Abstract: There is provided an optical system for an optical disc which requires a numerical aperture larger than or equal to 0.60. The optical system is provided with a light source, an objective lens, and a driving system that controls a position and an attitude of the objective lens. The driving system operates to move the objective lens in a direction perpendicular to a central axis of the objective lens for a tracking operation, and to change the attitude of the objective lens during the tracking operation so that the central axis on a light source side tilts toward the light source.

Abstract: A method for demodulating a tracking error signal comprising the steps of (A) demodulating the tracking error signal when starting motion, (B) demodulating the tracking error signal after motion has started, and (C) demodulating the tracking error signal before and after lens motion stops.

Abstract: An optical disc apparatus includes: an optical pickup; a sled drive section that moves the optical pickup in a radial direction of an optical disc; and position control means for controlling, after bringing the optical pickup to an end of a moving range of the sled drive section, the sled drive section to move the optical pickup a predetermined distance in the opposite direction to place the optical pickup at a predetermined reference position.

Abstract: An optical disc device includes an optical pickup for irradiating optical discs with laser and detecting light reflected by the disc to generate received light signals, optical pickup driving means for driving the pickup radially, traverse signal generation means for generating traverse signals forming a pulse at the pickup's crossing a track by binarizing the received light signal based on binary threshold, movement control means for recognizing moving amount and speed of the pickup based on the traverse signal and controlling the optical pickup driving means based on the recognition result for the pickup's seeking to the target, and abnormality monitoring means for sending abnormality notices to the movement control means when pulse interval of the traverse signal exceeds the threshold, the movement control means, after temporarily stopping seek according to the abnormality notice, recognizes the temporary stop position for the optical pickup's seeking from the position to the target.

Abstract: According to the present invention, a recording film is partially initialized using a first light beam (A) having a wavelength for initialization, focus adjustment is performed using a second light beam (B) having a wavelength corresponding to a wavelength for recording and reproducing information on and from an information recording medium, and then the recording film is initialized using the first light beam (A), thereby it is possible to securely initialize recording films of all information layers of a multilayer information recording medium.

Abstract: The present invention is embodied in a method for storing computer readable data on a removable storage medium, including using a first wavelength to write data to the removable storage medium, using a second wavelength to maintain radial tracking on the removable storage medium, wherein the second wavelength is shorter than the first wavelength, and maintaining axial tracking on the removable storage medium with at least one of the first wavelength or the second wavelength.

Abstract: An information recording apparatus which irradiates a laser light onto a recording medium such as a DVD+R to record information records an adjustment RF signal in a PCA used for calibration of the laser light (OPC process). Thereby, on the recording medium having no recorded area of an RF signal in an entire circumference, such as the DVD+R, it becomes possible that the adjustment RF signal is recorded in the PCA to be read out and a mechanism adjustment and the like are executed. In addition, the information recording apparatus searches the inside of the PCA in order from the area having highly possibility that the adjustment RF signal is recorded. Thereby, the adjustment RF signal in the PCA can be rapidly detected.

Abstract: An optical recording medium driving apparatus supporting an optical recording medium having multiple recording layers includes head means including a focusing mechanism and a spherical aberration correction mechanism; focusing control means for driving the focusing mechanism on the basis of a reflected light to perform focusing control on each recording layer; spherical aberration correcting means for driving the spherical aberration correction mechanism on the basis of a spherical aberration correction value to correct spherical aberration; and control means for controlling the focusing control means so as to set the spherical aberration correction value given by shifting the spherical aberration correction value appropriate for the midpoint between a target layer and a first recording layer by a desired value in the spherical aberration correcting means and controlling the focusing control means so as to perform the focusing control with the spherical aberration correction value after the shift being set.

Abstract: Embodiments of methods and systems for controlling access to information stored on memory or data storage devices are disclosed. In various embodiments, fluid-mediated modification of information or access to information is utilized. According to various embodiments, data storage devices designed for rotating access are described which include rotation-activated fluid control mechanisms.

Abstract: An objective lens is raised from below upwards with a DVD laser diode turned on and levels of detection signals A, B, C, and D from a four segment photodetector are acquired and stored in a RAM. A ratio (A+D)/(B+C) in a direction of the X-axis is then calculated. When the ratio exceeds a predetermined value, a lens shift correction amount is calculated for the calculated ratio based on a correction table. The objective lens is then shifted in the direction of the X-axis in accordance with the calculated lens shift correction amount. These processes are executed before a series of processes required for achieving a focus-on state.

Abstract: The present invention provides an information processing apparatus, a servo adjustment method, and the like realizing reduced time required for servo adjustment. An information reproducing apparatus according to the present invention is for reproducing information recorded on a recording medium having a plurality of recording layers. The apparatus includes: signal level measuring means for measuring a signal level of each of recording layers; and servo adjusting means for performing servo adjustment on at least one of the recording layers, storing a servo adjustment value in the servo adjustment, and in the case where the recorded information is reproduced from the recording layers, performing servo adjustment on the recording layers so as to become to the servo adjustment value.

Abstract: An information recording medium excellent in surface smoothness. The information recording medium has a data track pattern and a servo pattern formed on at least one surface of a substrate by a concave/convex pattern including a plurality of convex portions. The concave/convex pattern has concave portions each having a non-magnetic material embedded therein. An A concave/convex pattern forming the servo pattern includes a plurality of servo convex portions formed in a manner associated with servo data. At least part of the plurality of servo convex portions are formed by a B concave/convex pattern including a plurality of non-servo convex portions. This arrangement makes it possible to maintain excellent surface smoothness within a servo pattern area, thereby enabling the recording/reproducing apparatus to execute stable recording and reproducing on and from the information recording medium.

Abstract: An information recording and/or reproducing apparatus using a removable disk-shaped optical recording medium (51) is provided which includes a storage unit (31) to store an axial-runout amount in a predetermined radial position on the disk-shaped optical recording medium (51) being rotated, a near-field light projector (7) provided to condense a light beam emitted from a light source (3) and which projects the condensed light beam as near-field light when located in a field near the information recording surface of the disk-shaped optical recording medium (51), a first controller (30) which multiplies an axial-runout amount read from the storage unit (31) by a predetermined gain to generate a control signal and controls the near-field light projector (7) to follow the axial-runout amount of the disk-shaped optical recording medium (51), and a second controller (40) to control the near-field light projector (7) on the basis of the linear characteristic of the return-light amount of the near-field light to keep

Abstract: The invention provides an optical disk device that has a laser unit including a first objective lens and a second objective lens. A numerical aperture of the first objective lens is different from a numerical aperture of the second objective lens. The optical disk device has a first focus driver that detects a first voltage value indicating the value of a driving voltage to drive the first objective lens when light beams are irradiated onto the surface of an optical disk via the first objective lens and a focus is achieved. The optical disk device has a second focus driver that detects a second voltage value indicating the value of a driving voltage to drive the second objective lens when light beams are irradiated onto the recording surface of said optical disk via the second objective lens and a focus is achieved. The optical disk device has a controller that discriminates the type of an optical disk, based on a difference between the first voltage value and the second voltage value.

Abstract: A servo control signal generation device for discriminating a kind of an optical disk, changing over between top and bottom envelope signals of an RF signal, and generating a defect signal and a mirror signal includes an RF generator for generating the RF signal from reflected light of an optical disk, a disk discriminator for discriminating a kind of the optical disk from the RF signal, and a top envelope generator and a bottom envelope generator respectively for generating the top and bottom envelope signals of the RF signal. If the disk has reflectance after recording which is lower than that before recording, the defect and mirror signals are generated respectively from the top and bottom envelope signals. If the disk has reflectance after recording which is higher than that before recording, the defect and mirror signals are generated respectively from the bottom and top envelope signals.

Abstract: The present invention provides an optical disk apparatus and a focus jump method capable of reliably performing a focus jump by appropriately obtaining the amplitude of a signal such as a focus error signal in a multilayer optical disk. An optical disk includes jump areas which are provided separately from data areas and at which a focus jump is performed. When a focus jump is performed, an optical pickup is moved to the jump area, and the laser power level of the optical pickup is changed and set in accordance with a target layer to which the focus is jumped. A focus position is allowed to reach the target layer by counting the number of times of intersecting with recording layers using a reflected light from the optical disk while performing a focus sweep of an objective lens in the optical pickup.

Abstract: A system for supplying a driving voltage to move an optical pickup unit to a predetermined position includes a storage unit, an output unit, and a drive module. The storage unit is used for storing instructions. The instructions include a move-outwards instruction, a move-inwards instruction, and a move discriminate-position instruction. The output unit is constructed and arranged for outputting the instructions. The drive module is coupled to the output unit for supplying the driving voltage to move the optical pickup unit toward an outermost position based on the move-outwards instruction, move the optical pickup unit to an innermost position based on the move-inwards instruction, and move the optical pickup unit from the innermost position to the predetermined position based on the move discriminate-position instruction.

Abstract: The same contents having different recording rates are recorded on a multi-layer disk. A plurality of contents or the same contents having different recording rates are independently recorded respectively in different layers of an optical disk having a plurality of recording layers. In order to record a plurality of contents or the same contents having different recording rates in parallel at that time, recording on the multi-layer optical disk is conducted by repeating an operation of dividing each content into recording units, recording a recording unit of one kind of information in a recording layer, and recording a recording unit of the other kind of information in a different recording layer.

Abstract: One of the objects of the invention is to provide an optical disc apparatus capable of focusing on a signal surface regardless of appearance of a fake signal. The optical disc apparatus includes: an optical pickup for outputting a signal on the basis of reflection light of the optical disc, the optical pickup including an objective lens; a driving section for moving the objective lens of the optical pickup relative to an optical disc surface; and a focus controlling section for carrying out a focus detecting operation by detecting a reflection signal on a signal surface of the optical disc from the output signal of the optical pickup within a predetermined range of distance between the objective lens and the optical disc surface while the objective lens is being moved relative to the optical disc surface by means of the driving section.

Abstract: A method of inter-layer search of a multi-layer disk, the method including determining whether a search is required of a layer other than a currently accessed layer; searching the currently accessed layer for a position corresponding to a target address on the layer not currently accessed; and moving access to the layer not currently accessed according to the position corresponding to the target address.

Abstract: A method for track jumping for optical recording media exhibiting eccentricity, and to an apparatus for reading from and/or writing to optical recording media using such method is disclosed. The method for track jumping for optical recording media exhibiting eccentricity, whereby a sled and/or an actuator are moved from a start track to an end track, includes the steps of: determining the eccentricity of the optical recording medium, initiating the track jump at minimum eccentric acceleration, and completing the track jump at minimum eccentric acceleration.

Abstract: A servo control signal generation device for discriminating a kind of an optical disk, changing over between top and bottom envelope signals of an RF signal, and generating a defect signal and a mirror signal includes an RF generator for generating the RF signal from reflected light of an optical disk, a disk discriminator for discriminating a kind of the optical disk from the RF signal, and a top envelope generator and a bottom envelope generator respectively for generating the top and bottom envelope signals of the RF signal. If the disk has reflectance after recording which is lower than that before recording, the defect and mirror signals are generated respectively from the top and bottom envelope signals. If the disk has reflectance after recording which is higher than that before recording, the defect and mirror signals are generated respectively from the bottom and top envelope signals.

Abstract: A disc device includes a lens that focuses a laser light on an optical disc surface, a focus drive unit that drives the lens in a focusing direction, a focus control unit that controls to focus the laser light on the optical disc surface, a focus displacement detecting unit that detects a displaced amount in the focusing direction, a differentiation unit that differentiates a focus displacement detected signal, and a unit that inverts a sign of a differentiated signal, thereby, the disc device is driven intermittently to restrain a motion of an objective lens in a focusing direction and avoid colliding the objective lens with the optical disc surface.

Abstract: A driver IC 1 has a bias terminal 20a via which a bias voltage fed from a microcomputer 2 to drive and control a loading motor 4 is fed in and a bias terminal 20b via which a bias voltage fed from a DSP 3 to drive and control a focus coil 5, a tracking coil 6, a sled motor 7, and a spindle motor 8 is fed in.

Abstract: An optical disc drive apparatus includes: a laser beam source; a collector device disposed as facing a disc that can record a signal, which collects a laser beam emitted from the laser beam source onto the disc; a record processing module which records the signal on the disc through the collector device while modulating laser power of the laser beam source; a reflecting light level detecting module which receives the reflecting light when the signal is recorded and detects a level of the reflecting light; a laser power control module which controls the laser power when the signal is recorded based on the detected level of the reflecting light; a tilt control module which controls a tilt angle between the disc and the collector device based on the detected level of the reflecting light; and a switching module which switches between control of the laser power and the tilt angle.

Abstract: An apparatus for recording and reproducing an information signal on and from an optical disc includes a memory. The information signal is written into the memory. The information signal is read out from the memory. An optical head generates a laser beam in response to the readout information signal, and applies the laser beam to the optical disc to record the readout information signal on the optical disc. A test signal is recorded on a position of the optical disc near a recording position thereof via the optical head during the writing of the information signal into the memory. The test signal is reproduced from the optical disc. The reproduced test signal is evaluated to generate an evaluation result. An intensity of the laser beam is optimized in response to the evaluation result.

Abstract: The resistance against recording defects of a write-once optical disk is enhanced allowing realtime recording and playback of data streams with a single speed disk drive. A data stream is recorded in data blocks on the optical disk. An error correction block for one or more data blocks is generated and written on the same optical disk during recording. A spare data area is kept blank on the storage medium and used for storing a defect data block reconstructed by using the error correction block.

Abstract: This disk device includes a pickup head (PUH), a PUH shift control unit, and an inner circumference position detection unit. The PUH reads out data upon a disk. The inner circumference position detection unit detects whether or not the PUH has shifted to the inner circumferential edge of the disk. And, after having stopped the PUH in the neighborhood of a position at which the detection state of the inner circumference position detection unit changes over, the PUH shift control unit determines a shift time period T5 for the PUH when a predetermined operation has been performed. And, by supplying power during the time period T7, the PUH is stopped at a predetermined position.

Abstract: An optical disc drive uses a tracking error signal derived from the wobble-induced signal components of the optical detector signal. This tracking error signal is relatively insensitive to beamlanding errors, and to differences in the signal amplitudes of the output signal of individual detector segments. Further, the need for a 3-spot grating is eliminated. A distinction is made between a situation where the track being followed is empty, and a situation where the track being followed is written. In case the track being followed is empty, a tracking error signal is derived from the wobble-induced signal components of the optical detector signal, whereas, in case the track being followed is written, a tracking error signal is derived from the data-induced signal components of the optical detector signal.

Abstract: An optical disc apparatus, as a learning operation before a recording or reproducing operation, rotates an optical disc at a first speed to read PID information, discriminates between lands and grooves of the optical disc, detects switching positions between lands and grooves, sets a rotation angle position of tracking pull-in of an objective lens of a time length that allows the PID information to be stably read, with respect to the switching position, and stores the set position information of tracking pull-in as learning result information. During recording or reproducing, the optical disc apparatus rotates the optical disk at a second speed higher than the first speed, pulls in the objective lens for tracking based on the stored position information of tracking pull-in, reads PID information, and performs the recording or reproducing operation while discriminating between lands and grooves and detecting switching positions between lands and grooves.

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: A playback apparatus that plays back a recording medium having recording layers includes an optical head irradiating the recording layers with laser light using an objective lens and reading information recorded in the recording layers; an actuator holding the objective lens; focus servo means for driving the actuator to execute focus servo; layer movement driving means for driving the actuator to perform movement of the objective lens in an interlayer direction; tracking servo means for driving the actuator to execute tracking servo; center-point servo means for driving the actuator to execute center-point servo for setting the objective lens to a center point position; and layer jump sequence control means for performing a series of layer jump operations and causing the center-point servo means to execute the center-point servo in a predetermined time within a period during which the series of layer jump operations is performed.

Abstract: The purpose is to provide an optical disc apparatus which can accurately calculate a gain for focus control. An optical apparatus (100) includes: an FE generator (20) for generating an FE signal; an AS generator for generating an AS signal (21); a normalization operator (22); an Fc filter (23); a selector (24); a spherical aberration setting device (34); an FE amplitude measuring device (30); an Fc pull-in instructor (52); an after-pull-in AS measuring device (40); and a gain operator (32). The optical apparatus obtains an amplitude of the FE signal before the focus is pulled in, and obtains a level of the AS signal after the focus is pulled in to adjust a focus gain.

Abstract: Calibration of a focus offset in an optical drive. A calibration pattern, comprising a plurality of marked areas, is marked upon a medium. A user input is received, identifying a perceived darkest marked area of the calibration pattern. The focus offset is determined corresponding to the perceived darkest marked area.

Abstract: In an optical disc device employing a CLV method, executing pickup return processing when focus drop occurs during recording poses problems of increased waiting time for rotation and increased focus servo recovery processing time. When defocusing occurs and focus pull-in cannot be achieved by retry, a first rotation frequency at a radial position thereof is calculated. Next, a second rotation frequency at the innermost circumferential position at the current speed is calculated. Next, a third rotation frequency at a radial position where recording is restarted after focus servo recovery is calculated. Next, a fourth rotation frequency at pickup return position at a different speed is calculated.

Abstract: A disc drive apparatus (1) is described, for writing/reading information into/from a storage medium (2), such as an optical disc. After start-up, multiple recalibration processes are executed, wherein the recalibration processes are executed more frequently during an early phase of the write/read operation than during a later phase of the write/read operation.

Abstract: The method prevents an optical disk from being scraped by an optical apparatus of a pickup head of an optical disc drive is disclosed, it mainly includes: moving the optical apparatus of the pickup head to a detection position in which the laser-light emitted from the pickup head focuses on the optical disk; detecting the first-detection position and setting a movement boundary according to the first-detection position, wherein the movement boundary has a upper boundary and a bottom boundary; preventing the optical apparatus from moving out of the movement boundary. The present method can be implemented without installing any additional apparatus in the original video disc player, and can prevent the optical disk and the inner apparatus of the optical disc drive from being scraped or damaged by the pickup head during a read/write process to increase the service life of the optical disk and the optical disc drive.

Abstract: An optical pickup inspection device 3 sends to an actuator drive circuit 16 a command for changing defocus offset amount to set defocus offset amounts, and calculates jitter values for each of the defocus offset amounts based on a reproduction signal from a reproduction signal generation circuit 14. Then, the device 3 determines a quadric approximating curve of jitter values relative to the defocus offset amounts and calculates a correlation coefficient R2 of the quadric approximating curve and measured values. If the correlation coefficient R2 is lower than a threshold value, the setting of defocus offset amounts and the calculation of jitter values are executed once again, otherwise, a defocus offset amount corresponding to a bottom value of jitter in the quadric approximating curve is determined as an optimum value of the defocus offset amount. Thus, a less-error, high-accuracy optimum value of the defocus offset amount can be obtained.

Abstract: The optical disk recording/reproduction device is provided with an information recording area search means, comprising, a moving means which detects the presence and absence of information and return moves an optical pickup from inward to outward or from outward to inward direction of an optical disk, and a stopping means which stops the movement of optical pickup if an information recording area is detected in the movement of optical pickup. If the existence of information cannot be confirmed at a re-zeroing position in the initial operation, the optical pickup is moved to the inward of optical disk at a normal velocity; when the optical pickup passes through the information recording area, it is braked and stopped. If the existence of information can be confirmed at the stop position, the flow is shifted to normal reproduction; if it cannot be confirmed, the optical pickup is determined to pass through the information recording area and stop, returned from the stop position and moved outward at a low speed.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: A rewritable optical disk apparatus, optical information recording and reproducing apparatus or the like is allowed to automatically and properly adjust the optical system to the optimum focal condition regardless of the readout signal detector's positional error and the residual aberration in the optical system. The spherical aberration and defocus are coarsely adjusted using the amplitude (PP amplitude) of the tracking error signal and then finely adjusted using the amplitude (RF amplitude) of the readout signal. Since the spherical aberration can properly be adjusted, it is possible to raise the reliability of the readout signal.

Abstract: Disclosed is a system for detecting a location of an optical pick-up head on an optical disk, and the optical disk comprises a plurality of sectors and the optical pick-up head emitting light to the optical disk and detected the reflected light from the optical disk. The system comprises: a signal generator, a counter, and a processing unit. The signal generator is coupled to the optical pick-up head for receiving a detecting signal from the optical pick-up head to generate a sector determined signal. The counter is coupled to the signal generator for receiving the sector determined signal and a period determined signal for counting a number according to the sector determined signal and the period determined signal; and a processing unit for receiving the number and calculating the location of the optical pick-up head accordingly.

Abstract: A recording/reproduction apparatus includes a first recording medium (a flash memory) having a first time that is required for the first recording medium to go from a low-power consumption state to a state in which recorded video data can be read out, and a second recording medium (an HDD or a DVD drive) having a second time that is required for the second recording medium to go from a low-power consumption state to a state in which recorded video data can be read out, where the second time is longer than the first time. When a video content is reproduced from the second recording medium in the low-power consumption state, the first recording medium is caused to go to a readable state while the second recording medium is not in a readable state, and a leading portion of the content is reproduced from the first recording medium.

Abstract: The present invention aims to obtain a position control device which, even if the range within which a mechanical part can be pulled in for position control is narrow, enables quickly stabilizing the pull-in operation.

Abstract: An optical pickup is provided for preventing an objective lens from colliding with an optical recording medium at the stage of initial adjustments. The optical pickup device comprises a servo circuit, and a lens driver for driving an objective lens. In the servo circuit, a drive signal generator supplies the lens driver with one of a first focus drive signal for moving the objective lens in a direction closer to an information recording layer, and a second focus drive signal for moving the objective lens in a direction away from the information recording layer. A controller in a timing generator switches a signal supplied to the lens driver from the first focus drive signal to the second focus drive signal when the level changes by a predetermined range or more in a servo signal which is generated during a period in which the first focus drive signal is being supplied to the lens driver.

Abstract: The invention relates to a method for determining write strategy parameter values for writing data on an optical disk from a group of optical disks of different types using an optical disk drive, in particular to different types of BD disks. The method includes identifying the type of optical disk, the type of optical disk being associated with a standard write strategy with standard write strategy parameters; determining a cluster write strategy with cluster write strategy parameters, the number of cluster write strategy parameters being smaller than the number of standard write strategy parameters; initializing the cluster write strategy parameters with initial cluster write strategy parameter values; and optimizing cluster write strategy parameter values for at least a subset of the cluster write strategy parameters. The optimizing is preferably performed on optimization sets of cluster write strategy parameters in a pre-determined optimization order.

Abstract: In an optical disk recording and reproducing device which uses an optical disk having at least a first recording layer and a second recording layer, a thickness of a spacer section between the first recording layer and the second recording layer is measured, an amount of defocus with respect to the second recording layer is set based on the measured spacer thickness, and a focus servo operation is performed for focusing the laser light irradiated from an optical pickup device on the second recording layer.

Abstract: A method of controlling a servo in an optical disc device and a servo control device using the method, in which the servo control device controls a servo for printing on a label surface of an optical disc and includes an optical pickup unit, an error signal generation unit, and a control unit. The optical pickup unit outputs a plurality of signals corresponding to a position of an object lens in response to light reflected from the label surface. The error signal generation unit outputs an error signal by selecting or combining one or more of the plurality of signals. The control unit adjusts the position of the object lens in response to the error signal. Therefore, because the position of the object lens can be adjusted with an increased range, the spot size of a beam condensed by the object lens can be adjusted within an increased range, and a data recording time can be reduced. Moreover, data retention characteristics and recording quality can be improved.

Abstract: In a optical head, a beam is emitted from a light emitting element in which a plurality of light sources are integrally formed, the light sources being able to emit beams having different wave lengths from one another. An optical system converges the beam coming from any one of the light sources onto an optical information storage medium. An optical separator separates a reflected beam coming from the optical information storage medium from the beam coming from the light source. A light receiving element detects light quantities of the reflected beam separated by the optical separator.

Abstract: An optical disk apparatus comprises a focusing means for focusing a light beam on a recording medium having first and second information faces; means for moving a focal point of the light beam in a direction substantially perpendicular to the information faces of the recording medium; means for detecting a reflected light from the recording medium; means for detecting a focus condition of the light beam on the basis on an output signal from the reflected light detecting means; a focus control means for driving the focal point moving means on the basis of an output signal from the focus condition detecting means, and controlling the light beam so that the focus condition of the light beam becomes a prescribed focus condition; and a focus jumping means for moving the focal point of the light beam from the first information face to the second information face by driving the focal point moving means.