Browsing by Author "Marrugo A.G."

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A flexible and simplified calibration procedure for fringe projection profilometry
(SPIE, 2019) Vargas R.; Marrugo A.G.; Pineda J.; Romero L.A.; Bodermann B.; Frenner K.
Fringe Projection Profilometry (FPP) is a widely used technique for optical three-dimensional (3D) shape measurement. Among the existing 3D shape measurement techniques, FPP provides a whole-field 3D reconstruction of objects in a non-contact manner, with high resolution, and fast data processing. The key to accurate 3D shape measurement is the proper calibration of the measurement system. Currently, most calibration procedures in FPP rely on phase-coordinate mapping (PCM) or back-projection stereo-vision (SV) methods. The PCM technique consists in mapping experimental metric XYZ coordinates to recovered phase values by fitting a predetermined function. However, it requires accurately placing 2D or 3D targets at different distances and orientations. Conversely, in the SV method, the projector is regarded as an inverse camera, and the system is modeled using triangulation principles. Therefore, the calibration process can be carried out using 2D targets placed in arbitrary positions and orientations, resulting in a more flexible procedure. In this work, we propose a hybrid calibration procedure that combines SV and PCM methods. The procedure is highly flexible, robust to lens distortions, and has a simple relationship between phase and coordinates. Experimental results show that the proposed method has advantages over the conventional SV model since it needs fewer acquired images for the reconstruction process, and due to its low computational complexity the reconstruction time decreases significantly. © 2019 SPIE.
A model for the simulation of the chill block melt spinning (CBMS) process using OpenFOAM®
(Elsevier Masson SAS, 2020) Barone M.; Barceló F.; Pagnola M.; Larreteguy A.; Marrugo A.G.; Useche Vivero, Jairo
This work shows the results of a numerical model developed to simulate the CBMS technique for the production of the Fe78Si9B13 metallic magnetic ribbons for application in electronics. The model proposes a numerical approximation to a Vogel-Fulcher-Tammann (VFT) expression as a method in the solidification process. This approximation is introduced into the “compressibleInterFoam” routine, included in the OpenFOAM® suite, originally developed for the simulation of two immiscible, non-isothermal and compressible fluids. This routine solves, the phase fraction transport using the Volume of Fluids (VOF) approach. The boundary conditions imposed in the model were experimentally validated by digital image analysis with a high-speed camera at 5602 fps for the determination of the temperature profiles. The phase change is represented as a growth of several orders of magnitude of the alloy viscosity (μ) as the temperature (T) decreases, reaching solidification around the crystallization temperature (Tg). Also, we establish the condition of initial stability of CBMS process (R > 1.5) for Peclet numbers close to 400, and the validity up to limits of rotation in the wheel close to 40 m s−1. The proposed methodology is validated with previous work. Encouraging results show that the solution of the CBMS process can be adequately simulated with the proposed approach. © 2019 Elsevier Masson SAS
A particle swarm optimization approach to log-gabor filtering in fourier transform profilometry
(OSA - The Optical Society, 2018) Pineda J.; Meza J.; Marrugo A.G.; Vargas R.; Romero L.A.
In this work, we propose a particle Swarm Optimization approach to Log-Gabor filtering in Fourier transform profilometry. Encouraging experimental results show the advantage of the proposed method. © 2018 The Author(s)
A Structure-from-Motion Pipeline for Generating Digital Elevation Models for Surface-Runoff Analysis
(Institute of Physics Publishing, 2019) Meza J.; Marrugo A.G.; Ospina G.; Guerrero M.; Romero L.A.; Perez-Taborda J.A.; Avila Bernal A.G.
Digital Elevation Models (DEMs) are used to derive information from the morphology of a land. The topographic attributes obtained from the DEM data allow the construction of watershed delineation useful for predicting the behavior of systems and for studying hydrological processes. Imagery acquired from Unmanned Aerial Vehicles (UAVs) and 3D photogrammetry techniques offer cost-effective advantages over other remote sensing methods such as LIDAR or RADAR. In particular, a high spatial resolution for measuring the terrain microtopography. In this work, we propose a Structure from Motion (SfM) pipeline using UAVs for generating high-resolution, high-quality DEMs for developing a rainfall-runoff model to study flood areas. SfM is a computer vision technique that simultaneously estimates the 3D coordinates of a scene and the pose of a camera that moves around it. The result is a 3D point cloud which we process to obtain a georeference model from the GPS information of the camera and ground control points. The pipeline is based on open source software OpenSfM and OpenDroneMap. Encouraging experimental results on a test land show that the produced DEMs meet the metrological requirements for developing a surface-runoff model. © Published under licence by IOP Publishing Ltd.
A structure-from-motion pipeline for topographic reconstructions using unmanned aerial vehicles and open source software
(Springer Verlag, 2018) Meza J.; Marrugo A.G.; Sierra E.; Guerrero M.; Meneses J.; Romero L.A.; Serrano C. J.E.; Martínez-Santos, Juan Carlos
In recent years, the generation of accurate topographic reconstructions has found applications ranging from geomorphic sciences to remote sensing and urban planning, among others. The production of high resolution, high-quality digital elevation models (DEMs) requires a significant investment in personnel time, hardware, and software. Photogrammetry offers clear advantages over other methods of collecting geomatic information. Airborne cameras can cover large areas more quickly than ground survey techniques, and the generated Photogrammetry-based DEMs often have higher resolution than models produced with other remote sensing methods such as LIDAR (Laser Imaging Detection and Ranging) or RADAR (radar detection and ranging). In this work, we introduce a Structure from Motion (SfM) pipeline using Unmanned Aerial Vehicles (UAVs) for generating DEMs for performing topographic reconstructions and assessing the microtopography of a terrain. SfM is a computer vision technique that consists in estimating the 3D coordinates of many points in a scene using two or more 2D images acquired from different positions. By identifying common points in the images both the camera position (motion) and the 3D locations of the points (structure) are obtained. The output from an SfM stage is a sparse point cloud in a local XYZ coordinate system. We edit the obtained point in MeshLab to remove unwanted points, such as those from vehicles, roofs, and vegetation. We scale the XYZ point clouds using Ground Control Points (GCP) and GPS information. This process enables georeferenced metric measurements. For the experimental verification, we reconstructed a terrain suitable for subsequent analysis using GIS software. Encouraging results show that our approach is highly cost-effective, providing a means for generating high-quality, low-cost DEMs. © Springer Nature Switzerland AG 2018.
A vision-based system for the dynamic measurement of in-plane displacements
(Institute of Electrical and Electronics Engineers Inc., 2014) Marrugo W.; Sierra E.; Marrugo J.; Camacho C.; Romero L.A.; Marrugo A.G.; Marrugo A.G.
Computer vision has advanced markedly in the last decade and has had new applications such as the analysis of the behavior of structures. The analysis of displacement and deformation of structures is an important process in Structural Health Monitoring (SHM). There are different techniques and devices for measuring strains and displacements, such as linear-variable-differential-transducers (LVDTs) and the global position system (GPS), which can be expensive and may not provide sufficient accuracy. This paper proposes vision-based methods for non-contact measurement of displacements and deformations. These methods allow for accurate non-contact measurements at low cost using off-the-shelf components, basically a camera, a computer, and a target. In this work, we test propose a vision based method for the measurement of displacements and we discuss the trade-offs in terms of robustness, computational complexity and accuracy. Encouraging results show that the displacement of a structure can be both determined accurately and fast enough in real time. © 2014 IEEE.
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)
An experimental study on deformation analysis of an indented pipe via fringe projection profilometry and digital image correlation
(OSA - The Optical Society, 2018) Forero N.; Marrugo A.G.; Vargas R.; Pineda J.; Useche Vivero, Jairo; Romero L.A.
We studied the surface displacement of a steel pipe during indentation via Fringe Projection Profilometry and 2D-Digital Image Correlation. Experimental results show that a 3D strain approximation is possible for comparison with numerical simulation. © 2018 The Author(s)
Background intensity removal in Fourier transform profilometry: A comparative study
(OSA - The Optical Society, 2016) Vargas R.; Pineda J.; Romero L.A.; Marrugo A.G.
We study the removal of the background intensity of fringe patterns via Empirical Mode Decomposition and the Hilbert Transform. Simulation results show that the latter provides a suitable background compensation with minimal error 3D-reconstruction. © OSA 2016.
Background intensity removal in structured light three-dimensional reconstruction
(Institute of Electrical and Electronics Engineers Inc., 2016) Vargas R.; Pineda J.; Marrugo A.G.; Romero L.A.; Altuve M.
In Fourier Transform Profilometry, a filtering procedure is performed to separate the desired information (first order spectrum) from other unwanted contributions such as the background component (zero-order spectrum). However, if the zero-order spectrum and the high order spectra component interfere the fundamental spectra, the 3D reconstruction precision decreases. In this paper, we test two recently proposed methods for removing the background intensity so as to improve Fourier Transform Profilometry reconstruction precision. The first method is based on the twice piece-wise Hilbert transform. The second is based on Bidimensional Empirical Mode Decomposition, but the decomposition is carried out by morphological operations In this work, we present as a novel contribution, the sequential combination of these two methods for removing the background intensity and other unwanted frequencies close to the first order spectrum, thus obtaining the 3D topography of the object. Encouraging experimental results show the advantage of the proposed method. © 2016 IEEE.
Blind restoration of retinal images degraded by space-variant blur with adaptive blur estimation
(2013) Marrugo A.G.; Millan M.S.; Sorel M.; Sroubek F.
Retinal images are often degraded with a blur that varies across the gield view. Because traditional deblurring algorithms assume the blur to be space-invariant they typically fail in the presence of space-variant blur. In this work we consider the blur to be both unknown and space-variant. To carry out the restoration, we assume that in small regions the space-variant blur can be approximated by a space-invariant point-spread function (PSF). However, instead of deblurring the image on a per-patch basis, we extend individual PSFs by linear interpolation and perform a global restoration. Because the blind estimation of local PSFs may fail we propose a strategy for the identification of valid local PSFs and perform interpolation to obtain the space-variant PSF. The method was tested on artificial and real degraded retinal images. Results show significant improvement in the visibility of subtle details like small blood vessels. © 2013 SPIE.
Design of a brushed DC motors PID controller for development of low-cost robotic applications
(Institute of Electrical and Electronics Engineers Inc., 2014) Yime E.; Villa Ramírez, José Luis; Paez J.; Marrugo A.G.
This article present the design and construction of a PID controller for direct current motors motion control in low-cost robotic applications. The reasons which led us to the make the proposal and design of the system were, on the one hand, the need for robotic developments by students in Colombians academic environments with the resources available locally, and on the other hand, the need for a teaching of the robotics based on laboratory practices of the most commonly used control algorisms in this area, such as: the inverse kinematics based PID control and the dynamic control by calculated torque. © 2014 IEEE.
Design of an electrogoniometer based on accelerometers for the evaluation of sports gesture in weight lifting
(Institute of Electrical and Electronics Engineers Inc., 2014) De La Haye Chamorro G.I.; Aguirre I.M.M.; Contreras Ortiz, Sonia Helena; Marrugo A.G.
This article describes the design and implementation of an electrogoniometer to measure joint angles during the execution of weight lifting exercises. The electrogoniometer consists of four microelectromechanical accelerometers connected to a microcontroller. The microcontroller is connected via USB to a computer. Preliminary tests show that the system offers high precision and accuracy at angle measurement. Error in the measured values is less than 0.3% when comparing to a commercial digital goniometer, and it is low cost. © 2014 IEEE.
Design of an electronic system for monitoring muscle activity in weight-lifting
(Institute of Electrical and Electronics Engineers Inc., 2014) Mercado-Medina E.L.; Chavarro-Hernandez Z.D.; Domínguez Jiménez, Juan Antonio; Contreras Ortiz, Sonia Helena; Marrugo A.G.
Electronic systems based on body area networks can be used to monitor sports performance. These systems use sensors to acquire signals from the athlete while performing the exercises, and a communication system to transmit the data to a computer or smart phone to analyze it. That information can be used to evaluate sport performance quantitatively, prevent and treat injuries, and design personalized training programs. Surface electromyography (SEMG) is used to study muscle function during dynamic activities, and can be used for the biomechanical analysis of gait, sports gesture, muscle fatigue, and sports performance. This paper describes the design, construction and evaluation of an electronic circuit for monitoring muscle activation during weight-lifting exercises. The system has the following stages: an instrumentation amplifier to amplify the electromyographic (EMG) signal and reduce common-mode noise, a band-pass filter to limit the frequency content to the range 30 to 500 Hz, a precision rectifier, and a low-pass filter with cut-off frequency of 35 Hz, to obtain the signal envelope. The system uses two 9 V batteries, and is portable. Preliminary tests have been done and the acquired EMG signal has amplitudes in the order of volts. © 2014 IEEE.
Developing a Robust Acquisition System for Fringe Projection Profilometry
(Institute of Physics Publishing, 2019) Pineda J.; Marrugo A.G.; Romero L.A.; Perez-Taborda J.A.; Avila Bernal A.G.
Since Fringe Projection Profilometry (FPP) is an intensity-based coding strategy, it is prone to improper optical setup arrangement, surface texture and reflectance, uneven illumination distribution, among others. These conditions introduce errors in phase retrieval which lead to an inaccurate 3-D reconstruction. In this paper, we describe a dynamic approach toward a robust FPP acquisition in challenging scenes and objects. Our aim is to acquire the best possible fringe pattern image by adjusting the object closer to an ideal system-object setup. We describe the software implementation of our method and the interface design using LabVIEW. Experimental results demonstrate that the proposed method greatly reduces sources of error in 3-D reconstruction. © Published under licence by IOP Publishing Ltd.
Evaluating the influence of camera and projector lens distortion in 3D reconstruction quality for fringe projection profilometry
(OSA - The Optical Society, 2018) Vargas R.; Marrugo A.G.; Pineda J.; Meneses J.; Romero L.A.
We study the influence of geometric distortions of the camera and projector lenses on 3D reconstruction quality for fringe projection profilometry. Experimental results on real objects and their 3D models show the accuracy is improved. © 2018 The Author(s).
Experimental investigation of high-speed melt spinning by means of digital image analysis
(OSA - The Optical Society, 2016) Marrugo A.G.; Barone M.; Useche Vivero, Jairo; Pagnola M.
We carry out an experimental characterization via high-speed camera of Chill-Block Melt Spinning process by means of digital optical flow for melt ejection velocity calculation and temperature measurement. © OSA 2016.
Implementation of an image based focusing algorithm for non-mydriatic retinal imaging
(Institute of Electrical and Electronics Engineers Inc., 2014) Marrugo A.G.; Millan M.S.; Abril H.C.; Marrugo A.G.
Retinal photography is important for the assessment of eye diseases. The task of fine focusing the image is demanding and lack of focus is often the cause of suboptimal photographs. The advent of digital cameras has provided the opportunity to automate the focusing process. In this work, we propose an auto-focus system for non-mydriatic retinal imaging. The core of the system is based on a robust image-based focus measure. The measure is basically a quantification of image anisotropy computed by means of the normalized discrete cosine transform. Additionally, we optimize the autofocusing method by evaluating different focus search strategies. Encouraging experimental results reveal that the method is able to identify the best focus reliably with optimal speed. © 2014 IEEE.
Improving the blind restoration of retinal images by means of point-spread-function estimation assessment
(SPIE, 2015) Marrugo A.G.; Millán M.S.; Šorel M.; Kotera J.; Šroubek F.; Romero E.; Lepore N.
Retinal images often suffer from blurring which hinders disease diagnosis and progression assessment. The restoration of the images is carried out by means of blind deconvolution, but the success of the restoration depends on the correct estimation of the point-spread-function (PSF) that blurred the image. The restoration can be space-invariant or space-variant. Because a retinal image has regions without texture or sharp edges, the blind PSF estimation may fail. In this paper we propose a strategy for the correct assessment of PSF estimation in retinal images for restoration by means of space-invariant or space-invariant blind deconvolution. Our method is based on a decomposition in Zernike coefficients of the estimated PSFs to identify valid PSFs. This significantly improves the quality of the image restoration revealed by the increased visibility of small details like small blood vessels and by the lack of restoration artifacts. © 2015 SPIE.
LRemoving Dust Artifacts in Retinal Images via Dictionary Learning and Sparse-Based Inpainting
(Institute of Electrical and Electronics Engineers Inc., 2019) Barrios E.M.; Marrugo A.G.; Millán M.S.
In the field of ophthalmology, retinal images are essential for the diagnosis of many diseases. These images are acquired with a device called the retinal camera. However, often small dust particles in the sensor produce image artifacts that can be confused with small lesions, such as micro-aneurysms. The digital removal of artifacts can be understood as an inpainting process in which a set of pixels are replaced with a value obtained from the surrounding area. In this paper, we propose a methodology based on the sparse representations and dictionary learning for the removal of artifacts in retinal images. We test our method on real retinal images coming from the clinical setting with actual dust artifacts. We compare our restoration results with a diffusion-based inpainting technique. Encouraging experimental results show that our method can successfully remove the artifacts, while assuring the continuity of the retinal structures, like blood vessels. © 2019 IEEE.