What is the highest power all diode laser projector out there?

[planters]

Good point. Can we also get back to my question in post 30? Even if the beams are perfectly parallel, doesn't more gap between them cause loss of brightness before the beams converge because during that time individual weaker beams hit particles in the air?

No, this doesn't really make sense. As long as the dust is evenly distributed in the atmosphere then a single beam will hit the same number of particles no matter where it is directed. If a second beam also will encounter the same number of particles no matter where it is pointed then if these beams are far apart, or close or even follow the same path as they would if they if aligned on top of each other with a polarizing combiner the losses will be exactly the same. The beams do not interact.

[ghosttrain]

No, this doesn't really make sense. As long as the dust is evenly distributed in the atmosphere then a single beam will hit the same number of particles no matter where it is directed. If a second beam also will encounter the same number of particles no matter where it is pointed then if these beams are far apart, or close or even follow the same path as they would if they if aligned on top of each other with a polarizing combiner the losses will be exactly the same. The beams do not interact.

Yeah, I agree now. You're right, I was taught nonsense. It would make sense in a universe where particles illuminated by a beam didnt affect a second beam as much anymore.

[frostypaw]

No, this doesn't really make sense. As long as the dust is evenly distributed in the atmosphere then a single beam will hit the same number of particles no matter where it is directed.

Actually at the risk of making this thread diverge I've been thinking about this and it's either interesting or I imagine you'll be able to point me at research already done.

On a macro scale the luminous flux and particle density in air stays the same as such a set of beams individually diverge and meet so it could be assumed that the light reflected to the side and seen by an observer would be the same give or take some losses from earlier photon-particle collisions further down.

But I'm wary of the assumption that particle density/luminous flux relationship is linear - does a 2mm and 30mm beam of the same power scatter the same light?

I've become fascinated with beam light scatter physics after watching your 575nm yellow dye laser and then looking for myself about how the apparent brightness of a beam varies wildly with angle. A whole microscopic world of reflections, refractions and diffractions right there to my mind that somewhere must lead to the perfect haze with the best side-on visibility (and probably toxic)

[ghosttrain]

give or take some losses from earlier photon-particle collisions further down

Wasn't planters response to me about there not being more losses compared to having a single beam from the beginning?

[frostypaw]

Wasn't planters response to me about there not being more losses compared to having a single beam from the beginning?

I think what I'm asking should apply to one beam or twenty... with a sensitive enough light meter I could answer it all myself with a few nice graphs.

[planters]

At the intensities that we frequently encounter, the scattering will be linear. The one beam will not ionize and clear a path for the second as it rips a hole in the dust.

But I'm wary of the assumption that particle density/luminous flux relationship is linear - does a 2mm and 30mm beam of the same power scatter the same light?

Yes, both beams do and this is the basis for absorption spectroscopy. The absorption of light is proportional to the number of absorbing particles encountered. There is no factor for the intensity of the light. Each photon acts independently. A beam is a collection of photons, all traveling in the same direction. An array of many beams or a single beam, thin or thick are all just ways of grouping these independent photons.


However, the eye's response to light is not linear and a dust particle that scatters twice as many photons is not twice as bright. This is complex, I don't know the proportions, but it will depend on the level of light, ie are you near saturation and the color. Saturation will occur at much higher intensities at say 808nm than at 555nm because the eye is much less sensitive to 808nm light (68,000 times less). If you wear glasses, try viewing beams at night with and without them. The luminous flux is the same (except for the slight loss through the corrective lens), but the intensity of the beams will very greatly.

[frostypaw]

If you wear glasses, try viewing beams at night with and without them. The luminous flux is the same (except for the slight loss through the corrective lens), but the intensity of the beams will very greatly.

Cheers for the thorough answer, I'd figure then for their application they'd be better off expanding the beams greatly at ground level - from a distance it'd look the same and the beam would be less dangerous to view nearby while keeping tighter further up which isn't what's shown

That's fascinating about the glasses, I have my old pair I can try. Playing with the telescoping on the spatial filter the beams look brighter tighter to me rather than the suggestion that bigger beams=more particles hit=brighter so that tallies with the above and some bad head maths - the bits of the equation working out area of beam w.r.t. increased particles to strike and luminous flux should cancel out - but I've not the accuracy to say if it's 2.7 or whatever times as bright

[ghosttrain]

Thinking about it some more I missed some important point, if they are using a diode array rather than knife edging that means as many corrective optics as you have diodes, opposed to one corrective optics and mirror holders+mirrors. I don't know which would be more economical.

[planters]

I'd figure then for their application they'd be better off expanding the beams greatly at ground level

Yes, and that is why scanner mirror size is the bane of projectors. Even as little as 10 M from the projector, divergence is becoming a significant fraction of the beam diameter. If much larger mirrors were available (and ran as fast), then typical projectors would use them for the far field performance despite the larger initial beam diameters.

if they are using a diode array rather than knife edging that means as many corrective optics as you have diodes

No matter how you will combine and align the final output, you will always need a corrective collimator lens for each diode. The diode's raw divergence is measured in degrees or tens of degrees. This must be collimated before you do anything else. The knife edging is for compression of the array and alignment of the individual beams. Trying to set up a big array of individual diodes means a lot of knife edging, but the result will be tighter and better aligned. I certainly would do it this way. And, I have.

[ghosttrain]

No matter how you will combine and align the final output, you will always need a corrective collimator lens for each diode.

Sorry, I didnt mean the collimator lens, I meant the corrective lens/prisms for making the profile less of a long line than a point. I meant if you arrange them as an array instead of knife edging you'd need to add prisms or cylindrical lenses in front of each diode which I don't know if is better or worse compared to knife edging it all both economically and the time it would take to build.
But maybe for such a searchlight style fat beam this is not that much of an issue, I don't know. In the video the beams look very simmetrical but we've agreed the video has been edited.

Trying to set up a big array of individual diodes means a lot of knife edging, but the result will be tighter and better aligned. I certainly would do it this way.

I certainly agree with you here, but I guess they could have went the first route to save time and cost by sacrificing the beam quality. If it's meant to be viewed from a large distance maybe it looks acceptable.

And, I have.

I hope you still have that and would consider making a video showing it off