1. A method of controlling adaptive auto exposure, the method comprising: reading an image; dividing the image into an object region and a background region; calculating an average luminance of the object region and an average luminance of the background region; calculating a luminance difference between the average luminance of the object region and the average luminance of the background region; if the luminance difference is within a predetermined range, calculating a weight that is reverse proportional to the luminance difference; calculating an average luminance of the entire image by applying the weight to the average luminance of the object region; if the luminance difference is not within the predetermined range, determining the average luminance of the background region or the object region as the average luminance of the entire image; and controlling auto exposure based on the average luminance of the entire image.