Active target tracking: A simplified view aligning method for binocular camera model

While monitoring large-scale scenes, visual surveillance systems are often confronted with a dilemma between obtaining efficient coverage of the scene and getting sufficient resolution of the targets of interest. To alleviate the contradiction, a solution based on binocular cameras has been proposed. In the solution, an active pan–tilt–zoom (PTZ) camera and a fixed camera operate in a collaborative way by dynamically aligning their fields of view. However, due to the asymmetric camera distribution structure and fast-changing scenario, the accurate alignment is yet challenging. In this paper, a novel view aligning method is presented which introduces three reasonable and mild simplifications to transform the complex view aligning problem into a simple arctangent control function. These simplifications not only relax the restrictions of target depth and the intrinsic parameters of PTZ camera, but also constrain the relative external parameters with a coaxial structure. Meanwhile, a corresponding calibration method is designed to estimate the model parameters off-line. The proposed method was tested in comprehensive cases with relatively close target, wide-range scene and altitude variation. Both the simulation and real scene experiments demonstrate that our method outperforms other state-of-the-art methods on accuracy and effectiveness for active target tracking tasks.