Guy Le Brun - Profile on Academia.edu (original) (raw)
Papers by Guy Le Brun
Applied Optics, 2014
In this paper, we report a study where a laser biospeckle technique is used to detect the climact... more In this paper, we report a study where a laser biospeckle technique is used to detect the climacteric peak indicating the optimal ripeness of fruits. We monitor two batches of harvested Golden apples going through the ripening phase in low and room temperature environments, determine speckle parameters, and measure the emitted ethylene concentration using gas chromatography chosen as reference method. Speckle results are then correlated to the emitted ethylene concentration by a principal component analysis. From a practical point of view, this approach allows us to validate biospeckle as a non-invasive and an alternative method to respiration rate and ethylene production for the climacteric peak detection as a ripening index.
Le speckle pour mesurer la maturité des fruits climactériques
Photoniques, 2016
Evaluation of low viscosity variations in fluids using temporal and spatial analysis of the speckle pattern
Optics Letters, 2016
The noninvasive detection of a material&a... more The noninvasive detection of a material's viscoelasticity is of great importance in the medical field. In fact, certain diseases cause changes in tissue structure and biological fluid viscosity; tracking those changes allows for detection of these diseases. Rheological measurements are also imperative in the industrial field, where it is necessary to characterize a material's viscoelasticity for manufacturing purposes. In this Letter, we present a noncontact, noninvasive, and low cost method for determining low viscosity values and variations in fluids. Laser speckle and viscometric measurements are performed on test samples having low scattering coefficients and low viscosities. The speckle spatial analysis proved to be as accurate as the speckle temporal correlation method reported in previous studies. Very low viscosities of the order of 1 mPa.s were retrieved for the first time using speckle images with either a frame rate of 1950 fps or a single acquired image.
Influence of size, proportion, and absorption coefficient of spherical scatterers on the degree of light polarization and the grain size of speckle pattern
Applied Optics, 2015
In this paper, we present the evolution of speckle pattern polarimetric parameters in response to... more In this paper, we present the evolution of speckle pattern polarimetric parameters in response to controlled changes in scatterer sizes, proportions, and the absorption coefficient in media. The experimental study was performed on mixtures of polystyrene microspheres with dye in order to ensure biological medium-like properties. The speckle grain sizes and degrees of polarization for linear and circular light were monitored. We observed helicity flipping in the degree of circular polarization for small scatterer proportion around 25%. Furthermore, linear depolarization decreased slightly for media containing more small particles. Good agreement was shown with numerical results computed using a Monte Carlo simulation of polarized light taking into account our experimental configuration. Speckle grain size also evolves with the increase of small scatterers as well as the media absorption coefficient. Such variations of properties are encountered during fruit maturation, in tissues in precancerous stages, and any transformation that causes a modification in particle proportions and absorption coefficient in biological media. The computed parameters proved to be sensitive to these changes.
Early diagnosis of teeth erosion using polarized laser speckle imaging
Journal of Biomedical Optics, 2015
Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, alt... more Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, altering the tooth structure and making it more sensitive to mechanical erosion. Medical diagnosis of dental erosion is commonly achieved through a visual inspection by the dentist during dental checkups and is therefore highly dependent on the operator's experience. The detection of this disease at preliminary stages is important since, once the damage is done, cares become more complicated. We investigate the difference in light-scattering properties between healthy and eroded teeth. A change in light-scattering properties is observed and a transition from volume to surface backscattering is detected by means of polarized laser speckle imaging as teeth undergo acid etching, suggesting an increase in enamel surface roughness.
Optics Communications, 2007
Polarization measurements 70 days after irradiation of a living pig allowed us to distinguish bet... more Polarization measurements 70 days after irradiation of a living pig allowed us to distinguish between a healthy skin sample and a 15 Gy-or 20 Gy-irradiated one. In this way, polarization characteristics based on Mueller's matrix formalism for depolarizing media such as biological tissues can be analyzed via the entropy factor. But, in the case of a weakly-anisotropic depolarization like the one observed with cobalt-irradiated samples of skin, such an analysis is no longer applicable. We show, here, that another parameter called the polarization memory rate can highlight a quantitative evolution in the depolarization anisotropy of the irradiated samples under study. This potentially provides an interesting insight into the differences between the scattering properties of tissues and tissues phantoms.
Methodology for in situ laser-induced fluorescence spectral analysis: application to macroalgae recognition
Conference Digest. 2000 Conference on Lasers and Electro-Optics Europe (Cat. No.00TH8505), 2000
ABSTRACT Summary form only given. Finding an accurate and simple methodology to map the deep-sea ... more ABSTRACT Summary form only given. Finding an accurate and simple methodology to map the deep-sea macroalgae in the West Channel and West Brittany zones are of high interest to evaluate and survey the ecological and economical diversity of the seabed. Nowadays, only emerged or shallow-water macroalgae can be efficiently monitored by passive teledetection techniques based on the spectral analysis of their reflectance, whereas the deep-sea macroalgae are shaded by the water surface. This has led us to propose an in situ monitoring of the seabed using an active spectral methodology based on fluorescence imaging
Real-time monitoring of corks' water absorption using laser speckle temporal correlation
SPECKLE 2015: VI International Conference on Speckle Metrology, 2015
Analysis of the speckle pattern produced by mixtures of polystyrene microspheres: an attempt to explain fruits ripening process
SPECKLE 2015: VI International Conference on Speckle Metrology, 2015
Mueller matrix decomposition for biological tissue analysis
Optics Communications, 2013
ABSTRACT This study deals with the polarimetric characterization of biological tissues based on t... more ABSTRACT This study deals with the polarimetric characterization of biological tissues based on the Stokes–Mueller formalism. The optimal experimental conditions to study irradiated pig skin samples are analyzed. Two Mueller matrix decomposition techniques, the one developed by Lu and Chipman and the other by Ossikovski, are used. These decompositions allow identification of useful factors such as retardance, diattenuation and depolarization for differentiating between various levels of irradiation and for better interpreting the behavior of the skin with respect to irradiation.
Characterization of Bacillus thuringiensis parasporal crystals using laser speckle technique: effect of crystal concentration and dimension
Applied Optics, 2015
ABSTRACT In this paper, we report experimental results where laser speckle grain size and degree ... more ABSTRACT In this paper, we report experimental results where laser speckle grain size and degree of light polarization are used to distinguish different sizes of Bacillus thuringiensis spherical crystals and different concentration within fermentation products. Three strains of Bacillus thuringiensis, isolated from the Lebanese soil, are selected. After fermentation, crystals and spores are separated using a technique based on flotation in order to obtain large quantities of relatively pure crystals. Crystals are then embedded in an agarose matrix gel and illuminated by a laser. Speckle patterns are recorded and analyzed. Results show that when crystals concentrations increase in the sample, the values of light linear polarization degree and speckle grain size decrease, and the negative values of light circular polarization degree increase. A transition from a Rayleigh scattering regime to a Mie regime is also observed. Furthermore, when the diameter of spherical crystal increases, the normalized value of light linear polarization degree and the grain size diminish drastically for a given concentration of crystals in the matrix, whereas the normalized value of light circular polarization degree increases. This optical characterization constitutes an unambiguous signature of spherical crystals produced by fermentations of different Bacillus thuringiensis strains and shows that speckle may potentially be used at an industrial scale as a low-cost and non-invasive technique in order to characterize crystals geometry and to evaluate the yield of crystal production within fermentation.
Detection and Remediation Technologies for Mines and Minelike Targets II, 1997
ABSTRACT Detecting and identifying targets immersed in draught zone are necessary for a safe navi... more ABSTRACT Detecting and identifying targets immersed in draught zone are necessary for a safe navigation. But with today technologies it is very difficult to do it from a ship. Nowadays, this detection still stays a challenge, because sonars are inefficient in the zone just under the waterline. In our laboratory we succeeded in using lidar as a complementary tool of the sonar. With optical detection, active imagery, various immersed targets were detected, identified and classified according to a Mueller matrix and whatever the perturbations on the sea surface and the wind conditions. The possibility of using a particular polarimetric codage with optical signal is discussed in this paper. The aim was to demonstrate that our lidar tool can be improved by choosing the best polarimetric couple in emission and detection. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
Optics express, Jan 27, 2005
This report about backscattering measure-ments of the speckle produced by strongly-scattering liq... more This report about backscattering measure-ments of the speckle produced by strongly-scattering liquid media shows that the size of the backscattered speckle depends on scattering and anisotropy coefficients. These measurements were aimed at assessing the effects of polarization characteristics of the incident laser beam and of the scattered light on speckle size. The samples under study consisted of monodisperse polystyrene microspheres in solutions, mixtures of different sized-microspheres, milk, blood and pig skin. Such measurements of speckle size in polarization give information on strongly scattering media, allow their discrimination and enable one to characterize the undergone changes.
Speckle06: Speckles, From Grains to Flowers, 2006
ABSTRACT The investigation of the speckle fields obtained from biological fluids or tissues, can ... more ABSTRACT The investigation of the speckle fields obtained from biological fluids or tissues, can be used in medical applications, as an experimental non invasive method to get informations using low cost and low energy lasers. We give a few examples concerning the application of speckle and polarization analysis in the investigation of blood coagulation, platelets aggregation and deterioration of skin by gamma radiation.
Polarization and Remote Sensing, 1992
ABSTRACT Polarimetry has become an indispensable analysis tool, in remote sensing as well as in r... more ABSTRACT Polarimetry has become an indispensable analysis tool, in remote sensing as well as in radar metrology. In the same way, it is possible to characterize immersed targets illuminated by a laser beam, by using signal polarization. Here our purpose is to discriminate them in relation with their depolarizing and diffusing properties. Using the Stokes-Mueller formalism and Gil- Bernabeu depolarization criterion, we have synthesized two different types of images from which we build analysis methods. In this paper, we present different results for some characteristic samples.
Analysis of experimental depolarizing Mueller matrices through a hybrid decomposition
Applied Optics, 2014
We propose a new decomposition for depolarizing Mueller matrices. This decomposition, which consi... more We propose a new decomposition for depolarizing Mueller matrices. This decomposition, which consists of a product of four basic optical devices (two diattenuators, a retarder, and a depolarizer) is derived from a previous one known as "symmetric decomposition" [J. Opt. Soc. Am. A26, 1109 (2009)10.1364/JOSAA.26.001109JOAOD61084-7529] and makes it easier to interpret polarization properties of Mueller matrices and improves estimation of the extracted parameters. Its application is illustrated by several theoretical and experimental examples.
Optical Coherence Tomography and Coherence Techniques II, 2005
ABSTRACT We report on the use, in an Optical Coherence Tomography system, of a shaker with a freq... more ABSTRACT We report on the use, in an Optical Coherence Tomography system, of a shaker with a frequency-modulated driving waveform to avoid non-linearities. The device permits to modulate the interferometric signal simply by the displacing the shaker and to recover the OCT signal in depth.
Laser speckle dynamic for monitoring fruits maturation
Speckle 2012: V International Conference on Speckle Metrology, 2012
Characterisation of porous silicon composite material by spectroscopic ellipsometry
Thin Solid Films, 2004
Porous silicon materials are currently under intense investigation for optoelectronic application... more Porous silicon materials are currently under intense investigation for optoelectronic applications. Spectroscopic ellipsometry (SE) was used to study the optical properties of layers of composite material composed by porous silicon and disperse red one (a red dye ...
physica status solidi (c), 2005
Composite porous silica-DR1 films were obtained and have been analysed before and after poling by... more Composite porous silica-DR1 films were obtained and have been analysed before and after poling by a static electric field. Spectroscopic ellipsometry was used to study the optical properties of layers of these composite material in the UV-IR spectral range (0.75-4.5 eV). Second harmonic generation was performed in the near-infrared spectral range. Preferential alignment of the dye molecules parallel to the pores perpendicular to the surface was shown by second harmonic generation experiments after the poling treatment. Increasing of the absorption and of the dichroïsm were also observed by spectroscopic ellipsometry analysis.
Applied Optics, 2014
In this paper, we report a study where a laser biospeckle technique is used to detect the climact... more In this paper, we report a study where a laser biospeckle technique is used to detect the climacteric peak indicating the optimal ripeness of fruits. We monitor two batches of harvested Golden apples going through the ripening phase in low and room temperature environments, determine speckle parameters, and measure the emitted ethylene concentration using gas chromatography chosen as reference method. Speckle results are then correlated to the emitted ethylene concentration by a principal component analysis. From a practical point of view, this approach allows us to validate biospeckle as a non-invasive and an alternative method to respiration rate and ethylene production for the climacteric peak detection as a ripening index.
Le speckle pour mesurer la maturité des fruits climactériques
Photoniques, 2016
Evaluation of low viscosity variations in fluids using temporal and spatial analysis of the speckle pattern
Optics Letters, 2016
The noninvasive detection of a material&a... more The noninvasive detection of a material's viscoelasticity is of great importance in the medical field. In fact, certain diseases cause changes in tissue structure and biological fluid viscosity; tracking those changes allows for detection of these diseases. Rheological measurements are also imperative in the industrial field, where it is necessary to characterize a material's viscoelasticity for manufacturing purposes. In this Letter, we present a noncontact, noninvasive, and low cost method for determining low viscosity values and variations in fluids. Laser speckle and viscometric measurements are performed on test samples having low scattering coefficients and low viscosities. The speckle spatial analysis proved to be as accurate as the speckle temporal correlation method reported in previous studies. Very low viscosities of the order of 1 mPa.s were retrieved for the first time using speckle images with either a frame rate of 1950 fps or a single acquired image.
Influence of size, proportion, and absorption coefficient of spherical scatterers on the degree of light polarization and the grain size of speckle pattern
Applied Optics, 2015
In this paper, we present the evolution of speckle pattern polarimetric parameters in response to... more In this paper, we present the evolution of speckle pattern polarimetric parameters in response to controlled changes in scatterer sizes, proportions, and the absorption coefficient in media. The experimental study was performed on mixtures of polystyrene microspheres with dye in order to ensure biological medium-like properties. The speckle grain sizes and degrees of polarization for linear and circular light were monitored. We observed helicity flipping in the degree of circular polarization for small scatterer proportion around 25%. Furthermore, linear depolarization decreased slightly for media containing more small particles. Good agreement was shown with numerical results computed using a Monte Carlo simulation of polarized light taking into account our experimental configuration. Speckle grain size also evolves with the increase of small scatterers as well as the media absorption coefficient. Such variations of properties are encountered during fruit maturation, in tissues in precancerous stages, and any transformation that causes a modification in particle proportions and absorption coefficient in biological media. The computed parameters proved to be sensitive to these changes.
Early diagnosis of teeth erosion using polarized laser speckle imaging
Journal of Biomedical Optics, 2015
Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, alt... more Dental erosion starts with a chemical attack on dental tissue causing tooth demineralization, altering the tooth structure and making it more sensitive to mechanical erosion. Medical diagnosis of dental erosion is commonly achieved through a visual inspection by the dentist during dental checkups and is therefore highly dependent on the operator's experience. The detection of this disease at preliminary stages is important since, once the damage is done, cares become more complicated. We investigate the difference in light-scattering properties between healthy and eroded teeth. A change in light-scattering properties is observed and a transition from volume to surface backscattering is detected by means of polarized laser speckle imaging as teeth undergo acid etching, suggesting an increase in enamel surface roughness.
Optics Communications, 2007
Polarization measurements 70 days after irradiation of a living pig allowed us to distinguish bet... more Polarization measurements 70 days after irradiation of a living pig allowed us to distinguish between a healthy skin sample and a 15 Gy-or 20 Gy-irradiated one. In this way, polarization characteristics based on Mueller's matrix formalism for depolarizing media such as biological tissues can be analyzed via the entropy factor. But, in the case of a weakly-anisotropic depolarization like the one observed with cobalt-irradiated samples of skin, such an analysis is no longer applicable. We show, here, that another parameter called the polarization memory rate can highlight a quantitative evolution in the depolarization anisotropy of the irradiated samples under study. This potentially provides an interesting insight into the differences between the scattering properties of tissues and tissues phantoms.
Methodology for in situ laser-induced fluorescence spectral analysis: application to macroalgae recognition
Conference Digest. 2000 Conference on Lasers and Electro-Optics Europe (Cat. No.00TH8505), 2000
ABSTRACT Summary form only given. Finding an accurate and simple methodology to map the deep-sea ... more ABSTRACT Summary form only given. Finding an accurate and simple methodology to map the deep-sea macroalgae in the West Channel and West Brittany zones are of high interest to evaluate and survey the ecological and economical diversity of the seabed. Nowadays, only emerged or shallow-water macroalgae can be efficiently monitored by passive teledetection techniques based on the spectral analysis of their reflectance, whereas the deep-sea macroalgae are shaded by the water surface. This has led us to propose an in situ monitoring of the seabed using an active spectral methodology based on fluorescence imaging
Real-time monitoring of corks' water absorption using laser speckle temporal correlation
SPECKLE 2015: VI International Conference on Speckle Metrology, 2015
Analysis of the speckle pattern produced by mixtures of polystyrene microspheres: an attempt to explain fruits ripening process
SPECKLE 2015: VI International Conference on Speckle Metrology, 2015
Mueller matrix decomposition for biological tissue analysis
Optics Communications, 2013
ABSTRACT This study deals with the polarimetric characterization of biological tissues based on t... more ABSTRACT This study deals with the polarimetric characterization of biological tissues based on the Stokes–Mueller formalism. The optimal experimental conditions to study irradiated pig skin samples are analyzed. Two Mueller matrix decomposition techniques, the one developed by Lu and Chipman and the other by Ossikovski, are used. These decompositions allow identification of useful factors such as retardance, diattenuation and depolarization for differentiating between various levels of irradiation and for better interpreting the behavior of the skin with respect to irradiation.
Characterization of Bacillus thuringiensis parasporal crystals using laser speckle technique: effect of crystal concentration and dimension
Applied Optics, 2015
ABSTRACT In this paper, we report experimental results where laser speckle grain size and degree ... more ABSTRACT In this paper, we report experimental results where laser speckle grain size and degree of light polarization are used to distinguish different sizes of Bacillus thuringiensis spherical crystals and different concentration within fermentation products. Three strains of Bacillus thuringiensis, isolated from the Lebanese soil, are selected. After fermentation, crystals and spores are separated using a technique based on flotation in order to obtain large quantities of relatively pure crystals. Crystals are then embedded in an agarose matrix gel and illuminated by a laser. Speckle patterns are recorded and analyzed. Results show that when crystals concentrations increase in the sample, the values of light linear polarization degree and speckle grain size decrease, and the negative values of light circular polarization degree increase. A transition from a Rayleigh scattering regime to a Mie regime is also observed. Furthermore, when the diameter of spherical crystal increases, the normalized value of light linear polarization degree and the grain size diminish drastically for a given concentration of crystals in the matrix, whereas the normalized value of light circular polarization degree increases. This optical characterization constitutes an unambiguous signature of spherical crystals produced by fermentations of different Bacillus thuringiensis strains and shows that speckle may potentially be used at an industrial scale as a low-cost and non-invasive technique in order to characterize crystals geometry and to evaluate the yield of crystal production within fermentation.
Detection and Remediation Technologies for Mines and Minelike Targets II, 1997
ABSTRACT Detecting and identifying targets immersed in draught zone are necessary for a safe navi... more ABSTRACT Detecting and identifying targets immersed in draught zone are necessary for a safe navigation. But with today technologies it is very difficult to do it from a ship. Nowadays, this detection still stays a challenge, because sonars are inefficient in the zone just under the waterline. In our laboratory we succeeded in using lidar as a complementary tool of the sonar. With optical detection, active imagery, various immersed targets were detected, identified and classified according to a Mueller matrix and whatever the perturbations on the sea surface and the wind conditions. The possibility of using a particular polarimetric codage with optical signal is discussed in this paper. The aim was to demonstrate that our lidar tool can be improved by choosing the best polarimetric couple in emission and detection. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
Optics express, Jan 27, 2005
This report about backscattering measure-ments of the speckle produced by strongly-scattering liq... more This report about backscattering measure-ments of the speckle produced by strongly-scattering liquid media shows that the size of the backscattered speckle depends on scattering and anisotropy coefficients. These measurements were aimed at assessing the effects of polarization characteristics of the incident laser beam and of the scattered light on speckle size. The samples under study consisted of monodisperse polystyrene microspheres in solutions, mixtures of different sized-microspheres, milk, blood and pig skin. Such measurements of speckle size in polarization give information on strongly scattering media, allow their discrimination and enable one to characterize the undergone changes.
Speckle06: Speckles, From Grains to Flowers, 2006
ABSTRACT The investigation of the speckle fields obtained from biological fluids or tissues, can ... more ABSTRACT The investigation of the speckle fields obtained from biological fluids or tissues, can be used in medical applications, as an experimental non invasive method to get informations using low cost and low energy lasers. We give a few examples concerning the application of speckle and polarization analysis in the investigation of blood coagulation, platelets aggregation and deterioration of skin by gamma radiation.
Polarization and Remote Sensing, 1992
ABSTRACT Polarimetry has become an indispensable analysis tool, in remote sensing as well as in r... more ABSTRACT Polarimetry has become an indispensable analysis tool, in remote sensing as well as in radar metrology. In the same way, it is possible to characterize immersed targets illuminated by a laser beam, by using signal polarization. Here our purpose is to discriminate them in relation with their depolarizing and diffusing properties. Using the Stokes-Mueller formalism and Gil- Bernabeu depolarization criterion, we have synthesized two different types of images from which we build analysis methods. In this paper, we present different results for some characteristic samples.
Analysis of experimental depolarizing Mueller matrices through a hybrid decomposition
Applied Optics, 2014
We propose a new decomposition for depolarizing Mueller matrices. This decomposition, which consi... more We propose a new decomposition for depolarizing Mueller matrices. This decomposition, which consists of a product of four basic optical devices (two diattenuators, a retarder, and a depolarizer) is derived from a previous one known as "symmetric decomposition" [J. Opt. Soc. Am. A26, 1109 (2009)10.1364/JOSAA.26.001109JOAOD61084-7529] and makes it easier to interpret polarization properties of Mueller matrices and improves estimation of the extracted parameters. Its application is illustrated by several theoretical and experimental examples.
Optical Coherence Tomography and Coherence Techniques II, 2005
ABSTRACT We report on the use, in an Optical Coherence Tomography system, of a shaker with a freq... more ABSTRACT We report on the use, in an Optical Coherence Tomography system, of a shaker with a frequency-modulated driving waveform to avoid non-linearities. The device permits to modulate the interferometric signal simply by the displacing the shaker and to recover the OCT signal in depth.
Laser speckle dynamic for monitoring fruits maturation
Speckle 2012: V International Conference on Speckle Metrology, 2012
Characterisation of porous silicon composite material by spectroscopic ellipsometry
Thin Solid Films, 2004
Porous silicon materials are currently under intense investigation for optoelectronic application... more Porous silicon materials are currently under intense investigation for optoelectronic applications. Spectroscopic ellipsometry (SE) was used to study the optical properties of layers of composite material composed by porous silicon and disperse red one (a red dye ...
physica status solidi (c), 2005
Composite porous silica-DR1 films were obtained and have been analysed before and after poling by... more Composite porous silica-DR1 films were obtained and have been analysed before and after poling by a static electric field. Spectroscopic ellipsometry was used to study the optical properties of layers of these composite material in the UV-IR spectral range (0.75-4.5 eV). Second harmonic generation was performed in the near-infrared spectral range. Preferential alignment of the dye molecules parallel to the pores perpendicular to the surface was shown by second harmonic generation experiments after the poling treatment. Increasing of the absorption and of the dichroïsm were also observed by spectroscopic ellipsometry analysis.