1. An apparatus, comprising: a sensing part configured to photograph an image; a storage configured to store a background image frame; and a controller configured to obtain a first difference image and a second difference image from the photographed image and to determine an existence of an object and a position of the object using the first and the second difference images, wherein the first difference image is an image indicating a difference between a currently photographed image frame and a previously photographed image frame, and wherein the second difference image is an image indicating a difference between the currently photographed image frame and the background image frame stored in the storage.