Search results for "Electronic speckle pattern interferometry"
showing 10 items of 15 documents
Evaluation of the bending behaviour of laminated glass beams via electronic speckle pattern interferometry
2017
The paper is devoted to the experimental analysis of the kinematical and mechanical behaviour of laminated glass beam structures. In particular, the utilized laminated glass specimens are composed of two glass layers bonded by a polymer layer constituted by Ethylene-vinyl acetate whose thickness has been nominally considered as constant for all the specimens. The experimental behaviour of the analyzed specimens is deduced by applying Electronic Speckle- Pattern Interferometry technique; actually, among optical methods this technique (handled by phase-stepping technique) is very effective to obtain a full-field displacement map and to numerically achieve the longitudinal strain. In particula…
Phase-shifting of correlation fringes created by image processing as an alternative to improve digital shearography
2016
Abstract The adoption of digital speckle pattern shearing interferometry, or speckle shearography, is well known in many areas when one needs to measure micro-displacements in-plane and out of the plane in biological and non-biological objects; it is based on the Michelson's Interferometer with the use of a piezoelectric transducer (PZT) in order to provide the phase-shift of the fringes and then to improve the quality of the final image. The creation of the shifting images using a PZT, despite its widespread use, has some drawbacks or limitations, such as the cost of the apparatus, the difficulties in applying the same displacement in the mirror repeated times, and when the phase-shift can…
Speckle random coding for 2D super resolving fluorescent microscopic imaging.
2006
In this manuscript we present a novel super resolving approach based upon projection of a random speckle pattern onto samples observed through a microscope. The projection of the speckle pattern is created by coherent illumination of the inspected pattern through a diffuser. Due to local interference of the coherent wave front with itself, a random speckle pattern is superimposed on the sample. This speckle pattern can be scanned over the object. A super-resolved image can be extracted from a temporal sequence of images by appropriate digital processing of the image stream. The resulting resolution is significantly higher than the diffraction limitation of the microscope objective. The new …
Temporal difference method for processing dynamic speckle patterns
2010
A temporal difference method for processing dynamic speckle images is proposed. In the method two speckle images of an object, separated by a time interval, are subtracted one from the other to detect whether the speckle structure has changed or not. The rationale of the method is discussed. A variant of the method that allows measuring the area of an activity zone surrounded by a static region is tested in digital simulations. As a demonstrative experiment, that variant is employed to characterize the drying of a damp patch in filter paper.
Accuracy in dynamic laser speckle: optimum size of speckles for temporal and frequency analyses
2016
The dynamic laser-speckle phenomenon has been used as a potential tool to monitor the activity of many biological and nonbiological samples; however, a key tailoring of the experimental configuration must be taken into account to avoid wrong measurements, since the general rules addressed to speckle as information cannot be directly adopted in dynamic laser-speckle monitoring. The speckle/pixel size ratio is provided by the f-number and by the magnification of the macro lens, and attention is mainly directed toward adjusting a speckle/pixel ratio higher than 1. However, a speckle/pixel ratio much higher than one does not mean an optimum adjustment. This work tested different apertures with …
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…
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…
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…
Residual strain and stress analysis by speckle interferometry combined with the drill of a groove
2007
A new method for residual stresses determination combining Electronic Speckle Pattern Interferometry (ESPI) with the machining of a groove. The internal stress field is perturbed as the depth of the groove is increased incrementally [1]. The structure finds a new equilibrium state generating displacements which are measured using ESPI. This method was tested on an aluminium alloy plate treated locally by ultrasonic shot-peening. The investigation of the images obtained with the phase shifting technique and fringe patterns makes it possible to analyze, simultaneously, the stress profile along two directions: along the depth of the structure, and along the groove direction.