Two-dimensional scale structures and method usable in an absolute position transducer

A method for determining a high resolution position of a two-dimensional detector array along a two-dimensional absolute scale, wherein the two-dimensional absolute scale includes a two-dimensional integrated scale pattern extending along first and second measuring axes, the two-dimensional integrated scale pattern comprising:

• at least one periodic portion, each periodic portion extending along the first and second measuring axes, each periodic portion comprising:
• a plurality of strip-like first periodic scale element zones arranged periodically along a first direction according to an underlying first incremental pitch for at least a first range and extending along a second direction for at least a second range, a plurality of the first periodic scale element zones including a characteristic first arrangement of incremental scale features along the second direction, and
• a plurality of strip-like second periodic scale element zones arranged periodically along the second direction according to an underlying second incremental pitch for at least the second range and extending along the first direction for at least the first range, a plurality of the second periodic scale element zones including a characteristic second arrangement of incremental scale features along the first direction;
• and
• a plurality of code groups distributed within the two-dimensional integrated scale pattern and spaced apart along the first direction by at least a first distance that spans at least two first periodic scale element zones including the characteristic first arrangement of incremental scale features along the second direction and spaced apart along the second direction by at least a second distance that spans at least two second periodic scale element zones including the characteristic second arrangement of incremental scale features along the first direction, each code group comprising a plurality of code elements defining at least one code word, the at least one code word usable to identify a measurement value of a local datum along each of the first and second measuring axes;
• the method comprising:
• detecting an image of a portion of the two-dimensional integrated scale pattern corresponding to a current position using the detector array;
• determining a measurement value of a local datum along each of the first and second measuring axes 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 along each of the first and second measuring axes based at least partly on a plurality of incremental scale features included in the detected image;
• and
• combining the measurement value of the local datum along each of the first and second measuring axes and the measurement value of the offset of the detector array relative to the local datum along each of the first and second measuring axes to determine the high resolution position of the detector array along the first and second measuring axes of the two-dimensional absolute scale.