Search results for "speckle"
showing 10 items of 123 documents
Merits of vision in presence of light scattering using Tiffen ProMist filters
2020
Light scattering caused by Tiffen ProMist photographic filters of various grades at different laser radiation 640 nm, 532 nm and 405 nm was objectively studied and compared. The lack of removal of speckles from the scene of laser radiation scattering did not allow an accurate assessment of the effect of scattering on the decrease in image contrast. Subjective deterioration in visual acuity using various contrast optotypes and contrast sensitivity was assessed by scattering induction using filters up to grade #5. Vision contrast sensitivity diminishes within all studied spatial frequency range 0.5-18 cpd. The degradation of the impact factor to visual acuity without scattering filters when t…
A probabilistic framework for automatic prostate segmentation with a statistical model of shape and appearance
2011
International audience; Prostate volume estimation from segmented prostate contours in Trans Rectal Ultrasound (TRUS) images aids in diagnosis and treatment of prostate diseases, including prostate cancer. However, accurate, computationally efficient and automatic segmentation of the prostate in TRUS images is a challenging task owing to low Signal-To-Noise-Ratio (SNR), speckle noise, micro-calcifications and heterogeneous intensity distribution inside the prostate region. In this paper, we propose a probabilistic framework for propagation of a parametric model derived from Principal Component Analysis (PCA) of prior shape and posterior probability values to achieve the prostate segmentatio…
Texture Guided Active Appearance Model Propagation for Prostate Segmentation
2010
Fusion of Magnetic Resonance Imaging (MRI) and Trans Rectal Ultra Sound (TRUS) images during TRUS guided prostate biopsy improves localization of the malignant tissues. Segmented prostate in TRUS and MRI improve registration accuracy and reduce computational cost of the procedure. However, accurate segmentation of the prostate in TRUS images can be a challenging task due to low signal to noise ratio, heterogeneous intensity distribution inside the prostate, and imaging artifacts like speckle noise and shadow. We propose to use texture features from approximation coefficients of Haar wavelet transform for propagation of a shape and appearance based statistical model to segment the prostate i…
Left ventricular hypertrophy or storage disease? the incremental value of speckle tracking strain bull's-eye
2017
Left ventricular hypertrophy (LVH) develops in response to a variety of physical, genetic, and biochemical stimuli and represents the early stage of ventricular remodeling. In patients with LVH, subclinical left ventricular (LV) dysfunction despite normal ejection fraction (EF) may be present before the onset of symptoms, which portends a dismal prognosis. Strain measurement with two-dimensional speckle tracking echocardiography (STE) represents a highly reproducible and accurate alternative to LVEF determination. The present review focuses on current available evidence that supports the incremental value of STE in the diagnostic and prognostic workup of LVH. When assessing the components o…
Wooden Surface Investigation: an Optical Approach Based on Shadow Moiré
2007
The interest in the mechanical behaviour of wood is a very important task due to the increasing role played by wood structures in modern architecture as well as its applicability in restoration of ancient buildings. The behaviour of wooden surfaces experiencing variable humidity conditions is of great importance both with concern to performances of wooden building’s structures and to ensure correct restoration and conservation of art works like wooden sculptures and panel paintings [1]. In literature there are only a few studies dealing with the influence of moisture on the physical properties of wood [1,2]. The characterization of wooden behaviour related to changes in the humidity level c…
Shock-induced complex phase-space dynamics of strongly turbulent flows
2017
Shock waves have been thoroughly investigated during the last century in many different branches of physics. In conservative (Hamiltonian) systems the shock singularity is regularized by weak wave dispersion, thus leading to the formation of a rapidly and regular oscillating structure, usually termed in the literature dispersive shock wave (DSW), see e.g. [1]. Here, we show that this fundamental singular process of DSW formation can break down in a system of incoherent nonlinear waves. We consider the strong turbulent regime of a system of nonlocal nonlinear optical waves. We report theoretically and experimentally a characteristic transition: Strengthening the nonlocal character of the non…
Impact of self-steepening on incoherent dispersive spectral shocks and collapse-like spectral singularities
2014
International audience; Incoherent dispersive shock waves and collapselike singularities have been recently predicted to occur in the spectral evolution of an incoherent optical wave that propagates in a noninstantaneous nonlinear medium. Here we extend this work by considering the generalized nonlinear Schrödinger equation. We show that self-steepening significantly affects these incoherent spectral singularities: (i) It leads to a delay in the development of incoherent dispersive shocks, and (ii) it arrests the incoherent collapse singularity. Furthermore, we show that the spectral collapselike behavior can be exploited to achieve a significant enhancement (by two orders of magnitudes) of…
Rounding noise effects’ reduction for estimated movement of speckle patterns
2018
The problem of resolution enhancement for speckle patterns analysis-based movement estimation is considered. In our previous publications we showed that this movement represents the corresponding tilt vibrations of the illuminated object and can be measured as a relative spatial shift between time adjacent images of the speckle pattern. In this paper we show how to overcome the resolution limitation obtained when using an optical sensor available in an optical mouse and which measures the Cartesian coordinates of the shift as an integer number of pixels. To overcome such a resolution limitation, it is proposed here to use simultaneous measurements from the same illuminated spot by a few cam…
Suppression of the speckle noise in solid polymer samples: a light scattering study
1994
The speckle effect disturbs the measurement of spatial correlation functions in solid polymer samples by light scattering. To be able to extract the desired correlations from the measurements, the speckle noise must be suppressed. This is possible by moving the sample during the measurement. In this paper we demonstrate that a sufficient reduction of speckle contrast can be achieved even in samples of restricted dimensions or with a preferential direction.
Analysis of mechanical behaviour of wood species by speckle interferometry
2007
The understanding of the mechanical behaviour of wood is a very important task in modern structural engineering. This is due to the increasing role played by wood structures in modern architecture as well as to its use in the restoration of ancient buildings. However, solid mechanics of wood is very difficult since it is a complex, polymer-based, cellular, inhomogeneous material. Moreover, at the cellular scale wood is not a continuum due to the presence of vascular vacuums and it can be regarded as an anisotropic material. Conversely, at a macroscopic scale when the analysis is carried out on a structural member which is large in comparison to the size of cell, wood is usually considered a…