Examinando por Materia "Hologramas de Fresnel"

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    Ítem
    DC term filtering techniques in digital holography
    (SPIE, 2004-10-21) Velásquez-Prieto, Daniel; García Sucerquia, Jorge Iván; Herrera Ramírez, Jorge Alexis; 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
    Improvement of the signal-to-noise ratio in digital holography
    (Sociedad Mexicana de Física, 2005-02) Velásquez-Prieto, Daniel; Herrera Ramírez, Jorge Alexis; García Sucerquia, Jorge Iván; Velásquez-Prieto, Daniel; Herrera Ramírez, Jorge Alexis; García Sucerquia, Jorge Iván; Universidad EAFIT. Departamento de Ciencias Básicas; dvelas@eafit.edu.co; Óptica Aplicada
    A fundamental problem in optical and digital holography is the presence of speckle noise in the reconstruction process, which essentially diminishes the signal to noise ratio (SNR). For many applications, that reduction of the SNR makes the digital holography impractical, so great number of approaches have been carried out in order to overcome such a problem. They range from modifying the spatial coherence of the illumination to the application of image processing techniques. In this paper we propose the merged use of digital image processing techniques in order to increase this SNR by reducing the speckle noise in the digital reconstruction of optically recorded Fresnel’s holograms. The proposed techniques are illustrated with experimental results.
  • No hay miniatura disponible
    Ítem
    Reduction of speckle noise in digital holography
    (SPIE, 2004-10-21) Velásquez-Prieto, Daniel; García Sucerquia, Jorge Iván; Castañeda Sepúlveda, Román; Herrera Ramírez, Jorge Alexis; 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 i maging techniques in order t o reduce the speckle noise in digital reconstruction of optically recorded Fresnel's holograms -- The proposed filtering techniques are illustrated with experimental results --