1,630 research outputs found
Spatially resolved stress measurements in materials with polarization-sensitive optical coherence tomography: image acquisition and processing aspects
We demonstrate that polarization-sensitive optical coherence tomography
(PS-OCT) is suitable to map the stress distribution within materials in a
contactless and non-destructive way. In contrast to transmission
photoelasticity measurements the samples do not have to be transparent but can
be of scattering nature. Denoising and analysis of fringe patterns in single
PS-OCT retardation images are demonstrated to deliver the basis for a
quantitative whole-field evaluation of the internal stress state of samples
under investigation.Comment: 10 pages, 6 figures; Copyright: Blackwell Publishing Ltd 2008; The
definitive version is available at: www.blackwell-synergy.co
Beating the reaction limits of biosensor sensitivity with dynamic tracking of single binding events
The clinical need for ultrasensitive molecular analysis has motivated the development of several endpoint-assay technologies capable of single-molecule readout. These endpoint assays are now primarily limited by the affinity and specificity of the molecular-recognition agents for the analyte of interest. In contrast, a kinetic assay with single-molecule readout could distinguish between low-abundance, high-affinity (specific analyte) and high-abundance, low-affinity (nonspecific background) binding by measuring the duration of individual binding events at equilibrium. Here, we describe such a kinetic assay, in which individual binding events are detected and monitored during sample incubation. This method uses plasmonic gold nanorods and interferometric reflectance imaging to detect thousands of individual binding events across a multiplex solid-phase sensor with a large area approaching that of leading bead-based endpoint-assay technologies. A dynamic tracking procedure is used to measure the duration of each event. From this, the total rates of binding and debinding as well as the distribution of binding-event durations are determined. We observe a limit of detection of 19 fM for a proof-of-concept synthetic DNA analyte in a 12-plex assay format.First author draf
Determination of the diffusion constant using phase-sensitive measurements
We apply a pulsed-light interferometer to measure both the intensity and the
phase of light that is transmitted through a strongly scattering disordered
material. From a single set of measurements we obtain the time-resolved
intensity, frequency correlations and statistical phase information
simultaneously. We compare several independent techniques of measuring the
diffusion constant for diffuse propagation of light. By comparing these
independent measurements, we obtain experimental proof of the consistency of
the diffusion model and corroborate phase statistics theory.Comment: 9 pages, 8 figures, submitted to Phys. Rev.
Sparse And Low Rank Decomposition Based Batch Image Alignment for Speckle Reduction of retinal OCT Images
Optical Coherence Tomography (OCT) is an emerging technique in the field of
biomedical imaging, with applications in ophthalmology, dermatology, coronary
imaging etc. Due to the underlying physics, OCT images usually suffer from a
granular pattern, called speckle noise, which restricts the process of
interpretation. Here, a sparse and low rank decomposition based method is used
for speckle reduction in retinal OCT images. This technique works on input data
that consists of several B-scans of the same location. The next step is the
batch alignment of the images using a sparse and low-rank decomposition based
technique. Finally the denoised image is created by median filtering of the
low-rank component of the processed data. Simultaneous decomposition and
alignment of the images result in better performance in comparison to simple
registration-based methods that are used in the literature for noise reduction
of OCT images.Comment: Accepted for presentation at ISBI'1
The 2D Continuous Wavelet Transform: Applications in Fringe Pattern Processing for Optical Measurement Techniques
Optical metrology and interferometry are widely known disciplines that study and develop techniques to measure physical quantities such as dimensions, force, temperature, stress, etc. A key part of these disciplines is the processing of interferograms, also called fringe patterns. Owing that this kind of images contains the information of interest in a codified form, processing them is of main relevance and has been a widely studied topic for many years. Several mathematical tools have been used to analyze fringe patterns, from the classic Fourier analysis to regularization methods. Some methods based on wavelet theory have been proposed for this purpose in the last years and have evidenced virtues to consider them as a good alternative for fringe pattern analysis. In this chapter, we resume the theoretical basis of fringe pattern image formation and processing, and some of the most relevant applications of the 2D continuous wavelet transform (CWT) in fringe pattern analysis
A Sparsity-Based InSAR Phase Denoising Algorithm Using Nonlocal Wavelet Shrinkage
An interferometric synthetic aperture radar (InSAR) phase denoising algorithm using the local sparsity of wavelet coefficients and nonlocal similarity of grouped blocks was developed. From the Bayesian perspective, the double-l1 norm regularization model that enforces the local and nonlocal sparsity constraints was used. Taking advantages of coefficients of the nonlocal similarity between group blocks for the wavelet shrinkage, the proposed algorithm effectively filtered the phase noise. Applying the method to simulated and acquired InSAR data, we obtained satisfactory results. In comparison, the algorithm outperformed several widely-used InSAR phase denoising approaches in terms of the number of residues, root-mean-square errors and other edge preservation indexes
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