Patent ID: 6867412
Filing Date: 2005-03-15
Classification: G01D

Abstract:
1. An absolute position sensing device usable to measure a relative position between two elements, the absolute position sensing device including a readhead and a scale, the scale including an integrated scale track extending along a measuring axis, the integrated scale track comprising a plurality of coded segments within the integrated scale track along the measuring axis, each coded segment comprising a periodic portion and a code portion, the periodic portion comprising: the code portion comprising: wherein: the plurality of first incremental scale elements, the plurality of second incremental scale elements and the plurality of code elements are configured such that a detection window of the readhead includes a number of code elements sufficient to define a code word usable to identify an absolute measurement value of a local datum included in the detection window and at least 50% of a total area of the detection window includes the first incremental scale elements and the second incremental scale elements of at least one periodic portion, regardless of the position of the detection window along the measuring axis of the scale.