Ultra-high Scan Speed Based PIE Imaging Technology

Optical microscopic imaging technology is a powerful tool for human exploration of microscopic world,and is an indispensable research method in the biomedical field.Phase imaging method can image and detect the transparent sample.What is more,the phase distribution of the sample includes its thickness and three-dimensional topography.The detection of the phase information is of great significance research.Compared with amplitude imaging,phase imaging has higher resolution accuracy and higher contrast.The phase distribution of the sample can be observed with phase contrast microscope and differential interference contrast microscope.However,these methods only qualitatively analyze the phase.They belong to non-quantitative phase detection technology.Quantitative phase detection technology includes Harmant wavefront sensing technology,holographic measurement technology,transmission intensity equation and coherent diffraction imaging technology.Ptychographic Iterative Engine(PIE)imaging method is derived from coherent diffraction imaging,the observed sample is scanned laterally with the illumination beam.Compared with the traditional coherent diffraction imaging method,the method can obtain a reconstruction image with faster and higher quality.However,this method require the mechanical translation stage to move the observed sample,the accuracy of the translation stage directly affects the imaging quality.Due to the low speed of the mechanical translation stage,when a large sample is imaged,the data collection time is often long.To overcome these shortcoming of traditional PIE,the digital micro-mirror device is used for replacing the mechanical translation stage,which can be control moving the probe to scan the sample by the software.Compared with the mechanical translation stage,the adjustion speed of the micro-mirror is high,and the position error of each mirror is only a few nanometers.Ultra-high speed digital micro-mirror device based ptychographic iterative engine method was verified by experiment,and the data acquisition speed was improved by 45 times.Variable aperture based fast ptychographical iterative engine method is proposed.The adjustable aperture is used for restricting the size of illumination beam and changes the illuminated area of the observed sample.The diffraction patterns with different aperture illumination is acquired with the CCD camera.The modified PIE algorithm can be used for reconstructing the amplitude and phase distribution of the observed sample,and at the same time,the information of each illumination light can be reconstructed.In experiments,the DMD acts as an adjustable aperture and the DMD is controlled to change the size of the illumination beam by software.Experiments prove that,this method requires less diffraction patterns and data acquisition can be completed within 3 seconds in scanning the same field of view.In addition,the method can also be used for PIE imaging in X-rays and various factors affecting reconstruction quality are discussed using simulation methods.Ptychographic Iterative Engine technology based on sub-aperture transformation was proposed.During the scanning of the sample,the center sub-aperture is kept opened,and the surrounding sub-apertures are sequentially opened.These acquired diffraction patterns are brought into the modified update algorithm to calculate the phase diffraction of measured sample.A modified reconstruction algorithm was used to accurately reconstruct the amplitude and phase of the measured sample with the collected eight diffraction spots.In view of the shortcomings of the traditional PIE imaging in scanning speed and position error,the three improved PIE imaging methods based on DMD proposed in this dissertation greatly improve the acquisition speed,which overcomes the difficulty of the general mechanical scanning PIE due to slow data acquisition speed and difficulty The practical problems in biomedical applications can significantly broaden their application scope while improving the overall performance of PIE imaging.