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Multiple beams

RedCowboy

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There was a discussion on PhotonLexicon back in 2006 about producing a custom "axicon" optic that might be helpful to your build. (Despite the fact that there are axicon lenses, that's not what this was about.) The idea was to start with a rod with a conical tip and then grind 4 (or more) symmetrical flat faces into the tapered tip. Then cut off the tip, mount it on a backing plate, and drop the whole thing in a vacuum deposition oven to coat those flat faces with dielectric film to make them into high-efficiency first-surface mirrors.

Now you could aim an array of 4 (or more) diodes at those faces and the resulting output beam would be a tightly-packed cluster of collimated beams that were perfectly parallel to each other - no knife-edge mirrors required. There was even talk about drilling out the middle of the rod so you had room for a central beam.

The project never really went anywhere, but the physics were sound and the actual manufacturing process was fairly well described. I think something like this could still be done affordably, and it would certainly simplify any optical arrangement where you needed to combine several diodes together into a single, composite beam.

Food for thought...

Adam

We have had those ideas too and as the beam width is the limiting factor we could use cut mirrors about the width of a beam.:cool:

-----------------------------------

See this Thread....


A More advanced version of this IS now about 50% complete !!! C-19 slowed things down !!! The name of this project is...
" The Green Kraken " Alaskan has commissioned me to design and build. I MUST get his approval to post ANY details...but...I assure you...THIS will be completed by Fall 2020....and will be Epic !! We are hopeful to deliver 10.4 W out the front door in a small beam pattern array.
Hold on to your hat !! CDBeam

@ CDBeam777 : Aligning all those beams will be challenging, can't wait to see it. :)

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CDBEAM777

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Thanx Adam...THIS is surly my most complicated build to date !!! Alignment is just going to be a real TREAT !!! And yes...we are using special cut Front Surface mirror segments to form the final array of bounce mirror's. We have a company that will grind the modified flat facet Axicon but have decided to pursue a POC with discrete FS mirror segments. EPIC BUILD !!
 

RedCowboy

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I was thinking about a host with two beams and how they would appear to run together as the beams diverged if you put the bars horizontal, then I thought about using 2 of these 3 mode drivers I found for 4 dollars each and they always step through the same but the strobe is slightly different which gives a near effect.
This is a test bed, will put in a host later.

As one strobe rate catches up to the other and then gets 180 out, at 180 out it appears to shimmy, looks better live of course.

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YT Video is unavailable for some reason.
 
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RedCowboy

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I know a knife edge array will be the way to go, when I get enough 7A75's, HR reflectors and c-lens pairs, one for each beam then I plan to build one in a nice thick aluminum box......but this is fun and I am able to get really good far field convergence by adjusting the lens in the lens barrel to module thread slack under my lens locks. This is just a prototype, a finished build would be cleaned up/enclosed.

There are nubm05's from my block, pretty strong @ 3.5A doing 5W w/G2 and 4W w/3E .....I would use 7A75's in a finished build, yes I will add 2 more beams soon, just having fun.

The paper tubes hide any lens flair giving me clean looking beams, my holes are so close that only 1 roll of paper will fit between modules.

Because the spot/bar becomes wider than the spacing between my modules the beams appear to run together from about 20 meters to infinity in a bar shaped spot just like we see with a single beam in the far field.

It's raining and that's a rain drop seen in the left beam.

( YT video no longer available )

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RedCowboy

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Thinking about making a quad beam HH.......it could have the lasers rotated so the beams spot/bar overlap making an X that's the size of 2 bars crossed.....well only 1 bar wide or tall as top left and bottom right overlap completly as do top right and bottom left.
This would look good with 4 x nugm03 @ about 2A each, could be powered with 2 x 26650 or a pair of 21700 and mount the diodes to an aluminum disc ( flat of backing plates bonded to a disc with pin holes ) then drill and tap another disc for M9x0.5 threaded lens barrels......this is actually a better way to start really true, final adj. via. lens barrel thread slack and a retainer for each lens.

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Alaskan

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I thought about doing that with two diodes, but using four that way never occurred to me. Would love to see it.

Regarding the gball lens, I saw a post you made some time back, prob. years, where you were comparing the gball focus of several NUGM03 diodes. If I remember correctly, some were well collimated, some a bit off. Can you refresh my memory or point at that thread? I've been looking for it.

I am interested in how many were at infinity focus, and for the ones which weren't, which way and how far out of focus they were.
 

RedCowboy

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I have some nubm05's and nugm03's that are pretty much infinity focused via. the factory GBall, but the FL and spot width is not as good as when using a G8 and for c-lens correction the G2 is superior, I really haven't found much use for even a well focused GBall, my early GBall observations were a bit.....optimistic.

What were you thinking about doing ?

Knife edging is the way to go and you would want to either use a G2 and c-lens pair on each beam before the mirrors or use a G8 or similar, the GBall produces a much wider spot/bar at distance than the G8 even when well focused.

If you look at NDG7475 diodes or ndb7875's or ndb7a75's with G8 lenses focused to infinity the far field spot is a bar --- but the near field inches away from your infinity focused G8 lens is a vertical bar that becomes a horizontal bar far field. Knife edging 6 beams lllll all aligned to overlap at your max target range of say 50 feet or you can use infinity but you can leave your knife edge array with 5 beams knife edged being no wider than 8mm total and terminating all on top of each other no wider than a single normal spot/bar.

Just focus a ndg7475 or ndb7875 to infinity and burn a mark on a piece of cardboard ( or look at it through laser safety glasses ) just a few inches away with the far field orientation so that the bar will be horizontal.......you will see a small vertical bar a few mm tall and only about 1.5mm wide, you set up a row of beams and knife edge those vertical bars so they all overlap at infinity or your max target range and you will have a nice beam that you can run through a beam expander for even better effect.

If you want to get fancy you can knife edge several rows of knife edged beams just like the commercial arrays, you can end up with 6 rows of 6 beams.....36 beams total.....say 7875's each doing 3W so 108 watts minus losses so a 100 watt laser array that ends in a spot the size of a single diode/beam......note that not all front surface mirrors are the same, some I have found have more loss and all optics and mirrors works best when clean, it makes a big difference, I like the Zeiss lens wipes.....If you want it square maybe 3 rows of 8 as the starting spot/bar is about 5mm x 1.5mm for a 75 watt array, whatever you like.......Actually I just checked a ndg700 with DTR G8 and its 1.75mm wide x 5mm tall a few inches from the infinity focused G8.

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RedCowboy

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Started playing with knife edging to test some mirrors I have collected, you really need good front surface AR coated mirrors and they need to be clean or they will rob power, these type I have scavenged work well and can be cut down, I use UV curing glue to bond mirrors and optics which works well and in only seconds.

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RedCowboy

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Something I meant to add is I was drilling out the chrome module ends to use as retainers but I have found that drilling out the ends of the little thumb wheels and running a M9x0.5 tap through them make much better lens retainers so you can lock down infinity focus and you can adjust the lens barrel within the thread slack, gently snug the retainer and you can slide the lens up/down-left/right within the module end then tighten it and add a drop of glue if preferred, this actually works for truing up alignment in some cases where adjustability isn't otherwise built in, also you can easily use a drop of UV glue with these to make sure your infinity focus stays put if doing an enclosed build/c-lens corrected build or other.

Note I find it works best to drill with about a 1/2 inch bit and drill enough so that you leave a crown like the two on the right, either way make sure to run a tap through.

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These work well for locking down a nice infinity focus when using a G8 lens and you typically have room for an un-drilled thumb wheel after.
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RedCowboy

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I can't believe I waited so long to start playing with knife edging, this is the way to go, 4 x 7A75 w/ G8 lenses makes a nice knife edged 20w beam, now to miniaturize and fit a beam expander..... maybe do 3 rows of 4 for a nice 60w beam, I sure do love the single element G8.

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icecruncher

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Something I meant to add is I was drilling out the chrome module ends to use as retainers but I have found that drilling out the ends of the little thumb wheels and running a M9x0.5 tap through them make much better lens retainers so you can lock down infinity focus and you can adjust the lens barrel within the thread slack, gently snug the retainer and you can slide the lens up/down-left/right within the module end then tighten it and add a drop of glue if preferred, this actually works for truing up alignment in some cases where adjustability isn't otherwise built in, also you can easily use a drop of UV glue with these to make sure your infinity focus stays put if doing an enclosed build/c-lens corrected build or other.

Note I find it works best to drill with about a 1/2 inch bit and drill enough so that you leave a crown like the two on the right, either way make sure to run a tap through.

View attachment 73298

These work well for locking down a nice infinity focus when using a G8 lens and you typically have room for an un-drilled thumb wheel after.
View attachment 73299
thank you for awesome suggestion!
 

RedCowboy

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It is fun, as the beams transition from vertical bars at the mirrors to a horizontal bar at the backstop ( the size of just 1 normal beam spot/bar which is about a 2cm long line @ 5 meters ) it's a real fire maker in the middle, a big beam expander would work well, now I want to come up with a compact design that also has enough adjustability built in to keep it fun and enough material to yield at least a few minutes runtime as far as heat, that and I would like to use a lot more of a diode with better divergence, I've kinda of been waiting for a new diode with great divergence and at least a couple of watts output, something like the GH04W10A2GC maybe or hopefully we will see better/stronger 405's for the LEP lighting industry, off road lights, industrial search light , ect....I could use cylindrical correction on each beam...but that's a lot too do, plus expensive, a better diode that's mass produced will be the ticket.
 
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Unown (WILD)

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What about those cylindrical lenses that are extra long? I've seen those used in the past. They were tall enough to allow two diodes for one set. Maybe they make ones that are even longer for 3+ outputs?
 

RedCowboy

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It's a nice idea, but you can't correct multiple beams side by side all at once as each beam is diverging, you would correct the center beam but the ones beside it would skew, c-lens alignment is really critical, I could c-lens correct each beam before the mirrors, but I'm a cheapskate, otherwise I would do it, still might someday if better diodes don't come soon enough.....Also if c-lens correcting before the mirrors then each beam would need to be rotated 90 degrees in order to stack the beams, or each beam could be elevated by one beam width so as to stack from top to bottom rather that side to side, this is because after c-lens correcting this MM beam it exits the convex cyl lens as a flat ribbon and stays a flat ribbon with much improved divergence.

Normally with just a primary lens ( G8, 3E, G2 ) this multi mode beam itself transitions from a vertical I to a horizontal _ over about 8 feet, you can set up your own test with a multi mode blue ( focused to infinity ) and use a piece of cardboard to walk along the beam and see how it changes shape as the fast axis diverges so much more aggressively, or point it at a wall and walk backwards, carefully and while wearing the correct laser safety glasses so you can see the spot/bar.
 
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