Abstract: Provided is an optical disc device including: an optical pickup which includes an objective lens and a receiver unit which receives light reflected off an optical disc; a signal processing unit which generates a main push-pull signal and sub push-pull signals from signals from the receiver unit, and obtains a signal obtained by subtracting the main push-pull signal from the sub push-pull signal multiplied K times, to generate a tracking-error signal; and a control unit which performs a midpoint servo process, an offset process of adding an offset value to a lens-error signal indicating displacement of the objective lens, a stabilization awaiting process of waiting for oscillation of the optical disc to stabilize, a measurement process of measuring the tracking-error signal, and a K value adjusting process of adjusting a value of K in response to a result of the measurement process.

Abstract: A focus servo system for an optical disk drive includes an optical pick-up unit comprising at least one photodetector. At least one analog to digital converter is configured to digitize signals received from the at least one photodetector. At least one processor is configured to execute a digital servo algorithm to process the versions of the digitized signals to calculate a focus error signal (FES) from the versions of the digitized signals and to indicate a focus open condition based on the FES and the versions of the digitized signals.

Abstract: An apparatus and a method for reducing an offset error in a position of an objective lens of an optical disk reader by using a single beam push-pull signal. The apparatus includes a radial actuator that is configured to control the position of the objective lens. A controller that receives a push-pull signal that corresponds to the offset error of the objective lens and estimates the offset based on the push-pull signal. A sine generator generates a sine wave based on the estimated offset and further generates a feedback signal based on the sine wave to drive the radial actuator to reduce the offset error in the position of the objective lens. The apparatus also includes a data detector that is utilized to change the tracking method of the optical disk reader to a differential phase detection method upon detecting data in a data spire of the optical disk.

Abstract: A servo processor for an optical disk drive is provided that includes: an analog-to-digital converter for converting versions of photodetector output signals into digital signals; and a digital signal processor configured to receive the digital signals, the digital signal processor being further configured to determine a focus error signal (FES) and a tracking error signal (TES) from the digital signals, the digital signal processor being further configured to process TES and FES through servo algorithms to produce tracking and focus control signals.

Abstract: Provided are an apparatus and method of generating a tracking error signal, and an optical information storage system including the apparatus. The apparatus includes a bias signal generator for generating a bias signal for canceling a direct current (DC) offset of a push-pull signal using a tracking control signal generated by the tracking controller. Accordingly, an offset generated in a tracking error signal may be canceled or otherwise reduced using the bias single instead of using an additional side beam.

Abstract: There is provided a position control apparatus including a light radiating/receiving unit that performs radiation of laser light for recording and laser light for adjacent track servo onto an optical disc recording medium through a common objective lens, and receives return light of the laser light for the adjacent track servo and the laser light for the reference surface, a tracking mechanism unit that displaces the objective lens, a reference surface tracking error signal generating unit that generates a reference surface tracking error signal, a reference surface tracking servo control unit that controls the tracking mechanism unit, a recording layer tracking error signal generating unit that generates a recording layer tracking error signal, an integrating unit that integrates the recording layer tracking error signal, an offset providing unit that provides an integration output by the integrating unit, and a feedforward control unit that generates a control signal.

Abstract: A method in a signal processor includes equalizing, with an equalizer of the signal processor, a signal corresponding to data read from a storage medium to generate an equalized signal, determining a signal level of the equalized signal, determining an expected signal level of the equalized signal, performing a comparison between the signal level of the equalized signal and the expected signal level, adjusting, after the equalized signal is output from the equalizer, an amplitude of the equalized signal by an amount determined based on the comparison of the signal level of the equalized signal and the expected signal level, and decoding the equalized signal after adjusting the amplitude of the equalized signal.

Abstract: The optical disc device has a circuit which forms a focus error signal for focus servo control based on reflection light from an optical disc exposed to laser light. Also, the device has a data processing unit which can control by feedback a position to which an objective lens is moved by a focusing actuator based on a focus error signal. In label printing, the data processing unit controls, by feedforward, a position to which the objective lens is moved by the focusing actuator based on control data for label printing. The operation resolution of the focusing actuator in feedforward control is made higher than that in feedback control. Thus, an intended position control accuracy is achieved in feedforward control. For instance, in feedforward control, the gain of the driver circuit for the focusing actuator is switched to a smaller one in comparison to that in feedback control.

Abstract: An optical disc driving device includes a control circuit 4 for performing a gain adjustment for each of two recording surfaces of a multilayered optical disc 1 on the basis of an FE signal in such a way as to maintain a state in which light is focused onto either of the recording surfaces, to generate a focus servo loop signal, and for generating a focus jump signal for causing either a transition from a state in which the light is focused onto one recording surface to a state in which the light is focused onto the other recording surface, or a transition in the opposite direction from a threshold set up on the basis of an amount of gain adjustment, and a focus actuator driving circuit 5 for performing either a focus jump or an operation of maintaining the state in which the light is focused.

Abstract: A focus servo system for an optical disk drive includes an optical pick-up unit comprising at least one photodetector. At least one analog to digital converter is configured to digitize signals received from the at least one photodetector. At least one processor is configured to execute a digital servo algorithm to process the versions of the digitized signals to calculate a focus error signal (FES) from the versions of the digitized signals and to indicate a focus open condition based on the FES and the versions of the digitized signals.

Abstract: Provided are an apparatus and method of generating a tracking error signal, and an optical information storage system including the apparatus. The apparatus includes a bias signal generator for generating a bias signal for canceling a direct current (DC) offset of a push-pull signal using a tracking control signal generated by the tracking controller. Accordingly, an offset generated in a tracking error signal may be canceled or otherwise reduced using the bias single instead of using an additional side beam.

Abstract: A signal corresponding to data read from an optical storage medium is equalized to generate an equalized signal. A signal level of the equalized signal is determined, and an expected signal level of the equalized signal without high frequency distortion is determined. A comparison between the signal level of the equalized signal and the expected signal level is performed, and an amplitude of the equalized signal is adjusted based on the comparison of the actual signal level of the equalized signal and the expected signal level. The equalized signal is decoded after adjusting the amplitude of the equalized signal.

Abstract: An average servo control method is provided. A target level of at least a servo signal is first detected, which is corresponding to a present condition of the optical disc drive. The target level is then compared with a current level of the servo signal, and a average servo loop gain is adjusted based on the comparison result. A target level calibration may be performed before the gain adjustment. The target level calibration analyzes the servo signal to determine a plurality of preset target levels each corresponding to a different condition. The preset target levels and corresponding conditions are stored as a lookup table. In this way, the target level is acquired based on the lookup table and the present condition.

Abstract: An optical read/write apparatus as an embodiment of the present invention includes: a light-splitting element configured to split a light beam emitted from a light source into multiple light beams including a write beam and a read beam; an optical system configured to converge the write and read beams onto the same track on an optical storage medium; a photodetector including a light receiving element configured to detect the read beam reflected from the optical storage medium and output an electrical signal; and a divider configured to generate a read signal by dividing the signal detected by the light receiving element by a signal that represents a write modulated component and that is obtained by detecting a part of the light beam emitted from the light source.

Abstract: Method and device for generating a control voltage for a position actuator of a disk drive system for displacing a lens of a pick-up unit to a given X-position. The actuator is operated by an open loop control system. First, parameters of the control system are calibrated so that the control system produces a control voltage (Va) from an input position signal (Xact_setp). Then, the control voltage is processed in a feed forward system for generating a processed control signal (Va_p) which is fed to the position actuator for displacing said lens to the X-position. A Z-value corresponding to the axial distance of the lens from a calibrated axial position and a temperature of the pick-up unit are measured. The position actuator operates according to the formula: Xdc=Va—p*K(Temp,Z)/(R(Temp)*C(Temp,Z)).

Abstract: A low-cost technique to improve the performance of optical disk drives is presented. An algorithm is used to decouple electro-mechanical actuators thus compensating for inaccuracies in the control of the actuators. A similar method can be used to decouple the position sensors. Prior art methods treated cross-coupling between focus, tracking and sled control loops as noise and therefore increased the bandwidth of the system, also increasing the cost of the optical disk drive. The present disclosure actively decouples the control loops using a software algorithm to provide better performing optical disk drives. The cross-coupling effects are measured, a decoupling matrix is determined, and the output of the control laws is modified so as to decouple the actuators.

Abstract: An optical disk reproducing device includes: a signal reproducing section configured to read and decode information recorded on an optical disk by an optical pickup unit, and reproduce the information, wherein the signal reproducing section includes a gain controlled amplifier circuit configured to amplify an radio frequency signal generated from a light receiving element, an automatic gain control circuit configured to control a gain of the gain controlled amplifier circuit, and a signal processing section configured to derive a part of an automatic gain control value generated in the automatic gain control circuit, and generate a control signal for adjusting one of an optical system path and a detection system path for controlling the optical pickup unit.

Abstract: An apparatus and a method for compensating periodic signal in an optical disc drive are described. The control apparatus includes an amplitude processing unit, a phase processing unit, a wave generator, a first switch module and a second switch module. The amplitude processing unit processes the amplitude of the input signal based on a reference signal for generating an amplitude signal. The phase processing unit processes the phase of the input signal based on the reference signal for generating a phase signal. The first switch module switches the amplitude signal to select one of the amplitude value and a predetermined amplitude value. The second switch module switches the phase signal to select one of the phase value and a predetermined phase value. The wave generator generates a compensated wave signal based on the selected amplitude value and the selected phase value, and outputs the compensated wave signal.

Abstract: A servo processor for an optical disk drive is provided that includes: an analog-to-digital converter for converting versions of photodetector output signals into digital signals; and a digital signal processor configured to receive the digital signals, the digital signal processor being further configured to determine a focus error signal (FES) and a tracking error signal (TES) from the digital signals, the digital signal processor being further configured to process TES and FES through servo algorithms to produce tracking and focus control signals.

Abstract: A recording apparatus including: a light-illuminating/receiving-unit illuminating an optical-disc-recording-medium through a common object-lens with recording-light and ATS-light and receiving reflected-ATS-light; a rotation-driving-unit driving rotation of the medium; a tracking-mechanism driving the lens in a tracking-direction parallel to the radial direction; a tracking-error-signal-generation-unit generating a tracking-error-signal; and a tracking-servo-controller performing tracking-servo-control on the lens based on the tracking-error-signal, wherein the tracking-servo-controller includes: a servo-calculation-unit based on the tracking-error-signal in a feedback-loop as a tracking-servo-loop; and a feed-forward-controller calculating an estimated control-target-value of the tracking-servo-control based on an estimated illumination-spot-position value of the ATS-light obtained in a first-filter-process emulating a transfer-characteristic of the tracking-mechanism on an output of the servo-calculation-un

Abstract: A data storage system for detecting a location of a head relative to a magnetic media is described. This system comprises arms, a preamplifier circuit coupled to the arms for controlling the arms, a proximity sensing system positioned within the preamplifier circuit, the proximity sensing system comprising: an input stage for transmitting an input sense signal; a programmable gain stage coupled to receive the input sense signal and operative for transmitting a gain signal in response to receiving the input sense signal; a multiplexer coupled to receive the gain signal and at least one control signal, the multiplexer operative for transmitting a multiplexed signal; a detector coupled to receive the multiplexed signal and a second control signal, the detector operative for transmitting an output signal; wherein an amplitude associated with the output signal enables detecting the location of the head.

Abstract: A method and apparatus to control a position in which data is to be recorded on a holographic data recording medium by using interference between a reference light and a signal light, the method including: irradiating the reference light and the signal light on the holographic data recording medium; generating a focus error signal that indicates a distance difference between a first focus corresponding to a focus of the reference light on the holographic data recording medium and a second focus corresponding to a focus of the signal light on the holographic data recording medium, based on information about a reflective signal light generated when the irradiated signal light is reflected from a reflective transmission layer of the holographic data recording medium; and moving the second focus to a position of the first focus, based on the focus error signal.

Abstract: An optical reading system is provided to improve read signal quality with increasing its linear recording density. An optical recording medium in which the distance from a light incident surface to an information recording layer is less than 100 ?m is irradiated with a laser beam through an objective lens and information stored in the information recording layer is read by means of a PRML detection method. At this time, the constraint length n in the PRML detection method is set to an integer which satisfies 0.5×(?/NA)/(LV/f)?1<n<0.5×(?/NA)/(LV/f)+1, wherein ? represents the wavelength of the laser beam, NA represents the numerical aperture of the objective lens, LV represents the linear velocity of the optical recording medium when recording, and f represents a channel bit frequency when recording.

Abstract: A focus jump technique enables focus control on recording layers of a disc in such a manner that its effect is not absorbed by disturbance or a variation in the movement speed of an objective lens. The technique involves monitoring level of a focus error signal and rejecting noise from the error signal. A speed sensor detects movement speed of an objective lens; and a speed control circuit generates a voltage for controlling the objective lens, based on the detected movement speed. Movement speed of the objective lens is detected during focus jump, a corresponding lens drive signal is generated, and an end position is determined from behavior of the error signal immediately before the end of the jump. A focus control is pulled, from a focus point corresponding to one recording layer, into a focus point corresponding to another recording layer forcibly in a stable manner.

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

Abstract: In a servo controller and an optical disk device (FIG. 4), the following performance for disturbance is improved. By disposing a characteristic change section to change a characteristic to improve the following performance for disturbance, the disturbance is detected by use of a signal in a stage after the characteristic change section.

Abstract: An optical disc apparatus controls a relative position of an optical pickup with respect to a surface of an optical disc medium according to an output signal output from the optical pickup according to information recorded on the optical disc medium to implement servo control for maintaining a state where the information is readable, acquires an evaluation value for information reading accuracy when the servo control is implemented, and calculates a set value of a parameter to be set for the implementation of the servo control based on evaluation values respectively acquired for at least three set values of the parameter while changing the set value of the parameter for the servo control. The optical disc apparatus determines the set value to be set for further acquiring the evaluation value according to the evaluation values acquired for at least two set values of the parameter.

Abstract: When a focus error signal (FE signal) is detected with an astigmatic method, a track crossing component leaks into the FE signal. Another detection method for the FE signal would reduce the leaking signal, but is not applicable when the light use efficiency decreases. An optical crosstalk correction amount determination unit (1000) determines a correction amount to correct an output of a tracking error detection unit (120) based on optical crosstalk from a TE signal to an FE signal occurring in reflection light from an optical disc (102) when a spot crosses a track. An output of the tracking error detection unit (120) is multiplied by the determined correction amount, and added to an output of the focus error detection unit (118). A focus control unit (138) executes focus control based on the addition result. This effectively reduces a TE signal component that leaks into the FE signal due to optical crosstalk.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a data processing circuit is discussed that includes a summation circuit, a data detector circuit, an error feedback circuit, and an error calculation circuit. The summation circuit subtracts a low frequency offset feedback from an input signal to yield a processing output. The data detector circuit applies a data detection algorithm to a derivative of the processing output and provides an ideal output. The error feedback circuit includes a conditional subtraction circuit that conditionally subtracts an interim low frequency offset correction signal from a delayed version of the derivative of the processing output to yield an interim factor. The error calculation circuit generates an interim low frequency offset correction signal based at least in part on the interim factor and a derivative of the ideal output.

Abstract: This optical disk device includes a pickup, an offsetting means, a focus servo means, a layer jump means, and a shift means. The pickup irradiates laser light upon an optical disk having a plurality of recording layers via a correction lens and an objective lens, and detects light reflected back from the optical disk. The offsetting means generates a focus error (FE) signal on the basis of the reflected light, and applies an offset voltage to the focus error signal. The focus servo means performs focusing servo on the basis of the FE signal. And, before layer jumping is executed by the layer jump means, the focus servo means displaces the correction lens to an intermediate position after having adjusted the offset voltage to a balance value. Then the layer jump means performs layer jumping.

Abstract: A method of operating a channel module, including: receiving a plurality of sensor signals generated based on at least one detected characteristic of a laser beam of an optical drive; performing computations based on the plurality of sensor signals; generating a computation output signal based on the computations; generating a first control signal and a second control signal; generating a first input signal based on (i) the computation output signal, (ii) the first control signal, and (iii) a first set of filter values; generating a second input signal based on (i) the second control signal, (ii) a second set of filter values, and (iii) an accumulated output signal; generating the accumulated output signal based on a sum of products generated based on the first input signal and the second input signal; and adjusting the at least one detected characteristic of the laser beam based on the accumulated output signal.

Abstract: A phase error detection apparatus capable of performing offset correction of a tracking error signal accurately even when there is a defect or a non-recorded position on an optical disc. There are provided a phase difference detection circuit (107) which receives two sequences of digital signals, performs phase comparison using a distance between zerocross points of the two sequences of digital signals, and outputs a phase comparison result PCR and a phase comparison completion signal PCC, and an offset control circuit (11) which outputs an offset correction amount for each phase comparison completion signal PCC from the phase difference detection circuit (107), and the offset correction amount ?? is added to the phase comparison result PCR to avoid offset correction in a position where phase comparison is not carried out.

Abstract: Disclosed herein is an optical disk playback apparatus including: a signal playback device configured to read and decode information recorded to an optical disk through an optical pickup unit in order to reproduce the information; the signal playback device including a signal generation circuit, a first signal processing device, a second signal processing device, a modulator, a switch, an analog to digital converter, and a third signal processing device.

Abstract: The invention provides a tracking control device, a tracking control method, and an optical disc apparatus that enable to stably perform the tracking control, and reduce an influence of stray light from the other layer on the tracking control. A sub push-pull signal correcting section corrects a sub push-pull signal to be generated from returning light of a sub beam in such a manner that a track crossing component of a main push-pull signal to be generated from returning light of a main beam, and a track crossing component of the sub push-pull signal to be generated from the returning light of the sub beam are canceled. A low pass filter reduces a high frequency component of the sub push-pull signal corrected by the sub push-pull signal correcting section. A subtractor subtracts a sub push-pull signal passing the low pass filter from the main push-pull signal to thereby generate a tracking error signal.

Abstract: An optical disc apparatus according to the present invention steadily performs a focus jump operation and a track-crossing seek operation relative to an optical disc having a plurality of recording layers. A signal processing section generates a focus error signal based on a conventional astigmatism detection (CAD) system and a focus error signal based on a differential astigmatism detection (DAD) system from a detection signal generated by an optical detector. When a focus jump is to be performed from one recording layer of the optical disc to another recording layer, a focus drive signal that is generated from the focus error signal based on the CAD system is used. When a read/write operation is to be performed in relation to one recording layer, a focus drive signal that is generated from the focus error signal based on the DAD system is used.

Abstract: A method is provided to start calibrating TE signals in an optical disk drive by checking the change of focus balance, outputting a first TE signal by adjust to a predetermined gain, measuring the peak and trough of the first TE signal, changing the laser power to output a second TE signal on condition of the same focus balance and predetermined, measuring the peak and trough of the second TE signal, calculating and adjusting to a calibrated gain to quickly calibrate the TE signal.

Abstract: In order to cancel an offset caused by a variation of a signal inputted from an optical pickup, variations of elements in an integrated circuit, etc., a calibration circuit which generates and feeds back an offset adjustment amount that makes the offset zero by a comparison with a reference value, and an offset adjustment circuit that makes the offset zero using the fed-back control signal are provided in an analog front-end LSI. The offset adjustment by the calibration circuit is automatically done in response to commands supplied from a digital signal processing LSI, a host control device, etc. On the other hand, as for a signal on which arithmetic processing such as gain control, addition and subtraction, is performed, the offset adjustment is performed by sending the offset adjustment amount obtained by an arithmetic operation performed by software processing of the digital signal processing LSI to the analog front-end.

Abstract: A comparator includes a variable-gain amplifier circuit configured to vary an amplitude of an input signal by changing a gain in accordance with a control signal, and a comparison section configured to compare a slice level interlocked with a signal level received from the variable-gain amplifier circuit with an output signal received from the variable-gain amplifier circuit and generate an output signal in accordance with a comparison result.

Abstract: The present invention provides a method for adaptively driving a tracking element with mechanical deviation and a driving device using the same. The method comprises the following steps: recording standard moving time and a standard motor current value, supplying driving voltage to a motor for driving a tracking element, detecting a current value of the motor and detecting moving time of the tracking element, and adjusting a driving gain of the motor based on the relation between the current value of the motor and the standard motor current value, and based on the relation between the moving time of the tracking element and the standard moving time of the standard one.

Abstract: An integrated circuit includes a focus control section configured to perform focus control to generate a drive signal for the focus direction displacement section based on a focus error signal, a focus control error determination section configured to determine whether there is a focus control error or not, and a memory section configured to store error-time control signals which are used when there is a focus control error and correspond to a plurality of rotation angles. The focus control section stops the focus control and generates the drive signal for the focus direction displacement section, according to a rotation angle, based on the error-time control signals stored in the memory section at a radial position where it is determined by the focus control error determination section that there is a focus control error.

Abstract: In servo control of actuators of an optical disc unit, a gain margin is secured by measuring a mean current or mean voltage applied to each of a focus actuator and a tracking actuator, estimating a displacement quantity of each of the actuators from the measurement values, changing the frequency characteristic or overall servo loop characteristic of a focus servo filter and a tracking servo filter respectively by switching ON/OFF a notch filter according to a displacement condition of the corresponding actuator, and switching control operation between stages of servo control characteristic of each of the focus servo filter and tracking servo filter. The optical disc unit can achieve a stable servo control of the actuators thereof without performing disturbance injection or taking measurement of the disturbance. Thus, the optical disc unit can ensure stable operations.

Abstract: A signal processing device for optical disks includes a reflected light process section configured to convert reflected light received by an optical pickup into an electric signal based on a first gain, wherein the optical pickup emits laser light to an optical disk and receives reflected light from the optical disk; a servo signal generation section configured to generate a servo signal by using the electric signal generated by the reflected light process section; a servo signal control section configured to control the servo signal so that a change in the amplitude of the servo signal, in response to an increase or decrease of the amount of the reflected light from the optical disk, is suppressed using an attenuator that attenuates the servo signal generated by the servo signal generation section by a factor of a second gain; and a gain setting section configured to set the first gain to the reflected light process section and the second gain to the servo signal control section substantially simultaneously.

Abstract: An apparatus having switchable servo gains and offsets for an optical disk drive adjusts its gains and offsets through the coupling of a servo signal and a switch with several changeable paths. The servo signals are either designated to undergo signal reduction with respect to a first offset, through the switch and then be output after a first gain unit performed proportional conversion, or designated to undergo signal reduction with respect to a second offset and then be output after a second gain unit performed proportional conversion. The switch is switched on/off in the light of the working status of the pick-up head, for example, seeking or tracking, at a data area or at a blank area, and at a groove area or at a land area, so as to choose different offsets and gains to have the conversion of the servo signals.

Abstract: In a device for controlling a focus to an optical disc having a land section and a groove section, the control is performed so as to avoid a focus step difference at a land-area/groove-area switching point. When performing write-in or readout of data to an optical disc on which a land area and a groove area are continuously formed, using an optical pickup, there are provided a land learning unit (1) for determining a focus position in the land area, a groove learning unit (2) for determining a focus position in the groove area, and a focus position calculation unit (3) for determining a focus position in an area where the land area and the groove area are switched, and the focus position of the optical pickup is moved so that it is located at the third focus position when the switching signal is inverted according to the switching between the land area and the groove area.

Abstract: A method of reducing power dissipation in a variable-gain photo-detector circuit is described. The variable-gain photo-detector circuit has an output to output a main spot signal and at least one side spot signal. The main spot (M) and the side spot (Si or S2) are formed by separating a light beam into a main beam and at least one side beam and focusing the main beam on the main spot (M) and the side beam on at least one side spot (Si or S2) on an optical record carrier The method processes the main spot signal with a first averaging circuit having a first cut-off frequency. The side spot signal is processed with a second averaging circuit having a second cut-off frequency. The second cut-off frequency is lower than the first cut-off frequency. The above technique reduces power dissipation in the variable-gain photo-detector circuit and is useful for all optical devices.

Abstract: Provided is an optical disk device capable of recording and/or reproducing information on optical disks with high reliability; and a method for controlling the optical disk device. The position of an optical lens where the amplitude of a reproduction signal during the period corresponding to a minimum-length recording mark and a space having the same length reaches its maximum is detected; and the detected position is set as a reference position for the objective lens relative to the optical disk, for use in focus control. Also, the position of the objective lens where the result of multiplication of resolution and modulation becomes greatest is detected; and the detected position is set as a reference position for the objective lens relative to the optical disk, for use in focus control.

Abstract: The optical disc device has a circuit 4 which forms a focus error signal FER for focus servo control based on reflection light from an optical disc exposed to laser light. A data processing unit 2 can control by feedback a position to which an objective lens is moved by a focusing actuator 30 based on the focus error signal. In label printing, the data processing unit controls, by feedforward, a position to which the objective lens is moved by the focusing actuator based on control data for label printing. The operation resolution of the focusing actuator in feedforward control is made higher than that in feedback control. Thus, an intended position control accuracy is achieved in feedforward control. For instance, in feedforward control, the gain of the driver circuit 40 for the focusing actuator is switched to a smaller one in comparison to that in feedback control.

Abstract: A method of adjusting gain balance of an optical transducer includes the following steps. First, two external gains are predetermined. Next, the projection position of a reflection spot is adjusted toward one side of the optical transducer, and the current output values of the optical transducer each corresponding to one of the external gains are measured, respectively. Next, the projection position of the reflection spot is adjusted toward the other side of the optical transducer, and the current output values of the optical transducer each corresponding to one of the external gains are measured, respectively. Then, a gain balance value of the optical transducer is adjusted, and is set as the external gain. Next, the projection position of the reflection spot is adjusted. Finally, the projection position of the reflection spot, where the current output value of the transducer is equal to 0, is locked to complete the adjustment rapidly.

Abstract: An optical disc apparatus includes a laser diode for emitting a laser light, a beam splitter for dividing the laser light into a main beam and sub beam, a main photodetector for detecting the main beam to output a main push-pull signal, a sub photodetector for detecting the sub beam to output a sub push-pull signal, and a subtracter for calculating the main and sub push-pull signals to output a differential push-pull signal, in which an amplification degree of the sub push-pull signal is adjusted so that a DC offset on the differential push-pull signal is adjusted, even in the case where a laser intensity is varied.

Abstract: A tilt adjustment control method for a near-field optical system is provided. The method includes the following steps. A gap between a lens and a disc is detected. A gain corresponding to the gap is provided. A tilt signal is detected. A tilt compensation value according to the tilt signal and the gain is obtained. A tilt adjustment control is performed on the lens according to the tilt compensation value.