An optical disc system including a focusing mechanism and a tracking mechanism, wherein the mechanisms are controlled by feedback loops having electronic circuits for generating a servo error signals. The error signals are communicated in the feedback loop for effecting corrections of the focusing mechanism and the tracking mechanism. The optical disc system is provided with digital lead/lag compensation circuit assembly including a servo loop having servo loop transfer function and an error signal. The circuit assembly includes a motor or actuator having a mechanical resonance frequency being less than a predetermined sampling frequency and a compensation circuit for stabilizing the servo loop. The error signal of the servo loop is sampled at the pre-determined sampling frequency. Normalization of the error signals to the information signal occurs during sampling. The compensation circuit has a compensation transfer function including a single lead and a complex lag for producing a notch filter with a notch. The compensation transfer function is formulated so that the notch occurs at approximately one half the predetermined sampling frequency thereby reducing amplitude of the mechanical resonance frequency in the servo loop transfer function. The optical disc system also includes a mechanical isolator for vibration isolation and accommodation of thermal expansion, an oscillator with a tank circuit having an increased resistance, an improved focus capture system, and means for identifying blank sectors in a storage medium.

Servo control system for information storage device

A method and apparatus for increasing the amount of data capable of being stored in a magnetic storage device is disclosed. Basically, a magnetic characteristic of the disk to head interface is measured at several locations on the disk. The frequency for writing and reading the data is optimized in terms of the required resolution and the magnetic measurement. The read and write modes are then varied, based upon the optimized frequency, such that data is written on the disk at a frequency substantially equal to the optimized frequency and read from a disk having data recorded at the optimized frequency.

Method and apparatus for recording data

The rotation speed of a disc rotation motor is controlled such that a synchronizing signal derived from an output signal reproduced from a disc coincides with a reference oscillation frequency. The amount of data accumulated in a memory provided for absorbing jitter of the output signal reproduced from the disc is detected. In response to a result of the detection, a control signal in the disc rotation control is corrected such that the amount of data accumulated in the memory becomes substantially constant.

Disc rotation servo control apparatus in a disc player

An apparatus and method for moving a carriage assembly from an initial position to a target position relative to a storage medium rotating at a circumferential velocity. A processor determines a velocity trajectory relative to the radial distance of the initial position and the target position to the center of the medium, the circumferential distance between the initial position and the target position, and the initial circumferential velocity of the medium. The processor directs the drive to move the carriage assembly using the velocity trajectory so that the carriage assembly will arrive radially and circumferentially at the target position at substantially the same time. Additionally, the rotation of the storage medium may be changed from the initial circumferential velocity to a target circumferential velocity.

Method and apparatus for moving carriage assembly from initial position to target position and optical disc system including same

An optical disk recording/reproducing device for recording or reproducing information on or from an optical disk while rotatively driving the optical disk at a constant angular velocity. The disk has pre-recorded information cyclically formed along a track so as to provide rotation control at a constant linear velocity. The device, which includes a clock generating circuit for generating a clock signal for recording or reproducing in accordance with a recording frequency of the pre-recorded information derived from signals reproduced by an optical head, is designed to perform recording or reproducing operations with a recording frequency according to the clock signal. The device further includes a magnetic filed control circuit and a recording light power control circuit whereby a magnetic field and light power to be applied to the optical disk is varied according to the recording frequency during recording operations.

Optical disk recording/reproducing device utilizing a constant angular velocity method with a constant linear velocity formatted optical disk

Method and apparatus for rotating an information storage disc about its central axis at a prescribed angular velocity that varies according to the radial position of an optical transducer for recording information thereon, whereby a uniformly high density of information can be recorded over the entire disc. The apparatus includes a register for storing a digital measure of the radius of the current track being recorded by the transducer, along with velocity signal circuitry for producing a disc velocity signal having a frequency inversely proportional to the measure of radius, and a spindle motor servo, responsive to the disc velocity signal, for controlling the angular velocity of the information disc, accordingly. The velocity signal circuitry includes a crystal oscillator, a counter for counting the clock pulses produced by the oscillator, and a digital word magnitude comparator for generating a reset pulse to reset the counter to an initial zero count every time it determines that the count is equal to the digital measure of radius. The disc velocity signal is then derived by frequency dividing the successive reset pulses.

Digital method and apparatus for rotating an information storage disc

Method and apparatus for rotating an information storage disc (11) about its central axis at a prescribed angular velocity that varies according to the radial position of an optical transducer (15) for recording information thereon, whereby a uniformly high density of information can be recorded over the entire disc. The apparatus includes a register (21) for storing a digital measure of the radius of the current track being recorded by the transducer (15), along with velocity signal circuitry for producing a disc velocity signal having a frequency inversely proportional to the measure of radius, and a spindle motor servo (25) responsive to the disc velocity signal, for controlling the angular velocity of the information disc (11) accordingly. The velocity signal circuitry includes a crystal oscillator (29) a counter (31) for counting the clock pulses produced by the oscillator, (29) and a digital word magnitude comparator (35) for generating a reset pulse to reset the counter (31) to an initial zero count every time it determines that the count is equal to the digital measure of radius. The disc velocity signal is then derived by frequency dividing the successive reset pulses.

John S. Winslow

Papers

Digital method and apparatus for rotating an information storage disc

Method and apparatus for precisely controlling the angular velocity of an information storage disc