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OPT Lasers Cylindric lenses - NUBM44 beam correction tests

RedCowboy

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It looks like about 1/4 of an inch at 50 feet and 1/2 inch at 100 feet.
 
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Accutronitis

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Smaller than I can see from 50 feet because the light is so intense I can see the real shape through my safety glasses until a point when I zoom in tight until it goes back to looking round and then I just adjust back and forth in that small zone until it burns the best looking at the volume of smoke. It looks like about 1/8 of an inch but as a round spot at 50 feet and 1/4 inch at 100 feet, the holes I punch in leaves at 100 feet look like about 1/4 inch.

I think it's time for more power because even focused needle thin at 1 inch there are limits, 7 watts wont cut through a soup can or cut through a 1/2 inch branch of a bush, also distance through air seems to absorb some energy.

At 15 feet a 44 with 3 element and 3X makes a line like a large flathead screwdriver, with the addition of the 6X pair and trade the 3 element for a G2 and at 15 feet it just looks like a small round spot 1/8 of an inch because I can't see the real shape even with OD+6 glasses, I could try a 3 second burn at 15 feet and snap a pic, gibe me a couple minutes.
The beam using this new setup comes out of the beam expander is around 12mm x 14mm but I'm still testing different cyl lens spacing.....
 

Accutronitis

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Here's mine at 50 feet, I could have gotten it a little tighter but I didn't want to focus it and run to the spot to see what size it was and repeat more than a few times....



50 feet after 20 seconds.......



15 Feet 1/2 second burns, Turning the laser on & off the dot moved a little....



I think I'm get pretty similar results as your, What do you think Cowboy ?
 

RedCowboy

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The plywood is 81 feet in distance to the back of my house and I am in a 2nd story window but that only adds a very little so we can just call it 80 feet.

The lasers has a NUBM44 with a G2 with a 6X cyl pair topped off with a 3X BE.


Very cool ACC, I think we are both getting good results, the difference between edge clipping and the slower diverging axis catching up as it's not compressed via anamorphic lensing ( cylindrically ) is the tell-tell rounded spot edges, still I think a bigger beam expander will be most productive.

I know we both enjoy wood burning art so maybe another option would be more productive, these repurposed diodes are fun but a better tool should have better starting beam specs, still we will no doubt fight on to hone these MM diodes with their challenges.


Here it is from the 81 foot end.

-----edit-----

I'm enthusiastic about this expander, you want to aim for 80% I think but if it works man it works, see if you get wings or not, even if you do you can cheat into the wings a little to get a hotter spot, I have a bunch of optics too and as I understand it uncoated optics waste 5% but again it will be worth it, if we could order about a 3 inch wide objective or whatever fits tight into 3 inch PVC then use a cap and cut in for the concave....actually if we can find inner diameter and outer diameter in a large size to slip over and slide that's snug it should be good and dimensionally stable as it will be strong, and a real working 10X would be awesome on top of our radical axis correction.


I would like to make a 12 watt HH from 2 x NUBM44's combined via PBS cube with a wave plate and as big of an expander as possible.
The 2 diode block fits into the flashlight housing and the BE cover slips over the optics block.



 

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Cenobite9

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I received my 6x pair from Opt Lasers. Using the 6x pair by itself gave me a decent spot from a NUBM44. I tried combining a 6x with a 4x from LSP but 24x was a bit too much. I could not get a spot regardless of lens position. Just an ugly line and lots of splash. I might purchase a 3x from Opt Lasers so I can try 18x and 12x combinations. I have a testing rig built out of Legos that allows me to move the lenses back and forth while the laser is on.
 

paul1598419

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I believe you will find that when adding a 4X to a 6X cylindrical lens you get 10X, not the multiple of the two. :D
 

RedCowboy

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Lens alignment is critical, the added concave needs to be carefully aligned in 3D that is rotation, tilt as well as left to right beam path aligned, I would set each lens into place 1 at a time ( Hot/running with wavelength specific laser safety glasses on ) centering on a distant point ( 5 meters ) but you only add the concave from the 2nd pair, not the convex, just keep the original convex.

I have read that placing the extra concave flat to flat is easier, but I always set mine up running with the proper safety glasses on that attenuate the wavelength I am working with.

The bottom of your added concave must be clean and free of any debris that could throw off the alignment, the perpendicular of the flat bottom to the working face of the lens could be off on your added lens, you could try rotating it a little bit.

Unlike this pic I would rather use lenses all from the same maker.

 
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Accutronitis

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I finally have some focused to infinity numbers using my first home made beam expander and they go as follows...

focused to infinity at 175 feet or 70 paces the fast axis was 40mm and the slow axis was 18mm.

focused to infinity at zero feet it's 14mm fast axis 10.3mm slow axis.
 

Alaskan

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That's close to a half mRad, I still don't believe such is possible with that small of an expander lens, not when using that diode. If I am wrong good, I want that kind of divergence with such a small diameter lens.
 
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Accutronitis

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I can tell you I'm using a double concave with one side more concaved than the other (I think) and the convex lens is a double lens of some sort which has one lens glued to another, But I checked and re checked and the numbers are always the same ?

Just to make sure I understand "focused to infinity" correctly please explain how this is done ?
 
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Alaskan

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For myself, it's a judgment call when my laser is focused to infinity, I don't know for certain when my beam is focused to infinity, but I believe I am close when I get the focus so the beam is neither focused to a point, or diverging beyond it's normal divergence. I am sure there are better ways to say it and invite others to please put this in better word for me.

Perfectly collimated light is sometimes said to be focused at infinity. "Infinite focus" does not mean every point in the beam is focused to the smallest possible point. It means that the beam is focused so it maintains the minimum diameter at a distance. In other words, focusing your laser "at infinity" means focusing the laser for the lowest possible divergence. You just want to beam to be a tight tube (or rectangle of light for the NUBM44) for as far as possible without becoming smaller, or expanding more than the natural divergence of the diode and lens combination you are using.

Edit: more here - http://laserpointerforums.com/f38/how-infinite-focus-68808.html - I cut and paste some of my explanation from that thread.

Later edit: There is one other way, if you have a plano convex cylinder lens, shoot your laser into the flat side of the lens and adjust the focus so the line it produces at a distance, the further the better, is as fine as possible. When the line is as thin as you can get it, the pointer is at or very close to infinity focus.
 
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RedCowboy

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Hey, that's great, looks like you got all the energy downrange and made a good improvement on a very divergent diode. Now we need some bigger beam expanders and bigger diodes and stronger batteries and ........ but I digress, good work. :gj:
 

Accutronitis

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I'll have a much bigger beam expander after the first of the month thanks to our Mr ElectricPlasma and his 3D printer !



Which will house these two lenses.......



With the larger of the two lenses being 48mm across........





I received my 6x pair from Opt Lasers. Using the 6x pair by itself gave me a decent spot from a NUBM44. I tried combining a 6x with a 4x from LSP but 24x was a bit too much. I could not get a spot regardless of lens position. Just an ugly line and lots of splash. I might purchase a 3x from Opt Lasers so I can try 18x and 12x combinations. I have a testing rig built out of Legos that allows me to move the lenses back and forth while the laser is on.
You could not get a spot regardless of lens position, At what distance ?
 
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RedCowboy

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That sounds good because I really want to source some lenses, rather choose the right ones and have some BE's built, I know some others would like to have them as well.
 




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