Quantitative Phase Imaging Technology Based On Transport Of Intensity Equation

Currently, optical microscopy imaging techniques has been rapidly developed and widely applied in the field of biomedical research for the observation and detection of different organs, tissues, cells or macromolecules, which generally have different requirements, often involving the use of different microscopy techniques. When conventional microscopic imaging techniques such as intensity-based bright field microscopy, dark field microscope and fluorescence microscope, phase-modulation based contrast microscopy and differential interference contrast microscopy cannot meet the quantitative phase measurement requirements for colorless and transparent biological cell, a variety of quantitative phase imaging methods have been proposed and studied, such as interferometry-based quantitative interference microscopy and digital holographic technique, iterative-based G-S algorithm and IE imaging technology. Compared with these technologies, quantitative phase imaging based on transport of intensity equation(TIE) have gained more and more intention because of its outstanding advantages and have obtain rapid development and wide application.. This thesis discussed the TIE phase imaging in detail including historical development, domestic and international research actuality, derivation of TIE equation and phase retrieval method based on the Fast Fourier transform, and also focused on the real-time quantitative phase imaging based on TIE.Traditionally, TIE phase imaging obtains multi-focal intensity images capturing through axially scanning by image detector which is troublesome and time consuming in actual measurement and cannot realize phase imaging in real time. In order to break through the limitation of traditional TIE method, dual view TIE and single-shot TIE real-time phase retrieval methods based on transport of intensity equation are proposed respectively in this thesis. These studying achievements overcome disadvantages of traditional TIE method for realizing real-time quantitative phase imaging of live cells, which expand applications of TIE imaging technology in live science area.In dual view TIE system, two identical CCD detectors located at the binocular tubes of a commercial inverted microscope are used to capture the same field of view. Since the on-focus image can be approximated as the average of those images at over- and under-focal layers, the quantitative phase distribution of samples can be computed simultaneously. This method realized real-time quantitative phase imaging by combining the structure of an inverted microscopy and optimizing algorithm. Moreover, the feasibility and accuracy of dual view TIE were proved through numerical simulation and experimental measurements.Real-time quantitative phase imaging based on single-shot TIE method captured multi-focal images simultaneously with a single camera by building 4f system and introducing programed phase mask loaded into the spatial light modulator(SLM) which can realize beam splitter and optical zoom. This method is more flexible and accurate for realizing quantitative TIE phase imaging in real time.The proposed real-time phase imaging methods based on transport of intensity equation extends the range of application of TIE imaging technology in biomedical observation of live cells, which will provide a more efficient and flexible way for real-time quantitative phase imaging.