9W RGB special red beam!

[gashead]

Hey joost as hobbieists i would be keen to see how you got the good red beams
That would go a long way towards contributing to the community

I second that.

This thread is worthless without pictures

[norty303]

or 5mw on a 7mm aperture

Surely you mean 3.7mW through a 7mm aperture?

From my understanding and without naming the parties involved, the basic hypothesis is that you can forget about exposure duration / scan repeats etc. and all the other complex factors you might have to take into account even with the simple method. If you take a simple power meter reading from a static beam and at the closest audience point and its below 10mw on a 1cm 2 sensor or 5mw on a 7mm aperture then the show is safe provided it conforms to the normal parameters of what would be expected in a show ie no extreme effects.

This basically throws out of the window the whole concept of the necessity to take scan speed measurements using a fast photodiode to check the scanner velocity and calculate the dwell time etc based on the beam diameter etc.

Don't forget that the 4x MPE factor is related to the reduction of exposure time frame when limiting the longest possible exposure using a fast scanfail device (i.e. the longest possible exposure is 1ms, even in the event of a failure).

Remember, the combined exposure over a second of repeat pulses for a typical scanned effect (e.g. tunnel) is likely to be significantly shorter than the worst case scenario of a scanner failure, so therefore all of the pulse duration stuff can be discarded as it is no longer relevant. However, you do need to satisfy yourself (and others) that the total pulse duration is significantly shorter.

One thing I have learnt is that the Laser Safety Record calculations is as much about inspiring confidence and relating something complex in simple terms (to a layman more often than not), as it is about being theoretically correct. Given that MPE has a window for error and small deviation (a few extra mW here or there in a set of similar patterns is not going to make the difference between safe shows and unsafe shows), it is reasonable to take as straightforward approach as possible (imho).

[White-Light]

Surely you mean 3.7mW through a 7mm aperture?

It was relayed to me as 5mw but I think it was a late at night typo by the person concerned. 7mm aperture gives a 38.49mm2 area by my calculation not a 50mm2 area needed for 5mw, so without doing the additional maths, I'm sure you're correct there.

Don't forget that the 4x MPE factor is related to the reduction of exposure time frame when limiting the longest possible exposure using a fast scanfail device (i.e. the longest possible exposure is 1ms, even in the event of a failure).

Remember, the combined exposure over a second of repeat pulses for a typical scanned effect (e.g. tunnel) is likely to be significantly shorter than the worst case scenario of a scanner failure, so therefore all of the pulse duration stuff can be discarded as it is no longer relevant. However, you do need to satisfy yourself (and others) that the total pulse duration is significantly shorter.

One thing I have learnt is that the Laser Safety Record calculations is as much about inspiring confidence and relating something complex in simple terms (to a layman more often than not), as it is about being theoretically correct. Given that MPE has a window for error and small deviation (a few extra mW here or there in a set of similar patterns is not going to make the difference between safe shows and unsafe shows), it is reasonable to take as straightforward approach as possible (imho).

I think the point was that in an ordinary situation, these persons found out through calculation and experimentation that it's safe to assume it's less than 1ms always so the check can in theory always be discarded. If accepted by regulatory bodies, that would make calculating MPE very simple, as simple as a straight power measurement from a power meter sensor of known size. Even a cheap thermal meter would suffice if accurate. However, as you point out, its currently a requirement to prove that the velocity and pulse duration are shorter than the 1ms limit and anyone not doing so is likely to be in hot water regulatory wise and on thin ice from a law suit perspective.

Sorry for the slight thread hijack Verkoop.

[masterpj]

i have to chip in a bit that rgb laserverkoop is not a hobbyist, a hobbyist doesn't register as a company and does big shows on a regular basis or constantly advertises products.
Not trying to be mean here, but this is what i think about this.

[norty303]

I think the point was that in an ordinary situation, these persons found out through calculation and experimentation that it's safe to assume it's less than 1ms always so the check can in theory always be discarded. If accepted by regulatory bodies, that would make calculating MPE very simple, as simple as a straight power measurement from a power meter sensor of known size. Even a cheap thermal meter would suffice if accurate. However, as you point out, its currently a requirement to prove that the velocity and pulse duration are shorter than the 1ms limit and anyone not doing so is likely to be in hot water regulatory wise and on thin ice from a law suit perspective.

Sorry for the slight thread hijack Verkoop.

I think there's a little bit of confusion here over regulatory stuff, and simply demonstrating that your show is safe.
I can go out and do a show, with no Laser Safety Record, and demonstrate nothing to anybody, but I will not be in 'hot water' for not doing it, providing I a) don't scan over MPE (now law for employers), and b) don't hurt anyone.

I can write 'Since is is known that all fast scanned patterns have an exposure time-frame significantly below 1ms, we can reasonably assume that the maximum exposure time is 1ms'. It is up to the H&S to either take my word for it, or say I can't crowd scan.

Now, I would probably show a few sample calculations for tunnels, squares, any other effect likely to be in the crowd, etc to demonstrate the theory, to cover myself, but I don't really need to.

Basically, you can evaluate your show however you like, in order to demonstrate that it is safe, and you know your onions. It is up to the H&S folks to understand/believe it, or not, and allow it to happen. That is why there is no single prescribed way of presenting show evaluations - otherwise we would keep on having the debate

[sbk]

About the safety and those crowdscan photo's seen on his site: i'm surprised so far only badger commented on this.
Normally you guys would hop onto this directly, which I actually find a good thing since safety and keeping the name of laserist high is also a priority of the community.

Because last time I spoke about an unsafe show on this forum (was 4x 8W 532nm Kvant head shots of still beams after 5 meters), a guy who apparently knows alot better about lasers than me jumped onto this and said I was idiot and should be banned from the forum, for having said such stupid things...

Btw, this picture of crowd scanning with multiple projectors was not made with this "9W" projector, only with 1.8W and 2.3W RGB if I remember, so not so "unsafe", maybe even safe, at least not so unsafe that still shots with 8W of green!

[sbk]

Well far not as scaring as this one, but I believe you already saw it : http://www.youtube.com/watch?v=GGYrkz2bqGY

But don't worry, laws are becoming more and more harder as laser's power increases (and price decreases too much, this 9W for some peanuts is a great example). In my country in example, laws was just tightened last month, now we have to provide about 10 pages of laser related stuff and organisation to the authorities before each show...

[ClearBlu]

I'm with Norty on this

[norty303]

10 pages? I wish I could get my Laser Safety Record down to 10 pages!

But going back to the vid, knowing what I know, I find it hard to believe those beams in the audience are below MPE. No lenses were used otherwise we'd see the RGB splitting thru the lens, which we don't (or on the actual projectors being rigged). Do the calcs yourself, then look at an equivalent power beam show. Notice the large variation in step and colour as it enters any low power zone/bam. Then go back and try and rationalise that show. Like SBK, I'm also someone who's been told you can't make these calls based on vid/pics, and I still disagree. Moreso after doing my safety training...

As for being a hobbyist. Pull the other one. And if you're going to so blatantly lie about your status as a professional company doing sales as well as large shows, what else are you prepared to lie about?

[sbk]

10 pages? I wish I could get my Laser Safety Record down to 10 pages!

Haha, and you're not even doing audience scanning shows in the USA
But honestly, I have hard time imagining what you can explain about the security of a laser show, furthermore what it can add to the security of this show, in more than one dozen of pages full of text and calculations (drawings of room etc, not included).

But going back to the vid, knowing what I know, I find it hard to believe those beams in the audience are below MPE. No lenses were used otherwise we'd see the RGB splitting thru the lens, which we don't (or on the actual projectors being rigged). Do the calcs yourself, then look at an equivalent power beam show. Notice the large variation in step and colour as it enters any low power zone/bam. Then go back and try and rationalise that show. Like SBK, I'm also someone who's been told you can't make these calls based on vid/pics, and I still disagree. Moreso after doing my safety training...

As for being a hobbyist. Pull the other one. And if you're going to so blatantly lie about your status as a professional company doing sales as well as large shows, what else are you prepared to lie about?

Well, it's simple, very few of the shows we are seeing are really 100% below the MPE (10mW/cm^2 for a 1ms pulse), unless they have lenses and a divergence of 8 mrad, and/or the audience is dozen of meters away from projectors aperture. But there is over MPE and over MPE... That's what the 10x MPE proposal is all about