Abstract: A positioning control device and method in which the relative position error in tracking is reduced by using the periodicity of position shift. The positioning control device comprises a position detecting unit for measuring the relative position error between the desired position of an objective member and a moving member, an adding unit for adding a position error signal output from the position detecting unit and a delay signal, a signal delay unit for outputting the delay signal which is obtained by delaying an output of the adding unit at a period corresponding to the position shift of the objective member, a drive unit for moving a moving member, and an inputting unit for inputting the signal of the sum of the position error signal and the delay signal to the drive unit and addition-inputting the delay signal to the drive unit through a filter having a predetermined frequency characteristic in a specific frequency range.

Abstract: A tracking error detection apparatus comprises a photodetector comprising plural photoreceptor elements; zerocross detection circuits for detecting zerocross points at which two sequences of digital signals intersect the center levels of the respective digital signals, which digital signals are generated according to the amounts of light received by the respective photoreceptor elements and are outputted from the photodetector; a phase difference detection circuit for performing phase comparison using a distance between zerocross points of the two sequences of digital signals, and outputting a result of phase comparison; and a low-pass filter for performing band restriction to a signal outputted from the phase difference detection circuit, thereby to obtain a tracking error detection apparatus.

Abstract: A method and apparatus for detecting a signal to determine on-track/off-track and/or a track cross direction, using a detection signal corresponding to a reflected main light beam and detection signals respectively corresponding to reflected first and second sub light beams, and an optical recording and/or reproducing apparatus using the same are provided. When detection signals respectively corresponding to one side portions, in a direction corresponding to a radial direction of the optical information storage medium, of the respective main light beam and first and second sub light beams are referred to as a first main signal, a first sub signal, and a second sub signal, respectively, the method and apparatus include obtaining a first operational signal, which is used to determine on-track/off-track and/or a track cross direction, by performing a subtraction on the combination of the first and second sub signals, and the first main signal.

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: A method and an apparatus for reading and/or writing data on a disk (1) storing data in a continuous spiral form (2). The data is simultaneously read from or written to N tracks (4-8, 12-20) by N spots, N being an integer larger than or equal to 2. The reading and/or writing is performed by alternating between reading/writing and actuator jumps. In order to increase the efficiency of such multi track disk drives a next jump decision is calculated dynamically on the basis of a real-time analysis determining a next position of a unit (23) for reading/writing data relative to the disk (1).

Abstract: A position of an object is controlled based on a distance YS until the object is stopped, a target velocity VS of the object, acceleration time ta for accelerating the object, deceleration time td for decelerating the object, velocity variation &Dgr;Va within the acceleration time, and velocity variation &Dgr;Vd within the deceleration time, and a deceleration-start distance YSd. The distance YSd is a distance from where the object is made to start deceleration. The distance YSd is a sum of an integer part YSdq and a decimal part YSdr of the deceleration-start distance. Thus, management of decimal fractions is performed with respect to a pulse generation unit that outputs an output pulse corresponding to the velocity instruction.

Abstract: The present invention relates to a method for servo-controlling when a reproduction is requested to a multi-session disk for non-real-time data or real-time data of audio or video stream. This servo-control method using the information of table of contents reads information of a table of contents written in a disk when a data-requesting command is received from a connected host; distinguishes the type of data recorded in a target location based on the read information of the table of contents; checks whether the distinguished type is corresponding to the command type; and re-sets or maintains current parameters for servo-control operation if the distinguished type is matched to the received command, so that a servo-control mechanism is adjusted to the type of the requested data before a pickup starts to move to the target location.

Abstract: A method of automatically pausing an optical pickup in a DVD-RAM disc drive includes driving a DVD-RAM disc; determining whether a tracking error signal is generated during the driving of the DVD-RAM disc; generating a land/groove signal to discern land tracks and groove tracks of the DVD-RAM disc; determining from which track the tracking error signal has been generated in response to the determination that the tracking error signal has been generated; generating a jump signal in response to a state of the land/groove signal varying; and moving the optical pickup back by ½ of a track in response to the jump signal.

Abstract: In a scanning apparatus, a scanning spot is moved along a path from one track to another track of the information carrier, the scanning spot is accelerated in a first stage of the movement and decelerating in a second stage of the movement. Initially during the movement a displacement of the scanning spot is derived from a first and a second position signal. The velocity of the scanning spot is estimated during movement along the path. After the estimated velocity of the scanning spot exceeds a first predetermined value during the first stage of the movement, the displacement of the scanning spot is derived from the first position signal and independent from the second position signal, during movement along the path. After the estimated velocity has decreased below a second predetermined value during the second stage of the movement, the displacement of the scanning spot is again derived from both the first and the second position signal, during movement along the path.

Abstract: A tracking control system for outputting a tracking control signal for an optical pickup including a plurality of light detecting sections each of which converts reflected light of a light beam applied to an optical disk into an electric signal, and outputs the signal, includes: a balance correction amount calculating section for obtaining, as a balance correction amount, a value by which a differential phase tracking error signal based on each output of the light detecting sections should be shifted in accordance with a direct-current component of a differential amplitude tracking error signal based on each output of the light detecting sections such that a direct-current component of the differential phase tracking error signal approaches a given reference potential; a balance changing section for shifting the differential phase tracking error signal in accordance with the balance correction amount; and a tracking control section for generating the tracking control signal in accordance with the differential

Abstract: Optical disc systems and methods for controlling movement of an optical pickup to an innermost perimeter of an optical disc using track information are provided. For example, an optical disc system includes an optical pickup that includes a tracking actuator, a focus actuator, and an objective lens and radiates a laser beam onto the optical disc to detect light reflected from the optical disc. The optical disc system also includes a radio frequency amplifier, a sled motor, a servo driver, and a servo signal processor that includes an optical pickup movement determiner and outputs a servo control signal, the optical pickup movement determiner determining from a track-related signal whether tracks are detected on the optical disc at a current position of the optical pickup and outputting a track determination signal indicating whether the optical pickup has moved to the innermost perimeter of the optical disc, based on the determination result.

Abstract: A method of braking control in rapid track seeking for an optical drive. The optical drive has a pickup head for reading information from an optical disc therein. According to the method, a tracking error signal is obtained in the rapid track seeking motion of the pickup head. A seeking velocity is obtained by calculation according to the tracking error signal. Since the seeking velocity varies, a braking force is determined according to the seeking velocity for braking the pickup head.

Abstract: A method for processing error control for a seeking servo of an optical disk drive includes calculating a “track on” time when control of a pickup head is switched from a seeking servo system to a tracking servo system to start a “track on” process, moving the pickup head to the center of a movable range when the “rack on” process is not completed in a predetermined time, and switching control of the pickup head to the tracking servo system to start another “track on” process.

Abstract: The present invention relates to a track access apparatus and a method by which an optical pick-up unit quickly accesses a destination track of an optical disc by controlling a tracking actuator using a back electromotive force by detecting the vibration of an objective lens, the position variation, and the distortion of an actuator which occur when the optical pick-up unit is moved across the tracks of the optical disc at a high speed.

Abstract: A servo system with a multi-track seek algorithm is presented. The multi-track seek algorithm detects zero crossings in a tracking error signal, counts the number of zero crossings to form a count, and calculates a reference velocity from the count. The algorithm also determines a time period between successive zero crossings, calculates a velocity from the time period, calculates a difference signal between the reference velocity and the velocity, and adjusts the control signal so that the velocity follows the reference velocity. The reference velocity can follow a velocity profile with acceleration portions, coasting portions, and deceleration portions which move an optical pick-up unit from a starting position to a target position.

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: The present invention provides a method for controlling a focus speed of a pick-up head while performing a layer jump operation over a multi-layer optical disk in an optical information reproducing apparatus. The optical information reproducing apparatus includes the pick-up head, an actuator and a counter. The pick-up head has an objective lens positioned over a first focus of the multi-layer optical disk and in response to a signal reflected from the multi-layer optical disk, will generate a RF level signal and. The actuator is electronically connected to the pick-up head for driving the objective lens to perform the layer jump operation in response to a kick pulse signal. The counter generates a counter value in response to the kick pulse signal.

Abstract: In a configuration in which side beams scan in positions that are offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of an optical disk, a differential signal is generated from push-pull signals of the return lights of the side beams to generate a track-cross signal. In a configuration in which side beams scan in positions that are offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of an optical disk, far-side or near-side light detection results of the return lights of the side beams are processed and computed with respect to a push-pull signal of the return light of the main beam.

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 disk drive comprises an actuator servo control system including at least one disk, an actuator structure comprising at least transducer head for writing and/or reading data from the disk and providing a transducer head position error signal (PES), and a servo compensator applying a servo control algorithm to the PES to produce a servo control signal. An adaptive elliptic notch filter controller is adapted to analyze the PES for a transducer head at a disk track radii, identify resonant disturbances present in the PES, select two adjacent resonant disturbances having first and second frequencies, ascertain coefficients of at least a fourth-order elliptic notch filter transfer function having first and second zero-notches with frequencies substantially at the first and second resonant frequencies, apply the at least fourth-order elliptic notch filter transfer function with the ascertained coefficients in the servo system to thereby substantially attenuate the selected adjacent resonant disturbances.

Abstract: A method and apparatus for canceling noise from track cross signal includes binarizing the track cross signal with reference to at least two reference values, and removing noise from the binarized track cross signal based on a command speed according to which a tracking actuator moves a pickup. Accordingly, it is possible to remove noise from a track cross signal so as to obtain information regarding precise speed of track searching or position on the track, irrespective of the searching speed.

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: In track jumping operation, an acceleration/deceleration pulse generation portion measures the TE signal amplitude during track jumping, and modifies the acceleration/deceleration time of the acceleration/deceleration pulse according to the measured amplitude to drive a tracking actuator. Also, the acceleration/deceleration pulse generation portion measures the movement time from the start of acceleration until a certain location is reached, and modifies the peak value of the deceleration pulse according to the measured time to drive the tracking actuator.

Abstract: The invention relates to caching data in a data processing system including a host computer and a storage subsystem including at least one customer disk and a cache disk. Write transactions are received specifying data to be written to at least one customer disk and these are cached in a volatile memory of the storage subsystem and written to the cache disk. The transaction data is written sequentially to the cache disk when available. In the intervening periods (i.e., when no transaction data is available), padding data is instead written sequentially to the cache disk.

Abstract: A servo system with a multi-track seek algorithm with an accelerated servo function for regaining a closed tracking loop is presented. Upon completion of a multi-track seek operation, a gain of a tracking servo system is increased for a predetermined number of cycles. In some embodiments, the increased gain leads to a more aggressive track closing operation.

Abstract: A disk apparatus 10 includes a DSP 36. The DSP 36 controls each circuit component under the instruction from an MCU 44. When a braking pulse is applied to a driver 38b at the end of a jump, a corresponding tracking actuator control voltage is supplied to a tracking actuator 16. Then a DSP core 36a determines whether the TE signal level becomes equal to or below the predetermined value within a predetermined period shorter than the zero crossing cycle of the TE signal. In case the TE signal level does not become equal to or below the predetermined value within the predetermined period, the DSP core 36a determines that the travel direction of an objective lens 14 with respect to a disk 22 is reversed and applies a correction pulse having a polarity opposite to that of the braking pulse thus accelerating the objective lens 14.

Abstract: Device and method for detecting a non-writable region of an optical recording medium, wherein a read channel 1 signal and a read channel 2 signal are sliced at respective slice levels to produce header mask signals, and a header region which is a non-writable region is determined for the header mask signal taking the slice levels and written/unwritten regions ion the disk, whereby permitting stabilization of servos because servo error signals, such as a tracking error signal, and a focus error signal can be held exactly at a header region even if the servos are not stable, that prevents deterioration of a data quality in writing and reading, and permitting to shift an optical pickup to a desired position and accurate measurement of an amount of eccentricity because there is no influence of the header in a track jump and a disk eccentricity measurement.

Abstract: A focusing control apparatus includes method for an optical pickup having an objective lens and an aberration correcting unit includes the steps of detecting an amount of focus error of a light beam and an amount of aberration of the reflected light beam to generate a focus error value and an aberration value; controlling a focused position of the objective lens on the basis of the focus error value while adjusting an amount of aberration correction of the aberration correcting unit on the basis of the aberration value, and performing a focus jump from one recording layer to another recording layer after adjusting the amount of aberration correction of the aberration correcting unit for the another recording layer.

Abstract: A method for reducing the turn-back in response to an actual and a target speed in an optical storage device. The method includes the following steps: (a) determining whether the turn-back of the optical pickup head occurs; if the turn-back occurs, step (b) is executed and if the turn-back does not occur, a speed error is obtained according to the target speed and the actual speed; (b) determining whether the number of turn-back tracks is greater than a default value; if the number of turn-back tracks is not greater than the default value, the speed error is set to zero and if the number of turn-back tracks is greater than the default value, the speed error is obtained according to the target speed and an inversion of the actual speed and the actual track-seeking direction is inverted to correspond to the target track-seeking direction.

Abstract: The invention provides a method of adjusting a tracking location in an optical storage device. The method is illustrated as follows. Firstly, the optical pickup head reaches the first tracking location according to a tracking error (TE) signal. Secondly, the optical pickup head is finely moved to an adjusted tracking location where the value of the amplitude of RFRP signal is maximum. The method can avoid wrong tracking location by simply based on the TE signal, then enable the optical pickup head to reach the correct track center and improve the quality of data reading.

Abstract: A track-jump controlling apparatus that controls track-jump operations over disks complying with various DVD data formats includes a quad photodetector having quadrants B1 to B4, a DPDTE signal generator 13 for generating DPD tracking error signals, a push-pull signal generator 14 for generating push-pull signals, and a TZC signal generator 15 having a selector switch 15a for switching the path between the DPDTE signals and the push-pull signals and a comparator 15b for generating TZC signals. In order to prevent failure to obtain proper TZC signals in a seek operation with respect to a DVD-RW, etc. involving passage over an unrecorded area during reproduction, for example, the selector switch 15a is switched to the push-pull signal side to prevent track counting failure associated with the track-jump operation with respect to the DVD-RW.

Abstract: An apparatus and method conducts a high-speed search on an optical medium having a plurality of tracks on which information is recorded. At least a first light spot and a second light spot are directed by the apparatus onto the optical medium. The light spots traverse across the tracks in one of a first direction and a second direction. A photodetector unit receives a reflected component of the first light spot to form a first electrical signal and a reflected component of the second light spot to form a second electrical signal. Digital shaping circuitry respectively converts the first electrical signal and the second electrical signal into a first digital signal and a second digital signal. A quadrature detector is configured to receive the first digital signal and the second digital signal. The first digital signal and the second digital signal are arranged in a quadrature relationship to each other.

Abstract: Servo circuitry for counting tracks on an optical storage medium is disclosed. The servo circuitry is comprised of a differential phase detector and a digital phase-locked loop. The differential phase detector receives four signals from a quad-photodetector and correlates the four signals into a first correlation signal and a second correlation signal. The digital phase-locked loop receives an adjustable amplification value along with the positive correlation signal and the negative correlation signal. The digital phase-locked loop generates a track count signal based on the adjustable amplification value, the positive correlation signal, and the negative correlation signal. The track count signal represents track crossings on the optical storage medium. The digital phase-locked loop advantageously has an adjustable bandwidth based on the amplification value. The servo circuitry count tracks on both CDs and DVDs.

Abstract: A tracking error detecting apparatus converts photoelectric current obtained by a photo detector into voltage signals at current/voltage conversion circuits, and adds the voltage signals to generate two signal series at adders. The two signal series are digitalized at analog to digital converters, are subjected to interpolation processing at interpolation filters and have their zero cross points detected by zero cross point detector circuits respectively. A phase difference between the zero cross points of the two signal series is detected by a phase difference detector circuit, and the phase difference is subjected to band restriction by a low pass filter, thereby to obtain a tracking error signal. The tracking error detecting apparatus is capable of coping with speed doubling of an optical recording/reproducing apparatus and density enhancing of an optical recording medium with a small size and at low cost.

Abstract: A method and device of determining the slice level of a radio frequency ripple (RFRP) signal for performing a tracking operation in a tracking controller of an optical storage device. The optical storage device receives a tracking error (TE) signal, a radio frequency center (RFCT) signal, and the RFRP signal, and then outputs a TE_input signal related to the slice level. The method includes the following steps: a. obtaining a count value when the absolute value of the TE signal is smaller than a threshold value; otherwise, resetting the count value; b. executing step c when the count value is smaller than a predetermined count value; otherwise, outputting the TE signal as the TE_input signal; and c. outputting the TE signal as the TE_input signal when the RFRP signal is greater than the RFCT signal; otherwise outputting a peak value of the TE signal as the TE_input signal.

Abstract: An information storage device having a uniaxial tracking mechanism as a pickup which can perform a stable track pull-in operation is provided. A deceleration pulse amplitude á supplied to a tracking actuator is determined from a linear function á=K(V−V0) of a detected movement velocity of a beam in the vicinity of a target track. The deceleration pulse amplitude is divided into two, and is supplied to the tracking actuator on two different occasions.

Abstract: The present invention relates to a layer jump control apparatus of a multilayer disk and a method thereof, when a layer jump request between record layers of the multilayer disk is inputted from outside, a sled, a tracking, and a focusing servo are converted into inactive state, a microcomputer sets an operation voltage of an inner focus lens of an optical pickup to allotted ports in order to transfer the focus lens vertically to the layer jump request direction. The present invention is capable of jumping accurately and rapidly on a request layer of the multilayer disk by jumping on a target layer of the multilayer disk accurately by converting the focusing servo into active state at the jump position of the focus lens on the basis of a FOK signal and a FZC signal detected in accordance with transferring operation, and adjusting vertical transferring speed of an optical pickup by considering minus offset of the optical pickup.

Abstract: An optical disc device with high reliability, which is capable of performing a stable track jumping, is provided. In the optical disc device, a space (time interval) between an address part and the next address part in the address space measuring part 116 inside the DSP 111 is measured, and when the reproduction speed detected in the reproduction speed detection part 117 based on the measuring result is faster than a predetermined reproduction speed, an application timing of an accelerating pulse is switched in the accelerating/decelerating pulse generator 113 such that the application timing of an accelerating pulse or a decelerating pulse is matched with a transit timing in the address part.

Abstract: A method of detecting a servo error, an apparatus therefor, a disk which maintains quantity of a servo error signal, a method of controlling a servo of an apparatus for recording data on and reproducing data from a disk, a method of detecting the tracking error, and a method of detecting tilt error of the apparatus. The apparatus for recording data on and reproducing data from the disk in which a recording area is divided into sectors, each sector has a header for indicating an address, each header has a first header and a second header which are recorded to deviate from the center of the track in opposite directions, and the first header and the second header have address areas in which the addresses of sectors are recorded and synchronous signal areas in which synchronous signals for detecting the address signals recorded in the address area are recorded.

Abstract: In case of pulling a focusing servo in a recording surface 2 of an optical disk 1, the focusing servo is pulled in a substrate surface 3 of the optical disk 1, thereafter, a focusing servo pull-in position is allowed to transfer to the recording surface 2 of the optical disk 1 by means of a focusing jump control circuit 12, whereby a focusing servo pull-in operation is made upon the recording surface 2, while an objective lens retreating control circuit 14 outputs a control signal in a direction along which the objective lens 4 is allowed to go away from the optical disk 1 for a predetermined time, and then, another control signal in a direction along which the objective lens 4 is allowed to be close to the optical disk 1 for a predetermined time in the case when an abnormal focusing servo pull-in operation was detected.

Abstract: There is provided an optical recording medium processing apparatus comprising: a carriage including a lens to guide a light beam to a recording medium for moving in a direction extending across tracks on the recording medium; a detector for detecting a TES; and a controller for moving the carriage across the tracks from an innermost circumferential position of the medium or its vicinity, for counting the number of tracks in accordance with a TZC pulse generated by the TES having a predetermined level or higher detected by the detector, and after the carriage has been moved for a predetermined period of time, for positioning the light beam spot on a target track in accordance with the counted number of the tracks. Therefore, the initial seek control process, whereby the carriage is moved from the innermost circumferential position of the medium or its vicinity to the center, can be performed without a position sensor.

Abstract: A disk apparatus has a head, a positional signal detection section that detects a track of a medium, a feedback control section which computes a control signal for moving the head from the location of a positional signal generated by a position signal detector, and a learning control section which generates and stores an unknown function for one disk rotation, which includes a periodic disturbance, in a memory which is comprised of N number of memory cells by a learning algorithm as an approximate function which is approximated by the height of each of several blocks in the medium. The learning control section reads the learning result of the two memory cells at locations which are moved forward for a predetermined amount of time, and interpolates the results so as to generate a periodic disturbance compensation signal.

Abstract: A disk reading apparatus includes a binarizing unit 5 for binarizing a tracking error signal 21 with a hysteresis width and for generating a track count signal 22, a jump unit 8 for causing track-jump on the basis of the track count signal 22, a malfunction detecting unit 9 for transmitting a malfunction signal 24 when level inversion occurs to the track count signal 22 while follow of the track is being implemented, and a control unit 15 for widening the hysteresis width when the pickup 1 is caused to follow the track, and for narrowing the hysteresis width when the pickup 1 is caused to track-jump.

Abstract: A method for counting a number of tracks of an optical disc in an optical disc system. The optical disc system includes an optical pickup, a light source, and a plurality of optical sensors. The method includes emitting a light beam to the optical disc from the light source, detecting light reflected from the optical disc by the optical sensors, and generating a tracking error signal according to detected signals of the optical sensors while the optical pickup moves along a radial direction of the optical disc. The method further includes generating a tracking error zero crossing signal according to the tracking error signal, generating a peak detecting signal according to the tracking error signal, generating a pseudo radio frequency zero crossing signal according to the peak detecting signal, and generating a track count signal according to the pseudo frequency crossing signal.

Abstract: In an apparatus for reading from and/or writing to an optical recording medium (7), it is desirable, in particular in the case of track jumps, to detect the direction of the track jump, i.e. the direction of movement of an objective lens (6) of the apparatus relative to the optical recording medium (7) in order to be able to carry out corresponding track regulation. For this purpose, and also for determining the number of tracks crossed by the scanning beams (14-18), it is proposed to determine the number of zero crossings and also the phase difference between at least two error signals derived from the reflected scanning beams.

Abstract: A method and apparatus for control of a feed motor for an optical disk reproducing/recording device. If the center of an objective lens deviates from the optical axis beyond a predetermined level, a stepping motor driven by digital pulses moves the optical pickup so that the deviation decreases. Since the stepping motor is precisely controllable by the drive pulses, stable tracking capability is attainable even in the case where operating environment such as temperature changes. The method in accordance with the present invention comprises the steps of detecting the distance between the center of an objective lens and an optical axis, checking whether the detected distance exceeds a prescribed range, and changing the magnitude of each drive signal by a microstep depending upon the check result and applying the drive signals to a sled motor for moving an optical pickup containing the objective lens.

Abstract: A tracking error signal compensation device for removing an offset of a tracking error signal to be used for a tracking servo control includes: a low pass filter that extracts a direct current component and a low frequency component whose frequency is lower than a reference frequency from the tracking error signal, and generates a detection signal including the extracted direct current component and the extracted low frequency component; a determination device that determines whether or not a frequency of the tracking error signal is lower than a reference frequency; a holding device that generates a hold signal by holding the detection signal generated by the low pass filter, when the determination device determines that the frequency of the tracking error signal is lower than the reference signal; a detection device that detects the offset of the tracking error signal by using the detection signal and the hold signal; and a removing device that removes the offset detected by the detection device from the tr

Abstract: An apparatus for use in an optical disc includes an optical disc and an optical branching unit irradiating a main light beam and a sub-light beam, wherein the sub-light beam includes a optical aberration in a direction on a track of the optical disc. The apparatus further includes a photodetector including a plurality of portions receiving and processing the main light beam and a plurality of portions receiving and processing the sub-light beam. A track error signal detector detects a track error signal from the portions receiving the main light beam. A track cross signal detector detects a track cross signal from the portions receiving the main light beam and from the portions receiving the sub-light beam. A signal processor further compares the track error signal with the track cross signal to detect the seek direction of a light spot formed on the optical disc.

Abstract: Apparatus for scanning a rotating information carrier having mutually substantially parallel tracks for the recording of information. The apparatus includes a transducer for scanning the information carrier and for generating a position signal which indicates a position of a scanning point scanned by the transducer. The apparatus further includes means for rotating the information carrier about an axis and means for moving the scanning point in a radial direction with respect to the axis. The apparatus has a scanning mode in which the scanning point jumps both from one track to another in a first radial direction and from one track to another in an opposite second direction during reading or writing of a file.

Abstract: An optical disc system for efficiently controlling a sled motor is provided. The optical disc system has a sled motor for moving an optical pick-up; a digital servo core to generate a first and a second sled control signal; a microcomputer for generating a selecting signal, a third and a fourth sled control signal for controlling the sled motor; a first and a second selecting unit for receiving the selecting signal and selecting and outputting one of the first and third sled control signals and selecting and outputting one of the second and fourth sled control signals, respectively; and a third and a fourth selecting unit for respectively receiving the outputs of a first and second digital-to-analog converters and generating the respective outputs of the first and second digital-to-analog converters in response to the selecting signal to the sled motor.