Track jump controlling unit capable of correctly jumping light beam spot of photo pickup device from one of tracks to other one of tracks

摘要

In a track jump controlling unit, a tracking error detecting circuit detects a tracking error signal in response to a light beam detecting signal from a photo detecting circuit. A zero cross detecting circuit detects a zero cross of the tracking error signal to produce a zero cross detecting signal. A level comparing circuit compares a level of the tracking error signal with a predetermined reference level to produce a comparison signal when the level of the tracking error signal is higher than the predetermined reference level. A timer times first and second predetermined time periods from occurrence of a jump command signal to produce first and second time out signals. The second predetermined time period is greater than the first predetermined time period. A jump pulse producing circuit produces a kick pulse of a jump pulse signal in response to the jump command signal and holds the kick pulse regardless of the zero cross detecting signal until the jump pulse producing circuit is supplied with the first time out signal when the jump pulse producing circuit is not supplied with the comparison signal. The jump pulse producing circuit produces a brake pulse of the jump pulse signal when the jump pulse producing circuit is supplied with at least one of the zero cross detecting signal and the second time out signal after the kick pulse turns to the zero point. At least one of the timer and the level comparing circuit may be omitted.