Optical encoder comprising a main and reference light receiving portions with a three-phase signal generation for detecting displacement and direction of displacement of an incremental grating track

Abstract

In an optical encoder for measuring relative displacement, a scalehas a reference markcomposed of a reflection slit formed on at least one point of an incremental track, a detection portion () has a light irradiation portion (), main light receiving portionsandthat are disposed at the surrounding centering around the corresponding light irradiation portion and output incremental signals four phases of which are different from each other, and a pair of reference signal light receiving portionsandthat are disposed in the direction perpendicular to the length measurement direction using the light irradiation portion as the center of point symmetry, and a signal processing portionhas a three-phase signal generation portion, a quadrature sine wave signals generation portion, a direction judgment circuit, an internal period counter, and a reference signal processing portion, thereby bringing about a micro-sized optical encoder capable of detecting the reference.