变形镜高斯函数指数对迭代法自适应光学系统的影响

基于613单元自适应光学系统, 描述了迭代矩阵和斜率响应矩阵的特性. 在变形镜驱动器间距和交连值不变的情况下, 研究了变形镜高斯函数指数对迭代矩阵和斜率响应矩阵稀疏度的影响, 对自适应光学系统稳定性和校正能力的影响. 研究表明, 迭代矩阵和斜率响应矩阵的稀疏度随着变形镜高斯函数指数的增大而减小. 高斯函数指数过大或者过小都会影响自适应光学系统的稳定性和校正能力. 最后, 综合迭代矩阵和斜率响应矩阵的稀疏度、自适应光学系统的稳定性和校正能力, 给出了合理的变形镜高斯函数指数的取值范围.

Influence of Gaussian function index of deformable mirror on iterative algorithm adaptive optical system

Among all kinds of wavefront reconstruction algorithms in adaptive optical systems, the standard and mostly used algorithm is the direct gradient wavefront reconstruction algorithm. As the number of sub-apertures in Shack-Hartmann wavefront sensor and the actuators for deformable mirror increases, the reconstruction matrix in direct gradient wavefront reconstruction algorithm takes too much space and the number of multiplication in the algorithm increases sharply. So, the iterative algorithm is adopted in wavefront reconstruction for the high-resolution adaptive optical system. The number of multiplication and the required space of the iterative algorithm are directly related to the sparseness of both iterative matrix and slope response matrix. In an adaptive optical system, the sparseness of these two matrixes is connected with the system parameters. Therefore, it is necessary to study how to choose the proper parameters for an adaptive optical system when it uses iterative wavefront reconstruction algorithm. In this paper, the sparseness of slope response matrix and iterative matrix are analyzed based on a 613-actuator adaptive optical system. The influence of the Gaussian function index of deformable mirror on the sparsenesses of slope response matrix, iterative matrix, stability and correction qualities of the adaptive optical system are also studied under the condition of constant actuator spacing and coupling coefficient. A larger Gaussian function index results in a lower sparseness of the slope response matrix and the iterative matrix. Too large or too small a Gaussian function index will degrade the stability and the correction quality of an adaptive optical system. Finally, the optimal range of the Gaussian function index is provided by balancing the sparseness of slope response matrix, the correction quality, and the stability of the adaptive optical system.