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https://hdl.handle.net/10784/1123

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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.
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.
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.
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.
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.
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.

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