[ATM] Additional phase contrast and Foucault images

[Dominic-Luc Webb]

On Wed, 18 Apr 2007, Stephen Koehler wrote:

> Dominic-Luc,
>
> > Back to the multiple images, you could try playing with the
> > size and location of the phase plate.
>
> I'm quite sure the multiple images are due to diffraction, and are
> unavoidable, just as in the Ronchi test.
>
> --
> Steve Koehler

I have not spent much time investigating best ways to reduce this
effect or its exact origin, but in my lab we have different phase
contrast systems in which one may or may not have these multiple
images, so I have not viewed this as unavoidable, albeit not hard
to encounter. I have always associated this with the one clear
difference between these systems, which was size and location
of phase plate. BTW, in our systems, we have essentially
monochromatic green light in both cases, resulting from filters.
These are roughly optimal wavelengths for the optics in the
system.

Dominic