1. An article delivery system, comprising: a camera positioned adjacent to a conveyor and configured to capture an image of the conveyor and an area surrounding the conveyor, wherein the conveyor is configured to move articles placed thereon; at least one display; and a processor coupled to the camera and the display, wherein the processor, in operation: extracts a first image of the conveyor out of the image captured by the camera; in a second image other than the first image out of the image, detects a person included in the second image and applies mask processing to the person in the second image; extracts a third image of a location at which a person is continuously present out of the second image and applies mask processing to the location; and outputs a composite image of the first image, the second image minus the third image, and the third image to the display, where the first image shows the conveyor, the second image minus the third image shows the area surrounding the conveyor in which the person is masked, and in the third image the location at which a person is continuously present is masked.