Search results for "speckle"

3D displacement field measurement with correlation based on the micro-geometrical surface texture

2011

Image correlation methods are widely used in experimental mechanics to obtain displacement field measurements. Currently, these methods are applied using digital images of the initial and deformed surfaces sprayed with black or white paint. Speckle patterns are then captured and the correlation is performed with a high degree of accuracy to an order of 0.01 pixels. In 3D, however, stereo-correlation leads to a lower degree of accuracy. Correlation techniques are based on the search for a sub-image (or pattern) displacement field. The work presented in this paper introduces a new correlation-based approach for 3D displacement field measurement that uses an additional 3D laser scanner and a C…

Observational Approach and Perspective

1983

Well you did not cover more than half of my planned talk! (laughter). Let me comment on interferometric techniques, in particular speckle imaging which you mentioned. Doing speckle imaging with the largest telescopes now available will not give you better than the theoretical resolving power of the telescope. With a 4m telescope that is about 30 marc sec in the visible. That happens to be the radius of the supergiant Betelguese. So you are not going to achieve much with speckle imaging on these stars. One technique which has not been adequately exploited is that of lunar occultation which can give much better angular resolution than speckle, of the order of 2-3 marc sec. By using suitably c…

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.

Dynamic Laser Speckle Technique Sensing Long-Term Changes Caused by Painting Treatments in Restauration of Paintings

2017

Dynamic laser speckle is applied as a reliable sensor of activity in all sort of material. Traditional applications are based on a time rate that is usually higher than 10 frames-per-second (FPS). Even in drying processes, where there is a high activity in the first moments after the painting and a slow activity after some minutes or hours, the process is based on the acquisition of images in a time rate that is the same in both moments of high and low activity. In this work, we present an alternative approach to follow the drying of paint and the other processes related to restauration of paintings that takes long-term to reduce the activity. We illuminated, using three different wavelengt…

Deformation Imaging by Strain in Chronic Heart Failure Over Sacubitril-Valsartan: A Multicenter Echocardiographic Registry

2022

Aims: Sacubitril/valsartan has changed the treatment of heart failure with reduced ejection fraction (HFrEF), due to the positive effects on morbidity and mortality, partly mediated by left ventricular (LV) reverse remodelling (LVRR). The aim of this multicenter study was to identify echocardiographic predictors of LVRR after sacubitril/valsartan administration. Methods and results: Patients with HFrEF requiring therapy with sacubitril/valsartan from 13 Italian centres were included. Echocardiographic parameters including LV global longitudinal strain (GLS) and global peak atrial longitudinal strain by speckle tracking echocardiography were measured to find the predictors of LVRR [= LV end-…

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 …

Cardiac sarcoidosis: Matching speckle tracking echocardiography to macroscopic Ventricular pathology (a case report)

2016

Projection of speckle patterns for 3D sensing

2008

In this communication we present the use of projected speckle patterns coming from a phase random mask for sensing depths and thicknesses. The sensing is based on the change of the speckle pattern with propagation and the lack of correlation between speckle patterns recorded at different depths or lateral locations. The principle is used for mapping thickness of transparent media, for depth ranging and for 3D mapping of diffuse objects.

Advances in three-dimensional integral imaging: sensing, display, and applications [Invited]

2013

Three-dimensional (3D) sensing and imaging technologies have been extensively researched for many applications in the fields of entertainment, medicine, robotics, manufacturing, industrial inspection, security, surveillance, and defense due to their diverse and significant benefits. Integral imaging is a passive multiperspective imaging technique, which records multiple two-dimensional images of a scene from different perspectives. Unlike holography, it can capture a scene such as outdoor events with incoherent or ambient light. Integral imaging can display a true 3D color image with full parallax and continuous viewing angles by incoherent light; thus it does not suffer from speckle degrad…

Analisi del comportamento flessionale del legno attraverso la interferometria Speckle

2009

Nel lavoro vengono presentati i risultati di uno studio sperimentale effettuato sul comportamento flessionale di due differenti essenze di legno: l’abete rosso ed il ciliegio. L’analisi viene effettuata sottoponendo il provino al test di flessione a quattro punti ed utilizzando la interferometria speckle, una tecnica di misura non a contatto ed a campo intero, che consente di ottenere i campi di spostamento e di deformazione sulla superficie del provino. Al fine di mettere in evidenza le peculiarità del comportamento flessionale del legno i risultati ottenuti vengono confrontati con quelli di un provino di Plexiglas nelle stesse condizioni. Tale confronto conferma la complessità del comport…