Patent ID: 6683543
Filing Date: 2004-01-27
Classification: G01D,H03M

Abstract:
An encoder comprising:a sensing device that generates first and second encoder signals; a sensing surface comprising a plurality of uniformly spaced encoding marks, said surface moving with respect to said sensing device such that said first and second encoder signals are generated when said encoding marks pass said sensing device, said second encoder signal leading or lagging said first encoder signal depending on the direction of said movement of said sensing surface with respect to said sensing device; a reference mark detector for detecting said first reference mark and generating a first reference mark signal indicative of said detection; a register for storing a digital value; and a controller for receiving said first and second encoder signals and for incrementing or decrementing said digital register based on said received first and second encoder signals, wherein said controller resets said digital value to a first reference value when said encoder receives said first reference mark signal.