Multiplexed coded illumination for Fourier Ptychography with an LED array microscope

Abstract

Fourier Ptychography is a new computational microscopy technique that achieves gigapixel images with both wide field of view and high resolution in both phase and amplitude. The hardware setup involves a simple replacement of the microscope's illumination unit with a programmable LED array, allowing one to flexibly pattern illumination angles without any moving parts. In previous work, a series of low-resolution images was taken by sequentially turning on each single LED in the array, and the data were then combined to recover a bandwidth much higher than the one allowed by the original imaging system. Here, we demonstrate a multiplexed illumination strategy in which multiple randomly selected LEDs are turned on for each image. Since each LED corresponds to a different area of Fourier space, the total number of images can be significantly reduced, without sacrificing image quality. We demonstrate this method experimentally in a modified commercial microscope. Compared to sequential scanning, our multiplexed strategy achieves similar results with approximately an order of magnitude reduction in both acquisition time and data capture requirements.

3D intensity and phase imaging from light field measurements in an LED array microscope

“…These can be stitched together with synthetic aperture approaches [41,42] to create a high-resolution image in real space. The caveat is that phase is required, which the Fourier ptychography algorithm [23,24] provides by performing translational diversity phase retrieval [43][44][45][46] in Fourier space.…”

“…Research Article [23,24] reconstruction process, combined with the multislice inversion procedure in [26]. The reconstruction procedure aims to minimize the difference between the actual and estimated intensity measurements in a least-square sense:…”

“…This is possible because data with angular diversity provide both 3D information and phase contrast. 2D phase of thin samples can be computed from images taken at multiple illumination angles [20][21][22][23][24] because of asymmetry introduced in the pupil plane [25]. All of these approaches assume a thin sample; in thick samples, angle-dependent data usually represent tomographic information.…”

“…Using Fourier ptychography [23,24], we use these to build up a larger effective NA, limited by the sum of the illumination and objective NAs. Thus, a low-magnification objective having a large field of view (FoV) can recover highresolution gigavoxel-sized 3D intensity and phase images.…”

“…Our system is built on a commercial microscope in which the illumination unit has been replaced by a programmable LED array. This simple, inexpensive hardware modification enables not only 4D light field capture [35,38], but also dark field [38,39], phase contrast [35,39], Fourier ptychography [23,24], and digital aberration removal [40].…”