Michel Tallon

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We present what we believe to be a new algorithm, FRactal Iterative Method (FRiM), aiming at the reconstruction of the optical wavefront from measurements provided by a wavefront sensor. As our application is adaptive optics on extremely large telescopes, our algorithm was designed with speed and best quality in mind. The latter is achieved thanks to a(More)
We present a formalism for performance analyses of adaptive optics systems that use a polychromatic laser guide star to measure the tilt of atmospherically distorted wavefronts. This formalism can be applied to feasibility and design studies of polychromatic laser guide star tip-tilt systems that are used to make the adaptive optics system of a telescope(More)
An analysis of the problem of wave-front reconstruction from Shack-Hartmann measurements is presented. The wave-front aberration is assumed to result from passage of the wave front through Kolmogorov turbulence. Limitations of using Zernike polynomials as an orthogonal basis for wave-front reconstruction are highlighted, and the advantage of using the(More)
We study the so-called three-dimensional mapping of turbulence, a method solving the cone effect (or focus anisoplanatism) by using multiple laser guide stars (LGSs). This method also permits a widening of the corrected field of view much beyond the isoplanatic field. Multiple deformable mirrors, conjugated to planes at chosen altitudes among the turbulent(More)
The young stellar object MWC 297 is an embedded B1.5Ve star exhibiting strong hydrogen emission lines and a strong near-infrared continuum excess. This object has been observed with the VLT interferometer equipped with the AMBER instrument during its first commissioning run. VLTI/AMBER is currently the only near infrared interferometer which can observe(More)
LITpro is a software for fitting models on data obtained from various stellar optical interferometers, like the VLTI. As a baseline, for modeling the object, it provides a set of elementary geometrical and center-to-limb darkening functions, all combinable together. But it is also designed to make very easy the implementation of more specific models with(More)
Context. Interferometry can provide spatially resolved observations of massive star binary systems and their colliding winds, which thus far have been studied mostly by means of spatially unresolved observations. Aims. In this work, we present the first AMBER/VLTI observations, taken at orbital phase 0.32, of the Wolf-Rayet and O (WR+O) star binary system γ(More)
Up to now only a few numerical or experimental simulations of atmospheric turbulent layers have been performed in the laboratory. These are devoted mainly to show the validity of Kolmogorov behavior but are not suitable to implement in an optical bench to test light propagation. Here we present a small size experimental simulation of an optical turbulent(More)
We report the photometric observation of a polychromatic laser guide star (PLGS) using the AVLIS laser at the Lawrence Livermore National Laboratory (LLNL). The process aims at providing a measurement of the tilt of the incoming wave front at a telescope induced by atmospheric turbulence. It relies on the two-photon coherent excitation of the 4D5/2 energy(More)