Help doing calculations

[darkrider]

Good morning laser peeps.

I am new to lasers and am doing some outdoor stuff for a small local festival. I have been asked by Transport Canada to fill out some forms.
The Official government PDF can be viewed here.


The form is fairly straight forward until you get into the laser details. I don't have access to Skyzan and I was wondering if anyone could help me out?
I have 3 different colors that I will be working with.

All of these lasers will be in a fixed position. Some pointed vertical and some horizontal. We don't know about the horizontal ones yet, because it depends on the topography of the actual location for safety reasons. These lasers will be mounted 12 feet off the ground so people cant touch them.
I have purchased 3 test lasers, here are the links. (If you have a better suggestion for lasers, I am all ears)

Red
Blue
Green


Here are the details:
RED: 660nm
CW
Semiconductor
300mw
beam diameter 1.5 mm
beam divergence 1.5 mrad

Green: 532nm
CW
Semiconductor
100mw
beam diameter 1.5mm
beam divergence 1.5mrad

Blue: 405nm
CW
Semiconductor
100mw
beam diameter 1.5mm
beam divergence 1.2mrad

What I need for each one:
MPE w/cm-2
PCP
VCF
VCP
NOHD
SZED
CZED
LFED

What version of skyzan you use to calculate.

I am going to also go through the forum and do a lot more reading.
I am also looking for some safety goggles but a lot of them dont cover the 660nm range.

Regards,
Darkrider

[laserist]

Beam divergence is usually expressed in "milliradians"...

I'd say as a general rule if you have to ask how to calculate MPE - you're not ready to do that kind of show, but I'm an annoying old guy...

[mixedgas]

I have Skyzan at home. My question is why you would use such weak lasers for an outdoor show?
Doing it with a hand calculator, you have a ~60 meter NOHD, and will need to choke your audience on fog to do very short range beam effects with those.
Perhaps best to hire a local with experience and stronger lasers?
~
http://www.laserpointersafety.com/safetycalcs/
~
Why don't you start with the above and I'll run it with Skyzan late tonight and we'll compare answers.
~
Steve

[darkrider]

Beam divergence is usually expressed in "milliradians"...

I'd say as a general rule if you have to ask how to calculate MPE - you're not ready to do that kind of show, but I'm an annoying old guy...

I have done the math, once, no clue if its right.
Yes my MM is a typo on the divergence and has been corrected.

[darkrider]

I have Skyzan at home. My question is why you would use such weak lasers for an outdoor show?
Doing it with a hand calculator, you have a ~60 meter NOHD, and will need to choke your audience on fog to do very short range beam effects with those.
Perhaps best to hire a local with experience and stronger lasers?
~
http://www.laserpointersafety.com/safetycalcs/
~
Why don't you start with the above and I'll run it with Skyzan late tonight and we'll compare answers.
~
Steve

Being my first dive into any laser anything, I picked some very small very cheep ones to play with and learn some stuff.
I did get a small art grant to help me out on the costs, and that is one of the driving factors on what we use.

If you have recommendations for lasers, I would be more than happy to look into them. I also assume by "weak" you mean the power of the laser itself?
I did look at a few 2 watt units.

[darkrider]

Ok here is what I got so far for the red one: I will keep working on the math to learn.

RED: 660nm (Based on research this is a poor laser color or a cheaper laser color)
CW
Semiconductor
300mw
beam diameter 1.5 mm
beam divergence 1.5 mrad

MPE w/cm-2 = 2.5 mW/cm-2
PCP = .3
VCF = .23825 (Not positive on this, I think it should be closer to 0.0321 based upon my research.)
VCP = 0.071475
NOHD = 267.8002502 FT
(32.8 / milliradians) * (square root of (0.5 * milliwatts))
(32.8 / 1.5) = 21.8666 * (square root of (.5*300)) = 150 = 12.247
(21.8666) * (12.247) = 267.8002502 FT

50/50 distance = 84.75 feet
267.8 / 3.16 = 84.75 feet

CZED = 134.6811
SZED * 4.47
30.13 * 4.47 = 134.6811

SZED = 30.13

(32.8 / mrand) * (Square root of (12.7 * mwatts * VCF))
(32.8 / 1.5) * (Square root of (12.7 * 300 * .23825))
(21.866) * (Square root of (907.7325)) = 30.13

LFZED = 1346.811
CZED * 10
134.6811 * 10 = 1,346.811

[darkrider]

Well hopefully the math is close, I did it all by hand as you can see, to help understand the stuff. Please correct me where required.

Now that I have done the math fully by hand, I understand why you said "weak lasers" I am going to look for some in the 1,000 mW range, as they will be far better, now the price/quality is what concerns me, you can find 1w anywhere from 85 bucks, to multi thousands, I don't know what to actually look for in a good quality laser.
My budget is around 700 dollars CDN, for 4 towers. We are currently looking to bring the budget down so we have more laser money. Its obvious that I will need to have a bigger budget for next year.

Also...From my basic understanding, the green one at 100mw is going to look roughly the same brightness as the 300mw red, due to the fact that the eye sees green better?

[mixedgas]

By default, if your doing aerospace calculations, I can assume you are outdoors and un-terminated,
~
On a perfectly clear starlit night, with no other light fixtures or distant street lights, and little wind, while lofting an amazing amount of fog or haze, in a clearing in a dark national forrest, you could do a beam show for maybe 10 friends with a pair of 500 mW RGB Projectors. Your friends would be nice to you, a public audience would walk away after a few minutes. There simply is not enough raw power there for an outdoor show.
~
Your 660 nm and 405 nm wavelength pair cuts your beam visibility by a factor of about four or five , before you even begin. With what you specified, your beam would be pretty much green or cyan. Currently 170 milliwatt 635 nm diodes are widely available, and a pair of them combined with a polarizing cube makes a far better red then even 500 mW of six fifty. Blue diodes at 445 nm and 460 nm are widely available, and are much, much more visible then 405 nm.
~
Depending on the level of lighting present, and some lighting always needs to be there for audience safety when outdoors, you need a pair of FIVE WATT projectors (the minimum) to even get started...
~
I don't know what your budget is, but we haven't even discussed software and content yet...
~
One standard 100 watt Metal Halide streetlamp, near by, would bury you at those power levels.
'
I'll still run the numbers for you, just to see if my Skyzan machine still runs.. I'm sorry if I sound sarcastic, but I'm really trying to help. I started as a hobbyist over 25 years ago, and I cut my teeth on low power systems.
~
Look at the chart here, Laser shows are tyoically ran under conditions where the eye is somewhat between Scotopic and Photopic vision, a region called Mesoptic vision. Your 532 is fine. The well lit conditions chart is here: https://en.wikipedia.org/wiki/Photopic_vision. See the dramatic difference between 650 vs 635 on the Photopic chart?
Steve

[darkrider]

I do appreciate all the help, and no sarcasm taken, better for me to learn than to waste thousands of dollars.

This is in the middle of a field in the middle of no where, with little to no light. Any light that is provide will be by participants head lamps to walk. Its more of an installation, than a show, people will walk by check stuff out and move on. There are several ART installations in said field. Roughly 1000 people will be there.

We have allocated only 2,500 dollars CDN for this project, there is opportunity for more March 1st, and I will apply for an additional 2,500, this would be the maximum that we could get. I have already gotten the first 2,500. The second will have to go through the grant process.

We have built 4 towers, 3x3 and 12 feet high. Using EMT tubing and some standard shade structure parts.
At the top of each tower is a fog-Fury-Jet vertical fog machine (20k cubic feet/m as long as its too not windy) We used these units last year, and when the temp drops, the fog hangs nicely.
At the bottom is a york-4 post LED 270 watt LED light, this will light the column.

They are all using DMX and a controller.
In the center is a 3x3x3 cube suspended by black rope, so that it looks like it is floating. I was thinking of also doing fog/laser in this unit too. If I have to, ill buy a single D1000w.

I was looking at ORLaser107 which is a typical DJ setup, also lower mW. Not sure its going to cut it any more. I have emailed the rental company (because purchase is out of the budget) to see of they will get us the D1000w units for our project. There is another company locally that I will go and see as they have not responded to my email. Perhaps they will rent me a high powered unit.

I am now looking to see if I can hammer the budget down so that I can purchase a pair of D1000w units from Magnum Lighting.
The idea was to mount a laser at the top, something small and simple to draw people in, however it sounds like it might just not be enough OOMPH.
The small red/green ones I was going to mount horizontal to the ground, to say cross the walking path, I suspect it may dissipate after that. I have already ordered the small ones, so will play around with them and learn some stuff along the way. For 180 bucks CDN, its good learning experience.

Now keep in mind, that all this is running on generator power in the middle of said field, that we have to rent, and is also eating up some of the budget. Would be nice to have a 20k budget for the project, we just build on it, a little each year with grant money. Last year we only had two towers.

Unfortunately I cant see the 5w projectors being in the budget range at all, what so ever. Have a recommended company you like? I can always look and perhaps plan for next year.

[buffo]

Holy crap! You're going to have four towers, each with a 270 watt LED fixture at the base? That's a *SHITLOAD* of light! And if you cover the tower with anything (cloth), it will only be worse.

Even pointed straight up, that light is going to catch the fog coming out of the fog machines mounted at the tops of the towers. And that means the light will be scattered in all directions, lighting up the whole area and competing with the lasers for apparent brightness. Not good.

Based on your budget, I can tell you right now that this is not going to look bright enough for you with a 1 or 2 watt RGB projector. If the budget is firm and non-negotiable, then my advice is to forget about RGB and focus exclusively on green. It's the color that our eyes are most sensitive to, so it will show up brighter than any other color. Also, DPSS green has gotten a lot cheaper recently because everyone is flocking to the direct-diode greens. 532 nm green is the brightest line we've got in our toolbox, so you can get away with less of it and still have decent beams.

If you can score a pair of 1.5 to 2 watt green-only laser projectors (at 532 nm), you've got a shot at pulling this off. It's still going to need to be very still (to keep the fog in place) and those LED lights may yet prove to be your downfall, but it's at least theoretically feasible at this power level. Also, forget about sheets and fans and focus on fewer beams that will appear brighter because the power won't be spread out all over the sky.

For the future though, I completely agree with Steve: this is a show that would normally be done with much more power. One other option might be to RENT the equipment you need. If it's only for a short duration (say, up to a week), then for the budget you quoted you could rent some really nice stuff this year and probably make it work even in full color.

Bottom line: outdoor shows are notoriously difficult. The mantra is "go big or go home", and while that sounds like the rallying cry of a crusty old laserist, there is a lot of truth to the statement with regard to outdoor shows. There's just no adequate substitute for power. And even with really nice gear, sometimes you still get skunked. (I partnered with a major laser show company last year to put three 20-watt Kvant laser projectors outside for a 4th of July show, and it still looked lame because the 20 mph wind that night meant that we couldn't keep the scattering medium in place.)

Adam