The Research Of Fourier Ptychographic Microscopy Imaging Based On LED Array Optimization

The competition between resolution and the imaging field of view is a long-standing problem in traditional microscopic systems,only a small area image with fine details or a large area image with coarse details can be captured.Fourier ptychographic microscopy(FPM)technology is a new technology that solves this inherent contradiction in microscopic imaging systems.It takes the challenge of high-throughput and high-resolution imaging from the domain of improving the physical limitations of optics to the domain of computation.In a traditional FPM system,a programmable LED array is used as its light source.The camera captures a set of low-resolution images under different angles of illumination through the LED array.The computer updates these low-resolution images through iterative updates in frequency and spatial domains,and finally reconstructs them to produce high-resolution images.However,in practical applications,whether it is the problem of low FPM reconstruction efficiency caused by the long-term exposure of the programmable LED array or the problem of poor FPM reconstruction image quality caused by the positional offset of the programmable LED array,the performance of the FPM is limited.According to the basic principles of FPM,the thesis introduces the imaging mode and reconstruction algorithm of FPM,studies the important parameters in FPM and focuses on the research of LED array lighting system to analyze its overall impact on FPM.Based on the optimization of the LED array,explore and improve the image reconstruction efficiency and image reconstruction quality of the Fourier ptychographic microscopy:(1)According to the position relationship of the LED array,the sample and the objective lens,the theoretically expandable spectral distribution range of all LED lighting in Fourier space are obtained.Use the FPM reconstruction algorithm to reconstruct a series of low-resolution images recorded under only a single LED lighting and using the remaining LED lighting in order of position.The image quality evaluation function is introduced to analyze the difference between the reconstructed image under any LED lighting and the reconstructed image under full LED lighting and record it as a difference matrix.The difference matrix is analyzed for color differentiation,so as to summarize the important lighting positions of the LED based on the color difference,and infer the optimal angle lighting scheme.The experimental results show that the diamond illumination method proposed in this paper can effectively improve the imaging efficiency of FPM while maintaining the quality of the reconstructed image.(2)Analyze the offset effect of the position error of the LED array in the traditional FPM imaging system on the low-resolution image recorded by the CCD sensor,and study the impact of the lowresolution image on the quality of the reconstructed image after participating in the high-resolution image reconstruction.So as to solve the LED array error,proposes a position correction method based on genetic annealing optimization algorithm.First of all,the influence of the relative positions between the following three factors on the incident wave vector is analyzed,and the three factors are LED array,the sample and objective lens.Secondly,genetic annealing optimization algorithm is utilized to estimate global error parameters for LED array error locations.Finally,global error parameter is used to correct the position of the LED array quickly.Simulations and experiments prove the method can significantly improve the quality of reconstructed images.