Person:
Vargas Balbuena, Javier

First Name

Javier

Last Name

Vargas Balbuena

URI

https://hdl.handle.net/20.500.14352/75168

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Óptica

Area

Optica

Identifiers

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Now showing 1 - 10 of 22

Two-step interferometry by a regularized optical flow algorithm
(Optics Letters, 2011) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Sánchez Sorzano, Carlos Óscar; Estrada, Julio César; Carazo García, José María
A two-step phase-shifting method, that can demodulate open-and closed-fringed patterns without local sign ambiguity is presented. The proposed method only requires a constant phase-shift between the two interferograms. This phase-shift does not need to be known and can take any value inside the range (0, 2 π), excluding the singular case where it corresponds to π. The proposed method is based on determining first the fringe direction map by a regularized optical flow algorithm. After that, we apply the spiral phase transform (SPT) to one of the fringe patterns and we determine its quadrature signal using the previously determined direction. The proposed technique has been applied to simulated and experimental interferograms obtaining satisfactory results. A complete MATLAB software package is provided in [http://goo.gl/Snnz7].
Direct demodulation of closed-fringe interferograms based on active contours
(Optics Letters, 2010) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Belenguer Dávila, Tomás
We 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.
High dynamic range imaging method for interferometry
(Optics Communications, 2011) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Restrepo, R.; Belenguer Dávila, Tomás
We 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.
Incremental PCA algorithm for fringe pattern demodulation
(Optics express, 2022) Gómez Pedrero, José Antonio; Estrada, Julio César; Alonso Fernández, José; Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier
This 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
Windowed phase unwrapping using a first-order dynamic system following iso-phase contours
(Applied Optics, 2012) 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.
Local fringe density determination by adaptive filtering
(Optics Letters, 2011) Vargas Balbuena, Javier; Quiroga Mellado, Juan Antonio; Belenguer Dávila, Tomás
We demonstrate a method to easily and quickly determine the local fringe density map of a fringe pattern. The method is based on an isotropic adaptive bandpass filter that is tuned at different frequencies. The modulation map after applying a specific bandpass frequencies filter presents a maximum response in the regions where the bandpass filter and fringe frequencies coincide. We show a set of simulations and experimental results that prove the effectiveness of the proposed method.
Fringe pattern denoising by image dimensionality reduction
(Optics and Lassers in Engineering, 2013) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Estrada, Julio César; Carazo García, José María; Sánchez Sorzano, Carlos Óscar
Noise is a key problem in fringe pattern processing, especially in single frame demodulation of interferograms. In this work, we propose to filter the pattern noise using a straightforward, fast and easy to implement denoising method, which is based on a dimensionality reduction approach, in the sense of image rank reduction. The proposed technique has been applied to simulated and experimental ESPI interferograms obtaining satisfactory results.
Enhancement of Cryo-EM maps by a multiscale tubular filter
(Optics express, 2022) Vargas Balbuena, Javier; Gómez Pedrero, José Antonio; Quiroga Mellado, Juan Antonio; Alonso Fernández, José
We present an approach to enhance cryo-electron microscopy (cryo-EM) postprocessed maps based on a multiscale tubular filter. The method determines a tubularness measure locally by the analysis of the eigenvalues of the Hessian matrix. This information is used to enhance elongated local structures and to attenuate blob-like and plate-like structures. The approach, thus, introduces a priori information in the reconstructions to improve their interpretability and analysis at high-resolution. The proposed method has been tested with simulated and real cryo-EM maps including recent reconstructions of the SARS-CoV-2. Our results show that our methods can improve obtained reconstructions.
Calibration of a Shack-Hartmann wavefront sensor as an orthographic camera
(Optics Letters, 2010) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; González Fernández, Luis M.; Belenguer Dávila, Tomás
We demonstrate a method to calibrate a Shack-Hartmann sensor as an orthographic camera. This calibration method permits us to obtain the distance, the rotation matrix between the microlens array and CCD imaging planes, and the projection matrix, which models the projection of the incoming rays to the CCD imaging plane. The proposed calibration method introduces a very compact matrix notation and allows wavefront reconstruction without an explicit centroid search between the reference and distorted spot diagrams. We show a set of simulations in code V that prove the effectiveness of the proposed method.
Project number: 54
Desarrollo de material docente audiovisual online de apoyo para la asignatura: dispositivos de instrumentación óptica
(2023) Vargas Balbuena, Javier; Diez Garrote, Francisco; Quiroga Mellado, Juan Antonio; Canabal Boutureira, Héctor Alfonso; Boiso Calero, Antonio
En este proyecto de innovación docente se han desarrollado una serie de videos cortos para fijar visualmente conceptos clave sobre instrumentación óptica. Estos videos están enfocados en la mejora de la compresión y análisis de los estudiantes de la asignatura Dispositivos de Instrumentación Óptica de cuarto curso del Grado en Físicas. Es decir, nuestro objetivo es proporcionar a los estudiantes con experiencias virtuales de laboratorio que les permitan entender de forma sencilla y rápida conceptos esenciales de la asignatura. También estos videos serán utilizados en el aula por los profesores como material docente de apoyo.