Abstract: An apparatus for detecting abnormal states which prevents damage to a laser diode or data recorded on a disc and swiftly correcting the abnormal state. An overflow/underflow detector detects whether overflow or underflow of the laser diode occurs, by comparing a laser diode output power control value, which is output from the laser diode output power control circuit, with an overflow setting value and an underflow setting value. A mode switch switches an operation mode of the laser diode output power control circuit from a recording mode to a reproducing mode, in response to the detection result of the overflow/underflow detector.

Abstract: A read channel apparatus is disclosed for reading data recorded on an optical storage system at a predetermined baud rate. The apparatus asynchronously samples an analog read signal generating from the optical storage system and subtracts an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values. The asynchronous DC-removed sample values are separately interpolated by two interpolators to generate a sequence of synchronous even-time sample values and a sequence of synchronous odd-time sample values respectively. The synchronous even-time and odd-time sample values are separately equalized by two equalizers in accordance with a target spectrum to generate a sequence of even-time equalized sample values and a sequence of odd-time equalized sample values respectively. A DC offset estimator generates the estimated DC offset from the even-time equalized sample values and the odd-time equalized sample values.

Abstract: In a data slicer and data slicing method for an optical disc system, the data slicer for converting an analog input signal into a digital signal includes a comparator, a duty detector, and a low pass filter. The comparator compares the analog input signal with a feedback signal to generate the digital signal. The duty detector detects the duty of the digital signal. If the detected duty is longer than a preset duration, the duty detector converts the detected signal into a signal having the preset duration, and outputs the converted signal. The low pass filter integrates the output signal of the duty detector to generate the feedback signal.

Abstract: A sample-and-hold interface circuit of a pickup head uses a circuit switch to control a voltage divider. When the circuit switch receives a signal Break, a voltage divider does not consume extra power to decrease the driving power consumption of a pickup head. And a controller can sample an unattenuated input signal to increase the signal/noise ratio.

Abstract: An optical disk control device comprises a playback signal detection unit for detecting data recorded on a disk by irradiating the disk with a converged light beam; a signal switching unit for successively selecting plural data signals obtained by the playback signal detection unit, and performing time-division-multiplexing on the selected signals; an A/D conversion unit for converting an analog signal which has been time-division-multiplexed by the signal switching unit, into a digital signal; an A/D conversion command unit for generating an A/D conversion command of the A/D conversion unit; a serial transfer unit for serial-transferring the command signal generated by the A/D conversion command unit; a serial reception unit for receiving the signal from the serial transfer unit, and controlling the signal selection operation of the signal switching unit on the basis of the received signal; and an arithmetic unit for generating an optical disk drive controlling signal by performing arithmetic processing on t

Abstract: An RF signal that is a disk reproduction signal is binarized through an equalizer and a slicer, followed by data demodulation, and an error rate of the reproduction signal is detected in an error detection circuit. If the error rate in the error detection circuit is higher than a prescribed value, a slice balance adjustment circuit performs slice balance adjustment for the slicer and a boost adjustment circuit performs boost adjustment for the equalizer.

Abstract: A read channel apparatus is disclosed for reading data recorded on an optical storage system at a predetermined baud rate. The apparatus asynchronously samples an analog read signal generating from the optical storage system and subtracts an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values. The asynchronous DC-removed sample values are separately interpolated by two interpolators to generate a sequence of synchronous even-time sample values and a sequence of synchronous odd-time sample values respectively. The synchronous even-time and odd-time sample values are separately equalized by two equalizers in accordance with a target spectrum to generate a sequence of even-time equalized sample values and a sequence of odd-time equalized sample values respectively. A DC offset estimator generates the estimated DC offset from the even-time equalized sample values and the odd-time equalized sample values.

Abstract: It is an object of the present invention to provide a phase difference correction apparatus and a data reproduction apparatus including a data header detection apparatus that can synchronize the phase between a clock for reproducing data and an optimum sampling point of a reproduction signal with high accuracy and thus precisely detect a header of reproduced data even in a case where the S/N ratio of a signal is low.

Abstract: A system and method for generating sample control signals for a sample and hold circuit used to control access to optical media is provided. The sample control signals are generated with sufficient duration (width) to adequately sample a reflected laser power signal. The sample control signals are defined relative to a laser power command signal generated in response to an internal data stream, rather than directly in response to the internal data stream, thereby allowing for more precise control of the sample control signals. As a result, substantial portions of each pulse of the reflected laser power signal can be sampled, without sampling transition noise that exists when the reflected laser power signal changes states. Generating the sample control signals from a laser power command signal, rather than the input data signal, more accurately time shifts the sampling command to the reflected laser power.

Abstract: An information recording medium for recording main information and auxiliary information is provided. The auxiliary information is recorded on the information recording medium in a manner that edge positions of the pits or the recording marks indicating the main information are shifted either in a phase advancing direction or in a phase delaying direction along the track direction. A predetermined frequency is used to determine whether the edge position is shifted in the phase advancing direction or in the phase delaying direction in order to record the auxiliary information. The predetermined frequency is substantially consistently lower than ½ of a reference frequency of a recording clock for creating the pits or the recording marks and is higher than a response frequency of a PLL for generating a reproduction clock for reproducing the main information.

Abstract: In a PLL circuit, a phase error of a reproduced signal is extracted in either a way based on a zero-cross timing or a way based on a self-running timing. A decision is made as to whether the reproduced signal is in a continuous-wave interval where an inversion period of the reproduced signal remains constant or in a random-wave interval where the inversion period of the reproduced signal varies at random. When the reproduced signal is in a continuous-wave interval, a phase error is extracted on the self-running-timing basis. When the reproduced signal is in a random-wave interval, a phase error is extracted on the zero-cross-timing basis. A continuous-wave interval may be replaced by a specified-pattern repetition interval where the inversion period of the reproduced signal changes in accordance with a repetition of a specified pattern.

Abstract: A reproduction method for reproducing BCA data for optical discs using the defect signal. The reproduction method for reproducing BCA data includes the steps of: generating a defect signal as a BCA signal by detecting an RF signal of the BCA; generating a BCA data bit stream by sampling the BCA signal according to a sampling clock; and decoding the BCA data bit stream to generate BCA data. Because the defect signal is utilized as the BCA signal of the invention, no additional BCA signal extracting device is needed.

Abstract: An optical information recording medium (1) is composed of a pit recording area (2), wherein various control information is recorded by a prepit, and a user recording area (3) having a guide groove formed in a groove format, and a phase depth for the prepit and the groove are approximately the same wherein the phase depth is less than or equal to ?/10, wherein ? is a wavelength for reproducing light source. A recording/reproducing apparatus (4) for the optical information recording medium (1) includes decoding means (12) for decoding information by detecting a tangential push-pull reproduced signal from the prepit recording area (2) and detecting an aggregated signal from the user recording area (3).

Abstract: An information storage medium according to an embodiment of this invention includes a wobbled groove having a wobble period modulated by multi-frequency shift keying corresponding to playback control information.

Abstract: There is provided an information reproducing device which outputs an equalization signal P by applying equalization processing to a signal detected from a storage medium based on equalization coefficients C0 to CN, outputs a decoding signal d by applying maximum likelihood decoding processing based on reference levels R0 to R6, generates an ideal waveform signal I based on the equalization signal, and has a target waveform generator which generates a target waveform signal T by changing at least one level of the ideal waveform signal I, wherein erroneous decoding is reduced by optimizing reproduction processing parameters such as the equalization coefficients C0 to CN or the reference levels R0 to R6 based on the target waveform signal T and the information on the storage medium is stably reproduced.

Abstract: A method and related circuit for synchronizing a writing clock with a wobble clock of a compact disk (CD) drive. The CD drive is capable of rotating a CD that has a data track for recording data and a wobble track. The CD drive is capable of generating the wobble clock according to movement of the wobble track while the CD is rotating. Also the CD drive is capable of writing data on the data track according to the writing clock. The method includes adjusting the frequency of the writing clock so as to synchronize the writing clock and the wobble clock.

Abstract: An optical disc player having an optical pickup records and retrieves information on an optical disc while the optical disc is rotating. A rotation pulse is generated each time the optical disc rotates through a prescribed angle. A rotation frequency data representing a frequency of the rotation pulse is also generated. A servo processor performs servo processing for rotation control on the optical disc in accordance with the rotation frequency data. A sampling pulse generator performs computational processing on an input data signal to generate a sampling pulse. The sampling pulse generator also corrects the rotation frequency data based on a phase error between the sampling pulse and the rotation pulse to use a corrected rotation frequency data as the input data signal. Another servo processor performs servo processing for repetitive control on the optical pickup using the sampling pulse.

Abstract: A method for extracting information in a data signal stored on an optical disc. The information is stored in a plurality of channel bits. The method includes initializing a recovery period of a recovery clock to a predetermined value expressed in cycles of a first clock; sampling the data signal with the first clock; obtaining a leading edge time period expressed in cycles of the first clock of a pattern of bits from the sampled data in which at least a first bit has a first binary value, followed by a plurality of bits having a second binary value, and ending with a last bit having the first binary value, wherein the first and second binary values are not equal; updating the recovery period of the recovery clock to be equal to a new maximum period that is the leading edge time period divided by a division factor; extracting the information in the data signal based on the newest recovery period of the recovery clock; and detecting a predetermined code in the data signal.

Abstract: A data reproduction apparatus includes first and second sampling parts which sample a reproduced signal from a recording medium in synchronism with first and second clock signals synchronizing respectively with leading and trailing edges of the reproduced signal and output leading and trailing sampled values, respectively, and a combination part which generates combined sampled values based on the leading and trailing sampled values. Recorded data is reproduced based on transition states of the combined sampled values output from the combination part in accordance with a maximum likelihood decoding technique corresponding to a predetermined partial response waveform.

Abstract: A phase correction circuit includes a phase control data generation circuit which judges whether or not the present sector is a leading sector in an ECC block, which is the minimum recording unit in a magneto-optical disk, and generates phase control data by referring to a phase difference data of a previous sector when the present sector is not the leading sector, based on a phase difference detected by a phase difference detection circuit; and a phase control circuit for controlling the phase of a channel clock based on the output of the phase control data generation circuit. With this structure, it becomes possible to provide the phase correction circuit for a disk reproduction device which can generate a sampling clock even when there is a flaw, etc. in a fixed pattern area of the magneto-optical disk, by making a correction so as to avoid or reduce influence by the flaw, etc., and to provide the disk reproduction device using the circuit.

Abstract: A circuit in an optical read/write device for protecting synchronizing patterns is proposed. The protection circuit utilizes a clock with constant frequency as a reference clock. The circuit for protecting synchronizing patterns of this present invention includes a SYNC detector, a frame period counter, a valid-frame-period judgment unit, a frame period memory, a window generator, a real SYNC judgment unit, a SYNC lock judgment unit, and a SYNC signal generator. The circuit counts the pulse number of a reference clock with constant frequency for each frame to get a constant frame period. Then, the circuit can correctly interpolate the lost frame SYNC signal immediately by counting the reference clock, when the disk is defected.

Abstract: An apparatus for reproducing information that has been digitally recorded on a storage medium includes first and second waveform equalizers. The first waveform equalizer equalizes a read signal, corresponding to the information read out from the storage medium, thereby outputting a first equalized signal. The second waveform equalizer has an equalization characteristic different from that of the first waveform equalizer, outputs a second equalized signal and is selectively used to extract a read clock signal.

Abstract: A defect protecting circuit and a method for data slicer in an optical drive is disclosed. As a defect occurs in a disk, the gain of the data slicer is switched to a high gain. After the defect does not occur further, the gain is switched back to a normal gain. Therefore the slicing level can return back to a correct slicing level for reducing incorrect data after the defect terminates, and the jitter in the output data is also reduced.

Abstract: A signal of a run-length-limited code is reproduced from a recording medium. The reproduced signal is sampled to generate a sampling-resultant signal. An odd-sample signal and an even-sample signal are generated in response to the sampling-resultant signal. A first transversal filter subjects the odd-sample signal to first partial-response waveform equalization to generate an equalization-resultant odd-sample signal. The first partial-response waveform equalization depends on first tap coefficients. The first tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant odd-sample signal. A second transversal filter subjects the even-sample signal to second partial-response waveform equalization to generate an equalization-resultant even-sample signal. The second partial-response waveform equalization depends on second tap coefficients. The second tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant even-sample signal.

Abstract: A method and apparatus for real-time derivation of precise digital clock edges and synchronous logic samples from a digital signal having a clock channel and at least one data channel acquires a plurality of temporally offset analog samples during each of a sequence of sample periods and from consecutive samples where there is a logic level transition estimates an edge time. From the edge times for the clock channel an offset is added and applied to the at least one data channel to determine the synchronous logic samples for the data channel at each offset clock edge time.

Abstract: A read channel apparatus is disclosed for reading data recorded on an optical storage system at a predetermined baud rate. The apparatus asynchronously samples an analog read signal generating from the optical storage system and subtracts an estimated DC offset from the asynchronous sample values to generate a sequence of asynchronous DC-removed sample values. The asynchronous DC-removed sample values are separately interpolated by two interpolators to generate a sequence of synchronous even-time sample values and a sequence of synchronous odd-time sample values respectively. The synchronous even-time and odd-time sample values are separately equalized by two equalizers in accordance with a target spectrum to generate a sequence of even-time equalized sample values and a sequence of odd-time equalized sample values respectively. A DC offset estimator generates the estimated DC offset from the even-time equalized sample values and the odd-time equalized sample values.

Abstract: An apparatus and method for generating a radio frequency (RF) signal and control signals are provided. In an apparatus for generating a radio frequency (RF) signal and control signals in which the current output from a plurality of light receiving elements is converted into voltage signals and the RF signal and the control signals are generated in response to the voltage signals, the apparatus includes an input data processing unit, a digital filter, a servo signal generating unit, a digital RF data generating unit, and a reference comparator. The input data processing unit performs time-sharing sampling on the voltage signals and converts the voltage signals into first digital signals in response to an analog/digital conversion clock signal having a predetermined period and a sequentially applied selection signal. The digital filter filters each of the first digital signals to modify the shape of the waveforms of the first digital signals and outputs the modified waveforms as second digital signals.

Abstract: In an apparatus for recording information to an optical recording medium, a laser beam is irradiated to and reflected from the medium. A photodetector detects the light quantity of the irradiated or reflected light beam, and the detected laser beam is subjected to signal processing. Then, a sampler samples the laser beam at the timing of a sampling pulse which is supplied from a sampling pulse generator. Then, a controller controls the laser power according to the sampled laser beam. A pulse timing setting unit sets and adjusts the timing of the sampling pulse by taking into account the response time in the propagation path of the laser beam from the start of the irradiation to the sampling. Thus, the laser power can be monitored correctly, and the laser power can be optimized so as to stably and reliably reproduce an address signal and to generate a servo signal while data is being recorded.

Abstract: The apparatus and method for transferring audio data to a data recorder adopting a personal computer bus to receive audio data enters into data communication mode over a bus without conducting preparation steps for transferring data when a record request is received. The preparation steps include occupying the bus and issuing packet commands. Real-time data such as an audio signal are transferred with no delay to a general optical disk driver satisfying the personal computer (PC) bus interfacing requirement. This allows adoption of a general disk driver for data recording instead of an exclusive audio disk driver, thereby reducing manufacturing cost of a digital audio recorder and enabling the disk driver installed in a digital audio recorder to be used in other devices such as a PC.

Abstract: A first signal is read from a first track of a recording medium. A second signal is read from a second track of the recording medium which neighbors the first track. A filter processes the second signal into a filtering-resultant signal according to a controllable filtering characteristic. A first subtracter operates for subtracting the filtering-resultant signal from the first signal to generate a subtraction-resultant signal. A peak detector generates peak-point information representing a timing at which the level represented by the first signal peaks. A temporary decision circuit implements a temporary decision about the subtraction-resultant signal. A second subtracter generates an error signal indicative of a difference between the subtraction-resultant signal and a signal representative of the result of the temporary decision at a timing equal to the timing represented by the peak-point information. The filtering characteristic of the filter is controlled in response to the error signal.

Abstract: In a data reproducing apparatus, a monitor edge sample value is generated based on a second sample value at a trailing edge of the reproduction signal and a change amount of the monitor edge sample value is generated as an offset amount in a first processing part. Then, the offset amount is supplied to a second processing part where the second sample value is obtained by sampling the reproduction signal at the trailing edge. Then, the second processing part restores data based on the reproduction signal and the offset amount.

Abstract: A system and method for reading and writing in a multilevel optical data system is disclosed. The system provides control signals for timing acquisition, level calibration, DC control, AGC, equalizer training and data synchronization. The user data is ECC protected and optionally convolutionally encoded before being combined with the control signals in an information block. The multilevel information block can be written to an optical disc as a series of multilevel marks. The optical disc may also contain an Address in Pregroove signal (AIP) to facilitate synchronization during writing of an information block. The AIP signal has an integer number of address frames per information block.

Abstract: Creation and detection of synchronization marks for a multilevel data storage medium is disclosed. A sequence of symbols is generated and the sequence of symbols is written to the multilevel data storage medium. A corresponding sequence may be generated by a detector and correlated with read data to detect the synchronization mark.

Abstract: A recording medium for a disc etc. according to the present invention comprises at least a first recording region in which a first portion of audio signals supplied is recorded and a second recording region in which a second portion of audio signals supplied is recorded. The first and second portions of the audio signals recorded in the first and second recording regions are synthesized and reproduced or selected and reproduced to realize variegated audio reproduction.

Abstract: An asymmetry detection apparatus includes: a clock signal generator for generating a clock signal based on a reproduced signal; an A/D converter for sampling the reproduced signal in synchronization with the clock signal; a determiner for determining whether a level of each of a plurality of sampled data obtained by the sampling operation is equal to or greater than a predetermined level; and a detector for detecting asymmetry in the reproduced signal by using predetermined ones of the sampled data based on an output from the determiner.

Abstract: A system and method are disclosed for reading a multilevel signal from an optical disc. The method includes reading a raw analog data signal from a disc using an optical detector and adjusting the amplitude of the raw analog data signal. A timing signal is recovered from the amplitude adjusted analog data signal and correction is made for amplitude modulation of the raw analog data signal by processing the raw analog data signal and the timing signal.

Abstract: An apparatus and a method to accurately generate a bit clock synchronized with digital data. The apparatus includes an edge detecting unit, a first edge counter, a second edge counter, a first counter, and a bit clock generating unit. The edge detecting unit detects edges of the digital signal. The first edge counter counts a number of the detected edges during a first period. The second edge counter counts the number of the detected edges during a second period. The first counter is reset and counts a system clock if one of the edges is detected during the first period. The bit clock generating unit generates a bit clock based on a count value of the first counter or a channel bit interval, if one of the first edge count value and the second edge count value is equal to a first predetermined value.

Abstract: According to the present invention, a data reproduction apparatus sampling, at a given rate, a reproduced signal obtained from a recording medium and complying with a partial response waveform, and reproducing data from sampled values of the reproduced signal in accordance with the Viterbi decoding algorithm includes difference value calculation means for calculating a difference between compared ones of path metric values in selecting paths, alternative path selection means for selecting a path different from a corresponding one of the paths, which are selected in accordance with a given rule, as an alternative path based on the difference between the compared ones of the path metric values, and reproduced data determination means for determining data to be reproduced based on the paths selected in accordance with the given rule and the alternative path.

Abstract: In a digital modulation method, digital data is supplied to a conversion table, and the digital data is converted into serial data. The serial data is supplied to a first fixed contact of a selector and is switched to data for a sync pattern from a sync pattern table, the sync pattern being supplied to a second fixed contact. From the selector, 93-data serial data including the 2-data sync pattern at the head thereof is extracted. The serial data is supplied to an exclusive-OR circuit, and the exclusive-OR output is fed back through a delay circuit, thereby generating NRZI data to be recorded. A digital sum value (DSV) of the NRZI data varies in accordance with the selection of conversion tables. The DSV is arbitrarily controlled, and sub-information is inserted by performing the control in a predetermined format.

Abstract: A data recording device comprises a block division unit dividing a sequence of user data blocks into first blocks and second blocks, a plurality of multi-level data generating units generating multi-level data blocks from the first blocks and the second block, a group data storage unit storing first and second groups of code data corresponding to one user data block, a plurality of averaging units each calculating an average of DC levels based on the multi-level data of one of the blocks, a level comparison unit comparing each of the DC level averages with a predetermined value; a revision data generating unit generating a revision data using a result of the comparison, a data selection unit selecting one of the first and second groups of code data, and an output storage unit storing the first blocks, the second blocks generated using the selected code data, and the revision data.

Abstract: A sample of an information signal is periodically generated in response to a sampling clock signal. A level relation between successive ones of the information-signal samples is detected. A peak-corresponding sample is detected among the information-signal samples in response to the detected level relation and in response to a prescribed level range containing a “0” level. A level represented by the detected peak-corresponding sample is outside the prescribed level range. Calculation is made regarding a level difference between information-signal samples immediately preceding and immediately following the detected peak-corresponding sample. A phase error signal is generated in response to the calculated level difference. The sampling clock signal is controlled in response to the phase error signal to lock the sampling clock signal in phase with the information signal.

Abstract: An apparatus and related operating method for generating slice levels adapted to an optical system is disclosed. The apparatus basically encompasses a multiplexer, a low-pass filter, a digital signal processor (DSP), a digital-to-analog converter, and a comparator. In the beginning of the track-crossing operation, the optical system will enter the first DAC mode that a pre-stored slice level derived from a calibration process is accessed and converted by the digital-to-analog converter before being referred as the slice level in the first DAC mode. When the low-pass filter can follow the RFRP signal variations, the low-pass filter is used to receive the RFRP signal and derive the slice level in the low-pass-filter mode. When a track-on command is given, the optical system will enter the second DAC mode and find an average value of the last peak-hold and bottom-hold values derived at the end of the low-pass-filter mode.

Abstract: An information recording/reproducing apparatus, which includes a binary/multi-level data converting unit converting binary data into multi-level data, a test data generating unit generating test data forming part of the multi-level data, a data recording unit recording the multi-level data including the test data to an information recording medium, a signal reproducing unit outputting reproduction signals of the multi-level data including the test data from the information recording medium, a test data examining unit examining the reproduction signals of the multi-level data including the test data to determine whether the test data is normal, a waveform equalization unit equalizing a waveform of the examined test data when the test data examining unit determines that the test data is normal, and a multi-level determining unit determining multi-level data by referring to a pattern table generated using the examined test data.

Abstract: The present invention provides a control loop bandwidth adjusting system for adjusting a control loop bandwidth of an optical reproducing device. The optical reproducing device comprises a data signal processing circuit, which uses the control loop bandwidth to process the data signal. The control loop bandwidth adjusting system comprises a control loop bandwidth generator for generating the control loop bandwidth and a control loop bandwidth adjusting module for adjusting the control loop bandwidth according to whether a defect signal corresponding to the defective data is received or not. If the control loop bandwidth adjusting module receives the defective data entry signal, the defective data duration signal, and the defective data exit signal, the control loop bandwidth is adjusted to a first bandwidth value, a second bandwidth value, and a third bandwidth value respectively.

Abstract: An optical reproducing method using an optical medium having a disk-like substrate with plural levels associated with grooves, and a plurality of zones. Each track is divided into a plurality of recording and radially adjacent recording units of a respective zone are delimited by a pair of radial lines joined to form a central angle at an apex proximate to a center of the disk-like substrate. The grooves are wobbled in the radial direction of the disk-like substrate with a length of each recording unit being an integer multiple of a cycle of the wobble, and the integer multiple being the same for the different zones. An optical spot is irradiated on the optical medium, a reflected beam from the optical medium is detected, and information on the optical medium is reproduced by using a signal obtained by the reflected beam.

Abstract: A phase adjusting circuit (128) detects an amount of phase shift of a reproduction signal RFn sampled in synchronization with clock CLKn−1 from a waveform equalizing circuit (108), and corrects clock CLKn−1 in accordance with the amount of phase shift to produce a corrected clock RCLKn. A clock setting circuit (127) arithmetically determines a moving average of the clock CLKn−1 and the corrected clock RCLKn to produce a clock CLKn used for sampling reproduction signal RFn. The clock setting circuit (127) arithmetically determines the average of n phases of n clocks CLKn, and sets the clock having the average phase as the reproduction clock. Consequently, it is possible to produce the clock allowing accurate sampling of the reproduction signal reproduced from the optical disk.

Abstract: A disk apparatus (10) includes a spindle (62) to which a magnetooptical disk (60) is attached. An FCM is formed on the magnetooptical disk (60) along a track at intervals of a predetermined period, a laser beam having a different light amount depending on a time of an execution and an interruption of a recording process is incident upon the track. The FCM signal detection circuit (36) detects an FCM signal based on the laser beam reflected from the track, a comparator (42) compares a level of the FCM signal and a slice level, and a PLL circuit (54) generates a clock signal based on a comparison result by the comparator (42). When a change request between an execution/interruption of the recording process is applied, a predetermined first slice level is set to the comparator (42) until 200 mili seconds passes since a reception of the change request. When 200 mili seconds passes, a second slice level calculated based on a peak level of the FCM signal is set to the comparator (42).

Abstract: To provide an asymmetry correcting circuit capable of canceling an asymmetry simultaneously with quantization in an ADC and utilizing the dynamic range of the ADC effectively, and also to provide an information reproducing apparatus using such a correcting circuit.

Abstract: In a PLL circuit, a phase error of a reproduced signal is extracted in either a way based on a zero-cross timing or a way based on a self-running timing. A decision is made as to whether the reproduced signal is in a continuous-wave interval where an inversion period of the reproduced signal remains constant or in a random-wave interval where the inversion period of the reproduced signal varies at random. When the reproduced signal is in a continuous-wave interval, a phase error is extracted on the self-running-timing basis. When the reproduced signal is in a random-wave interval, a phase error is extracted on the zero-cross-timing basis. A continuous-wave interval may be replaced by a specified-pattern repetition interval where the inversion period of the reproduced signal changes in accordance with a repetition of a specified pattern.

Abstract: An optical disc drive usable with discs to which data is continuously recorded and discs having a sector format can quickly resume playback signal output after passing imperfection causing potential reading errors, and plays disc with few read errors. A detection signal generator detects DC level fluctuation in the playback signal read from the disc and generates a detection signal tracking the DC level fluctuation. A selector selects a detection signal or a null signal without valid polarity based on the detection signal generated by the detection signal generator and input to the selector. A clamping unit performs a clamping process to suppress DC level fluctuation in the playback signal based on the detection signal when the selection unit selects the detection signal, and does not perform the clamping process when the selection unit selects the null signal. A signal processor performs specific signal processes based on clamping unit output.