1. A method for automatically adjusting a size of characters using a camera, comprising: receiving an image containing characters; adjusting a focus of the image and detecting a region and a size of characters in the image; determining whether the size of the characters, in the image falls within a preset range; if the size of the characters falls within the preset range, recognizing the characters in the image and displaying recognition results; and if the size of the characters does not fall within the preset range, automatically adjusting a zoom ratio of the image and recognizing the characters in the resized image.