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DIY Beam Expander.

Glutton

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Ok, I have a -9(9mm diameter) lens and a +72(18mm diameter) lens on the way.

I am going to try to make an 8x expander out of this. I will keep posted on my progress.

I also did some tests with my 50mm lens making a 20x expander and I will post about that when I get time.

Krutz, How did your rifle scope come along?
 



Krutz

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i started looking at surplusshed for suitable lens-combinations, but no luck (for a green-only expander). so i changed my plan, now i want to try to make a "zoomable" expander, adjustable for green 1mm beams and diodes 5mm beams. there are two moveable lens-mounts in the scope, moving with different "speed" when zooming.

too complicated and timeconsuming for me now, but i will have a look again next year once i have "technical optics" courses. ..or earlier, should i find time and lose my patience about it! :)

good luck, report your findings, yes?

manuel
 

Glutton

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Krutz, You could use a non-zoom expander and just unfocus your diode laser to get the beam to fit your exit lens.

Just design the expander for green beam specs, then when you want to use your diode laser all you need to do is focus it to a positive FL until it fits your expander specs.

Update:
I got my lenses Tuesday but I accidentally ordered the wrong PCX(35mm FL) waste of 30 dollars! I got the correct lens on the way now (70mm FL).

On a side note, the 9mm mounting was extremely easy with a few bike parts I had. I did mess around with the 18mm lens and found that working with it is very difficult. So I ordered a 20mm one which will be easier to mount.
 

tsteele93

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Krutz, You could use a non-zoom expander and just unfocus your diode laser to get the beam to fit your exit lens.

Just design the expander for green beam specs, then when you want to use your diode laser all you need to do is focus it to a positive FL until it fits your expander specs.

Update:
I got my lenses Tuesday but I accidentally ordered the wrong PCX(35mm FL) waste of 30 dollars! I got the correct lens on the way now (70mm FL).

On a side note, the 9mm mounting was extremely easy with a few bike parts I had. I did mess around with the 18mm lens and found that working with it is very difficult. So I ordered a 20mm one which will be easier to mount.
So did this project ever come to fruition?
 

Alaskan

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I'm getting parts together for a Galilean beam expander (as above) using a concave negative lens and a large PCX or plano-convex lens but there is one thing I don't quite understand which is the exact placement of the negative lens. Someone please check me on this:

My understanding is that a negative lens has a focal point for a virtual image in front of the lens (towards and in between itself and the PCX lens). From the above diagram I found on the Newport web site, it appears I just add the two focal points together and that is the distance between the two lenses for optimum magnification. Is it that simple? Maybe another way of doing this is to place the negative lens far enough away from the PCX or output lens so that the larger lens is neither under or over illuminated by the laser light diverging through the first lens, making sure the available light does not over or under shoot its diameter? If this is the case, no need to measure if you do it that way, you would just need to know the approximate focal lengths and move the lens around until you had it right.

I imagine you could under illuminate the output lens, or have the spot of light 1/2 the size of the lens and it would work fine, just that you would not have near the possible expansion that you could otherwise have. The above diagram does not show most of the laser light falling upon the entire surface of the PCX lens, if the spot should be close to the diameter of that lens for maximum expansion, then this drawing is somewhat misleading to me.

If all of my assumptions are correct, a zoom beam expander of this type is simply a negative lens which can move in or out enough so that the PCX lens (with a much longer focal length) is entirely illuminated (or has a spot of light upon its surface big enough to cover the whole lens) and when wanting a tighter or smaller output beam, the negative lens is pulled back so the spot of light only partially covers it and thus less magnification of the beam size.

If I'm wrong about any of this someone please show me the light, so to speak :) THANKS for reading my post/questions!
 
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steve001

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I'm getting parts together for a Galilean beam expander (above) using a concave negative lens and a large PCX or plano-convex lens but there is one thing I don't quite understand which is the exact placement of the negative lens. Someone please check me on this:

My understanding is that a negative lens has a focal point for a virtual image in front of the lens (towards and in between itself and the PCX lens). From the above diagram I found on the Newport web site, it appears I just add the two focal points together and that is the distance between the two lenses for optimum magnification. Is it that simple? Maybe another way of doing this is to place the negative lens far enough away from the PCX or output lens so that the larger lens is neither under or over illuminated by the laser light diverging through the first lens, making sure the available light does not over or under shoot its diameter? If this is the case, no need to measure if you do it that way, you would just need to know the approximate focal lengths and move the lens around until you had it right.

I imagine you could under illuminate the output lens, or have the spot of light 1/2 the size of the lens and it would work fine, just that you would not have near the possible expansion that you could otherwise have. The above diagram does not show most of the laser light falling upon the entire surface of the PCX lens, if the spot should be close to the diameter of that lens for maximum expansion, then this drawing is somewhat misleading to me.

If all of my assumptions are correct, a zoom beam expander of this type is simply a negative lens which can move in or out enough so that the PCX lens (with a much longer focal length) is entirely illuminated (or has a spot of light upon its surface big enough to cover the whole lens) and when wanting a tighter or smaller output beam, the negative lens is pulled back so the spot of light only partially covers it and thus less magnification of the beam size.

If I'm wrong about any of this someone please show me the light, so to speak :) THANKS for reading my post/questions!
The correct distance for least divergence in this type of expander will be less than the focal length of the pcx lens.

FYI. in a Keplarian type expander the correct placement of the pcx lens is the focal lengths added together.
 

Alaskan

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Thanks, appreciate the feed back on this.
 

Argz

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Hello everyone,

I'm trying to build my own beam expander.

I have 1mm 532nm laser pointer and i want to expand beam diameter to 60mm.



I bought lenses on surplusshed.com but i didn't find any big FL to reduce lenth of my setup (about 10cm long).
If someone got some advise on my project ?

If i increased the laser beam, would i reduce power then reduce classification ? I want to build a 2M laser to be safe.

Do you have any formulas about power and safety issues ?

I hope the post isnt outdated :)
Thanks
(sorry for my english)
 
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diachi

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Hello everyone,

I'm trying to build my own beam expander.

I have 1mm 532nm laser pointer and i want to expand beam diameter to 60mm.



I bought lenses on surplusshed.com but i didn't find any big FL to reduce lenth of my setup (about 10cm long).
If someone got some advise on my project ?

If i increase the laser beam, did i reduce power then reduce classification ? I want to build a 2M laser to be safe.

Do you have any formulas about power and safety issues ?

I hope the post isnt outdated :)
Thanks
(sorry for my english)

So you want an expansion factor of 60x?

To have a refractive beam expander 10cm long with a magnification of 60x is going to be impractical due to the short focal length required for your objective lens - it'd need to be <2mm FL by my calculations.

Look at this document, do the calculations for yourself: http://assets.newport.com/webdocuments-en/images/how_to_build_a_beam_expander_5.pdf

If you make the beam wider the overall power is the same and thus the class is the same. The power density is lower, but the power remains the same. Power and safety is a complicated subject, and it's not something I'd feel comfortable advising on past "Don't put the beam in anyone or anythings eyes". The subject would require far more than a brief forum post. If you'll be exposing eyes, contact a trained Laser Safety Officer and have evaluate the situation for you.
 
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RedCowboy

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I had a video but can't find it where I used a NUBM06 ( with the GBall intact ) and with this simple double concave and double convex to expand the beam then zoom it to a point 15 feet away. The hot glue I stuck to smooth aluminum then broke free so it's a footing for the lenses, they are moveable and just held by gravity.

If you calculate your lenses right you can avoid those massive wings when you zoom in, such as the sanwu 3X, it is well calculated for our diodes, I would like a bigger one just like it only 10X or 20X

Let me know if someone wants to build them, I will buy some.

 

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diachi

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I had a video but can't find it where I used a NUBM06 with this simple double concave and double convex to expand the beam then zoom it to a point 15 feet away. The hot glue I stuck to smooth aluminum then broke free so it's a footing for the lenses, they are moveable and just held by gravity.

If you calculate your lenses right you can avoid those massive wings when you zoom in, such as the sanwu 3X, it is well calculated for our diodes, I would like a bigger one just like it only 10X or 20X

Let me know if someone wants to build them, I will buy some.


What expansion factor was that setup?
 

RedCowboy

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I was getting about a 50 to 75% or so reduction in the burning bar size, you can see the beam diameter in this clip but not the bar, just the splash, I had to re upload off my cam, I have another showing the shrunken burning bar, the splash looks round, but the little burning bar is just drowned out in this clip, I will upload another in a minute and add it, but these are just misc. lenses I was playing with, with the right lenses we should get 5-7 X out of that diameter with the 06 output beam profile.



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This pic below is straight out of the 06 GBall that came on my diode, some may be different or may not, 1 person told me his 07 GBall printed different than mine.

But this is before the simple expedient expander test from the same 15 feet, same unit, same diode.

p.s. It's 14 feet 2 inches to the edge of the washing machine so I set back a foot or so, yes the lenses are forward but it's within the range.

 

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Bradford717

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I'm brainstorming myself on this and considering setting a specific focus for mine using lens and a female threaded tube with male threading on the outside. It might be easier to build and set each lens as I thread them into my tube... but what to drop my tube in 12 mm heatsink hmm
 

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thebigfotos

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Hello all,

I am also trying to build my own beam expander for my laser systems. I have one with 640nm and another with 473 nm. I want the power density of between 50 and 100mw/cm2 at the point of exposure. The beam diameter for 640nm is 2mm and for 473 is 5mm. Right now the power density if somewhere around 3W/cm2 and I think beam can help reduce the power density. Can you please help me with this?
Thanks all.
 




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