61单元自适应光学系统随机并行梯度下降算法动态实验研究

随机并行梯度下降(SPGD)算法是一种无波前探测自适应光学(AO)控制技术,具有很强的应用潜力。设计并实现了基于现场可编程门阵列(FPGA)的SPGD算法处理机,使用热风式湍流模拟装置产生动态波前扰动,搭建了61单元自适应光学系统SPGD算法动态波前畸变校正实验系统。用于性能指标测量的CCD帧频为2900 Hz,SPGD算法处理机迭代速度可达近千次每秒,自适应光学系统实现了对动态波前畸变的补偿。实验结果表明该自适应光学系统对动态模拟湍流具有良好的校正效果,闭环后的性能指标比开环时平均提高了30倍以上,远场光斑峰值平均提升了10倍。通过对性能指标的频谱分析,表明该基于SPGD算法的自适应光学系统的有效带宽为10 Hz。

Abstract

The stochastic parallel gradient descent (SPGD) algorithm is a promising control algorithm for adaptive optics (AO) system without wave-front sensor. In this paper,a 61-element laser beam focusing AO system for correcting dynamical wave-front distortion was established,which used a hot-wind experimental atmospheric turbulence generator and SPGD algorithm controller based on field programmable gate array (FPGA). Up to one thousand iterations per second′s speed of the controller and the sub-millisecond response time of the deformable mirror and tilt mirror provided quick compensation for dynamic wave-front distortion induced by the hot-wind experimental atmospheric turbulence generator. The experimental results demonstrated that this AO system can significantly improve the laser beam quality with 30 times′ increase of the averaged performance metric and 10 times′ increase of the peak-values of far-field intensity distributions. The spectral analysis of performance metric showed that the AO system had an effective bandwidth of 10 Hz.

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张金宝, 陈波, 王彩霞, 李新阳. 61单元自适应光学系统随机并行梯度下降算法动态实验研究[J]. 中国激光, 2010, 37(3): 668. Zhang Jinbao, Chen Bo, Wang Caixia, Li Xinyang. Dynamical Wave-Front Distortion Correction Experiment Based on Stochastic Parallel Gradient Descent Algorithm for 61-Element Adaptive Optics System[J]. Chinese Journal of Lasers, 2010, 37(3): 668.

61单元自适应光学系统随机并行梯度下降算法动态实验研究

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