problem is this. Suppose it isn't? The above represents my own theories on the matter, but I myself am not a biological scientist. If something goes wrong and if someone is claimed to have been injured (whether the claim was frivolous or not), and it went to court, I am sure there would be some experts who would agree with me, and some experts who would not. The question is, what would a jury decide? Another question is -- how much money is spent on attorney's fees and flying in expert witnesses to testify on behalf of my theory?

So yes, there could very well be an orange zone. It could very well be that the green zone is a hell of a lot wider than we think. After all, audience scanning has been going on for 30 years and ... no body bags. However, to me it comes down to how well you want to sleep at night. For myself, I sleep very well, even during the day time, because I simply never break the law. If someone claims to have been hurt by a laser show and we can prove that we are at the MPE or lower, that's an entirely different argument in a court of law, when compared to the argument of "well we were exceeding the MPE but we are allowed to because of A, B and C"...

But all of the above is more of a philosophical discussion about the MPE itself. We can say that the four paragraphs above are nothing more than mental masturbation... To me, the real question is this -- is audience scanning done at the MPE enjoyable to audiences yes or no. Greg and I have done countless demonstrations, even below the MPE, and the overwhelming conclusion is that the answer is YES! So if it can be done enjoyably at the MPE, why exceed it?
 

But would you for example like the construction company of your house to exceed the weight of a roof 10 times, just because the engineer in charge knows, that the underlying standards include a safety margin of 10 times?

There is sound reasoning behind the MPE being set at 1/10 of the ED50, and at this exposure level, the probability of injury is nil. Exposures above the MPE increase the probability of injury, to the point of 10X the MPE, where the probability is 50%.

I see this as parallel to clearance areas around pyrotechnics. Certainly one can be closer to the product than the given range (75 feet per inch of product size, if I recall correctly), but if something happens catastrophically (product explodes on ground), then your probability and severity of injury is in proportion to how close you where to the product when it exploded. If you were outside the clearance area when such an explosion occurs, the probability of injury is slight.

We have to be clear on the meaning of the MPE. It is a level BELOW WHICH we don't expect there to be harm. That does not mean that just exceeding the MPE is immediately dangerous. The MPE values are based on biological studies, usually using rabbit or mokey eyes. However, there is supporting data from medical applications on people. Biological systems do not all behave the same way, so there is variation in response from one "subject" to another. For this reason, the data is analysed on the basis of probability. A useful concept in this is the amount of laser radiation that causes an injury in 50% of the subjects. It would clearly be unacceptable to set a safety limit at this point, so the value is reduced by a factor. For laser beams in the visible (400 to 700 nm) region this factor is about 10. However, this still represents a theoretical 3% risk of an injury. In crude terms, if you exposed 100 people to laser radiation at the MPE, you would expect to get injuries in 3 of them. The MPE values for the eye in the visible region have not altered much since they were first derived in the mid 1960s. Experience has shown that over the last 40 years people tend not to report injuries at the MPE level. This gives us confidence with the initial statement - that we are safe if below the MPE. The challenge is where the real risk exists above the MPE. The laser classification scheme partly addresses this with Class 3R or US Class IIIA. A risk of injury exists up to 5 x the MPE, but it is not considered great FOR MOST PEOPLE. Accepting that we all may respond differently, some people may be at real risk. Going above 5 x the MPE and certainly exceeding 10 x is certainly pushing the probability. Remember that the 50% probability is 10 x the MPE. This would mean that in an audience of 100 people, 50 are likely to get an injury.

There is an additional philosophical factor here. The injuries considered in determining the MPE are based on what a scientist or ophthalmologist can "see" when either looking into the eye or by disection of an animal eye. These do not directly relate to the effect on a person "looking out" from the damages eye. It also doesn't take account of the target site. Damage in the peripheral vision at several times the MPE is unlikely to be noticed, but the same damage in the central region of the fovea could seriously compromise the ability to undertake detailed visual tasks. Therefore, is it acceptable to injure people when it has not impact on theie quality of life?

A Directive was issued by the European Parliament in 2006 covering artificial optical radiation. This has to be implemented as national law in the European Member States by April 2010. Although the Directive only applies to occupational exposure, it has implications for audience scanning. This is because there are likely to be persons at work in the audience environment, such as security staff. The Directive makes the MPE values legally binding. It will become an offence to exceed them. This means that Member States have no means of using judgement.

4) You've all have seen certified safe legal audience scanning (internationally known laser safety officers present taking measurements and doing the calculations), and the colors have been dim. Only when the laser was turned up beyond this point did the laser colors look really good. Is this the experience of the panel, and how do you make your shows look good using legal safe audience scanning? In short, how safe is audience scanning, and why have we not seen widespread use in the US?

In short, how safe is audience scanning, and why have we not seen widespread use in the US?

Empirically we can say that audience scanning -- even when done by nearly complete idiots -- must be pretty safe, because of the fact that it has gone on for 30 years and.... no body bags. More people go to emergency rooms in a single day because of accidents involving everyday things like a telephone or sofa, than have collectively over the last 30 years as a result of audience scanning. (This is no BS -- Pangolin has a study to show that something like 17000 people go to an emergency room every year because of an accident involving a telephone.) So this means that, even when done poorly, it's safer than operating a telephone or sitting in a sofa.

Why haven't we seen it in the US? Well, it's because historically there has been a large barrier to entry insomuch as CDRH insisting that people *prove* that it is safe. This proof must be done both mathematically, and also procedurally. As a rule, laserists are not very mathematically inclined, and also are not very procedurally inclined, so those individuals could not prove it, and thus, get approval.

More recently we have seen audience scanning in the US. Some examples are the recent Roger Waters tours as well as things that LSDI have done publicly. And, with the advent of what is essentially off-the-shelf projectors that people can buy from LSDI, audience scanning is sure to increase in the USA.

I think it is one huge factor that in the US with the 3 Meter Rule laser effects just are not cool, desirable, effective, or neccssary anymore. I bet if Audience scanning was previlant in the US the industry which is barely breathing anymore just may get a new kidney and live to light another decade!

I believe in safety for certain but I also believe in freedom. Freedom comes with risks and as long as you know the risks you can make the choice. Like my Russian friend tells me, if you kow the lion you can get into the cage. So I say if you know the laser and if you know the laser and project it safely there is absolutely no reason not be be able to get into the light. The unfortunate reality is there are allot of stupid people with lasers because allot of lasers have been sold with inadequate safety systems and training. I have travelled the world a bit and I have seen some pretty scary things. I have lived in China and been inside the light hundreds of times and have not had any laser damage because of it.

It is in my opinion highly hypocritical to allow other things in society that pose more of a threat to be readily avaialable such as alcohol, tobacco, guns, prescription medication, power tools, nail guns, etc, and lasers which can only cause some damage to the eyes and perhaps decrease the ability to see are left 3 meters away from humans. Do all things in moderation it was once said.

We have seen many approaches to solve this problem, which do not really work in practice:

Measuring static beams and trying to determine on this basis, whether a setup for an audience scanning show is safe or not. As static exposure is totally different to scanned radiation, this undoubtedly will lead to wrong assumptions or dim shows.

Taking the specifications of the lasers and the given distance of the audience as the basis for a real-time calculation of MPEs will fail, as lasers will never be in practice as they are expected in theory.

Hardly any laser we tested in our labs corresponded to the specifications of the manufacturer. But also the beam shape of the laser or slight variations in the optical setup of the system (e.g. just dirt, unwanted reflections,…) might have a significant influence on the final MPEs.

Even if you measured a reference point in the audience area as the calculation basis of a whole show to trigger a real-time compensation, there will be significant changes regarding MPEs when for example just changing the location of the detector head (e.g. depending on deflection of scanners, distance when using collimators,...).

In addition, regarding real-time compensation using directly modulated lasers, will be a problem, as the power response of the laser to the modulation signal very much depends on the given modulation patterns (for example some lasers have a very poor response on color ramps or fast color changes). So, perhaps the measured reference pattern might be OK, but the show still exceeds MPEs due to the modulation characteristics of the lasers. This is the same reason, why a real-time compensation with directly modulated lasers will never deliver the expected results. There are solutions for linearizing a laser – but this costs money.

Turning down the laser until a certain MPE is reached sometimes delivers poor results, as some lasers will return a bad color response at lower power levels. Then it is a question, if the system compensates this effect or not.

So, what is the consequence to perform good looking shows within the given MPEs?

Making the measurement of MPEs an integral part of setting up of every new show. Before you perform a show in front of your audience, it should be checked following a worst-case scenario.

Change/adapt the show when required.

Have a technical setup, with safety monitoring coupled to fast safety interlock systems. They ensure the safe playback of a show even if unforeseen things happen.

On the other hand, there is a delicate balance between beam divergence and allowable power. The "softness" of the scanned pattern is usually a function of the enhanced divergence, which allows more laser power to be used. But this is certainly an artistic judgment, and can be accommodated by adjustment, as long as the measured irradiance is within the limits. The problem with very tight beams is that the irradiance limit imposes a very low power limit on the beam, so the question becomes do you prefer dim and tight, or brighter and softer. This can only be done by experiment.

What I have seen, and do regard as a problem area, is when audience scanning is used in an uncontrolled environment or with too much lighting. The temptation to "turn it up" is strong, and this is dangerous. Audience scanning, in my opinion, should be used in the darkest possible environment. I believe that this can be done effectively and safely.

In terms of pure safety, this is the riskiest activity that can be done in a laser show, because of the exposure levels approaching the MPE. To do this reliably requires good equipment, design, and procedures. On the other hand, one can sometimes get away with uncontrolled exposures, because the statistical exposure probability as a result of scanning is low. So you can watch a show of many times the MPE, thinking it looks really good, until you get NAILED by the beam, and then you don't want to watch anymore!

CDRH, the US regulatory agency, had some early "run-ins" with early laser pioneers such as David Infante, who did the famous Blue Oyster Cult tour. In this show, massive mirror ball scanning at very high powers seriously scared some safety people, and caused the development of the current situation where a laser show is considered a product, and hence can be regulated. David, thank you for foisting the Variance requirement on us!

CDRH published some documentation concerning laser scanning analysis, with a specific example citing a 1 W laser (Argon laser presumably) and the requirement for a scanfail device to react in 200 nanoseconds. As I have said, this cause most people to simply stay away from audience scanning. Honestly, I think many people are confused with the concept of classification, after all nobody wants to be exposed to a Class 4 laser. With the advent of the ANSI standard, and more examination of exposure to the beam versus the nature of the products, it became easier to understand that even a Class 4 laser was safe to view if outside the NOHD.
 

My only experience of this is from reviewing installations and a small amount of laboratory work using our own research laser display system. One of the best audience scanning installations I experienced was a white light laser with multiple diffraction gratings. We assessed all of the beams with the gratings stationary. It took some time, but each beam had just under 1 mW into a 7 mm aperture. This was impressive enough, but was amazing when we set the gratings to rotate. The important thing was that with the beams moving, the beams did not trigger the aversion response. This is one area where we have done quite a lot of research. Audience love to be surrounded by the laser beams but they do not like them in their eyes if they are too bright. They will tell you this - plus we did some video of audiences some time back and many of them take evasive action having been scanned once. My perception as a non-artist, is that the performance has now become a threat rather than a pleasure.

5) What happened in Russia?

Unfortunately, there are plenty of fricken complete idiots in the world, whether they get their hands on a laser or not. For example, take a look at the number of people killed by drunk drivers every day. As Jessie Ventura says, you can't legislate against stupidity. Although I wish you could...

Just take a look at trade shows. Some people (especially Chinese) handle lasers like any common light source. They do not really know or care about the risk of harming themselves or other people. Do you really expect their buyers to be more experienced than the manufacturers of the lasers?

I also know renowned laser companies who use pulsed lasers at almost every show. Think for example of the wide-spread use of Jenlas Whitelight lasers for audience scanning. Without any doubt, this is a pulsed laser. Without any doubt, it is not allowed under given MPE standards to use any pulsed laser for audience scanning. But those companies are aware of this fact and they even show off using this laser for audience scanning, as it looks crisp and bright - but there is no reaction in the industry to avoid this.

My best guess is that this was initially setup in a reasonably safe manner, intending to project beams overhead (which is quite reasonable with the Q-switched laser). A second guess is that the tech who setup this laser was not present when the laser was redirected into the audience. I honestly don't believe that anyone competent and experienced enough to set up a laser system of this nature would simply project it into the audience in such a careless manner.

We have heard numbers of 30 watts, which is quite believable given this technology, and certainly could cause the type of damage reported.

Part of my assessment was looking at the same show from last year, which also used lasers, and seemed reasonably sane and safe, just sort of a smallish outdoor party. The bad weather this year, plus the temporary tarps to protect from rain, lead to a very bad decision by someone without knowledge of laser safety.

Or maybe it was some misanthropic miscreant who hates ravers, and would love to see them all go blind....
 

We are still trying to find this out. I have reservations about the claims that the injuries were caused by drugs.

6) What baseline of knowledge is needed to do audience scanning? Do I need to take an IEC safety course, or are there a few simple principles I can apply? Do I need a special laser show meter to calculate safe audience scanning? Is a projector with a scan-fail safeguard (to ensure that the beam is shut off if it stops moving) 100% safe?

An IEC safety course may do little to foster the understanding of how to do audience scanning itself, but it may be helpful to understand laser safety basics, and how the MPE works.

As for "special laser show meter", this is not necessarily needed. You would certainly need some kind of instrumentation -- for example, a light energy meter capable of measuring relatively low light levels, and having a detector area that is 1 square centimeter.

Of course a projector with any kind of scan fail safeguard is not 100% safe. Going even further than this, even a projector with a scan fail safeguard and good safety practices might not be 100% safe. Many scan fail safeguards are not designed very well at all. This is a somewhat historical problem in this industry. It could be that the scan-fail safeguard itself will fail right at the moment when it is needed, thus making an unsafe situation even worst. Unfortunately, there are very few scan-fail safeguard systems that are properly designed, and have been verified by laser safety professionals.

However, lets set this aside for a moment, and look at the problem from another angle. An unsafe projector and show scenario with a scan-fail safeguard will be unsafe. BUT, a projector and show scenario that are properly configured for safe audience scanning will be safe (at least until something goes wrong when the scan fail safeguard would be required to act). Therefore the emphasis should be on making shows safe, not on the equipment itself.

It could be said that, when designed properly, a scan-fail safeguard does not make a show safe, but it can keep a safe show safe.

And the bottom line is that, despite the high degree of mystery around audience scanning safety calculations and measurements, it's all quite easy to setup and perform, if you have the light energy meter mentioned above, you could perform a single measurement at the closest point of audience access, and that one measurement will give you a good indication as to whether the entire show will be safe or not, pretty much regardless of the actual show content itself. I will allow Greg Makhov to describe how this is done, and the theory behind it...
 

Not much but to do it according the ANSI standard will require some knowledge and equipment.

Do I need to take an IEC safety course, or are there a few simple principles I can apply?

It is always wise to take a safety course I do not if you MUST do this according the law for your country. I believe you live in the USA so you will need to get a variance to start with.

Do I need a special laser show meter to calculate safe audience scanning?

If you do not mind to do some calculations then a laser power meter will be enough and even better if you have a scope.

Is a projector with a scan-fail safeguard (to ensure that the beam is shut off if it stops moving) 100% safe?

I believe only PASS is 100% safe because it does not use a processor and CDRH approved this device and it will do much more then only be a scan-fail save guard.

According to our experience there is no valid recipe or what you call a "baseline knowledge".

Finally it is a game between visibility vs. safety. In practice, the one and only way to make laser shows look safe and good: Take a safety meter and measure the MPE at the location of the audience and modify you show accordingly. You will be astonished how safe some really bright effects can be, while others, looking not very spectacular could be quite dangerous. So, many factors influence MPEs, that even for experienced show designers it is hard to estimate them in advance.

Scan fail systems are good in general. But sometimes I have my doubts regarding their practical use. For example DDL has a reaction time of less than 1ms. I have seen so called „scan safety“ systems having a reaction time of more than 300 ms. This is far too much. Within one third of a second, many things can happen. Unfortunately I experienced that many resellers want to make their client believe, that the laser system is safe, just as it features a scan-fail safety system. In most of all cases it is not true, as even good safety system in fact does no provide an adequate level of safety. The most important factor for a safe performance, no safety system can influence: the operator.

This is the reason, why LOBO provides free and individual laser safety training for each client who purchases a LOBO system. This gives you the practical knowledge of how applying the system you have purchased in a safe way. Again, this costs time and money. But I believe, it is worth the investment.

My philosophy is to have multiple parameters independently interlocked so that a failure of any one parameter will shut off the beam, even though more than one parameter would have to fail for the MPE to be exceeded. The interlocks should fail in a safe mode and their reaction time should be much faster than the scan failure time.

Since then, with a lot of discussion and research into scanning parameters, and how they can affect exposure, I believe we can make a valid generalization that will effectively limit the exposure within the MPE for normal scanning behavior, particularly if we have a highly responsive scanfail monitor. However, it is important to understand that limiting the irradiance is far more important than monitoring the scanning.

With the development of the PASS system, it is possible to have a pre-calibrated laser projector that can be used at a pre-set range, and only a confirmation measurement is required in the field. This was all that was necessary with the set up of the projector at the ILDA Theater last fall.

Calibration of such a projector should not be a field procedure, and may be too technical for many laserists. The calibration is specific to a unique laser projector, and obviously has to be tested to ensure that it is actually doing what is intended. There is little worse than a safety system that does not protect.

Currently, I am unaware of any laser safety course that would cover all of the aspects necessary for audience scanning evaluation. If the equipment can be simplified, as I describe above, then shorter and more basic training is practical. Having instrumentation is desirable, and of course it has to be the right instrument, and have recent calibration (most radiometers require annual calibration).

Most current scanfail monitors only monitor the scanning parameters, and most of them are too slow in reaction time to be considered as a safety system. As mentioned earlier, it is more important to measure and limit irradiance than to monitor the scanner performance. Fast reaction time is essential, and confirmation of behavior should be required. Finally, since this is human exposure to lasers, these should be designed as failsafe systems, with single point failure analysis, etc., in the design phase.

To be really clear on this issue - so that there is no misunderstanding - a laser projector with a scanfail device, and no means of limiting irradiance, is a dangerous product, with only the appearance of safety.
 

In an ideal world, this should be done with equipment that can manage the beam parameters and can deal with reasonably foreseeable failure modes. However, there are many misconceptions about scan failure systems. They have to act fast enough - and that depends on the irradiance at the critical location in the audience compared with the appropriate MPE. A set time is not appropriate for all applications.

I would certainly like to see international agreement on competency - which is more than knowledge. This should apply to all involved, as detailed in IEC TR 60825-3. The operator is critical, but there are many others involved.

The reliance on software in some installations to protect the audience (and others) is worrying. I have seen too many computer crashes at venues to be confident. Any such software should be considered "safety critical" and meet the appropriate international standards.

The simplest assessment of an installation is to measure the irradiance for the static CW beam at the closest access point for a member of the public. If this is below the MPE (for the appropriate exposure duration) then all other effects will be OK. However, a note of concern is that it is increasingly difficult to get a static CW beam from many modern commercial systems. Our experience with a range of moving effects is that scanning instead of static beams only makes the beams "safer" by about a factor of 3-5.

We should also consider "brightness" and what happens as we increase the irradiance on the front of the eye. The eye's response to bright light depends on the ambient light level (adaption to it) and that the brightness response is logarithmic rather than linear. So, as a rough guide, increasing the power by a factor of ten only roughly doubles the brightness.
 

7) What can a producer do to hire a company that 'knows what they are doing' versus one that is full of hot air?

I also think it is not such a bad idea to ask to see their insurance policy or other "bonding" credentials.

Getting back to the ILDA member -- my personal theory -- if they are the lowest level of ILDA member paying the least amount of dues, they probably have no business doing audience scanning. I know this is a controversial statement but... sorry... If you want to do audience scanning, you need money, at the very least, for insurance. You can't be paying the lowest dues in ILDA if you have the money to pay for the insurance (presumably made by top-level shows you should be doing for top-level clients).
 

Part of the problem is that there is so much technical jargon associated with laser displays, even people inside the industry can get confused. When you start throwing in terms like "mode locked, synchronously pumped OPO", or "optically pumped semiconductor laser", this will lose anybody not in the laser business.

As we go forward, we may develop some industry qualification for laser projectors that provide audience scanning, which would be a significant step forward.
 

The approach I use to help promoters and to guide inspectors is to have a set of questions with model answers. Depending on the responses, I will provide further guidance or allow them to proceed. One of the critical questions is "do you intend to scan the audience with any laser beams?".

8) Finally, why should I produce/hire/attend an audience scanning show?

Simply put, this is one of the most powerful and dramatic effects that can be produced in a laser display.
 

There is no doubt that being surrounded by the laser beams is unlike any other optical effect. As I said above, this is only a fantastic experience if the beams are kept away from your eyes - unless the beams are not capable of triggering an aversion response.