4 research outputs found
Banc de caractérisation pour lentilles panoramiques
Les particularitĂ©s des lentilles panoramiques font de leur caractĂ©risation un dĂ©fi. Pour les applications de vision, une connaissance de la distorsion est essentielle pour produire des vues naturelles. Aussi, toutes les directions Ă©tant importantes, la qualitĂ© de l'image doit ĂȘtre uniforme sur tout le champ de vue. Nous avons donc dĂ©veloppĂ© un banc de caractĂ©risation pour lentilles panoramiques. Avec des cibles rĂ©fĂ©rencĂ©es, nous avons obtenu avec rapiditĂ© et facilitĂ© les profils de distorsion, ce qui a permis de calculer la rĂ©solution instantanĂ©e linĂ©aire sur tout le champ de vue. Ăgalement, des cibles inclinĂ©es ont Ă©tĂ© utilisĂ©es pour dĂ©terminer la frĂ©quence spatiale oĂč la MTF est de 50% en fonction de l'angle dans le champ de vue. Ă l'aide de deux camĂ©ras, nous avons testĂ© deux lentilles panomorphes et deux lentilles fisheyes pour lesquelles nous avons calculĂ© la rĂ©solution instantanĂ©e et les courbes de MTF et comparĂ© certains rĂ©sultats Ă des simulations
Paire stĂ©rĂ©oscopique Panomorphe pour la reconstruction 3D d'objets d'intĂ©rĂȘt dans une scĂšne
Il existe dĂ©sormais une grande variĂ©tĂ© de lentilles panoramiques disponibles sur le marchĂ© dont certaines prĂ©sentant des caractĂ©ristiques Ă©tonnantes. Faisant partie de cette derniĂšre catĂ©gorie, les lentilles Panomorphes sont des lentilles panoramiques anamorphiques dont le profil de distorsion est fortement non-uniforme, ce qui cause la prĂ©sence de zones de grandissement augmentĂ© dans le champ de vue. Dans un contexte de robotique mobile, ces particularitĂ©s peuvent ĂȘtre exploitĂ©es dans des systĂšmes stĂ©rĂ©oscopiques pour la reconstruction 3D dâobjets dâintĂ©rĂȘt qui permettent Ă la fois une bonne connaissance de lâenvironnement, mais Ă©galement lâaccĂšs Ă des dĂ©tails plus fins en raison des zones de grandissement augmentĂ©. Cependant, Ă cause de leur complexitĂ©, ces lentilles sont difficiles Ă calibrer et, Ă notre connaissance, aucune Ă©tude nâa rĂ©ellement Ă©tĂ© menĂ©e Ă ce propos. Lâobjectif principal de cette thĂšse est la conception, lâĂ©laboration et lâĂ©valuation des performances de systĂšmes stĂ©rĂ©oscopiques Panomorphes. Le calibrage a Ă©tĂ© effectuĂ© Ă lâaide dâune technique Ă©tablie utilisant des cibles planes et dâune boĂźte Ă outils de calibrage dont lâusage est rĂ©pandu. De plus, des techniques mathĂ©matiques nouvelles visant Ă rĂ©tablir la symĂ©trie de rĂ©volution dans lâimage (cercle) et Ă uniformiser la longueur focale (cercle uniforme) ont Ă©tĂ© dĂ©veloppĂ©es pour voir sâil Ă©tait possible dâainsi faciliter le calibrage. Dans un premier temps, le champ de vue a Ă©tĂ© divisĂ© en zones Ă lâintĂ©rieur desquelles la longueur focale instantanĂ©e varie peu et le calibrage a Ă©tĂ© effectuĂ© pour chacune dâentre elles. Puis, le calibrage gĂ©nĂ©ral des systĂšmes a aussi Ă©tĂ© rĂ©alisĂ© pour tout le champ de vue simultanĂ©ment. Les rĂ©sultats ont montrĂ© que la technique de calibrage par zone ne produit pas de gain significatif quant Ă la qualitĂ© des reconstructions 3D dâobjet dâintĂ©rĂȘt par rapport au calibrage gĂ©nĂ©ral. Cependant, lâĂ©tude de cette nouvelle approche a permis de rĂ©aliser une Ă©valuation des performances des systĂšmes stĂ©rĂ©oscopiques Panomorphes sur tout le champ de vue et de montrer quâil est possible dâeffectuer des reconstructions 3D de qualitĂ© dans toutes les zones. De plus, la technique mathĂ©matique du cercle a produit des rĂ©sultats de reconstructions 3D en gĂ©nĂ©ral Ă©quivalents Ă lâutilisation des coordonnĂ©es originales. Puisquâil existe des outils de calibrage qui, contrairement Ă celui utilisĂ© dans ce travail, ne disposent que dâun seul degrĂ© de libertĂ© sur la longueur focale, cette technique pourrait rendre possible le calibrage de lentilles Panomorphes Ă lâaide de ceux-ci. Finalement, certaines conclusions ont pu ĂȘtre dĂ©gagĂ©es quant aux facteurs dĂ©terminants influençant la qualitĂ© de la reconstruction 3D Ă lâaide de systĂšmes stĂ©rĂ©oscopiques Panomorphes et aux caractĂ©ristiques Ă privilĂ©gier dans le choix des lentilles. La difficultĂ© Ă calibrer les optiques Panomorphes en laboratoire a menĂ© Ă lâĂ©laboration dâune technique de calibrage virtuel utilisant un logiciel de conception optique et une boĂźte Ă outils de calibrage. Cette approche a permis dâeffectuer des simulations en lien avec lâimpact des conditions dâopĂ©ration sur les paramĂštres de calibrage et avec lâeffet des conditions de calibrage sur la qualitĂ© de la reconstruction. Des expĂ©rimentations de ce type sont pratiquement impossibles Ă rĂ©aliser en laboratoire mais reprĂ©sentent un intĂ©rĂȘt certain pour les utilisateurs. Le calibrage virtuel dâune lentille traditionnelle a aussi montrĂ© que lâerreur de reprojection moyenne, couramment utilisĂ©e comme façon dâĂ©valuer la qualitĂ© dâun calibrage, nâest pas nĂ©cessairement un indicateur fiable de la qualitĂ© de la reconstruction 3D. Il est alors nĂ©cessaire de disposer de donnĂ©es supplĂ©mentaires pour juger adĂ©quatement de la qualitĂ© dâun calibrage.A wide variety of panoramic lenses are available on the market. Exhibiting interesting characteristics, the Panomorph lens is a panoramic anamorphic optical system. Its highly non-uniform distortion profile creates areas of enhanced magnification across the field of view. For mobile robotic applications, a stereoscopic system for 3D reconstruction of objects of interest could greatly benefit from the unique features of these special lenses. Such a stereoscopic system would provide general information describing the environment surrounding its navigation. Moreover, the areas of enhanced magnification give access to smaller details. However, the downfall is that Panomorph lenses are difficult to calibrate, and this is the main reason why no research has been carried out on this topic. The main goal of this thesis is the design and development of Panomorph stereoscopic systems as well as the evaluation of their performance. The calibration of the lenses was performed using plane targets and a well-established calibration toolbox. In addition, new mathematical techniques aiming to restore the symmetry of revolution in the image and to make the focal length uniform over the field of view were developed to simplify the calibration process. First, the field of view was divided into zones exhibiting a small variation of the focal length and the calibration was performed for each zone. Then, the general calibration was performed for the entire field of view. The results showed that the calibration of each zone does not lead to a better 3D reconstruction than the general calibration method. However, this new approach allowed a study of the quality of the reconstruction over the entire field of view. Indeed, it showed that is it possible to achieve good reconstruction for all the zones of the field of view. In addition, the results for the mathematical techniques used to restore the symmetry of revolution were similar to the results obtained with the original data. These techniques could therefore be used to calibrate Panomorph lenses with calibration toolboxes that do not have two degrees of freedom relating to the focal length. The study of the performance of stereoscopic Panomorph systems also highlighted important factors that could influence the choice of lenses and configuration for similar systems. The challenge met during the calibration of Panomorph lenses led to the development of a virtual calibration technique that used an optical design software and a calibration toolbox. With this technique, simulations reproducing the operating conditions were made to evaluate their impact on the calibration parameters. The quality of 3D reconstruction of a volume was also evaluated for various calibration conditions. Similar experiments would be extremely tedious to perform in the laboratory but the results are quite meaningful for the user. The virtual calibration of a traditional lens also showed that the mean reprojection error, often used to judge the quality of the calibration process, does not represent the quality of the 3D reconstruction. It is then essential to have access to more information in order to asses the quality of a lens calibration
New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World
The two-planet transiting system LHS 1140 has been extensively observed since
its discovery in 2017, notably with , HST, TESS, and ESPRESSO, placing
strong constraints on the parameters of the M4.5 host star and its small
temperate exoplanets, LHS 1140 b and c. Here, we reanalyse the ESPRESSO
observations of LHS 1140 with the novel line-by-line framework designed to
fully exploit the radial velocity content of a stellar spectrum while being
resilient to outlier measurements. The improved radial velocities, combined
with updated stellar parameters, consolidate our knowledge on the mass of LHS
1140 b (5.600.19 M) and LHS 1140 c (1.910.06 M)
with unprecedented precision of 3%. Transits from , HST, and TESS are
jointly analysed for the first time, allowing us to refine the planetary radii
of b (1.7300.025 R) and c (1.2720.026 R).
Stellar abundance measurements of refractory elements (Fe, Mg and Si) obtained
with NIRPS are used to constrain the internal structure of LHS 1140 b. This
planet is unlikely to be a rocky super-Earth as previously reported, but rather
a mini-Neptune with a 0.1% H/He envelope by mass or a water world with a
water-mass fraction between 9 and 19% depending on the atmospheric composition
and relative abundance of Fe and Mg. While the mini-Neptune case would not be
habitable, a water-abundant LHS 1140 b potentially has habitable surface
conditions according to 3D global climate models, suggesting liquid water at
the substellar point for atmospheres with relatively low CO concentration,
from Earth-like to a few bars.Comment: 31 pages, 18 figures, accepted for publication in ApJ
New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World
LHS 1140 b and c are two small temperate exoplanets transiting a nearby M4.5 dwarf. The planetary system was observed with multiple facilities since its discovery in 2017, including MEarth, , HARPS, ESPRESSO, HST, and TESS, placing strong constraints on the physical parameters of the planets and star. Here, we reanalyse the publicly available ESPRESSO observations of LHS 1140 with the novel line-by-line framework designed to fully exploit the radial velocity content of a stellar spectrum while being resilient to outlier measurements. This analysis reduces radial velocity uncertainties by 60% compared with published values derived from the cross-correlation function method. This improvement, combined with updated stellar parameters, consolidates our knowledge on the mass of LHS 1140 b (5.600.19 M) and LHS 1140 c (1.910.06 M) with unprecedented precision (3%). A joint analysis of transit data obtained with , HST, and TESS allows us to refine the planetary radius for b (1.7300.025 R) and c (1.2720.026 R). Stellar abundance measurements of refractory elements (Fe, Mg and Si) obtained with NIRPS are used to constrain the internal structure of LHS 1140 b. This habitable zone planet is unlikely to be a rocky super-Earth, but rather a mini-Neptune with a 0.1% H/He-rich mass envelope or a water world with a water-mass fraction between 9 and 19% depending on the atmospheric composition and relative abundance of Fe and Mg. Although LHS 1140 c remains consistent with a rocky planet, we detect a 4 discrepancy in the transit depths measured by and TESS. Finally, we find no evidence of the candidate LHS 1140 d and attribute this 80-day signal to stellar activity