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Versailles, France

Cord A.,UniverSud | Aubert D.,University Paris Est Creteil
IEEE Intelligent Vehicles Symposium, Proceedings | Year: 2011

Advanced Driver Assistance Systems (ADAS) based on video camera tends to be generalized in today's automotive. However, if most of these systems perform nicely in good weather conditions, they perform very poorly under adverse weather particularly under rain. We present a novel approach that aims at detecting raindrops on a car windshield using only images from an in-vehicle camera. Based on the photometric properties of raindrops, the algorithm relies on image processing technics to highlight raindrops. Its results can be further used for image restoration and vision enhancement and hence it is a valuable tool for ADAS. © 2011 IEEE. Source

Hautiere N.,University Paris Est Creteil | Tarel J.-P.,University Paris Est Creteil | Halmaoui H.,UniverSud | Bremond R.,University Paris Est Creteil | Aubert D.,University Paris Est Creteil
Machine Vision and Applications | Year: 2014

Free-space detection is a primary task for car navigation. Unfortunately, classical approaches have difficulties in adverse weather conditions, in particular in daytime fog. In this paper, a solution is proposed thanks to a contrast restoration approach on images grabbed by an in-vehicle camera. The proposed method improves the state-of-the-art in several ways. First, the segmentation of the fog region of interest is better segmented thanks to the computation of the shortest routes maps. Second, the fog density as well as the position of the horizon line is jointly computed. Then, the method restores the contrast of the road by only assuming that the road is flat and, at the same time, detects the vertical objects. Finally, a segmentation of the connected component in front of the vehicle gives the free-space area. An experimental validation was carried out to foresee the effectiveness of the method. Different results are shown on sample images extracted from video sequences acquired from an in-vehicle camera. The proposed method is complementary to existing free-space area detection methods relying on color segmentation and stereovision. © 2011 Springer-Verlag. Source

Gallen R.,CETMEF | Gallen R.,UniverSud | Cord A.,UniverSud | Hautiere N.,University Paris Est Creteil | Aubert D.,University Paris Est Creteil
IEEE Intelligent Vehicles Symposium, Proceedings | Year: 2011

Compared to daytime, a larger proportion of accident happens during nighttime. The altered visibility of the road scene for the drivers may partially explain this situation. The latter becomes worse in fog presence. In this paper, two camera-based methods are proposed to detect the presence of night fog in images grabbed by in-vehicle multipurpose cameras. They rely on the visual effects of night fog. A first approach can assess the presence of fog around the vehicle thanks to the detection of the backscattered veil induced by the vehicle ego lights. It aims at detecting fog when the vehicle is alone in absence of exterior public lighting. A second approach can assess the presence of fog thanks to the detection of halos around light sources in the vehicle environment. It aims at detecting fog in presence of road traffic or public lighting. Both methods are presented and illustrated with actual images of fog. Their complementarity makes it possible to envision a complete night fog detection system. There are numerous applications for such a system: automation or adaptation of vehicle lights, contextual speed computation and reliability improvement for camera-based systems. © 2011 IEEE. Source

Bui D.T.,UniverSud | Journet B.,UniverSud
ICCE 2010 - 3rd International Conference on Communications and Electronics | Year: 2010

In this paper, we present a study concerning the stabilization of an electrooptic modulator (EOM) by controlling its optical bias point. A digital proportional-integral-derivative (PID) controller using an auto-tuning algorithm has been developed with a PSOC microcontroller in order to keep the bias point at an optimal value. The evolution of the modulator characteristics can be followed through its nonlinear behavior by detecting the second harmonic of a low-frequency modulating signal. By such a bias point control of the EOM it is possible to compensate completely the effects of the modulator drift for duration of at least two hours. ©2010 IEEE. Source

Bui D.T.,UniverSud | Vu V.Y.,Hanoi University of Science and Technology | Journet B.,UniverSud
International Conference on Advanced Technologies for Communications | Year: 2011

In an optoelectronic oscillator (OEO) system, it is crucial to keep the frequency as constant as possible. Electrooptic modulator (EOM) is a key component in this system having a big influence on OEO stabilization. The EOM is characterized by its voltage to optical output transfer function which unfortunately undergoes a drift during time leading to changes of the EOM characteristics and finally to a drift of the oscillation frequency. A twofold instrumentation system has been developed for controlling the EOM. Its first part is dedicated to the EOM temperature control. By using this part, the OEO frequency drift can be reduced by a factor 1.39 for one hour duration. The second part of the instrumentation system is used for compensating the drift of the EOM transfer function. With these two parts operating simultaneously, the frequency drift reduction can reach a factor up to 3.44 for one hour. These results demonstrate the efficiency of the compensation method. © 2011 IEEE. Source

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