中国巨型太阳望远镜主动对准建模分析

Active Alignment Modeling and Analysis of Chinese Giant Solar Telescope

针对中国巨型太阳望远镜(CGST)主副镜的对准需求,提出了基于激光干涉测距的激光桁架主动对准方法。首先总体介绍CGST激光桁架测量系统的光学结构和测量原理;然后建立激光桁架运动学模型和主动对准光学模型并讨论系统的误差传播特性;接着通过大气光学模型来讨论温度场和局地大气湍流对该主动对准方法的影响。运动分析与光学建模结果表明,在可见光波段,当激光桁架的测距误差在5μm以内、环境温度梯度小于0.381 K/m时,由对准误差引起的波前均方根优于λ/10。另外,在Kolmogorov湍流和典型昼间近地面湍流的条件下,大气湍流并不会严重降低激光桁架测量的灵敏度。由此可知,所提方法能够满足CGST副镜主动对准的需求。

In order to meet the alignment requirements of the primary and secondary mirrors of the Chinese giant solar telescope(CGST),an active alignment method of laser truss based on laser interferometry is proposed.First,the optical structure and measurement principle of the CGST laser truss measurement system are introduced,then the laser truss kinematics model and active alignment optical model are established,and the error propagation characteristics of the system are discussed.Then,the effects of temperature field and local atmospheric turbulence on the active alignment method are discussed through the atmospheric optical model.The results of motion analysis and optical modeling show that in the visible band,when the ranging error of the laser truss is less than 5μm and the environmental temperature gradient is less than 0.381 K/m,the wavefront root-mean-square caused by alignment error is better thanλ/10.In addition,under the conditions of Kolmogorov turbulence and typical daytime near-surface turbulence,atmospheric turbulence does not seriously reduce the sensitivity of laser truss measurement.It can be seen that the proposed method can meet the requirements of active alignment of CGST secondary mirror.