Integral temperature hybrid laser sensor

An integral temperature sensor based on Brillouin laser ring that is feed by a Fourier Domain mode-locking (FDML) laser is here proposed. The source FDML laser ring emits at 1532 nm within a range of 5 nm. The working wavelength is given by tuning the offset voltage applied to a Fabry-Perot tunable filter (FFP-TF). In the present work, the FDML laser linewidth is set at 0.136 nm. This linewidth allows a more efficient Brillouin response in the optical fiber without increasing the Brillouin threshold. The FDML laser linewidth is controlled by setting the amplitude modulation of the drive signal offset applied on the FFP-TF

Acoustic detection of laser-induced plasma emission by means of a fiber-Bragg grating sensor

Laser-induced breakdown spectroscopy (LIBS) is an analytical tool able to estimate the atomic composition of materials, without sample preparation and in a short time. One drawback of this technique is that the quantitative analysis is not as precise as other established methods, in part because of the pulse-to-pulse fluctuations of the energy delivered to the sample. These fluctuations can be compensated by monitoring the acoustic wave emitted by the plasma, which is related to the ablated mass. In this paper, we propose the use of a fiber-Bragg grating sensor to detect and measure the acoustic shockwave. A processing scheme is proposed to derive the acoustic energy from the sensor waveform. The experiments show that there is a correlation between the sensor’s response and the laser pulse energy, so it can be used as a monitoring signal of the ablation process

Infrared imaging spectroscopic system based on a PGP spectrograph and a monochrome infrared camera

Hyperspectral imaging spectroscopy has been widely used in remote sensing. However, its potential for applications in industrial and biological fields is enormous. Observation line spectrographs, based on the reflectance of the material under study in each field, can be obtained by means of an imaging spectrometer. In this way, imaging spectroscopy allows the simultaneous determination of the optical spectrum components and the spatial location of an object in a surface. A simple, small and low-cost spectrometer, such as those ones based on passive Prism-Grating-Prism (PGP) devices, is required for the abovementioned application fields. In this paper a non-intrusive and non-contact near infrared acquisition system based on a PGP spectrometer is presented. An extension to the whole near infrared range of the spectrum of a previously designed system in the Vis-NIR range has been performed. The reason under this investigation is to improve material characterization. To our knowledge, no imaging spectroscopic system based on a PGP device working in this range has been previously reported. The components of the system, its assembling, alignment and calibration procedures will be described in detail. This system can be generalized for a wide variety of applications employing a specific and adequate data processing

Support vector machines in hyperspectral imaging spectroscopy with application to material identification

A processing methodology based on Support Vector Machines is presented in this paper for the classification of hyperspectral spectroscopic images. The accurate classification of the images is used to perform on-line material identification in industrial environments. Each hyperspectral image consists of the diffuse reflectance of the material under study along all the points of a line of vision. These images are measured through the employment of two imaging spectrographs operating at Vis-NIR, from 400 to 1000 nm, and NIR, from 1000 to 2400 nm, ranges of the spectrum, respectively. The aim of this work is to demonstrate the robustness of Support Vector Machines to recognise certain spectral features of the target. Furthermore, research has been made to find the adequate SVM configuration for this hyperspectral application. In this way, anomaly detection and material identification can be efficiently performed. A classifier with a combination of a Gaussian Kernel and a non linear Principal Component Analysis, namely k-PCA is concluded as the best option in this particular case. Finally, experimental tests have been carried out with materials typical of the tobacco industry (tobacco leaves mixed with unwanted spurious materials, such as leathers, plastics, etc.) to demonstrate the suitability of the proposed technique

Spectral marks for qualitative discriminant analysis

In this paper, 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 the data and it is also capable of automatic outlier removal. Preliminary discrimination results have been evaluated on the classification of different oil samples from seeds and olives. The system here proposed could be easily and efficiently implemented in hardware platforms, improving in this way the system performance

Early diagnosis of frailty: Technological and non-intrusive devices for clinical detection

This work analyses different concepts for frailty diagnosis based on affordable standard technology such as smartphones or wearable devices. The goal is to provide ideas that go beyond classical diagnostic tools such as magnetic resonance imaging or tomography, thus changing the paradigm; enabling the detection of frailty without expensive facilities, in an ecological way for both patients and medical staff and even with continuous monitoring. Fried's five-point phenotype model of frailty along with a model based on trials and several classical physical tests were used for device classification. This work provides a starting point for future researchers who will have to try to bridge the gap separating elderly people from technology and medical tests in order to provide feasible, accurate and affordable tools for frailty monitoring for a wide range of users.This work was sponsored by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (ERDF) across projects RTC-2017-6321-1 AEI/FEDER, UE, TEC2016-76021-C2-2-R AEI/FEDER, UE and PID2019-107270RB-C21/AEI/10.13039/501100011033, UE

Welding quality evaluation by means of feature selection and optimization algorithms

RESUMEN: Este trabajo es una continuación de una publicación anterior en la que se demostró la viabilidad de establecer un análisis de la calidad de procesos de soldadura basado en la generación de espectros sintéticos y en el posterior empleo de algoritmos de optimización para determinar la participación relativa de cada especie en el plasma. En dicho estudio se comprobó que existía una correlación directa entre los perfiles de participación y la aparición de defectos en los cordones, lo que permite, no sólo disponer de una técnica de monitorización alternativa, sino también aportar mayor información sobre el propio proceso y su dinámica. En esta contribución se proponen mejoras al modelo original, como el uso del algoritmo PSO (Particle Swarm Optimization) y de una etapa previa basada en un algoritmo de selección de características que permita seleccionar una región espectral determinada sobre la que llevar a cabo la optimización.ABSTRACT: This work is a continuation of a previous paper where the feasibility of establishing an analysis of the quality of welding processes based on the generation of synthetic spectra and the use of optimization algorithms to determine the relative participation of the species in the plasma was demonstrated. In that paper the correlation between the participation profiles and the quality of the resulting seams was shown, allowing, not only to employ an alternative monitoring technique, but also to help in trying to understand the process itself and its dynamics. In this contribution new improvements are proposed to the original model, as the employment of the PSO (Particle Swarm Optimization) algorithm and a previous stage based on a feature selection algorithm able to facilitate a selection of the spectral region where the optimization should take place

Comparative study between on-line monitoring systems based on photodiodes or spectrometers for on-line welding defect detection

RESUMEN: En este trabajo se presenta un análisis experimental donde se compara el rendimiento del uso de fotodiodos dentro de un sistema de monitorización en línea de la calidad en solda-dura, concretamente de arco. Dentro del ámbito de la espectroscopía óptica de plasmas aplicada a esta problemática, es típico el uso de espectrómetros CCD en el montaje ópti-co, ya que permiten un detallado análisis de los espectros del plasma de soldadura. Mon-tajes basados en fotodiodos han sido empleados, pero típicamente orientados a detectar una defectología limitada, por ejemplo faltas de penetración. En este trabajo se ha estu-diado la respuesta de un sistema basado en fotodiodos a diferentes defectos de soldadura simulados en el laboratorio. Los resultados indican que, especialmente mediante el uso de filtros ópticos centrados en regiones de interés, el uso de fotodiodos es viable para la de-tección de varios defectos de soldadura, lo que implica un importante ahorro frente a los montajes basados en espectrómetros CCD.ABSTRACT: An experimental analysis of the performance derived from the employment of photodi-odes within an on-line welding quality monitoring system in comparison to the use of CCD-spectrometers is presented in this work. CCD-spectrometers are commonly chosen where plasma optical spectroscopy is to be applied for on-line welding diagnostics, given that they allow a detailed analysis of the welding plasma spectra. Setups based on photo-diodes have been already studied, but they have been typically limited to the detection of some basic defects, e.g. lack of penetration. The response of a photodiode-based system to different weld flaws simulated in the laboratory has been analyzed in this contribution. The obtained results suggest that, especially if optical filters are included, the employ-ment of photodiodes is suitable to detect several defects, thus implying a significant re-duction in terms of system costs

Active spectroscopy for solid materials analysis

Máster en Tecnologías de la Información y Comunicaciones en Redes Móviles (TICRM