1. An image processing device comprising: an imaging unit for obtaining an input image by imaging a subject; a recognition unit for recognizing an object, corresponding to a registered image, from the input image, wherein the registered image is registered beforehand in the image processing device; an image correcting unit for correcting at least one of a luminance of the object within the input image and a luminance of the registered image such that the luminance of the object within the input image is identical to the luminance of the registered image; and a detection unit for detecting, based on the registered image corresponding to the object recognized from the input image, an overlapped area where another object is overlapped with the object, wherein the detection unit detects the overlapped area based on a difference between the luminance of the object within the input image and the luminance of the registered image, at least one of which has been corrected by the image correcting unit.