Person:
Belenguer Dávila, Tomás

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First Name
Tomás
Last Name
Belenguer Dávila
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Department
Óptica
Area
Optica
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UCM identifierORCIDScopus Author IDWeb of Science ResearcherIDDialnet IDGoogle Scholar ID

Search Results

Now showing 1 - 10 of 26
  • 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, 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.
  • Publication
    Direct demodulation of closed-fringe interferograms based on active contours
    (2010-11-01) 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.
  • Publication
    Solderjet bumping technique used to manufacture a compact and robust green solid-state laser
    (SPIE, 2015-06-01) Ribes Pleguezuelo, Pol; Burkhardt, Thomas; Hornaff, M.; Kousar, S.; Burkhardt, D.; Becker, Erik; Gilaberte, Marta; Guilhot, D.; Montes, David; Galán, Miguel; Ferrando, Sergi; Laudisio, Marco; Belenguer Dávila, Tomás; Ibarmia, S.; Gallego, P.; Rodríguez, J.A.; Eberhardt, Ramona; Tünnermann, Andreas
    Solder-joining using metallic solder alloys is an alternative to adhesive bonding. Laser-based soldering processes are especially well suited for the joining of optical components made of fragile and brittle materials such as glasses, ceramics and optical crystals due to a localized and minimized input of thermal energy. The Solderjet Bumping technique is used to assemble a miniaturized laser resonator in order to obtain higher robustness, wider thermal conductivity performance, higher vacuum and radiation compatibility, and better heat and long term stability compared with identical glued devices. The resulting assembled compact and robust green diode-pumped solid-state laser is part of the future Raman Laser Spectrometer designed for the Exomars European Space Agency (ESA) space mission 2018.
  • Publication
    Phase-shifting interferometry based on principal component analysis
    (The Optical Society Of America, 2011-04-15) Quiroga Mellado, Juan Antonio; Vargas Balbuena, Javier; Belenguer Dávila, Tomás
    An 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.
  • Publication
    A Novel Photoconductive PVK/SiO_2 Interpenetrated Network Prepared by the Sol−Gel Process
    (Amer Chemical Soc, 2003-01-09) Ramos Zapata, Gonzalo; Belenguer Dávila, Tomás; Monte Muñoz de la Peña, Francisco de; Levy, David; Bernabeu Martínez, Eusebio
    In this work, we describe the preparation of a novel photoconductive sol−gel material based on an organic/inorganic interpenetrating network (IPN). The composition of the sol−gel photoconductive material mimics the well-known polymeric one based on poly(N-vinylcarbazole) (PVK) as the charge-transporting matrix and 2,4,7-trinitro-9-fluorenone (TNF) as the sensitizer. The resulting photoconductive material (PVK/SiO_2 IPN) shows a photosensitivity of 10^-11 cm/(Ω W) in range to that reported for some analogue polymeric compounds and the highest ever reported for hybrid sol−gel materials.
  • Publication
    Shack-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, Tomás
    In 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.
  • Publication
    Two-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 César
    A 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.
  • Publication
    SAFARI optical system architecture and design concept
    (SPIE, 2016) Pastor Sempere, Carmen; Jellema, Willem; Zuluaga Ramírez, Pablo; Arrazola, David; Fernández Rodríguez, M.; Belenguer Dávila, Tomás; González Fernández, Luis M.; Audley, Michael D.; Evers, Jaap; Eggens, Martin; Torres Redondo, Josefina; Najarro, Francisco; Roelfsema, Peter
    SpicA FAR infrared Instrument, SAFARI, is one of the instruments planned for the SPICA mission. The SPICA mission is the next great leap forward in space-based far-infrared astronomy and will study the evolution of galaxies, stars and planetary systems. SPICA will utilize a deeply cooled 2.5m-class telescope, provided by European industry, to realize zodiacal background limited performance, and high spatial resolution. The instrument SAFARI is a cryogenic grating-based point source spectrometer working in the wavelength domain 34 to 230 μm, providing spectral resolving power from 300 to at least 2000. The instrument shall provide low and high resolution spectroscopy in four spectral bands. Low Resolution mode is the native instrument mode, while the high Resolution mode is achieved by means of a Martin-Pupplet interferometer. The optical system is all-reflective and consists of three main modules; an input optics module, followed by the Band and Mode Distributing Optics and the grating Modules. The instrument utilizes Nyquist sampled filled linear arrays of very sensitive TES detectors. The work presented in this paper describes the optical design architecture and design concept compatible with the current instrument performance and volume design drivers.
  • Publication
    Substrate mode hologram for optical interconnects
    (Elsevier Science BV, 1998-03-01) Cheben, Pavel; Calvo Padilla, María Luisa; Belenguer Dávila, Tomás; Núñez Peral, Armonía
    A novel method of substrate mode hologram (SMH) design and fabrication is presented. The coupling between a homogeneous plane wave and an arbitrary free propagating wave is achieved via a total internally reflected (TIR) wave. The input slanted plane grating, recorded in an orthochromatic holographic medium, accomplishes the homogeneous plane wave to TIR wave coupling. The TIR wave is transformed to the free propagating wave by the output aperiodic aplanar inhomogeneous grating recorded in a panchromatic holographic medium. Aberration-free conversion between the incident plane wave and the Gaussian wave is reported for coupling efficiency of 57%.
  • Publication
    Optical inspection of liquid crystal variable retarder inhomogeneities
    (The Optical Society Of America, 2010-02-01) Quiroga Mellado, Juan Antonio; Uribe Patarroyo, Néstor R.; Vargas Balbuena, Javier; Álvarez Herrero, Alberto; Belenguer Dávila, Tomás
    Liquid crystal variable retarders (LCVRs) are starting to be widely used in optical systems because of their capacity to provide a controlled variable optical retardance between two orthogonal components of incident polarized light or to introduce a known phase shifting (PS) between coherent waves, both by means of an applied voltage. Typically, the retardance or PS introduced by an LCVR is not homogeneous across the aperture. On the one hand, the LCVR glass substrates present a global bend that causes an overall variation of the retardance or PS. On the other hand, in the manufacturing process of an LCVR, there sometimes appears a set of micro-air bubbles that causes local retardance or PS inhomogeneities. In this work, we present an interferometric technique based on a Mach-Zehnder interferometer that is insensitive to vibrations and capable of inspecting and characterizing the LCVR's retardance or PS inhomogeneities. The feasibility of the proposed method is demonstrated in the experimental results, where the LCVR retardance is measured with an error of about 0:2 rad. The thickness of possible micro-air bubbles is obtained with a resolution of about 50 nm.