Abstract: A data recording method according to one aspect of this invention comprises specifying a plurality of regions with different radial positions on a disk, and detecting the tilt amounts of the respective regions with respect to the optical axis of a light beam on the basis of a focus control signal used to just-focus the light beam on a recording surface of the disk, calculating tilt correction amounts for the respective regions in accordance with the tilt amounts of the respective regions, correcting a tilt of the optical axis with respect to a predetermined region on the basis of the tilt correction amount corresponding to the predetermined region, and recording data on the predetermined region while the tilt of the optical axis with respect to the predetermined region is corrected.

Abstract: An optical disk device comprises position control portions which carry out position control of at least one of an optical head and an objective lens based on a detection signal from the optical head, and disturbance learning portions which reduce a compensation gain of the position control portion in a range in which servo control is not deviated, and detect disturbance information of the optical disk to store it as learning disturbance information. Fine disturbance information can be reliably learned because the information is not affected by the compensation gain.

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: In the tilt correction method, information about inclination of an object lens relative to an information recording medium is acquired. A direct current signal Sdc for correcting the inclination is produced based on the information. An alternating current signal Sac having a prescribed signal characteristic is superposed onto the direct current signal Sdc to produce a driving signal Sout. The driving signal Sout is supplied to a driving mechanism to correct the inclination of the object lens against friction.

Abstract: An apparatus for scanning a track on a record carrier has a head (22) and front end circuitry (31) for scanning the track and generating scanning signals. A detection unit (32) detects anomalies in the scanning signal, for example for adjusting a tracking servo. The detection unit (32) calculates a mean value of the scanning signal and compares the mean value to a threshold for providing an anomaly detection signal (33). Further a classification unit (34) provides an indication of the type of defect for determining a suitable responsive or corrective action.

Abstract: A device capable of detecting vibration/shock includes a laser diode capable of transmitting a laser beam and a vibration/shock detector capable of detecting vibration or shock, wherein the laser diode and the vibration/shock detector are formed on one chip.

Abstract: An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including tracks having prescribed grooves; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals; and a light division element for dividing a reflected light reflected by the information memory medium.

Abstract: In an optical head apparatus for an optical recording medium, including a light source for emitting a light beam, an objective lens for focusing the light beam at the optical recording medium and receiving a reflected light beam from the optical recording medium, and a photodetector for receiving the reflected light beam from the objective lens, a unit is provided between the light source and the objective lens to generate a main beam and a sub beam from the light beam. The intensity distributions of the main beam and the sub beam are different from each other, and the sub beam is divided into a plurality of portions having different phase distributions from each other. The photodetector includes photodetecting portions for each of the main beam and the sub beam, thus obtaining a push-pull signal from each of the main beam and the sub beam.

Abstract: Method and apparatus for use in an optical disk tilt servo system of an optical disk drive. The tilt servo system is for adjusting an angle between a surface of an optical disk and a pick-up head of the optical disk drive. The method includes: measuring focusing results of the optical disk at multiple locations and estimating tilt angles, i.e. deviation from the horizontal, of the surface of the optical disk according to a physical model that reflects that the optical disk has different tilt angles at different locations. The tilt servo system is calibrated accordingly.

Abstract: A tilt angle detection device and method which generates, as a first push-pull signal, a difference between light reception signals corresponding to two light receiving surfaces of one side of a photodetector, which are divided along the track tangent direction; generates, as a second push-pull signal, a difference between the light reception signals corresponding to two light receiving surfaces of the other side of the photodetector; and generates a tilt signal that indicates a tilt angle defined by a normal on the recording surface of the optical recording medium at a position of irradiation of the laser beam and the optical axis of the laser beam in accordance to a difference between amplitudes of the first and second push-pull signals.

Abstract: An optical disk apparatus has an optical head having a lens of converging light from a light source onto an optical disk and a photodetector for detecting the light thus converged and then reflected from the optical disk. A tracking error signal is generated in order to perform tracking control on the basis of the detected light. A disk tilt DT is detected to indicate the amount of tilt of the optical head relative to the optical disk. A calculation is performed to calculate a lens shift LS indicating the amount of shift of the lens relative to the optical head, according to a predetermined rule on the basis of the generated tracking error signal and the detected disk tilt DT.

Abstract: An information recording apparatus includes: an information recording part performing information recording on a recording medium divided into a plurality of sectors each including a plurality of information units; a prediction part detecting or predicting an occurrence of a recording failure during the information recording; a suspension control part suspending the information recording at the present one of the information units of the recording medium and storing suspension information indicating a suspension position where the information recording is suspended; a determination part determining whether the recording failure is over after the suspension of the information recording; and a resumption control part causing the information recording part to resume the information recording at a position determined based on the suspension information so that information is continuously recorded on the recording medium over the suspension position.

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: At the initialization, a tilt mechanism 9 is activated in a state where an optical pick-up 3 is fixed, and set up at a position where an E-F phase difference obtained in a signal processing portion 4 is 180°. Thereafter, a reproducing operation is started. During the reproducing operation, the tilt mechanism 9 is not activated and the focus control is made with the focus servo by moving the optical pick-up 3 up or down, while the level of a focus error signal is within a certain range. Further, if the level of focus error signal is beyond the certain range because the optical disk 1 is greatly inclined, the tilt mechanism 9 is activated to cause the optical disk 1 to come closer to the optical pick-up 3 to enable the control of the focus servo.

Abstract: In a state in which an optical disk having a warping amount equal to or smaller than a predetermined amount is attached to a spindle motor, an output of tilt detection result is stored as a reference tilt value in a memory. At this time, a control signal corresponding to a driving inclining amount in which inclining the objective lens by the driving inclining amount minimizes the inclination of the objective lens from the attached optical disk is stored as a reference control value in the memory. An CPU a multiplies difference between a detection result of the tilt detection and the reference tilt value by a control constant, and adds the reference control value to the multiplied difference, and provides the thus-obtained control signal to a tilt driving circuit.

Abstract: A tilt of a light beam to be radiated onto an information recording disk is corrected without using a dedicated tilt sensor. The correction is performed based on the characteristic that an offset amount between a tilt amount maximizing an RF signal amplitude and a further tilt amount maximizing an LPP signal amplitude is constant and independent of positions on the same disk. A pre-pit signal indicative of an existence/nonexistence of a pre-pit formed on the disk is produced from returned light of the light beam, while an RF signal is produced from bits of information recorded on the disk on the basis of the returned light. An optimum tilt-correcting amount is decided by making use of a relationship between the pre-pit signal and the RF signal at a particular tilt amount. The tilt amount is corrected using the optimum tilt-correcting amount.

Abstract: A screw axis and a guide axis are provided in parallel in a base plate, and both sides of an optical pickup are supported by the screw axis and the guide axis. The base plate is provided with a first supporting portion for supporting one end portion of the screw axis in a side of a driven gear, and a second supporting portion for supporting another end portion of the screw axis. The first supporting portion has a first elastic member which presses the screw axis in an axial direction of a turn table, and the second supporting portion is provided with a second elastic member and a tilt adjusting screw which are opposed to each other with holding a collar therebetween in the axial direction of the turn table. One end portion of the screw axis is rotatably fitted to the collar, and the collar is pressed toward the tilt adjusting screw by the second elastic member.

Abstract: An apparatus for automatically adjusting tilting of an optical disc drive, having placing parts, a plurality of height measurers, adjusters, a mirror disc, two mirror plates, an autocollimator, a photo detector, and a controller. The optical disc drive is placed on the placing parts. The plurality of height measurers measure heights of two portions of each of the pair of rails. The adjusters adjust the adjusting parts. The mirror disc is mounted on the turntable and spins. The two mirror plates are installed on the pair of rails. The autocollimator radiates parallel light beams onto the mirror disc and the two mirror plates. The photo detector detects focused points of the light beams reflected from the mirror disc and the two mirror plates and passing through the autocollimator. The controller calculates an amount of tilting from a distance between the focused points.

Abstract: To provide a light receiving device, a light detecting device, and an optical signal reproducing device each of which allows one to perform many different computations in detecting aberration amounts and focus error quantities without requiring exact position relations between laser light to be received and light receiving elements, and between the light receiving elements. First and second light receiving elements 43+ and 43? are used which receive condensed light at positions equidistantly spaced from an focal point X before and after the light images, respectively.

Abstract: An apparatus for generating tracking error signals including: an optical detection unit having a plurality of divided light receiving elements to allow beams reflected from a recording surface of the optical disks to be incident; a comparator for outputting after comparing the signals from light receiving elements, which correspond to the set group of the optical detection unit, with the reference signals set for the each group; an error correction unit for correcting and outputting errors if there are any errors after mutual comparison with signals of the groups output from the comparator; a phase-difference detection unit for outputting the signals for each group that correspond to a phase-difference after mutual comparison of the signals of the groups output from the error correction unit; a subtractor for mutually subtracting the signals for each group from the phase-difference detection unit and outputting the tracking error signals.

Abstract: The present invention discloses a method of detecting orientation of an optical disk drive. Firstly, a first moving distance is measured by using a first force driven on a movable optical pick up head of the optical disk drive for a preset period. Next, a second moving distance is measured by using a second force driven on the movable optical pick up head for the preset period, wherein the second force and the first force have opposite direction but the same amplitude. Next, it is determined that the optical disk drive is horizontal orientation when the difference between the first and second moving distances falls within a pre-determined value. Additionally, a first moving time is measured by using a first force driven on a movable optical pick up head for a pre-determined distance.

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: An optical disc system and a method of managing shock while recording or playing data in the optical disc system are provided. The optical disc system includes an optical pick-up unit for applying a laser beam to a track of an optical disc and detecting reflected light, a servo unit for controlling tracking and focus of the optical pick-up unit and a monitoring unit for comparing a monitoring signal, which is output from the optical pick-up unit and the servo unit, with a reference signal and generating a blocking signal and a blocking release signal. Recording or playing of data on the optical disc is stopped in response to the blocking signal, and recording or playing of the data on the optical disc is resumed in response to the blocking release signal based on a state of the optical disc system when recording or playing was stopped.

Abstract: An error signal detection method includes detecting light incident through an objective lens after having been reflected and diffracted from a recording medium, as eight light portions in a matrix including four inner light portions and four outer light portions, wherein the rows and columns of the matrix are parallel to the tangential and radial direction of the recording medium, respectively; calculating a first sum signal by summing a detection signal from at least one outer light portion located in a first diagonal direction, and a detection signal from an inner light portion located in a second diagonal direction; calculating second sum signal by summing a detection signal from an inner light portion located in the first diagonal direction, and a detection signal from an outer light portion located in the second diagonal direction; and comparing phases of the first and second sum signals to detect a tilt error signal.

Abstract: It is an object of the present invention to provide an optical pickup astigmatism adjusting method capable of easily correcting an astigmatism even if the spot shape of a light beam converged on an optical disc is not a true circle. An optical pickup astigmatism adjusting system of the present invention finds an inter-focal distance L0 between a focal position where a light beam is converged in RAD direction and another focal position where a light beam is converged in TAN direction, and a further inter-focal distance L45 between a focal position where a light beam is converged in a direction inclined 45 degrees from RAD direction and another focal position where a light beam is converged in a direction inclined 45 degrees from TAN direction, thereby measuring an astigmatism in accordance with the inter-focal distances L0 and L45. Then, an installation angle of a reflection mirror is adjusted in accordance with the inter-focal distances L0 and L45, thus correcting the astigmatism.

Abstract: An optical disc apparatus has a crosstalk level determining section which, when a track jump is performed without applying a tracking servo, determines whether a crosstalk component is larger than a predetermined level or not. If the crosstalk level determining section determines that the crosstalk component is larger than the predetermined level, a crosstalk correcting section performs a calculation for reducing the crosstalk component. If the crosstalk level determining section determines that the crosstalk component is not larger than the predetermined level, the crosstalk correcting section does not reduce the crosstalk component.

Abstract: A DC voltage value is obtained at least at an inside position, an intermediate position, and an outside position on a disc (1) from a drive signal that is supplied to a focusing coil (4) built into an optical pickup (2). From the DC voltage values is obtained a relationship of a position between the respective positions and the DC voltage value, and this relationship is stored into a memory circuit (12). Then, during recording or playback, the DC voltage value that is calculated on the basis of the recording or playback position of the signal at that time and the AC signal included in the drive signal that is supplied to the focusing coil (4) are added to create a signal to be supplied to a tilt adjustment coil (6).

Abstract: An optical disk apparatus includes a rotary driving unit rotating an optical disk which is flexible, an optical pickup irradiating light upon a recording surface of the optical disk on which writing/reading of information is performed, a stabilizing unit stabilizing vibration of the optical disk in a rotary axial direction by using pressure difference of air flow at least on a portion where writing/reading is performed, and being disposed on a side of the optical disk opposite to a side on which the recording surface is provided, and a control-adjustment unit analyzing a value of a tracking error signal of the optical disk obtained by scanning along a groove of the optical disk with use of the optical pickup, comparing the analyzed value of the tracking error signal of the optical disk and a value priorly obtained by scanning along a groove of a standard disk prepared beforehand, and adjusting a positional relation between the optical disk and the stabilizing member in a three dimensional space according to t

Abstract: A Differential Phase Detecting (DPD) tracking error generating section generates a DPD tracking error signal from a plurality of sense signals supplied from an optical sensor. A Push Pull (PP) tracking error generating section generates a PP tracking error signal from a plurality of sense signals supplied from the optical sensor. The amplitude of each of the DPD tracking error signal and PP tracking error signal is adjusted suitably under the control of a CPU. The suitably adjusted signals are added by an adder, thereby generating a tracking error signal.

Abstract: A circuit for generating tracking error signal using differential phase detection, comprising a quadrant photodetector for receiving optical signal and inducting splitting signal A, splitting signal B, splitting signal C and splitting signal D, two adders for generating group signal (A+C) and group signal (B+D). A plurality of equalizers for receiving, equalizing and amplifying splitting signal A, splitting signal B, splitting signal C, splitting signal D, group signal (A+C) and group signal (B+D). A plurality of phase detectors for receiving the output of equalizers and comparing phase difference of splitting signal A and group signal (A+C), group signal (A+C) and splitting signal B, splitting signal C and group signal (B+D), and group signal (B+D) and splitting signal D, and outputting a plurality of adjustment signals respectively. A circuit for eliminating the phase difference by adding and subtracting some adjustment signals with same phase difference.

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: A tilt servo control device of an apparatus for recording information on and reproducing information from an optical recording medium set in the apparatus, the apparatus comprising an optical system for leading a laser beam emitted from a light source to a recording surface of the optical recording medium and a laser beam reflected by the recording surface of the recording medium to a photo detector and a read signal generator for generating a read signal in accordance with an output signal of the photo detector. The tilt servo control device determines a type of the optical recording medium, generates a tilt drive signal so as to reduce a tilt angle at a position of the laser beam irradiating the recording surface and an optical axis of the laser beam by a method for generating a tilt drive signal corresponding to the recording medium type, and drives a tilt angle adjuster for adjusting the tilt angle in accordance with the tilt drive signal.

Abstract: A method of tracking error correction, primarily for utilization in optical disc drives using single beam optical pick-up heads. Delinearization in the tracking servo of a single beam optical pick-up head, contributed to by inherent design properties, is minimized by extracting a value proportional to a tracking error signal offset component from a tracking servo demand signal, applying a scaling factor to match the scaling applied to the tracking servo demand signal with scaling applied to the amplified tracking error signal, and subtracting the product of this function from the source signal i.e. the tracking error signal. The modified source signal, following this operation, has a reduced order of tracking error offset.

Abstract: A tilt control apparatus includes an orthogonal shift detector (9) which detects an orthogonal shift by comparing a pair of a plurality of tap coefficients (C1, . . . , C7) of a FIR filter and generates an orthogonal shift signal, and an actuator varies the inclination of the optical axis of the light beam to correct the orthogonal shift, and a tilt controller (10) controls the drive of the actuator in accordance with the orhogonal shift signal to minimize the orthogonal shift. In the information recording operation, the orthogonal shift obtained based on a recording track is previously stored in a temporary storage portion and the stored orthogonal shift is used to conduct the tilt control.

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: A controller configures a balance position of a tracking error signal at a point at which an error rate indicates a minimum value while the balance position of the tracking error signal from an optical pickup is shifted from the center in reproducing the optical disk. Therefore, even when a pit on the track of the optical disk is asymmetrical with respect to the center, the error rate in reproducing the optical disk is reduced and the precision of the reproducing signal is enhanced.

Abstract: The present invention provides a control loop bandwidth adjusting system for adjusting a control loop bandwidth of an optical reproducing device. The optical reproducing device comprises a data signal processing circuit, which uses the control loop bandwidth to process the data signal. The control loop bandwidth adjusting system comprises a control loop bandwidth generator for generating the control loop bandwidth and a control loop bandwidth according to whether a defect signal corresponding to the defect data is received or not. If the control loop bandwidth adjusting module receives the defect data entry signal, the defect data duration signal, and the defect data exit signal, the control loope bandwidth is adjusted to a first bandwidth value, a second bandwidth value, and a third bandwidth value respectively.

Abstract: An optical disc apparatus in which the inclination of an optical axis of laser light relative to an optical disc is adjusted. When data is recorded, laser light is irradiated at recording power in mark periods and irradiated at reproducing power or erasing power in space periods. Immediately after the beginning of the mark periods, no pits are ye formed even though recording power is applied and the amount of reflected light has a level corresponding to the inclination of the optical axis of laser light relative to the optical disc without influence exerted by the pits. Also in the space period, the amount of reflected light has a level corresponding to the inclination of the optical axis of laser light relative to the optical disc. By sampling the reflected light signal at the instant following to the beginning of the mark period or space periods, the inclination is adjusted so as to maximize the sampled signal level.

Abstract: A light-converging optical system has an objective lens arranged at a position to be opposite to an optical information recording medium and including at least one plastic lens, and an aberration correcting element provided on an optical path between the light source and the objective lens and structured by two groups of a positive lens and a negative lens both being a plastic lens. At least one of the positive lens and the negative lens has at least one diffractive surface on which a diffractive structure is formed and a total paraxial power of the aberration correcting element has a temperature dependency satisfying a formula of: PT1<PT0<PT2, or PT1>PT0>PT2, where PT0, PT1 and PT2 are the total paraxial power (mm?1) of the aberration correcting element under the temperature of 25° C., ?5° C. and 55° C. respectively.

Abstract: A system and method for adjusting optical drives. Rotating disc datum, and leader pin datum, must be adjusted to a specific position during a packaging process. An autocollimator according to the present invention senses tilt and sway of the rotating disc, outputting a first bright spot through a switch box to a monitor. In addition, an optimum tilt angle of the optical pickup head is obtained by a reader through calculation by a host, outputting a second bright spot through the switch box to the monitor. Therefore, the first bright is coincided with the second bright spot by a adjustment mechanism and according to picture switch by the switch box, reading optimum tilt angle adjustment. Furthermore, individual tilt angle of each optical pickup head is calculated by a host for satisfying adjustment of different tilt angles with different optical paths in reading CD and DVD discs.

Abstract: An aberration correcting unit is provided for correcting an aberration of a light beam radiated onto an object to be detected and then reflected from the object. This unit comprises an aberration correcting device comprising a first corrector configured to correct the aberration of the light beam radiated onto the object; and a second corrector configured to correct the aberration of the light beam reflected from the object and to divide the reflected light beam into a plurality of light beams. The aberration correcting unit further comprises a first driver configured to drive the first corrector and a second driver configured to drive the second corrector.

Abstract: Techniques for reading data from a storage medium (150) having a high track density prone to adjacent track interference are disclosed. One or more sensing elements (120) are used to extract data stored on adjacent tracks. Multiuser detection (130) is then used to detect/decode a single track that is closely spaced to its neighboring tracks, resolve interference from adjacent tracks, or to simultaneously detect/decode multiple adjacent closely packed tracks.

Abstract: The astigmatic aberration in an optical system is to be adjusted. Specifically, in an optical disc device on which can be selectively loaded a first optical disc having a first index of double refraction or a second optical disc having a second index of double refraction larger than said first index of double refraction, and which includes a liquid crystal device 31 between a light source 11 and an objective lens 15 converging a light beam radiated from said light source on the optical disc 2 loaded on the optical disc device, the voltage applied to the liquid crystal device 31 is adjusted to correct the coma aberration or the astigmatic aberration for the first disc or the second disc, respectively.

Abstract: Tilt (?(r, ?)) is measured in a measuring location (P(r, ?) optical disc (2). A pivotable objective lens (34) is brought to a first focus measuring location such as to focus a light beam (32) in a first anchor point (P1(r??r1, ?))having the same angular coordinate ? as said measuring location (P(r, ?)) and having a small radial distance ?r1 from said measuring location. The objective lens is brought to a second focus measuring location such as to focus the light beam in a second anchor point (P2(r+?r2, ?)) having the same angular coordinate ? as said measuring location and having a small radial distance ?r2 from said measuring location, wherein said first and second anchor pints are located on opposite sides of said measuring location. Tilt in said measuring location is calculated from the coordinates of said two focus measuring locations of said objective lens.

Abstract: An optical disk device and a tilt correction method capable of high precision tilt correction with a smaller number of measurement positions are provided. Prior to data recording and reproduction, a number of measurement positions are set in the radial direction on an optical disk with intervals between two adjacent measurement positions shorter and shorter from the inner region to the peripheral region of the optical disk. The tilt at each of the measurement positions is measured, and the resulting tilt data are stored in a memory. The tilt data are used for making tilt corrections when recording or reproducing data on the optical disk.

Abstract: Method and apparatus for reducing effect of jitter is described. More particularly, one or more taps of a delay line are selected for a reference clock signal. These selected taps each have an associated index, which is stored, and stored indices are statistically processed to select a tap of another delay line.

Abstract: An apparatus for recording data on and reproducing data from the disk in which a recording area is divided into sectors, includes a reproducing signal generator for generating a reproducing signal including sum signals V1 and V2 of radial pairs, a sum signal RF_sum, and a push-pull signal RF_pp from an optical signal reflected from the disk, a header area detector for generating a header area signal including a header area from the reproducing signal, a first synchronous signal level detector for detecting a magnitude Ivfo1 of a first synchronous signal in the first header by being synchronized with the header area signal, a second synchronous signal level detector for detecting a magnitude Ivfo3 of a second synchronous signal in the second header by being synchronized with the header area signal, and a balance calculator for calculating the balance of the magnitude Ivfo1 and the magnitude Ivfo3.

Abstract: An optical disk read/write apparatus detects a shift in the tilt during a write operation and corrects it before resuming the write operation. Specifically, when the ROPC control signal detector of the optical disk read/write apparatus controlling the write power determines that the write power has exceeded a predetermined value after a control operation, the optical disk read/write apparatus suspends the write operation through control of the laser power and controls the shift in the tilt with the tilt controller before resuming the write operation.

Abstract: A lens actuator includes a lens holder to support an objective lens and having a pair of first side surfaces in a tracking direction and a pair of second side surfaces in a tangential direction, a fixed magnet disposed to confront the second side surface and comprising four regions having approximately the same area and are magnetic, such that magnetic directions of the four regions are perpendicular to a plane including a focusing direction and the tracking direction but are in opposite directions between two mutually adjacent regions, a pair of tracking coils disposed between the second surface and the magnet and having centers located on an outer side of corresponding centers of the four regions in the tracking direction, a focusing coil disposed between the second surface and the magnet and having a center located on an outer side of corresponding centers of the four regions in the focusing direction, and a radial tilt coil disposed between the second surface and the magnet and having a center located on

Abstract: In an optical disk reproducing device capable of rotating an optical disk at a selected one of a plurality of preset linear velocities, vibrations or shock of the device is detected during rotation of the disk, and the linear velocity of the disk is determined based on the result of the detection of the vibration or shock to restrain the vibration and shock within a permissible range. A limit rotational velocity above which the vibration or shock is excessive may be determined during a test conducted each time a disk is inserted, and the linear velocity of the disk during reproduction may be determined such that the rotational velocity does not exceed the limit rotational velocity.