Infrared photothermal heterodyne imaging (IR-PHI) is an all-optical table top approach that enables super-resolution mid-infrared microscopy and spectroscopy. The underlying principle behind IR-PHI is the detection of photothermal changes to specimens induced by their absorption of infrared radiation. Because detection of resulting refractive index and scattering cross section changes is done using a visible (probe) laser, IR-PHI exhibits a spatial resolution of ∼300 nm.
View Article and Find Full Text PDFA key challenge for addressing micro- and nanoplastics (MNPs) in the environment is being able to characterize their chemical properties, morphologies, and quantities in complex matrices. Current techniques, such as Fourier transform infrared spectroscopy, provide these broad characterizations but are unsuitable for studying MNPs in spectrally congested or complex chemical environments. Here, we introduce a new, super-resolution infrared absorption technique to characterize MNPs, called infrared photothermal heterodyne imaging (IR-PHI).
View Article and Find Full Text PDFThis paper proposes a line segment-based image registration method. Edges are detected from images by a modified Canny operator, and line segments are then extracted from these edges. At registration, triplets (quaternions) of line segment correspondences are tentatively formed by applying the distance and orientation constraints, which determine an intermediate transformation.
View Article and Find Full Text PDFPassive underwater listening devices are often deployed to listen for narrowband signals of interest in time-varying background ocean noise. Such tonals are generated mechanically by ships, submarines, and machines, or acoustically by aquatic wildlife. Quantization of the sensor data for storage or low bit-rate transmission adds white noise which can overwhelm weak narrowband signals if the background noise is sufficiently colored.
View Article and Find Full Text PDFThis paper describes a studentized dynamical system (SDS) for robust target tracking using a subspace representation. Dynamical systems (DS) provide a powerful framework for the probabilistic modeling of temporal sequences. Visual tracking problems are often cast as a sequential inference problem within the DS framework and a compact way to model the observation distributions (i.
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