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Trying to inquire information about beam expanders, help?

ElectricPlasma

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I've been doing a little bit of research on beam expanders and their relations with lasers, I've come across the obvious but it's a bit hard to understand the exact logic behind them, and also their availability.

So I have indeed discovered that beam expanders can expand the beam. :p
But what I would like to know is this; from all the images and articles I've read on them, is that they must decrease divergence by a ton.

Is this true?

If it is, it seems like that would fix the crappy divergence on blue laser beams. Also, another question, where would I be able to buy something like this? :thinking:

Thanks. :D
 

RedCowboy

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Basically any lens has a focal length where it can reproduce an exact image of the point source of light, but the longer the distance the larger the image/dot will be, this is just a matter of physics, now an expander expands the beam allowing you to get a smaller dot at a longer distance.

Beam expanders work well with single mode tem00 that is round beams.

Multimode lasers like our 445nm projector diodes diverge more rapidly on one axis than the other, also there are shadow bars adjacent to the center bar which is the dominant wavelength, so there will be shadowing or wings.

Others who are tech savvy and know the exact terminology may correct what I have said, but my concept is basically what you will see.

You can get better than just a simple single or compound lens result by employing an expander, but to get the full benefit you would first use beam shaping optics to correct the beam then use an expander, otherwise you clip the edges of your beam and your range is limited by the horrible divergence.

The best result I have seen using a nice multi lens expander after a multi mode projector diode was this superb build by Minamoto Kobayashi, he lost a little less than 1/3 of his total output power but the divergence more than makes up for it, this is a very nice result with an expander that would cost over 1000 dollars to buy new, but bargains can be found if you keep an eye out on ebay.

http://laserpointerforums.com/f42/6...-adapted-355nm-linos-beam-expander-95471.html
 
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ElectricPlasma

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Basically any lens has a focal length where it can reproduce an exact image of the point source of light, but the longer the distance the larger the image/dot will be, this is just a matter of physics, now an expander expands the beam allowing you to get a smaller dot at a longer distance.

Beam expanders work well with single mode tem00 that is round beams.

Multimode lasers like our 445nm projector diodes diverge more rapidly on one axis than the other, also there are shadow bars adjacent to the center bar which is the dominant wavelength, so there will be shadowing or wings.

Others who are tech savvy and know the exact terminology may correct what I have said, but my concept is basically what you will see.

You can get better than just a simple single or compound lens result by employing an expander, but to get the full benefit you would first use beam shaping optics to correct the beam then use an expander, otherwise you clip the edges of your beam and your range is limited by the horrible divergence.

The best result I have seen using a nice multi lens expander after a multi mode projector diode was this superb build by Minamoto Kobayashi, he lost a little less than 1/3 of his total output power but the divergence more than makes up for it, this is a very nice result with an expander that would cost over 1000 dollars to buy new, but bargains can be found if you keep an eye out on ebay.

http://laserpointerforums.com/f42/6...-adapted-355nm-linos-beam-expander-95471.html
Thanks for the feedback!

1000 dollars? :eek: Way outa my price range! Sweet looking build though.

Besides that, your info gave me a much better understanding. So from what I read, basically it allows the focus point to go out much much further - now here's a question and I apologize if it is noobish, but is it possible to have infinite focus? :thinking:

Getting pretty curious, this hobby is pretty interesting and intricate.

About eBay, I was browsing along, and I came across this thing: M8 Frame Beam Expander Collimation Lens DIY Green Laser | eBay

...What is it? It says it's a "Beam expander" but it looks nothing what I've seen.There's a frame, lens, and not sure what the hell the other thing is, my first guess would be another lens. Appreciate the help! :thanks:

+rep :D
 

Gabe

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It's just the way light is being a wave (most of the time) and all, that you can't have a laser with 0 divergence, not spreading out at all. Your light will always be either be diverging and/or converging between two points.
Not all expander a have to be that expensive. Jetlasers sells a fine expander, but it's means of fastening is a threaded end, so it's not entirely compatible with random lasers. Hell, you could do what I did and chop up a pair of binoculars, dick around with PVC fittings and o-rings and such until you find a way to easily attach it to any laser. All you need for an expander is one double-concave lens to spread out the beam, and a double convex lens at the right spot to refocus the beam. Lucky for us, this is exactly what the cheapest binoculars are! You don't want the ones with fancy glass prisms in them, that noticably reduces the output and it's heavy.
 
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So from what I read, basically it allows the focus point to go out much much further - now here's a question and I apologize if it is noobish, but is it possible to have infinite focus? :thinking:

Getting pretty curious, this hobby is pretty interesting and intricate.
If I understand correctly what you're asking then no, infinite focus is not possible. Hopefully Alaskan will comment here, I think he is an expert on beam expanders, he likes his lasers to be able to put a dot on the clouds.

Alan
 
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If I understand correctly what you're asking then no, infinite focus is not possible. Hopefully Alaskan will comment here, I think he is an expert on beam expanders, he likes his lasers to be able to put a dot on the clouds.

Alan
I could use help here too. My understanding is a beam expander requires a collimated beam to begin with. Then isn't infinite focus simply the expanded beam (i.e. that converges at infinity) where a focusable beam expander allows you to bring that focus from infinity toward you thus causing the beam to intersect/converge to a dot (then spread back out as it moves further away from the dot)?
 
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I could use help here too. My understanding is a beam expander requires a collimated beam to begin with. Then isn't infinite focus simply the expanded beam (i.e. that converges at infinity) where a focusable beam expander allows you to bring that focus from infinity toward you thus causing the beam to intersect/converge to a dot (then spread back out as it moves further away from the dot)?
I am not sure if that is an accurate description or not. The beam expander expands the diameter of the beam and decreases the divergence, so at some distance the laser with the beam expander will make a smaller dot than the same laser would without the expander, the beam will still expand over distance, just not as much as it would without the expander.

Alan
 

diachi

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It doesn't appear to be an animated gif. Alan
Must be the way/place I'm storing it. I looked at other posts' with gifs 'code' and it looks like it's handled the same way as an image. :thinking:

EDIT: Put it on Imgur instead. Working now.
 
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hakzaw1

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I was (AFAIK) mis-informed when I was told that a BE makes you able to 'burn stuff' from a greater distance- -

confusion between divergance and small beam size is one problem-
no it wont be smaller but should enlarge at a slower rate as you go farther away.

The JL 10X at GB is 90$ when buying any Pro-PL-E (free ship for conus in GBers)

looks both foggy and froggy tonite- may take some pics and post them here 1400 mW 462 w & w/o 10X BE
 




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