Pangolin Safety Scan lenses - looking for "rough" experience-based advice

[jbinks]

Hey guys

I know asking for any kind of "ballpark" figures or standards in the domain of laser safety is a bad idea because of the precedent it sets for others to follow but I can't think of any way around this particular issue.

Essentially I am aware of the calculations required to determine NOHD and beam intensities etc. I am about to purchase a set of six Pangolin Safety Scan lenses with two of each diopter value (I have two identical projectors). I don't really want to buy TWO complete sets of six lenses.

Unfortunately, I can't see any mathematical way in which I can calculate which lenses would be most appropriate to my needs as one of the key factors is the beam quality (M²). I have no way to measure this and even so I would always want to use physical measurements as my "source of truth".

In an ideal world I would simply setup a demo scenario and measure the beam intensity (7mm diameter) at various distances from the projector with each of the six diopter lenses in place. From this data I would easily be able to determine which lenses would be most useful for me to have in my kit.

As I can't just magic up these six lenses to test with and to be honest I don't really have the time to do the full initial testing session anyway I'm looking for some rough guidance on the diopters that are more likely to be useful for my application.

I would be taking measurements for each actual performance and swapping the lenses from my kit until I got the optimum intensity output in the crowd area.

So, can I ask anyone who has experience with actually MEASURING beam intensities when using these lenses to give me opinions on the most useful three diopters. I'm guessing that I probably want to have -3, -4 and -5 but I might be a bit off and would rather not end up with lenses that I will never use.

My projectors are Lightspace Pluto II 2.7wRGB with the following:
Red637nm 720mw, G532nm 1000mw, B445nm
Unfortunately I don't know the beam specifics per colour. The only specs I have are "Beam Divergence: <1.0 mrad (full angle), Beam Diameter: <4 mm".

I need to be able to cater for performance scenarios where the projector-audience distance is anything from 3m to 25m.
I fully appreciate that in smaller venues it may be more sensible to configure the angle so that crowd exposure is limited to further back in the crowd as a tradeoff.


Finally, can I please urge anyone else who is reading this not to take anything I have said or anything said by others who might reply to be factually correct or best practice.

Please DON'T try to "guess" what is safe. My approach is based on actual measurements of the emissions at every performance during setup to ensure that the show will be safe.

If you want to perform audience scanning my ONLY advice is that you do ONE of the following:

• DO NOT perform audience scanning!
• Attend a reputable Laser Show Safety Training course, such as the excellent one run by James Stewart in the UK

Anyone reading this who would prefer to reply to me via. PM, please do so. I completely understand why.

Thanks in advance!

PS: I managed to get a LaserCheck for the bargain price of £230 delivered in the UK! Quite a result seeing as £350+ is the more common price.

Cheers,
John

[Bradfo69]

I don't have a scientific answer for you. Only a philosophical one. Admittedly in the US you can't audience scan without a variance (and I don't) but, I did get some safety scan lenses for the benefit of myself and other laserists and my theory was get the 6 diopter lenses, as that's ultimately the safest bet. The others are all obviously for those going through precise calculations, distances, and powers. I don't know that "safe" divergence observed between the different lenses after doing calculations should visually look "that" that much different to an audience so, I just simply went with the strongest one. MPE is MPE whether it's 6 diopter on a 2.5 watt at 60 feet or a 4 diopter on a 1.8 watt at 60 feet or whatever. At least that's my theory (and I've been wrong before.)

[jbinks]

Sure, totally agree with the theory!
I am planning to buy a set that covers a good range so I will have both the "safe" option and the "better performance" options.

Ultimately one of the main issues that I have that makes it important to get the right lenses is the differing effect that optical lenses have on wavelengths. As I use white light projectors I really don't want to lose my (very nice) white into a mess of diverging primary colours that looks rubbish because I only have lenses that are far too strong (obviously, in some situations if the venue is such that I need that level of divergence then sure, that's the way it's going to have to be!).

Another important factor is that some of my higher-profile shows will be in larger venues where I can get the projectors right at the back of a large stage with pit so I can use a much tighter beam and still be under MPE at the front of the crowd. If I only have -6 lenses then the show is going to turn to mush really quick! For this kind of scenario I would need something a lot less severe (but exactly what!?).

Just out of curiosity, do you have a LaserCheck (or other suitable measuring device) and did you perform any measurements of the beam properties from your Pluto IIs using the -6 lens? I seem to remember that you have Pluto IIs that are of similar spec to mine so it would be interesting to know what the measured NOHD is for your particular projector is with the -6 fitted (obviously measured properly across each of the three wavelengths and summed). If you have this information, can you also include the MPE you were working to? (eg: 0.4mw/7mm dia., 0.96mw/7mm dia. or other)
Feel free to PM the specifics if you like.

Cheers,
John

[fuzzpop]

Hi John

We're based in UK and have been doing shows for many years - we don't and won't even if asked perform crowd scanning full stop. Our RAMS reflect this and our PL Insurers have this in a sub clause. We do use -6 Panglin lens on all our projectors but this is only a safety precaution in case a locked down unit slips or crowd on shoulder situation etc. Venues with low ceilings we have refused shows due to them not meeting the 3m clearance recommended in the HSG 95 guidelines. We find that most local councils and venues prohibit it anyway.

Self confessed laser addict.....
2 x 6w Kvant
4 x Lightspace Pluto II 4w
1 x RTI 14w

[jbinks]

Hi

Thanks for your reply. I have a very specific question in this topic so I don't really want to spawn off loads of sub-topics on insurance, vertical/horizontal separation distances as per HS(G)95, projector stability/masking, venue policies and licensing clauses etc.

I'm really only concerned about actual experience with measuring the beam intensity from a similar projector to mine when using Pangolin lenses. The objective is to get a relative "feel" for the range of diopter I am likely to need as this can't be calculated (missing M² parameter).

Although the approach is "rough", the final application will be backed by the usual calculations and, most-importantly, comprehensive measurements.

You mentioned that you use the -6 lenses. Did you ever perform any measurements on the beams produced when using these lenses (ideally when used with your 4w Pluto IIs)? Presumably as you specify them as a safety feature you must have calculated/measured the NOHD below the lens horizon as just fitting a lens doesn't automatically guarantee that the exposure will be below the relevant MPE value (I presume your projectors are unmodified and don't feature any kind of high-performance scanfail to allow for higher energy beams).

Regards,
John

[Bradfo69]

Hi John,

No I don't own a Laser Check and have not actually done the measurements you're inquiring about. I've not mounted mine yet although it's on the "to do" list prior to SELEM. As I said, my answer was going to be purely non-scientific however, I know a number of people use them quite regularly as I expect will be along at some point to relate their experience.

[White-Light]

Hi John

We're based in UK and have been doing shows for many years - we don't and won't even if asked perform crowd scanning full stop.

Whereas I applaud you if you don't have the means to do audience scanned shows, I have to say that personally I will not attend any show where the beams are overhead. The effects are simply not the same.

I see it as a duty of laserists who are capable of performing safe audience scanned shows, to be promoting SAFE audience scanned shows rather than retreating to overhead beams and a position of accepting ever tighter H&S rules from over zealous Councils / Law Makers.

There are far too many fun police these days, and all these rules do is force people down the road of illegal shows which then often results in shows being carried out often by operators with no clue about safe scanning and using effects which are massively over MPE. You only have to look at the US to see this happening and there are plenty of examples in the UK.

..and the more laserists allow them to squeeze what is permitted, the closer we become to a total laser ban.

I understand that in the UK there was recently a proposal to reduce the permitted safe laser levels to take into account the effects of "flash blindness" (viewing a bright source), in case someone tripped following viewing a laser effect. I mean how ridiculous. Why don't we just ban all bright light sources eg strobes, blinders, LED's, bright moving heads etc and just return to the days of a 100W spot reflected from a disco ball. That's what we're faced with folks and it's time people woke up to this.

@ OP, Norty in the UK uses Pangolin lasers at his audience scanned events. It might be worth sending him a PM and seeing if he can offer any guidance. I'm unsure if he does events with widely differing distances to the audience, but it might be worth an ask.

Also, might be worth asking if anyone has a beam profiler in the UK , and if so if they might let you bring your laser and have it profiled. That might be another way out.

[gashead]

Whereas I applaud you if you don't have the means to do audience scanned shows, I have to say that personally I will not attend any show where the beams are overhead. The effects are simply not the same.

You don't attend many public shows then Al ? :P

[White-Light]

You don't attend many public shows then Al ? :P

Nope I don't attend for various reasons, but there's plenty of legal audience scanning in my area at hard dance events and at least some event organisers I know would do it illegally, if it wasn't legal, as its what many of the hard dance crowd want to experience.

I applaud people on here who do it commercially and legally and safely in their areas as this is about education of the authorities that it is safe and that there's no liability in licensing legal (within MPE) events, and that permitting audience scanning within MPE levels is enjoyable as well as safe for the crowd.

[danielbriggs]

{Non-audience scanning}...The effects are simply not the same.

You're right, non-audience scanning shows done well are often better.

promoting SAFE audience scanned shows rather than retreating to overhead beams and a position of accepting ever tighter H&S rules from over zealous Councils / Law Makers.

This isn't some tug-of-war battle you play with the parties involved; you won't get very far if that is your attitude.
You have also forgotten another important party, the venue. Any "proper" venue has a clearly defined policy of what it will and will not permit.

the closer we become to a total laser ban.

That was the opening gambit of the EU's laser safety directive when it was last open for revision.

might be worth asking if anyone has a beam profiler in the UK , and if so if they might let you bring your laser and have it profiled. That might be another way out.

I fail to see how this would get you anywhere... if you can provide a decent case for it, I would offer the use of mine.