ROTARY ENCODER, ROTARY MOTOR AND ROTARY MOTOR SYSTEM

It is an object to provide a rotary encoder, a rotary motor, and a rotary motor system capable of detecting an origin of a position with detection accuracy improved by using diffraction interference light and of facilitating downsizing and manufacturing, for example. To achieve the object, the encoder includes a disk (110) in a disk shape that is arranged rotatably about a rotation axis and that includes one track (TC) in a ring shape on which a rotating grating is formed and one or more origin detection areas (h) serving as partial areas on which a rotating grating is formed, and a mask that is fixed and arranged in a manner facing the disk (110) and on which one or more fixed gratings are formed so as to constitute a diffraction interference optical system together with the rotating gratings. A plurality of slits (SLA) and (SLB) included in at least one rotating grating are formed along a curved line obtained by curving a plurality of radial lines about the rotation axis in the circumferential direction at predetermined curvature such that pitches (pLA) and (pLB) of the slits (SLA) and (SLB) can be set to a predetermined value.