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Stereo vision based mapping and immediate virtual walkthroughs

This thesis investigates stereo vision based techniques for supporting work with teleoperated mobile robots. In particular, the tasks of navigation and control of the robot in unknown environments as well as control of the manipulator are considered. Support is required with map overviews and images from novel viewpoints. Challenges are to create maps and novel images in real time, exclusively from image sequences of a calibrated stereo camera that is allowed to move arbitrarily in three dimensions. Furthermore, no assumptions are made about the environment. These requirements have led to research in the areas of stereo vision, camera motion estimation, mapping and novel view synthesis. Several contributions have been made in these areas. Firstly, the behaviour of stereo correlation is analysed and a new real time stereo algorithm derived, which has reduced matching errors compared to traditional algorithms. Secondly, a new robust real time camera motion estimation method is described, which exclusively uses stereo images and permits arbitrary camera motion. Thirdly, a new method for creating two-dimensional maps from images of a stereo camera under arbitrary three-dimensional motion is presented. Finally, novel view synthesis is performed in disparity space of source stereo images using a new method. All the proposed techniques have been integrated into the Immediate Reality Scanner (IRIS) system. The system performs incremental mapping, immediate virtual walkthroughs and dynamic novel views exclusively from a stereo camera under arbitrary three-dimensional motion. Mapping and immediate virtual walkthroughs can be performed in real time, concurrently to scanning the environment. The thesis describes camera calibration, stereo processing, camera motion estimation, map building, novel view synthesis and the integration into IRIS, including evaluations in all areas. It is concluded that IRIS does not only fulfil the requirements of the anticipated application on teleoperated mobile robots, but could also be used in a wide range of robotics and non-robotics applications. It is believed that IRIS is the first system that allows incremental mapping and immediate virtual walkthroughs in real time concurrently to scanning an unconstrained environment with an arbitrarily moving stereo camera.