Seeking advice for dance laser

[wineboxcutter]

Back story:
I love to dance so I have disco lights and a fog machine in my home. The laser is a $99 "Micro Galaxian" by American DJ. It has a 30mw 532nm green laser and an 80mw 650mw red laser. They shine through a pair of diffraction gratings, one of which spins. This creates approximately 64 beams that split into around 512 smaller beams. The beams near the middle are brighter than those on the edges. I dance in the beams with no ill effects, at least none that I've noticed.

Question:
Can I upgrade the red laser to something that allows me to see the beams when the other lights are flashing?

Here is a link to a video that shows the problem: YouTube - ‪Micro Galaxian + Dual Jem Pulse in light fog‬‏


Additional info:
I found a chart that shows 532nm appears 8x brighter than 650nm per watt in darkness. This means I'd need 240mw of 650nm to match the apparent brightness of the 30mw 532nm. I'm afraid that 240mw would be too dangerous for dancing in the beams. Is that true?

I did some searching and found three other wavelengths that might be affordable: 635, 445, and 405. I'm concerned that the 405 wouldn't be any more visable at a safe power level, that 445 is only available at high power levels, and that 635 might would be too expensive at a power level that can compete in terms of apparent brightness.

Advice?

 

[Skywalker]

I have a Chauvet Cirrus, ADJ Micro Galaxian and an Eliminator Electro Swarm. I usually take them to friends houses for parties. That Dual Jem Pulse looks awesome!

 

[Jacob32123]

I have a eliminator scatter star, an omnisistem magic box, and a pyro fog. Amazing.

 

[JBTexas]

Additional info:
I found a chart that shows 532nm appears 8x brighter than 650nm per watt in darkness. This means I'd need 240mw of 650nm to match the apparent brightness of the 30mw 532nm. I'm afraid that 240mw would be too dangerous for dancing in the beams. Is that true?

I did some searching and found three other wavelengths that might be affordable: 635, 445, and 405. I'm concerned that the 405 wouldn't be any more visable at a safe power level, that 445 is only available at high power levels, and that 635 might would be too expensive at a power level that can compete in terms of apparent brightness.
Advice?

You might be interested in this... I think RHD put it up:

http://rohanhill.com/tools/relativebrightness/

 

[wineboxcutter]

Thanks for that calculator JBTexas... it looks like bad news for me.

It appears that the 80mw 650nm red has only 14% the beam visability of the 30mw 532nm green. That seems about right from my subjective point of view.

I would like the alternate beam color to be at lease 3x brighter than the current 14% so that puts me looking for something in the 42% range. I plugged in some numbers and came up with the following possibilities:
a) 589nm yellow 20mw 38%
b) 473nm cyan 70mw 44%
c) 445nm blue 200mw 41%
d) 650nm red 240mw 42%

Of these, I think only the first two might be safe to dance around in the beams; that is after it passes through the pair of defraction gratings. They seem to have short duty cycles and slow start-up times. I need something that can flash to the beat of the music for sevarl hours. These first two are also very expensive, far surpassing the $99 I spent on the Micro Galaxian unit.

There seem to be affordable 445nm blues that were repurposed from projectors but, from what I have read so far I wonder if they will have any output if fed *only* 200mw ... the reveiws seem to start at 500mw and go up from there. The good news I guess is that if it came out of a projector I'd guess duty cycle wouldnt be a problem since the Micro Galaxihousing is basically a big aluminum heat sink with a dedicated fan. I'm also not sure if 200mw is safe for dancing.

The cheapest route might be to upgrade the red to 240mw but, again, that seems perhaps unsafe. When the spinning grating momentarily aligns with the stationary one there would be ~64 beams for an average of 3.75mw per but really the ones in the middle are a tad brighter so I think 4mw is probably too high to be safe.


So it seems even if money is no object (and it is) the options are limited by duty time and warm up time for the yellow and cyan or by safety for the blue and red.

Am I failing to consider something? Am I just out of luck?

 

[qumefox]

You are aware that a 70mW 473nm will set you back $500-$700 and while i'm not sure how much a 589nm labby would run, a 20mW portable is around $700.

If money truly is no object, why don't up upgrade to a true RGB scanner? It'll be much more versatile in the long run.

 

[wineboxcutter]

Sorry, I was trying to say that money is a concern but, even if it were not, I'm not sure I could get a good combinaton of a safe power level with a long duty cycle.

I checked the specs of several RGB scanners and they all used lasers with > 200mw of power. So I infer this means that a) RGB scanners should not be configured to shine directly onto dancing people or b) The scanner beam moves so fast it can't cause damage.

Is it possible to use a collimator or optics to make a fatter, weaker beam out of a thin powerful beam? That would be better for my purposes anyway.

 

[chipdouglas]

"crowd scanning" is doable. it is not common in the US. I do not know the laws on it. But done by a professional with most/all variables accounted for it can be relatively safe.
Some variables are:
distance to crowd from aperature
laser power and divergence calculated for distance to crowd.
mechanical and/or electronic aperature shutter in case laser scanners stop.
etc, etc...

go to the multimedia section and look for a thread started by me. I took it at a festival i went to in the netherlands.

edit, i found the link... ignore the poor sound quality. http://laserpointerforums.com/attachment.php?attachmentid=33468&stc=1&d=1309881727

michael.

 

[qumefox]

The MPE levels required in the US for crowd scanning make it not worth it.

It's more common in europe due to less stringent regulations.. Usually when it's done in the US, it's not a sanctioned and varianced event.

 

[wineboxcutter]

The 80mw red 650nm looks reasonably OK in dense fog but it is basically worthless in light fog.

I watched your video ChipDouglas and at first I couldn't understand how those people were not blinded. But then I got to thinking... if the optics were such that the beam were quite wide instead of in tight focus, it could have a lot more total power but a lot less power per square inch.

I made this image to explain what I mean:

If my math is correct a circle with a 1 inch diameter has 16 times the area of a circle with a quarter inch diameter. In other words, a wide been could be 8 times as powerful yet half as dangerous as a focused beam. Am I making sense? Are there optics easily available to do this?

 

[qumefox]

You also have to realize that a moving beam has a lot lower power density than a static beam, depending on it's rate of motion.

Wide scanned effects 'generally' won't cause problems eye wise unless your dealing with really high powers. Say a couple of watts or more.. and even then, there are other factors like divergence, distance of audience from the projectors, etc, that come in to play.

The main safety concern with audience scanning is what happens if you lose a galvo and end up with a static beam pointed in somebody's face. It's something that can't be planned for that could very well happen. There are scan fail systems around but only one I know of that's been approved for audience scanning in the US.. And saying it's not cheap doesn't even do it justice heh. Most 'scan fail' systems used in the US consist of pretty much a thick metal plate, that physically makes it impossible for beams to get near the audience. heh.

To answer your question though. Yes 'fat beams' are safer... However.. they're also less visible. And something that compounds the problem is that they would require larger galvo mirrors.. Which means more mass.. Which means slower scan rates, which means longer dwell times.. which makes them more dangerous..