Scale structures and methods usable in an absolute position transducer

An absolute position sensing device for measuring the relative position of two elements, the absolute position sensing device including a readhead and an absolute scale, the absolute scale including an integrated scale track extending along a measuring axis, the integrated scale track comprising:

• a plurality of code groups usable to identify respective absolute measurement values along the scale, each code group having a plurality of individual code elements placed along the integrated scale track, each code element extending across substantially all of the integrated scale track in a direction perpendicular to the measuring axis;
• and
• a plurality of incremental scale elements arranged to correspond to an underlying incremental pitch that is continuously periodic along the measuring axis for a distance spanning at least 3 code groups, each incremental scale element extending across substantially all of the integrated scale track in a direction perpendicular to the measuring axis;
• wherein:
• the plurality of incremental scale elements are interleaved between the code groups along the integrated scale track;
• and
• at least some of the individual code elements have a width that is narrower in a direction along the measuring axis than the width of the incremental elements in the direction along the measuring axis.

A method for determining a high resolution position of a detector array along an absolute scale, wherein the absolute scale includes an integrated scale track extending along a measuring axis, the integrated scale track comprising:

• a plurality of code groups usable to identify respective absolute measurement values along the scale, each code group having a plurality of individual code elements placed along the integrated scale track and each code element having an extent across the integrated scale track in a direction perpendicular to the measuring axis that is substantially greater than the extent of the code element in a direction along the measuring axis;
• and
• a plurality of incremental scale elements arranged to correspond to an underlying incremental pitch, wherein the plurality of incremental scale elements are interleaved between the code groups along the integrated scale track and each incremental scale element has an extent across the integrated scale track in a direction perpendicular to the measuring axis that is substantially greater than the extent of the incremental scale element in a direction along the measuring axis;
• the method comprising:
• detecting an image of a portion of the integrated scale track corresponding to a current position using the detector array;
• determining a measurement value of a local datum based on at least one code group included in the detected image;
• determining a measurement value of an offset of the detector array relative to the local datum based at least partly on a plurality of incremental scale elements included in the detected image;
• and
• combining the measurement value of the local datum point and the measurement value of the offset of the detector array relative to the local datum to determine the high resolution position of the detector array along the absolute scale.