Patent ID: 7694889

Claim:
A two-dimensional coordinate identification apparatus comprising: an image reading portion that reads an image provided in a given area on a printed material on which first code information of coordinate values identifying a location on the printed material and second code information of an identification number identifying the printed material are recorded in each of multiple encode units provided on an area to be encoded; a detecting portion that detects the first code information and the second code information, with the image provided in the given area that has been read; and a decoding portion that decodes the first and second code information and invisibly outputs the identification number and the coordinate values; wherein: the first code information of the coordinate values is composed of a pseudo random M-sequences code, having the characteristic of any two partial sequences are not identical when partial sequences having a length of m are extracted from the M-sequences code having a length of 2m−1, and wherein the M-sequences code denotes the code having a longest cycle (2p−1) from among the sequences created with the p-th degree recurrence equation a t =c 1 a t-1 +c 2 a t-2 + . . . +c p a t-p (mod 2), where a and t are variables and c and p are constants; and the two-dimensional coordinate identification apparatus further comprises an error-detecting portion that determines whether a partial sequences of the M-sequences code corresponds to another occurring partial sequences and detects an error in the first code information upon determining a correspondence.