1. A method for recognition of a character string in a scene image, comprising: binarization means for obtaining a plurality of mutually different binary images from an input image; pre-segmentation means for detecting a set of pixels as a character subimage candidate that is assumed as a character from each binary image obtained; means for detecting a pair of character subimage candidates that are derived from the same binary image or different binary images and are located close to each other from a set of the character subimage candidates obtained by the character subimage candidate detecting means; means for performing character recognition on the character subimage candidates; and means for obtaining a combination of the characters that is most plausible as a character string by concatenating character subimage candidates that are adjacent to each other.