New Methods for Triangulation-based Shape Acquisition using Laser Scanners

摘要

EnglishTraditionally, the reproduction of the real world has been shown to us by means of at images. These images used to be materialised by means of paint on canvas, drawings or the like. Today, we still see hand made pictures, by fortune, although most of the images are acquired by cameras and they are either directly shown to an audience, like in the cinema, television or photographs, or they are processed by a computer system in order to obtain a particular result, like in industrial quality assurance or bleeding edge artificial intelligence research. Applying mid-level processing algorithms, 3D images can be obtained from 2D ones, using well known techniques called Shape From X, where X is the method for obtaining the 3rd dimension. While the evolution to the 3D camera begun in the 90s, the techniques for obtaining the most accurate 3D shape need to be continuously improving. The application of 3D scanners has spread signi cantly in the recent years, specially in elds like entertainment, assisted diagnosis/ surgery, robotics, etc. One of the most used techniques to obtain 3D information from a scene is triangulation, and more concretely, triangulationbased laser scanners. Since their formal appearance in scienti c publications, in 1971 [SS71], there have been contributions for solving inherent problems like occlusion avoidance, accuracy improvement, acquisition speed, shape description, etc. All of the methods for obtaining 3D points of a scene is accompained with a calibration procedure, and this procedure plays a decisive role in the performance of the acquisition device. The goal of this thesis is to provide a holistic approach to the problem of shape acquisition, giving a wide survey of triangulation laser scanners, testing the performance of di erent systems, and to give contributions for both improving acquisition accuracy under adverse conditions and solving the calibration problem. In addition, the calibration approach is based on previous works that used projective geometry to this end. EnglishTradicionalment, la reproduccio del mon real sens ha mostrat a traves dimatges planes. Aquestes imatges se solien materialitzar mitjancant pintures sobre tela o be amb dibuixos. Avui, per sort, encara podem veure pintures fetes a ma, tot i que la majoria dimatges sadquireixen mitjancant cameres, i es mostren directament a una audiencia, com en el cinema, la televisio o exposicions de fotografies, o be son processades per un sistema computeritzat per tal dobtenir un resultat en particular. Aquests processaments sapliquen en camps com en el control de qualitat industrial o be en la recerca mes puntera en intelligencia artificial. Aplicant algorismes de processament de nivell mitja es poden obtenir imatges 3D a partir dimatges 2D, utilitzant tecniques ben conegudes anomenades Shape From X, on X es el metode per obtenir la tercera dimensio, i varia en funcio de la tecnica que sutilitza a tal nalitat. Tot i que levolucio cap a la camera 3D va comencar en els 90, cal que les tecniques per obtenir les formes tridimensionals siguin mes i mes acurades. Les aplicacions dels escaners 3D han augmentat considerablement en els darrers anys, especialment en camps com el lleure, diagnosi/cirurgia assistida, robotica, etc. Una de les tecniques mes utilitzades per obtenir informacio 3D duna escena, es la triangulacio, i mes concretament, la utilitzacio descaners laser tridimensionals. Des de la seva aparicio formal en publicacions cientifiques al 1971 [SS71], hi ha hagut contribucions per solucionar problemes inherents com ara la disminucio doclusions, millora de la precisio, velocitat dadquisicio, descripcio de la forma, etc. Tots i cadascun dels metodes per obtenir punts 3D duna escena te associat un proces de calibracio, i aquest proces juga un paper decisiu en el rendiment dun dispositiu dadquisicio tridimensional. La nalitat daquesta tesi es la dabordar el problema de ladquisicio de forma 3D, des dun punt de vista total, reportant un es