>I read in previous messages that you are using a PSI setup.
>I am also interested in this technique, mainly because it's a lot of
>fun setting this up, but I haven't found out yet, what exactly the
>advantages / differences to static Bath interferometry are.
This is an important question. I will answer to my ability but will
also kindly ask others to drop in with more elaborated and better
>and the conclusion seemed to be that you get better spatial
> resolution when doing PSI.
Yes you are right. From three methods used in data reduction software
made available by Dale and Stephen for non PSI and Michael for PSI,
(the methods are fringe tracing, Fourier transform, and PSI). The PSI
method calculates the biggest number of points on the surface of the mirror
>As far as I remember the phase shift was realized by
>varying the length of the reference path in an uneven path
>interferometer with piezo actuators.
This is correct. In PSI method outlined in Wiki the phase shift is introduced
by polarizing methods. There is no linear movement of any kind like piezo
actuators, but the rotating the polarizing sheet which is very simple and cheep
method easy for ATM purpose.
>My only information source so far has been the picture by Dave Rowe in
>the Wiki. Are there more resources on Bath-PSI in this group or the
>net, my search hasn't come up with something substancial.
I have used and started from the mentioned picture and explanation provided by David Rowe
in the Wiki. That was sufficient for me to construct and use PSI Bath interferometer
successfully. Therefore it was enough "substantial" for me. I have also a book
Optical Shop Testing by Malacara, where there is a chapter on PSI. This satisfied
my curiosity but played no role in actual realization of the PSI interferometer.
It was done entirely by the instructions in Wiki.
>The hardware I have are scrap parts from an laser ellipsometer and
>include two polarizers and a quarter wave plate, which as I understand
>is all I need.
That is correct. I have seen pictures of your Bath and you are just a short step
of PSI Bath. The only new component you need is polarizing beam splitter cube
which can be most expensive part of the setup. Since I have got one from
David Rowe as a gift, I have not looked into what is offered on the market
and at which price.
>What analysis software do you use for data reduction?
I use the only one available to ATM, free, and very likely among the best one among
commercial stuff as well, It is Written by Michael Peck. He is using R language
and he introduced me into using this language which is also free. Stephen Koehler
learned me all of what was needed for its use( and much more).
The program is at: http://home.earthlink.net/~mlpeck54/astro/astro.html
This is Michael's ATM site.
What is most important is that Michael, Stephen and Dale are very active in
giving support to all using their programs, and luxury of being able to communicate
with authors must be grabbed while it lasts, the opportunity which should be
not neglected or overlooked.
>I admit that the whole math thing is way beyond my scope
>From my personal experience I can tell that in spite that my math is also
beyond the scope, when I asked I always got answers and tutorials far beyond
dedicated textbooks. It was pleasure in itself.
>but I think I can handle the experimental setup.
You will be surprised how easy it will be.
>I will let you know when I take first steps into phase shifting, but
>first things first. There is still a lot to optimize on my static Bath
>setup, mainly image quality has to be better.
I have a good news for you. Something that I also learned from Michael and Stephen.
I have also wandered about quality of images (interferograms) especially when I saw
what Dale, Abrahamian, Gert to mention some, were capable of. What I had was
not nearly as good and yet Michael PSI method takes care of it in astonishing way.
One of many PSI advantages.
Thank you for formulating your questions in very consistent manner.
I hope it will be interesting reading for all thinking and considering PSI .
"Time to take a BATH !"