Active visual scene exploration

This thesis addresses information theoretic methods for control of one or several active cameras in the context of visual surveillance. This approach has two advantages. Firstly, any system dealing with real inputs must take into account noise in the measurements and the underlying system model. Secondly, the control of cameras in surveillance often has different, potentially conflicting objectives. Information theoretic metrics not only yield a way to assess the uncertainty in the current state estimate, they also provide means to choose the observation parameters that optimally reduce this uncertainty. The latter property allows comparison of sensing actions with respect to different objectives. This allows specification of a preference for objectives, where the generated control will fulfil these desired objectives accordingly. The thesis provides arguments for the utility of information theoretic approaches to control visual surveillance systems, by addressing the following objectives in particular: Firstly, how to choose a zoom setting of a single camera to optimally track a single target with a Kalman filter. Here emphasis is put on an arbitration between loss of track due to noise in the observation process, and information gain due to higher accuracy after successful observation. The resulting method adds a running average of the Kalman filter’s innovation to the observation noise, which not only ameliorates tracking performance in the case of unexpected target motions, but also provides a higher maximum zoom setting. The second major contribution of this thesis is a term that addresses exploration of the supervised area in an information theoretic manner. The reasoning behind this term is to model the appearance of new targets in the supervised environment, and use this as prior uncertainty about the occupancy of areas currently not under observation. Furthermore, this term uses the performance of an object detection method to gauge the information that observations of a single location can yield. Additionally, this thesis shows experimentally that a preference for control objectives can be set using a single scalar value. This linearly combines the objective functions of the two conflicting objectives of detection and exploration, and results in the desired control behaviour. The third contribution is an objective function that addresses classification methods. The thesis shows in detail how the information can be derived that can be gained from the classification of a single target, under consideration of its gaze direction. Quantitative and qualitative validation show the increase in performance when compared to standard methods.EThOS - Electronic Theses Online ServiceGBUnited Kingdo