Abstract: A stabilization part stabilizes surface vibration of a flexible optical disk along a rotation axis direction of the optical disk by means of pressure difference of air flow created according to Bernoulli's law at a portion on which information writing/reading is performed, provided on a side of the optical disk opposite to a side on which information recording/reproducing is performed. In this case, areas are provide on the upstream side and down stream side along the disk rotation direction of the portion of the optical disk which is stabilized by said stabilization part, said areas of the optical disk not having pressure difference created thereon by the air flow.

Abstract: In the optical disk drawing apparatus of the present invention, an automatic adjusting area where the drawing operation is not carried out is provided in the optical disk, laser light is irradiated onto the formed automatic adjusting area so as to control the focus servo gain, so that a stable focus servo control can be carried out.

Abstract: An objective lens is moved with a disc irradiated with laser light. A maximum value FEmax and a minimum value FEmin of the focus error signal, and a maximum value FSmax of the amplitude of a focus sum signal are measured. “(FEmax?FEmin)/FSmax” is compared with a determination value to determine the type of a disc.

Abstract: An information-recording medium having a substrate and a recording part formed on the substrate allowing three-dimensional formation of recording pits, the recording part, comprising multiple recording layers, in which the recording pits are formed with a converged recording light at a wavelength of ?2 and reproduced with a converged reproducing light with a wavelength ?1 shorter than the wavelength ?2, and intermediate layers alternately laminated between the recording layers, wherein the reflectance at the recording light wavelength of ?2 in the unrecorded region is smaller than the reflectance at the reproducing light wavelength of ?1 in the unrecorded regions of the recording layers.

Abstract: For achieving pulling operation into tracking servo during seek operation at high-speed and with stability, in timing thereof, even on an optical disk forming lands and grooves on a recording surface thereof, in a seek control method, according to the present invention, for moving an optical spot onto an arbitrary track through movement of an optical pickup 110 into the radial direction on the optical disk forming the lands and the grooves, thereby forming a track on the recording surface thereof, in particular, in the seek operation, measurement is made on a period of a tracking error (TE) signal generated due to the movement in the radial direction, and a time point when the measured period of the tracking error signal exceeds a predetermined value is determined to be a starting point for pulling the optical spot of the optical pickup into the track, through the tracking servo, thereby pulling it selectively, into either one of the land and the groove building up the track.

Abstract: A system and method for calibrating a recording track offset of an optical storage device accessing an optical storage medium of land/groove type. The system includes: a tracking servo loop arranged to control tracking operations of an optical head of the optical storage device; a track offset control loop arranged to control the recording track offset for the tracking servo loop; a controller arranged to enable a latest value of the recording track offset to be a readout value for utilization in a recording process performed later; and a comparator arranged to compare a recording length with a threshold value and generate a flag to represent whether the recording length is a long recording length, wherein the latest value is derived from the track offset control loop.

Abstract: There is provided a servo controller that can automatically set a filter intended for stabilizing a closed loop. The servo controller includes a repetitive controller. The repetitive controller implements repetitive control of a servo error signal (observation signal y(t)) by producing, by an adaptive line spectrum enhancer or adaptive linear prediction unit, a second error signal (including mainly a rotational sync signal) resulted from reduction of an irrotational sync component from a first error signal resulted from subtraction of the observation signal y(t) from a target signal r(t) and producing a third error signal obtained by sequentially updating the first error signal while making one-period delay of the second error signal.

Abstract: There are obtainable reliable and proper tracking correction and CTC even when fluctuations occur in an irradiation position of a sub-beam in a track at the time of performing tracking correction and CTC using three beams. Five beams (a main beam, sub-beams inA and inB, and sub-beams outA and outB) are generated. Reflection beams of the five beams are received, and a differential push pull signal DPPin corresponding to the sub-beams “in” as ± first-order beams and a differential push pull signal DPPout corresponding to the sub-beams “out” as ± second-order beams are generated. By assigning weights to the differential push pull signals DPPin and DPPout and computing the sum of the weighted signals, a tracking error signal Ste having an amplitude value which can perform tracking correction is generated.

Abstract: An optical disc playback apparatus with which collision of a lens and an optical disc is avoided is provided. Processes executed by a microcomputer of the optical disc playback apparatus when a disc is played back include: the step of outputting a signal for performing focus search at a predetermined speed; the step of outputting a signal for reducing search speed when reflection of laser light from a surface of the optical disc is detected; and the step of outputting a signal for indicating disc error when S-shape is not detected and a certain time has elapsed since the detection of the reflection.

Abstract: To provide an interlayer movement apparatus of an optical disc apparatus which can perform the interlayer movement stably even when the interlayer distances of the multi-layer optical disc which are specified by the disc specification are different between the respective layers.

Abstract: An optical disk apparatus according to the present invention includes: a rotation driving section on which an optical disk is to be mounted and which drives the optical disk so as to be rotated; a light source; an objective lens for converging light from the light source onto an optical disk mounted on the rotation driving section; a photodetector having at least two detection sections for detecting reflected light, from the optical disk, of the light; and an error signal generation section for deriving a difference signal and a sum signal of respective outputs from the two detection sections of the photodetector, adjusting an offset in at least the sum signal among the difference signal and the sum signal, and thereafter dividing the difference signal by the sum signal whose offset has been adjusted to generate a position error signal of the objective lens.

Abstract: A high-density read-only optical disc, and an optical disc apparatus and method using the same. The apparatus and method record data on a lead-in area of a high-density read-only optical disc such as a BD-ROM (Blu-ray disc ROM (Read Only Memory)) in the form of pre-pit strings associated with an HFM (High-Frequency Modulated) groove applied to a BD-RW (Blu-ray Disc Rewritable). Moreover, the apparatus and method continuously apply the same tracking servo operation to an entire area of the same high-density read-only optical disc or rewritable optical disc. Therefore, the apparatus and method can simplify an algorithm for controlling a plurality of tracking servo operations, and avoid an increased size of the optical disc apparatus.

Abstract: A second tracking error detector detects the displacement between the track and the light beam and outputs a second displacement detection result based on the comparison of the reproduction signals between first and second pit strings respectively. A second tracking error controller corrects a target position for push-pull control based on the second displacement detection result. A third tracking error controller calculates a correction data of a first displacement detection result based on the correction amount of the target position by the second tracking error controller, and corrects the first displacement detection result based on the calculated correction data.

Abstract: Provided is a recording and retrieval apparatus for a multi-layer optical disk. A multi-layer optical disk in which a plurality of recording layers and a single servo layer are combined to form a set is used. A spot for the servo layer and a spot for the recording layers are turned on in a time-sharing manner. Servo signal detection areas are formed discretely in the servo layer. The servo signal detection areas and data recording areas are provided so as not to overlap each other when viewed from the spot incident side. Thus, separation of data from each of the layers can be done by even a single photodetector without interference.

Abstract: An optical disk unit, for reading signals stored on an optical disk medium, is provided with an optical pickup 23 selectively irradiating light of one wavelength, from several mutually different wavelengths, to an optical disk medium by means of a single objective lens and outputting signals based on light reflected by the optical disk medium, a drive section for causing relative movement of the objective lens of the optical pickup with respect to a surface of the optical disk medium, wherein a peak level of a fake signal generated in the received light signal based on surface reflection at the optical disk surface while the objective lens is being moved relative to the optical disk medium surface by the drive section is detected, and the received light signal is compared with a threshold value that is set based on the detected peak level, to detect reflected light of a data storage layer.

Abstract: The present invention relates to a method for calibrating a focus position of an optical pick-up. The optical pick-up is located on a focus position at a preset distance from a recordable optical medium to emit a recording beam of a preset power to the recordable optical medium so that corresponding optical data are recorded in the recordable optical medium. The method includes: altering a focus position of the optical pick-up during a recording process to generate a corresponding write radio frequency (RF) signal; detecting a minimum value of the write RF signal and a corresponding object focus position; and moving the optical pick-up to the object focus position so that the optical pick-up performs recording at the object focus position in the recordable optical medium.

Abstract: The method for estimating recording power Pow_tilting of a tilting part of a tilting disk is shown based on a power compensation formula: Pow_comp=A*(A*K). After a focus error (FE) signal of the tilting part of the tilting disk is manipulated as a focus servo output (FOO) signal, the parameter A is derived by low-pass filtering the FOO signal. Thereafter, another parameter K is then derived from a reference lookup table by using curve fitting approach based on parameter A such that the power compensation Pow_comp could be estimated by substituting parameters A and K into the above formula. A recording power Pow_tilting of the tilting part of the tilting disk could be estimated by adding a given recording power Piwrtpwr to the power compensation Pow_comp.

Abstract: A detector is scanned across an optical storage medium having groove tracks and land tracks, each track having a wobble structure, to detect light reflected from the optical storage medium. A wobble signal and a tracking error signal are generated based on an output of the detector, and the wobble signal is sampled according to the tracking error signal. A determination about whether the detector is at the groove track or the land track is made based on the tracking error signal and a comparison of sampled values of the wobble signal.

Abstract: The present invention is embodied in a recording device and media for storing computer readable data on a removable storage medium that includes using a first wavelength to write data to the removable storage medium and creating marks while writing the data that have predetermined wide spot sizes so that the marks can be read with a second wavelength, different from the first wavelength, of another computer readable storage device.

Abstract: An optical disk device includes a DPDTE signal generating section that detects misalignment between a light spot and a mark or a pit, an FE signal generating section, an optical crosstalk correcting section which corrects a signal output by the FE signal generating section using the DPDTE signal generating section, and a focus control section which controls an actuator so that a light beam converges on an information layer. The DPDTE signal generating section detects the misalignment on the basis of phase information obtained from signals received from predetermined light receiving areas. The optical crosstalk correcting section performs a correcting operation of removing a signal component from predetermined receiving areas of a detector which component is used for a DPDTE signal, the signal component being contained in the signals from the predetermined light receiving areas of the detector which signals are used by the FE signal generating section.

Abstract: A method for determining a bias voltage of a servo signal of an optical disc drive is disclosed. The method includes: generating a plurality of sensing signals via an optical sensor of the optical disc drive; generating a first and a second servo signals according to the sensing signals; adjusting the first and the second servo signals to generate a first and a second adjusted signal respectively; and determining the bias voltage of the servo signal according to the first and the second adjusted signals.

Abstract: The present invention relates to an information reproducing apparatus that includes an objective lens that focuses a light beam toward a rotating optical disc medium and uses the objective lens to focus the light beam onto the optical disc medium and detect the reflected light of the light beam so as to reproduce information stored on the optical disc medium. The present invention allows measurement of surface deflection of the optical disc medium with no risk of collision between the objective lens and the optical disc medium. The objective lens is brought closer to the optical disc medium from a separate position apart from the optical disc medium and immediately moved away from the optical disc medium when the light beam is focused onto the optical disc medium.

Abstract: A layer-jumping control device and method for an optical disc device includes a calculator, a controller, and a driver. The calculator is configured to receive an error-focusing signal, and to determine a peak and a trough of the error-focusing signal. The controller, coupled to the calculator, is configured to process the error-focusing signal to generate a control-focusing signal. The driver, coupled to the controller, is configured to convert the control-focusing signal to a control-driving signal. The device further includes a counter coupled to the calculator, and enables the layer jump when the counter reaches a predetermined value.

Abstract: A multi-zone calibration system is disclosed. The multi-zone calibration system calibrates the operating parameters of an optical disk drive over a plurality of zones over an optical media. The optical media, in addition, can have writeable and premastered portions. The operating parameters can be calibrated for each of the media types in each of the zones. Additionally, the operating parameters can be calibrated for each type of operation (e.g., read or write) in each zone.

Abstract: An optical disk apparatus can reliably detect the target recording layer of an optical disk having two recording layers. The optical disk apparatus is adapted to recording information on and reproducing information from an optical disk formed by sequentially laying a first recording layer, a second recording layer and a cover layer. The focal point of the light beam is moved closer to the optical disk from the side of the cover layer and the focal point of the light beam is determined to be coming close to the recording layer when the signal level of the focus error signal falls below a positive focus error threshold value after rising above the latter or rises above the negative focus error threshold value after falling below the latter.

Abstract: An optical recording medium driving apparatus supporting an optical recording medium having multiple recording layers includes head means including a focusing mechanism and a spherical aberration correction mechanism; focusing control means for driving the focusing mechanism on the basis of a reflected light to perform focusing control on each recording layer; spherical aberration correcting means for driving the spherical aberration correction mechanism on the basis of a spherical aberration correction value to correct spherical aberration; and control means for controlling the focusing control means so as to set the spherical aberration correction value given by shifting the spherical aberration correction value appropriate for the midpoint between a target layer and a first recording layer by a desired value in the spherical aberration correcting means and controlling the focusing control means so as to perform the focusing control with the spherical aberration correction value after the shift being set.

Abstract: Calibration methods are provided for determining servo parameters to enhance an optical drive in reading and writing a blank optical disc. First, test data is written on the blank disc with various writing parameters. Second, the written test data is read from the optical disc with various reading parameters. A plurality of quality measures are obtained, each corresponds to a specific combination of the writing parameter and the reading parameter. An optimal writing parameter and an optimal reading parameter are determined by comparing the quality measures with respect to both the reading and writing parameters respectively.

Abstract: An optical disc apparatus comprises, an optical pickup, a signal extracting unit for reading address information and an RF signal from an optical disc based on signal read by the optical pickup, and a main controller for performing jitter control and focus control. At an initial reading of the optical disc, the main controller determines whether an address information detector succeeds in reading the address information. If not successful (NO in S3), the main controller offsets a defocus position to two points in plus and minus directions from a defocus position giving best jitter (S7), calculates an approximate curve of signal level characteristics with a peak value (S8), and adjusts and allows the defocus value to correspond to this peak value (S9). If the optical disc apparatus cannot read address information, depending on the defocus value, it increases the signal level of the address information by the defocus position adjustment.

Abstract: A pickup control device includes a servo system which processes a first signal for error control read from an optical disk to generate a servo control signal. A clock signal is synchronized with the rotation of the optical disk. Two memories store a frequency component at or lower than a predetermined frequency contained in the first signal and a rotational frequency component contained in the first signal. A first adder adds data from the first memory to the first signal and a second adder, in synchronization with the clock signal, data from the memories to generate a second signal. A correction unit writes into the second memory the frequency component or the rotational frequency component and reads data and supplies data to the first adder, and reads and updates data stored in the first memory.

Abstract: In an information reproducing apparatus in which a liquid crystal lens element is used for the selection and switching of layers, the instability of servo control during the switching of the layers due to the overlapping of signals from two layers is eliminated and the focal point is shifted onto the correct switched layer. During the switching of the liquid crystal lens, a focus bias is added depending on the direction in which the layers are switched so as to stabilize servo control. Alternatively, the objective lens is held during the switching and after the switching of the liquid crystal lens element, the hold state is released in synchronization with the rotation of the disk.

Abstract: The present invention is to provide an apparatus and method for calibrating focus balance in an optical disk drive. A focus servo unit controls a pick-up head to focus and read a mark for generating an RF signal. A jitter generator separates a jitter signal from the RF signal to form a jitter frequency. A focus balance unit compares sequential jitter frequencies to check the convergence and the goal, and determines the direction and variable of calibrating focus balance to generate an error signal. A compensator receives the error signal through the focus servo unit to control the pick-up head for calibrating focus balance.

Abstract: A focal control adjusting method according to the present invention comprises a first step for detecting a focal error signal obtained through condensing and irradiating a light beam on a rotating recording medium, and a second step for setting a focal control gain for controlling a positional shift between a recording surface of the recording medium and the light beam based on the focal error signal detected in the first step, wherein a result obtained by multiplying the position detection signal (sub light beams) by a preset coefficient is added to the position detection signal (main light beam), and a result of the addition is detected as the focal error signal in the first step, and the coefficient is set in accordance with the focal error signal in the first step.

Abstract: A method for pre-calibrating a balance gain of an analog front end in an optical disk drive to calibrate a variation of a focus balance. The method includes the steps of: adjusting the balance gain of the focus balance; moving a lens and getting an S curve; and comparing a positive half cycle of the S curve with a negative half cycle of the S curve. When the positive half cycle is equal to the negative half cycle, it represents that the balance gain of the focus balance is optimized and the procedure ends; or otherwise the above-mentioned steps are repeated to adjust the balance gain of the focus balance again. Because the balance gain is pre-calibrated, the optimal power calibration, the successful disk-reading possibility, the write-in quality and the stability of the disk judging mechanism can be enhanced and the consistency and the stability of the product can be improved.

Abstract: A focus servo apparatus which comprises an optical pickup having a power lens that changes an incidence angle of laser light incident on an objective lens and a power lens actuator that drives the power lens along an optical axis direction. In a focus search operation, the focus servo apparatus controls the power lens actuator to drive the power lens along the optical axis direction and detects having been brought into the focus servo area on the basis of a focus error signal obtained from photo-reception outputs from a photo-detector of the optical pickup, and then allows a focus servo to be in lock and returns the power lens to its initial position with driving the objective lens so as to maintain the lock state.

Abstract: An optical disk device for recording or reproducing an optical disk has: an objective lens for irradiating a laser beam to the optical disk; an actuator for moving the objective lens in the radial direction of the optical disk; and a spindle motor for rotating the optical disk. After the laser beam irradiated to the optical disk passed through a PID portion of the optical disk, the actuator moves the objective lens in the radial direction of the optical disk at a timing corresponding to a rotational speed. Between signals to drive the actuator, an output time of a deceleration signal is set to a predetermined ratio of a time during which an acceleration signal is outputted. While the deceleration signal is outputted, a light spot passes through the PID portion.

Abstract: A system and methods for evaluating the response of an optical digital disk player to anomalies in optical digital disks are provided. The system includes a simulator configured to provide digital simulated output signals simulating the output of an optical digital disk player during playback of an optical digital disk having an anomaly. The system also includes digital-to-analog converter circuitry to convert the digital simulated output signals to analog simulated output signals and provide the analog simulated output signals to processing circuitry. The processing circuitry generates control signals based on the value of the analog simulated output signals, and provides the control signals as outputs.

Abstract: An optical disk apparatus includes: a light source that emits laser light; an optical section including an objective lens group positioned in close proximity to an optical recording medium to generate near-field light from laser light emitted from the light source; a gap servo section configured to control a gap between the optical recording medium and the optical section on the basis of a return light quantity of the laser light via the optical section; a focus adjusting section configured to adjust focus of the near-field light radiated onto the optical recording medium of the optical section, in a state where gap servo is being performed by the gap servo section; and a gap servo correcting section configured to correct the gap servo by the gap servo section when focus of the near-field light is adjusted by the focus adjusting section.

Abstract: In an optical recording medium drive apparatus, an optical recording medium is illuminated with a laser beam emitted from a head via an objected leans, and the head detects light reflected from the optical recording medium being illuminated with the laser beam. A signal generator generates a reflected light signal in accordance with the reflected light detected by the head. A controller drives the objective lens via a focusing unit, and detects peaks in the reflected light signal obtained when the objective lens is driven in a focusing direction. The controller determines whether the optical recording medium is of a single layer type or a multiple layer type by determining whether a pattern of the detected peaks is similar to one of patterns which can occur if the optical recording medium is of the single layer type.

Abstract: A method and system for obtaining focus optimization in an optical disc system is disclosed. The focus offset of a recording unit is set to a first of a plurality of predetermined values. A HF quality value is measured and stored for the selected focus offset value of the recording unit. The focus offset is then set to a best-known focus offset value. Tracks on the optical media being read are then jumped. The above steps are then repeated for each of the plurality of predetermined focus offset values. The optimal focus setting is then determined from the stored HF quality measurements.

Abstract: An optical disk apparatus includes: a servo control unit, operable to execute a servo control of focusing based on a focus error signal and to execute a servo control of tracking based on a tracking error signal; a detrack regulating unit, operable to execute a detrack regulation for setting an offset voltage, which is to be added to the tracking error signal, to be a voltage for giving the highest signal quality of an output of an optical pickup; and a defocus regulating unit, operable to execute a defocus regulation for setting an offset voltage, which is to be added to the focus error signal, to be a voltage for giving the highest signal quality of the output of the optical pickup. The defocus regulation is executed in a state in which the servo control of the focusing and the servo control of the tracking are executed. The defocus regulation is executed after the detrack regulation is executed, in the state in which the servo control of the focusing and the servo control of the tracking are executed.

Abstract: A beam spot position control device, for controlling multiple beam spot positions irradiated onto an optical recording medium so as to be disposed linearly, includes a light detecting unit for detecting the amount of return light for each of a plurality of beam spots disposed linearly, a tracking control unit for performing tracking control based on tracking error signals of at least one of the beam spots detected with the optical detecting unit, and a rotation control unit for rotating the plurality of beam spots which are disposed linearly, based on the DC offset amount of the tracking error signals of at least two of the beam spots detected with the optical detecting unit.

Abstract: This optical disk device includes a pickup head, a spindle motor, a signal generation unit, a runout amount calculation unit, and an out of balance disk detection unit. The signal generation unit generates a tracking error signal. The runout amount calculation unit controls the rotational speed of the spindle motor to first and second disk rotational speeds, and obtains, at these rotational speeds, runout amounts TE1 and TE2 of a tracking error signal, and runout amounts FE1 and FE2 of a focus error signal. And an out of balance disk detection unit detects that this optical disk is an out of balance disk, if the absolute value of (TE2×FE2)/(TE1×FE1) is greater than or equal to a threshold value.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical disk device is disclosed that includes loop gain adjustment means for finding the first tracking loop gain of a first region, and loop gain estimation means for estimating the second loop gain of a second region on the basis of the loop gain of the first region. Accordingly, it is possible to set the optimal tracking control loop gain for all regions. As a side benefit, good tracking control stability can be ensured regardless of the region, which improves the reliability of reproduction and recording.

Abstract: In an optical disc apparatus, whether an unrecorded recording layer without information recorded thereon is included in the multiple recording layers of the optical disc mounted inside the apparatus is judged. then when the unrecorded recording layer is judged to be present, a signal for focus offset adjustment is recorded in a non-user data recording area of the unrecorded recording layer, and reproduction of the recorded focus offset adjusting signal is followed by its quality evaluation, which is further followed by calculation and setup of an appropriate focus offset value based on evaluation results.

Abstract: An optical disk apparatus includes an optical pickup head (PUH) which outputs a laser beam through an objective lens. When a control unit receives an instruction to halt data read-out from an optical disk, the control unit moves the PUH to a predetermined position, stores a focus driving voltage corresponding to a position of the objective lens in a memory unit, and halts the output of the laser beam from the PUH. When the control unit receives an instruction to resume the data read-out, the control unit resumes the output of the laser beam from the PUH, starts a focus search on the basis of the focus driving voltage that is stored in the memory unit, moves the objective lens in a direction toward the optical disk, and achieves focus adjustment.

Abstract: An object of the present invention is to provide a focus out detecting apparatus which detects focus out with accuracy during reproducing or recording of data from/on an optical disc having a plurality of recording layers. Further, another object of the present invention is to provide an optical disc apparatus in which a recording or reproducing performance of data is improved by use of the focus out detecting apparatus. A focus out detection signal is output when a level of a focus error signal exceeds a first predetermined level, then reflected light quantity from the optical disc becomes lower than a third predetermined level in a predetermined period, and then the level of the focus error signal exceeds a second predetermined level of an opposite polarity to the first predetermined level.

Abstract: In an optical disk apparatus, for reproducing information recorded on a recording surface of an optical disk, by setting such a focus condition that a tracking servo-error level comes to be maximum with a reflection light from the recording surface, while irradiating a light beam of a semiconductor laser, within a signal processor portion 300 for amplifying a RF signal reproduced from the optical disk is provided an equalizer 330 for lifting up high-frequency region of the RF signal, wherein an optimal control is made on an amount of lifting (i.e., EQ Boost Value) by the equalizer, depending upon a difference (?AF) between a focus offset amount at which the RF signal reproduced comes to be maximum and a focus offset amount at which jitter of the RF signal reproduced come to be minimum.

Abstract: In response to the trend toward the increase in the number of data layers of optical discs, the invention provides a data erasure method and its optical disc apparatus that enable faster data erasures with a simpler configuration. Test erasures are performed on the test areas T of data layers of an optical disc while the power level Pe of data erasure laser light and the defocus amount ?f of the data erasure laser light from a target data layer are changed. Based on the results of the test erasures, the optimal erasure condition that enables a simultaneous data erasure from the greatest number of data layers is determined. Based on the determined optimal erasure condition, then, the optimal erasure sequence that enables data erasure from all of the data layers with the fewest number of times is determined.

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