High-order aberration compensation with multi-frame blind deconvolution and phase diversity image restoration techniques
2010 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 521, A68- p.Article in journal (Refereed) Published
Context. For accurately measuring intensities and determining magnetic field strengths of small-scale solar (magnetic) structure, knowledge of and compensation for the point spread function is crucial. For images recorded with the Swedish 1-meter Solar Telescope (SST), restoration with multi-frame blind deconvolution (MFBD) and joint phase diverse speckle (JPDS) methods lead to remarkable improvements in image quality but granulation contrasts that are too low, indicating additional stray light. Aims. We propose a method to compensate for stray light from high-order atmospheric aberrations not included in MFBD and JPDS processing. Methods. To compensate for uncorrected aberrations, a reformulation of the image restoration process is proposed that allows the average effect of hundreds of high-order modes to be compensated for by relying on Kolmogorov statistics for these modes. The applicability of the method requires simultaneous measurements of Fried's parameter r(0). The method is tested with simulations as well as real data and extended to include compensation for conventional stray light. Results. We find that only part of the reduction of granulation contrast in SST images is due to uncompensated high-order aberrations. The remainder is still unaccounted for and attributed to stray light from the atmosphere, the telescope with its re-imaging system and to various high-altitude seeing effects. Conclusions. We conclude that statistical compensation of high-order modes is a viable method to reduce the loss of contrast occurring when a limited number of aberrations is explicitly compensated for with MFBD and JPDS processing. We show that good such compensation is possible with only 10 recorded frames. The main limitation of the method is that already MFBD and JPDS processing introduces high-order compensation that, if not taken into account, can lead to over-compensation.
Place, publisher, year, edition, pages
2010. Vol. 521, A68- p.
techniques: high angular resolution, techniques: image processing, instrumentation: adaptive optics, methods: numerical, atmospheric effects, Sun: granulation
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-51330DOI: 10.1051/0004-6361/201014800ISI: 000284150900129OAI: oai:DiVA.org:su-51330DiVA: diva2:385062
authorCount :42011-01-112011-01-102014-04-29Bibliographically approved