A diffusion mechanism for obstacle detection from size-change information

A new immediacy measure, representing the imminence of collision between an object and a moving observer, is defined. A diffusion process on the image domain, whose initial condition is determined by the motion field normal to the object´s boundary, is shown to converge asymptotically to the immediacy measure. Bounds on the convergence time for the diffusion process are described. A network of locally connected neurons, derived from a finite-difference approximation of the diffusion equation, estimates the immediacy measure from normal velocity and boundary information provided by layers of motion measurement and segmentation cells. The network´s performance on real image sequences is demonstrated. The proposed scheme is shown to be consistent with observations on the biological visual system