Olga Vilardell Conde - Academia.edu (original) (raw)

Papers by Olga Vilardell Conde

In welding processes, specially in those involved in critical applications, as the aerospace an a... more In welding processes, specially in those involved in critical applications, as the aerospace an automotive sectors, extensive non-destructive testing (NDT) is commonly used for quality assurance. Therefore, the possibility of avoiding those procedures by means of on-line, real-time monitoring techniques is of high interest. Several different approaches have been contemplated for the analysis of welding processes, from the measurement of the charge voltage induced by the plasma on the welding nozzle, to acoustic and imaging techniques. Spectroscopic analysis of the plasma emission spectrum is known to offer rich information about the process, allowing direct correlation between the weld quality and some plasma parameters. Despite its benefits, spectroscopic analysis exhibits the drawbacks of its high computational requirements and the difficulty of a non-invasive arrangement of the optical light-capturing system. In a previous paper a new spectroscopic technique allowing real-time full-spectroscopic analysis of arc welding processes, and, hence, detection of common defects in the weld seam, was presented. In this paper a welding monitoring sensor system in which the optical fiber capturing the light is embedded into the welding torch is presented. Several tests showing the feasibility of the proposed system are also presented.

Biomedical Applications of Light Scattering V, 2011

Multi-spectral spatially modulated light is used to guide localized spectroscopy of surgically re... more Multi-spectral spatially modulated light is used to guide localized spectroscopy of surgically resected tissues for cancer involvement. Modulated imaging rapidly quantifies near-infrared optical parameters with sub-millimeter resolution over the entire field for identification of residual disease in resected tissues. Suspicious lesions are further evaluated using a spectroscopy platform designed to image thick tissue samples at a spatial resolution sensitive to the diagnostic gold standard, pathology. MI employs a spatial frequency domain sampling and model-based analysis of the spatial modulation transfer function to interpret a tissue's absorption and scattering parameters at depth. The spectroscopy platform employs a scanning-beam, telecentric dark-field illumination and confocal detection to image fields up to 1cm 2 with a broadband source (480:750nm). The sampling spot size (100µm lateral resolution) confines the volume of tissue probed to within a few transport pathlengths so that multiple-scattering effects are minimized and simple empirical models may be used to analyze spectra. Localized spectroscopy of Intralipid and hemoglobin phantoms demonstrate insensitivity of recovered scattering parameters to changes in absorption, but a non-linear dependence of scattering power on Intralipid concentration is observed due to the phase sensitivity of the measurement system. Both systems were validated independently in phantom and murine studies. Ongoing work focuses on assessing the combined utility of these systems to identify cancer involvement in vitro, particularly in the margins of resected breast tumors.

Optical Design and Engineering, 2004

17th International Conference on Optical Fibre Sensors, Pts 1 and 2, 2005

2009 Ieee Sensors, Vols 1-3, 2009

A method for the automatic synthesis of the Ultraviolet-Visible-Near Infrared (UV-Vis-NIR) absorp... more A method for the automatic synthesis of the Ultraviolet-Visible-Near Infrared (UV-Vis-NIR) absorption and transmission spectra of dye mixtures based on the absorption characteristics of their individual dyes is proposed in this paper. Multiple Linear Regression models (MLR) of each dye are obtained using a fiber-optic set-up operating in the 200-1100 nm wavelength range. Textile dyes are thick and dense and, consequently, optically opaque. This gives rise to high absorbance values which do not permit the direct comparison of different textile dye spectra for quality assurance purposes. The proposed multivariate method allows to construct a general model adjusted to the number and concentration of the dyes in the mixture. Furthermore, this dye spectrum synthesis can provide the optimum dilution factor needed to compare two different dye mixtures and test their similarity degree. With the proposed system, the obtained spectral correlation coefficients between the measured and synthesized spectra of a dye mixture are greater than 99% for both the transmission and absorption spectra.

Clinical and Biomedical Spectroscopy, 2009

An automated algorithm and methodology is presented to pathologically classify the scattering cha... more An automated algorithm and methodology is presented to pathologically classify the scattering changes encountered in the raster scanning of normal and tumor pancreatic tissues using microsampling reflectance spectroscopy. A quasiconfocal reflectance imaging system was used to directly measure the tissue scatter reflectance in situ, and the spectrum was used to identify the scattering power, amplitude and total wavelength-integrated intensity. Pancreatic tumor and normal samples were characterized using the instrument and subtle changes in the scatter signal were encountered within regions of each sample. Discrimination between normal vs. tumor tissue was readily performed using an Artificial Neural Network (ANN) classifier algorithm. A similar approach has worked also for regions of tumor morphology when statistical pre-processing of the scattering parameters was included to create additional data features. This automated interpretation methodology can provide a tool for guiding surgical resection in areas where microscopy imaging do not reach enough contrast to assist the surgeon.

Optical Sensing and Detection, 2010

In this paper a new spectroscopic monitoring parameter is proposed for the on-line monitoring of ... more In this paper a new spectroscopic monitoring parameter is proposed for the on-line monitoring of welding processes, the plasma RMS signal, which is determined by considering the contribution from the spectral samples over a particular spectral window. This parameter is directly related to the heat input that can be estimated by measuring both welding voltage and current, but it exhibits a higher sensitivity to the appearance of weld defects. A comparison between the results obtained from the different spectroscopic parameters will be presented, with data from both experimental and field arc-welding tests.

2010 Ieee Sensors, 2010

A method for the automatic qualitative discrimination of liquid samples based on their absorption... more A method for the automatic qualitative discrimination of liquid samples based on their absorption spectrum in the ultraviolet, visible and near-infrared regions is presented. An alternative implementation of conventional spectrum matching methodologies is proposed working towards the improvement of the response time of the discrimination system. The method takes advantage of not making assumptions on the probability density function of

Advanced Sensor Systems and Applications Iv, 2010

Structural Health Monitoring (SHM) has assumed a significant role in assessing the structures saf... more Structural Health Monitoring (SHM) has assumed a significant role in assessing the structures safety and integrity. SHM can be understood as the integration of sensing intelligence and possibly also actuation devices to allow the structure loading and damaging conditions to be recorded, analyzed, localized and predicted in such a way that non-destructive testing becomes an integral part of the structure. SHM sensing requirements are very well suited for fiber optic sensing technology. So in this paper, after a very brief introduction of the basic SHM concepts, the main fiber optic technologies for this application will be reviewed, several examples and the main current technical challenges will be addressed and, finally, the conclusions summarized.

Biomedical Applications of Light Scattering VII, 2013

Texture analysis of light scattering in tissue is proposed to obtain diagnostic information from ... more Texture analysis of light scattering in tissue is proposed to obtain diagnostic information from breast cancer specimens. Light scattering measurements are minimally invasive, and allow the estimation of tissue morphology to guide the surgeon in resection surgeries. The usability of scatter signatures acquired with a micro-sampling reflectance spectral imaging system was improved utilizing an empirical approximation to the Mie theory to estimate the scattering power on a per-pixel basis. Co-occurrence analysis is then applied to the scattering power images to extract the textural features. A statistical analysis of the features demonstrated the suitability of the autocorrelation for the classification of notmalignant (normal epithelia and stroma, benign epithelia and stroma, inflammation), malignant (DCIS, IDC, ILC) and adipose tissue, since it reveals morphological information of tissue. Non-malignant tissue shows higher autocorrelation values while adipose tissue presents a very low autocorrelation on its scatter texture, being malignant the middle ground. Consequently, a fast linear classifier based on the consideration of just one straightforward feature is enough for providing relevant diagnostic information. A leave-one-out validation of the linear classifier on 29 samples with 48 regions of interest showed classification accuracies of 98.74% on adipose tissue, 82.67% on non-malignant tissue and 72.37% on malignant tissue, in comparison with the biopsy H&E gold standard. This demonstrates that autocorrelation analysis of scatter signatures is a very computationally efficient and automated approach to provide pathological information in real-time to guide surgeon during tissue resection.

2012 9th IEEE International Symposium on Biomedical Imaging (ISBI), 2012

A surgeon-guided independent component analysis from optical reflectance measurements is proposed... more A surgeon-guided independent component analysis from optical reflectance measurements is proposed for breast tumor delineation. Independent Component Analysis is first applied to extract the most relevant features from local measures of broadband reflectance and then a tumor probability indicator is obtained and provided utilizing surgeon assistance to resolve the inherent ambiguities in the independent component calculation. A set of 29

Thermosense XXX, 2008

The search for an efficient on-line monitoring system focused on the real-time analysis of the we... more The search for an efficient on-line monitoring system focused on the real-time analysis of the welding quality is an active area of research, mainly due to the widespread use of both arc and laser welding processes in relevant industrial scenarios such as aeronautics or nuclear. In this work, an improvement in the performance of a previously designed monitor system is presented. This improvement is accomplished by the employment of a dual spatial-spectral technique, namely imaging spectroscopy. This technique allows the simultaneous determination of the optical spectrum components and the spatial location of an object in a surface. In this way, the spatially characterization of the plasma emitted during a tungsten inert gas (TIG) welding is performed. The main advantage of this technique is that the spectra of all the points in the line of vision are measured at the same time. Not only are all the spectra captured simultaneously, but they are also processed as a batch, allowing the investigation of the welding quality. Moreover, imaging spectroscopy provides the desired real-time operation. To simultaneously acquire the information of both domains, spectral and spatial, a passive Prism-Grating-Prism (PGP) device can be used. In this paper the plasma spectra is captured during the welding test by means of a near infrared imaging spectroscopic system which consists of input optics, an imaging spectrograph and a monochrome camera. Technique features regarding on-line welding quality monitoring are discussed by means of several experimental welding tests.

Optical and Digital Image Processing, 2008

A multispectral system based on a monochrome camera and an adaptive illumination source is presen... more A multispectral system based on a monochrome camera and an adaptive illumination source is presented in this paper. Its preliminary application is focused on material discrimination for food and beverage industries, where monochrome, color and infrared imaging have been successfully applied for this task. This work proposes a different approach, in which the relevant wavelengths for the required discrimination task are selected in advance using a Sequential Forward Floating Selection (SFFS) Algorithm. A light source, based on Light Emitting Diodes (LEDs) at these wavelengths is then used to sequentially illuminate the material under analysis, and the resulting images are captured by a CCD camera with spectral response in the entire range of the selected wavelengths. Finally, the several multispectral planes obtained are processed using a Spectral Angle Mapping (SAM) algorithm, whose output is the desired material classification. Among other advantages, this approach of controlled and specific illumination produces multispectral imaging with a simple monochrome camera, and cold illumination restricted to specific relevant wavelengths, which is desirable for the food and beverage industry. The proposed system has been tested with success for the automatic detection of foreign object in the tobacco processing industry.

Thermosense XXVIII, 2006

An inspection process of rad ian! heaters is presented in this paper. The proposed non destructiv... more An inspection process of rad ian! heaters is presented in this paper. The proposed non destructive testing and evaluation (NDT&E) technique for defect assessment of radian! heaters is based on infrared thermography images properly acquired and processed. Toe technique can be used in on-line fabrication quality control radian! heaters rnanufacturing processes. By exciting the heater with a very short electrical pulse, a sequence of thermographic irnages is captured by an infrared carnera and then analyzed. Regardless of the electrical excitation applied to the heating element of the heater, the electrical power supplied will dissipate al the resistor. Provided enough spatial resolution, the heaters could be tested with an infrared camera capturing the radiated heat. The analysis of the heating wire during the heating flank shows differences arnong pixels corresponding to defective points and pixels belonging to non-defective areas of the wire. Toe automation is provided by the development of an algorithm that looks for the slope of the heating evolution of each pixel. A Radon Transforrn based algorithm is here proposed to reduce human intervention providing just one irnage where an operator could quickly locate possible defects.

Biomedical Optics Express, 2014

Degradation of the wall of human ascending thoracic aorta has been assessed through Optical Coher... more Degradation of the wall of human ascending thoracic aorta has been assessed through Optical Coherence Tomography (OCT). OCT images of the media layer of the aortic wall exhibit micro-structure degradation in case of diseased aortas from aneurysmal vessels. The OCT indicator of degradation depends on the dimension of areas of the media layer where backscattered reflectivity becomes smaller due to a disorder on the morphology of elastin, collagen and smooth muscle cells (SMCs). Efficient pre-processing of the OCT images is required to accurately extract the dimension of degraded areas after an optimized thresholding procedure. OCT results have been validated against conventional histological analysis. The OCT qualitative assessment has achieved a pair sensitivity-specificity of 100%-91.6% in low-high degradation discrimination when a threshold of 4965.88µm 2 is selected. This threshold suggests to have physiological meaning. The OCT quantitative evaluation of degradation achieves a correlation of 0.736 between the OCT indicator and the histological score. This in-vitro study can be transferred to the clinical scenario to provide an intraoperative assessment tool to guide cardiovascular surgeons in open repair interventions.

Third European Workshop on Optical Fibre Sensors, 2007

A new spectral processing technique designed for its application in the on-line detection and cla... more A new spectral processing technique designed for its application in the on-line detection and classification of arc-welding defects is presented in this paper. A non-invasive fiber sensor embedded within a TIG torch collects the plasma radiation originated during the welding process. The spectral information is then processed by means of two consecutive stages. A compression algorithm is first applied to the data allowing real-time analysis. The selected spectral bands are then used to feed a classification algorithm, which will be demonstrated to provide an efficient weld defect detection and classification. The results obtained with the proposed technique are compared to a similar processing scheme presented in a previous paper, giving rise to an improvement in the performance of the monitoring system.

Optical Sensing and Detection, 2010

Optical spectroscopy has been utilized in various fields of science, industry and medicine, since... more Optical spectroscopy has been utilized in various fields of science, industry and medicine, since each substance is discernible from all others by its spectral properties. However, optical spectroscopy traditionally generates information on the bulk properties of the whole sample, and mainly in the agri-food industry some product properties result from the heterogeneity in its composition. This monitoring is considerably more challenging and can be successfully achieved by the so-called hyperspectral imaging technology, which allows the simultaneous determination of the optical spectrum and the spatial location of an object in a surface. In addition, it is a nonintrusive and non-contact technique which gives rise to a great potential for industrial applications and it does not require any particular preparation of the samples, which is a primary concern in food monitoring. This work illustrates an overview of approaches based on this technology to address different problems in agri-food and industrial sectors. The hyperspectral system was originally designed and tested for raw material on-line discrimination, which is a key factor in the input stages of many industrial sectors. The combination of the acquisition of the spectral information across transversal lines while materials are being transported on a conveyor belt, and appropriate image analyses have been successfully validated in the tobacco industry. Lastly, the use of imaging spectroscopy applied to online welding quality monitoring is discussed and compared with traditional spectroscopic approaches in this regard.

In welding processes, specially in those involved in critical applications, as the aerospace an a... more In welding processes, specially in those involved in critical applications, as the aerospace an automotive sectors, extensive non-destructive testing (NDT) is commonly used for quality assurance. Therefore, the possibility of avoiding those procedures by means of on-line, real-time monitoring techniques is of high interest. Several different approaches have been contemplated for the analysis of welding processes, from the measurement of the charge voltage induced by the plasma on the welding nozzle, to acoustic and imaging techniques. Spectroscopic analysis of the plasma emission spectrum is known to offer rich information about the process, allowing direct correlation between the weld quality and some plasma parameters. Despite its benefits, spectroscopic analysis exhibits the drawbacks of its high computational requirements and the difficulty of a non-invasive arrangement of the optical light-capturing system. In a previous paper a new spectroscopic technique allowing real-time full-spectroscopic analysis of arc welding processes, and, hence, detection of common defects in the weld seam, was presented. In this paper a welding monitoring sensor system in which the optical fiber capturing the light is embedded into the welding torch is presented. Several tests showing the feasibility of the proposed system are also presented.

Biomedical Applications of Light Scattering V, 2011

Multi-spectral spatially modulated light is used to guide localized spectroscopy of surgically re... more Multi-spectral spatially modulated light is used to guide localized spectroscopy of surgically resected tissues for cancer involvement. Modulated imaging rapidly quantifies near-infrared optical parameters with sub-millimeter resolution over the entire field for identification of residual disease in resected tissues. Suspicious lesions are further evaluated using a spectroscopy platform designed to image thick tissue samples at a spatial resolution sensitive to the diagnostic gold standard, pathology. MI employs a spatial frequency domain sampling and model-based analysis of the spatial modulation transfer function to interpret a tissue's absorption and scattering parameters at depth. The spectroscopy platform employs a scanning-beam, telecentric dark-field illumination and confocal detection to image fields up to 1cm 2 with a broadband source (480:750nm). The sampling spot size (100µm lateral resolution) confines the volume of tissue probed to within a few transport pathlengths so that multiple-scattering effects are minimized and simple empirical models may be used to analyze spectra. Localized spectroscopy of Intralipid and hemoglobin phantoms demonstrate insensitivity of recovered scattering parameters to changes in absorption, but a non-linear dependence of scattering power on Intralipid concentration is observed due to the phase sensitivity of the measurement system. Both systems were validated independently in phantom and murine studies. Ongoing work focuses on assessing the combined utility of these systems to identify cancer involvement in vitro, particularly in the margins of resected breast tumors.

Optical Design and Engineering, 2004

17th International Conference on Optical Fibre Sensors, Pts 1 and 2, 2005

2009 Ieee Sensors, Vols 1-3, 2009

A method for the automatic synthesis of the Ultraviolet-Visible-Near Infrared (UV-Vis-NIR) absorp... more A method for the automatic synthesis of the Ultraviolet-Visible-Near Infrared (UV-Vis-NIR) absorption and transmission spectra of dye mixtures based on the absorption characteristics of their individual dyes is proposed in this paper. Multiple Linear Regression models (MLR) of each dye are obtained using a fiber-optic set-up operating in the 200-1100 nm wavelength range. Textile dyes are thick and dense and, consequently, optically opaque. This gives rise to high absorbance values which do not permit the direct comparison of different textile dye spectra for quality assurance purposes. The proposed multivariate method allows to construct a general model adjusted to the number and concentration of the dyes in the mixture. Furthermore, this dye spectrum synthesis can provide the optimum dilution factor needed to compare two different dye mixtures and test their similarity degree. With the proposed system, the obtained spectral correlation coefficients between the measured and synthesized spectra of a dye mixture are greater than 99% for both the transmission and absorption spectra.

Clinical and Biomedical Spectroscopy, 2009

An automated algorithm and methodology is presented to pathologically classify the scattering cha... more An automated algorithm and methodology is presented to pathologically classify the scattering changes encountered in the raster scanning of normal and tumor pancreatic tissues using microsampling reflectance spectroscopy. A quasiconfocal reflectance imaging system was used to directly measure the tissue scatter reflectance in situ, and the spectrum was used to identify the scattering power, amplitude and total wavelength-integrated intensity. Pancreatic tumor and normal samples were characterized using the instrument and subtle changes in the scatter signal were encountered within regions of each sample. Discrimination between normal vs. tumor tissue was readily performed using an Artificial Neural Network (ANN) classifier algorithm. A similar approach has worked also for regions of tumor morphology when statistical pre-processing of the scattering parameters was included to create additional data features. This automated interpretation methodology can provide a tool for guiding surgical resection in areas where microscopy imaging do not reach enough contrast to assist the surgeon.

Optical Sensing and Detection, 2010

In this paper a new spectroscopic monitoring parameter is proposed for the on-line monitoring of ... more In this paper a new spectroscopic monitoring parameter is proposed for the on-line monitoring of welding processes, the plasma RMS signal, which is determined by considering the contribution from the spectral samples over a particular spectral window. This parameter is directly related to the heat input that can be estimated by measuring both welding voltage and current, but it exhibits a higher sensitivity to the appearance of weld defects. A comparison between the results obtained from the different spectroscopic parameters will be presented, with data from both experimental and field arc-welding tests.

2010 Ieee Sensors, 2010

A method for the automatic qualitative discrimination of liquid samples based on their absorption... more A method for the automatic qualitative discrimination of liquid samples based on their absorption spectrum in the ultraviolet, visible and near-infrared regions is presented. An alternative implementation of conventional spectrum matching methodologies is proposed working towards the improvement of the response time of the discrimination system. The method takes advantage of not making assumptions on the probability density function of

Advanced Sensor Systems and Applications Iv, 2010

Structural Health Monitoring (SHM) has assumed a significant role in assessing the structures saf... more Structural Health Monitoring (SHM) has assumed a significant role in assessing the structures safety and integrity. SHM can be understood as the integration of sensing intelligence and possibly also actuation devices to allow the structure loading and damaging conditions to be recorded, analyzed, localized and predicted in such a way that non-destructive testing becomes an integral part of the structure. SHM sensing requirements are very well suited for fiber optic sensing technology. So in this paper, after a very brief introduction of the basic SHM concepts, the main fiber optic technologies for this application will be reviewed, several examples and the main current technical challenges will be addressed and, finally, the conclusions summarized.

Biomedical Applications of Light Scattering VII, 2013

Texture analysis of light scattering in tissue is proposed to obtain diagnostic information from ... more Texture analysis of light scattering in tissue is proposed to obtain diagnostic information from breast cancer specimens. Light scattering measurements are minimally invasive, and allow the estimation of tissue morphology to guide the surgeon in resection surgeries. The usability of scatter signatures acquired with a micro-sampling reflectance spectral imaging system was improved utilizing an empirical approximation to the Mie theory to estimate the scattering power on a per-pixel basis. Co-occurrence analysis is then applied to the scattering power images to extract the textural features. A statistical analysis of the features demonstrated the suitability of the autocorrelation for the classification of notmalignant (normal epithelia and stroma, benign epithelia and stroma, inflammation), malignant (DCIS, IDC, ILC) and adipose tissue, since it reveals morphological information of tissue. Non-malignant tissue shows higher autocorrelation values while adipose tissue presents a very low autocorrelation on its scatter texture, being malignant the middle ground. Consequently, a fast linear classifier based on the consideration of just one straightforward feature is enough for providing relevant diagnostic information. A leave-one-out validation of the linear classifier on 29 samples with 48 regions of interest showed classification accuracies of 98.74% on adipose tissue, 82.67% on non-malignant tissue and 72.37% on malignant tissue, in comparison with the biopsy H&E gold standard. This demonstrates that autocorrelation analysis of scatter signatures is a very computationally efficient and automated approach to provide pathological information in real-time to guide surgeon during tissue resection.

2012 9th IEEE International Symposium on Biomedical Imaging (ISBI), 2012

A surgeon-guided independent component analysis from optical reflectance measurements is proposed... more A surgeon-guided independent component analysis from optical reflectance measurements is proposed for breast tumor delineation. Independent Component Analysis is first applied to extract the most relevant features from local measures of broadband reflectance and then a tumor probability indicator is obtained and provided utilizing surgeon assistance to resolve the inherent ambiguities in the independent component calculation. A set of 29

Thermosense XXX, 2008

The search for an efficient on-line monitoring system focused on the real-time analysis of the we... more The search for an efficient on-line monitoring system focused on the real-time analysis of the welding quality is an active area of research, mainly due to the widespread use of both arc and laser welding processes in relevant industrial scenarios such as aeronautics or nuclear. In this work, an improvement in the performance of a previously designed monitor system is presented. This improvement is accomplished by the employment of a dual spatial-spectral technique, namely imaging spectroscopy. This technique allows the simultaneous determination of the optical spectrum components and the spatial location of an object in a surface. In this way, the spatially characterization of the plasma emitted during a tungsten inert gas (TIG) welding is performed. The main advantage of this technique is that the spectra of all the points in the line of vision are measured at the same time. Not only are all the spectra captured simultaneously, but they are also processed as a batch, allowing the investigation of the welding quality. Moreover, imaging spectroscopy provides the desired real-time operation. To simultaneously acquire the information of both domains, spectral and spatial, a passive Prism-Grating-Prism (PGP) device can be used. In this paper the plasma spectra is captured during the welding test by means of a near infrared imaging spectroscopic system which consists of input optics, an imaging spectrograph and a monochrome camera. Technique features regarding on-line welding quality monitoring are discussed by means of several experimental welding tests.

Optical and Digital Image Processing, 2008

A multispectral system based on a monochrome camera and an adaptive illumination source is presen... more A multispectral system based on a monochrome camera and an adaptive illumination source is presented in this paper. Its preliminary application is focused on material discrimination for food and beverage industries, where monochrome, color and infrared imaging have been successfully applied for this task. This work proposes a different approach, in which the relevant wavelengths for the required discrimination task are selected in advance using a Sequential Forward Floating Selection (SFFS) Algorithm. A light source, based on Light Emitting Diodes (LEDs) at these wavelengths is then used to sequentially illuminate the material under analysis, and the resulting images are captured by a CCD camera with spectral response in the entire range of the selected wavelengths. Finally, the several multispectral planes obtained are processed using a Spectral Angle Mapping (SAM) algorithm, whose output is the desired material classification. Among other advantages, this approach of controlled and specific illumination produces multispectral imaging with a simple monochrome camera, and cold illumination restricted to specific relevant wavelengths, which is desirable for the food and beverage industry. The proposed system has been tested with success for the automatic detection of foreign object in the tobacco processing industry.

Thermosense XXVIII, 2006

An inspection process of rad ian! heaters is presented in this paper. The proposed non destructiv... more An inspection process of rad ian! heaters is presented in this paper. The proposed non destructive testing and evaluation (NDT&E) technique for defect assessment of radian! heaters is based on infrared thermography images properly acquired and processed. Toe technique can be used in on-line fabrication quality control radian! heaters rnanufacturing processes. By exciting the heater with a very short electrical pulse, a sequence of thermographic irnages is captured by an infrared carnera and then analyzed. Regardless of the electrical excitation applied to the heating element of the heater, the electrical power supplied will dissipate al the resistor. Provided enough spatial resolution, the heaters could be tested with an infrared camera capturing the radiated heat. The analysis of the heating wire during the heating flank shows differences arnong pixels corresponding to defective points and pixels belonging to non-defective areas of the wire. Toe automation is provided by the development of an algorithm that looks for the slope of the heating evolution of each pixel. A Radon Transforrn based algorithm is here proposed to reduce human intervention providing just one irnage where an operator could quickly locate possible defects.

Biomedical Optics Express, 2014

Degradation of the wall of human ascending thoracic aorta has been assessed through Optical Coher... more Degradation of the wall of human ascending thoracic aorta has been assessed through Optical Coherence Tomography (OCT). OCT images of the media layer of the aortic wall exhibit micro-structure degradation in case of diseased aortas from aneurysmal vessels. The OCT indicator of degradation depends on the dimension of areas of the media layer where backscattered reflectivity becomes smaller due to a disorder on the morphology of elastin, collagen and smooth muscle cells (SMCs). Efficient pre-processing of the OCT images is required to accurately extract the dimension of degraded areas after an optimized thresholding procedure. OCT results have been validated against conventional histological analysis. The OCT qualitative assessment has achieved a pair sensitivity-specificity of 100%-91.6% in low-high degradation discrimination when a threshold of 4965.88µm 2 is selected. This threshold suggests to have physiological meaning. The OCT quantitative evaluation of degradation achieves a correlation of 0.736 between the OCT indicator and the histological score. This in-vitro study can be transferred to the clinical scenario to provide an intraoperative assessment tool to guide cardiovascular surgeons in open repair interventions.

Third European Workshop on Optical Fibre Sensors, 2007

A new spectral processing technique designed for its application in the on-line detection and cla... more A new spectral processing technique designed for its application in the on-line detection and classification of arc-welding defects is presented in this paper. A non-invasive fiber sensor embedded within a TIG torch collects the plasma radiation originated during the welding process. The spectral information is then processed by means of two consecutive stages. A compression algorithm is first applied to the data allowing real-time analysis. The selected spectral bands are then used to feed a classification algorithm, which will be demonstrated to provide an efficient weld defect detection and classification. The results obtained with the proposed technique are compared to a similar processing scheme presented in a previous paper, giving rise to an improvement in the performance of the monitoring system.

Optical Sensing and Detection, 2010

Optical spectroscopy has been utilized in various fields of science, industry and medicine, since... more Optical spectroscopy has been utilized in various fields of science, industry and medicine, since each substance is discernible from all others by its spectral properties. However, optical spectroscopy traditionally generates information on the bulk properties of the whole sample, and mainly in the agri-food industry some product properties result from the heterogeneity in its composition. This monitoring is considerably more challenging and can be successfully achieved by the so-called hyperspectral imaging technology, which allows the simultaneous determination of the optical spectrum and the spatial location of an object in a surface. In addition, it is a nonintrusive and non-contact technique which gives rise to a great potential for industrial applications and it does not require any particular preparation of the samples, which is a primary concern in food monitoring. This work illustrates an overview of approaches based on this technology to address different problems in agri-food and industrial sectors. The hyperspectral system was originally designed and tested for raw material on-line discrimination, which is a key factor in the input stages of many industrial sectors. The combination of the acquisition of the spectral information across transversal lines while materials are being transported on a conveyor belt, and appropriate image analyses have been successfully validated in the tobacco industry. Lastly, the use of imaging spectroscopy applied to online welding quality monitoring is discussed and compared with traditional spectroscopic approaches in this regard.