1. A system for generating background image information of a scene comprising: (a) a video camera suitable for viewing the scene and generating video signals representing image information for the scene; (b) a frame grabber connected to the video camera for generating a stream of video frames, each video frame comprising image information for the scene at an instant of time; and (c) a processor connected to the frame grabber, the processor being programmed to update image information for a background image for the scene during a background update cycle based upon image information for a video frame, by: (i) selecting a region of the video frame; (ii) analyzing image information for smaller subregions within the region to determine whether any subregion is substantially occluded by an object; (iii) updating the background image based upon image information for the region if it is determined that any subregion within the region is substantially occluded by an object; and (iv) repeating steps (ii) and (iii) for each of the subregions when it is determined that the none of the subregions is substantially occluded by an object.