Method of determining a coordinate value with respect to patterns printed on a document

摘要

A method is disclosed of determining a coordinate value with respect to patterns printed on a document. Each pattern represents a sequence, with each sequence consisting of a repeating codeword of a cyclic position code. The pattern is sensed, and from each sensed pattern a respective sub-sequence of symbols is obtained. Each of the sub-sequences is then mapped to a respective mapped codeword of the cyclic position code. An offset between each mapped codeword and the codeword is determined, and a difference is derived between pairs of offsets. The coordinate value is derived by interpreting one of the differences as a marker separating the coordinate value from an adjacent coordinate value, and the remaining differences as digits of the coordinate value.