Multilevel two-dimensional phase unwrapping

Iddit Shalem, M.Sc. Thesis Seminar
Wednesday, 21.6.2006, 11:30
Taub 701
Prof. I. Yavneh

In this work we study the problem of two-dimensional phase unwrapping and propose two algorithms for its solution. Two-dimensional phase unwrapping is the problem of deducing unambiguous ``phase" from values known only modulo $2\pi$. Many authors agree that the objective of phase unwrapping should be to find a weighted minimum of the number of places where adjacent (discrete) phase values differ by more than $\pi$ (called discontinuities). This NP-hard problem is of considerable practical interest, largely due to its importance in interpreting data acquired with synthetic aperture radar (SAR) interferometry. Consequently, many heuristic algorithms have been proposed. Our first algorithm considers the wrapped phase array as a grey level image and applies the image segmentation problem to this image. Based on the segmentation, we develop an efficient relaxation method for decreasing discontinuities in the phase image. The second algorithm presents an efficient multi-level graph algorithm for the approximate solution of an equivalent problem---minimal residue cut in the dual graph.

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