Abstract: A circuit for controlling the moving of a pickup (track jump) between tracks of a recording medium, such as a CD-ROM. The circuit includes a first circuit which generate a pulse signal corresponding to changing points of a track jump signal and an off track signal. A second circuit generates a signal for controlling the moving speed or deceleration of the pickup, as it approaches a target track, in accordance with the pulse signal.

Abstract: A pickup drive apparatus for recording or reproducing with respect to a recording medium such as a CD and a DVD. In the apparatus, return light produced by irradiating an optical spot is detected by a photodetector, and a push-pull signal is produced from this detection output. A tracking error signal is produced from the push-pull signal by a low-pass filter and a phase compensating circuit. A quasi-ON/OFF control signal having information of an irradiation position of the optical spot is produced from the push-pull signal by a high-pass filter, a comparator, and a single pulse generator. When the quasi-ON/OFF control signal is produced which indicates that the optical spot is positioned on a groove, the tracking error signal is outputted via switching circuits in synchronism with this signal production. A pickup is servo-controlled based on this output signal.

Abstract: A method for determining vertical or horizontal operation of optical disk driver is proposed. A feedback signal from a pick-up head of the optical disk driver is sent to a pre-amplifier to generate a focus error signal. The focus error signal is sent to a compensator to generate a compensation voltage. A low-pass filter removes high-frequency components of the compensation voltage to obtain a DC component of the compensation voltage. A comparator compares the DC component of the compensation voltage with a predetermined threshold value to discriminate the vertical or horizontal operation of optical disk driver.

Abstract: An optical apparatus includes a generator for generating a sine wave based on a rotating disc-shaped information carrier, and an eccentricity measuring device for measuring gain and phase of a sine wave corresponding to eccentricity of the information carrier based on the driving signal from the tracking control and on the measured rotation frequency. Also included is a waveform shaper for shaping the gain and phase of the sine wave generated by the sine wave generator using the measured gain and phase obtained by the eccentricity measuring device. An eccentricity correction is applied by adding together the sine wave shaped by the waveform shaper and the driving signal from the tracking control to drive an optical beam on a desired track of the rotating disc.

Abstract: An optical-system driving apparatus of the present invention comprises a plurality of positioning means for positioning a spot of a light beam in an information recording position on an optical disk, sensing means for sensing the reflected light from the optical disk, a plurality of driving signal generating means for generating a plurality of driving signals for driving the plurality of positioning means respectively on the basis of the result of sensing the reflected light, converting means for converting the plurality of driving signals into a single multiple signal, decoding means for decoding the multiple signal into a plurality of signals, and driving means for driving the plurality of positioning means independently on the basis of the plurality of decoded signals.

Abstract: A method for generating a tracking error signal includes the steps of detecting a first signal representing the amount of reflected light, judging presence or absence of a pit on the current track, and averaging the first signal with respect to time while inverting the detected signal obtained during the presence or absence of the pit. An effective tracking error signal can be obtained in the case of a track pitch smaller than a pitch resolution limit.

Abstract: An optical information recording medium according to the present invention includes at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other. The optical information recording medium further includes: an identification signal region including a pre-pit array, the pre-pit array indicating identification information concerning the groove track and the land track; and a servo control region disposed ahead of the identification signal region along the groove track and the land track, the servo control region including wobble pits positioned so as to shift to opposite sides of a center line of either the groove track or the land track.

Abstract: An optical disc drive for accessing data stored on an optical disc is disclosed. The optical disc drive includes: a sled inside the optical disc drive, the sled sliding relative to the optical disc; an actuator on the sled, the actuator wobbling relative to the optical disc; and a control circuitry for controlling the optical disc drive. The control circuitry includes a focus compensation device for compensating focus errors caused by wobbles of the optical disc generated during rotations of the optical disc; and a high frequency compensator for compensating focus errors caused by wobbles of the optical disc generated during rotations of the optical disc at a frequency higher than a predetermined frequency. The focus compensation device controls the actuator to wobble upward and downward according to wobbles of the optical disc so as to substantially keep up wobbles of the actuator with the wobbles of the optical disc.

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: A tracking servo system with a at least one second order digital filter is presented. The system calculates an error signal and offsets, amplifies, and filters the error signal before a l signal is calculated. The control signal is then utilized to position an optical pick-up unit provides signals from which the error signal is calculated. Filters in the servo system can e a low-pass integrator, a phase lead filter, notch filters, or other filters. At least one of the is a second order digital filter.

Abstract: A servo system that calibrates a cross-talk gain parameter in a tracking error signal to focus error signal crosstalk correction is provided. The cross-talk gain parameter can be optimized such that the effects of a perturbation applied to the tracking servo loop on an adjusted focus error signal, i.e. a focus error signal that has been corrected for crosstalk, is minimized. The optimized cross-talk gain, then, can be set to the cross-talk gain of a set of cross-talk gains that results in the lowest value of a frequency component of the adjusted focus error signal while a perturbation at the frequency is being applied to the tracking servo loop.

Abstract: A device for compensating the error signal produced by a high-speed disk system. The error signal is fed to a compensator and a bandpass filter respectively. The processed signals produced by the compensator and the bandpass filter are summed to output a compensated signal. The bandpass filter processes the rotating frequency portion of the error signal. The compensator includes a lead compensator and a lag compensator either serially connected or parallel connected.

Abstract: An optical disc apparatus corrects the tilting of the optical disc with a high accuracy using first and second tracking error signals. A first tracking error signal, which is an output of subtractor (125), obtained by the push-pull method is corrected by detecting a second tracking error signal. The second tracking error signal is obtained by using the difference of amplitude of first and second signals, which are outputs of adder (130). The first signal is obtained when the light beam passes over a first pit sequence formed in a position offset in one direction orthogonal to the track of disc (100). The second signal is obtained when the light beam passes over a second pit sequence formed in a position offset in the other direction orthogonal to the track.

Abstract: To finely remove an offset from a tracking-error signal which is processed in the digital form at the stage of tracking servo control, an apparatus and method of correcting the offset is provided. In the apparatus and method, an oscillating tracking-error signal used for positionally controlling an optical beam irradiated onto a storage medium to reproduce information recorded thereon is produced. The tracking-error signal is produced in an analog form, then converted into a digital form for use of control of the optical beam. First, set are a first adjustment amount to correct an offset included in the analog-form tracking-error signal as well as a second adjustment amount to correct a further offset included in the digital-form tracking-error signal in the digital form. The analog-form tracking-error signal is corrected with the first adjustment amount (i.e., coarse adjustment), then the digital-form tracking-error signal is corrected with the second adjustment amount (fine adjustment).

Abstract: A focus servo system with a focus close algorithm is disclosed. The focus close algorithm provides a bias control effort to the focus servo system when focus is closed. A method of closing focus includes positioning an optical pick-up unit at a first position away from an optical medium, moving the optical pick-up unit towards a second position by altering a focus control effort, monitoring a sum signal obtained from signals received from the optical pick-up unit, and setting the bias control effort to the focus control effort when a closure criteria is satisfied. In some embodiments, the closure criteria includes that a sum signal exceeds a threshold value. In some embodiments, the closure criteria includes that a focus error signal is below a FES threshold.

Abstract: A servo system with in an optical disk drive with an inverse non-linearity compensation is disclosed. An error signal calculated from signals received from an optical pick-up unit can be offset by an offset value and amplified by a gain in the early stages of a calculation of a control signal for controlling a position of the optical pick-up unit. The non-linearity compensation adjusts the gain based on the offset value so that the response of the servo system to changes in the error signal is substantially linear. The error signal can be the tracking error signal in a tracking servo system and can be the focus error signal in a focus servo system.

Abstract: A method for determining vertical or horizontal operation of optical disk driver is proposed. A feedback signal from a pick-up head of the optical disk driver is sent to a pre-amplifier to generate a focus error signal. The focus error signal is sent to a compensator to generate a compensation voltage. A low-pass filter removes high-frequency components of the compensation voltage to obtain a DC component of the compensation voltage. A comparator compares the DC component of the compensation voltage with a predetermined threshold value to discriminate the vertical or horizontal operation of optical disk driver.

Abstract: A device for finding the focus between an optical pickup head and an optical disk by tapping signals from a radio frequency amplifier comprises a high-pass filter for receiving a focus error signal from the radio frequency amplifier and generating a focus error high-pass signal; and a decision circuit that couples to the high-pass filter for receiving the focus error high-pass signal and using a focus zero cross level as a reference for determining a correct focusing point. The focus between the optical pickup head and the optical disk is found when the focus error high-pass signal reaches the positive focus zero cross level or the focus error high-pass signal reaches the negative focus zero cross level.

Abstract: A method for compensating track offset in an optical disk drive is provided, which achieves complete compensation of the track offset and than reduces the compensation time for the track offset. (a) An optical disk with wobbled grooves is provided, the wobbled grooves being used for generating a wobbling signal with a wobbling period. (b) A beat-inducing signal is recorded on the disk. The period of she beat-inducing signal has a specific relationship with the wobbling period in such a way that a beat signal is induced by the beat-inducing signal and the wobbling signal. (c) A tracking-error signal is generated using a push-pull method by optically reading the wobbled grooves of the disk and the beat-inducing signal recorded on the disk. The tracking-error signal contains a bear signal induced by the beat-inducing signal and the wobbling signal. (d) Track offset is compensated based on the beat signal contained in she tracking-error signal.

Abstract: An analog to digital circuit assembly includes a circuit for multiplexing a reference voltage input of an analog to digital converter to produce alternating normalized and referenced digital outputs of an analog signal input at a rate controlled by a sampling clock which includes a switch including first and second inputs, an output, and a control input for alternately connecting the first and the second inputs to the output, the output being applied to the reference voltage input. An information detection device having a detection output and a servo mechanism that controls operations on detected information is provided in conjunction with a signal summing circuit, a direct current voltage reference, a control clock connected, a servo error signal circuit having a servo error signal output and input, a sampling clock, and a processing circuit having an input connected to a digital output of the analog to digital converter and an output for controlling the servo mechanism.

Abstract: An optical information recording medium according to the present invention includes at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other.

Abstract: The present invention provides an information storage apparatus generating a tracking error signal in which apparatus and method the differential push-pull method is applied to a three spot method using a main beam and two sub-beams, the main beam for writing data on a recording medium and reading data from the recording medium, the information storage apparatus including the following parts. A beam moving part moves the main beam from a blank track to a recorded track. A center value calculating part calculates a center value of the tracking error signal when said main beam is moved from the blank track to the recorded track so that a reference value of the tracking error signal is corrected in accordance with the center value when said main beam writes data on the recording medium.

Abstract: An optical pickup including a light detection element to divide light reflected from an optical recording medium into first through fourth light beam portions in a radial direction of the optical recording medium. From detection signals from the light detection element, a reproduction signal detection portion detects an information signal, and a tracking error signal detection portion detects a tracking error signal. The light source emits light that is focused as a single light spot on a main track of the optical recording medium. The tracking error signal detection portion gain controls and sums push-pull signals from the detection signals to detect, during a recording operation, a tracking error signal with reduced push-pull offset without erasing existing signals on adjacent tracks. The reproduction signal detection portion sums and gain controls the detection signals to detect an information signal containing reduced crosstalk from adjacent tracks.

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: A wobble detecting apparatus for an information recording and/or reproducing for an optical disk, includes a wobble detecting unit for detecting a wobble on the basis of a signal from a light receiving element which receives light reflected from the optical disk; an offset voltage generating unit for generating an offset voltage; an adder unit for adding said offset voltage to a control signal to an actuator for the optical disk; an actuator switch for on/off controlling a control signal to said actuator; and a control unit for turning on said actuator for wobble detection to decide whether or not the wobble has been detected by said wobble detecting unit, and if the wobble has not been detected, causing said offset voltage generating unit to generate a positive or negative prescribed voltage to decide further whether or not the wobble has been detected by said wobble detecting unit. In this configuration, the wobble can be detected with high accuracy.

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: An optical pick-up generates a 0-th order diffraction light and ±1st order diffraction lights by a diffraction grating and irradiates the same to an optical disc. The ±1st order diffraction lights have phase distributions equivalent to a wavefront aberration of the optical disc when there is a tilt in the optical disc. Distances between the center of the main optical spot and centers of sub optical spots in a disc radial direction on a recording surface are whole multiples of a track pitch. The generation circuit generates a main push-pull signal corresponding to the 0-th order diffraction light and first and second sub push-pull signals corresponding to the ±1st order diffraction lights and generates tracking error signals TE as differential push-pull signals obtained by subtracting a sum signal of the first and second sub push-pull signals from the main push-pull signal.

Abstract: An error signal detection method and apparatus for an optical recording/reproducing system.

Abstract: A method of tracking servo for an optical pickup device comprises the steps of generating each individual push pull signal (an SPP1 signal, an SPP2 signal and an MPP signal) with a photo detector composed of a main photo detector having four photo-detecting sections crosswise and two side photo detectors having respectively two photo-detecting sections left and right, and generating a tracking error signal (a DPP signal) on the basis of operational output from the push pull signals resulting from respectively canceling the amounts of DC offset produced in each of the push pull.

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: An optical-disk play-back system has a lens that receives a light beam reflected from a data surface of an optical disk. The lens focuses the light on four quadrant photodiodes. The position of the lens relative to the photodiodes is adjusted by a standard tracking control loop. In addition, the sledge position is controlled by a sledge-center-error signal. Since the sledge position changes only infrequently, the center error is a low-frequency signal. A non-linear center-error-generating circuit uses two op-amp stages. Signals from an inner pair of photodiodes are summed and applied to one input of the first-stage op amp, while signals from an outer pair of photodiodes are summed and applied to the other input of the first-stage op amp. The first-stage op amp output an overall error signal that includes high-frequency errors. A high-pass filter removes low-frequency components output from the first-stage op amp. The high-pass filter drives an inverting input of the second-stage op amp.

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 tracking servo apparatus in which reflection light obtained when a laser beam is irradiated onto a recording surface of an optical disc is photoelectrically converted, thereby obtaining a photoelectric conversion signal, a tracking error signal showing a deviation amount of an irradiating position of said laser beam for a track in a disc radial direction on the recording surface is generated by the photoelectric conversion signal, a spherical aberration occurring in an optical system is detected, a level of the tracking error signal is corrected on the basis of the detection result, and the irradiating position of the laser beam is moved in the disc radial direction in accordance with the level-corrected tracking error signal.

Abstract: A tracking error generating device which is capable of correctly detecting a phase difference and generating a normal tracking error even when recording marks (or spaces) on an optical disc have short lengths. The tracking error generating device employs, as evaluation target signals, respective output signals of light receiving elements or a signal generated by performing predetermined addition processing on the respective output signals of the light receiving elements, and has a determination circuit for determining whether the evaluation target signals each have a sufficiently large amplitude or time width to generate a tracking error signal, and a selective phase difference supply circuit for selectively supplying a phase difference signal to a smoothing circuit on the basis of a determination result of the determination circuit.

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 and method is disclosed for focus control of a beam of radiant energy, wherein a detector of the beam has first and second outputs responsive to a position of the beam. A circuit is coupled to the outputs of the detector for producing an error signal representing a displacement of the focus from a predetermined position, wherein the error signal has a periodic characteristic relative to the displacement. A servo responsive to the error signal restores the displaced beam to the predetermined position. A local feedback loop is coupled to the outputs of the detector, and includes first and second periodic function generators, each responsive to the error signal. The second periodic function generator has an output that differs from an output of the first periodic function generator by a phase angle, preferably 90 degrees. A first multiplier multiplies the first output of the detector by the output of the first periodic function generator.

Abstract: A recording medium that is adapted to maximize the recording capacity and to simplify the configuration of an information recording/reproducing apparatus including a pickup. In the medium, a different type of wobbling signals are preformatted in each of the adjacent land and groove signal tracks. A same-phase wobbling signal provided by wobbling each side of the respective land and groove signal tracks in the same phase and a different-phase wobbling signal provided by wobbling each side of the respective land and groove signal tracks in a different phase are used as the different type of wobbling signals. The physical positions of all the land and groove signal tracks are indicated by the same-phase wobbling signal.

Abstract: The present invention provides a focusing and tracking servo circuit used in an optical disk device that can maintain stability of the focusing and tracking servo at a time of recording or reproduction. This focusing and tracking servo circuit includes: a first storage unit that stores a parameter corresponding to light beam power at a time of recording; a second storage unit that stores a parameter corresponding to light beam power at a time of reproduction; and a selector unit that selects from the parameters stored in the first and second storage units upon switching between recording and reproduction, and sets the selected parameters in a detector unit. With this structure, the parameters can be instantly switched at the same time as the switching between recording and reproduction, and the stability of the focusing and tracking servo can be maintained.

Abstract: A method of generating a lens position detection signal for optical disc apparatus. The signal is generated in a way which provides continuous position information. The signal is also independent of changes in reflectivity on the surface of the optical disc. Moreover, the signal can be calibrated for DC offset due to misalignment and changes in photo-detector output.

Abstract: A device for compensating the error signal produced by a high-speed disk system. The error signal is fed to a compensator and a bandpass filter respectively. The processed signals produced by the compensator and the bandpass filter are summed to output a compensated signal. The bandpass filter processes the rotating frequency portion of the error signal. The compensator includes a lead compensator and a lag compensator either serially connected or parallel connected.

Abstract: A tracking servo control apparatus for muting a tracking error signal when a mirror signal is generated, in an optical disk system, such as a compact disk player or a digital video disk, compensates for tracking gain and phase according to the tracking error signal. The apparatus includes a mirror setting unit for receiving the generated mirror signal and for generating a mirror signal by defining the mirror signal to predetermined minimum and maximum time intervals, a switch for outputting a muted tracking error signal while the defined mirror signal is activated, and otherwise, outputting the tracking error signal, and a tracking gain/phase compensator for receiving the output signal from the switch and compensating for the tracking gain and phase. Thus, the system can be stabilized by muting a tracking servo loop according to a mirror signal whose pulse width is defined to a predetermined window section.

Abstract: Disclosed is a method of tracking control for an optical disc recorder and reproducer, which includes the steps of detecting a land/groove switching position, storing tracking error signals for a predetermined time if the land/groove switching position is detected, obtaining a mean value of the stored tracking error signals, and judging whether the mean value is larger than a predetermined permissible tracking level, and if it is judged that the mean value is larger than the predetermined tracking level, determining a direction of a track center, correcting the track center, and compensating for a DC offset.

Abstract: The invention concerns an apparatus for reading or writing optical recording carriers, the apparatus using the differential phase detection process for tracking purposes. This process exhibits shortcomings when optical recording carriers of different pit depths are to be used. The object of the invention is to design an apparatus of this type which can also be used with said optical recording carriers. This object is achieved in that delay members are disposed between the photodetector and phase detector. The apparatus according to the invention is used as a playback or recording apparatus for optical recording carriers, such as CDs, CD-ROMs, CD-Is, CD-Rs, DVDs, DVD-ROMs, DVD-Rs, etc.

Abstract: An optical disk drive for reading and/or writing information from/on an optical disk includes an auxiliary lens to compensate for optical aberrations and a servo loop for positioning the auxiliary lens relative to a main lens. The servo loop includes an actuator for driving the auxiliary lens and a controller to feed the actuator coil with a drive current dependent on a position signal which is derived from the actual inductance of the actuator coil and a reference signal which indicates a desired position of the scan element. The disk drive also includes an inductance influencing device to vary the inductance of the actuator coil as a function of the position of the scan element.

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: An apparatus and method for automatically controlling the focusing of a compact disc player (CDP) performs more reliable automatic control operation upon abnormal conditions of a disc, such as a scratch and dust. The automatic focus controlling apparatus includes a pickup assembly for reading recorded data from a disc; and RF signal converter for converting the output signal read by the pickup assembly into an RF signal; a signal separator for separating a signal corresponding to a 3T component from the RF signal; a phase comparator for comparing the separated 3T signal with a predetermined frequency to provide a phase difference value; and a controller for controlling a focusing operation of an objective lens based on the phase difference value to provide a focus control signal.

Abstract: An optical disc device including a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc, a laser light volume detection unit for detecting the light volume of the laser light radiated from the laser light source, an automatic power controlling unit for controlling a laser output of the laser light source so that a detection output by the laser light volume detection unit will be constant, a return light detection unit for detecting the return light of the laser light beam radiated by the laser light source and reflected by the signal surface of the optical disc, a focusing control unit for displacing the objective lens along the optical axis responsive to focusing error signals generated on the basis of a detection output of the return light detection unit for controlling the focusing state of a beam spot of the laser light on the signal surface of the optical disc and a controlling unit for controlling the closed-loop gain of the automat

Abstract: A correction processing unit for correcting a level fluctuation appearing on a tracking error signal when a laser beam passes an ID area on a medium track during an on-track control is provided. That is, in the correction processing unit, a correction value determined by a correction value determining unit at a correction timing detected by a correction timing discriminating unit is subtracted by a correcting unit from a signal value obtained by sampling and converting the tracking error signal into digital data by an A/D converter at a predetermined period and reading, thereby performing the correction.

Abstract: A tracking servo control method for preventing a tremble of an object lens installed in a pickup in an optical disk drive. A determination is made whether a distance between a target track and a current track where the pickup is presently placed is longer than a first distance. When the distance between the target track and the current track is longer than the first distance, both ends of a tracking coil through which a driving current for moving the object lens flows, are shorted. In the meantime, when the distance between the target track and the current track is shorter than a second distance as the pickup moves to the target track, both ends of the tracking coil are opened. The first distance is equivalent to a distance of 1000 tracks, and the second distance is equivalent to a distance of 100-200 tracks.

Abstract: While discerning whether the laser beam spot is positioned on a land track or a groove track according to the L/G switch signal LGS from the land groove detection unit 34, the focus position rough detection unit 50 and the focus position precise detection unit 60 detect two new focus positions (for the land and the groove) so that the bit error rate BER that is measured in the error rate measurement unit 33 and the envelope of and the jitter in the reproduction signal RF would improve, and output two control signals (FBAL and FOFF) for changing the control target position into the new two focus position to the focus error detection unit 36.1.