Examinando por Autor "Velásquez Prieto, Daniel"
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Ítem Design of a control system for interferometric fringe stabilization system with remote access(SPIE, 2013-11-18) Espitia-Gómez, Javier; Ángel Toro, Luciano; Velásquez Prieto, Daniel; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaStability 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) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.Ítem Evaluation between methods for the color measurement in holograms by using a CMOS-RGB camera and a spectrometer(SPIE, 2013-07-22) Palacios Ortega, Natalith; Velásquez Prieto, Daniel; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaMany models and methods commonly used in colorimetry have been incorporated to the study and knowledge of the colorimetric properties in the reflection color holograms; these methods have reported the possibilities of color reproduction in holograms. One method is based in calculating the color differences between the CIE-L*a*b* coordinates of the original object compared to the same values obtained for the reconstructed hologram; these values are calculated through the measurement of the spectral composition of the light in the reproduced hologram which are made with spectrometers. Other methods are based in the use of cameras for the color measurement, although, they are not commonly used for that ending in holography. This work presents the results of a comparative study between the use of spectrometers and RGB digital cameras for the color measurement in holograms. The diffraction efficiency of the holograms for a GretagMacbeth Colorchecker samples is measured through a spectrometer and their CIE-L*a*b* coordinates are calculated; the color differences are also calculated by taking as theoretical values the coordinates of the original object. A similar procedure is made by capturing the reconstructed images of the hologram through a CMOSRGB camera, which requires a linearizing and characterizing procedure. The RGB coordinates of the original object are compared with the RGB coordinates of the reproduced hologram too. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.Ítem Obtención de estructuras de relieve en materiales de registro de haluros de plata(Sedoptica, 2013-09-19) Velásquez Prieto, Daniel; Giraldo Castaño, Lady Marcela; Velásquez Prieto, Daniel; Giraldo Castaño, Lady Marcela; Universidad EAFIT. Departamento de Ciencias Básicas; lmgc15@gmail.com; Óptica AplicadaDiffraction transmission gratings were recorded in AGFA-8E75 film, chemically treated under processes with D-19 + potassium ferrocyanide and a chemical processing technique proposed for PE-2 film to obtain embossed stripes. Holographic structures were measured topographically by the technique of atomic force microscopy in noncontact mode (NC-AFM) and we observe changes in the depths under variations in exposures and used photochemistry. We find that the best performance in terms of relief depth obtained is given by the conventional process which reached depths between 0.15 m and 0.3 m for spatial frequencies of the order of 400Ítem Reflections on How to Address Questions(Universidad EAFIT, 2009-11-01) Velásquez Prieto, Daniel; Colaborador