Early detection of independent motion from active control of normal image flow patterns

An important initial step in interpreting a dynamic scene is to detect moving objects in the environment. This paper presents a novel solution to the problem of early motion detection by a moving observer. The solution requires the observer to be active in the acquisition of images thereby controlling the optical flow pattern due to egomotion. A theoretical analysis is done based on geometric considerations to establish conditions that are necessary and sufficient to guarantee motion detection at a point. The detection problem is posed in terms of locally computable image quantities (the normal image flow) which this makes it implementable in real time. The performance of the technique can be improved by imposing any applicable constraint; this is demonstrated for the detection of the motions of "compact" objects satisfying a size bound. The goal is to design a flexible and efficient early motion detection strategy that can be tailored to the needs of a particular navigation system.