Abstract: An optical disk apparatus has a first optical system having an objective lens with a first NA, a second optical system having an objective lens with a second NA lower than the first NA. The optical disk apparatus at the time of processing the optical disk, when the optical system suitable recording/reproduction process of the optical disk is the second optical system, via the first optical system detecting a surface run-out of the optical disk and execute the focus lead-in process of the second optical system on the basis of a surface run-out detected; and when at the time of processing the optical disk, when the optical system suitable recording/reproduction process of the optical disk is the first optical system, processing the optical disk with the first optical system without detecting the surface run-out of the optical disk.

Abstract: Disclosed are an optical information recording/reproducing apparatus and an optical information recording/reproducing method for simultaneously optimizing a distance between lenses constituting a two-objective lens and an offset in focus control. The apparatus includes a first electromagnetic actuator and a second electromagnetic actuator for cyclically moving a first lens and a second lens in the direction of the optical axis thereof; and a position control circuit for performing, upon focusing operation, the positional adjustment of the first lens and the second lens after start-up of focus control, on the basis of reproducing signals obtained from an optical disk at both ends of the cyclic movement of the first and second lenses by the first and second electromagnetic actuators.

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: A method and apparatus for detecting a signal to determine on-track/off-track and/or a track cross direction, using a detection signal corresponding to a reflected main light beam and detection signals respectively corresponding to reflected first and second sub light beams, and an optical recording and/or reproducing apparatus using the same are provided. When detection signals respectively corresponding to one side portions, in a direction corresponding to a radial direction of the optical information storage medium, of the respective main light beam and first and second sub light beams are referred to as a first main signal, a first sub signal, and a second sub signal, respectively, the method and apparatus include obtaining a first operational signal, which is used to determine on-track/off-track and/or a track cross direction, by performing a subtraction on the combination of the first and second sub signals, and the first main signal.

Abstract: A method of disc protection during servo focusing is disclosed. First, the disc device performs a servo focusing on a disc at a first speed, and records the first focusing time accordingly. Afterward, the disc device calculates a second focusing time required for another servo focusing if the disc requires re-focusing, and re-focuses the disc if the second focusing time exceeds the first focusing time.

Abstract: A method for adjusting a focus bias in an optical disc drive comprises the steps of: rotationally driving an optical disc in a state that only focus servo is engaged without engaging tracking servo; driving an actuator of an optical pick-up so that a laser beam projected from the optical pick-up is moved in a tracking direction to obtain an HF signal; and determining a focus bias by which a proper focusing point can be obtained based on the HF signal. The driving of the actuator is carried out by supplying an actuator drive control signal to a tracking actuator of the optical pick-up in a state that tracking servo is not engaged.

Abstract: An optical disk drive capable of detecting a surface deviation of a disk during a very short period includes an analog-to-digital converter (ADC) converting a focus error signal output from a pickup into digital data, and a central processing unit (CPU) writing an output of the ADC to a memory during one rotation of a motor according to a timing of a pulse signal output from a spindle motor. After that, the CPU reads data written to the memory and obtains a sine curve that minimizes the sum of squares of errors among data by a least square method. The CPU obtains a peak-to-peak value of the obtained sine curve and compares the peak-to-peak value to a predetermined threshold value, thereby determining the existence of the surface deviation of the disk.

Abstract: A determination of a focus sum threshold in a tracking and focus servo system of an optical disk drive is presented. The focus sum threshold can be determined by moving an optical pick-up unit sinusoidally through a focus position, for example by moving the optical pick-up unit between its closest position to an optical media and its farthest position from the optical media. While moving the optical pick-up unit, a sum signal is monitored. In some embodiments, the sum signal is the sum of signals from a plurality of detectors in the optical pick-up unit. The focus sum threshold is set to a fraction of a peak value of the sum signal.

Abstract: An optical head includes an integrated unit (9) having a light-receiving portion for converting reflected light from a disc-shape recording medium (13) into an electric signal and a light source, an objective lens (11), a tracking coil (18a) for driving the objective lens (11) in a radial direction of the disc-shape recording medium (13), a focusing coil (18b) for driving the objective lens (11) in a focus direction of the disc-shape recording medium (13), a signal generation portion (102) for generating a focus error signal and a tracking error signal from the electric signal converted at the light-receiving portion, and a control portion (101) for controlling the tracking coil (18a) and the focusing coil (18b) on the basis of the focus error signal and the tracking error signal.

Abstract: The invention relates to an optical scanning device (17) for scanning an information track which is present on an information carrier (9). The scanning device comprises a radiation source (31), a lens system (43) with an optical axis (45) for focusing a radiation beam (47) supplied by the radiation source into a scanning spot (55) on the information carrier, and a focusing actuator (65) for displacing the lens system relatively to a basic part (29) of the scanning device in a direction parallel to the optical axis. The actuator comprises an electric coil (69) which is arranged around the lens system and provided with a passage (95) for a radiation beam path (49) which extends in a direction perpendicular to the optical axis.

Abstract: Two light sources radiating two light beams having different wavelengths are simultaneously operated. Reflected beams of these two types of laser beams from an optical recording medium are simultaneously detected by two detectors. When one of the two types of light beams having different wavelengths is used while being focused on an optical recording medium, the spot diameter of the other non-focused metering beam on the optical recording medium is set larger than that of the one of the two light beams. A reflected light having a larger spot diameter is used to reduce DC offset in a tracking error signal.

Abstract: An optical recording medium used as a recording medium for information signals in which, in forming a groove along a recording track, a first groove and a second groove are formed to a first depth x to describe a double helix and a third groove having a second depth y shallower than the first depth x is formed between the first and second groves describing double helices. By setting the phase depths of these grooves to a pre-set range, signals required for tracking servo or seek are obtained to sufficient levels to realize stable tracking servo and seek.

Abstract: An error signal detection apparatus for an optical recording/reproducing system including a light source emitting a light beam and an objective lens focusing the light beam to form a light spot on a recording medium, the apparatus including: a photodetecting unit dividing at least a part of the light beam passed through the objective lens after being reflected/diffracted from an information stream of the recording medium into light beam portions, and detecting the light beam portions; and a signal processor detecting phase differences between detection signals from the light beam portions to detect a tangential error signal, a defocus error signal, and/or a radial tilt error signal.

Abstract: A tracking control system for outputting a tracking control signal for an optical pickup including a plurality of light detecting sections each of which converts reflected light of a light beam applied to an optical disk into an electric signal, and outputs the signal, includes: a balance correction amount calculating section for obtaining, as a balance correction amount, a value by which a differential phase tracking error signal based on each output of the light detecting sections should be shifted in accordance with a direct-current component of a differential amplitude tracking error signal based on each output of the light detecting sections such that a direct-current component of the differential phase tracking error signal approaches a given reference potential; a balance changing section for shifting the differential phase tracking error signal in accordance with the balance correction amount; and a tracking control section for generating the tracking control signal in accordance with the differential

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 follow-up control system follows up a head of a storage device to a storage medium. A sine wave signal learning section (82) which learns sine wave signals according to follow-up error signals which are input to a feedback control system (80), and performs time lead compensation corresponding to a delay of the feedback system (80), is provided. Since the time lead compensation is used for the sine wave signal learning model which can learn at high-speed, frequency disturbance of high frequency, for which phase lag must be considered, can be a compensation target, and the present invention contributes to the improvement of follow-up accuracy of the storage device.

Abstract: An actuator control device is provided for performing some modifications such as making the output of a disturbance observer zero for quickly restoring the proper tracking control if the out-of-track state takes place and if the outside force exceeding the maximum force generated by an actuator is applied to the device itself. In the actuator control device, a disturbance observer estimates disturbance added to the actuator. The second control signal corresponding to the estimated disturbance is added to the first control signal. The added signal is made to be a third control signal. Further, the second control signal is stored in a storage unit. The stored value is further added to the third control signal as the fifth control signal. By performing some modifications such as making the second control signal zero according to the abnormal state, this arrangement makes it possible to quickly restore the proper tracking control even if the out-of-track state takes place.

Abstract: Herein disclosed is a optical disc driving apparatus for driving an optical disc having a central axis, comprising: a turntable having a central axis, said turntable being adapted to retain an optical disc under the condition that said central axis of said turntable is axially aligned with said central axis of said optical disc; an optical pickup unit movable toward and away from said central axis of said turntable, said optical pickup unit being adapted to write or retrieve information from said optical disc retained by said turntable; a stepping motor having a plurality of coils; a detecting unit for detecting an exterior vibration while being vibrated in response to said exterior vibration; a driver IC for controlling said stepping motor to have said stepping motor assume two different operation states consisting of a first operation state to drive said stepping motor to ensure that said optical pickup unit is moved toward and away from said central axis of said turntable, and a second operation state to d

Abstract: The present invention provides a method for controlling a focus speed of a pick-up head while performing a layer jump operation over a multi-layer optical disk in an optical information reproducing apparatus. The optical information reproducing apparatus includes the pick-up head, an actuator and a counter. The pick-up head has an objective lens positioned over a first focus of the multi-layer optical disk and in response to a signal reflected from the multi-layer optical disk, will generate a RF level signal and. The actuator is electronically connected to the pick-up head for driving the objective lens to perform the layer jump operation in response to a kick pulse signal. The counter generates a counter value in response to the kick pulse signal.

Abstract: A pickup inspecting apparatus inspecting performance of a pickup to be mounted on a disk drive and reading data from a disk includes a disk driving unit rotatably supporting a disk, and a plurality of pickup transferring units disposed around the disk driving unit and each holding the pickup and transferring the pickup to the disk driving unit so as to read data recorded on the disk, so that a plurality of pickups are inspected at once. An inspection efficiency of the pickup inspecting unit is improved.

Abstract: The present invention shortens a time to be elapsed from a recording interruption to a recording restart, thereby realizing a reliable recording restart. In one embodiment, an optical disk apparatus comprises an optical pickup and a processor, which includes a reproduction system circuit, a speed information detection circuit, and a position detection circuit. The reproduction system circuit is configured to generate a reproduction signal used in restarting recording of the optical disk after an interruption, based on the electrical signal from the optical pickup and setting values. The speed information detection circuit is configured to detect speed information before or after an interruption of a recording on the optical disk based on the electrical signal from the optical pickup. The position detection unit is configured to detect a recording restart position and a current position of the optical disk.

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 for calibrating a center error offset in an optical drive and a control system capable of calibrating the center error offset. The method includes the steps of: controlling a focusing coil to focus on a rotating disk; controlling a tracking coil with different tracking coil control values; measuring and storing the amplitude of a tracking error TE signal and a center level of the center error CE signal responding to each control value; and selecting a largest amplitude of the tracking error TE signal and setting the responding center level of the center error CE signal as an optimal center error offset. Because the calibrating method determines the optimal center error offset by outputting different tracking coil control signals, it considers not only the unbalance of the gains of photo detectors and the optical deviation due to the assembly misalignment, but also the offset in a power drive.

Abstract: A method of one embodiment of the invention is disclosed that determines optical disc vertical displacement information at a number of positions on an optical disc. The method interpolates optical disc vertical displacement information at a number of other positions on the optical disc from the vertical displacement information determined.

Abstract: An adaptive focusing apparatus and method thereof of an optical disc drive having a focus servo controller moves a pickup head to an optimal focus point. A disc driver rotates an optical disc and includes a reflected signal detector detecting a signal reflected from the optical disc by the pickup head and a signal processor preventing spikes between a surface of the optical disc and the pickup head in response to the reflected signal and generating a focus drive signal for the focus servo controller using an adaptive focus search algorithm. The algorithm includes a static part and a dynamic part to reduce a focus search time. Accordingly, damage to the optical disc due to spikes between the surface of the optical disc and the pickup head can be prevented and a focus search time can be reduced.

Abstract: Device and method for detecting a non-writable region of an optical recording medium, wherein a read channel 1 signal and a read channel 2 signal are sliced at respective slice levels to produce header mask signals, and a header region which is a non-writable region is determined for the header mask signal taking the slice levels and written/unwritten regions ion the disk, whereby permitting stabilization of servos because servo error signals, such as a tracking error signal, and a focus error signal can be held exactly at a header region even if the servos are not stable, that prevents deterioration of a data quality in writing and reading, and permitting to shift an optical pickup to a desired position and accurate measurement of an amount of eccentricity because there is no influence of the header in a track jump and a disk eccentricity measurement.

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: A focus control is performed on the basis of a focus error signal indicative of a deviation amount from a focus state in a recording layer of a laser beam emitted for reproducing information to an optical disk having a plurality of recording layers. Specifically, at the time of focus-jumping a laser beam from a recording layer to another recording layer, an acceleration pulse or a deceleration pulse as a brake signal for making a focus jump is applied to a focus drive signal for controlling driving of an optical pickup for emitting a laser beam. The timing of applying each of the brake signals is variably set on the basis of the level of a focus error signal of a recording layer as an object of the focus jump. As a result, the focus jump can be accurately made in accordance with variations in the level of the focus error signal caused by variations in transmittance of light according to materials of the recording layers.

Abstract: Of (A+B) signal and (C+D) signal for detecting a radial push-pull signal, the (A+B) signal is multiplied with a predetermined coefficient k. The predetermined coefficient k is changed appropriately depending on an error rate upon decoding a land pre-pit, a lens shift amount of an objective lens of an optical pickup, and the levels of a land pre-pit signal and a wobbling signal relative to the level of (A+B+C+D) signal. Consequently, the land pre-pit on an optical disc can be detected securely at a high precision at any time of recording time and reproduction time.

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: A disc apparatus according to one aspect of this invention includes a detection unit configured to detect a first tracking balance value by first adjustment in a tracking balance adjustment mode for controlling a light beam to trace along a track on a disc, and to detect a second tracking balance value by second adjustment different from the first adjustment, and an adjustment unit configured to adjust tracking balance on the basis of the first and second tracking balance values.

Abstract: A coma aberration correcting apparatus of an optical pickup includes an optical pickup main body having a photo diode, and an actuator mounted on an objective lens focusing a beam emitted from the photo diode onto a recording medium. The coma aberration correcting apparatus includes a main supporting unit, a holding unit, an optical system, a driving part, and a controller. The main supporting unit detachably supports the optical pickup main body. The holding unit holds and releases the actuator on the optical pickup main body supported by the main supporting unit. The optical system magnifies and photographs the beam emitted from the photo diode through the objective lens of the actuator held by the holding unit. The driving part adjusts a position of the actuator relative to the optical pickup main body. The controller controls the driving part to correct the coma aberration of the objective lens.

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 aberration correction apparatus includes a first aberration correction element having aberration correction portions, a second aberration correction element which causes the wave front of the transmitted light beam to have a blaze hologram shape, a discriminator which discriminates the aberration of the reflected light beam, a coarse phase adjuster which drives the second aberration correction element on the basis of the magnitude of the aberration of the reflected light beam, and a fine phase adjuster which corrects aberration remained after the aberration correction by the coarse phase adjuster.

Abstract: When reproducing a multilayer optical disk using a high-numerical-aperture objective, the period of time required before the disk is reproduced is reduced by discriminating recording layers. A spherical aberration signal is detected as a differential signal between focus position fluctuation signals respectively in a central section and in a peripheral section of a reproduced flux of light. A recording layer is discriminated using a quantity of correction of spherical aberration at a zero-crossing point of a level or a spherical aberration signal associated with the differential signal. After adding the spherical aberration for the correction of the discriminated layer, residual spherical aberration is corrected by feedback control using a residual spherical aberration signal.

Abstract: Four types of optical systems, a polarization optical system including an objective lens having a high numerical aperture, a polarization optical system including an objective lens having a low numerical aperture, a non-polarization optical system including an objective lens having a high numerical aperture and a non-polarization optical system including an objective lens having a low numerical aperture, are selectively used at the time of irradiating light from a semiconductor laser on a target disk for measurement, and the in-plane birefringence characteristic and perpendicular birefringence characteristic of the target disk are separately acquired based on the amounts of received light obtained by measuring reflected light from the target disk by a photosensor.

Abstract: A method for minimizing spherical aberration in an optical read/write drive caused by variances in lens thickness and laser wavelength. The method provides an economic solution that pairs objective lenses with laser diodes such that the spherical aberration caused by the objective lens is offset by the spherical aberration caused by the laser wavelength, thereby minimizing or completely canceling the overall spherical aberration.

Abstract: An optical information recording and reproducing apparatus capable of recording and reproducing information data accurately with respect to an optical recording medium. The optical information recording and reproducing apparatus includes an aberration correction part which corrects aberration of the optical system. The apparatus determines whether or not an aberration correction by the aberration correction part is completed based on the signal level read from the optical recording medium, while changing a spherical aberration correction amount of the aberration correction part. The apparatus commences a recording operation or a reproducing operation of the optical information recording and reproducing apparatus if it is determined that the aberration correction was completed.

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 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: A focus servo control is performed by changing a condition of a focus servo loop from an open condition to a close condition in correspondence with a level of a reflection light signal, which is obtained as a reflection light of a light beam reflected from an information record medium is detected by a light receiving element such as an optical pickup.

Abstract: A method and device of determining the slice level of a radio frequency ripple (RFRP) signal for performing a tracking operation in a tracking controller of an optical storage device. The optical storage device receives a tracking error (TE) signal, a radio frequency center (RFCT) signal, and the RFRP signal, and then outputs a TE_input signal related to the slice level. The method includes the following steps: a. obtaining a count value when the absolute value of the TE signal is smaller than a threshold value; otherwise, resetting the count value; b. executing step c when the count value is smaller than a predetermined count value; otherwise, outputting the TE signal as the TE_input signal; and c. outputting the TE signal as the TE_input signal when the RFRP signal is greater than the RFCT signal; otherwise outputting a peak value of the TE signal as the TE_input signal.

Abstract: A device for assembling and adjusting an optical unit of the present invention includes an adjusting device including a collimator lens, an object lens, a disk, and a signal sensing system. A light beam output from the optical unit is incident to the collimator lens. Parallel rays output from the collimator lens are incident to the object leans. Further, a spot converged by the object lens is incident to the disk. The signal sensing system receives a light beam reflected by the disk via the object lens to thereby determine a distance between the object lens and the disk and a positional relation between the spot on the disk and the groove of the disk. The device allows the position of a light emitting element to be accurately determined and therefore allows the angular deviation of the intensity distribution of the light emitting element from a designed value to be easily grasped.

Abstract: In order to generate a lens position signal (LCE), which describes the position of the optical axis of an objective lens (6) of an apparatus for reading from and/or writing to an optical recording medium (7) with regard to the optical axis of the remaining components (2, 3, 4, 5, 8, 9) contained in an optical scanner (21), the application of the DPP method is proposed in accordance with a first exemplary embodiment, wherein a primary-beam error signal (CPP) and a secondary-beam error signal (OPP) are obtained with the aid of the DPP method, wherein the desired lens position signal (LCE) is generated by addition of the primary-beam error signal (CPP) and the secondary-beam error signal (OPP).

Abstract: An optical data-processing apparatus is provided for writing data to a data storage disk or reading data from the disk. The data-processing apparatus includes first and second light splitters. The first splitter splits reflected light from the storage disk into two semicircular rays. The second splitter splits these two semicircular rays into non-biased light and biased light. The data-processing apparatus also includes an optical detector for receiving the non-biased light and the biased light, thereby producing a first signal corresponding to the non-biased light and a second signal corresponding to the biased light. Based on the first and the second signals, a focus error signal and a spherical aberration signal are produced.

Abstract: Two magnetically sensitive poles are disposed on one chip with theoretically required dimensional accuracy. Therefore, the two magnetically sensitive poles can be disposed on a motor with high positional accuracy. Moreover, the simultaneous formation of the two magnetically sensitive poles in the same chip enables accurate matching of sensitivities between both magnetically sensitive poles when a magnetically sensitive film is printed on the chip.

Abstract: A method and apparatus for control of a feed motor for an optical disk reproducing/recording device. If the center of an objective lens deviates from the optical axis beyond a predetermined level, a stepping motor driven by digital pulses moves the optical pickup so that the deviation decreases. Since the stepping motor is precisely controllable by the drive pulses, stable tracking capability is attainable even in the case where operating environment such as temperature changes. The method in accordance with the present invention comprises the steps of detecting the distance between the center of an objective lens and an optical axis, checking whether the detected distance exceeds a prescribed range, and changing the magnitude of each drive signal by a microstep depending upon the check result and applying the drive signals to a sled motor for moving an optical pickup containing the objective lens.

Abstract: A spherical aberration correcting apparatus is incorporated in an information recording system and gives the system a function of correcting spherical aberration in a real-time and effective manner under a recording operation of pieces of information. The spherical aberration correcting apparatus comprises a recording unit, reflected-light level detecting unit, correction amount deciding unit, and spherical aberration correcting unit. The recording unit records a piece of information through radiation of an optical beam onto an optical disk. The detecting unit detects a level of light formed of the optical beam reflected from the optical disk under a recording operation for the information, while the deciding unit decides a correction amount for spherical aberration on the basis of the level of the reflected-light. The correcting unit corrects the spherical aberration by using the correction amount.

Abstract: An apparatus for generating tracking error signals including: an optical detection unit having a plurality of divided light receiving elements to allow beams reflected from a recording surface of the optical disks to be incident; a comparator for outputting after comparing the signals from light receiving elements, which correspond to the set group of the optical detection unit, with the reference signals set for the each group; an error correction unit for correcting and outputting errors if there are any errors after mutual comparison with signals of the groups output from the comparator; a phase-difference detection unit for outputting the signals for each group that correspond to a phase-difference after mutual comparison of the signals of the groups output from the error correction unit; a subtractor for mutually subtracting the signals for each group from the phase-difference detection unit and outputting the tracking error signals.