基于相位差异的地基望远镜高速高分辨率成像研究

The high resolution imaging of ground-based telescope can achieve space target surveillance and survey that has significance in space science development strategy. However, the imaging resolution of ground-based telescope is limited by the effects of the atmosphere turbulence induced distortion that makes the performance of imaging degraded, with the results that the detection ability of large ground-based telescope is restricted. So designing a telescope which can overcome wavefront distortion is one of the most important tasks right now. Phase diversity is competent for wavefront distortion. It is a high performance-price ratio method of simple configuration, low cost and well fit for both point and extended sources. It has great potential in the filed of high resolution imaging. This project is to propose an efficient high resolution imaging algorithm based on Phase diversity theory and GPU computing platform, and develop a high speed and high resolution imaging processing system combined with optical design. Then it will be applied to the large ground-based telescope imaging system so as to overcome the impact of atmosphere turbulence on high resolution imaging efficiently that will make system imaging quality approach diffraction limit.

地基望远镜的高分辨率成像技术可以实现对空间目标的监视和详查，是实现我国空间科学发展战略目标的重要技术手段。但是，地基望远镜受到大气湍流引起的波前畸变等因素的影响，目标成像质量下降，分辨率降低，从而限制了地基望远镜的探测能力。因此发展具有抗波前畸变性能的地基大口径望远镜仍然是当前最重要的任务。相位差异正是针对波前相位畸变发展起来的图像恢复方法，具有光路简单、系统构建简易，适应的目标范围广等特点，在高分辨率成像领域有着巨大的发展潜力。本项目以相位差异理论为基础，以GPU为计算平台，形成高效快速的高分辨率成像算法，结合光学设计，实现基于相位差异技术的高速高分辨率图像处理系统，并将其应用于地基大口径望远镜高分辨率成像输出终端，快速、有效地抑制大气扰动对地基大口径望远镜高分辨率成像的影响，提高成像系统分辨能力，使其成像质量接近衍射极限。

本项目针对地基光电望远镜受大气湍流和光学系统误差影响，目标成像质量下降、探测能力受限的问题，开展了基于相位差异技术的地基望远镜高速高分辨率成像研究。完成了相位差异算法的设计和优化：依据傅里叶光学理论，建立了高斯噪声模型下的相位差异算法数学模型，并构造了稳定且全局收敛的非线性优化算法；针对相位差异算法中的图像噪声及配准误差等问题，改进和完善了相位差异数学模型，提高了图像恢复精度和解算速度。完成了相位差异算法在CPU+GPU异构模式下的并行优化，提高图像恢复效率，相比CPU平台获得了百倍的加速比。完成了基于相位差异技术的图像恢复实验，能够恢复0.4角秒双星，恒星FWHM下降了约80%。相位差异技术是地基大口径光电望远镜一种较为理想的图像恢复技术，将成为地基成像望远镜的标准模块，为空间目标的相关研究提供优质的观测资料。