采用400 mm口径,12 mm厚的球面反射镜进行了主动光学实验。实验镜支撑结构由背部12个主动支撑点和3个固定支撑点组成。主动支撑点用压电陶瓷促动器和压力传感器组成力促动器,用于控制实验镜面形;固定支撑点用于控制实验镜的定位。实验中通过干涉仪测试镜面面形。分别测量出反射镜在单独一个促动器施加单位作用力前后的镜面面形,求出这两个面形之差得到该促动器的响应函数,由各促动器的响应函数组成刚度矩阵,然后用阻尼最小二乘法计算各支撑点的校正力。最后,通过PID算法闭环控制各促动器施加力的过程。经过3次校正,将初始状态的1.22λRMS的面形误差校正到0.12λRMS,接近了镜面加工的0.1λRMS面形精度,说明所采用的主动校正算法和过程正确可行。

An active optical experiment was carried out by a mirror with a diameter of 400 mm and a thickness of 12 mm. The support construction of the mirror included 12 active supports and 3 fixed supports,in which the active support was implemented by force actuators consisting of piezoelectric ceramic actuators and loadcells. The active supports were used for controlling the surface of the mirror,and the fixed points were used for positioning the mirror. In the experiment,the mirror surface was tested by a Zygo interferometer. The surface error of the mirror was tested before and after an actuator exerted a unit force on it lonely,then the difference between the two surface errors was calculated to be as the response function of the actuator,and the response functions of all the actuators made up a stiffness matrix. Afterwards,the damp least square method is used to determine the active corrective force and the process of exerting force of the actuator was controlled by a PID arithmetic. The experimental results show that the surface error is corrected from 1.22λRMS to 0.12λRMS,which is close to 0.1λ that is the surface quality after polishing. The experiment shows the active correct arithmetic and procedure is correct and feasible.