Crowd scanning

Now ive read up on safety and regulations as much as i could in two weeks. I understand that crowd scanning is very dangerous but i still feel that its something id want to do.

This will be my first build, i was planing on a RGV but i havnt found all the components i want because first i have some questions.



first i understand that if i want to consider crowd scanning i should purchase a power meter, thats fine i can do that.




second i was wondering if anyone know of threshold values for crowd scanning. scan speed, vs power or something.


and say i built my laser with a power two high for crowd scanning, but i had analogue drivers, and i used them to turn down the lasers for crowd scanning, is that possible. id like my laser to be somewhere between .5 and 1 w max power,(how low could i dim lasers between 100 and 400 mw?)



finally i understand that commercially available lasers contain safety features such as scan failure, is there oem versions of these failsafes?




id like my laser to be multipurpose is basically my goal.

and also almost worry-free crowd scanning.

A simple search produced: Audience scanning - Wikipedia, the free encyclopedia

And: Laser safety information from the International Laser Display Association

Don't know how accurate it is but it's interesting reading.

Chuck

the ilda site is helpful,

but does anyone know the lowest power a 200mw laser can be operated at when dimming it via analogue driver,

also id like to know if there is failsafes for sale

Check this out...... Laser Show Resource Guide - Laser safety article - Pangolin Laser Systems

For crowd scanning, depending on where you live, requires a variance at the very least, You are then required to do MPE (maximum possible exposure) calculations for every part of your show. You also must file event reports and have your projector registered.

It's doable, but it takes an extremely long time and is a real PITA process.

Well i doubt by the sounds of it the op wants to go threw the official way but just a safe way.
It is done all the time in armature settings.
But i doubt those settings even give a crap.
i help setup a concert once and they just threw up the projectors and off they went no one calculated anything. and it was a large concert.
I know lasers are powerful focused light but i have gotten more than sick from some strobes at a concert they were huge and a whole wall of them. you could feel the heat every time they blinked.

To do it right, you need a oscilloscope, a power meter, and decent control software that outputs with good, accurate, repeatable timing.

The effects are cumulative, effects that are able to run 24/7/365 are at the same power levels a bar code scanner in a grocery store hits you with.

Speeding up the repeat rate and the scan speed really doesn't help you, in fact it can put more energy on target. The actual math is easy unless your doing mirror balls or static beams. It is however time consuming

European audience scanning, especially the German stuff, IS often certfied and tested, just they don't talk about it, considering it a trade secret. UK and Germany do require some considerable work to do it.

It is wrong to assume that just because the guys tossed the laser up on the truss, that it is ok to do things that way. Because the person who would be most exposed to the untested effects, on average, is you, the operator. So why risk it? Do the math. For a flat scan its easy. For a circular 2D scan, its easy. Get going and get set up, safely, and if I'm still around, post here again and I'll link you to where I have the math on line.

Steve

Here's some very good info w/math:

Laser Show Resource Guide - Laser safety article - Pangolin Laser Systems

http://www.physics.leidenuniv.nl/edu/bachelor/safety_instrucions/MPE-tables.pdf

the pangolin website was helpful and the mpe tables i like, cause im an engineer, i like numbers to work with.

few questions, the pangolin site assumed that a still beam at a sensor where the closest person in the crowd would be would be large enough to fill a cm^2 , i thought the beams were a few mm thick with only a few mrad divergence, that would not be a cm^2 or am i wrong?

ive heard of using neutral density optical filter, at the aperture along the horizon so that anything below the horizon would receive a lower power beam, does anyone know if that could work?

in addition does anyone know about Canadian rules and regulations

ramsoh said:

few questions, the pangolin site assumed that a still beam at a sensor where the closest person in the crowd would be would be large enough to fill a cm^2 , i thought the beams were a few mm thick with only a few mrad divergence, that would not be a cm^2 or am i wrong?

ive heard of using neutral density optical filter, at the aperture along the horizon so that anything below the horizon would receive a lower power beam, does anyone know if that could work?

Click to expand...

If you're going to audience scan, you need to make sure that the nearest audience member is far enough away that the beam cross-section can be measured in cm^2. Divergence is part of what makes a show safe or not.. Sometimes people use special lenses to increase the divergence so they can safely crowd-scan at a closer distance. The MPE measurements only need to be taken at the closest audience members position. If the irradiance there is acceptable, so is everything further back. Just how close is too close depends on divergece, output power, the kind of effect being produced, and several other factors.

Filters are one way to do it, but I really don't recommend attempting crowd-scanning unless you've got a professional software/hardware interface capable of attenuation mapping.

ElektroFreak said:

software/hardware interface capable of attenuation mapping.

Click to expand...

what software can do that?

For the best answer to that question you should go to photonlexicon.com and start a thread there. The people there are far more knowledgeable about this than I and can give you some very good input.. I don't ever audience scan myself.

You can guess what their answers will be ... Pangolin!

There may be more software that has attenuation mapping, but I've really only heard about it from Pangolin. The FB3 is their cheapest controller, and can do attenuation.

one quick last question, why is it that ppl tell me to use dpss lasers whats better about them than just a diode

DPSS lasers are the only way to get green, which is the most visible color. Green diodes were only very recently created for the first time, and they're not available to the general public quite yet.