Self-Referenced Speckle Holography-high Resolution Imaging Method Using Wavefront Sensing from Deconvolution

The angular resolution of ground-based telescopes is essentially limited by atmo spheric turbulence. Over the past 20 years, new techniques have been proposed to over come this natural limitation in high-resolution imaging. They can be divided into two main kinds: one is active predetection compensation.eg, Adaptive Optics, which detects wave-front by wave-front sensor and controls the deformable mirror to compensate the distorted wavefront in real-time. The other is passive postdetection com pensation. Namely, Speckel imaging technology, which constructs phase-corrected images through historical records by digital processing.eg, Knox-Thom pson method, speckle masking, shift and add method, etc. SRSH(Self-Referenced Speckle Hologarphy) described in the thesis is new technique proposed in the late 80's com bining Adaptive Optics with speckle imaging. It uses wave-front sensing and reconstruction tech nology in Adaptive Optics to get the instan taneous OTF(Optical Transfer Function) including the atmosphere and records short exposure images at the same time, then reconstructs the object image by deconvolution. SRSH has many advantages compared with Adaptive Optics and speckle imaging technology. It needs farless short-exposure images and processing time than that by using the speckle interferom etrym ethods, and it canalso achieve the same type of good restoration. The time delay error due to the finite loop band width is a main limitation for Adaptive Optics systems. In SRSH it can be avoided by detecting wave-front and recording short-exposure images at the same time. Theoretically, SRSH can achieve better restoration results than Adaptive Optics and can have similar speed. Moreover, this method is a complement to Adaptive Optics. If the compensation by Adaptive Optics is not perfect for technological reasons, the restoration of the observed object can be complimented. In the thesis a new wave-front sensing method— curvature sensing is presented. Current Adaptive Optics systems can use only a small number of bright natural stars as guide stars, which limit their use to astronomy. Ho wever curvature sensing technique can use fainter natural guide stars. Thus wave-front of most of the objects in the sky can be detected. Curv ature sensing also has other adva ntages compared with the other wave-front sensing methods.