196 research outputs found
An Improved Observation Model for Super-Resolution under Affine Motion
Super-resolution (SR) techniques make use of subpixel shifts between frames
in an image sequence to yield higher-resolution images. We propose an original
observation model devoted to the case of non isometric inter-frame motion as
required, for instance, in the context of airborne imaging sensors. First, we
describe how the main observation models used in the SR literature deal with
motion, and we explain why they are not suited for non isometric motion. Then,
we propose an extension of the observation model by Elad and Feuer adapted to
affine motion. This model is based on a decomposition of affine transforms into
successive shear transforms, each one efficiently implemented by row-by-row or
column-by-column 1-D affine transforms.
We demonstrate on synthetic and real sequences that our observation model
incorporated in a SR reconstruction technique leads to better results in the
case of variable scale motions and it provides equivalent results in the case
of isometric motions
Single Frame Image super Resolution using Learned Directionlets
In this paper, a new directionally adaptive, learning based, single image
super resolution method using multiple direction wavelet transform, called
Directionlets is presented. This method uses directionlets to effectively
capture directional features and to extract edge information along different
directions of a set of available high resolution images .This information is
used as the training set for super resolving a low resolution input image and
the Directionlet coefficients at finer scales of its high-resolution image are
learned locally from this training set and the inverse Directionlet transform
recovers the super-resolved high resolution image. The simulation results
showed that the proposed approach outperforms standard interpolation techniques
like Cubic spline interpolation as well as standard Wavelet-based learning,
both visually and in terms of the mean squared error (mse) values. This method
gives good result with aliased images also.Comment: 14 pages,6 figure
Numerical methods for phase retrieval
In this work we consider the problem of reconstruction of a signal from the
magnitude of its Fourier transform, also known as phase retrieval. The problem
arises in many areas of astronomy, crystallography, optics, and coherent
diffraction imaging (CDI). Our main goal is to develop an efficient
reconstruction method based on continuous optimization techniques. Unlike
current reconstruction methods, which are based on alternating projections, our
approach leads to a much faster and more robust method. However, all previous
attempts to employ continuous optimization methods, such as Newton-type
algorithms, to the phase retrieval problem failed. In this work we provide an
explanation for this failure, and based on this explanation we devise a
sufficient condition that allows development of new reconstruction
methods---approximately known Fourier phase. We demonstrate that a rough (up to
radians) Fourier phase estimate practically guarantees successful
reconstruction by any reasonable method. We also present a new reconstruction
method whose reconstruction time is orders of magnitude faster than that of the
current method-of-choice in phase retrieval---Hybrid Input-Output (HIO).
Moreover, our method is capable of successful reconstruction even in the
situations where HIO is known to fail. We also extended our method to other
applications: Fourier domain holography, and interferometry. Additionally we
developed a new sparsity-based method for sub-wavelength CDI. Using this method
we demonstrated experimental resolution exceeding several times the physical
limit imposed by the diffraction light properties (so called diffraction
limit).Comment: PhD. Thesi
Sparsity-based single-shot sub-wavelength coherent diffractive imaging
We present the experimental reconstruction of sub-wavelength features from
the far-field intensity of sparse optical objects: sparsity-based
sub-wavelength imaging combined with phase-retrieval. As examples, we
demonstrate the recovery of random and ordered arrangements of 100 nm features
with the resolution of 30 nm, with an illuminating wavelength of 532 nm. Our
algorithmic technique relies on minimizing the number of degrees of freedom; it
works in real-time, requires no scanning, and can be implemented in all
existing microscopes - optical and non-optical
- …