Abstract: An optical recording/reproduction method and device that can perform control for optimizing the amount of spherical aberration in a multilayered optical disc in a short period of time. When the objective lens is displaced in the focusing direction, the amplitude value of the focusing error signal detected just after leaving the focal position of a given first recording layer and the amplitude value of the focusing error signal detected just before passing through the focal position of a given second recording layer other than the first recording layer are measured with a particular spherical aberration, the amplitude ratio of amplitude values is calculated, the difference between spherical aberration and the optimal spherical aberration for the second recording layer is approximated as a function of the amplitude ratio, the optimal spherical aberration is calculated on the basis of this approximation, and the spherical aberration is set.

Abstract: The present invention discloses a method and an apparatus for compensating astigmatism in an optical storage system. Firstly, the optical storage system focuses on an optical disc and proceeds track seeking. While track seeking, the astigmatism compensator continues adjusting and an astigmatism index signal is also measured. At last, an optimal astigmatism compensated value of the astigmatism compensator is acquired based on the measured result of the astigmatism index signal.

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: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into four third areas by a first area having a certain width and formed along a straight line in parallel to a first direction, and by a second area having a certain width and formed along a straight line in parallel to a second direction. The spectral element is configured to guide the reflected light passing through the four third areas to respective corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area and into the second area to the sensors.

Abstract: An optical pickup device includes a light source for emitting a light beam, an objective lens for collecting the light beam which is emitted and for irradiating an optical disc with the collected light beam, a diffraction element with a plurality of areas for dividing the light beam which is reflected from the optical disc, a detector with a plurality of detection parts for receiving the light beam which is made to diverge by the diffraction element, and a branching mirror for making the light beam branch into an optical path from the light source to the objective lens and an optical path from the objective lens to the detector. The diffraction element gives an aberration to the light beam diffracted at a specified area.

Abstract: An optical pickup device includes an objective lens portion which converges laser light at a first focal point and a second focal point; an actuator which positions the first focal point or the second focal point on a recording layer in a disc; an astigmatism element which sets a first focal line position and a second focal line position of the laser light reflected on the disc away from each other in a propagating direction of the laser light; a spectral element which disperses four light fluxes obtained by dividing the laser light reflected on the disc in four from each other; and a photodetector having a sensor group which receives the four light fluxes dispersed by the spectral element.

Abstract: An optical storage focus servo system may include an optical pickup unit that includes an astigmatic focusing lens, a focusing actuator that controls a position of the lens relative to an optical media, and a plurality of detectors that detect an intensity and shape of a reflected beam from the media. The system may also include a controller that controls the focusing actuator based on the intensity and shape of the reflected beam.

Abstract: Before tracking control is turned on, there is determined a correction formula for correcting a balance value of a tracking error signal depending on a position of a movable lens for spherical aberration correction. Then, after the tracking control has been turned on, using an RF signal as an index, the adjustment of the position of the movable lens for spherical aberration correction is performed, while the balance value of the tracking error signal is corrected by use of the correction formula. An adjustment value for adjusting the balance value of the tracking error signal at a time point of completing the adjustment of the position of the movable lens for spherical aberration correction is stored.

Abstract: An optical disk device is configured such that when an optical disk including three or more recording layers on one side is inserted into the optical disk device, a movable lens position adjustment device performs adjustment using as an index a tracking error signal provided with a limit to an amount of movement of a movable lens for spherical aberration correction at start-up of the optical disk device and sets an upper limit to the number of retries of the adjustment at the recording layer farthest away from the side on which the laser beam is incident to 1 or more.

Abstract: An optical pickup device has an astigmatism element which imparts astigmatism to reflected light of laser light reflected on a recording layer, and a spectral element into which the reflected light is entered, and which separates the reflected light. The spectral element is divided into six second areas by a straight line in parallel to a first direction, a straight line in parallel to a second direction, and a first area having a predetermined width and formed along a straight line in parallel to a third direction inclined from the first direction by 45 degrees. The spectral element is configured to guide the reflected light passing through the six second areas to corresponding sensors on a photodetector while making propagating directions of the reflected light different from each other, and to avoid guiding the reflected light entered into the first area to the sensors.

Abstract: The present invention provides a unit and method for implementing an optical head and optical drive device whose configuration is simple, and which allows the generation of a track error signal in which no offset is caused to occur. The optical drive device includes a light source for emitting light beams, an objective lens for converging the light beams onto an optical disc, an optical-signal generation element for dividing the light beams into at least four regions by using a division line extending in the radial direction of the optical disc, and a division line extending in the track direction of the optical disc, the light beams being reflected by the optical disc, and an optical detector for receiving the light beams divided by the optical-signal generation element, wherein the up and down or right and left areas of the four regions are made different from each other.

Abstract: An optical system of an optical pickup device includes an astigmatism element which imparts astigmatism to BD light reflected on BD and CD light reflected on CD, and a spectral element which disperses four light fluxes of BD light and four light fluxes of CD light by diffraction, the four light fluxes of BD light and the four light fluxes of CD light being obtained by dividing the BD light reflected on the BD and the CD light reflected on the CD by a first straight line parallel to a converging direction by the astigmatism element, and a second straight line perpendicular to the first straight line. A photodetector of the optical pickup device is provided with first and second sensor groups for respectively receiving the four light fluxes of BD light and the four light fluxes of CD light dispersed by the spectral element.

Abstract: The optical information recording and reproducing device utilizing holography requires the optical system to generate the signal beam and the reference beam to be irradiated to the holographic storage medium as well as another optical system to generate the curing light beam to be irradiated to the holographic storage medium. Furthermore, from the viewpoint of backward compatibility, if the same device is used for recording or reproduction on the conventional optical discs represented by Blu-ray Disc, another optical system adaptable to recording and reproduction on these optical disks is required. This means the optical system configurations become complicated and larger in size. One solution for downsizing is to use the reference beam also as the curing light beam. Another way is sharing of optical path for curing light beam and for the reference beam. Furthermore, it is possible to share the light source for generating the curing light beam and for generating the recording or reproducing light beam.

Abstract: It is aimed to provide an optical head, an optical head manufacturing method and an optical disc device capable of correcting coma aberration generated due to different positions of emission points of a plurality of laser lights having different wavelengths. A two-wavelength laser light source 1 is arranged to correct coma aberration generated in a radial direction of a CD 80 in the case where an objective lens 6 is tilted to locate an inner peripheral end of the objective lens 6 in the radial direction of the CD 80 lower than an outer peripheral end thereof, and an objective lens actuator 9 tilts the objective lens 6 to locate the inner peripheral end of the objective lens 6 in the radial direction of the CD 80 lower than the outer peripheral end thereof.

Abstract: The present invention relates to an aberration correcting device comprising: an aberration correcting element which modulates the phase of incident light; and a position adjusting section which can move the aberration correcting element in a direction perpendicular to an optical axis of the incident light, wherein the aberration correcting element includes first and second aberration correction plates, each of which is disposed such that the phase of transmitted light beam differs with transmission position of the incident light beam with the same phase, and the aberration correcting element has a reference arrangement which is an arrangement of the first and second aberration correction plates in which the light beams transmitted through the aberration correcting element have the same phase, and assuming that a point on the first aberration correction plate crossing the optical axis is a point Oa and a point on the second aberration correction plate crossing the optical axis is a point Ob in the reference ar

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: The optical disk device can stably control an aberration correction lens even when one end of a movable range of the aberration correction lens is set as a reference position. The optical disk device comprises an optical pickup unit including the aberration correction lens and a stepping motor for moving the aberration correction lens, wherein, when an optical disk is inserted into the optical disk device, the aberration correction lens is moved to the reference position within the movable range and near one end thereof, and wherein, when moving the aberration correction lens to the reference position, driving pulses are applied to the stepping motor to press the aberration correction lens against the one end of the movable range, and thereafter a predetermined number of pulses are applied to reversely rotate the stepping motor and to set a stop position where the aberration correction lens stops as the reference position.

Abstract: A focus servo control device includes a first detector, first controller, second detector, and second controller. The first detector detects a first focus error signal. The first controller controls the objective lens based on the first focus error signal, so that a focal point of the first laser agrees with the guide layer. The second detector detects a second focus error signal. The second controller changes a relative distance between the focal point of the second laser and the focal point of the first laser, so that the focal point of the second laser agrees with a target recording/reproducing layer.

Abstract: An optical pickup device is provided with a spectral element which imparts diffraction in such a manner that four light fluxes of the first laser light are separated from each other, when a light flux of the first laser light and a light flux of the second laser light reflected on a recording medium having laminated recording layers and servo layers are divided into four by a first straight line in parallel to a converging direction by an astigmatism element, and a second straight line perpendicular to the first straight line, and that the four light fluxes of the first laser light propagate on an outer side than the light flux of the second laser light; and a photodetector including a first sensor group which receives the first laser light, and a second sensor group which receives the second laser light.

Abstract: An optical pickup device or an optical disk device includes: a light source 11 that emits a laser beam toward an optical disk 25; an optical receiver 18 that detects light reflected from the optical disk 25; and an astigmatism-generating element 31 that generates light used for focus control in a condition where a focusing position on one of two perpendicular cross sections including an optical axis of the light reflected from the optical disk 25 is located ahead of the optical receiver 18 and a focusing position on the other cross section is located behind the optical receiver 18. The astigmatism-generating element 31 is a Fresnel mirror 31a configured to include a plurality of reflecting mirrors, and an imaginary surface 31d that connects the tips of the reflecting mirrors is curved in a concave shape toward a light incidence side.

Abstract: A system includes an objective lens, an imaging module, and a measurement module. The objective lens is configured to receive light emitted by a light source, focus the emitted light onto a target object, and receive light reflected by the target object. The imaging module is configured to receive a first portion of the reflected light. The measurement module is configured to receive a second portion of the reflected light and includes a photo detector and an astigmatic lens configured to direct the second beam onto the photo detector.

Abstract: There is provided an optical disc drive, which includes a light source emitting a light beam, a beam dividing element that divides the light beam into main and sub-beams, an objective lens, an astigmatism producing unit that gives astigmatism to the main and sub-beams, a signal generation unit that has sensors for the beams and generates a focus error signal based on output signals of the sensors; and an optical element that has a function of adjusting intensity distribution of the main beam such that the main beam incident on the optical disc has a predetermined intensity distribution where a maximum intensity level is positioned at a predetermined height within a range of 70% of a pupil diameter, the predetermined height is not equal to an optical axis, and an intensity of the main beam decreases gradually from the predetermined height to a peripheral portion of the pupil.

Abstract: An optical head capable of recording or playing back optical discs is provided. The optical disc comprises a light source to emit a beam, an objective to focus the beam on an optical disc, a beam dividing element having a plurality of divided areas with which to divide a cross section of the beam reflected from the optical disc, and a light detector to receive the beams divided by the beam dividing element, wherein the beam dividing element has in at least one of the plurality of areas an aberration imparting function of imparting an astigmatism or defocus aberration to a beam passing through that area.

Abstract: An optical pickup device includes a semiconductor laser which emits a light beam, first and second objective lenses which focus the light beam onto a first and second optical disc, respectively, a grating which branches a light beam reflected from the second optical disc, an optical detector having a plurality of light receiving parts, which receives light beams branched by the grating, and an actuator which displaces the first and second objective lenses in a radial direction of the first optical disc and the second optical disc. The grating has a first area on which a 0-order diffraction light beam and a +1-order diffraction light beam upon reflection at the second optical disc enter, and a second area on which a 0-order diffraction light beam and a ?1-order diffraction light beam upon diffraction through the second optical disc enter.

Abstract: An apparatus includes a waveguide shaped to direct light to a focal point, and a near-field transducer positioned adjacent to the focal point, wherein the near-field transducer includes a dielectric component and a metallic component positioned adjacent to at least a portion of the dielectric component. An apparatus includes a waveguide shaped to direct light to a focal point, and a near-field transducer positioned adjacent to the focal point, wherein the near-field transducer includes a first metallic component, a first dielectric layer positioned adjacent to at least a portion of the first metallic component, and a second metallic component positioned adjacent to at least a portion of the first dielectric component.

Abstract: An optical disc identifying device includes an optical pickup head, a digital signal processor and a radio frequency amplifier. The optical pickup head has a plurality of laser diodes and a lens. During a start-up procedure, a non-blue laser diode of the optical pickup head is turned on to irradiate a loaded optical disc, thereby generating an electronic signal. The digital signal processor outputs a driving signal, thereby controlling a motor driver to move the lens in a focusing direction. The radio frequency amplifier receives the electronic signal during the movement of the lens, thereby generating a first signal. The digital signal processor includes a detecting unit for comparing the first signal with a slicing signal to generate a pulse signal, and determining whether the optical disc is a blue-ray disc or a non-blue-ray disc according to a pulse number of the pulse signal.

Abstract: An optical pickup device imparts different astigmatisms from each other to light fluxes in four light flux areas formed around an optical axis of laser light, out of the laser light reflected on a disc. The optical pickup device also changes the propagating directions of the light fluxes in the light flux areas to separate the light fluxes in the light flux areas each other. A signal light area where only signal light exists is defined on a detection surface of a photodetector. Eight sensing portions are arranged at a position corresponding to the signal light area. According to this arrangement, only the signal light is received by the sensing portions to thereby suppress deterioration of a detection signal resulting from stray light. Further, a push-pull signal, whose DC component is suppressed, is obtained by computing an output from the eight sensing portions by a predetermined formula.

Abstract: Provided is an objective lens that allows securing of a long working distance for a laser beam with a long wavelength and has a predetermined thickness or larger, and an optical pickup apparatus including the objective lens. In an objective lens of the present invention, a first region that focuses laser beams of a BD, DVD, and CD standards, a second region that focuses the laser beams of the DVD and CD standards, and a third region that focuses the laser beams of the BD and the DVD standards are provided in this order from a center portion of the objective lens. An optical super resolution with the laser beam of the BD standard is achieved by preventing a portion of the laser beam of the BD standard transmitted through the second region from contributing to spot formation.

Abstract: With a high-density optical disc drive, although it is necessary to correct spherical aberrations which depend on a disc substrate thickness error, operation of an aberrations correction element takes time and therefore easy correction according to a disc radius degrades the operability of the apparatus. The present invention comprises an optical pickup unit including an objective lens and an aberrations correction lens, a focus actuator, a tracking actuator, a aberrations correction motor, a seek motor, an aberrations correction lens control module, a radius information detecting module, and a system control module.

Abstract: An optical disc apparatus, for executing recording or reproducing on an optical disc having at least two recording/reproducing layers, includes an optical pickup, having a sphere aberration compensating portion, an objective lens, a driver portion, and an obtaining portion. The sphere aberration compensating portion sets up a compensation volume corresponding to an intermediate position laying between a deepest layer and a most front layer from the optical pickup, and the driver portion drives the objective lens in a direction approaching to the optical disc in accordance with the set compensation volume. When the sphere aberration compensating portion sets up the compensation volume corresponding to the deepest layer, and when the objective lens is driven in a direction approaching the optical disc, the driver portion drives the objective lens in a direction of separating from the optical disc.

Abstract: An aberration correction element including a diffraction plane that corrects a spherical aberration caused by the difference among a first optical recording medium, a second optical recording medium, and a third recording medium by transmitting first beams of light having a wavelength of ?1 emitted from a first light source to read and write data on the first recording medium, and diffracting second beams of light having a wavelength of ?2 emitted from a second light source to read and write data on the second recording medium, and third beams of light having a wavelength of ?3 emitted from a third light source to read and write data on the third recording medium; and a phase shifter plane generating a spherical aberration ??SA having a reverse direction to a spherical aberration ?SA generated at an objective lens optimized for the first optical recording medium according to a temperature change.

Abstract: An aspheric lens includes at least one aspheric lens surface, and an angle of inclination on the aspheric lens surface is smaller than or equal to 65°. The aspheric lens surface is given by the equation Z ? ( r ) = cr 2 1 + 1 - ( 1 + K ) ? c 2 ? r 2 + Lr 2 + Ar 4 + Br 6 + Cr 8 + Dr 10 + Er 12 + Fr 14 + Gr 16 + Hr 18 + Jr 20 where L?0, c is a curvature, r2=x2+y2, K is a conic integer, and L and A through J are aspheric coefficients.

Abstract: A method for servoing when reading out a recorded holographic disk or recording in a preformatted holographic disk is disclosed. The method includes detecting a primary signal of a reflected primary beam from a target data track of a target data layer of the holographic disk, wherein the primary beam of radiation has a first wavelength. The method also includes comparing a power measurement of the primary signal with a threshold value of power. The method also includes detecting a tracking signal of a reflected tracking beam from a reference layer of the holographic disk in an event that the power measurement of the primary signal is below the threshold value of power, wherein the tracking beam of radiation has a second wavelength. The method also includes generating a servo error signal based upon the primary signal or the tracking signal.

Abstract: An optical pickup device includes a light source to emit light, an objective lens to focus the light on a recording medium to form a light spot, an optical path changer on an optical path between the light source and the objective lens to change the path of incident light, a chromatic aberration correction lens disposed on an optical path between the light source and the objective lens, and a photodetector to receive light which is reflected from the recording medium and is then incident thereon through the optical path changer. The chromatic aberration correction lens corrects a chromatic aberration occurring due to a change in the wavelength and/or due to an increase in a wavelength bandwidth of the light. The chromatic aberration correction lens includes at least two lenses such that a lens having a positive power and a lens having a negative power are adjacent to each other.

Abstract: Of the beams reflected by an optical disk, only peripheral beams excluding the push-pull region are used to generate a DPD signal in order to optimize internal wire connections among the light receiving areas of the optical detector and thereby reduce the amplification factor of the lens error signal, required for generating the tracking error signal of the DPP method. A beam reflected from a multilayered optical disk is divided into some beam diffraction areas. The divided beam diffraction areas and the light receiving areas are so arranged that the divided beams focus at different positions on the optical detector and that, when a beam is focused on a target recording layer of the disk, stray light from other than the target recording layer being reproduced does not enter into the servo signal light receiving area of the optical detector.

Abstract: An optical pickup device includes a plurality of laser light sources emitting laser beams of different oscillation wavelengths, and a plurality of objective lenses on which the laser beams in the form of diverging beams emitted by the plurality of laser light sources are incident, and which directly focus the laser beams onto a recording surface of an optical disc. A rising mirror reflects a laser beam in the form of a diverging beam emitted by a laser light source of a predetermined oscillation wavelength among the plurality of laser light sources so as to lead the laser beam to one of the plurality of objective lenses, and transmits the laser beam in the form of a diverging beam emitted by the other laser light source. As the rising mirror transmits the laser beam in the form of the diverging beam emitted by said other laser light source, astigmatism is generated so as to correct existing astigmatism of the laser beam emitted by said other laser light source.

Abstract: An optical disc apparatus in which a bias of a focusing error signal is changed to a value according to a recording power at timing corresponding to a predetermined address position before starting the recording and a defocus of an opposite polarity is preliminarily caused so as to set off a defocus which occurs at the start of the recording.

Abstract: An integrated circuit is provided in an optical disc apparatus for drawing a visible image on an optical disc including a discoloration layer which is discolored by heat or light by irradiating the optical disc with laser light. The integrated circuit includes a tracking direction displacement section configured to execute, when the visible image is drawn, oscillation control to oscillate a position irradiated with the laser light in a radial direction of the optical disc, and a laser modulation section configured to change, when the visible image is drawn, an intensity of the laser light so that the higher a displacement rate of the position irradiated with the laser light in the radiation direction is, the higher the intensity of the laser light becomes.

Abstract: A photodetector detecting reflected light components from an optical medium, the photodetector including a first detector divided into eight sections detecting the reflected light components and converting the light components into electrical signals, a first calculating portion calculating a first tracking error signal from the electrical signals by a differential push-pull method, a second calculating portion calculating a first focusing error signal by an astigmatism method and calculating a second tracking error signal by a differential phase detection method from the electrical signals converted by the first detector; a second detector divided into four sections detecting the reflected light components reflected by the optical recording medium to convert the light components into electrical signals; and a third calculating portion calculating a second focusing error signal by the astigmatism method and calculating a third tracking error signal by the differential phase detection method from the electrica

Abstract: According to one embodiment, an optical recording medium is provided in which interlayer crosstalk is low and in which stable and high-quality recording characteristics can be obtained. To this end, an optical recording medium comprises a first recording part which includes a first recording layer and a first light reflecting layer and which is disposed on a side closer to a light receiving surface, and a second recording part which includes a second recording layer and a second light reflecting layer and which is disposed on a side farther from the light receiving surface, the first recording part and the second recording part being stacked, wherein the thickness of the second light reflecting layer is larger than the thickness of the first light reflecting layer.

Abstract: An optical pickup device includes a photodetector which receives laser light reflected on a recording medium, and an optical system which guides laser light to the photodetector as convergent light. A light transmitting plate which imparts astigmatism to the laser light is disposed between the optical system and the photodetector with an inclination with respect to an optical axis of the laser light. The optical pickup device further includes an optical element which separates four light fluxes of the laser light from each other. The four light fluxes are obtained by dividing the laser light by two straight lines respectively in parallel to a first focal line direction of the laser light transmitted through the light transmitting plate, and a second focal line direction orthogonal to the first focal line direction.

Abstract: An optical storage system and a spherical aberration (SA) compensation apparatus and method thereof are provided. The SA compensation apparatus includes a microprocessor and a digital-signal-processor (DSP). The microprocessor repeatedly regulates a compensation value of an SA compensation driver in the optical-pickup-head (OPH) after the microprocessor has determined the type of an optical storage medium and before the OPH has focused on the optical storage medium. The DSP processes a plurality of electrical signals converted through the OPH whenever the microprocessor has regulated the compensation value of the SA compensation driver, so as to obtain width values of a plurality of focus-error (FE) signals. Accordingly, the microprocessor makes the SA compensation driver to drive an SA compensation unit according to the width values of the FE signals, so as to compensate an SA of the light point generated by the OPH and focused on the optical storage medium.

Abstract: Disclosed is an objective lens used for an optical pickup apparatus to perform writing and/or reading of an optical information recording medium, comprising an antireflective film on a surface of a light source side, wherein a light flux of wavelengths including a wavelength ?1 of 380 nm??1?420 nm and a wavelength ?2 of 630 nm??2?810 nm, is condensed on the medium, a numerical aperture on the light source side with respect to the wavelength ?1 is within a range of 0.8-0.9, and that with respect to the wavelength ?2 is 0.7 or less, and a band of the antireflective film is within a range of 700 nm-800 nm in a state where a reflectance of a light flux perpendicularly entering a central portion of the surface in a wavelength region from 400 nm to 1200 nm is 3.0% or less.

Abstract: A method and apparatus for recording and/or reproducing holographic data and a holographic information storage medium, wherein the apparatus for recording and/or reproducing holographic information includes an optical pickup emitting light onto a holographic information storage medium and receiving the emitted light. The optical pickup includes: a light source unit emitting a signal beam and a reference beam in a recording mode; and a focusing optical system focusing the signal beam and the reference beam on one focal point in the holographic information storage medium so that information can be recorded by using an interference pattern formed along a depth direction of the holographic information storage medium in the vicinity of the focal point, wherein the numerical aperture of the focusing optical system for the signal beam is different from the numerical aperture of the focusing optical system for the reference beam.

Abstract: A method for determining a type of an optical disk includes following steps. A laser beam of a first type is focused on a disk to generate a first optical reflection signal. A first spherical aberration estimate is generated according to the degree of dispersion and strength of the first optical reflection signal. A laser beam of a second type is focused on the disk to generate a second optical reflection signal. A second spherical aberration estimate is generated according to the degree of dispersion and strength of the second optical reflection signal. The type of the disk is determined based on the first spherical aberration estimate and the second spherical aberration estimate.

Abstract: A focus error amplitude obtaining device is configured to obtain amplitudes of a focus error signal. An error amplitude difference calculation device is configured to calculate an error amplitude difference which is a difference between the amplitudes of the focus error signal obtained at two different positions in a moving range of a spherical aberration correction device. An appropriate position search control device is in charge of overall control of structural elements; spherical aberration correction device movement control device, focus error amplitude obtaining device, and error amplitude difference calculation device. The appropriate position search control device decides an appropriate position of the spherical aberration correction device based on the error amplitude difference.

Abstract: A distance control circuit keeps constant the distance between a condensing member and the surface of an optical disk using return light from a region where near field light is generated. Additionally, a focus control circuit controls the focus position of the near field light to sustain it at the position of an information layer using reflection light from the information layer.

Abstract: An optical pickup apparatus changes a propagation direction of luminous fluxes, out of a laser light reflected by a disc, in four luminous flux regions set about a laser optical axis so as to mutually disperse these luminous fluxes. A signal light region in which only a signal light is present appears on a detection surface of a photodetector. A plurality of sensors for a signal light are placed at positions irradiated with the signal light within the region. When an arithmetic process is performed on a detection signal outputted from each sensor, a DC component occurring in a tracking error signal is suppressed.

Abstract: In an optical disk drive mounting a drive unit 20 having a control use circuit 21, and a pickup 1 having an aberration correction liquid crystal element 13 and a drive use circuit 2 which drives the aberration correction liquid crystal element, wherein the drive use circuit 2 stores astigmatic data for correcting a static astigmatism peculiarly provided in an optical system in the pickup 1 in an astigmatic data storage 6, and drives the aberration correction liquid crystal element 13 based on the astigmatic data. By storing the static astigmatic data peculiar to the pickup, inside the pickup, it is possible to transfer the stored astigmatic data to the optical disk drive side easily, and to correct the astigmatism by driving the aberration correction liquid crystal element based on the astigmatic data.

Abstract: An optical head device according to the present invention includes a splitting section for splitting a light beam having been reflected from an optical storage medium. The splitting section includes: a first main region transmitting a first interfering portion; a second main region transmitting a second interfering portion; and first and second sub-regions through which the first interfering portion is transmitted with a lower rate than in the first main region and through which the second interfering portion is transmitted with a lower rate than in the second main region. The splitting section splits the reflected light beam into: a first main light beam transmitted through the first main region; a second main light beam transmitted through the second main region; a first sub-light beam transmitted through the first sub-region; and a second sub-light beam transmitted through the second sub-region.