Single-shot super-resolution quantitative phase imaging allowed by coherence gate shaping

Abstract

Biomedical and metasurface researchers repeatedly reach for quantitative phase imaging (QPI) as their primary imaging technique due to its high-throughput, label-free, quantitative nature. So far, very little progress has been made toward achieving super-resolution in QPI. However, the possible super-resolving QPI would satisfy the need for quantitative observation of previously unresolved biological specimen features and allow unprecedented throughputs in the imaging of dielectric metasurfaces. Here we present a method capable of real-time super-resolution QPI, which we achieve by shaping the coherence gate in the holographic microscope with partially coherent illumination. Our approach is based on the fact that the point spread function (PSF) of such a system is a product of the diffraction-limited spot and the coherence-gating function, which is shaped similarly to the superoscillatory hotspot. The product simultaneously produces the PSF with a super-resolution central peak and minimizes sidelobe effects commonly devaluating the superoscillatory imaging. The minimization of sidelobes and resolution improvement co-occur in the entire field of view. Therefore, for the first time, we achieve a single-shot widefield super-resolution QPI. We demonstrate here resolution improvement on simulated as well as experimental data. A phase resolution target image shows a resolving power improvement of 19%. Finally, we show the practical feasibility by applying the proposed method to the imaging of biological specimens.Biomedical and metasurface researchers repeatedly reach for quantitative phase imaging (QPI) as their primary imaging technique due to its high-throughput, label-free, quantitative nature. So far, very little progress has been made toward achieving super-resolution in QPI. However, the possible super-resolving QPI would satisfy the need for quantitative observation of previously unresolved biological specimen features and allow unprecedented throughputs in the imaging of dielectric metasurfaces. Here we present a method capable of real-time super-resolution QPI, which we achieve by shaping the coherence gate in the holographic microscope with partially coherent illumination. Our approach is based on the fact that the point spread function (PSF) of such a system is a product of the diffraction-limited spot and the coherence-gating function, which is shaped similarly to the superoscillatory hotspot. The product simultaneously produces the PSF with a super-resolution central peak and minimizes sidelobe effects commonly devaluating the superoscillatory imaging. The minimization of sidelobes and resolution improvement co-occur in the entire field of view. Therefore, for the first time, we achieve a single-shot widefield super-resolution QPI. We demonstrate here resolution improvement on simulated as well as experimental data. A phase resolution target image shows a resolving power improvement of 19%. Finally, we show the practical feasibility by applying the proposed method to the imaging of biological specimens.