Research On The Principle And Technology Of Fourier Ptychography Microscopic Imaging Based On An LED Array Illumination

With the development of society and the progress of medical technology,more and more attention has been paid to the research of cells,especially in the fields of cell life,pathology and histopathology.For cell morphological research,it is necessary to capture the cell as high resolution imaging as possible,but the traditional microscope system is limited by its own spatial-bandwidth-product and can not improve the resolution,so the no lens and mechanical scanning microscope imaging technology appeared to enhance the pixel level.Both imaging methods are only infinitely close to the original resolution limit and don't really increase the pixel level of their system,and the lens-free contact microscope requires samples to be close to the sensor,while the mechanical scanning microscope also requires precise motion calibration and precise motion tracking,which make their application areas narrow and difficult to control.In order to improve the shortcomings of the above-mentioned microscopic imaging,a programmable LED array illumination light source instead of the traditional microscopic illumination light source becomes necessary.The platform can flexibly and conveniently provide any angle and any pattern illumination without mechanical operation.At the same time,starting with Ptychography principle,light field principle and imaging principle of optical field camera,combining with axis and off-axis illumination and Fourier analysis of the microscopic imaging,the principle of Fourier Ptychography microscopic imaging is explained.The reconstructed image based on Fourier Ptychography microscopic imaging platform with programmable LED array illumination has a high spatial bandwidth product,and the resolution of the images have been improved from Megapixel level to Gigapixel level.Starting from the light path and component module of the microscope experimental platform,this paper designs the calibration methods for the LED board,microscope and camera.In order to select the best imaging mode and static MBI 5041 with STM32 ARM microcontroller chip,the camera imaging module and LED control module are explored in depth.According to the requirement of experiment,the patterns and modes of LED illumination based on 4-fold objective field of view are selected.The indexes correlation between the collected image and the sequence of LED illumination are established,and the super-resolution iterative reconstruction algorithm based onGauss-Newton phase reconstruction is deduced.Thirdly,The actual structure of the Fourier Ptychography microscopic imaging system based on LED array illumination was described,and the influence of exposure time,wavelength of light wave and system calibration factors on the imaging of the microscopic system was shown.At the same time,the resolution enhancement effect of the system was demonstrated,and the wide Field of view reconstruction results of the actual biological sample collection was given.In this paper,experiments are completed on a programmable LED array illumination microscope platform.The effects of exposure time and wavelength on reconstruction results,calibration on Phase reconstruction of imaging system,different exposure time reconstruction results of USAF target super-resolution and wide-field super-resolution imaging results of real biological samples are analyzed.The experimental results show that the image reconstructed by the imaging system has a minimum resolution of 274 nm(equivalent to 40 times the resolution of the objective),while the field of view can reach 4 times the wide field of view of the objective,i.e.,the wide field of view under 4 times of the objective and the resolution of 40 times of the objective.Finally,the improvement of the experimental platform is analyzed,and the future application of 3D tomography is prospected.