نتایج جستجو برای: speckle
تعداد نتایج: 8844 فیلتر نتایج به سال:
Speckle patterns produced by random optical fields with two (or more) widely different correlation lengths exhibit speckle spots that are themselves highly speckled. Using computer simulations and analytic theory we present results for the point singularities of speckled speckle fields, namely, optical vortices in scalar (one polarization component) fields and C points in vector (two polarizati...
An approach for speckle reduction and feature enhancement under a framework of multiscale wavelet analysis is presented. The advantages of both soft thresholding and hard thresholding wavelet shrinkage techniques are utilized to eliminate noise and preserve the sharpness of salient features. We integrate a method of wavelet shrinkage with nonlinear processing to enhance contrast within structur...
Constructive role of sensors nonlinearities in the acquisition of partially polarized speckle images
We study the impact of the level of the speckle noise on data acquisition in a partially polarized coherent imaging system with the presence of a nonlinearity in the imaging sensor characteristic. In perfectly linear acquisition conditions, due to the essentially multiplicative action of the speckle, the image contrast is unchanged as the speckle noise level increases, and so it has no impact o...
INTRODUCTION AND OBJECTIVES The development of left ventricular dysfunction after mitral valve replacement is a common problem in patients with chronic severe mitral regurgitation. Assessment of myocardial deformation enables myocardial contractility to be accurately estimated. Our aim was to compare the value of the preoperative strain and strain rate derived by either speckle-tracking echocar...
SPECKLE NOISE REDUCTION IN MEDICAL ULTRASOUND IMAGES USING PARTICLE SWARM OPTIMIZATION WITH ARTIFICIAL NEURAL NETWORKS: COMPARATIVE APPROACH Er. Manpreet Kaur1 and Er. Danvir Mandal2 1CEC, Landran, Mohali E-mail: Manpreet.n.kaur @gmail.com 2IET BHADDAL, Ropar E-mail: [email protected] Medical images are normally affected by noise due to various sources of interferences and other pheno...
Speckle Tracking is one of the most prominent techniques used to estimate the regional movement of the heart based on ultrasound acquisitions. Many different approaches have been proposed, proving their suitability to obtain quantitative and qualitative information regarding myocardial deformation, motion and function assessment. New proposals to improve the basic algorithm usually focus on one...
Recently we presented novel methods for acousto-optic (AO) imaging of biological tissues, taking (1) the mean square difference of speckle patterns (subtraction method) or (2) the contrast of the summation of speckle patterns (summation method) acquired from nanosecond pulses of coherent light, fired at different ultrasound phases. In this study we relate the two methods both analytically and e...
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