| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical encoder for detecting an absolute angle by using an optical scale in which in-plane polarizers have one polarizing direction.SOLUTION: An optical encoder comprises a light source 41, an optical scale 11, an angle sensor including a first photodetector PP(-) with a polarizing layer and a second photodetector PP(+) with a polarizing layer, a position sensor including a light intensity photodetector PDx(+), a light intensity photodetector PDx(-), a light intensity photodetector PDy(+) and a light intensity photodetector PDy(-), arithmetic means, and a rotational/straight conversion mechanism. The arithmetic means is capable of computing an absolute angle of the optical scale 11 by computing relative moving amounts of the optical scale 11 and an optical sensor unit 31 from light intensity of first separated light and light intensity of second separated light detected by the angle sensor on the basis of a shortest position P. |
