Search results for "Speckle pattern"

Superresolved imaging based on wavelength multiplexing of projected unknown speckle patterns

2015

We propose a method for resolution enhancement of a diffraction limited optical system based on the capture of a set of low resolution images. These images are obtained after projection of an ensemble of unknown speckle patterns on top of the high resolution object that is to be imaged. Each speckle pattern is generated by the same thin (and unknown) diffuser, but illuminated with a slightly different wavelength. From the ensemble of low resolution images, we obtain a system of equations that can be solved in an iterative manner that enables reconstruction of the high resolution object. As a result, we also achieve the projected high resolution speckle patterns used for the encoding.

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…

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…

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.

Speckle based sensing device for fast detection of malaria

2012

We propose a new technique for malaria detection. It is based upon extraction of correlation based statistics of speckle patterns generated while illuminating red blood cells with a laser and inspecting them under a microscope.

Optoelectronic Information Encryption with Incoherent Light

2005

Echocardiographic Image Analysis Based on the Evaluation of first Order Speckle Statistics

1992

Basic theoretical considerations on the statistical properties of the speckle phenomenon indicate that a conventional quantization (intervals of uniform width) of the received and envelope detected RF — signal is not adequate. We therefore propose a quantization scheme which is based on the application of quantization intervals producing always the same confidence level (adaptive quantization). The advantages are: homogenous distribution of speckle noise reduction to about 10 – 20 significant quantization levels (with neglectable loss of morphological information) quantitative measure (confidence level) of the separability of regions represented with different quantization levels. We furthe…

P1450Effect of overweight and obesity on left ventricular longitudinal multi-layer strain: a speckle tracking two-dimensional echocardiographic study

2017

Assessment of image quality of intracoronary ultrasound systems with tissue-equivalent vessel phantoms

2002

Imaging of vascular structures by intracoronary ultrasound (ICUS) is finding more and more applications in coronary diagnosis and in the assessment of interventional access. The authors describe a method for easy and quick production of tissue-equivalent vessel phantoms from a special hydrocolloid. The mechanical tolerance is less than 3/100 mm. With these phantoms the authors tested the calibration and measured the resolution properties of the SONOS intravascular ultrasonic system (Hewlett Packard). The measurements revealed a slight space related underestimation of diameters up to 280 /spl mu/m. Using cross correlation and auto correlation functions the authors analyzed digitized ultrason…