集成应变反馈层的横向压电驱动变形镜面形预测及闭环控制

Surface figure prediction and closed-loop control for novel unimorph deformable mirror integrated strain feedback layer

作为校正光学像差的主要器件,横向压电驱动变形镜在自适应光学系统中应用十分广泛。哈特曼等波前传感器通过反射光得到镜面面形,然而并没有直接反映压电陶瓷的工作状态,并且这些波前探测器增加了系统的成本。以单层横向压电变形镜为对象,建立了压电陶瓷驱动器单电极的横向应变与镜面变形之间的映射关系。制备了集成应变层的单电极横向压电变形镜,进行静态面形预测实验。预测结果表明,添加应变反馈层能够预测单电极的影响函数,拟合误差在7.3%以内。模型的主要误差源是压电陶瓷的迟滞非线性,采用PID控制器对变形镜驱动陶瓷的应变输出进行了闭环控制,镜面位移迟滞率降低至1.74%。针对超连续谱光纤激光器像差进行了闭环校正分析,相比于开环和哈特曼的校正结果,校正精度提升至0.79,实现了横向压电变形镜无波前探测校正像差的一种新方式。

As the main device to correct optical aberrations,the unimorph or bimorph deformable mirror（DM） is widely used in adaptive optics. The Shack-Hartmann Wave-front sensor et al. obtains the surface figure through the mirror＇s reflected light. However,it does not directly receive the motion state of the piezoelectric ceramic,and the wave-front sensors increase the system cost. In this paper,the mapping relationship between the electrode＇ s transverse strain and the mirror deformation is established for single-electrode unimorph deformable mirror. A single-electrode unimorph DM witch bonded on the rosette is fabricated. Deformation prediction experiments are carried out. The results show that the influence function can be predicted through integrating the feedback layer. And the fitting error is within 7. 3%. The main error of the model is the nonlinear hysteresis of the piezoelectric ceramic. The PID controller is used to correct the strain feedback signal error. As a result,the hysteresis rate of mirror displacementis is reduced to 1. 74%. On the other hand,the aberration of the super-continuum fiber laser beam is corrected by the unimorph DM at closed loop. Compared with the correction results with Shack-Hartmann Wave-front sensor or strain gages at open loop,the accuracy is increased to 0. 79,which realizes a new mean for DMs＇ no wave front detection.