Encoder

An encoder that reads a plurality of incremental patterns respectively having graduation array pitches different from each other and performs an arithmetic operation to output a measurement value, the encoder comprising:

• a reading device that moves relative to the plurality of incremental patterns to read the plurality of incremental patterns as respective electric signals;
• a control device that calculates the measurement value, based on the electric signals;
• and an output device that outputs the measurement value calculated by the control device, wherein
• the control device includes:
• an absolute position synthesis unit that synthesizes the plurality of electric signals read by the reading device to generate a synthesized absolute position;
• a detection unit that detects a plurality of relative positions from the plurality of respective electric signals read by the reading device;
• a position calculation unit that performs an arithmetic operation between at least any one relative position of the plurality of relative positions and the synthesized absolute position to calculate a calculated absolute position;
• an absolute position comparison unit downstream of the position calculation unit and downstream of the absolute position synthesis unit, the absolute position comparison unit comparing the calculated absolute position with the synthesized absolute position;
• and
• a relative position comparison unit downstream of the detection unit, the relative position comparison unit comparing the plurality of relative positions detected by the detection unit with each other, and
• the output device includes:
• a measurement value output unit that outputs the calculated absolute position, based on the measurement value;
• a first error output unit that outputs error information, based on a comparison result in the absolute position comparison unit;
• and
• a second error output unit that outputs error information, based on a comparison result in the relative position comparison unit.