Topic
Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
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TL;DR: In this paper, the influence of photon noise on the bispectrum of an image-intensity distribution is discussed, and it is shown theoretically that bispectral analysis in speckle masking should yield true, diffraction-limited images in all those cases in which the specckle-interferometry process has been successful in reconstructing the object autocorrelation.
Abstract: The bispectrum is the Fourier transform of the triple correlation, sometimes also referred to as the triple-product integral. The influence of photon noise on the bispectrum of an image-intensity distribution is discussed. As an example, the astronomical speckle-masking method is considered. Speckle masking is a method to overcome image degradation that is due to the turbulent atmosphere. It is shown theoretically that bispectral analysis in speckle masking should yield true, diffraction-limited images in all those cases in which the speckle-interferometry process has been successful in reconstructing the object autocorrelation.
101 citations
TL;DR: An in vivo measurement in a human forearm muscle is presented using SCOS in two modalities: one with the dependence of the speckle contrast on the source-detector separation and another on the exposure time.
Abstract: We introduce a new, non-invasive, diffuse optical technique, speckle contrast optical spectroscopy (SCOS), for probing deep tissue blood flow using the statistical properties of laser speckle contrast and the photon diffusion model for a point source. The feasibility of the method is tested using liquid phantoms which demonstrate that SCOS is capable of measuring the dynamic properties of turbid media non-invasively. We further present an in vivo measurement in a human forearm muscle using SCOS in two modalities: one with the dependence of the speckle contrast on the source-detector separation and another on the exposure time. In doing so, we also introduce crucial corrections to the speckle contrast that account for the variance of the shot and sensor dark noises.
101 citations
TL;DR: This work derives in a concise form the equations describing the phase-estimation problem, relate these equations to the general form of elliptic partial differential equations, and illustrates results of reconstructions on large M by N grids, using existing, published, and readily available FORTRAN subroutines.
Abstract: Obtaining robust phase estimates from phase differences is a problem common to several areas of importance to the optics and signal-processing communities. Specific areas of application include speckle imaging and interferometry, adaptive optics, compensated imaging, and coherent imaging such as synthetic-aperture radar. We derive in a concise form the equations describing the phase-estimation problem, relate these equations to the general form of elliptic partial differential equations, and illustrate results of reconstructions on large M by N grids, using existing, published, and readily available FORTRAN subroutines.
100 citations
TL;DR: In this article, it is shown that if these cases are excluded from the analysis procedure either implicitly or explicitly, then under the usual definition of SNR, the overall SNR of an estimate can increase by up to a factor of N¯−1/2, where N¯≪1 is the average number of detected photons per realization.
Abstract: Calculations of the signal-to-noise ratio (SNR) of estimates of the power spectra of spatially varying random processes, such as stellar speckle patterns, usually include realizations that contain less than two detected photons. It is shown in this paper that if these cases are excluded from the analysis procedure either implicitly or explicitly, then under the usual definition of SNR, the overall SNR of an estimate can increase by up to a factor of N¯−1/2, where N¯≪1 is the average number of detected photons per realization.
100 citations
TL;DR: An off-axis quantitative phase microscopy that works for a light source with an extremely short spatial coherence length in order to reduce the diffraction noise and enhance the spatial resolution and depth selectivity is developed.
Abstract: We developed an off-axis quantitative phase microscopy that works for a light source with an extremely short spatial coherence length in order to reduce the diffraction noise and enhance the spatial resolution. A dynamic speckle wave whose coherence length is 440 nm was used as an illumination source. To implement an off-axis interferometry for a source of low spatial coherence, a diffraction grating was inserted in the reference beam path. In doing so, an oblique illumination was generated without rotation of the wavefront, which leads to a full-field and single-shot phase recording with improved phase sensitivity of more than a factor of 10 in comparison with coherent illumination. The spatial resolution, both laterally and axially, and the depth selectivity are significantly enhanced due to the wide angular spectrum of the speckle wave. We applied our method to image the dynamics of small intracellular particles in live biological cells. With enhanced phase sensitivity and speed, the proposed method will serve as a useful tool to study the dynamics of biological specimens.
100 citations