Computational illumination for high-speed in vitro Fourier ptychographic microscopy

TL;DR

This paper introduces a computational illumination technique for Fourier ptychographic microscopy that enables high-resolution, wide field-of-view imaging of live in vitro samples at sub-second capture times, facilitating dynamic biological studies.

Contribution

The authors develop a new source coding scheme and real-time control system, along with an improved algorithm, to significantly accelerate Fourier ptychographic microscopy for live cell imaging.

Findings

Achieved 0.8 NA resolution over 4x FOV with sub-second capture times.

Demonstrated high-quality imaging of live cell cultures and dynamic phenomena.

Enabled long-term phase reconstruction in time-lapse experiments.

Abstract

We demonstrate a new computational illumination technique that achieves large space-bandwidth-time product, for quantitative phase imaging of unstained live samples in vitro. Microscope lenses can have either large field of view (FOV) or high resolution, not both. Fourier ptychographic microscopy (FPM) is a new computational imaging technique that circumvents this limit by fusing information from multiple images taken with different illumination angles. The result is a gigapixel-scale image having both wide FOV and high resolution, i.e. large space-bandwidth product (SBP). FPM has enormous potential for revolutionizing microscopy and has already found application in digital pathology. However, it suffers from long acquisition times (on the order of minutes), limiting throughput. Faster capture times would not only improve imaging speed, but also allow studies of live samples, where motion artifacts degrade results. In contrast to fixed (e.g. pathology) slides, live samples are continuously evolving at various spatial and temporal scales. Here, we present a new source coding scheme, along with real-time hardware control, to achieve 0.8 NA resolution across a 4x FOV with sub-second capture times. We propose an improved algorithm and new initialization scheme, which allow robust phase reconstruction over long time-lapse experiments. We present the first FPM results for both growing and confluent in vitro cell cultures, capturing videos of subcellular dynamical phenomena in popular cell lines undergoing division and migration. Our method opens up FPM to applications with live samples, for observing rare events in both space and time.