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Thread: Divergence vs. Focal Length, Large Ashperic

  1. #1
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    Thumbs up Divergence vs. Focal Length, Large Ashperic

    I am looking for a cost effective solution to reduce the divergence of a 445nm diode, without the complexity of cylindrical optics, prisms or beam expanders. It occurred to me that you would get the same effect of a beam expander by just using a larger lens at a longer focal length.

    Most available such as the 405-G1 have a focal length around 4mm and NA of .6; I found this linked one from Thorlabs:

    http://www.thorlabs.com/thorProduct....tNumber=A240-A

    It Has a focal length of 8mm, am I right in thinking this will have a 2x improvement in divergence vs. a focal length of 4mm? Any other considerations here?

    The only con i see is that the NA is 0.5, so I will lose some of the beam. However, the most intense part of the beam is in the middle, so I do not know how to calculate how much power I will lose. Any ideas on this?

    I have a Mech Eng. background but am new to lasers in general so appreciate any input. Great info here at this site.

    Thanks

    -J

  2. #2
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    no need to spend that much on lenses just for an experiment.

    you can try the long FL lens from o-like that many PL members use. (just an example here http://cgi.ebay.com/405nm-laser-445n...item27b95554f7).
    this way, you can see for yourself what figures you get. haven't tried it myself, even though i have a couple, as i stick to the 405-g-2 and prisms for the time being

    using prisms is not hard at all though. you could find nice prisms through dave http://www.photonlexicon.com/forums/...=zoof+template or rob http://www.stanwax.co.uk/ and a template how to set the prisms here (thanks to mr Zoof!!) Check the pdf http://www.photonlexicon.com/forums/...176#post161176


    ad if you need general theory behind prisms, try this (tab "Specifications!) http://www.edmundoptics.com/onlineca...productID=2429

    cheers!
    "its called character briggs..."

  3. #3
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    Many people here have spent a lot of time, including me, finding the ultimate lensing combination for collimating the 445nm diode and the summed up results would be:

    1.) Single lens solution with a longer FL (=8mm) would be the O-Like lens giving a divergence <2mrad with a loss of about 7%, large aperture beam size of ~ 4.5mm x 1mm
    2.) O-Like lens (long FL 8mm) with prism correction giving a divergence of <0.7mrad with a total loss of 16.8%, aperture beam size of ~ 4.5mm x 4.5mm.
    3.) 405-G-2 lens (short FL 4mm) with cylinder correction giving a divergence <0.7mrad with a total loss of 15%, aperture beam size of ~ 3.5mm x 3.5mm.

    Here some further info’s with Pictures http://www.photonlexicon.com/forums/...ion-correction

    cheers!

  4. #4
    swamidog's Avatar
    swamidog is online now Jr. Woodchuckington Janitor III, Esq.
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    you might take a look at this:



    http://www.photonlexicon.com/forums/...ight=swami+445

    i'm working on a prototype for combining 445's for use in graphic projectors. it's kind of lossy, but the beam quality is excellent. about .6mrad with a 4mmx4mm beam at aperture.




    Quote Originally Posted by Solarfire View Post
    Many people here have spent a lot of time, including me, finding the ultimate lensing combination for collimating the 445nm diode and the summed up results would be:

    1.) Single lens solution with a longer FL (=8mm) would be the O-Like lens giving a divergence <2mrad with a loss of about 7%, large aperture beam size of ~ 4.5mm x 1mm
    2.) O-Like lens (long FL 8mm) with prism correction giving a divergence of <0.7mrad with a total loss of 16.8%, aperture beam size of ~ 4.5mm x 4.5mm.
    3.) 405-G-2 lens (short FL 4mm) with cylinder correction giving a divergence <0.7mrad with a total loss of 15%, aperture beam size of ~ 3.5mm x 3.5mm.

    Here some further info’s with Pictures http://www.photonlexicon.com/forums/...ion-correction

    cheers!
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  5. #5
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    Lightbulb

    Not sure if this will help, but it is kinda cool to play with:
    http://www.ee.buffalo.edu/faculty/ca...ets/index.html#
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

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