339 research outputs found
Sampling and Super-resolution of Sparse Signals Beyond the Fourier Domain
Recovering a sparse signal from its low-pass projections in the Fourier
domain is a problem of broad interest in science and engineering and is
commonly referred to as super-resolution. In many cases, however, Fourier
domain may not be the natural choice. For example, in holography, low-pass
projections of sparse signals are obtained in the Fresnel domain. Similarly,
time-varying system identification relies on low-pass projections on the space
of linear frequency modulated signals. In this paper, we study the recovery of
sparse signals from low-pass projections in the Special Affine Fourier
Transform domain (SAFT). The SAFT parametrically generalizes a number of well
known unitary transformations that are used in signal processing and optics. In
analogy to the Shannon's sampling framework, we specify sampling theorems for
recovery of sparse signals considering three specific cases: (1) sampling with
arbitrary, bandlimited kernels, (2) sampling with smooth, time-limited kernels
and, (3) recovery from Gabor transform measurements linked with the SAFT
domain. Our work offers a unifying perspective on the sparse sampling problem
which is compatible with the Fourier, Fresnel and Fractional Fourier domain
based results. In deriving our results, we introduce the SAFT series (analogous
to the Fourier series) and the short time SAFT, and study convolution theorems
that establish a convolution--multiplication property in the SAFT domain.Comment: 42 pages, 3 figures, manuscript under revie
Speckle pattern interferometry : vibration measurement based on a novel CMOS camera
A digital speckle pattern interferometer based on a novel custom complementary metaloxide-
semiconductor (CMOS) array detector is described. The temporal evolution of the
dynamic deformation of a test object is measured using inter-frame phase stepping. The
flexibility of the CMOS detector is used to identify regions of interest with full-field time
averaged measurements and then to interrogate those regions with time-resolved
measurements sampled at up to 7 kHz.
The maximum surface velocity that can be measured and the number of measurement
points are limited by the frame rate and the data transfer rate of the detector. The custom
sensor used in this work is a modulated light camera (MLC), whose pixel design is still
based on the standard four transistor active pixel sensor (APS), but each pixel has four
large independently shuttered capacitors that drastically boost the well capacity from that
of the diode alone. Each capacitor represents a channel which has its own shutter switch
and can either be operated independently or in tandem with others. The particular APS of
this camera enables a novel approach in how the data are acquired and then processed.
In this Thesis we demonstrate how, at a given frame rate and at a given number of
measurement points, the data transfer rate of our system is increased if compared to the
data transfer rate of a system using a standard approach. Moreover, under some
assumptions, the gain in system bandwidth doesn’t entail any reduction in the maximum
surface velocity that can be reliably measured with inter-frame phase stepping
The Affine Uncertainty Principle, Associated Frames and Applications in Signal Processing
Uncertainty relations play a prominent role in signal processing, stating that a signal can not be simultaneously concentrated in the two related domains of the corresponding phase space. In particular, a new uncertainty principle for the affine group, which is directly related to the wavelet transform has lead to a new minimizing waveform. In this thesis, a frame construction is proposed which leads to approximately tight frames based on this minimizing waveform. Frame properties such as the diagonality of the frame operator as well as lower and upper frame bounds are analyzed. Additionally, three applications of such frame constructions are introduced: inpainting of missing audio data, detection of neuronal spikes in extracellular recorded data and peak detection in MALDI imaging data
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