Quiroga Mellado, Juan Antonio

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First Name
Juan Antonio
Last Name
Quiroga Mellado
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
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Now showing 1 - 10 of 15
  • 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
    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.
  • Publication
    Colorimetric matching by minimum-square-error fitting
    (The Optical Society of America, 1994-09-10) Quiroga Mellado, Juan Antonio; Alonso Fernández, José; Zoido, J.; Bernabeu Martínez, Eusebio
    Least-squares approximation can be used in image-based colorimetry once the set of sampling functions is selected. We discuss the accuracy obtained in earlier research, and we compare it with a better calculation method.
  • Publication
    On the dependence on isoclinics of the modulation of isochromatic phase maps
    (Gustav Fischer Verlag, 1999) Quiroga Mellado, Juan Antonio; González Cano, Agustín
    In this work we evaluate the dependence on isoclinics of the modulation of the isochromatic phase maps when phase-shifting algorithms are applied to experiments of photoelasticity. This dependence makes conventional phase-shifting algorithms unsuitable for that application.
  • Publication
    Phase measuring algorithm for extraction of isochromatics of photoelastic fringe patterns
    (The Optical Society of America, 1997-11-10) Quiroga Mellado, Juan Antonio; González Cano, Agustín
    In recent years phase-measuring techniques have been applied to the problem of extracting information of photoelastic data. We present a new phase-measuring algorithm for extraction of the isochromatics of photoelastic fringe patterns. The algorithm permits the extraction of the isochromatic phase with almost no influence from the isoclinics, thus avoiding the usual problems of low-modulation areas associated with isoclinics. The isochromatic phase map obtained with this algorithm is well suited for a full separation of the stress components in a sample. The algorithm can be used with any commercial diffuse-light circular polariscope.
  • Publication
    Automatic processing in Moiré deflectometry by local fringe direction calculation
    (The Optical Society of America, 1998-09-01) Quiroga Mellado, Juan Antonio; Canabal Boutureira, Héctor; Bernabeu Martínez, Eusebio
    An algorithm for accurately extracting the local fringe direction is presented. The algorithm estimates, in the neighborhood of n × n points, the direction of the gradient that points normal to the local fringe direction. The performance of four different derivative kernels is also compared. Since this method is sensitive to noise and variations in background and amplitude, a preprocessing step is used to limit these error sources. The method has been applied to the moiré deflectogram of a spherical and a progressive addition ophthalmic lens, resulting in a map of the refractive power of these lenses. The results are compared with the data obtained with a commercial focimeter. This technique is useful for analyzing the fringe patterns where the fringe direction is variable and must be obtained locally.
  • Publication
    Automatic techniques for evaluation of moire deflectograms
    (SPIE--The International Society for Optical Engineering, 1999) Quiroga Mellado, Juan Antonio; Villa Hernández, José de Jesús; Crespo Vázquez, Daniel
    In this work we present two methods for the analysis of moire deflectograms. The first method is a Fourier-transform technique. The second method uses a regularization based method. Both methods are applied to realistic deflectograms and their performances are discussed.
  • Publication
    Stable-marriages algorithm for preprocessing phase maps with discontinuity sources
    (The Optical Society of America, 1995-08-10) Quiroga Mellado, Juan Antonio; González Cano, Agustín; Bernabeu Martínez, Eusebio
    A new algorithm is proposed for solving the problems associated with discontinuity sources in phase maps. It is based on the stable-marriages algorithm and is implemented as a recursive procedure. With this technique, discontinuity sources of opposite sign are connected by a set of cut lines that fulfills a stability criterion and possesses the minimum cut length of the stable sets. The algorithm is fast and easy to implement and has proved efficient, as experimental results show.