Absolute rotary encoder

An absolute rotary encoder comprising:

• a scale having a plurality of marks, including a plurality of types of marks, arranged with a space therebetween and with a period in a circumferential direction, and configured to be rotated around a rotation axis;
• a first detector including a first plurality of elements, and configured to detect marks of the plurality of marks by the first plurality of elements;
• a second detector disposed opposite to the first detector with respect to the rotation axis, including a second plurality of elements, and configured to detect marks of the plurality of marks by the second plurality of elements;
• and
• a signal processor configured to obtain an absolute rotation angle of the scale based on periodic signals with a plurality of periods output from each of the first detector and the second detector,
• wherein the signal processor is configured:
• to generate a data string by quantizing an amplitude of the periodic signals output from the first detector with respect to each of the plurality of periods, and to obtain first angle data, with a resolution of the period, based on the data string,
• to normalize the periodic signals, with respect to at least one of the plurality of periods, output from each of the first detector and the second detector, to average the normalized periodic signals obtained with respect to the first detector and the normalized periodic obtained with respect to the second detector, and to obtain second angle data, with a resolution higher than that of the first angle data, based on a phase of the averaged normalized periodic signals, and
• to generate data representing the absolute rotation angle based on the first angle data and the second angle data.