Image processing method for detecting objects using relative motion

摘要

An image based obstacle detection method. A camera mounted on a vehicle provides a set of image frames while the vehicle is in motion. The image frames define an image plane having a vertical aspect and a horizontal aspect. The relevancy of an object is determined by (i) selecting first and second feature points from the object that are spaced apart vertically in a first image frame; (ii) tracking the positions of the first and second feature points over at least a second image frame; and (iii) deciding the object to be relevant if the first and second feature points move dissimilar distances in physical space, within a tolerance, and deciding the object to be irrelevant otherwise. The motion of relevant objects is then estimated to determine if any relevant object is likely to become an obstacle to the vehicle.

主权项

1. An obstacle detection method, comprising:
(a) provisioning a vehicle with a camera having an external field of view, the camera having an imager defining an image plane having a vertical aspect and a horizontal aspect, wherein the imager comprises an array of sensing pixels; (b) acquiring a set of image frames captured by the camera while the vehicle is in motion; (c) determining an object present in the set of captured image frames by edge detection; (d) determining a relevancy of the determined object by
(i) selecting first and second feature points of the determined object that are spaced apart vertically in a first captured image frame,(ii) tracking positions of the first and second feature points of the determined object over at least a second captured image frame, and(iii) determining that the determined object is a relevant object responsive to a determination that the first and second feature points move dissimilar distances in physical space between the first and second captured image frames and within a tolerance; (e) estimating motion of determined relevant objects relative to the vehicle to determine if any determined relevant object is likely to become an obstacle to the vehicle; wherein step (d)(iii) is determined by reference to the image plane and, where the first feature point is vertically lower than the second feature point, and wherein the method includes: estimating, from the first captured image frame, a physical distance D1 of the first feature point O1b to the camera in a selected physical horizontal plane; estimating, from the first captured image frame, a physical location DT of the second feature point O1T assuming that the second feature point physically lies at a height T above the selected physical horizontal plane; estimating, from the second captured image frame, a physical distance D2 of the first feature point O2b to the camera in the selected physical horizontal plane, and determining the distance ΔD between D2 and D1; estimating a physical location D*T which is equivalent to DT+ΔD, with D*T being located at a height T above the selected physical horizontal plane; computing a nominal feature point coordinate O*2t in the image plane corresponding to D*T; and determining that the determined object is the relevant object responsive to a determination that the absolute distance between the nominal feature point coordinate O*2t and the second feature point coordinate in the first captured image frame O1T is less than the absolute distance between the second feature point coordinate in the second captured image frame O2T and the second feature point coordinate in the first captured image frame O1T.