Quantitative phase imaging by wide-field interferometry with variable shearing distance uncoupled from the off-axis angle

Published on 2020-02-13T16:21:47Z (GMT) by
We introduce a new shearing interferometry module for digital holographic microscopy, in which the off-axis angle, which defines the interference fringe frequency, is not coupled to the shearing distance, as is the case in most shearing interferometers. Thus, it enables the selection of shearing distance based on the spatial density of the sample, without losing spatial frequency content due to overlapping of the complex wave fronts in the spatial frequency domain. Our module is based on a 4f imaging unit and a diffraction grating, in which the hologram is generated from two mutually coherent, partially overlapping sample beams, with adjustable shearing distance, as defined by the position of the grating, but with a constant off-axis angle, as defined by the grating period. The module is simple, easy to align, and presents a nearly common-path geometry. By placing this module as an add-on unit at the exit port of an inverted microscope, quantitative phase imaging can easily be performed. The system is characterized by a 2.5 nm temporal stability and a 3.4 nm spatial stability, without using anti-vibration techniques. We provide quantitative phase imaging experiments of silica beads with different shearing distances, red blood cell fluctuations, and cancer cells flowing in a micro-channel, which demonstrate the capability and versatility of our approach in different imaging scenarios.

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Guo, Rongli; Mirsky, Simcha; Barnea, Itay; Dudaie, Matan; Shaked, Natan (2020): Quantitative phase imaging by wide-field interferometry with variable shearing distance uncoupled from the off-axis angle. The Optical Society. Collection. https://doi.org/10.6084/m9.figshare.c.4773479.v1