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 controller includes a servo-controller for performing nonlinear and linear control of the read/write position according to an error signal to drive an actuator for driving the pickup; a switch for switching the servo-controller from open-mode to closed-mode according to the error signal; and an adjuster for adjusting the gains of the nonlinear and linear control so that the nonlinear control component is larger than the linear control component at the time of switching and the linear control component is larger than the nonlinear control component after the elapse of a predetermined time from the time of switching.

Abstract: A driving device for an optical storage medium, includes: an optical pickup for reading out information from an information track on the optical storage medium; a tracking error signal generator for generating a tracking error signal from the information read out by the optical pickup; a tracking controller for controlling the optical pickup to follow the information track on the optical storage medium based on the tracking error signal generated by the tracking error signal generator; a disturbance detector for detecting a magnitude of a disturbance of the tracking error signal caused by impediments existing on the optical storage medium; a correction signal generator for generating a correction signal corresponding to the magnitude of the disturbance of the tracking error signal detected by the disturbance detector; and a limiting unit for limiting an operation of the tracking controller in accordance with the correction signal generated by the correction signal generator.

Abstract: In an optical disc device that selectively implements a tracking servo and a spot position servo, a discontinuation cancellation unit is provided so that, when switching from the tracking servo to the spot position servo, and when switching in the opposite direction, the low-frequency component of the tracking drive signal and the low-frequency component of the spot position servo connect smoothly so that there is no step difference.

Abstract: An optical system including an objective lens applies five light beams (31 to 35) generated by an optical pickup to a plurality of adjacent tracks on a signal plane of a CD-ROM. Light beams reflected from the signal plane are detected with photodetectors (PD1, to PD6), and in accordance with the detection outputs of the photodetectors (PD1 to PD5), a record data read system reads at the same time data recorded on respective tracks applied with the light beams (31 to 35), and outputs to read data in the record order of CD-ROM by preventing the read data from being duplicated or omitted. Prior to reading record data, a system controller performs an offset bias adjustment of a focus servo system.

Abstract: A direction sensor in a tracking and focus servo system of an optical disk drive is presented. The direction sensor calculates a direction sum signal and a tracking error signal from side elements of detectors in an optical pick-up unit of the optical disk drive. A first direction can be indicates when the signs of a high-pass filtered sum signal and a high pass filtered tracking error signal are opposite and a second direction opposite the first direction if the signs are the same.

Abstract: A digital servo system for controlling tracking or focus in an optical disk driver is presented. A servo system according to the present invention includes an optical pick-up with detectors providing optical signals, an analog processor receiving the optical signals and providing a digital signal, and digital processors receiving the digital signal and providing a control signal that controls the position of the optical pick-up unit. The digital processor executes an algorithm that calculates an error signal, provides amplification and biasing to the error signal, provides filtering for the error signal, and computes the control signal. The error signal can be the focus error signal or the tracking error signal.

Abstract: An optical storage system includes a pickup head for picking up data from a storage medium. Firstly, the maxima of a tracking error signal and runout are obtained in a calibration procedure in a close loop formed by an optical pickup head, a pre-amplifier, a compensator, a band-pass filter and a maximum detector. A calibration factor is then defined and derived by using the obtained maxima and nominal factors of a power amplifier and the optical pickup head of the optical storage system. The path formed by the series-connected band-pass filter and maximum detector is then disabled, while the calculated calibration factor is then stored in the compensator. The optical storage system may operate in a close loop formed by the optical pick head, pre-amplifier, compensator, a power amplifier under a normal operation procedure so that the optical storage system may record or read data onto/from an optical disc under the compensation provided by the calibration factor.

Abstract: An unknown optical disc is identified as a CD when an all sum signal value AS-max by a photodetector on a signal surface of the unknown optical disc is larger than an all sum signal value AS-cdref for CD signal surface reference for identifying the CD and the hybrid SACD as a CD based on each CD signal surface thereof, and a focus search driving voltage Y corresponding to the signal surface of the unknown optical disc is lager than a voltage value acquired by a predetermined relational expression between a focus search driving voltage Q corresponding to a DVD signal surface of a reference DVD and a focus search driving voltage R corresponding to a CD signal surface of a reference CD.

Abstract: A method of controlling an optical drive to perform a braking process in a layer jump process. The optical drive has a vertically movable pickup head, a preamplifier, a controller, and a low pass filter. The controller receives a focus error signal produced by the preamplifier to produce a focus control signal, and sends the focus control signal to the low pass filter to produce a layer distance balancing signal, so that the pickup head is controlled by the layer distance balancing signal to perform the layer jump process. The method of the present invention comprises the steps of: performing the braking process in accordance with a braking signal and the layer distance balancing signal when the focus error signal reaches a braking start point; and performing a closed-loop focusing control process when the focus error signal reaches a closed-loop focusing control point.

Abstract: Audio data of 20 bits is separated into first data of upper 16 bits and second data of lower 4 bits. EFM modulation data is formed from the first data. A laser beam is on/off controlled in correspondence to the logic level of channel data obtained by NRZI modulating a serial data train. The first data, therefore, is recorded in a manner similar to the case of a compact disc. Each pit is controlled so as to have a displacement in the right/left direction for the track center in accordance with the second data and the deviated pit is formed. When data is recorded by the displacement of the pit, since a high frequency component of a tracking error signal changes upon reproduction, the second data can be extracted from the tracking error signal.

Abstract: An optical-disk recording method, recording apparatus and reproducing apparatus are provided which are capable of continuously recording/reproducing a hologram with ultra-high density. In the case of recording a hologram to a holographic recording area, a holographic recording spot HSP on one track of the holographic recording area and a holographic recording spot HSP on a track adjacent thereto are recorded in circumferentially different positions. At least one holographic recording spot HSP is formed on each track, making the process continuous. Recording is made such that, provided that the holographic recording spot HSP has a diameter D and a multiplex number of holographic recording spots HSP is m, a pitch P between adjacent holographic recording spots HSP is P=D/m. Consequently, it is possible to efficiently record a hologram with density to a holographic recording area of an optical disk recording medium, and to achieve the density increase of holographic recording capacity.

Abstract: When a setup is performed by reproducing conditions corresponding to the first kind of optical disk and a setup is subsequently performed by reproducing conditions corresponding to the second kind of optical disk, the reproducing conditions which succeed to at least a part of the reproducing conditions corresponding to the first kind of optical disk are used as reproducing conditions corresponding to the second kind of optical disk and the setup is performed. When the setup is completed, the reproducing conditions corresponding to the optical disk as a target of the setup are stored. When the same optical disk is set up again, the stored reproducing conditions are used.

Abstract: An optical drive tracking control method allowing an optical drive to select a first tracking error detecting method or a second tracking error detecting method to generate tracking error signals when reading a CD is provided. First of all, a CD is read and the first tracking error detecting method is used to generate a first tracking error signal. Next, determine if the first tracking error signal is correct or not: if yes, continue to use the first tracking error detecting method, otherwise, change to the second tracking error detecting method. Of which, the first tracking error detecting method can be the three-beam method or the differential push pull method (DPP method), while the second tracking error detecting method can be the differential phase detection method (DPD method).

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: In an optical disc apparatus for reading data from an optical disc, levels of photo-detecting signals outputted from a plurality of photo-detecting areas of a photo-detector are adjusted to be substantially even for canceling error components due to positioning error of the photo-detector on an optical pickup. Analogous signals outputted from the photo-detecting areas of the photo-detector are amplified by amplifiers and converted to digital signals by A/D converters. A processor takes the converted digital signals and adjusts gains of the amplifiers with using the digital signals.

Abstract: In an optical disk apparatus, a sensitivity adjusting circuit measures a time between a reflection on a surface and a reflection on a recoding layer of an optical disk when moving an objective lens. This time is considered to be in accordance with sensitivity of an actuator during layer jumping, and thereby the magnitudes of a kick pulse and a brake pulse to be applied to the coil of the actuator is increased or decreased in accordance with the time between the reflection on the surface and the reflection on the recording layer. Thereby, the sensitivity dispersion of the actuator of the optical pickup is adjusted.

Abstract: A disk drive comprises an actuator servo control system including at least one disk, an actuator structure comprising at least transducer head for writing and/or reading data from the disk and providing a transducer head position error signal (PES), and a servo compensator applying a servo control algorithm to the PES to produce a servo control signal. An adaptive elliptic notch filter controller is adapted to analyze the PES for a transducer head at a disk track radii, identify resonant disturbances present in the PES, select two adjacent resonant disturbances having first and second frequencies, ascertain coefficients of at least a fourth-order elliptic notch filter transfer function having first and second zero-notches with frequencies substantially at the first and second resonant frequencies, apply the at least fourth-order elliptic notch filter transfer function with the ascertained coefficients in the servo system to thereby substantially attenuate the selected adjacent resonant disturbances.

Abstract: An optical disk drive has a positioner for mounting an optical unit, such as an objective lens and a tracking error signal detector, and a motor for moving the positioner. The positioner is moved in the radial direction of the disk by the motor through gear train. The motor is driven by a signal that includes a compensating current, and this signal controls the positioner to move in accordance with any eccentric displacement of a data track as caused by misalignments between the center of the data track and the axis of the optical disk rotation. The current is synthesized with an amplitude of the eccentricity, as detected by the tracking error signal, and a phase angle, as detected by both the error signal and an index signal indicative of a reference angular position of a spindle motor for the optical disk rotation.

Abstract: In track jumping operation, an acceleration/deceleration pulse generation portion measures the TE signal amplitude during track jumping, and modifies the acceleration/deceleration time of the acceleration/deceleration pulse according to the measured amplitude to drive a tracking actuator. Also, the acceleration/deceleration pulse generation portion measures the movement time from the start of acceleration until a certain location is reached, and modifies the peak value of the deceleration pulse according to the measured time to drive the tracking actuator.

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: The invention relates to caching data in a data processing system including a host computer and a storage subsystem including at least one customer disk and a cache disk. Write transactions are received specifying data to be written to at least one customer disk and these are cached in a volatile memory of the storage subsystem and written to the cache disk. The transaction data is written sequentially to the cache disk when available. In the intervening periods (i.e., when no transaction data is available), padding data is instead written sequentially to the cache disk.

Abstract: A disk apparatus 10 includes a DSP 36. The DSP 36 controls each circuit component under the instruction from an MCU 44. When a braking pulse is applied to a driver 38b at the end of a jump, a corresponding tracking actuator control voltage is supplied to a tracking actuator 16. Then a DSP core 36a determines whether the TE signal level becomes equal to or below the predetermined value within a predetermined period shorter than the zero crossing cycle of the TE signal. In case the TE signal level does not become equal to or below the predetermined value within the predetermined period, the DSP core 36a determines that the travel direction of an objective lens 14 with respect to a disk 22 is reversed and applies a correction pulse having a polarity opposite to that of the braking pulse thus accelerating the objective lens 14.

Abstract: A servo system with a multi-track seek algorithm with an accelerated servo function for regaining a closed tracking loop is presented. Upon completion of a multi-track seek operation, a gain of a tracking servo system is increased for a predetermined number of cycles. In some embodiments, the increased gain leads to a more aggressive track closing operation.

Abstract: A method of eliminating home-in noise of an optical disc drive without a home limit switch and using a variable step counter, includes: resetting the variable step counter, which counts steps of a stepping motor of an optical pickup, to zero regardless of a position of the optical pickup, when power is applied to the optical disc drive; driving a servomechanism at the position of the optical pickup and then reading a sub-code value of the optical disc to confirm a current position of the optical pickup; calculating a number of tracks from the current position of the optical pickup to a home position and converting the number of tracks into a step counter value to obtain a step counter value of the home position; and moving the optical pickup to the home position through an access operation. The step counter value of the home position is an integer varying depending on the position of the optical pickup when power is applied.

Abstract: The present invention discloses a startup procedure of optical drive after recording or erasing on an optical disc. After disc writing, startup procedure begins, a chipset reads the recorded data on the disc directly using the track information and focus servo parameter in the memory. Thus, the invention reduces time spent in the reading procedure.

Abstract: An optical recording/reproducing apparatus having drive means for rotating a recording medium, an optical head for applying light to the recording medium being rotated by the drive means, thereby to record data signals on the recording medium or reproducing data from the recording medium, and a signal-processing circuit for processing a signal detected by the optical head. The optical head comprises a light source for emitting light, an objective lens, and signal detecting means. The objective lens has a numerical aperture NA, where 0.5<NA≦0.6. The apparatus can reliably record data on and reproduce data from high-density optical recording media that have different track pitches.

Abstract: A light receiving unit 20A has a half mirror 20Aa and a photoreceptor device 20Af. A signal processing member 20B generates a focus error signal e from photoelectric conversion signals a, b, c and d which are outputted from the light receiving unit 20A, and further generates a focus error signal e1 from photoelectric conversion signals a1, b1, c1 and d1 which are outputted from a photoreceptor device 7 of an optical pickup P subject to adjustment. A control member 20C performs attitude control on an actuator 5A of an objective lens of the optical pickup P based on the focus error signal e, and creates data for adjusting the optical pickup P based on the focus error signal e1.

Abstract: In an optical information recording/reproducing apparatus, in which two sets of circuits (including a comparator 104 and a time counting device 105 (i.e., pulse width detector), and a comparator 110 and a time counting device 111 (i.e., pulse width detector)) are provided for detecting that the fluctuation larger than a comparison level continues in the TE signal for a time period, each being set at the respective comparison level and the time duration, differently, thereby the operation of write or erase onto an optical disc 101 is stopped even if only one of them is detected. Also, a position or location information in the PID portion to be reproduced, being outputted from a PID register 107, and a location information which is read out by the PID decoder 106 are compared by a comparator 108, thereby stopping the operation of write or erase onto the optical disc 101 if they are inconsistent with.

Abstract: A wobble detecting apparatus for an information recording and/or reproducing for an optical disk, includes a wobble detecting unit for detecting a wobble on the basis of a signal from a light receiving element which receives light reflected from the optical disk; an offset voltage generating unit for generating an offset voltage; an adder unit for adding said offset voltage to a control signal to an actuator for the optical disk; an actuator switch for on/off controlling a control signal to said actuator; and a control unit for turning on said actuator for wobble detection to decide whether or not the wobble has been detected by said wobble detecting unit, and if the wobble has not been detected, causing said offset voltage generating unit to generate a positive or negative prescribed voltage to decide further whether or not the wobble has been detected by said wobble detecting unit. In this configuration, the wobble can be detected with high accuracy.

Abstract: A recording information reproducing apparatus is disclosed for performing a searching operation. The recording information reproducing apparatus according to the invention is for reproducing recording information from a recording disc on which information data has been divided and recorded into a plurality of concentric zones. The apparatus selects a suitable one of a tracking servo by a sampled servo system and a tracking servo by a continuous servo system in accordance with a zone for reading information data.

Abstract: A track-jump controlling apparatus that controls track-jump operations over disks complying with various DVD data formats includes a quad photodetector having quadrants B1 to B4, a DPDTE signal generator 13 for generating DPD tracking error signals, a push-pull signal generator 14 for generating push-pull signals, and a TZC signal generator 15 having a selector switch 15a for switching the path between the DPDTE signals and the push-pull signals and a comparator 15b for generating TZC signals. In order to prevent failure to obtain proper TZC signals in a seek operation with respect to a DVD-RW, etc. involving passage over an unrecorded area during reproduction, for example, the selector switch 15a is switched to the push-pull signal side to prevent track counting failure associated with the track-jump operation with respect to the DVD-RW.

Abstract: Prior to actual reproduction of an optical disk, test reproduction is performed with respect to a plurality of testing radial locations of the optical disk. In the test reproduction, waveform-equalization-characteristic parameters of the waveform equalization section are adjusted to optimal settings so as to optimize jitter of a reproduced RF signal detected at each of the testing radial locations of the optical disk. In the actual reproduction of the optical disk, the waveform-equalization-characteristic parameters of the waveform equalization section are adjusted to optimal settings that are predicted, from the optimal settings determined by the test reproduction, in accordance with a radial position or address, on the optical disk, of each location to be reproduced.

Abstract: An optical disc drive includes: a light source; a focusing section; a focus shifting section for shifting the focal point of light by changing the position of the focusing section perpendicularly to a data storage layer of a given optical disc in accordance with a control signal; a light receiving section for receiving, at multiple areas, the light reflected from the data storage layer and generating light quantity signals; a signal generating section for generating a focus error signal based on the light quantity signals; and a control section for generating the control signal responsive to the focus error signal such that the focal point is transferred to a focus controllable range. The control section generates the control signal such that the focal point is decelerated at a first acceleration and then at a second acceleration. The absolute value of the second acceleration is smaller than that of the first acceleration.

Abstract: A recording and reproduction apparatus, for irradiating a recording medium having a track with an optical beam to record information on and reproduce information from the recording medium, includes a tracking error detection section for detecting a positional offset between the optical beam and the track and outputting a tracking error signal corresponding to the positional offset; an amplification section for amplifying, based on a prescribed value of a gain, the tracking error signal to be output, wherein the prescribed value of the gain is adjustable; a tracking control section for controlling a position of the optical beam based on the tracking error signal amplified by the amplification section; and a control section for adjusting the prescribed value of the gain of the amplification section. The control section adjusts the prescribed value of the gain of the amplification section based on a linear velocity of the recording medium.

Abstract: A fuzzy-neuro method uses a neuro network to discriminate optical disk type. The fuzzy-neuro method establishes a plurality of characteristic signal sets corresponding to the optical disks of various formats; and uses the neuro network to match the optical disk under question to the characteristic signal sets for finding the type thereof.

Abstract: In advance of the playback of an optical disk 11, the peaks of a focus error signal are detected, and the reference values of the focus error signal are set on the basis of the values of the peaks. In executing a layer jump, a kick signal for an object lens 13a is stopped from being outputted when the focus error signal exceeds the reference value of one polarity. A brake signal is outputted when the focus error signal exceeds the reference value in the opposite polarity. A time period for which the brake signal is outputted, is set on the basis of a time period for which the kick signal has been outputted. After the stop of the output of the brake signal, the peak of the focus error signal is waited for, whereupon a focusing servo 21 is turned ON.

Abstract: An apparatus and method conducts a high-speed search on an optical medium having a plurality of tracks on which information is recorded. At least a first light spot and a second light spot are directed by the apparatus onto the optical medium. The light spots traverse across the tracks in one of a first direction and a second direction. A photodetector unit receives a reflected component of the first light spot to form a first electrical signal and a reflected component of the second light spot to form a second electrical signal. Digital shaping circuitry respectively converts the first electrical signal and the second electrical signal into a first digital signal and a second digital signal. A quadrature detector is configured to receive the first digital signal and the second digital signal. The first digital signal and the second digital signal are arranged in a quadrature relationship to each other.

Abstract: A tracking error detecting apparatus converts photoelectric current obtained by a photo detector into voltage signals at current/voltage conversion circuits, and adds the voltage signals to generate two signal series at adders. The two signal series are digitalized at analog to digital converters, are subjected to interpolation processing at interpolation filters and have their zero cross points detected by zero cross point detector circuits respectively. A phase difference between the zero cross points of the two signal series is detected by a phase difference detector circuit, and the phase difference is subjected to band restriction by a low pass filter, thereby to obtain a tracking error signal. The tracking error detecting apparatus is capable of coping with speed doubling of an optical recording/reproducing apparatus and density enhancing of an optical recording medium with a small size and at low cost.

Abstract: A bottom hold circuit generates a bottom hold signal (BH signal) from an RFDC signal from an RF amplifier, and sends it to a comparator. The comparator compares a reference level and the BH signal, and generates an Rfdet signal having H level if the BH signal was found to be lower than the reference level. The Rfdet signal is a signal having H level when a laser spot falls in a data-recorded area on an optical disk, and having L level when in a non-recorded area. When it was detected that Rfdet signal had H level throughout a single turn of the disk, a servo-processing microcomputer controls an optical pickup so as to apply tracking servo. This makes it possible to precisely detect a boundary position between the data-recorded area and non-recorded area. If the optical disk is decentered, the boundary area corresponded to the amount of decentering can successfully be isolated from the data-recorded area.

Abstract: A method and apparatus preventing a disc from being scratched by an objective lens. A focus pull-in operation is performed. If a level of a pull-in signal remains lower than a predetermined critical level for a predetermined critical period of time or more, the objective lens is controlled so as to move away from the disc.

Abstract: Provided are a focus search apparatus and method for performing a focus search after moving an optical pickup to a focus-on point according to a signal output from a sine wave generator so that a stable and smooth focus search is performed. In the focus search method, a sine wave is generated in response to a focus search command. The focus search is performed using an optical pickup in response to the sine wave. The optical pickup is driven in response to an amplitude of the sine wave during the focus search and in response to a filtered focus error signal during a focus servo.

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: A method and apparatus identifying a type of a recordable disc according to whether a land pre-pit (LPP) is formed on the disc. The apparatus includes an RF (radio frequency) amplifier amplifying light reflected by the disc to a predetermined value; an LPP signal detector detecting an LPP (Land Pre-Pit) signal from output signals of the RF amplifier; and a system controller identifying a type of the disc according to whether the LPP signal is detected by the LPP signal detector. Since a disc type is discriminated and operational conditions of a disc drive are adequately set during an early stage of a disc driving period, a lead-in time of a disc can be reduced.

Abstract: An optical information recording and reproducing apparatus for recording and reproducing an information signal on/from both concave portions and convex portions of guide grooves formed on a recording medium is disclosed.

Abstract: The present invention provides an optical disc apparatus which solves a problem that the tracking control takes off when an objective lens is displaced in the tracking direction due to its weight. In this optical disc apparatus, a spot position detector 108 generates a spot position signal which indicates a position of a light spot on a light receiving element 105, and supplies the signal to a traverse loop filter 111 and a spot position loop filter 109. A controller 115 supplies an output from the spot position loop filter 109 to a tracking actuator 104, before supplying an output from the traverse loop filter 111 to a traverse motor 113, previously moves the light spot near the center of the light receiving element 105, and starts the traverse control in a state where a value of the spot position signal at starting of the traverse control is reduced.

Abstract: Disclosed herein is an optical pickup unit and information recording and reproducing apparatus. The present invention provides an optical pickup unit which can store and maintain the characteristics of the optical pickup unit itself, and further provides an information recording and reproducing apparatus, which enables mass production without increasing costs even though optical pickup units having different characteristics are assembled, and enables maintenance to be easily performed without increasing costs. The optical pickup unit (10) of the present invention has an LD (11), an object lens (13) for focusing light emitted from the LD (11) on a disk, actuators (15 and 16) for driving the object lens (13) to vary the position of the object lens (13) relative to the disk, and a PD (14) for detecting light reflected from the disk. In addition, the optical pickup unit (10) has an EEPROM (18) for storing optical pickup information of the optical pickup unit (10) therein.

Abstract: In an optical disk device in which the focus offset for writing of data can be optimized, a mark is written onto an optical disk at a predetermined focus offset and a change in the signal quality is detected by replaying the mark at various focus offsets. The predetermined focus offset is adjusted based on the change in the signal quality so that the focus offset is set at an optimal value. When an error rate is employed to represent the change in the signal quality, a range of focus offset in which the error rate does not exceed a predetermined value is found. By adjusting the predetermined focus offset for the reference optical disk based on the detected range of focus offset, an optimal focus offset is set.

Abstract: The present invention provides a method for calibrating focus positions of a pickup head. The pickup head is in a focus position of a predetermined distance from an optical recording medium for producing a recording light beam of a predetermined power for recording corresponding data onto the optical recording medium. A predetermined position adjustment procedure is performed to adjust the focus position of the pickup head during data recording. The procedure comprises the steps of sensing a reflected light beam from the optical recording medium by means of a sensor to generate a corresponding write RF signal; searching an extreme value of the write RF signal and obtain a target focus position corresponding to the searched extreme value; and adjusting the pickup head to the target focus position, so as to enable further data recording onto the optical recording medium by the pickup head in the target focus position.

Abstract: A laser diode applies a laser beam through a grating, a beam splitter, and an objective to a compact disc. A laser beam reflected by the compact disc is applied through the objective and the beam splitter to a photodiode. The objective has a large numerical aperture of 0.6 in order to be able of play back a digital video disc that has a thin substrate and contains information recorded at a high density. To prevent the photodiode from suffering aberrations caused due to the large numerical aperture of the objective, the photodiode has a relatively small photodetector unit having a normalized detector size ranging from 3 &mgr;m to 16 &mgr;m, for detecting only returning light up to a numerical aperture of 0.3 and not detecting light of greater numerical aperture values.