Subject: [interferometry] Digest Number 922
From: interferometry@yahoogroups.com
Date: 9/18/2007, 7:21 AM
To: interferometry@yahoogroups.com

interferometry
interferometry

Messages In This Digest (4 Messages)

1a.
Re: Noise free champ From: Dale Eason
2a.
New file uploaded to interferometry From: interferometry@yahoogroups.com
2b.
New file uploaded to interferometry From: interferometry@yahoogroups.com
3a.
Re: possible improvement in fringe unwrapping From: Kieran Larkin
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Messages

1a.

Re: Noise free champ

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

Mon Sep 17, 2007 8:28 pm (PST)

OK Bill didn't resond maybe he is not available. So I have upload a
jpg version see Files \Dale Eason\billThomas.jpg

Dale Eason

--- In interferometry@yahoogroups.com, "Dale Eason" <atmpob@...> wrote:
>
> I hope Bill Thomas posts his narrow fringe igram that he sent to me.
I
> think it is the all time cleanest we have seen on this list. It
could
> stand to have more tilt but boy is it noise free.
>
> Dale Eason
>

2a.

New file uploaded to interferometry

Posted by: "interferometry@yahoogroups.com" interferometry@yahoogroups.com

Mon Sep 17, 2007 9:10 pm (PST)


Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the interferometry
group.

File : /Bill_Thomas/9170766.jpg
Uploaded by : bthomas32000 <bjthomas@yubagold.com>
Description : next after Noise Free Champ

You can access this file at the URL:
http://groups.yahoo.com/group/interferometry/files/Bill_Thomas/9170766.jpg

To learn more about file sharing for your group, please visit:
http://help.yahoo.com/help/us/groups/files

Regards,

bthomas32000 <bjthomas@yubagold.com>


2b.

New file uploaded to interferometry

Posted by: "interferometry@yahoogroups.com" interferometry@yahoogroups.com

Mon Sep 17, 2007 9:52 pm (PST)


Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the interferometry
group.

File : /Bill_Thomas/160751.jpg
Uploaded by : bthomas32000 <bjthomas@yubagold.com>
Description : Noise free champ Dale Eason mentioned

You can access this file at the URL:
http://groups.yahoo.com/group/interferometry/files/Bill_Thomas/160751.jpg

To learn more about file sharing for your group, please visit:
http://help.yahoo.com/help/us/groups/files

Regards,

bthomas32000 <bjthomas@yubagold.com>


3a.

Re: possible improvement in fringe unwrapping

Posted by: "Kieran Larkin" kieran.larkin@cisra.canon.com.au   gezthemutant

Tue Sep 18, 2007 12:01 am (PST)

At 11:27 AM 13/09/2007, Stephen Koehler wrote:

>Group,
>.....
>
>Mike, Kieran, or anyone else: Is this technique mentioned in the
>literature on phase unwrapping, e.g., Ghiglia and Pritt? It's so
>simple, and so apparently effective, that I'm surprised that I haven't
>heard of it, before. Unless I am thinking of this problem wrong, I
>see no problem with unwrapping twice with a removal of tilt, defocus
>and SA in the middle.
>
>--
>Steve Koehler

Hi Steve

The idea of removing some background level of phase (with significant phase
gradient) is rather like the sub-Nyquist idea of John Greivenkamp. There
is a nice explanation of it on the following website:

http://www.engsynthesis.com/pdfs/white_papers/Intellium%20Asphere%20Overview.pdf

I have also seen early, oblique suggestions of essentially removing linear
and quadratic phase terms in Bones' papers:

1. D. J. Bone, "Fourier fringe analysis: the two-dimensional phase
unwrapping problem," Applied Optics 30, 3627(1991).
2. D. J. Bone, H.-A. Bachor, and R. J. Sandeman, "Fringe-pattern
analysis using a 2-D Fourier transform," Applied Optics 25, 1653-1660 (1986).
3 J. E. Greivenkamp, "Sub-Nyquist interferometry," Appl. Opt. 26,
5245- (1987)

One possible interpretation is that in your example the fringes are below
the Nyquist limit, but by removing the local phase gradient your are
shifting the residual phase to very low variation whilst the noise is still
fairly high frequency and more easily removed.

Regards

Kieran
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