Optical encoder with variable fiber/phase angle adjustment

In an optical encoder having a code member on which a plurality of indicia portions are arranged at a predetermined pitch spacing, means for moving said code member and said indicia portions in one moving direction, and an optical sensor disposed relative to said indicia portions of said code member in order to derive two output signals having a phase difference between them,

• the improvement wherein said indicia portions are alternating light reflective and non-reflective portions, said sensor comprises a signal head disposed proximate one side of said code member facing said indicia portions and having arranged in a row along a sensor axis a light emission portion between two light reception portions closely adjacent on each side thereof such that light emitted by said light emission portion is reflected by said reflective portions and not reflected by said non-reflective portions and the reflection and non-reflection of light by said alternating portions moving in said moving direction is detected by said two light reception portions to provide two output signals having a phase difference between them,
• said light emission and light reception portions being constituted by tip ends of optical fibers arranged in close contact with each other along the sensor axis, and the other ends of the optical fibers being connected to light emission element and light reception elements, respectively, which are remote from the sensor head, and
• means for rotating said sensor head in order to adjust an azimuth angle between the sensor axis and the moving direction of the indicia portions of said code member such that a predetermined phase difference between the two output signals is obtained.