Development of imaging techniques in gamma-ray astronomy using coded mask systems : application to the telescope LEGRI = Desarrollo de técnicas de obtención de imágenes en astronomía gamma usando sistemas de máscara codificada : aplicación al telescopio LEGRI

In the energy range of gamma radiation we can not use lenses or mirrors to form images, it is therefore necessary to use other systems. A solution to the problem is the coded mask telescope concept, consisting of a flat detector and a pattern of transparent and opaque elements before it. What we detect is the mask pattern shadows that different gamma sources produce in the detector plane. From this and knowning the pattern that produces these shadows (the mask), one can reconstruct the source field. In this work, and applied to the telescope LEGRI, we have studied four reconstruction algorithms (fine sampling balanced correlation, delta decoding, maximum entropy and the EM algorithm, the latter being applied to gamma astronomy for the first time). We perform a detailed analysis of them in order to verify their suitability for LEGRI telescope, obtaining the best results with the EM algorithm.