Person: Quiroga Mellado, Juan Antonio
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 27
PublicationWindowed 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. PublicationHigh 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. PublicationDirect 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. 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 PublicationRole of the filter phase in phase sampling interferometry(The Optical Society Of America, 2011-10-10) Quiroga Mellado, Juan Antonio; Servín Guirado, Manuel; Estrada, Julio César; Vargas Balbuena, Javier; Torre Belizón, Francisco Javier de laAny linear phase sampling algorithm can be described as a linear filter characterized by its frequency response. In traditional phase sampling interferometry the phase of the frequency response has been ignored because the impulse responses can be made real selecting the correct sample offset. However least squares methods and recursive filters can have a complex frequency response. In this paper, we derive the quadrature equations for a general phase sampling algorithm and describe the role of the filter phase. PublicationAdaptive spatiotemporal structured light method for fast three-dimensional measurement(Spie-Soc Photo-Optical Instrumentation Engineers, 2006-10) Quiroga Mellado, Juan Antonio; Crespo Vázquez, Daniel; Vargas Balbuena, Javier; Gómez Pedrero, José AntonioWe present a high-speed 3-D spatiotemporal shape measurement technique by means of structured light. Current methods use a constant number of images that do not take into account the available temporal continuity of the measured object. That is, they focus on acquiring and processing as quickly as possible a fixed number of images to solve for the correspondence problem and later obtain the 3-D shape by triangulation. The number of images used imposes the use of some spatial support. The major contribution of our research is a new spatiotemporal scheme that, depending on the object's movement, adaptively uses the maximum number of projected images consistent with the local temporal continuity, therefore solving the correspondence problem with the minimum possible spatial support for each position. This is achieved by the use of a hybrid color pattern composed of an analog sinusoidal periodic code in the red channel and a digital binary spatial code in the blue channel that is cyclically displaced. No subpixel calculation is used and it is possible to implement error correction strategies that make the method fast and reliable, enabling dynamic online 3-D measurement of objects in movement. PublicationPhase-shifting interferometry based on principal component analysis(The Optical Society Of America, 2011-04-15) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Belenguer Dávila, TomásAn asynchronous phase-shifting method based on principal component analysis (PCA) is presented. No restrictions about the background, modulation, and phase shifts are necessary. The presented method is very fast and needs very low computational requirements, so it can be used with very large images and/or very large image sets. The method is based on obtaining two quadrature signals by the PCA algorithm. We have applied the proposed method to simulated and experimental interferograms, obtaining satisfactory results. PublicationShack-Hartmann centroid detection method based on high dynamic range imaging and normalization techniques(The Optical Society of America, 2010-05-01) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; González Fernández, Luis M.; Belenguer Dávila, TomásIn the optical quality measuring process of an optical system, including diamond-turning components, the use of a laser light source can produce an undesirable speckle effect in a Shack-Hartmann (SH) CCD sensor. This speckle noise can deteriorate the precision and accuracy of the wavefront sensor measurement. Here we present a SH centroid detection method founded on computer-based techniques and capable of measurement in the presence of strong speckle noise. The method extends the dynamic range imaging capabilities of the SH sensor through the use of a set of different CCD integration times. The resultant extended range spot map is normalized to accurately obtain the spot centroids. The proposed method has been applied to measure the optical quality of the main optical system (MOS) of the mid-infrared instrument telescope smulator. The wavefront at the exit of this optical system is affected by speckle noise when it is illuminated by a laser source and by air turbulence because it has a long back focal length (3017 mm). Using the proposed technique, the MOS wavefront error was measured and satisfactory results were obtained. PublicationTwo-step self-tuning phase-shifting interferometry(The Optical Society Of America, 2011-01-11) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Belenguer Dávila, Tomás; Servín Guirado, Manuel; Estrada, Julio CésarA two-step self-tuning phase-shifting method is presented. The phase-step between the two interferograms is not known when the experiment is performed. Our demodulating method finds, in a robust way, this unknown phase-step. Once the phase-step is estimated we proceed to phase demodulate the interferograms. Moreover our method only requires the fringe patterns to have a constant unknown phase-shift between them. As a consequence, this technique can be used to demodulate open and closed-fringed patterns without phase-sign ambiguity. The method may be regarded as a self-tuning quadrature filter, which determines the phase-shift between the two fringe patterns and finally estimates the demodulated phase map. The proposed technique has been tested with simulated and real interferograms obtaining satisfactory results. PublicationFlexible calibration procedure for fringe projection profilometry(Spie-Soc Photo-Optical Instrumentation Engineers, 2007-02) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Terrón López, M. JoséA novel calibration method for whole field three-dimensional shape measurement by means of fringe projection is presented. Standard calibration techniques, polynomial- and model-based, have practical limitations such as the difficulty of measuring large fields of view, the need to use precise z stages, and bad calibration results due to inaccurate calibration points. The proposed calibration procedure is a mixture of the two main standard techniques, sharing their benefits and avoiding their main problems. In the proposed method, an absolute phase is projected over marked planes placed at unknown positions. The corresponding absolute phase and marks positions are recovered for each plane location. Using Zhang's calibration method, internal camera parameters (also called intrinsic parameters) and the spatial position for each plane are computed. Later on, a polynomial fit of depth with respect to the phase is performed. To obtain the absolute position of an object point, the depth coordinate is obtained by means of the polynomial calibration and its absolute phase. Then the lateral coordinates are computed from the depth, the internal parameters, and the pixel coordinates of the imaged point. Experimental results comparing the proposed method with the standard polynomial- based calibration are shown, demonstrating the feasibility of the proposed technique.