Rotary encoder and rotation mechanism including the same

A rotary encoder including

• a detection unit, and
• a scale that is rotatable relative to the detection unit, the scale having a pattern for detecting a rotation angle,
• wherein the detection unit includes two first detection units and a second detection unit, the two first detection units being disposed at positions that are symmetrical about a center of the rotation, each of the first detection units outputting an incremental signal having a plurality of periods for one rotation of the scale, and the second detection unit outputting an absolute signal corresponding to a rotation angle of the scale within one rotation of the scale, and
• wherein the rotary encoder detects a relative rotation angle of the scale based on phases of the two incremental signals and a value of the absolute signal, the phases of the two incremental signals being detected by the two first detection units,
• the rotary encoder comprising:
• a storage unit that stores a plurality of formulas for correcting errors of the incremental signals, the formulas being different from each other in accordance with the value of the absolute signal, and the errors being generated due to deviation of the center of the rotation from a center of the pattern;
• a calculation unit that calculates a corrected phase by performing an operation on the phases of the two incremental signals by using one of the formulas corresponding to the value of the absolute signal that is output from the second detection unit;
• and
• a generation unit that generates the rotation angle of the scale based on the corrected phase and the value of the absolute signal.