ROTARY ENCODER HAVING A PLURALITY OF BEAMS EMITTED BY A DIFFRACTION GRATING

摘要

A rotary encoder wherein coherent beams are caused to be incident at different positions of a diffraction grating mounted on a rotary object, different beams diffracted from the diffraction grating are caused to overlap and form interference fringes, the fringes are detected by a light receiving detector to detect a rotational state of the rotary object, and the parallelism a of the rotary object satisfies the following inequality: a