| 摘要 |
PROBLEM TO BE SOLVED: To increase fineness of an encoder stripe without increasing the diameter of a rotational encoder. SOLUTION: A detector module 25 is provided with a light source 26 and a photodetector 27. On the surface of a drum 22 turning with the shaft of an object, from which its rotation is detected, striped non-reflective areas 23 are arranged at equal intervals. When light from the light source 26 reflected on a reflective area is led to the photodetector 27, the light is expanded by an optical action of the cylindrical shape on the surface of the drum 22. COPYRIGHT: (C)2005,JPO&NCIPI
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