Deceleration control system for positioning an optical head in an optical disk unit

A deceleration control system having a velocity control and a tracking servo operation for an optical disk unit which includes an optical head for recording information on and/or reproducing information from tracks of an optical disk by use of a light beam emitted form the optical head, a track actuator for moving the light beam in a direction traversing the tracks of the optical disk, and a tracking error signal generation circuit for deriving a tracking error signal TES from a signal which is output from the optical head and is dependent on a light beam received from the optical disk, said tracking error signal being generated every time the light beam traverses a track, said deceleration control system comprising:

• velocity control means coupled to the optical head, said velocity control means including first means for generating a target velocity V.sub.t, second means for detecting a beam moving velocity V based on the tracking error signal TES derived by the tracking signal error signal generation circuit, and a third means for detecting a velocity error V.sub.e of the beam moving velocity V with respect to the target velocity V.sub.t and for controlling the track actuator so as to minimize the velocity error V.sub.e ;
• and
• deceleration means for decelerating the track actuator, said deceleration means including first means for deriving a deceleration time T based on the beam moving velocity V at a track which precedes the target track and supplying a single deceleration pulse to the track actuator for the deceleration time T starting from a time when the light beam is a predetermined distance form the target track, and second means for calculating a start timing of the deceleration pulse so that the beam moving velocity V becomes zero at a center of the target track, wherein said deceleration pulse is output before said tracking servo operation begins.

A deceleration control system for an optical disk unit which includes an optical head for recording information on and/or reproducing information from tracks of an optical disk by use of a light beam emitted from the optical head, a track actuator for moving the light beam in a direction traversing the tracks of the optical disk, and a tracking error signal generation circuit for deriving a tracking error signal TES from a signal which is output from the optical head and is dependent on a light beam received from the optical disk, said tracking error signal being generated every time the light beam traverses a track, said deceleration control system comprising:

• velocity control means coupled to the optical head, said velocity control means including first means for generating a target velocity V.sub.t, second means for detecting a beam moving velocity V based on the tracking error signal TES derived by the tracking signal error signal generation circuit, and a third means for detecting a velocity error V.sub.e of the beam moving velocity V with respect to the target velocity V.sub.t and for controlling the track actuator so as to minimize the velocity error V.sub.e ;
• and
• deceleration means for decelerating the track actuator, said deceleration means including first means for deriving a deceleration time T based on the beam moving velocity V at a track which precedes the target track and supplying a deceleration pulse to the track actuator for the deceleration time T starting from a time when the light beam is a predetermined distance from the target track, and second means for calculating a start timing of the deceleration pulse so that the beam moving velocity V becomes zero at a center of the target track, wherein said second means calculates the start timing of the deceleration pulse by calculating a loss time (T)loss from a time when the light beam passes a predetermined track located one track pitch before the target track and a time when the deceleration pulse starts, using a formula T.sub.p =V.times.(T)loss+VT/2, where T.sub.p denotes a track pitch of the tracks of the optical disk.

A deceleration control system for an optical disk unit which includes an optical head for recording information on and/or reproducing information from tracks of an optical disk by use of a light beam emitted from the optical head, a track actuator for moving the light beam in a direction traversing the tracks of the optical disk, and a tracking error signal generation circuit for deriving a tracking error signal TES from a signal which is output from the optical head and ia dependent on a light beam received from the optical disk, said tracking error signal being generated every time the light beam traverses a track, said deceleration control system comprising:

• velocity control means coupled to the optical head, said velocity control means including first means for generating a target velocity V.sub.t, second means for detecting a beam moving velocity V based on the tracking error signal TES derived by the tracking signal error signal generation circuit, and a third means for detecting a velocity error V.sub.e of the beam moving velocity V with respect to the target velocity V.sub.t and for controlling the track actuator so as to minimize the velocity error V.sub.e ;
• and
• deceleration means for decelerating the track actuator, said deceleration means including first means for deriving a deceleration time T based on the beam moving velocity V at a track which precedes the target track and supplying a deceleration pulse to the track actuator for the deceleration time T starting from a time when the light beam is a predetermined distance form the target track, and second means for calculating a start timing of the deceleration pulse so that the beam moving velocity V becomes zero at a center of the target track, wherein said second means calculates the start timing of the deceleration pulse by calculating a loss time (T)loss from a time when the light beam passes a predetermined track located one-half track pitch before the target track and a time when the deceleration pulse starts.