| 摘要 |
PROBLEM TO BE SOLVED: To prevent erroneous correction of the rotation speed of a motor assembly due to inability to measure the rotation speed of a movable medium, such as a photoconductor drum, caused by the boundary between a pattern formation portion and a pattern interruption portion, without increase in cost. SOLUTION: Based on a pattern portion 4 for minimal distance detection, a detection pulse signal is produced by a magnetic sensor 5, and the rotating speed of a drum is determined, based on the period of the detection pulse signal on a minimal distance-by-minimal distance basis (12). When the detection pulse signal is judged to has lasted for a prescribed time, the starting point of a pattern interruption portion 4B is recognized. When the point in time of starting of a pattern formation portion 4A is thereafter judged, the total number of the detection pulse signals is counted (14), and at the same time, based on the period of the detection pulse signal, the rotating speed of the drum is determined on a minimal distance-by-minimal distance basis. The rotation speed of the motor is corrected (18), until the count reaches a prescribed value (15). When the count reaches the prescribed value, the correction is interrupted, until the point in time of starting of the pattern formation portion is recognized. |
