My First Project (2W RGY)

[mccarrot]

Let me start with a quote from Hugo Bunk, on of the best laserists in the world (laserimage):
"since we entered the age of cheap high power DPSS lasers and more amateurs with that I see more and more shows where I am concerned about safety."

Also please read trough this article: http://www.laserist.org/safety-basics.htm

Ok back to your projector.

As you are into audience scanning, wich scanfail are you planning to use. here you can find some information about a nice USB programmable scanfail: http://www.photonlexicon.com/forums/...ead.php?t=9482 A working scanfail is mandantory when audience scanning.

Do you also have remote emergency kill switch connected to your projector?

these are all items you MUST take care of when audiance scanning with a <1W projector.

[White-Light]

Please take loss in to account because of the optics and mirrors that are moving continuously.

Irrelevant. There's no losses through movement. What there is increased scan speed and here theres slight relevance if the scan is moving very fast through the audience ie from one part of the audience to the next, because you then don't get as much repetition as the pattern has moved away. However, with 99.9% of scans, the fact that they're static or relatively slow moving (what you might call fast I'd probably still call slow for MPE purposes) means the fact you have fast scan speed makes no difference because the faster the scan, the more times the laser has to repeat the scan to keep the pattern in place so the scan speed or rather the short duration of exposure caused by the scan speed is cancelled out by the repetition rate as exposure is cumulative. Given that the dangerous exposure time to a laser of this power can be measured in thousandths of a second a fast scan rate is not going to save you as the cumulative repetition rate means MPE is still exceeded within milliseconds.

No dots are used at all.

If by that you mean there's an absence of hots spots, thats good. However, don't fool yourself into thinking that there are no concentrated beams. A fan is just a pencil beam being scanned so quickly through the air that your eye sees a continuos wall of light rather than an individual beam. So the size of the beam and the divergence for a fan is exactly the same as for a pencil beam. The only difference is the scan rate for which see the relevance above.

At last the divergence of the 1W 635nm module is way more than 1mRad. The used mirrors can't even pick up the whole 4x6mm beam.

Divergence is different to beam size. The beam size is the physical size of the beam at any given distance. The divergence is how much that beam spreads out at distance. If some of the beam is missing the mirrors then there are losses within the projector and from an MPE point of view thats good. However, it doesn't mean its safe, what you need to be doing is measuring the power after the aperture to find out the actual output when warm.

As for divergence, divergence helps at distance once the beam becomes larger than 8mm diameter because then exposure is reduced. However, at the closest point of entry to the laser, the effects of the divergence are the smallest and this is why the only true way to ensure you're within MPE is to take a measurement at the closest point of entry and do the maths (the simple method is the easiest to comply with).

The fact you have a huge divergence at distance is of no relevance. The fact a beam is 3 feet across at the back of the room is irrelevent if its 3mm across at the point of entry.

As I'm far from an expert on this, if any more experience member wants to correct me on aspects of MPE, please feel free to do so.

[mccarrot]

I have attached a pdf with a presentation I did at the snowLEM a few weeks ago.

In this PDF is described how to measure MPE for audiance scanning.

[madgadget]

Is an English version available

[dave321]

Is an English version available

i second that ! would be useful to read up on

dave321

[pimm87]

Irrelevant. There's no losses through movement. What there is increased scan speed and here theres slight relevance if the scan is moving very fast through the audience ie from one part of the audience to the next, because you then don't get as much repetition as the pattern has moved away. However, with 99.9% of scans, the fact that they're static or relatively slow moving (what you might call fast I'd probably still call slow for MPE purposes) means the fact you have fast scan speed makes no difference because the faster the scan, the more times the laser has to repeat the scan to keep the pattern in place so the scan speed or rather the short duration of exposure caused by the scan speed is cancelled out by the repetition rate as exposure is cumulative. Given that the dangerous exposure time to a laser of this power can be measured in thousandths of a second a fast scan rate is not going to save you as the cumulative repetition rate means MPE is still exceeded within milliseconds.

According the PDF file above movement is relevant for spreading the output power. But I have to admit that my statement isn't based on any calculation.

Divergence is different to beam size. The beam size is the physical size of the beam at any given distance. The divergence is how much that beam spreads out at distance. If some of the beam is missing the mirrors then there are losses within the projector and from an MPE point of view thats good. However, it doesn't mean its safe, what you need to be doing is measuring the power after the aperture to find out the actual output when warm.

I Know The first sentence didn't refer to the first.

I do appreciate that you're all worried about my audience. I will go deeper on this, although I think this safety things are often exaggerated.

[Doc]

That's it, I'm outta here...........

[mccarrot]

I do appreciate that you're all worried about my audience. I will go deeper on this, although I think this safety things are often exaggerated.

Yes and no,

The US rules are simply unacceptable for our customers in Europe. But we must not exeed the MPE in very high values or eye damage WILL! occur, offcourse you will not get blind instant but there will be "changes" to the eye, some noticeable some not.

But please keep big distance between audience and the beam, each meter you are further away from the audience will improve the "safety" with a multiplier due to several parameters.

[edison]

MCcarrot , sell him your magic lens just to be save

[madgadget]

although I think this safety things are often exaggerated.

omg.

Course all the rules are made up for no reason at all, lets just ignore them!