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DIY Beam Expander.

Glutton

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EDIT: This thread is now an on-going tutorial for a DIY beam expander.
 
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steve001

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Re: dioptika beam expander?

It might be cheaper to have one of the members with a metal lathe machine a beam expander housing for you.
 

HIMNL9

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Re: dioptika beam expander?

^ If you find someone that can do it, i can draw the plans and measures of a prototype (for free, ofcourse) ..... the most simple scheme requires two identical lenses, both AR coated (preferably for the wavelenght you want to use :p), with at least one plane face, and being a prototype, can start with a FL of 15 to 20 mm, for keep it not too much long (a FL of 40 mm can be better, but need a tube holder of at least the double, and becomes excessive)

I think that with two lenses of 10 to 15 mm diameter and 15 mm FL, can keep the whole assembly not more long than 40 mm (plus the connecting flange, ofcourse)

More compact units can be built using a positive and a negative lens, but needs to find a couple of lenses with the same identical curvature, and when is matter of positive / negative couples, this becomes usually ordered on specific draws to the lens producers ..... instead, is much more easy find stocks of positive lenses all identical, already on the market (or in surplus stores, sometimes :p)

BTW, the expanders works on a beam already focused to the infinite, ofcourse, so if you want to start from a different source, like as example an aixiz module, need to draw it in a different way, for have one part that focus the beam and one that act as expander (but this can be done using an already-mounted glass lens from the aixiz ..... only need an external guide tube for the stability)

Edit: before someone start to shoot me, left me clarify: i'm ofcourse speaking about NORMAL beam expanders, like the ones linked in the post, and that these companies sell for portable lasers ..... one fixed part, and one focusing moving part ..... if you're speaking about special variable-geometry collimators, like the ones for cutting machines or astronomy, i still can draw one for you, if you want, but doubt that it can be built at home, also with machines ..... considering that the more simple that i know have 3 moving tubes plus one fixed (main holder), holding 7 custom lenses in groups 1-3-2-1, that are moving interdipendent one inside the other, each one drived from the precedent, with logarithmic spiral guides :p :D
 
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Glutton

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Re: dioptika beam expander?

hmm I will ask around, I think I might be able to get one of the fabricators at my work to do the housing or even try myself as we have a good machine shop there. Any of you know of a good place to get the lenses.

Also I pulled the optics out of an old video recorder which looks like it expands the beam about 10-15x. The only problem is that lenses don't move far enough apart to focus it so it just gets expanded then spreads rapidly.

HIMNL9 do you know if I can use these lenses to do the job? It uses four lenses (2 of which are mobile on sleds) but I cant tell what type of they are because I have not pulled it apart yet. Got any guesses?
 

Krutz

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Re: dioptika beam expander?

..if anyone offered a (self-build) halfway decent beamexpander, i bet it would sell quick!
it cant be that hard.. two lenses, two tubes, threads.. see how cheaply binoculars are produced, with all the mechanics inside..

make a poll in groupbuys? :)

oh, and i no fkn way i can see a pricetag of 500$ justified for anything like this, as it seems to be "normal"!

manuel
 

Krutz

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Re: dioptika beam expander?

..and what the heck is it with your avatar, glutton?!? still cant decide if that is possibly real!
there was no such hypnotic avatar since the bouncing, uhm, nevermind :)

manuel
 

HIMNL9

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Re: dioptika beam expander?

Well, first, there is a consideration to do, about expanders ..... theorically, you can build an expander smaller as the pen-size host of a pen type laser, but, apart the difficult to work with very small metal parts with high precision and very fine threads, more you keep the lenses small, more increase the possible distortion and decrease the possibility to "expand" linearly the beam.

Said this, admitting to keep it not excessively small (cause, without specific tools, i guess isn't too easy, have to machine parts with small lens holders and moving parts), i think any lens that is coated for the wavelenght you want (or broadband), can be ok ..... as example, if for you work with small parts is not a problem, can make a trial with a pair of the lenses that are in the PHR units, not the front lens, the one under the correction lcd panel .... they have a diameter of 6,5mm, and a focal lenght of 20 / 25mm, so probably you can keep all the unit as compact as 14 or 15mm diameter, and 50 to 60 mm of lenght ..... the only problem i see with them, is that the AR coating is not broadband, probably is a multilayer optimized for BR and red/IR, don't know how it work with green (also, are acrylate, don't works good with high powers).

If you want to use it with an aixiz mount, considerate also other 10 to 15 mm of lenght, for the glass aixiz lens, for the focusing part (as far as i know, there is no expanders that can work with a unfocused beam, except the multi-elements ones) ..... for a permanent use with an aixiz unit, it need also an external tube for guide and reinforcement, but for some tests, it's not indispensable.

Or, for better results, need some glass lenses from suppliers or surplus ..... give me some time for check some sites (and for lunch, now :p ;))
 

Krutz

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Re: dioptika beam expander?

as an even simpler testsetup, how about using regular collimating lenses and either some aixiz housings, or a tube with 9x0.5mm threads tapped into? simple setup, easy adjusting of the lens' position. lenses are available. main problem would be the tiny aperture, 5mm, which would be the maximum beamsize when widened. no use for diode lasers, they already have that diameter. but perhaps worth it for a green?

manuel
 

steve001

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Re: dioptika beam expander?

50$ can buy you one of these and base you new design around it. It's a two lens Galilean beam expander system This unit can be easily disassembled for inspection without damage

Laser Accessories- Optics


There are 3 parts to this device from right to left
An inside threaded tube. length ~4cm [ grooved part ]
A threaded part that screws into the long tube
A small internal threaded lens mount plate for the diverging lens not visible


The diverging lens is close to 6mm in diameter and the collimating lens is 15mm in diameter.
the only part that really needs to be replaced it the long tube. It should have a larger inside diameter to except larger diameter positive collimating lenses. And there should also be an internal threaded lens mount for this lens.
With this basic design a variety of tube lengths and diameters could be easily machined for increasing beam expander powers beyond 10x.

For lenses wide selection that are top notch off the shelf AR coated for various wavelengths
Optics, Imaging, and Photonics Technology - Edmund Optics
 

HIMNL9

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Re: dioptika beam expander?

The problem, with the commercial ones, is that the lens are different diameters, so are made on request with custom curvatures ..... in an inverting (or galileian, if you prefer) expander, the two lenses must have the same identical FL, also if different in diameter, and this is the wrong part, trying to build an unit at hobbyst level (cannot ask for custom lenses and hope they are cheap :p)

The better choice, for hobbysts, is start with two identical lenses also in diameters, also if this sacrificate a bit the mechanical aspect ..... as example, i found these ones:

SIMPSON OPTICAL PCX FIELD LENS 23MM DIA X 40MM FL CTD - Surplus Shed

4$ for AR coated glass lenses, don't look too high, as price :p ..... and with 23mm of diameter, can also be achieved a decent 18 / 20mm of expansion, with tube long enough (but i suppose the more searched use for these things is to shrink the beam, not to expand it, or not ? :D)

Otherwise, need something similar to these ones, with 15 mm FL or similar, for keep it more short (but this increase a bit the distortion)

Then all can be built with a principal tube (holder for all), a front tube threaded (expander moving lens), a rear cap with a threaded border and a threaded hole (threaded border go in the main tube and keep the first lens fixed, threaded hole is for screw in the aixiz glass lens holder .....

like in the schematic draw attached (is a draw made on-the-fly, if you need measures, i need to know diameters and FL of the lenses)


Edit: @ Krutz : the regular collimating lenses have a short FL, and introduces too much distortion ..... can work the same, anyway, for make some experiments ..... i think that, if you use a pair of them, considering their FL and shape, you can achieve some results in fact of better collimatoin with an unit not much more long than 5 or 6 cm (all the assembly)
 

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steve001

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Re: dioptika beam expander?

The problem, with the commercial ones, is that the lens are different diameters, so are made on request with custom curvatures ..... in an inverting (or galileian, if you prefer) expander, the two lenses must have the same identical FL, also if different in diameter, and this is the wrong part, trying to build an unit at hobbyst level (cannot ask for custom lenses and hope they are cheap :p)

The better choice, for hobbysts, is start with two identical lenses also in diameters, also if this sacrificate a bit the mechanical aspect ..... as example, i found these ones:

SIMPSON OPTICAL PCX FIELD LENS 23MM DIA X 40MM FL CTD - Surplus Shed

4$ for AR coated glass lenses, don't look too high, as price :p ..... and with 23mm of diameter, can also be achieved a decent 18 / 20mm of expansion, with tube long enough (but i suppose the more searched use for these things is to shrink the beam, not to expand it, or not ? :D)

Otherwise, need something similar to these ones, with 15 mm FL or similar, for keep it more short (but this increase a bit the distortion)

Then all can be built with a principal tube (holder for all), a front tube threaded (expander moving lens), a rear cap with a threaded border and a threaded hole (threaded border go in the main tube and keep the first lens fixed, threaded hole is for screw in the aixiz glass lens holder .....

like in the schematic draw attached (is a draw made on-the-fly, if you need measures, i need to know diameters and FL of the lenses)


Edit: @ Krutz : the regular collimating lenses have a short FL, and introduces too much distortion ..... can work the same, anyway, for make some experiments ..... i think that, if you use a pair of them, considering their FL and shape, you can achieve some results in fact of better collimatoin with an unit not much more long than 5 or 6 cm (all the assembly)
the two lenses must have the same identical FL
No identical focal lengths lenses won't do a thing.

This person is willing to spend $500-700 US dollars, buying 2 lenses one negative one positive won't break the bank. They can purchase an AR coated -6mm EFL, 6mm dia PCV lens * Antireflection Coated for 425 - 675nm
* Less Than 0.4% Reflectance Per Surface
* Designed for 0* Angle of Incidence
link TECHSPEC® VIS 0° Coated PCV Lenses - Edmund Optics
lens for around $26.50 and a PCX of the proper diameter and desired focal length.
starting around 15mm dia. 40mm EFL for $32.50. Link TECHSPEC® VIS 0° Coated PCX Lenses - Edmund Optics

They can also determine the proper lens diameter by using this applet
gausian beam rev 2.0.xls
All they need to know is the divergence of their laser and the beams diameter. Then input those figures into the top two boxes and the lenses focal lengths into the next 2 boxes. This is just an estimation. Using a -6mm efl lens and assuming that the lasers beam diameter and divergence are 1mm and 1.2 mrd the beams diameter at the collimating lens would be 6.5mm. Divergence 0.18mrd.
Call for free catolog
 

HIMNL9

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Re: dioptika beam expander?

Sorry, steve001, but i think you made a little bit of confusion.

Perhaps you're speaking about a noninverting (or keplerian) expander, that use a positive and a negative (and in some particular configurations, a third positive one as corrector) lenses ..... where instead i was speaking about an inverting (or galileian) expander, that usually use only 2 positive lenses that must be identical curvature (or FL, if you prefer)


(sorry, can't post pics bigger than 800 pixels, script limit)



the keplerian unit is also more difficult to build, at hobby level, cause also in this case, you need an identical curvature, but here you have a positive and a negative lenses, and these are usually matched pairs, built on special requests (more difficult to find at hobby level), and also in these cases, sometimes they need a corrector at the end, cause it's more difficult to compensate distortions from a negative lens.

As example, i tried just for the fun and for see what happens, with 2 of the "middle" lenses from a pair of PHR sleds (identical, ofcourse), using paper tubes as holders (ok, ok, it's not professional, i know, but i'm at work and have nothing better at hand, at the moment :p), and perhaps it work ..... putting it on the top of my old 50mW pen, i can change the beam diameter from half millimeter to 3 or 4 mm (can't go more, the lenses are 6,6mm diameter and the holders are cardboard :D), keeping it more or less the same diameter from 5 cm to a pair of meters (considering the provvisory nature of the assembly, it's not a bad result, after all :))


EDIT: sorry, just forgot to upload second draw :p
 

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Gryphon

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Re: dioptika beam expander?

I can't tell ya how long i've been sitting here looking at you avatar, trying to replicate it with my own two hands :D
 

HIMNL9

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Re: dioptika beam expander?

You don't need two hands for replicate it ..... just put some gasoline on your right hand, then ignite it and stay with no expression til when you got the video long enough .....

Oh, wait, you was speaking about Glutton's one that replicate the skeleton hands lock movement from old Elemental pc game ..... nevermind, then .....

(J/K :D)
 




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