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Galilean beam expander and spherical aberration

  1. Dec 2, 2008 #1
    Sorry for posting this post in two different place, I could not decide where is the best place to post it.

    I am trying to build a Galilean beam expander/contraction using a plano-convex and plano-convace lenses. My question is how should I arrange them to reduce the spherical aberration?
    Should the two plano surfaces face each other (Here and Here), the two curvatures surfaces facing one another, or some different way.

    I need to know that both for a beam expander and beam contraction.

    Thank you
  2. jcsd
  3. Dec 2, 2008 #2


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    General rule is 'split the powers' = minimise the amount of curvature at each face.
    That is the curved face should face the colimated beam and the flat face - the diverging/converging beam.
  4. Dec 2, 2008 #3
    Thank you for your answer.

    What is confusing me is that according to this document from Melles Griot
    they should be aligned in a different way ( see figure 1.32 )

    So what way reduces the spherical aberration better?

  5. Dec 2, 2008 #4


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  6. Dec 3, 2008 #5
  7. Dec 13, 2008 #6


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    Surpisingly, they are showing it wrong for the negative lens. Note in Fig. 1.31, that arrangement has worse aberration than the other way around (1.069 vs. 0.272)

    mgb_phy's link to Edmund has the correct figure at the top of the web page.

    The way I remember it is: never have the flat face facing a collimated beam.
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