Systems and methods for absolute positioning using repeated quasi-random pattern

摘要

An absolute 2D position-sensing device is usable to measure the position of a first element with respect to a second element. A 2D absolute scale includes an integrated 2D absolute scale pattern extending over the 2D scale area along each measuring axis of the scale. The integrated 2D absolute scale pattern includes a predetermined quasi-random pattern repeatedly interleaved with a plurality of code portions along each axis. Each code portion includes a plurality of code elements indicative of an absolute measurement value. The offset of the quasi-random pattern relative to a readhead of the device is combined with the absolute measurement value to determine an absolute position to a very high resolution over a relatively large 2D range.