Abstract: According to one embodiment, a focus position control method includes irradiating a beam to an optical disc via an objective lens, receiving reflected light and outputting a signal, generating a focus error signal, detecting an amplitude of a signal high-pass-filtering the signal, detecting an intensity of a signal low-pass-filtering the signal, supplying a driving voltage corresponding to the focus error signal to a drive coil configured to move the objective lens to an optical axis direction of the beam when the amplitude is larger than the first value, or when the amplitude is not larger than the first value and the intensity is smaller than the second value, and supplying a driving voltage having a constant voltage value to the drive coil when the amplitude is not larger than the first value and the intensity is not smaller than the second value.

Abstract: Disclosed is a TE signal polarity determining method, which includes: (a) obtaining a detection signal from an optical disc; (b) obtaining characteristics of the detection signal corresponding to different polarities of the TE signal; and (c) determining whether an original polarity of the TE signal should be changed or not according to the obtained characteristics.

Abstract: When a remaining number of tracks is smaller than a first threshold value, a coarse seek operation is determined to be normal, and therefore, a learning process is not executed. If the remaining number of tracks is not smaller than a second threshold value, the coarse seek operation is determined to be abnormal, and a voltage learning process id executed. If the remaining number of tracks is not smaller than the first threshold value and smaller than the second threshold value and prescribed conditions are satisfied, the operation is determined to be abnormal, and a time learning process is executed.

Abstract: A disc-driving apparatus has an optical pickup including an objective lens. The objective lens has an optical axis that is met on a line excluding a central axis of revolution of a disc. The apparatus has storage device that stores plural correction values obtained by detecting fluctuations in amplitude of a tracking error signal with respect to a radial direction of the disc or a quantity of de-tracking with respect to the radial direction thereof. The apparatus has control device that reads the correction value from the storage device and, when the optical pickup is operating, corrects the tracking error signal to conduct servo control based on the corrected tracking error signal.

Abstract: The present invention relates to a device (1) for scanning an optical recording medium (3), comprising an optical unit (5) for reading data from and/or writing data to said recording medium (3) by scanning said recording medium (3) with a radiation beam (21), said radiation beam (21) being positioned on said recording medium (3) in response to a tracking error signal, a tracking means (7) for generating said tracking error signal and a position control means (11) for controlling a radial scanning position of said radiation beam (21) in respect to a track on said recording medium (3).

Abstract: An optical-information recording medium includes a substrate that includes a servo surface having a servo pattern thereon; an information recording layer laminated on the servo surface of the substrate capable of recording information as a hologram produced by interference between an information beam containing the information and a reference beam; an address servo area that is formed as a part of the servo pattern, and that records therein address information and clock information for aligning a beam, emitted from an optical-information recording apparatus for recording information in the information recording layer, to a target position in the information recording layer; and a following up servo area that is formed as a part of the servo pattern, and that is to be irradiated by the beam to make the beam follow a rotation of the optical-information recording medium.

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 disc device for recording and/or reproducing information with respect to a disc having flexibility includes a head for writing and/or reading, the head being disposed below the disc; a disc rotating section which rotates the disc; and a head retracting section which retracts the head to a retracted position where contact with the disc is avoidable, based on a judgment that power supply to the disc device is cut off.

Abstract: A tracking offset is reduced. The effect of an SPP signal fluctuation is reduced by using a variable mixing ratio DPP method, and a residual tracking offset is minimized.

Abstract: An optical head device may include a twin laser light source which is integrally provided with a first laser beam emitting element and a second laser beam emitting element, a light receiving element, and an optical system including an objective lens for converging a laser beam on an optical recording medium. The optical system is provided with a detection lens structured of a toric lens. The toric lens applies an astigmatic difference caused by a toric face to the one of the return light beams, and the toric lens applies the other of the return light beams an astigmatic difference caused by a toric face and astigmatism composed of astigmatism and curvature of image field caused by passing off-axis position to coincide a focusing position of the first laser beam with that of the second laser beam.

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: The present invention relates to a drive for accessing an optical record carrier (2) comprising means (4) for determining the type of record carrier, in particular for distinguishing a read-only record carrier from a recordable or rewritable record carrier having a wobbled groove in the lead-in zone, said means comprising: a DPD measuring unit (41) for measuring the differential phase detection (DPD) signal, a PP measuring unit (42) for measuring the push-pull (PP) signal in case no DPD signal could be measured, a wobble locking unit (43) for locking, in case a PP signal could be measured, to the wobble embedded in said wobbled groove using a first and/or a second polarity setting, and an indication unit (44) for generating a first indication signal indicating that the record carrier is a read-only record carrier if a DPD signal could be measured and that the record carrier is a recordable or rewritable record carrier if no DPD signal but a PP signal could be measured and if locking to the wobble has been suc

Abstract: The invention provides a method for performing track-seeking in an optical disk drive. In one embodiment, the optical disk drive is about to perform a series of operations comprising a plurality of prior operations and a track-seeking operation, and the track-seeking operation is divided into a pre-seek procedure and a true-seek procedure. First, a microprocessor of the optical disk drive performs the prior operations. Whether the microprocessor is unoccupied is then detected before performing the prior operations is completed. When the microprocessor is detected to be unoccupied, the microprocessor performs the pre-seek procedure. The true-seek procedure is then performed according to results of the pre-seek procedure to move the pick-up head to a destination address of an optical disk.

Abstract: An apparatus for detecting a probe position error includes a position error extracting unit extracting probe position errors from signals detected by a probe; a position error adding unit calculating the probe position errors in units of a predetermined time; and a signal processing unit storing a past probe position error calculated by the position error extracting unit and generating a probe position error by processing the past probe position error and a current probe position error. An apparatus for tracking data includes a scanner moving a data storage medium; a probe detecting the signals from a data storage medium; an error detector detecting probe position errors in a half-period of an error extracting signal by applying the error extracting signal used to extract the probe position errors to the signal detected by the probe; and a compensator compensating for the probe position errors detected by the error detector.

Abstract: A simple circuit configuration allows an optical disc apparatus to reduce a problem of sound skips occurring due to damage on an optical disc. To this end, an LPF extracts a low-frequency component from a tracking actuator drive signal obtained by a tracking actuator driver. When the optical disc apparatus reads and writes information to and from the optical disc, a sled drive signal supplier outputs a sled pulse signal, as a drive signal for a sled motor, for a set-up predetermined time within each interval of a predetermined length, the sled pulse signal having a level corresponding to a level of the low-frequency component obtained by the LPF. On the other occasions, the sled drive signal supplier outputs the low-frequency component obtained by the LPF as the drive signal for the sled motor.

Abstract: A method of determining whether an optical pick-up of an optical device passes through a data track of a storage device during track-seeking based on a radio frequency (RF) signal, a radio frequency zero cross (RFZC) signal radio and a track-seeking signal of the optical device. When the optical pick-up of the optical device passes through a data track of the storage device during track-seeking, a trigger signal is sent to a data phase locked loop of the optical device for frequency and phase adjustment. The method can activate the data phase locked loop of the optical device while the optical device is performing track-seeking.

Abstract: A method of inter-layer search of a multi-layer disk, the method including determining whether a search is required of a layer other than a currently accessed layer; searching the currently accessed layer for a position corresponding to a target address on the layer not currently accessed; and moving access to the layer not currently accessed according to the position corresponding to the target address.

Abstract: A tracking error control system includes a tracking error signal generator in communication with an optical pickup head, a DC detector in communication with the tracking error signal generator and a comparator in communication with the DC detector and the tracking error signal generator. The operating optical signals received by the optical pickup head are operated with an offset signal to generate a tracking error signal. A direct current voltage of the tracking error signal is detected and compared with a reference voltage. The offset signal is adjusted according to the comparison result and fed back to the tracking error signal generator to adjust the tracking error signal.

Abstract: An optical disk drive is designed to read and/or write data from/on a spiral string of tracks where land and groove tracks are alternated. The drive includes: a light source for radiating a light beam; a lens for converging the light beam; a mechanism for moving the lens; a photodetector for generating an electrical signal based on at least a part of the light beam reflected from the optical disk; and a control section for controlling the light source and the mechanism responsive to the electrical signal. While performing a seek operation by having the lens moved by the mechanism such that a target track, from/on which the data should start being read or written, is irradiated with the light beam, the control section tries to get a PLL locked by irradiating another track, which precedes the target track by at least one, with the light beam.

Abstract: A servo control apparatus includes: a drive section that applies a thrust to move a driven object; a storage section that stores a control circuit output initial value; an approaching control section that moves the driven object toward a target position; an error signal detection section that detects an error signal varying according to a difference between the position of the driven object and the target position; a start position calculation section that calculates a start position of a servo control process; an arrival detection section that detects whether the driven object reaches the start position; a control circuit initial value calculation section that calculates a control circuit initial value of a control system and supplies it to a control circuit of the control system; and a servo control starting section that starts the servo control process when detecting that the driven object has reached the start position.

Abstract: A disc drive apparatus (1) for optical discs (2) comprises: a frame (3); a sledge (10) displaceably mounted with respect to said frame (3); a lens actuator (43, 21) displaceably mounted with respect to said sledge (10); and a control unit (90) for generating a control signal (SCL) for the lens actuator (43, 21). The control unit (90) is designed, during a jump operation, to generate said control signal (SCL) for the lens actuator (43, 21) on the basis of an actuator deviation signal (SAS) representing a difference between actuator position (XA) and sledge position (XS).

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

Abstract: A light beam is emitted to an optical disc from an optical pickup. The optical pickup is moved over the optical disc so that a light spot of the light beam crosses tracks formed on the optical disc. Detected are tracking error signals carried by a light beam reflected from the optical disc. Each tracking error signal is detected when the light spot crosses a corresponding track among the tracks formed on the optical disc. Track crossing pulses are generated based on the tracking error signals. Each track crossing pulse is generated for the corresponding track. Measured next is a half period of each track crossing pulse. It is determined whether a defect occurs to each track crossing pulse, based on a latest half period measured at present and an anterior half period measured one half-period before the latest half period. Generated when determined that no defect occurs is an average half period of the latest and the anterior half periods.

Abstract: The invention relates to a tilt controller for controlling the tilt (radial and/or tangential) of an actuator relative to a recording surface of an optical storage medium, compensation for the radial to tilt crosstalk being effected by feeding a filtered version of the radial control signal (r) into the tilt branch, and/or compensation for the focus to tilt crosstalk being effected by feeding a filtered version of the focus control signal (f) into the tilt branch.

Abstract: A device for protecting a slicer in reading signals on a defect disc from disturbance and instability is provided. The device includes a defect detection unit, a slicer and a logic combination unit. The defect detection unit receives a plurality of defect detection signals to detect various defects for setting a plurality of defect flag signals, wherein the plurality of defect detection signals at least include an envelope signal of a RF signal and bit modulation signals. The slicer receives and digitalizes the RF signal. The logic combination unit performs logic operation on the defect flag signals in order to detect a specified defect and to trigger defect protection for the slicer. A method for protecting a slicer in reading signals on a defect disc is also provided.

Abstract: This disk device includes a pickup head (PUH), a PUH shift control unit, and an inner circumference position detection unit. The PUH reads out data upon a disk. The inner circumference position detection unit detects whether or not the PUH has shifted to the inner circumferential edge of the disk. And, after having stopped the PUH in the neighborhood of a position at which the detection state of the inner circumference position detection unit changes over, the PUH shift control unit determines a shift time period T5 for the PUH when a predetermined operation has been performed. And, by supplying power during the time period T7, the PUH is stopped at a predetermined position.

Abstract: An off-track duty measurement unit measures off-track detection sensitivity on the basis of an off-track signal, and track cross cycle information that is obtained from a tracking error signal measured by a track cross cycle measurement unit, whereby off-track detection sensitivity can be measured more accurately. Further, an off-track detection sensitivity controller changes the detection sensitivity of an off-track signal detector according to the obtained off-track detection sensitivity, whereby the off-track sensitivity can be kept constant for various kinds of discs, and accordingly, stabilities of off-track detection, track pull-in judgement, and track jumping can be secured.

Abstract: An appropriate track calculation equation is inducted according to a relationship between a storage area and a track pitch of a compact disc, and a pickup unit is instantly shifted to a location calculated with the track calculation equation. Therefore, an error after performing a track jump modulation is reduced to a smallest degree, and in other words, the pickup unit may access a location on the disc currently required by a user without frequent or time-consuming long seeks. As a result, when the pickup unit accesses compact discs having unknown formats, which indicate different capacities or properties, a track error may be calculated in a shortest time so as to shift the pickup unit accordingly and to fix track jumps, and the user may browse any location on the compact discs having unknown formats smoothly.

Abstract: A method for determining a track searching direction is disclosed. The method takes advantage of the characteristic that the movement of the photo-diode with respect to the optical disk is not perpendicular to the track direction. Therefore, the phase difference between the front side and the rear side of the photo-diode could be used to define a seeking error signal. The seeking error signal is used, together with a tracking error (TE) signal and a radio frequency ripple (RFRP) signal, to determine the track searching direction. Because the seeking error signal has a better signal-to-noise ratio, the phase lead or lag can be determined more accurately. As a result, the accuracy of detecting the track searching direction on a blank disk is improved.

Abstract: A method for determining a kind of optical recording medium includes: performing focus searching and track searching on an optical recording medium; and determining a kind of optical recording medium according to an optical signal generated by the focus searching and an optical signal generated by the track searching.

Abstract: In an integrated optical unit of the present invention, a photo detector (12) and a holding member (17) that sustains a semiconductor laser (11) are provided on a polarizing beam splitter (14). This makes it possible to reduce a deviation from a designed value due to tolerance, and adjust a relative positional relationship between the semiconductor laser (11) and the photo detector (12). Therefore, returned light from an optical disk (4) is accurately adjusted with respect to a division line of a photo-detecting device (13). As a result, stable servo-control is realized, and an information signal with fine quality is obtained.

Abstract: An acceleration pulse waveform adjusting circuit (10) and a deceleration pulse waveform adjusting circuit (11) change the amplitude of a track jump pulse in accordance to linear velocity, so as to stably carry out track jump over a wide range of linear velocities. In case tracking gain is to be changed according to the linear velocity, the acceleration pulse waveform adjusting circuit (10) and the deceleration pulse waveform adjusting circuit (11) make the amplitude of acceleration pulse larger and the amplitude of deceleration pulse smaller, respectively, when the tracking gain is high, so as to stably carry out track jump operation with the given tracking gain.

Abstract: An optical scanning device for scanning a record carrier (22), the record carrier has an outer face (24) and the optical scanning device comprises a radiation source system (2) arranged to generate a radiation beam; an objective system (20) having an exit face (76) and which is arranged between the radiation source system and the record carrier and provides for evanescent coupling of the radiation across a gap between the exit face of the objective system and the outer face of the record carrier; and a radiation detector arrangement for detecting radiation after interaction with the record carrier. The radiation detector arrangement is arranged to produce a tilt error signals (?, ?) representing a tilt misalignment between the exit face of the objective system and the outer face of the record carrier.

Abstract: A method for controlling a stepper motor in an optical disc system, comprising the steps of (A) measuring a static offset of a center error signal, (B) measuring a maximum value, minimum value and an average value of the center error signal in response to rotating the optical disc, (C) computing one or more upper threshold values and one or more lower threshold values of the center error signal, (D) sampling the center error signal, (E) comparing the center error signal to the one or more upper threshold values and to the one or more lower threshold values and (F) computing a control output to control the stepper motor in response to comparing the center error signal to the one or more upper and lower threshold values.

Abstract: A diffractive part for an optical scanning device is described. The device is for scanning a first information layer by means of a first radiation beam having a first wavelength and a first polarisation, a second information layer by means of a second radiation beam having a second wavelength and a second polarisation, and a third information layer by means of a third radiation beam having a third wavelength and a third polarisation. The first, second and third wavelengths differ from each other. The device includes a radiation source for supplying the first, second and third radiation beams, an objective lens system for converging the radiation beams on the respective information layer, and a diffractive part arranged in the optical path of the radiation beams.

Abstract: A track-jump control system and method are provided. The track-jump control system applied in an optical disc drive comprises a signal generator, a protection device, a velocity estimator, and a controller. The signal generator receives the signal from the PUH and generates a tracking signal and a position signal. The protection device receives the position signal and when the position signal represents the PUH pass a predetermined position of the optical disc, the protection device generates a protection signal. The velocity estimator estimates the velocity of the PUH according to the tracking signal, and then generates a velocity signal. The controller receives the velocity signal and the protection signal, protects the velocity signal according to the protection signal, and generates a control signal to control the track-jump according to the protected velocity signal.

Abstract: The invention proposes an appliance for recording or playing back information having means for detecting or moving the position of a scanning device over a disc with a wobble track, said appliance being able to be used both in recorded and in unrecorded areas of the disc and hence being able to be used both for write-once and for rewriteable recording media with a wobble track, and said appliance additionally permitting fast determination of the scanning location without decoding of scanned-location information which is contained in the wobble track. According to the invention, a wobble signal is scanned from the wobble track on the disc using a scanning device, and a wobble frequency contained in the wobble signal detected from the disc is used for detecting or moving the position of the scanning device.

Abstract: An appropriate track calculation equation is inducted according to a relationship between a storage area and a track pitch of a compact disc, and a pickup unit is instantly shifted to a location calculated with the track calculation equation. Therefore, an error after performing a track jump modulation is reduced to a smallest degree, and in other words, the pickup unit may access a location on the disc currently required by a user without frequent or time-consuming long seeks. As a result, when the pickup unit accesses compact discs having unknown formats, which indicate different capacities or properties, a track error may be calculated in a shortest time so as to shift the pickup unit accordingly and to fix track jumps, and the user may browse any location on the compact discs having unknown formats smoothly.

Abstract: An apparatus comprising a center error creation circuit, a center error offset injection circuit and a center error controller. The center error creation circuit may be configured to generate a center error signal in response to one or more photo-diode signals. The center error offset injection circuit may be configured to (i) offset the center error signal and (ii) generate an offset signal. The lens controller may be configured to adjust a lens in a sled housing at a mechanical center is response to the offset signal when the apparatus is in a rough seek mode.

Abstract: An apparatus comprising a center error creation circuit, a center error controller, and a center error repeatable run out circuit. The center error creation circuit may be configured to generate a center error signal in response to photo-diode signals. The center error controller may be configured to adjust a lens to a center position in a sled housing with a step motor in response to a center error measure signal. The center error repeatable run out circuit may be configured to generate a center error run out signal and the center error measure signal in response to the center error signal. The center error repeatable run out circuit may generate the center error measure signal by measuring the center error signal when the center error run out signal is in a peak phase.

Abstract: An optical pickup device includes: a light source; a light receiving sensor, having main tracking light detection faces and sub-tracking light detection faces; and a hologram, having tracking areas that are divided into main tracking areas and sub-tracking areas along division lines in the tangential direction. In the hologram, each of the tracking areas is alternately divided into the main tracking areas and the sub-tracking areas along the division lines in the radial direction, and the same width is employed in the radial direction for the main tracking areas and the sub-tracking areas.

Abstract: A servo control device couples with an optical pickup head, which outputs a TEZC (tracking error zero crossing) signal. The servo control device includes a detection module, a signal generation module, and a selection module. In this case, the detection module detects emboss areas in an optical disk to output an emboss indication signal. The signal generation module generates a pseudo signal in accordance with the moving speed of the optical pickup head and the TEZC signal. The selection module generates a modified TEZC signal in accordance with the emboss indication signal, the pseudo signal and the TEZC signal. An optical disk drive including the servo control device and a servo control method thereof are also provided.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: A signal generator generates a track traversing signal, and a driver causes a pick-up to traverse across tracks of a disc in accordance with the track traversing signal. An error signal generator generates a tracking error signal from the pick-up traversing across the tracks of the disc in accordance with the track traversing signal. A parameter calculator determines a value of a calibration parameter from the tracking error signal that is generated without delay and without signal distortion from low frequency components.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: An optical disc drive device has an FE signal generator which generates a focus error signal, a TE signal generator which generates a tracking error signal, a return beam detector which detects a return beam reflected by an optical disc after irradiated by an optical pickup to generate a return beam level signal, a return beam gain setting part which sets amplitude adjustment amount of the return beam level signal so that a signal level of the return beam level signal generated by the return beam detector coincides with a predetermined reference level, an FE gain setting part which sets amplitude adjustment amount of the focus error signal in accordance with the signal level of the return beam level signal adjusted by the return beam gain setting part so that a signal amplitude of the focus error signal is constant, and a TE gain setting part which sets amplitude adjustment amount of the tracking error signal in accordance with the signal level of the return beam level signal adjusted by the return beam gain

Abstract: The present invention relates to optical disc drives including a carriage which is movable radially of an optical disc and an objective lens which is supported on the carriage movably in radial directions of the disc for formation and placement of a beam spot on the disc. The invention aims at reducing minute vibration of the objective lens during a seek control stably and reliably. According to the present invention, the minute vibration of an objective lens (104) is reduced by moving the objective lens (104) at a relative speed of zero with respect to a carriage (101) during the seek operation, based on a TZC signal which indicates that the beam spot has crossed over a track in an optical disc (2). In this control, a position of the objective lens (104) in the carriage (101) right before starting the seek operation is detected and stored in a memory (802). Then, a position of the objective lens (53) in the carriage (101) is detected during the seek operation.

Abstract: A method capable of detecting spherical aberration caused by a storage medium includes generating a plurality of light beams having distinct phases by diffracting light emitted from a light source using a diffractive optical element, measuring optical signals of the plurality of light beams having distinct phases after being reflected by the storage medium, measuring optical signals of the plurality of light beams having distinct phases after being reflected by a reflective mirror, and updating settings of an adjusting device disposed on an optical path between the diffractive optical element and the storage medium in order to compensate for the spherical aberration caused by the storage medium.

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

Abstract: A disk calibration and search method in a disk drive is provided, in which, after an initialization step, a pickup is jumped to a first position and moved radially in a predetermined direction in response to pulses generated by a frequency generator. During this radial movement the number of tracks crossed are is counted. The counting is continued until a predetermined number of the pulses generated by the frequency generator have been generated. A calculated frequency generator track number is then obtained by dividing the counted number of tracks by the predetermined number of pulses generated by the frequency generator, i.e., calculating a unit track number of the disk per a single movement of the pickup, that is, the number of tracks the pickup moves per pulse generated by the frequency generator. The calculated frequency generator track number is stored in memory used to control the frequency generator for jumping the pickup during a search for a target track.