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Help with Focusing Lens Block

  1. Sep 29, 2014 #1
    Posted a while back but to no avail. I've since done some tinkering but need a little bit of help perfecting the math.
    2vv3qyo.jpg

    I've constructed an experimental version of the above set up with success. Moving the plano-concave element away from the plano convex element brings the focal point towards the sensor. Moving the concave element back towards the convex element pushes the focal point further away.

    What I'm trying to figure out is what power or focal length lenses I need to construct this. I want minimal movement (around 5-10mm) and to be able to achieve infinity (afocal). Any advice is much appreciated!
     
  2. jcsd
  3. Sep 29, 2014 #2
    Are you familiar with ray transfer matrix analysis?

    http://en.wikipedia.org/wiki/Ray_transfer_matrix_analysis

    You should be able to model your configuration with such matrices, leaving the geometrical parameters (radius of lens elements, distance between the plano-convex and plano-concave elements) as variables.

    You then solve for the distance for focus to the nearest point and to infinity.
     
  4. Sep 29, 2014 #3
    I should have specified, I only hold a BA. I'll do some research on this.
     
  5. Sep 29, 2014 #4
    As long as you manage to multiply 2x2 matrices you'll be fine.

    In the worst case you can write a little computer program in python or basic and tweak the parameters until you get what you want.
     
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