Research On Polarization Parallel Phase-Shifting Digital Holography For Quantitative Phase Imaging

Quantitative phase imaging is an important means to achieve 3D measurement of target structures,which has broad prospects for development in high-tech industries such as biomedical engineering and industrial device manufacturing.Coherent digital holography is one of the main methods to realize quantitative phase imaging,which theoretically can achieve depth measurement with higher precision under the same measurement range,lateral resolution and measurement time with the help of digital focusing ability.However,various problems such as zero-order diffraction and twin image,and non-common-path interference background limit the measurement accuracy of digital holography in practical applications.In view of the above problems,the polarization parallel phase-shifting in-line digital holography based on focal plane division is used to eliminate zero-order diffraction and twin image in this paper,and the following main research work is carried out for this method:1)The physical optical model of imaging process of the polarization parallel phase-shifting digital holography based on focal plane division is derived,and the factors of detector aperture diffraction,non-common-path interference background and folded phase unwrapping errors that affect the phase measurement accuracy,as well as the factors of sampling interval of light field and numerical aperture of system that affect the imaging resolution are analyzed through this model.The imaging process and the factors affecting the imaging performance are verified through numerical simulation and platform experiments with spherical phase plate and resolution plate as test targets.The standard deviations of phase error are respectively 3.625rad(0.577λ)and 3.327rad(0.530λ)measured by simulation and experiment,and the limit resolution is about12.41μm measured by the super-pixel image reconstruction method.2)Aiming at the main influencing factors of the phase measurement accuracy of parallel phase-shifting digital holography,a phase aberration correction method based on comprehensive apodization filtering,double exposure and quality map guidance is proposed.The standard deviations of the phase errors between the compensated spherical phase target and the theoretical value are 3.619rad(0.576λ),3.090rad(0.492λ),0.050 rad(0.008λ)and 3.323rad(0.529λ),2.355rad(0.375λ),0.709rad(0.113λ)measured by numerical simulation and platform experiments,respectively.Compared with the direct reconstruction method,the proposed method can effectively compensate for the factors of aperture diffraction,interference background and unwrapping errors,and the measurement error can be reduced by about 2 orders of magnitude in theory.3)Aiming at the problem of reducing the spatial bandwidth product of the superpixel image reconstruction method of parallel phase-shifting digital holography,an oversampled super-pixel image reconstruction method with three implementations of image stitching,translation and interpolation is proposed,which increases the 12.41μm limit imaging resolution of the super-pixel method to about 6.90μm and achieves pixel resolution imaging.Aiming at the problem of the small numerical aperture of the lensless holography system,the image plane holography method based on objective lens imaging is used,which further improves the 6.90μm limit resolution of the proposed oversampled super-pixel method to 1.23μm and realizes the diffractionlimited imaging resolution of the 20 x objective lens.Both lensless imaging and microscope objective imaging have reached the limit resolution capability of the system.