High-resolution Large Field-of-view Fast-speed Fourier Ptychographic Microscopy

Fourier ptychographic microscopy(FPM)is a computational imaging technique and quantitative phase imaging(QPI)technique of next generation.Sharing its root with coherent synthetic aperture and phase retrieval,it effectively tackles the trade-off between resolution and field-of-view(FOV)in conventional microscopy.It can obtain a gigapixel image without mechanical scanning and has been successfully applied to digital pathology in recent years.This dissertation introduces the significant roles that FPM plays in the development of optical microscopy and introduces the principle and development trends of FPM systematically.It is expected to address several significant problems,such as the system errors,the limitation of resolution and collection efficiency,which improves the measurement accuracy,imaging resolution and efficiency,achieving QPI of label-free specimens with millimeter FOV,subwavelength resolution and single shot time-lapse imaging.The main contents and innovation points of the dissertation are summarized as follows:1.An FPM system with a R/G/B LED board was built and used to verify the performances of FPM.We found the system was sensitive to the LED intensity fluctuation,noise,mixed system errors and vignetting effect,so that a correction method for LED intensity fluctuation,a series of data preprocessing methods,system calibration algorithm(SCFPM)and two strategies for vignetting effect were reported.These methods can solve the LED intensity fluctuation fundamentally,suppress the noise directly,eliminate the effect of stray light,remove the artifacts,and improve the algorithm robustness.Finally,we concluded a complete set of artifact-free FPM imaging methods.2.A subwavelength resolution FPM(SRFPM)platform with hemispherical digital condenser was reported to achieve HR imaging,attaining a 4×/0.1NA objective with the final effective imaging performance of 1.05 NA at a resolution of 244 nm with the incident wavelength of 465 nm across a wide FOV of 14.60 mm2 and a DOF of 300 ?m,corresponding to a space-bandwidth product(SBP)of 245 megapixels.It has many advantages such as subwavelength resolution,wide FOV,and high energy utilization.Compared with traditional bright field microscopy via a 4×/0.1NA objective,the SBP is 65 times higher.Compared with traditional FPM with LED board,SBP is improved from 97 to 245 megapixels with a factor of 2.5.And compared with bright field microscopy via a 40×/0.6NA objective,SRFPM recovers both phase and intensity images,and the SBP is245 times higher.3.A fast FPM method based on defocus images via annular monochromatic illumination,termed s FPM,was reported to achieve real-time dynamic QPI.A single defocus image is required for sparse samples,while two asymmetric defocus images are only required for normal dense samples.Note that single shot imaging can also be achieved via dual-camera common optical path method for this case.Though s FPM only captures the bright field images and improves twice better resolution,a 20×/0.4NA objective is used to obtain synthetic NA of 0.8,which still meets most biological applications.4.We participated in the development of the cell culture imaging system(96 Eyes)based on parallel FPM.There are three challenges in both engineering and technology: how to design those low-cost and compact objective lenses,defocus due to the variation of plates and variation of wells within a plate,and meniscus-induced distortion,field curvature,and wavevector misalignment.We introduce the third technical problems in detail and provide solutions,termed AWC-FPM algorithm to adaptively align the wavevector and solve the raster grid noise of pupil function under low redundancy information.Combined with the digital refocusing,the field curvature is compensated,and high image quality without artifacts is achieved.The system will have a broad market prospect in the future.