Real-Time Time-to-Collision from Variation of Intrinsic Scale

Time-to-collision can be directly measured from a spatio-temporal image sequence obtained from an uncalibrated camera. This it would appear to offer a simple, elegant measurement for use in obstacle avoidance. However, previous techniques for computing time to collision from an optical flow have proven impractical for real applications. This paper present a new approach for computing time to collision (TTC) based on the idea of measuring the rate of change of the "intrinsic scale". Intrinsic scale is a geometric invariant that is valid at most points in an image, and can be rapidly determined using a multi-resolution pyramid. In this paper we develop the approach and demonstrate its feasibility by comparing the results with range measurements obtained from a laser ranging device on a moving vehicle. Experimental results show that this is a simple method to obtain reliable TTC with a low computational cost.