Browsing by Author "Altamar Mercado, Hernando"

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Adaptive filtering of interference fringes by polar transformation and empirical mode decomposition
(OSA - The Optical Society, 2018) Altamar Mercado, Hernando; Patiño Vanegas, Alberto; Marrugo A.G.
We designed an adaptive filter based on empirical mode decomposition for the removal of fringes in an interference microscopy image. Promising results show the possibility for extended depth-of-field imaging. © 2018 The Author (s)
Desarrollo de aplicaciones con técnicas de programación paralela para el análisis del procesamiento 3D de imágenes de microscopía /
(2015) Hernández Anillo, Luis Felipe; Zúñiga Silgado, Isaac; Altamar Mercado, Hernando
La programación paralela, lleva bastante tiempo siendo desarrollada e implementada, sin embargo, en los últimos años ha crecido el interés debido a las limitaciones físicas que impiden el aumento de la frecuencia en los procesadores. La programación paralela nace para solucionar los problemas que requieren mucho tiempo de ejecución y grandes recursos informáticos. A través del uso simultáneo de procesadores se resuelven problemas de manera más rápida que lo que se puede realizar en un solo procesador. La programación paralela se basa en la división del problema en pequeñas partes para ser resueltos cada uno de estos en paralelo. El paralelismo ha sido utilizado con éxito en muchos campos como la informática de alto rendimiento, servidores, aceleradores gráficos, y muchos sistemas embebidos. El punto de inflexión multinúcleo, sin embargo, afecta a la totalidad del mercado, en particular el espacio del cliente, donde el paralelismo no ha sido previamente extendido. Los programas con millones de líneas de código debe ser convertido o reescrito para aprovechar el paralelismo, sin embargo, tal como se practica hoy en día, la programación en paralelo para el cliente es una tarea difícil, puesto que es realizada por pocos programadores. Los programas paralelos son notoriamente difíciles para poner a prueba, debido a los tipos de datos, intercalaciones no deterministas y modelos complejos de memoria. En el grupo de investigación de física aplicada y procesamiento de imágenes y señales de la Universidad Tecnológica se vienen desarrollando proyectos de inspección de muestras microscópicas metálicas que requieren el procesamiento de un gran volumen de datos. El procesamiento de estos datos se hace supremamente lento cuando se utilizan técnicas de programación secuenciales. Actualmente la Universidad Tecnológica de Bolívar no cuenta con una guía que permita probar, comparar y seleccionar la herramienta adecuada para desarrollar aplicaciones utilizando técnicas de programación paralela. Lo cual dificulta el trabajo de los grupos de investigación que trabajan en esta área del conocimiento en proyectos que requieren mejorar los tiempos de respuesta de sus aplicaciones.
Microscopic shape from focus using white light interferometric fringes
(OSA - The Optical Society, 2018) Altamar Mercado, Hernando; Patiño Vanegas, Alberto; Marrugo A.G.
In this work we study the use of a focus measure to improve the 3D reconstruction of low reflectivity microscopic samples using white light interference microscopy. Simulation and experimental results show the improved reconstruction. © 2018 The Author(s).
Robust 3D surface recovery by applying a focus criterion in white light scanning interference microscopy
(OSA - The Optical Society, 2019) Altamar Mercado, Hernando; Patiño Vanegas, Alberto; Marrugo A.G.
White light scanning interference (WLSI) microscopes provide an accurate surface topography of engineered surfaces. However, the measurement accuracy is substantially reduced in surfaces with low-reflectivity regions or high roughness, like a surface affected by corrosion. An alternative technique called shape from focus (SFF) takes advantage of the surface texture to recover the 3D surface by using a focus metric through a vertical scan. In this work, we propose a technique called SFF-WLSI, which consists of recovering the 3D surface of an object by applying the Tenegrad Variance (TENV) focus metric to WLSI images. Extensive simulation results show that the proposed technique yields accurate measurements under different surface roughness and surface reflectivity, outperforming the conventional WLSI and the SFF techniques. We validated the simulation results on two real objects with a Mirau-type microscope. The first was a flat lapping specimen with R a 0.05 μm for which we measured an average value of R a 0.055 μm and standard deviation σ 0.008 μm. The second was a metallic sphere with corrosion, which we reconstructed with WLSI versus the proposed SFF-WLSI technique, producing a better 3D reconstruction with less undefined depth values. © 2018 Optical Society of America.
Speckle free optical watermarking based on pseudo-random phase encoding
(Institute of Electrical and Electronics Engineers Inc., 2016) Patino A.; Altamar Mercado, Hernando; Martínez-Santos, Juan Carlos; Altuve M.
Watermarking is a process of embedding copiright information into an image to verify the ownership without any kind of corruption. In optical applications, the usage of diffusers is required to obtain a homogeneously distributed spectrum. However, the use of a diffuser in the input plane and the finite size of the sensor leave the recovered watermark with noise speckles. This noise affects negatively the verification process. We propose the usage of pseudo-random band-limited diffusers to place watermarks on optical images using a method based on Fourier-transform and random phase encoding algorithm. Such diffusers can help to recover a free-speckle watermark. The robustness to typical attacks is analyzed. Numerical results have shown its effectiveness. © 2016 IEEE.
Toward an automatic 3D measurement of skin wheals from skin prick tests
(SPIE, 2019) Marrugo A.G.; Romero L.A.; Pineda J.; Vargas R.; Altamar Mercado, Hernando; Marrugo J.; Meneses J.; Harding K.G.; Zhang, Song
The skin prick test (SPT) is the standard method for the diagnosis of allergies. It consists in placing an array of allergen drops on the skin of a patient, typically the volar forearm, and pricking them with a lancet to provoke a specific dermal reaction described as a wheal. The diagnosis is performed by measuring the diameter of the skin wheals, although wheals are not usually circular which leads to measurement inconsistencies. Moreover, the conventional approach is to measure their size with a ruler. This method has been proven prone to inter- and intra-observer variations. We have developed a 3D imaging system for the 3D reconstruction of the SPT. Here, we describe the proposed method for the automatic measurements of the wheals based on 3D data processing to yield reliable results. The method is based on a robust parametric fitting to the 3D data for obtaining the diameter directly. We evaluate the repeatability of the system under 3D reconstructions for different object poses. Although the system provides higher accuracy in the measurement, we compare the results to those produced by a physician. Copyright © 2019 SPIE.
Toward the generation of reproducible synthetic surface data in optical metrology
(2020-05-19) Pineda, Jesus; Altamar Mercado, Hernando; Romero, Lenny A.; Marrugo Hernández, Andrés Guillermo
The implementation and generation of synthetic data for testing algorithms in optical metrology are often difficult to reproduce. In this work, we propose a framework for the generation of reproducible synthetic surface data. We present two study cases using the Code Ocean platform, which is based on Docker and Linux container technologies to turn source code repositories into executable images. i) We simulate interference pattern fringe images as acquired by a Michelson interferometric system. The reflectivity changes due to surface topography and roughness. ii) We simulate phase maps from rough isotropic surfaces. The phase data is simultaneously corrupted by noise and phase dislocations. This method relies on Gaussian-Laplacian pyramids to preserve surface features on different scales. The proposed framework enables reproducible surface data simulations, which could increase the impact of algorithm development in optical metrology.