Study On Wavefront Phase Retrieving And Coherent Diffractive Imaging Based On Sampling Arrays

Since the existing optical recording material or device only responds to the intensity oflight waves, thus, how to quickly and accurately detect and recover the wave front phaseinformation of the to-be-detected light wave from the recorded optical field intensity patternhas long been a key issue that requires to be addressed in many research fields of modernoptics. Furthermore, due to universality of wave motion phenomenon, the detection of wavefront phase information is not only just an optical problem, but also an important issue thatcauses concerns from many other research fields of physics. In particular, along with thesuccessful application of adaptive optics technology that bases upon wave front real-timedetection and compensation in laser fusion, high-resolution observation of celestial bodies,human retinal imaging and other areas, as well as the rapid unfolding of the research onapplication of lensless diffraction imaging technology that bases upon wave front phaserecovery in extreme-ultraviolet or X-ray phase contrast imaging, the fast wave front phasedetection or recovery technology, suitable for different applications and wavelengths, hasbecome one frontier and research hotspot of this research field.Focusing on the wave front detection method and coherent diffraction imaging, thisdissertation has conducted theoretical analysis and experimental researches, and the researchcontents of major chapters are listed as below:1. The main content of Chapter1summarizes the research advances in wave frontreconstruction and coherent diffraction imaging, and introduces the theories andapplications regarding iterative reconstruction of wave front and slope wave frontmeasurement, according to the existing classic and traditional wave front detection methods.In addition, it also highlights the theory of holographic interferometry, as well as the wideapplications and progresses of Hartmann wave front sensor in atmospheric optics,optometry and other areas. The chapter touches upon the development of diffractionimaging technology in the up-to-date research progresses in phase inversion wave frontreconstruction, and respectively points out the research progresses and shortcomings ofvarious existing methods. Finally, it explains that the key research contents are based on thesampled periodic array diffraction imaging theory, and describes the progresses in thisresearch direction and the next step of application prospects.2. The main content of Chapter2summarizes the theory relating to scalar diffraction andinformation optics in coherent diffraction imaging (CDI）. It derives the scalar diffractiontheory via Maxwell scalar wave equation, further provides the integral equation and discrete form of Fresnel diffraction and Fraunhofer diffraction, and offers simple analysisof angular spectrum propagation method. It describes the Fourier transform and property inthe information optics required in our research work, and discusses the sampling principleto be followed in CDI experiments and simulations.3. In the third chapter, the phase unwrapping algorithm research shows that the phaseunwrapping algorithm based on reliability can effectively avoid error propagation, andimprove the reliability of the phase unwrapping in comparing the four algorithms. In thesection, example is presented.4. To restore the shape of original object, it is required to know its amplitude and phaseinformation. Therefore, it is a core issue to obtain the phase information of object wavefrom the diffraction intensity distribution. The phase reconstruction capability serves as animportant factor in the reconstruction of image quality and enhancement of resolution.The main content of Chapter3introduces the classic and traditional GS method, andsubsequently analyzes ER algorithm principle and hybrid input-output algorithm.Furthermore, it also conducts the algorithm simulation comparison against the currentdevelopment of hybrid algorithm, provides experimental results and analysis, summarizesthe advantages and disadvantages of iteration algorithm, and points out the problems to beresolved in our next study. Based on the iterative algorithm, put forward a new methodwhich is about the random sampling screen of wavefront phase for the phase Retrieval andcoherent diffraction imaging. By inserting a random sample screen between the objectplane and the recording plane, the object wave through the sampling record screen we canobtain Fresnel diffraction intensity distribution on recording plane with CCD. It could beRetrieved wave front using iterative algorithm of on the sample screen position. In thefourth chapter, the phase unwrapping algorithm research shows that the phase unwrappingalgorithm based on reliability can effectively avoid error propagation, and improve thereliability of the phase unwrapping in comparing the four algorithms. In the section,example is presented.5. On the basis of the law on periodic array of diffraction, the main content of Chapter5and6offers a detailed analysis of the sampling-based periodic array of diffraction principle,designs the sampling array of special period, finds out a kind of lensless coherentdiffraction imaging method, provides the imaging analysis of two periodic array screens,and conduct comparisons. Furthermore, it also conduct further detailed analysis of theimpact of recorded aperture in array sampled diffraction imaging on reconstructed images.6. On the basis of the front studies, the main content of Chapter7further discusses thecoherent diffractive wave front detection method of sampling-based Fresnel diffraction.This method restricts the complex amplitude information of to-be-detected object wavethrough sampling the Fresnel diffraction intensity distribution of sampled object wave ofhexagonal periodic array. This chapter gives a detailed theoretical analysis, provides thereconstruction simulation of amplitude and phase object and comparison of imaging resultsof different diffraction distances. The experimental comparison proves that this method canimprove the imaging resolution. 7. The main content of Chapter8introduces the slope measurement and Hartmann sensorprinciple, outlines the method for wave front reconstruction via the modal method, andspecifically analyzes the diffraction theory of two micro-pore sizes, i.e. circle&ring. Themicro-circular ring can obtain smaller focusing spot than that of circular pore. In addition,the chapter experiments, by way of simulation, the wave front reconstruction of periodicarray at the best diffraction position, and compare these two ways of reconstruction.