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Thread: demagnification lens?

  1. #1
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    Default demagnification lens?

    What kind of lens am I looking for and what are they called? Basically I want to demagnify a phone screen viewed through a lens by 8x instead of magnifying it. This is for simulating a microdisplay before I actually get one and work on that instead.


    Viewing binoculars from the opposite side it appears to do what I want. Everything is shrinken but slightly out of focus.

  2. #2
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    Quote Originally Posted by joec View Post
    What kind of lens am I looking for and what are they called? Basically I want to demagnify a phone screen viewed through a lens by 8x instead of magnifying it. This is for simulating a microdisplay before I actually get one and work on that instead.


    Viewing binoculars from the opposite side it appears to do what I want. Everything is shrinken but slightly out of focus.
    If you have the luxury of fixed focus, then a simple concave lens will work.

    If you need collimation, then a telescopic collimator also works in reverse.

  3. #3
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    Can you please tell me what you're referring to by a telescopic collimator? Thanks.

  4. #4
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    ... look for "beam-expander" ...

    Viktor

  5. #5
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    I always thought beam expanders are used for lasers and only work with a collimated beam and specific wavelength so use fewer lens elements.
    But if that's not the case I can definitely use them, in reverse.

  6. #6
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    Quote Originally Posted by joec View Post
    I always thought beam expanders are used for lasers and only work with a collimated beam and specific wavelength so use fewer lens elements.
    But if that's not the case I can definitely use them, in reverse.
    You are semi-correct, inexpensive beam expanders will show chromatic aberration around the edges, but the amount is usually negligible as long as the ratio is low.
    In comparison, it should be less aberration than say a binocular or telescope in reverse.

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