Performance validation of phase diversity image reconstruction techniques

¹ Max-Planck-Institut für Sonnensystemforschung, 37434 Katlenburg-Lindau, Germany
e-mail: hirzberger@mps.mpg.de
² School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-71, Korea

Received: 8 September 2010
Accepted: 23 March 2011

Abstract

We present a performance study of a phase diversity (PD) image reconstruction algorithm based on artificial solar images obtained from MHD simulations and on seeing-free data obtained with the SuFI instrument on the Sunrise balloon borne observatory. The artificial data were altered by applying different levels of degradation with synthesised wavefront errors and noise. The PD algorithm was modified by changing the number of fitted polynomials, the shape of the pupil and the applied noise filter. The obtained reconstructions are evaluated by means of the resulting rms intensity contrast and by the conspicuousness of appearing artifacts. The results show that PD is a robust method which consistently recovers the initial unaffected image contents. The efficiency of the reconstruction is, however, strongly dependent on the number of used fitting polynomials and the noise level of the images. If the maximum number of fitted polynomials is higher than 21, artifacts have to be accepted and for noise levels higher than 10^-3 the commonly used noise filtering techniques are not able to avoid amplification of spurious structures.