US Patent 10188365 X-ray apparatus and controlling method of the same

An X-ray apparatus including an X-ray source configured to radiate X-rays; a collimator configured to adjust an irradiation region of X-rays radiated from the X-ray source; an image acquirer configured to acquire an image by imaging an object; and a controller configured to detect, in the image, a marker projected on the object by the collimator, and to determine a source to object distance (SOD) based on a location of the marker in the image, wherein the SOD comprises a distance between the X-ray source and the object.