Abstract
Fourier ptychographic microscopy (FPM) is a newly developed super-resolution technique, which employs angularly varying illuminations and a phase retrieval algorithm to surpass the diffraction limit of a low numerical aperture (NA) objective lens. In current FPM imaging platforms, accurate knowledge of LED matrix's position is critical to achieve good recovery quality. Furthermore, considering such a wide field-of-view (FOV) in FPM, different regions in the FOV have different sensitivity of LED positional misalignment. In this work, we introduce an iterative method to correct position errors based on the simulated annealing (SA) algorithm. To improve the efficiency of this correcting process, large number of iterations for several images with low illumination NAs are firstly implemented to estimate the initial values of the global positional misalignment model through non-linear regression. Simulation and experimental results are presented to evaluate the performance of the proposed method and it is demonstrated that this method can both improve the quality of the recovered object image and relax the LED elements' position accuracy requirement while aligning the FPM imaging platforms.
Highlights
Fourier ptychography (FP) [1, 2] is a recently developed phase retrieval technique which overcomes the physical space-bandwidth-product (SBP) limit of a low numerical aperture (NA) imaging system
Similar to conventional ptychography, FP suffers from a positional misalignment problem, which is rarely mentioned in those developed FP techniques
Similar to the developed correction routines for conventional ptychography introduced in [30, 31], we propose an iterative method, named pcFPM, to correct positioning errors based on the simulated annealing (SA) algorithm and non-linear regression technique in this paper
Summary
Fourier ptychography (FP) [1, 2] is a recently developed phase retrieval technique which overcomes the physical space-bandwidth-product (SBP) limit of a low NA imaging system. For some particular segments in the FOV, if the incident angle of one LED element is accidentally shifted out of the objective lens’s NA, the corresponding recorded image would become a dark-field (DF) image instead of a bright-field (BF) image Without positioning correction, this DF image would greatly degrade the recovery accuracy of conventional FPM since a lot of low-frequency information is distorted unexpectedly. Both the simulation and experimental results demonstrate that robust positioning correction is achievable utilizing our pcFPM method Such a numerical correction scheme is able to improve the quality of the recovered object’s complex image, and relax the LED array’s positioning accuracy requirement while aligning the FPM platforms.
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