| 摘要 |
A photoelectric rotary encoder is provided with an arc-shaped optical grating (12) disposed on the side surface of a rotating body (10). In this rotary encoder, a binary optical grating (40) is employed as the optical grating, and the binary optical grating (40) is detected by means of a combination of a light receiving element (60) and an object-side telecentric optical system (50) provided with a lens (54) at least on an object (10) side of a pin hole (52). In this manner, the detection can be achieved by means of a simple detection system even when the binary optical grating formed on the side surface of the rotating body is employed, whereby the cost reduction is achieved.
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