Person: Gómez Pedrero, José Antonio
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Now showing 1 - 10 of 60
PublicationMeasurement of surface topography by RGB Shadow-Moiré with direct phase demodulation(Elsevier Sci. Ltd., 2006-12) Quiroga Mellado, Juan Antonio; Gómez Pedrero, José Antonio; Terrón López, M. José; Crespo Vázquez, DanielIn this paper we present the application of a direct demodulation method for the measurement of surface topography by means of Shadow-Moiré. In our set-up, we use three LEDs (with green, red and blue peak wavelengths) to illuminate the grating. Due to the different position of these light sources, a polychromatic Shadow-Moiré fringe pattern is produced, which can be described as the superposition of three monochromatic (red, green and blue) fringe patterns. Taking the image of this polychromatic fringe pattern with a RGB CCD camera, we get a monochromatic fringe pattern stored at each RGB channel of the CCD. The direct demodulation algorithm employed uses these fringe patterns to calculate the wrapped phase map. After unwrapping the phase map using a standard multi-grid technique, we implemented an automatic procedure to detect the area of interest of the phase map by removing low modulation zones and to calculate the absolute value of the phase. In this way it is possible to determine the topography of a surface with a single RGB snapshot maintaining a simple experimental set-up, which is an important feature, especially for the study of dynamic phenomena such as deformations. We present the experimental results obtained after measuring different objects with both smooth and rough surface textures. PublicationPhDAY 2020 -FOO (Facultad de Óptica y Optometría)(Facultad de Óptica y Optometría (UCM), 2020) Carpena Torres, Carlos; Pintor, Jesús; Pérez de Lara, María Jesús; Toral, Fernando; Crooke, Almudena; Pastrana, Cristina; Carracedo Rodríguez, Juan Gonzalo; Cayuela López, Ana; Sorzano Sánchez, Óscar; Charbel, Carla; Garzón Jiménez, Nuria; Carballo Álvarez, Jesús; Diz Arias, Elena; Fernández Jiménez, Elena; Peral Cerdá, Assumpta; Gómez Pedrero, José Antonio; Durán Prieto, Elena; López Alonso, José Manuel; Fernández Torres, Miguel Ángel; Guzmán Aránguez, Ana Isabel; Gómez Manzanares, Ángela; Vázquez Moliní, Daniel; Martínez Antón, Juan Carlos; Bernárdez Vilaboa, Ricardo; Mayorga Pinilla, Santiago; Álvarez Fernández-Balbuena, Antonio; Benítez, AntoJ.; El Youssfi, Asmae Igalla; León Álvarez, Alejandro; Palomo Álvarez, Catalina; LLedó Mayans, Victoria Eugenia; Awad Alkozi, Hanan; Sánchez Naves, Juan; Martínez Alberquilla, Irene; García Montero, María; Ruiz Alcocer, Javier; Madrid Costa, David; Martínez Florentín, Gema; Papas, Eric B.; Medrano Muñoz, Sandra Milena; Molina, Nancy; Jurado, Sandra; Oliveiros López, Juan; Platero Alvarado, Nadiuska Cristine; Garrido Mercado, Rafaela; Pérez Garmendia, Carlos; Antona Peñalba, Beatriz; Barrio de Santos, Ana Rosa; González Pérez, Mariano; Pérez Garmendia, Carlos; Serramito Blanco, María; Privado Aroco, Ana; Almalki, Wael; Bodas Romero, Julia; Ouzzani, Mohamed; Paune, Jaume; Calderón García, Raquel; Pitarch Velasco, Aida; Cebrián, José Luis; Sánchez Pérez, Isabel; García Rojo, Marta María; Bonnin Arias, Cristina; Sánchez Ramos, Celia; Gutiérrez Jorrín, Sara Carmen; Rodríguez Alonso, Xabier; Laucirica Sáenz, Gorka; Arranz Márquez, Esther; Alonso Castellanos, Miriam; Teus Guezala, Miguel Ángel; Hernández Verdejo, José Luis; Mármol Errasti, Esther; Martín García, Beatriz; Arriola Villalobos, Pedro; Gómez de Liaño, Rosario; Mínguez Caro, N; Orduña Azcona, Javier; Navarro Gil, Francisco Javier; Huete Toral, Fernando; Rodríguez Pomar, Candela; Pastrana Robles, Cristina; Martínez Águila, Alejandro; Martín Gil, Alba; Tomé de la Torre, Miguel ÁngelPor cuarto año consecutivo los doctorandos de la Facultad de Óptica y Optometría de la Universidad Complutense de Madrid cuentan con un congreso propio organizado por y para ellos, el 4º PhDAY- FOO. Se trata de un congreso gratuito abierto en la que estos jóvenes científicos podrán presentar sus investigaciones al resto de sus compañeros predoctorales y a toda la comunidad universitaria que quiera disfrutar de este evento. Apunta en tu agenda: el 15 de octubre de 2020. En esta ocasión será un Congreso On-line para evitar que la incertidumbre asociada a la pandemia Covid-19 pudiera condicionar su celebración. PublicationWavefront measurement by solving the irradiance transport equation for multifocal systems(Spie-Soc Photo-Optical Instrumentation Engineers, 2001-12) Quiroga Mellado, Juan Antonio; Gómez Pedrero, José Antonio; Martínez Antón, Juan CarlosA method for sensing wavefronts is presented. The method is based on the resolution of the irradiance transport equation, which relates the irradiance distribution and the shape of the wavefront of a light beam propagating along a given direction. The method presents no restrictions in the locations of the measurement planes and incorporates an improved procedure to geometrically correct the acquired images to take into account the effect of ray deflection in the propagation of the irradiance distributions. With the proposed technique, we measure the wavefront at the exit pupil of a progressive addition lens and find good agreement with an alternative deflectometric method. PublicationRecent advances in automatic demodulation of single fringe patterns(Springer Verlag Berlin, 2006) Quiroga Mellado, Juan Antonio; Crespo Vázquez, Daniel; Gómez Pedrero, José Antonio; Martínez Antón, Juan Carlos PublicationImproved method for isochromatic demodulation by RGB calibration(The Optical Society of America, 2002-06-10) Quiroga Mellado, Juan Antonio; García Botella, Ángel; Gómez Pedrero, José AntonioThe red-blue-green (RGB) calibration technique consists in constructing an a priori calibration table of the isochromatic retardation versus the triplet of RGB values obtained with a RGB CCD camera. In this way a lookup table (LUT) is built in which the entry is the corresponding RGB triplet and the output is the given retardation. This calibration (a radiometric quantity) depends on the geometric and chromatic parameters of the setup. Once the calibration is performed, the isochromatic retardation at a given point of the sample is computed as the one that minimizes the Euclidean distance between the measured RGB triplet and the triplets stored in the LUT. We present an enhanced RGB calibration algorithm for isochromatic fringe pattern demodulation. We have improved the standard demodulation algorithm used in RGB calibration by changing the Euclidean cost function to a regularized one in which the fidelity term corresponds to the Euclidean distance between RGB triplets; the regularizing term forces piecewise continuity for the isochromatic retardation. Additionally we have implemented a selective search in the RGB calibration LUT. We have tested the algorithm with simulated as well as real photoelastic data with good results. PublicationIncremental PCA algorithm for fringe pattern demodulation(The Optical Society Of America, 2022-04-11) Gómez Pedrero, José Antonio; Estrada, Julio César; Alonso Fernández, José; Quiroga Mellado, Juan Antonio; Vargas Balbuena, JavierThis work proposes a new algorithm for demodulating fringe patterns using principal component analysis (PCA). The algorithm is based on the incremental implantation of the singular value decomposition (SVD) technique for computing the principal values associated with a set of fringe patterns. Instead of processing an entire set of interferograms, the proposed algorithm proceeds in an incremental way, processing sequentially one (as minimum) interferogram at a given time. The advantages of this procedure are twofold. Firstly, it is not necessary to store the whole set of images in memory, and, secondly, by computing a phase quality parameter, it is possible to determine the minimum number of images necessary to accurately demodulate a given set of interferograms. The proposed algorithm has been tested for synthetic and experimental in ter ferograms showing a good performance. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement PublicationOptical method for the surface topographic characterization of Fresnel lenses(SPIE--The International Society for Optical Engineering, 2011) Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Alonso Fernández, José; Quiroga Mellado, Juan AntonioFresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices. As applications are more exigent this characterization is of increasing importance. We present a technique to characterize the surface topography of optical surfaces. It is especially well adapted to Fresnel lenses where abrupt surface slopes are usually difficult to handle in conventional techniques. The method is based on a new photometric strategy able to codify the height information in terms of optical absorption in a liquid. A detailed topographic map is simple to acquire by capturing images of the surface. Some experimental results are presented. A single pixel height resolution of similar to 0.1 mu m is achieved for a height range of similar to 50 mu m. A surface slope analysis is also made achieving a resolution of similar to +/- 0.15 degrees. PublicationTemporal phase evaluation by Fourier analysis of fringe patterns with spatial carrier(Taylor and Francis Ltd., 2001-11-20) Quiroga Mellado, Juan Antonio; Gómez Pedrero, José AntonioA new method is presented for the temporal evaluation of fringe patterns with spatial carrier. The proposed technique involves recording the irradiance fluctuations obtained when a linear variation of the set-up sensitivity is introduced. In this condition, the use of a spatial carrier introduces a linear temporal carrier frequency. In this way, Fourier analysis can be performed to obtain the phase and, finally, the quantity to be measured. The optimum conditions for the sensitivity variation have been studied in order to minimize the errors associated with the Fourier analysis. The technique has been applied to measure the distribution of ray deflections on the surface of two ophthalmic lenses using a deflectometric set-up. PublicationImproved Analytical Theory of Ophthalmic Lens Design(MDPI, 2021-06-19) Pascual, Eduardo; Gómez Pedrero, José Antonio; Alonso Fernández, JoséA revisited form of the classic third-order ophthalmic lens design theory that provides a more precise and meaningful use of aspheric surfaces and a generalization of the standard oblique errors is presented. The classical third-order theory follows from the application of the Coddington equations to a ray trace through the lens and the expansion of the incidence angles and the surface sagittas appearing on them up to order two of the radial coordinate. In this work we show that the approximations for surface sagittas and angles can be decoupled, and the lens oblique powers predicted by the proposed theory provides a better fit to the numerical results obtained by exact raytracing and multi-parametric optimization than the classical third-order theory does. Modern ophthalmic lens design uses numerical optimization and exact ray tracing, but the methods presented in this paper provide a deeper understanding of the problem and its limitations. This knowledge and the more general merit functions that are also presented may help guide the numerical approaches. PublicationTheoretical performance of progressive addition lenses with poorly measured individual parameters(WILEY-BLACKWELL Publishing, 2023-01-09) Pascual, Eduardo; Gómez Pedrero, José Antonio; Alonso Fernández, JoséPurpose: The aim of this paper was to present a theoretical study of how poorly measured individual parameters affect the optical performance of progressive addition lenses (PALs). Modern progressive lenses can be prescribed based on parameters such as vertex distance, pantoscopic and wrap angles. These parameters can be measured from the lens wearer using specific devices; however, not all of them can be measured with the same precision, and the impact of measurement errors on the lens performance is still unknown. Methods: Data from 1900 patients were used to simulate the performance of four PAL designs with different degrees of complexity: perfect individual design, individual design with induced errors in the individual parameters, optimised design and conventional/basic design. For each patient and design, a quality metric was calculated to describe the optical performance of the lens. Results: The design having the best performance was the perfect individual design, followed by the individual design with induced errors, the optimised design and finally the conventional/basic design. Conclusions: Individual designs with measurement errors have better optical performance than lenses with less complexity, such as the optimised or conventional designs. This knowledge is useful for the eye care professional to make informed choices when dispensing these lenses.