TRACKING SERVO CIRCUIT FOR OPTICAL DISK

PURPOSE:To provide a tracking servo circuit for an optical disk whose mechanical system and electric system can be simplified. CONSTITUTION:A tracking error signal photoelectrically converted by a photodetector 3d of a pickup 3 is amplified by a sensor amplifier 4. Then, by an error signal processing device 5, it is process into the wave form of a saturation value which becomes a sine wave when it is near the target track and whose polarity, positive or negative, changes depending on its position, before or after the target track, in case it is not near the target track. A velocity estimating observer 6 constitutes a state feedback computing element which estimates position and velocity by considering this work tracking error signal, and the position and velocity estimated by the velocity estimating observer 6 is added, by an adder 8, to the integration value of the work tracking error signal, and then it is applied to an actuator driving amplifier 9 of an actuator 3e as a servo signal.