163 research outputs found
Posterior Mean Super-Resolution with a Compound Gaussian Markov Random Field Prior
This manuscript proposes a posterior mean (PM) super-resolution (SR) method
with a compound Gaussian Markov random field (MRF) prior. SR is a technique to
estimate a spatially high-resolution image from observed multiple
low-resolution images. A compound Gaussian MRF model provides a preferable
prior for natural images that preserves edges. PM is the optimal estimator for
the objective function of peak signal-to-noise ratio (PSNR). This estimator is
numerically determined by using variational Bayes (VB). We then solve the
conjugate prior problem on VB and the exponential-order calculation cost
problem of a compound Gaussian MRF prior with simple Taylor approximations. In
experiments, the proposed method roughly overcomes existing methods.Comment: 5 pages, 20 figures, 1 tables, accepted to ICASSP2012 (corrected
2012/3/23
Confidence-aware Levenberg-Marquardt optimization for joint motion estimation and super-resolution
Motion estimation across low-resolution frames and the reconstruction of
high-resolution images are two coupled subproblems of multi-frame
super-resolution. This paper introduces a new joint optimization approach for
motion estimation and image reconstruction to address this interdependence. Our
method is formulated via non-linear least squares optimization and combines two
principles of robust super-resolution. First, to enhance the robustness of the
joint estimation, we propose a confidence-aware energy minimization framework
augmented with sparse regularization. Second, we develop a tailor-made
Levenberg-Marquardt iteration scheme to jointly estimate motion parameters and
the high-resolution image along with the corresponding model confidence
parameters. Our experiments on simulated and real images confirm that the
proposed approach outperforms decoupled motion estimation and image
reconstruction as well as related state-of-the-art joint estimation algorithms.Comment: accepted for ICIP 201
Comparison of super-resolution algorithms applied to retinal images
A critical challenge in biomedical imaging is to optimally balance the trade-off among image resolution, signal-to-noise ratio, and acquisition time. Acquiring a high-resolution image is possible; however, it is either expensive or time consuming or both. Resolution is also limited by the physical properties of the imaging device, such as the nature and size of the input source radiation and the optics of the device. Super-resolution (SR), which is an off-line approach for improving the resolution of an image, is free of these trade-offs. Several methodologies, such as interpolation, frequency domain, regularization, and learning-based approaches, have been developed over the past several years for SR of natural images. We review some of these methods and demonstrate the positive impact expected from SR of retinal images and investigate the performance of various SR techniques. We use a fundus image as an example for simulations
Superresolution imaging: A survey of current techniques
Cristóbal, G., Gil, E., Šroubek, F., Flusser, J., Miravet, C., Rodríguez, F. B., “Superresolution imaging: A survey of current techniques”, Proceedings of SPIE - The International Society for Optical Engineering, 7074, 2008. Copyright 2008. Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Imaging plays a key role in many diverse areas of application, such as astronomy, remote sensing, microscopy, and
tomography. Owing to imperfections of measuring devices (e.g., optical degradations, limited size of sensors) and
instability of the observed scene (e.g., object motion, media turbulence), acquired images can be indistinct, noisy,
and may exhibit insufficient spatial and temporal resolution. In particular, several external effects blur images.
Techniques for recovering the original image include blind deconvolution (to remove blur) and superresolution
(SR). The stability of these methods depends on having more than one image of the same frame. Differences
between images are necessary to provide new information, but they can be almost unperceivable. State-of-the-art
SR techniques achieve remarkable results in resolution enhancement by estimating the subpixel shifts between
images, but they lack any apparatus for calculating the blurs. In this paper, after introducing a review of
current SR techniques we describe two recently developed SR methods by the authors. First, we introduce a
variational method that minimizes a regularized energy function with respect to the high resolution image and
blurs. In this way we establish a unifying way to simultaneously estimate the blurs and the high resolution
image. By estimating blurs we automatically estimate shifts with subpixel accuracy, which is inherent for good
SR performance. Second, an innovative learning-based algorithm using a neural architecture for SR is described.
Comparative experiments on real data illustrate the robustness and utilization of both methods.This research has been partially supported by the following grants: TEC2007-67025/TCM, TEC2006-28009-E,
BFI-2003-07276, TIN-2004-04363-C03-03 by the Spanish Ministry of Science and Innovation, and by PROFIT
projects FIT-070000-2003-475 and FIT-330100-2004-91. Also, this work has been partially supported by the
Czech Ministry of Education under the project No. 1M0572 (Research Center DAR) and by the Czech Science
Foundation under the project No. GACR 102/08/1593 and the CSIC-CAS bilateral project 2006CZ002
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