Abstract: An optical information processing method and apparatus performs a light irradiating and receiving step, a signal processing step, and an adjusting step of a spherical aberration and a focus offset on the basis of shift amount of first and second control devices and a performance evaluation value. The performance evaluation values for first, second, third and fourth points in an x and y coordinate system are detected, in which an x-coordinate is one of the shift amount of the first control device and the shift amount of the second control device and a y-coordinate is the other, the first point, second and third points having the same y-coordinate and different x-coordinates with each other, the fourth point being provided on a first straight line passing through the first point and being different from the first point.

Abstract: Aspects of the disclosure provide a sync mark detector. The sync mark detector includes a first unit configured to decay over time a value indicating a length of a bit format, a second unit configured to compare the decayed value with a detected length of the bit format to determine a new length, and a third unit configured to detect a sync mark based on the detected length and the new length.

Abstract: Provided is a lens driving unit for an optical pickup and an optical disc drive employing the lens driving unit. First and second driving coils are directly wound around a coil winding unit included in the lens frame, which is different from a conventional lens frame in which a driving coil is manufactured as a separate element and is separately attached to a lens frame.

Abstract: The invention solves the problem that data cannot be recorded on a disc because the number of registered Defect Lists (DFLs) has reached a limit and the problem that the access performance is reduced at recording data reproduction time. A cluster, which is normally reproduced during verification processing and is preceded and followed by one or more defective blocks, is also treated as a defective block and, together with the preceding and following defective clusters, recorded in an spare area for extending the range in which clusters are registered as Contiguous Re-allocated Defect (CRD) entries. This reduces the number of DFLs to solve the problem that data cannot be recorded on the disc and, in addition, reduces the number of seek operations to prevent the access performance from being reduced at reproduction time.

Abstract: An unbalanced disc determining apparatus is provided. The unbalanced disc determining apparatus includes a noise reduction unit configured to reduce noise components of a center error signal obtained from a signal configured to detect light reflected by a disc revolved by a spindle motor, and a determination unit configured to determine whether the revolving disc is unbalanced by determining whether the center error signal of which noise is reduced exceeds a reference value.

Abstract: Methods and systems are described for correcting repeatable runout. In one aspect, an open loop tracking signal is received and squared. A discrete Fourier transform (DFT) of the squared open loop tracking signal is obtained. A velocity magnitude and an absolute value of the phase of the open loop tracking signal is determined. A RRO correction signal is iteratively constructed by performing a partial correction based on an initial phase selected and an initial velocity amplitude, measuring a relative velocity amplitude, performing a partial control correction using the initial phase and relative velocity amplitude if the amplitude is smaller than an initial amplitude or using the initial phase rotated by one hundred eighty degrees and the relative velocity amplitude if the amplitude is larger than an initial amplitude, and repeating the above steps until a tracking controller can perform closed loop control of the track to optical pickup unit velocity.

Abstract: The invention provides an optical pickup device that ensures complete curing of adhesive when a tilt adjusting holder is glued to an objective lens holder. The optical pickup device comprises: a light source; an objective lens for focusing light emitted from the light source onto an optical storage medium; a tilt adjusting holder to which to secure the objective lens; and an objective lens holder to which to glue the tilt adjusting holder. The objective lens holder includes: adhesive joint sections for securing the tilt adjusting holder to the objective lens holder using an adhesive; a seat section on which the tilt adjusting holder abuts; and adhesive anti-overflow pockets, located between the adhesive joint sections and the seat section, for receiving the adhesive when the adhesive flows from the adhesive joint sections.

Abstract: A system and method for adjusting the radial tilt, tangential tilt, or a combination of radial and tangential tilt of an optical detection unit in an optical disc reading system can include applying different weighting factors to different signal components depending on which detection area detects the component, measuring a value of a signal characteristic, such as signal-to-noise ratio, of two signals with different sets of weighting factors, and determining an adjustment factor to the radial tilt as a function of the of the measured signal characteristic values.

Abstract: A plurality of sensors are used to sense disturbances in a data storage system. An adaptive gain component is associated with each of the sensors and provides a gain for each of the sensor signals. The gain of each sensor signal is adapted, individually, based on a correlation of each given sensor signal to the position error signal. This adaptation produces a position correction signal. The position correction signal is applied to a position signal that is used to position the reading and writing components and the storage medium relative to one another. This compensates for both rotary and linear vibration disturbances at the same time.

Abstract: A position control method of an optical pickup head of an optical disc drive is provided. The optical disc drive has an optical pickup head for reading data from an optical disc and a step index for controlling the movement of the optical pickup head. The position control method includes: calculating a first position information of the optical pickup head according to the step index; reading an address information from the optical disc, calculating a second position information of the optical pickup head according to the address information; determining whether a difference between the first position information and the second position information is greater than a predetermined value; updating the step index when the difference is not greater than the predetermined value; moving the optical pickup head to an initial position when the difference is greater than the predetermined value, and setting the step index as zero.

Abstract: An optical disc apparatus includes: a light irradiation/reception section to irradiate an optical disc recording medium with light via an objective lens and receive return light of the light; a tilt adjustment section to tilt the lens; a focus servo control section to exert focus servo control over the lens; a focus bias application section to apply a focus bias to a focus servo loop; a tracking direction error signal generation section to generate a tracking direction error signal representing an error between light-reception signals; and a control section to perform a tilt adjustment value search process for making a search for a tilt adjustment value with which the tracking direction error signal is maximized, a tilt adjustment value revision process for revising the tilt adjustment value found by the tilt adjustment value search process, and an adjustment control process for causing the tilt adjustment section to perform tilt adjustment.

Abstract: An optical system for optical pickup includes a magnification conversion optical element moving along an optical axis direction in accordance with each of optical recording medium recording surfaces, and an objective lens element converging a light beam incident through the magnification conversion optical element, to form a spot on a corresponding one of the recording surfaces, and satisfies the following formula: 4.0×10?4<Mn/(tn?tc)×f<6.0×10?4. Here tc is the thickness [?m] of a recording-medium base material at which a third-order spherical aberration occurring when a parallel light beam is incident on the objective lens element is the minimum, f is the focal length [mm] of the objective lens element, and Mn is the imaging magnification of the objective lens element when a spot is formed through a thickness tn [?m]of the base plate.

Abstract: Erroneous data erasure owing to radiation of laser beam with excessive power to the recording layer of the multilayered optical disc upon servo-off while reproducing data of the disc is prevented. When detecting the servo-off based on the amplitude of the tracking error signal or the focus error signal, the laser beam power is reduced to a predetermined minimum value, and the laser beam power value is set again based on the address of the recording medium, which has been obtained later for reproduction. The laser beam power value is changed by applying an offset to the drive current or changing the target value under APC.

Abstract: A reproduction signal evaluation method evaluates the quality of a reproduction signal reproduced from an information recording medium based on a binary signal generated from the reproduction signal using a PRML signal processing system. A pattern extraction step extracts, from the binary signal, a specific state transition pattern which has the possibility of causing a bit error; a step computes a differential metric based on the binary signal; an extraction step extracts the differential metric which is not greater than a predetermined signal processing threshold; a step determines a mean value of the differential metrics which are not greater than the signal processing threshold and extracted in the extraction step; a standard deviation computing step determines a standard deviation which corresponds to an error rate predicted from the mean value; and an evaluation step evaluates a quality of the reproduction signal using the standard deviation.

Abstract: An optical disc device and a recording method is provided in which information can be additionally recorded on an optical disc, which has a servo layer and recording layers separately formed, by accurately correcting a relative angle between a light beam and the optical disc used in the previous recording without providing an area where recording is not performed while maintaining the stability of tracking servo. The above subject can be solved by studying with high accuracy the relative angle between the optical disc and the optical axis used in the previous recording by applying a radial tilt servo according to a signal from the recording layers with the tracking servo applied by the servo layer. Further, the additional recording can be performed stably by fixing the radial tilt at the previously studied angle when the recording is performed.

Abstract: A tilt can be detected highly accurately by minimizing the tilt detection error. An optical head includes: an objective lens for converging a light beam from a light source onto an optical disc; a photodetector section receiving the beam, reflected from the disc, at divided areas on its photodetection plane and outputting light detection signals from those areas; and a tilt detecting section for detecting a relative tilt between the lens and disc based on the detection signals.

Abstract: When applying an electron beam to a master substrate of disk-shaped recording medium placed on a rotation stage, while rotating the master substrate by rotating the rotation stage, to write a master pattern of disk-shaped recording medium on the master substrate, causing the writing to be suspended based on abnormality information of environment and storing a rotation angle of the master substrate when the writing is suspended and causing, thereafter, the writing to be resumed from a suspended position of the writing on the master substrate based on the rotation angle.

Abstract: A method for driving an optical pickup apparatus which improves the durability of components that drive a movable lens that moves back and forth between an original position and a drive-limit position and achieves stable operability and an extended lifetime of the optical pickup apparatus performs a first step-drive in which a movable lens moves to an original-restoration start position by being driven a specified distance toward a drive-limit position, a second step-drive in which the movable lens thereafter moves to an original position by being driven toward the original position a distance equivalent to the distance from the drive-limit position to the original position, and a third step-drive in which the movable lens thereafter moves to a default position by being driven a specified distance.

Abstract: An optical disk driving apparatus includes an optical head device having a laser light source, a converging optical system converging a light beam emitted by the laser light source onto an optical disk, a photo detector receiving reflected light reflected by the optical disk, and an aberration correcting optical system controlling aberration of the converging optical system; a motor rotating the optical disk; and a control section receiving a signal from the photo detector, wherein the converging optical system has an objective lens formed using resin as a main material, the aberration correcting optical system has a spherical aberration correcting element correcting spherical aberration, and the control section evaluates quality of a reproduction signal for information in the optical disk by using the reflected light received by the photo detector, and utilizes a result of the evaluation to perform closed loop control on the spherical aberration correcting element.

Abstract: The present invention accurately operates a tilt servo even if a gap servo is operated with a small gap.

Abstract: A method for adjusting at least one alignment control axis of a holographic data storage system or device to or towards a sufficiently optimal recovery position for recovery of a hologram based on a derived feedback error signal and/or a derived feed-forward signal. For the next hologram in the sequence, the derived feedback error signal estimates the direction and magnitude of misalignment of the at least one alignment control axis for one or more previously recovered holograms based on alignment-indicating data. The derived feed-forward signal estimates an optimal alignment value for the at least one alignment control axis for one or more holograms based on recording and recovery operating condition data for the holograms. An iterative alignment procedure may also be used to derive a feedback error signal for one hologram.

Abstract: An optical disc apparatus includes an optical pickup, a signal generation section which generates a total reflection signal and a focus error signal, and a servo control section which controls optical pickup. The optical disc apparatus further includes a main control section which binarizes the track cross signal by using a predetermined threshold value and, by using the binarized track cross signal, checks the tracing state of a track. The main control section controls the servo control section to check, by tracing one turn of the track of an optical disc, whether or not a tracking servo deviation occurs. When a tracking servo deviation occurs during the tracing, the main control section controls the servo control section to make the check once again. When, in the check made once again, a tracking servo deviation is found to occur again, the main control section increases the threshold value used in binarization.

Abstract: An apparatus and a method for compensating periodic signal in an optical disc drive are described. The control apparatus includes an amplitude processing unit, a phase processing unit, a wave generator, a first switch module and a second switch module. The amplitude processing unit processes the amplitude of the input signal based on a reference signal for generating an amplitude signal. The phase processing unit processes the phase of the input signal based on the reference signal for generating a phase signal. The first switch module switches the amplitude signal to select one of the amplitude value and a predetermined amplitude value. The second switch module switches the phase signal to select one of the phase value and a predetermined phase value. The wave generator generates a compensated wave signal based on the selected amplitude value and the selected phase value, and outputs the compensated wave signal.

Abstract: An astigmatism element converges laser light in a first direction for generating a first focal line, and converges the laser light in a second direction perpendicular to the first direction for generating a second focal line. A light separating element guides the laser light entered into two first areas and into two second areas to four respective positions different from each other, and guides the laser light entered into a third area to a position different from the four positions. When an intersection of two straight lines extending in parallel to the first direction and the second direction and intersecting with each other is aligned with an optical axis of the laser light, the third area is disposed at the intersection of the two straight lines.

Abstract: An SPM driver drives a spindle motor. A VCM driver drives a VCM. A DC/DC converter (switching regulator) receives a power supply voltage from an external circuit, and generates a stabilized voltage. Linear regulators each receive a power supply voltage from an external circuit, and each generates a stabilized voltage. A shock detection circuit detects vibration of a device mounting the driving circuit. A power monitoring circuit monitors the power supply voltage, and generates a power-on reset signal which is switched to a predetermined level whenever the power supply voltage is cut off. An ADC converts the back electromotive voltage that occurs at the VCM into a digital signal. A serial interface receives data from an external host processor, which is used to control the driving circuit. Cutoff circuits are arranged between the capacitors, which are to be charged using the induced current that occurs at the SPM, and the power supply terminal.

Abstract: A lens pull-in method is used in a near-field optical accessing system. When a lens is in a far-field range, the lens is driven to approach a surface of an optical disc in an open loop control state. If the lens enters a near-field range, a first GES level is inputted as a set value and the lens is driven in a close loop control state. When the gap error signal decreases to the first GES level, the set value is changed to a second GES level, which is higher than the first GES level. When the gap error signal increases to the first GES level, the set value is changed to a target GES level, so that the gap error signal is maintained at the target gap error signal.

Abstract: A method comprising recording data related to a start-up procedure on at least one of a plurality of recording layers disposed on an optical record carrier for reading back the recorded data during subsequent start-ups, the selection of the at least one recording layer based on properties of the at least one recording layer is disclosed. The technique reduces the optical record carrier start-up time and is useful for DVD, HD-DVD and BD recorders and/or players.

Abstract: An instantaneous jitter information detection section detects, based on first and second digital values indicating different polarities relative to a predetermined reference value, an instantaneous gradient value corresponding to a difference value between the first and second digital values, and an instantaneous deviation value corresponding to a difference value between an intermediate value between the first and second digital values and the reference value. An information conversion section converts, based on an inversely proportional conversion table, the instantaneous gradient value to an inversely proportional value. An arithmetic section detects an instantaneous variance value by multiplying the instantaneous deviation value and the inversely proportional value together, and squaring a value obtained by the multiplication, and detects an integrated value by accumulating the instantaneous variance value.

Abstract: A circuit for preventing destruction of a semiconductor laser element of an optical disc device comprises a light-emission-directing circuit part for outputting a light-emission-directing signal for directing the semiconductor laser element to emit light; a voltage-monitoring circuit part for monitoring a light-emitting voltage and, when a judgment is made that the light-emitting voltage is normal, outputting a light-emission-permitting signal for permitting the semiconductor laser element to emit light, the light-emitting voltage being supplied from a power source for the semiconductor laser element to an optical-output-controlling circuit part in order to cause the semiconductor laser element to emit light; and a light-emission-permitting circuit part for using the optical-output-controlling circuit part to cause the semiconductor laser element to emit light only when the light-emission-directing signal and the light-emission-permitting signal are inputted.

Abstract: Various embodiments of the present invention provide systems and methods for data regeneration. For example, a system for regenerating data is disclosed. The system includes a media defect detector that is operable to identify a potential media defect associated with a medium from which an input signal is derived, an attenuation amplitude detector that generates an attenuation factor, and a data detector. The data detector includes a first data path and a second data path. The first data path includes a bank of two or more selectable noise prediction filters and the second data path includes a fixed noise prediction filter and the attenuation factor. The data detector processes a derivative of the input signal using the second data path when the potential media defect is indicated, and processes the derivative of the input signal using the first data path when a media defect is not indicated.

Abstract: The invention provides an optical disk drive. In one embodiment, the optical disk drive comprises a feeding device, a power driver, and a controller. The feeding device comprises a spherical aberration (SA) lens and a stepping motor, wherein the SA lens corrects spherical aberration of a light beam emitted by a pickup head, and the stepping motor moves the SA lens according to a plurality of control signals. The power driver generates the control signals to drive the stepping motor to move the SA lens. The controller directs the power driver to drive the stepping motor to move the SA lens with only stable steps when the SA lens is required to move, so that the stepping motor is in a stable state without inducing step errors after the stepping motor rotates with the stable steps.

Abstract: An astigmatism element converges laser light in a first direction for generating a first focal line, and converges the laser light in a second direction perpendicular to the first direction for generating a second focal line. A light separating element guides the laser light entered into two first areas and into two second areas to four positions different from each other. The light separating element imparts a light separating function to the laser light entered into the first two areas in directions identical to each other and with magnitudes different from each other, and imparts a light separating function to the laser light entered into the two second areas in directions identical to each other and with magnitudes different from each other.

Abstract: An optical disk apparatus driving an optical disk includes a tilt-angle adjusting unit configured to adjust a tilt angle indicating the tilt of an optical axis of laser light emitted from a pickup to detect an optimal tilt angle at which a traverse signal has the maximum amplitude and a storing unit configured to store information about the optimal tilt angle. When the optical disk has multiple recording layers on one side, the tilt-angle adjusting unit adjusts the tilt angle with respect to each of the multiple recording layers to detect the optimal tilt angle and the storing unit stores information about the optimal tilt angle with respect to each of the multiple recording layers. The tilt angle with respect to each of the multiple recording layers is controlled in accordance with the information about the optimal tilt angle with respect to each of the multiple recording layers.

Abstract: An optical pickup control circuit includes an adding portion that adds a tracking driving signal which is for moving an objective lens, provided to face a discoid optical information recording medium, in a tracking direction of the corresponding optical information recording medium, to a tilt driving signal which is for moving the corresponding objective lens in a tilt direction of the corresponding optical information recording medium, and supplies the signal to a tilt actuator.

Abstract: A disk drive determines, from eccentric amounts of individual prescribed rotation phases for one round of an optical disk 1, a rotation phase range in which a lens shift amount after tracking pulling-in of an object lens constituting an optical pickup 3 does not exceed a movable range of the object lens in a preset tracking direction, sets the rotation phase range as a tracking pulling-in range, and carries out tracking pulling-in of the optical pickup 3 while the rotation phase of the optical disk 1 is placed within the tracking pulling-in range.

Abstract: A method for determining an optimal combination of focus bias and spherical aberration compensating value (SA value) in an optical disc drive is provided. Firstly, a first focus bias is set, the SA values are adjusted and the corresponding tracking error signal values are measured. Second-order-approximation is performed to obtain a first maximum value of tracking error signal. Secondly, a second focus bias is set, the SA values are adjusted and the corresponding tracking error signal values are measured. Second-order-approximation is performed to obtain a second maximum value of tracking error signal. Thirdly, a third focus bias is set, the SA values are adjusted and the corresponding tracking error signal values are measured. Second-order-approximation is performed to obtain a third maximum value of the tracking error signal. The three maximum values are compared to obtain the optimal combination of focus bias and SA compensating value in the optical disc drive.

Abstract: A method for detecting whether vertical deviation of an optical disc occurs is provided. First, before a pickup head is successfully focused on the optical disc, a pickup head is actuated based on an input control signal so as to generate a focus error signal with a plurality of S-curves. Then, a plurality of zero crossing points of the S-curves in the focus error signal is identified and a plurality of input control values respectively corresponding to the zero crossing points is obtained. A variation of the input control values is then calculated. Whether vertical deviation of the optical disc occurs can be determined according to the variation of the input control values.

Abstract: An offset corrector of an information readout apparatus receives a digital signal DRF output from an A/D converter, and performs offset correction. The offset corrector is capable of switching between a level-correction operation that corrects the offset so that the DC level of the shortest period signal included in the readout signal assumes a zero amplitude reference and a HPF operation that matches the level of the readout signal with the zero amplitude reference. The offset corrector corrects the offset in the level correction operation during a normal reproduction, and switches to the HPF operation for offset correction when a defect judgment unit detects a defective area. The information readout apparatus is stable and has a superior performance without a symmetry deviation if there occurs a waveform fluctuation caused by a defect etc.

Abstract: An optical pickup, mounting a lens actuator 101 thereon, the lens actuator comprises: a lens 1 having an optical axis in direction in parallel with an optical disc; a holder 2, which holds the lens thereon; a first guide shaft 3 holding the holder, so as to regulate the holder to change a position thereof, into an inner surface direction of a surface having the optical axis of the lens as a normal line vector thereof; a second guide shaft 4, which regulates the holder to change the position thereof, into a normal line vector of an optical disc; and a reed screw, which moves the holder into direction of the optical axis of the lens, wherein a distance between the optical axis of the lens and the optical disc, a distance between a central axis of the first guide shaft and the optical disc, and a distance between a central axis of the second guide shaft and the optical disc are lager than a distance between a central axis of the reed screw and the optical disc.

Abstract: An optical-recording-medium driving apparatus includes: a light irradiating/receiving section configured to irradiate light on a medium so as to form a first side spot, a main spot, and a second side spot, and to receive reflection light from the individual spots; a first delay section configured to delay a light reception signal on the first side spot in accordance with a disposition interval between the first and the second side spots; a second delay section configured to delay a light reception signal on the main spot in accordance with a disposition interval between the main and second side spots; and a tracking-error-signal generation section configured to generate a tracking error signal on the basis of a correlation between delayed light reception signals on the first side spot and the main spot, and a correlation between the light reception signals on the second side spot and the main spot.

Abstract: An optical disc apparatus includes: a light irradiation/reception section to irradiate an optical disc recording medium with light via an objective lens and receive return light of the light; a tilt adjustment section to tilt the lens; a focus servo control section to exert focus servo control over the lens; a focus bias application section to apply a focus bias to a focus servo loop; a tracking direction error signal generation section to generate a tracking direction error signal representing an error between light-reception signals; and a control section to perform a tilt adjustment value search process for making a search for a tilt adjustment value with which the tracking direction error signal is maximized, a tilt adjustment value revision process for revising the tilt adjustment value found by the tilt adjustment value search process, and an adjustment control process for causing the tilt adjustment section to perform tilt adjustment.

Abstract: The present invention accurately operates a tilt servo even if a gap servo is operated with a small gap.

Abstract: An optical disc apparatus includes an optical pickup, a signal generation section which generates a total reflection signal and a focus error signal, and a servo control section which controls optical pickup. The optical disc apparatus further includes a main control section which binarizes the track cross signal by using a predetermined threshold value and, by using the binarized track cross signal, checks the tracing state of a track. The main control section controls the servo control section to check, by tracing one turn of the track of an optical disc, whether or not a tracking servo deviation occurs. When a tracking servo deviation occurs during the tracing, the main control section controls the servo control section to make the check once again. When, in the check made once again, a tracking servo deviation is found to occur again, the main control section increases the threshold value used in binarization.

Abstract: An optical head (10) transmits a light beam to an optical disc (30), in which light-transmitting layers largely change in thickness, and includes a degree-of-diversion/convergence enlarging member (20) fixed between a collimating lens (4) and an objective lens (6). The diversion/convergence enlarging member (20) reduces a moving range of the collimating lens (4), and allows the optical head (10) to be miniaturized.

Abstract: An optical disc apparatus includes an optical pickup unit which reads data recorded on an optical disc and converts the data into a radio frequency (RF) signal. A defect detection unit detects a defect on the optical disc using the RF signal output from the optical pickup unit. A servo signal processing unit holds a servo control signal in a corresponding defective section when the defect is detected on the optical disc. A control unit detects the variance of the servo control signal after the defective section, and uses that as feedback so as to control a servo control signal of a subsequent defective section.

Abstract: A disk drive determines, from eccentric amounts of individual prescribed rotation phases for one round of an optical disk 1, a rotation phase range in which a lens shift amount after tracking pulling-in of an object lens constituting an optical pickup 3 does not exceed a movable range of the object lens in a preset tracking direction, sets the rotation phase range as a tracking pulling-in range, and carries out tracking pulling-in of the optical pickup 3 while the rotation phase of the optical disk 1 is placed within the tracking pulling-in range.

Abstract: An FE·FS ratio, which is a ratio of a focus error signal amplitude and a focus sum signal amplitude which are measured by using one kind of light source of at least two kinds of light sources that are compatible with different kinds of optical discs, is calculated; it is determined whether the FE·FS ratio is unusual or not by comparing the calculated FE·FS ratio with a threshold value; a focus servo is turned on in a case where the FE·FS ratio is usual; thereafter, a focus error signal amplitude adjustment value is calculated based on a focus sum signal amplitude measurement value; and in a case where the FE·FS ratio is unusual, the kind of the light source is changed and a retrial is performed to calculate the FE·FS ratio.

Abstract: The relation between the cover layer thickness of a data recording surface and ratio ? of SCO to SCD is previously calculated and stored in a storage unit, where SCD denotes coma aberration which occurs when the data recording medium is tilted by unit angle and SCO denotes coma aberration which occurs when the objective lens is tilted by unit angle. When ?1 denotes ratio ? for a data recording surface corresponding to the smallest cover layer thickness, tilting angle ?1 of the objective lens is determined based on the ?1 and a tilt adjustment of the objective lens is made. Also, when ?2 denotes ratio ? for a target data recording surface, tilting angle ?2 of the objective lens is estimated based on the ratio of ?2 to ?1 and a tilt correction of the objective lens is made.

Abstract: An objective lens driving device includes an objective lens holder that holds an objective lens, plural elastic supporting members through that support the objective lens holder, tracking coils and that drive the objective lens holder in the tracking direction, tilting coils that tilt the objective lens holder with respect to the optical axis passing through the objective lens, a tracking control circuit that drives the tracking coils, and a tilting control circuit that drives the tilting coils. The tilting control circuit drives the tilting coils using a signal yielded by multiplying a tracking driving signal from the tracking control circuit by a specific scaling factor so as to cancel out a tilting force of the objective lens holder generated by the tracking coils.

Abstract: A method for determining a direct current (DC) level involved in an alternating current signal is provided. The alternating current signal is transmitted from an amplifier to an A/D (analog-to-digital) converter. When any of the extreme values of the alternating current signal is beyond the input range of the A/D converter, the alternating current signal is shifted to make both of the peak and bottom values located within the input range of the A/D converter. Then, the real extreme values are realized according to the shift level(s), the relative peak and bottom values realized after the shifting procedure, and the input range of the A/D converter. Finally, the DC level is determined according to the real peak and bottom values.