References of "Thizy, Cédric"
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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)

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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 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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See detailDynamic holography for the space qualification of large reflectors
Thizy, Cédric ULg; Stockman, Yvan ULg; Doyle, D. et al

in Optical Fabrication, Testing, and Metrology II (2005, October)

The next generation of infrared - sub mm space telescopes requires reflectors with large dimensions, high quality and, according to weight issues, are based on composite or new materials technology. The ... [more ▼]

The next generation of infrared - sub mm space telescopes requires reflectors with large dimensions, high quality and, according to weight issues, are based on composite or new materials technology. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of these reflectors shape and antenna structures and to verify their performance under simulated space conditions (vacuum, low-high temperatures). A holographic camera for the verification and validation of this type of reflector in a space environment is presented. A diffuser is implemented to measure the deformations of reflective surfaces in a more flexible way. The system has been made compatible with the vacuum conditions. Some elements of the holographic camera (camera lenses, CCD, crystal, optical fibre) have been adapted and tested under vacuum. The metrological certification of the whole system is realised by the measurement of a parabolic CFRP reflector with a 1.1 meter diameter. The results are compared to the one achieved with a high spatial resolution IR interferometer on the same reflector in laboratory conditions and under thermal vacuum conditions. This later test consists in measuring the deformations of the reflector between an initial state at a selected temperature and a final state at another temperature. The comparison between the high spatial resolution IR interferometer and this dynamic holographic method showed very good qualitative and quantitative agreement between the techniques, thus verifying the potential of this new Holographic approach. [less ▲]

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See detailDouble-pulsed holographic interferometry with photorefractive crystals
Georges, Marc ULg; Thizy, Cédric ULg; Lemaire, Philippe ULg et al

in Zhang, G.; Kip, D.; Nolte, D. (Eds.) et al Photorefractive Effects, Materials, and Devices (2005, July)

We present the achievement of the European PHIFE project (pulsed holographic interferometer for the analysis of fast events) and which consisted in the development of holographic head principles connected ... [more ▼]

We present the achievement of the European PHIFE project (pulsed holographic interferometer for the analysis of fast events) and which consisted in the development of holographic head principles connected to a YAG Q-switch double pulsed laser. An industrial prototype has been built with the aim of Hill-field out-of-plane displacement measurement at a high repetition rate. In parallel, a new double pulse laser with 25 Hz repetition rate, high energy (800 mJ/pulse in single pulse operation), variable delay between pulses (from 1 to 200 mu s) and based on a single cavity is studied [less ▲]

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See detailComparison between finite element calculations and holographic interferometry measurements, of the thermo-mechanical behaviour of satellite structures in composite materials
Thizy, Cédric ULg; Lemaire, Philippe ULg; Georges, Marc ULg et al

in Zhang, G.; Kip, D.; Nolte, D. (Eds.) et al Photorefractive Effects, Materials, and Devices (2005, July)

The stability requirements for the satellite structures evolve increasingly. To predict this one during the design phase a more and more used tool is the finite element calculation of thermo-elastic ... [more ▼]

The stability requirements for the satellite structures evolve increasingly. To predict this one during the design phase a more and more used tool is the finite element calculation of thermo-elastic models. The verification by measurement of these predictions on operational systems or testing rods is a key element allowing to validate these calculations and also to improve the simulations in order to study more complex cases in a reliable manner. We present the results of such a comparative study carried out on prototype structures using dynamic holographic interferometry, based on a sillenite photorefractive crystal, to measure the thermo-mechanical behavior [less ▲]

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See detailQualification of large reflectors in space environment with a holographic camera based on a BSO crystal
Thizy, Cédric ULg; Stockman, Yvan ULg; Lemaire, Philippe ULg et al

in Zhang, G.; Kip, D.; Nolte, D. (Eds.) et al Photorefractive Effects, Materials, and Devices (2005, July)

The next generation of infrared - sub mm space telescopes requires some reflectors with large dimensions and high quality. These ones, according to weight issues, are based on composite materials for ... [more ▼]

The next generation of infrared - sub mm space telescopes requires some reflectors with large dimensions and high quality. These ones, according to weight issues, are based on composite materials for which the behaviors at low temperatures are badly known. A holographic interferometry method for the verification and validation of this type of reflectors in a space environment is presented. It is based on a dynamic holographic camera observing a diffuser illuminated by the object beam coming from the reflecting surface. Photorefractive crystals being self-processing and reusable mediums, the measuring range of the holographic camera is increased with respect to other optical interferometric methods. The metrological certification of the whole system was realised by the measurement of a parabolic antenna with a 1.1 meter diameter, a known behavior and placed in a simulated space environment [less ▲]

Detailed reference viewed: 26 (2 ULg)