[seminarios-tcrp] summary of next seminar
- From: "Luis B. Almeida" <luis.almeida@xxxxxxxx>
- To: seminarios-tcrp@xxxxxxxxxxxxx
- Date: Tue, 21 Oct 2008 14:30:28 +0100
Hi all,
Here is the summary of the seminar of next Friday.
Title: PHASE IMAGING: UNWRAPPING AND DENOISING WITH DIVERSITY AND
MULTI-PRECISION
Gonçalo Valadão
Abstract:
Many imaging techniques, e.g., interferometric synthetic aperture radar
(InSAR), and magnetic resonance imaging (MRI), yield phase images. In
these, generally, each pixel retrieves the phase up to a modulo-$2\pi$
rad ambiguity, i.e., the phase wrapped around the principal interval
$[-\pi\;\pi[$. Phase unwrapping (PU) is, then, a crucial operation to
obtain absolute phase, which is where physical information relies on. If
the phase difference between neighbor pixels is less than $\pi$ rad,
then, phase unwrapping can be obtained unambiguously. This, however, is
not always the case. E.g., in InSAR, where absolute phase is
proportional to terrain altitude, we often face neighbor phase
differences much larger than $\pi$ rad. The PU problem is even more
challenging for noisy images. We propose a diversity approach, which
consists of using two (or more) images of the same scene acquired with
different frequencies. Diversity grants an enlargement of the ambiguity
interval $[-\pi\;\pi[$, thus, allowing to unwrap images with higher
phase rates. Furthermore, we present a multi-precision technique to
make denoising. We formulate the problem with a MAP - MRF rationale, and
apply energy minimization techniques based on graph cuts. We illustrate
the performance of the algorithm by showing experimental results, and
argue that it is, as far as we know, state-of-the art.
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