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Thread: Need some thoughts....

  1. #1
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    Need some thoughts....

    Hello all. Big fan of this site!

    I need some help. What are some good ideas for checking correct polarization axis on a lens that is plano powered and is already edged?

    Thanks!

  2. #2
    OptiBoard Professional
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    Take it outside and look at a car windshield.

    See where the Lens appears darkest. That should be your 180 line.

  3. #3
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    Take a marked polarized lens and rotate it with the marked polarization axis to 90/270 degrees. Hold it in front of the questionable lens, the view should be near black. Rotate the known lens back and forth 10-15 degrees, if it gets darker as you rotate it, the edged lens is off the 180 polarized axis.

  4. #4
    Master OptiBoarder pseudonym's Avatar
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    Possible stupid question but I've never let that stop me before: Does the patient experience any ill effects if the polarization is, say, 10 degrees off?

  5. #5
    ABOM Wes's Avatar
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    Yes. If both are off in the same direction, horizontally polarized light will only be cancelled if the person tilts his head. If they're not symmetrical, it can cause severe asthenopia; one cancels glare, one doesn't. Very uncomfortable ; I haven't met anyone who will wear one off axis polarized lens for more than a few minutes.
    Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA

    “As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein

  6. #6
    Master OptiBoarder
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    Quote Originally Posted by Wes View Post
    Yes. If both are off in the same direction, horizontally polarized light will only be cancelled if the person tilts his head. If they're not symmetrical, it can cause severe asthenopia; one cancels glare, one doesn't. Very uncomfortable ; I haven't met anyone who will wear one off axis polarized lens for more than a few minutes.
    +1,..............I agree with Wes.

  7. #7
    Master OptiBoarder OptiBoard Silver Supporter Barry Santini's Avatar
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    They'll sometimes describe the view as "3D"

    B

  8. #8
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    Quote Originally Posted by Barry Santini View Post
    They'll sometimes describe the view as "3D"

    B
    ...and think they won't have to pay extra for the 3D glasses /SARC

  9. #9
    Master OptiBoarder pseudonym's Avatar
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    Thanks- I haven't been checking them for alignment. Didn't know how. Now I do.

  10. #10
    Master OptiBoarder
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    I always keep a plano polarized blank handy for such issues. A necessary tool in the ole optical toolbox.
    Clinton Tower

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