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Can you build an afocal zoom system with only one stage. It looks like you would have to use more than three lenses. You would probably have to have all but one of the lenses be fixed; but it might be possible to have more than one moving, as long as they are all moving the same distances (i.e. they are on the same stage).

If not; can you prove that you can't do it?

Some helpful links: http://en.wikipedia.org/wiki/Zoom_lens http://spiedigitallibrary.org/oe/resource/1/opegar/v36/i4/p1249_s1

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I need some clarifications. By "stage" do you mean something like a lens on a linear rail? In other words, are you asking if a zoom can be built with only one moving lens? It sounds like you are talking about a variable beam expander, is that correct? Lastly, are you talking about a design that maintains collimation while the magnification is varied, while performing only simple lens motions? In other words, a system without mechanical focus compensators? –  Colin K Mar 2 '11 at 2:19
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Yes you can, I believe there is even an illustration of how to do it in the wikipedia article you linked to. It's not an ideal solution and if you want something better than "it works" you will probably need to beg around for more kit.

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a simplistic afocal system is a plain glass! but then if one can use any lens system, then convergence or divergence is sure! –  Vineet Menon Sep 20 '11 at 7:21
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