Examinando por Autor "Garcia-Sucerquia, J."
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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 AplicadaIn 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.Ítem Improvement of the signal-to-noise ratio in digital holography(Sociedad Mexicana de Fisica, 2005-01-01) Garcia-Sucerquia, J.; Ramírez, J.H.; Prieto, D.V.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaA 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.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 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 AplicadaA 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.