Joint contrast optimization and object segmentation in active polarimetric images

International audienceWe present a method for automatic target detection based on the iterative interplay between an active polarimetric imager with adaptive capabilities and a snake-based image segmentation algorithm. It successfully addresses the difficult situations where the target and the background differ only by their polarimetric properties. This method illustrates the benefits of integrating digital processing algorithms at the heart of the image acquisition process rather than using them only for postprocessing

Target detection in active polarization images perturbed with additive noise and illumination nonuniformity.

International audienceActive imaging systems that illuminate a scene with polarized light and acquire two images in two orthogonal polarizations yield information about the intensity contrast and the orthogonal state contrast (OSC) in the scene. Both contrasts are relevant for target detection. However, in real systems, the illumination is often spatially or temporally nonuniform. This creates artificial intensity contrasts that can lead to false alarms. We derive generalized likelihood ratio test (GLRT) detectors, for which intensity information is taken into account or not and determine the relevant expressions of the contrast in these two situations. These results are used to determine in which cases considering intensity information in addition to polarimetric information is relevant or not

Design and experimental validation of a snapshot polarization contrast imager

International audienceWe present a degree of polarization imaging system based on a Wollaston prism and a single CCD camera. This architecture eliminates technical inaccuracies and noise sources that are present in experimental setups containing a polarization switching element. After the acquisition of two images corresponding to two orthogonal states of polarization, one can compute the orthogonal state contrast image (OSCI), which is an estimate of the local degree of polarization of the backscattered light when the observed materials are purely depolarizing. The instrument design coupled to an efficient calibration enables the estimation of the OSCI from a single image acquisition and significant reduction of technical noise present in other polarization imaging systems. The setup was tested in realistic conditions where it represents a real asset

Detection in polarimetric images in the presence of additive noise and non-uniform illumination

International audienceActive 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 no

Comparative study of the best achievable contrast in scalar, Stokes and Mueller images

International audienceWe compare the relative performance of different active polarimetric imaging architectures for target detection applications. We show that if the noise that affects the measurements is additive and if the only relevant parameter is the contrast between an object of interest and a background with different Mueller matrices, the most efficient imaging architecture consists in acquiring a single intensity image while optimizing the illumination and analysis states of polarization

Dynamic saturation in semiconductor optical amplifiers: accurate model, role of carrier density, and slow light

We developed an improved model in order to predict the RF behavior and the slow light properties of the SOA valid for any experimental conditions. It takes into account the dynamic saturation of the SOA, which can be fully characterized by a simple measurement, and only relies on material fitting parameters, independent of the optical intensity and the injected current. The present model is validated by showing a good agreement with experiments for small and large modulation indices.Comment: 9 pages, 5 figure

Photonic integrated circuit based FMCW coherent LiDAR

We present the demonstration of an integrated Frequency Modulated Continuous Wave LiDAR on a silicon platform. The waveform calibration, the scanning system and the balanced detectors are implemented on chip. Detection and ranging of a moving hard target at up to 60 m with less than 5 mW of output power is demonstrated here

Near-infrared active polarimetric and multispectral laboratory demonstrator for target detection

International audienceWe report on the design and exploitation of a real-field laboratory demonstrator combining active polarimetric and multispectral functions. Its building blocks, including a multiwavelength pulsed optical parametric oscillator at the emission side and a hyperspectral imager with polarimetric capability at the reception side, are described. The results obtained with this demonstrator are illustrated on some examples and discussed. In particular it is found that good detection performances rely on joint use of intensity and polarimetric images, with these images exhibiting complementary signatures in most cases

Dual frequency emission in a compact semiconductor laser for coherent population trapping cesium atomic clocks

We present the dual-frequency emission of a diode-pumped vertical external-cavity semiconductor laser at 852 nm dedicated to coherent population trapping experiments. With a compact cavity more than 10mW is demonstrated in each polarization, with a frequency difference in the GHz range. One polarization has been stabilized on an atomic transitio