Abstract: A system which calibrates notch filters in a digital servo system is presented. A notch filter can be calibrated by obtaining a frequency response curve of the digital servo system in a range of frequencies, searching the frequency response curve for at least one peak frequency, and adjusting parameters of the notch filter to filter out signals at the at least one peak frequency. The digital servo system, for example, can be a tracking servo system or a focus servo system of an optical disk drive.

Abstract: A close tracking algorithm for a tracking servo system is disclosed. The track crossing rate of an optical pick-up unit positioned over an optical media is determined. When the track crossing rate is below a threshold value, then a tracking servo algorithm is enabled. The tracking servo algorithm provides control signals to control an actuator arm that controls the position of the optical pick-up unit over the tracks of the optical media. In some embodiments, the track crossing rate can be determined by monitoring the zero crossings of a tracking error signal derived from optical signals measured in the optical pick-up unit.

Abstract: A calibration of a focus error signal gain in a focus servo system of an optical disk drive is presented. The focus error signal gain can be calibrated by oscillating an optical pick-up unit in a focus direction through a focus point and determining a focus sum threshold. The optical pick-up unit can then be oscillated around a focus control effort that results in a sum signal equal to the focus sum threshold and the peak-to-peak value of a focus error signal can be measured. The focus error signal gain can be determined from the peak-to-peak value of the focus error signal.

Abstract: A system, method, and apparatus for coordinating tasks in a control system for an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The optical disc drive includes a first processor operable to communicate with a second processor, wherein the first processor includes instructions for performing non-time-critical tasks, and the second processor includes instructions for performing time-critical tasks, such as reading from and writing to optical media in the disc drive. The first processor monitors the status of the time critical tasks in the second processor and transmits commands to perform operations in the second processor. The first processor also controls power mode, manages recovery from errors, controls focus, tracking/seeking, spin, physical sector address (PSA), a laser, adjusts gains, and monitor cartridge load/eject.

Abstract: A method of storing calibrated optical parameters is presented. In some embodiments, calibrated optical parameters are stored in place of stored parameters. In some embodiments, averages between the calibrated operating parameters and stored optical parameters are stored. In other embodiments, the stored optical parameters are allowed to vary only by a maximum amount. In some embodiments, if the calibrated parameters vary by more than threshold values, then the calibrated parameters are not stored.

Abstract: A method of an optical disk drive for determining both an optimum write power and an optimum tracking offset value using a test area reserved for a conventional OPC operation by determining a coarsely adjusted laser power using a portion of the test area, determining an optimum tracking offset using another portion of the test area, and determining an optimum write power using the remaining portion of the test area. The optimum tracking offset ensures that the RF signal is not affected by a wobble formed on a groove.

Abstract: A calibration of input signal offset in an optical disk drive is presented. The input signal offsets the input signals received from an optical pick-up unit before digitization. In some embodiments, the input signal offset is set such that the digitized input signals are zero when laser power is off. Further, a thermal drift correction is presented.

Abstract: A digital servo system of an optical disk drive with a calibrated inverse non-linearity function is disclosed. A look-up table is determined, for example, with a focus error signal gain corresponding with a focus error signal offset so that the response of the focus servo system is substantially linear. Additionally, the look-up table can include tracking error signal gain, tracking error signal offset, or tracking loop gain parameters corresponding with the focus error signal offset.

Abstract: An optical disc apparatus and method for recording and reproducing information to/from an optical disc, including discrimination of the optical disc, reading control information in an un-recordable area formed in an inner periphery of the optical disc, conducting focus control based on a focus error signal in a recordable area formed outside of the un-recordable area, and determining an optimum offset value of the focus error signal in the recordable area. Further, adjustment in amplitude of a reproduced signal from an inner periphery of the recordable area is conducted, test-writing in the inner periphery of the recordable area is conducted, test-writing in an outer periphery of the recordable area is conducted, and adjustment in amplitude of a reproduced signal from the outer periphery of the recordable area is conducted. The respective operations are conducted sequentially so as to make the optical disc in a reproducible and recordable condition.

Abstract: A digital servo system for controlling tracking or focus in an optical disk driver is presented. A servo system according to the present invention includes an optical pick-up with detectors providing optical signals, an analog processor receiving the optical signals and providing a digital signal, and digital processors receiving the digital signal and providing a control signal that controls the position of the optical pick-up unit. The digital processor executes an algorithm that calculates an error signal, provides amplification and biasing to the error signal, provides filtering for the error signal, and computes the control signal. The error signal can be the focus error signal or the tracking error signal.

Abstract: A calibration for a tracking error signal gain in a tracking servo system of an optical disk drive is presented. The calibration determines the peak-to-peak tracking error signal when the tracking servo system is open, calculates a gain factor in response to the peak-to-peak tracking error signal, and calculates a new tracking error signal gain based on the tracking error signal gain and the gain factor. New tracking error signal gains are calculated until the gain factor is approximately one.

Abstract: An apparatus and method for controlling tracking for an optical recording/reproducing apparatus is disclosed. A track center level is determined at a point where a high width of a TE signal generated during free-running or traverse is equal to its low width. Alternatively, a TE detection level at a TZC point of the TE signal in which asymmetry is adjusted is determined as the track center level. The determined track center level is used for normal recording/reproduction, so that the tracking servo is activated at the actual track center position. Thus, initial stable tracking performance can be obtained, and bias of the tracking can be avoided during tracking control by estimating the exact track center value.

Abstract: Optical disk device, in which tracking adjustment systems and a sled adjustment system are controlled independently, has offset value acquisition capability, which detects drive signals output from tracking adjustment systems and acquires tracking drive offset values. Such disk also has an offset value comparison capability, which compares the acquired tracking offset value and the offset center value in the state in which no tracking adjustment control is done, a search direction acquisition capability, which acquires the search direction of optical pickup from the control instruction that is output from the control system and sled drive decision capability, which decides whether to drive sled adjustment system based on the comparison result and the acquired search direction.

Abstract: The present invention relates to loop gain adjustment of a focus/tracking servo in an optical disk apparatus, and provides an optical disk apparatus which can make the loop gain adjustment converge normally even in an optical disk in which prerecorded areas and recorded areas are mixed, and further which always has a stable servo system even when a gain is significantly varied due to changes in the disk state.

Abstract: A system with a plurality of servo algorithms executing on a digital signal processor is presented. The digital signal processor receives a sensor interrupt, indicating availability of digitized data from optical sensors, and decides which of a plurality of servo algorithms to service in response to the interrupt. In some embodiments, the plurality of servo algorithms includes a tracking servo algorithm. In some embodiments, the plurality of servo algorithms includes a focus servo algorithm. In some embodiments, multi-track seek operations or one-track jump operations can also be serviced during the interrupt period.

Abstract: A tracking servo system with a feed-forward control loop is presented. Periodic variations in a control signal can be detected. These periodic variations can be added into the control signal to form a new control signal so that on subsequent cycles the control signal does not include the periodic variations.

Abstract: When a lens 4a reaches a position which is a half track short of an objective track in a track jump, a servo processor 7 conducts a braking operation of an amount corresponding to the movement velocity of the lens 4a at the timing when the lens crosses the immediately preceding track. The movement velocity of the lens 4a is detected from the period of a tracking error signal. Therefore, a phenomenon in which a braking operation is not effective and the lens overshoots the objective track is prevented from occurring, and a track-on in the objective track can be surely attained.

Abstract: An optical disc apparatus includes: a converging section for converging a light beam and irradiating a rotating information medium with the converged light beam; a moving section for moving the converging section, thereby moving a converging point of the converged light beam in a direction perpendicular to an information surface of the information medium; a converging state detection section for generating a focus servo signal which represents a converging state of the light beam on the information medium based on reflected light or transmitted light of the light beam from the information medium; a focus servo control section for controlling the moving section based on the focus servo signal, so that the light beam reaches a predetermined converging state on the information medium; and a focus pull-in section for turning ON the control by the focus servo control section, wherein the focus pull-in section turns ON the control by the focus servo control section in a case where the focus pull-in section determin

Abstract: This invention is applicable to an apparatus using an optical pickup to reproduce information recorded on an optical recording medium. By enabling the automatic setting of reproducing conditions applicable to a mounted optical recording medium so that a plurality of types of optical recording media can be compatibly mounted, the present invention enables recorded information to be reliably reproduced even if the recording medium has a low recording density.

Abstract: A disc-like record carrier (1) has control information recorded. The control information comprises diameter information which is indicative of the diameter of the record carrier. An information recording and/or reading apparatus involves a drive structure for rotatingly driving the disc-like record carrier. The apparatus includes a control unit which adapts the loop gain of a control loop for controlling the number of revolutions per minute of the record carrier in dependence on the control information recorded on the record carrier.

Abstract: There is provided an optical disk drive capable of appropriately effecting recording and reproducing operations without being affected by offset values and a laser output value, which are set at startup of the disk drive, even when changes have arisen in the internal temperature of the disk drive because of changes in ambient temperature. In an optical disk drive, a temperature sensor provided on a pickup measures a temperature. When changes in temperature are greater than a predetermined level, a focus offset value, a tracking offset value, and a value of laser output from the pickup are reset.

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 pickup including a light source for radiating a light beam, a diffraction element for separating a light beam radiated from the light source into at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a four-segment first light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions arranged on both sides of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, and a calculation unit for generating a first tracking signal based on respective outputs of the first light receiving portion and for generating a second tracking signal based on outputs of the second and third light receiving portions.

Abstract: A device for recording and/or reproducing an optical record carrier (1), comprises an optical system for projecting a first, a second and a third optical beam at a first (11), a second (12) and a third spot (13) at the record carrier (1). The device further comprises detection elements primary position signals (D5, C, D1) which is indicative for an amount of radiation reflected by the record carrier at said thoses spots (11). The device further comprises signal processing means (34.1, . . . 34.4; 35.1, . . . 35.4) for generating a plurality of secondary position signals (S1, S2, S3, S4) in response to the primary position signals (D5, C, D1). A selection element (36) selects one of the position signals (S1, S2, D1, S3, S4) as an output signal (WRE) in response to a selection signal (SEL). The selection signal (SEL) is derived from the output signal (WRE) of the selection element (36).

Abstract: An optical disk drive apparatus for recording a predetermined signal on an optical disk by varying predetermined recording conditions and detecting recording characteristics based on a reproduction signal of the predetermined signal is provided. The optical disk drive apparatus includes a reproducing part for reproducing the predetermined signal for a plurality of times; and recording characteristics detecting part for detecting the recording characteristics based on a plurality of reproduction signals supplied from the reproducing part.

Abstract: The present invention provides an information storage apparatus that generates a tracking error signal based on a detection signal, and performs various control operations based on the tracking error signal. When the operation mode is a seek operation mode, the information storage apparatus generates a tracking error signal by holding the peak value of the detection signal. When the operation mode is a tracking operation mode, the information storage apparatus generates a tracking error signal directly from the detection signal. With this information storage apparatus, stable control operations can be performed, regardless of changes of conditions.

Abstract: In a seek operation, in which a head is moved to a target track, the detection output of a head-position detection unit is integrated in each track. Each integrated value is a positive or negative value proportional to an offset given to a center value obtained from the maximal value and the minimal value of the detection output. The center value is compensated for by a compensation value obtained by multiplying the integrated value by a coefficient. As a result, the offset is reduced and a highly precise positional detection is allowed.

Abstract: The present invention provides a large scale integrated circuit (LSI) for calculating servo signals (e.g., a focusing signal, a tracking signal, etc.) from the output signals received from a plurality of photo detectors, as used within an optical disk apparatus. The invention provides a switching circuit and a gain changing circuit coupled to the LSI such that a single LSI may be used for at least two different photo detector configurations as may be found in at least two different pick-up devices.

Abstract: An apparatus of forming an evaluation signal used in adjusting focus bias and adjusting skew of a disk drive in which phase error information between a phase of a read data signal and a phase of a clock signal formed in synchronism with the read data signal, is detected, the phase error signal is converted into an analog signal and is outputted as an evaluation signal having a signal level in accordance with the phase error amount and the evaluation signal is inputted after A/D conversion to a portion for carrying out signal quality evaluation by using the evaluation signal whereby pertinent signal evaluation can be carried out by a simple constitution.

Abstract: A tracking servo circuit for stopping movement of a pickup device at a target position on a recording track of a recording medium, such as a CD, includes an A/D converter that generates error data from a tracking signal. The tracking error signal has a positive value when the pickup device is located at a first side of the recording track and a negative value when the pickup device is located on the opposite side of the recording track. The error data includes a code bit indicating the polarity of the tracking signal. A selector control circuit generates a selection signal using the code bit. A selector connected to the A/D converter and the selector control circuit selects either the error data or a fixed data value based on the selection signal. A drive signal generator receives the selected data and generates a drive signal to stop the radial movement of the pickup device.

Abstract: A servo method for an optical recording medium for detecting a tracking error signal by a push-pull method is disclosed. Before a servo operation, an amount of DC offset per track is obtained as an object lens of an optical pickup is moved in a specified direction, and a tracking servo is performed by compensating for a tracking error signal based on an initial amount of DC offset obtained by multiplying the amount of DC offset generated per track by the number of jumped tracks when the object lens is shifted. After movement of a sled by driving a sled servo, a sled servo is performed by compensating for the tracking error signal based on a value obtained by subtracting an amount of sled movement from the initial amount of DC offset, and thus an optical beam can always follow a track center even when the DC offset is generated in the tracking error signal.

Abstract: When a setup is performed by reproducing conditions corresponding to the first kind of optical disk and a setup is subsequently performed by reproducing conditions corresponding to the second kind of optical disk, the reproducing conditions which succeed to at least a part of the reproducing conditions corresponding to the first kind of optical disk are used as reproducing conditions corresponding to the second kind of optical disk and the setup is performed. When the setup is completed, the reproducing conditions corresponding to the optical disk as a target of the setup are stored. When the same optical disk is set up again, the stored reproducing conditions are used.

Abstract: An optical disk apparatus comprising a device for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; a device for detecting a reflected light from the disk; and a device for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. In this apparatus, a maximum value AS1Lmax of an output signal from the reflected light detecting device and a maximum value ENVmax of an amplitude of an information reproducing signal are detected while driving the focal point moving device so that the focal point passes through the information face, and the discriminating device discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate, on the basis of the ratio of ENVmax to AS1Lmax.

Abstract: This disc reproducing apparatus comprises an optical pickup for reproducing a signal recorded in a disc from the disc, an amplifier for amplifying the signal outputted from this optical pickup at a predetermined gain, a focus servo circuit for matching the focus of the optical pickup with the disc using the signal outputted from this amplifier, and control means. The control means executes focusing of the optical pickup using the gain of the amplifier as a predetermined gain when starting reproduction of the signal from the disc, starts reproduction of the signal from the disc when this focusing is successful, and executes the second focusing of the optical pickup by setting the gain of the amplifier to a higher gain than the predetermined gain and starts reproduction of the signal when the focusing is unsuccessful.

Abstract: A servo-control apparatus is provided for use with an optical disc player for reading and/or recording information. The apparatus includes an adjustment section for performing coarse and fine adjustment of a servo loop gain in accordance with a storage medium loaded in the player; a memory for storing a gain adjustment value; a discriminator for determining, upon one of reading and recording information, that the storage medium has already been subjected to the coarse and fine adjustment; and a controller. The controller allows the adjustment section to perform the fine adjustment of the servo loop gain in accordance with the stored adjustment value when it is determined that the storage medium has already been subjected to the coarse and fine adjustment.

Abstract: An optical disc apparatus and method for recording and reproducing information to/from an optical disc, including discrimination of the optical disc, reading control information in an un-recordable area formed in an inner periphery of the optical disc, conducting focus control based on a focus error signal in a recordable area formed outside of the un-recordable area, and determining an optimum offset value of the focus error signal in the recordable area. Further, adjustment in amplitude of a reproduced signal from an inner periphery of the recordable area is conducted, test-writing in the inner periphery of the recordable area is conducted, test-writing in an outer periphery of the recordable area is conducted, and adjustment in amplitude of a reproduced signal from the outer periphery of the recordable area is conducted. The respective operations are conducted sequentially so as to make the optical disc in a reproducible and recordable condition.

Abstract: A control unit positions a laser beam toward a target track on a medium on the basis of a tracking error signal (TES) Y indicative of a positional deviation amount from a track center as a zero point on the basis of return light from the medium. A position signal correcting unit executes a correcting arithmetic operation using a non-linear function such as a quadratic polynomial, a quadratic monomial equation, or the like to the TES Y and outputs a corrected TES Z obtained by correcting detection sensitivity characteristics to desired characteristics so that a feedback is sufficiently performed when a lead-in control to the track center by the control unit is executed.

Abstract: A servo device for controlling a reading operation of a pickup in a recording medium player, which generates a servo error signal indicative of an amount of deviation of a position at which the pickup of the recording medium player is reading for playing a recording medium. The servo device detects a blemish at a reading point focused by the pickup on the recording medium to generate a blemish detecting signal when a blemish is detected, and generates a servo hold signal based on a low frequency component of the servo error signal. The servo hold signal includes, immediately after the generation of the blemish detecting signal, a signal of opposite polarity to the polarity of the servo error signal immediately before generation of the blemish detecting signal. Further, the servo device controls the reading operation of the pickup in accordance with the servo hold signal in place of the servo driving signal during the time that the blemish detecting signal is generated.

Abstract: An apparatus of forming an evaluation signal used in adjusting focus bias and adjusting skew of a disk drive in which phase error information between a phase of a read data signal and a phase of a clock signal formed in synchronism with the read data signal, is detected, the phase error signal is converted into an analog signal and is outputted as an evaluation signal having a signal level in accordance with the phase error amount and the evaluation signal is inputted after A/D conversion to a portion for carrying out signal quality evaluation by using the evaluation signal whereby pertinent signal evaluation can be carried out by a simple constitution.

Abstract: In an optical information reproduction method and apparatus with a tracking servo system using a tracking error signal in the phase difference method, the effect of the offset which varies depending on the pit depth and the lens position can be corrected and a tracking error detecting means free from the offset can be obtained. To this end, the phase comparison means are made to receive a certain set of input signals during the offset correction, and a different set of input signals during the tracking error signal detection. The offset in the tracking error signal which varies depending on the pit depth and the lens position is obtained as a voltage value, and through repeated learning control, this offset is corrected.

Abstract: In order to more quickly produce read and/or write readiness of an apparatus for reading from and/or writing to an optical recording medium, in particular a DVD-ROM disc, it is proposed to read or to detect identification features, such as, for example, the “BCA data area” which individually identifies the respective recording medium and, after identification of the respectively inserted optical recording medium, to check whether adjustment parameters for the write and/or read unit of the apparatus have already been stored beforehand for this optical recording medium in a storage device. If this is the case, the adjustment parameters can be read from the storage device and be used as start values for the adjustment of the write and/or read unit.

Abstract: A multi-layer recording medium reproducing device having an automatic adjustment mode of automatically performing servo adjustment to reproduce a multi-layer optical disk. The device includes a storing section which, during the automatic adjustment mode, performs the servo adjustment of recording layers of the optical disk respectively for predetermined periods of time, and stores the resultant service adjustment values respectively for the recording layers; and a servo adjustment control section which, during a reproduction of the optical disk, reads from the storing section a servo adjustment value corresponding to one of the recording layers to be reproduced, and performs the servo adjustment to reach the servo adjustment value thus read.

Abstract: A multi-layer recording medium reproducing device having an automatic adjustment mode of automatically performing servo adjustment to reproduce a multi-layer optical disk. The device includes a storing section which, during the automatic adjustment mode, performs the servo adjustment of recording layers of the optical disk respectively for predetermined periods of time, and stores the resultant service adjustment values respectively for the recording layers; and a servo adjustment control section which, during a reproduction of the optical disk, reads from the storing section a servo adjustment value corresponding to one of the recording layers to be reproduced, and performs the servo adjustment to reach the servo adjustment value thus read.

Abstract: In order to carry out optimization adjustment of a distance between a first lens and a second lens and optimization adjustment of focus offset of two group object lenses in a short period of time, after focusing is operated, while the distance between the first lens and the second lens of the two group object lenses is being adjusted by a first electromagnetic actuator, the two group object lenses are integrally moved by a second electromagnetic actuator, an amplitude variation caused by spherical aberration and an amplitude variation caused by focus servo error which are produced in an RF signal S2 are separated by an envelope detection unit A33 and an envelope detection unit B34 and the two adjustments are carried out simultaneously.

Abstract: An optical pickup position control device according to the present invention automatically adjusts tracking with precision and in a short time. Two deviation signals, which express deviation of a light beam, projected by a pickup which uses the three-beam method, from a target track of a disk, are digitized by two AD converters. Two high-pass filters extract from the deviation signals AC signals, producing a tracking error signal. Further, two low-pass filters extract from the deviation signals DC signals (offset components). Two other low-pass filters extract from the deviation signals low-band signals containing DC components. Using the various foregoing signals, a control circuit calculates correction values to be applied to two offset correcting circuits and to two gain/balance correcting circuits, and corrections are performed collectively and simultaneously on the basis of these correction values.

Abstract: The object of the present invention is to realize a stable control and a stable signal reproduction in an optical disc device. When a head unit (110) is shifted in a radial direction or a reproduction speed is varied, a reproduction speed is detected based on a radial position at which the head unit is located and the number of rotaions of a motor (111), and settings of a focusing gain, a tracking gain, an amplification factor of an equalizer circuit (130), a band-limited frequency, a loop gain of a PLL circuit (131) and a divide ratio are varied based on said reproduction speed. Further, an accurate detection of an out of focus operation can be executed by using either one signal of a reflected-light quantity, an RF signal amplitude and a drive of a focusing actuator, or combined signals thereof. Thereby, a stable control and signal reproduction can be provided.

Abstract: An apparatus for reproducing a multiple layer disk, which comprising a plurality of layers each having an information record surface on which record information is recorded, is provided with: a read device for reading the record information from each of the layers; a reproduction process device for applying a predetermined reproduction process to the record information read by the read device in accordance with a reproduction process parameter, which is set therein and which comprises at least one of a gain value and an equalizer value, to thereby output a reproduction information signal; a drive device for driving the read device to jump from one reading state for reading one of the layers to another reading state for reading another of the layers; a memory for storing a plurality of reproduction process parameters corresponding to the layers in advance of reproduction; and a set device for reading out one of the stored reproduction process parameters, corresponding to another of the layers as a destination

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: Deterioration of an error rate due to disturbance of a reproduced signal is prevented by carrying out focus balance adjustment and tracking balance adjustment, with use of a focus control section for causing a focus servo to control the focus balance, based on a jitter value measured by a jitter measurement section, and a balance-adjusted FE signal generated by an error signal generating section, and a tracking control section for causing a tracking servo to control the tracking balance, based on an error center value measured by an error center measurement section and a balance-adjusted TE signal generated by an error signal generating section. Also, the focus servo carries out focus down-search thereby to switch on correctly the focus.

Abstract: An optical disc apparatus for writing data on an optical disc 11 and/or reading data from the optical disc 11 by performing seek control for moving an optical pickup 15 to a target track on the optical disc 11 and focus servo of the optical pickup 15 according to a detected focus error signal and a first transfer function. This optical disc apparatus is provided with a memory 17a for holding a second transfer function different from the first transfer function, and executes the focus servo according to the first transfer function when the seek control is not performed or executes the focus servo according to the second transfer function when the seek control is performed. It is therefore possible to reduce the gain of a focus servo system without lowering the stability, for elimination of noise generated during the seek control.