Apport de l’optique Freeform pour l’imagerie multi bandes spectrales compacte

In aerospace applications, recent developments aim to reduce the allocated volume and mass of optical instruments. My studies focus on the use of freeform surfaces, which are surfaces that are not rotationally symmetric, to design compact catoptric systems to be used in multi spectral bands imaging instruments. Reflective designs have the advantage of being light, achromatic, and potentially low-cost due to cheaper materials involved, but are usually limited in field of view and aperture. The use of freeform allows an increase in performance such as on the field of view and F-number of obscuration-free reflective systems, with the drawback of being more complex to calculate, manufacture and align. A method to design such systems while taking into account all these difficulties has been invented and has been successfully used to generate a classical three mirror anastigmat for nanosatellite imaging. Finally, the same method has been proven efficient to optimize a patented system based on an unusual geometry called the alpha-Z configuration, for optronic pods applications. The alpha-Z system has been manufactured and tested both in thermal infrared and visible domains. These results demonstrate that large field of view and large aperture compact multi spectral band imaging systems can be successfully designed using freeform surfaces.Les récents développements dans la recherche aérospatiale visent à réduire le volume alloué aux instruments optiques ainsi que leur masse. Cette étude se focalise sur l’utilisation de surfaces freeform, qui sont des surfaces sans symétrie de révolution, pour concevoir des imageurs multi bandes spectrales basées sur des systèmes optiques catoptriques compacts. Les concepts réflectifs ont l’avantage d’être légers, achromatiques et potentiellement peu coûteux en raison de l’utilisation de matériaux moins chers. Cependant ils ont habituellement un champ de vue et une ouverture limités. L’utilisation de surfaces freeform permet d’augmenter ces paramètres d’ouverture et de champ de vue pour des systèmes décentrés avec l’inconvénient d’être plus complexes à calculer, fabriquer et aligner. Une méthode pour concevoir ces systèmes tout en prenant en compte ces difficultés à été développée et utilisée avec succès pour générer un système classique à trois miroirs pour de l’imagerie nanosatellitaire. Enfin, la même méthode à été utilisée pour optimiser un concept breveté basé sur une configuration innovante appelée alpha-Z compatible avec les spécifications de systèmes optiques pour boules optroniques gyrostabilisées. Ce concept à été fabriqué et testé à la fois dans le spectre visible et infrarouge thermique. Ces résultats démontrent la faisabilité de systèmes catoptriques à large ouverture et large champ de vue grâce à l’utilisation de surfaces freeform

Conception et fabrication d'un système d'imagerie thermique catoptrique grand champ dans une configuration AlphaZ

International audienceA geometry of a catoptric imaging system using three mirrors in an AlphaZ configuration is presented. This geometry allows large field of view and large aperture catoptric systems, useful for optronic pods as an example. A proof of concept with an 18×24 degree full field of view and a F/1.5 aperture is built using slow tool servo and 5 axis machining and characterized in the long wave infrared domain. The built system achieves nearly diffraction limited performance.Une nouvelle géométrie utilisant trois miroirs freeforms pour l'imagerie catoptrique grand champ est présentée. Cette géométrie permet des systèmes catoptriques grand champ et large ouverture. Une preuve de concept avec un champ de 18 par 24 degrés et ouvert à F/1.5 est fabriquée par usinage diamant STS et une machine 5 axes puis caractérisée dans l'infrarouge lointain

Freeform TMA without planar symmetry for compact catoptric imaging system

In this article, the impact of the suppression of planar symmetry in three mirror reflective designs is studied through the example of a reference TMA optimized to be diffraction limited in the near infrared (NIR) spectrum. This reference TMA has a symmetry over the YZ plane, and a bounded volume of one cubic decimeter (volume of 1U cubesat) with the parabasal ray being normal to one side of the cube. A second TMA is then derived from this reference with no planar symmetry. This second TMA is still diffraction limited in the NIR spectrum while having a 11% longer focal length for the same maximal volume. A study of manufacturing complexity of the surfaces show no added complexity of the surface other than the removal of any symmetry. Parameters such as freeform sag and orthoradial slopes are compared suggesting that surfaces of the asymmetric system are simpler to manufacture

Comment analyser les échanges de professionnels sur une liste de discussion : le cas des juges pour enfants

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Stratégies de conception d'un télescope à trois mirroirs freeforms sans obstruction pour l'imagerie infrarouge par nanosatellite

International audienceThe new degrees of freedom offered by the new family of freeform surfaces helps compensating for off axis aberrations in optical designs. We define a freeform surface as a non-rotationally symmetric surface which cannot be described as an off-axis part of a conicoid. The use of freeform surfaces allows an increase in performance such as on the field of view, the F-number and compactness of unobscured all reflective telescopes. Reflective designs have the advantage of being light, achromatic, and potentially low-cost due to cheaper materials involved. It could result in industrial production of compact panchromatic systems for various applications ranging from automotive sensors to imaging nanosatellites. In this paper we address the challenges posed by the use of these surfaces in optical design optimization, specifically the minimization of the surface counting, in order to simplify the manufacturing, assembly and integration phases. We focus on three mirror designs and work on the compactness with various flavors in the 3D space. We will discuss our results on a fast, unobscured, non reimaging and well corrected three mirror anastigmat (TMA) design for a nanosatellite thermal imaging payload using uncooled bolometers. Optimization method of a TMA under volume and straylight constraints is described. A tolerance analysis is performed and minimal alignment is required even for large tolerances.Les nouveaux degrés de liberté offerts par la récente famille des surfaces freeform permet de compenser les aberrations optiques des systèmes hors d'axe. Nous définissons une surface freeform comme une surface sans symmétrie de révolution qui ne peut être décrite comme une sous partie d'une conicoïde. L'usage de surfaces freeform permet une augmentation des performances comme le champ de vue, l'ouverture et la compacité des systèmes réflectifs sans obstruction. Les concepts à miroirs ont l'avantage d'être légers, achromatiques, et potentiellement bas coût en raison du faible prix des matériaux utilisés. Cela pourrait mener vers une production industrielle de systèmes panchromatiques compacts pour de multiples applications allant des capteurs automobiles à l'imagerie par nanosatellite. Dans cet article, nous discuterons des défis posés par l'utilisation de ces surfaces dans l'optimisation de systèmes optiques, et en particulier la minimisation du nombre de surfaces pour simplifier la fabrication, l'assemblage et l'intégration de ces systèmes. Nous nous concentrons sur les systèmes à trois miroirs et travaillons à maximiser la compacité de ces systèmes dans un volume tridimensionnel. Les résultats seront présentés sur un téléscope à trois miroirs très ouvert, sans obstruction, non réimageant et très bien corrigé des aberrations conçu pour de l'imagerie thermique non refroidie depuis un nanosatellite en orbite basse. La méthode d'optimisation est décrite et une étude en lumière parasite et de tolérancement est faite

Freeform pour les applications visibles et infrarouges thermiques

International audiencePanchromatic catoptric systems using the freeform technology are investigated. We study a classical Three Mirror Anastigmat configuration and a more uncommon αZ configuration. Images in infrared and visible are presented for the αZ configuration.Les systèmes catoptriques panchromatiques utilisant la technologie freeform sont étudiés. Nous étudions une configuration classique Anastigmat à trois miroirs et une configuration αZ plus rare. Des images dans l'infrarouge et le visible sont présentées pour la configuration αZ

Management of rigorous optomechanical constraints using non planar symmetrical systems

International audienceAn exploration of non planar symmetric geometries for a three mirror anastigmat telescope is performed and show that for some highly constrained systems, such assymetric designs could represent a viable solutio

Steroid-Free Deep Remission at One Year Does Not Prevent Crohn's Disease Progression: Long-Term Data From the TAILORIX Trial

Background & Aims: Crohn's disease (CD) patients included in the Tailored Treatment With Infliximab for Active Crohn's Disease (TAILORIX) trial started infliximab in combination with an immunosuppressant for 1 year. The aim of the present study was to determine the long-term disease course beyond the study period. Methods: We compared the outcomes of patients who did or did not reach the primary end point of the TAILORIX trial, defined as sustained corticosteroid-free clinical remission from weeks 22 through 54, with no ulcers on ileocolonoscopy at week 54. The primary outcome of this follow-up study was the progression-free survival of CD defined by anal or major abdominal surgery, CD-related hospitalization, or the need for a new systemic CD treatment. Results: The 95 patients (median disease duration, 4.5 mo; interquartile range, 1.0–56.6 mo) analyzed, including 45 (47%) who achieved the primary end point, were followed up for a median duration of 64.2 months (interquartile range, 57.6–69.9 mo) after the end of the study period. There was no significant difference in CD progression-free survival at 1, 3, and 5 years between patients who achieved the TAILORIX primary end point and patients who did not (P =.64). No difference was observed between both groups for each component of CD progression: anal surgery, major abdominal surgery, CD-related hospitalization, or the need for a new systemic CD treatment. Conclusions: Achieving a sustained clinical remission off steroids with complete endoscopic remission in this cohort of 95 patients with early CD was not associated with less disease progression. Prospective trials to define the therapeutic goals that change the natural history of CD and prevent complications are needed

Steroid-Free Deep Remission at One Year Does Not Prevent Crohn's Disease Progression: Long-Term Data From the TAILORIX Trial.

peer reviewedBACKGROUND & AIMS: Crohn's disease (CD) patients included in the Tailored Treatment With Infliximab for Active Crohn's Disease (TAILORIX) trial started infliximab in combination with an immunosuppressant for 1 year. The aim of the present study was to determine the long-term disease course beyond the study period. METHODS: We compared the outcomes of patients who did or did not reach the primary end point of the TAILORIX trial, defined as sustained corticosteroid-free clinical remission from weeks 22 through 54, with no ulcers on ileocolonoscopy at week 54. The primary outcome of this follow-up study was the progression-free survival of CD defined by anal or major abdominal surgery, CD-related hospitalization, or the need for a new systemic CD treatment. RESULTS: The 95 patients (median disease duration, 4.5 mo; interquartile range, 1.0-56.6 mo) analyzed, including 45 (47%) who achieved the primary end point, were followed up for a median duration of 64.2 months (interquartile range, 57.6-69.9 mo) after the end of the study period. There was no significant difference in CD progression-free survival at 1, 3, and 5 years between patients who achieved the TAILORIX primary end point and patients who did not (P = .64). No difference was observed between both groups for each component of CD progression: anal surgery, major abdominal surgery, CD-related hospitalization, or the need for a new systemic CD treatment. CONCLUSIONS: Achieving a sustained clinical remission off steroids with complete endoscopic remission in this cohort of 95 patients with early CD was not associated with less disease progression. Prospective trials to define the therapeutic goals that change the natural history of CD and prevent complications are needed

Steroid-Free Deep Remission at One Year Does Not Prevent Crohn's Disease Progression: Long-Term Data From the TAILORIX Trial

Background & Aims: Crohn's disease (CD) patients included in the Tailored Treatment With Infliximab for Active Crohn's Disease (TAILORIX) trial started infliximab in combination with an immunosuppressant for 1 year. The aim of the present study was to determine the long-term disease course beyond the study period. Methods: We compared the outcomes of patients who did or did not reach the primary end point of the TAILORIX trial, defined as sustained corticosteroid-free clinical remission from weeks 22 through 54, with no ulcers on ileocolonoscopy at week 54. The primary outcome of this follow-up study was the progression-free survival of CD defined by anal or major abdominal surgery, CD-related hospitalization, or the need for a new systemic CD treatment. Results: The 95 patients (median disease duration, 4.5 mo; interquartile range, 1.0–56.6 mo) analyzed, including 45 (47%) who achieved the primary end point, were followed up for a median duration of 64.2 months (interquartile range, 57.6–69.9 mo) after the end of the study period. There was no significant difference in CD progression-free survival at 1, 3, and 5 years between patients who achieved the TAILORIX primary end point and patients who did not (P =.64). No difference was observed between both groups for each component of CD progression: anal surgery, major abdominal surgery, CD-related hospitalization, or the need for a new systemic CD treatment. Conclusions: Achieving a sustained clinical remission off steroids with complete endoscopic remission in this cohort of 95 patients with early CD was not associated with less disease progression. Prospective trials to define the therapeutic goals that change the natural history of CD and prevent complications are needed