Experimental validation of opto-thermo-elastic modeling in OOFELIE Multiphysics

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 ▲]

INTER-BAND COHERENCE OF SPLIT WIDE BAND SAR IMAGES; A POTENTIALLY NEW INFORMATION CHANNEL

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 ▲]

Dynamic holographic interferometry development for dilatometry measurement of composites under vacuum-thermal conditions

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 ▲]

First Steps Towards Georeferencing of 3D VHR Optical and X-Band SAR Imagery

in Proc. IGARSS'07 Symposium (2007)

InSAR Coherence for Crop Parameter Monitoring

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

Quality Assessment of InSAR Topographic Mapping : The Example of Belgium

in SPIE (Ed.) Proc. SPIE (1998)

Spatial Organization of Hydrological Processes in Small Catchments Derived from Advanced SAR Image Processing : Field Work and Preliminary Results

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

A Frequency-Domain Processor for Maximum Resolution and Quicklook Processing of Wide-Swath ASAR Images

in Proc. EUSAR'96 Conference (1996)

Numerical Techniques for Fast Multilook ScanSAR

in SPIE (Ed.) Proceeding SPIE (1995)

SAR Image Data Processing at CSL

in Belgian Science Policy (Belspo) (Ed.) Space Scientific Research in Belgium (1995)