基于干涉仪测量的变形镜面形展平标定研究

为了全面地了解变形镜的性能,以便自适应光学系统更好地工作,进行了基于干涉仪测量的变形镜面形展平标定研究.首先,给变形镜的压电陶瓷驱动器施加一半的控制电压;再用Zygo干涉仪测得变形镜的面形,计算对应各个驱动器位置的镜面高度,并算得各个位置镜面高度相对平均镜面高度的偏差;最后,控制驱动器运动使偏差量为零.测试及实验表明,受压电陶瓷迟滞的影响,上述过程需要迭代4到6次镜面面形才会收敛到希望的准确度;对镜面周边无驱动器约束的21单元变形镜,展平之后其80%口径的面形接近λ/20(λ=632.8 nm);对镜面周边有驱动器约束的137单元变形镜,展平后的面形优于λ/50.在望远镜不同的观测条件下,该技术可以快速地对变形镜进行展平标定,以适应不同的工作环境.

Flatten Calibration of Deformable Mirror Based on the Measurement of the Interferometer

In order to make the adaptive optical system function well, it needs to have a full understanding of the performance of the deformable mirror, so a technique for the flatten calibration of the deformable mirror based on the measurement of the interferometer is presented. Firstly, all the PZT actuators are set to the midrange of their control voltage; and then, the height of the mirror surface with the ZYGO interferometer is measured, the height of mirror surface at each actuator is calculated, and the differences between the height of the mirror surface at each actuator and the average height of the mirror surface are figured out; finally, the actuators are controlled to reduce the differences to zero. The results show that affected by the hysteresis of the PZT actuator, the mirror surface needs 4 to 6 iterative processes showed above to reach the same preset desired flatness; for the 21-elements deformable mirror, which without the actuators under the periphery of the mirror, an rms surface figure near λ/20(λ=632.8 nm) at its 80% aperture is achieved; for the 137-elements deformable mirror, which has actuators under the periphery, the rms surface figure is better than λ/50. Under different observation conditions of the telescope, this technique can flat the deformable mirror rapidly in the adaptive optical system, in order to adapt to changing working conditions.