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笔者利用Seelight中的光场相机模块与PZT变形镜模块搭建了自适应光学仿真系统,如图8所示。验证以光场相机作为波前传感器,与89单元变形镜配合在闭环工作模式下校正大气湍流相位屏的效果。
大气湍流相位屏模型采用基于傅里叶谱的数值方法[10],大气垂直传输距离10 km,湍流强度Cn2为10−15。光场相机模型的参数为:光束口径6 mm,探测波长633 nm,主透镜的f数为30,微透镜阵列的大小为10×10,微透镜元口径200 μm,微透镜阵列f数15,CCD像元尺寸5 μm,动态调制半径为d,d为微透镜元的口径。89单元变形镜致动器以六边形排布。点光源发出光经过湍流相位屏后到达望远镜入瞳处的波前畸变和变形镜的致动器排布方式分别如图9和图10所示。
将光场相机测得光场数据经过动态调制后,利用直接斜率法计算重构矩阵,生成电压信号控制变形镜致动器形成共轭面形补偿波前畸变。表1给出了在闭环控制模式下对大气湍流波前畸变校正后远场光斑随着迭代次数的变化趋势。从结果中可以看出在动态调制时光场相机的闭环校正效果明显,远场光斑的收敛显著,当迭代进行到第三次时远场光斑已经趋于稳定。
Number of iterations 0 1 2 3 Closed loop Number of iterations 4 5 6 7 Closed loop Table 1. Far field spot distribution changing tendency at closed loop of AO system
Simulation research on adaptive optics system based on light field camera
doi: 10.3788/IRLA20201043
- Received Date: 2020-06-15
- Rev Recd Date: 2020-07-20
- Available Online: 2020-11-03
- Publish Date: 2020-11-03
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Key words:
- wavefront sensing /
- light field camera /
- multi-layered conjugation /
- simulation system
Abstract: In adaptive optics (AO) system, the traditional Hartmann wave-front sensor can only be used to effectively correct atmospheric turbulence within a small field of view, while the light field camera served as the wave-front sensor has the characteristics of large field of view and multi-angle directional turbulence information obtained by one single exposure, which can replace multiple wave-front sensors in the traditional multi-layered conjugation adaptive optics (MCAO) system and simplify the system and save costs. In this paper, the light field camera module in Seelight, an optical system simulation software independently developed, was used to restore the complete wavefront of the large field of view combining the optical field digital refocusing technology and the mode atmospheric analysis technology. An adaptive optical simulation system was built with a light field camera and a 89 unit deformable mirror. The simulation results show that the optimized AO system can effectively correct the wavefront distortion caused by atmospheric turbulence in a large field of view under the closed loop working mode.