增加激光导星的散射层采样厚度可以提高波前探测器的探测能量,但是存在探测光斑弥散问题.针对该问题,分析并设计了动态聚焦系统.首先分析了采样厚度对波前探测能量的影响,结果显示,波前探测能量随着采样厚度非线性增大,当采样厚度为4 km、激光脉冲能量为10 mJ时,望远镜子孔径接收到的光子数为120,满足探测精度要求.然后分析了光斑弥散对波前探测精度的影响,当采样厚度为4 km 时,波前探测误差约为0.5 λ,探测误差较大.为了实现精确探测,依据分析结果设计了动态聚焦系统,将聚焦反射镜的移动距离由111 mm 缩小到100 μm、移动速度由4200 m/s降低到3.8 m/s,满足应用需求.最后利用Zemax软件进行优化,结果表明,对于4 km采样厚度,光学系统均能实现理想成像.

By increasing the sample scattering layer thickness of laser guide star,the detection energy of wavefront sensor is enhanced but makes the detection spot diffused.To solve this problem,a dynamic focus system is designed.Influence of the sample thickness on the wave-front detection energy is analyzed and result shows that the wave-front detection energy increases nonlinearly with the sample thickness.When the sample thickness is 4 km with the laser pulse energy of 10 mJ,the number of received photons is 120 per sub-aperture of telescope,which meets the detection requirements.Then effect of diffusion spot on wave-front detection accuracy is analyzed,the result shows that the wave-front measurement error is about 0.5 λ when the sample thickness is 4 km,which leads accurate detection unfeasible.In order to achieve accurate detection,dynamic focus system is designed based on the analysis results,moving distance of the focusing mirror is reduced from 111 mm to 100 μm,and moving speed from 4200 m/s to 3.8 m/s,which meet the application requirements.Zemax softwave optimized results show that the optical system can achieve the ideal imaging for 4km sample thickness range.