Abstract: In a focus controlling method of a laser beam for an optical disk, achieving a stable focus drawing-in, lowering ill influences due to stray lights, detecting an electric signal, which is obtainable upon basis of a reflection light from the optical disk loaded, in advance, while executing a focus sweep operation of gradually approaching the laser to a recoding surface of the optical disk, at an unnecessary light detection gain being higher than a gain of normal operation, thereby counting a number of signals generated due to unnecessary lights; and thereafter, detecting the electric signal, which is obtainable upon basis of the reflection light from the optical disk loaded, and thereby conducting a focus drawing-in, by considering an electric signal, which is generated just after a number detected thereof reaches to the counted number of signals generated due to the unnecessary lights, to be a signal reflected from the recording surface of the optical disk loaded.

Abstract: Adjusting a servo control system includes identifying a gain crossover frequency for the servo control system, generating a sensitivity function for the servo control system, measuring a sensitivity peak in the sensitivity function, comparing a frequency of the sensitivity peak to the gain crossover frequency, and adjusting the servo control system in response to the comparison of the frequency of the sensitivity peak to the gain crossover frequency.

Abstract: A tracking error detection apparatus comprises a photodetector comprising plural photoreceptor elements; zerocross detection circuits for detecting zerocross points at which two sequences of digital signals intersect the center levels of the respective digital signals, which digital signals are generated according to the amounts of light received by the respective photoreceptor elements and are outputted from the photodetector; a phase difference detection circuit for performing phase comparison using a distance between zerocross points of the two sequences of digital signals, and outputting a result of phase comparison; and a low-pass filter for performing band restriction to a signal outputted from the phase difference detection circuit. When a phase difference between the two sequences of digital signals, which is detected by the phase difference detection circuit, is larger than a maximum value of a theoretical tracking error signal, the output from the phase difference detection circuit is limited.

Abstract: An optical storage apparatus, a preamplifier and a method of generating a tracking error signal. The optical storage apparatus includes a pickup head, a preamplifier, and a servo control. The pickup head generates radio frequency (RF) signals. The preamplifier includes a signal adjusting apparatus, a phase detector, a charge pump, and a circuit. The signal adjusting apparatus has input terminals for receiving the RF signals. At least two of the input terminals are substantially short-circuited when the optical storage apparatus is in a calibration mode. The phase detector generates control signals based on the phase differences between the radio frequency signals. The circuit generates current control signal based on the tracking error signal when the optical storage apparatus is in the calibration mode. The current magnitude of at least one of the current sources in the charge pump is determined according to the current control signal.

Abstract: A positioning control device and method in which the relative position error in tracking is reduced by using the periodicity of position shift. The positioning control device comprises a position detecting unit for measuring the relative position error between the desired position of an objective member and a moving member, an adding unit for adding a position error signal output from the position detecting unit and a delay signal, a signal delay unit for outputting the delay signal which is obtained by delaying an output of the adding unit at a period corresponding to the position shift of the objective member, a drive unit for moving a moving member, and an inputting unit for inputting the signal of the sum of the position error signal and the delay signal to the drive unit and addition-inputting the delay signal to the drive unit through a filter having a predetermined frequency characteristic in a specific frequency range.

Abstract: A receiver is described for delivering a data sequence (ak) at a data rate 1/T from an analog signal (Sa), the receiver comprising: a) converting means (40) for generating a received sequence (rn) by sampling the analog signal (Sa) with a sample rate of 1/Ts, whereby the sample rate 1/Ts of the received sequence (rn) is controllable by a preset value (Pv); b) digital processing means (12) for delivering a processed sequence (yn) by processing the received sequence (rn); c) a first sample rate converter (13) converting the processed sequence (yn) into an equivalent processed sequence (ye) at the data rate 1/T, whereby the data rate of the equivalent processed sequence (ye) is controllable by a control signal (Sc); d) an error generator (14) for delivering an error sequence (ek) from the equivalent processed sequence (ye); e) a control signal generating means (15) for generating the control signal (Sc) dependent on the error sequence (ek); f) a detector (16) for deriving the data sequence (ak) from the equivale

Abstract: A tracking and servo system with a one-track jump is disclosed. The one track jump algorithm holds a control signal from the tracking servo system. The one track jump algorithm adds an acceleration control signal to the held control signal for a first period of time, delays for a second period of time, and adds a deceleration control signal to the held control signal for a third period of time. The algorithm then frees the control signal to close tracking on a new track separated by one track from the starting track.

Abstract: A method and a related apparatus for diagnosing crosstalk within an optical pick-up unit by utilizing firmware. The method includes calculating a tracking driving signal and a focusing driving signal according to a tracking error signal and a focusing error signal respectively, adding a noise to the focusing driving signal to form a test focusing driving signal through executing firmware, driving an optical pick-up unit by the tracking driving signal and the test focusing driving signal, and diagnosing characteristics of the pick-up unit through observing the tracking error signal.

Abstract: Test writing is executed while skipping areas where deviations are present on an optical disk to thereby improve accuracy and reliability of an optimum recording condition to be derived. A deviation detecting unit detects the deviations of a guide groove on the optical disk on the basis of a fluctuation amount of a focus error signal or a tracking error signal, and registers information of the detected deviations onto a memory. A test writing processing unit refers to the memory, and records and reproduces a test signal while skipping the areas where the deviations are detected.

Abstract: A method for deriving a tracking error signal based on a first analog detection signal and a second analog detection signal. The method includes summing the first analog detection signal and the second analog detection signal to generate an analog sum signal. An analog delay device is utilized to delay the analog sum signal to be a delay signal. The delay signal is digitalized into a digital delay signal. The first analog detection signal and the second analog detection signal are respectively transformed into a first digital detection signal and a second digital detect signal. The tracking error signal is then generated utilizing a comparing operation among the digital delay signal, the first digital detect signal, and the first digital detect signal.

Abstract: A track locking method and an apparatus thereof enable an optical disk drive to rapidly and stably read data recorded on a target track from a seeking mode to a track locking mode. An optical pick-up head can switch from the on-track interval of a target track to an adjoining off track period only if the tracking servo control system memorizes the last-minute level of the tracking servo output signal of the on-track interval and keeps the tracking servo output signal at the level, so as to generate a pulling force whereby the optical pick-up head is moved back to the on-track interval from the off-track interval.

Abstract: A tracking error detection apparatus comprises a phase difference detection circuit for receiving two sequences of digital signals, and performing phase comparison using a distance between zerocross points of the two sequences of digital signals to output a result of phase comparison, and an LPF for generating a tracking error signal from the result of phase comparison. The phase difference detection circuit does not carry out phase composition in a position that is not appropriate as a target position to perform phase comparison, and outputs the result of phase comparison as a pulse signal corresponding to one sampling clock. Therefore, even when a disc is played at CAV or a flaw or the like exists on the disc, an accurate tracking error signal can be detected.

Abstract: A method, apparatus, and computer readable medium controlling a servo of a recording and/or reproducing apparatus, using a detected header field signal. An optical recording and/or reproducing apparatus includes a playback signal detector that detects a playback signal and a track error signal from information recorded on a DVD-RAM disc, as picked up by a pickup. A header field signal detecting circuit detects a header field signal by comparing a sampled playback signal for a signal representing the presence of a header field with a reference level and holding the comparison result for a predetermined period of time to generate the header field signal. Accordingly, a tracking servo can be stably controlled by using a tracking driving signal that is not affected by the presence of a header. Also, in a seek mode, the track error signal can be held based on the header field signal to generate a track count signal that is similarly not affected by the header.

Abstract: The invention relates to an electronic circuit for decoding a read signal from an optical storage medium, the electronic circuit comprising a limit equalizer for amplification of high frequency read signal components without substantially increasing inter-symbol interference, a Viterbi detector being coupled to an output of the limit equalizer for providing the decoded read signal, a coefficient adaptation circuit for tuning the limit equalizer to a partial response target.

Abstract: An optical disc drive is used to read and/or write data from/on an optical disc having a data storage layer. The drive corrects electrical offset while reading and/or writing data. The drive updates a correction value based on an electrical offset detected at correcting operation or a value derived using electrical offset values that has been detected and stored, without detecting an electrical offset at correcting operation. Therefore, the optical disc drive can correct the electrical offset less often.

Abstract: An apparatus for scanning a track on a record carrier has a head (22) and front end circuitry (31) for scanning the track and generating scanning signals. A detection unit (32) detects anomalies in the scanning signal, for example for adjusting a tracking servo. The detection unit (32) calculates a mean value of the scanning signal and compares the mean value to a threshold for providing an anomaly detection signal (33). Further a classification unit (34) provides an indication of the type of defect for determining a suitable responsive or corrective action.

Abstract: A moved distance detecting means (15) detects the moved distance in a tracking direction of an object lens, a position signal generating means (60) generates a position signal corresponding to the position of the object lens based on the detection, and a drive signal modulating means (40) modulates the drive current of a magnetic head (20) according to this position signal. Therefore, a drive current can be controlled according to the moved distance of the object lens to enable the magnetic head to be driven with a small current when a moved distance is small and with a large current according to a moved distance only when it is large, whereby it is possible to reduce an average drive current and hence reduce power consumption as a whole.

Abstract: A method for deriving a tracking error signal based on a first analog detection signal and a second analog detection signal. The method includes summing the first analog detection signal and the second analog detection signal to generate an analog sum signal. An analog delay device is utilized to delay the analog sum signal to be a delay signal. The delay signal is digitalized into a digital delay signal. The first analog detection signal and the second analog detection signal are respectively transformed into a first digital detection signal and a second digital detect signal. The tracking error signal is then generated utilizing a comparing operation among the digital delay signal, the first digital detect signal, and the first digital detect signal.

Abstract: A data access method for improving performance of an optical disk drive is applied on a predetermined data access operation. A predetermined application program and the optical disk drive are used to run first, second, and third processes for accomplishing the predetermined data access operation. The predetermined application program runs the first process, and the optical disk drive runs the second process. The data access method includes the predetermined application program running the first process and outputting a control command to command the optical disk drive to start the second process, and the predetermined application program running the third process for controlling the optical disk drive to access an optical disk after the first process and the second process are finished. In addition, the time for the predetermined application program to complete the first process overlaps the time for the optical disk drive to complete the second process.

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.

Abstract: There are provided a balance adjustment circuit (6) for adjusting levels of first and second detection signals from a tracking detector, a differential circuit (8) for generating a difference signal between the adjusted first and second detection signals, an AD conversion circuit (10) for digitizing the difference signal, a wobble signal detection circuit (14) for detecting a wobble signal from the digitized difference signal, an adder circuit (30) for generating a sum signal of the adjusted first and second detection signals, a binarization circuit (32) for converting the sum signal into a binarized signal, a latch circuit (33) for latching the binarized signal and converting the same into a timing signal, a control signal generation circuit (34) for generating a control signal based on the timing signal and the digitized difference signal, a residual component removal circuit (18) for removing a residual signal component included in the digitized difference signal based on the control signal and outputting

Abstract: The present invention relates to an apparatus for reading from and/or writing to optical recording media, which has a tracking device, a four-quadrant detector, two summation points and a phase comparator for tracking in accordance with the differential phase detection method, and also various delay elements that can be set by a control device. The object of the present invention is to propose an apparatus of this type which exhibits the best possible compensation of the error in the track error signal and thus in the tracking signal, the said error being caused on account of the lens movement. To that end, the invention provides for analogue delay elements to be arranged upstream and digital delay elements to be arranged downstream of the summation points. The present invention is suitable for apparatuses for reading from and/or writing to optical recording media, such as CD, CDI, CD-ROM, DVD, CDR and others.

Abstract: It is an object of the present invention to provide an optical pickup astigmatism adjusting method capable of easily correcting an astigmatism even if the spot shape of a light beam converged on an optical disc is not a true circle. An optical pickup astigmatism adjusting system of the present invention finds an inter-focal distance L0 between a focal position where a light beam is converged in RAD direction and another focal position where a light beam is converged in TAN direction, and a further inter-focal distance L45 between a focal position where a light beam is converged in a direction inclined 45 degrees from RAD direction and another focal position where a light beam is converged in a direction inclined 45 degrees from TAN direction, thereby measuring an astigmatism in accordance with the inter-focal distances L0 and L45. Then, an installation angle of a reflection mirror is adjusted in accordance with the inter-focal distances L0 and L45, thus correcting the astigmatism.

Abstract: An optical disc apparatus has a crosstalk level determining section which, when a track jump is performed without applying a tracking servo, determines whether a crosstalk component is larger than a predetermined level or not. If the crosstalk level determining section determines that the crosstalk component is larger than the predetermined level, a crosstalk correcting section performs a calculation for reducing the crosstalk component. If the crosstalk level determining section determines that the crosstalk component is not larger than the predetermined level, the crosstalk correcting section does not reduce the crosstalk component.

Abstract: An information recording apparatus is provided, which can control over the power of light beams emitted from a light source and various types of servo control with higher accuracy. A laser beam is emitted from a semiconductor laser to write information onto an optical disc. A detection signal indicative of the power of the laser beam output from a light-receiving device is sampled and held with a sample and hold circuit via an I-V converter at a timing delayed by the time corresponding to the delay time of the I-V converter. A tracking error generation circuit and a focus error generation circuit generate a tracking error signal and a focus error signal, respectively, on the basis of a detection signal having information about tracking error and focus error and output from a light-receiving device. Sample and hold circuits sample and hold the tracking error signal and the focus error signal at a timing delayed by the time corresponding to the delay time of each of the generation circuits, respectively.

Abstract: A signal processing apparatus is provided with a converter for converting at least one analog light detection signal into a digital light detection signal, and a signal generator for generating at least one servo error signal by subjecting the digital light detection signal to a predetermined operation process. The signal generator has a function of modifying contents of the operation process.

Abstract: An optical disc apparatus in which the inclination of an optical axis of laser light relative to an optical disc is adjusted. When data is recorded, laser light is irradiated at recording power in mark periods and irradiated at reproducing power or erasing power in space periods. Immediately after the beginning of the mark periods, no pits are ye formed even though recording power is applied and the amount of reflected light has a level corresponding to the inclination of the optical axis of laser light relative to the optical disc without influence exerted by the pits. Also in the space period, the amount of reflected light has a level corresponding to the inclination of the optical axis of laser light relative to the optical disc. By sampling the reflected light signal at the instant following to the beginning of the mark period or space periods, the inclination is adjusted so as to maximize the sampled signal level.

Abstract: A circuit to improve the SN characteristic of a tracking error signal. This tracking error detection circuit is formed as a push-pull system utilizing a quadrant type photo-detector and provided with 4 gain control amplifiers 20, 22, 24, and 26, 4 bottom envelope circuits 28, 30, 32, and 34, a pair of subtracting circuits 36 and 38, adding (subtracting) circuit 40, offset circuit 42, and gain control circuit 44. Bottom envelope circuits 28, 30, 32, and 34 are configured with a capacitor-type peak-hold circuit, for example, whereby bottom envelopes of RF signals SA, SB, SC, and SD given from light receiving areas A, B, C, and D of a photo-detector via gain control amplifiers 20, 22, 24, and 26 are detected, and bottom envelope signals SAbtm, SBbtm, SCbtm, and SDbtm representing the waveforms of the respective bottom envelopes are output.

Abstract: A wobble signal detecting circuit for optical disc system includes at least a sample-and-hold circuit for carrying out sample-holding steps on each of first and second photoelectric signals, and a high range frequency limiting circuit for removing frequency components equal to, or higher than, a predetermined cut-off frequency from the first and second photoelectric signals. By selectively enabling either the sample-and-hold circuit or high range frequency limiting circuit, depending on recording conditions during the period of recording information into an optical information recording medium, noise components which may unduly affect wobble signals can be removed efficiently, irrespective of recording conditions.

Abstract: A device for reading and/or writing information from an optical carrier, the device comprising an imager for imaging a radiation beam into scanning spot to scan the carrier, and a detector for generating a read signal indicative of the intensity of the radiation reflected from the carrier. The device has an information transfer mode, wherein the scanning spot is moved in a first direction. The device has a displacement mode, wherein the scanning spot is moved in a second direction transverse to the first direction. The device includes a controller for controlling the imager in response to a measurement signal indicative of the degree of focusing of the radiation beam. The controller samples and holds the measurement signal in response to a sample signal causing the measurement signal to be sampled when the intensity is comparatively high thus reducing radial-to-vertical crosstalk.

Abstract: A circuit for tracking error signal detection on an optical storage medium, which has a plurality of digitizers, a plurality of logic comparators and a difference amplifier, is disclosed. The circuit involves summing the signals to be compared and obtaining a delay signal via a delayer. Therefore, the phase difference of the signals is detected via the delay signal to obtain the tracking error signal of the optical storage medium.

Abstract: A method and apparatus for tracking error detection in an optical disk reproduction system. The tracking error detecting apparatus generates a tracking error signal as a difference signal of optical detection signals generated by more than two optical detectors positioned along a diagonal line from a track center and includes binarizers which binarize each output of the optical detectors, phase locked loops (PLLs) which generate respective clock signals synchronized with the outputs of each of the binarizers, a phase difference detector which detects a phase difference between the synchronized signals output from the PLLs, and low-pass filters which filter the output of the phase difference detector to output the result as the tracking error signal. The tracking error detecting apparatus generates a tracking error signal which is not dependent on the lengths of pits or marks recorded on an optical disk, enhancing the reliability of the tracking error signal.

Abstract: An apparatus and method for detecting a wobble signal read from an optical disc. The wobble signal detection apparatus comprises an analog/digital (A/D) converter for A/D-converting an analog wobble signal, read from the optical disc and then band pass filtered, a slope detector for detecting a slope of the A/D-converted wobble signal according to a variation thereof, and a wobble signal detector for detecting a peak point of the A/D-converted wobble signal using the detected wobble signal slope, and detecting/outputting a square-wave wobble signal with a high level or low level transition at the detected peak point. The slope detector calculates variations of data values of the A/D-converted wobble signal sampled within a predetermined period on the basis of predetermined different weights, accumulates the calculated values and detects the slope of the A/D-converted wobble signal on the basis of the accumulated value.

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: Disclosed is a method and apparatus for controlling the record and reproduction of optical record medium in which plural non-record regions having different phase are arranged between recordable data regions for the distinction in the shape of the data region. The method and apparatus performs the servo using focus error signal and tracking error signal averaged by the low pass filter at the header region of the optical disc. Especially, the tracking servo is performed by holding a fixed DC off-set value at the header region existing on the L/G switching or holding the tracking error value of the previous same track region. As a result, the exact header region is detected, the track sliding phenomenon is removed, and the tracking servo is stabilized, resulting in preventing the degeneration of the record and reproduction characteristics.

Abstract: A recording and playback apparatus comprises, a drive unit configured to rotate an optical recording medium including a recording track, a recording and playback unit configured to irradiate a light beam on the recording track, and to perform recording and playback of an information detected a reflected light beam by an upside photo detection area and a downside photo detection area bisected in a tangential direction of the recording track, and a recording and playback controller configured to generate a position tracking signal based on the reflected light beam detected by the upside photo detection area and the downside photo detection area, and to compensate a level of the position tracking signal when the position tracking signal and a record mark on the recording track are detected.

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: When a run-away phenomenon of an optical disk occurs, a control circuit detects a rotational direction of the optical disk that runs away by comparing an initial track count value and a braking time track count value. The initial track count value is a value calculated by counting track pulses corresponding to a tracking error signal for a predetermined time when a tracking servo is turned off. The braking time track count value is a value calculated by counting the track pulses corresponding to the tracking error signal for a predetermined time, when a brake pulse is applied to the spindle motor.

Abstract: A disk drive servo system for eccentricity compensation and a method thereof includes an error detector detecting a position error between an actual position and a predetermined nominal reference position of a turntable actuator, a feedback unit generating and outputting a first control value to compensate for the position error received from the error detector, a learning controller calculating, storing, and outputting a second control value to compensate for eccentricity at one or more predetermined speeds of the disk drive, and a gain/phase adjustor providing gain and phase compensation information corresponding to the second control value of the learning controller according to frequency response characteristics of the turntable actuator at the one or more predetermined speeds.

Abstract: A motor controlling device includes an acceleration detector for detecting an acceleration of a motor; a motor driver for supplying a driving current to the motor; a heat quantity calculator for calculating a heat quantity generated in the motor at least based on an output from the acceleration detector; and a motor controller for controlling the motor driver based on the heat quantity.

Abstract: A system with a plurality of servo algorithms executing on a digital signal processor is presented. The digital signal processor receives a sensor interrupt, indicating availability of digitized data from optical sensors, and decides which of a plurality of servo algorithms to service in response to the interrupt. In some embodiments, the plurality of servo algorithms includes a tracking servo algorithm. In some embodiments, the plurality of servo algorithms includes a focus servo algorithm. In some embodiments, multi-track seek operations or one-track jump operations can also be serviced during the interrupt period.

Abstract: A tracking error detection apparatus includes a phase error detection unit for detecting a phase error of an output signal according to the amount of reflected light that is obtained when a light beam is applied to an information recording medium and a low-band pass unit for performing band restriction to obtain a tracking error signal from the phase error signal. The tracking error detection apparatus also includes a clock generation unit for generating a clock and a clock control unit having a frequency divider for generating a frequency-divided clock of the clock that is generated by the clock generation unit, wherein the clock control unit uses the frequency-divided clock as an operation clock for the tracking error detection apparatus. Therefore, the operation rate of each unit when generating a tracking error signal can be reduced, whereby a reduction in power consumption is achieved.

Abstract: Header regions are formed by dividing a groove or grooves. Each of the header regions is provided with two ID sections G-ID1, G-ID2 storing address information and a track center detection mark section, arranged between the two ID sections, so as to be used for detecting the track center.

Abstract: The invention relates to a system for reading a magnetic medium having several tracks of data which can be read in parallel with a detection device having at least as many detectors as there are tracks, making it possible to read simultaneously and at regular intervals a sample of data on each track. This system furthermore includes a processing circuit configured to receive each sample of data to be processed from each track together with sample of a first adjacent track and sample of a second adjacent track and to calculate the cross-talk affecting the sample of data to be processed due to the adjacent tracks. An integration circuit configured to receive the cross-talk value calculated by the processing circuit, integrates these values at each read time, and at subsequent read times. The systems also include a relative track-following control circuit configured to receive the result of integration of the integrator circuit and to supply a track-following control signal for the detection device.

Abstract: A differential phase detection device receives first through fourth detection signals from a photodetector and detects a differential phase signal therefrom, the differential phase detection device includes a slicer slicing and digitizing each of the detection signals with respect to a reference level. A synthesizer synthesizes the digitized detection signals and generates therefrom synthesis signals. A phase difference detector compares phases of the synthesis signals and outputs a first phase difference signal and a second phase difference signal. A matrix circuit processes the first and second phase difference signals to output the differential phase signal.

Abstract: When record information is recorded on a recording medium with recording control information pre-recorded thereon by forming pre-pits so that the recording control information will be used to control the recording of the record information to be recorded on the recording medium, a first light beam having first power and a second light beam having second power different from the first power are irradiated to the pre-pits on a time-shared basis according to the record information to generate read signals generated from electrical signals according to the amounts of reflected light of the respective beams so that the pre-pits will be detected from inputs of the read signals. In this configuration, the pre-pits are detected from only the read signals input during a period of irradiation of the second light beam.

Abstract: An optical pickup apparatus for reproducing information from an optical information recording medium or for recording information onto an optical information recording medium, is provided with a first light source for emitting first light flux having a first wavelength; a second light source for emitting second light flux having a second wavelength, the first wavelength being different from the second wavelength; a converging optical system having an optical axis and a diffractive portion, and a photo detector; wherein in case that the first light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the first light flux is greater than that of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through the diffractive portion to generate at least one diffracted ray, an amount of n-th ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted

Abstract: In a first mode, an R/W channel starts to monitor read information to thereby detect a servo mark contained in servo information, each time a servo controller generates a servo gate pulse. Upon detecting the servo mark, the R/W channel detects, from the read information, position information contained in the servo information and following the servo mark, at a timing determined by the detection timing of the servo mark. When the first mode has been switched to a second mode, the R/W channel detects the servo mark and position information using the synchronous method.

Abstract: A notch filter that filters a focus error signal during a multi-track seek operation is presented. The notch filter has a center frequency that relates to the seek reference velocity of a multi-rack seek algorithm. During the multi-track seek operation, a focus control signal is calculated from the filtered focus error signal from the notch filter.

Abstract: A system for detecting a tracking error comprises a two-divided type light detector (2), LPFs (4a, 4b), first and second waveform generator (5a, 5b), first and second delay circuits (6a, 6b), first and second adders (7a, 7b) and a phase comparator (8). The detector (2) has two photo detecting elements (2a, 2b) disposed separately in the radius direction of an optical disc. The LPFs (4a, 4b) remove high frequency components from the outputs of the elements (2a, 2b). The first waveform generator (5a) generates a sine wave (B1) with amplitude corresponding to the output level of a signal (A1), which passed the LPF (4a). The second waveform generator (5b) generates a sine wave (B2) having the identical frequency to the wave (B1), with amplitude corresponding to the output level of a signal (A2), which passed the LPF (4b). The first delay circuit (6a) delays the wave (B1) by the prescribed amount of delay to form a sine wave (C1).