Search results for "Speckle pattern"
showing 10 items of 83 documents
Dynamic laser speckle analyzed considering inhomogeneities in the biological sample
2017
Dynamic laser speckle phenomenon allows a contactless and nondestructive way to monitor biological changes that are quantified by second-order statistics applied in the images in time using a secondary matrix known as time history of the speckle pattern (THSP). To avoid being time consuming, the traditional way to build the THSP restricts the data to a line or column. Our hypothesis is that the spatial restriction of the information could compromise the results, particularly when undesirable and unexpected optical inhomogeneities occur, such as in cell culture media. It tested a spatial random approach to collect the points to form a THSP. Cells in a culture medium and in drying paint, repr…
Contrast sensitivity of the visual system in speckle imagery
1994
The contrast sensitivity function (CSF) of the whole visual system is determined with the use of coherent diffuse illumination. This function provides supplementary data about the effect of speckle on the ability of the visual system to perceive the spatial information contained in an image. The results show that speckle not only prevents perception of the finest details (highest frequencies) but also reduces the visibility of lower frequencies (especially where contrast is low). The difference between the CSF's determined with and without speckle is quantitatively very important. And the ratio between the two CSF's is a measure of the retinal ability to perceive contrast in the presence of…
A Survey of Prostate Segmentation Methodologies in Ultrasound, Magnetic Resonance and Computed Tomography Images
2012
Prostate segmentation is a challenging task, and the challenges significantly differ from one imaging modality to another. Low contrast, speckle, micro-calcifications and imaging artifacts like shadow poses serious challenges to accurate prostate segmentation in transrectal ultrasound (TRUS) images. However in magnetic resonance (MR) images, superior soft tissue contrast highlights large variability in shape, size and texture information inside the prostate. In contrast poor soft tissue contrast between prostate and surrounding tissues in computed tomography (CT) images pose a challenge in accurate prostate segmentation. This article reviews the methods developed for prostate gland segmenta…
Speckle correlation technique to determine roughness in the dermatologic interval.
1988
A non-invasive method is proposed to determine human skin roughness. The technique is based on measurement of the correlation between two field distributions scattered by a metallised triafol (cellulose acetate foil) replica of the epidermal area to be analysed. The two speckle patterns are produced from the same rough surface illuminated by two coherent plane waves (He-Ne laser) under two slightly different angles. The accuracy of the method is highlighted by measurements made on a set of standard samples with roughnesses previously determined by mechanical profilometry. Analysis of the results indicates a precision of around 10%, and an applicability within the interest range of very roug…
Evaluation of continuous filament mat influence on the bending behaviour of GFRP pultruded material via Electronic Speckle Pattern Interferometry
2017
Abstract Pultrusion is a process allowing the production of unidirectional (roving) fibre-reinforced polymer (FRP) structural elements with constant cross section. Recently, also civil engineers focused their attention on pultruded composite materials as alternative to traditional ones (e.g., concrete, steel). Furthermore, to improve the transverse strength and stiffness with respect to the fibres direction, continuous filament mat (CFM) is often placed within the stacking sequence. The CFM influence on the global mechanical behaviour is not considered by appropriate actual international standards. In this paper, the influence of the CFM layers on the mechanical behaviour of glass fibres pu…
On the Effect of Interference Fits in Composite Pin-Joints
1999
The Finite Element Method is used to determine the effect of pin/hole interference fits on the elastic membranal behavior of an orthotropic plate loaded in tension through a pin. A complete contact analysis is performed to handle the nonlinear contact problem. The study encompasses two levels of interference fits, two degrees of anisotropy of the plate, and two load levels. Friction effects are not included. Experimental results from Digital Speckle Pattern Interferometry are also presented. It is shown that the stress changes in the plate vary linearly with load when no pin/plate separation occurs. It is also shown that interference fits can have beneficial effects on the static and fatig…
Laser Vibrometer Interferometry for Speckle Patterns Tracking Systems
2017
In this paper we propose a modulated laser system combining a speckle pattern tracking method for surface tilting changes sensing with an interferometer for surface z-axis changes sensing at the same scan time.
Young's modulus measurement of the radius bone using a shearing interferometer with carrier fringes
2010
Abstract A technique for measuring Young's modulus of the radius bone by using electronic speckle-shearing pattern interferometry is proposed. The technique is based on the introduction of carrier fringes and the use of a phase unwrapping algorithm to obtain a phase map corresponding to the out-of-plane displacements of a radius bone without sign ambiguities. The carrier fringes are obtained by the correlation algorithm of two consecutive speckle fields with a translation of the illuminating beam between each recording, then the spatial synchronous detection (SSD), an unwrapping phase algorithm and integration process along shear direction are successfully applied for obtaining a displaceme…
Improved noncontact optical sensor for detection of glucose concentration and indication of dehydration level.
2014
The ability to extract different bio-medical parameters from one single wristwatch device can be very applicable. The wearable device that is presented in this paper is based on two optical approaches. The first is the extraction and separation of remote vibration sources and the second is the rotation of linearly polarized light by certain materials exposed to magnetic fields. The technique is based on tracking of temporal changes of reflected secondary speckles produced in the wrist when being illuminated by a laser beam. Change in skin’s temporal vibration profile together with change in the magnetic medium that is generated by time varied glucose concentration caused these temporal chan…
In Depth Flow Inspection based on Spatial Analysis of Dynamic Laser Speckle
2018
A novel optical approach based on statistical analysis of spatial laser speckle pattern for tissue in-depth flow characteristics is presented. Properties such as flow orientation and speed can be estimated. In-vitro experimental results are demonstrated.