大行程大阵列驱动磁液变形镜系统关键技术研究

Adaptive optics (AO) systems use the deformable mirror to correct the wavefront aberration, which have been successfully applied in the areas such as high quality imaging, laser shaping and free space laser communication, etc. However, the currently used solid mirrors have the disadvantages of low stroke, high cost per actuator and difficulty of scalability, etc. Confronted with these limitations, an innovative liquid mirror technology that utilized the concept of magnetic fluid deformation shaped with magnetic fields has been proposed recently for precise aberration correction. These magnetic fluid deformable mirrors (MFDMs) have major advantages over solid ones with large strokes, low cost per actuator and ease of scalability. This proposal will study some key problems in building MFDMs with (ultra-) high stroke and large actuator array property. The first objective involves the development of a comprehensive model of the MFDM surface shape response to the applied control magnetic field. Through the dynamic property analysis based on the analytical model, the optimal design of MFDM with large stroke and large actuator array properties can then be formulated. The second object is to develop the corresponding distributed linearized state space model within an infinite input-output dimension, based on which an optimal distributed shape control algorithm is further proposed. The robustness and optimal control performance of the resulting closed loop system with the distributed control approach will be analyzed. The third objective concerns the design and development of a prototype MFDM to be used in the validation of the mirror model and in the evaluation of the designed controllers. It also includes the design and assembly of an experimental AO setup to test the performance of the MFDM for potential applications,such as the retinal imaging and astronomical imaging.

自适应光学技术利用变形镜来实时校正光束的波前像差，在高清晰成像、激光整形和激光通讯等领域得到广泛的应用，但现今使用的固态变形镜存在变形幅度小、制造成本高和不易扩展等缺点，而基于纳米磁性液体的液态变形镜技术通过控制磁液周边的磁场使液体表面发生变形，从而实现精确的像差校正功能，相比固态镜有变形幅度大、制造成本低、易于扩展和布局等优点。本课题将对研制具有大行程大阵列驱动特征的磁液变形镜系统若干关键问题进行研究，包括建立大行程下磁液变形镜多场耦合解析动力学模型及进行相应的动力学特性分析；推导系统无穷维状态空间表述的分布式线性化模型，并提出有效的分布式优化控制算法；探索大行程大阵列驱动磁液变形镜性能优化的设计方法，针对视网膜高清晰成像和亚精密天文望远镜成像中的像差特征分别优化设计和制作原型样机；以潜在的实际应用为背景，搭建实验平台验证变形镜的性能，及建模理论和控制方法的有效性。

自适应光学技术利用波前校正器来完成对光波波前的实时校正和控制，从而使光学系统自动适应外界环境的变化，实现达到衍射极限的成像能力或精确的光束控制能力。波前校正器作为自适应光学系统中的关键部件，其动态性能和校正精度对系统的整体性能和应用范围起着决定性的作用。现有两种基本的波前校正器为固态变形镜和液晶空间相位调节器，然而受器件材料和制造技术条件的限制，目前波前校正器的校正幅值普遍较小，在有限孔径内难以开发出同时具有大行程量和高空间驱动分辨率的单一波前校正器件。. 本项目利用磁性液体既具有液体的流动性，又具有可以被外磁场磁化而拥有磁性的特点，通过改变磁性液体周围的磁场来精确控制磁性液体表面的变形，从而设计出同时具有大行程量和高空间驱动分辨率的单一波前校正器件。本项目以磁液变形镜在自适应光学中的应用为背景，重点探索了磁液镜面在大行程工作条件下的多场耦合动力学特性，建立了变形镜多输入多输出解析动力学模型。推导了驱动变量为无穷维情况下的系统分布式模型，针对有波前传感器和无波前传感器的应用环境，分别提出了基于波前检测的分布式Youla参数化自适应控制方法和无波前检测的迭代式控制方法。基于推导的变形镜动力学模型，提出了大行程和大阵列驱动的磁液变形镜系统参数优化设计和制作方法，为提高磁液变形镜的镜面反射率，提出了一种液面自组装的液态状银纳米薄膜配置方法。以磁液变形镜在光镊微操作系统、自适应光学共聚焦扫描生物显微成像系统和液态天文望远镜像差校正应用为背景，分别搭建了相应的自适应光学试验平台，试验验证了磁液变形镜的像差校正性能及像差校正控制方法的有效性。. 相比于传统的固态变形镜和液晶空间光调制器，本项目提出的磁液变形镜具有镜面连续平滑、变形行程大、制造成本低、驱动器易扩展等优点，有望在自适应光学领域得到成功的应用。