Table of contents

The time-domain degree of polarization of a stationary, random optical beam differs in general from its spectral degree of polarization. We elucidate the origin of the differences and consider examples in which the two degrees of polarization either are, or are not, the same.

The large dispersive properties of wave mixing in liquid crystal light-valves allow obtaining fast and slow light with tunable group velocities. A slow light interferometer is shown by using this interaction.

The field of photonics finds applications in information technology, health care, lighting, and sensing. This paper explores the role of nanotechnology with focus on nanophotonics in dielectric and inhomogeneous metamaterials.

The method of photon-counting integral imaging (PCII) has been introduced recently for three-dimensional object sensing, visualization, recognition and classification of scenes under photon-starved conditions. This paper presents an information-theoretic model for the PCII method, thereby providing a rigorous foundation for our understanding of its demonstrated success in compressive imaging and classification.

We adapt concepts from matched filtering to propose a method for generating reconfigurable multiple beams. Combined with the Generalized Phase Contrast (GPC) technique, the proposed method coined mGPC can yield dynamically reconfigurable optical beam arrays with high light efficiency for optical manipulation, high-speed sorting and other parallel spatial light applications [1].

The field of Quantum Imaging exploits the quantum nature of light and the intrinsic parallelism of optical signals to devise novel techniques for optical imaging and for parallel information processing at the quantum level (see [1] and references quoted therein). In this presentation, we will shortly discuss two topics in this area: the first is the so-called ghost imaging which, however, is not necessarily quantum; the second is the detection of faint amplitude objects with a sensitivity beyond the standard quantum limit, and in this case we are fully in the quantum domain. Both topics are related to the phenomenon of optical parametric down-conversion (PDC), in which a fraction of the pump photons of a laser beam, injected into a crystal with a quadratic non-linearity, are down-converted to a pair of signal and idler photons, with conservation of total energy and total momentum. A feature of paramount importance is that the signal and idler beams are spatially correlated both in the near field (position correlation) and in the far field (momentum correlation).The simultaneous presence of position and momentum correlation implies quantum entanglement, as it has been also observed experimentally [2].

In this paper we present a new approach allowing the surpassing of the diffraction based limitation for the achievable resolution provided by imaging systems. It is based on an encoding-decoding process of various spatial pixels or regions in the field of view of the imaged object by orthogonal and differently time varying polarization states. The reconstruction of the original spatial information is obtained by applying a decoding process in a way similar to the encoding one. Although all the spatial information is summed and mixed together by the system, the decoding provides super resolved imaging since in every spatial position the undesired spatial information having time varying polarization dependence, that is uncorrelated to the decoding sequence applied on that specific spatial position, is averaged to zero and, on the other hand, the information which corresponds to that specific spatial region is being reinforced. The proposed approach can be used not only for super resolved imaging but also for imaging module that maintains the same spatial resolution while providing enlarged field of view

We address two different methods to enhance the depth of focus (DOF) according to the application, using amplitude and/or phase masks. The first application consists in increasing the length of the focal line of a lens while preserving its transverse resolution. We propose a mask inspired from holographic principles. We then address DOF enhancement with an hybrid imaging system composed of a pupil mask followed by a digital deconvolution step. We use an optimization criterion based on the final image quality to determine the optimal parameters of phase masks.

The basic principles of laser refractography (LR), a new method for diagnostics of optically inhomogeneous media and flows, are described. This technology is based on the refraction of the structured laser radiation (SLR) in transparent inhomogeneity, digital registration and computer processing of the refraction pattern. The experimental setup allowed quantitative visualization of the inhomogeneous transparent media by using 2D or 3D-refractograms. The 3D-refractograms are used for diagnostics of the boundary layer near the hot or cold bodies in water are present.

We propose a very simple method for the flexible production of 1D structured illumination for high resolution 3D microscopy. Specifically, we propose the insertion of a Fresnel biprism after a monochromatic point source for producing a pair of twin, fully coherent, virtual point sources. The resulting interference fringes are projected into the 3D sample and, by simply varying the distance between the biprism and the point source, one can tune the period of the fringes, while keeping their contrast, in a very versatile and efficient way.

Two types of newly developed nonlinear optical microscopes namely stimulated parametric emission (SPE) microscope and stimulated Raman scattering (SRS) microscope were presented together with their biological applications.

This paper reviews opportunities of optical signal form conversion as typified by time-space conversion in optical signal processing. Several examples of typical ultra-fast optical signal processing using optical signal form conversion are described and their applications are introduced in respect to photonic networks, ultra-fast measurement, and so on.

Far-infrared ultrashort-pulse in the wavelength range of 10 −30 μm is generated using an organic nonlinear crystal DAST. The frequency down conversion is performed by the difference frequency generation between the signal and idler waves from an optical parametric amplifier pumped by the 120 fs Ti: sapphire laser pulses. The pulse width is measured using the cross-correlation with the pump. In the present paper, the shortest pulse width of 210 fs was obtained with the spectrum range of 10 – 30 THz.

Active polarimetric imaging systems yield information about the intensity contrast and the Orthogonal State Contrast (OSC) in the scene. However, in real systems, the illumination is often spatially or temporally non uniform which creates artificial intensity contrasts that can lead to false alarms. We derive the Generalized Likelihood Ratio Test (GLRT) detectors when intensity information is taken into account or not. These results are used to determine in which cases considering intensity information in addition to polarimetric information is relevant or not.

Recently, optical sensors for detection of carbon dioxide (CO₂) have been explored for variety of applications in chemistry, industry, and medicine. This paper deals with the development of a planar optical remission sensor employing a dye immobilized in a polymer layer designed for gaseous CO₂ detection. The principle of CO₂ detection was based on colour changes of Tetraethylammonium Cresol red immobilized in a special composed polymer layer that was irradiated by LED diodes. Absorption properties of the dye were changed due to its chemical reaction with CO₂ and corresponding colour changes were detected by PIN diodes. These changes were analyzed by using a PC-controlled board connected by USB. The sensitivity, response time, and the detection limit of the remission sensor were characterized.

This paper deals with preparation of optical probes based on tapered optical fibres and their using for local detection of pH in samples simulating native conditions of plant cells. Optical probes, so-called V-tapers were prepared for this purpose. Fluorescence pH transducer 2',7'-Bis(2-carbonylethyl)-5(6)-carboxyfluorescein was immobilized onto the end-face of cut V-tapers in a thin xerogel layer. Changes of fluorescence-intensity spectra caused by pH changes were employed for pH measurements. Indium-tin oxide or aluminium coated fibre probes with suitable optical and mechanical properties were successfully tested. It has been confirmed that the selected pH transducer is suitable for pH detection from 5.0 to 7.0. This approach has allowed us to determine extra-cellular pH of in-vitro samples.

Off-the-shelf twisted nematic liquid crystal displays (TNLCDs) show some interesting features such as high spatial resolution, easy handling, wide availability, and low cost. We describe a compact adaptive optical system using just one TNLCD to measure and compensate optical aberrations. The current system operates at a frame rate of the order of 10 Hz with a four level codification scheme. Wavefront estimation is performed through conventional Hartmann-Shack sensing architecture. The system has proved to work properly with a maximum rms aberration of 0.76 microns and wavefront gradient of 50 rad/mm at a wavelength of 514 nm. These values correspond to typical aberrations found in human eyes. The key of our approach is careful characterization and optimization of the TNLCD for phase-only modulation. For this purpose, we exploit the so-called retarder-rotator approach for twisted nematic liquid crystal cells. The optimization process has been successfully applied to SLMs working either in transmissive or in reflective mode, even when light depolarization effects are observed.

In a previous work we presented a compressed imaging approach that uses a row of rotating sensors to capture indirectly polar strips of the Fourier transform of the image. Here we present further developments of this technique and present new results. The advantages of our technique, compared to other optically compressed imaging techniques, is that its optical implementation is relatively easy, it does not require complicate calibrations and that it can be implemented in near-real time.

We study the impact of the level of the speckle noise on data acquisition in a partially polarized coherent imaging system with the presence of a nonlinearity in the imaging sensor characteristic. In perfectly linear acquisition conditions, due to the essentially multiplicative action of the speckle, the image contrast is unchanged as the speckle noise level increases, and so it has no impact on the quality of the acquired images. On the contrary, in nonlinear conditions the acquisition is affected by the speckle noise level. However, this effect of the speckle is not always detrimental. We show that, in definite nonlinear conditions, there is usually an optimal level of the speckle noise that leads to a maximum quality of the acquired images. We theoretically analyze such nonlinear regimes with partially polarized speckled images. We specifically exhibit the existence of an optimal speckle noise level in the interesting case of images realized only by a depolarization contrast. Illustrations are given with a simple 1-bit hard limiter and binary images. Then, we propose and discuss as perspectives an experimental optical setup to confront theory and experiment.

Beam shaping is a technique, by which a known input irradiance is transformed into a desired output irradiance by changing the local propagation vector of the wave front. Unlike one-dimensional beam-shaping, which leads to a simple differential equation which can be integrated in a straight forward manner, the two-dimensional beam shaping problem leads to a Monge-Ampere type equation, which is difficult to solve. In this paper, we generalize the problem to refractive and reflective systems and use to shifted-base-function approach to obtain a general solution.

When using a single emitter and a single receiver, the Synthetic Aperture Radar (SAR) data gives information in the Fourier domain of the scene over a line segment whose width is related to the bandwidth of the emitted signal. The mathematical problem of image reconstruction in SAR then becomes a Fourier Synthesis (FS) inverse problem. When there are more than one emitter or receiver looking at the same scene, the problem becomes fusion and inversion. In this paper we report a Bayesian joint data fusion and inversion method to obtain a super resolution image. The proposed method shows a good performance on real data obtained at ONERA in France.

A method for recording on-axis single-shot digital holograms based on the self-imaging phenomenon is reported. A simple binary two-dimensional periodic amplitude is used to codify the reference beam in a Mach-Zehnder interferometer, generating a periodic three-step phase distribution with uniform irradiance over the sensor plane by fractional Talbot effect. An image sensor records only one shot of the interference between the light field scattered by the object and the codified parallel reference beam. Images of the object are digitally reconstructed from the digital hologram through the numerical evaluation of the Fresnel diffraction integral. This scheme provides an efficient way to perform dynamic phase-shifting interferometric techniques to determine the amplitude and phase of the object light field. Unlike other parallel phase-shifting techniques, neither complex pixelated polarization devices nor special phase diffractive elements are required. Experimental results confirm the feasibility and flexibility of our method.

Digital Holographic Microscopy (DHM), is a new imaging technique allowing to provide quantitative phase images with a high accuracy and stability making possible to explore a large variety of relevant processes, occurring on the μs to day time scale, in the fields including material research as well as cell biology. As a non invasive and real time imaging technique, DHM is particularly well suited for high throughput screening

Digital in-line holography is a 3D imaging technique which has been widely developed during the last two decades. This technique achieves the 3D reconstruction of volume objects from a 2D image-hologram. It is a metrological tool and therefore the improvement of resolution is one of the current challenges. However the resolution depends on several experimental parameters and the experimenters have to choose the parameters which will lead to the best resolution. This paper presents the study of resolution in in-line digital holography from the asymptotical bounds of the covariance of estimators used in hologram reconstruction.

We have studied several speckle reduction techniques, applicable to digital holography. These include the use of optical diffusers, wavelet filtering, simulating temporal incoherence and filtering in the Fourier domain. The Digital Holograms (DHs) used in this study are captured using a Phase Shift Interferometric (PSI) in-line setup and subsequently reconstructed numerically.

Digital Holography is an imaging modality made up of two parts: (i) Recording an interference pattern on a CCD, where an object wave field and a known reference wave are coincident and extracting the complex object wave field from this interference pattern and (ii) Replaying or reconstructing the hologram on a computer by simulating the propagation of the object wave field back to the object plane. Thus an image is obtained. We show how to adapt the reconstruction algorithm in a simple way to allow it to generate any output range and in any location making it far more versatile for zooming in on specific regions of our reconstructed image.

We present a new method to manage the depth of focus in holograms numerical reconstructions through an adaptive deformation of the digital holograms. We demonstrate that this technique can be applied both to Fourier and Fresnel holograms. The experimental results, in agreement with the theoretical model, are shown and commented for both these configurations.

The method to improve of a viewing-zone angle and an image quality of a digital hologram is presented. A number of digital holograms of a central object are recorded from the position on the circumference. The holograms are used for a hologram synthesis to improve the image quality from whole viewing-zone angle. The synthesis is achieved by a correlation between a hologram and numerically propagated holograms. The large-sized synthesized digital hologram has a wide viewing-zone angle and less speckles. Some experimental results are shown to confirm the proposed method.

In digital holography a 3D scene is captured optically and often the perspectives are reconstructed numerically. In this study we digitally process the holograms to allow them to be displayed on autostereoscopic displays. This study is conducted by subjective visual perception experiments comparing single reconstructed images from left and right perspective to the resulting stereo image.

Pansharpening is a technique that fuses the information of a low resolution multispectral image (MS) and a high resolution panchromatic image (PAN), usually remote sensing images, to provide a high resolution multispectral image. In the literature, this task has been addressed from different points of view being one of the most popular the wavelets based algorithms. Recently, the contourlet transform has been proposed. This transform combines the advantages of the wavelets transform with a more efficient directional information representation. In this paper we propose a new pansharpening method based on contourlets, compare with its wavelet counterpart and assess its performance numerically and visually.

This paper is a short introduction to the modeling of complex microstructures by models of random sets, and to their use for predicting the effective properties of materials by means of numerical simulations.

n×n symmetrical positive definite matrices are present in many applications. In the n = 2 case, these matrices constitute a 3D-space, denoted by S⁺₂. The determinant of AS⁺₂ a natural quadratic form, giving S₂⁺ a Minkowski space structure. This paper shows how this theory quite naturally provides a graphical interpretation to formulas that have been defined elsewhere. An original application to discrete curves is given.

Often, the problem of automatic target recognition can be reduced down to two separate but related problems, feature extraction and classifier design. The best classifier only works as well as the input data provided to the system. In this presentation, we will outline a new approach to classification known as geometric diffusion as proposed by Coifman et al, and demonstrate the power of this new metric for classification of imagery.

Designed to maximize information transmission in the presence of noise, independent component analysis (ICA) could appear in certain circumstances as a statistics-based tool for robust visual hashing. Several ICA-based scenarios can attempt to reach this goal. A first one is here considered.

This work aims to embed an object authentication process in a secure electronic architecture for distant verification via imaging. Firstly, the extraction of print signatures [1] is revisited for an implementation in a logical hardware system. Secondly, a protocol scheme to authenticate the verification device and to ensure its integrity is suggested.

Strong and powerful attacks are able to make the watermark extraction impossible even if there is some watermarking. In this work, we call this residual information the scar and we use it to prove the existence of an attacked watermark. We evaluate the Scar by the mutual information between the embedded watermark and the attacked copies. It is well known that the mutual information between two random variables gives an evaluation of the shared information between the two variables. Thus, the attack can compromise the correct decoding by removing partialy the watermarking information. However, it is possible to make the watermarking existence proof possible when the mutual information between the embedded message and the attacked copies is above a certain threshold. We propose a practical way to use the scar by measuring the correlation between the attacked watermark and the original one.

We have developed a new type of television named FTV (Free-viewpoint TV). FTV is an innovative visual media that enables us to view a 3D scene by freely changing our viewpoints. FTV is based on the ray-space method that represents one ray in real space with one point in the ray-space. We have also developed new type of ray capture and display technologies such as a 360-degree mirror-scan ray capturing system and a 360 degree ray-reproducing display. The international standardization of FTV has been conducted in MPEG.