A sensing device for sensing a position relative to a surface. The surface has printed therein or thereon coded data including at least one data portion, and visible information, at least some of the coded data being coincident with the visible information. The sensing device includes a sensor for sensing...http://www.google.fr/patents/US7936343?utm_source=gb-gplus-shareBrevet US7936343 - Sensing device for sensing a position relative to a surface
Sensing device for sensing a position relative to a surface
