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 apparatus of the present invention includes: a light irradiator operable to converge a light beam and to irradiate an information carrier (a recording medium) with the converged light beam; a moving means operable to move a converging point of the light beam in a direction substantially perpendicular to a surface of the information carrier; and a focusing controller operable to control the moving means to place the converging point of the light beam at a predetermined position.

Abstract: An optical disc player, which compensates for an eccentricity, is provided including: a spindle controller, a pickup, an RM amplifier, a focusing servo, a tracking servo and an eccentricity compensator. The spindle controller rotates an optical disc. The pickup has a focusing actuator and a tracking actuator and reads information on the optical disc. The RF amplifier detects and amplifies a focusing error signal and a tracking error signal from information on the optical disc obtained from the pickup. The focusing servo controls the focusing actuator in response to the amplified focusing error signal. The tracking servo outputs a tracking control signal in response to the amplified tracking error signal. The eccentricity compensator outputs a signal which compensates for the eccentricity of an optical disc in response to the output signal of the spindle controller, the amplified tracking error signal and the amplified tracking control signal.

Abstract: A method and an apparatus for measuring eccentricity of the tracks of a disk. The apparatus includes a spindle for driving a turntable carrying a disk, an angle detecting device for detecting the angle of rotation of the spindle, a reproducing head for reproducing information from the disk, a pair of servos for controlling the tracking operation of the head, an eccentricity measuring device for measuring the extent of eccentricity from a signal reproduced by the head, an error detecting device for obtaining a tracking error signal by turning on the tracking servos, and an operation device for determining the direction of eccentricity from the angle of rotation and the tracking error signal, determining a vector quantity of the eccentricity of the tracks from the extent of eccentricity and the direction of eccentricity, and for performing a vector operation to determine the quantity of eccentricity of the tracks.

Abstract: A method and apparatus for measuring the crosstalk of an optical disc of an optical disc player adapted to reproduce signals recorded on the disc, in which there are concentrically or spirally formed continuous recorded signal strings or signal recording regions and in which there is provided a positioning aperture at the center of the disc substantially concentric with said recorded signal strings or signal recording regions. A light beam is wobbled at a predetermined amplitude in the direction along the radius of the optical disc. The wobbling period is set so as to be asynchronous with the period of the optical disc rotation. The ratio between the quantity of the traverse signal obtained by the optical pickup and the quantity of strays signals is measured as crosstalk.

Abstract: A method and apparatus for measuring the eccentricity of an optical disk. The method for measuring the eccentricity of an optical disk in accordance with the present invention comprises the steps of activating tracking servo while the optical disk is rotating, detecting the center value of tracking error signal and setting the center value as a reference value, and detecting the eccentricity of the optical disk by comparing the center value and the tracking error signal received right after the reference value is set. The method in accordance with the present invention precisely measures the eccentricity of an optical disk and adjusts focus and track servo gains and disk rotation speed based upon the measured disk eccentricity, which provides stable data reproduction performance.

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: Method for regulating the control signal for adjustment of the optical path between a data disc and a signal pick-up detector system in a data disc drive, where the control signal is regulated as a response to the deviation of the actual reading signals from expected reading signals, and wherein the control signal is regulated in dependence of the tendency of said deviation.

Abstract: A light beam emitted from a light source is diffracted into a first light beam and a pair of second light beams, which in turn are furnished with spherical aberration components based on an externally applied control input signal. The first light beam and the pair of second light beams furnished with spherical aberration components are focused by an objective lens on the recording layer of an optical disk. Each of the first light beam and the pair of second light beams reflected from the recording layer of the optical disk and transmitted through the objective lens is received by a corresponding photodetector.

Abstract: An unbalance disc detection apparatus with a photodetector for receiving at its photo reception region reflection light from a disc on which a laser light is irradiated, and a push-pull signal calculation section for obtaining a change of a light quantity detected by the photo reception region as a push-pull signal, whereby an unbalance disc discriminating section discriminates whether or not a level of the push-pull signal exceeds a threshold value set in correspondence to a predetermined measurement rotation speed.

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 of elimination of interference created on CDR/W run-out motors on sledge servers, especially for the elimination of interference created by the run-out of the combination of CDR/W spindle motor on track-seeing servers, where a general evaluating device is provided linking the controller output of the data access module driven by the sledge server motor and the final track signal output, including a speed evaluating device and a run-out evaluating device that may have access to the run-out factor of the CDR/W motor and the CD in the data access module for evaluation of the elimination function of the speed and the run-out tolerance, so that the run-out evaluating device could emit run-out compensation signals for amplification by a relay amplifier and the spindle motor synchronized signal before a negative feedback calculation by playing the final output signal of the module, with access to a play control signal for the elimination of run-out to the CDR/W sledge server, so that the CD may be read, wri

Abstract: A holographic digital data storage apparatus detects a wobbling in a disc shaped storage medium, wherein the apparatus includes a beam generator and finding means, the disc including therein one or more holographically generated patterns. The beam generator projects at least two wobble detection beams to the holographically generated patterns, the wobble detection beams having different diffraction efficiencies provided at respective characteristic angles, wherein the characteristic angle is an angle between an optical path of one wobble detection beam and that of its corresponding pattern forming beam used in forming one of the holographically generated patterns and a diffraction efficiency is given by a ratio of a power of a diffracted beam of one of the wobble detection beams to a power of said one of the wobble detection beams. The finding means finds at least a difference between the diffraction efficiencies to thereby determine the wobbling in the disc.

Abstract: A method for reading data from an unbalanced disk in a disk drive is disclosed. The method includes the steps of measuring a degree of unbalance of the disk while starting up a rotation of the disk, determining a suitable rotating speed for error-free reading (e.g., a maximum error-free reading speed) corresponding to the measured degree of unbalance, based on a previously stored relationship between degree of unbalance and suitable rotating speed, and beginning a reading operating while rotating the disk at the determined rotating speed. In accordance with the method, it is possible to suppress an unbalanced disk from vibrating, thereby achieving a stable data reading from the disk.

Abstract: A self-calibrating radial runout cancellation method for DVD optical disc media. The radial runout of an optical disc is first measured, during closed-loop tracking, for amplitude and phase. During tracking, a sine wave corresponding in phase and amplitude to the radial runout of the optical disc is synthesized. This sine wave is used in a feed-forward configuration to precompensate for the radial runout of the optical disc.

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: An optical disk apparatus of the present invention measures a surface deflection component (shape of surface deflection) from a low-pass component of a compensating filter in a surface deflection measuring part provided in a DSP. Furthermore, the optical disk apparatus calculates timing at which a positional change in a surface deflection component in time required for focus jumping is a predetermined value or less in a timing calculating part, and starts focus jumping at the timing. Because of this, stable focus jumping is made possible.

Abstract: The present invention relates to an apparatus of measuring how much an eccentricity affects each phase of a disk and controlling disk tracking based on the each effect rate. The present apparatus with disk phase identifying means stores information on dense/sparse state of a tracking error (TE) signal in connection with characteristic of an output signal from said means while a tracking servo is inactivated, and, in data reproduction mode, it identifies a current disk phase based on characteristic of the output signal from said means, and adjusts tracking characteristic of the tracking servo based on the stored information in connection with signal characteristic in order to compensate 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, whereby, tracking for an eccentric disk becomes easier and more reliable.

Abstract: The present invention provides an optical disk device that reduces a track lead-in time associated with a seek time. A switching means 50 includes a multiplier A 11 for multiplying an output of a speed control means 5 by &agr; and a multiplier B 12 for multiplying an output of a position control means 6 by (1−&agr;), and an adder 13 for adding an output of the multiplier A 11 and an output of the multiplier B 12 to output a result of the addition as control input to an actuator driving means 8. At the time of movement of an optical pickup 3 toward a target track, the multiplier factor &agr; for the multipliers A 11 and B 12 is set at 0, thereby performing control of the actuator driving means 8 by means of the position control means 6.

Abstract: Methods and apparatus are provided for reducing cross-talk and jitter caused by track offsets in multi-beam optical disks. The method and apparatus involve using split detectors and cross-talk cancellation algorithms in the multi-element photodetector of the multi-beam optical disks. The cross-talk cancellation algorithms are applied according to the value of the track offset as a function of the track pitch.

Abstract: An apparatus and method for servo control in an optical disk driver. The amount of disk eccentricity is measured, and a compensation value corresponding to the measured disk eccentricity is calculated and stored. The stored compensation value is used in the track search mode so that a more stable and precise track search operation is achieved despite the disk eccentricity caused by imperfect disk manufacturing processes or disk clamping errors. Also, when a track jump is requested during a track-following operation, the jump start point is adjusted properly, thereby reducing the time needed to complete the track jump operation, as well as reducing track jump errors.

Abstract: In order to perform stable focusing jump in accordance with the wobble of a disk, an optical pickup is moved radially inward toward a central area of the disk where the amount of wobble is small. A focusing error signal in accordance with wobble is feed-forwarded during focusing jump so as to also follow the wobble during the focusing jump. Furthermore, the position of an objective lens is maintained while waiting for the signal recording surface of the disk to reach a focus position due to wobble. In addition, the rotation speed of the disk is controlled in accordance with the amount of wobble.

Abstract: A learning control unit is provided between a feedback calculating unit and a driving unit. When a period for one medium rotation period is assumed to be TL, an unknown drive current function Irepeat(t) which repeats for a period of time from a start time t=0 for one medium rotation period to an end time t=TL is obtained by a learning algorithm as an approximated function Iˆ repeat(t) that is approximately presumed by a set of the heights Ci of N rectangular functions having interval numbers i=0˜(N−1) whose time widths are obtained by dividing the period for one medium rotation period into N intervals. After the learning, a learning control signal Iˆ repeat is outputted synchronously with the medium rotation and a feed-forward control is performed.

Abstract: To correct for run-out in an optical disk drive, a run-out reducing gain factor is selected. A run-out correction signal is produced by applying the run-out reducing gain factor to a center error signal. A servo drive signal is refined with the run-out correction signal to produce an adjusted servo drive signal. A tracking actuator is driven with the adjusted servo drive signal.

Abstract: A method of elimination of interference created on CDR/W run-out motors on sledge servers, especially for the elimination of interference created by the run-out of the combination of CDR/W spindle motor on track-seeing servers, where a general evaluating device is provided linking the controller output of the data access module driven by the sledge server motor and the final track signal output, including a speed evaluating device and a run-out evaluating device that may have access to the run-out factor of the CDR/W motor and the CD in the data access module for evaluation of the elimination function of the speed and the run-out tolerance, so that the run-out evaluating device could emit run-out compensation signals for amplification by a relay amplifier and the spindle motor synchronized signal before a negative feedback calculation by playing the final output signal of the module, with access to a play control signal for the elimination of run-out to the CDR/W sledge server, so that the CD may be read, wri

Abstract: The present invention provides an optical disc apparatus which is able to accurately correct eccentricity even when an optical disc slides in the rotating direction. A minimum value detection means 20 detects amplitude of a TE signal, a comparator 10 compares the amplitude with a reference value to detect sliding of the optical disc, and an eccentricity amount to be held in a storage means 5 is obtained by remeasurement when a flaw detection signal 22 is not outputted.

Abstract: A disk drive servo system for eccentricity compensation and a method thereof includes an error detector detecting a position error between an actual position and a predetermined nominal reference position of a turntable actuator, a feedback unit generating and outputting a first control value to compensate for the position error received from the error detector, a learning controller calculating, storing, and outputting a second control value to compensate for eccentricity at one or more predetermined speeds of the disk drive, and a gain/phase adjustor providing gain and phase compensation information corresponding to the second control value of the learning controller according to frequency response characteristics of the turntable actuator at the one or more predetermined speeds.

Abstract: The present invention discloses a method for compensating the laser energy of optical disk drives, which is used for adjusting and correcting the light source energy run-out for the laser light source of an optical disk drive, comprising the step of writing in the signal by several different laser illumination parameters when the optical disk drive is under the mode of data write; then using the bottom curve fit to take samples on a plurality of read signals; comparing the data at adjacent points to obtain the data of its relative slope; repeating the previous steps for several times to obtain a complete run-out factor and the maximum optimal laser illumination control parameter; and writing said maximum laser illumination value into the laser illumination control system of the optical disk drive such that the laser light source energy can be optimally compensated and controlled.

Abstract: An optical apparatus includes a generator for generating a sine wave based on a rotating disc-shaped information carrier, and an eccentricity measuring device for measuring gain and phase of a sine wave corresponding to eccentricity of the information carrier based on the driving signal from the tracking control and on the measured rotation frequency. Also included is a waveform shaper for shaping the gain and phase of the sine wave generated by the sine wave generator using the measured gain and phase obtained by the eccentricity measuring device. An eccentricity correction is applied by adding together the sine wave shaped by the waveform shaper and the driving signal from the tracking control to drive an optical beam on a desired track of the rotating disc.

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 optical disk device and a track hold control method thereof which can prevent runaway during tracking and carry out stable tracking even if the optical disk has a large eccentricity. An offset of a lens is monitored during track hold and kicking is effected at a timing at which the offset is the smallest when the lens passes over a track hold position, thus minimizing the offset upon tracking. Since there is no offset of the lens at the time of shifting to the tracking, a track hold processing is carried out stably.

Abstract: An optical recording apparatus for writing information on an optical recording medium in which a recording surface is covered with a transparent layer. The information to be written on the optical recording medium is converted into a pulse signal, and spherical aberration occurring due to an error of a thickness of the transparent layer is detected, the pulse signal being controlled in accordance with the detected spherical aberration.

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, addition means for adding focus error signals detected by the first and second optical systems, and alignment means for aligning the objective lens in accordance with the addition result of the addition means.

Abstract: An optical disc player, which compensates for an eccentricity, is provided including: a spindle controller, a pickup, an RM amplifier, a focusing servo, a tracking servo and an eccentricity compensator. The spindle controller rotates an optical disc. The pickup has a focusing actuator and a tracking actuator and reads information on the optical disc. The RF amplifier detects and amplifies a focusing error signal and a tracking error signal from information on the optical disc obtained from the pickup. The focusing servo controls the focusing actuator in response to the amplified focusing error signal. The tracking servo outputs a tracking control signal in response to the amplified tracking error signal. The eccentricity compensator outputs a signal which compensates for the eccentricity of an optical disc in response to the output signal of the spindle controller, the amplified tracking error signal and the amplified tracking control signal.

Abstract: An apparatus or method for estimating a radial speed of a disc is suitable for an optical storage device. The apparatus is used in an optical storage device for receiving a pulse signal and an eccentricity, and generating an estimated radial speed of the disc. The apparatus comprises a frequency detector and a sinusoidal wave generator. The frequency detector is used for receiving the pulse signal and then outputs a rotation frequency. The sinusoidal wave generator is used for receiving the rotation frequency and the eccentricity, and then outputs an estimated radial speed value of the disc.

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: 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: 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 method for reading data from an unbalanced disk in a disk drive is disclosed. The method includes the steps of measuring a degree of unbalance of the disk while starting up a rotation of the disk, determining a suitable rotating speed for error-free reading (e.g., a maximum error-free reading speed) corresponding to the measured degree of unbalance, based on a previously stored relationship between degree of unbalance and suitable rotating speed, and beginning a reading operating while rotating the disk at the determined rotating speed. In accordance with the method, it is possible to suppress an unbalanced disk from vibrating, thereby achieving a stable data reading from the disk.

Abstract: A repeatable runout compensator that allows a transducer of a servo system in a storage device employing rotating media to follow the eccentricity on the media is disclosed. In exemplary embodiments, the repeatable runout compensator utilizes error values generated by the servo system, which represent the radial and/or axial eccentricity of the media, to generate an output signal having a sinusoidal waveform that is approximately 180 degrees out of phase with the eccentricities and the harmonics of eccentricities on the media.

Abstract: A servo control apparatus and method that adjust the allowable maximum rotation speed of an optical disk based upon the amount of disk axial vibration. The servo control apparatus in accordance with the present invention includes a driver for rotating the optical disk, a detector for detecting the amount of axial vibration of the optical disk, and a controller for controlling the rotation speed of the optical disk based upon the detected amount of disk axial vibration. The servo control apparatus and method in accordance with the present invention prevents data read error due to disk axial vibration by adjusting the allowable maximum disk rotation speed in consideration for the amount of disk axial vibration caused by imperfect disk manufacturing process, disk clamping error, or disk tilt.

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: An apparatus of the present invention is an optical disk apparatus for irradiating a track on an information carrier on which information is recorded with a light beam so as to reproduce information from the track. The optical disk apparatus includes: a tracking error detector for detecting a tracking error signal representing a displacement between the light beam and the track; a fine movement section for moving the light beam in a substantially radial direction of the information carrier; a coarse movement section for moving the fine movement section in the substantially radial direction of the information carrier; a tracking controller for controlling the fine movement section and the coarse movement section based on the tracking error signal detected by the tracking error detector so that the light beam is positioned along the track; and an eccentricity detector for detecting an amount of eccentricity of the track on the information carrier.

Abstract: An optical axis angle adjusting device is provided, which can adjust the optical axis angle, which can prevent sound skipping or noise in the image of the optical reproduction device even when the disk has certain surface undulation. In the adjusting device, an adjustment disk 10 is inclined relative to the turn table. Rotation phases of the disk are detected, and incident angle is detected at the respective rotation phases. The optical axis angle is adjusted so that the incident angles at the respective phases are identical with each other. Because the disk is inclined, the incident angle can be detected accurately, and the optical axis adjustment can be achieved accurately.

Abstract: A recording method includes a reading step of detecting a reflection light from a recording layer to which a recording is to be made and converting the detected light into a read signal; a detecting step of detecting a position of a preformatted area of a recording layer which the optical beam transmits therethrough other than the recording layer to which a recording is to be made; and a correcting step of correcting intensity of an irradiation light beam or a reproduced signal on the basis of the read signal and the preformatted area position. An apparatus for carrying out the recording method is also provided.

Abstract: An eccentricity amplitude of a medium in an eccentricity measuring unit and an eccentricity phase for a start position of one rotation are measured. A region from the start position to end position of one rotation of the medium which was measured is divided into a plurality of regions every predetermined rotational angle, addresses are sequentially allocated to those regions, a sine value of a rotational angle which is increased every predetermined rotational angle has been stored in each address in an eccentricity memory. A read control unit forms an address (a) in an eccentricity memory corresponding to a rotating position of the medium where a light beam is irradiated at present while using the start position of one rotation of the medium as a reference and reads out a corresponding sine value sin&thgr;a from the eccentricity memory by the designation of the address (a).

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: An optical information recording and playback apparatus for recording and playing back an optical information recording medium having a transparent protective layer comprises a tilt detection device and an off-track adding device, and includes means for determining an optimum direction in which the center of a light spot is to be displaced from the centerline of an information track on the optical information recording medium to compensate for the tilting of the optical information recording medium relative to the light beam, means for setting the amount of displacement as fixed values, and means for splitting the optical information recording medium into a number of areas and for activating a tilt detection function each time switching is made from one area to another during recording or playback.

Abstract: A disturbance compensation module using learning control generates a control input to compensate for track position errors due to a periodic disturbance occurring in an optical recording medium in an optical recording medium drive servo system of an optical recording/reproducing apparatus. The module includes a first filter to filter the track position errors and a memory to store control inputs to compensate for a track control cycle in a corresponding address. A second filter filters the control inputs stored in the memory. An adder adds the filtered track position errors from the first filter to the filtered control inputs from the second filter and outputs a result to the memory, updating the control inputs to compensate for the track position errors.

Abstract: When a deviated gravity disc is reproduced at a higher rate with the disc reproducing apparatus, an excessive vibration is generated and this vibration gives adverse effect on the disc reproducing apparatus and peripheral components/apparatuses, and/or may represent an annoyance to a user. A vibration information detector for detecting vibration of the disc reproducing apparatus or a deviated gravity information detector for detecting amount of gravity deviation of disc is provided, and as a result of such detection of an imbalance (i.e., excessive vibration or mass eccentricity), and a reproducing rate switching control controls sets and limits the reproducing rate of the disc reproducing apparatus to a substitute speed which is lower or higher than a normal reproducing speed.