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Authors: G. Desiderà, B.Anconelli, M. Bertero, P. Boccacci, and M. Carbillet
Abstract: Context. The paper is about methods for multiple image deconvolution and their application to the reconstruction of the images aquired by the Fizeau interferometer, denoted LINC-NIRVANA under development for the Large Binocular Telescope (LBT). The multiple images of the same target are obtained with different orientations of the baseline. Aims. To propose and develop a blind method for dealing with cases where no knowledge or very poor knowledge of the point spread function (PSF) is available. Methods. The approach is an iterative one where object and PSFs are alternately updated using deconvolution methods related to the standard Richardson-Lucy method. It is basically an extension, to the multiple image case, of iterative blind deconvolution methods proposed in the case of a single image. Results. The method is applied to simulated LBT LINC-NIRVANA images and its limitations are investigated. The algorithm has been implemented in the module BLI of the software package AIRY (Astronomical Image Reconstruction in interferometrY), avaible under request. The preliminary results we have obtained are promising but an extensive simulation program is still necessary for a full understanding of the applicability of the method in the practice of the reconstruction of LINC-NIRVANA images.

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Posted by: admin, on 11/1/2006, in category "2006"
Views: this article has been read 8013 times
Authors: B.Anconelli, M.Bertero, P.Boccacci, G.Desiderà, M.Carbillet, and H.Lanteri
Abstract: Context. The standard Richardson-Lucy method (RLM) does not work well in the deconvolution of astronomical images containing objects with very different angular scales and magnitudes. Therefore, modifications of RLM, applicable to this kind of objects, must be investigated. Aims.We recently proposed a regularization of RLM which provides satisfactory results in the case of particular test objects with high dynamic range. In this paper we extend this method to the case of multiple image deconvolution, having in mind application to the reconstruction of the images provided by Fizeau interferometers such as LINC-NIRVANA, the German-Italian beam combiner for the Large Binocular Telescope. Methods.RLM is an iterative method for the minimization of the Csiszár divergence, a problem equivalent to maximum likelihood estimation in the case of photon noise. In our approach, the problem is regularized by adding a suitable penalization term to the Csiszár divergence and an iterative method converging to the minimum of the resulting functional is derived from the so-called split gradient method (SGM). Results.The method is tested on a model of young binary star consisting of a core binary surrounded by a dusty circumbinary ring. The results are quite good in the case of exact knowledge of the point spread functions (PSF). However, in the case of approximate knowledge of the PSFs, the accuracy of the reconstruction depends on the difference of magnitude between the ring and the central binary.

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Posted by: andrea, on 7/30/2008, in category "2006"
Views: this article has been read 8040 times
Authors: B.Anconelli, M. Bertero, P. Boccacci, M. Carbillet, and H. Lanteri
Abstract: Our approach proposed in a previous paper for the reduction of boundary effects in the deconvolution of astronomical images by the Richardson-Lucy method (RLM) is extended here to the problem of multiple image deconvolution and applied to the reconstruction of the images of LINC-NIRVANA, the German-Italian beam combiner for the Large Binocular Telescope (LBT). We investigate the multiple image RLM, its accelerated version ordered subsets expectation maximization (OSEM), and the regularized versions of these two methods. In addition we show how the approach can be extended to the iterative space reconstruction algorithm (ISRA), which is an iterative method converging to non-negative least squares solutions. Numerical simulations indicate that the approach can provide excellent results with a considerable reduction of the boundary effects.

Rating: 10 user(s) have rated this article Average rating: 5.0
Posted by: admin, on 11/1/2006, in category "2006"
Views: this article has been read 7839 times