Patent ID: 7133537

Claim:
A method of tracking an object moving relative to a scene, the method including: (a) generating a background image by acquiring a plurality of images of the scene, dividing each image into a plurality of background image elements, determining a value of a characteristic of each said background image element for each image to obtain a set of values, and determining from said set of values a background value for each of said background image elements, wherein determining said background value involves determining the mode of said set of values; (b) comparing a pair of comparison images with said background image by: (i) acquiring a pair of comparison images, dividing each said comparison image into a plurality of comparison image elements corresponding to respective ones of the background image elements, and determining a comparison value of said characteristic for each of said comparison image elements; (ii) comparing each said comparison value with said background value of said corresponding background image element to determine whether said comparison value is sufficiently similar to said background value to thereby determine whether or not each said comparison image element is sufficiently similar to the corresponding background image element; and (iii) determining from which comparison image elements are not sufficiently similar to the corresponding background image element which comparison image elements relate to potential objects and determining a spatial characteristic of each said potential object; (c) matching potential objects in said pair of comparison images by comparing spatial characteristics of potential objects of a following image of said pair of comparison images with spatial characteristics of potential objects of a preceding image of said pair of comparison images to match potential objects in the following image to potential objects in the preceding image; and (d) treating each matched potential object as a moving object to thereby track the movement of each said moving object relative to said scene.