Abstract: A highly accurate and stable tilt servo system is provided. A liquid crystal device for phase correction is driven based on drive data stored in a lookup memory to thereby make a tilt correction. Upon pre-processing, a pickup is moved to a predetermined position on the inner circumference of a disc for a tilt correction to employ tilt error data delivered from a tilt sensor as reference tilt error data and drive data served for the tilt correction as a reference tilt correction quantity. After the pre-processing, when the pickup is moved, the difference between the tilt error data delivered from the tilt sensor at each position of movement and the reference tilt error data is employed as a relative correction quantity. The drive data equivalent to the relative correction quantity is acquired from the lookup memory. The drive data acquired is added to the reference correction quantity to thereby determine a tilt correction quantity.

Abstract: In an optical disk apparatus, after chucking an optical disk, the optical disk apparatus defers the start of the rotation of the optical disk, and measures the focusing drive voltage at two points, i.e., a point near a center of the optical disk and a point near an outer edge of the optical disk. Then, based on the measured values, the optical disk apparatus determine the angle at which the optical disk is slanted. Therefore, when the optical disk has been chucked inappropriately, the chucking state can be determined without rotating the optical disk, and scratching of the optical disk and damage to the optical disk apparatus can be prevented.

Abstract: A method for adjusting an optical axis of an optical disc drive. The method includes the following steps. A first reflecting member is disposed on a turntable of the optical disc drive, and is rotated along with the turntable. A laser light is emitted on the first reflecting member by a laser collimator, and a normal vector of the turntable is measured based on a light point reflected to the laser collimator from the first reflecting member. A second reflecting member and a third reflecting member are disposed on a guide bar of the optical disc drive. A first initial vector and a second initial vector are measured based on a light point reflected to the laser collimator from the second reflecting member and the third reflecting member.

Abstract: An apparatus and method for detecting a tilted disc, and an apparatus and method for reproducing data from the tilted disc are provided.

Abstract: A thickness servo system using optical aberrations, wherein a photodetector detects an aberration amount corresponding to thickness irregularity, and a thickness irregularity correction section operates to minimize the detected aberration amount. The thickness irregularity of a transparent layer can also be calculated from the detected aberration amount.

Abstract: An on-screen calibration system for disc drives and the operating method thereof. The calibration system includes an autocollimator detecting the inclined angle of the stage of a disc drive. A control module is connected to the on-screen display module and a bar code scanner to receive the bar code of the pick-up module and compute a predetermined position data. A monitor displays a moving point according to the inclined angle and a target point according to the predetermined position data through an on-screen display module. The tilt-adjusting mechanism supporting the pick-up module is adjusted to shift the moving point overlapping the target point.

Abstract: A data recording method according to one aspect of this invention comprises specifying a plurality of regions with different radial positions on a disk, and detecting the tilt amounts of the respective regions with respect to the optical axis of a light beam on the basis of a focus control signal used to just-focus the light beam on a recording surface of the disk, calculating tilt correction amounts for the respective regions in accordance with the tilt amounts of the respective regions, correcting a tilt of the optical axis with respect to a predetermined region on the basis of the tilt correction amount corresponding to the predetermined region, and recording data on the predetermined region while the tilt of the optical axis with respect to the predetermined region is corrected.

Abstract: There is employed a configuration to detect, by making use of an optical pick-up (104) when tracking servo is performed along wobble grooves of an optical disc (102), phase errors between main wobble signal outputted as the result of the fact that reflected light beams corresponding to main spot of the optical disc (102) are received at a main light receiving section (321) of light detecting means (32) and side wobble signals outputted every side spot as the result of the fact reflected light beams corresponding to respective side spots of the optical disc (102) are received at a first sub-light receiving section (322) and a second sub-light receiving section (323) to calculate difference between the both phase errors at a difference calculating circuit (59) to generate, from this difference, a skew signal including inclination direction and inclination quantity of the optical disc (102).

Abstract: In the tilt correction method, information about inclination of an object lens relative to an information recording medium is acquired. A direct current signal Sdc for correcting the inclination is produced based on the information. An alternating current signal Sac having a prescribed signal characteristic is superposed onto the direct current signal Sdc to produce a driving signal Sout. The driving signal Sout is supplied to a driving mechanism to correct the inclination of the object lens against friction.

Abstract: An optical pickup unit is provided with a knife-edged support mechanism, which tiltably supports a suspension holder on a vertical support portion of a base such that the suspension holder can be tilted in a tilting direction with respect to an axis line extending perpendicular to both the focusing direction, i.e. z-axis direction, and the tracking direction, i.e. x-axis direction.

Abstract: An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including tracks having prescribed grooves; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals; and a light division element for dividing a reflected light reflected by the information memory medium.

Abstract: In an optical head apparatus for an optical recording medium, including a light source for emitting a light beam, an objective lens for focusing the light beam at the optical recording medium and receiving a reflected light beam from the optical recording medium, and a photodetector for receiving the reflected light beam from the objective lens, a unit is provided between the light source and the objective lens to generate a main beam and a sub beam from the light beam. The intensity distributions of the main beam and the sub beam are different from each other, and the sub beam is divided into a plurality of portions having different phase distributions from each other. The photodetector includes photodetecting portions for each of the main beam and the sub beam, thus obtaining a push-pull signal from each of the main beam and the sub beam.

Abstract: Method and apparatus for use in an optical disk tilt servo system of an optical disk drive. The tilt servo system is for adjusting an angle between a surface of an optical disk and a pick-up head of the optical disk drive. The method includes: measuring focusing results of the optical disk at multiple locations and estimating tilt angles, i.e. deviation from the horizontal, of the surface of the optical disk according to a physical model that reflects that the optical disk has different tilt angles at different locations. The tilt servo system is calibrated accordingly.

Abstract: An optical disk apparatus has an optical head having a lens of converging light from a light source onto an optical disk and a photodetector for detecting the light thus converged and then reflected from the optical disk. A tracking error signal is generated in order to perform tracking control on the basis of the detected light. A disk tilt DT is detected to indicate the amount of tilt of the optical head relative to the optical disk. A calculation is performed to calculate a lens shift LS indicating the amount of shift of the lens relative to the optical head, according to a predetermined rule on the basis of the generated tracking error signal and the detected disk tilt DT.

Abstract: At the initialization, a tilt mechanism 9 is activated in a state where an optical pick-up 3 is fixed, and set up at a position where an E-F phase difference obtained in a signal processing portion 4 is 180°. Thereafter, a reproducing operation is started. During the reproducing operation, the tilt mechanism 9 is not activated and the focus control is made with the focus servo by moving the optical pick-up 3 up or down, while the level of a focus error signal is within a certain range. Further, if the level of focus error signal is beyond the certain range because the optical disk 1 is greatly inclined, the tilt mechanism 9 is activated to cause the optical disk 1 to come closer to the optical pick-up 3 to enable the control of the focus servo.

Abstract: In a state in which an optical disk having a warping amount equal to or smaller than a predetermined amount is attached to a spindle motor, an output of tilt detection result is stored as a reference tilt value in a memory. At this time, a control signal corresponding to a driving inclining amount in which inclining the objective lens by the driving inclining amount minimizes the inclination of the objective lens from the attached optical disk is stored as a reference control value in the memory. An CPU a multiplies difference between a detection result of the tilt detection and the reference tilt value by a control constant, and adds the reference control value to the multiplied difference, and provides the thus-obtained control signal to a tilt driving circuit.

Abstract: A tilt of a light beam to be radiated onto an information recording disk is corrected without using a dedicated tilt sensor. The correction is performed based on the characteristic that an offset amount between a tilt amount maximizing an RF signal amplitude and a further tilt amount maximizing an LPP signal amplitude is constant and independent of positions on the same disk. A pre-pit signal indicative of an existence/nonexistence of a pre-pit formed on the disk is produced from returned light of the light beam, while an RF signal is produced from bits of information recorded on the disk on the basis of the returned light. An optimum tilt-correcting amount is decided by making use of a relationship between the pre-pit signal and the RF signal at a particular tilt amount. The tilt amount is corrected using the optimum tilt-correcting amount.

Abstract: An error signal detection method includes detecting light incident through an objective lens after having been reflected and diffracted from a recording medium, as eight light portions in a matrix including four inner light portions and four outer light portions, wherein the rows and columns of the matrix are parallel to the tangential and radial direction of the recording medium, respectively; calculating a first sum signal by summing a detection signal from at least one outer light portion located in a first diagonal direction, and a detection signal from an inner light portion located in a second diagonal direction; calculating second sum signal by summing a detection signal from an inner light portion located in the first diagonal direction, and a detection signal from an outer light portion located in the second diagonal direction; and comparing phases of the first and second sum signals to detect a tilt error signal.

Abstract: A DC voltage value is obtained at least at an inside position, an intermediate position, and an outside position on a disc (1) from a drive signal that is supplied to a focusing coil (4) built into an optical pickup (2). From the DC voltage values is obtained a relationship of a position between the respective positions and the DC voltage value, and this relationship is stored into a memory circuit (12). Then, during recording or playback, the DC voltage value that is calculated on the basis of the recording or playback position of the signal at that time and the AC signal included in the drive signal that is supplied to the focusing coil (4) are added to create a signal to be supplied to a tilt adjustment coil (6).

Abstract: An optical head for recording/reproducing signals to/from a high-density multi-layer optical recording medium is provided, which is capable of performing stable recording and reproducing with an aberration in each layer being minimized even when the optical recording medium tilts. The optical head includes a light source (1), an objective lens (7) for focusing light emitted from the light source (1) on an optical recording medium (8), and an objective lens tilting means (13) for correcting an aberration that occurs when the optical recording medium (8) tilts. It is configured so as to vary a tilted amount through which the objective lens tilting means (13) tilts the objective lens according to information concerning a tilt of the optical recording medium (8) and information concerning a substrate thickness of the optical recording medium (8).

Abstract: A tilt servo control device of an apparatus for recording information on and reproducing information from an optical recording medium set in the apparatus, the apparatus comprising an optical system for leading a laser beam emitted from a light source to a recording surface of the optical recording medium and a laser beam reflected by the recording surface of the recording medium to a photo detector and a read signal generator for generating a read signal in accordance with an output signal of the photo detector. The tilt servo control device determines a type of the optical recording medium, generates a tilt drive signal so as to reduce a tilt angle at a position of the laser beam irradiating the recording surface and an optical axis of the laser beam by a method for generating a tilt drive signal corresponding to the recording medium type, and drives a tilt angle adjuster for adjusting the tilt angle in accordance with the tilt drive signal.

Abstract: A tilt control apparatus includes an orthogonal shift detector (9) which detects an orthogonal shift by comparing a pair of a plurality of tap coefficients (C1, . . . , C7) of a FIR filter and generates an orthogonal shift signal, and an actuator varies the inclination of the optical axis of the light beam to correct the orthogonal shift, and a tilt controller (10) controls the drive of the actuator in accordance with the orhogonal shift signal to minimize the orthogonal shift. In the information recording operation, the orthogonal shift obtained based on a recording track is previously stored in a temporary storage portion and the stored orthogonal shift is used to conduct the tilt control.

Abstract: An optical disc apparatus in which the inclination of an optical axis of laser light relative to an optical disc is adjusted. When data is recorded, laser light is irradiated at recording power in mark periods and irradiated at reproducing power or erasing power in space periods. Immediately after the beginning of the mark periods, no pits are ye formed even though recording power is applied and the amount of reflected light has a level corresponding to the inclination of the optical axis of laser light relative to the optical disc without influence exerted by the pits. Also in the space period, the amount of reflected light has a level corresponding to the inclination of the optical axis of laser light relative to the optical disc. By sampling the reflected light signal at the instant following to the beginning of the mark period or space periods, the inclination is adjusted so as to maximize the sampled signal level.

Abstract: A system and method for adjusting optical drives. Rotating disc datum, and leader pin datum, must be adjusted to a specific position during a packaging process. An autocollimator according to the present invention senses tilt and sway of the rotating disc, outputting a first bright spot through a switch box to a monitor. In addition, an optimum tilt angle of the optical pickup head is obtained by a reader through calculation by a host, outputting a second bright spot through the switch box to the monitor. Therefore, the first bright is coincided with the second bright spot by a adjustment mechanism and according to picture switch by the switch box, reading optimum tilt angle adjustment. Furthermore, individual tilt angle of each optical pickup head is calculated by a host for satisfying adjustment of different tilt angles with different optical paths in reading CD and DVD discs.

Abstract: An optical disk device and a tilt correction method capable of high precision tilt correction with a smaller number of measurement positions are provided. Prior to data recording and reproduction, a number of measurement positions are set in the radial direction on an optical disk with intervals between two adjacent measurement positions shorter and shorter from the inner region to the peripheral region of the optical disk. The tilt at each of the measurement positions is measured, and the resulting tilt data are stored in a memory. The tilt data are used for making tilt corrections when recording or reproducing data on the optical disk.

Abstract: Tilt (?(r, ?)) is measured in a measuring location (P(r, ?) optical disc (2). A pivotable objective lens (34) is brought to a first focus measuring location such as to focus a light beam (32) in a first anchor point (P1(r??r1, ?))having the same angular coordinate ? as said measuring location (P(r, ?)) and having a small radial distance ?r1 from said measuring location. The objective lens is brought to a second focus measuring location such as to focus the light beam in a second anchor point (P2(r+?r2, ?)) having the same angular coordinate ? as said measuring location and having a small radial distance ?r2 from said measuring location, wherein said first and second anchor pints are located on opposite sides of said measuring location. Tilt in said measuring location is calculated from the coordinates of said two focus measuring locations of said objective lens.

Abstract: A holographic digital data storage apparatus detects a wobbling in a disc shaped storage medium, wherein the apparatus includes a beam generator and finding means, the disc including therein one or more holographically generated patterns. The beam generator projects at least two wobble detection beams to the holographically generated patterns, the wobble detection beams having different diffraction efficiencies provided at respective characteristic angles, wherein the characteristic angle is an angle between an optical path of one wobble detection beam and that of its corresponding pattern forming beam used in forming one of the holographically generated patterns and a diffraction efficiency is given by a ratio of a power of a diffracted beam of one of the wobble detection beams to a power of said one of the wobble detection beams. The finding means finds at least a difference between the diffraction efficiencies to thereby determine the wobbling in the disc.

Abstract: An apparatus for recording data on and reproducing data from the disk in which a recording area is divided into sectors, includes a reproducing signal generator for generating a reproducing signal including sum signals V1 and V2 of radial pairs, a sum signal RF_sum, and a push-pull signal RF_pp from an optical signal reflected from the disk, a header area detector for generating a header area signal including a header area from the reproducing signal, a first synchronous signal level detector for detecting a magnitude Ivfo1 of a first synchronous signal in the first header by being synchronized with the header area signal, a second synchronous signal level detector for detecting a magnitude Ivfo3 of a second synchronous signal in the second header by being synchronized with the header area signal, and a balance calculator for calculating the balance of the magnitude Ivfo1 and the magnitude Ivfo3.

Abstract: An optical disk read/write apparatus detects a shift in the tilt during a write operation and corrects it before resuming the write operation. Specifically, when the ROPC control signal detector of the optical disk read/write apparatus controlling the write power determines that the write power has exceeded a predetermined value after a control operation, the optical disk read/write apparatus suspends the write operation through control of the laser power and controls the shift in the tilt with the tilt controller before resuming the write operation.

Abstract: A lens actuator includes a lens holder to support an objective lens and having a pair of first side surfaces in a tracking direction and a pair of second side surfaces in a tangential direction, a fixed magnet disposed to confront the second side surface and comprising four regions having approximately the same area and are magnetic, such that magnetic directions of the four regions are perpendicular to a plane including a focusing direction and the tracking direction but are in opposite directions between two mutually adjacent regions, a pair of tracking coils disposed between the second surface and the magnet and having centers located on an outer side of corresponding centers of the four regions in the tracking direction, a focusing coil disposed between the second surface and the magnet and having a center located on an outer side of corresponding centers of the four regions in the focusing direction, and a radial tilt coil disposed between the second surface and the magnet and having a center located on

Abstract: A recording apparatus to record a mark on a recording medium includes an aberration detecting part and an optical power controller. The aberration detecting part detects an aberration signal corresponding to the amount of an aberration contained in a light beam radiated onto a recording surface of the recording medium by using an optical pickup system which includes a light source and an objective lens. The light source emits a light beam having a power to record the mark on the recording medium. The objective lens condenses the light beam to focus the light beam as an optical spot on the recording surface of the recording medium. The optical power controller controls the power output from the light source according to the detected aberration signal, so as to have the light source output an optical power to record the mark, in which a deformation due to the aberration is compensated for, on the recording medium.

Abstract: An optical pickup apparatus for compensating for the deviation in the thickness of the optical disk and method therefor.

Abstract: An optical disk apparatus includes a laser diode, and a light from the laser diode becomes a parallel light by a collimator lens, which is reflected toward an object lens by a reflection mirror. The parallel light transmitted through a through-hole provided on an object lens holder is reflected by a disk, and a reflected light is incident upon a light-receiving sensor via the collimator lens, a polarizing beam splitter and a prism. The parallel light reflected by the reflection mirror is reflected by a mirror integrated with the object lens holder, and incident upon the light-receiving sensor via the collimator lens, the polarizing beam splitter and the prism. A disk tilt and/or an object lens tilt are/is detected from output signals of divided light-receiving sensors of the light-receiving sensor.

Abstract: An objective lens supporting apparatus of an optical pickup includes a lens frame in which an objective lens is mounted; receiving member for receiving driving forces for displacing the objective lens in the direction of the optical axis and in a direction perpendicular to the optical axis is disposed; a support base in which generating member for generating the driving forces is disposed; an elastic member W extended from the support base and fixed to the lens frame for swingably supporting the lens in a cantilevered manner; and a tilting member for inclining the optical axis of the objective lens with respect to the support base by tilting the lens frame.

Abstract: An optical disk medium and a drive system are provided that enable high density recording to be carried out. In the optical disk medium, recorded information tracks are formed in a concentric or spiral manner, and information is recorded and played back by irradiating the recorded information tracks with a laser beam through a transparent substrate or a transparent cover layer. A change in tilt of the optical disk medium over one circuit of each of the tracks is set equal to or less than an allowed value, a change in tilt over the entire surface of the optical disk medium is permitted to be larger than the allowed value, and low frequency bandwidth tilt control is carried out by the drive system.

Abstract: A method for compensating for tilt in reproducing an optical reproducing medium is performed by determining an initial tilt driving direction so as to not interrupt a reproducer when tilt compensation is performed on the optical recording medium. The tilt compensation method involves comparing the amount of jitter detected over a certain period of time when the optical recording medium is reproduced with a reference value; determining the direction of tilt compensation in the direction of reproducing a track of the optical recording medium, before performing tilt compensation, when the amount of jitter detected, according to a comparison result of the comparator, exceeds a reference value; and resuming reproduction of the optical recording medium after performing tilt compensation so that the jitter decreases in the direction of the determined tilt compensation.

Abstract: A tilt servo control device of an apparatus for recording information on and reproducing information from an optical recording medium set in the apparatus, the apparatus comprising an optical system for leading a laser beam emitted from a light source to a recording surface of the optical recording medium and a laser beam reflected by the recording surface of the recording medium to a photo detector and a read signal generator for generating a read signal in accordance with an output signal of the photo detector. The tilt servo control device determines a type of the optical recording medium, generates a tilt drive signal so as to reduce a tilt angle at a position of the laser beam irradiating the recording surface and an optical axis of the laser beam by a method for generating a tilt drive signal corresponding to the recording medium type, and drives a tilt angle adjuster for adjusting the tilt angle in accordance with the tilt drive signal.

Abstract: In a method and an apparatus for aberration correction according to the invention, aberration occurring in recording/reproducing information derived from causes such as thickness variation of a substrate, a tilt, a focus error and a tracking error is detected, and the aberration is corrected by correcting these causes.

Abstract: A spindle motor inclination angle adjusting mechanism for an optical disk device includes two adjusting mechanisms to provide two rotational freedom for the base dock of the spindle motor to adjust the inclination angle of the spindle motor. The first adjusting mechanism has three support points that are not on the same straight line to support the base dock. Two of the support points are fixed and the third support point is movable relative to the other two support points to change the inclination angle of the base dock of the spindle motor. The second adjusting mechanism is a rotary element for carrying the first adjusting mechanism and driving the first adjusting mechanism to rotate and change the direction of the inclination angle of the base dock to adjust the spindle motor inclination angle.

Abstract: The present invention is to disclose a SIL near-field flying head flying state control structure in which the SIL is installed in a lens holder that can be biased. The lens holder includes three detection points spaced around the SIL for detecting the distance between each detection point and an optical disk, and a number of single-axis displacement devices for controlling the corresponding lateral side of the lens holder to move axially relative to the optical disk. A server can control the single-axis displacement devices to adjust the posture of the lens holder subject to the distance between each detection point and the optical disk measured, keeping the parallelism between the SIL and the optical disk within a predetermined level.

Abstract: A deformable mirror according to the invention comprises a substrate, a reflector which is supported by said substrate and the shape of whose reflecting areas is variable, and a plurality of drive units for independently driving a plurality of regions of the reflector and thereby controlling the distances between said plurality of regions and said substrate. Each of the plurality of drive units comprises a plurality of electrodes disposed over said substrate, a tilt member which is rotated round the axis of tilt by being attracted by the selected one of the plurality of electrodes, and an action member for varying the distance between a specific region of the reflector and said substrate following the motion of the tilt member.

Abstract: Disclosed is an optical pick-up actuator configured to achieve a multiaxial driving operation using a combination of a moving magnet system and a moving coil system. The optical pick-up actuator includes a first magnet unit, and a second magnet unit. The first magnet unit serves to conduct a tilt compensation, and the second magnet serves to conduct focusing and tracking operations. The first magnet unit for the tilt compensation is configured to conduct a tilt compensation in a tangential direction and a tilt compensation in a radial direction in an independent fashion.

Abstract: A tilt adjusting method for a recording medium driving apparatus including a linear driving device including first and second parallel guide shafts. The method provides a flat mirror on a turntable, an auto-collimator, and a skew angle adjusting jig including an optically flat surface. In a first state of the jig, a height of the second end of the first shaft is adjusted so that a tilt of the first shaft in a radial direction matches a tilt of the mirror, and a height of the first end of the second shaft is adjusted so that a tilt of the first shaft in a tangential direction matches the tilt of the mirror. And, in a second state of the jig, a height of the second end of the second shaft is adjusted so that a tilt of the second shaft in a radial direction matches the tilt of the mirror.

Abstract: A circuit element driver includes a control section and a driving section. The control section receives a number n of instruction values of a first group (where n?2) and produces and outputs a number p of instruction values of a second group (where (n+1)?p<2n) in accordance with the n instruction values of the first group. The instruction values of the first group are issued to generate voltages to be applied to n two-terminal circuit elements. The driving section generates and outputs p drive voltages in accordance with the p instruction values of the second group. At least one of the p drive voltages changes with at least one of the instruction values of the first group and is applied in common to two or more of the circuit elements at one terminal thereof.

Abstract: A tilt servo control device of an apparatus for recording information on and reproducing information from an optical recording medium set in the apparatus, the apparatus comprising an optical system for leading a laser beam emitted from a light source to a recording surface of the optical recording medium and a laser beam reflected by the recording surface of the recording medium to a photo detector and a read signal generator for generating a read signal in accordance with an output signal of the photo detector. The tilt servo control device determines a type of the optical recording medium, generates a tilt drive signal so as to reduce a tilt angle at a position of the laser beam irradiating the recording surface and an optical axis of the laser beam by a method for generating a tilt drive signal corresponding to the recording medium type, and drives a tilt angle adjuster for adjusting the tilt angle in accordance with the tilt drive signal.

Abstract: This tilt correcting method includes the step of monitoring jitter values while adjusting a turntable or guide rail after a wobble disc is placed on the turntable. Thereafter, it is determined whether the depths of valleys of monitored jitter values are different, it is determined that the reference tilt is a radial tilt if it is determined that the depths of valleys of the monitored jitter values are different, and the radial tilt is corrected. If it is determined that the depths of valleys of the monitored jitter values are not different, it is determined whether the heights of peaks of the monitored jitter values are different, it is determined that the reference tilt is a tangential tilt if it is determined that the heights of peaks of the monitored jitter values are different, and the tangential tilt is corrected.

Abstract: A recording/reproducing apparatus includes an optical pickup having an objective lens, an actuator for operating the lens, an aberration correction element, and a detector for generating a reading signal; a servo control section; a driver for operating the aberration correction element; a generator for generating a focus disturbance signal and an aberration correction disturbance signal having a period different from that of the focus disturbance signal; and a controller for adjusting the focusing position and the aberration correction amount on the basis of a change in a predetermined characteristic value of the reading signal when the disturbance signals are simultaneously applied.

Abstract: An information recording/reproducing apparatus includes a focusing optical system for focusing light from a light source on an information recording medium as a light spot and an error signal generation system for generating an error signal that represents the positional deviation between an information track and the light spot on the information recording medium from the light reflected by the information recording medium. The apparatus further includes a tilt measurement system for measuring the amount of relative inclination between the focusing optical system and the information recording medium and an offset application system for performing off-track of the light spot by applying an electric offset corresponding to the measured amount of inclination to the error signal.

Abstract: A method of unbalanced disc detection in a slim type optical drive. In the method of the present invention, the slim type optical drive obtains a first tracking count per round of the disc at a first rotation speed to obtain a first runout. Then, the optical drive obtains a second tracking count per round of the disc at a second rotation speed to obtain a second runout. Finally, deviation of the disc is assessed according to the first runout and the second runout, so that the disc can be determined to be a gravitationally eccentric disc or not.

Abstract: A method of recording and reproducing an optical recording medium which detects a defocus and a tilt of the optical recording medium and compensates the detected defocus and tilt in a high-density optical recording medium. In a free running state in which only a focus servo is turned on, the amount of defocus offset that corresponds to a maximum level of a tracking error signal is detected in a plurality of positions on inner and outer peripheries of a disc, and a tilt-zero in the respective position is detected and stored, so that a tilt servo and a focus servo are performed with the value stored in the corresponding position during an actual recording/reproduction. The method can prevent the deterioration of quality of data due the defocus during recording/reproduction, enabling real time recording by quickly stabilizing the focus servo, and stable operation of the system.