Rapid Full-color Fourier Ptychographic Microscopy

Pathology serves as the "gold standard" for the diagnosis of cancer and early screening,acting as a bridge between basic research and clinical practice.With the development of imaging devices,digital pathology utilizes digitized imaging combined with mechanical scanning to obtain high resolution and large field of view images of single slides,known as Whole Slide Imaging(WSI)technology.However,existing digital pathology scanners still have some limitations.Fourier Ptychographic Microscopy(FPM)is a computational optical imaging technology that combines synthetic aperture and iterative phase recovery to achieve high-throughput imaging with both large field of view and high resolution,while also recovering the phase and coherent transfer function(CTF)of the sample.In its 10 years of development since its inception in 2013,FPM has undergone improvements in accuracy,efficiency,throughput,and modes.However,two major issues currently hinder its application in digital pathology: first,due to the limitation of the coherent light imaging model,FPM requires R/G/B sequential illumination to obtain color results,which significantly reduces its high-throughput advantage;second,current FPM prototype principles are semi-automated and have not yet considered functions necessary for commercialization,such as automated processing of batches of samples.Therefore,this thesis primarily focuses on the implementation of high-precision and high-efficiency color FPM technology and its mass production prototype for processing batches of samples,aiming to facilitate better application of FPM in digital pathology.The main research work includes:(1)Current colorization FPM solutions cannot simultaneously balance efficiency and accuracy;thus,this paper proposes a Color Transfer FPM(CFPM)method.The color texture information of a low-resolution full-color image is directly transferred to a high-resolution grayscale FPM image captured by only one wavelength.Since CFPM only uses a single wavelength and requires no iterative optimization process,it can be considered as a physics-based unsupervised transfer learning model.To solve the white balance problem and facilitate image transmission and display on different devices,a color space for FPM based on the standard CIE-XYZ color model is established.This paper analyzes different FPM coloring schemes and compares them with 30 biological samples,finding that traditional R/G/B sequential illumination methods and CFPM have average RMSE errors that are 5.3% and 5.7% higher than the true results,respectively.Furthermore,the reconstruction time is significantly reduced by 2/3 and the accuracy error is only 0.4%.Additionally,the CFPM method is compatible with advanced fast-FPM methods to further reduce computation time.(2)The CFPM method lacks spatial constraints during the color transfer process,making it unsuitable for appropriate staining of samples with two or more dyes,and also requiring high computational costs in histogram matching.This article proposes a Color-transfer Filtering FPM(CFFPM)method that replaces the original histogram matching process with a combination of block processing and tri-directional space filtering.The former reduces the search in solution space,while the latter introduces matching spatial constraints.Furthermore,the algorithm further employs an iterative process to refine results.Results show that CFFPM can accurately and rapidly perform color transfer on various samples,reducing reconstruction time from 3 hours to 3minutes compared to CFPM.This indicates that CFFPM provides a key solution for computational optical imaging in digital pathology.(3)This thesis proposes a low-cost,high-throughput,and fully colorized Whole Slide Imaging(WSI)platform that utilizes only a programmable LED array,lowmagnification objective lens,and low-cost automation system.Unlike traditional WSI platforms,this system uses symmetrical LED illumination for real-time autofocus.By using a 4×/0.1NA objective lens and a 19 × 19 programmable LED array,the platform is able to achieve a 5 mm diameter field of view,775 nm spatial imaging resolution,full-field data acquisition in 4 s,full-color reconstruction in less than 2 min,and automated batch scanning and reconstruction of 4 slides.The platform proposed in this thesis provides a key solution for making high-end and expensive WSI equipment widely available at a lower cost.