References of "Georges, Marc"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDigital holographic interferometry with CO2 lasers and diffuse illumination applied to large space reflectors metrology
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Applied Optics (2013), 52(1), 102-116

Digital holographic interferometry in the long wave infrared domain has been developed by combining a CO2 laser and a microbolometer array. The long wavelength allows large deformation measurements which ... [more ▼]

Digital holographic interferometry in the long wave infrared domain has been developed by combining a CO2 laser and a microbolometer array. The long wavelength allows large deformation measurements which are of interest in the case of large space reflectors undergoing thermal changes when in orbit. We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements. For the design of our digital holographic interferometer we studied the possibility of illuminating specular objects by a reflective diffuser. We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test. [less ▲]

Detailed reference viewed: 74 (11 ULg)
Full Text
See detailLong-wave infrared digital holography for the qualification of large space reflectors
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Georges, Marc ULg et al

Conference (2012, October 09)

Deformation metrology of complex and large space reflectors is a recurrent problem addressed by ESA. The challenging tasks of on-ground qualification and verification testing are to achieve the required ... [more ▼]

Deformation metrology of complex and large space reflectors is a recurrent problem addressed by ESA. The challenging tasks of on-ground qualification and verification testing are to achieve the required accuracy in the measurement of these reflectors deformation and to verify their performance under simulated space conditions (vacuum, low temperature). A long-wave infrared digital holographic interferometer for the verification and validation of this type of reflector in a space environment is presented. It has been developed to fill the gap between holography/interferometry techniques in the visible wavelengths and methods based on structured light illumination like videogrammetry, stereocorrelation, and fringe/pattern projection. The former provide a good measurement uncertainty but the displacements are often too large to be measured and they require a very stable environment, while the latter provide large measurement range but with higher measurement uncertainty. The new instrument is based on digital holography and uses a CO2 lasers emitting at 10.6 µm combined with a commercial thermographic camera. A diffuser is illuminated by the laser beam, producing a speckle wavefront which is observed after reflection on the reflector surface. This reflected speckle wavefront behaves exactly as if the reflector was a diffusive surface, producing its own speckle, allowing the measurement of its deformation. The advantage of this configuration compared to a classical interferometer working at 10.6 µm, is that it requires no specific optics such as a null lens (in the case of parabola) or expensive illumination/collection optics (in the case of ellipse). The metrological certification of the system was performed in the laboratory by measuring the tilts of a 1.1 meter diameter parabolic reflector. The displacements are measured in parallel with a Doppler effect interferometer and the measurement uncertainty is estimated. The application of the new interferometer to the measurement of an elliptic reflector is also presented. The technique has been certified during a thermal-vacuum test. The deformation of the parabolic reflector is measured for a temperature variation from 288 K down to 113 K. The results are compared to previous results obtained on the same reflector with a high spatial resolution infrared interferometer, also developed at CSL. [less ▲]

Detailed reference viewed: 70 (7 ULg)
Full Text
See detailUV radiation effects on liquid crystal variable retarders for aerospace applications
Garcia Parejo, Pilar; Alvarez-Herrero, Alberto; Uribe-Patarroyo, Nestor et al

Conference (2012, August)

Liquid-Crystal Variable Retarders (LCVRs)1 are optical devices that provide a variable optical retardance accomplished by the application of electric fields. Traditionally, they have been used as light ... [more ▼]

Liquid-Crystal Variable Retarders (LCVRs)1 are optical devices that provide a variable optical retardance accomplished by the application of electric fields. Traditionally, they have been used as light polarization modulators for polarimetric applications in ground telescopes2, and more recently they took part in the polarisation modulation package of the Imaging Magnetograph eXperiment (IMaX)3, where the LCVRs were launched successfully on-board the Sunrise mission, a stratospheric balloon that was flown from Antarctica to study the solar magnetic fields. This mission was the precursor of the Solar Orbiter mission of the European Space Agency (ESA), where the liquid crystals will be used as polarisation modulators onboard a space mission for the first time in two instruments: the Polarimetric and Helioseismic Imager (SO/PHI) and the Multi-Element Telescope for Imaging and Spectroscopy (METIS). Any on-board element used for aerospace applications must be able to survive the harsh environmental space conditions including UV radiation, gamma radiation, vibrational tests, thermal-vacuum... In this sense, LCVRs have been recently validated to be used under the space conditions of the Solar Orbiter mission, in the framework of the ESA project: “Validation of LCVRs for the Solar Orbiter Polarisation Modulation Package”. In this project, a set of LCVRs with different design parameters has been analyzed under the different space environmental conditions. These design parameters include the architecture of the LCVR cell, using Anti-Parallel Aligned Nematic (APAN) and Hybrid Aligned Nematic (HAN) architectures, the type of liquid crystal molecules, using different commercial nematic liquid crystal mixtures with high and low birefringence and positive and negative dielectric anisotropy, different homogeneous and homeotropic polyimide alignment layers and different glass plates. Among the space environmental components, the UV radiation needs special consideration due to the organic nature of the liquid crystal molecules and the alignment layers that consisted of rubbed polyimide layers. In this work, we present the main results of the UV radiation test campaign carried out in the LCVRs consisting of the performance of a thorough optical characterization of the LCVRs, including optical retardance and response times measurements at different voltages performed by the ellipsometry technique, and optical transmission measurements, before and after irradiating the LCVRs with UV light at different doses, in two different spectral ranges: 200 -400 nm and 160-200 nm. The main degradation effects observed in the LCVRs was a progressive reduction of the retardance range of the LCVRs which points out a decrease of the birefringence of the liquid crystal molecules or the increase of the pretilt angle due to the degradation of the polyimide layers, and an increase of the response times of the cells. Nevertheless, the changes observed do not involve the destruction of the LCVRs and they keep fulfilling the requirements for the Solar Orbiter mission becoming in a promising technology for aerospace applications. [less ▲]

Detailed reference viewed: 296 (2 ULg)
Full Text
Peer Reviewed
See detailInvestigation on the High Efficiency Volume Bragg gratings performances for spectrometry in space environment: Preliminary results
Loicq, Jerôme ULg; Georges, Marc ULg; Gaspar Venancio, Luis Miguel

in Telescope and systems (2012, July)

The special properties of Volume Bragg Gratings (VBGs) make them good candidates for spectrometry applications where high spectral resolution, low level of straylight and low polarisation sensitivity are ... [more ▼]

The special properties of Volume Bragg Gratings (VBGs) make them good candidates for spectrometry applications where high spectral resolution, low level of straylight and low polarisation sensitivity are required. Therefore it is of interest to assess the maturity and suitability of VBGs as enabling technology for future ESA missions with demanding requirements for spectrometry. The VBGs suitability for space application is being investigated in the frame of a project led by CSL and funded by the European Space Agency. The goal of this work is twofold: first the theoretical advantages and drawbacks of VBGs with respect to other technologies with identical functionalities are assessed, and second the performances of VBG samples in a representative space environment are experimentally evaluated. The performances of samples of two VBGs technologies, the Photo-Thermo-Refractive (PTR) glass and the DiChromated Gelatine (DCG), are assessed and compared in the H, O2-B and NIR bands. The tests are performed under vacuum condition combined with temperature cycling in the range of 200 K to 300K. A dedicated test bench experiment is designed to evaluate the impact of temperature on the spectral efficiency and to determine the optical wavefront error of the diffracted beam. Furthermore the diffraction efficiency degradation under gamma irradiation is assessed. Finally the straylight, the diffraction efficiency under conical incidence and the polarisation sensitivity is evaluated. [less ▲]

Detailed reference viewed: 17 (5 ULg)
Full Text
See detailSpeckle interferometry at 10 µm with CO2 lasers and microbolometers array
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Kieffer, Jean-Claude (Ed.) Photonics North 2012 (2012, June 06)

Detailed reference viewed: 29 (3 ULg)
Full Text
See detailDigital Holographic Interferometry and ESPI at Long Infrared Wavelengths with CO2 Laser (invited paper)
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Digital Holography and 3D Imaging (DH2012) (2012, April 28)

Detailed reference viewed: 24 (4 ULg)
Full Text
See detailHigh Efficiency Volume Bragg Gratings for Spectrometry and space applications: Space qualification report
Loicq, Jerôme ULg; Georges, Marc ULg

Report (2012)

This document presents the results of the assembly, integration and validation of the VBG test benches

Detailed reference viewed: 11 (0 ULg)
Full Text
See detailHigh Efficiency Volume Bragg Gratings for Spectrometry and space applications:VBG experimental characterization program
Loicq, Jerôme ULg; Georges, Marc ULg

Report (2012)

This document presents a validation program plan on Volume Bragg grating. The objectives are to define and describe the test to be performed on VBG’s for space component. qualification.

Detailed reference viewed: 9 (0 ULg)
Full Text
See detailHigh Efficiency Volume Bragg Gratings for Spectrometry and space applications: Technology survey & Trade-off analysis
Loicq, Jerôme ULg; Barbier, Christian ULg; Georges, Marc ULg

Report (2012)

This document presents the results of the technology trade-off on gratings technologies. The first part of this document presents a technology survey which describes following technologies: - Surface ... [more ▼]

This document presents the results of the technology trade-off on gratings technologies. The first part of this document presents a technology survey which describes following technologies: - Surface relief grating - Volume Bragg grating - Grisms or immersed grating In the case of VBG’s two specific material are considered: - Dichromated gelatine (DCG) - Photothermal refractive grating (PTR). These cases are considered in two configurations transmission and reflection mode. The second part of the document presents the results of trade-off analysis focused on VBG’s technologies. A whole set of parameters about PTR and DCG are presented. These parameters were obtained by Kogelnik theory and RCW analysis. Manufacturing and physical parameters have been chosen to be compliant with ESA specifications. Results of this analysis will drive the choices of adequate spectral bands and related VBG technologies to test in the next steps of the project. [less ▲]

Detailed reference viewed: 10 (2 ULg)
Full Text
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)

Detailed reference viewed: 45 (9 ULg)
Full Text
See detailUsing Holography to reduce aircraft costs
Georges, Marc ULg

Article for general public (2011)

Detailed reference viewed: 18 (10 ULg)
Full Text
See detailImaging polarimeters based on Liquid Crystal Variable Retarders: an emergent technology for space instrumentation
Alvarez-Herrero, A.; Uribe-Patarroyo, N.; Garcia Parejo, P. et al

in Show, J. A.; Scott Tyo, J. (Eds.) Proc. SPIE Vol 8160 on Polarization Science and Remote Sensing V (2011, September 09)

Detailed reference viewed: 65 (1 ULg)
Full Text
See detailSpace-qualified liquid-crystal variable retarders for wide-field-of-view coronographs
Uribe-Patarroyo, N.; Alvarez-Herrero, A.; Garcia Parejo, P. et al

in Fineschi, Silvano; Fennelly, Judy (Eds.) Proc. SPIE Vol 8148 on Solar Physics and Space Weather Instrumentation IV (2011, August)

Detailed reference viewed: 63 (2 ULg)
Full Text
See detailLIBS : Identification rapide de composants chimiques. Application au recyclage des matériaux et détection de pollution du sol
Georges, Marc ULg

Conference (2011, May 13)

La technique LIBS (Laser Induced Breakdown Spectroscopy) permet une analyse rapide in situ des éléments chimiques sans préparation de l'échantillon. La LIBS consiste à illuminer un échantillon à analyser ... [more ▼]

La technique LIBS (Laser Induced Breakdown Spectroscopy) permet une analyse rapide in situ des éléments chimiques sans préparation de l'échantillon. La LIBS consiste à illuminer un échantillon à analyser avec une impulsion laser nanoseconde et concentrée par un système optique. Il en résulte la production en surface du matériau d'un plasma qui émet de la lumière dont le contenu spectral est ensuite analysé à distance. La LIBS a diverses applications dans le secteur de l'environnement. Dans la présentation, nous mettons en avant les applications dans la recherche de polluants ainsi que la possibilité de trier les vitrocéramiques dans les déchets verriers. Cette dernière application a été mise au point par le Centre Spatial de Liège avec le support financier de FOST Plus. [less ▲]

Detailed reference viewed: 59 (4 ULg)
Full Text
See detailMesures LASER
Georges, Marc ULg

Learning material (2011)

Nous passons en revue les différentes méthodes de mesures laser, par champ complet ou ponctuelles, que ce soit pour la mesure de déformation, les mesures de distance, vitesse, épaisseur, ou les mesures ... [more ▼]

Nous passons en revue les différentes méthodes de mesures laser, par champ complet ou ponctuelles, que ce soit pour la mesure de déformation, les mesures de distance, vitesse, épaisseur, ou les mesures dans les fluides, les gaz ainsi que des techniques particulières comme la LIBS utilisées en analyse chimique [less ▲]

Detailed reference viewed: 19 (7 ULg)