Oak Technology, Inc.

Data Technology, Inc.

Laserdrive Ltd.

John L Grimsley

Patrick J Champagne

Kai C Sun

Robin J Freeze

Thomas A Quan

Kai C Sun, Deceased

Processing of disc-drive pickup signals in a manner that maintains an approximate quadrature relationship. Second order matching filters (353, 303) process pickup signals to remove high frequency components and maintain an approximate quadrature relationship.

Processing of disc-drive pickup signals

The invention provides methods and apparatus for compensating for disc runout. In an exemplary embodiment, a data-storage device is provided which includes a rotatable disc and a data head for accessing the disc. The device includes a runout calibration system comprising positioning mechanics coupled to the head for moving the head relative to the disc. A servo loop incorporates the positioning mechanics and generates a drive signal used to control the positioning mechanics. A memory, having an input and an output coupled to the loop, is also provided for recording a plurality of samples of the drive signal. The memory then plays back those samples into the feedback loop at first periodic angular increments forming a calibrating drive signal.

Runout calibration for disc drive system

Adjustment of disc-drive pickup signals in a manner that responds dynamically to changes in such signals while in use. Adjustment is directed toward achieving an approximately symmetric (i.e., 50-50) duty cycle. A variable integration rate of symmetry error responds to fluctuations in pickup signal frequency to achieve more accurate adjustment of quadrature track crossing signals during a search operation.

Dynamic adjustment of disk-drive pickup signals

An optical disk drive in which changes in rotational speed are achieved under closed loop control, avoiding significant undershoots or overshoots in speed, increasing access time and reducing power. The speed control is suitable for use in a CLV system, in an CAV/CLV scheme, or in any system in which the speed of the disk must be changed at various times. Feedback from the motor, rather than data read from the disk, determines and controls motor speed during all search operations. The disk motor servo determines the desired motor speed for a target track through a speed profile table. The speed profile table can be designed to accommodate a combination of CAV mode and CLV mode of operation such that the disk drive system can run at the maximum data transfer rate permitted by the data processing electronics, or to minimize power consumption. Through closed loop control, the system ensures that the speed of the motor is quickly and accurately changed to the desired speed, typically by the time the optical pickup reaches a target track during a search operation. The closed loop control also allows the disk drive system to be designed for a lower tolerance level and still achieve jitter-free control. Thus the data rate can be increased due to the lower tolerance required. The access time is minimized because the CD-DSP can begin retrieving data as soon as the target track is reached, since the optical disk will generally already at the desired speed.

Optical disk motor servo and method for closed loop speed control

A linear motor with uniform force constant across the full stroke length achieved by varying the width of the air gap face area of the permanent magnet such that the width is reduced towards the center of the magnet in relation to the widths at the ends thereof to compensate for reducing field strength at the magnet ends caused by fringing effects on the field.

Voice coil motor with linearized force constant

A velocity servo system for a disk drive, the servo system being responsive to digital signals and generating a control signal for moving a read head of the disk drive from a current track position to a commanded track position. The servo system includes a circuit for reading current track address information and servo bursts recorded on a disk in said disk drive and for generating threshold signals when said read servo bursts are of a predetermined amplitude. An appropriately programmed data processing system provides a decoder responsive to the current track address read by the reading means and to the threshold signals for generating a current half track address, a first comparator which compares the current half track address with the commanded track position to generate half tracks-to-go digital data in response thereto; and generates commanded acceleration data in response to the half tracks-to-go data and to successive half track addresses. The servo system further includes a digital to analog converter for converting said commanded acceleration data to said control signal.

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Los Altos, CA, United States of America

John L Grimsley