| 摘要 |
PURPOSE:To improve reliability and performance and increase resolution by providing plural slits for an origin signal at irregular intervals. CONSTITUTION:Main slits 2 for obtaining a main signal are provided at the circumference of a phase plate 1 and slits 9 for the origin signal are also provided fixedly. Slits 4 for obtaining the main signal are provided at the circumference of a code wheel 3 and slits 10 for the origin signal are also provided; and the wheel is fixed on a shaft 5, and a light emitting element 6 and a photodetecting element 7 are arranged. Four slits are provided each as the slits 9 and 10 for the origin signal; and they are disposed in such a way that, when the width is represented by T, intervals are T, 2T, and 3T.
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