Examinando por Materia "Imaging systems"
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Ítem Digital material laboratory: Wave propagation effects in open-cell aluminium foams(PERGAMON-ELSEVIER SCIENCE LTD, 2012-09-01) Saenger, E. H.; Uribe, D.; Jaenicke, R.; Ruiz, O.; Steeb, H.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis paper is concerned with numerical wave propagation effects in highly porous media using digitized images of aluminium foam. Starting point is a virtual material laboratory approach. The aluminium foam microstructure is imaged by 3D X-ray tomography. Effective velocities for the fluid-saturated media are derived by dynamic wave propagation simulations. We apply a displacement-stress rotated staggered finite-difference grid technique to solve the elastodynamic wave equation. The used setup is similar to laboratory ultrasound measurements and computed results are in agreement with our experimental data. Theoretical investigations allow to quantify the influence of the interaction of foam and fluid during wave propagation. Together with simulations using an artificial dense foam we are able to determine the tortuosity of aluminium foam. © 2012 Elsevier Ltd. All rights reserved.Ítem EMIR mechanical design status(SPIE-INT SOC OPTICAL ENGINEERING, 2004-09-01) Fuentes, F. J; Sánchez, Vicente; Barrera, Sonia; Correa, Santiago; Pérez, Jaime; Redondo, Pablo; R. Restrepo; Tenegi, Fabio; Villegas, Alejandro; Patrón, Jesus; Garzón, Francisco; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaEMIR is the NIR multi-object imager and spectrograph for the GTC (Gran Telescopio Canarias). The instrument PDR phase was held successfully in March 2003, and we are at present in the middle of the ADR (Advanced Design Phase) during which a number of mechÍtem EMIR: the GTC NIR multi-object imager spectrograph(SPIE-INT SOC OPTICAL ENGINEERING, 2004-09-01) Garzón, Francisco; Abreu, David; Barrera, Sonia; Correa, Santiago; Díaz, Jose; Fragoso, Ana; Fuentes, F.J; Gago, Fernando; Gonzalez, Carlos; López, Pablo; Manescau, Antonio; Patrón, Jesus; Pérez, Jaime; Redondo, Pablo; R. Restrepo; Sánchez, Vicente; Villegas, Alejandro; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaWe present the final global design and performances of EMIR, the NIR multi-object spectrograph of the GTC, as well as the plan for its early scientific exploitation.Ítem EMIR: The GTC NIR multi-object imager-spectrograph(SPIE-INT SOC OPTICAL ENGINEERING, 2006-01-01) Garzón, F.; Abreu, D.; Barrera, S.; Becerril, S.; Cairós, L.M.; Díaz, J.J.; Fragoso, A.B.; Gago, F.; Grange, R.; González, C.; López, P.; Patrón, J.; Pérez, J.; Rasilla, J.L.; Redondo, P.; Restrepo, R.; Saavedra, P.; Sánchez, V.; Tenegi, F.; Vallbé, M.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaEMIR, currently entering into its fabrication and AIV phase, will be one of the first common user instruments for the GTC, the 10 meter telescope under construction by GRANTECAN at the Roque de los Muchachos Observatory (Canary Islands, Spain). EMIR is being built by a Consortium of Spanish and French institutes led by the Institute de Astrofisica de Canarias (IAC). EMIR is designed to realize one of the central goals of 10m class telescopes, allowing observers to obtain spectra for large numbers of faint sources in an time-efficient manner. EMIR is primarily designed to be operated as a MOS in the K band, but offers a wide range of observing modes, including imaging and spectroscopy, both long slit and multiobject, in the wavelength range 0.9 to 2. 5 µm. It is equipped with two innovative subsystems: a robotic reconfigurable multislit mask and disperssive elements formed by the combination of high quality difracction grating and conventional prisms, both at the heart of the instrument. The present status of development, expected performances, schedule and plans for scientific exploitation are described and discussed. The development and fabrication of EMIR is funded by GRANTECAN and the Plan Nacional de Astronomia y Astrofisica (National Plan for Astronomy and Astrophysics, Spain).Ítem An integrated system for virtual scene rendering, stereo reconstruction and accuracy estimation(2006-01-01) Marichal-Hernández, J.G.; Pérez Nava, F.; Rosa, F.; Restrepo, R.; Rodríguez-Ramos, J.M.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaThis article depicts an integrated system capable of generating virtual stereo scenes, reconstructing a three-dimensional map of distances, and calculating the accuracy of the results obtained. This tool is particularly useful for verifying the validity of distance reconstruction techniques, and is robust enough to use in a wide variety of scenarios since it avoids the need for an image-capture system in laboratory simulations. The importance of the distance reconstruction problem lies in the range of its applications: industrial inspection and quality control, surveillance and security, autonomous vehicles, robotic systems, medical image analysis, image databases, virtual reality, telepresence, and telerobotics. The system is based on the VRML standard for three-dimensional geometric scene representation, on OpenGL for rendering virtual scenes, and on the TRW algorithm for the problem of three-dimensional reconstruction. © 2006 IEEE.Ítem Multi-wavelength digital in-line holographic microscopy(2012-01-01) Velaquez, D.; Garcia-Sucerquia, J.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaThe use of multiple wavelength illumination in digital in-line holographic microscopy is presented. A biological sample is illuminated sequentially with three different optical sources and the separate holograms reconstructed with the appropriate wavelength. For controlling the scale of the reconstructed holograms, a reconstruction algorithm that allows for choosing the pixel size at the reconstruction plane independently of the wavelength and the reconstruction distance is used. The method is illustrated with experimental results. © OSA 2012.Ítem Status of the EMIR mechanical system(SPIE-INT SOC OPTICAL ENGINEERING, 2006-06-28) Sánchez, V.; Barrera, S.; Becerril, S.; Correa, S.; Pérez, J.; Redondo, P.; Restrepo, R.; Saavedra, P.; Tenegi, F.; Patrón, J.; Garzón, F.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaEMIR is the NIR multi-object imager and spectrograph for the GTC (Gran Telescopic Canarias). The instrument ADR (Advanced Design Review) was held successfully in March 2006. During the AD phase, a number of mechanical concepts were tested on development prototypes to ensure the feasibility of the PDR proposed designs. This presentation contains an overview of the current mechanical status of the instrument, as well as the prototypes development. It contains the prototype tests results of the collimator first lens barrel, the support trusses, the grisms wheel and the demonstration programme for the cryogenic reconfigurable slit mechanism.Ítem Vortex-enhanced coherent-illumination phase diversity for phase retrieval in coherent imaging systems(OSA - The Optical Society, 2016-04-15) Echeverri-Chacón, S.; Restrepo, R.; Cuartas-Vélez, C.; Uribe-Patarroyo, N.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaWe propose a phase-retrieval method based on the numerical optimization of a new objective function using coherent phase-diversity images as inputs for the characterization of aberrations in coherent imaging systems. By employing a spatial light modulator to generate multiple-order spiral phase masks as diversities, we obtain an increase in the accuracy of the retrieved phase compared with similar state-of-the-art phase-retrieval techniques that use the same number of input images. We present simulations that show a consistent advantage of our technique, and experimental validation where our implementation is used to characterize a highly aberrated 4F optical system. (C) 2016 Optical Society of America