Re: 2" Non-rotating focus tube?


armstron@xxxxxxxxxxxxxx wrote:
> I'm part of a team that is building a solar physics insturment. We
> have two places in the insturment where we need to be able to adjust
> the spacing between lenses, and the adjustment should not rotate the
> lenses relative to each other, should have better precision than a
> simple rail system, and we would like to take the set of lenses out of
> the instrument as a set without changing the spacing.
>
> I have found a couple of solutions of the type we need e.g. Helicoid
> barrel. Unfortunately the first set of lenses is 50mm in diamteter.
> The second is 30mm in diameter. The diameter is too large to fit in
> the barrel solutions I have found.
>
> We would rather not make a custom part on this. Does anyone have some
> ideas for an off-the-shelf or minorly modified off-the-shelf solution?
>
> Thanks,
> JD
JD:

You didnt say much about the distances of movement (1um, 1mm, or 1
meter?) the precision of adjustment?

Can you just use two linear stages with micrometer on a base plate with
a kinematic mount on the bottom. Adjust the spacing of the two lenses
to within a couple tens of microns and lock the stages positions.
Remove the base plate and when you need to put it back in, it will be
very close (within 10's of microns) with your 3 hemispherical balls on
the bottom of the plate that rest in 3 vee grooves (or for purists, vee
groove, cone, and plate).

Rolyn Optics of Covina CA has a std product that might be what your
looking for with a threaded axial adjustment but only 1.6 inches of
travel and no optical axis runout spec listed. They also carry the
rack and pinon ideas previously mentioned.

You can also get a used zoom lens of sufficient diameter to hold your
lenses and use the zoom mechanism with the cam action, of course you
mignt not like the nonlinear axial movement of the two elements wrt
each other.

You might check out a couple of book on opto-mechanical engineering by
Paul Yoder, Anees Amahad, and Precision Mechanics by David Kittell.

If we can help you please contact me:
http://www.oscintl.com/services.htm

Michael

.

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