Abstract: A track error detection device that removes a phase offset and a phase offset removing method thereof removes an error signal generated by device circuit errors. The device includes an equalizing unit for equalizing the inputted signals A, B, C and D at a level, a comparison unit for quantizing the equalized signals A, B, C and D, and a phase shifting unit for removing phase offsets among the quantized signals A, B, C and D, based on control signals. A system control unit provides the control signals to the phase shifting unit. The track error detection device can remove all types of phase offsets which occur in the track error detection device. The accuracy and reliability of the detected track error signal is thus improved. By adjusting the phases of the quantized signals in the process of removing the phase offsets, power consumption and size of hardware is reduced.

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: An optical disc drive includes an optical head, a read signal processor, and a controller. The optical head outputs a first read signal representing light reflected from an optical disc and detected at a photodetector. The read signal processor receives the first read signal and outputs the second read signal responsive to a first or second control signal. The second read signal has a predetermined level when output responsive to the first control signal but a level corresponding to that of the first read signal when output responsive to the second control signal. The controller outputs the first and second control signals during first and second periods, respectively. The first period begins before marks are formed on the disc and ends while the marks are formed, and the second period follows the first period. The optical disc drive controls the data write operation in accordance with the second read signal.

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 method for generating a center error signal in an optical storage system, as well as an optical storage system, is disclosed. Through the use of the method and system in accordance with the present invention, a decrease in manufacturing costs is achieved since very precise and expensive mirrors and/or photo detectors are not needed. A first embodiment of the invention includes a method for generating a center error signal in an optical storage system, the optical storage system comprising a tracking coil and an optical pick up unit, the optical pick up unit including a light beam. The method comprises the steps of sensing a voltage by a tracking coil, providing the voltage to a center error generation circuit, generating a center error signal from the center error generation circuit based on the voltage and utilizing the center error signal to center the light beam. A second embodiment of the invention includes an optical storage system.

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: An optical disc recording and reproducing apparatus is provided. The apparatus detects the level of a focus error signal output from an optical pickup and a peak of the focus error signal occurred before the focus is obtained while an objective lens of the optical pickup moves in the focusing direction, discriminates a type of the loaded optical disc based on a first reference level or a second reference level, and actuates a focus servo before the objective lens moving in the focusing direction reaches a focalized position. Thus, a read only disc or a recordable disc can be rapidly reproduced.

Abstract: An amplifier may include an output stage including first and second output transistors, and a biasing stage for generating first and second biasing voltages at control terminals of the first and second output transistors, respectively, based upon a supply voltage and an input signal of the amplifier. The amplifier may also include a clamping stage having first and second clamping transistors for clamping outputs of the first and second output transistors to upper and lower clamping voltages, respectively. Additionally, the amplifier may also advantageously include a saturation detector connected to the clamping stage for providing a saturation signal for at least one of (a) the output of the first output transistor being clamped to the upper clamping voltage, and (b) the output of the second output transistor being clamped to the lower clamping voltage.

Abstract: An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including at least one of a track having a mark or a space selectively arranged, and a track having a prescribed groove; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a division element for dividing the light reflected by the information memory medium and allowing the light to be received by the light detector; a switch element for receiving a first signal and a second signal, which are respectively obtained in accordance with the reflected light incident on a first prescribed area and a second prescribed area of the division element and outputting either one of the first signal or the second signal, the first and second prescribed areas being obtained by dividing the division e

Abstract: A focus offset setting portion gives a predetermined quantity of offset to a focus control quantity used to reduce a focus error signal to zero based on the focus error signal generated by a focus error generation portion, and outputs a result. An adaptive equalizer including an adaptive control portion and an FIR filter subjects a reproduction signal RF provided from an optical pickup to waveform equalization based on a signal decoded by a Viterbi decoder. A controller obtains an optimum point of a focus offset by using a tap coefficient of the adaptive equalizer, and changes a set value of a focus offset setting portion.

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: An apparatus for controlling a monitor photo diode (PD) of an optical pickup system monitors an optical power signal output for writing data on or reading data from a disk. The apparatus includes a comparator which compares a voltage signal corresponding to the optical power signal output from the LD with a predetermined reference voltage signal, and a gain selector which selectively issues a gain output from the comparator depending on the type of the optical power signal output from the LD.

Abstract: An optical disc drive includes an optical system, a photodetector, a filter, a phase difference detecting section, a signal generating section, and a control section. The optical system focuses a light beam on an optical disc loaded. The photodetector includes areas to receive the light beam reflected from the disc and generates read signals representing quantities of light received. The filter receives the read signals and outputs processed signals with a frequency component of the read signals attenuated according to mark lengths. The phase difference detecting section detects a phase difference between the processed signals. The signal generating section generates a tracking error signal, representing a positional relationship between the focal point and a target track, based on the phase difference. The control section generates a control signal based on the tracking error signal such that the focal point is controlled across the tracks on the disc.

Abstract: An information reproducing method for reproducing information recorded on a medium by irradiating a laser beam and detecting a reflected light beam from the medium. The method includes detecting a plurality of reflected light beams in which the polarities of variations in reflected light beam intensity distributions are substantially inverted to each other, the distribution variation being produced when a light spot of the laser beam crosses a track on the medium, generating components of a focus error signal and components of a tracking error signal, adding the components of the focus error signal of the plurality of reflected light beams to generate a focus error signal, and taking a difference between the components of the tracking error signal of the plurality of reflected light beams to generate a tracking error signal.

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: An apparatus and method of controlling tracking in a disc drive using a tracking actuator, a feed motor, and an objective lens, including monitoring whether the tracking actuator deviates from a dynamic range based on a signal controlling the feed motor when tracking is performed; and returning the objective lens connected to the tracking actuator to a neutral point when it is determined that the tracking actuator deviates from the dynamic range.

Abstract: An optical disc player, which compensates for an eccentricity, is provided including: a spindle controller, a pickup, an RM amplifier, a focusing servo, a tracking servo and an eccentricity compensator. The spindle controller rotates an optical disc. The pickup has a focusing actuator and a tracking actuator and reads information on the optical disc. The RF amplifier detects and amplifies a focusing error signal and a tracking error signal from information on the optical disc obtained from the pickup. The focusing servo controls the focusing actuator in response to the amplified focusing error signal. The tracking servo outputs a tracking control signal in response to the amplified tracking error signal. The eccentricity compensator outputs a signal which compensates for the eccentricity of an optical disc in response to the output signal of the spindle controller, the amplified tracking error signal and the amplified tracking control signal.

Abstract: In an optical disk drive having the structure of rotating an optical disk under the alternative control of CAV or CLV, when the optical disk is rotated under the CLV control, the loop gains for at least one of the focus servo system and the tracking servo system for controlling the operation of the pickup of the optical disk drive are adjusted based on angular velocity detected by an angular velocity detector which is also used for rotating the optical disk under the CAV control, and, when the optical disk is rotated under the CAV control, the loop gains for at least one of the focus servo system and the tracking servo system are adjusted based on linear velocity detected by a linear velocity detector which is also used for rotating the optical disk under CLV control. The above structure enables the effective saving of electricity and cost in the optical disk drive.

Abstract: A servo error detector usable in an optical disk system is provided. An envelope detecting unit (24) detects the top envelopes and bottom envelopes of RF signals SA−SH, and top envelope signals SAtop−SHtop and bottom envelope signals SAbtm−SHbtm that represent the top envelope waveforms and bottom envelope waveforms of RF signals output from an optical detector. An analog/digital conversion unit (26) converts analog top envelope signals SAtop−SHtop and bottom envelope signals SAbtm−SHbtm corresponding to all input RF signals SA−SH to digital top envelope signals QAtop−QHtop and bottom envelope signals QAbtm−QHbtm, respectively. A digital operation unit (28) performs digital operation treatment for digital top envelope signals QAtop−QHtop and bottom envelope signals QAbtm−QHbtm to generate various servo error signals.

Abstract: A focus controller for focusing a light beam and positioning the focused light beam onto a signal recording layer of a signal recording media is disclosed. The controller comprises a light beam focusing means having a numerical aperture of 0.6 or more; a focus controlling means for positioning the light beam focused by the light beam focusing means onto the signal recording layer of the recording media; and an offset adjusting means for adjusting an offset between the focused light beam positioned by the focus controlling means and the signal recording layer of the recording media.

Abstract: An optical disk apparatus includes: a light irradiator operable to converge a light beam and irradiate an information carrier with the converged light beam; a moving means operable to move the light beam in a direction traversing a track formed on a surface of the information carrier; and a tracking controller operable to control the moving means to scan the track with the light beam. The tracking controller includes a deviation detector operable to generate a detection signal, a tracking driving means operable to generate a driving signal, an integrator operable to integrate a magnitude of a signal corresponding to the driving signal over a predetermined time period and an abnormal state detector operable to detect an abnormal state of the moving means based on an output of the integrator.

Abstract: The present invention relates to a device and a method of temperature control for an optical storage and retrieving apparatus. When the internal temperature of the optical storage and retrieving apparatus reaches a predetermined temperature, the temperature control device is able to bid the optical storage and retrieving apparatus steadily retrieve data by lowering the rate of a carry device of the optical storage and retrieving apparatus, or by instructing a servo control device to lower the tracking loop gain, or by lowering the velocity and the braking slope of a data read/write device of the optical storage and retrieving apparatus.

Abstract: An apparatus for and a method of producing a push-pull tracking error signal in an optical disc system having four light-receiving sections A, B, C, and D arranged in a radial direction of the optical disc. Pairs of signals PA, PB, PC and PD, corresponding to light receiving sections A, B, C and D, respectively are differentially combined to provide differential signals. One differential signal is filtered, amplified and differentially combined with another differential signal to output a tracking error signal. Accordingly, distortion of the tracking error signal during jumping to a desired track and distortion of the tracking error signal due to a defect of the optical disc are prevented.

Abstract: A servo control apparatus of an optical pickup is provided for reading recorded information from a recording medium and generates a read signal. The apparatus includes an error signal extracting part for extracting an error signal which indicates a deviation amount of a reading position from a target reading position of the optical pickup; a drive part for driving the optical pickup to change the reading position; an equalizer for equalizing the error signal and supplying a drive signal which indicates a driving amount of the drive part; a detecting part for detecting a dropout portion in the read signal; an identifying part for identifying a form of the dropout portion detected in the detecting part; and a controller. The controller performs control to change a gain of the equalizer in accordance with the identified form of the dropout portion.

Abstract: An optical disk drive includes an optical pickup unit, a tracking coil motor and a sled motor that drive movement of the optical pickup unit, and a servo control system. The optical pickup generates a tracking error signal indicative of amount of shift of the optical pickup unit relative to a track position of an optical disk, and a central error signal indicative of amount of shift of the optical pickup unit relative to an optical path. The servo control system generates a tracking coil control signal based on the tracking error signal for controlling operation of the tracking coil motor to adjust the optical pickup unit relative to the track position of the optical disk, and generates a sled motor control signal based on the central error signal for controlling operation of the sled motor to adjust the optical pickup unit relative to the optical path.

Abstract: An optical information reproducing device enables enhancement of information reading accuracy by correcting spherical aberration even if the spherical aberration occurs due to a thickness error in the transparent substrate of an optical disk. The correction amount of the spherical aberration is always changed such that the tracking servo gain in the tracking servo becomes maximum.

Abstract: In a focus control of an optical disk with a fast reproduction velocity and a large face deflection, the present invention can effect a mistakeless and reliable focus pull-in method. The present invention comprises: means for applying a braking signal to a focus actuator before closing a focus control loop; means for detecting a reversal of a relative velocity between an objective lens performing a focus search operation and an optical disk which effects an up-and-down motion due to the face deflection; and means for detecting the relative velocity between the objective lens and the optical disk from a focus error signal which is detected in each layer of a multi-layer disk.

Abstract: Methods and systems for controlling a servo are provided. One method includes calculating at least a first switching time to change an amplitude of a command signal to a servo, providing a first amplitude to the servo for the first switching time, and switching the amplitude of the command signal to the servo from the first amplitude to a second amplitude at the first switching time. The second amplitude is the command signal amplitude.

Abstract: A digital servo controller generates a control signal from an analog observation signal using an output equation, state equation or a transfer function, and performs high precision servo-control with an inexpensive configuration. In a digital servo which executes an output equation yd[k]=C·x[k]+D·ud[k] and state equation x[k+1]=A·x[k]+B·ud[k]. The digital servo comprises a digital processor which outputs the second term D·ud[k] of the output equation by an analog circuit, and outputs the first term C·x[k] earlier for Ts/2. The digital servo also comprises a digital processor which executes the direct term of the output equation at period Ts/N (N is a 2 or higher natural number), which is 1/N of the basic operation period Ts, and updates the first term with the same delay time as the average delay time Ts/(2N) of the direct term.

Abstract: In an optical disk apparatus for focusing a light beam on a track of an optical disk by using a tracking control loop to perform at least one of recording and reproducing operations upon the optical disk, a loop level calculating unit calculates loop levels of the tracking control loop. A control unit calculates a loop gain of the tracking control loop in accordance with the loop levels of the tracking control loop and compensates for a radial tilt of the optical disk in accordance with the calculated loop gain of the tracking control loop.

Abstract: A DPD tracking error generating section generates a DPD tracking error signal from a plurality of sense signals supplied from an optical sensor. A PP tracking error generating section generates a PP tracking error signal from a plurality of sense signals supplied from the optical sensor. The amplitude of each of the DPD tracking error signal and PP tracking error signal is adjusted suitably under the control of a CPU. The suitably adjusted signals are added by an adder, thereby generating a tracking error signal.

Abstract: A servo adjustment apparatus for setting an adjustment value for servo control of at least one of optical recording of information on information recording surfaces and optical reproduction of information recorded on the information recording surfaces, is provided. A setting device sets an adjustment value corresponding to one of the information recording surfaces. Another setting device sets another adjustment value corresponding to another one of the surfaces other than the one of information recording surfaces. Then a calculation device calculates a relational value indicating a relationship between the adjustment value and another adjustment value. A storage device stores calculated relational value. A resetting device resets the adjustment value using another adjustment value set previously and the relational value when the adjustment value is reset, and resets another adjustment value using the adjustment value set previously and the relational value when another adjustment value is reset.

Abstract: An offset measuring method is for measuring an offset based on an optical beam reflected by an information medium, in a recording and reproduction apparatus including an optical pickup placed on transportation means so as to be driven along a radial direction of the information medium. The method includes the steps of directing an optical beam toward a first measuring position, thereby measuring a first offset amount based on the optical beam reflected at the first measuring position; moving the transportation means by a first distance in a first direction along the radial direction; driving the optical pickup by a second distance, which is equal to the first distance, in a second direction; and directing an optical beam toward a second measuring position, thereby measuring a second offset amount based on the optical beam reflected at the second measuring position.

Abstract: The present invention relates to method and apparatus for controlling the slide of an optical pickup installed in the optical disk device so that deviation of an optical lens from an optical axis may be corrected. The corrective action is taken when the deviation reaches or is beyond a predetermined range. The predetermined is narrower than the maximum movable range of the optical lens. Also the corrective action is accomplished by adjusting either the DC component or the overall bandwidth of the servo gain loop depending on whether the rotational rate of an optical disk is high or low. Such method prevents or minimizes object lens from over-shifting or freely oscillating.

Abstract: Servo error signal circuitry apparatus and methods are described. The difference between two bottom envelope signals SEbtm and SFbtm is calculated by a subtracter (40) to generate a difference signal (SEbtm−SFbtm). The difference signal (SEbtm−SFbtm) is input as an alignment signal (AL) to an equalizer (42) and as a basic tracking error signal to the positive input terminal of a second subtracter (52). On the other hand, the difference between two top envelope signals SEtop and SFtop is calculated by a third subtracter (48) to generate a difference signal (SEtop−SFtop). The signal K(SEtop−SFtop) obtained by multiplying a coefficient K with the difference signal using a coefficient multiplier (50) is input to the negative input terminal of the second subtracter (52). The difference signal {(SEbtm−SFbtm)−K(SEtop−SFtop)} output from the second subtracter (52) is used as an offset corrected tracking error signal.

Abstract: An optical pickup including a light detection element to divide light reflected from an optical recording medium into first through fourth light beam portions in a radial direction of the optical recording medium. From detection signals from the light detection element, a reproduction signal detection portion detects an information signal, and a tracking error signal detection portion detects a tracking error signal. The light source emits light that is focused as a single light spot on a main track of the optical recording medium. The tracking error signal detection portion gain controls and sums push-pull signals from the detection signals to detect, during a recording operation, a tracking error signal with reduced push-pull offset without erasing existing signals on adjacent tracks. The reproduction signal detection portion sums and gain controls the detection signals to detect an information signal containing reduced crosstalk from adjacent tracks.

Abstract: When a MD is inserted (step S1), AGC is executed for reading the TOC area of the MD 1, and thereafter the information stored in the TOC area of the MD are read to detect the kind and recording capacity, etc. of the MD (step S2, S3). Next, the data relative to the executing position of AGC corresponding to the kind of the detected MD is read out from the memory (step S4). Now, where the MD is of a pre-mastered type, according to the recording capacity, either the first executing position P1 or the second executing position P2 is read as occasion demands. On the other hand, where the MD is of the recordable type, two AGC executing positions of the first executing position R1 in a pit area and the second executing position R2 in a groove area are read out. At each of the executing positions thus read out, the AGC is executed (step S5).

Abstract: A servo-control apparatus is provided for use with an optical disc player for reading and/or recording information. The apparatus includes an adjustment section for performing coarse and fine adjustment of a servo loop gain in accordance with a storage medium loaded in the player; a memory for storing a gain adjustment value; a discriminator for determining, upon one of reading and recording information, that the storage medium has already been subjected to the coarse and fine adjustment; and a controller. The controller allows the adjustment section to perform the fine adjustment of the servo loop gain in accordance with the stored adjustment value when it is determined that the storage medium has already been subjected to the coarse and fine adjustment.

Abstract: An optical disk checkup/measuring apparatus capable of shortening measuring time and of being incorporated into a manufacturing line and has a simple structure includes rotation driving elements (2,3) for driving rotation of an optical disk to be measured (10), a light emitting portion LD for emitting a light beam LF onto the optical disk to be measured (10), an optically detecting portion (D1, D2) for receiving and detecting the light beam LR reflected from the optical disk to be measured (10) and an operation processing portion (4, 5) for processing a signal received and detected by the optically detecting portion (D1, D2) so as to form a specified signal. The light emitting portion is composed of a plurality of light emitting elements LD provided in a radial direction of the optical disk to be measured (10), and the light beams are emitted successively from the light emitting elements LD onto the optical disk to be measured (10).

Abstract: A vibration quantity measuring apparatus and method, and a loop design method in which a vibration quantity generated in a focus and tracking loop is accurately measured to optimally design a focus and tracking loop of an optical disc drive. The vibration quantity measuring apparatus includes an error gain adjusting unit which adjusts an amplitude of a focus and tracking error which occurs where a disc rotates, so as to maintain the amplitude of the focus and tracking error constant, a loop gain adjusting unit which compares a closed loop phase of a focus and tracking loop and a predetermined reference closed loop phase, and maintains a constant gain of the focus and tracking loop to compensate for a gain difference of an actuator, and a measuring unit which calculates and outputs a vibration quantity using an error adjusted by the error gain adjusting unit and the loop gain adjusting unit, and an output of a controller which controls a focus and tracking of the disc.

Abstract: An optical disc 1 has spiral grooves GR formed on a data recording surface thereof and in which information is written to, and read from, both a land between the grooves and the grooves as tracks. Each track has a plurality of address areas AR1 and user areas AR2 formed thereon, and each of the address areas AR1 has embossed pits for a groove header GRH and embossed pits for a land header LH. Each of the address areas AR1 has provided in a leading part thereof a header mark area HM formed from a mirror finished surface. That is, this optical disc is of an on-land/in-groove recording type. An offset taking place in a tracking error signal and focus error signal is removed to accurately control the tracking and focus of an optical head.

Abstract: An optical disk device capable of data recording. A tracking error signal is generated from return light from an optical disk, and the tracking error signal to which a tracking offset signal is further added is supplied to a tracking servo circuit. A tracking offset signal in accordance with the driving current when recording data is determined based on the relationship between the driving current of the laser diode and the optimum tracking offset. Tracking control is performed using a fixed tracking offset signal when reproducing data and using a tracking offset signal which is variable in accordance with the driving current when recording data.

Abstract: To increase the vibration resistance of an optical disk device with respect to vibrations in the focus direction. More specifically, an optical disk device is provided with a multiplication means for generating a focus vibration component FC from the focus error signal FE, a multiplication means for generating a tracking vibration component TC from the tracking error signal TE, an adder for adding the focus vibration components FC and TC, and a low-pass filter for extracting the vibration component VC from the added results. Thus, the vibration component VC is extracted considering not only vibrations in the tracking direction but also vibrations in the focus direction, so that vibrations acting on the device can be more accurately detected, and vibration resistance is increased.

Abstract: A control device for a focusing system of a compact disk (CD) reader is provided. The control device uses fuzzy logic incorporated to the audio data processing system of the CD reader which is adapted to detect and segregate a light beam reflected by the surface of the compact disk from an incident light beam to the surface. The fuzzy logic control device receives a focus error signal and a derivative of the focus error. It then calculates, using appropriate membership functions, output signals to provide to a focusing servo-system of the CD reader to adjust the distance of the focal plane from the light beam detecting circuitry.

Abstract: A servo control apparatus of an optical pickup in which an offset and a gain can be adjustable for each servo control apparatus, and influences caused by changes in environmental conditions and changes with time are reduced without a decrease in operational speed, and increase in size and an increase in cost is disclosed. The servo control apparatus includes a nonvolatile memory for storing compensatory values which correspond to differences of servo characteristics of each servo apparatus and which are measured with the assistance of external measurement instruments, and a compensation portion for compensating an optical pick-up servo signal according to the compensatory values stored in the nonvolatile memory.

Abstract: An optical disk device for writing data onto an optical disk having an undulating track comprises an optical pickup for illuminating laser light of a writing power and laser light of a replaying power onto an optical disk and for converting return light from the optical disk into an electrical signal, a filter for extracting a wobble component contained in the return light signal when the laser of a writing power is illuminated, a processor for detecting the direction of track deviation based on the phase of the wobble component, and an actuator for driving the optical pickup in the width direction of the track based on the direction of the track deviation in order to control the tracking. Because the phase of the wobble component differs for a case when a light spot is deviated radially inward and for a case when a light spot is deviated radially outward, the direction of the track deviation can be detected based on the phase of the wobble component and the tracking can be controlled during data writing.

Abstract: An apparatus for driving an optical pickup for a tracking servo control. The apparatus includes an emitting device disposed in the optical pickup for emitting a main beam to a first position on an information track of a recording medium and emitting at least two subsidiary beams to a second position and a third position on the information track of the recording medium, respectively. The positions of the main beam and the subsidiary beams are determined appropriately for a three beam method.

Abstract: Focusing method and exposure apparatus for focusing both a parallel light beam and a non-parallel light beam through a movable objective lens onto an object. A negative feedback loop is provided which has a detector for receiving a reflection light beam of the non-parallel light beam passed through the movable objective lens, reflected at the object and passed through the movable objective lens, for generating a detection signal corresponding to a focus deviation of the non-parallel light beam, and a driver for receiving the detection signal to control a position of the movable objective lens in accordance with the detection signal, so that the detection signal is decreased. The negative feedback loop further includes a correction signal generator for generating a correction signal and supplying it to the negative feedback loop as a disturbance of the loop so that the parallel light beam is focused onto the object.

Abstract: A tracking error balance adjustment circuit, and a current control circuit used for a variable gain RF amplifier automatically controlled to output a signal having a predetermined amplitude. The tracking error balance adjustment circuit comprises two separate gain adjusting circuits, each having variable attenuation circuit having first gm amplifier of variable gm type, a second gm amplifier of variable gm type connected to the variable attenuation circuit, and an output circuit connected to the second gm amplifier, comprising an operational amplifier circuit having feedback resistor, wherein the first and second gm amplifiers are differentially controlled commonly by a control current.

Abstract: A tracking control method carries out a tracking control based on a tracking error signal which indicates an error of a beam spot formed on a recording medium by a light beam from a light source with respect to a track. The tracking control method includes detecting a change in a light emission power of the light source, calculating a correction quantity which is used to correct a shift and/or fluctuation of the tracking error signal generated due to the change in the light emission power, and carrying out a correction by adding the correction quantity to the tracking error signal when the change in the light emission power is detected.