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Modeling and control of a magnetic fluid deformable mirror for ophthalmic adaptive optics systems.

机译：用于眼科自适应光学系统的磁性流体可变形反射镜的建模和控制。

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摘要

Adaptive optics (AO) systems make use of active optical elements, namely wavefront correctors, to improve the resolution of imaging systems by compensating for complex optical aberrations. Recently, magnetic fluid deformable mirrors (MFDM) were proposed as a novel type of wavefront correctors that offer cost and performance advantages over existing wavefront correctors. These mirrors are developed by coating the free surface of a magnetic fluid with a thin reflective film of nano-particles. The reflective surface of the mirrors can be deformed using a locally applied magnetic field and thus serves as a wavefront corrector. MFDMs have been found particularly suitable for ophthalmic imaging systems where they can be used to compensate for the complex aberrations in the eye that blur the images of the internal parts of the eye. However, their practical implementation in clinical devices is hampered by the lack of effective methods to control the shape of their deformable surface.;The research work reported in this thesis presents solutions to the surface shape control problem in a MFDM that will make it possible for such devices to become integral components of retinal imaging AO systems. The first major contribution of this research is the development of an accurate analytical model of the dynamics of the mirror surface shape. The model is developed by analytically solving the coupled system of fluid-magnetic equations that govern the dynamics of the surface shape. The model is presented in state-space form and can be readily used in the development of surface shape control algorithms. The second major contribution of the research work is a novel, innovative design of the MFDM. The design change was prompted by the findings of the analytical work undertaken to develop the model mentioned above and is aimed at linearizing the response of the mirror surface. The proposed design also allows for mirror surface deflections that are many times higher than those provided by the conventional MFDM designs. A third contribution of this thesis involves the development of control algorithms that allowed the first ever use of a MFDM in a closed-loop adaptive optics system. A decentralized proportional-integral (PI) control algorithm developed based on the DC model of the wavefront corrector is presented to deal mostly with static or slowly time-varying aberrations. To improve the stability robustness of the closed-loop AO system, a decentralized robust proportional-integral-derivative (PID) controller is developed using the linear-matrix-inequalities (LMI) approach. To compensate for more complex dynamic aberrations, an Hinfinity controller is designed using the mixed-sensitivity Hinfinity design method. The proposed model, design and control algorithms are experimentally tested and validated.
机译：自适应光学（AO）系统利用有源光学元件（即波前校正器）来补偿复杂的光学像差，从而提高成像系统的分辨率。近来，磁流体可变形反射镜（MFDM）被提出作为一种新型的波前校正器，其相对于现有的波前校正器具有成本和性能上的优势。这些反射镜是通过在磁性流体的自由表面上覆盖一层纳米颗粒反射薄膜而制成的。反射镜的反射表面可以利用局部施加的磁场而变形，因此用作波前校正器。已经发现MFDMs特别适用于眼科成像系统，在该系统中，它们可用于补偿眼睛中使眼睛内部部分的图像模糊的复杂像差。然而，由于缺乏有效的方法来控制其可变形表面的形状，它们在临床设备中的实际应用受到了阻碍。;本论文报道的研究工作提出了解决MFDM中表面形状控制问题的方法，这将使其成为可能。这样的设备成为视网膜成像AO系统的组成部分。这项研究的第一个主要贡献是开发了镜面形状动力学的精确分析模型。该模型是通过解析求解控制表面形状动力学的流体电磁方程组的耦合系统而开发的。该模型以状态空间形式表示，可以很容易地用于表面形状控制算法的开发中。研究工作的第二个主要贡献是MFDM的新颖创新设计。设计变更是由于开发上述模型而进行的分析工作的发现而引起的，旨在使镜面响应线性化。所提出的设计还允许镜面挠度比传统MFDM设计所提供的镜面挠度高很多倍。本论文的第三点贡献是控制算法的发展，该算法允许在闭环自适应光学系统中首次使用MFDM。提出了一种基于波前校正器的DC模型开发的分散比例积分（PI）控制算法，该算法主要用于处理静态或慢时变像差。为了提高闭环AO系统的稳定性，使用线性矩阵不等式（LMI）方法开发了一种分散的鲁棒比例积分微分（PID）控制器。为了补偿更复杂的动态像差，使用混合灵敏度Hinfinity设计方法设计了Hinfinity控制器。对所提出的模型，设计和控制算法进行了实验测试和验证。

著录项

  • 作者

    Iqbal, Azhar.;

  • 作者单位

    University of Toronto (Canada).;

  • 授予单位 University of Toronto (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 226 p.
  • 总页数 226
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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