Repositorio Institucional Universidad EAFIT ::Examinando por Autor "Angel-Toro, Luciano"

Examinando por Autor "Angel-Toro, Luciano"

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Design of a control system for interferometric fringe stabilization system with remote access
(SPIE-INT SOC OPTICAL ENGINEERING, 2013-01-01) Espitia-Gomez, Javier; Angel-Toro, Luciano; Velasquez, Daniel; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
Stability in a fringe pattern is a necessary condition in interferometric processes, such as holography, and not always is enough the use of passive stabilization systems, like holographic tables, in particular, when perturbations are caused by thermal or acoustic variations. For these cases, active systems are required. In this work it is presented the implementation of a control system for interferometric fringes stabilization. The interferometric arrangement characteristics are also discussed, which permits to act independently over each of the interferometer's arms by means of two piezoelectric actuators that change the length of the optical path of light that goes through, in order to perturb the system and simultaneously compensate this perturbation in real time. It is also shown that the proposed system allows evaluating the control system's performance subjected to diverse perturbations, and it is shown how remote access was given to the implemented platform. © 2013 SPIE.
Double exposure specklegrams obtained by using scaled aperture pupils
(SPIE, 2001-08-14) Angel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
In speckle photography the pupil aperture is usually not modified between exposures. In our work, the change of the pupil aperture scale between exposures is analyzed on the basis of double-exposed image speckle, before and after a diffuse in-plane displacement is done. The apertures have the same shape but its scale is modified between exposures. Note that the relative position of the aperture is maintained. In particular, we analyze a simple case that uses a circular aperture whose diameter is modified for recording each image. The intensity in the image plane and the fringe visibility are evaluated, in terms of the geometric characteristics of the pupils. © (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Effect of the internal modulation of speckles in displacement measurements in optical vortex metrology
(SPIE-INT SOC OPTICAL ENGINEERING, 2013-01-01) Gomez-Tejada, Daniel; Sierra-Sosa, Daniel; Castaneda, Roman; Angel-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 SPIE.
In-plane displacement measurement in vortex metrology
(2013-10-09) Angel-Toro, Luciano; Sierra-Sosa, Daniel; Tebaldi, Myrian; Bolognini, Néstor; Angel-Toro, Luciano; Sierra-Sosa, Daniel; Tebaldi, Myrian; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
Recently we proposed an alternative method of displacement analysis in vortex metrology, based on the application of the Fourier optics techniques, that is suitable for an intermediate range of displacement measurements ranging below the resolution of speckle photography and above that of the conventional vortex metrology. However, for smaller displacements, we introduce an approach to perform the Fourier analysis from vortex networks. In this work, we present an enhanced method for measuring uniform in-plane displacements, taking advantage of the capability of determining the subpixel locations of vortices and having the ability to track the homologous vortices onto a plane. It is shown that high-quality fringe systems can be synthesized and analyzed to accurately measure in an extended range of displacements and for highly decorrelated speckle patterns. Experimental results supporting the validity of the method are presented and discussed. © 2013 Optical Society of America
In-plane displacement measurement in vortex metrology by synthetic network correlation fringes.
(OPTICAL SOC AMER, 2013-03-01) Angel-Toro, Luciano; Sierra-Sosa, Daniel; Tebaldi, Myrian; Bolognini, Nestor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
Recently we proposed an alternative method of displacement analysis in vortex metrology, based on the application of the Fourier optics techniques, that is suitable for an intermediate range of displacement measurements ranging below the resolution of speckle photography and above that of the conventional vortex metrology. However, for smaller displacements, we introduce an approach to perform the Fourier analysis from vortex networks. In this work, we present an enhanced method for measuring uniform in-plane displacements, taking advantage of the capability of determining the subpixel locations of vortices and having the ability to track the homologous vortices onto a plane. It is shown that high-quality fringe systems can be synthesized and analyzed to accurately measure in an extended range of displacements and for highly decorrelated speckle patterns. Experimental results supporting the validity of the method are presented and discussed.
New multiple aperture arrangements for speckle photography
(Elsevier B.V, 2000-08-01) Angel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Angel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Universidad EAFIT. Departamento de Ciencias Básicas; Angel-Toro, Luciano (langel@eafit.edu.co); Óptica Aplicada
Abstract. We propose a multiple exposure specklegram by using an optical system whose multiple aperture pupil changes between exposures. In particular, we analyze experimentally two arrangements and we show that it is possible to store the required information by employing a minimum number of registers if an adequate selection of the pupil is done. We study the effect of the decorrelation (among the stored speckle pattern) introduced by changing the multiple aperture pupil arrangements between exposures. The fundamentals and the relative benefits of the new scheme proposed are discussed on the basis of a fringe visibility analysis.
Novel vortex-transform for high frequency modulated patterns
(OPTICAL SOC AMER, 2013-10-07) Sierra-Sosa, Daniel; Angel-Toro, Luciano; Bolognini, Nestor; Tebaldi, Myrian; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
A novel vortex-transform is proposed. This transform allows for generating complex-valued functions from modulated intensity patterns, including high frequency components from modulation, without the generation of unstable phase singularities. From these complex-valued functions it is possible to obtain intensity and pseudo-phase maps to analyze the intensity recordings without the necessity of phase retrieval techniques. The intensity and pseudo-phase maps obtained by using this transform preserve the modulation structure onto the intensity and phase modulo 2? maps, including stable phase singularities. ©2013 Optical Society of America.
Phase-object detection by use of double-exposure fringe-modulated speckle patterns
(OSA, 2003-01) Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Angel-Toro, Luciano; Tebaldi, Myrian; Trivi, Marcelo; Bolognini, Néstor; Angel-Toro, Luciano; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
We study the properties of a double-exposure image specklegram of a diffuse object obtained by use of a doubleaperture pupil. A phase object is placed in front of one aperture during the first or the second exposure. Also, it is assumed that a uniform displacement of the diffuser between exposures is produced. The recorded specklegram is coherently illuminated and analyzed by Fourier transform operations. The average intensity distribution and the interference fringe visibility in the Fourier plane are investigated. On this basis, an alternative interference technique to detect phase objects is proposed.
Remote access to an interferometric fringes stabilization active system via RENATA
(SPIE-INT SOC OPTICAL ENGINEERING, 2013-01-01) Espitia-Gomez, Javier; Angel-Toro, Luciano; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
The Advanced Technology National Network (RENATA, for its acronym in Spanish) is a Colombian, collaborative work tool, linked to other networks worldwide, in which take participation researchers, teachers and students, by sharing laboratory resources located in different universities, institutes and research centers throughout the country. In the Universidad EAFIT (Medellín, Colombia) it has been designed an interferometric fringes stabilization active system, which can be accessed remotely via the RENATA network. A Mach-Zehnder interferometer was implemented, with independent piezoelectric actuators in each arm, with which the lengths of optical path of light that goes over in each of them can be modified. Using these actuators, one can simultaneously perturb the system and compensate the phase differences caused by that perturbation. This allows us to experiment with different disturbs, and analyze the system response to each one of them. This can be made from any location worldwide, and especially from those regions in which optical and optoelectronic components required for the implementation of the interferometer or for the stabilization system are not available. The device can also be used as a platform in order to conduct diverse experiments, involving optical and controlling aspects, constituting with this in a pedagogic tool. For the future, it can be predicted that remote access to available applications would be possible, as well as modifications of the implemented code in labVIEWTM, so that researchers and teachers can adapt and improve their functionalities or develop new applications, based on the collaborative work. © 2013 SPIE.
Speckle decorrelation influence on measurements quality in vortex metrology
(ELSEVIER SCIENCE BV, 2012-10-01) Angel-Toro, Luciano; Sierra-Sosa, Daniel; Tebaldi, Myrian; Bolognini, Nestor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
We study speckle decorrelation effects in connection with conventional vortex metrology techniques. Our proposal is based on processing speckled images recorded by using two different experimental set-ups. In both schemes two laterally displaced patterns are generated: one scheme allows for obtaining undecorrelated speckle distributions and the other for decorrelated ones. Vortex networks associated with speckle patterns are analyzed by employing the usual tools developed for vortex metrology. For each recorded image, a 2D pseudo-phase map is generated on the basis of the Reisz transform. Then the vortices are located, and parameterized in terms of their topological charge, eccentricity, vorticity and angles between the zero crossing lines from the real and the imaginary parts of the analytical signal. After tracking the homologous vortices onto the maps, the histograms corresponding to the coordinate displacements are analyzed. We show that histograms interpretation is prone to failure due to its high sensitivity to decorrelation. Experimental evidences are presented to support the restrictions imposed by decorrelation of actual speckles due to uniform in-plane displacements. © 2012 Elsevier B.V. All rights reserved.
Vortex metrology using Fourier analysis techniques: vortex networks correlation fringes.
(OPTICAL SOC AMER, 2012-10-20) Angel-Toro, Luciano; Sierra-Sosa, Daniel; Tebaldi, Myrian; Bolognini, Nestor; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
In this work, we introduce an alternative method of analysis in vortex metrology based on the application of the Fourier optics techniques. The first part of the procedure is conducted as is usual in vortex metrology for uniform in-plane displacement determination. On the basis of two recorded intensity speckled distributions, corresponding to two states of a diffuser coherently illuminated, we numerically generate an analytical signal from each recorded intensity pattern by using a version of the Riesz integral transform. Then, from each analytical signal, a two-dimensional pseudophase map is generated in which the vortices are located and characterized in terms of their topological charges and their core's structural properties. The second part of the procedure allows obtaining Young's interference fringes when Fourier transforming the light passing through a diffracting mask with multiple apertures at the locations of the homologous vortices. In fact, we use the Fourier transform as a mathematical operation to compute the far-field diffraction intensity pattern corresponding to the multiaperture set. Each aperture from the set is associated with a rectangular hole that coincides both in shape and size with a pixel from recorded images. We show that the fringe analysis can be conducted as in speckle photography in an extended range of displacement measurements. Effects related with speckled decorrelation are also considered. Our experimental results agree with those of speckle photography in the range in which both techniques are applicable.

Examinando por Autor "Angel-Toro, Luciano"

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