| 摘要 |
PURPOSE:To obtain a high-reliability encoder by providing a least three position detecting means and regarding position information detected by the majority of them as effective information. CONSTITUTION:One group of position sensors is formed of respectively opposite light emitting elements 10, 12, and 14, and light receiving elements 11, 13, and 15 are so arranged that when one of the sensors is at a light transmission part position, other sensors are all at light transmission parts and when one sensor is at a light shielding part, others are at light shielding part positions. Here, light beams from the elements 10, 12, and 14 reach or do not reach the elements 11, 13, and 15 at the same timing through the rotation of a rotary disk 20. Then, a detection signal from the element 11 (or 13 or 15) is inputted to logic circuits 41 and 42 (or 42 and 43, or 41 and 43) respectively and only when both inputs to those circuits 41-43 are '1', their outputs are driven. Consequently, the majority of detection signals are signified, so the encoder which has extremely high reliability is obtained.
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