Research On PIE Imaging With Structured Illumination

A complete description on the spatial distribution of a stable light field requires two physical parameters,intensity and phase.Traditional optical imaging techniques only use light intensity information to observe and measure samples,leading to low contrast and less details in imaging.The phase or the wavefront of the light field can reflect important information such as the optical thickness and refractive index distribution of the sample.The phase image of the sample often has better contrast than the intensity image.Besides the well-known traditional phase contrast imaging,conputational methods such as transport-of-intensity equation(TIE),digital holography,and coherent diffraction imaging are also widely used for sample phase imaging to obtain high-contrast images without sample staining.As a newly developed coherent diffraction imaging technology,Ptychographic Iterative Engine(PIE)has many advantages such as simple device,large field of view,fast reconstruction speed and high precision,but its resolution in the optical band still needs to be improved.This thesis combines PIE,structured light illumination and conventional lens imaging to propose a structured light illumination PIE technique to significantly improve the imaging resolution.In structured light illumination PIE,the localized illumination beam passes through a highly random phase plate to generate a speckle field composed of random structures.After irradiating it on the sample to be imaged,the sample is magnified and imaged using a common lens,and an image recorder placed behind the image plane is used to record the intensity of the formed diffraction patterns.By scanning the sample with transverse array and recording the diffraction patterns at corresponding positions,the specially designed PIE reconstruction algorithm can be used to obtain the high-resolution intensity and phase images.In the verification experiments,this method successfully doubled the lateral resolution of PIE,which proves that this method has a series of outstanding advantages such as simple experimental device,fast convergence speed and high imaging resolution.The main content of this thesis can be divided into the following aspects:(1)The background,the development,main advantages and disadvantages of PIE are discussed in details with regard to coherent diffraction imaging.(2)Lens imaging based PIE with large field of view is designed which can improve spatial resolution.The feasibility of the improved PIE is verified by numerical simulations and experiments.(3)Structured light illumination PIE based on speckle illumination is designed,and it can double the spatial resolution,which is verified by both numerical simulations and experiments.