Displacement-measuring optical scale and optical encoder using same

Abstract

When a convex lenscomes close to 0-th order transmitted light Twith rotation of an optical scale, the 0-th order transmitted light Tderived from a light beam L emitted from a light sourceand transmitted through a diffraction gratingaround is converged and incident on a reference position signal detection sensor. At that time, a large output is obtained from the reference position signal detection sensor. This signal constitutes a reference position signal. On the other hand, reflective diffracted light beams La, Lb having been reflected by the diffraction grating are detected by a diffraction light detection sensorafter interference, so that the speed and the angle etc. of the scaleare detected. In this way, the reference position signal and an incremental signal are detected at the same position on the optical scale.