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Thread: Cylindrical lenses are 'go'

  1. #1
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    Default Cylindrical lenses are 'go'

    edit: this will be wrapping up in the next few days. If you want some, or to change your order, now is the time to make contact!

    The test units from the final manufacturer have arrived and check out good. They are broadband coated < 0.5% reflectivity. The final total losses including bk7 glass are 3%, vs an estimated 10% for prisms. <0.9 mrad emission is achievable with these (after an ashperic collimator) used to expand the slow axis of 445nm diodes and other multimode diodes with similar emitters, incl. the 500mW reds.

    GET LENSES HERE


    Beam at 56 feet (17 meters)


    dimensions: 12hx9wx3t, 8hx3wx2.5t (mm)
    Material: BK7
    AR Coating Range: 350-700nm
    Surface Quality: 60-40 Scratch/Dig
    Surface accuracy: λ/2 curved, λ/4 flat


    Set-up distance between lenses: 20mm

    To take a note from p1t8ull,
    Features compared to anamorphic prisms:
    Fixed magnification setup
    Less Power loss compared with prisms
    Same space taken up as prisms
    Beam(s) stay centered after correction optics, offset for prisms

    "I can confirm that both beam correcting methods are a bit fiddly to set up, but neither should be beyond the capability for most people here if the basics are correct and time and care is taken."

    These are the lenses that will be used in the Blue Lava II kit, please only order from here if you are not getting the kit. These will be ordered along with the kit lenses.

    GET LENSES HERE


    Paypal instructions: Calculate the total using the above google checkout page, then add 1% to cover the paypal fee difference. Then PM me for the paypal address.


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    Last edited by drlava; 09-23-2010 at 20:46.

  2. #2
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    Hi, can you tell what the (negative) focal lengths are ?

    BTW, the losses for prisms are essentially the same, as approx the same distance in the glass is travelled, and it's again two times two surfaces.

    -W

  3. #3

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    PM Sent....
    Thanks for your work on these lenses...

    Jerry
    See the LaserBee II and all other LaserBee LPM products here....
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  4. #4
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    Quote Originally Posted by RedlumX View Post
    Hi, can you tell what the (negative) focal lengths are ?

    BTW, the losses for prisms are essentially the same, as approx the same distance in the glass is traveled, and it's again two times two surfaces.

    -W
    PM sending. The reason these have less losses are: the beams enter the surfaces at a near perpendicular angle, and the total glass path is 5mm. If the beam enters the prisms near the center, I estimate a total glass path near 10mm. Have you measured the losses of the prisms directly?

  5. #5
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    I don't see how the losses in the glass could be big. If the glass actually absorbed this blue light it would have a distinct yellow tone.

  6. #6
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    Quote Originally Posted by tocket View Post
    I don't see how the losses in the glass could be big. If the glass actually absorbed this blue light it would have a distinct yellow tone.
    Just going by posted BK7 transmission curves which estimate 5-8% losses at 10mm..
    http://www.pgo-online.com/intl/katal...BK7_kurve.html

    But this isn't really the main point here. There are other benefits to this solution that make it worthwhile.

  7. #7
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    Quote Originally Posted by drlava View Post
    Have you measured the losses of the prisms directly?
    Yes I have, upon carefully optimizing the adjustment it boiled down to approx 3%, see here:
    http://www.photonlexicon.com/forums/...121#post154121
    It is mostly a matter of the coatings, the glass does not much to it (if BK7 and not SF11). Other optics like beam splitter cubes also can have a transmission of 97% or so, so there is no reason why prisms should be worse.

    I will send PM in a moment ;-)

  8. #8
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    Quote Originally Posted by drlava View Post
    PM sending. The reason these have less losses are: the beams enter the surfaces at a near perpendicular angle, and the total glass path is 5mm. If the beam enters the prisms near the center, I estimate a total glass path near 10mm. Have you measured the losses of the prisms directly?
    you are getting less loss because they are AR coated.

    not to correct the good DR...but as I understand it...the angle at which the beam enters a piece of glass does not affect its reflectance ratio a great deal (with the exception of brewesters angle). If they are broadband coated AR then that will lower the reflectance significantly (therefore throughput efficiency). IF they are not coated for AR you can expect on average 4% per surface the beam encounters (no matter what angle you enter it at (or thickness of glass the beam propagates...(within reason of course)...other than brewesters of course)). When dealing with prisms, the preferred rotational angle of the prism is called the "critical angle". Minimum reflectance of incident beam is achieved by rotating the prism while monitoring power from reflected incident beam (generally brewesters angle). You can also find "critical angle" by rotating the prism until the refracted beams make the least angle when measured from the incident beam...Finding critical angle is how one optimizes the throughput of light through a prism....if that makes sense, tough to explain..easier to do on the test bench

    anyway...I'll take a pair
    Pat B on alt.lasers


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  9. #9

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    IŽd also like to know the focal lengths of the lenses, thanks.


  10. #10
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    Quote Originally Posted by Roy G. Biv View Post
    IŽd also like to know the focal lengths of the lenses, thanks.
    hehe why would anyone want to know the focal length of the lenses unless they were trying to second source them throw the dog a bone for the love of god...he researched them

    20mm separation might give you a hint
    Pat B on alt.lasers


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