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Funny story of PBS combining of two 9mm Ushio reds

Light superglue

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CDBEAM reported that the divergence of this 9mm red LD is awful and yes it is but since I have them I decided to combine (Alaskan, you asked someone to try this, here I am).

First subject was cooling: These red things like cold to perform and deadshadow has made a portable with TEC cooled P73 earlier. But TEC consumes power and most of all - produces heat, so to avoid fans and many batteries for TEC(s) I just decided to experiment with ice cooling like any chemist would.

So I purchased an aluminium box with dimentions to fit two 5cm ice cubes (common bar size for drinks) and isolated its sides with armaflex foam. To use the lid (only 2mm thick but this is OK) as baseplate for combining.

With 2 ice cubes in the box an LSP mount with Ushio inside kept cold at max 15-17ºC at 1.5A current - so during continous beaming there should be no moisture condensation on G-2 collimator lens.

Then I added 2nd mount with LD connected in series, PBS and WP. The problem, however, was now moisture condensation on optics which do not have any "heating unit" like LD inside the brass mount. So I inserted 4mm cork board under optic mounts and it worked to delay moisture condensation significantly except for PBS cube mount where the screw position was not symmetrical and cork sheet under mount lead to instability. But OK with mecanics for now.

Then I adjusted beams directions to have 2 lines as a horizontal cross - can anyone say how to rotate LDs in these mounts in order to make spot lines really parallel???

Added OL 6x pair of cylindricals to make lines 6 times shorter and noticed that there was no power at all in the beam!
The reason was that I made my setup as I have always done for blue NUBM44 LDs and it looks like red crystals are differently oriented than blue ones!!!
So the spots on wall I saw are just light passing through internal PBS mirror from which it should be reflected and the opposite.

The setup has to be rebuilt to have WP in the path of the straight beam and not the beam coming from the side!

Remarkably funny is that earlier I made the same (or oppositely same) mistake at design of the setup (now happily finished and working) to combine 4 blue LDs into a 16-20W single beam!
https://laserpointerforums.com/threads/need-reverse-pbs-for-20w-laser-tank-gun-prototype-do-they-exist.100803/
 

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Light superglue

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To continue the story:

I changed the design drilling more holes in the Al box lid. This time position of the parts is so that WP is in the path of the straight beam and not the beam coming from the side.

Also replaced Lasertack PBS mount by a more expensive (60usd worth) Newport MM-050 mount - this one by construction should be more stable on "cork baseplate" because of symmetrically positioned bottom mount hole. In addition, it allows to routinely adjust the PBS orientation once the 2nd beam gets out of the overlapping with the 1st one (because cork deforms with time or such).

Now testing at 0.3A - after 6x expansion the lines on the wall 5m away are a liitle more than 2cm long. It sems to me that 12x expansion would be better - it would make the beam 12mm wide out of the cylndricals but less diverging far away.

And if I had a scanner with 10x20mm mirror - this could do bright figures on the wall (or sky?) once at full 2x2W power...

Hak, if you read this - could there be a scanner for this type of "custom made module"? (or just a rotating mirror with a motor to make circles)
 

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hakzaw1

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And if I had a scanner with 10x20mm mirror - this could do bright figures on the wall (or sky?) once at full 2x2W power...

Hak, if you read this - could there be a scanner for this type of "custom made module"? (or just a rotating mirror with a motor to make circles)
Just now saw your reply..
Not sure and 'regular' Galvo scanners have mirrors that big( at least those I have seen..

--steppers use big mirrors. and for funky beam shows that are useful as Sat. PJs --a show with many PJs often has Satilite projectors. for 'fill'
BUT for other uses like abstracts-animations- etc Stepper are a big FAIL.
VERY glad you are still working this project.. It has changed somewhat my plan for the 4 modules (less driver)
I bought from'Platinum'.& they came with LASORBS .. in Dave's brass mounts.
Might do a quad or myb two duals.. Jonathon sold because of poor beam..
I am not that picky..
Let me take a good look at your pics and I will add whatever I have to this.
all new to me so..wish I knew more..

more pics Vlad!!!
 

hakzaw1

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reserved for project pics.
My reds. one of. 700 mW20170922_184108  RED 700  resized.jpg
 

Light superglue

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Here are more pics for you, Hak!

My old LPM has "zero line" at -0.15W, so you can see that the output at 2.5A reaches 4.24+0.15= 4.39W when LDs are cold but quickly falls to 4W after some warming up. Well, ice-box is a good cooler but not perfect because the lid T cannot be under 0ºC. Anyway it allows me not to burn the LDs while experimenting. Maybe I should try mixing ice with salt to make the box colder?
The width of each beam out of the 6x cylindricals is 8mm (I have 10mm wide beam here because could not combine 2 beams very well) - so at 5m it becomes 22-25mm wide what is not good divergence. But I was surprised that when I directed it onto a black polystryrene sheet it started to melt a hole very quickly. This is the mark after less than half a minute. Indeed the power density in this red spot might be close to non-corrected line from NUBM08.

As I already said it would be better to expand this beam 12x but then it would only fit into wide cylindricals from CDbeam. BTW he is doing the 2nd run of the Group Buy now...
Also Knife-Edging many LDs under each other would be interesting to make a square red superbeam but this is not easy to build.

This PS sheet I put it on the wall as beam stopper to make less light spreaded in the room and take better picture in the night (at day I could not take picture of the beam because it is not very bright) but it was not a good idea taking into account that I have smoke detectors installed here:)

I held this device on at 5.1V, 2.0A with 2 chunks of ice in the box and after 10 min the mount T stabilised at 24ºC. What is very close to rt and LDs might not be super efficient with this kind of "cooling" but it is fun for me to make strange things... Maybe ice-salt mix would indeed be worth a try!
 

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logsquared

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Looks like your positive cylinder is about 12mm wide. If you want a little better divergence try moving the beam expander further from the diodes. Keep moving until the output is almost as wide as the lens. Then re-focus the beam expander. Should give 20-30 percent better divergence.
 

Light superglue

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Hi logsquared,

So you want to say that the divergence only depends on the final wideness (section) of the beam no matter how far away the Beam Expander is apart from the emitter?

I had an impression (maybe wrong) that most of the builds tried to position the BE as close as possible to the laser module.
Was it just for space reasons and not for the better divergence of the beam?
 




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