Patent ID: 7191943

Claim:
A location monitoring system, comprising: a movable member, said movable member being movable along a path, said movable member having a surface, and a plurality of markings disposed thereon; a reader circuit, said reader circuit configured to expose a part of said surface of said movable member to light, and to generate a sense signal in response to a portion of said light emanating from said part of said surface of said movable member, said part of said surface including a subset of said plurality of markings; and a processor circuit configured to receive said sense signal, and determine a plurality of probability values associated with said sense signal, each of said plurality of probability values being associated with a corresponding subset of said plurality of markings, said processor identifying said subset of said plurality of markings included in said part of said surface based upon at least some of said plurality of probability values, and identifying a position of said movable member along said path corresponding to said identified subset of said plurality of markings.