Re: Varable Beam Expander

On Wed, 18 Jul 2007 07:34:32 -0700, Blour <youzpalang@xxxxxxxxxxxx>
wrote:

On Jul 17, 2:12 am, J <johnknuhtse...@xxxxxxx> wrote:
On Mon, 16 Jul 2007 18:51:00 -0700, Blour <youzpal...@xxxxxxxxxxxx>
wrote:



1-How does a variable beam expander work (what are its elements)?
Can we get expansion ratios 1:1, 3:1, and 6:1 from such beam
expander?

2- Can this be done using mirrors instead of lenses?

Now you write variable and not zoom. The variable expander can switch
the ocular wavelength and have a fixed objective.

A very simple setup is a galileian telescope. For smaller ratios the
negative element can a single lens, where the shape of it corrects for
spherical aberrations. For larger ratios it must have more than one
lens element.

It can be done with mirror too, - off axis of course. But ordinary
mirrors have poor reflections and might absorb energy. Multilayer
mirrors are expensive.
For UV quartz elements can be used.

The variable principle here can be with no compromizes and can have
much less aberrations than a zoom. But they put some demands on
mechanics. Alignment tolerances are very small, so it has to be
precision. A revolver design is feasible.

best regards

John



Can we achieve 1:1, 3:1, and 6:1 expansion ratios in one device
(i.e beam exapnder) using only mirrors?

Yes, why not use concentric spheres ?
There will be astigmatism, I should think. One idea could therefore be
to split 6:1 up over 2 pairs. One pair working in the orthogonal plane
of the other.

best regards

John


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