| 摘要 |
PROBLEM TO BE SOLVED: To provide a detector capable of detecting revolution speed highly precisely and reliably with a simple structure. SOLUTION: A disk device 10 having a turntable 20 on which a disk 11 is placed, a clamper 30 which adheres to the turntable 20 and is for fixing the disk 11 placed on the turntable 20, a motor 13 for giving revolving force to the turntable 20, is provided with the number of turnings detecting means for detecting the number of turnings of the disk 11, for instance, an optical sensor provided a light emitting element and a light receiving element and a reflecting plate 40 that is provided integrally with the clamper 30 and reflects light from the light emitting element.
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