Oki Electric Industry Co., Ltd.

Oki Electric Industrial Co., Ltd.

Shizuo Nagata

Masahiro Takahashi

Yasuhiro Suzuki

Yasuo Shimizu

Katsuhide Tanoshima

Tutomu Tabata

Minoru Ohtsuka

Tsutomu Tabata

Katsushide Tanoshima

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. Futher, 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.

Tracking adjustment using the sum of the maximum and minimum tracking

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.

Adjustment of tracking servo and focusing servo in optical data

An optical disc system is provided with a focusing error signal generator for detecting any focusing error from light reflected by an optical disc and outputting a focusing error signal; a driver for outputting a focusing drive current on the basis of the focusing error signal; and an actuator for shifting an optical pickup in a focusing direction in accordance with the focusing drive signal. The optical disc system also has a signal detection and processing unit for detecting each index point (ID) on the optical disc and generating an index gate signal indicating an address between the index point and another index point next to the first-mentioned index point in the tracking direction; and an inter-ID holder for holding, based on the index gate signal, the focusing error signal at a signal level right before the first-mentioned index point.

Optical disc system

In an optical head apparatus for recording or reproducing information onto or from an optical disc, a carriage is movable along a guide shaft extending in a direction parallel with the radial direction of the optical disc, and an armature is mounted on the carriage so that it can rotate about a pivotal axis perpendicular to the surface of the optical disc. An objective lens is fixed to the armature and positioned to traverse the tracks on the optical disc when the armature rotates. Guide yokes extend in parallel with the guide shaft. Tracking and carriage-servo coils are fixed to the armature and have a hollow through which the guide yokes loosely extend. A magnetic field means creates magnetic lines of force perpendicular to the longitudinal direction of the guide yokes and parallel with the surface of the optical disc. A drive circuit supplies currents to the tracking and carriage-servo coils in such directions as to produce electromagnetic forces in parallel with each other thereby driving the armature along the guide yokes or in such directions as to produce electromagnetic forces in antiparallel with each other to rotate the armature about the pivotal axis.

Rotatable read/write optical head apparatus

Optical head

An external magnetic field generating device includes a pole piece mounted on a face of a magnetic plate, and a coil which is in contact with the face of the magnetic plate, the coil being wound flatly around the pole piece so that it spreads out radially. The coil generates a magnetic field through the pole piece when an electric current passes through the coil, the pole piece is projectable beyond the face of the coil opposite the magnetic plate.

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Tokyo, Japan

Shizuo Nagata