Proposal of a mobile camera system for moving object detection

Abstract

We describe a system for detecting moving elements from a moving camera using a simplified background constraint technique. The hardware implementation of the method is done in an intelligent camera form. In order to keep the design small and able to operate at video frame rate the algorithm is for a large part implemented in FPGAs. The camera moves in a locally planar environment and is tilted enough to exclude the horizon line from the image. In this paper we assume the camera moves only in translation and the objects to detect are moving in the same direction as the camera does (and obviously at higher speed). If the instantaneous speed of the camera is known and is constant between two successively processed images, it is easy to predict (for a big part) the next image to process by using the reverse perspective transform. In order to transform such a prediction in a simple translation of the image and in order to obtain a uniform spatial resolution in the observed scene, we resample the lines and apply to each resampled line a specific horizontal scale factor. With each transformed image we 'compute' a predicted image. The predicted and true images are subtracted and objects moving in the scene correspond to a noticeable difference area. The direction and speed of the displacement are estimated with one-dimensional correlation functions between vertical windows in subtracted images. A study of the limitations and experimental results obtained by simulation with real images are presented.