Superresolution Pupil Filtering Based On Adaptive Optics And Its Application On Visual Function Research

The development of imaging technology is an important driving force for promoting the progress of science and technology.The capable of high resolution or super-resolution imaging is helpful for human to get to known the outside world deeply.Objectively,the optical imaging resolution is limited by the diffraction limitation.It is a hot issue how to break the diffraction barrier to realize super-resolution imaging in many fields.Pupil filtering is one of the core technologies in super-resolution imaging.Presently,two main elements are used as pupil filter to realize super-resolving,one is binary diffractive super-resolving elements,the other is liquid crystal spatial light modulator(LCSLM).In this thesis,deformable mirror is employed as a programmable super-resolution pupil phase filter.Deformable mirror can overcome the shortcomings of the existing pupil filters,permit the analysis of various filter designs and allow the filters to be changed rapidly to modify the dynamic response of an optical system.Also,this method,with little energy loss,has no wavelength and polarization light requirement.The existing super-resolution imaging technology is mainly used in biological microscope,laser processing and optical storage etc.This thesis focuses on the design of deformable pupil filter,and the purpose is to apply super-resolution technology to enhance the human visual performance,and explore the method of breaking the limit of human visual function.The main contents are as follows.Two types of phase pupil filter are designed: polynomial pupil filter and Zernike polynomials pupil filter.The design principle of the polynomial pupil filter is presented.The designed polynomial filter is simulated by 37-element and 145-element deformable mirror respectively.The results show that the 37-element deformable mirror is not suitable for fitting the phase structure because of its limited electrodes and low resolution.For 145-element deformable mirror,the 3mm distance between spacing piezoelectric actuators lead to high spatial resolution.The simulation results indicate that 145-element deformable mirror can fit the designed phase structure of pupil filter successfully.In the pupil filter design based on Zernike polynomial,genetic algorithm(GA)is adopted to explore the optimal solution.According to the design requirements,two Zernike polynomial functions are chosed for further analysis,one with bigger S,the other with smaller GT.Different Adaptive Optical(AO)systems were designed and built to perform different super-resolution test.Simply,the deformable mirror,located in pupil plane of optical system,generates the phase structure by software programming to realize super-resolution imaging.The phase is measured by wave-front sensors.The measurement results are fed into the computer and compared with the designed phase structure.According to the difference,the deformable mirror is further modified.The closed-loop phase fitting of pupil filter is achieved by modifying the closed-loop reference matrix of the adaptive optics system.After the simulation of the pupil filter,the super-resolution effect of point spread function(PSF)and the resolution board(USAF1951)are tested further.With wave-front is modified by 145-element deformable mirror,the focus spots are obtained in the focal plane under different correction conditions.The experimental results are in agreement with theoretical predictions.Furthurmore,this super-resolution technology is applied to test the visual function improvement.The Point Spread Function(PSF)and Contrast Spread Funtion(CSF)were tested under the wavefront modulation by two super-resolution filters respectively with improved AO system.For PSF,the experimental results conform to the expected super-resolution effect.For CSF,the experimental results are different under different super-resolution filter,one(SR1)is better,the other(SR2)has no effect.In view of this result,the paper has carried on the thorough analysis and discussion.In sum,a new superresolution pupil filter is designed and implementation in this thesis.The superresolution effect is simulated and tested.Part of visual function of human eyes is improved by this way,meanwhile some problems occured during the research process as well.It is worthwhile to do further research and solve the problems.