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

[jbinks]

Cool.
Sounds like I should just save the cash and get -6's for now.

BAM would work, but I won't use that approach as there is nothing stopping the scanners failing in the audience area and the program continuing "thinking" that it's outputting to a "safe" area, thus at full power. Obviously... this is incredibly unlikely, but I'm designing my shows with "rock solid" paperwork principals so need to account for this kind of thing.

One thing that might be a good idea would be a combination of the lens and a ND filter. The issue for me would be the mounting of this as the Pangolin lens holder has no additional receptacle for a filter. Such a filter would need to only affect the beam below the horizon too. Has anyone got any experience of this (specifically the mounting of the ND filter in addition to the Pangolin lens)?

Thanks,
John

[norty303]

BAM would work, but I won't use that approach as there is nothing stopping the scanners failing in the audience area and the program continuing "thinking" that it's outputting to a "safe" area, thus at full power. Obviously... this is incredibly unlikely, but I'm designing my shows with "rock solid" paperwork principals so need to account for this kind of thing.

It might be stating the obvious, but this is precisely why audience scanning shows should really have a scanfail device in place.
Obviously, if your static beam is at or below MPE then it's technically ok, but even then there's something I find uncomfortable about that situation.

[jbinks]

I partially agree. As long as the failure of the scanning system (worst case, both scanners, in the crowd, at the closest point to the projector) CAN'T result in an exposure greater than the relevant MPE then it's inherently "safe" (according to the definition of the MPE, as you know). Sure, if the beam was allowed to rest in the position and some drunk punter decided to have a stareout with the beam then I guess it probably wouldn't be very good for their retina, but the theory is that they would need to stare into the beam for an extended period before the risk of harm became significant. By which point, one of the e-stops would have been triggered!
I refer to my warning in my original post. Do not take anything that I have said as fact or basis for your own actions to expose an audience with laser light. My comments are in the context of having received appropriate training and my own safety processes.

This is why I will be using the "static beam/0.25s" approach. I don't have the equipment to measure scanned exposure or the scanfail to guarantee the continuous exposure time limit.

I may, in the future, be looking to invest in a PASS (or similar) system for each projector so I can increase the beam intensity (slightly) in line with the higher MPE associated with the shorter (but repeated) exposure time. (I would also be going back to James for the "advanced" training course)

For now, it's a "keep it simple" approach.

I'm also pursuing diffraction effects in order to get a good, safe, show without the need for scanfails or higher beam intensities.

Cheers,
John

[danielbriggs]

One thing that might be a good idea would be a combination of the lens and a ND filter. The issue for me would be the mounting of this as the Pangolin lens holder has no additional receptacle for a filter. Such a filter would need to only affect the beam below the horizon too. Has anyone got any experience of this (specifically the mounting of the ND filter in addition to the Pangolin lens)?

John,
You will be up against the damage threshold of the ND filters.
A decent quality filter with a given damage threshold will only be good for a couple of watts (2W max realistically, but obviously depends on the ND power and exact filter) before you'll start to damage the optic - that power has to go somewhere!

In all honesty... it seems a shame to neuter PJ's like this; full power in safe areas all the way for me. (as we're always up aginst kW of fine pitch LED screens, and MW's of lampy-lampy stuff.) It is kind of mega to have beams punching out clear as day when the LD has his finger stuck down and 30 At3k's are blazing.

[norty303]

Absolutely John, I mostly agree with you, and I know you are applying sensible logic to the situation (which is most of the way to doing things correctly, even without the measurement kit, intense knowledge, etc!)

I don't know what the production costs are for PASS, but if it was a bit more affordable, I'd probably be integrating it instead of the solution i currently use.

The problem is that with projector costs coming down all the time, especially in the range where people are likely to want to use for crowd scanning (~3W), the respective proportion of cost on PASS becomes significant.

I wonder how much of a price drop Pangolin could bear on PASS to encourage more people to use it, and at the same time make more money from it due to increased volumes.

There are only a few other options really available on the market for scan fail, and although PASS is clearly better featured (particularly importantly for the US market), I think the rest of the world (mostly) choose a more affordable option.

[White-Light]

The problem is that with projector costs coming down all the time, especially in the range where people are likely to want to use for crowd scanning (~3W), the respective proportion of cost on PASS becomes significant.

The problem with PASS though is it's still reliant on the operator to be competent to take the measurements, make the calculations and the set the correct thresholds.

For a competent laserist who understands MPE calculations such as yourself, it's not going to be an issue, but for DJ Joe Public who spies a 3W on ebay and fancies crowd scanning, PASS isn't going to guarantee safety beyond what it's designed to do and that is prevent static beams through hardware failure and protect the powers in the audience from exceeding the pre-set levels.

[norty303]

The problem with PASS though is it's still reliant on the operator to be competent to take the measurements, make the calculations and the set the correct thresholds.

As is every other scanfail device. At least Pangolin provide decent docs to work from, and obtainable support.

For a competent laserist who understands MPE calculations such as yourself, it's not going to be an issue

Fantastic, job done.


I really can't concern myself with DJ Joe Public, I have more than enough on my own plate, and DJ Joe Public's lack of knowledge or desire to find it should not impact on me being able to buy PASS and integrate it.

I'm not even sure how we got onto 'simple safety for everyone'

[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.)

STOP! If you haven't spent your money yet, ignore my advice. Finally (I bought them 6 months ago.) I attached a lens holder to a projector, dropped in a 6 diopter and ran a show. Big disappointment at this point.

Actually I set up 5 identical projectors all set for overhead beams for a sales demonstration I'm doing tonight and while testing, figured why not put the lens in position on one of them, readjust projection area and watch the show. I stood in the ballroom about 65-70 feet away from the projector and, a: the divergence was huge - the beams crossing me were about 6" wide. I also found the flash from the projector as it crossed my face to be very distracting and took away from the overhead beams. Imagine sitting at floor level in the theater at SELEM watching an overhead beam show terminated on the face of the balcony and suddenly someone walks out from behind the curtain with a normal - say, D battery style Mag Light and shines it slowly through the seats and past your face every few seconds.

I have no idea of exposure power as I don't have the correct instruments to check it yet but, now I'd like to see what a 4 or 5 diopter does. As it stands right now, I wouldn't even want to use the 6's for my own enjoyment or use at a laserist event... I'd rather get scanned full power as we always seem to do and take my chances averting my eyes or holding a thumb up to block the projector and close one eye or something or whatever little tricks we do. Maybe this will be something to explore at SELEM if anyone has the correct meter there.

[Bradfo69]

Update... ImageLight stopped by yesterday after reading my post and we looked at it a little more closely. At 102 feet away, the beam from a 2.5 watt projector was spread out to about 18 inches wide and was so faint on the wall as to be hardly perceptible. At approximately 30 feet, it was not too bad - maybe 4-5 inches so probably not bad for close distances although, the power would still need to be measured. But I do now see the need to have multiple diopter lenses if you want satisfying results.

[norty303]

I still say, the beam where it hits you is not the bit you look at when viewing a show, your focal point is usually the first third of the beam out of the projector.
At this point it is still pretty tight, so I find the part of the beam you end up 'receiving' is largely irrelevant to perceptions of the show (imho, subjective mumbo jumbo, YMMV, etc)