Examinando por Autor "Ramirez, J.A.H."

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    Ítem
    DC term filtering techniques in digital holography
    (SPIE-INT SOC OPTICAL ENGINEERING, 2004-01-01) Garcia-Sucerquia, J.; Ramirez, J.A.H.; Prieto, D.V.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    In numerical hologram reconstruction like in optical holography, there exist different diffraction orders, which many times produce difficulties for the image visualizations. In numerical reconstruction, the filtering of the DC term, or zero order diffraction, provides an improved utilization of the dynamic range of the visualization systems, which is needed for the right displaying purposes of reconstructed images. In the case of the in-line set-ups, the zero diffraction order has even more devastating effects because it does not allow reconstructing the images itself as in Gabor's holograms, so it is necessary to attempt a filtering of this DC term. In this work is shown a qualitative assessment of different techniques of DC term filtering applied to numerical reconstruction of Fresnel's holograms recorded by means of off-line set-ups.
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    Ítem
    Reduction of speckle noise in digital holography
    (SPIE-INT SOC OPTICAL ENGINEERING, 2004-01-01) Garcia-Sucerquia, J.; Ramirez, J.A.H.; Castaneda, R.; Prieto, D.V.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    A fundamental problem in holography, as well optical as digital, is the presence of speckle noise in the reconstruction process. Many approaches have been carried out in order overcome such a problem, ranging from altering the spatial coherence (optical techniques) of the illumination to imaging processing techniques (digital techniques). This work shows the merged use of digital imaging techniques in order to reduce the speckle noise in digital reconstruction of optically recorded Fresnel's holograms. The proposed filtering techniques are illustrated with experimental results.