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Resolution Improvement Mechanism And Experimental Study On Digital Holographic Microscopic Imaging

Posted on:2018-08-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q W LinFull Text:PDF
GTID:1318330563452209Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Digital holography is the technology of the combination of the traditional optical microscopy,computer and photoelectric detection technology.With the rapid development of photoelectric technology and computer technology,the digital holographic quantitative phase-contrast imaging is developed rapidly.Digital holography not only has the characteristics of fast,real-time,non-contact,the full field and obtaining the quantitative amplitude and phase information of the object at the same time,and but also has the advantages of flexible processing,storage.Digital holography has growing applications in the imaging of transparent or translucent objects such as biological cell,microstructure detection,temperature field measurement,particle field analysis,and deformation measurement etc.With the development of nanometer science and life science,The three-dimensional topography measurement of the nanostructure objects is urgently needed in the future.So improving the resolution of the digital holographic quantitative phase-contrast imaging system has important research significance and application value.This thesis mainly studies the methods to improve the resolution of digital holographic quantitative phase-contrast imaging system,and the main content includes the following several aspects: 1.A resolution enhancement quantitative phase-contrast imaging method using dynamic grating in digital holography is researched based on amplitude type liquid-crystal spatial light modulator.We have analyzed the spectrum range of the object in the imaging system and the point spread function.The separation condition for multiple diffraction orders is analyzed.The relation between the imaging resolution and the grating period is also analyzed.The correctness of theoretical analysis is verified by numerical simulation.A digital holographic imaging experimental system using dynamic grating is built based on amplitude type liquid crystal spatial light modulator.The imaging resolution is improved from 55.7 ?m to 31.3 ?m compared with traditional lensless Fourier transform digital holography.The imaging resolution enhancement is verified by the experiments.The imaging resolution of the system is changed by dynamically adjusting the period and the direction of grating loaded on the amplitude type liquid crystal spatial light modulator,which makes the system flexible and convenient.2.The mathematical model of coupling evanescent wave on the surface of the sample into transmission wave in the far field imaging by the microsphere is established.The mechanism of the microsphere-assisted super-resolution imaging is analyzed.The mutual constraint relationship between resolution and field of view based on microsphere imaging system and the radius and refractive index of the microsphere is quantitatively analyzed.The focusing characteristics of microspheres are simulated by using the COMSOL Multiphysics.The simulation results illustrate the microspheres have the ability to transform the evanescent wave into propagating waves.The experimental system of white light microscopic intensity imaging based on the microsphere is built.The one-dimensional grating and the two-dimensional point array are imged by white light microscopic intensity imaging system based on the silica and other microspheres.The results show that it can distinguish the details of 140 nm.The experiment verified the mechanism that the microspheres coupled the evanescent waves on the surface of the sample into transmission wave in the far field imaging.3.A super-resolution quantitative phase-contrast imaging method using high refractive index microsphere in the digital holographic microscopy is presented.The quantitative amplitude and phase contrast imagings of the micro-nano structure samples can be obtained at the same time.The inverted image-plane super-resolution quantitative phase-contrast imaging system of digital holographic microscopy based on the microsphere is designed and built.The super-resolution imaging is completed by using the 255 nm line width of cosine grating.The imaging resolution of the system less than ?/2 is verified by the results of the experiment.Because of the microsphere with circular symmetry,the lateral resolution of the imaging system in all directions can be improved at the same time by using only single hologram.The method for quantitative phase-contrast imaging research of micro-nano structure sample opens a new route.4.The inverted pre-magnification off-axis image-plane imaging system of digital holography is designed and built.The USAF test target is used as a standard object.The experimental results show that the lateral resolution is 0.87 ?m.The system has a good imaging quality.The dynamic change process of the living MDA-MB-231 breast cancer cells is real-time monitoring by the system.It is applied to visualize the moving and division process of cells,and the average velocity of the moving cells are calculated,also time of the cell division cycle is obtained.Furthermore,the blebbing phenomenon of the cells is observed after treated by paclitaxel,and the distribution of the drug inside the molecular is detected,which is near the border of the cells,or stay the end of the microtubules.The experimental results can help to reveal the anticancer agent of paclitaxel to breast cancer cells in the subcellular scale.
Keywords/Search Tags:digital holography, phase-contrast imaging, super-resolution imaging, spatial light modulator, microsphere
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