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    Energy efficiency of a new trifocal intraocular lens  Open access

     Vega Lerin, Fidel; Alba Bueno, Francisco; Millan Garcia Varela, Maria Sagrario
    Journal of the European Optical Society: rapid publications
    Vol. 9, p. 14002-1-14002-8
    DOI: 10.2971/jeos.2014.14002
    Date of publication: 2014-01-15
    Journal article

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    The light distribution among the far, intermediate and near foci of a new trifocal intraocular lens (IOL) is experimentally determined, as a function of the pupil size, from image analysis. The concept of focus energy efficiency is introduced because, in addition to the theoretical diffraction efficiency of the focus, it accounts for other factors that are naturally presented in the human eye such as the level of spherical aberration (SA) upon the IOL, light scattering at the diffractive steps or the depth of focus. The trifocal IOL is tested in-vitro in two eye models: the aberration-free ISO model, and a so called modified-ISO one that uses an artificial cornea with positive spherical SA in instead. The SA upon the IOL is measured with a Hartmann-Shack sensor and compared to the values of theoretical eye models. The results show, for large pupils, a notorious reduction of the energy efficiency of the far and near foci of the trifocal IOL due to two facts: the level of SA upon the IOL is larger than the value the lens is able to compensate for and there is significant light scattering at the diffractive steps. On the other hand, the energy efficiency of the intermediate focus for small pupils is enhanced by the contribution of the extended depth of focus of the near and far foci. Thus, while IOLs manufacturers tend to provide just the theoretical diffraction efficiency of the foci to show which would be the performance of the lens in terms of light distribution among the foci, our results put into evidence that this is better described by using the energy efficiency of the foci.

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    Images encryption system based on a fractional joint transform correlator and nonlinear filtering  Open access

     Vilardy Ortiz, Juan Manuel; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Óptica pura y aplicada
    Vol. 47, num. 1, p. 35-41
    DOI: 10.7149/OPA.47.1.35
    Date of publication: 2014
    Journal article

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    A new optical security system for image encryption based on a fractional joint transform correlator and nonlinear filtering is proposed. The position of the lens in the proposed optical encryption setup can be chosen, so that an additional key is introduced in the security system. The distributions at the input and output planes of the encryption system are related by a fractional Fourier transform (FrFT) at a given fractional order that is defined, among other parameters, by the focal length and the position of the lens in the setup; this fractional order acts as an additional key of the security system. The optical intensity of the complex distribution in the fractional Fourier domain (output plane) is captured by a CCD camera. The nonlinearity introduced in the last step of the encryption process, maintains the encrypted function as a real-valued function. The security system proposed in this work is an generalization of the encryption system based on a conventional joint transform correlator (JTC), from the Fourier domain to the fractional Fourier domain. Additional advantages of the proposed system are: new degrees of freedom for the optical setup, alleviated alignment requirement, and the introduction of an additional key (the fractional order of the FrFT) that improves security. Numerical simulations verify the validity of this new optical security system

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    Nonlinear optical security system based on a joint transform correlator in the Fresnel domain  Open access

     Vilardy Ortiz, Juan Manuel; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Applied optics
    Vol. 53, num. 8, p. 1674-1682
    DOI: 10.1364/AO.53.001674
    Date of publication: 2014-03-10
    Journal article

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    A new optical security system for image encryption based on a nonlinear joint transform correlator (JTC) in the Fresnel domain (FrD) is proposed. The proposal of the encryption process is a lensless optical system that produces a real encrypted image and is a simplified version of some previous JTC-based encryption systems. We use a random complex mask as the key in the nonlinear system for the purpose of increasing the security of the encrypted image. In order to retrieve the primary image in the decryption process, a nonlinear operation has to be introduced in the encrypted function. The optical decryption process is implemented through the Fresnel transform and the fractional Fourier transform. The security system proposed in this paper preserves the shift-invariance property of the JTC-based encryption system in the Fourier domain, with respect to the lateral displacement of the key random mask in the decryption process. This system shows an improved resistance to chosen-plaintext and known-plaintext attacks, as they have been proposed in the cryptanalysis of the JTC encrypting system. Numerical simulations show the validity of this new optical security system. (C) 2014 Optical Society of America

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    Programmable diffractive lens for ophthalmic application  Open access

     Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet; Romero Perez, Lenny Alexandra; Ramirez, Natalia
    Optical engineering
    Vol. 53, num. 6, p. 1-12
    DOI: 10.1117/1.OE.53.6.061709
    Date of publication: 2014-03-18
    Journal article

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    Pixelated liquid crystal displays have been widely used as spatial light modulators to implement programmable diffractive optical elements, particularly diffractive lenses. Many different applications of such components have been developed in information optics and optical processors that take advantage of their properties of great flexibility, easy and fast refreshment, and multiplexing capability in comparison with equivalent conventional refractive lenses. We explore the application of programmable diffractive lenses displayed on the pixelated screen of a liquid crystal on silicon spatial light modulator to ophthalmic optics. In particular, we consider the use of programmable diffractive lenses for the visual compensation of refractive errors (myopia, hypermetropia, astigmatism) and presbyopia. The principles of compensation are described and sketched using geometrical optics and paraxial ray tracing. For the proof of concept, a series of experiments with artificial eye in optical bench are conducted. We analyze the compensation precision in terms of optical power and compare the results with those obtained by means of conventional ophthalmic lenses. Practical considerations oriented to feasible applications are provided. © 2014 Society of Photo-Optical Instrumentation Engineers.

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    Stereo-Acuity in Patients Implanted with Multifocal Intraocular Lenses: Is the Choice of Stereotest Relevant?  Open access

     Varon Puentes, Maria Consuelo; Gil Arnal, Miguel Ángel; Alba Bueno, Francisco; Cardona Torradeflot, Genis; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario; Buil Calvo, José Antonio
    Current eye research
    Vol. 39, num. 7, p. 711-719
    DOI: 10.3109/02713683.2013.865758
    Date of publication: 2014-07-01
    Journal article

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    Purpose: A randomized and double-blinded study design was implemented to assess the stereo-acuity in patients symmetrically implanted with four types of multifocal intraocular lenses (MIOLs), compared to a monofocal lens (control group). In addition, the influence of the type of test employed for the evaluation of stereo-acuity was explored.; Materials and Methods: Six months after cataract intervention, stereo-acuity was measured with the Titmus and TNO stereotests in 143 patients implanted with one of the following MIOL lens types: hybrid spherical SN60D3, hybrid aspheric SN6AD1, diffractive aspheric ZMA00 and refractive spherical NXG1. A control group implanted with the monofocal aspheric ZA9003 (in which stereo-acuity was measured with a near addition) was also included in the study.; Results: Statistically significant better stereo-acuity was found in the monofocal group with both stereotests (except for the SN60D3 group with the Titmus test) (all p<0.001). No significant differences in stereo-acuity between MIOLs were found using the Titmus test. However, with the TNO, patients implanted with hybrid diffractive MIOLs exhibited statistically significant worse stereo-acuity than those with the refractive design (SN60D3, p<0.001; SN6AD1, p = 0.006).; Conclusions: Patients implanted with MIOLs have worse stereo-acuity than those implanted with monofocal IOLs due to the decrease in retinal image contrast originating in the simultaneous presence of two images. Awavelength-based stereotest such as the TNO induces large differences in image contrast between fellow eyes implanted with diffractive-based MIOLs, which may result in an underestimation of the real stereo-acuity of the patient.

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    Restoration of retinal images with space-variant blur  Open access

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; ¿orel, Michal; ¿roubek, Filip
    Journal of biomedical optics
    Vol. 19, num. 1
    DOI: 10.1117/1.JBO.19.1.016023
    Date of publication: 2014-01-01
    Journal article

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    Retinal images are essential clinical resources for the diagnosis of retinopathy and many other ocular diseases. Because of improper acquisition conditions or inherent optical aberrations in the eye, the images are often degraded with blur. In many common cases, the blur varies across the field of view. Most image deblurring algorithms assume a space-invariant blur, which fails in the presence of space-variant (SV) blur. In this work, we propose an innovative strategy for the restoration of retinal images in which we consider the blur to be both unknown and SV. We model the blur by a linear operation interpreted as a convolution with a point-spread function (PSF) that changes with the position in the image. To achieve an artifact-free restoration, we propose a framework for a robust estimation of the SV PSF based on an eye-domain knowledge strategy. The restoration method was tested on artificially and naturally degraded retinal images. The results show an important enhancement, significant enough to leverage the images' clinical use. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

  • Caracterización Óptica de Lentes Intraoculares

     Alba Bueno, Francisco
    Universitat Politècnica de Catalunya
    Theses

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    La caracterización óptica de las lentes intraoculares (IOLs del inglés Intraocular Lenses) proporciona una información objetiva y cuantitativa que es necesaria para comprender su funcionamiento como implante que sustituye al cristalino en el sistema visual humano. Además, permite predecir el rendimiento de los nuevos diseños. Dicha caracterización se debe llevar a cabo mediante pruebas in vivo en pacientes ya implantados así como con pruebas in vitro en banco óptico o mediante simulación teórica. Esta tesis analiza las fuentes de error en el cálculo de la potencia de las lentes intraoculares y la compensación de los errores refractivos residuales mediante el uso de grados de libertad no convencionales. Se centra, fundamentalmente, en la caracterización in vitro de una variedad de lentes comercialmente disponibles (monofocales, multifocales, esféricas, asféricas, apodizadas, no--apodizadas, y distintos materiales, potencias y adiciones) en un banco óptico. Para ello se ha diseñado y puesto a punto los métodos de medida, un montaje experimental que reproduzca las condiciones en las que las lentes se implantan en el ojo y de acuerdo con la normativa internacional. Se ha medido la calidad óptica a través de la Función de Transferencia de Modulación o la visibilidad de franjas (contraste). Se ha desarrollado e implementado un método para la cuantificación experimental de la eficiencia energética de los distintos modelos de IOLs. Este método ha servido para explicar algunos resultados clínicos obtenidos al evaluar la visión estereoscópica con dos tests con diferente principio de funcionamiento. Se ha desarrollado e implementado un método para caracterizar el halo que perciben algunos pacientes implantados con IOLs multifocales.

  • Sistemas de profundidad de foco extendida y lentes intraoculares multifocales para la salud visual

     Pérez Cabré, Elisabet; Escofet Soteras, Jaume; Rallo Capdevila, Miguel; Vega Lerin, Fidel; Varon Puentes, Maria Consuelo; Jaroszewicz, Zbigniew; Cardona Torradeflot, Genis; Marrugo Hernandez, Andrés Guillermo; Kolodziejczyk, Andrzej; Millan Garcia Varela, Maria Sagrario
    Competitive project

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  • Estereopsis en pacientes implantados con lentes intraoculares multifocales: la influencia del test de medida

     Varon Puentes, Maria Consuelo; Gil Arnal, Miguel Ángel; Alba Bueno, Francisco; Cardona Torradeflot, Genis; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario; Buil Calvo, José Antonio
    Congreso Internacional de Optometría, Contactología y Óptica Oftálmica
    Presentation's date: 2014-04-05
    Presentation of work at congresses

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  • Journal of Optics Highlights of 2012

     Millan Garcia Varela, Maria Sagrario
    Award or recognition

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  • Comprehensive Retinal Image Analysis: Image Processing and Feature Extraction Techniques Oriented to the Clinical Task  Open access

     Marrugo Hernandez, Andrés Guillermo
    Universitat Politècnica de Catalunya
    Theses

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    La captura de imagen digital es una parte fundamental de los procedimientos médicos modernos. Provee de documentación visual, un registro permanente para los pacientes y más importante la posibilidad de extraer información sobre muchas enfermedades. La oftalmología es un rama de la medicina que depende considerablemente del análisis de imágenes digital. Por medio de la imagen digital se puede establecer un diagnóstico temprano incluso antes que los primeros síntomas comiencen a aparecer. Este trabajo contribuye al análisis digital de tales imágenes y los problemas que surgen a lo largo del proceso de formación de imagen. Este campo se le conoce como análisis de imagen retiniana. En esta tesis se han propuesto soluciones a problemas asociados con la adquisición de imagen retiniana y el monitoreo de cambios temporales en patologías retinianas. Específicamente, los problemas de iluminación no-uniforme, baja calidad de imagen, enfoque automático, y análisis multi-canal. Sin embargo, existen situaciones inevitables en que se adquieren imágenes de baja calidad, como imágenes emborronadas debido a las aberraciones del ojo. Este problema lo hemos abordado utilizando dos metodologías para la deconvolución ciega de imágenes emborronadas. En la primera aproximación, consideramos que el emborronamiento es invariante espacialmente y en la segunda aproximación extendimos el trabajo y propusimos un método más general espacialmente variante.Para el desarrollo de algoritmos hemos construido soluciones de preprocesado que han permitido la extracción de características de relevancia médica, como la segmentación del disco óptico y la detección y visualización de cambios temporales en la retina. Resultados experimentales significativos obtenidos en imágenes reales provenientes de la práctica clínica demuestran la aplicabilidad de las soluciones propuestas.

    Tesi per compendi de publicacions

    Medical digital imaging has become a key element of modern health care procedures. It provides a visual documentation, a permanent record for the patients, and most importantly the ability to extract information about many diseases. Ophthalmology is a field that is heavily dependent on the analysis of digital images because they can aid in establishing an early diagnosis even before the first symptoms appear. This dissertation contributes to the digital analysis of such images and the problems that arise along the imaging pipeline, a field that is commonly referred to as retinal image analysis. We have dealt with and proposed solutions to problems that arise in retinal image acquisition and longitudinal monitoring of retinal disease evolution. Specifically, non-uniform illumination, poor image quality, automated focusing, and multichannel analysis. However, there are many unavoidable situations in which images of poor quality, like blurred retinal images because of aberrations in the eye, are acquired. To address this problem we have proposed two approaches for blind deconvolution of blurred retinal images. In the first approach, we consider the blur to be space-invariant and later in the second approach we extend the work and propose a more general space-variant scheme. For the development of the algorithms we have built preprocessing solutions that have enabled the extraction of retinal features of medical relevancy, like the segmentation of the optic disc and the detection and visualization of longitudinal structural changes in the retina. Encouraging experimental results carried out on real retinal images coming from the clinical setting demonstrate the applicability of our proposed solutions.

  • Elementos ópticos difractivos programables con aplicabilidad en óptica oftálmica

     Romero Perez, Lenny Alexandra
    Department of Optics and Optometry, Universitat Politècnica de Catalunya
    Theses

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    Los elementos difractivos programables (DOEs del inglés Diffractive Optical Elements) reproducidos mediante moduladores espaciales de luz son de gran importancia en la construcción de sistemas ópticos formadores de imagen. La principal razón tiene que ver con la versatilidad de los moduladores y el uso de menor número de elementos ya que en modulador se pueden combinar distintos DOEs en un solo elemento. Esta tesis consiste en el diseño, caracterización y análisis de diversos DOEs programables tales como: lentes de Fresnel, lentes multifocales, combinaciones integradas de máscaras de fase con lentes y elementos con capacidad de extender la profundidad de campo (DOF del ingles depth of field), como el Light Sword optical element y el Peacock Eye. Este trabajo busca solventar por medio del uso de DOEs en un modulador espacial de luz diversos problemas de la visión humana, como la miopía, hipermetropía, astigmatismo y la presbicia. La implementación se llevó a cabo en un modulador Holoeye LCoS (del inglés Liquid Crystal on Sylicon) de 1080P. Hemos desarrollado e implementado distintos algoritmos para la generación de los elementos ópticos necesarios para la compensación de las ametropías. Los resultados obtenidos mediante pruebas de simulación y experimentación permiten contrastar las propiedades de los DOEs analizados y destacar aquéllos que por su funcionalidad en la compensación de ametropías pueden alcanzar una mayor aplicabilidad.

  • Static and dynamic amplitude modulation of light in a twisted nematic liquid crystal display

     Vilardy Ortiz, Juan Manuel; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Iberoamerican Conference on Optics, Latinamerican meeting on Optics Lasers and Applications
    p. 87853O-1-87853O-8
    DOI: 10.1117/12.2020913
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    A SLM has been experimentally characterized in terms of amplitude modulation versus the gray level distribution (input signal) electronically addressed to the pixelated display in two conditions: input constant with time, and time variant input with increasing frame rate. The SLM considered in this work was a twisted nematic liquid crystal display manufactured by CRL (XGA2 model) that operates on the transmitted light. The influence of some technical specications such as gamma correction, brightness and contrast of this SLM have been considered as well.

    A SLM has been experimentally characterized in terms of amplitude modulation versus the gray level distribution (input signal) electronically addressed to the pixelated display in two conditions: input constant with time, and time variant input with increasing frame rate. The SLM considered in this work was a twisted nematic liquid crystal display manufactured by CRL (XGA2 model) that operates on the transmitted light. The influence of some technical speci cations such as gamma correction, brightness and contrast of this SLM have been considered as well.

  • Blind restoration of retinal images degraded by space-variant blur with adaptive blur estimation

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; ¿orel, Michal; ¿roubek, Filip
    Iberoamerican Conference on Optics, Latinamerican meeting on Optics Lasers and Applications
    DOI: 10.1117/12.2025134
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Retinal images are often degraded with a blur that varies across the gield view. Because traditional deblurring algorithms assume the blur to be space-invariant they typically fail in the presence of space-variant blur. In this work we consider the blur to be both unknown and space-variant. To carry out the restoration, we assume that in small regions the space-variant blur can be approximated by a space-invariant point-spread function (PSF). However, instead of deblurring the image on a per-patch basis, we extend individual PSFs by linear interpolation and perform a global restoration. Because the blind estimation of local PSFs may fail we propose a strategy for the identification of valid local PSFs and perform interpolation to obtain the space-variant PSF. The method was tested on artificial and real degraded retinal images. Results show significant improvement in the visibility of subtle details like small blood vessels.

  • Experiment design for through-focus testing of intraocular lenses

     Millan Garcia Varela, Maria Sagrario; Alba Bueno, Francisco; Vega Lerin, Fidel
    Iberoamerican Conference on Optics, Latinamerican meeting on Optics Lasers and Applications
    DOI: 10.1117/12.2025474
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Eye models to test intraocular lenses (IOLs) in an optical bench are commonly designed in agreement with the ISO 11979-2 and 11979-9 standard requirements. However, modifications to the ISO eye model have been proposed to test IOLs in conditions closer to real human eye. Wavefront analysis and aberration characterization, wavelength dependence, efficiency, off-axis performance and imaging degradation under certain amount of misalignment can thus be measured in vitro. The main parts of the system to test IOLs are: the illumination system and object test, the eye model including the IOL immersed in a wet cell and a microscope assembled to a sensor that magnifies and captures the aerial image of the object formed by the eye model. A problem concerning the simultaneous variation of defocus and magnification arises when using the microscope to capture out-of-focus images in a through-focus study. Using the eye model, we study the problem of implementing a through-focus measurement of the imaging quality of an IOL. We find a solution based on geometrical optics and compare it with other proposals reported in the literature. The effects on the measurement of the Modulation Transfer Function and the Point Spread Function are predicted. Experimental results are obtained and discussed.

  • Joint transform correlator-based encryption system using the Fresnel transform and nonlinear filtering

     Vilardy Ortiz, Juan Manuel; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Iberoamerican Conference on Optics, Latinamerican meeting on Optics Lasers and Applications
    DOI: 10.1117/12.2020912
    Presentation's date: 2013-07
    Presentation of work at congresses

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    A new optical security system for image encryption based on a nonlinear joint transform correlator (JTC) and Fresnel transform is proposed. A lensless optical encryption system, which is a simplifried version of previous JTCbased encryption systems, produces a complex distribution in the Fresnel domain, whose intensity is captured by a power-law sensor and nonlinearly modified to yield the real-valued encrypted image. The nonlinearity plays an essential role in the decryption system which, in turn, contains an optical fractional Fourier transform to retrieve the primary image. The security system proposed in this work is a novel extension of the conventional JTC-based encryption system from the Fourier domain to the Fresnel domain. Additional advantages of the proposed system are: simplification of the optical setup, alleviated alignment requirements, and an additional key (the propagation distance) that improves security. Numerical simulations verify the validity of this new optical security system.

  • Ophthalmic compensation of visual ametropia based on a programmable diffractive lens

     Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet; Romero Perez, Lenny Alexandra; Ramirez, Natalia
    Iberoamerican Conference on Optics, Latinamerican meeting on Optics Lasers and Applications
    DOI: 10.1117/12.2025472
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Pixelated liquid crystal displays have been widely used as spatial light modulators to implement programmable diffractive optical elements (DOEs), particularly diffractive lenses. Many different applications of such components have been developed in information optics and optical processors that take advantage of their properties of great flexibility, easy and fast refreshment, and multiplexing capability in comparison with equivalent conventional refractive lenses. In this paper, we explore the application of programmable diffractive lenses displayed on the pixelated screen of a liquid crystal on silicon spatial light modulator (LCoS-SLM) to ophthalmic optics. In particular, we consider the use of programmable diffractive lenses for the visual compensation of some refractive errors (myopia, hyperopia). The theoretical principles of compensation are described and sketched using geometrical optics and paraxial ray tracing. A series of experiments with artificial eye in optical bench are conducted to analyze the compensation accuracy in terms of optical power and to compare the results with those obtained by means of conventional ophthalmic lenses. Practical considerations oriented to feasible applications are provided.

  • Experiment design for through-focus intraocular lens testing in optical bench

     Millan Garcia Varela, Maria Sagrario; Alba Bueno, Francisco; Vega Lerin, Fidel
    Iberoamerican Conference on Optics, Latinamerican meeting on Optics Lasers and Applications
    Presentation's date: 2013-07-22
    Presentation of work at congresses

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    Improved decryption quality and security of a joint transform correlator-based encryption system  Open access

     Vilardy, Juan Manuel; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Journal of Optics
    Vol. 15, num. 2
    DOI: 10.1088/2040-8978/15/2/025401
    Date of publication: 2012-12-06
    Journal article

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    Photon-counting double-random-phase encoding for secure image verification and retrieval  Open access

     Pérez Cabré, Elisabet; Abril Baez, Hector C.; Millan Garcia Varela, Maria Sagrario; Javidi, Bahram
    Journal of Optics
    Vol. 14, num. 9, p. 2-12
    DOI: 10.1088/2040-8978/14/9/094001
    Date of publication: 2012-09
    Journal article

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  • Advanced optical correlation and digital methods for pattern matching¿50th anniversary of Vander Lugt matched filter

     Millan Garcia Varela, Maria Sagrario
    Journal of Optics
    Vol. 14, num. 10
    DOI: 10.1088/2040-8978/14/10/103001
    Date of publication: 2012-10-03
    Journal article

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  • Anisotropy-based robust focus measure for non-mydriatic retinal imaging

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; Cristobal, Gabriel; Gabarda, Salvador; Abril Baez, Hector C.
    Journal of biomedical optics
    Vol. 17, num. 7, p. 1-10
    DOI: 10.1117/1.JBO.17.7.076021 Text S
    Date of publication: 2012-07-17
    Journal article

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  • Extended focal depth imaging using single and double peacock eye phase diffractive elements

     Romero Perez, Lenny Alexandra; Millan Garcia Varela, Maria Sagrario; Jaroszewicz, Zbigniew; Kolodziejczyk, Andrzej
    Proceedings of SPIE, the International Society for Optical Engineering
    Vol. 8429, num. 84291R, p. 1-9
    DOI: 10.1117/12.923028
    Date of publication: 2012
    Journal article

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  • Medida del índice de modulación de tejidos textiles transparentes a partir de la MTF

     Escofet Soteras, Jaume; Mitja, Carles; Rallo Capdevila, Miguel; Millan Garcia Varela, Maria Sagrario
    Reunión Nacional de Óptica
    p. 449-452
    Presentation's date: 2012-09-04
    Presentation of work at congresses

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    Los tejidos textiles transparentes permiten el paso de luz e información de baja frecuencia a través de ellos. A plena luz del día un observador situado en el interior de una habitación, al mirar a través de un tejido transparente los objetos situados en el exterior, percibe una imagen del objeto original mucho menos nítida y, en algunos casos, con ruido añadido. En este trabajo se presenta un método objetivo de medida de la nitidez de la imagen cuando es vista a través de un tejido transparente. Se reemplaza el sistema visual humano por una cámara fotográfica y se fotografía la imagen de un Test de Borde Inclinado a través del tejido. La función de modulación de la transferencia del sistema (MTF) caracteriza la imagen observable a través del tejido textil.

  • View-through characterization of translucent fabrics based on opto-digital image analysis

     Escofet Soteras, Jaume; Mitja, Carles; Rallo Capdevila, Miguel; Millan Garcia Varela, Maria Sagrario
    Proceedings of SPIE, the International Society for Optical Engineering
    Vol. 8436
    DOI: 10.1117/12.922329
    Date of publication: 2012
    Journal article

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  • Image Analysis in Modern Ophthalmology: From Acquisition to Computer Assisted Diagnosis and Telemedicine

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; Cristobal, Gabriel; Gabarda, Salvador; ¿orel, Michal; ¿roubek, Filip
    Proceedings of SPIE, the International Society for Optical Engineering
    Vol. 8436
    DOI: 10.1117/12.921299
    Date of publication: 2012
    Journal article

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  • Toward computer-assisted diagnosis and telemedicine in ophthalmology

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; Cristobal, Gabriel; Gabarda, Salvador; ¿orel, Michal; ¿roubek, Filip
    SPIE Newsroom
    p. 1-3
    DOI: 10.1117/2.1201205.004256
    Date of publication: 2012-06-08
    Journal article

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  • Double peacock eye optical element for extended focal depth imaging with ophthalmic applications

     Romero Perez, Lenny Alexandra; Millan Garcia Varela, Maria Sagrario; Jaroszewicz, Zbigniew; Kolodziejczyk, Andrzej
    Journal of biomedical optics
    Vol. 17, num. 4, p. 1-9
    DOI: 10.1117/1.JBO.17.4.046013
    Date of publication: 2012-04-27
    Journal article

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  • Expected Visual Acuity and Depth of Focus with spherical and aspheric Intraocular Lenses

     Alba Bueno, Francisco; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario; Navarro Belsue, Rafael
    European Meeting on Visual and Physiological Optics
    Presentation's date: 2012-08-20
    Presentation of work at congresses

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  • Stereo-acuity in patients symmetrically implanted with multifocal intraocular lenses

     Gil Arnal, Miguel Ángel; Varon Puentes, Maria Consuelo; Alba Bueno, Francisco; Vega Lerin, Fidel; Cardona Torradeflot, Genis; Millan Garcia Varela, Maria Sagrario; Buil Calvo, José Antonio
    The International Society of Presbyopia
    Presentation's date: 2012-09
    Presentation of work at congresses

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    Mejora del nivel de seguridad y de la calidad de la imagen desencriptada en un sistema de encriptación basado en un correlador de transformadas conjuntas  Open access

     Vilardy, Juan Manuel; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Reunión Nacional de Óptica
    p. 62-65
    Presentation's date: 2012-09-04
    Presentation of work at congresses

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  • Defocus correction in the optical system of the eye: unconventional degrees of freedom

     Alba Bueno, Francisco; Millan Garcia Varela, Maria Sagrario
    Journal of biomedical optics
    Vol. 16, num. 1, p. 1-8
    DOI: 10.1117/1.3528619
    Date of publication: 2011-01
    Journal article

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  • Retinal image restoration by means of blind deconvolution

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; ¿orel, Michal; ¿roubek, Filip
    Journal of biomedical optics
    Vol. 16, num. 11
    DOI: 10.1117/1.3652709
    Date of publication: 2011-10-31
    Journal article

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    Energy balance in apodized diffractive multifocal intraocular lenses  Open access

     Alba Bueno, Francisco; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario
    Proceedings of SPIE, the International Society for Optical Engineering
    Vol. 8011, p. 80119G-1-80119G-10
    DOI: 10.1117/12.902895
    Date of publication: 2011
    Journal article

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  • Design of a test bench for intraocular lens optical characterization

     Alba Bueno, Francisco; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario
    Journal of physics: conference series
    Vol. 274, p. 1-7
    DOI: doi:10.1088/1742-6596/274/1/012105
    Date of publication: 2011
    Journal article

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  • Optical Data Encryption

     Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    DOI: 10.1002/9783527635245
    Date of publication: 2011
    Book chapter

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    New trends in intraocular lens imaging  Open access

     Millan Garcia Varela, Maria Sagrario; Alba Bueno, Francisco; Vega Lerin, Fidel
    Proceedings of SPIE, the International Society for Optical Engineering
    Vol. 8011, p. 80119I-1-80119I-8
    DOI: 10.1117/12.903389
    Date of publication: 2011
    Journal article

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    Energy Distribution between Distance and Near Images in Apodized Diffractive Multifocal Intraocular Lenses  Open access

     Vega Lerin, Fidel; Alba Bueno, Francisco; Millan Garcia Varela, Maria Sagrario
    Investigative ophthalmology and visual science
    Vol. 52, num. 8, p. 5695-5701
    DOI: 10.1167/iovs.10-7123
    Date of publication: 2011-07
    Journal article

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  • Optical Data Encryption. Supplements

     Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    DOI: 10.1002/9783527635245
    Date of publication: 2011
    Book chapter

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  • Energy balance in apodized diffractive multifocal intraocular lenses

     Alba Bueno, Francisco; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario
    General Congress of the International Commission for Optics (ICO)
    DOI: doi:10.1117/12.902895
    Presentation's date: 2011-08-15
    Presentation of work at congresses

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  • Assessment of the quality of multifocal intraocular lenses through contrast measurements

     Alba Bueno, Francisco; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario
    Engeenering the Eye
    Presentation's date: 2011-06-09
    Presentation of work at congresses

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    Multichannel Blind Deconvolution in Eye Fundus Imaging  Open access

     Marrugo Hernandez, Andrés Guillermo; ¿orel, Michal; ¿roubek, Filip; Millan Garcia Varela, Maria Sagrario
    International Symposium on Applied Sciences in Biomedical and Communication Technologies
    p. 1-5
    DOI: 10.1145/2093698.2093705
    Presentation's date: 2011
    Presentation of work at congresses

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  • New trends in intraocular lens imaging

     Millan Garcia Varela, Maria Sagrario; Alba Bueno, Francisco; Vega Lerin, Fidel
    Congress of the International Commission for Optics
    DOI: 10.1117/12.903389
    Presentation's date: 2011
    Presentation of work at congresses

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  • No-reference quality metrics for eye fundus imaging

     Marrugo Hernandez, Andrés Guillermo; Millan Garcia Varela, Maria Sagrario; Cristobal, Gabriel; Gabarda, Salvador; Abril Baez, Hector C.
    International Conference on Computer Analysis of Images and Patterns
    p. 486-493
    DOI: 10.1007/978-3-642-23672-3
    Presentation's date: 2011-08-30
    Presentation of work at congresses

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    Information compression for remote readable ID tags  Open access

     Horrillo, Sergi; Pérez Cabré, Elisabet; Millan Garcia Varela, Maria Sagrario
    Journal of Optics
    Vol. 12, p. 1-10
    DOI: 10.1088/2040-8978/12/11/115404
    Date of publication: 2010-10-29
    Journal article

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  • Unsupervised flaw segmentation in textile materials under visible and NIR illumination

     Millan Garcia Varela, Maria Sagrario; Escofet Soteras, Jaume; Rallo Capdevila, Miguel
    Proceedings of SPIE, the International Society for Optical Engineering
    Vol. 7723, p. 77230Q-77230Q-8
    DOI: 10.1117/12.854895
    Date of publication: 2010
    Journal article

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  • Spherical lens versus aspheric artificial cornea for intraocular lens testing

     Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario; Wells, Benjamin
    Optics letters
    Vol. 35, num. 10, p. 1539-1541
    Date of publication: 2010-05-15
    Journal article

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  • PROCESADO DE LA INFORMACION OPTICA CON APLICACIONES A LA INDUSTRIA, LA SALUD VISUAL Y LA SEGURIDAD

     Romero Perez, Lenny Alexandra; Marrugo Hernandez, Andrés Guillermo; Rallo Capdevila, Miguel; Millan Garcia Varela, Maria Sagrario
    Competitive project

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    Lente programable multifocal: Combinación coaxial y multieje  Open access

     Romero Perez, Lenny Alexandra; Millan Garcia Varela, Maria Sagrario; Pérez Cabré, Elisabet
    Óptica pura y aplicada
    Vol. 43, num. 2, p. 101-112
    Date of publication: 2010
    Journal article

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  • Design of a test bench for intraocular lens optical characterization

     Alba Bueno, Francisco; Vega Lerin, Fidel; Millan Garcia Varela, Maria Sagrario
    Reunión Iberoamericana de Óptica, Encuentro Latinoamericano de Óptica, Láseres y Aplicaciones
    Presentation's date: 2010-09-21
    Presentation of work at congresses

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