Search results for "Illumination"

Bias artifact suppression on MR volumes.

2007

RF-Inhomogeneity correction is a relevant research topic in the field of Magnetic Resonance Imaging (MRI). A volume corrupted by this artifact exhibits nonuni- form illumination both inside a single slice and between adjacent ones. In this work a bias correction technique is presented, which suppresses this artifact on MR vol- umes scanned from different body parts without any a-priori hypothesis on the artifact model. Theoretical foundations of the method are reported together with experimental results and a comparison is presented with both the 2D version of the algorithm and other techniques that are widely used in MRI literature.

Automatic fringe pattern enhancement using truly adaptive period-guided bidimensional empirical mode decomposition.

2020

Fringe patterns encode the information about the result of a measurement performed via widely used optical full-field testing methods, e.g., interferometry, digital holographic microscopy, moiré techniques, structured illumination etc. Affected by the optical setup, changing environment and the sample itself fringe patterns are often corrupted with substantial noise, strong and uneven background illumination and exhibit low contrast. Fringe pattern enhancement, i.e., noise minimization and background term removal, at the pre-processing stage prior to the phase map calculation (for the measurement result decoding) is therefore essential to minimize the jeopardizing effect the mentioned error…

Efficient Skin Detection under Severe Illumination Changes and Shadows

2011

International audience; This paper presents an efficient method for human skin color detection with a mobile platform. The proposed method is based on modeling the skin distribution in a log-chromaticity color space which shows good invariance properties to changing illumination. The method is easy to implement and can cope with the requirements of real-world tasks such as illumination variations, shadows and moving camera. Extensive experiments show the good performance of the proposed method and its robustness against abrupt changes of illumination and shadows.

Comparison of single-spot technique and RGB imaging for erythema index estimation

2016

A commercially available point measurement device, the Mexameter(®), and an experimental RGB imaging prototype device were used for erythema index estimation of 50 rosacea patients by analysing the level of skin redness on the forehead, both cheeks and both sides of a nose. Results are compared with Clinician's Erythema Assessment (CEA) values given by two dermatologists. The Mexameter uses 568 nm and 660 nm LEDs and a photodetector for estimation of erythema index, while the used prototype device acquired RGB images at 460 nm, 530 nm and 665 nm LED illumination. Several erythema index estimation algorithms were compared to determine which one gives the best contrast between increased eryth…

Investigating the performance of reconstruction methods used in structured illumination microscopy as a function of the illumination pattern's modula…

2016

Surpassing the resolution of optical microscopy defined by the Abbe diffraction limit, while simultaneously achieving optical sectioning, is a challenging problem particularly for live cell imaging of thick samples. Among a few developing techniques, structured illumination microscopy (SIM) addresses this challenge by imposing higher frequency information into the observable frequency band confined by the optical transfer function (OTF) of a conventional microscope either doubling the spatial resolution or filling the missing cone based on the spatial frequency of the pattern when the patterned illumination is two-dimensional. Standard reconstruction methods for SIM decompose the low and hi…

Fast and robust phase-shift estimation in two-dimensional structured illumination microscopy.

2019

A method of determining unknown phase-shifts between elementary images in two-dimensional Structured Illumination Microscopy (2D-SIM) is presented. The proposed method is based on the comparison of the peak intensity of spectral components. These components correspond to the inherent structured illumination spectral content and the residual compo- nent that appears from wrongly estimated phase-shifts. The estimation of the phase-shifts is carried out by finding the absolute maximum of a function defined as the normalized peak intensity difference in the Fourier domain. This task is performed by an optimization method providing a fast estimation of the phase-shift. The algorithm stability an…

Le paon et la rhétorique des couleurs au sein du manuscrit : Rythme, unité et équilibre dans les Évangiles de Gundohinus

2013

Multispectral image denoising with optimized vector non-local mean filter

2016

Nowadays, many applications rely on images of high quality to ensure good performance in conducting their tasks. However, noise goes against this objective as it is an unavoidable issue in most applications. Therefore, it is essential to develop techniques to attenuate the impact of noise, while maintaining the integrity of relevant information in images. We propose in this work to extend the application of the Non-Local Means filter (NLM) to the vector case and apply it for denoising multispectral images. The objective is to benefit from the additional information brought by multispectral imaging systems. The NLM filter exploits the redundancy of information in an image to remove noise. A …

Space and Light, Towards an Interactive Simulation of Lighting

2003

International audience; Une image est une vue, à un instant donné, de l'équilibre lumineux présent dans une scène. Cet équilibre résulte d'un système complexe où l'énergie provenant des sources est re-distribuée dans l'espace par les matériaux appliqués aux formes. Si cet équilibre est perturbé par une modification des conditions lumineuses, l'image précédente n'est plus valide. En cela elle ne représente qu'un instant d'un lieu et non le lieu lui même. Nous proposons ici une approche pour la simulation interactive de l'éclairage dans une scène complexe. Une application à cette étude étant la production d'images vivantes et confondantes dans le cadre de la réalité augmentée.

Application of gas separation membranes to detritiation systems

2002

The use of gas separation membranes in tritium removal systems has been studied to develop a new detritiation process. The main advantage of this new process is to reduce the number and/or the size of equipments in comparison to conventional detritiation systems. The objective of this study is to choose the best suited membrane for this application. The hydrogen or its isotopes recovery performance of several commercial hollow fiber organic membranes has been analyzed thanks to three devices. Experiments are performed with small quantities of hydrogen gas or deuterium gas or tritium gas in the range representative of the radioactive contamination level in tritium handling gloveboxes. A math…