3DC2 : a multiple view interactive platform

International audienceCet article présente un prototype de 3DC21, un système interactif multi-opérateur multi-vues. Ce système a pour principale caractéristique la possibilité de présenter deux vues 3D stéréoscopiques distinctes à deux opérateurs travaillant sur la même surface interactive. Il a pour cible applicative des contextes de travail coopératif pour lesquels la 3D est primordiale. Il est démontré sur un scénario de surveillance urbaine à base de drones aéroportés

Etude et développement de tableaux non diffractants pour la conception de systèmes imageurs spécialisés

La capacité actuelle d accéder à des détecteurs très performants et de faible coût amène la communauté des concepteurs de systèmes optiques à un changement de paradigme. Plutôt que de réaliser des caméras généralistes, aptes à réaliser un grand nombre de missions d observation différentes, il est maintenant de plus en plus courant de développer des systèmes imageurs adaptés à une seule mission et/ou à une seule classe d objets. Prendre en compte ces connaissances a priori sur la scène et la mission, au moment de la conception, permet d envisager des systèmes plus simples, mais aussi dotés de nouvelles compétences. L'objectif de la thèse est d'explorer les potentialités des tableaux non diffractants pour la conception de systèmes imageurs spécialisés. Pour cette étude nous considérons l'environnement des drones aéroportés de faible capacité d'emport pour lesquels les systèmes imageurs embarqués doivent être simples et robustes. Nous considérons de plus que la mission du système imageur est de détecter les obstacles. Pour cela, il doit délivrer une information 3D sur la scène observée. Dans un premier temps, j'ai analysé les propriétés d'imagerie du système imageur constitué d'un composant non diffractant et d'un détecteur matriciel. L'analyse comparative de deux composants, l'axicon et le tableau non diffractant, m'a permis de montrer que c'est le second composant qui est le mieux adapté pour remplir ce type de mission. J'ai ensuite réalisé un système imageur de démonstration, ce qui m'a permis au final de mettre en évidence sa capacité à faire de l'imagerie 3D. Cette étude a montré que les tableaux non diffractants ont un très fort potentiel pour réaliser un système imageur simple, robuste et dédié à l'imagerie 3D. Ce travail doit être poursuivi en partenariat avec des industriels pour appliquer la démarche de conception à une mission précise et transformer ce travail théorique en un système industrialisable.Currently, detectors with high performances and a low cost are available and lead the community of optical designers to a new paradigm. Instead of designing generalist cameras, suitable for fulfilling a high number of different observation missions, it is now more and more common to develop imaging systems adapted to a unique mission and/or a unique object class. Taking this a priori knowledge on the observed scene or on the mission into account, at the beginning of the design process, allows us to consider simpler imaging systems with new properties. The aim of this thesis is to investigate the possibilities of nondiffracting array for the design of specialized imaging systems. For this study we consider the environment of unmanned aerial vehicles with a small payload capacity, for which embedded imaging systems must be simple and robust. We consider in addition that the mission of the imaging system is to detect obstacles. To do this, it must provide a 3D information on the observed scene. At first, I have analysed the properties of the imaging system composed by a nondiffracting optical device and a focal plane array. The comparison between two devices, axicon and nondiffracting arrays, allowed me to show that the second one is best suited for achieving this kind of mission. Then, I have made a practical implementation of such an imaging system. Finally, I have used it to demonstrate the 3D imaging property. This study has demonstrated the potential of nondiffracting array to design a simple and robust imaging system dedicated to 3D imaging. This work must be continued in partnership with the industry to apply the co-design process to a more precise mission, transforming this way this theoretical work into an industrial prototype.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Tunable grating-assisted surface plasmon resonance by use of nano-polymer dispersed liquid crystal electro-optical material

This paper reports on the experimental observation of the displacement of a surface plasmon resonance (SPR) excited by a metallic diffraction grating. This effect is achieved by the use of an electro-optical material composed of nano-sized droplets of liquid crystals dispersed in a host polymer. The average refractive index of this material in the form of a thin film on the undulated metal surface can be modified with the application of an external electric field and to tune the wavelength at which the SPR excitation leads to a reflection minimum. The theoretical design and experimental demonstration of the principle of this component are described

Multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals: static and dynamic studies

The optimization of the experimental parameters of two multiplexed holographic transmission gratings recorded in holographic polymer-dispersed liquid crystals is investigated. Two methods are used to record the holograms: simultaneous and sequential multiplexing. These two processes are optimized to produce two multiplexed Bragg gratings that have the same and the highest possible diffraction efficiencies in the first order. The two methods show similar results when suitable recording parameters are used. The parameters of the recorded gratings (mainly the refractive-index modulation) are retrieved by use of an extension of the rigorous coupled-wave theory to multiplexed gratings. Finally, the response of the holograms to an electric field is studied. We demonstrate few coupling effects between the behavior of both gratings, and we expect a possibility of switching from one grating to the other

Turbidimeter based on a refractometer using a charge-coupled device

International audienceSalinity and turbidity are two important seawater properties in oceanography. We have studied the use of a high resolution refractometer to measure the salinity of seawater. The requirement of a multifunctional sensor makes the turbidity measurement based on our refractometer valuable. We measure turbidity according to the attenuation of the laser beam caused by the scattering. With the configuration of our refractometer, several issues impact the laserbeamattenuation measurement, while the measurement of salinity is impacted by the scattering as well. All these issues make light distribution nonsensitive sensors such as position sensitive devices unsuitable for building the refracto-turbidimeters. To overcome these issues, a charge-coupled device combined with a new location algorithm is used to measure both the refractive index and the attenuation. Several simulations and experiments are carried out to evaluate this new method. According to the results, the way to improve the resolution is discussed as well. The validation of our method is proved by comparison to the nephelometer specified by the nephelometric turbidity unit standar

Principle and implementations of a refracto-nephelo-turbidimeter for seawater measurements

International audienceSalinity and turbidity are two important seawater properties in physical oceanography. The study of physical oceanography requires a compact high-resolution in-situ salino-turbidimeter to measure these two parameters in different ocean zones. Refractometry has proved to be an effective method to measure seawater salinity with a high resolution. Previous studies have shown that the transmission and scattering of light in a turbid medium impact the light beam deviation measurements, which makes the combination of salinity and turbidity measurements with the same sample mandatory. In this paper, we analyze the requirements and challenges of a refracto-turbidimeter design from their measurement principles and correlations. According to these requirements, we propose a miniature refracto-nephelo-turbidimeter with a CCD, providing a salinity measurement resolution of 2 mg.kg-1 and a turbidity measurement resolution of 1 % of the measurement range. Based on this refracto-nephelo-turbidimeter, different embodiments are discussed to meet the different requirements for different ocean zones

Génération optique de signaux millimétriques à base de modulateurs de phase optiques sans filtrage optique ou RF et sans polarisation électrique

National audienceUn système de génération optique d'ondes millimétriques accordable à base de modulateurs de phase sans filtre RF ni optique et sans tension de polarisation DC est proposé dans cet article. Un signal de 60 GHz est généré par multiplication par 8 à partir d'un signal de 7.5 GHz avec un ratio de suppression électrique en simulation d'environ 50 dB

Filterless millimetre-wave optical generation using optical phase modulators without DC bias

International audienceA tunable millimetre-wave generator using optical phase modulators with no DC bias and no filters (neither RF nor optical filters) is proposed in this paper. A 60 GHz RF signal is optically generated by multiplying the frequency of an input RF signal at 7.5 GHz by a factor of 8. The electrical suppression ratio is around 50 dB as shown by simulations

Supervised stereo visual acuity tests implemented on 3D TV monitors

International audienceIn this paper we discuss under which conditions standard stereo visual acuity tests can be implemented on 3D TV monitors. In particular, we emphasize the role of environmental lighting conditions, on the measurement of the stereo visual acuity, when using conventional 3D tests, such as Wirt stereotests. We investigate the impact of parameters such as luminance, backlight and contrast when these tests are implemented on 3D TV monitors. We demonstrate that some deviations are observed when modifying the room luminance and the type of displays used (e.g. plasma (PDP) or liquid crystal (LCD) displays). Our measurements carried out on an human sample are supervised by pupil size measurements, using an eyes-tracker, enabling a better interpretation of the results. Finally, we discuss the benefit of using 3D tools to implement stereo visual acuity measurements