Abstract
Optical diffraction tomography (ODT) is an emerging microscopy technique for three-dimensional (3D) refractive index (RI) mapping of transparent specimens. Recently, the digital micromirror device (DMD) based scheme for angle-controlled plane wave illumination has been proposed to improve the imaging speed and stability of ODT. However, undesired diffraction noise always exists in the reported DMD-based illumination scheme, which leads to a limited contrast ratio of the measurement fringe and hence inaccurate RI mapping. Here we present a novel spatial filtering method, based on a second DMD, to dynamically remove the diffraction noise. The reported results illustrate significantly enhanced image quality of the obtained interferograms and the subsequently derived phase maps. And moreover, with this method, we demonstrate mapping of 3D RI distribution of polystyrene beads as well as biological cells with high accuracy. Importantly, with the proper hardware configuration, our method does not compromise the 3D imaging speed advantage promised by the DMD-based illumination scheme. Specifically, we have been able to successfully obtain interferograms at over 1 kHz speed, which is critical for potential high-throughput label-free 3D image cytometry applications.
Highlights
Optical diffraction tomography (ODT) has recently become a popular microscopy technique for measuring three-dimensional (3D) refractive index (RI) distributions of optically transparent microscopic specimens such as biological cells [1,2,3,4]
Undesired diffraction noise always exists in the reported digital micromirror device (DMD)-based illumination scheme, which leads to a limited contrast ratio of the measurement fringe and inaccurate RI mapping
The reported results illustrate significantly enhanced image quality of the obtained interferograms and the subsequently derived phase maps. With this method, we demonstrate mapping of 3D RI distribution of polystyrene beads as well as biological cells with high accuracy
Summary
Optical diffraction tomography (ODT) has recently become a popular microscopy technique for measuring three-dimensional (3D) refractive index (RI) distributions of optically transparent microscopic specimens such as biological cells [1,2,3,4]. Two orthogonal galvanometric mirrors, placed at the conjugate planes of the sample through a 4f system, have been used to control the illumination angle by mechanically tilting the mirrors through changing the applied voltage values [15]. This technique suffers from a relatively long mechanical settling time for the mirrors (settling time for the mirror of 1 inch size and angle change magnitude of 10% full scale is typically ~3 ms), which affects 3D imaging throughput. Over the last three years, DMD has been successfully applied to ODT with its high-speed control and extraordinarily stable operation without mechanical movements [17,19]
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