Patent ID: 7619209

Claim:
A system to detect motion of a device, the system comprising: an encoder configured to generate periodic channel signals indicative of movement of a moving part of the device, the encoder comprising: a coding element coupled to the moving part of the device, the coding element comprising a combined position and index track with a track pattern of a plurality of optically distinguishable sections, wherein the plurality of optically distinguishable sections comprises a plurality of position sections, an index section, and an index-bar section; an index photodiode to generate an index output signal corresponding to the index section of the coding element; and an index-bar photodiode to generate an index-bar output signal corresponding to the index section of the coding element; a decoder coupled to the encoder, the decoder to generate at least one count signal corresponding to the periodic channel signals; and a microprocessor coupled to the decoder, the microprocessor to determine a rotational position and a rotational count of the moving part based on the at least one count signal from the decoder.