Complementary Speckle Patterns : deterministic interchange of intrinsic vortices and maxima through Scattering Media

Intensity minima and maxima of speckle patterns obtained behind a diffuser are experimentally interchanged by applying a spiral phase delay of charge $\pm 1$ to the impinging coherent beam. This transform arises from the intuitive expectation that a tightly focused beam is so-changed into a vortex beam and vice-versa. The statistics of extrema locations and the intensity distribution of the so-generated "complementary" patterns are characterized by numerical simulations. It is demonstrated experimentally that the incoherent superposition of the three "complementary speckle patterns" yield a synthetic speckle grain size enlarged by a factor $\sqrt{3}$. A cyclic permutation of optical vortices and maxima is unexpectedly observed and discussed.Comment: 9 pages, 9 figure

Topological transformations of speckles

Deterministic control of coherent random light is highly important for information transmission through complex media. However, only a few simple speckle transformations can be achieved through diffusers without prior characterization. As recently shown, spiral wavefront modulation of the impinging beam allows permuting intensity maxima and intrinsic $\pm 1$-charged optical vortices. Here, we study this cyclic-group algebra when combining spiral phase transforms of charge $n$, with $D_3$- and $D_4$-point-group symmetry star-like amplitude modulations. This combination allows statistical strengthening of permutations and controlling the period to be 3 and 4, respectively. Phase saddle-points are shown to complete the cycle. These results offer new tools to manipulate critical points in speckles.Comment: 14 pages, 10 figures, 4 table

Reference-less complex wavefields characterization with a high-resolution wavefront sensor

Wavefront sensing is a widely-used non-interferometric, single-shot, and quantitative technique providing the spatial-phase of a beam. The phase is obtained by integrating the measured wavefront gradient. Complex and random wavefields intrinsically contain a high density of singular phase structures (optical vortices) associated with non-conservative gradients making this integration step especially delicate. Here, using a high-resolution wavefront sensor, we demonstrate experimentally a systematic approach for achieving the complete and quantitative reconstruction of complex wavefronts. Based on the Stokes' theorem, we propose an image segmentation algorithm to provide an accurate determination of the charge and location of optical vortices. This technique is expected to benefit to several fields requiring complex media characterization.Comment: 7 page

Understanding and Integrating Resolution, Accuracy and Sampling Rates of Temperature Data Loggers Used in Biological and Ecological Studies

International audienceDuring the 5 th Workshop about Temperature-Dependent Sex Determination held in the 38 th International Sea Turtles Symposium (16-22 February 2018) in Kobe, Japan, we discussed the uncertainty of temperatures recorded by data logger and their calibration. We report here an extension of this discussion. First, we propose a way to estimate the uncertainty of the average temperature recorded using data loggers considering the accuracy of the data logger (repeatability of measurements), resolution of the data logger (resolution of its indicating device) and period of sampling temperature. Second, a general procedure of calibration is described. Functions to perform the estimates are provided in R package embryo growth freely available

Analyzing the evolution of deterioration patterns: A first step of an image-based approach for comparing multitemporal data sets

International audienceWhen documenting and analyzing cultural heritage, the monument states can be described by multitemporal data sets, which however present a complication for the elaboration and examination process. This difficulty leads to the necessity to improve the analyze process in order to expand the documentation process and help experts to enrich and share information about the historical buildings. Therefore an approach of change measurement, which supports the chronical comprehension of a building by visualizing and quantifying the dimensional temporal effects was elaborated, where the analyze process of a multitemporal data set was based on the interpretation of depth map images. These maps were obtained by generating ortho images of an object that was created on purpose by setting up an experimentation to acquire a multitemporal data set. This approach is the first step of a wider ongoing research about change detection processes on multitemporal data sets. Index Terms-Change measurements, multitemporal data set, depth map, ortho image, evolution of deterioration patterns

Matière altérée, couleurs modifiées : apports des techniques analytiques et d’imagerie pour la compréhension des décors originaux sur les plafonds peints médiévaux, l’exemple de la maison du viguier à Puisserguier

Le plafond à la française de l’ancienne maison du viguier à Puisserguier (Hérault) montre d’intéressants restes de polychromies datant du tout début du XVIe siècle. L’état de dégradation avancé de la matière picturale est cependant à l’origine de certaines modifications chromatiques qui ont pu être mises en évidence par le biais d’analyses physico-chimiques et de l’imagerie scientifique. Nous verrons comment ces outils technologiques ont permis la compréhension des processus d’altération de la matière mais aussi comment ils ont joué un rôle fondamental dans la connaissance du décor original et des modifications qu’il a subi depuis sa création jusqu’à nos jours.The French-style ceiling of the former house of the medieval judge in Puisserguier (Hérault) has interesting remains of paintings from the early 16th century. However, advanced ageing of the pictorials is causing chromatic changes which were highlighted by means of physicochemical analysis and technical imaging. We will see how these techniques have constituted a very useful tool for the understanding of material degradation processes and helped to figure out how the original decoration was without the climate modifications it has been subjected to since its creation

Dispersion en milieux poreux insaturés (modélisations et mesures RMN de distributions de vitesse)

La dispersion dans des milieux poreux homogènes (empilements de grains) a été étudiée par des mesures par résonance magnétique nucléaire (RMN) et des simulations de marches aléatoires dans un réseau de pores. La RMN permet de mesurer l ensemble des déplacements des molécules d eau durant un temps t , et d obtenir propagateurs et moments caractéristiques. L évolution temporelle du second moment ( 2 ta ) permet de caractériser de manière précise le régime de dispersion des molécules (Gaussien ou anormal). Des mesures pour des écoulements de 15 < Pe < 45 dans un empilement de grains de 30 m ont permis d observer une dispersion anormale faiblement super-dispersive (a = 1.17) en écoulement saturé et une augmentation progressive du caractère super-dispersif avec la diminution de la saturation en eau (jusqu à a = 1.5 pour 42 %)lors d une co-injection stationnaire eau-huile. En écoulement saturé, les propagateurs et courbes de percée sont quasi-gaussiennes, tandis qu en écoulement insaturé, les propagateurs sont asymétriques et les courbes de percée présentent des trainées aux grands temps. Dans ces conditions, on montre que la dispersion anormale observée est mieux décrite par des lois stables de Lévy que par des lois gaussiennes. Des simulations de marche aléatoire ont été réalisées dans un réseau de pores extrait d un milieu poreux réel par imagerie microscanner.Elles permettent d obtenir les mêmes informations que la RMN, les marcheurs se déplaçant par advection et diffusion. Ces simulations montrent l existence d une stagnation non observée dans les expériences, montrant que la simplification du réseau poreux est trop importante et empêche de reproduire certains aspects du champ de vitesses détecté par la RMN. Toutefois, l évolution temporelle du second moment a également un caractère super-dispersif à temps long à 100 % de saturationWe investigated dispersion in homogeneous porous media (grain packs) by nuclear magnetic resonance (NMR) measurements and random walk simulations in pore networks. We measured water molecules displacements during a time interval t by NMR measurements, which allows us to obtain propagators and charateristic cumulants of displacements such as the mean square displacement . The evolution of the cumulant as a function of time t ( 2 ta ) is a very sensitive test of Gaussian behaviour compared to the analysis of the shape of propagators. In a homogeneous 30 m grain pack and low Peclet numbers (15 < Pe < 45), we observed weak super dispersion in saturated conditions (a = 1.17) and gradually stronger super-dispersionas the water saturation decreases (up to a = 1.5 for 42 %) during steady-state oil-water two phase flow. Insaturated conditions, propagators and breakthrough curves are Gaussian or nearly Gaussian, whereas in two phase conditions, propagators are non symmetric and breakthrough curves show thick tails at long time. Weshow that the anomalous dispersion observed is better explained by Lévy stable laws (asymetric for longitudina ldispersion, and symetric for transverse dispersion) than by Gaussian laws. Random walk simulations were performed in a pore network constructed using high resolution images of the grain pack. They allow us to obtain the same informations than the NMR, with walkers submitted to diffusive and advective effects. The simulations show the existence of an anomalous stagnation not observed in experiments, highlighting the oversimplification of the pore network that prevent reproducing some aspects of the velocity field detected by NMR. However, the simulations indicate similarly a super-dispersion at long time in saturated conditionsAVIGNON-Bib. numérique (840079901) / SudocSudocFranceF

Imagerie numérique et conservation-restauration : état de l’art et perspectives

L’imagerie scientifique est un outil incontournable des sciences de la conservation-restauration. La modification du support de la photographie, devenu numérique, le développement du rendu tridimensionnel qualitatif et quantitatif de l’image ont transformé la photographie technique en un outil d’investigation non destructif à part entière, indispensable et complémentaire des approches physiques et physico-chimiques classiques et en un outil-support de documentation. L’ensemble des développements et travaux menés en imagerie scientifique et sur l’intégration dans des plateformes collaboratives d’annotation sémantique 3D permet, outre une production plus facile de documents, de mettre en synergie les résultats provenant de différentes techniques d’analyse. Elle va modifier, dans un futur proche, l’approche sur le terrain des acteurs de la conservation et conduire à une meilleure synergie interprofessionnelle. Ils auront ainsi la possibilité de mieux mettre en cohérence leurs observations, leurs conclusions quant aux analyses faites à différentes échelles, dans une dynamique temporelle qui intègre les données de la restauration, de son histoire passée. À terme, et par l’intégration des données environnementales, ces plateformes seront un outil de suivi de l’évolution de l’état matériel du bien culturel et aussi de transmission des connaissances vers un public large.Technical imaging has always been an essential tool in conservation science. Thanks to today’s digital photography and its quantitative and qualitative tridimensional aspects, this imaging has become an autonomous and vital nondestructive instrument that complements classic physical and chemical analyses. It is also an essential tool for documentation purposes. Results coming from different techniques of analysis can now be synthesized by means of new developments in technical imaging and their insertion into collaborative 3D semantic annotation platforms. Technical imaging can modify the infield approach of conservation professionals and will help lead to better interprofessional dialogue in the future. Conservation professionals will have the assurance of better consistency in their observations, which can cover different time frames for restoration projects and historical data and conclusions drawn from analyses made at different scales. In the long term and after integration of environmental data, these platforms will become monitoring tools dedicated to following the state of conservation of cultural heritage objects and a tool for transmitting knowledge about these objects to a wider audience