HAL Portal IOGS (nstitut d'Optique Graduate School)
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Increasing the spatial bandwidth product in Light Field Microscopy with remote scanning
No full textAchieving fast, large-scale volumetric imaging with micrometer resolution has been a persistent challenge in the field of biological microscopy. To address this challenge, we report an augmented version of light field microscopy, incorporating a motorized tilting mirror upstream the camera. Depending on the scanning pattern, the field of view and/or the lateral resolution can be greatly improved. Our microscope technique is simple, versatile and configured for both bright-field and epifluorescence modes. We demonstrate its performances with imaging of multi-cellular aggregates of various shape and sizes
Relaxed Threshold Implementations
No full textInternational audienceIoT devices by nature are prone to side-channel attacks. Indeed, it is easy for an attacker to get physical access to such devices. Masking is one of the most widespread side-channel attack countermeasures. Among masking, hardware threshold implementations have the advantage of being resistant in the presence of glitches, while maintaining relatively low share refreshing costs. To this end, threshold implementations rely on three properties that should be satisfied: correctness, uniformity, and non-completeness. Recently, some research has relaxed these properties to present more efficient schemes (e.g. two shares threshold).In this paper, we study the security that can be achieved by relaxing these properties. We show that, in some cases, we need a local additional property to ensure provable security. This local property allows us to prove the security of a threshold implementation of Friet-P presented in the original paper. Next, thanks to this new property, we show that we can reduce by 25% the required randomness for the threshold implementation of Friet-P. Finally, we show how this property allows us to propose some implementations of 3-share 4-bit s-boxes that were not possible with classical threshold implementation rules. CCS CONCEPTS• Security and privacy → Side-channel analysis and countermeasures.</div
Unsupervised radiometric change detection from synthetic aperture radar images
No full textInternational audienceChange detection is an important data processing task in remote sensing, with applications such as deforestation monitoring or natural disaster assessment. Synthetic Aperture Radar (SAR) imaging offers key advantages for change detection, in particular due to its robustness to weather condition and cloud coverage. Because of the speckle phenomenon, the intensity of SAR images suffer from strong fluctuations, making the detection of radiometric changes challenging. Our method builds on a recently introduced self-supervised despeckling technique. It estimates despeckling uncertainty to better identify meaningful differences between two despeckled images. Conformal prediction permits to approach the change detection problem from the angle of anomaly detection. Thus, we develop a fully unsupervised change detection approach with a controlled probability of false alarm. Experimental results on TerraSAR-X satellite images with metric resolution show the capability of our method to detect changes without any supervision
Biosensing in the optical switch configuration on strong plasmonic gratings enabling differential referenced detection
No full textInternational audienc
Combinaison cohérente d'amplificateurs à semi-conducteurs : applications au lidar atmosphérique et à l'imagerie acousto-optique
No full textDiode lasers are compact, robust, and efficient which are in demand in the commercial market. However, the output power of individual diode devices are limited by the material damage threshold. Coherent beam combination, based on the constructive interference between coherent beams, is a power scaling technique that can improve the laser power while maintaining the beam quality of the individual combined emitters. This work targets the development of compact diode-laser-based setups based on coherent beam combination in QCW regime and the demonstration of their applications in atmospheric microlidar and acousto-optic imaging. The laser source is arranged in a master-oscillator power-amplifier configuration with a single-frequency distributed Bragg reflector laser at 828 nm injecting two commercial pulse-driven high-brightness tapered semiconductor optical amplifiers. The phase difference between the two beams is actively corrected to maintain long-term phase stabilization. Due to the delay of the project in collaboration with the Laboratoire des Sciences du Climat et de l'Environnement (LSCE), the demonstration of the laser source on lidar applications is conducted on an atmospheric microlidar designed by Cimel Electronique. A simplified version of the laser source based on the polarization beam combination of two tapered amplifiers (1 µs-10 kHz) is constructed to be compatible with the microlidar. The transmitted peak power reaches 6.1 W. The water vapor profile is successfully retrieved in good agreement with the radiosonde measurement. Another laser source based on coherent beam combination of two 100 µs-100 Hz tapered amplifiers with a maximal combined peak power of 8.9 W is applied to the Fourier Transform acousto-optic (FT-AOI) imaging setup in Institut Langevin. The first experimental acousto-optic images of two absorbing ink inclusions within a hydrogel are obtained with good signal-to-noise ratio.Les diode lasers sont compacts, robustes, efficaces et sont très demandés sur le marché commercial. Cependant, la puissance de sortie des dispositifs à diodes individuels est limitée par le seuil de dommage. La combinaison de faisceaux cohérents, basée sur l'interférence constructive, est une technique d'augmentation de la puissance tout en maintenant la qualité du faisceau des émetteurs combinés individuels. Ce travail vise le développement de configurations compactes basées sur la combinaison cohérente en régime Quasi-continu et la démonstration de leurs applications en microlidar atmosphérique et imagerie acousto-optique. La source laser est basée sur une diode laser monomode à 828 nm injectée dans deux amplificateurs optiques à semi-conducteurs évasées de haute luminance. La différence de phase entre les deux faisceaux est activement corrigée pour maintenir une stabilisation de phase à long terme. En raison du retard du projet de collabration avec le Laboratoire des Sciences du Climat et de l'Environnement (LSCE), la démonstration de la source laser sur les applications lidar est réalisée à partir d'un microlidar atmosphérique conçu par la société Cimel Electronique. Une version simplifiée de la source laser basée sur la combinaison par polarisation des faisceaux issus des deux amplificateurs évasés (1 µs-10 kHz) est construite pour être compatible avec le microlidar. La puissance crête maximale transmise atteint 6,1 W en sortie du microlidar. Le profil de vapeur d'eau enregistré est en bon accord avec la mesure par radiosonde. Une autre source laser basée sur la combinaison cohérente de faisceaux issus de deux amplificateurs évasés a permis de produire une puissance crête de 8,9 W pour une durée de 100 µs à la cadence de 100 Hz. Elle a été utilisée dans une expérience d'imagerie acousto-optique à transformée de Fourier (FT-AOI) réalisée à l'Institut Langevin. Les premières images expérimentales ont permis de détecter deux inclusions d'encre absorbantes dans un hydrogel avec un bon rapport signal/bruit
Ce/Gd-codoped sol-gel silica glasses: towards temperature-independent radiation dosimeters
No full textInternational audienc
Une borne PAC-Bayésienne sur une mesure de risque pour l'apprentissage équitable
No full textInternational audienceNous étudions la Conditional Value at Risk (CVaR) une mesure de risque définie comme une combinaison de risques de sous-groupes et qui se focalise uniquement sur les plus hauts risques. En apprentissage équitable, un sous-groupe est défini par l’ensemble des individus partageant la même valeur de l’attribut sensible étudié. La CVaR a donc l’intérêt de se concentrer sur les valeurs de l’attribut sensible amenant a` un risque élevé. Dans ce travail, nous dérivons une borne en généralisation PAC-Bayésienne pour la CVaR qui fait non seulement intervenir une distribution sur l’ensemble d’hypothèses (classique en PAC-Bayes), mais également une distribution sur l’ensemble des valeurs de l’attribut sensible permettant de contrôler l’importance de chaque sous-groupe intervenant dans la CVaR
Toward Microwave Electromagnetic Jets for Detection, Imaging and Local Characterization Applications
No full textInternational audienceWe present an overview of our latest investigation regarding microwave electromagnetic jet (EMJ) dedicated to detection, imaging and characterization applications. First EMJ proposed is a parallel plate waveguide loaded with Teflon and terminated with both single and dual elliptically shaped tips. The experimental result shows the generation, respectively, of a single or a double EMJ as numerically expected. To simplify the manufacture of the tips, a rectangular tip replaced the elliptical termination. The numerical results demonstrated an increase in intensity and low FWHM of the beam, especially when using a multi-rectangular section of the tip. Furthermore, a rectangular waveguide with a rectangular tip was also introduced as an alternative to produce the EMJ in two transverse directions. Finally, to obtain a rotationally symmetrical jet, a horn antenna loaded with Teflon and ended with a cylindrical Teflon shape was proposed. In term of application, the developed microwave electromagnetic jet demonstrates the capability to detect extremely small objects not detectable by conventional microwave systems. In addition, at the focal point, the jet exhibits an almost planar wavefront, indicating the possibility of using the jet for local characterization applications in mesoscale free space measurements
Expanding the palette of SWIR emitting nanoparticles based on Au nanoclusters for single-particle tracking microscopy
No full textInternational audienceSingle-molecule localization microscopy has proved very promising to unravel the dynamics and molecular architecture of thin biological samples down to the nanoscale. However, achieving meaningful results in complex, thick biological tissues requires shifting the observation wavelengths to the shortwave-infrared (SWIR) region, where biological tissues are most transparent. In consequence, nanomaterials with optical activity in the SWIR exhibiting brightness and photostability suitable for detection at the single-molecule level are needed. Currently mainly single-walled carbon nanotubes (SWCNTs) satisfy this, but are inherently 1D objects. Here we present 0D ultra-small gold nanoclusters (AuNCs, <3nm) and ~25 nm AuNC-loaded-polymeric particles that can be detected at the single-particle level in the SWIR. Thanks to their high brightness and excellent photostability, we show that the dynamics of the spherical polymeric particles can be followed at the single-particle level in solution at video rates for minutes. Analysis of the mean square displacement confirms the diameter of the particles in aqueous media, and enables us to compare their brightness with that of biocompatible SWCNTs. This extends the library of SWIR emitting nanomaterials to 0D nano-objects of variable size for single-molecule localization microscopy in the second biological window, opening unprecedented possibilities for mapping structure and dynamics of complex biological systems