References of "Lemaire, Philippe"
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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 detailRewritable VPHGs based on photochromic materials
Bianco, A.; Toso, G.; Dassa, G. et al

in Attad-Ettedqui, A.; Lemke, D. (Eds.) Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation (2008, June)

Volume phase holographic gratings (VPHGs) are becoming an interesting alternative to the ruled gratings in modern astronomical instrumentation. Photochromic materials with thermal stability are good ... [more ▼]

Volume phase holographic gratings (VPHGs) are becoming an interesting alternative to the ruled gratings in modern astronomical instrumentation. Photochromic materials with thermal stability are good candidates for the development of holographic optical elements and in particular for VPHGs. VPHGs based on photochromic materials can be written and erased many times without the degradation of the material; moreover the material does not need any developing process after the exposure, making the writing process very simple. We have already studied photochromic materials for this aim in the framework of the JRA6 (Opticon Project, FP6) and we found that large modulations of the refractive index can be achieved using diarylethene polymers. Going from the materials characterization to technology, substrates with larger thickness and good optical properties are required. Herein we present the development of new technique to tailor the thickness of the photochromic films in two ranges: 5 - 30 micron and 700 - 1000 micron. The former are suitable for the development of broadband VPHGs, whereas the latter are suitable for narrow band tunable filters application. Details on the optical properties of the films are reported. Finally, a holographic set-up based on an Ar+ laser has been optimized in order to write the gratings. [less ▲]

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See detailDynamic holographic interferometry: Devices and applications
Lemaire, Philippe ULg; Georges, Marc ULg

in Günther, P.; Huignard, J.-P. (Eds.) Photorefractive Materials and Their Applications 3. Applications (2007)

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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 ▲]

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See detailVolume phase holographic gratings: large size and high diffraction efficiency
Blanche, Pierre-Alexandre ULg; Gailly, Patrick ULg; Habraken, Serge ULg et al

in Optical Engineering (2004), 43(11), 2603-2612

Volume phase holographic gratings (VPHGs) possess unique properties that make them attractive for numerous applications. After reviewing major VPHG characteristics through theory, we discuss some aspects ... [more ▼]

Volume phase holographic gratings (VPHGs) possess unique properties that make them attractive for numerous applications. After reviewing major VPHG characteristics through theory, we discuss some aspects of the dichromated gelatin recording material and the holographic recording process. The large-scale VPHG research facility set up at the Center Spatial de Liege enables production of VPHGs up to 380 mm in diameter, with fringe frequencies from 315 to 3300 Ip/mm. We describe the work that has been undertaken in our laboratory to remove the last limitations inherent in VPHGs. (C) 2004 Society of Photo-Optical Instrumentation Engineers. [less ▲]

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See detailDevelopment of optical ground verification method for mum to sub-mm reflectors
Stockman, Yvan ULg; Thizy, Cédric ULg; Lemaire, Philippe ULg et al

in 5th International Conference on Space Optics (2004, June 01)

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. Scientific ... [more ▼]

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. Scientific observatories require large telescopes with precisely shaped reflectors for collecting the electro-magnetic radiation from faint sources. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of the reflector shapes and antenna structures and to verify their performance under simulated space conditions (vacuum, low temperatures). Due to the specific surface characteristics of reflectors operating in these spectral regions, standard optical metrology methods employed in the visible spectrum do not provide useful measurement results. The current state-of-the-art commercial metrology systems are not able to measure these types of reflectors because they have to face the measurement of shape and waviness over relatively large areas with a large deformation dynamic range and encompassing a wide range of spatial frequencies. 3-D metrology (tactile coordinate measurement) machines are generally used during the manufacturing process. Unfortunately, these instruments cannot be used in the operational environmental conditions of the reflector. The application of standard visible wavelength interferometric methods is very limited or impossible due to the large relative surface roughnesses involved. A small number of infrared interferometers have been commercially developed over the last 10 years but their applications have also been limited due to poor dynamic range and the restricted spatial resolution of their detectors. These restrictions affect also the surface error slopes that can be captured and makes their application to surfaces manufactured using CRFP honeycomb technologies rather difficult or impossible. It has therefore been considered essential, from the viewpoint of supporting future ESA exploration missions, to develop and realise suitable verification tools based on infrared interferometry and other optical techniques for testing large reflector structures, telescope configurations and their performances under simulated space conditions. The first one is an IR-phase shifting interferometer with high spatial resolution. This interferometer shall be used specifically for the verification of high precision IR, FIR and sub-mm reflector surfaces and telescopes under both ambient and thermal vacuum conditions. The second one presented hereafter is a holographic method for relative shape measurement. The holographic solution proposed makes use of a home built vacuum compatible holographic camera that allows displacement measurements from typically 20 nanometres to 25 microns in one shot. An iterative process allows the measurement of a total of up to several mm of deformation. Uniquely the system is designed to measure both specular and diffuse surfaces. [less ▲]

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See detailAdvances in pulsed holographic interferometry with photorefractive crystals
Georges, Marc ULg; Pauliat, B.; Alexeenko, I. et al

in Tomasini, E. (Ed.) 6th Intl Conf on Vibration Measurements by Laser Techniques : Advances and Applications (2004, June)

Photorefractive crystals offer many advantages over other classical holographic recording media. They allow fast in-situ processable holographic recording as well as indefinite reusability. Moreover high ... [more ▼]

Photorefractive crystals offer many advantages over other classical holographic recording media. They allow fast in-situ processable holographic recording as well as indefinite reusability. Moreover high signal-to-noise ratio can be reached as well as high resolutions. We present the results obtained by pulsed holographic interferometry obtained with photorefractive crystals. First experiments showing the potentiality of photorefractive crystals for such applications will be reviewed. Some limitations were pointed out and led us to consider new developments under the frame of an European-funded project. The PHIFE European project (Pulsed Holographic Interferometer for the analysis of Fast Events) aims at developing a full field measurement system at a high repetition rate, based on a double-pulse YAG Q-switch laser. This device will be used for the analysis of vibrations and for aerodynamic studies. Different crystals are considered which are adapted to the fundamental line of the YAG (AsGa or CdTe crystals) or after frequency doubling at 532 nm (Bi/sub 12/SiO /sub 20/). Different crystal configurations and recording geometries are compared. Also different innovative phase quantification techniques are studied and take into account some special properties of the PRCs. We present the results obtained so far in the first development phases of the project [less ▲]

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See detailDevelopment of optical ground verification method for mu m to sub-mm reflectors
Stockman, Yvan ULg; Thizy, Cédric ULg; Lemaire, Philippe ULg et al

in Warmbein, B. (Ed.) Proceedings of the 5th International Conference on Space Optics (ICSO) (2004, April 02)

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. The ... [more ▼]

Large reflectors and antennas for the IR to mm wavelength range are being planned for many Earth observation and astronomical space missions and for commercial communication satellites as well. The challenging tasks of on-ground testing are to achieve the required accuracy in the measurement of the reflector shapes and antenna structures and to verify their performance under simulated space conditions (vacuum, low temperatures). A small number of infrared interferometers have been commercially developed over the last 10 years but their applications have also been limited due to poor dynamic range and the restricted spatial resolution of their detectors. It has therefore been considered essential, from the viewpoint of supporting future ESA exploration missions, to develop and realise suitable verification tools based on infrared interferometry and other optical techniques for testing large reflector structures, telescope configurations and their performances under simulated space conditions. Two methods and techniques are developed at CSL. The first one is an IR-phase shifting interferometer with high spatial resolution. This interferometer shall be used specifically for the verification of high precision IR, FIR and sub-mm reflector surfaces and telescopes under both ambient and thermal vacuum conditions. The second one presented hereafter is a holographic method for relative shape measurement. The holographic solution proposed makes use of a home built vacuum compatible holographic camera that allows displacement measurements from typically 20 nanometres to 25 microns in one shot. An iterative process allows the measurement of a total of up to several mm of deformation. Uniquely the system is designed to measure both specular and diffuse surfaces [less ▲]

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See detailDynamic holographic interferometry with photorefractive crystals : review of applications and advanced techniques
Georges, Marc ULg; Thizy, Cédric ULg; Scauflaire, W. et al

in Gastinger, K.; Lokberg, O.; Winther, S. (Eds.) Speckle Metrology 2003 (2003, June)

We will present the basic properties of photorefractive crystals and show how they can be used efficiently in holographic interferometry experiments. We then will present some holographic systems and ... [more ▼]

We will present the basic properties of photorefractive crystals and show how they can be used efficiently in holographic interferometry experiments. We then will present some holographic systems and their numerous applications. With continuous illumination, we will show classical non destructive testing (defect detection), displacement metrology, vibration mode shape visualization, as well as a study for the use of photorefractive crystals in microgravity monitoring of fluid (FSL experiment aboard the International Space Station). With pulsed illumination we will present the possibilities of the photorefractive crystals in vibration measurement (and will introduce the ongoing EC-funded PHIFE research project). The purpose of the paper is to unmystify photorefractive crystals and to show that they could be a good alternative to traditional speckle-based techniques for highly demanding applications. For that we will highlight the highest resolution achieved as well as the high temporal dynamics of the holographic recording [less ▲]

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See detailHolographic interferometry with a 90 degrees photorefractive crystal geometry
Georges, Marc ULg; Pauliat, G.; Weidner, E. et al

in Delaye, Ph; Denz, C.; Mager, L. (Eds.) Photorefractive Effects, Materials, and Devices (2003, June)

Holographic interferometers are generally designed in the common geometry where both interfering waves (reference and object) enter the crystal by the same window (co-propagating configuration). The ... [more ▼]

Holographic interferometers are generally designed in the common geometry where both interfering waves (reference and object) enter the crystal by the same window (co-propagating configuration). The alternative presented here consists in using a reference beam entering the crystal by a lateral face. The crystal has to be cut adequately in order to obtain electro-optic properties similar to that of the co-propagating configuration but with a smaller optical scattering noise. Therefore higher signal-to-noise ratios are expected in the interferograms. We will present the main features and constraints of this configuration together with the experimental study of its noise characteristics. This work has been performed for sillenite and semiconductor crystals [less ▲]

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See detailIn-plane and out-of-plane holographic interferometry with multibeam photorefractive recordings in sillenite photorefractive crystals
Thizy, Cédric ULg; Georges, Marc ULg; Scauflaire, V. et al

in Delaye, Ph; Denz, C.; Mager, L. (Eds.) Photorefractive Effects, Materials, and Devices (2003, June)

In this paper we present results of the multiple beams recording in photorefractive crystals for multidirectional measurement of object displacement by holographic interferometry. Taking advantage of the ... [more ▼]

In this paper we present results of the multiple beams recording in photorefractive crystals for multidirectional measurement of object displacement by holographic interferometry. Taking advantage of the possibility to record several holograms in the photorefractive crystal without noticeable cross-talk and loss of signal-to-noise ratio, we demonstrate the applicability of this technique to high resolution metrology and nondestructive testing. A first part of the paper is devoted to metrological certification of the process. On the basis of known "in-plane" and "out-of plane" movements, we certify the measurement deconvolution algorithm and error. A second part will concern the measurement of thermo-mechanical composite material properties (Poisson coefficient, ...) with a compact transportable head using double recording illumination [less ▲]

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See detailQualification of BSO crystals for use onboard the International Space Station
Georges, Marc ULg; Dupont, Olivier ULg; Zayer, I. et al

in Delaye, Ph; Denz, C.; Mager, L. (Eds.) Photorefractive Effects, Materials, and Devices (2003, June)

BSO crystals are excellent recording media for use in the holographic instrument of a multiple diagnostic instrument (Fluid Science Laboratory), for monitoring fluid phenomena onboard the ISS. Some ... [more ▼]

BSO crystals are excellent recording media for use in the holographic instrument of a multiple diagnostic instrument (Fluid Science Laboratory), for monitoring fluid phenomena onboard the ISS. Some experiments have been already presented that showed the potentiality of BSO for this kind of application. Here we present the crystals qualification for use within FSL with respect to gamma rays and protons radiations [less ▲]

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See detailStudy and comparison of multibeam photorefractive recordings and photorefractive crystals stack to holographic interferometry
Thizy, Cédric ULg; Georges, Marc ULg; Scauflaire, V. et al

in Delaye, Ph; Denz, C.; Mager, L. (Eds.) Photorefractive Effects, Materials, and Devices (2003)

Two techniques with the common objective to integrate multiple view holographic interferometry in one optical head are presented: multi recordings in a photorefractive BSO crystal and the use of a series ... [more ▼]

Two techniques with the common objective to integrate multiple view holographic interferometry in one optical head are presented: multi recordings in a photorefractive BSO crystal and the use of a series of BSO crystals as the recording medium. After a description of the principles we will show their application to holographic interferometry. The results will be presented and a comparison of the two methods, based on the quality of the interferograms, will be performed, showing the respective advantages and limitations of each technique compared to the other and to classical experiment of holographic interferometry. Up to four holograms have been recorded in one crystal, or two holograms in two crystals, corresponding to the four positions of illumination of the object [less ▲]

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See detailPhotorefractive ZnTe grown by traveling heater method
Verstraeten, David; Launay, Jean-Claude; Delaye, Philippe et al

in Trends in Optics and Photonics (2003), 87

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