References of "Thizy, Cédric"
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See detailDevelopment of digital holography in the long wave infrared range for assessment of space reflectors
Thizy, Cédric ULg; Vandenrijt, Jean-François ULg; Georges, Marc ULg et al

in Proceedings of ICSO 2010 - International Conference on Space Optics (2010, October)

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See detailThermo-elastic distortion measurements by holographic interferometry and correlation with finite element models for SiC connections/junctions on spacecraft
Thizy, Cédric ULg; Stockman, Yvan ULg; Eliot, Fabienne et al

Conference (2010, September)

Scientific, earth observation and telecommunication spacecrafts are submitted to severe thermal environments while their mission performance requires more and more high stable structures. Due to on-ground ... [more ▼]

Scientific, earth observation and telecommunication spacecrafts are submitted to severe thermal environments while their mission performance requires more and more high stable structures. Due to on-ground constraints, the verification by test of the performances of these stable structures is usually limited. However accurate prediction methodology and verification capability of thermal distortions becomes mandatory for ensuring the in-orbit performance objectives of future programs. The main thermo-elastic contributors of the final stability performances are: - Material and assembly physical properties knowledge (Coefficient of Thermal Expansion, Young modulus, Poisson ratio…) - Modeling and simulation capabilities: temperature mapping, accurate thermo-elastic finite element models… - Verification test performances: advanced measurement techniques are required to characterize and determine the different main contributors to the final end to end performance and to perform accurate correlation. In this study, material characteristics are assumed to be well known. The objective was to improve and develop analytical predictions and verification of thermo elastic distortions using sample testing for modeling correlation. The samples have been chosen to be representative of the connections/junctions that can be encountered in stable structures on spacecraft and can have a dominant impact on the instrument stability. The results presented in this paper concern SiC/SiC and SiC/TA6V bonded and bolted samples. For the tests, temperature variations between -20°C and +15°C from ambient have been applied to the samples. Thermo-elastic distortions have been measured with a holographic camera. This holographic camera can measure displacements in the range of 20 nm to 20 m without physical contact with the samples. The tests results have been compared to the predictions obtained by Finite Element Modelling. From this comparison modelling guidelines have been issued with the aim of improving the accuracy of computed thermo elastic distortions: the FEM predictions lead to quite good correlation with the test data, with most of the time less than 10% discrepancies. A second phase to this study is planned. The objective is to implement all the benefits on improvement of thermo-elastic distortions predictions and verification achieved during the first phase on real spacecraft hardware. [less ▲]

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See detailDisplacement measurements of a parabolic reflector by holographic interferometry in the long-wavelength infrared
Vandenrijt, Jean-François ULg; Georges, Marc ULg; Thizy, Cédric ULg et al

in International Astronautical Congress 2010 (2010, September)

Deformation metrology of complex shape space structure and reflectors is a recurrent problem addressed by ESA. Consequently, suitable measurement techniques have to be developed and validated to support ... [more ▼]

Deformation metrology of complex shape space structure and reflectors is a recurrent problem addressed by ESA. Consequently, suitable measurement techniques have to be developed and validated to support relevant on-ground qualification and verification testing. Holographic techniques in the visible wavelengths are common for measuring the surface displacement of object. However the short wavelength induces high stability criteria which are so severe that they often prevent the measurement of large space structures under good conditions. We propose to use a wavelength longer than the usual visible ones to render such holographic displacement measurement techniques less sensitive to external perturbations. For this we consider CO2 laser emitting at 10.6 μm which correspond to the long-wavelength infrared (LWIR) spectrum. The most important element for performing holography is to use an adequate recording medium. However no convincing holographic recording media exists in LWIR and we decided to investigate the possibility of electronic hologram recording, such as electronic speckle pattern interferometry (ESPI). This possibility is feasible nowadays thanks to various thermal imaging technologies such has uncooled microbolometers sensors commonly found in thermographic cameras. In this study, we analyse how it is possible to measure surface displacements of specular objects, which do not produce speckle, using speckle interferometry by the mean of a scattering diffuser. We then apply the ESPI technique at LWIR for measuring displacements of a large parabolic reflector. [less ▲]

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See detailDigital holographic interferometry by using long infrared radiation (CO2 laser)
Alexeenko, Igor; Vandenrijt, Jean-François ULg; Georges, Marc ULg et al

in Advances in Experimental Mechanics VII (2010, September)

We show how digital holographic interferometry in the Long Wave InfraRed (LWIR) spectral range can be used for the investigation of mechanical structures. The 10.6 μm radiation is produced by a CO2 Laser ... [more ▼]

We show how digital holographic interferometry in the Long Wave InfraRed (LWIR) spectral range can be used for the investigation of mechanical structures. The 10.6 μm radiation is produced by a CO2 Laser. Experimental results showing that the method can be used to locate defect in a panel are presented and advantages and disadvantages of this approach are discussed [less ▲]

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See detailElectronic Speckle Pattern Interferometry at Long Wave Infrared Wavelengths. Scattering Requirements
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Alexeenko, Igor et al

in Fringe 2009 (2009, September)

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See detailAutomated Phase Map Referencing Against Historic Map Data
Groves, Roger; De Rauw, Dominique ULg; Thizy, Cédric ULg et al

in Osten, W.; Kujawinska, M. (Eds.) Fringe 2009 (2009, September)

Holography and shearography techniques are in common use for precise measurements in high technology industries, such as aerospace, automotive, precision manufacturing and for the structural diagnostics ... [more ▼]

Holography and shearography techniques are in common use for precise measurements in high technology industries, such as aerospace, automotive, precision manufacturing and for the structural diagnostics of artwork. The phase map data generated by these instruments allows precise measurements of parameters such as displacement, strain and shape. The comparison of data from different measurement campaigns is useful for null testing components and for studying changes. However, the comparison of data with previous measurements is non-trivial due to the sensitivity of these techniques to alignment and to sample loading parameters. This paper addresses image and phase registration issues for holography and shearography. This manuscript describes 2D spatial co-registration to compensate for differences between the field of view between the measurements and a phase referencing to calculate the difference between the phase maps. These techniques are implemented after following a standardised measurement procedure. [less ▲]

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See detailElectronic Speckle Pattern Interferometry at Long Infrared Wavelengths. Scattering Requirements
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Alexeenko, Igor et al

in Osten, Wolfgang; Kujawinska, Malgorzata (Eds.) Fringe 2009 (2009, September)

Detailed reference viewed: 52 (5 ULg)
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 detailInterférométrie holographique photoréfractive : nouveaux développements et applications récentes
Thizy, Cédric ULg; Georges, Marc ULg; Hustinx, Guy-Michel et al

Conference (2008, November)

Les cristaux photoréfractifs permettent l'enregistrement holographique dynamique in-situ et une réutilisabilité infinie. Aussi ils possèdent des propriétés spécifiques que d'autres matériaux ... [more ▼]

Les cristaux photoréfractifs permettent l'enregistrement holographique dynamique in-situ et une réutilisabilité infinie. Aussi ils possèdent des propriétés spécifiques que d'autres matériaux holographiques n'ont pas et qui peuvent être utilisées de manière avantageuse en interférométrie holographique. Depuis 15 ans, le CSL développe des techniques d'interférométrie holographique et des instruments basés sur des cristaux de Bi12SiO20 (BSO). Le comportement dynamique de ces derniers permet une grande souplesse d'utilisation de l'interférométrie holographique, à l'instar des techniques basées sur l'enregistrement numérique, tout en fournissant des interférogrammes de meilleure résolution que celles-ci (pas de bruit de speckle, pas de filtrage nécessaire). Par le passé, nous avons déjà présenté une large gamme d'applications en métrologie, contrôle non destructif et mesures vibratoires. Ici nous présentons des applications industrielles récentes obtenue avec une caméra holographique photoréfractive commercialisée. Cette dernière a été utilisée avec succès dans des applications très demandeuses, notamment en terme de résolution. [less ▲]

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See detailRole of photorefractive holographic interferometry in Impact Assessment Procedure applied to movable cultural heritage
Thizy, Cédric ULg; De Rauw, Dominique ULg; Georges, Marc ULg et al

in Proceedings of the International Symposium to Commemorate the 60th Anniversary of the Invention of Holography (2008, October)

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See detailHolographic interferometry with photorefractive crystals : recent industrial applications
Thizy, Cédric ULg; Georges, Marc ULg; Hustinx, Guy-Michel et al

in Proceedings of the International Symposium to Commemorate the 60th Anniversary of the Invention of Holography (2008, October)

Photorefractive crystals allow in-situ dynamic holographic recording and indefinite reusability. Also they exhibit specific properties that other recording materials do not and which can be advantageously ... [more ▼]

Photorefractive crystals allow in-situ dynamic holographic recording and indefinite reusability. Also they exhibit specific properties that other recording materials do not and which can be advantageously used in holographic interferometry. For 15 years we have been developing holographic interferometry techniques and devices with Bi12SiO20 (BSO) crystals. The dynamic behaviour of the latter allows a high degree of userfriendliness of holographic interferometry (like techniques based on electronic recording), together with higher resolution interferograms (no speckle noise - no need of filtering). In the past we already have presented a wide range of applications in metrology, NDT and vibrations measurement. Here we present recent industrial applications obtained with a device which is now commercially available. It has proven successful applications in highly demanding applications where high resolution was required [less ▲]

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See detailPhase control for the stabilization of a photorefractive holographic camera in perturbed environments
Thizy, Cédric ULg; Georges, Marc ULg; Lemaire, philippe

in Hesselink, Lambertus; Feinberg, Jack (Eds.) Controlling Light with Light: Photorefractive Effects, Photosensitivity, Fiber Gratings, Photonic Materials and More (2007, October)

The holographic interferometer developed by CSL, and which uses a BSO crystal, exhibits a response time of a few seconds. This prevents us to properly record holograms under perturbated environmental ... [more ▼]

The holographic interferometer developed by CSL, and which uses a BSO crystal, exhibits a response time of a few seconds. This prevents us to properly record holograms under perturbated environmental conditions due to optical phase variations between reference and object beams. We present hereafter several active phase control strategies to overcome this problem [less ▲]

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See detailPhotorefractive holographic interferometry for movable artwork assessment
Thizy, Cédric ULg; Georges, Marc ULg; Koulompi, Eleni et al

in Hesselink, Lambertus; Feinberg, Jack (Eds.) Controlling Light with Light: Photorefractive Effects, Photosensitivity, Fiber Gratings, Photonic Materials and More (PR07) (2007, October)

Photorefractive holographic interferometry is applied to assessment of movable cultural heritage. Its role is to observe tiny signatures resulting from internal artwork characteristics. In the future, the ... [more ▼]

Photorefractive holographic interferometry is applied to assessment of movable cultural heritage. Its role is to observe tiny signatures resulting from internal artwork characteristics. In the future, the system will be used for both antifraud and restoration [less ▲]

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See detailAdaptation of photorefractive holographic camera for observation of micro-mechanical structures
Georges, Marc ULg; Thizy, Cédric ULg; Loicq, Jerôme ULg et al

in Hesselink, L.; Feinberg, J. (Eds.) Controlling Light with Light: Photorefractive Effects, Photosensitivity, Fiber Gratings, Photonic Materials and More (PR07) (2007, October)

The photorefractive holographic camera initially working on large scattering objects has been adapted to observe centimetric to micrometric objects. Application on micro-mechanical systems is presented

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See detailRole of dynamic holography with photorefractive crystals in a multi-functional sensor for the detection of signature features in movable cultural heritage
Thizy, Cédric ULg; Georges, Marc ULg; Doulgeridis, M. et al

in Fotakis, C.; Pezzati, L.; Salimbeni, R. (Eds.) O3A: Optics for Arts, Architecture, and Archaeology (2007, June)

This paper is one of a series submitted by the Multi-Encode Project consortium and covers the development of holographic interferometry with dynamic photorefractive crystals. The aim of the first phase of ... [more ▼]

This paper is one of a series submitted by the Multi-Encode Project consortium and covers the development of holographic interferometry with dynamic photorefractive crystals. The aim of the first phase of the project is to assess the existing techniques for detection of signatures in various types of artworks. The trademark of our technique is a very high resolution in the fringe pattern. We will show the potentiality of our technique for the present application. [less ▲]

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See detailAdaptation of a photorefractive holographic interferometer for analysis of centimetric to micrometric objects
Georges, Marc ULg; Thizy, Cédric ULg; Tiberghien, J. et al

in Slangen, P.; Cerruti, C. (Eds.) Speckle06 : Speckles, From Grains to Flowers (2006, September)

The holographic camera developed by CSL was aimed at observing of medium to large opaque scattering objects. In the recent times, we received an increasing demand of measurement on small objects (a few ... [more ▼]

The holographic camera developed by CSL was aimed at observing of medium to large opaque scattering objects. In the recent times, we received an increasing demand of measurement on small objects (a few centimetres wide) or micrometric systems (MEMS). In the last case, most of them are specular objects ranging to a few microns. The imaging and illumination systems of our holographic device was naturally not adapted to such new objects. Therefore we decided to study a new optical extension to the current system which matches these new needs. Nevertheless the type of displacement that can be measured remain similar to the ones covered by the previous system. We present various examples of applications brought by industrial partners. [less ▲]

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See detailPhase control strategies for stabilization of photorefractive holographic interferometer
Thizy, Cédric ULg; Georges, Marc ULg; Lemaire, Philippe ULg et al

in Slangen, P.; Cerruti, C. (Eds.) Speckle06 : Speckles, From Grains to Flowers (2006, September)

A current problem encountered in holographic interferometry systems is the phase variations that arise from vibrations, from the use of optical fiber in one arm, by air convection or by unwanted movement ... [more ▼]

A current problem encountered in holographic interferometry systems is the phase variations that arise from vibrations, from the use of optical fiber in one arm, by air convection or by unwanted movement between the object and the measurement device. The holographic device developed by CSL based on photorefractive BSO crystals has the advantage of high resolution fringes with the capability of self-processing and indefinite reusability. The weakness of the technique is a response time that is often slow compared to external perturbations. For applications outside the laboratory, we decided to find solutions adapted to the holographic camera and which tend to limit or to eliminate the effect of such phase variations. An error signal is measured from one or another technique which measure the phase variations and which counteracts on an active element in the interferometer to stabilize the phase during recording. Different solutions have been analysed and are presented here. Interferograms were obtained with and without implementation of the phase control system that show the interest of such approach. Some of the system presented are only adapted to photorefractive holographic interferometry, making use of some crystal diffraction properties. Other systems can be used with other kind of interferometers. [less ▲]

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