Adjustment of tracking servo and focusing servo in optical data

Abstract

An optical pickup emits a light beam onto a recording medium and outputs, in response to a reflection from the medium, a first and a second signal for controlling focusing servo control and tracking servo control, respectively. A signal generating section generates a focus error signal and a tracking error signal in response to the first and second signals, respectively. A driving section is responsive to the output of the signal generating section for outputting a first and a second drive current assigned to focusing and tracking, respectively. An actuator moves the pickup in a focusing direction and a tracking direction by the first and second drive currents, respectively. An adjusting section detects two values close to the maximum and minimum values of the tracking error signal at the start of the focusing servo control and adjusts the gain of the second signal on the basis of a difference between the detected values. Alternatively, the offset of the second signal may be adjusted by the sum of the two detected values. Further, the offset of the first signal may be adjusted by a focus offset occurring when the amplitude of the first and second signals appearing after the start of the focusing servo control or the amplitude of a third signal also outputted by the pickup and representative of recorded data and appearing after the start of tracking servo is close to the maximum.