Pattern MPE measurements for safety

[norty303]

Quick question:
Whilst we have a range of different ways of evaluating shows for MPE levels, is it acceptable to simply measure each of the scanned patterns to determine if over MPE or not?

E.g. say I was doing a simply beam show, could I measure the flat beam, finger beam gate, square tunnel at their brightest points to determine if they were going to be over MPE or not?

When I read some of the older literature on safety it seems to make lots of references to evaluating 'scanned patterns' and wondered if this was the old school way of doing it anyway?

[mixedgas]

somewhere I have a post on here on measurements and calculations, old skool/

I'll try to find it for you, it has a series of PDFs.

but if you have a simple photodetector and a oscilloscope, its fairly easy to come up with good, accurate numbers. Once you have those you can calculate the cumulative exposure as a sum of the measured exposures. I'll find the pdfs. If not, I'll scan them again. Pun intended.

and yes, you can measure the hotspots.

Steve

[norty303]

Thanks. The reason I asked was because I've just got my Laserbee II 3.2w and have been measuring anything that moves , and I've been trying to see how respective scanned patterns and modulated patterns actually measure, and whether I can go by what I'm seeing from a safety standpoint.

What is most overwhelming is that for a projector that does a combined CW across 640 and 532 of around 800mW, for most scanned patterns (e.g. modulated) when measuring at about 2m from aperture at 16kpps, I struggle to hit over 30mW on any of the test frames I've been using. Even directly in front of the aperture it struggles to get over 80mW on the 'TOP' test frame.

[mccarrot]

A thermophile meter is not fast enough to measure the pulse power of a scanned effect.

With your meter you could use the simplified approach method, with this method you should measure not more than 3,6mW with a 7mm aperture in front of the detector. than you will have 10mW/cm2 = MPE
But you can only use this value if you have a working scanfail.

[mixedgas]

Here you go, everything but the mirrorball. And I'm keeping that one to myself.

http://www.photonlexicon.com/forums/...nning+mixedgas

Steve