| 摘要 |
PROBLEM TO BE SOLVED: To highly accurately control a peripheral velocity of a rotating body by reducing an influence of a variation of distances between sensors for detecting marks or slits.SOLUTION: A time T1 from timing t1 when a photosensor 130 detects an optical mark 101 to timing t2 when a photosensor 140 detects the optical mark 101 is counted. Further, a time T2 from timing when the photosensor 130 detects an optical mark 101 to timing when the optical mark 101 goes round and is detected again by the photosensor 130 is counted. The time T2 is free of an influence of an error &Dgr;L2 of a distance between the photosensors 130 and 140 and an influence of an error &Dgr;L1 of a distance between a plurality of optical marks 101. On the other hand, an average peripheral velocity V1ave obtained from the time T1 includes the influence of the error &Dgr;L2. A motor is so controlled to reduce the influence of the error &Dgr;L2 on the basis of the relation between T1 and T2. |
