Patent Document ID: 20080193053
Application ID: 12025754
Patent Status: 0

Claim One:
1. A method of imaging a coding pattern disposed on a surface of a substrate, said method comprising the steps of: (a) positioning a nib of an optical reader on said surface and capturing an image of a portion of said coding pattern, said coding pattern comprising: a plurality of target elements defining a target grid, said target grid comprising a plurality of cells, wherein neighboring cells share target elements; a plurality of data elements contained in each cell; and a plurality of tags, each tag being defined by a plurality of contiguous cells, each tag comprising respective local tag data encoded by a respective set of said data elements, wherein each tag comprises at least 9 target elements; (b) locating at least 9 target elements in said imaged portion; (c) observing a perspective distortion of said target elements due to a 3D orientation of said reader relative to said surface; (d) calculating a 2D perspective transform using said target elements; and (e) determining a position of said nib on said surface using at least said 2D perspective transform and said local tag data, wherein said portion of said coding pattern has a diameter of at least one tag diameter and less than two tag diameters.