Patent ID: 9322675
Filing Date: 2016-04-26
CPC Classification: G01D

Claim Text:
1. An absolute encoder comprising a scale on which a plurality of marks are arrayed at a first pitch, a detector which includes a plurality of photoelectric conversion elements disposed at a second pitch smaller than a third pitch corresponding to the first pitch thereon and configured to detect light modulated by a predetermined number of marks of the plurality of marks, and a processor configured to obtain an absolute position of the detector or the scale based on output signals from the plurality of photoelectric conversion elements, wherein the plurality of marks include a first mark, a transmittance value or reflectance value of which falls within a first range, and at least two types of a second mark, transmittance values or reflectance values of which fall within a second range different from the first range and are different from each other, the first marks and the second marks are alternately arrayed, and wherein the processor is configured to specify a signal range of a plurality of periods of the output signals based on extrema of the output signals, obtain a data sequence constituted by a plurality of quantized data based on a plurality of extrema, corresponding to the second marks, of the output signals within the specified signal range, obtain a phase of periodic signals of the output signals within the specified signal range, and obtain data representing the absolute position based on the data sequence and the phase.