Abstract: A method for measuring an eccentricity of an optical disk is provided. The method includes steps of: rotating the optical disk with a spindle motor; irradiating a light beam emitted from an optical pickup on the optical disk; detecting the light beam reflected from the optical disk with a detector; generating tracking error signals; receiving electronic signals from the spindle motor; calculating a quantity of tracks traversed by the light beam during determined revolutions of the optical disk based on the tracking error signals and the electronic signals from the spindle motor; and determining the eccentricity of the optical disk based on the quantity of the tracks.

Abstract: An apparatus is provided for disc rotation control in an optical storage system, which is capable of generating a focusing error signal from light that was reflected by a loaded optical disc. The apparatus includes a focus controller for processing the focusing error signal to obtain a focus output signal, a low pass filter unit for processing the focus output signal by low pass filtering to obtain a filtered signal, a direct current level remover for removing a direct current component of the filtered signal to obtain a warp-indicating signal, and a speed controller for comparing the warp-indicating signal with a predetermined threshold value to determine extent of warping of the optical disc. The speed controller is operable to control the optical storage system so as to limit maximum rotation speed of the optical disc according to result of the comparison made by the speed controller.

Abstract: A digital signal processing device is provided for disc rotation control in an optical storage system, which is capable of generating a focusing error signal from light that was reflected by an optical disc loaded in the optical storage system. The digital signal processing device includes a low pass filter for removing a high-frequency component of the focusing error signal to obtain a filtered signal, a direct current level remover for removing a direct current component of the filtered signal to obtain a warp-indicating signal, and a controller for comparing the warp-indicating signal with a predetermined threshold value to determine extent of warping of the optical disc. The controller functions to control the optical storage system so as to limit maximum rotation speed of the optical disc according to result of the comparison made by the controller.

Abstract: A method and apparatus cancel repeatable run-out (RRO) errors in positioning on a recording medium using a RRO cancellation control voltage. The RRO cancellation includes (a) estimating a rotation period of the recording medium, (b) determining an update interval for the RRO cancellation control voltage based on the estimated rotation period and a desired number of updates to be performed per rotation, (c) updating a value of the RRO cancellation control voltage if a time period passed from a last update is greater than the update interval, and (d) applying the updated RRO cancellation voltage to control the positioning. A phase and a magnitude of the RRO cancellation control voltage may be determined for a RRO frequency range.

Abstract: A method and apparatus compensating for disc eccentricity includes extracting eccentricity data from a tracking error signal having one period, generated by a tracking servo, detecting parameter values of an eccentricity component extracted during the extraction of the eccentricity data and transforming a reference sine wave based on the detected parameter values of the eccentricity component. The eccentricity data is replaced with the transformed reference sine wave and the replaced eccentricity data is added to the tracking error signal to compensate for the disc eccentricity.

Abstract: An objective lens in which a first wavelength is used in reading a first optical disk, a second wavelength is used in recording or reading a second optical disk, and a phase shifter provided with annular step portions having a center coincident with an optical axis is formed in a single surface of the objective lens, the phase shifter producing a phase difference with respect to light having the first wavelength and light having the second wavelength, is presented. The objective lens can read well both a CD and a DVD.

Abstract: An optical head performs recording and/or reproducing of a signal to an optical recording medium and comprises a light source, an objective lens converging the light emitted from the light source to the optical recording medium, and objective lens tilting mechanism for tilting the objective lens in order to correct aberration generated when the optical recording medium is tilted, and the optical head is assembled so that a direction of the coma aberration of the objective lens itself perpendicularly crosses a direction tilted by the objective lens tilting mechanism.

Abstract: A controller of an optical disk apparatus moves a pickup head to a data area of an optical disk, and radiates a first DVD laser beam to the optical disk. The controller measures, as a first eccentricity amount, a number of beams, which have crossed a track on the optical disk, from a first tracking error signal from a head amplifier. The controller determines that the optical disk is a data-recorded first DVD optical if the controller determines that the measured first eccentricity amount is less than a predetermined reference value. The controller determines that the optical disk is a second DVD optical disk or the first DVD optical disk with a large eccentricity amount if the controller determines that the measured first eccentricity amount is greater than the predetermined reference value.

Abstract: An optical disc drive includes a spindle motor and a computer program. The spindle motor is adapted for rotating an optical disc. The computer program configures the optical disc drive to perform consecutive steps of a method for detecting eccentricity of the optical disc, including: a) while the optical disc drive operates under focused and track-locked conditions, controlling the spindle motor to rotate the optical disc at a specified rotation speed; b) measuring an eccentricity value of the optical disc being rotated by the spindle motor; and c) comparing the eccentricity value measured in step b) with a reference value to determine extent of eccentricity of the optical disc.

Abstract: In an optical disk apparatus, after chucking an optical disk, the optical disk apparatus defers the start of the rotation of the optical disk, and measures the focusing drive voltage at two points, i.e., a point near a center of the optical disk and a point near an outer edge of the optical disk. Then, based on the measured values, the optical disk apparatus determine the angle at which the optical disk is slanted. Therefore, when the optical disk has been chucked inappropriately, the chucking state can be determined without rotating the optical disk, and scratching of the optical disk and damage to the optical disk apparatus can be prevented.

Abstract: A method of one embodiment of the invention is disclosed that outputs an oscillating wave towards a surface of an optical disc. A proximity signal is detected in response to the oscillating wave being output towards the output of the optical disc, and denotes closeness of the oscillating wave to the surface. A number of peaks within the proximity signal are determined. Each peak corresponds to the oscillating wave crossing the surface of the optical disc. The time at which each peak within the proximity signal occurs is correlated with a value of the oscillating wave at that time, yielding a number of time-value pairs. The topology of the surface of the optical disc is approximated from these time-value pairs.

Abstract: A method of one embodiment of the invention is disclosed that determines optical disc vertical displacement information at a number of positions on an optical disc. The method interpolates optical disc vertical displacement information at a number of other positions on the optical disc from the vertical displacement information determined.

Abstract: A bottom hold circuit generates a bottom hold signal (BH signal) from an RFDC signal from an RF amplifier, and sends it to a comparator. The comparator compares a reference level and the BH signal, and generates an Rfdet signal having H level if the BH signal was found to be lower than the reference level. The Rfdet signal is a signal having H level when a laser spot falls in a data-recorded area on an optical disk, and having L level when in a non-recorded area. When it was detected that Rfdet signal had H level throughout a single turn of the disk, a servo-processing microcomputer controls an optical pickup so as to apply tracking servo. This makes it possible to precisely detect a boundary position between the data-recorded area and non-recorded area. If the optical disk is decentered, the boundary area corresponded to the amount of decentering can successfully be isolated from the data-recorded area.

Abstract: An optical disk reproducing apparatus for compensating for a tracking error by using a real-time repetitive control and a method of driving the optical reproducing apparatus are provided. The optical disk reproducing apparatus repetitively compensates for the tracking error in a real time and with high resolution in accordance with the tracking error frequency by using a sampling frequency obtained by performing frequency multiplication on a disk rotation detection signal, corresponding to one rotation of a disk, without initially compensating the tracking error by using tracking error signals in one or several disk rotations. Accordingly, it is possible to cope with a frequency change of the tracking error due to a rotational frequency difference between inner and outer circumferences in a CLV mode or a rotational frequency change generated when the speed changes in a CAV mode. In addition, it is possible to stably compensate for the tracking error without additionally compensating for a phase or gain.

Abstract: Information about the number of traversed tracks is acquired with a code at a first rotational speed and a second rotational speed in each area provided by dividing one rotation into m (m is a natural number equal to or larger than 1). As to the information about the number of traversed tracks, a difference is calculated between the areas. A value proportionate to the sum of absolute values of the information about the traversed tracks in the areas is used as a vibration detection value proportionate to vibration amplitude.

Abstract: An adaptive feed forward controller inserts signals into control loops of an optical disc player and/or recorder at a frequency of the rotation of the disc and one or more harmonics thereof, while at the same time maintaining the stability of the control loops. This makes the control loops more responsive to harmonic components of eccentric and/or tilt motion of a track being followed, a characteristic of poor quality optical discs. The quality of playback or recording such discs is thereby improved. Signal processing forming the control loops including the adaptive feed forward controller is carried out by a software controlled processor on an integrated circuit chip within the optical disc instrument. A signal representing the frequency of rotation of the disc, which is used in the signal processing, can be derived from the control loop rather than by directly measuring rotation with a transducer in the rotating system.

Abstract: As the result of the detection of the runaway of the optical disc when the light pickup cannot detect sync signal in the reproducing signal sent from the optical disc, the control circuit turns off the tracking servo mechanism which controls the tracking of the optical disc by the light pickup. The direction of rotation of the optical disc that is running away is detected by comparing the initial mirror count value obtained by counting for a predetermined period of time the mirror pulse detected in correspondence with the RF signal based on the reproducing signal, with the mirror count value during braking obtained by counting the mirror pulse for the predetermined period of time when the spindle motor is applied with the brake pulse. The brake signal working in the direction opposite to the detected direction of rotation is applied to the spindle motor so as to stop the rotation of the optical disc.

Abstract: A follow-up control system follows up a head of a storage device to a storage medium. A sine wave signal learning section (82) which learns sine wave signals according to follow-up error signals which are input to a feedback control system (80), and performs time lead compensation corresponding to a delay of the feedback system (80), is provided. Since the time lead compensation is used for the sine wave signal learning model which can learn at high-speed, frequency disturbance of high frequency, for which phase lag must be considered, can be a compensation target, and the present invention contributes to the improvement of follow-up accuracy of the storage device.

Abstract: Provided are a method and apparatus for removing vibration due to the imbalance of weight of a disc in a disc drive, in which the allowable high multi-speed of a disc is determined based on the allowable amount of vibration in the disc drive and the disc drive is actuated within a range of the allowable high multi-speed. The method includes detecting the amount of vibration corresponding to the degree of imbalance of the weight of a disc inserted into the disc drive and increasing a set high multi-speed of the disc drive until the amount of vibration reaches an allowable amount of vibration with respect to the disc drive. Accordingly, vibration in a disc drive can be controlled such that a user cannot perceive it and damages to the disc drive due to the vibration can be minimized.

Abstract: An apparatus includes a controller storing information on dense/sparse state of the tracking error signal in connection with characteristic of the signal generated by a phase encoder while tracking servo of a servo unit is inactivated, and, in data reproduction mode, identifying a current disk phase based on characteristic of the signal generated by the phase encoder, and adjusting tracking characteristic of the servo unit based on the stored information in connection with the signal characteristic in order to compensate an effect rate of eccentricity on the identified disk phase. Through minute adjustment of servo characteristic for each disk phase, error range of TE signal to track in real time is reduced. Therefore, tracking for an eccentric disk becomes easier and more reliable.

Abstract: An eccentricity compensating apparatus of a disk drive servo system using frequency response characteristics of an actuator actuating a head to a position on a disk to read data on or reproduce data from the disk. The apparatus includes an error detector that detects a position error between a reference head position and an actual position of the head on the disk and a first compensation controller that receives the position error from the error detector and changes the actual position of the head to compensate for the position error.

Abstract: A process for computing an eccentric amount of a disk upon rotating is provided. The process includes steps of starting a servo control system of a disk drive to rotate the disk at a specified angular velocity, measuring a track crossing speed of the servo control system at a focusing point on the disk, and computing the eccentric amount of the disk according to the specified angular velocity and the track crossing speed. A process for controlling rotation of a disk loaded in a disk drive is also provided. The process includes steps of realizing an eccentric amount of the disk, and rotating the disk at an operating speed corresponding to the eccentric amount.

Abstract: A storage apparatus rotates an optical recording medium at two or more kinds of rotational speeds. The rotational speed is decreased when a read or write margin becomes less than or equal to a first predetermined value or, when a frequency of generation of a servo abnormality of a tracking servo and/or a focus servo is greater than or equal to a first predetermined frequency. On the other hand, the rotational speed is increased when the read or write margin becomes greater than or equal to a second predetermined value or, when the frequency of generation of the servo abnormality of the tracking servo and/or the focus servo is less than or equal to a second predetermined frequency.

Abstract: A rotation control circuit comprising, a pickup controller configured to amplify an error signal detected by a pickup from an optical disk, and to generate both a low-frequency component in the error signal and a pickup control signal so as to control the pickup, a memory controller configured to generate a memory address control signal in synchronization with a frequency generator signal provided by a disk motor, a memory circuit configured to store the low-frequency component by using the memory address control signal at a specified timing, a compensation signal adder configured to add the low-frequency component to the pickup control signal at another specified timing, and a system controller configured to control operational timing of the memory controller and the compensation signal adder.

Abstract: Preceding to the reading out of the recording information of the optical disk by the pick-up, the height of the foreign material existing at the light converging position on the information reading surface is detected by the detector, and when the height of the foreign material is higher than the floating height h of the SIL, the magnetic field is generated by applying the control current corresponding to the height of the foreign material to the coil as the magnetic field generator at the timing before the foreign material is moved to the information reading position of the pick-up by the rotation of the optical disk. Then, when the magnetic field is provided to the magnetic substance fixedly holding the SIL which is floating, the movement operation to separate the SIL to the higher position than the height of the foreign material from the information reading surface together with the magnetic substance, is conducted.

Abstract: An optical storage system includes a pickup head for picking up data from a storage medium. Firstly, the maxima of a tracking error signal and runout are obtained in a calibration procedure in a close loop formed by an optical pickup head, a pre-amplifier, a compensator, a band-pass filter and a maximum detector. A calibration factor is then defined and derived by using the obtained maxima and nominal factors of a power amplifier and the optical pickup head of the optical storage system. The path formed by the series-connected band-pass filter and maximum detector is then disabled, while the calculated calibration factor is then stored in the compensator. The optical storage system may operate in a close loop formed by the optical pick head, pre-amplifier, compensator, a power amplifier under a normal operation procedure so that the optical storage system may record or read data onto/from an optical disc under the compensation provided by the calibration factor.

Abstract: Systems and methods are provided through which the current to a spindle motor of the recording medium of a mass storage device is modulated to avoid anomalies in the operation of mass storage device and reduce power consumption. In the example of a disc drive, the current is modulated to prevent expected or predicted disturbances in the air bearing between a read/write head and the recording medium, and to reduce the power consumption when no disturbances are predicted or expected.

Abstract: A method of unbalanced disc detection in a slim type optical drive. In the method of the present invention, the slim type optical drive obtains a first tracking count per round of the disc at a first rotation speed to obtain a first runout. Then, the optical drive obtains a second tracking count per round of the disc at a second rotation speed to obtain a second runout. Finally, deviation of the disc is assessed according to the first runout and the second runout, so that the disc can be determined to be a gravitationally eccentric disc or not.

Abstract: A method and apparatus for reproducing data from an optical disc in which a disc inducing vibration is detected and the speed of the disc is adjusted to an appropriate speed which does not cause vibration. The method includes obtaining the frequency of vibration by subtracting the count value of track traverse pulses at the lowest speed factor from the count value of track traverse pulses at the highest speed factor; and varying the speed factor of reproducing data from the disc based upon a comparison of the obtained frequency of vibration with a predetermined base value.

Abstract: An optical disc drive for accessing data stored on an optical disc is disclosed. The optical disc drive includes: a sled inside the optical disc drive, the sled sliding relative to the optical disc; an actuator on the sled, the actuator wobbling relative to the optical disc; and a control circuitry for controlling the optical disc drive. The control circuitry includes a focus compensation device for compensating focus errors caused by wobbles of the optical disc generated during rotations of the optical disc; and a high frequency compensator for compensating focus errors caused by wobbles of the optical disc generated during rotations of the optical disc at a frequency higher than a predetermined frequency. The focus compensation device controls the actuator to wobble upward and downward according to wobbles of the optical disc so as to substantially keep up wobbles of the actuator with the wobbles of the optical disc.

Abstract: An information recording medium according to an embodiment of this invention has a plurality of disk-like information recording layers, which are adhered to each other within an allowable decentering error range, and an embossed lead-in area assured on each information recording layer has first guard tracks which are formed within the range of the first radial distance from the radial position of the innermost periphery of the embossed lead-in area toward the outer periphery side, and second guard tracks which are formed within the range of the second radial distance from the radial position of the outermost periphery of the embossed lead-in area toward the inner periphery side.

Abstract: An information recording medium according to an embodiment of this invention has a plurality of disk-like information recording layers, which are adhered to each other within an allowable decentering error range, and a data area assured on each information recording layer, and has guard tracks within the range of a predetermined radial distance from the radial position of the innermost periphery of the data area toward the outer periphery.

Abstract: A method is provided for determining whether a rotating disk in an optical disk reading device is unbalanced. According to the method, the disk is first rotated at a preset rotational speed, and a lens is then located to a first position. Then, as the lens is moved towards a second position at a predetermined speed, a time duration during which a preliminary signal is generated is determined. The disk is determined to be unbalanced if the time duration exceeds a preset value.

Abstract: A method of STW (servo track write) for improving the quality of the servo tracks by suppressing the misalignment of the write start position caused by the asynchronous continuous vibration of a disk drive is disclosed. The disk drive includes a spindle motor, a disk medium, a write/read head and a head moving mechanism for carrying out the sector servo operation. The STW method comprises the steps of detecting the continuous vibration asynchronous with the rotational frequency of the spindle motor, detecting the phase of the asynchronous continuous vibration detected, determining the write start sector of each servo track based on the detected phase of the asynchronous continuous vibration, determining the write start time of each servo track in accordance with the clock signal, and moving the head onto the servo track where the head positioning information is written, by the head moving mechanism and writing the information in the servo track based on the write start time.

Abstract: A tilt detection apparatus capable of detecting the tilt of the optical disk, provided with a laser for outputting a laser beam, a diffraction grating for diffracting the laser beam from said laser to generate a 0th order diffraction beam and +-first order diffraction beams which have the phase distribution equal to the phase distribution due to the wave front aberration generated on an optical disk when the optical disk is tilted, an objective lens for collecting said diffraction beams and exposing the beams to the optical disk, a photodetector for generating signals corresponding to said +-first order diffraction beams reflected at said optical disk, a signal generation circuit for generating the push-pull signals based on the generated signals, and a tilt detection circuit for detecting the tilt of the optical disk based on the push-pull signals.

Abstract: An optical disk apparatus has a first optical system having an objective lens with a first NA, a second optical system having an objective lens with a second NA lower than the first NA. The optical disk apparatus at the time of processing the optical disk, when the optical system suitable recording/reproduction process of the optical disk is the second optical system, via the first optical system detecting a surface run-out of the optical disk and execute the focus lead-in process of the second optical system on the basis of a surface run-out detected; and when at the time of processing the optical disk, when the optical system suitable recording/reproduction process of the optical disk is the first optical system, processing the optical disk with the first optical system without detecting the surface run-out of the optical disk.

Abstract: There is provided an apparatus for compensating for an eccentricity of an optical disc, including a driver on which an optical disc is mounted for rotation, an optical head for emitting optical beams to the optical disc and receiving optical beams reflected from the optical disc, a mover to which the optical head is secured and which moves in a radius-wise direction of the optical disc, a track cross generating circuit which receives a track error signal from the optical disc and transmits a track cross pulse, and a controller which receives the track cross pulse to thereby determine an eccentricity of the optical disc in view of the optical beams reflected from the optical disc, and controls a rotational frequency of the optical disc in accordance with the thus determined eccentricity. The apparatus provides an advantage that an average transfer rate is increased for the long run.

Abstract: A method for detecting an unbalanced optical disc in an optical disc drive. The unbalanced optical disc is detected by a pick-up head of the optical disc drive to obtain a tracking error signal. A first track-across number at which the pick-up head travels on the unbalanced optical disc is determined when the unbalanced optical disc rotates at a first rotational speed. A second track-across number at which the pick-up head travels on the unbalanced optical disc is determined when the unbalanced optical disc rotates at a second rotational speed. The first track-across number and second track-across number are computed to obtain a resulting value. The unbalanced level of the unbalanced optical disc is determined according to the resulting value.

Abstract: An information carrier apparatus for accessing an information carrier having at least one track formed therein includes a times crossed detection section for detecting the number of times that a head structured to access the information carrier has crossed the track; an eccentricity direction detection section for detecting an eccentricity direction of the information carrier based on the number of times; an eccentricity distance detection section for detecting an eccentricity distance of the information carrier based on the eccentricity direction and the number of times; and an eccentricity correction section for correcting eccentricity of the information carrier based on the eccentricity direction and the eccentricity distance.

Abstract: An information storage apparatus includes an optical element, a detector, an adjustment mechanism, a memory and a controller. The optical element emits and/or receives a radiation beam along an optical axis. The detector produces a first signal representing a tilt angle of the storage medium with respect to the detector. The adjustment mechanism compensates a tilt angle between the optical axis of the radiation beam and a direction normal to the optical storage medium in response to a second signal. The memory stores calibration data obtained based on relationship information between the first and second signals and tilt-angle information about the deleted tilt angle. The controller generates the second signal referring to the calibration data such that the tilt angle is substantially canceled. The relationship information reflects a deviation of a property of at least one of the detector and the adjustment mechanism measured by an individual test.

Abstract: An optical pickup actuator and an optical recording and/or reproducing apparatus and method using the same. The optical pickup actuator includes a blade, a plurality of suspensions, first and second coil members, and a magnet member. An objective lens is placed on one side of the blade. Each of the suspensions is coupled at one end to the blade and fixed at the other end to a holder provided at one side of a base, such that the suspensions movably support the blade. The first and second coil members are installed on the base to be separated from each other, with the magnet member being installed on the blade between the first and second coil members.

Abstract: An optical storage system includes a pickup head for picking up data from a storage medium. Firstly, the maxima of a tracking error signal and runout are obtained in a calibration procedure in a close loop formed by an optical pickup head, a pre-amplifier, a compensator, a band-pass filter and a maximum detector. A calibration factor is then defined and derived by using the obtained maxima and nominal factors of a power amplifier and the optical pickup head of the optical storage system. The path formed by the series-connected band-pass filter and maximum detector is then disabled, while the calculated calibration factor is then stored in the compensator. The optical storage system may operate in a close loop formed by the optical pick head, pre-amplifier, compensator, a power amplifier under a normal operation procedure so that the optical storage system may record or read data onto/from an optical disc under the compensation provided by the calibration factor.

Abstract: A CD-RW resonance removing apparatus comprises a first holding-down plate where at least the driving plate, the sliding rods and the read/write head are mounted; a second holding-down plate to balance the total weight of the first holding-down plate and other components mounted on it; multiple elastic pads attached to the first holding-down plate, called first elastic pads, for connecting the first holding-down plate to the chassis frame; and multiple elastic pads attached to the second holding-down plate, called second elastic pads, connect the second holding-down plate to the first holding-down plate. The first and second elastic pads could be with different K values and damping values. The balancing weight by the second holding-down plate, the absorbing vibration by the second elastic pads, and the isolating vibration function of the first elastic pads, all together, eliminate resonance during operation.

Abstract: A follow-up control system follows up a head of a storage device to a storage medium. A sine wave signal learning section (82) which learns sine wave signals according to follow-up error signals which are input to a feedback control system (80), and performs time lead compensation corresponding to a delay of the feedback system (80), is provided. Since the time lead compensation is used for the sine wave signal learning model which can learn at high-speed, frequency disturbance of high frequency, for which phase lag must be considered, can be a compensation target, and the present invention contributes to the improvement of follow-up accuracy of the storage device.

Abstract: A reproducer provided with a vibration value measuring means which has functions of, prior to data reproducing, detecting vibration of, and determining vibration value for, a disc, and which measures a vibration value obtained when the disc with a known mass eccentricity is mounted on the reproducer and is rotated, characterized in that values relating to the measured vibration value are stored in a storage in the reproducer as threshold values indicating allowable limits of the vibration value, thereby preventing unstable vibration detection due to differences between individually manufactured reproducers when a disc with a large mass eccentricity is reproduced at high speed, and permitting a reproducing operation that will not give a user an unpleasant feeling.

Abstract: Disclosed is an apparatus for controlling eccentricity in a photo-record player and a control method thereof. A relative eccentric quantity is found from a TE signal (or, tracking driving voltage) induced per one revolution of disc ‘on track’and an eccentricity phase to be controlled is found from a periodicity of TE (or, tracking driving voltage) per one revolution of disc. A suitable compensating value for the relation between the found eccentricity quantity and phase is generated by taking FG representing a period of revolution as a reference. Then, the compensating value is used for an eccentricity control ‘on track’, or driving the tracking actuator on ‘seek’. Therefore, the present invention reduces a seek location error due to the eccentricity on ‘seek’, thereby enabling to increase a seek performance.

Abstract: A track jump is set so as to be normally carried out even if a DC offset is added to a tracking control signal.

Abstract: An optical disk drive has a positioner for mounting an optical unit, such as an objective lens and a tracking error signal detector, and a motor for moving the positioner. The positioner is moved in the radial direction of the disk by the motor through gear train. The motor is driven by a signal that includes a compensating current, and this signal controls the positioner to move in accordance with any eccentric displacement of a data track as caused by misalignments between the center of the data track and the axis of the optical disk rotation. The current is synthesized with an amplitude of the eccentricity, as detected by the tracking error signal, and a phase angle, as detected by both the error signal and an index signal indicative of a reference angular position of a spindle motor for the optical disk rotation.

Abstract: A method of one embodiment of the invention is disclosed that determines optical disc vertical displacement information at a number of positions on an optical disc. The method interpolates optical disc vertical displacement information at a number of other positions on the optical disc from the vertical displacement information determined.

Abstract: To provide an optical recording medium and an eccentricity amount detecting device using the same that can detect an eccentricity amount representing a relative displacement amount in a radiation direction between a beam spot irradiated onto the optical recording medium and the optical recording medium. In the optical recording medium, a plurality (N) of servo areas (113) each including a first wobble mark (211) and a second wobble mark (212) and a plurality (N) of data areas for performing information recording and reproduction are arranged alternatively in a circumferential direction. Each of the servo areas is composed of a plurality of servo pattern areas (210a to 210c) arranged in the radial direction, which vary in a distance in the circumferential direction between the first wobble mark and the second wobble mark. The plurality of servo pattern areas include the same number of tracks, and the number is less than N/(2×&pgr;).