I am trying to find a stage that can be positioned along any planar
axis of rotaion through its center.  Like a plate riding on top of a
hemisphere.  The stage needs to be controllable though, either with
micrometers or some other method.  It can also be controlled through
servos or some other electro-mechanical means.  The stage needs to be
at least 3" square (or diameter) and no larger than 4" square (or
diameter).  Thanks for your help

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Clarification of Question by sgeist-ga on 20 Sep 2005 11:18 PDT

Sorry, I forgot to mention, the axes of rotation need to be on a plane
offset from the surface of the stage and through its center.  So back
to the stage on a hemisphere analogy, if you attach a stick through
the sphere side through its radius and rest the hemisphere on a ring,
then when you move the stick you'll be rotating the stage through an
axis that is offset from the stage by a distance equal to the radius
of the hemisphere you used.  Again, the stage doesn't need to work
this way, it just needs to accomplish the same thing.  Thanks!

Let's confirm: You need to rotate your sample - the thing you want to
position with your stage - about 2 mutually perpendicular axes. The
axes of rotation intersect.  The sample will be a distance D from the
intersection of these axes.

Over what range of the 2 angles do the sample need to rotate? 
Do you need to measure the angles?
What is the smallest change you need to make in each of the angles? 
What does the sample weigh?