Person:
Quiroga Mellado, Juan Antonio

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First Name
Juan Antonio
Last Name
Quiroga Mellado
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Óptica
Area
Optica
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Search Results

Now showing 1 - 10 of 72
  • Publication
    Measurement 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, Daniel
    In 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.
  • Publication
    Noise in phase shifting interferometry
    (The Optical Society Of America, 2009-05-25) Quiroga Mellado, Juan Antonio; Estrada, Julio César; Servín Guirado, Manuel; Mosiño, Juan Francisco; Cywiak Garbarcewics, Moisés
    We present a theoretical analysis to estimate the amount of phase noise due to noisy interferograms in Phase Shifting Interferometry (PSI). We also analyze the fact that linear filtering transforms corrupting multiplicative noise in Electronic Speckle Pattern Interferometry (ESPI) into fringes corrupted by additive gaussian noise. This fact allow us to obtain a formula to estimate the standard deviation of the noisy demodulated phase as a function of the spectral response of the preprocessing spatial filtering combined with the PSI algorithm used. This phase noise power formula is the main result of this contribution.
  • Publication
    Improved regularised phase-tracking technique for the processing of squared-grating deflectograms
    (The Optical Society of America, 2000-02-01) Quiroga Mellado, Juan Antonio; Villa Hernández, José de Jesús; Servín Guirado, Manuel
    We propose a robust procedure based on the regularized phase-tracking (RPT) technique to demodulate squared-grating deflectograms. The use of squared gratings, already reported, lets us multiplex the information of the deflections in two orthogonal directions in a single image, thus avoiding the necessity of rotating the gratings. The good noise-rejection characteristics of the RPT technique are improved by use of a quasi-Newton optimization algorithm and a quality-map-based algorithm for the crystal-growing process.
  • Publication
    Wavefront 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 Carlos
    A 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.
  • Publication
    Fourier transform method for automatic processing of moiré deflectograms
    (Spie-Soc Photo-Optical Instrumentation Engineers, 1999-06) Quiroga Mellado, Juan Antonio; Crespo Vázquez, Daniel; Bernabeu Martínez, Eusebio
    In this work, a Fourier transform technique for automatic analysis of moire deflectograms is presented. A squared grating is used to multiplex the information of the deflection in two orthogonal directions in one image. This procedure avoids the necessity of rotating the gratings to obtain the complete deflection information. With this method only two fringe patterns. reference and distorted, are needed to determine the complete deflection information. To deal with irregularly shaped processing areas, a Gerchberg extrapolation method is used. The automatic determination of the carrier as well as the size and position of the reconstruction windows permit the complete and automatic measurement of the deflection produced by an ophthalmic lens in two orthogonal directions. Afterwards, the refractive power maps can be obtained, Experimental results obtained with a progressive addition lens are presented and comparison with measurements obtained with a commercial focimeter are shown showing a good agreement.
  • Publication
    Robust isoclinic calculation for automatic analysis of photoelastic fringe patterns
    (SPIE--The International Society for Optical Engineering, 2008) Quiroga Mellado, Juan Antonio; Pascual Ramírez, Sergio; Villa Hernández, José de Jesús
    There are two main steps in the analysis of photoelastic fringe patterns: the isoclinics and isochromatics computation. For the isochromatic computation there exist several possibilities but one of the best, from the point of view of reliability and automatization, is the phase shift technique. However all phase shift isochromatic algorithms need a good estimation of the isoclinic direction angle that is a challenging task in presence of low birrefringence, isotropic points and monochromatic illumination. In this work we discuss the application of a novel isoclinic direction calculation method based in a phase shifting technique and a fast direction estimation regularized filter. Experimental results show that the proposed method together with a standard phase shifting isochromatic estimation is a good option for the automatic analysis of photoelastic fringe patterns under different illumination conditions, load levels and sample complexity, making possible further processing steps as full-field stress separation.
  • Publication
    Spectral analysis of phase shifting algorithms
    (The Optical Society Of America, 2009-09-14) Quiroga Mellado, Juan Antonio; Estrada, Julio César; Servín Guirado, Manuel
    Systematic spectral analysis of Phase Shifting Interferometry (PSI) algorithms was first proposed in 1990 by Freischlad and Koliopoulos (F&K). This analysis was proposed with the intention that "in a glance" the main properties of the PSI algorithms would be highlighted. However a major drawback of the F&K spectral analysis is that it changes when the PSI algorithm is rotated or its reference signal is time-shifted. In other words, the F&K spectral plot is different when the PSI algorithm is rotated or its reference is time-shifted. However, it is well known that these simple operations do not alter the basic phase demodulation properties of PSI algorithms, except for an unimportant piston. Here we propose a new way to analyze the spectra of PSI algorithms which is invariant to rotation and/or reference time-shift among other advantages over the nowadays standard PSI spectral analysis by F&K.
  • Publication
    Phase-unwrapping algorithm for noisy phase-map processing
    (The Optical Society of America, 1994-10-10) Quiroga Mellado, Juan Antonio; Bernabeu Martínez, Eusebio
    Automated fringe-pattern processing is important in a great number of industrial applications, such as optical data testing and quality control. One of the main problems that arises with these processes is the automated phase unwrapping of the phase map associated with the fringe pattern. Usually the phase map presents problems such as noise, and low-modulation areas. A new phase-unwrapping algorithm with high noise immunity is presented. The algorithm is easily implemented and can process arbitrary shapes. The main features of this algorithm are the use of a queue for the processing of arbitrary shapes and a selection criterion that determines which pixels are going to be processed.
  • Publication
    A fast method to measure the irradiance response of image processing systems
    (IOP Publishing Ltd., 1995-02) Quiroga Mellado, Juan Antonio; González Cano, Agustín; Bernabeu Martínez, Eusebio
    A method to estimate in a fast and simple way the response of an image acquiring system (such as a charge-coupled device camera plus an image-processing board) for a monochromatic light source is presented. Two images, whose irradiances are related in a known way, are acquired, and the corresponding grey levels of the responses of the system are correlated pixel to pixel. From this correlation and the relationship between the irradiances of the images, a relative estimation of the irradiance response of the system can be obtained by means of simple algorithms. This method is fast and easy to implement and the results obtained are satisfactory.
  • Publication
    Piecewise smooth phase reconstruction
    (The Optical Society of America, 1999-12-15) Quiroga Mellado, Juan Antonio; Marroquín Zaleta, José Luis; Rodríguez Vera, Ramón
    A well-founded and computationally fast method is presented for filtering and interpolating noisy and discontinuous wrapped phase fields that preserves both the 2π discontinuities that come from the wrapping effect and the true discontinuities that may be present. It also permits the incorporation of an associated quality map, if it is available, in a natural way. Examples of its application to the computation of the isoclinic phase from photoelastic data and to the recovery of discontinuous phase fields from speckle interferometry are presented.