Examinando por Materia "Measurements"

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    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.
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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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    Mesh Segmentation and Texture Mapping for Dimensional Inspection inWeb3D
    (Association for Computing Machinery, Inc, 2017-01-01) Mejia D.; Sánchez J.R.; Segura Á.; Ruiz-Salguero O.; Posada J.; Cadavid C.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
    Traditionally, the data generated by industrial metrology so.ware is stored as static reports that metrology experts produce for engineering and production departments. Nevertheless, industry demands new approaches that provide ubiquitous and real time access to overall geometry, manufacturing and other data. Web3D technologies can help to improve the traditional metrology methods and o.er new ways to convey this information in web-based continuous friendly manner. However, enriched point clouds may be massive, thus presenting transmission and display limitations. To partially overcome these limitations, this article presents an algorithm that computes efficient metrology textures, which are then transferred and displayed through Web3D standards. Texture coordinates are computed only once for the reference CAD mesh on the server using in-house thermal-based segmentation and Hessian-based parameterization algorithms. The metrology data is then encoded in a texture le, which becomes available instantly for interactive visual inspection through the Web3D platform. © 2017 ACM.
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    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.