We propose a novel approach for reflective measurements using utilizes high temporal coherence and low spatial coherence illumination in a full-field reflective geometry. This allows the reference plane to be shifted to the camera, eliminating the need for meticulous alignment and enabling the use of a single high numerical aperture (NA) objective lens.
To enhance the quality of our measurements, we perform deconvolution and digital aberration correction on the measured data. We achieve a resolution close to the theoretical limit of our system: 100nm-100nm-500nm and demonstrate the unique capabilities of our experimental setup on both biological and industrial samples.
Quantitative phase imaging (QPI) techniques require multiple measurements to obtain the refractive index (RI) distribution of a sample. Here, we present a single-shot RI imaging method using spectral multiplexing and optical transfer function reshaping. In the present method, we simultaneously measure three intensity images of a sample with three optimized illumination patterns. Deconvolution of the measured intensity images is then performed to obtain the RI distribution of the sample. As a proof-of-concept, we measured both microspheres and biological cells.
The dielectric tensor is a physical quantity which characterizes birefringent materials with principal refractive indices and orientations of optic axes. Recently, three-dimensional dielectric tensor distribution was directly measured using dielectric tensor tomography (DTT). However, since the original DTT uses two cameras to acquire polarization-sensitive fields, position disagreement between the two fields deteriorates reconstruction quality. Here, we present multiplexed DTT using only one camera. To avoid the position disagreement, we exploit holographic multiplexing, interfering two orthogonally polarized reference beams with a sample beam on the camera. We validate the present method via measurement of anisotropic structures in liquid crystal particles.
Histopathology relies upon the staining and sectioning of biological tissues, which can be laborious and may cause artifacts and distort tissues. We develop label-free volumetric imaging of thick-tissue slides, exploiting refractive index distributions as intrinsic imaging contrast. The present method systematically exploits label-free quantitative phase imaging techniques, volumetric reconstruction of intrinsic refractive index distributions in tissues, and numerical algorithms for the seamless stitching of multiple three-dimensional tomograms and for reducing scattering-induced image distortion. We demonstrated label-free volumetric imaging of thick tissues with the field of view of 2 mm × 1.75 mm × 0.2 mm with a spatial resolution of 170 nm × 170 nm × 1400 nm. The number of optical modes, calculated as the reconstructed volume divided by the size of the point spread function, was ∼20 giga voxels. We have also demonstrated that different tumor types and a variety of precursor lesions and pathologies can be visualized with the present method.
Three-dimensional (3D), label-free, and long-term imaging in organ-on-a-chip research is necessary to assess the dynamic development of multicellular structures inside a microfluidic chip and relevant physiological functions. However, imaging on-chip multicellular landscapes generally relies on the use of exogenous labels, which limits the long-term imaging of live cells due to photobleaching and phototoxicity. Here, we demonstrate the 3D label-free observation of 5-day on-chip vasculogenesis of human umbilical vein endothelial cells using optical diffraction tomography. The proposed method enables us to quantify both morphological and biochemical alterations during the vasculogenesis.
Optical diffraction tomography (ODT) is a label-free three-dimensional (3D) microscopy technique allowing to retrieve the refractive-index distributions of optically translucent samples. Until recently, the histopathological applications of ODT have been impeded by the difficulty of imaging thick and wide tissues. Here, we demonstrate rapid, wide-field 3D ODT for imaging biological tissues. We designed a high-speed stitching ODT platform exploiting a digital micromirror device and a motorized stage. Developing a fast algorithmic framework that relieves the stitching artifacts and contrast loss due to multiple scattering, we demonstrate high-contrast 3D imaging of 100-m-thick, square-millimeter-wide pathological tissues at sub-micrometer resolution.
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