As much as you need, or as much as you can afford?

[The_Doctor]

Higher Power will always be what sells to the average 'promotor' or high street night club. Bigger numbers are always better, right?

Lasers work on sharpness of beam, power density. You could sell that. Most cheap in-car and domestic boom-boxes trade on PMPO, or 'Peak Music Power Output'. This is inane, pathetic, but it sells. If you have a very sharp TEM00 beam finely focussed with a 2mm fl lens you can make a 100 mW beam look as good as a fat 1W beam. Its reflection won't light the room the same way, but in the air, or in fast scanned graphics, it will whip the ass of the big fat diode. And on smaller mirrors it can scan faster too.

If some promoter boasts of his big fat power, but the guy down the road at the next club steals his punters with a show that dazzles with clean sharp brilliance, he's going to look like a fat man in a speedo contest. Power isn't everything. If it was, audio 'pro gear' scammers would never have had to invent terms like PMPO in the first place. Perception counts for so much more. If it didn't, every kiddie with a boom-box would know what RMS means.

EDIT:
Another way to look at this, also based on the audio scene... Domestic and car stuff tends to pump the POWAH! As if nothing else matters. But at a gig it isn't the power but the size of the horns and bass drivers that counts most. Efficient coupling of audio signal to human perception. But only a sound engineer ever talks about sound pressure (SPL). Same thing with laser beam power density. Thin beams are the equivalent of big horns. And that, ladies and gentlemen, will be my soundbite for the day.

[norty303]

When specifying a sound system for a job, the only important thing is that it is 'enough'.
How many amps you have up the back end of it are of no importance to the success of the job.
Whether it is point source, 'line' (hahahaha) array, horn or reflex matters not, so long as it is enough to do the job. And so 'kW' ratings become meaningless.

But still, they get jobs based on K's and some markets/scenes still use K's as a marketing tool.

And so it will be, my 5W laser may be more than enough for a small room, but that doesn't mean that I won't lose a job to someone with a 20W projector turned down to 5W, because the promoter thinks he's getting 'more'.


P.S. I like horns for their efficiency, but a decent reflex system in adequate quantities is still a lovely experience. And lots of 'line' (hahahaha) systems use BR or variations on bandpass boxes for their bottom end still.

[JohnYayas]

Quality is my limiting factor. I'm interested in buying the best quality laser that suits my power needs. If the best is under my price ceiling (which it usually isn't) then I might go higher in power.

[absolom7691]

Quality is my limiting factor. I'm interested in buying the best quality laser that suits my power needs.

This is spot on with what I have finally decided. I used to run a 1W +\- projector and it looked decent. Once I knocked together my first single-mode DI diode build, I was sold. I ditched my 1W system and allocated those lasers for my lumia. The color of 520nm along with the super tight, pencil thin beams of those single mode diodes, completely blew me away as far as quality goes. Granted, I don't do beams and I don't do commercial shows but for my living room wall, those images sizzle. For the quality, I don't mind that I gave up 2/3W. I think it was a good choice and I am very happy with the results.

[The_Doctor]

And so it will be, my 5W laser may be more than enough for a small room, but that doesn't mean that I won't lose a job to someone with a 20W projector turned down to 5W, because the promoter thinks he's getting 'more'.

It's a good strategy anyway, but if I did it my real reason would be that running higher power diodes at less power makes them last longer, make sharper beams, be less likely to fail, etc, that driving small ones hard. Nothing wrong in adding a few unpowered diodes just so it's not a lie when the promoter is told that there's X Zooberwatts of laser power capability in there. So long as someone with a real 20W laser isn't impressing people more than the 5W output used well, it's a winning position, especially if you ever have to prove your real power in a court to defend against a litigious person who sees what they think is a fast source of extra income.

Rather than high power, I bet fast scanners and a fast scanfail system are a better spend for a bright show. Especially in public with risk of court claims.

PS. What's with the 'line' (hahaha) bit? Do you mean those things that churches hang on pillars beside the aisle? Got to say they used to impress me as a kid, but now they do so only for their weird ability to project a wavefront a long way. But they sound atrocious. And it's a long time since I heard one.

[norty303]

but if I did it my real reason would be that running higher power diodes at less power makes them last longer

A waste of time.
The technology moves on so quickly that you only need a diode to last 3 or 4 years before it becomes very cheaply replacable with the next big leap.
Given that the diodes are designed for use in TV's and projectors that are going to have significantly more 'on' time than a laser projector, running them at or above ratings is going ot be just fine.
How many people will have blown M140 diodes before they end up replacing them with the bigger power 9mm variants? Very few I suspect, even those that really abuse them.
Longevity really isn't our problem in this game. (imho)

[norty303]

Also, James Stewart makes an interesting point about safety and liability in the safety lens thread.
Given that you are going to need to 'turn down' your 20W projector to do audience scanning (or use a -30 diopter lens!), how can you be sure that it didn't hit a full power beam in someone's face?
A 3W projector simply can't do it due to its possible output, but who's to say that your ziggawatt laser didn't have a whoopsy in the software?
As he says, you should control exposure by messing with the power density and irradiance, not by playing with the power output. You aren't going to be able to do that with 20W in a 20mx20m room.

[The_Doctor]

Well that's why scanfail systems exist.
Separate the issues of why use 20W capability at 5W. My reason may not count for much, but like any engine, or speaker, or most other gadgets, a strong one run modestly usually runs better, never mind longer. The other reason for 20W, to lay claim to raw power, is not a thing I'd do. Which is why I spoke of it the way I did. Nothing wrong with that IF you have a very sound way to lay stronger claim to safety, but a person running with less than ideal cover would be better off being able to prove that their diodes were physically incapable of more. But even that is a bad policy given the cost of an expert witness capable of defending this claim.

[norty303]

Well that's why scanfail systems exist.

I'm not talking about a failure scenario. I'm saying that it reaches a point where regardless of how you are scanning, the high power at short range exceeds MPE by a decent margin. Then you add in the 1ms exposure time (which is many times longer than your already unsafe exposure level from scanning) for when a failure DOES occur and you are WAAAY over MPE.

Scanfail allows some safety margin, but it is not a panacea for firing as much as you want at people.

[The_Doctor]

Ok, 'fail' is the wrong word, I was thinking of the energy in a moment of passing across an eye. This debate is now spanned on two threads so is getting slightly weird. Anyway, relying on any one thing is bad. Can't trust software to scan right, can't trust a scanfail to prevent the limit on energy in a moment of exposure, can't trust reducing power. Can we trust diverging the beam with a safety lens? Perhaps not if the diode collimation slips due to heat in the mount and counters the intent of the safetyscan lens. In short, we can't ignore context.