Rotation direction detector for motor of CD player etc. by detecting if leading edges of detected pattern are arranged at regular intervals

摘要

A signal pattern on a turntable (4) comprises high level and low level regions alternately arranged with a ratio 2:1:1:2. A rotation direction determining unit detects that the motor is rotating in its normal direction if the leading edges of the signal pattern detected by a light detector are arranged at regular intervals, and determines that it is rotating in the opposite direction if the leading edges are arranged at irregular intervals. The speed of the motor is determined based on the spacing between adjacent leading edges when the motor is rotating in the normal direction, and between two leading edges on external sides of sequential leading edges when the motor is rotating in the opposite direction.