Study On The Technology Of White Light Common-path Digital Holographic Microscopy

Digital holographic microscopy is a quantitative phase imaging technique,based on the combination of digital holography and optical microscopy,which can accurately obtain high-resolution phase information of the measured sample and the physical quantities relative to the phase information.Compared with other techniques,digital holographic microscopy has irreplaceable advantages,such as non-marking,non-destructive and quantitative full-field measurement,which is an ideal quantitative phase imaging method.However,there are two insuperable difficulties in the traditional digital holographic microscopy.On one hand,a high-coherent light source(e.g.laser source)used as the illumination source inevitably produces laser speckle and parasitic fringe noise which cannot be eliminated.On the other hand,the system structure,in which the object light and the reference light passes the different optical path,results that the system is easily affected by external disturbance.Therefore,the purpose of this thesis is to conduct research and develop the digital holographic microscopy with low noise and high stability.White-light common-path digital holographic microscopy,compared with traditional digital holographic microscopy,has unique advantages:From the point of view of light source,white light(bromine tungsten lamp)is used as illumination source,and its coherent length is very short.Therefore,the coherent noise and the parasitic stripe noise caused by the strong coherence of the light source can be avoided in essence;From the point of view of structure,the common-path structure has the advantages of stable structure and strong anti-interference ability due to its property of common-path.Therefore,the white-light common-path digital holographic microscopy has been paid more attention and widely studied.However,due to the use of the extended white light source,it's temporal and spatial coherence is very low,the system has very high requirement for optical path design.At present,the domestic research in this field is still in blank.This paper mainly includes the following parts:Firstly,based on the basic principle of the grating diffraction common-path digital holographic microscopy,and according to the three terms separation conditions of the off-axis hologram,the sampling conditions of the hologram recording and the diffraction principle of the grating,through analysis and calculation,the optical parameters of each optical components and structure parameters of the optical system are obtained.Then according to the calculated parameters,a set of common-path off-axis digital holographic microscopy system based on grating diffraction which adopt halogen lamps as the light source is developed.By analyzing the spatiotemporal noise of the system,the spatial noise is 0.5nm and the temporal noise is 0.02nm,which shows that the system has very low noise effect.And quantitative phase imaging is carried out,which select 2?m standard polystyrene as standard samples,it proves that the system has high accuracy imaging capability.Then,a large number of experimental studies on biological samples have been carried out on the established system.The accurate quantitative phase images are obtained by using living blood red blood cells and escherichia coli as samples.Moreover,a series of dynamic quantitative phase imaging of spore germination in water are obtained by recording the fungal spores for a long time.The experimental results show that the system has high imaging precision,good stability and the ability to observe biological living cells for a long time.Finally,the white-light common-path slightly off-axis digital holographic microscopy based on grating diffraction is studied.In order to make full use of the space bandwidth product of a CCD camera,according to the characteristics of white-light common-path digital holography based on grating diffraction,a new two-step blind phase-shift algorithm for slightly off-axis is proposed.First of all,it can be derived from the theory that the phase-shift can be generated by the movement of the grating,and the phase-shift is proportional to the moving value of the grating;Then,a new two-step slightly off-axis blind phase-shift algorithm is established;Finally,a white-light common-path slightly off-axis quantitative phase imaging digital holographic microscopy system with blind phase-shift by stepping motor moving grating is established.The experiment proves that the white-light common-path slightly off-axis digital holographic microscopy with two-step blind phase-shift is feasible.