Examinando por Autor "Ángel-Toro, Luciano"

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    Analysis of vibrations in a plate using interferometric methods
    (SPIE, 2004-10-21) Ángel-Toro, Luciano; Prieto, Daniel Velasquez; Rueda Muñóz, Edgar Alberto; 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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    Effect of the internal modulation of speckles in displacement measurements in optical vortex metrology
    (SPIE, 2013-11-08) Gómez-Tejada, Daniel; Sierra-Sosa, Daniel; Castañeda, Román; Ángel-Toro, Luciano; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    The Optical Vortex Metrology is based on the possibility of characterizing, through topological and morphological parameters, each one of the vortices existing in the phase of the optical field, or in a pseudo-phase obtained by means of the Hibert, Reisz or Laguerre-Gauss transforms. On this basis, it is possible tracking and pairing the homologous vortices. Then, the locations and relative displacements between the homologous vortices are determined with sub-pixel precision. Because of the statistical nature of the measurements, their quality is determined, among other factors, by the amount of available vortices per unit area. In this work, it is proposed to use the internal modulation of the speckles to generate a significant increase in the vortex density, which can be achieved by employing a double aperture pupil optical system. Simulations of the speckle distributions are presented to analyze the increase of the vortex density as a function of the distance between the apertures, and to evaluate the influence of the increment of this density in the quality of uniform in-plane displacements measurements. The results corresponding to modulated speckles are compared with those obtained with a single aperture. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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    Features on photorefractive registered speckles
    (SPIE, 1999-04-29) Ángel-Toro, Luciano; Bolognini, Néstor; Tebaldi, Myrian; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    The recording and read-out of a volume speckle pattern is investigated for transmission geometry. The modulation of the 3D speckle grains appears when the image of a coherently illuminated random diffusor is formed onto the crystal by an optical system whose pupil consists of two identical holes. The intensity distribution of the speckle pattern imaged onto the BSO crystal leads to a space-charge field by drift of photocarriers, resulting in a refractive index modulation. The main features of diffracted read-out light at the Fourier plane are discussed. © (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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    Logic operations by using modulated speckle
    (SPIE, 2001-08-14) Tebaldi, Myrian; Ángel-Toro, Luciano; Trivi, Marcelo; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    An alternative image multiplexing technique is proposed. In the arrangement implemented, the input is imaged by introducing a multiple aperture pupil in the imaging lens. Then, the speckle pattern is modulated by several system of fringes. The input images are sequentially encoded by using a different pupil during each exposure. The pupil arrangements implemented are selected to concentrate in each spot the spectral information corresponding to not more than two exposures. The spectral amplitude components for a pari of exposures are added into the common diffraction spots. All the diffraction spots contain information about a pair of inputs. Then, an image binary operation can be carried out in each spot. The technique is implemented by using as recording media photographic films and photorefractive crystals. The BSO crystal as recording medium is quite adequate in the applications proposed because it permits multiple storage in real time. However, due to its volume nature, each speckle grain exhibits angular selectivity in addition to those features observed in bidimensional media. © (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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    Multiple rotation assessment through isothetic fringes in speckle photography
    (OSA, 2007-04-20) Ángel-Toro, Luciano; Tebaldi, Myrian; Bolognini, Néstor; Ángel-Toro, Luciano; Tebaldi, Myrian; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    The use of different pupils for storing each speckled image in speckle photography is employed to determine multiple in-plane rotations. The method consists of recording a four exposure specklegram where the rotations are done between exposures. This specklegram is then optically processed in a whole field approach rendering isothetic fringes, which give detailed information about the multiple rotations. It is experimentally demonstrated that the proposed arrangement permits the depiction of six isothetics in order to measure either six different angles or three nonparallel components for two local general in-plane displacements. © 2007 Optical Society of America
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    Multiple-aperture speckle method applied to local displacement measurements
    (Elsevier B.V, 2007) Ángel-Toro, Luciano; Tebaldi, Myrian; Bologninic, Néstor; Ángel-Toro, Luciano; Tebaldi, Myrian; Bologninic, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Luciano Angel Toro (langel@eafit.edu.co); Óptica Aplicada
    The goal of this work is to analyze the measurement capability of the modified speckle photography technique that uses different multiple aperture pupils in a multiple exposure scheme. In particular, the rotation case is considered. A point-wise analysis procedure is utilized to obtain the fringes required to access to the local displacement measurements. The proposed arrangement allows simultaneous displaying in the Fourier plane several fringes system each one associated with different rotations. We experimentally verified that the local displacement measurements can be determined with a high precision and accuracy.
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    Optical processing by fringed speckles registered in a BSO crystal
    (SPIE, 2000-07-28) Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Ángel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Ángel-Toro, Luciano; Universidad EAFIT. Departamento de Ciencias Básicas; langel@eafit.edu.co; Óptica Aplicada
    An alternative image multiplexing technique, employing a multiple-aperture pupil for each exposure, is presented. The aperture arrangement of the pupil is modified between exposures. A thick photorefractive BSO crystal is used as recording material. The technique allows concentrating the spectral components of a pair of images selectively into isolated spots in the Fourier plane. Two applications are proposed, in image processing and optical metrology. © 2000 Society of Photo-Optical Instrumentation Engineers. © 2000 Society of Photo-Optical Instrumentation Engineers
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    Phase stepping in Lau interferometry
    (Elsevier, 1999-06-15) Ángel-Toro, Luciano; Tebaldi, Myrian; Henao, Rodrigo; Ángel-Toro, Luciano; Tebaldi, Myrian; Henao, Rodrigo; Universidad EAFIT. Departamento de Ciencias Básicas; langel@eafit.edu.co; Óptica Aplicada
    The implementation of phase shifting interferometry to analyze the Lau interferometric fringe patterns is proposed. The fundamentals of this application are theoretically discussed and the basis of the phase map interpretation is outlined. The three steps algorithm is used to depict the phase maps of lens-like test objects and an application for measuring focal lengths of lenses is reported. Experimental results are presented. q1999 Elsevier Science B.V. All rights reserved.
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    Photorefractive optical processing: some proposals
    (SPIE, 1999-04-29) Ángel-Toro, Luciano; Bolgnini, Néstor; Tebaldi, Myrian; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Some proposals on Lau and Talbot fringes formation based on a grating registered as birefringence modulation in a photorefractive crystal, will be presented. In the Talbot case, the stored grating can be replicated if read-out with coherent light. The system for the Lau arrangement behaves as a combination of an amplitude and a birefringence phase grating. In both cases, it is possible to control the visibility and to produce a contrast reversion of fringes by using an analyzer. Besides, Lau and Talbot interferometers based on the mentioned approach and their alternative experimental arrangements will be discussed. © (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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    Propierties of speckle patterns generated through multiaperture pupils
    (Elsevier, 2001-05-15) Ángel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Ángel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Ángel-Toro, Luciano (langel@eafit.edu.co); Óptica Aplicada
    The characteristics of the image speckles obtained through multiple aperture pupils are theoretically analyzed in terms of the parameters defining the pupils. The possibility of interpreting and synthesizing the image speckle distribution in terms of rather elementary structures is considered, based on the Fourier optics analysis. Then, first and second order statistical properties of the speckle patterns are studied by evaluating both the mutual intensity and the auto-correlation intensity of speckle distributions obtained by means of pupils consisting of identical apertures. Experimental results are presented to confirm the analysis.
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    Soap film analysis by speckle interferometer
    (SPIE, 2003-11-18) Tebaldi, Myrian; Ángel-Toro, Luciano; Trivi, Marcelo; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    In this paper a soap film is characterized by using a speckle interferometer. The arrangement consists of a double-exposure specklegram obtained through a double-aperture system, by introducing a wedge in front of one aperture in one exposure. It is assumed that a uniform displacement of the diffuser is produced between exposures. The average intensity distribution and the changes experimented by the interferometric fringe visibility in the Fourier plane due to the introduction of a soap film in each exposure are analyzed.