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How is the focal length of an objective calculated?

  1. Nov 6, 2014 #1
    Hi,

    I am using an objective lens to illuminate my object by a collimated beam. The magnification and NA is available on the objective. How can I calculate the focal length from this information? The objective is not infinity corrected. Thank you
     
  2. jcsd
  3. Nov 7, 2014 #2

    Simon Bridge

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    IIRC: You need to measure the LDDV.
     
  4. Nov 7, 2014 #3

    Andy Resnick

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    Non-infinity corrected microscope lenses are typically based on a tube length of either 160mm (RMS or DIN standard) or 170mm (JIS). Of course, just to be different, Olympus used 180mm.....

    The magnification is (tube length)/(lens focal length). Note the focal length is not the front working distance.
     
  5. Nov 7, 2014 #4

    Simon Bridge

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    ... or you could just know how people build these things :)
     
  6. Nov 7, 2014 #5
    Thank you for all the answers. Using the tube length in my calculations worked. Thanks :)
     
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