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 article, a 50 cm confocal Fabry-Perot interferometer was used to analyze speckle from back-scattered laser light, which can be used to detect 4-mm diameter drill holes with resolutions of ± 0·5 mm.
16 citations
TL;DR: A time-resolved tomographic reconstruction of the velocity field associated with pulsatile blood flow through a rotationally-symmetric stenotic vessel model is presented and the probability density functions of blood-cell displacement within the vessel are analyzed.
Abstract: We present a time-resolved tomographic reconstruction of the velocity field associated with pulsatile blood flow through a rotationally-symmetric stenotic vessel model. The in-vitro sample was imaged using propagation-based phase contrast with monochromated X-rays from a synchrotron undulator source, and a fast shutter-synchronized detector with high-resolution used to acquire frames of the resulting dynamic speckle pattern. Having used phase retrieval to decode the phase contrast from the speckle patterns, the resulting projected-density maps were analysed using the statistical correlation methods of particle image velocimetry (PIV). This yields the probability density functions of blood-cell displacement within the vessel. The axial velocity-field component of the rotationally-symmetric flow was reconstructed using an inverse-Abel transform. A modified inverse-Abel transform was used to reconstruct the radial component. This vector tomographic phase-retrieval velocimetry was performed over the full pumping cycle, to completely characterize the velocity field of the pulsatile blood flow in both space and time.
16 citations
TL;DR: Results were obtained from the different skin phantoms, showing that it is possible to identify the vessel region for different morphologies, even up to 900 μm in depth, and a methodology is proposed for automatic blood vessel location based on the kurtosis analysis.
Abstract: Visualization of deep blood vessels in speckle images is an important task as it is used to analyze the dynamics of the blood flow and the health status of biological tissue. Laser speckle imaging is a wide-field optical technique to measure relative blood flow speed based on the local speckle contrast analysis. However, it has been reported that this technique is limited to certain deep blood vessels (about ρ=300 μm) because of the high scattering of the sample; beyond this depth, the quality of the vessel’s image decreases. The use of a representation based on homogeneity values, computed from the co-occurrence matrix, is proposed as it provides an improved vessel definition and its corresponding diameter. Moreover, a methodology is proposed for automatic blood vessel location based on the kurtosis analysis. Results were obtained from the different skin phantoms, showing that it is possible to identify the vessel region for different morphologies, even up to 900 μm in depth.
16 citations
TL;DR: In this paper, an optical fiber based speckle shearing interferometer is described, which uses a highly birefringent optical fibre to illuminate a test object with equal intensities of light guided by the orthogonal polarisation eigenstates of the fibre.
16 citations
TL;DR: In this paper, the authors describe the use of speckle interferometry for gas-side temperature profile measurement in engines, which may provide valuable information regarding surface heat transfer as well as information on other fluid characteristics such as boundary layer thickness.
Abstract: Gas-side temperature profile measurement in engines may provide valuable information regarding surface heat transfer as well as information on other fluid characteristics such as boundary layer thickness. Due to the typical cyclic variation of fluid variables in engines, profile measurement must be accomplished essentially instantaneously. This paper describes the use of speckle interferometry for acquiring such data. The advantages and disadvantages of the method are briefly described with respect to current spectroscopic and other interferometric techniques. The method has been applied to measure temperature profiles normal to the cylinder head in a motored two-cycle engine.
16 citations