Printer

摘要

An encoder is adapted to oppose to a scale provided with a plurality of marks or slits arranged in a first direction at predetermined intervals. A plurality of detectors is arranged in a second direction perpendicular to the first direction while being staggered in the first direction, each of which detects a position of each of the marks or slits, and the plurality of detectors being operable to respectively output an detection signal which have a first frequency. A first signal generator is operable to generate a first output signal which has a second frequency which is 2ⁿ-times of the first frequency based on the detection signal output from a first detector of the plurality of detectors. A second signal generator is operable to generate a second output signal which has the second frequency based on the detection signal output from a second detector of the plurality of detectors. A third signal generator is operable to generate a third output signal which has the second frequency based on the detection signal output from a third detector of the plurality of detectors. A fourth signal generator is operable to generate a fourth output signal which has the second frequency based on the detection signal output from a fourth detector of the plurality of detectors. A controller detects a rotational position of the motor and a rotational speed of the motor based on at least one of the first output signal, the second output signal, the third output signal, and the fourth output signal, and which controls the rotational speed of the motor by PID control based on the detected rotational position and the detected rotational speed. The controller stores a target speed table having a target rotational speed corresponding to the rotational position. The target speed table has the target rotational speed corresponding to the rotational position which is detected on the basis of at most three signals of one of the first output signal, the second output signal, the third output signal, and the fourth output signal.