Galilean beam expander and spherical aberration

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Discussion Overview

The discussion revolves around the arrangement of lenses in a Galilean beam expander and contraction system, specifically focusing on how to minimize spherical aberration. Participants explore different configurations of plano-convex and plano-concave lenses and their implications for optical performance.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the optimal arrangement of lenses to reduce spherical aberration, asking whether the plano surfaces should face each other or if the curved surfaces should face one another.
  • Another participant suggests a general rule of "split the powers" to minimize curvature at each face, recommending that the curved face should face the collimated beam while the flat face should face the diverging/converging beam.
  • A participant expresses confusion due to conflicting information from a document by Melles Griot, questioning which arrangement better reduces spherical aberration.
  • One participant argues that the Melles Griot catalogue is merely illustrative, while another counters that it provides a specific example that should not be dismissed.
  • A later reply notes that the arrangement shown in the Melles Griot document may be incorrect for the negative lens, indicating that one configuration has worse aberration than another, referencing specific figures for comparison.
  • Another participant emphasizes the importance of not having the flat face facing a collimated beam as a mnemonic for remembering the correct arrangement.

Areas of Agreement / Disagreement

Participants express differing views on the optimal lens arrangement for minimizing spherical aberration, with no consensus reached on which configuration is definitively better.

Contextual Notes

Participants reference specific figures from external documents to support their claims, indicating that the discussion may depend on the interpretation of these diagrams and the assumptions underlying them.

Shaddyab
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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 (http://www.mellesgriot.com/glossary/imagesDir/Gallilean.gif" ), 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
 
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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.
 
Thank you for your answer.

What is confusing me is that according to this document from Melles Griot
http://www.mellesgriot.com/pdf/CatalogX/X_01_27-28.pdf"
they should be aligned in a different way ( see figure 1.32 )

So what way reduces the spherical aberration better?

Thanks
 
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I think their catalogue is just showing a diagram, this one has more detail
http://www.edmundoptics.com/TechSupport/DisplayArticle.cfm?articleid=270
 
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mgb_phys said:
I think their catalogue is just showing a diagram, this one has more detail
http://www.edmundoptics.com/TechSupport/DisplayArticle.cfm?articleid=270

I do not think it is only a diagram, they are driving an example.
 
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Shaddyab said:
Thank you for your answer.

What is confusing me is that according to this document from Melles Griot
http://www.mellesgriot.com/pdf/CatalogX/X_01_27-28.pdf"
they should be aligned in a different way ( see figure 1.32 )

So what way reduces the spherical aberration better?

Thanks

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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