Long range laser projection?

[norty303]

Interesting info!
Phritzler, the 15W diode system, what were the powers involved and wavelengths, and over what range was it useful?
Is it the one on the right in your image, and how far away was that range?

[planters]

I'm going to ask this question, but even though I have done one of these projections both Dsli Jon and Phritzlar have done more and they do this professionally. Why the importance of super low divergence? If the atmospheric conditions are poor, the size of a beam does not determine the amount of absorption. At these intensities we are not cutting a channel through the air. The width of the far field spot is proportional to the distance and the apparent width is inversely proportional to the distance. A projector that looks good 20M away should look good 1200M away. Because the scattering angle x the distance determines the brightness then power is unquestionably important.

[steve-o]

Niiiice pic Phritzler. Gave me goose bumps looking at that. Wish I was there.
--oops posting same time as you Eric ..

[dsli_jon]

...Some of our 15W Diodesystems (OPSL green + red/blue...specially low divergency) and some only OPSL lasersystems with 20W..

Killer shoot, Man! And.. thanks for 'validating my advice'.. Especially on those 'slate-rocks', imho, he'll really-need 10-20W of Green.. Or, ya, I could also see 10W 532 + 10W 462 OPSL to make a 'quazi-Argon' color.. That '488-ish' result is also very-visible.. You, of course, had *the* Ideal venue.. Very-low 'humidity' in the Air (therefore, little water-particulate to attenuate the projections..) there in the mountains, a HUGE 'screen'.. and.. WHITE! It just doesn't get any-better than that.. (well, save-for perfect-low cloud cover in Centro 'Merica.. Good show!

...Why the importance of super low divergence? If the atmospheric conditions are poor, the size of a beam does not determine the amount of absorption. ..

Well, simply put, to 'go the distance', w/O becoming 'laser-oatmeal'.. Ie: If you've got a 2-3 or more mRad beam - vs a 0.7 one - you'll quickly see the 'difference', at such distances, *unless* you can go fairly-large, then even, perhaps up to 4-5mRad (heck, more, since even the 'well-collimated KTP' is well-above that, 8-9mRad-ish...) If you've got to 'crunch size', tho, larger-div + long-distance quickly turns to 'laser mud'...

.02
j

[Laser Wizardry]

" 15 characters"

[planters]

OK., I guess I didn't appreciate the numbers. 2-3mrad, 4-5mrad and above 8-9 mrad will appear fat at all projection distances. 20/20 vision is equal to 0.3 mrad resolution and most people can't do that. So, I would think that 0.5mrad is a floor. Any better than that and the eye will see the line, the same.

[dsli_jon]

...4-5mrad and above 8-9 mrad will appear fat at all projection distances...

..Unless, that is, you can make your image-size 'really big', ie: http://www.photonlexicon.com/forums/...3&d=1349779297 ..then, even a KTP-fat beam will 'feel (reasonably..) sharp'.. Again, 'Phritzler', there, shows the 'ultimate' / ideal situ for this all: HUGE projection area, nice, 'clean' / clear air (low-humidity), and WHITEy-tighty surface.. Short of these 'ideal' conditions, Moar Power + super-tight beams, are the best shot you have, of pulling a decent-shot off, at these distances...

.05
j

[norty303]

I expect we'll be quite lucky with the air, we're quite high at the projection point. I'll see if I can find out the elevation

[Phritzler]

Hello!
Thanks!
About the shot : We had luck with these, it was the shot for adjusting the lasers. On the show day it snowed and was a bit foggy - but with our systems there was no trouble to do the show!
The Diodes systems are the right and middle ones - the maximum distance of them was about ~1200m.
The left and not seen projections where done by OPSL systems from 2-6000m.
Our diodesystem was a 8w 530nm opsl, 5.5W red (637+655 coubled) and 6W 448nm at a beam of <4.2mm (1/e²) @ 0.7mrad full angle.
About the brightness : It is absolutely essential to have a sharp good beam to see it after the big distances !
Just a small calculation for reference :
20W OPSL : <4,5mm (1/e²) / <0.6mrad / 500m distance)
Beamdiameter : 304,5mm / 0,275mW/mm²
Our 18W Diodesystem : <4,5mm (1/e²) / <0.7mrad full angle / 500m distance :
Beamdiameter : 354,5mm / 0,1824mW/mm²
KVANT 20W : <5mm (FWHM) / <1.6mrad full angle / 500m distance :
Beamdiameter : 805mm / 0,0393mW/mm²
You see : The beamquality is absolutely essential. Don´t forget the way the light needs to come back, and if you have bad environmental influences, you see nothing with >1mrad divergence !
For such a job you need to have the best beamquality as possible.
All the best,
Phil

[danielbriggs]

...For such a job you need to have the best beamquality as possible.

Can not agree more with this + above calcs!