Patent ID: 8575876
Filing Date: 2013-11-05
Classification: G01D

Abstract:
1. An optical entire-circumference encoder comprising: a rotation track which is rotatable to follow a rotor rotatable around a rotation axis and which is provided to be in a ring shape around the rotation axis as a center; a plurality of rotation slits provided to transmit light at an equal pitch radially around the rotation axis as the center in the rotation track; a fixed track which is fixedly set in a ring shape in correspondence with the rotation track on one side of the rotation track and which is divided into a plurality of regions in a circumferential direction of the fixed track; a plurality of fixed slits provided to transmit light at an equal pitch in the plurality of regions radially around the rotation axis as the center in the fixed track; a light source provided to emit light and disposed in a vicinity of the rotation axis; a light guide including a first light guide and a second light guide, the first light guide extending outwardly from the vicinity of the rotation axis in a radial direction perpendicular to the rotation axis and being provided to guide light in the radial direction between the light source and the second light guide, the second light guide extending in an axial direction parallel to the rotation axis from an outer periphery of the first light guide toward the plurality of fixed slits provided in the plurality of regions and being provided to guide light in the axial direction between the first light guide and the plurality of fixed slits provided in the plurality of regions, the light guide being provided to guide light emitted from the light source to the plurality of fixed slits provided in the plurality of regions through the first light guide and the second light guide and to guide light which passed through the plurality of fixed slits provided in the plurality of regions and the plurality of rotation slits toward the vicinity of the rotation axis while condensing the light guided by the first light guide and the second light guide; and a plurality of light receivers disposed in the vicinity of the rotation axis to receive the light guided by the light guide from the plurality of regions respectively, the plurality of fixed slits in one of the plurality of regions and the plurality of fixed slits in another region adjacent to the one of the plurality of regions in the circumferential direction among the plurality of regions in the fixed track being formed so that a phase difference by which a rotation direction of the rotor is determined occurs between light reception signals generated by the plurality of light receivers based on light guided by the first light guide and the second light guide of the light guide from the plurality of regions of the fixed track.