Studies on high-resolution stellar imaging by use of phase diversity

在地面观测中，由于大气湍流的影响，空间分辨率受到严重限制。本研究的目的是利用相位分集方法克服空间分辨率的下降。相位分集散斑成像是一种从两幅同时记录的散斑图像重建高空间分辨率图像的方法，其中一幅散斑图像是在呈现已知的相位分集后形成的。当散焦被视为相位分集时，简化的光学系统足以获得高分辨率的图像。我们发展了相位分集图像的迭代重建算法。重建算法基于迭代盲解卷积方法和Gerchnerg-Saxfon相位恢复过程。我们对双星、行星物体和太阳光片进行了计算机模拟重建。对于紧凑的物体，我们得到了满意的结果。为了重建大范围扩展的物体，变迹滤波是成功重建的有效方法。进一步的研究是必要的，以提高重建图像的质量。由于太阳的高分辨率观测是太阳物理学的迫切需求之一，因此需要研究新的成像技术和相位分集方法。

In ground-based observations the spatial resolution is severely limited due to atmospheric turbulence.The purpose of this research is to overcome the degradation of the spatial resolution by use of phase-diversity method.Phase-diversity speckle imaging is a method for reconstructing a high-spatial resolution image of a stellar object from two simultaneously recorded speckle images, one of which is formed afer rendering a known phase-diversity.When a defocus ia taken as a phase-diversity, a simplified optical setup is enough for high-resolution imaging.We developed on iterative reconstruction algorithm for phase-diversity imaging.The reconstruction algorithm is based on the iterative blind deconvolution method and the Gerchnerg-Saxfon phase retrieval procedure.We conducted computer simulations for reconstructing binary stars, planetary objects and solar photoshere.We obtained satisfactory results for compact objects.In order to reconstruct largely extended objects, it is shown that an apodization filtering ia effective fo successful reconstructions.Further studies are necessary to improve the quality of reconstructed images.Since high-resolution obsevation of the sun is one of urgent demands in solar physics, new imaging techniques along with the phase-diversity method should be investigated.