Patent 7183536 was granted and assigned to Nokia on February, 2007 by the United States Patent and Trademark Office.
A motion encoder for use with a rotating key. The motion encoder allows the direction of rotation to be determined by providing elements having different characteristics for the transmission of a IR beam. These elements are arranged in a pattern that allows an IR beam impinging on the elements to trace a path detected as the rotating key turns. The beam being detected after changes in the reflected or transmitted beam indicating the direction of rotation of the beam.