Re: [ATM] Too Small Optics

["Peter John Smith" <pjifl@bigpond.com>]

One basic way to test a miniature concave mirror is to use a microscope
objective essentially as a relay lens.  A modified microscope is ideal.  The
beam splitter is on the other side of the lens working at maybe F:20 - or use a
pellicle.  The Ronchi or Foucault sources and other bits and pieces are now in
the top of the modified microscope doing the testing.  The microscope objective
is focused on the centre of curvature of the cancave surface.  Microscope
objectives work at very wide ray cones and may be highly corrected.

With thought, you will see how this can also be applied to a convex mirror.  The
microscope objective then needs to have a long working distance such that it is
focused on the centre of curvature behind the convex surface.

Of course, you are not sure of the quality of the objective.  This can be tested
by making miniature artificial 'stars' on the microscope slide.  Just squish a
very small blob of mercury.  Or 'autocollimate' back from known a good plane
mirror used as a microscope slide.  Autocollimate aint the 'correct' word
because the light isnt parallel.  Each ray is returned at exactly the same
angle - but reversed.

All these methods are closely related to microspherometers.  There is a little
on my web site on this.

http://www.users.bigpond.com/pjifl/

Another way to make small reference optical surfaces is to make a complete
sphere.  Then testplate from it

Peter Smith

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