Simulation Theories And Technologies For Digital Holographic Phase Imaging Of Biological Cells

With the development of the life sciences from descriptive science to quantitative science, the biological cells optical quantitative detective technology has attracted wide attention. The phase imaging technology provides a powerful tool for the quantitative study of biological cells with its advantages of non-invasive, no damage and allowing quantitative. Over the past decade, different varieties of the holography-based quantitative phase imaging technologies have been developed and successfully used for quantitative phase imaging of biological cells. However, the information of biological cells, which useful for cell biologists and medical diagnostics, often can not be directly obtained from the quantitative phase information. The resreach on quantitative detection technology of the cells especially heterogeneous cells, which are based on the quantitative phase imaging technology, is still in its infancy and needs to be further improved and perfected. Therefore, the simulation technology of quantitative phase imaging of the biological cells including homogeneous and heterogeneous cells is studied in this dissertation after in-depth analysising on a variety of quantitative phase imaging theory. The dual-medium quantitative measurement simulation method has been proposed and realized via MATLAB. Based on this method, the subsurface imaging of cells with simply substructure, the impact of relative lateral and light axial position of the substructure on the phase imaging and the impact of the pose of red blood cells in the detection on morphology geometric parameters measurement are discussed in this dissertation.Combined on-axial four-step phase-shifting digital holographic interferometry and the numerical calculation of the angular apectrum diffraction and its inverse diffraction, quantitative phase imaging simulation method for biological cells simulation imaging is proposed. A single spherical model and a heterogeneous HeLa cell with irregular shape model are simulated for phase imaging by using this simulation method. The feasibility and reliability of the simulation method are confirmed by comparing the phase maps obtained through simulation, through theoretical calculation and the experiments of other team.The dual-media quantitative measurement simulation method is present for research on inhomogenous cells, which is realized by combining on-axial four-step phase-shifting digital holography with dual-medium quantitative analysis. A homogeneous cell (RBC) and a heterogeneous cell (HeLa cell) are studied by this simulation method and their physical thicknesses and average refractive indices are obtained from the quantitative phase information. The simulation results show that the obtained physical thickness of either the homogeneous cell or the non-homogeneous cell using this method is reliable in the any imaging area, due to that the deviation between simulation value and theoretical value is within the allowable range. But the simulated axial average refractive index of the two cell models is reliable in the effective area, of which the physical thickness h≥0.01μm.A subsurface imaging method of heterogeneous phase object is proposed based on dual-medium quantitative measurement method. The feasibility of this method is confirmed by subsurface imaging simulation experiments of a two-sphere model and a monocyte model. Split-step optical propagation theory is introduced to the object wave simulation of series two-sphere model, of which the internal small sphere positions are different, for studying the impact of relative lateral and light axial position of the substructure on the phase imaging. The simulation results show that for the two-sphere model, the relative lateral position of the internal small sphere makes the higher area of the unwrapping phase map appear at the corresponding position and the relative light axial position of internal small sphere does not affect the unwrapping phase morphology deeply, but there are some minute differences in the edge of the small sphere. By comparing the theoretical value without considering the diffraction effect, the curve of the relationship between the axial position of internal small sphere and the maximum positive deviation of the phase value in the edge of the internal small sphere is obtained.Based on the idea of rotation curve into surface and the3D graphics rotation transform, the more precise biconcave disk models of the erythrocytes with different poses are established. And then these models are simulated for phase imaging by using the quantitative phase imaging simulation method proposed above and their geometrical parameter information such as thickness, volume, surface area and sphericity are obtained from the simulated phase information. Then the impaces of the different poses of an erythrocyte in the detection on morphology geometric parameters measurement are discussed. The results show that the phase maps of the same erythrocyte with different pose are different, as well as thickness distributions, which indicates that it is difficult to determine an erythrocyte normal or not by its morphology distribution obtained from phase information. The deviations of measured thicknesses, volumes, surface areas and sphericities of erythrocytes with different poses by using quantitative phase imaging simulation technology are within the allowable range, which confirms the feasibility and reliability of the erythrocyte morphology geometric parameters measurement by using quantitative phase imaging technology. However when the cell surface areas were measured through using the phase imaging technology, it is needed to pay attention to the method application scope, for which the ratio of the cell thickness to the cell diameter is greater than0.3, at the same time, the influence of cell inner concave structure also need to be taken into account in the measurement.