Optimal Defocus for Phase Diversity Wave Front Retrieval

Phase diversity techniques are widely employed in solar astronomy to evaluate and correct the aberrations stemming from atmospheric turbulences, the telescope, and its instruments. The method uses information provided by a pair of images. One of them is usually focused while the other one is defocus...

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Bibliographic Details
Published in:The Astrophysical journal. Supplement series 2022-11, Vol.263 (1), p.8
Main Authors: Bailén, F. J., Orozco Suárez, D., Blanco Rodríguez, J., del Toro Iniesta, J. C.
Format: Article
Language:English
Subjects:
Aberration
Astronomical instrumentation
Astronomical instruments
Astronomical techniques
Astronomy
Incident waves
Numerical experiments
Optimization
Phase diversity
Signal to noise ratio
Solar images
Solar instruments
Wave fronts
Zernike polynomials
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Summary:Phase diversity techniques are widely employed in solar astronomy to evaluate and correct the aberrations stemming from atmospheric turbulences, the telescope, and its instruments. The method uses information provided by a pair of images. One of them is usually focused while the other one is defocused. The amount of defocus to be induced is somehow arbitrary, though. In this work we carry out a series of numerical experiments with artificial solar images to investigate the performance of phase diversity for different choices of the relative defocus among the two images. The experiments allow us to determine the amount of defocus that produces the best wave front restoration when changing: (1) the number of Zernike polynomials of the retrieved and/or incident wave fronts; (2) the signal-to-noise ratio of the images; (3) the amplitude of the incident aberrations; and (4) the observed scene. We find a correlation between the amount of defocus needed for optimal restorations and the number of Zernike polynomials employed in the optimization. Values larger than the typically accepted choice of 1 λ (peak to peak) are obtained in most cases.
ISSN:0067-0049
1538-4365
DOI:10.3847/1538-4365/ac966c