Research On Structured Light Illumination Digital Holographic Microscopy

Digital holographic microscopy under structured illumination(SI-DHM)is a combination of structured illumination microscopy and digital holographic microscopy,which combines the advantages of both of them,allowing label-free,wide-field and superresolution imaging of living biologieal sample.The traditional structured lighting techniques usually need to record three images in each illuminating direction,which makes it impossible to take photographs of dynamic sample in real-time.The phase factor of microseopic imaging system not only bring the phase aberrations but also cause the errors of spectrums synthesizing.This thesis centers on the study of these two questions and introduces the related basic theories.Firstly,this thesis introduces the principle of recording and reconstruction in digital holography.The most appropriate angle between object wave and reference wave in the off-axis digital holography is analyzed from the point of spectrums,and three common types of reconstruction algorithms are introduced in detail.The cause of linear and quadratic phase aberrations in the digital holographic microscopic system is analyzed,and the traditional physical and numerical compensation methods are discussed.Secondly,the principle of traditional SI-DHM is studied,and the methods of decomposing and shifting the object spectrum are discussed.The sinulation validates the principle of resolution enhancement in traditional SI-DHM system.There are some questions such as phase aberrations,spectrum decomposing,and etc,in practical application of traditional SI-DHM system.To solve these questions,we propose a reconstruction method based on the principal component analysis(PCA)algorithm.The simulation is performed to validate the feasibility and validity of the proposed method.Besides,the proposed method is applied to the resolution enhancement for phase-contrast imaging in experiment.Finally,we propose a phase-shifting-free method based on the PCA algorithm to solve the question that the real time imaging eannot be achieved in traditional SI-DHM system,that is,the single-shot SI-DHM system we proposed.The polarization and angular multiplexing techniques are used to separate the sample high-frequency components,and the PCA algorithm is applied to perform the accurate spectrum shifting.The question about the isotropic resolution enhancement using structured illumination is discussed.The simulation is performed to validate the eorrectness and feasibility of the proposed scheme.The experiments using three different samples are performed to validate the applications of the proposed system in the field of amplitude-contrast,phase-contrast,and biological sample imaging.The problem existing in the reconstructed image is analyzed and solved.