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  • Ítem
    HIPAE helicopter-borne in-situ pollution assessment experiment: Plataforma alternativa para la medición de contaminantes en capas verticales
    (Institute of Electrical and Electronics Engineers Inc., 2019-01-01) Botero A.Y.; Florez J.; Duque J.F.; Rendon A.; Lopez-Restrepo S.; Pinel N.; Quintero O.L.; Oquinte1@eafit.edu.co; Rodriguez J.S.; Galvez J.; Lopera D.V.; Montilla E.; Marulanda J.I.; Isaza C.; Lainez M.L.A.; Zapata A.F.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
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    Design of a linear in wavenumber spectrometer
    (OSA - The Optical Society, 2018-01-01) Ruiz-Lopera S.; Restrepo R.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    We describe the optical design of a linear in wavenumber spectrometer that combines a grating and a prism. OpticStudio software was used to validate the performance of the design. High lineartiy in k-space was achived. © 2018 The Author (s)
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    Monoscopic multifocus in polarization images for biological samples segmentation
    (OSA - The Optical Society, 2018-01-01) Cano C.; Restrepo R.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    We present an implementation based on polarization images acquisition for different focus planes in a microscope, allowing the volumetric segmentation of structured biological samples like onion cellular walls. © 2018 The Author (s)
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    Detection of saharan mineral dust aerosol transport over brazilian northeast through a depolarization lidar
    (EDP Sciences, 2018-01-01) Guedes A.G.; Landulfo E.; Montilla-Rosero E.; Lopes F.J.S.; Hoelzemann J.J.; Fernandez J.H.; Silva M.P.A.; Santos R.S.S.; Guerrero-Rascado J.L.; Alados-Arboledas L.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    In this study we present results of linear volume depolarization ratio profiles obtained by a depolarization lidar in operation in Natal, Brazil. The DUSTER system has 4 channels, namely: 1064, 532 s/p and 355 nm. This system is calibrated with a half-wave plate using the 90° methodology. The data obtained from this system is correlated with AERONET sunphotometer data, and, when available, CALIPSO satellite data. In addition a trajectory model (HYSPLIT) is used to calculate backward trajectories to assess the origin of the dust polluted air parcels. The objective is to create a transport database of Saharan dust. © The Authors, published by EDP Sciences, 2018.
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    Lalinet status - Station expansion and lidar ratio systematic measurements
    (EDP Sciences, 2018-01-01) Landulfo E.; Lopes F.; Moreira G.A.; Da Silva J.; Ristori P.; Quel E.; Otero L.; Pallota J.V.; Herrera M.; Salvador J.; Bali J.L.; Wolfram E.; Etala P.; Barbero A.; Forno R.; Sanchez M.F.; Barbosa H.; Gouveia D.; Santos A.V.; Hoelzemann J.; Fernandez J.H.; Guedes A.; Silva A.; Barja B.; Zamorano F.; Legue R.P.; Bastidas A.; Zabala M.V.; Velez J.; Nisperuza D.; Montilla E.; Arredondo R.E.; Marrero J.C.A.; Vega A.R.; Alados-Arboledas L.; Guerrero-Rascado J.L.; Sugimoto N.; Yoshitaka J.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    LALINET is expanding regionally to guarantee spatial coverage over South and Central Americas. One of the network goals is to obtain a set of regional representative aerosol optical properties such as particle backscatter, extinction and lidar ratio. Given the North-South extension and influence of distinct airmass circulation patterns it is paramount to distinguish these optical parameters in order to gain better perfomance in radiation transfer models. A set of lidar ratio data is presented. © The Authors, published by EDP Sciences, 2018.
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    Reduction of speckle noise in digital holography
    (SPIE-INT SOC OPTICAL ENGINEERING, 2004-01-01) Garcia-Sucerquia, J.; Ramirez, J.A.H.; Castaneda, R.; Prieto, D.V.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    A fundamental problem in holography, as well optical as digital, is the presence of speckle noise in the reconstruction process. Many approaches have been carried out in order overcome such a problem, ranging from altering the spatial coherence (optical techniques) of the illumination to imaging processing techniques (digital techniques). This work shows the merged use of digital imaging techniques in order to reduce the speckle noise in digital reconstruction of optically recorded Fresnel's holograms. The proposed filtering techniques are illustrated with experimental results.
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    Monocolor and color holography of pre-Hispanic Colombian goldwork: A way of Colombian heritage appropriation
    (SPIE-INT SOC OPTICAL ENGINEERING, 2018-01-01) Madrid Sánchez, A.; Giraldo, L.M.; Velásquez Prieto, D.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Optically indistinguishable copies of 3D real objects or holograms are known to be suitable to replace exhibited artistic pieces in museums. In this paper, we discuss holography as an alternative to protect, share and preserve finely crafted gold pieces belonging to the indigenous treasure inherited by Colombians. We present high diffraction efficiency monocolor and color holograms of native goldwork. As reference objects and proof of concept, we use replicas of the renowned and emblematic Poporo Quimbaya, pre-Hispanic gold pendants and anthropomorphic gold pieces. We report experimental details to deal with different types of commercial holographic recording materials, as for example, PFG-03M and PFG- 03C silver halides or C-RT20 photopolymers. And its general feasibility for reproducing high-quality holograms suitable for museum exhibitions or traveling art-collections. Copyright © 2018 SPIE. Downloading of the abstract is permitted for personal use only.
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    DC term filtering techniques in digital holography
    (SPIE-INT SOC OPTICAL ENGINEERING, 2004-01-01) Garcia-Sucerquia, J.; Ramirez, J.A.H.; Prieto, D.V.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    In numerical hologram reconstruction like in optical holography, there exist different diffraction orders, which many times produce difficulties for the image visualizations. In numerical reconstruction, the filtering of the DC term, or zero order diffraction, provides an improved utilization of the dynamic range of the visualization systems, which is needed for the right displaying purposes of reconstructed images. In the case of the in-line set-ups, the zero diffraction order has even more devastating effects because it does not allow reconstructing the images itself as in Gabor's holograms, so it is necessary to attempt a filtering of this DC term. In this work is shown a qualitative assessment of different techniques of DC term filtering applied to numerical reconstruction of Fresnel's holograms recorded by means of off-line set-ups.
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    Design, development, and implementation of a low-cost full-parallax holoprinter
    (SPIE-INT SOC OPTICAL ENGINEERING, 2018-02-19) Madrid S, A.; D. Velásquez; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Synthetic holograms have achieved a great impact in a variety of fields like architecture, advertising, army and art, and have proven their importance in advancing the holographic displays as visual communication media. Printing synthetic holograms needs the development of a holographic printer that from a set of 2D images allows to create 3D holographic images of real objects and computer generated objects. With the purpose of developing a holoprinter, we have implemented three related components: i) design and implementation of an optical system for direct writing of hogels, ii) a computational implementation to generate parallax 2D images and finally, iii) the implementation of an opto-mechanical and control system for automatic recording of the synthetic holograms. The three components have been developed under the restricted conditions of our holographic laboratory. In this way, a direct write optical setup was implemented using He-Ne laser, and an optical system for hogel writing with a field of view (FOV) of 60° was designed by using commercial lenses. To generate 2D parallax images, an application was created in the free computer graphics software Blender, applying different camera configurations. And a LabView application was made to automatically control obturation and displacement of the holographic plate. The system developed can record computer generated objects and real objects. Real objects are digitized by using a conventional photographic camera. Reflection full parallax holographic stereograms were recorded on PFG-01 plates and their holographic reconstructions are presented and discussed. Copyright © 2018 SPIE. Downloading of the abstract is permitted for personal use only.
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    Monocolor and color holography of pre-Hispanic Colombian goldwork: a way of Colombian heritage appropriation
    (2018-02-19) Madrid S, A.; Giraldo, Leidy Marcela; D. Velásquez; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Optically indistinguishable copies of 3D real objects or holograms are known to be suitable to replace exhibited artistic pieces in museums.
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    Use of optical vortices for the compression of fingerprint recognition systems
    (IOP PUBLISHING LTD, 2017-06-13) Martín R.-V.; René R.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    In this article, an algorithm is presented for the processing and verification of fingerprints by analyzing optical vortices present in the orientation of the fringes of the fingerprint. The algorithm presents a compression factor of 1200, but is highly susceptible to the presence of noise. © Published under licence by IOP Publishing Ltd.
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    Computer graphic method for direct correspondence image acquisition used in full parallax holographic stereograms
    (SPIE-INT SOC OPTICAL ENGINEERING, 2016-01-01) Madrid Sanchez, Alejandro; Velasquez Prieto, Daniel; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    The holoprinter technology based on holographic stereograms has generated a fast development in holographic display applications by the holographic recording of a 2D image sequence with information of a 3D scene, which could be real or computer generated. The images used in holographic stereograms initially start from the acquisition of the different image perspectives of the 3D scene by the re-centering camera configuration and then, this images must be rearranged before the optical recording. This paper proposes a method to acquire the required images or hogel images in one step without using rearrange algorithms, the method uses a virtual camera that moves along a virtual rail by conventional computer graphics software. The proposed method reduced the time required to obtain the hogel images and enhance the quality of the 3D holographic images; it also can be applied in different computer graphics software. To validate the method, a full parallax holographic stereogram was made for a computer generated object.
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    Inspection of an extended surface by an active 3D multiresolution technique
    (Springer-Verlag Berlin Heidelberg, 2009-01-01) Vargas, J.; Restrepo, R.; Quiroga, J.A.; Belenguer, T.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Reliable inspection of large surfaces with low depth recovery error is needed in a wide variety of industrial applications, for example in deformation measurement or defect inspection of extended surfaces as communication antennas. Active triangulation measurement systems present a compromise between the depth recovery error and the measured area. For an optimized active three-dimensional measuring system the expected ratio between the depth resolution and the inspected area is in the rage of 10-4. Therefore, if we want to scan a large object with a high level of detail we need multiresolution techniques. In this work we demonstrate the application of an active triangulation multiresolution method for the inspection of communication antennas. The technique is based on a standard camera-projector system. The result is a global measurement formed by a set of superposed local measurement with high depth resolution. © 2009 Springer-Verlag Berlin Heidelberg.
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    Improving on-axis optical vortex generation by transmissive spatial light modulator using coherent phase diversity
    (OSA - The Optical Society, 2016-01-01) Cuartas-Vélez, C.; Restrepo, R.; Echeverri-Chacón, S.; Uribe-Patarroyo, N.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    We present a modification of numerical optimization coherent phase diversity in order to detect and correct undesired effects of non-linear and incomplete phase modulation of transmissive spatial light modulators for on-axis optical vortices. © OSA 2016.
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    Consumed fatigue life assessment of composite material structures by optical surface roughness inspection
    (Trans Tech Publications Ltd., 2013-01-01) Zuluaga, P.; Frövel, M.; Restrepo, R.; Trallero, R.; Atienza, R.; Pintado, J.M.; Belenguer, T.; Salazar, F.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    A strong knowledge of the fatigue state of highly advanced carbon fiber reinforced polymer composite (CFRP) structures is essential to predict the residual life and optimize intervals of structural inspection, repairs, and/or replacements. Current techniques are based mostly on measurement of structural loads throughout the service life by electric strain gauge sensors. These sensors are affected by extreme environmental conditions and by fatigue loads in such a way that the sensors and their systems require exhaustive maintenance throughout system life. This work is focused on providing a new technique to evaluate the fatigue state of CFRP structures by means of evaluating the surface roughness variation due to fatigue damage. The surface roughness is a property that can be measured in the field by optical techniques such as speckle and could be a useful tool for structural health monitoring. The relation between surface roughness and fatigue life has been assessed on CFRP test specimens. A tensile fatigue load with an R=0.1 (T-T) and a maximum load of 60% of the material ultimate strength has been applied. The surface roughness of the specimens has been determined from the surface topography measured by a high precision confocal microscope. Results show that the surface roughness of the specimens increases with the accumulation of fatigue cycles in such a way that the roughness could be taken into account as a fatigue damage metrics for CFRP. © (2013) Trans Tech Publications.
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    Analysis of vibrations in a plate using interferometric methods
    (SPIE-INT SOC OPTICAL ENGINEERING, 2004-01-01) Rueda, E.; Angel, L.; Velasquez, D.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    In this work some frequencies and modes of vibration of a thin plate were determined using interferometric methods like: real-time holographic interferometry, time-average holographic interferometry, digital speckle pattern interferometry DSPI. And the results obtained are compared with those obtained with the program of finite elements COSMOS.
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    A computational method to acquired hogel images used in full parallax holographic stereograms
    (OSA - The Optical Society, 2016-01-01) Sánchez, A.M.; Velásquez, D.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Holographic stereogram displays require 2D image sequences with a distribution of multiple perspectives of the object. This paper propose a computational method to generate the required images to record full parallax holographic stereograms. © OSA 2016.
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    Analysis of optomechanicalMethod for materials selection in optical design
    (OSA - The Optical Society, 2016-01-01) Cano-Barrera, C.; Restrepo, R.; Zuluaga-Ramírez, P.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    We present a technique to determine the wavefront error and polarization changes introduced by a loaded optical material based on its optical, thermal and mechanical properties through an integrated optomechanical simulation process. © OSA 2016.
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    Optical vortex metrology from phase modulo 2 p maps
    (2012-01-01) Sierra-Sosa, D.-E.; Angel-Toro, L.; Tebaldi, M.; Bolognini, N.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Conventional Optical Vortex Metrology techniques rely on the generation of pseudophase maps for image processing and measuring. In our work, as a novel alternative the application of this techniquefrom phase modulo 2p maps is discussed. © OSA 2012.
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    Applications of spatial light modulators in speckle interferometry
    (SPIE-INT SOC OPTICAL ENGINEERING, 2012-01-01) Bodendorfer, T.; Restrepo, R.; Belenguer, T.; Koch, A.W.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    High resolution spatial light modulators (SLM) have been used in many different ways during the last years. Regarding speckle interferometry, different applications can be realized by integrating SLMs in interferometric setup. In this work the influence of a liquid crystal based phase-only SLM on the measurement quality concerning deformation and shape measurement using two wavelengths is discussed. © 2012 Copyright SPIE.
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