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See detailMulti-Chromatic Analysis of SAR Images for Coherent Target Detection
Bovenga, Fabio; Barbier, Christian ULg; De Rauw, Dominique ULg et al

in Remote Sensing (2014), 6

This work investigates the possibility of performing target analysis through the Multi-Chromatic Analysis (MCA), a technique that basically explores the information content of sub-band images obtained by ... [more ▼]

This work investigates the possibility of performing target analysis through the Multi-Chromatic Analysis (MCA), a technique that basically explores the information content of sub-band images obtained by processing portions of the range spectrum of a synthetic aperture radar (SAR) image. According to the behavior of the SAR signal at the different sub-bands, MCA allows target classification. Two strategies have been experimented by processing TerraSAR-X images acquired over the Venice Lagoon, Italy: one exploiting the phase of interferometric sub-band pairs, the other using the spectral coherence derived by computing the coherence between sub-band images of a single SAR acquisition. The first approach introduces the concept of frequency-persistent scatterers (FPS), which is complementary to that of the time-persistent scatterers (PS). FPS and PS populations have been derived and analyzed to evaluate the respective characteristics and the physical nature of the targets. Spectral coherence analysis has been applied to vessel detection, according to the property that, in presence of a random distribution of surface scatterers, as for open sea surfaces, spectral coherence is expected to be proportional to sub-band intersection, while in presence of manmade structures it is preserved anyhow. First results show that spectral coherence is well preserved even for very small vessels, and can be used as a complementary information channel to constrain vessel detection in addition to classical Constant False Alarm Rate techniques based on the sole intensity channel. [less ▲]

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See detailVérification expérimentale de modèles opto-thermo-élastiques simulés avec le logiciel OOFELIE Multiphysics
Mazzoli, Alexandra ULg; Saint-Georges, Philippe; Orban, Anne ULg et al

in 12ème colloque international francophone sur les Méthodes et Techniques Optiques pour l'Industrie (2011, November)

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See detailExperimental validation of opto-thermo-elastic modeling in OOFELIE Multiphysics
Mazzoli, Alexandra ULg; Saint-Georges, Philippe; Orban, Anne ULg et al

in SPIE, Optical Systems Design (Marseille 5-8 septembre 2011) (2011)

The objective of this work is to demonstrate the correlation between a simple laboratory test bench case and the predictions of the Oofelie MultiPhysics software in order to deduce modelling guidelines ... [more ▼]

The objective of this work is to demonstrate the correlation between a simple laboratory test bench case and the predictions of the Oofelie MultiPhysics software in order to deduce modelling guidelines and improvements. For that purpose two optical systems have been analysed. The first one is a spherical lens fixed in an aluminium barrel, which is the simplest structure found in an optomechanical system. In this study, material characteristics are assumed to be well known: BK7 and aluminium have been retained. Temperature variations between 0 and +60°C from ambient have been applied to the samples. The second system is a YAG laser bar heated by means of a dedicated oven. For the two test benches thermo-elastic distortions have been measured using a Fizeau interferometer. This sensor measures wavefront error in the range of 20 nm to 1 μm without physical contact with the optomechanical system. For the YAG bar birefringence and polarization measurements have also been performed using a polarimetric bench. The tests results have been compared to the predictions obtained by Oofelie MultiPhysics which is a multiphysics toolkit treating coupled problems of optics, mechanics, thermal physics, electricity, electromagnetism, acoustics and hydrodynamics. From this comparison modelling guidelines have been issued with the aim of improving the accuracy of computed thermo-elastic distortions and their impact on the optical performances. [less ▲]

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See detailWide band SAR sub-band splitting and inter-band coherence measurements
De Rauw, Dominique ULg; Orban, Anne ULg; Barbier, Christian ULg

in Remote Sensing Letters (2010), 1(3), 133-140

Range resolution of SAR images is determined by transmitted radar signal bandwidth. Most recent SAR sensors use wide band signals in order to achieve metric range resolution, whereas metric azimuth ... [more ▼]

Range resolution of SAR images is determined by transmitted radar signal bandwidth. Most recent SAR sensors use wide band signals in order to achieve metric range resolution, whereas metric azimuth resolution can be achieved in spotlight mode. As an example, ENVISAT ASAR sensor uses a 15-MHz bandwidth chirp whereas TerraSAR-X spotlight mode uses signals having a 150-MHz bandwidth leading to a potentially 10 times higher resolution. One can also take advantage of wide band to split the full band into sub-bands and generate several lower resolution images from a single acquisition, each being centred on slightly different frequencies. These sub-images can then be used in a classical interferometric process to measure inter-band coherence of a given scene. This inter-band coherence reveals scatterers keeping a stable-phase behaviour along with frequency shift. A simple coherence model derived from Zebker model for randomly distributed surface scatterers is proposed. Examples are presented, showing that scatterers can have a behaviour that deviates from the model, leading to a new information channel. [less ▲]

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See detailINTER-BAND COHERENCE OF SPLIT WIDE BAND SAR IMAGES; A POTENTIALLY NEW INFORMATION CHANNEL
De Rauw, Dominique ULg; Orban, Anne ULg; Barbier, Christian ULg

in EARSel Newsletter (2009), 79

Recently-launched SAR sensors like TerraSAR-X or CosmoSkyMed are equipped with wide bandwidth radar signal emitters. Working at large bandwidth allows reaching metric range resolution, which combined with ... [more ▼]

Recently-launched SAR sensors like TerraSAR-X or CosmoSkyMed are equipped with wide bandwidth radar signal emitters. Working at large bandwidth allows reaching metric range resolution, which combined with spotlight mode, leads to Very High Resolution (VHR) SAR imagery. One can also take advantage of this wide band to split it into sub-bands and generate several lower resolution images from the same master one, each centered on a slightly different cen- tral frequency. These sub-images can then be used in a classical interferometric process to estimate inter- band coherence of a given scene. This inter-band coherence reveals scatterers keeping a stable phase behaviour along with frequency shift. In this paper, a simple model derived from Zebker model for randomly distributed surface scatterers is proposed and examples are pre- sented showing that scatterers can have a behaviour that deviates from the model, leading to a new information channel. [less ▲]

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See detailDynamic holographic interferometry for dilatation measurements in vacuum-thermal conditions
Thizy, Cédric ULg; Barbier, Christian ULg; Barzin, Pascal ULg et al

in Lehmann, Peter (Ed.) Proc. SPIE Vol 7398 on Optical Measurement Systems for Industrial Inspection VI (2009, June)

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See detailDynamic holographic interferometry development for dilatometry measurement of composites under vacuum-thermal conditions
Thizy, Cédric ULg; Barbier, Christian ULg; Tychon, Isabelle ULg et al

in Dirckx, J.; Buytaert, J. (Eds.) Proceedings of the 4th International Conference on Optical Measurement and Techniques for Systems & Structures (OPTIMESS 2009) (2009)

The Centre Spatial de Liège develops since 1993 holographic interferometry techniques and instruments based on photorefractive crystals for high resolution measurement of structures deformation, mainly ... [more ▼]

The Centre Spatial de Liège develops since 1993 holographic interferometry techniques and instruments based on photorefractive crystals for high resolution measurement of structures deformation, mainly for aerospace applications. In this paper we present the early results of development of a holographic technique and facility for deformation and expansion measurement of aerospace composites components. Here the holographic technique consists in using several illumination beams for retrieving different components of the displacement vector. In our case the components and structures to be measured in the future will undergo temperatures excursions up to 150°C typically. Since holographic techniques are sensitive to air turbulences, it is necessary to place the samples in a vacuum chamber. We will present some early examples of measurements with this facility, obtained for temperatures excursions ranged between ambient and 29°C as first steps before going further to higher temperatures excursions. [less ▲]

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See detailFirst Steps Towards Georeferencing of 3D VHR Optical and X-Band SAR Imagery
Belmonte, Antonella; De Rauw, Dominique ULg; Barbier, Christian ULg et al

in Proc. IGARSS'07 Symposium (2007)

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See detailA Combined Optical/Digital SAR Processor for Quicklook Applications
Litovchenko, Konstantin Ts.; Lemaire, Philippe; Barbier, Christian ULg

in Proc. EUSAR'02 Conference (2002)

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See detailInSAR Coherence for Crop Parameter Monitoring
Blaes, Xavier; Defourny, Pierre; De Rauw, Dominique ULg et al

in ESA (Ed.) Proc. FRINGE'99 Symposium (1999)

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See detailCartography of Microclimatic Zones Using InSAR DTM
Closson, Damien; Cornet, Yves ULg; Ozer, André ULg et al

in ESA (Ed.) Proc. FRINGE'99 Symposium (1999)

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See detailSpatial Organization of Hydrological Processes in Small Catchments Derived from Advanced SAR Image Processing : Field Work and Preliminary Results
Troch, P. A.; De Troch, F. P.; Grayson, R. et al

in ESA (Ed.) ESA Special Publication (1997)

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See detailA New Quicklook Optical Processor with Digital Input/Output
Litovchenko, Konstantin Ts.; Lemaire, Philippe; Barbier, Christian ULg

in Proceedings IGARSS'96 Symposium (1996)

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See detailA Frequency-Domain Processor for Maximum Resolution and Quicklook Processing of Wide-Swath ASAR Images
Barbier, Christian ULg; Piette, François; Renson, Luc et al

in Proc. EUSAR'96 Conference (1996)

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See detailA Frequency-Domain Processor for ScanSAR Images
Barbier, Christian ULg; Rosello-Guasch, Josep

in Preparing for the Future (1995), 5(4), 6-7

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See detailNumerical Techniques for Fast Multilook ScanSAR
Cantraine, Guy; Dendal, Didier; Barbier, Christian ULg et al

in SPIE (Ed.) Proceeding SPIE (1995)

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See detailVariational Calculationof the Dynamic Third-Order Susceptibility of Water
Gabryl, Jean-René; Barbier, Christian ULg; Lemaire, Philippe et al

in Journal of Molecular Structure : Theochem (1995), 357

Detailed reference viewed: 19 (4 ULg)