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DIY Beam Expander.

Glutton

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Re: dioptika beam expander?

Update: here are two monoculars I am going to start with. The second one seems kinda long and heavy but I think if I avoid the aixiz attachment it should be ok. Plus with the longer one I should be able to get pretty close to a 20x expansion with a small diameter green. When they get here I will make measurements and then order up some nice edmund lenses.

DealExtreme: $14.99 Focusable Compact 7x18mm Zoom Pocket Monocular

DealExtreme: $22.85 Nikula 7x~21x25 Zoom Monocular
 



Krutz

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Re: dioptika beam expander?

so, did anyone experiment with diy beamexpanders or plain monoculars yet? i have one to four more-or-less broken digicams here which i may take some lenses out for an expander.. no negative lenses, though.

-anyone has an idea how to mount the lenses, so its compact, secure and adjustable? oh, and payable too? :)

-what speaks against using two random positive lenses with different focal length (keplerian telescope)? use one to focus the beam, place the other (larger) lens at its own focal length away from the beams focal point? should result in a collimated beam! depending on the lenses, it will be narrower or wider than the original beam. i cant see any disadvantages from not using two lenses with the same focal length? in fact, then it would be exactly the same beam diameter?

ah well, i guess its impossible to build without fancy machinery (internal threads to adjust the distance between the lenses)

and probably my cams are more worth than ordering single lenses from edmund or surplusshed..

where is the groupbuy for a "standard" diy expander? will do a poll right away.. :)
edit: http://laserpointerforums.com/f55/feeler-diy-beam-expander-44565.html

manuel
 
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Krutz

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Re: dioptika beam expander?

i disassembled a cheap binocular. two lenses, as expected, but has a prismatic "image rotator" too. no surprise, if you think about it. it has some magnification, so i couldnt simply remove it. it will surely absorb its part from the laserpower.. the tube isnt of much use neither..

manuel
 

Glutton

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Re: dioptika beam expander?

Here is my dis-assembly (DOUBLE POSTED/SPAMMED IN 2 THREADS!)

The eye piece is disassembled like this...



^there are 2 lenses that just drop into the holder and are separated by a spacer and held in place by the threaded ring(larger black ring) the lenses are 12.7mm. Once in the holder it screws into the main housing.

Next the front piece...




^This is just a single lens (18mm) held in place the same way as the others, it is dropped into the bigger holder and held in place by a threaded ring then the whole thing screws into the main housing, which looks like this when fully assembled...



^The main housing has an adjustable length of 2 1/2 inches-3 1/4 inches. In the middle of the housing is an optic piece that just flips images (prismatic image rotator?) and has no FL(not pictured) The center piece will be removed and discarded because orientation of the beam wont matter.

Tomorrow if I have time I will check out edmund optics and work on getting the correct FL lenses ordered and get this show on the road.
 
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Glutton

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Re: dioptika beam expander?

Small update,

I plan on using just 2 lenses in this build, and today while tinkering with the eyepiece I noticed that the little spacer fits an aixiz nut perfectly. All I will have to do is glue the aixiz nut into the spacer, drop it in, then set the lens in and screw it all together!!! This is going to be a very simple build all I need to do now is find the right lenses and FLs, then I will have a beam expander that will screw onto the aixiz nut for my own DIY builds.

I will probably order 2 sets of lenses because the aixiz acrylic gives a thick beam but I also have a 405-G-1 that has a very thin beam maybe 1mm? Anybody have any idea of the beam diameter of an acrylic? I think Jayrob just sent FML 3 aixiz lenses to test beam diameters and such, so I will wait for his results. But what about the meredith lens?
 

Krutz

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Re: dioptika beam expander?

standard collimators (like the various aixiz acrylic and glass) all have the same focal length, i think 8mm. therefore they have the same beam thickness, which is the full diameter of the lens' aperture, 5 to 6 mm (depending on axiz, the dot isnt uniform necessarily).

your plan sounds good! so the setup should do the collimating too? would solbe some problems. only one additional lens, when the collimator is the first lens of the expander. you can focus the whole thing by simply screwing it into the aixiz module, no other threads or moving parts needed!

manuel

manuel
 

Glutton

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Re: dioptika beam expander?

standard collimators (like the various aixiz acrylic and glass) all have the same focal length, i think 8mm. therefore they have the same beam thickness, which is the full diameter of the lens' aperture, 5 to 6 mm (depending on axiz, the dot isnt uniform necessarily).

your plan sounds good! so the setup should do the collimating too? would solbe some problems. only one additional lens, when the collimator is the first lens of the expander. you can focus the whole thing by simply screwing it into the aixiz module, no other threads or moving parts needed!

manuel

manuel
Whoa! I wouldn't even know how to get that done...what FL lenses would I need? Isn't every type of diode different with the FL they emit?

I was thinking that I could just pre-collimate the beam with the aixiz lens then screw the expander on. Might be difficult unless I use alot of teflon to hold the lens in place while i thread the expander onto the setup.

Anyways here are some pics



 
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Krutz

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Re: dioptika beam expander?

..or to take it one last step further: just use one single lens altogether! forget the collimating, forget the widening, the bare "beam" from the diode spreads enough without any help! mount a 50mm lens to the laser, with its focal point at the diode. if the angle of the diode and the numeric aperture of the lens (which is just a factor from the diameter and focal length) fit, you will have a 50mm wide collimated beam! should be of higher quality than with two or three lenses too. of course it would probably only work with one type of diode, i expect blu-ray and red to have too different beam characteristics. and green would be all out. except if you remove some of the internal lens(es).. *evil*

manuel
 

Glutton

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Re: dioptika beam expander?

..or to take it one last step further: just use one single lens altogether! forget the collimating, forget the widening, the bare "beam" from the diode spreads enough without any help! mount a 50mm lens to the laser, with its focal point at the diode. if the angle of the diode and the numeric aperture of the lens (which is just a factor from the diameter and focal length) fit, you will have a 50mm wide collimated beam! should be of higher quality than with two or three lenses too. of course it would probably only work with one type of diode, i expect blu-ray and red to have too different beam characteristics. and green would be all out. except if you remove some of the internal lens(es).. *evil*

manuel
I like the way you think! but what is the focal length of an 8x and a LPC? It would take alot of trial and error without knowing the focal lengths.
 
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Glutton

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Re: dioptika beam expander?

I like the way you think! but what is the focal length of an 8x and a LPC? It would take alot of trial and error without knowing the focal lengths.
<facepalm> I cant believe nobody called me a moron for that post. FL of a diode?:wtf:</facepalm>

So this is me thinking outloud : In terms of a bare diode (without lens) y=radius of the dot, and x=the distance between the diode and dot.

So then 2y<the lens diameter needed, and x=the FL of the lens. An aspheric would be best here correct?

Also, if I measure the dot diameter and the distance between the diode and dot, I can use a little bit of trigonometry to find out the exact beam diameter a 405-G-1 will produce. arctan(y/x)=1/2radiating angle of light... then once I have the the angle* I can replace x with the FL of a 405-G-1 to find my diameter...like so...y=(405-g-1FL)tan(1/2radiating angle) This will help with my 2 lens expander

Somebody tell me if this is correct or if I need another facepalm(I'm still in trig)
 
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Krutz

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Re: dioptika beam expander?

why that facepalm? nothing wrong with the focal length of a bare diode! ..just like braking is acceleration, just a negative one ;-)
negative lenses are stated with a negative focal length too.. ;-)

how about the other way? decide, what diameter your final beam should have. find out at what distance the bare beam has that diameter. try to find a lens with s bit larger diameter than the beam you want, with a focal length at the distance between that point and the diode!
..a somewhat larger lens helps, so you dont lose (much) energy which shines wider than the lens (NA), as well as keeping distortions and reflections from the lens' edge low, as well as to have a bit margin to fine-adjust the distance between lens and diode.
for such large distances, a regular spheric lens is sufficient. an aspheric would be better, still, but probably not noticeable..

but then, again, as always, the housing?

manuel
 

Glutton

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Re: dioptika beam expander?

Yep, the housing...

I can only get a up to a <18mm diameter beam with my current monocular housing which is only like a 3x expander in terms of a diode laser...I will snoop around the interwebs for a housing and try to find a way to build my own housing for this single lens collimater.

I have a 50mm housing that is already being used but I can tinker around with it to get a better idea of how to get this to work.
 

Krutz

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Re: dioptika beam expander?

hmm, how about a riflescope? would be nice to adjust! should be thick and short. remove the prismatic rotator, replace one or both of the lenses, build something to be able to attach it to the laser. should be pretty cheap too?

wait, have an old, thin and long one somewhere.. and then theres ebay.. brbafkbbl!

manuel
 

Glutton

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Re: dioptika beam expander?

Ok, The exact diameters of the monocular lenses are 18mm and 12.7 mm, The smallest -FL I can find for a 12.7 is -15 and the largest FL of a 18mm is +72.

I may have to contact jayrob (or do myself) to make a custom spacer to convert a 6mm lens to fit a 12.7mm set-up, this way I can use the smaller 6mm/-6 lens to make a 12x expander that will work just fine with a <1.5mm beam diameter. Other wise it would require that I use two 12.7 mm lenses in order to get to 12x expansions.
 
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Krutz

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Re: dioptika beam expander?

..i had a look at my scope. its a "zension", says "zoom 3x-7x 20" and "coated image moving, japan".

5 (!) lenses in there. two and one at each end, two in the middle which are movable several cm.
if i find fitting lenses, the housing could be converted, i think. cut half of it away, shorten some things, insert one 20mm lens at the end, insert a 9mm lens into the part that is moving. will post pics and details once i have a cam again.

general question, if i got this right:
any lens-combination will work as a beam-expander. only the two focalpoints have to be on each other. a 50mm focal length lens (1) and a 100mm focallength lens (2) would work like this:

(lens1) ------ 50mm ----- X ---------------- 100mm ------------------- (lens2)

the expanding would be the ratio between the two distances, in this case 50/100, enlargement (or shrinking) of two.
of course the beam has to fit the lenses' diameter, especially the second one! all values have to be right (focal lengths vs diameter), but it basically boils down to overlapping the focal points, not?

by changing the distance between the two lenses (so the two focal points are distanced) i can make the outgoing beam either diverge or focus. not?

manuel
 

Krutz

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Re: dioptika beam expander?

ah, ok, i see what i did! i can draw a "steepness triangle" to calculate it. but the incoming beam-diameter is critical, so i need to know this precisely. will try again with a red diode one with a long-focal aixiz glass lens, for round and defined beamdiameter!

manuel
 




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