Subject: [interferometry] Digest Number 1229
From: interferometry@yahoogroups.com
Date: 11/20/2008, 1:31 PM
To: interferometry@yahoogroups.com

interferometry
interferometry

Messages In This Digest (10 Messages)

1a.
OpenFringe version 8.10 From: Dale Eason
1b.
Re: OpenFringe version 8.10 In use already! From: John Abrahamian
2a.
Re: Attempting PSI Bath From: manawatu2005
2b.
Re: Attempting PSI Bath From: Vladimir Galogaza
2c.
Re: Attempting PSI Bath From: Michael Peck
2d.
Re: Attempting PSI Bath From: Vladimir Galogaza
2e.
Re: Attempting PSI Bath From: Michael Peck
2f.
Re: Attempting PSI Bath From: Stephen Koehler
2g.
Resolution was Re: Attempting PSI Bath From: Dale Eason
2h.
Re: Resolution was Re: Attempting PSI Bath From: Vladimir Galogaza
View All Topics | Create New Topic

Messages

1a.

OpenFringe version 8.10

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Wed Nov 19, 2008 9:05 pm (PST)

Guess what,

I found an important bug. There has been a bug in the unwrap code that
kept it from doing as good of an unwrap as Steve Koehler was getting.
I think I found it and to my surprise it was also the cause of the
crash when using a non-circular mirror boundary. Actually I was
looking for that bug and discovered the stange association in the
unwrapper.

So now you can once again use a non-circular mirror boundary if you
need to.

You should also be able to unwrap noisier igrams in FT mode.

See Files section uner OpenFringe beta.

Dale Eason

1b.

Re: OpenFringe version 8.10 In use already!

Posted by: "John Abrahamian" imas1@aol.com   owl1820002000

Wed Nov 19, 2008 10:25 pm (PST)

--- In interferometry@yahoogroups.com, "Dale Eason" <atmpob@...> wrote:
>
> Guess what,
>
> I found an important bug. There has been a bug in the unwrap code that
> kept it from doing as good of an unwrap as Steve Koehler was getting.
> I think I found it and to my surprise it was also the cause of the
> crash when using a non-circular mirror boundary. Actually I was
> looking for that bug and discovered the stange association in the
> unwrapper.
>
> So now you can once again use a non-circular mirror boundary if you
> need to.
>
> You should also be able to unwrap noisier igrams in FT mode.
>
> See Files section uner OpenFringe beta.
>
> Dale Eason
>

Very Good Dale-
I've been using OpenFringe alot this month on my long focal length
f/11 mirror. Thanks for the new version. My version was crashing too
until I read your post mentioning the outline of the edge of the mirror.
Thanks,John

2a.

Re: Attempting PSI Bath

Posted by: "manawatu2005" AndreasD2004@web.de   manawatu2005

Thu Nov 20, 2008 5:26 am (PST)

Vladimir,

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.

I read a bit on phase shifting interferometry a while ago, and the
conclusion seemed to be that you get better spatial resolution when
doing PSI. 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.

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.

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.

What analysis software do you use for data reduction? I admit that the
whole math thing is way beyond my scope, but I think I can handle the
experimental setup.

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.

Regards,
Andreas

> This is a sound plan. I can hardly wait for your excursion into
> PSI domain for which you are well equipped. Bath interferometry took
> finally off at accelerated pace, each day somebody new tries it
successfully.
> It is time also to take PSI Bath into consideration.
> Keep us informed.
>
> Regards
> Vladimir.
>

2b.

Re: Attempting PSI Bath

Posted by: "Vladimir Galogaza" vladimir.galogaza1@zg.t-com.hr   vgalogaza

Thu Nov 20, 2008 6:30 am (PST)

Andreas,

>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
founded replies.

>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
under test.

>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 .

Regards
Vladimir.

"Time to take a BATH !"
(Mel Bartels)

2c.

Re: Attempting PSI Bath

Posted by: "Michael Peck" mpeck1@ix.netcom.com   mikepeck5440

Thu Nov 20, 2008 8:52 am (PST)

At 08:30 11/20/2008, Vladimir Galogaza wrote:

>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
under test.
No, there's no meaningful difference in spatial resolution
between PSI and FT methods. Both are superior to fringe tracing
in that regard though.

The main advantages of PSI (IMO) are:

a) it combines data from multiple interferograms in a
mathematically well defined way; and
b) it estimates directly the background contribution and removes
it, again in a mathematically well defined way. This is why
cosmetic defects are somewhat less of a problem.
c) The phase calculation is faster than the vortex transform
computation that Dale uses in Openfringe. I think it will scale
better to higher resolution images or more frames worth of data
too.
d) It's amenable to a fully automated data collection and
processing setup.



>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
<http://home.earthlink.net/~mlpeck54/astro/astro.html>
This is Michael's ATM site.
Vladimir, did you forget the link I gave you already? The current
version will always be maintained at

< http://wildlife-pix.com/rpackages/
<http://wildlife-pix.com/rpackages/> >.

I'm going to go erase the obsolete version on my earthlink page
right now.



------
Michael Peck
mpeck1@ix.netcom.com
http://www.wildlife-pix.com

<http://www.wildlife-pix.com/>
2d.

Re: Attempting PSI Bath

Posted by: "Vladimir Galogaza" vladimir.galogaza1@zg.t-com.hr   vgalogaza

Thu Nov 20, 2008 9:09 am (PST)

Michael,

>Vladimir, did you forget the link I gave you already?

Ups, it seems so. I thought I gave the right one in my post. I have shortcut
with it. I have to change it. Thanks for warning and apology for sloppiness.

Regards
Vladimir.
2e.

Re: Attempting PSI Bath

Posted by: "Michael Peck" mpeck1@ix.netcom.com   mikepeck5440

Thu Nov 20, 2008 9:27 am (PST)

At 11:09 11/20/2008, Vladimir Galogaza wrote:
Michael,

> Vladimir, did you forget the link I gave you already?

Ups, it seems so. I thought I gave the right one in my post. I
have shortcut
with it. I have to change it. Thanks for warning and apology for
sloppiness.


That's alright. I needed the reminder to do some version control.
I've now edited my earthlink cover page to redirect to the
correct location for the R packages.

Mike P.


------
Michael Peck
mpeck1@ix.netcom.com
http://www.wildlife-pix.com

<http://www.wildlife-pix.com/>
2f.

Re: Attempting PSI Bath

Posted by: "Stephen Koehler" s.c.koehler@gmail.com   steve_koehler

Thu Nov 20, 2008 9:32 am (PST)

I would like to add to what Mike said.

> No, there's no meaningful difference in spatial resolution between PSI and
> FT methods. Both are superior to fringe tracing in that regard though.

I believe spatial resolution in FT is proportional to the number of
fringes (tilt). At the high end (fringe spacing of 4 pixels per
fringe) the spatial resolution approaches PSI, but it does not
approach PSI at a larger fringe spacing. I think this is so even with
Vortex, if the background is removed by filtering out the area around
the DC. It may be the case that Vortex resolution is less dependent
on fringe spacing if you can remove the background by differencing
interferograms of different phase. But, if you're doing this, you
might as well be doing PSI.

> a) it combines data from multiple interferograms in a mathematically well
> defined way; and
> b) it estimates directly the background contribution and removes it, again
> in a mathematically well defined way. This is why cosmetic defects are
> somewhat less of a problem.
> c) The phase calculation is faster than the vortex transform computation
> that Dale uses in Openfringe. I think it will scale better to higher
> resolution images or more frames worth of data too.
> d) It's amenable to a fully automated data collection and processing setup.

... and, of course:

e) it can be done with little or no tilt, which reduces possible
retrace error when compared to the high tilt needed for FT.

--
Steve Koehler

2g.

Resolution was Re: Attempting PSI Bath

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Thu Nov 20, 2008 11:18 am (PST)

I'm not convinced that the number of fringes control the resolution
in FT method. I think the number of fringes only help us remove
fringe print through.

The data is there even in wide fringes and that is why some of the
old school interferometerist who evaluate the igram visually like as
few of fringes as possible. One can see tiny surface details in the
color gradations.

Dale Eason

--- In interferometry@yahoogroups.com, "Stephen Koehler"
<s.c.koehler@...> wrote:
>
> I would like to add to what Mike said.
>
> > No, there's no meaningful difference in spatial resolution
between PSI and
> > FT methods. Both are superior to fringe tracing in that regard
though.
>
> I believe spatial resolution in FT is proportional to the number of
> fringes (tilt). At the high end (fringe spacing of 4 pixels per
> fringe) the spatial resolution approaches PSI, but it does not
> approach PSI at a larger fringe spacing. I think this is so even
with
> Vortex, if the background is removed by filtering out the area
around
> the DC. It may be the case that Vortex resolution is less dependent
> on fringe spacing if you can remove the background by differencing
> interferograms of different phase. But, if you're doing this, you
> might as well be doing PSI.
>
> > a) it combines data from multiple interferograms in a
mathematically well
> > defined way; and
> > b) it estimates directly the background contribution and removes
it, again
> > in a mathematically well defined way. This is why cosmetic
defects are
> > somewhat less of a problem.
> > c) The phase calculation is faster than the vortex transform
computation
> > that Dale uses in Openfringe. I think it will scale better to
higher
> > resolution images or more frames worth of data too.
> > d) It's amenable to a fully automated data collection and
processing setup.
>
> ... and, of course:
>
> e) it can be done with little or no tilt, which reduces possible
> retrace error when compared to the high tilt needed for FT.
>
> --
> Steve Koehler
>

2h.

Re: Resolution was Re: Attempting PSI Bath

Posted by: "Vladimir Galogaza" vladimir.galogaza1@zg.t-com.hr   vgalogaza

Thu Nov 20, 2008 12:01 pm (PST)

Dale,

> One can see tiny surface details in the color gradations.

Please elaborate.

Regards
Vladimir.

Yahoo! News

Fashion News

What's the word on

fashion and style?

Yahoo! Finance

It's Now Personal

Guides, news,

advice & more.

Moderator Central

Get answers to

your questions about

running Y! Groups.

Need to Reply?

Click one of the "Reply" links to respond to a specific message in the Daily Digest.

Create New Topic | Visit Your Group on the Web
Messages | Files | Photos | Links | Database | Polls | Members | Calendar
MARKETPLACE
Yahoo! Groups
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Individual | Switch format to Traditional
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe