EVALUATION OF PHASE-DIVERSITY TECHNIQUES FOR SOLAR-IMAGE RESTORATION

Phase-diversity techniques provide a novel observational method for ov ercoming the effects of turbulence and instrument-induced aberrations in ground-based astronomy. Two implementations of phase-diversity tech niques that differ with regard to noise model, estimator, optimization algorithm, method of regularization, and treatment of edge effects ar e described. Reconstructions of solar granulation derived by applying these two implementations to common data sets are shown to yield nearl y identical images. For both implementations, reconstructions from pha se-diverse speckle data (involving multiple realizations of turbulence ) are shown to be superior to those derived from conventional phase-di versity data (involving a single realization). Phase-diverse speckle r econstructions are shown to achieve near diffraction-limited resolutio n and are validated by internal and external consistency tests, includ ing a comparison with a reconstruction using a well-accepted speckle-i maging method.