نتایج جستجو برای: speckle

تعداد نتایج: 8844  

Elham Farzaneh Bahalgerdy Fereydoon Nowshiravan Rahatabad,

Introduction One of the most important pre-processing steps in optical coherence tomography (OCT) is reducing speckle noise, resulting from multiple scattering of tissues, which degrades the quality of OCT images. Materials and Methods The present study focused on speckle noise reduction and edge detection techniques. Statistical filters with different masks and noise variances were applied on ...

پدیده Speckle جزء طبیعت تصاویر رادار می‌باشد که باعث کاهش دقت تفسیر، طبقه‌بندی، قطعه‌بندی و ... در این تصاویر می-شود. محققین توسط روش‌های مختلف سعی در کاهش این پدیده در تصاویر رادار داشته‌اند. یکی از روش‌های کاهش پدیده Speckle در تصاویر رادار فیلترهای حیطه مکان می‌باشند. عمده روش‌های فیلتر حیطه مکان از حدآستانه‌هایی برای طبقه‌بندی انواع اهداف استفاده می‌کنند، سپس بر مبنای نوع هدف پدیده Speckle ...

Journal: :iranian journal of medical physics 0
a. nurouzi m.sc. in medical physics, tehran university of medical sciences, tehran, iran. m. j. abolhasani assistant professor, physics and biomedical engineering dept., tehran university of medical sciences, tehran, iran. research center for science & technology in medicine, imam khomeini hospital, tehran, iran. a. takavar professor, physics and biomedical engineering dept., tehran university of medical sciences, tehran, iran. m. a. oghabian assistant professor, physics and biomedical engineering dept., tehran university of medical sciences, tehran, iran. research center for science & technology in medicine, imam khomeini hospital, tehran, iran. h. ghanaati associate professor, radiology dept., medical imaging center, imam khomeini hospital, tehran university of medical sciences , tehran, iran.

introduction:  the  success  of  hyperthermia  depends  on  the  accuracy  of  the  temperature  monitoring in the tumor and the surrounding normal tissue. in this study, the temperature changes  were determined by computing the speckle displacement in the ultrasound digital images. speckle  tracking algorithm was used to compute the displacement.  materials and methods: the experiment was perf...

Journal: :Optics express 2008
Julio C Ramirez-San-Juan Ruben Ramos-García Ileana Guizar-Iturbide Gabriel Martínez-Niconoff Bernard Choi

Since blood flow is tightly coupled to the health status of biological tissue, several instruments have been developed to monitor blood flow and perfusion dynamics. One such instrument is laser speckle imaging. The goal of this study was to evaluate the use of two velocity distribution assumptions (Lorentzian- and Gaussian-based) to calculate speckle flow index (SFI) values. When the normalized...

Synthetic Aperture Radar (SAR) images are inherently affected by a multiplicative noise-like phenomenon called speckle, which is indeed the nature of all coherent systems. Speckle decreases the performance of almost all the information extraction methods such as classification, segmentation, and change detection, therefore speckle must be suppressed. Despeckling can be applied by the multilooki...

2012
Desmond C. Ong Sanjeev Solanki Xinan Liang Xuewu Xu

The conventional speckle contrast measures only speckle severity, and is unable to characterize granularity and anisotropy in displayed images, which are easily picked up by human observers. Here, we propose a comprehensive method based on the power spectral density which allows the simultaneous measurement of three components of laser speckle-severity, granularity and anisotropy—as a superior ...

Journal: :iranian journal of medical physics 0
fereydoon nowshiravan rahatabad department of biomedical engineering, science and research branch, islamic azad university, tehran, iran

introduction one of the most important pre-processing steps in optical coherence tomography (oct) is reducing speckle noise, resulting from multiple scattering of tissues, which degrades the quality of oct images. materials and methods the present study focused on speckle noise reduction and edge detection techniques. statistical filters with different masks and noise variances were applied on ...

Journal: :Journal of the Optical Society of America 1981
D L Fried

The implications of speckle statistics on laser eye-safety considerations are evaluated. The concept of speckled speckle is introduced, and its statistics are shown to correspond to the K0 function. Speckled speckle is defined in terms of the retinal power density when the eye is viewing an optically rough surface that is illuminated by a laser beam diffused through a ground-glass screen-a situ...

Journal: :Physics in medicine and biology 2015
S G Resink W Steenbergen

Recently we presented acousto-optic (AO) probing of scattering media using addition or subtraction of speckle patterns due to tandem nanosecond pulses. Here we present a theoretical framework for ideal (polarized, noise-free) speckle patterns with unity contrast that links ultrasound-induced optical phase modulation, the fraction of light that is tagged by ultrasound, speckle contrast, mean squ...

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