Surface Reconstruction Assessment in Photogrammetric Applications.

The image-based 3D reconstruction pipeline aims to generate complete digital representations of the recorded scene, often in the form of 3D surfaces. These surfaces or mesh models are required to be highly detailed as well as accurate enough, especially for metric applications. Surface generation can be considered as a problem integrated in the complete 3D reconstruction workflow and thus visibility information (pixel similarity and image orientation) is leveraged in the meshing procedure contributing to an optimal photo-consistent mesh.

Integrated fault detection and control design for continuous-time switched systems under asynchronous switching.

This paper focuses on the integrated fault detection and control design (IFDCD) problem for continuous-time switched systems under asynchronous switching. Main goal is to design an observer by using piecewise Lyapunov function, H∞ control technique and average dwell time approach. In addition, switched controllers are designed such that the closed-loop switched system is asymptotically stable.

Fast Visual Odometry for a Low-Cost Underwater Embedded Stereo System .

This paper provides details of hardware and software conception and realization of a stereo embedded system for underwater imaging. The system provides several functions that facilitate underwater surveys and run smoothly in real-time. A first post-image acquisition module provides direct visual feedback on the quality of the taken images which helps appropriate actions to be taken regarding movement speed and lighting conditions.

Post-keratoplasty astigmatism management by relaxing incisions: a systematic review.

Postoperative visual acuity can be limited by post-keratoplasty astigmatism, even with a clear corneal graft. Astigmatism management can be performed by selective suture removal, adjustment of sutures, optical correction, photorefractive procedures, wedge resection, intra-ocular lens implantation, intracorneal ring segments, relaxing incisions with or without compression sutures and repeated keratoplasty. Relaxing incisions can be made in the graft, graft-host interface or host cornea.

Direct imaging of molecular symmetry by coherent anti-stokes Raman scattering.

Nonlinear optical methods, such as coherent anti-Stokes Raman scattering and stimulated Raman scattering, are able to perform label-free imaging, with chemical bonds specificity. Here we demonstrate that the use of circularly polarized light allows to retrieve not only the chemical nature but also the symmetry of the probed sample, in a single measurement. Our symmetry-resolved scheme offers simple access to the local organization of vibrational bonds and as a result provides enhanced image contrast for anisotropic samples, as well as an improved chemical selectivity.

In vivo single human sweat gland activity monitoring using coherent anti-Stokes Raman scattering and two-photon excited autofluorescence microscopy.

Background: Eccrine sweat secretion is of central importance for control of body temperature. Although the incidence of sweat gland dysfunction might appear of minor importance, it can be a real concern for people with either hypohidrosis or hyperhidrosis. However, sweat gland function remains relatively poorly explored.

Simple approach for the fabrication of PEDOT-coated Si nanowires.

The synthesis of a conformal poly(3,4-ethylenedioxythiophene) (PEDOT) layer on Si nanowires was demonstrated using a pulsed electrodeposition technique. N-type Si nanowire (SiNWs) arrays were synthesized using an electroless metal-assisted chemical etching technique. The dependence of the SiNW reflection on the concentration of the AgNO3 solution was identified.

Quantitative 3D molecular cutaneous absorption in human skin using label free nonlinear microscopy.

Understanding the penetration mechanisms of drugs into human skin is a key issue in pharmaceutical and cosmetics research. To date, the techniques available for percutaneous penetration of compounds fail to provide a quantitative 3D map of molecular concentration distribution in complex tissues as the detected microscopy images are an intricate combination of concentration distribution and laser beam attenuation upon deep penetration. Here we introduce and validate a novel framework for imaging and reconstructing molecular concentration within the depth of artificial and human skin samples.

Background-free stimulated Raman spectroscopy and microscopy.

We propose a three-color, double-modulation scheme for the background-free detection of stimulated Raman scattering (SRS). We call the scheme stimulated Raman gain and opposite loss detection (SRGOLD). It exploits the symmetric nature of potential parasitic signals (cross phase modulation, two-photon absorption, and thermal effects) to the end of suppressing them.

Automatic segmentation and measurement of vasculature in retinal fundus images using probabilistic formulation.

The automatic analysis of retinal blood vessels plays an important role in the computer-aided diagnosis. In this paper, we introduce a probabilistic tracking-based method for automatic vessel segmentation in retinal images. We take into account vessel edge detection on the whole retinal image and handle different vessel structures.

Metamaterial filters at optical-infrared frequencies.

We propose two distinctive designs of metamaterials demonstrating filtering functions in the visible and near infrared region. Since the emissivity is related to the absorption of a material, these filters would then offer a high emissivity in the visible and near infrared, and a low one beyond those wavelengths. Usually, such a system find their applications in the thermo-photovoltaics field as it can find as well a particular interest in optoelectronics, especially for optical detection.

Flat-top and patterned-topped cone gratings for visible and mid-infrared antireflective properties.

Achieving a broadband antireflection property from material surfaces is one of the highest priorities for those who want to improve the efficiency of solar cells or the sensitivity of photo-detectors. To lower the reflectance of a surface, we are concerned with the study of the optical response of flat-top and patterned-topped cone shaped silicon gratings, based on previous work exploring pyramid gratings. Through rigorous numerical methods such as Finite Different Time Domain, we first designed several flat-top structures that theoretically demonstrate an antireflective character within the middle infrared region.

Toward endoscopes with no distal optics: video-rate scanning microscopy through a fiber bundle.

We report a step toward scanning endomicroscopy without distal optics. The focusing of the beam at the distal end of a fiber bundle is achieved by imposing a parabolic phase profile across the exit face with the aid of a spatial light modulator. We achieve video-rate images by galvanometric scanning of the phase tilt at the proximal end.

Adaptive Perfectly Matched Layer for Wood's anomalies in diffraction gratings.

We propose an Adaptive Perfectly Matched Layer (APML) to be used in diffraction grating modeling. With a properly tailored co-ordinate stretching depending both on the incident field and on grating parameters, the APML may efficiently absorb diffracted orders near grazing angles (the so-called Wood's anomalies). The new design is implemented in a finite element method (FEM) scheme and applied on a numerical example of a dielectric slit grating.

Comparative study of total absorption of light by two-dimensional channel and hole array gratings.

A detailed study of light absorption by silver gratings having two-dimensional periodicity is presented for structures constructed either of channels or of holes with subwavelength dimensions. Rigorous numerical modelling shows a systematic difference between the two structures: hole (cavity) gratings can strongly absorb light provided the cavity is sufficiently deep, when compared to the wavelength, whereas very thin channel gratings can induce total absorption. A detailed analysis is given in the limit when the period tends towards zero, and an explanation of the differences in behavior is presented using the properties of effective optical index of the metamaterial layer that substitutes the periodical structure in the limit when the period tend to zero.

Instantaneous spatially resolved acquisition of polarimetric and angular scattering properties in optical coatings.

A CCD angular resolved scattering setup is presented. This new high sensitivity instrument allows both spatial and angular resolved measurement of scattered field intensity and polarimetric features. Applications to the comprehensive characterization of optical coatings are given.

Plasmonic antiresonance through subwavelength hole arrays.

It has been shown both experimentally and numerically that the phenomenon of extraordinary transmission through subwavelength hole arrays is generally associated with a drop in transmission located very close to it. Paradoxically, this antiresonant drop occurs at the wavelength that, at first glance, should provoke a resonant excitation of a surface plasmon propagating along the metallic surface of the screen. The present paper gives a theoretical demonstration of this phenomenon, which dispels the paradox.

Human graft cornea and laser incisions imaging with micrometer scale resolution full-field optical coherence tomography.

Micrometer scale resolution full-field optical coherence tomography (FF-OCT) is developed for imaging human graft corneas. Three-dimensional (3-D) images with ultrahigh resolution (respectively, 1 and 1.5 μm in the axial and transverse directions), comparable to traditional histological sections, are obtained allowing the visualization of the cells and the precise structure of the different layers that compose the tissue.

Compact metallo-dielectric optical antenna for ultra directional and enhanced radiative emission.

We report the design of highly efficient optical antennas employing a judicious synthesis of metallic and dielectric materials. In the proposed scheme, a pair of metallic coupled nanoparticles permits large enhancements in both excitation strength and radiative decay rates, while a high refractive index dielectric microsphere is employed to efficiently collect light without spoiling the emitter quantum efficiency. Our simulations indicate potential fluorescence rate enhancements of 3 orders of magnitude over the entire optical frequency range.

Photonic methods to enhance fluorescence correlation spectroscopy and single molecule fluorescence detection.

Recent advances in nanophotonics open the way for promising applications towards efficient single molecule fluorescence analysis. In this review, we discuss how photonic methods bring innovative solutions for two essential questions: how to detect a single molecule in a highly concentrated solution, and how to enhance the faint optical signal emitted per molecule? The focus is set primarily on the widely used technique of fluorescence correlation spectroscopy (FCS), yet the discussion can be extended to other single molecule detection methods.

Statistical signatures of random media and their correlation to polarization properties.

A single procedure based on speckle statistics is proposed to identify the scattering origins of light (surface or bulk). Successful results are obtained with high-scattering samples, which offers complementary techniques for imaging or characterization in random media. The speckle statistics are shown to be correlated to partial polarization.

Channel coding and time-diversity for optical wireless links.

Atmospheric turbulence can cause a significant performance degradation in free space optical communication systems. An efficient solution could be to exploit the temporal diversity to improve the performance of the transmission link. Depending on the tolerable delay latency, we can benefit from some degree of time diversity that we can exploit by employing channel coding and interleaving.

Nanoaperture-enhanced signal-to-noise ratio in fluorescence correlation spectroscopy.

The fluorescence enhancement found in gold nanoapertures is demonstrated to increase the signal-to-noise ratio (SNR) in fluorescence correlation spectroscopy (FCS). Starting from a general discussion on noise in FCS experiments, we show that fluorescence enhancement leads to a dramatic increase in the SNR. This prediction is confirmed by experiments where we report an experimental gain in SNR of about 1 order of magnitude, corresponding to a 100-fold reduction of the experiment duration.

Irreversible effects of random unitary transformations on coherence properties of partially polarized electromagnetic fields.

We demonstrate monotonic, irreversible effects on the entropy, the degree of polarization, and different degrees of coherence when random, energy-preserving unitary transformations are applied to vectorial electromagnetic fields.