Image Restoration Algorithm For Optical Sparse Aperture Systems

Enlarge the aperture size is a traditional method to improve the resolution of conventional diffraction-limited optical systems,while it may results in many problems in optical systems,such as huge volume,heave weight,high cost,difficult machining,etc.How to improve the resolution of optical systems meanwhile overcome the aforementioned shortcomings effectively is still a hot research field in recent years.The basic idea of optical sparse aperture systems(OSAS)was first put forward by Golay who proposed the famous Golay N non-redundant array.OS AS are utilized to synthesize a large aperture telescope by using several in-phase circular submirrors to replace a monolithic primary mirror,which solve the difficulties of improving the resolution of conventional optical systems via enlarging aperture size.However,due to the discretization of pupil distribution,OSAS pay the penalty of significant decrease at midband spatial frequencies of the modulation transfer function(MTF).Moreover,the signal-to-noise ratio(SNR)of images is attenuated by the reduction of photon collecting area.Coupled with the adverse impact of environmental factors,the imaging quality of OSAS is overall poor.Therefore,it is necessary to restore the degraded image of OSAS.In this article,the study of OSAS can be devided into two aspects,the simulation modeling of OSAS and image restoration algorithm,mainly organized as follows:First,based on the structure of conventional Cassegrain telescope,modeling and simulation of typical sharing second mirror configuration sparse aperture arrays with different fill factors were presented,furthermore,the analyses of imaging performance of typical OSAS were demonstrated detailedly.Second,based on the comparative study of image restoration results via Wiener filter,an improved Wiener filtering algorithm was proposed to accurately restore the degraded image of OSAS.Differing from Wiener filter which needs to estimate the priori information,an optimum restored image can be gotten without additional estimation via improved Wiener filter.Moreover,in the case of application to OSAS,the analyses of correlation between the image restoration results via improved Wiener filter and the sparse aperture array together with fill factor are expounded.