ENCODER, ENCODER-EQUIPPED MOTOR, AND SERVO SYSTEM

An encoder includes a disk on a rotor. First slit tracks each include slits in an incremental pattern in a measurement direction. A second slit track includes slits in an absolute pattern in the measurement direction. A light source emits light to the first and second slit tracks. First light reception arrays are offset from each other in a width direction perpendicular to the measurement direction. The first light reception arrays receive light reflected by the first slit tracks to output first light reception signals. The second light reception arrays receive light reflected by the second slit track to output second light reception signals. A selector selects one of the second light reception signals based on the first light reception signals. A position data generator generates position data of the rotor based on one of the first light reception signals and the one second light reception signal.