References of "Blain, Pascal"
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See detailSpectral splitting planar solar concentrator : Design and Experimental testing Preliminary results
Blain, Pascal ULg; Michel, Céline ULg; Clermont, Lionel ULg et al

in Proceedings of SPIE (2014, May 15), 9140

We present a new concept in solar concentrator: spectral splitting. It implies reflective, refractive and diffractive elements that allow two spectrally differentiated beams to reach different and/or ... [more ▼]

We present a new concept in solar concentrator: spectral splitting. It implies reflective, refractive and diffractive elements that allow two spectrally differentiated beams to reach different and/or unmatched lattice solar cells. Those cells efficiencies are then enhanced. The aimed geometrical concentration factor is 5× and the theoretical optical efficiency of that concentrator concept reaches 82%. [less ▲]

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See detailFirst prototypes of vortex retarders obtained by polarization holography
Piron, Pierre ULg; Blain, Pascal ULg; Décultot, Marc ULg et al

in Proceedings of SPIE (2014, May), 9099

This paper will present the first prototypes of vortex retarders made of photo-orientable liquid crystals polymers recorded without mechanical action using only polarization holography. Vortex retarders ... [more ▼]

This paper will present the first prototypes of vortex retarders made of photo-orientable liquid crystals polymers recorded without mechanical action using only polarization holography. Vortex retarders are birefringent plates characterized by a uniform phase retard and a rotation of their fast axis along their center. Liquid crystals are anisotropic molecules possessing birefringent properties. They are locally orientable and their orientation defines the fast axis orientation of the retarder. Their alignment depends on the local orientation of the recording electric field. The superimposition of several polarized beams will be used to shape the electric field to achieve the recording of vortex retarders. The mathematical aspects of the superimposition process, as well as several numerical simulations are exposed. Finally, the first prototypes are presented, characterized and compared to the numerical simulations. [less ▲]

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See detailÉléments optiques biréfringents pour interféromètre à chemins optiques quasi-communs
Blain, Pascal ULg

Doctoral thesis (2014)

Notre étude porte sur l’utilisation de composants optiques biréfringents en tant qu’élément séparateur dans un interféromètre à chemins optiques communs ou quasi-communs. Pour ce type d’interféromètre, la ... [more ▼]

Notre étude porte sur l’utilisation de composants optiques biréfringents en tant qu’élément séparateur dans un interféromètre à chemins optiques communs ou quasi-communs. Pour ce type d’interféromètre, la seule différence introduite dans les chemins optiques des faisceaux objet et de référence est celle résultant du relief de la surface testée. Utiliser un élément biréfringent permet de n’avoir qu’un seul élément pour créer les faisceaux référence et objet. On parle d’auto-référencement. Cette propriété désensibilise l’interféromètre vis-à-vis de certaines perturbations extérieures car les faisceaux sont identiquement affectés par celles-ci. La biréfringence des cristaux étant bien souvent faible mais l’interféromètre à construire devant être le plus compact possible, le cisaillement entre les deux faisceaux s’en retrouve faible comparé à la taille de l’objet observé. Une séparation totale des faisceaux émergents n’est possible qu’avec un faisceau « ponctuel » collimaté. La configuration des interféromètres que nous étudierons sera donc différentielle. Deux types d’éléments biréfringents sont étudiés. Le premier est un assemblage de deux cristaux uniaxes taillés à 45° et dont l’orientation de l’axe de l’un des cristaux est tournée à 90° par rapport à celle de l’autre. Il s’agit de la lame de Savart. Les propriétés de cette lame sont détaillées pour justifier l’intérêt de son utilisation dans l’interféromètre. Ce dernier a été utilisé en shearographie et en profilométrie par projection de franges interférométriques. Une installation originale permet l’association des deux méthodes dans un unique montage compact. Dans la configuration proposée, seule l’orientation du cisaillement par l’interféromètre est possible. Pour faire varier la taille du cisaillement, nous avons décidé d’évoluer vers un autre type d’élément biréfringent. L’essor des éléments optiques à biréfringence spatialement variable nous a incités à investiguer cette voie. Ces éléments ont la particularité de permettre une variation spatiale de l’orientation de l’axe optique. Les réseaux de polarisation font partie de cette famille. Après avoir décrit et simulé leur comportement, nous proposons notre propre méthode d’enregistrement de tels réseaux par holographie de polarisation à l’aide d’une lame de Savart. Nous prouvons par la suite que deux réseaux de polarisation circulaire de même orientation et disposés l’un à la suite de l’autre créent un élément séparateur à taille et orientation de cisaillement variables pour un interféromètre à chemins optiques quasi-communs. Nous proposons une application en shearographie. [less ▲]

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See detailPolarization holography for vortex retarders recording
Piron, Pierre ULg; Blain, Pascal ULg; Mawet, Dimitri et al

in Applied Optics (2013), 52(28), 7040-7048

We present an original static recording method for vortex retarders (VRs) made from liquid crystal polymers (LCPs) using the superimposition of several polarized beams. VRs are birefringent plates ... [more ▼]

We present an original static recording method for vortex retarders (VRs) made from liquid crystal polymers (LCPs) using the superimposition of several polarized beams. VRs are birefringent plates characterized by a rotation of their fast axis about their center. The new method is based on polarization holography and photo-orientable LCP. Combining several polarized beams induces the polarization patterns required for the recording process of VRs without mechanical action. A mathematical description of the method, the outcomes of the numerical simulations, and the first experimental results are presented. [less ▲]

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See detailCombining shearography and interferometric fringe projection in a single device for complete control of industrial applications
Blain, Pascal ULg; Michel, Fabrice; Piron, Pierre ULg et al

in Optical Engineering : The Journal of the Society of Photo-Optical Instrumentation Engineers (2013), 52(8), 0841021-7

Non-contact optical measurement methods are essential tools in many industrial and research domains. A family of new non-contact optical measurement methods based on the polarization states splitting ... [more ▼]

Non-contact optical measurement methods are essential tools in many industrial and research domains. A family of new non-contact optical measurement methods based on the polarization states splitting technique and monochromatic light projection as a way to overcome ambient lighting for in-situ measurement has been developed. Recent works on a birefringent element, a Savart plate, allow to build a more flexible and robust interferometer. This interferometer is a multipurpose metrological device. On one hand the interferometer can be set in front of a CCD camera. This optical measurement system is called a shearography interferometer and allows to measure micro displacements between two states of the studied object under coherent lighting. On the other hand by producing and shifting multiple sinusoidal Young’s interference patterns with this interferometer, and using a CCD camera, it is possible to build a 3D structured light profilometer. [less ▲]

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See detailAn in-line shearography setup based on circular polarization gratings
Blain, Pascal ULg; Piron, Pierre ULg; Renotte, Yvon ULg et al

in Optics & Lasers in Engineering (2013)

The shearing amount defines the resolution of a speckle shearing interferometer and the shearing direction defines the sensitivity direction of the setup. The properties of circular (cycloid) holographic ... [more ▼]

The shearing amount defines the resolution of a speckle shearing interferometer and the shearing direction defines the sensitivity direction of the setup. The properties of circular (cycloid) holographic polarization gratings recorded in liquid crystal polymers can be used to build a new multi-shearing direction and amount shearography setup. The polarization states of the diffracted beams offer an easy way to produce phase shifts and thus to compute the phase contained in the shearograms. The theoretical bases of such a device are highlighted and an original compact and full in-line setup is proposed. First experimental results of delamination detection and flaw detection by shearography are presented. A discussion on the importance of the grating recording and the polarization orientation points out the best working requirements. [less ▲]

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See detailPolarization Holography with liquid crystals polymers and applications
Piron, Pierre ULg; Blain, Pascal ULg; Habraken, Serge ULg et al

Conference (2012, December 10)

Liquid Crystals Polymers are birefringent molecules locally orientable. By recording the polarization pattern due to the overlap of differently polarized beams on LCP, space-variant retarders are realized ... [more ▼]

Liquid Crystals Polymers are birefringent molecules locally orientable. By recording the polarization pattern due to the overlap of differently polarized beams on LCP, space-variant retarders are realized. We present two applications polarization holography and coronagraphy [less ▲]

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See detailPolarization Holography with liquid crystals polymers and applications
Piron, Pierre ULg; Blain, Pascal ULg; Habraken, Serge ULg et al

in International Conference on Fibre Optics and Photonics (2012, December)

Liquid Crystals Polymers are birefringent molecules locally orientable. By recording the polarization pattern due to the overlap of differently polarized beams on LCP, space-variant retarders are realized ... [more ▼]

Liquid Crystals Polymers are birefringent molecules locally orientable. By recording the polarization pattern due to the overlap of differently polarized beams on LCP, space-variant retarders are realized. We present two applications polarization holography and coronagraphy. [less ▲]

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See detailCarrier and aberrations removal in interferometric fringe projection profilometry
Blain, Pascal ULg; Michel, Fabrice; Renotte, Yvon ULg et al

in Gorecki, Christophe; Asundi, Anand K.; Osten, Wolfgang (Eds.) Optical Micro- and Nanometrology IV (SPIE proceedings vol.8430) (2012, April 17)

A profilometer which takes advantage of polarization states splitting technique and monochromatic light projection method as a way to overcome ambient lighting for in-situ measurement is under development ... [more ▼]

A profilometer which takes advantage of polarization states splitting technique and monochromatic light projection method as a way to overcome ambient lighting for in-situ measurement is under development [1, 2]. Because of the Savart plate which refracts two out of axis beams, the device suffers from aberrations (mostly coma and astigmatism). These aberrations affect the quality of the sinusoidal fringe pattern. In fringe projection profilometry, the unwrapped phase distribution map contains the sum of the object’s shape-related phase and carrier-fringe-related phase. In order to extract the 3D shape of the object, the carrier phase has to be removed [3, 4]. An easy way to remove both the fringe carrier and the aberrations of the optical system is to measure the phases of the test object and to measure the phase of a reference plane with the same set up and to subtract both phase maps. This time consuming technique is suitable for laboratory but not for industry. We propose a method to numerically remove both the fringe carrier and the aberrations. A first reference phase of a calibration plane is evaluated knowing the position of the different elements in the set up and the orientation of the fringes. Then a fitting of the phase map by Zernike polynomials is computed [5]. As the triangulation parameters are known during the calibration, the computation of Zernike coefficients has only to be made once. The wavefront error can be adjusted by a scale factor which depends on the position of the test object. [less ▲]

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See detailVirtual Leodium - vidéo de présentation
Billen, Roland ULg; Carré, Cyril ULg; Van Ruymbeke, Muriel ULg et al

Diverse speeche and writing (2011)

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See detailPolarization measurement with space-variant retarders in liquid crystal polymers
Piron, Pierre ULg; Blain, Pascal ULg; Habraken, Serge ULg

in SPIE proceedings 8160, SPIE Optics +Photonics 2011 San Diego (2011)

We present a real-time polarization measurement method with a space-variant phase retarder in liquid crystal polymers. This retarder presents a continuous and periodical variation of its optical axis ... [more ▼]

We present a real-time polarization measurement method with a space-variant phase retarder in liquid crystal polymers. This retarder presents a continuous and periodical variation of its optical axis orientation. The method computes the Stokes parameters of an incident beam by studying the intensity distribution after the retarder and a linear polarizer. This paper contains the mathematical modelization, the numerical simulation, the description of the experimental setup, the results for several completely polarized beams and the future developments of this method. [less ▲]

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See detailApplication of shearography to crack detection in concrete structures subjected to traffic loading
Muzet, Valérie; Blain, Pascal ULg; Przybyla, David

in Armando Albertazzi, Armando Jr.; Kaufmann, Guillermo H. (Eds.) Speckle 2010: Optical Metrology (2010, September 13)

Early detection of defects in concrete structures, such as bridges or dams, is essential to optimize the maintenance of civil engineering facilities. Optical methods constitute non-destructive means of ... [more ▼]

Early detection of defects in concrete structures, such as bridges or dams, is essential to optimize the maintenance of civil engineering facilities. Optical methods constitute non-destructive means of control and measurement but they are generally confined in laboratories where both the setup and environnement are controlled. The method of shearography is especially well adapted to detect damages due to both its capacity to distinctly visualize strain concentration zones and its robustness. The experimental set-up is relatively compact, which enables to examine an extensive surface area by simply moving the shearographic head. In this paper, the application of this methodology for the detection of cracks is presented on concrete samples and circulated outside concrete structures. Due to its sensitivity to strain concentration, shearography is able to detect structural cracks, even when they were not through-cracks. Operational implementation is made on two circulated structures with experts in manual cracks detection. No stimulation device is used. In the first structure, cracks are detected on the bridge deck and on the bridge abutment. In the second structure, cracks on the intrados of the bridge deck are detected and also beginning of cracks which have not been detected by the visual inspection. Different areas are scanned and the results are in agreement with the visual inspection. This technique enables detecting cracks on structures subjected to traffic load. The natural loading of an engineering structure, i.e. the rolling traffic it bears, proves well suited for cracks detection by means of shearography, provided traffic patterns are regular enough. [less ▲]

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See detailUsing a Savart plate in optical metrology
Blain, Pascal ULg; Michel, Fabrice ULg; Renotte, Yvon ULg et al

in Proceedings of SPIE (2010, August), 7791

Non-contact optical measurement methods are essential tools in many industrial and research domains. A family of new non-contact optical measurement methods based on the polarization states splitting ... [more ▼]

Non-contact optical measurement methods are essential tools in many industrial and research domains. A family of new non-contact optical measurement methods based on the polarization states splitting technique and monochromatic light projection as a way to overcome ambient lighting for in-situ measurement has been developed1,2. Recent works3 on a birefringent element, a Savart plate, allow to build a more flexible and robust interferometer. This interferometer is a multipurpose metrological device. On one hand, the interferometer can be set in front of a CCD camera. This optical measurement system is called a shearography interferometer and allows to measure micro displacement between two states of the studied object under coherent lighting. On the other hand, by producing and shifting multiple sinusoidal Young’s interference patterns with this interferometer, and using a CCD camera, it is possible to build a 3D structured light profilometer. After giving the behavior of the Savart plate, an overview of the two devices will be given as well as their specifications and some applications. [less ▲]

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See detailComparison of Spectral Colorimetric Measurements vs. Color Pictures in Dermatology
Blain, Pascal ULg; Michel, Fabrice; Moreau, Vincent et al

Poster (2010, April 13)

We studied scars and wounds depths and surfaces thanks to our interferometric fringes projector 3D scanner1, 2. Color information of a wound indicates its deterioration level. That’s why the visual color ... [more ▼]

We studied scars and wounds depths and surfaces thanks to our interferometric fringes projector 3D scanner1, 2. Color information of a wound indicates its deterioration level. That’s why the visual color restitution, as realistic as possible, is a highly important parameter. Firstly our acquired 3D pictures were color mapped with an image recorded by a RGB camera. The results were not efficient enough. In order to improve our technique and provide more precise information, we add a spectral characterization to the set-up. Before adding the spectral information and a realistic color mapping to the 3D measurements, we evaluate the performances of colorimetric measurements. The tests have been made on mice with scars on their back. [less ▲]

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See detailVirtual Leodium
Billen, Roland ULg; Blain, Pascal ULg; Habraken, Serge ULg et al

Report (2010)

Detailed reference viewed: 89 (22 ULg)
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See detailContrer les effets du manque de lumière : La luminothérapie
Blain, Pascal ULg

Conference given outside the academic context (2009)

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See detailVirtual model of the city of Liège in the eighteen century - "Virtual Leodium"
Billen, Roland ULg; Blain, Pascal ULg; Donneau, Olivier ULg et al

in Verly, Jacques (Ed.) Proceedings of 3D Stereo MEDIA 2009, International 3D Stereo Film and Technology Festival (3D Stereo MEDIA), Liège, Belgium, 1-3 Dec. 2009. (2009, December 01)

Virtual Leodium is a project aiming to scan and digitize a master piece of the collection of the University of Liège, the historical model of the city of Liège around 1730 realised by Gustave Ruhl. The ... [more ▼]

Virtual Leodium is a project aiming to scan and digitize a master piece of the collection of the University of Liège, the historical model of the city of Liège around 1730 realised by Gustave Ruhl. The two main originalities of the approach are to use a projected-fringes scanning technique and to generate a geo-database as a support for archaeological information. This interdisciplinary project gathers physicists, geomaticians, librarians, and archaeologists. [less ▲]

Detailed reference viewed: 343 (87 ULg)