Beam size issues RGB

[steve-o]

for SELEM, I might save a couple to bring along...

That would be awesome.
I cant see this happening around a church..
Uhh- it is out of the city limits?

When your pan is flying it looks like a ufo! I was trying to figure out how to transfer that aerial footage and loop it...
I've set off a few M-80s
"mortar shells" as in military with the fragmentation devices removed?
Cool!

[buffo]

For certain the pyrotechnics will only be detonated at the private residence, and then only if I get the green light from our host. (Fireworks are not stricktly legal in North Carolina - at least not to the extent that they are in South Carolina.) But I believe the house is far enough from the interstate that I think we'd be OK. (For sure the chuch would be out for that sort of the thing though!)

Concussion powder sounds cool... Similar to flash powder I'll bet. Got a recipie for that stuff lying around here somewhere, but never got up the nerve to actually make any. (My wife would kill me...)

RE: the flying pan... Yeah - it's pretty damn cool the first time you see it. You can't imagine it flying that high! As for the "mortar shells" - eh, that's just the industry term for them. Technically they're "reloadable aerial shells", but some dude in marketing must have decided that "mortar shells" sounded cooler, so that's what they print on the box.

And technically they are a type of mortar, in that the shell is propelled from a tube that is sealed at the bottom end by an explosion that is separate from the main charge in the head of the shell. But beyond that the shells I have bear little resemblence to actual military mortar shells. (For one thing, the Army doesn't use fuses to light their mortars!) These things have a few tens of grams of explosive that is tightly wrapped in paper. Nevertheless, they are quite powerful. (The bottom of the 1 quart saucepan that was sent flying in the last part of the clip is now bent into a slight hemisphere!)

Basically they're smaller cousins of the shells that professional pyro guys use for your typical 4th of July show. Except that the smallest "professional" shell I've ever seen was a 3 inch, and I've seen them as big as 12 inches. (I've read that they get even larger, but once you get past a 12 inch shell you're talking stupid money for each shot.) These little 1 inchers are toys by comparison, but the design (and the underlying physics) are identical.

Adam

[steve-o]

Adam-
Well I hope the private residence comes through then..
Concussion powder is more of a 'knock ya back' thing more than a sound thing- I had a tape recorder going and you couldnt even hear it on the tape, the only thing you could hear is the girls screaming after the shockwave passed
I think that's when the neighbors called the cops..

[steve-o]

speaking of alt.lasers tho--somebody put this up..

[Pitts]

Hi guys,

Have enjoyed all of your posts... even learned the spectrum of Tampax and Depends pads...
Greatly enjoyed the back and fore as the thread wandered here and there..

All good but guess what !! I am not a lot better informed than when I started this on the actual question of beam size and issues related..

Have I been hijacked or what ??

Anyway enjoyed it all..

Hey whats the thought on Marconi's twin beamers they get good right ups no worry, I am referring to the 'apparent' brightness when compared to 635 units ( with fat beams of course) which is the best way to go ??

Cheers

Ray
NZ

[steve-o]

Oh.. hey Ray..we wandered a bit eh?
I got the dual Marconi rig and I like it a lot but I can't compare to 635. My 7 mw he-ne's not running and I dont think that would be adequate for comparison so I cant comment on that. The Marconi's are great, they have a thin bright beam and color mixes well , also heard 635 fat beam and lousy beam quality, FWIW
-Steve

[buffo]

Hi Ray;

Yeah, we hijacked your thread big time. Sorry about that.

So, back on topic - which is beam quality... If memory serves, you currently have two high power DPSS green units - a 1.5 watt and a 1.7 watt. To get enough red to mix with that is going to be difficult. Even if you dial the green down to a watt, you're still going to want 2-4 watts of red to mix with it. That really limits your choices, simply because there are so few lasers that can make that much red.

The dual Maxyz module rigs that Marconi sells will only give you around 450 mw. (I've heard of people pushing them to 500 mw, but that is an absolute max.) Even his 4-diode experimental rig only makes 800 mw, which is still way too low for your application. (And isn't available yet in any case.)

To get several watts of red, you're looking at a pair of 635 nm diodes and a PBS cube, or a krypton ion laser. (OK, a DPSS red at 671 nm is another option, but that red is so low in the spectrum that it's hard to see, so you'd need even MORE power.)

Given that the high power 635 nm diodes are really expensive (once you get above a watt) and that beam quality is important to you, I'd say you might want to seriously consider the krypton laser. (Find a deal on E-bay and you might actually come out quite a bit cheaper for the same power level.) Sure, it will be large, heavy, water cooled, and need lots of juice, but the beam quality will more closely match your green laser. Plus you'll be able to ramp your green way up without shooting your color balance all to hell.

Now, if you're only looking to build a low-power RGB rig, then I'd recommend the Maxyz modules because they have very good beam specs and will look great. But that means you only need around 150 mw of green to balance it. Sorta wasteful considering that your weakest green laser is putting out 10 times that much power!

If you go with the 635 nm diodes, you're going to have to live with the large beam diameter. I've seen one 500 mw diode where the beam was so divergent that it spilled off the mirrors of the galvos! (We're talking about a throw of less than a foot, and already it was big enough to spill!)

To the untrained eye the larger beam diameter from that unit wasn't all that easy to see during a beam show, but it was *plainly* obvious when doing graphics - even to a newbie. One solution would be to increase the size of the green beam to match the red. But then you're probably going to want larger mirrors on your scanners...

Adam

[Pitts]

Thanks Adam,
You have confirmed my fears..
However, no I don't intend to use the 1.7 and the 1.5 for the RGB.
I think it was you way back that pointed out to me that nothing beats an RGB with two bright green beams on the sides. The big greens are for that job.
I now understand that I need to be more modest with my RGB power (so does the bank manager and "she who would be obeyed" ) .. Probably thinking in the 1 to 1.2 watt area (total). So I would be buying three more lasers + galvo etc.
I guess my concern with the Maxy's is the wavelength (based entirely on my ignorance and a photopic list I have donwloaded from PL here).. the Maxy's look great to me and I am sure they are well made but the chart seems to suggest they will be way down in brightness by comparison to 635. .. But then who wants a giant fat beam that looks yuk ?? ( like 5 or even 6mm)..
Any ideas.. I also like the idea of using CNI's Green and blue. What do you think.
Thanks
Ray
NZ

[Pitts]

Thanks Steve-O. appreciated.

[steve-o]

Sure thing, Ray
I actually wanted to try a 622 diode, but the best they could do was $500 for the bare diode. (well, w/ the C block.) Just for kicks. But-
635 is a little too orange for good color mix from what I've read. I believe Adam uses 650 if I'm not mistaken. Is that right Adam?