Differential method for freeform optics applied to two-mirror off-axis telescope design

International audienceIn this Letter, we present a method to design the freeform surfaces of an off-axis unobscured two-mirror telescope by integration of a system of differential equations. The system is derived from the differentiation of Fermat’s path principle and is integrated as an ordinary differential equation problem. The method is used to design the freeform surfaces of a telescope whose performance is verified in off-the-shelf optical design software (Zemax)

In Honor of Fred Gray: The Meaning of Montgomery

International audienceWe present a new method for depth estimation, based on a stereoscopic camera with various camera focus setting. Depth isestimated using a criterion derived from a maximum likelihood estimator, which jointly analyses the data likelihood with respect to the disparity and the defocus blur of each camera. Benefit of this approach is studied, in particular for scene having repetitive patterns with respect to classical stereoscopy, then we present experimental results on outdoor scenes from a real infra-red stereoscopic system.Nous présentons une nouvelle méthode d’estimation de profondeur, qui repose sur l’utilisation de deux caméras en configuration stéréoscopique avec chacune une mise au point différente. La profondeur est estimée via un critère dérivé d’un maximum de vraisemblance qui intègre conjointement des informations de disparité et les flous de défocalisation de chaque caméra. Nous étudions les apports de cette approche, notamment sur des scènes à motifs répétitifs, par rapport à la stéréoscopie classique sur des images issues de caméras opérant dans le visible.Enfin nous montrons des exemples de résultats sur des images IR thermique acquises en extérieur

Compact infrared cryogenic wafer-level camera: design and experimental validation

International audienceWe present a compact infrared cryogenic multichannel camera with a wide field of view equal to 120 degrees. By merging the optics with the detector, the concept is compatible with both cryogenic constraints and wafer-level fabrication. The design strategy of such a camera is described, as well as its fabrication and integration process. Its characterization has been carried out in terms of the modulation transfer function and the noise equivalent temperature difference (NETD). The optical system is limited by the diffraction. By cooling the optics, we achieve a very low NETD equal to 15 mK compared with traditional infrared cameras. A postprocessing algorithm that aims at reconstructing a well-sampled image from the set of undersampled raw subimages produced by the camera is proposed and validated on experimental images. (C) 2012 Optical Society of Americ

Compact infrared pinhole fisheye for wide field applications

International audienceThe performances of a compact infrared optical system using advanced pinhole optics for wide field applications are given. This concept is adapted from the classical Tisse design in order to fit with infrared issues. Despite a low light gathering efficiency and a low resolution in comparison with classical lenses, pinhole imagery provides a long depth of field and a wide angular field of view. Moreover, by using a simple lens that compresses the field of view, the angular acceptance of this pinhole camera can be drastically widened to a value around 180{\textdegree}. This infrared compact system is named pinhole fisheye since it is based on the field lens of a classical fisheye system

Waveform Modelling for the Laser Interferometer Space Antenna

LISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave astronomy. As the first anticipated space-based gravitational-wave detector, it will expand our view to the millihertz gravitational-wave sky, where a spectacular variety of interesting new sources abound: from millions of ultra-compact binaries in our Galaxy, to mergers of massive black holes at cosmological distances; from the beginnings of inspirals that will venture into the ground-based detectors' view to the death spiral of compact objects into massive black holes, and many sources in between. Central to realising LISA's discovery potential are waveform models, the theoretical and phenomenological predictions of the pattern of gravitational waves that these sources emit. This white paper is presented on behalf of the Waveform Working Group for the LISA Consortium. It provides a review of the current state of waveform models for LISA sources, and describes the significant challenges that must yet be overcome.Comment: 239 pages, 11 figures, white paper from the LISA Consortium Waveform Working Group, invited for submission to Living Reviews in Relativity, updated with comments from communit

Approche frugale pour la conception de caméras infrarouges

As a research scientist in optical design at ONERA, I have worked on a frugal strategy for infrared optical systems in order to simplify them and miniaturize them. The implementation of advanced imagery functions like 3D imagery and multispectral imagery has been studied as well. The aim of this research is to integrate infrared cameras in vehicles with small payload capacities like UAV and to spread infrared imagery in the industrial and consumer markets. This context has allowed me to explore three research fields :•Design of infrared cryogenic eyes in a co-design strategy between the optics and the detection block.•Study of a minimalist approach with diffractive optics to functionalize thin and lightweight optical plates. This was the opportunity to revisit the imagery properties of pinholes, high order Fresnel lenses and continuously self-imaging gratings. •Study of bio-inspired invertebrate eyes to design multichannel systems for miniaturizing cameras, for 3D imagery with plenoptic cameras and for multispectral imagery.En tant que chercheur en instrumentation à l’ONERA, j’ai développé une approche frugale dans la conception de systèmes optiques infrarouges en vue de leur simplification et de leur miniaturisation. L’intégration de fonctions d’imagerie avancées comme l’imagerie 3D et l’imagerie multispectrale a également été étudiée. Les objectifs sont l’intégration de caméras infrarouges dans des systèmes à faible capacité d’emport comme les drones et la diffusion de l’infrarouge dans le milieu industriel et civil. Ce contexte m’a permis d’aborder trois thèmes de recherche :•Le développement d’yeux infrarouges cryogéniques avec une démarche de conception conjointe entre le bloc de détection cryogénique et l’optique.•L’étude des optiques diffractives pour développer une approche de conception minimaliste fonctionnalisant des lames optiques en revisitant le sténopé, les lentilles de Fresnel à ordre de diffraction élevé et les composants continûment auto-imageants.•L’étude d’architectures multivoies s’inspirant de la vision des invertébrés pour développer des caméras miniaturisées, des caméras plénoptiques pour l’imagerie 3D et des caméras multispectrales

Nouvelles briques de conception de systèmes intégrés pour la vision infrarouge

Huge efforts are made in the research and industrial areas to design miniature and cheap optical systems. Indeed these new breakthroughs will contribute to spread these systems in new outlets. The aim of this thesis is to investigate new kinds of cooled infrared optical devices. I have shown that a first step in the miniaturization process can be done by integrating the optics inside the dewar, which is called dewar-level integration. However, cryogenic constraints require a more extensive miniaturization and simplification in order to be able to cool down the additional mass. At first, I have carried out a minimalist strategy, which aims to give an imagery property to the dewar without integrating a single optic. In this way, I have designed an infrared \textit{camera obscura} by replacing the cooled diaphragm with a pinhole. This approach has been improved by coding a circular grating on this diaphragm, so that the angular resolution is improved while keeping the huge focal depth of the pinhole. Despite their outstanding simplicity, both devices suffer from a low throughput. This can be improved by integrating a Wollaston meniscus lens inside the cold chamber (patent pending). I have thus shown that a single cooled lens can lead to a well corrected optical system. Finally, different ways to miniaturize this optical system have been investigated. They are based on multichannel architectures inspired by the apposition compound eye of invertebrates and by the vision of Xenos Peckii. This study will lead to a further step of integration called wafer-level integration since the optical system could be integrated directly on the focal plane array.L'intégration de systèmes optiques au plus près des détecteurs est un domaine en pleine expansion dans le monde scientifique et industriel. La diminution de l'encombrement et des coûts de ces systèmes contribuerait en effet à une meilleure diffusion de ces derniers dans des applications très diverses. L'objectif de la thèse est d'explorer de nouvelles briques de conception pour les systèmes infrarouges refroidis. J'ai montré qu'une première étape de miniaturisation peut être apportée en intégrant les systèmes optiques directement à l'intérieur du cryostat (intégration dewar-level). Les contraintes cryogéniques imposent cependant une simplification et une miniaturisation plus poussée de manière à réduire au maximum la charge supplémentaire à refroidir. Je me suis orienté, dans un premier temps, vers une approche minimaliste qui a consisté à rendre imageant le cryostat sans intégrer la moindre optique supplémentaire. J'ai ainsi réalisé une camera obscura infrarouge en donnant un effet sténopé au diaphragme froid. Ce concept a été amélioré en codant sur ce diaphragme un réseau circulaire qui associe la propriété de grande profondeur de champ du sténopé avec une bonne résolution angulaire. Les deux solutions proposées, bien que remarquables par leur simplicité, souffrent néanmoins d'un faible bilan radiométrique. Celui-ci peut être amélioré en intégrant une architecture de type ménisque de Wollaston, qui a fait l'objet d'une demande de brevet. J'ai alors montré qu'une seule optique refroidie permet d'atteindre simplement une très bonne qualité optique. Enfin, une réflexion a été menée pour miniaturiser cette architecture. Elle s'appuie sur des systèmes multivoies s'inspirant de l'œil à facettes apposées des invertébrés et de la vision du Xenos Peckii. Cette réflexion permettra de franchir une étape d'intégration supplémentaire en proposant d'aménager directement au niveau du détecteur (intégration wafer-level) des architectures optiques

Nouvelles briques de conception de systèmes intégrés pour la vision infrarouge. D'une approche minimaliste à la caméra sur puce.

Huge efforts are made in the research and industrial areas to design miniature and cheap optical systems. Indeed these new breakthroughs will contribute to spread these systems in new outlets. The aim of this thesis is to investigate new kinds of cooled infrared optical devices. I have shown that a first step in the miniaturization process can be done by integrating the optics inside the dewar, which is called dewar-level integration. However, cryogenic constraints require a more extensive miniaturization and simplification in order to be able to cool down the additional mass. At first, I have carried out a minimalist strategy, which aims to give an imagery property to the dewar without integrating a single optic. In this way, I have designed an infrared amera obscura by replacing the cooled diaphragm with a pinhole. This approach has been improved by coding a circular grating on this diaphragm, so that the angular resolution is improved while keeping the huge focal depth of the pinhole. Despite their outstanding simplicity, both devices suffer from a low throughput. This can be improved by integrating a Wollaston meniscus lens inside the cold chamber (patent pending). I have thus shown that a single cooled lens can lead to a well corrected optical system. Finally, different ways to miniaturize this optical system have been investigated. They are based on multichannel architectures inspired by the apposition compound eye of invertebrates and by the vision of Xenos Peckii. This study will lead to a further step of integration called wafer-level integration since the optical system could be integrated directly on the focal plane array

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

Sperm resistance to hypotonic stress: comparative analysis among three species of mammals

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