NDLI: "Codes" on images and iterative phase unwrapping

Content Provider	IEEE Xplore Digital Library
Author	Frey, B.J. Koetter, R. Petrovic, N.
Copyright Year	2001
Description	Author affiliation: Probabilistic Inference Group, Univ. of Toronto, Ont., Canada (Frey, B.J.)
Abstract	Many imaging techniques, including magnetic resonance imaging and interferometric synthetic aperture radar, produce "phase-wrapped" images. In a phase-wrapped image, the original image values are measured modulus a known wavelength, A. The goal of phase unwrapping is to produce an estimate of the original image using an a priori preference for smooth images. We formulate phase unwrapping as the problem of computing a vector field that is an estimate of the gradient field of the original image. A preference for smooth images is obtained using a Gaussian prior on the vector field. For a vector field to be a gradient field, it must satisfy the constraint that the sum of the vectors around every closed loop is zero. We enforce this constraint using "zero-curl checks" in a factor graph on the vector field. The sum-product algorithm in this factor graph is used to approximately compute the posterior probabilities of the vectors. Hard decisions are used to produce a vector field, which is integrated to obtain the unwrapped image. Experimental results show that this method can work significantly better than existing techniques for phase unwrapping. Although phase unwrapping for general image priors is NP-hard, we conjecture that the sum-product algorithm in an appropriate factor graph will lead to a near-optimal unwrapping algorithm for Gaussian process sources.
Sponsorship	IEEE Inf. Theory Soc
Starting Page	9
Ending Page	11
File Size	458619
Page Count	3
File Format	PDF
ISBN	0780371194
DOI	10.1109/ITW.2001.955119
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2001-09-02
Publisher Place	Australia
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Wavelength measurement Phase measurement Sum product algorithm Surface topography Magnetic resonance imaging Phase estimation Surface reconstruction Magnetic field measurement Wrapping Image processing
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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