## 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

##### Identifiers

80 results

## Search Results

Now showing 1 - 10 of 80

Publication Windowed phase unwrapping using a first-order dynamic system following iso-phase contours(The Optical Society Of America, 2012-11-12) Quiroga Mellado, Juan Antonio; Estrada, Julio C.; Vargas Balbuena, Javier; Flores Moreno, Mauricio J.In this work, we show a windowed phase-unwrapping technique that uses a first-order dynamic system and scans the phase following its iso-phase contours. In previous works, we have shown that low-pass first-order dynamic systems are very robust and useful in phase-unwrapping problems. However, it is well known that all phase-unwrapping methods have a minimum signal-to-noise ratio that they tolerate. This paper shows that scanning the phase within local windows and using a path following strategy, the first-order unwrapping method increases its tolerance to noise. In this way, using the improved approach, we can unwrap phase maps where the basic dynamic phase-unwrapping system fails. Tests and results are given, as well as the source code in order to show the performance of the proposed method.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, 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.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, MoisésWe 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, ManuelWe 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 Anisotropic phase-map denoising using a regularized cost-function with complex-valued Markov-random-fields(Elsevier Sci. Ltd., 2010-06) Quiroga Mellado, Juan Antonio; Villa Hernández, José de Jesús; Rodríguez-Vera, Ramón; Rosa Vargas, José Ismael de la; González Ramírez, EfrénIn our recently reported work [1] (Villa et al., 2009) we derived a regularized quadratic-cost function, which includes fringe orientation information, for denosing fringe pattern images. In this work we adopt such idea for denoising wrapped phase-maps. We use a regularized cost-function that uses complex-valued Markov random fields (CMRFs) with orientation information of the filtering direction along isophase lines. The advantage of using an anisotropic filter along isophase lines is that phase and noise can be properly separated while 2 pi phase jumps are preserved even in high frequency zones. Apart from its robustness, the outstanding advantage of our method is its minimal computational effort. We present some results processing simulated and real phase-maps.Publication High dynamic range imaging method for interferometry(Elsevier Science B. V., 2011-08-15) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Restrepo, R.; Belenguer Dávila, TomásWe demonstrate a method to easily and quickly extend the dynamic range imaging capabilities of the camera in a typical interferometric approach. The camera dynamic range is usually low and limited to 256 gray levels. Also, it is well known that one may have over or under-exposed regions in the interferogram (due to non-uniform illumination) which makes these image regions not reliable. In our proposed method it is not necessary to obtain or use the non-linear camera response curve in order to extend the camera dynamic range. We obtain a sequence of differently exposed interferograms, typically five or six; after that, we compute the corresponding normalized fringe patterns and modulation maps using a typical normalization method. These normalized patterns are combined through a temporal weighted average using as weights the corresponding modulation maps. We show a set of experimental results that prove the effectiveness of the proposed method.Publication Direct demodulation of closed-fringe interferograms based on active contours(2010-11-01) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Belenguer Dávila, TomásWe demonstrate a method to directly demodulate closed-fringe interferograms using a kind of active contour called a snake. This method can be used to demodulate a single closed-fringe interferogram when its background illumination and/or contrast terms have a spatial frequency similar to the spatial frequency of the equivalent normalized interferogram. Among other cases, this problematic usually appears in interferometry when spurious reflection appears in the interferogram. In these situations, typical Fourier-based methods are of no help. We show a set of simulations and experimental results that prove the effectiveness of the proposed method.Publication Spectral analysis of phase shifting algorithms(The Optical Society Of America, 2009-09-14) Quiroga Mellado, Juan Antonio; Estrada, Julio César; Servín Guirado, ManuelSystematic 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, EusebioAutomated 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, EusebioA 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.