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  • DISEÑO E IMPLEMENTACIÓN DE UN SISTEMA MULTIESPECTRAL EN EL RANGO ULTRAVIOLETA, VISIBLE E INFRARROJO. APLICACIÓN AL ESTUDIO Y CONSERVACIÓN DE OBRAS DE ARTE

     Herrera Ramirez, Jorge Alexis
    Defense's date: 2014-03-25
    Universitat Politècnica de Catalunya
    Theses

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    Los sistemas multiespectrales tienen la caracteristica principal de proporcionar acceso a informaci6n espectral de una muestra con alta resoluci6n espacial. En esta tesis, como principal objetivo, se ha disefiado e implementado un sistema multiespectral para aplicarlo al estudio de obras de arte. Este sistema comprende dos m6dulos: el m6dulo 1 UV-Vis, con una camara CCD con sensibilidad entre 370nm y930nm, acoplada a una fuente de diodos emisores de luz(LED) con 16 canales diferentes, es decir 16 1ongitudes de onda de emisi6n; yel m6dulo 2 IR, con una camara lnGaAs con sensibilidad entre 930nm y 1650nm, acoplada a una fuente LED con 71ongitudes de onda de emisi6n. Por tanto, el sistema completo abarca desde 370nm a 1650nm con un total de 23 canales.Se caracterizaron Ios elementos del sistema y se han realizado simulaciones para evaluar su rendimiento en la reconstrucci6n de reflectancias espectrales bajo condiciones ideales, condiciones de ruido de cuantificaci6n y aditivo. Su rendimiento se evalu6 empleando la formula de diferencia de color CIEDE2000,el error cuadratico medio (RMSE) y el coeficiente de bondad del ajuste (GFC). Los resultados de las simulaciones mostraron un buen rendimiento general del sistema, aunque con mejores resultados para el m6dulo 1 UV-Vis debido a la mayor cantidad de canales LED en su rango espectral.Paralelamente se implementaron Ios programas computacionales con sus respectivas interfaces graficas necesarias para el control del hardware usado y para el procesamiento de la informaci6n proporcionada por el sistema. Para la reconstrucci6n espectral empleamos un metodo de interpolaci6n directa basado en splines, y Ios metodos depseudoinversa indeterminada (PSE-l) y pseudoinversa simple (PSE) que necesitan de un entrenamiento con un conjunto de muestras con respuestas digitales del sistema y reflectancias espectrales conocidas. El equipo se evalu6 sobre muestras reales de la carta de colores Color Checker CCCR y sobre un conjunto de pinturas alfresco realizadas con pigmentos comunmente presentas en obras de arte. Los resultados de las metricas CIEDE2000,RMSE yGFC mostraron que Ios metodos de la PSE-1 y PSE tienen desempefios similares,con resultados ligeramente mejores para el segundo metodo. El metodo de interpolaci6n present6 un rendimiento ligeramente menor, aunque tiene el valor practico de no necesitar entrenamiento. Los resultados reales para el metodo del PSE fueron similares a Ios obtenidos mediante simulaci6n, y se mostr6 una vez m as que el m6dulo 2 IR tiene un rendimiento inferior. Se concluy6 que en general el desempefio delsistema era bueno, con valores CIEDE2000 y RMSE promedio para Ios metodos basados en PSE del orden de 1 unidad enambos casos.El sistema desarrollado fue aplicado a obras de arte en elmuseo de Monasterio de Pedralbes, en Barcelona, y Ias lglesias de Sant Pere, en Terrassa.En el Monasterio de Pedralbes se capturaron diferentes imagenes de pinturas murales de la capilla de San Miguel y se evalu6 el desempefio del sistema para esta aplicaci6n de museo, mostrando un desempeno similar al reportado en las pruebas de laboratorio. Tambien se accedi6 a la obra Virgen de la Leche que es un 61eo en tabla de gran formato. En esta obra se aprovech6 el diseno modular y de facil movimiento del sistema para generar por composici6n una imagen completa a partir de varias imagenes menores.En las iglesias de Sant Pere se exploraron pinturas murales que se estima datan de las epocas visigoda (siglos VI-VII) y romanica (siglos XII-XIII) para evaluar si existian caracteristicas en Ias pinturas que no fueran evidentes en el rango visible y que silo fueran en otros rangos espectrales. Para ello se implementaron algoritmos de realce de la informaci6n. Los resultados obtenidos en esta tesis doctoral ponen de manifiesto las potencialidades del sistema multiespecral desarrollado para la obtenci6n de informaci6n espectral en las regiones ultravioleta, visible e infrarrojo.

  • Age-related changes in accommodation measured with a double-pass system

     Aldaba Arevalo, Mikel; Vilaseca Ricart, Meritxell; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume
    Ophthalmic and physiological optics
    Date of publication: 2013-07
    Journal article

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    To measure the accommodative response in a wide age range population using the retinal image quality assessments provided by a double-pass system.

  • Spherical refractive correction with an electro-optical iquid lens in a double-pass system

     Sanàbria Ortega, Ferran; Díaz Doutón, Fernando; Aldaba Arevalo, Mikel; Pujol Ramo, Jaume
    Journal of the European Optical Society: rapid publications
    Date of publication: 2013-09-06
    Journal article

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    In this study we show a novel double-pass configuration to correct the spherical refractive error by means of an electro-optical liquid lens. The proposed method enables spherical correction in the -12 D to +7 D range without movable parts using an electro-optical liquid lens. We have measured the optical performance of the spherical corrector in terms of power, pupil size and optical quality verifying that it fits the requirements to be applied to a double-pass system. We have also evaluated the performance of the proposed method in patients by comparison with a conventional double-pass system using a Badal optometer.

  • Non-cycloplegic spherical equivalent refraction in adults: comparison of the double-pass system, retinoscopy, subjective refraction and a table-mounted autorefractor

     Vilaseca Ricart, Meritxell; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume; Peris March, Maria Elvira; Martínez Rodríguez, Vanessa
    International Journal of Ophthalmology
    Date of publication: 2013-10-18
    Journal article

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    AIM: To evaluate the accuracy of spherical equivalent (SE) estimates of a double pass system and to compare it with retinoscopy, subjective refraction and a table mounted autorefractor. METHODS: Non cycloplegic refraction was performed on 125 eyes of 65 healthy adults (age 23.5 +/- 3.0 years) from October 2010 to January 2011 using retinoscopy, subjective refraction, autorefraction (Auto kerato - refractometer TOPCON KR-8100, Japan) and a double pass system (Optical Quality Analysis System, 0QAS, Visiometrics S.L., Spain). Nine consecutive measurements with the double -pass system were performed on a subgroup of 22 eyes to assess repeatability. To evaluate the trueness of the 0QAS instrument, the SE laboratory bias between the double - pass system and the other techniques was calculated. RESULTS: The SE mean coefficient of repeatability obtained was 0.22D. Significant correlations could be established between the OQAS and the SE obtained with retinoscopy (r=0.956, P<0.001), subjective refraction(r = 0.955, P<0.001) and autorefraction (r=0.957, P<0.001). The differences in SE between the double pass system and the other techniques were significant (P<0.001), but lacked clinical relevance except for retinoscopy; Retinoscopy gave more hyperopic values than the double pass system 0.51 0.500 as well as the subjective refraction 0.23 0.50D; More myopic values were achieved by means of autorefraction 0.24 0.49D. CONCLUSION: The double -pass system provides accurate and reliable estimates of the SE that can be used for clinical studies. This technique can determine the correct focus position to assess the ocular optical quality. However, it has a relatively small measuring range in comparison with autorefractors (-8.00 to +5.00D), and requires prior information on the refractive state of the patient.

  • Método de cálculo de desalineamientos en sistemas ópticos. Aplicación mediante redes neuronales.

     Oteo Lozano, Esther
    Defense's date: 2013-09-27
    Universitat Politècnica de Catalunya
    Theses

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  • Diagnosis of skin cancer using optics

     Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume; Ares Rodriguez, Miguel; Riu Gras, Jordi; Azcona Guerrero, Francisco Javier; Herrera Ramirez, Jorge Alexis; Delpueyo Español, Xana; Jha, Ajit; Royo Royo, Santiago
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  • Spectral signatures : a way to identify species and conditions of vegetables

     Sandoval, José; Gor, Sergio; Sfer, Ana María; Ramallo, Jacqueline; Colombo, Elisa; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Date of publication: 2012
    Book chapter

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    Confirming the statement from Shlens (2009), that is, that the goal of PCA is to identify the most meaningful basis to reexpress a dataset, the results obtained in this work show that the careful selection and suitable preparation of samples together with the precise collection of spectral signature data and the application of an adequate statistical analysis like PCA conform a powerful and reliable technique to recognize and classify plants, allowing us to identify the origin of a given vegetable sample. That technique could be considerably improved by developing a database of standardized spectral signatures of the main crops in each stage and status. This could be the basis for higher level of plant and crop analysis, allowing us the prediction, diagnosis, and solution of different health and phenologic affections of plants.

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    Optics of astigmatism and retinal image quality  Open access

     Vilaseca Ricart, Meritxell; Diaz Douton, Fernando; Luque, Sergio Oscar; Aldaba Arevalo, Mikel; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume
    Date of publication: 2012-02
    Book chapter

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    In the first part of this chapter, the optical condition of astigmatism is defined. The main causes and available classifications of ocular astigmatism are briefly described. The most relevant optical properties of image formation in an astigmatic eye are analysed and compared to that of an emmetropic eye and an eye with spherical ametropia. The spectacle prescription and axis notation for astigmatism are introduced, and the correction of astigmatism by means of lenses is briefly described. The formation of the retinal image for extended objects and the related blurring are also analysed, and the real limits of tolerance of uncorrected astigmatism are provided. Simulations of retinal images in astigmatic eyes, obtained by means of commercial optical design software, are also presented. Finally, the clinical assessment of retinal image quality by means of wavefront aberrometry and double-pass systems in eyes with astigmatism is presented, and current trends in research related to this topic are highlighted.

  • Early fungus infection detection in lemon fruits by means of spectral and colour analysis

     Sandoval, José; Gor, Sergio; Ramallo, Jacqueline; Colombo, Elisa; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Interim Meeting of the International Color Association
    Presentation's date: 2012-09-25
    Presentation of work at congresses

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    Sistema multiespectral basado en LEDS para el estudio de obras de arte en el rango espectral desde los 370 a los 1600nm  Open access

     Herrera Ramirez, Jorge Alexis; Vilaseca Ricart, Meritxell; Burgos, Francisco Javier; Senserrich, Rosa; Font, Lídia; Pujol Ramo, Jaume
    Red temática "Ciencia y tecnología del color"
    Presentation's date: 2012-03-22
    Presentation of work at congresses

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    Este trabajo muestra el diseño e implementación de un sistema de imágenes multiespectral basado en diodos e misores de luz (LED) que cubre los rangos de longitudes de onda desde los 370 nm a los 1600 nm. El sistema permite la estimación del espectro de reflectancia píxel a píxel, a partir de la infonnación de 23 canales espectrales dados por una iluminación LED multiplexada. La infonnación de reflectancia se estima usando dos métodos diferentes: a través de interpolación a partir de las respuestas digitales de los sensores de imagen y por medio del método de la pseudoinversa. Los resultados desimulaciones y de medidas experimentales fueron validados mediante métricas de ajuste entre espectros y diferencias de color, mostrando la cercanía entre las simulaciones y las mediciones y un buen desempeño del equipo. Este sistema está siendo usado para el estudio de las pinturas al fresco de la Capilla de San Miguel del Museo-Monasterio de Pedralbes en la ciudad de Barcelona.

  • Studying Art Paintings through a Multispectral Imaging System Composed of Light-Emitting Diodes Covering the Spectral Range from 370 to 1600 nm

     Herrera Ramirez, Jorge Alexis; Vilaseca Ricart, Meritxell; Burgos, Francisco Javier; Font, Lídia; Senserrich, Rosa; Pujol Ramo, Jaume
    Interim Meeting of the International Color Association
    Presentation's date: 2012-09
    Presentation of work at congresses

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    Multispectral systems are implemented in many ways and are intended for different purposes. Some of them have been used for the study of art work but they have been mostly based on filters. In this work we assess the feasibility of a multispectral system based on Light-Emitting Diodes (LED) for the study of art work paintings. This system is comprised of two cameras and two sets of LEDs with different peak wavelengths of emission. Images from the 23 channels of the system give access to pixel-wise information of color and spectrum in the range of 370nm to 1600nm. The spectrum for each pixel is calculated via two methods: the pseudo-inverse estimation method using a training set of samples and the interpolation method using splines. The performance of the system in terms of color and spectral reconstruction is evaluated using three different metrics. The results obtained in spectral estimation shows a good performance of the system. In addition, some of the possibilities that the system offers are shown with images and spectra estimation of pixels for real wall paintings.

  • Comparison of colorimetric features of some current lighting booths for obtaining a right visual and instrumental correlation for gonio-apparent coatings and plastics

     Martínez Verdú, Francisco Miguel; Perales, Esther; Viqueira, Valentín; Chorro, Elísabet; Burgos Fernandez, Francisco Javier; Pujol Ramo, Jaume
    Commission Internationale de l'Éclairage
    Presentation's date: 2012-09
    Presentation of work at congresses

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  • Fuente de luz sintonizable basada en diodos emisores de luz (LEDs)

     Burgos Fernandez, Francisco Javier; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Reunión Nacional de Óptica
    Presentation's date: 2012-09
    Presentation of work at congresses

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  • Repeatability and reproducibility of a hyperspectral camera as a means of measuring color

     Schael, Barbara; Vilaseca Ricart, Meritxell; Ferrer Serrano, Edgar; Pujol Ramo, Jaume
    Interim Meeting of the International Color Association
    Presentation's date: 2012-09-24
    Presentation of work at congresses

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  • New methodology to select light source spectral distribution for use in museums to properly exhibit and preserve artwork

     Pujol Ramo, Jaume; arana, fernando; ajmad, raul; Sandoval, José D.
    Commission Internationale de l'Éclairage
    Presentation's date: 2012-09-26
    Presentation of work at congresses

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  • Sistema multiespectral basado en LEDs en los rangos ultravioleta, visible e infrarrojo. Aplicación al estudio y conservación de obras de arte

     Vilaseca Ricart, Meritxell; Burgos Fernandez, Francisco Javier; Senserrich, Rosa; Font, Lídia; Pujol Ramo, Jaume; Herrera Ramirez, Jorge Alexis
    Reunión Nacional de Óptica
    Presentation's date: 2012-09
    Presentation of work at congresses

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  • Buscando la correlación instrumental y visual óptima para colores goniocromáticos mediante cabinas de iluminación y multi-gonio-espectrofotómetros

     Martínez Verdú, Francisco Miguel; Perales, Esther; Chorro, Elísabet; Viqueira, Valentín; Burgos Fernandez, Francisco Javier; Pujol Ramo, Jaume
    Reunión Nacional de Óptica
    Presentation's date: 2012-09
    Presentation of work at congresses

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  • Optical quality after myopic photorefractive keratectomy and laser in situ keratomileusis: Comparison using a double-pass system

     Ondategui Parra, Juan Carlos; Vilaseca Ricart, Meritxell; Arjona Carbonell, Maria Montserrat; Montasell, Ana; Cardona Torradeflot, Genis; Güell, José L.; Pujol Ramo, Jaume
    Journal of cataract and refractive surgery
    Date of publication: 2012
    Journal article

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  • Comparison between an objective and a psychophysical method for the evaluation of intraocular light scattering

     Barrionuevo, Pablo; Colombo, Elisa; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume; Issolio, Luis Alberto
    Journal of the Optical Society of America A. Optics image science and vision
    Date of publication: 2012-07-01
    Journal article

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    Measuring the accommodative response with a double-pass system: comparison with the Hartmann-Shack technique  Open access

     Aldaba Arevalo, Mikel; Vilaseca Ricart, Meritxell; Diaz Douton, Fernando; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume
    Vision research
    Date of publication: 2012-04
    Journal article

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  • Medida de la respuesta acomodativa con un sistema de doble paso. Aplicación al estudio de la acomodación en función de la edad.  Open access

     Aldaba Arevalo, Mikel
    Defense's date: 2012-10-22
    Department of Optics and Optometry, Universitat Politècnica de Catalunya
    Theses

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    Accommodation, defined as the dioptric change of the eye, enables clear vision at different distances. Its study is interesting due to different aspects: the progressive loss of amplitude of accommodation known as presbyopia, the recent interest in accommodative restauration techniques in pseudophakic patients, its possible relation to myopia development and the associated pathologies. The most widely used techniques to measure accommodation are the subjectives, although it has been shown that they overestimate accommodation due to pseudoaccommodation. There are also several objective techniques as retinoscopy, autorefractometers or aberrometers. In the last years it has been suggested that a more realistic accommodative measurement is done when all the aberrations of the eye are taken into acount, and not just defocus. The goal of this thesis has been to develop a method based on the double pass technique for the accommodative response measurement and its application to the study of accommodation with age. Double pass technique is based on projecting a point source on the retina and recording images after retinal reflection and double pass through the ocular media. This technique provides information about the optical quality of the eye and takes into acount all the factors influencing the retinal image quality, thus it is ideal for being applied in the measurement of tha accommodative response. In the first part of the thesis the method for the accommodative response measurement based on double pass technique has been developed and it has been validated by comparison with Hartmann-Shack measurements. The developed experimental setup combines both techniques, double pass and Hartmann-Shack, and it is specifically designed for accommodative response measurements, including elements like the open field fixation test that allows a more natural accommodative stimulation. The method developed is based on finding the vergence that maximizes the quality of the double pass image. Several double pass images are recorded by means of an axial scanning and the vergence of the best double pass image is related to accommodative response. Double pass measurements showed a good agreement with Hartmann-Shack measurements and no statistically significant differences, thus validating our method. In the second part of the thesis, the method has been applied for the study of the accommoditve response in a wide age range population. The accommodative response measured in young patients was higher than the published in the literature, due to our measurements being based on the retinal image quality and not on defocus. While in older patients, the accommodative response measurements are in good agreement with previous works. The accommodative stimulus-response curve and its slope also showed a worsening with age, with a more noticeable change in the accommodation after the age of 35-40 years. The work done during the thesis led to articles in journals and several contributions to congresses, as well as to a patent being comercially exploited.

    La acomodación, cambio dióptrico del ojo, permite una visión nítida a diferentes distancias. El interés que despierta su estudio es grande debido a diferentes factores: la progresiva pérdida de acomodación con la edad, la restauración de la acomodación en pacientes pseudfáquicos, su posible relación con el desarrollo de la miopía y las patologías asociadas a la acomodación. Aunque las técnicas más habituales para la medida de la acomodación son las técnicas subjetivas, presentan el problema de sobrevalorar la amplitud de acomodación debido a la pseudoacomodación, rango en el que sin cambio dióptrico del cristalino se ve nítidamente gracias a la profundidad de foco. Entre las objetivas se han propuesto diversas técnicas como la retinoscopía, autorrefractómetros o aberrómetros. En los últimos años se ha sugerido que una correcta medida de la acomodación no sólo debería tener en cuenta el desenfoque si no el global de las aberraciones que afectan a la calidad de la imagen retiniana. El objetivo de esta tesis ha sido desarrollar un nuevo método para la medida de la respuesta acomodativa basado en la técnica de doble paso y su aplicación al estudio de la acomodación con la edad. La técnica de doble paso consiste en proyectar una fuente puntual de luz en la retina y registrar la imagen formada tras su reflexión en la retina y doble paso por los medios oculares. Esta técnica da información acerca de la calidad óptica del ojo y tiene en cuenta los dos factores que afectan básicamente a la calidad de la imagen retiniana: aberraciones y difusión intraocular, lo que la convierte en una candidata ideal para su aplicación en la medida de la respuesta acomodativa. En la primera parte de la tesis se ha desarrollado un método y un montaje para la medida de la respuesta acomodativa con un sistema de doble paso y se ha validado mediante comparación con medidas realizadas con un aberrómetro de Hartmann-Shack. El montaje experimental desarrollado combina ambas técnicas, doble paso y Hartmann-Shack, y además está optimizado para la medida de la respuesta acomodativa con un test de fijación de campo abierto que permite una estimulación de la acomodación más natural que los test internos. El método desarrollado se basa en hallar la vergencia de la luz que maximiza la calidad de la imagen de doble paso. Para ello se registran diversas imágenes de doble paso correspondientes a diferentes vergencias de la luz y la de mayor calidad se relaciona con la respuesta acomodativa. Las medidas realizadas con el sistema de doble paso se han comparado con medidas simultáneas realizadas con un aberrómetro de Hartmann-Shack, obteniendo resultados similares con ambas técnicas. Una vez validado el método para la medida de la respuesta acomodativa con el sistema de doble paso, se ha aplicado al estudio de los cambios en la acomodación con la edad realizando medidas en una población extensa con un rango amplio de edad. La respuesta acomodativa medida en los pacientes jóvenes es mayor que en otros trabajos, básicamente debido a que la técnica empleada está basada en la calidad de la imagen retiniana y no en el desenfoque como sucede en los otros estudios. Mientras que en pacientes mayores, los resultados concuerdan con los de otros estudios. La curva de estímulo-respuesta acomodativa y su pendiente muestran un empeoramiento con la edad, observándose que la edad que marca los cambios más notables está en torno a los 35-40 años. El trabajo realizado durante el desarrollo de la tesis ha dado lugar a publicaciones en revistas y diversas contribuciones a congresos, así como una patente actualmente explotada comercialmente.

  • Novel approach to improve the assessment of biodiversity of phytoplankton communities based on hyperspectral data analysis  Open access

     Torrecilla Ribalta, Elena
    Defense's date: 2012-07-27
    Department of Optics and Optometry, Universitat Politècnica de Catalunya
    Theses

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    La gestió sostenible dels ecosistemes marins requereix d'un millor coneixement de la distribució de certs paràmetres ecològics com les comunitats de fitoplàncton, inclosos aquells grups algals causants d'afloraments. La caracterització acurada dels patrons espacio-temporals de la biodiversitat del fitoplàncton és essencial per tal d'avaluar el paper de cada grup algal en l'ecosistema global marí i els cicles biogeoquímics. En l'intent d'abordar aquesta qüestió, observacions espectromètriques adquirides in situ i per teledetecció han demostrat proporcionar informació valuosa sobre la distribució de diversos components òpticament actius presents a l'aigua de mar, tant a escala local com global, i en particular, sobre l'estructura de les comunitats fitoplanctòniques. En aquest sentit, l'aparició de sensors òptics d'alta resolució espectral (hiperespectrals) ha augmentat les expectatives per discriminar la composició de les comunitats de fitoplàncton, permetent anar més enllà de l'estimació del pigment primari del fitoplàncton, la clorofil·la-a, utilitzat convencionalment com un indicador global de la biomassa i la producció primària de fitoplàncton ja que és un pigment comú a tots els grups taxonòmics. Aquesta tesi doctoral s'ha dut a terme amb l'objectiu de millorar la nostra capacitat d'extraure informació sobre l'estructura de les comunitats de fitoplàncton en l'oceà, mitjançant el desenvolupament i avaluació d'una nova aproximació basada en l'anàlisi de dades hiperespectrals. En particular, s'ha proposat una tècnica de classificació, on s'examinen les dissimilituds entre les signatures hiperespectrals de cada mostra d'aigua, i que ha estat aplicada en combinació amb l'espectroscopia derivativa, tècnica amb la qual s'exploren les característiques de la forma de l'espectre analitzat. Com a novetat, es proposa també una eina de validació per demostrar l'eficàcia d'aquesta nova tècnica de classificació. En el procés de validació es demostra que les classificacions obtingudes amb les dades òptiques i la metodologia proposada són molt semblants a les obtingudes amb dades basades en l'anàlisi de la composició pigmentària (utilitzant un cromatògraf líquid d'alta resolució, HPLC), tècnica habitualment utilitzada per la comunitat científica com a indicador de la composició de fitoplàncton. La viabilitat d'aquesta metodologia ha estat demostrada inicialment utilitzant una aproximació basada en simulacions, on la distribució del fitoplàncton està predeterminada i on s'han generat diferents escenaris lumínics d'aigües en mar obert i costaneres mitjançant un model de transferència radiativa. Per altra banda, escenaris reals de mar obert corresponents a diferents estacions en l'oceà Atlàntic han estat classificats satisfactòriament mitjançant les tècniques proposades, aplicades a dades hiperespectrals incloent espectres d'absorció i reflectància, així com els seus espectres derivats. Aquesta classificació ha servit per identificar una aplicació potencial de la metodologia proposada: l'establiment de diferents províncies bio-òptiques a partir de l'anàlisi de mesures hiperespectrals oceanogràfiques, donant lloc a l'examen de la seva rellevància biogeogràfica en comparació amb províncies ecològiques proposades prèviament en la literatura. Aquesta tesi conclou amb la confirmació de la hipòtesi principal: una millor discriminació de l'estructura i dinàmica de les comunitats de fitoplàncton és possible mitjançant l'ús d'observacions hiperespectrals oceanogràfiques. Cal destacar que l'aproximació proposada és en general aplicable a diferents conjunts de dades, més enllà de la composició pigmentària o dades òptiques obtingudes in situ també a dades obtingudes per teledetecció, dades biogeoquímiques i altres paràmetres hidrogràfics.

    Sustainable management of marine ecosystems requires a better knowledge about the space-time distribution and dynamics of ecological parameters such as phytoplankton communities, including critical bloom-forming algal groups. Better understanding of phytoplankton biodiversity and dynamics is essential in evaluating the role of each algal group in the global marine ecosystem and biogeochemical cycles. In attempting to address this question, in situ and remotely-sensed spectrometric optical observations have demonstrated to provide previously unavailable information regarding several optically active constituents in seawater at local and global scales, in particular, regarding phytoplankton community structure. In this sense, the advent of high spectral resolution (hyperspectral) optical sensors have raised new expectations about the possibilities of discriminating phytoplankton community composition in the ocean, beyond the estimation of only the primary pigment in phytoplankton, chlorophyll-a, a proxy for the phytoplankton biomass and primary production since it is common to all taxonomic groups. This PhD thesis has been carried out with the aim of improving our ability to extract information regarding phytoplankton community structure in the ocean by developing and evaluating a novel approach based on hyperspectral data analysis. In particular, a dissimilarity-based cluster technique, which accounts for complete spectral behaviour of hyperspectral data of each seawater sample, has been applied in combination with derivative spectroscopy, which exploits the spectral shape features of each analyzed spectrum. As a novelty, a validating tool has been proposed and proven useful to illustrate the effectiveness of the optical-based classification for discriminating different phytoplankton assemblages. This novel validation approach is based on the pigment composition analyzed in conjunction with concurrently obtained optical data, information which has been commonly used by the scientific community as a proxy for the phytoplankton composition. The feasibility of this methodology has initially been demonstrated using a simulation-based approach, i. e. using a radiative transfer modeling framework for open ocean and shallow coastal environments. In addition, different real open ocean environments corresponding to several stations in the eastern Atlantic Ocean have successfully been classified by applying the cluster analysis to different hyperspectral data sets including absorption and remote-sensing reflectance spectra and their second derivative spectra. This classification has served to identify a potential application of the proposed methodology: the establishment of different bio-optical provinces from the analysis of hyperspectral oceanographic observations, leading to examination of its biogeographical relevance by comparison to ecological provinces previously proposed in the literature. This thesis concludes by confirming the main hypothesis that discrimination of phytoplankton community structure and dynamics in the ocean can be enhanced while using hyperspectral oceanographic observations. It is noteworthy that the proposed approach is generally applicable to different data sets, besides in-situ pigment or optical data data also to remotely-sensed, biogeochemical or hydrographic data sets.

  • NUEVOS DESARROLLOS EN OPTICA VISUAL, VISION Y SISTEMAS HIPERESPECTRALES: APLICACIONES CLINICAS E INDUSTRIALES

     Arjona Carbonell, Maria Montserrat; Vilaseca Ricart, Meritxell; Ondategui Parra, Juan Carlos; Martinez Roda, Juan Antonio; Herrera, Jorge Alexis; Pujol Ramo, Jaume
    Participation in a competitive project

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  • Grading nuclear, cortical and posterior subcapsular cataracts using an objective scatter index measured with a double-pass system

     Vilaseca Ricart, Meritxell; Romero Vallés, M.José; Arjona Carbonell, Maria Montserrat; Luque, Sergio Oscar; Ondategui Parra, Juan Carlos; Salvador Playà, A.; Güell, José L.; Artal, Pablo; Pujol Ramo, Jaume
    British journal of ophthalmology
    Date of publication: 2012-09
    Journal article

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  • Método para la detección de pérdidas de función visual

     Pujol Ramo, Jaume; Ondategui Parra, Juan Carlos; Vilaseca Ricart, Meritxell; Arjona Carbonell, Maria Montserrat; Borras Garcia, M. Rosa
    Date of request: 2012-05-04
    Invention patent

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    Método para la detección de pérdidas de función visual.

    Comprende analizar la calidad óptica de un ojo de un paciente a partir de una o más imágenes retinianas del mismo, o de información relacionada con imágenes retinianas, correspondientes a un ojo con un segmento anterior y unos medios intraoculares sanos, comprendiendo el método detectar, en función del resultado del análisis, una pérdida de función visual de etiología funcional o patológica del sistema visual, y determinar que ésta es debida a una respuesta neural reducida y/o limitada, que induce alteraciones en la inervación de la musculatura intrínseca ocular del ojo.

  • Multispectral imaging system with multiplexed illumination for spectral and color measurements

     Herrera Ramirez, Jorge Alexis; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Interim Meeting of the International Color Association
    Presentation's date: 2011-06-07
    Presentation of work at congresses

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  • Automatic multispectral ultraviolet, visible and near-infrared capturing system for the study of artwork

     Herrera, J.; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Computer Vision and Image Analysis of Art
    Presentation's date: 2011-01-26
    Presentation of work at congresses

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  • Objective optical assessment of tear-film quality dynamics in normal and mildly symptomatic dry eyes

     Benito, Antonio; Pérez, Guillermo M; Mirabet, Sandra; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume; Marín*2, José M; Artal, Pablo
    Journal of cataract and refractive surgery
    Date of publication: 2011-08-01
    Journal article

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    PURPOSE: To evaluate and compare the tear-film dynamics in normal eyes and in eyes with mild dry-eye symptoms using a new noninvasive optical method based on a double-pass instrument. SETTING: Hospital Universitario Virgen de la Arrixaca, Murcia, Spain. DESIGN: Evaluation of diagnostic test or technology. METHODS: Dynamic recording of double-pass retinal images during unforced tear-film breakup was performed in eyes with mild dry-eye symptoms (study group) and in an asymptomatic control group. Series of consecutive retinal images were recorded every 0.5 seconds while the patient avoided blinking. Measurements were performed under low-light conditions to naturally increase pupil diameter and maximize the method’s sensitivity. Additional clinical tests were performed for comparison and included tear breakup time (TBUT), Schirmer I tests, and a normalized questionnaire (McMonnies). From the retinal images, a quality metric, the intensity distribution index, was calculated. An objective TBUT value was estimated in each eye when the intensity distribution index surpassed a defined threshold value compared with the initial baseline. RESULTS: The study group comprised 20 eyes and the control group, 18 eyes. Symptomatic dry eyes had a typical exponential increase in the intensity distribution index with time. The objective TBUT values in the study group were comparable to the clinical TBUT estimates. CONCLUSIONS: The new objective optical method to evaluate the quality and stability of the tear film was sensitive in detecting mild symptoms of dry eye and differentiating from normal cases. The procedure may allow early detection and follow-up of patients’ tear film–related complaints.

  • Iris Color and Texture: A Comparative Analysis of Real Irises, Ocular Prostheses, and Colored Contact Lenses

     Herrera Ramirez, Jorge Alexis; Vilaseca Ricart, Meritxell; Düll, Jochen; Arjona Carbonell, Maria Montserrat; Torrecilla Ribalta, Elena; Pujol Ramo, Jaume
    Color research and application
    Date of publication: 2011-10
    Journal article

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  • Response to the letter to the editor by Dr van den Berg

     Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Clinical and experimental optometry
    Date of publication: 2011-07-01
    Journal article

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  • Nuevas evidencias sobre la anisotropía del espacio visual y la influencia del entorno en el rendimiento visual  Open access

     Torrents Gomez, Aurora
    Defense's date: 2011-12-22
    Department of Optics and Optometry, Universitat Politècnica de Catalunya
    Theses

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    Desde hace años se han realizado múltiples investigaciones que tratan sobre la fiabilidad de la percepción de las distancias en profundidad y la influencia del entorno. En ocasiones, las pistas presentes en el espacio visual entran en conflicto y/o su interpretación conduce a sesgos y errores, produciendo efectos ilusorios al no corresponder las medidas físicas con las percibidas. El objetivo global de esta tesis doctoral ha sido poner de manifiesto nuevas evidencias de la anisotropía del espacio visual y de la influencia del entorno en relación al juicio de distancias entre objetos. Para ello, se han diseñado y ejecutado tres grupos de experimentos cuyos objetivos parciales fueron: Analizar el rol de las disparidades verticales en tareas de juicio de distancias relativas entre objetos situados en diferentes planos de profundidad, en función de la orientación del estímulo. Determinar la influencia del fondo y de la orientación del estímulo en tareas de juicio de distancias relativas entre objetos, situados en un mismo plano frontoparalelo o en diferentes planos de profundidad. Verificar la naturaleza neural de la anisotropía del espacio visual desde un enfoque psicofísico no invasivo mediante el uso de SIRDS. Los resultados obtenidos en esta tesis contribuyen a la comprensión sobre la integración de claves en Visión Binocular y los sesgos visuales perceptivos en la percepción de distancias.

    Recent decades have witnessed multiple studies investigating the accuracy of our visual system in depth perception, as well as the influence of environmental factors during depth judgment tasks. It is not uncommon for Virtual Space cues to offer contradictory or conflicting information, thus leading to bias and error, which in turn originate illusory effects resulting from discrepancies between real and perceived dimensions. Our research in the integration of cues in Binocular Vision aimed at determining the influence of background characteristics (curved, flat, etc) on the perception of visual stimuli presented over it. Therefore, three different experimental settings were designed and conducted, with partial objectives defined as follows: To evaluate the influence of vertical disparities in depth judgment tasks when stimuli were located at different depth planes and presented different orientations. To determine the influence of background configuration and stimulus orientation on depth judgment tasks, both with stimuli at the same frontoparallel plane or at different depth planes. To evidence the neural origin of the Visual Space anisotropy from a non invasive psychophysical approach with the use of SIRDS. The findings of the present PhD thesis contribute to our understanding of the integration of cues in Binocular Vision, as well as of the nature of visual bias in depth perception.

  • Diagnóstico y compensación del error refractivo

     Guisasola Valencia, Laura; Caum Aregay, Jesus Maria; Rius Ulldemolins, Anna; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume; Torrents Gomez, Aurora; Borras Garcia, M. Rosa; Sanchez Herrero, Eulalia; Martinez Roda, Juan Antonio; Olalla Domínguez, Carmen; Pizarro Bondia, Carlos
    Date of publication: 2011-03-10
    Book

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  • An objective scatter index based on double-pass retinal images of a point source to classify cataracts

     Artal, Pablo; Benito, A.; Pérez, G. M.; Alcón, E.; de Casas, A.; Pujol Ramo, Jaume; Marin, Jose M.
    PLoS One
    Date of publication: 2011
    Journal article

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  • Access to the full text
    Task oriented visual satisfaction and wearing success with two different simultaneous vision multifocal soft contact lenses  Open access

     Gispets Parcerisas, Joan; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume; Vilaseca Ricart, Meritxell; Cardona Torradeflot, Genis
    Journal of Optometry
    Date of publication: 2011
    Journal article

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  • Use of light-emitting diodes in multispectral systems design: variability of spectral power distribution according to angle and time of usage

     Martínez, Oscar; Vilaseca Ricart, Meritxell; Arjona Carbonell, Maria Montserrat; Pizarro Bondia, Carlos; Pujol Ramo, Jaume
    Journal of imaging science and technology
    Date of publication: 2011
    Journal article

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    Multispectral systems allow the spectral and color characterization of objects using images obtained from several acquisition channels with different spectral sensitivities. Light sources based on light-emitting diodes have started to be used in multispectral systems, mainly to develop low-cost devices for the industry. In this study, the authors examine the variability of spectral power distribution according to the viewing angle of white and single color light-emitting diodes, which can have a significant impact on spectral and color accuracy. This must be taken into account if they are to be used in multispectral systems design. The spectrum drift according to the time of usage of white light-emitting diodes is also analyzed.

  • Luminance adaptation model for increasing the dynamic range of an imaging system based on a CCD camera

     de Lasarte, Marta; Arjona Carbonell, Maria Montserrat; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Optik
    Date of publication: 2011-06-01
    Journal article

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  • Optical quality and intraocular scattering in a healthy young population

     Martinez Roda, Juan Antonio; Vilaseca Ricart, Meritxell; Ondategui Parra, Juan Carlos; Giner Tort, Anna; Burgos, Francisco Javier; Cardona Torradeflot, Genis; Pujol Ramo, Jaume
    Clinical and experimental optometry
    Date of publication: 2011-03
    Journal article

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  • Retinal image quality three months after photorefractive keratectomy for myopia of up to -5.75 Diopters

     Ondategui Parra, Juan Carlos; Vilaseca Ricart, Meritxell; Arjona Carbonell, Maria Montserrat; Boniquet, Sandra; Cardona Torradeflot, Genis; Güell, José L.; Pujol Ramo, Jaume
    Journal of Emmetropia
    Date of publication: 2011
    Journal article

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  • Comparative Study of Optical Quality and Intraocular Scattering Parameters between Healthy Young and Adult Population

     Martinez Roda, Juan Antonio; Ondategui Parra, Juan Carlos; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    European Meeting on Visual and Physiological Optics
    Presentation's date: 2010-08-22
    Presentation of work at congresses

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  • Evaluation of the repeatability and reproducibility levels for colour measurement obtained by digital imaging capture devices

     Chorro, Elisabeth; Vilaseca Ricart, Meritxell; Herrera Ramirez, Jorge Alexis; Perales, Esther; Martínez Verdú, Francisco Miguel; Pujol Ramo, Jaume
    European Conference on Colour in Graphics, Imaging and Vision
    Presentation's date: 2010-06-14
    Presentation of work at congresses

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    Conventional and multi-spectral digital imaging capture devices can be used for colorimetric measurements. However, a preliminary study of their repeatability and reproducibility is very advisable if they want to be used for this purpose. In this work, a methodology to study the repeatability and reproducibility of such systems is proposed and two digital imaging capture devices working as spectroradiometers with three and seven filters, respectively, are analyzed with respect to a reference tele-spectra-colorimeter. The results of the statistical test show that both have good levels of repeatability, although not the same conclusion is reached regarding the reproducibility, due to some systematic errors.

  • Spectral reflectance analysis of tobacco leaves and fungus infection detection

     Gor, Sergio; Sandoval, José; Ramallo, Ana; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Interim Meeting of the International Color Association
    Presentation's date: 2010-09
    Presentation of work at congresses

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    Optical properties of vegetable matter and associated analytical techniques such as VIS and NIR reflectance spectroscopy were used for several decades in the foodstuff industry. By means of these techniques, is possible to study and determine the plant pathology of crops: health or disease conditions, water stress, growth, etc., being a good alternative to traditional chemical or biological tests, generally very invasive and even destructive. The aim of this work is to analyse and quantify the effect of the presence and development of the pathogen Fusarium on spectral signatures of Burley tobacco leaves, and to evaluate the potential of radiometric techniques as tools for diagnosis.

  • Spectral variability of light-emitting diodes with angle

     Martínez, Óscar; Vilaseca Ricart, Meritxell; Pizarro Bondia, Carlos; Ferrer Serrano, Edgar; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume
    European Conference on Colour in Graphics, Imaging, and vision
    Presentation's date: 2010-06-14
    Presentation of work at congresses

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    Multispectral systems allow the spectral characterization of the scene through several acquisition channels with different spectral features. The spectral sampling can be done by using transmittance filters and a white light source or illuminating the scene using light sources with different spectral emission characteristics. Light-emitting diodes based light sources have started to be used in multispectral systems, mainly to develop low-cost devices for the industry. In this study we analyze the spectral power distribution and color variability of white and single color light-emitting diodes relative to the viewing angle, and highlight some aspects that must be taken into account if these light sources want to be used in a multispectral system.

  • Desarrollo de un sistema hiperespectral para la medida del color en muestras extensas con patrones especialmente complejos

     Ferrer Serrano, Edgar; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume; Arjona Carbonell, Maria Montserrat
    Congreso Nacional del Color
    Presentation of work at congresses

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    Cada vez son más los distintos dispositivos para la medida del color basados en sensores optoelectrónicos de imagen. En los últimos años se ha generalizado el uso de sistemas multiespectrales y, en particular, se han empezado a emplear sistemas hiperespectrales que combinan un sistema espectrográfico con una cámara monocromática capaz de realizar medidas de alta calidad con información espectral y espacial. Además, estos sistemas tienen la ventaja de proporcionar el espectro de cada uno de los píxeles de una línea de la imagen. En este trabajo se presenta el método de puesta a punto y validación de un sistema hiperespectral para fines colorimétricos y aplicados a muestras extensas con patrones especialmente complejos. Para ello se ha desarrollado el software que permite obtener imágenes hiperespectrales de alta calidad y se han aplicado losa algoritmos necesarios para la determinación de los espectros de reflectancia y diferencias de color de las muestras. También se ha validado la incertidumbre del sistema comparando los resultados hallados con los obtenidos con un instrumento de referencia a través de la comparación de curvas de reflectancia espectral. Por último se ha aplicado a la medida de muestras reales extensas con patrones especialmente complejos, concretamente para aplicaciones relacionadas con la industria de la madera.

  • Evaluación del nivel de repetibilidad para medidas de color obtenidas mediante dos sistemas de captura digital de imagen

     Chorro, Elisabeth; Vilaseca Ricart, Meritxell; Herrera Ramirez, Jorge Alexis; Perales, Esther; Martínez Verdú, Francisco Miguel; Pujol Ramo, Jaume
    Congreso Nacional del Color
    Presentation's date: 2010-06-30
    Presentation of work at congresses

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  • Utilización de LEDs en sistemas multiespectrales: influencia del ángulo y del tiempo en la emisión espectral

     Martínez, Óscar; Vilaseca Ricart, Meritxell; Pizarro Bondia, Carlos; Arjona Carbonell, Maria Montserrat; Pujol Ramo, Jaume
    Congreso Nacional del Color
    Presentation of work at congresses

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    Los sistemas multiespectrales permiten la caracterización espectral y colorimétrica de objetos con elevada resolución espacial a partir de la adquisición de la escena a través de varios canales de una cámara con diferente sensibilidad espectral. Recientemente han empezado a utilizarse LEDs (diodo emisor de luz) como fuentes de luz en sistemas de este tipo, principalmente para desarrollar equipos de medida de bajo coste para la industria. En este estudio, ponemos de manifiesto y evaluamos algunas de las consideraciones que deben tenerse en cuenta si quieren utilizarse LEDs en sistemas multiespectrales. Dos aspectos a tener en cuenta tanto en LEDs blancos como de color son la variación de su emisión espectral con el ángulo y el cambio del espectro de la luz emitida con el tiempo de utilización. Estas características no son normalmente especificadas en los catálogos de fabricantes pero deben ser previamente consideradas y corregidas si se quiera desarrollar e implementar un sistema multiestpectral con LEDs, puesto que pueden tener un gran impacto en la exactitud de medida del color y de las propiedades espectrales. En este trabajo de estudian ambos aspectos, y se halla que la temperatura de color de los LEDs blancos disminuye fe forma notable al aumentar el ángulo de observación, siendo este cambio más acusado en LEDs de elevada direccionalidad, es decir, si su patrón de emisión espacial es más estrecho. Sin embargo se observa que la emisión de los LEDs de color es casi invariable con el ángulo. Por otro lado, se pone de manifiesto que el cambio en la emisión espectral de los LEDs blancos con el tiempo, y por tanto su temperatura de color, es menos importante que la variabilidad observada con el ángulo de observación.

  • Spectral signatures: A way to identify species and conditions of vegetables

     Sandoval, José; Gor, Sergio; Ramallo, Jacqueline; Sfer, Ana María; Colombo, Elisa; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Interim Meeting of the International Color Association
    Presentation's date: 2010-09
    Presentation of work at congresses

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    This work shows the results obtained by the application of suitable techniques for the acquisition and processing of spectral absorbance data of several vegetable species, allowing its identification –assignment of each spectral signature to one specific plant- which in turn allows the control of origin of products (foodstuffs or not) and their characteristics. Spectral measurements of absorbance were performed on samples of two sugarcane varieties and four citrus types (orange, lemon, tangerine and grapefruit) taken periodically from a controlled crop, using a spectrophotometer FOSS-NIR 6500 in the range of 400-2500 nm by 2 nm. The measured samples were about 240 in the case of sugarcane and 160 in the case of citrus. A Principal Component Analysis was applied to the data by means of STATA 9 software and the results were interpreted in that PCA context. This procedure allowed us not only to clearly identify which variety of sugarcane corresponds to each spectral absorbance function, but also to determine which wavelength or wavebands have significant relevance for that identification. Similarly, this technique allows us to identify and classify the spectral functions coming from different types of citrus. The main conclusion is that the proposed technique is capable to precisely identifying the species each sample comes from; besides, this technique would allow us to determine the nutritional or health condition of them at the moment of the analysis, as could be seen from the obtained results.

  • Effect of laser in situ keratomileusis on vision analyzed using preoperative optical quality

     Vilaseca Ricart, Meritxell; Padilla, Adenay; Ondategui Parra, Juan Carlos; Arjona Carbonell, Maria Montserrat; Güell, José L.; Pujol Ramo, Jaume
    Journal of cataract and refractive surgery
    Date of publication: 2010-11
    Journal article

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  • Intra- and Intersession Repeatability of a Double-Pass Instrument

     Vilaseca Ricart, Meritxell; Peris March, Maria Elvira; Pujol Ramo, Jaume; Borras Garcia, M. Rosa; Arjona Carbonell, Maria Montserrat
    Optometry and vision science
    Date of publication: 2010-09
    Journal article

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  • Camera-based colour measurement

     Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume; Martínez Verdú, Francisco Miguel; Chorro, Elisabeth; Perales, Esther
    Date of publication: 2010-08-01
    Book chapter

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  • Influence of the Number of Samples of the Training Set on Accuracy of Color Measurement and Spectral Reconstruction

     de Lasarte Rigueiro, Marta; Arjona Carbonell, Maria Montserrat; Vilaseca Ricart, Meritxell; Pujol Ramo, Jaume
    Journal of imaging science and technology
    Date of publication: 2010-05
    Journal article

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