Characterization of spatially varying aberrations for wide field-of-view microscopy

Abstract

Abstract:We describe a simple and robust approach for characterizing the spatially varying pupil aberrations of microscopy systems. In our demonstration with a standard microscope, we derive the locationdependent pupil transfer functions by first capturing multiple intensity images at different defocus settings. Next, a generalized pattern search algorithm is applied to recover the complex pupil functions at ~350 different spatial locations over the entire field-of-view. Parameter fitting transforms these pupil functions into accurate 2D aberration maps. We further demonstrate how these aberration maps can be applied in a phaseretrieval based microscopy setup to compensate for spatially varying aberrations and to achieve diffraction-limited performance over the entire field-of-view. We believe that this easy-to-use spatially-varying pupil characterization method may facilitate new optical imaging strategies for a variety of wide field-of-view imaging platforms.

Embedded pupil function recovery for Fourier ptychographic microscopy

“…However, because the phase retrieval algorithm only renews the sample spectrum while keeping the pupil function unchanged, an imprecisely estimated pupil function will result in a poor recovery. Such inaccuracy in the pupil function estimation can be caused by the limited orders of aberration considered in pre-characterization process [3] or by mechanical or optical changes in the microscopy system.…”

“…For a large FOV microscope system, the aberration and, by extension, pupil function can be expected to show spatial variations [3,24]. To ensure the effectiveness of the EPRY-FPM algorithm, we segment the entire FOV into small tiles where in each tile the aberration can be considered as constant [1,3].…”

“…To ensure the effectiveness of the EPRY-FPM algorithm, we segment the entire FOV into small tiles where in each tile the aberration can be considered as constant [1,3]. For our FPM system with a 6mm radius FOV, the entire area is segmented into tiles sized 350um*350um, and the EPRY-FPM algorithm is run on the data set of each tile independently, using the aforementioned process.…”

“…To exploit the full throughput of the FPM imaging platform, Zheng et al [1] introduced a digital wavefront correction strategy to correct for the spatially varying aberration [3][4][5] and demonstrate a high-resolution (0.78 um, 0.5 NA), wide-FOV (~120 mm 2 ) microscope with a final SBP of ~1 gigapixel [1], which is highly desired for many biomedical applications such as digital pathology, haematology and immunohistochemistry.…”

“…One of the drawbacks of the aforementioned wavefront correction is that a precharacterization of the spatially varying aberration of the microscopy system is needed [3]. Such a characterization can be computationally onerous, and is sensitive to the movement of the elements in the system.…”