高分辨率太阳图像重建方法

High Resolution Solar Image Reconstruction

高空间分辨率的太阳观测数据有助于深入研究太阳大气现象、太阳物理基本问题。地基大口径太阳望远镜常通过自适应光学技术和图像重建技术获取高空间分辨率图像。目前太阳图像重建技术主要有斑点成像术和斑点相位差法两类。介绍了斑点成像术中几类方法的原理,阐述了斑点成像术重建太阳像的流程以及几个关键步骤,介绍了多帧盲反卷积和相位差法的原理,比较了斑点成像术和斑点相位差法的特点,最后阐述了它们在太阳高分辨率观测中的应用和发展趋势。

High spatial resolution solar observations contribute to the in-depth studying of the solar atmosphere and solar physics problems. Ground-based large diameter solar telescopes often obtain high spatial resolution images by the adaptive optics （AO） technique and the image reconstruction technique. The AO can well reduce the low-order aberrations but still remains residuals significant. As the AO correction is partial, the image reconstruction technique is being in demand to further correct the higher-order aberrations. Current solar image reconstruction techniques mainly include the speckle imaging and the phase diversity. The speckle imaging techniques are some kinds of high resolution reconstruction methods based on statistical computation. The most used methods are the speckle interferometry and the speckle masking. The phase diversity is a method to recover the object from the focal image and the defocused image in the absence of the atmospheric information. In this paper, firstly, we introduce the principle of the speckle imaging methods. Then describe the basic processes and several key steps of the solar reconstruction of the speckle imaging. The main steps include fiat-field correction, data alignment, segmentation, amplitude and phase recovery. We also introduce the principle of the multi-frame blind de-convolution and the phase diversity. A simple diagram is shown to distinguish their differences. We compare the characteristics of the speckle imaging and the phase diversity. Finally, we expound the application and the development trend in the solar high resolution observations. The main methods of the solar image reconstruction for the next generation big telescopes are still the speckle imaging technique and the phase diversity, and we believe the real-time observation of the sun will achieve with the development of the modern computer technology.