Low coherence interferometry for central thickness measurement of rigid and soft contact lenses

International audienceIn this paper we propose contact lens central thickness measurement with a low coherence interferometry technique using either a SLED source or a broadband continuum generated in air-silica Microstructured Optical Fiber (MOF) pumped with a picosecond microchip laser. Each of these sources associated with the interferometer provides, at the same time, good measurement resolution and quick signal recording without moving any optical elements and without need of a Fourier Transform operation. Signal improvement is performed afterwards by a numerical treatment for optimal correlation peaks detection leading to central thickness value of several contact lenses

Comparison of the efficiency, MTF and chromatic properties of four diffractive bifocal intraocular lens designs

International audienceThe aim of this paper is to compare the properties of four different profiles which can be used as multifocal intraocular lens. The Hankel transform based on the theory of scalar diffraction is applied to a binary profile, a parabolic one, a parabolic profile with holes, and finally a sinusoidal one. This enables to study the various distributions of the diffractive efficiencies and the axial chromatism. The image quality is evaluated by means of simulations of the MTFs with Zemax®. Finally we propose a new way to graphically synthesize all the properties of these lenses, using a radar graph

Comparison of the efficiency, MTF and chromatic properties of four diffractive bifocal intraocular lens designs

International audienceThe aim of this paper is to compare the properties of four different profiles which can be used as multifocal intraocular lens. The Hankel transform based on the theory of scalar diffraction is applied to a binary profile, a parabolic one, a parabolic profile with holes, and finally a sinusoidal one. This enables to study the various distributions of the diffractive efficiencies and the axial chromatism. The image quality is evaluated by means of simulations of the MTFs with Zemax®. Finally we propose a new way to graphically synthesize all the properties of these lenses, using a radar graph

Shack-Hartmann multiple spots with diffractive lenses

International audienceIn this Letter we aim to bring an understanding to the apparition of multiple spots when using a Shack-Hartmann (SH) wavefront sensor behind diffractive lenses. In contrast to previous work, this phenomenon is described in terms of diffractive orders. It is illustrated with Zemax simulations, where three kinds of diffractive lenses (monofocal, bifocal, and trifocal) are set behind a microlens array. The presence of multiple spots is related to the phase jump of the diffractive profile and also to the number of steps seen through the microlens pupil. The possibility of assessing the optical quality of such lenses using SH measurements is discussed, in particular within the field of ophthalmology, where the need for precautions is underline

Renouveler les modèles de la communication et de la coopération par l'improvisation : Org’impro, une recherche-action innovante

Cette contribution s’inscrit dans la continuité des recherches qui questionnent la formation en compétences communicationnelles des futurs cadres (professionnels de la communication et managers). Elle met en évidence la place du non verbal dans l’élaboration du faire ensemble et interroge les modèles enseignés sur le rôle de ce type de communication dans la construction d’un projet collectif. Par le compte-rendu et l’analyse d’une proposition pédagogique originale intitulée « Org’impro », recherche-action dans le domaine de la formation ayant impliqué des chorégraphes spécialistes de l’improvisation et portée par l’Université Grenoble Alpes, notre propos est de nourrir la pédagogie par la recherche et de développer des dispositifs de formation transférables dans les organisations. This contribution takes place into the field of researches that question the communication skills training for future managers (communication professionals and managers). It highlights importance of nonverbal communication in cooperative work and questions the models taught about the role of this type of communication for building a collective project. By the report and analysis of an original educational proposal entitled « Org’impro « , an action research in the field of training that involved specialists choreographers of improvisation and managed by the University of Grenoble Alpes, our purpose is to increase the pedagogy research and develop training devices transferable in organizations

Three red suns in the sky: A transiting, terrestrial planet in a triple M-dwarf system at 6.9 pc

We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of ${1.38}_{-0.12}^{+0.13}$ ${R}_{\oplus }$, an orbital period of ${5.35882}_{-0.00031}^{+0.00030}$ days, and an equilibrium temperature of ${433}_{-27}^{+28}$ K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 ${M}_{\oplus }$ on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.Accepted manuscrip

Vulnerability and Hardening Studies of Optical and Illumination Systems at MGy Dose Levels

In the framework of the fusion for energy radiation hard imaging system project, the main radiation effects affecting the image quality of a miniaturized complementary metal-oxide-semiconductor-based camera exposed to radiation doses up to 1 MGy(SiO 2 ) are investigated for ITER applications. The radiation effects related to two of the three subcomponents of the camera are investigated: the optical system (OS) and the illumination system (IS). Subsystem demonstrators have been manufactured selecting radiation tolerant or hardened materials and components to demonstrate the feasibility to withstand such high dose levels while fulfilling the ITER remote handling needs in terms of optical performances and miniaturization. Regarding the OS, the observed degradation of the radiation-hardened optical glasses used for the OS lenses is characterized in terms of both radiation-induced attenuation and radiation-induced refractive-index change. At the system level, impact of these phenomena on the OS demonstrator performances is discussed in terms of image contrast. Radiation test results highlight the high radiation tolerance of manufactured monochrome and color OS to both degradation mechanisms. Regarding the IS, the selected architecture consists in a ring of 20 commercially available light-emitting diodes (LEDs) with monochrome (amber) or white emissions. An appropriate choice for the LEDs allows designing an IS with the requested performances and slight degradation of its output power at the MGy dose levels. From the obtained results, developing miniaturized IS and OS subcomponents for MGy dose operation levels appears realistic using commercially available technologies and appropriate hardening procedures

A super-Earth transiting a nearby low-mass star

A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. As such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9-10 times the Earth's mass (M_Earth), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b, but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55 M_Earth and a radius 2.68 times Earth's radius (R_Earth), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen-helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. As the star is small and only 13 parsecs away, the planetary atmosphere is amenable to study with current observatories.Comment: 13 pages, 3 figures, published in Natur

A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780

We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, $V=13.07$, $K_s=8.204$, $R_s$=0.374 R$_{\odot}$, $M_s$=0.401 M$_{\odot}$, d=22 pc). The two planet candidates are identified in a single TESS sector and are validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of $P_b=0.77$ days, $P_c=12.25$ days and sizes $r_{p,b}=1.33\pm 0.07$ R$_{\oplus}$, $r_{p,c}=2.30\pm 0.16$ R$_{\oplus}$, the two planets span the radius valley in period-radius space around low mass stars thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 63 precise radial-velocity measurements from HARPS and HARPS-N, we measure planet masses of $m_{p,b}=2.62^{+0.48}_{-0.46}$ M$_{\oplus}$ and $m_{p,c}=8.6^{+1.6}_{-1.3}$ M$_{\oplus}$, which indicates that LTT 3780b has a bulk composition consistent with being Earth-like, while LTT 3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and from core-powered mass loss models. The brightness and small size of LTT 3780, along with the measured planetary parameters, render LTT 3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley.Comment: Accepted to AJ. 8 figures, 6 tables. CSV file of the RV measurements (i.e. Table 2) are included in the source cod

Etude et réalisation de lasers solides a modes couples (yag dope néodyme et saphir dope tiane). Compression d'impulsions.

xxCe mémoire présente différentes techniques permettant de produire des impulsions lumineuses très brèves. Dans un premier temps, nous avons conçu et réalisé un laser nd:yag continu a modes couples activement et double en fréquence. Ce laser délivre des impulsions dont la largeur a mi-hauteur en intensité est voisine de 60 picosecondes a 532 nanomètres, repetitives a 82 mhz. La puissance moyenne des impulsions est suffisante pour permettre le pompage d'un laser a colorant en mode synchrone. Ce dernier délivre des impulsions lumineuses dont la durée est voisine de 10 picosecondes et répétitives a 82 mhz. L'ensemble du système a été caractérise en utilisant des caméras a balayage de fente en mode sinusoïdal ou en mode monocoup. Nous avons ensuite étudié la possibilité de produire des impulsions femtosecondes (10##1#5 s) en comprimant les impulsions délivrées par un laser a colorant a deux jets (milieu amplificateur rh6g), absorbant saturable (dodci). Avant compression, ces impulsions ont une largeur a mi-hauteur en intensité voisine de une picoseconde et sont répétitives a environ 80 mhz. Nous avons pu comprimer ces impulsions jusqu'a des durees voisines de 130 femtosecondes. Les résultats expérimentaux sont très proches des prévisions théoriques. Enfin, nous avons produit directement des impulsions lumineuses femtosecondes a partir d'une cavité laser dont le milieu amplificateur est un cristal de saphir dope au titane (ti:al#2o#3). Dans un premier temps, le couplage des modes est réalisé a l'aide d'un modulateur acousto-optique. Dans cette configuration, le laser produit des impulsions dont la durée est aussi courte que 10 picosecondes, répétitives a 125 mhz et dont le domaine d'accord en longueur d'onde est limite par les miroirs entre 72 et 800 nanomètres. Dans un second temps, le couplage des modes est réalisé en utilisant un absorbant saturable (hitci) et la dispersion intracavite est aju