[ATM] Additional phase contrast and Foucault images

[Dominic-Luc Webb]

On Thu, 19 Apr 2007, Stephen Koehler wrote:

> Dominic,
>
> > Out of curiousity, what is the most significant defect you
> > would exoect to identify?

Sorry, typo: "exoect" = expect

You mainly answered my question. We've (many of us here) been
making mirrors a long time and there really have been some
spectacular scopes built without this test and I sometimes
wonder if these techniques are just some form of new
entertainment or could lead to a better mirror.

I use phase contrast with a very valid application. I do
microinjection of cells under a microscope. I pretty much
require phase contrast to place the injection needle at
the sweet spot where it can penetrate the cell without
skipping over the top or crashing into the bottom (in
which case it breaks). For mirrors, I reckoned it would
be convenient mainly for looking for derangements relating
to bad protective coatings and generalized filth. That
being said, I do not know anyone to have gone back to the
coaters with a phase contrast image, complaining of a
surface defect, but believe I may have seen a few.

Dominic