Abstract: An optical reading apparatus includes an objective lens for focusing an optical beam; an actuator for driving the objective lens; an aberration detector for detecting spherical and coma aberration of the optical beam; an aberration correction element, including a liquid crystal element, for correcting the spherical and coma aberration by applying voltages to the liquid crystal element; a lens location detector for detecting displacement of the objective lens with respect to a reference location; and a controller for controlling the amount of aberration correction of the aberration correction element in accordance with the spherical aberration, the coma aberration, and the displacement.

Abstract: Light emitted from a semiconductor laser is separated by a diffractive optical element into a main beam, first sub beams, and second sub beams. The distribution of the intensity of each of the first sub beams is the same as the distribution of the intensity of the main beam. The distribution of the intensity of each of the second sub beams is different from the distribution of the intensity of the main beam. The sum of the focusing error signals relating to the main beam and the first sub beams is a final focusing error signal. The difference between the tracking error signal relating to the main beam and the tracking error signal of each of the first sub beam is a final tracking error signal. The deviation of the thickness of the substrate of the disk and the radial tilt thereof are detected on the basis of the deviation of the zero crossing points of the focusing error signal and the tracking error signal relating to the main beam and each of the second sub beams.

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 optical disk apparatus has a first optical system having an objective lens with a first NA, a second optical system having an objective lens with a second NA lower than the first NA, addition means for adding focus error signals detected by the first and second optical systems, and alignment means for aligning the objective lens in accordance with the addition result of the addition means.

Abstract: An optical pickup assembly having an elastically supported tilt mechanism. The optical pickup assembly includes a bobbin at which an objective lens is mounted and an elastic support member which supports the bobbin in elastic motion with respect to a holder installed at a base. A focus coil and a tracking coil are installed at the bobbin and form a conducting path for driving the objective lens in a focusing direction and a tracking direction. Tilt coils are installed at one side of the bobbin and form a conductive path for driving tilt of the objective lens. A first magnet and a first yoke generate an electromagnetic force to driving the objective lens together with the current carrying focus coil and tracking coil. A second magnet and a second yoke generate an electromagnetic force to driving the objective lens together with the current carrying tilt coils.

Abstract: A tilt detector and tilt detection method which are capable of detecting a tilt in a radial direction of an optical disc at a high degree of precision and being cost-effective and simple in head part construction.

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: The present invention relates to a tilt control device and method for an optical disc player, wherein an output offset of a tilt detecting means (3) is calibrated by using an output of a focus controller (7). Since the offset is calibrated based on the focus controlling output, the calibration can be performed for all written and non-written discs. As an alternative, a tilt control with high accuracy can be performed by adjusting a tilt frame based on at least two measurements of the controlling output of said focus control means at different radial positions. Thereby, the disc can be positioned in a radial tilt zero position with the aid of the focus controlling output. Now, the tilt detecting means is no longer required for tilt adjustment.

Abstract: A tilt detection method and tilt detector which can make the size of an optical pickup small, improve an installation efficiency of the pickup and reduce a manufacturing cost of the pickup. A first light receiver and second light receiver output detected results corresponding to the amounts of received light to a comparator, respectively. The comparator detects a difference between output signals from the first and second light receivers and outputs the detected result as a tangential tilt signal. An analog delay element delays an output signal from the comparator for a predetermined period of time corresponding to the rotation of an optical disc by 90° and outputs the delayed result as a radial tilt signal.

Abstract: An adjustment method for optical pick-up including a light source for emitting light beams, an object lens for irradiating light beams onto an optical disc for adjustment and a drive portion for driving the object lens in a direction in parallel to the optical axis of the object lens and in a direction perpendicular to the optical axis thereof, wherein in the state where the light source is movably held with respect to the object lens and the drive portion is movably held with respect to the light source, light beams are irradiated onto an optical disc for adjustment concentrically having recording tracks from the optical pick-up to adjust relative position of the object lens with respect to the light source and inclination of the optical axis of the object lens, and an optical disc for adjustment used in such an adjustment method.

Abstract: In a tilt compensation method and an apparatus thereof, an apparatus that compensates for a tilt of a recordable and reproducible optical recording medium includes a tilt detector detecting a tilt of the optical recording medium and a recording compensator. The recording compensator compensates for a recording signal having a predetermined recording pattern by using a predetermined system according to the tilt detected by the tilt detector, in which the tilt detector detects a tilt with respect to an optical recording medium in which a tilt margin is greater than 0 and less than 0.0052 (0<tilt margin<0.0052) and the recording compensator compensates for the detected tilt. Thus, a desired size (length and width) of a mark can be recorded by controlling the power level and the recording time needed for recording according to the detected tilt. Also, the above method and apparatus are suitable for a high density optical disc system.

Abstract: The present invention provides an optical information recording/reproducing device which comprises a light source for emitting a light, a light transmitting system including an objective lens for focusing the emitted light onto an optical storage medium and a photo-detector system for detecting a reflected light from the optical storage medium, wherein before the light is incident into the objective lens, the light has been divided into a main beam and at least a sub-beam which are different in intensity distribution from each other, and the photo-detector system detects first and second track error signals from the main beam and the sub-beam separately, and said photo-detector system further obtains a difference in phase between the first and second track error signals in order to detect a radial tilt of the optical storage medium on the basis of the difference in phase, and further a compensation of the radial tilt is made on the basis of the detected radial tilt.

Abstract: An optical pickup assembly includes a base, a bobbin having an objective lens mounted thereon, the bobbin being installed at the base so as to be movable and having a pair of first side surfaces parallel to a radial direction of a disk and a pair of second side surfaces parallel to the tangential direction of a disk track, a focus coil wound around the bobbin for driving the objective lens in a focus direction, a track coil installed at the first side surfaces for driving the objective lens in a radial direction of the disk, a driving magnet installed at the base to face the first side surfaces, a tilt coil installed at the second side surfaces for driving the objective lens in response to the relative inclination between the objective lens and the disk, a first tilt magnet installed at the base such that one polarity thereof faces the tilt coil, a second tilt magnet installed at an upper portion of the first tilt magnet such that another polarity opposite to the one polarity thereof faces the tilt coil, an i

Abstract: An optical disc drive apparatus having a skew servo mechanism in which end portions of a pair of parallel running guide shaft members for guiding an optical pickup unit are slidably secured to a chassis on which a spindle motor having a turntable is mounted to be rotationally driven in a radial direction by a pair of pivot members, and other end portions of the pair of the guide shaft members are rotatably driven in the radial direction by first and second cam surfaces of a sliding cam which is driven in a direction orthogonally intersecting the pair of the guide shafts based on a result detected by a skew detecting element.

Abstract: A micro-adjustment apparatus for the spindle motor installation angle in an optical disk player is provided. The optical disk player includes a traverse, and the traverse includes a pickup, a first guide rail, and a framework. The pickup includes a light source for supplying a light beam, and the first guide rail guides the pickup during data reproduction. A spin surface is defined while the spindle is spinning. The micro-adjustment apparatus includes a supporting plate, a pivotal device, a first adjustable pivotal device, and a second adjustable pivotal device. The supporting plate supports the spindle motor and is adjustably coupled to the framework. The pivotal device is disposed at a first predetermined location on the supporting plate and contacts the first guide rail. The first adjustable pivotal device is disposed at a second predetermined location on the supporting plate for adjusting an elevation angle of the supporting plate such that the light beam is substantially vertical to the spin surface.

Abstract: A tilt detecting apparatus of an information-recording medium having a photo diode for detecting a light reflected from an information-recording medium and outputting a light amount signal according to the detected light amount; and a calculating unit for calculating a radial tilt amount by using the light amount signal, wherein the photodiode is divided into a plurality of cells which are identified as regions according to a light amount of the reflected light, based on which a tilt signal is detected. A portion of the reflected light diffracted at the information-recording medium is detected by using the 8-divided photo diode, the region having a large difference in a light amount by the tilt and the region having a small difference in a light amount by the tilt in view of the characteristic of the reflected light are detected.

Abstract: In order to correct the change in the offset and amplitude of a tracking error signal because of the change in the position of an object lens from the center of an optical pickup, the offset amount and amplitude value of the tracking error signal with respect to the displacement amount of the object lens from the center of the optical pickup are checked beforehand, and the displacement amount of the object lens is estimated on the basis of a tracking correction signal by using an object lens displacement observer.

Abstract: An optical recording apparatus of the present invention has a semiconductor laser 5 for generating a light spot used for information recording, detection means 6 of detecting the aberration amount of the light spot, and control means 7 of controlling the output of the semiconductor laser 5 by use of the detected aberration amount.

Abstract: Optical disk device, in which tracking adjustment systems and a sled adjustment system are controlled independently, has offset value acquisition capability, which detects drive signals output from tracking adjustment systems and acquires tracking drive offset values. Such disk also has an offset value comparison capability, which compares the acquired tracking offset value and the offset center value in the state in which no tracking adjustment control is done, a search direction acquisition capability, which acquires the search direction of optical pickup from the control instruction that is output from the control system and sled drive decision capability, which decides whether to drive sled adjustment system based on the comparison result and the acquired search direction.

Abstract: A tilt servo control apparatus for an optical disk is provided, which is able to keep a high reproduction quality by correcting tilt errors with its construction simplified and compact. The tilt servo-control apparatus includes: an optical pickup for irradiating an optical beam onto an optical disk and detecting a reflected light from the optical disk; a tilt-correction unit for correcting, using a correction amount, a tilt error due to aberration caused by a tilt angle formed between an optical axis of the optical beam and a normal line of the optical beam at an emitted position on the optical disk; an amplitude detecting unit for detecting a maximum amplitude and a minimum amplitude of a detected signal by the optical pickup within a period of one rotation of the optical disk; and a tilt-correction controlling unit for providing a control signal to control the correction amount used in the tilt-correction unit.

Abstract: Method and apparatus for controlling high-speed rotation of optical disc, wherein the amount of disc vibrations caused by the disc rotation is calculated and the disc rotation speed is increased based on the calculated amount of disc vibrations to maximize the data transfer rate under given disc vibrations. The apparatus of the present invention comprises a pickup for retrieving data recorded on an optical disc, a drive unit for driving motors, an R/F unit for equalizing and shaping signals reproduced from the optical disc, a servo unit for controlling the drive unit and detecting sync signals from the output signal of the R/F unit, a digital signal processing unit for retrieving original digital data from the output signal of the R/F unit, a timer for measuring the elapse time between specific events, and a microprocessor for controlling the rotation speed of the optical disc based on the elapse time measured by the timer.

Abstract: The present invention relates to a recording and/or reproducing apparatus that records or reproduces information signals by scanning a signal recording surface of a rotated disk using a light beam irradiated from an optical pickup. Further, the present invention provides a skew adjustment based on a detection result from a detection unit detecting a return light beam that is irradiated onto the disk and is reflected thereon.

Abstract: A method for calibrating a tilt in a disc player includes a disc insertion judgment step, a focus error output time judgment step, a subtraction step, a disc recording surface judgment step, and a tilt calibration step. In the focus error output time judgment step, an optical pickup unit is made to ascend and then descend for a predetermined time, to then judge a first focus error output time at which a focus error is output during ascending and a second focus error output time at which a focus error is output during descending. A focus error output difference time is obtained by subtracting the FET1 from the FET2. In the tilt calibration step, if the FET is not same as a reference focus error output difference time (FETrf), the turntable is made to rotate, to calibrate a tilt between the optical pickup unit and the disc.

Abstract: A tilt detector is adapted to be used for a storage medium provided with a recording track on which information is recorded and a first and a second header portions, each arranged in a manner shifted in opposite directions to each other from a center line of the recording track. The detector includes a light irradiation unit for irradiating a light beam onto the first header portion, the second header portion and the recording track; a light receiving unit having a first light receiving surface and a second light receiving surface arranged adjacently and for receiving the light beam reflected by the storage medium, the first light receiving surface outputting a first output and the second light receiving surface outputting a second output; an operation unit for executing an arithmetic operation of the first output and the second output to generate an operation result signal; and an error signal generation unit for generating a tilt error signal based on the operation result signal.

Abstract: An apparatus for reading an optical data carrier (1) in accordance with the invention, comprises a transducer (5) for optically reading an optically readable pattern recorded in substantially parallel data tracks of the data carrier (1). The transducer (5) generates a read signal (S0(t)) which is an indication of the optically readable pattern. The apparatus further includes unit for realizing a relative movement of the transducer (5) with respect to the data carrier (1). The apparatus also has correction unit (16, 17, 18) for reducing tangential tilt (IT) and error, signal generating unit (20) for generating an error signal (SE(t) for the correction unit. The apparatus characterized in that the error signal generating unit (20) are adapted to derive the error signal (SE(t)) from a temporal asymmetry of the response of the read signal (S0(t)) to the optically readable pattern.

Abstract: An optical disk apparatus has

Abstract: At least part of a light beam reflected from an optical disc is divided into first through fourth light areas in directions corresponding to the radial and tangential directions of the disc, and first through fourth detection signals are output from the light areas. The first through fourth light areas are ordered counterclockwise or clockwise. A phase difference is obtained between a first sum signal obtained by summing the first and third detection signals and a second sum signal obtained by summing the second and fourth detection signals and first and second phase difference signals are output based upon the phase difference. The phase difference signals are summed to generate an optical recording/reproducing system monitoring signal for system adjustment even for high density optical discs, the monitoring signal being proportional to the degrees of a radial tilt, tangential tilt, a defocus, or a detrack.

Abstract: An optical disk control device comprises a playback signal detection unit for detecting data recorded on a disk by irradiating the disk with a converged light beam; a signal switching unit for successively selecting plural data signals obtained by the playback signal detection unit, and performing time-division-multiplexing on the selected signals; an A/D conversion unit for converting an analog signal which has been time-division-multiplexed by the signal switching unit, into a digital signal; an A/D conversion command unit for generating an A/D conversion command of the A/D conversion unit; a serial transfer unit for serial-transferring the command signal generated by the A/D conversion command unit; a serial reception unit for receiving the signal from the serial transfer unit, and controlling the signal selection operation of the signal switching unit on the basis of the received signal; and an arithmetic unit for generating an optical disk drive controlling signal by performing arithmetic processing on t

Abstract: An aberration compensation device includes: a phase difference generator for receiving an input signal and for generating a phase difference used for compensating for an aberration induced in a light beam; a temperature detector for detecting a temperature of the phase difference generator; and a corrector for controlling the input signal to be inputted to the phase difference generator based on the temperature detected by the temperature detector thereby to correct a variation of a characteristic of the phase difference generator resulting from a temperature variation.

Abstract: An optical axis angle adjusting device is provided, which can adjust the optical axis angle, which can prevent sound skipping or noise in the image of the optical reproduction device even when the disk has certain surface undulation. In the adjusting device, an adjustment disk 10 is inclined relative to the turn table. Rotation phases of the disk are detected, and incident angle is detected at the respective rotation phases. The optical axis angle is adjusted so that the incident angles at the respective phases are identical with each other. Because the disk is inclined, the incident angle can be detected accurately, and the optical axis adjustment can be achieved accurately.

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 tilt servo control device of an apparatus for recording information on and reproducing information from an optical recording medium, 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 split type 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 generates a push-pull component signal including a differential component of output signals of respective split portions of the photo detector, generates a tilt error signal representing a tilt angle at a position of the laser beam irradiating the recording surface and an optical axis of the laser beam based on the push-pull component signal, and drives a tilt angle adjuster for adjusting the tilt angle so as to reduce the tilt error signal.

Abstract: A four-axial driving actuator for an optical pickup with improved bobbin dynamic characteristics, in which the winding starting ports for a focus coil, tracking coil, and tilt coil are separate from one another, and the winding end ports thereof are combined as a common ground. The four-axial driving actuator includes: a base; a holder fixed on the base; a bobbin to which an objective lens is fixed; spring wires connected between the bobbin and the holder; and a magnetic driving unit driving the bobbin in the focus, track, or tilt direction with a focus coil, a tracking coil, and a tilt coil, wherein the magnetic driving unit comprises a circuit unit including winding starting ports for the focus coil, tracking coil, and tilt coil, and a common ground port at which winding end ports for the focus coil, tracking coil, and tilt coil are grounded, and the circuit unit applies a voltage to the tracking coil, tracking coil, and tilt coil.

Abstract: An optical pickup device comprises an objective lens unit having an objective lens, a support member for supporting the objective lens and an objective-lens driving mechanism for driving the objective lens in a radial direction and a focusing direction of an optical disc in such a way that a light beam is focused on an information recording surface of the optical disc; and a main unit having an optical irradiation system which includes a light source for emitting a light beam and guides the light beam to the objective lens, and an optical detection system which includes a photo-sensor and guides reflected light from the information recording surface to the photo-sensor via the objective lens.

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: An optical pickup device includes a light source for generating and emitting light, optical path changing means for changing a proceeding path of incident light, an objective lens for focusing incident light on a recording medium which has a recording surface where information is recorded and a protection layer, at the side where light is input, for protecting the recording surface, a main photodetector for detecting the information signal and/or an error signal by receiving the light reflected by the recording surface of the recording medium and passing through the objective lens and the optical path changing means, and an inclination detecting unit for detecting inclination of the recording medium by receiving the light emitted from the light source and reflected by the surface of the protection layer or the recording surface of the recording medium.

Abstract: Disclosed is a tilt controlling method and apparatus in which an RE signal track at a point where an RF signal is the maximum or an RE signal track at a point where a jitter is the minimum is detected as a tilt control signal to induct a DC component according to the disk shape and an AC component according to the surface vibration of the disk. Further, the fact is used that an RF envelope has the maximum value when the disk is parallel to an object lens or there is no tilt. Thus, in a tilt initialization step, a tilt track as the RF Max. is obtained for one rotation and the central potential of this track is set as a tilt control reference voltage, and when the RF envelope becomes a phase corresponding to a condition of a controller or a differential value of the RF envelope in the tilt window signal becomes a desired phase, tilt control is started so that the RF envelope always has the maximum value.

Abstract: A thickness servo system using optical aberrations is provided. This system includes an objective lens facing a recording layer covered with a transparent layer accompanying thickness irregularity, a laser source for supplying a laser beam to the recording layer through the objective lens and transparent layer, a photodetector for detecting the laser beam reflected by the recording layer through the transparent layer and objective lens, and a thickness irregularity correction section which is placed in a laser beam optical path between the laser source and the recording layer to correct an optical aberration of the objective lens due to the thickness irregularity of the transparent layer. In this servo system, the photodetector detects an aberration amount corresponding to thickness irregularity, and the thickness irregularity correction section operates to minimize the detected aberration amount. The thickness irregularity of the transparent layer can also be calculated from the detected aberration amount.

Abstract: An optical disc and an optical disc drive for the optical disc are provided which are suitable for recording data with a high density.

Abstract: A liquid crystal driving signal generating apparatus comprises a PWM signal generator, a low pass filter for limiting a frequency band of a PWM signal outputted from the PWM signal generator, a liquid crystal panel connected to an output of the low pass filter, and a control means for controlling the PWM signal generator. The control means controls the PWM signal generator such that the PWM signal generator generates a PWM signal with a duty ratio corresponding to a refractive index to be set in the liquid crystal panel.

Abstract: The invention provides an optical disk wherein a spherical aberration caused by a displacement of the thickness of a transparent substrate of the optical disk can be corrected without giving rise to an increase in scale of the apparatus or an increase of the cost. The recording face of an information recording layer of the optical disk on which a very small spot for recording or playing back information is formed is covered with the transparent substrate. A particular region is provided at a portion of a lead-in region formed in a disk innermost circumference region of the recording face of the information recording layer, and a particular pattern with which a spherical aberration of a very small spot appearing in accordance with a displacement of the thickness of the transparent substrate from a prescribed value is formed in the particular region.

Abstract: An optical axis angle adjusting device is provided, which can adjust the optical axis angle, which can prevent sound skipping or noise in the image of the optical reproduction device even when the disk has certain surface undulation. In the adjusting device, an adjustment disk 10 is inclined relative to the turn table. Rotation phases of the disk are detected, and incident angle is detected at the respective rotation phases. The optical axis angle is adjusted so that the incident angles at the respective phases are identical with each other. Because the disk is inclined, the incident angle can be detected accurately, and the optical axis adjustment can be achieved accurately.

Abstract: An optical recording apparatus includes: a tilt detecting device for detecting a circumferential direction component of a tilt of a recording medium with respect to a laser beam light axis; a recording pulse signal generating device for generating a recording pulse signal by coding an information signal to be recorded and outputting the generated recording pulse; a modulating device for receiving the recording pulse from the recording pulse signal generating device, and modulating an intensity of a laser beam based on the received recording pulse signal; a laser beam irradiating device for applying the modulated laser beam onto the recording medium; and a recording pulse signal control device for controlling a sending timing at which the recording pulse signal is sent from the recording pulse signal generating device to the modulating device, based on the circumferential direction component detected by the tilt detecting device.

Abstract: A drive device has a feed mechanism that causes a control object to move in order to control the positioning of the control object, a motor that serves as the drive source of said feed mechanism, and a control means that controls this motor The control means has an operation history memory unit that stores the operation history of whether the motor is doing an initial start or a restart, and a command selection unit that selects control commands and outputs them to said motor based on information stored in said operation history memory unit. Because intermittent operation that repeatedly drives and stops the motor occurs when there is a restart, the thermal shutdown associated with overheating of the driver IC is avoided, and any difference between the feed amount due to the control means and the actual feed amount can be prevented.

Abstract: An optical pickup apparatus includes a photodetector for receiving a diffracted light reflected from the recording medium; and a tilt detector for detecting a tilt amount of the recording medium on the basis of a light intensity within an interference region of a 0th-order diffraction light and at least one diffraction light other than the 0th-order diffraction light of the reflected light received by the photodetector.

Abstract: An apparatus for calibrating a tilt in a disc player includes a deck base, an optical pickup unit reciprocating in the radial direction of a disc and irradiating optical beams with respect to of the recording surface of the disc, a regulation plate supported on the deck base, a spindle motor secured to the regulation plate, a turntable driven and rotated by the spindle motor, on which the disc is loaded, and a revolving unit for rotating the regulation plate according to the crookedness of the recording surface on the disc. In the disc player tilt calibration apparatus, a cam unit is driven and rotated by a motor which rotates in the forward and reverse directions according to the crooked states on the disc recording surface, to thereby tilt the regulation plate. Accordingly, the tilt of the turntable can be adjusted to resultantly make a regulation work simplified and convenient.

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: An optical head apparatus capable of stably obtaining a detection signal of spherical aberration even with a high density optical disk. A spherical aberration error signal is obtained by: dividing the returning light from the optical disk into a transmitted light and a diffracted light; reproducing information with the transmitted light having a larger amount of light while dividing the diffracted light having a small amount of light into two regions, i.e., region near the optical axis and a region distant from the optical axis; determining amounts of focus deviation in respective regions as focus error signals; and taking the difference signal therebetween. Thus, it is possible to detect the amount of spherical aberration with the SN ratio of the information reproducing signal kept at high level.

Abstract: An aberration correcting apparatus for correcting an aberration of beam which is emitted from a light source and focused on an information recording medium by an optical system, the aberration correcting apparatus includes a wave front aberration correcting component aligned in an optical path between the light source and the information recording medium for correcting a wave front aberration of an incident beam by changing a refractive index corresponding to an applied voltage. A detector also detects a tilt-angle of the information recording medium, and a controller for controlling the wave front aberration correcting component corresponding to an output of the detector.

Abstract: An optical disc drive apparatus comprising a skew servo mechanism M1 in which one end portions of a pair of parallel running guide shaft members for slidably guiding an optical pickup unit are slidably secured to a chassis on which a spindle motor having the turn table is mounted to be rotationally driven in the radial direction by a pair of pivot members, and then, based on the result detected by a skew detecting means, the other end portions of the pair of the guide shaft members are rotatably driven in the radial direction by the first and second cam surfaces of a sliding cam which is slidably driven in the direction orthogonally intersecting the pair of the guide shafts.