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Thread: Correcting ld with pair prisms

  1. #1
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    Default Correcting ld with pair prisms

    Hi All,
    Recently purchased 2 anamorphic prisms from Thorlabs.
    Just testing Oclaro 638nm (HL63193MG) 700mw on 3-element glass from DTR trying to obtain a better beam.

    -What have surprised me: I obtain the same results with 2 prisms than with only 1 prism

    PLEASE see pics attached!! Measures are taken 21ft (6,5m) far.

    So, why the need to use 2 prims? these are not cheap... Also, less losses with only 1 prism...

    Any ideas??

    Thank you so much
    Attached Thumbnails Attached Thumbnails 1 prism.png  

    2 prism.png  

    uncorrected.png  


  2. #2
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    Default

    I've used the single prism method on several builds. Some say that it does not correct symmetrically, personally I didn't see much difference. There is a lot of loss with prisms though. Almost everyone has switched to cylindrical lenses now. Slightly harder to align but less loss with them.

  3. #3
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    Default

    Hi Steve,
    I see.. this is the recomendation from Thorlabs too, BUT I have no skills with Cylindrical yet
    Building rgb projector for hobby now. My idea is to correct the beam "white light" before reach galvos. (Setting and average correction for all LD's)
    But don't know which lenses need lot of options!

    Anyway here are my LD's:

    -RED OCLARO HL63193MG-700mw 638nm: 5x1mm output (aprox) // 30x2mm @5 meters (3 Element glass on aixiz module)
    -GREEN NICHIA NDG7475-1W 520nm: 5x1mm output (aprox) // 9x4mm @ 5 meters (G2 glass on aixiz module)
    -BLUE 445 NICHIA NDB7875 2,5W: 5x1mm output (aprox) // 12x4mm @ 5 meters (G2 glass on aixiz module)

    Any ideas on lens on this setup?

    Thank you so much!

  4. #4
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    Default courtesy of edmund

    well, if you check here there is a good explanation of what happens with anamorphic prism pairs (tab specifications).http://www.edmundoptics.com/optics/p...specifications

    the second prism plays a role, although i think it is subjective judgement if this role is major or minor

    I have also used a single prism in modules, and for quick and dirty setups, the results were very much ok.
    Try both, make careful measurements and decide
    Attached Thumbnails Attached Thumbnails 5493.gif  

    "its called character briggs..."

  5. #5
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    Default

    Thanks Lanek!
    Maybe less divergence with 2? At 6m the sot size is the same....don't know far away. After careful measurements with both prisms, I CAn't see smaller spot than with single prism.
    Anyway I'll try to go with cylindrical as Steve recommends.
    any tips please?
    many thanks!

  6. #6
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    Default

    Dave sells a set, Dr Lava too still may have them .. I don't remember who else ..
    Dave's is here: (well, in Australia "here")

    http://lasershowparts.com/store/inde...&productId=307

  7. #7
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    Default

    however, I don't think that your idea of a prism for all three beams will work
    the reason? a pink floyd album is to blame



    A prism is used to seperate light into its components, so not what you want...
    "its called character briggs..."

  8. #8
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    Default

    Thanks Steve. Just ordered 2 correction sets to Dave. Many thanks!

  9. #9
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    Default

    hahahah yes I know, so the idea is to re-adjust dichros to overlap beams again

  10. #10
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    Default

    but what about if you put different wavelengths into a prism at the right angles, would it combine.

    Quote Originally Posted by LaNeK779 View Post
    however, I don't think that your idea of a prism for all three beams will work
    the reason? a pink floyd album is to blame



    A prism is used to seperate light into its components, so not what you want...
    Eat Sleep Lase Repeat


    Aluminium Optic Mounts

    http://www.laser-man.co.uk/opticmounts/

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