Chapter 2 Use of a Depth Camera as a Contactless Displacement Field Sensor Jean Michel Franco, Johannio Marulanda, and Peter Thomson Abstract During experimental tests, optical displacement measures can provide reliable data about the behavior of structural elements without altering key parameters, such as damping, stiffness, or mass, with low cost and high spatial density of measurements. Motion capture Systems are used in different application from medicine to cinematography, involving different types of image processing techniques, but its application to measure the response of civil structures is costly and of limited value in terms of real implementations. Range/Depth Cameras, on the other hand, can provide a 3-D imaging Solution to capture motion and displacements at an affordable cost. These cameras are widely available and used in the videogames industry. This paper presents the first steps for the implementation of a large-displacement measurement methodology and its application. Keywords Artificial vision • Instrumentation • Displacement measures • Depth camera 2.1 Introduction Kinect for Xbox360™[1] is essentially a set of sensors which comprises a triaxial accelerometer, an RGB camera and an infrared camera, initially developed for detecting human features in three dimensions, with a primary application in the field of video games Through a pattern generated by an infrared laser a Range/Depth camera is achieved for three-dimensional scene detection where lighting stops playing an important role as it is in other artificial vision systems, making it a sensor with good performance [2–4] and remarkably low cost. (<150 US $) [5, 6]. The methodology is proposed based on improvements over the Kinect for Xbox360™raw data using 3D interpolations and a 3D correspondence technique [7] for the measurement of the actual displacement field at a certain time. Test were made using two acquisition methodologies, one based on a continuous 3D reconstruction using Kinect Fusion that is included on the Microsoft Kinect Framework; other extracting raw Kinect depth using Matlab through the Image Acquisition Toolbox that supports Kinect for Xbox360™devices. Once an acquisition is made, it is performed a 3d interpolation for a normalization of the scattered data in aims to provide normalized data and a posterior processing with a 3D correspondence technique to improve results. Due to the measuring characteristics and low cost, has become a multipurpose sensor, in different areas from surveys of complex three-dimensional scenes [8], applications focused on improving and reducing costs in augmented reality systems [5], to characterization of turbulent flows using multiple Kinect’s [9]. There are studies of the use of the Kinect for the realization of whole plant phenotypes [10], evaluation of postures in the human body and on-line medical evaluation using Kinect generated point clouds from a clinical environment [3, 6, 11]. There are applications for tracking objects in 3D space [16], machine vision applications in robotics for automated three-dimensional survey [12], also there are multiple calibration approaches [13–15] and even improvements to sensor characteristics [16] as are further comparisons with instruments such as laser scanners commonly used for three-dimensional surveys [13] demonstrating the versatility of this sensor. J.M. Franco (*) • J. Marulanda • P. Thomson Escuela de Ingenier´ıa Civil y Geoma´tica, Universidad del Valle, Cali, Colombia Grupo de Investigaci on en Ingenier´ıa S´ısmica, E olica, Geote´cnica y Estructural (G-7), Cali, Colombia e-mail: jean.franco@correounivalle.edu.co #The Society for Experimental Mechanics, Inc. 2016 A. Brandt, R. Singhal (eds.), Shock & Vibration, Aircraft/Aerospace, Energy Harvesting, Acoustics & Optics, Volume 9, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-30087-0_2 13
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