采用模式控制对能动光学系统的有效运行是十分重要的。针对 1.2 m能动镜, 对常见的泽尼克模式、主镜的自由振荡模式和本征模式进行了分析, 其中本征模借鉴于薄膜反射镜的模式分析, 但尚未见到用于能动主镜的模式控制, 从能动镜对各模式的拟合精度以及选用的模式数量与能动镜系统的校正能力的关系考虑, 选择离焦、三阶彗差和 9阶本征模作为 1.2 m能动光学系统的校正模式, 其中离焦和三阶彗差由次镜的平移和倾斜进行校正, 9阶本征模由主镜背面的力驱动器阵列进行校正。

Modal control is very important for effective operations of active optical systems. Several types of modes are studied for a 1.2 m active mirror, such as Zernike modes, free vibration modes of the primary mirror and eigen modes. Eigen modes are referred to modal analyses of membrane deformable mirrors and modal control based on eigen modes of the primary mirror haven’t been found yet. Considering the fitting accuracy of the active mirror for various modes and the relationship between fitting capability and the number of modes adopted, defocus, 3rd coma and 9 eigen modes are used for modal control of the 1.2 m active mirror. Defocus and 3rd coma are corrected through the movement and tilt of the secondary mirror and 9 eigen modes are corrected through force actuators at the back of the primary mirror.