2,997 research outputs found
From 3D Point Clouds to Pose-Normalised Depth Maps
We consider the problem of generating either pairwise-aligned or pose-normalised depth maps from noisy 3D point clouds in a relatively unrestricted poses. Our system is deployed in a 3D face alignment application and consists of the following four stages: (i) data filtering, (ii) nose tip identification and sub-vertex localisation, (iii) computation of the (relative) face orientation, (iv) generation of either a pose aligned or a pose normalised depth map. We generate an implicit radial basis function (RBF) model of the facial surface and this is employed within all four stages of the process. For example, in stage (ii), construction of novel invariant features is based on sampling this RBF over a set of concentric spheres to give a spherically-sampled RBF (SSR) shape histogram. In stage (iii), a second novel descriptor, called an isoradius contour curvature signal, is defined, which allows rotational alignment to be determined using a simple process of 1D correlation. We test our system on both the University of York (UoY) 3D face dataset and the Face Recognition Grand Challenge (FRGC) 3D data. For the more challenging UoY data, our SSR descriptors significantly outperform three variants of spin images, successfully identifying nose vertices at a rate of 99.6%. Nose localisation performance on the higher quality FRGC data, which has only small pose variations, is 99.9%. Our best system successfully normalises the pose of 3D faces at rates of 99.1% (UoY data) and 99.6% (FRGC data)
Phase Retrieval with Application to Optical Imaging
This review article provides a contemporary overview of phase retrieval in
optical imaging, linking the relevant optical physics to the information
processing methods and algorithms. Its purpose is to describe the current state
of the art in this area, identify challenges, and suggest vision and areas
where signal processing methods can have a large impact on optical imaging and
on the world of imaging at large, with applications in a variety of fields
ranging from biology and chemistry to physics and engineering
Correlating Fourier phase information with real-space higher order statistics
We establish for the first time heuristic correlations between harmonic space
phase information and higher order statistics. Using the spherical full-sky
maps of the cosmic microwave background as an example we demonstrate that known
phase correlations at large spatial scales can gradually be diminished when
subtracting a suitable best-fit (Bianchi-) template map of given strength. The
weaker phase correlations lead in turn to a vanishing signature of anisotropy
when measuring the Minkowski functionals and scaling indices in real-space and
comparing them with surrogate maps being free of phase correlations. Those
investigations can open a new road to a better understanding of signatures of
non-Gaussianities in complex spatial structures by elucidating the meaning of
Fourier phase correlations and their influence on higher order statistics.Comment: 6 pages plus 1 supplemental page, 4 figures, submitte
Feature Extraction for Music Information Retrieval
Copyright c © 2009 Jesper Højvang Jensen, except where otherwise stated
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