| Re: Phase Unwrapping Algorithms? [message #7450] |
Wed, 20 November 1996 00:00  |
Christian Soeller
Messages: 46
Registered: August 1996
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Member |
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wsryu@fas.harvard.edu (William Ryu) writes:
> I am interesting in phase unwrapping algorithms which can handle noisy
> data. I understand this to be a common procedure when doing FFT analysis
> of interference patterns, and was wondering if anyone has implemented such
> routines in IDL.
First of all, it is definitely a non-trivial problem in the presence of noise.
When I was doing phase shift interferometry I came across a very clever
paper on the subject in which the authors makes use of the (again
clever) observation that the phase unwrapping problem can be
formulated in a way that is formally similiar to the digitized poisson
equation. It can therfore be solved with the same methods used for
numerically solving the poisson equation. A colleague of mine
implemented the algorithm in C and found it to work well with noisy
data.
The reference is (in Bibtex format):
@Article{Ghiglia94,
author = {D. C. Ghiglia and L. A. Romero},
title = {Robust two-dimensional weighted and unweighted phase
unwrapping that uses fast transforms and iterative methods},
journal = {J. Opt. Soc. Am. A},
year = 1994,
volume = 11,
pages = {107-117}
}
I am not aware of an IDL implementation but it should be worthwile implementing
as it uses FFTs and similiar stuff that is easily done within IDL.
There are many more articles on the subject which is important in the automated
analysis of phase shift interferograms, etc. Journals of special interest are
JOSA and Applied Optics. Another reference is:
@Article{Huntley89,
author = {J. M. Huntley},
title = {Noise-immune phase unwrapping algorithm},
journal = aop,
year = 1989,
volume = 28,
number = 15,
pages = {3268-3270}
}
Hope this get's you started,
Christian
------------------------------------------------------------ --------
Christian Soeller mailto: csoelle@sghms.ac.uk
St. Georges Hospital Medical School Dept. of Pharmacology
Cranmer Terrace London SW17 0RE
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