Abstract: An optical disc controller of the present invention servo-controls an optical disc device which comprises a disc motor rotating an optical disc and an optical head emitting a light beam for recording data on the optical disc and/or reproducing data from the optical disc. The optical disc controller comprises: a variable clock output section for outputting a plurality of clock signals of different frequencies, and a control section which receives from the optical head a signal indicating a deviation from a predetermined target value to servo-control the light beam of the optical disc device and performs an operation according to the signal indicating the deviation so as to obtain and output a signal indicating a control amount.

Abstract: A method and device are provided for controlling a beginning point of an optical pick-up unit. The optical pick-up unit moves to a beginning point of an optical disc such as a DVD (Digital Versatile Disc) to execute a servo-tuning function at the beginning point. The method includes a) performing a focus search operation on an optical disc and at the same time determining whether there is a reflection signal from the optical disc; b) after performing the focus search operation, moving the optical pick-up unit toward a predetermined beginning point of the optical disc based on the result of the determining step; and c) based on the reflection signal from the optical disc, determining whether or not the optical pick-up unit has moved to the beginning point of the optical disc while the optical pick-up unit is in motion.

Abstract: The present invention is directed to a drive device comprising an electromechanical transducer (25) attached to one end of a drive shaft (24) and adapted to be expanded and contracted in the axial direction of the drive shaft (24) in accordance with drive voltage to thereby allow the drive shaft (24) to undergo displacement in the axial direction thereof, and an optical pick-up (14) movably supported in the axial direction of the drive shaft (24) and moved along the drive shaft (24) as the result of the fact that the drive shaft (24) is caused to undergo displacement by the electromechanical transducer (25) to apply a drive voltage higher than that at the time of steady transfer to the electromechanical transducer (25) at the time of starting.

Abstract: An optical disc unit 2001 comprises: reflective surface detection means 1010 for detecting a reflective surface; focus control means (1202, 1003, 1009, 1008, 1003, 1012, 1005 and 1204) for performing focus control to a reflective surface so that the distance between the focal point of an optical beam applied to an optical disc 2100 and the reflective surface is within a predetermined error limit; shift means 1007 for shifting the focal point of the optical beam in a direction perpendicular to the optical disc; and control means 1006 for controlling the focus control means and the shift means.

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: A method and device are provided for adjusting a focus bias of an objective lens of an optical pickup for an optical disc using a level of a tracking error signal. The level of the tracking error signal outputted when the optical disc is rotated and driven is detected for a predetermined period of time. An operation of adjusting the focus bias of the objective lens is carried out on the basis of the detected level of the tracking error signal. A focus bias adjustment value is set as an optimum focus bias value at a time when the detected level of the tracking error signal is maximized. In accordance with the method, a period of time for adjusting the focus bias is very short, on the order of “0” to several hundred milliseconds, in comparison with periods of time for adjusting the focus bias in conventional methods, such that the focus bias can be quickly adjusted.

Abstract: A detecting device includes an optical pickup which receives a first reference potential supplied thereto through a transmission line, sets the potential to a second reference potential affected by a noise component in the transmission line, generates detection signals from photodetector on the basis of the second reference potential, and outputs the detection signal and the second reference potential through the transmission line, and differential amplifiers which receive the detection signal and the second reference potential from the optical pickup through the transmission line to output potential difference between the detection signal and the second reference potential. The detecting device can remove the noise from a cable.

Abstract: The optical disc apparatus comprises a convergence lens 12, a light detection device 14 for outputting a first and a second detection signals after detecting reflected optical beam area by area, an actuator 13 for shifting the convergence lens 12, a gain balance circuit 30 for changing a gain balance of the first and the second detection signals, an addition circuit 123 for outputting the addition signal AS after adding the first detection signal to the second detection signal in response to the shift in lens position and the change in gain balance made by the gain balance circuit 30 and the actuator 13, and an addition signal measurement unit 361 and a gain balance adjustment unit 362 operable to obtain the addition signal AS from the addition circuit 123, specify the gain balance that equalizes the detection sensitivities in the respective areas of the light detection device 14 based on the obtained result, and control the gain balance circuit 30 that realizes the determined gain balance.

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: An optical detector for detecting at least three optical beams reflected by an optical information recording medium and outputting an electric signal, the optical detector having three light receiving areas each of which receives a respective one of the three optical beams and each of which has four light receiving surfaces, twelve signal lines to transmit an electric signal obtained on respective ones of the four light receiving surfaces of the three light receiving areas, selected ones of the twelve signal lines connected to the four light receiving surfaces of different ones of the three light receiving areas being joined together within the optical detector, and less than nine signal output lines formed by joining the selected ones of the twelve signal lines extend from the optical detector to a signal processing circuit.

Abstract: The optical disc drive reads and/or writes data from/on an optical disc having an information storage layer. In an optical disc drive 100, light from a light source 3 is focused by a focusing section 1, and each of the peripheral and non-peripheral part of light reflected by the information storage layer is received by a photodetector 4. Then, for each part of light, the drive 100 generates a focus signal and a light quantity signal, and normalizes the focus signal based on the light quantity signal. As a result, it is possible to generate a spherical aberration signal according to a quantity of spherical aberration produced at the focusing position of the light. Hence, the signal is not affected by defocusing and thus it is possible to precisely detect a spherical aberration caused by an uneven thickness of the disc and to detect a spherical aberration with high accuracy.

Abstract: An apparatus for setting an offset in a DVD player includes: an offset measuring unit which measures one or more offset parameters for initial reproducing operations of the DVD player; and an offset setting unit which, when the offset measuring unit measures the one or more offset parameters a number of times, calculates an average value of the measured offset values of the one or more offset parameters and sets, for each of the one or more offset parameters of the DVD player, the average value as a set offset value.

Abstract: In order to generate a lens position signal (LCE), which describes the position of the optical axis of an objective lens (6) of an apparatus for reading from and/or writing to an optical recording medium (7) with regard to the optical axis of the remaining components (2, 3, 4, 5, 8, 9) contained in an optical scanner (21), the application of the DPP method is proposed in accordance with a first exemplary embodiment, wherein a primary-beam error signal (CPP) and a secondary-beam error signal (OPP) are obtained with the aid of the DPP method, wherein the desired lens position signal (LCE) is generated by addition of the primary-beam error signal (CPP) and the secondary-beam error signal (OPP).

Abstract: A recording and/or reproducing apparatus for recording and/or reproducing data on or from an optical disc, in which the tracking error signal format for a recordable optical disc differs from that for a replay-only optical disc. The recording and/or reproducing apparatus includes a read-out processing unit for reading out data from the optical disc, a write processing unit for writing data on the optical disc and a system controller for managing control to verify the recordable optical disc having data recorded by the write processing unit by a reproducing system conforming to the standard for the replay-only optical disc. The recordable optical disc is verified by the reproducing system for the replay-only optical disc.

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: An optical disc drive compatible with optical discs of different types, for example, is provided. For focusing, through an optical system used in common with the different types of optical discs, a laser beam emitted from a selected one of a plurality of light sources disposed apart from each other radially of the optical disc, the optical system is moved radially of the optical disc correspondingly to the selection of the light source for emitting the laser light. Namely, it is possible to prevent the optical property from being deteriorated when a single optical pickup is used in common with such optical discs of different types.

Abstract: An optical disc recording and reproducing apparatus realizes stable tracking control for correcting the displacement of an objective lens caused by gravity depending on the positional attitude of the apparatus.

Abstract: A focus servo compensation apparatus of a pickup reads information from an optical disc and outputs signals indicative thereof. The focus servo compensation apparatus includes an RF processing unit receiving the output signals from the pickup and generating therefrom tracking error (TE) and focus error (FE) signals, a tracking servo, and a focus servo. A system controller of the focus servo compensation apparatus receives the TE and RF signals, turns off the tracking servo, and, while the focus servo is on, determines an initial compensation value for the focus servo based on an average value of the TE signals by applying a predetermined bias adjustment value to an output of the focus servo. When the tracking servo is turned on, the system controller controls a compensation of the focus servo by applying the determined initial compensation value to the focus servo.

Abstract: A recording information reproducing apparatus is disclosed for performing a searching operation. The recording information reproducing apparatus according to the invention is for reproducing recording information from a recording disc on which information data has been divided and recorded into a plurality of concentric zones. The apparatus selects a suitable one of a tracking servo by a sampled servo system and a tracking servo by a continuous servo system in accordance with a zone for reading information data.

Abstract: In an optical disk drive having the structure of rotating an optical disk under the alternative control of CAV or CLV, when the optical disk is rotated under the CLV control, the loop gains for at least one of the focus servo system and the tracking servo system for controlling the operation of the pickup of the optical disk drive are adjusted based on angular velocity detected by an angular velocity detector which is also used for rotating the optical disk under the CAV control, and, when the optical disk is rotated under the CAV control, the loop gains for at least one of the focus servo system and the tracking servo system are adjusted based on linear velocity detected by a linear velocity detector which is also used for rotating the optical disk under CLV control. The above structure enables the effective saving of electricity and cost in the optical disk drive.

Abstract: A device according to the invention for scanning a rotating information carrier (2) comprises a transducer (10) and controller (20, 22) for controlling a scanning parameter of the transducer (10), such as the radial position and the setting of a focus. The controller comprise difference signal generator (20) for generating a difference signal (RE) which is indicative of a difference between a current value and a desired value of the scanning parameter, and correction signal generator (22) for generating a correction signal (SC) in response to the difference signal. The correction signal generator (22) comprise a delay loop (25) having first in first out memory (36) for generating a delayed signal (SDL1) and feedback filter (38) for filtering the delayed signal (SDL1).

Abstract: In a CLV(constant linear velocity) or MCLV(substantially constant linear velocity)-type optical disk apparatus, instability of servo at inner and outer circumferences of an optical disk is prevented by adjusting a servo-loop gain of tracking servo control or focus servo control in accordance with the radial-direction position of an optical spot, i.e., in accordance with the rotation frequency of the optical disk.

Abstract: The present invention relates to an optical disk apparatus which performs information recording or reproduction into/from an optical disk, and provides an optical disk apparatus which makes the amount of optical pickup movement performed before adjustment of a track error signal suited and enables reduction of a start-up time. When a track error signal is subjected to adjustment, it is previously detected in a signal amplitude detecting circuit 17 whether an optical pickup 1 is located in an area where a required track on an optical disk medium 2 exists or not, and a micro processing unit 6 executes the procedure which uses only the necessary but minimum moving time, even when the optical pickup is required to be moved.

Abstract: A focus controller for focusing a light beam and positioning the focused light beam onto a signal recording layer of a signal recording media is disclosed. The controller comprises a light beam focusing means having a numerical aperture of 0.6 or more; a focus controlling means for positioning the light beam focused by the light beam focusing means onto the signal recording layer of the recording media; and an offset adjusting means for adjusting an offset between the focused light beam positioned by the focus controlling means and the signal recording layer of the recording media.

Abstract: A light-pickup device has a constitution in which a microcomputer executes control for applying offset voltage to a focus error signal by changing over connection of an FE offset circuit when a servo-processor kicks focus drive voltage for acceleration in order to change over information recording layers of an optical disk having two information recording layers on a plane thereof. Then, a signal output level at a zone in which no focus error signal is occurred, does not coincide with focus zero cross. Owing to this constitution, the servo-processor detects focus zero cross point of the focus error signal even in a simple circuit structure.

Abstract: The disclosed device is directed towards an optical data storage system. The optical data storage system comprises an optical medium including a servo plane and at least one data plane. A first laser is positioned to generate a servo laser beam and address the servo plane with a first servo focus spot. A second laser is positioned to generate a read-write laser beam and address the data plane with a second read-write focus spot. A first servo system is associated with the first laser and is configured to provide focus and tracking error correction according to servo information associated with the servo plane. A second servo system is associated with the second laser and is configured to provide focus and tracking error correction according to servo information associated with the data plane.

Abstract: An optical information recording and reproducing apparatus for recording and reproducing an information signal on/from both concave portions and convex portions of guide grooves formed on a recording medium is disclosed.

Abstract: With a CD laser, a focusing search is carried out to detect a value CD-FE(pp) which is a difference between a maximum value and a minimum value of a focusing error signal, and to detect a value CD-AS which is a maximum value of a full-added signal. With a DVD laser, the focusing search is carried out to detect a value DVD-FE(pp) which is a difference between a maximum value and a minimum value of the focusing error signal, and to detect a value DVD-AS which is the maximum value of a full-added signal. The value that DVD-FE(pp) is divided by DVD-AS(max), is divided by the value that CD-FE(pp) is divided by CD-AS(max). According to whether the computed result by division is larger or not than a threshold value, it is determined whether the disk 100 is of a CD standard or of a DVD standard.

Abstract: An optical storage device decreases the influence of return light to the laser light source and prevents an increase of power consumption even if high frequency superimposing is performed. The optical storage device applies drive current, to which a high frequency signal is superimposed, to the laser light source, and reads/writes data from/in the storage medium. The high frequency superimposing is set to OFF as a default to save power consumption, and high frequency superimposing is turned ON only when it is judged that servo is unstable, and high frequency superimposing is turned OFF when it is judged that servo is stable.

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: When a run-away phenomenon of an optical disk occurs, a control circuit detects a rotational direction of the optical disk that runs away by comparing an initial track count value and a braking time track count value. The initial track count value is a value calculated by counting track pulses corresponding to a tracking error signal for a predetermined time when a tracking servo is turned off. The braking time track count value is a value calculated by counting the track pulses corresponding to the tracking error signal for a predetermined time, when a brake pulse is applied to the spindle motor.

Abstract: An optical disc reproduction apparatus is provided for permitting appropriate automatic adjustment to a servo control system, particularly a CD and a DVD-ROM having a BCA.

Abstract: An optical reproducing apparatus that uses a hologram laser module and is applicable to a DVD Multi drive, wherein five sub spots of light in total that are most suitable to perform the differential push-pull tracking both for DVD-RAM and for DVD-R/RW are irradiated on the disk, respectively, and influence of several sub spots that are unnecessary in recording and reproducing a disk is canceled out by calculation, to realize an optical head that is compatible with the DVD Multi drive using a hologram laser module, and thereby providing a small-size, high-performance optical reproducing apparatus.

Abstract: An optical disc drive compatible with optical discs of different types, for example, is provided. For focusing, through an optical system used in common with the different types of optical discs, a laser beam emitted from a selected one of a plurality of light sources disposed apart from each other radially of the optical disc, the optical system is moved radially of the optical disc corresponding to the selection of the light source for emitting the laser light. Namely, it is possible to prevent the optical property from being deteriorated when a single optical pickup is used in common with such optical discs of different types.

Abstract: The present invention relates to a device and a method of temperature control for an optical storage and retrieving apparatus. When the internal temperature of the optical storage and retrieving apparatus reaches a predetermined temperature, the temperature control device is able to bid the optical storage and retrieving apparatus steadily retrieve data by lowering the rate of a carry device of the optical storage and retrieving apparatus, or by instructing a servo control device to lower the tracking loop gain, or by lowering the velocity and the braking slope of a data read/write device of the optical storage and retrieving apparatus.

Abstract: A method for controlling an optical pickup head of an optical processing apparatus is provided. A first lead-lag compensator is disabled and a second lead-lag compensator is enabled when the optical pickup head switches from a following mode to a seeking mode. Then, an initial operating factor of the second lead-lag compensator is determined according to a last input value and a last output value of the first lead-lag compensator. An initial kick force of the actuator in the seeking mode is calculated by realizing the last input value and the last output value of the first lead-lag compensator immediately before the first lead-lag compensator is disabled. Finally, the optical pickup head is actuated to perform a seeking operation with the initial kick force.

Abstract: In a disk device, a focus servo activating circuit causes an RF amplifier 3 to amplify a focus error signal within a predetermined gain adjusting range, causes a control circuit 4 to multiply the amplitude of the focus error signal obtained by the RF amplifier 3 by two coefficients to calculate two threshold values, and starts up a focus servo upon the amplified focus error signal passing the two threshold values. The focus servo can be started up normally even for optical disks of extremely low reflectivity.

Abstract: An optical disc drive includes: an optical head with an actuator and a photodetector; a tracking driver outputting a drive signal to the actuator; a first tracking error signal generator for generating a first tracking error signal based on an output signal of the photodetector; first and second lens position control sections for respectively outputting first and second lens position control signals to the tracking driver; and a selector for selectively supplying the first tracking error signal to the first or second lens position control section according to a moving velocity of the optical head during a seek operation. The first lens position control signal is obtained by extracting signal components, of which the frequencies are equal to or lower than a predetermined frequency, from the first tracking error signal. The second lens position control signal is obtained by extracting DC components of the first tracking error signal at on-track points thereof.

Abstract: A servo control apparatus of an optical pickup is provided for reading recorded information from a recording medium and generates a read signal. The apparatus includes an error signal extracting part for extracting an error signal which indicates a deviation amount of a reading position from a target reading position of the optical pickup; a drive part for driving the optical pickup to change the reading position; an equalizer for equalizing the error signal and supplying a drive signal which indicates a driving amount of the drive part; a detecting part for detecting a dropout portion in the read signal; an identifying part for identifying a form of the dropout portion detected in the detecting part; and a controller. The controller performs control to change a gain of the equalizer in accordance with the identified form of the dropout portion.

Abstract: Apparatus and methods are provided for using a single multi-element detector and multi-channel signal conditioning circuitry to simultaneously read multiple tracks from either a CD disk or a DVD disk. The multi-element detector has a staggered arrangement and includes elongated detector elements, so that multiple reading beams reflected from multiple tracks of a CD disk are projected onto the detector, as are multiple reading beams reflected from multiple tracks of a DVD disk. The multi-channel signal conditioning circuitry conditions the signals produced by the multi-element detector, and produces signals for each of the tracks that is simultaneously read, as well as a tracking error signal, a focus error signal, a magnification error signal, and signals useful for reading DVD-RAM disks and for rapidly accessing tracks on an optical disk.

Abstract: In an optical information recording medium having at least two information layer, guide grooves for tracking or sample pits or information pits corresponding to information signals are formed on a surface of a first substrate. A first information layer formed by a thin film for reflecting a portion of a light beam made incident on the first substrate and permitting penetration of a portion of the light beam is formed on a surface of the first substrate. Guide grooves for tracking or information pits corresponding to information signals are formed on a surface of a second substrate. A second information layer having a reflectance higher than that of the first information layer is formed on a surface of the second substrate. Between the first information layer and the second information layer, there is formed a transparent separation layer for positioning the first information layer and the second information layer to be spaced a predetermined distance apart from each other.

Abstract: An optical pickup apparatus which, assuming that a distance from a first light source to a first grating is a, a distance from a second light source to a second grating is b, a first predetermined grating pitch is I, a second predetermined grating pitch is J, the wavelength of a first laser beam is &lgr;1, and the wavelength of a second laser beam is &lgr;2, satisfies &lgr;1/&lgr;2>(I·b)/(J·a), and which is capable of preventing a drop in the level of a tracking error signal resulting from decentering of an optical recording medium, even in the case of using either of optical recording media of different recording densities.

Abstract: An optical disc drive includes a light source, a lens, a focusing section, a spherical aberration corrector, a focus signal generator, a gain calculator and a processor. The focusing section forms a beam spot in a focusing state on the information storage layer of an optical disc by controlling the position of the lens. The spherical aberration corrector changes a spherical aberration with the beam spot in a focusing state according to a drive value of a driving signal supplied to the spherical aberration corrector. The focus signal generator generates a focus signal representing the focusing state of the beam spot. The gain calculator calculates a loop gain of a focus control system in response to the focus signal. The processor determines the drive value for the spherical aberration corrector by the loop gain.

Abstract: A recording disc and recorded information reproducing apparatus and method for immediately starting reproduction of information when a push-pull based tracking control is employed to reproduce recorded information from the recording disc. The recording disc comprises an information data area for recording recording marks which carry information data in columns, and a control data area for recording identification information indicative of a recording pattern of the recording marks in the information data area.

Abstract: A focus control device includes a moving member integral with an object lens, a focus actuator for moving the object lens toward or away from a recording surface of an optical disc in a direction of focusing, a tracking actuator for moving the object lens in a direction of tracking, and a control unit for biasing the moving member in the direction of tracking so that the moving member is pressed against a fixed member by using the tracking actuator, and for enabling the moving member to carry out a focusing operation while the moving member is pressed against the fixed member by using the focus actuator. Thus the focus control device can surely carry out a focusing operation without being under the influence of turbulence vibrations or the like that may be generated.

Abstract: A method for detecting and compensating inclination of an objective lens includes the steps of: initially driving an optical disk and detecting a record signal while travelling on the track of the optical disk; checking whether a GFS signal according to the rotation of the optical disk is normally detected; checking a center error signal value outputted from the optical pick-up which reads a record data on the optical disk in case that the GFS signal is abnormally detected; and discriminating inclination of the objective lens on the basis of the checked center error signal value, thereby judging inclination of the objective lens quickly and accurately. In order to discriminate inclination of the objective lens by the optical disk driving apparatus, the GFS signal and the center error signal generated according to the rotation of the optical disk are all taken into consideration, so that the inclination of the objective lens in the optical pick-up is accurately and quickly discriminated.

Abstract: In a focus control of an optical disk with a fast reproduction velocity and a large face deflection, the present invention can effect a mistakeless and reliable focus pull-in method. The present invention comprises: means for applying a braking signal to a focus actuator before closing a focus control loop; means for detecting a reversal of a relative velocity between an objective lens performing a focus search operation and an optical disk which effects an up-and-down motion due to the face deflection; and means for detecting the relative velocity between the objective lens and the optical disk from a focus error signal which is detected in each layer of a multi-layer disk.

Abstract: The present invention relates to a storage device and a servo recovery method for the storage device, which restores the head to a track when the head goes off from the track of a storage medium, and whereby it prevents the servo recovery process from being continuously called over a short period of time. The storage device comprises a storage medium, a head and a control circuit which performs the servo recovery process. The servo recovery process, having multiple recovery processes, is called up when off track is detected. The frequency that the recovery process is called up is detected, and one of the multiple recovery processes is executed according to the detected call-up frequency. A different recovery process is performed when the call-up frequency is high, therefore this recovery process makes it possible to prevent frequent occurrence of the off-track state.

Abstract: A recording disk and a recording apparatus prevent illegal copying. In a reproduction control data area, pits of a pit train on a plurality of adjacent tracks are aligned in the directions which cross the tracks perpendicularly, wherein the pit train represents reproduction control data indicative of a reproduction control method to be used for reproducing information data.

Abstract: When an optical disk apparatus 1 determines that it is timing of switching a recording layer for reading data from one recording layer to the other recording layer with respect to an optical disk 10, regardless of the amount of data stored in buffer memory 6 at this point in time, the optical disk apparatus 1 moves a pickup head 2 in a radial direction of the optical disk 10, and acquires a waveform of a tracking error signal, and also moves an objective lens in a direction going toward the optical disk 10, and acquires a waveform of a focus error signal, and readjusts tracking servo gain and focus servo gain based on these signal waveforms.