Regularization te hniques for the numeri al solution of nonlinear inverse s attering problems in two spa e dimensions are dis ussed. Assuming that the boundary of a s atterer is its most prominent feature, we exploit as model the lass of artoon-like fun tions. Sin e fun tions in this lass are asymptoti ally optimally sparsely approximated by shearlet frames, we onsider shearlets as a means for ...

In this paper, we first briefly review the directional properties of the Dual-Tree complex wavelet transform and we investigate how the directional selectivity of the transform can be increased (i.e., to obtain more than 6 orientations per scale). To this end, we describe a new augmented Lagrangian optimization algorithm to jointly perform the 2D spectral factorization of a set of 2D directiona...

The fast digital shearlet transform (FDST) was recently introduced as a means to analyze natural images efficiently, owing to the fact that those are typically governed by cartoon-like structures. In this paper, we introduce and discuss a first-order hybrid sigma-delta quantization algorithm for coarsely quantizing the shearlet coefficients generated by the FDST. Radial oversampling in the freq...

Volumetric data acquisition and increasingly massive data storage have increased the need to develop better analysis tools for three-dimensional data sets. These volumetric data sets can provide information beyond that contained in standard two-dimensional images. Common strategies to deal with such data sets have been based on sequential use of two-dimensional analysis tools. In this work, we ...

To reduce the x-ray dose in computerized tomography (CT), many constrained optimization approaches have been proposed aiming at minimizing a regularizing function that measures lack of consistency with some prior knowledge about the object that is being imaged, subject to a (predetermined) level of consistency with the detected attenuation of x-rays. One commonly investigated regularizing funct...

In this paper we show that the shearlets, an affine-like system of functions recently introduced by the authors and their collaborators, are essentially optimal in representing 2–dimensional functions f that are C2 except for discontinuities along C2 curves. More specifically, if fS N is the N–term reconstruction of f obtained by using the N largest coefficients in the shearlet representation, ...

Under the linear approximation model for error diffusion halftoning, a shearlet-based inverse halftoning (SIH) algorithm is proposed. The SIH algorithm performs inverse halftoning by first inverting the modelspecified convolution operator and then reducing the residual color noise using scalar shearlet-domain thresholding. The optimal thresholds are derived by using the maximum a posteriori rul...

This paper presents a new filtering approach for Synthetic Aperture Radar (SAR) interferometric phase noise reduction in the shearlet domain, depending on the coherent statistical characteristics. Shearlets provide a multidirectional and multiscale decomposition that have advantages over wavelet filtering methods when dealing with noisy phase fringes. Phase noise in SAR interferograms is direct...