Technology And Application Of Aberration Correction Based On Micromachined Membrane Deformable Mirror

As an emerging comprehensive technology which is growing rapidly in recent years, in the application of human fundus microscopic observation, adaptive optics provides a new way of diagnosis and treatment for human ophthalmology diseases and other systemic diseases because of the advantages of exact and rapid real time measurement, control and correction of human aberration, which can improve resolution of imaging system. On the basis of adaptive optics and visual optics theory, this thesis carries out a further research on human aberration correction theory and technology based on micromachined membrane deformable mirror, which can provide theoretical support and engineering practice guidance for the development of low-cost high precision living human retina imaging system. The content of this thesis mainly includes:(1) The human eyeball structure is described in detail. The human wavefront aberration is defined, and its representation model is established on the basis of Zernike polynomial. The principle and method of Hartmann-Shack wavefront sensor based human wavefront aberration reconstruction is systematically studied, and a wavefront aberration reconstruction algorithm of human eyes based on singular value decomposition is put forward, which lays the foundation for human aberration correction.(2) The structure and principle of micromachined membrane deformable mirror is described in detail, and the relationship between micromachined membrane deformable mirror deformation and driving electrode control signal is analyzed theoretically and verified experimentally. On the basis of influence function matrix, the relationship model between deformable mirror control signal and the mode parameter of aberration to be compensated is built, and the micromachined membrane deformable mirror fitting ability and correcting range of Zernike model aberration is analyzed, which provides theoretical basis for the design of aberration compensation algorithm based on micromachined membrane deformable mirror.(3) The spatial domain aberration compensation model based on micromachined membrane deformable mirror is built. In the open-loop correction mode, two control signal solving algorithms based on multiplier penalty function method and effective constraint sets method respectively are put forward. The first method converts the original problem into an unconstrained optimization problem by multiplier vector and penalty function. The second method converts the original problem into an equality constrainted problem. The two methods both have the advantages of high speed and precision, which are very suitable for the system with small system error and a high-accuracy influence function matrix.(4) In the close-loop correction mode, a control signal solving algorithm based on singular value decomposition is proposed, by which the correctable aberration mode space of the micromachine membrane deformable mirror is constructed. The system correction characteristic for the constructed orthogonal basis modes and the principle of improving the deformable mirror correctable ability by selecting aberration correction modes are analyzed in detail. Through computer simulation and model eye correction experiments, the influence of selecting aberration modes is analyzed. At last, the aberration compensation algorithm which can realize aberration modes fitering based on singular value decomposition is determinated as the optimal human eye aberration correction algorithm.(5) The dynamic characteristics of human eye aberration are summarized. The control model of adaptive optics is established and the system transfer function is derived. Taking the improvement of control system bandwidth as the optimization objective, system performance of integral control algorithm and smith control algorithm are comparative analyzed, and a wavefront correction algorithm based on smith control and singular value decomposition is proposed, which offers an appropriate method for human eye aberration correction based on micromachined membrane deformable mirror.(6) According to theoretical research results in this thesis, the hardware system and software system of the first domestic retina cell microscope based on micromachined membrane deformable mirror is designed, which can realize real time measurement and correction of human aberration and acquire retina cell images. By the correction experiments of model eye and human eye, the high definition model eye fundus images and the living human eye retina cell images are obtained successfully. At present, the microscope has successfully passed the test from Supervising and Testing Center of Hangzhou Zhejiang Institute for the control of Medical Device.