Abstract: An analog filter is placed at a stage previous to an analog-digital converter (ADC), and a waveform equalizer is placed at a stage subsequent to the ADC. The sampling frequency of the ADC is determined by a clock generation section according to the relationship between the bit rate of an input reproduction signal and the characteristic of the analog filter. The number of taps is changed according to the relationship between the bit rate of the input reproduction signal and the characteristic of the analog filter. Further, the tap coefficients of a waveform equalizer are changed according to the height of the frequency band of the input reproduction signal. A waveform evaluation section generates a signal that evaluates a waveform equalization signal transmitted from the waveform equalizer to a Viterbi decoder, whereby adaptive waveform equalization is realized.

Abstract: A method for adjusting a reference level of an analog signal from a plurality of periodically sampled points includes the following steps. Firstly, a first level shift from an preliminary reference level to the last second sampled point within a specified period and a second level shift from the preliminary reference level to the last sampled point within the specified period is determined when one of a first level of the last second sampled point and a second level of the last sampled point is higher than the preliminary reference level and the other is lower than the preliminary reference level. Then, the preliminary reference level is moved toward the first level when an absolute value of the first level shift is greater than an absolute value of the second level shift, and the preliminary reference level is moved toward the second level when the absolute value of the first level shift is less than the absolute value of the second level shift, thereby defining an adjusted reference level.

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: 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: A first set of data is detected in a signal having synchronous samples and interpolated samples, wherein the first set of data is detected asynchronously as corresponding to one of the samples. A time to transmit a data-found signal is determined based on an offset between the data-detected sample and one of the synchronous samples, and the data-found signal is transmitted at the determined time to enable the synchronous processing of the synchronous samples. In one implementation, the synchronous samples correspond to a readback signal read from a data recording channel, the first set of data corresponds to servo address mark (SAM) data in a servo sector in the readback signal, and the synchronous processing is demodulation of burst data in the servo sector.

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: The present invention relates to a disk recording medium such as a CD or a DVD in which data is recorded in high-density, and method and apparatus for reproducing data recorded in the high-density disk recording medium. The data reproducing method and apparatus according to the present invention converts a high-frequency signal reproduced from the disk into a plurality of binary signals through comparing the reproduced signal with two or more slicing levels which are different each other, selects one of the plurality of binary signals or a periodic pulse signal based on the difference magnitude between the plurality of binary signals, synchronizes a reference clock with the selected signal, and restores the selected signal into bit stream using the synchronized reference clock.

Abstract: A dynamic compensation device for radio frequency ripple signals of an optical storage system is disclosed. The device is composed of a radio frequency ripple signal process circuit, a radio frequency signal process circuit, a radio frequency signal peak detector, a first analog to digital converter, a second analog to digital converter, a defect detector, and a fingerprint detector. The drop-out of the central level of the radio frequency ripple signal is eliminated, and the track cross waveform is prevented from being damaged.

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 bi-phase mark reproduction apparatus which reduces an error rate of demodulated data by half and improves demodulation ability of ATIP and an optical disk drive device are provided. The bi-phase mark reproduction apparatus includes a data conversion unit which takes out a synchronous code portion, a data portion and an error detection code portion from a bi-phase mark input signal by means of a data separating signal and demodulates data of the data portion and the error detection code portion. The data conversion unit includes a pattern retrieval unit which detects a predetermined error pattern contained in the data portion and a conversion table which decodes the error pattern in accordance with a replacement rule based on bi-phase mark modulation.

Abstract: The invention has an object to provide a disk evaluation apparatus capable of performing a highly reliable disk evaluation even on a recording disk on which information is recorded in high density. Amplitude-limited read sample value sequence are obtained by limiting read sample value sequence to a predetermined amplitude limit value, the read sample value sequence obtained by sampling a read signal read out from the recording disk as timed to a clock having the same frequency as that of a channel clock. Where a gap between a maximum sample value and a minimum sample value of the amplitude-limited read sample value sequence is equivalent to a predetermined distance of high-frequency wavelength, the maximum sample value and the minimum sample value are increased thereby to obtain high-frequency enhanced read sample value sequence enhanced at the high region thereof.

Abstract: A method for locating an electric level distribution range of sampled signals is provided. The electric level distribution range includes a plurality of reference levels. Firstly, a plurality of initial values are provided. Then, each of the sampled signals is corresponded to one of the plurality of initial values, which is closest thereto. Then, the initial values corresponded are and adjusted by the sampled signals according to a predetermined operation, thereby realizing the reference levels. A method for recovering data from an optical storage medium is also provided. The signals associated with data from an optical storage medium are firstly sampled. Then, an electric level distribution range of the sampled signals is located. Afterwards, the sampled signals are decoded to recover data according to the electric level distribution range.

Abstract: When an optical disc is set to the motor, the slice level is set to a slice level Sk as a reference slice level and a measured jitter value A (S0, S1) is produced. The slice level is incremented in steps of a fixed quantity Si (S2). Then, a measured jitter value B obtained at the incremented slice level is compared with the previous measured jitter value A (S3, S4). This sequence of process is repeated, and when the measured jitter value A is smaller than the counter value, it is judged that the jitter changes its quantity varying direction to a decreasing direction. Then, the incrementing operation of the slice level is immediately stopped, and the slice level is decremented in steps of another fixed quantity Sd (<Si). The previous measured jitter value C is compared with a measured jitter value D after the slice level is decremented (S5 to S8). When the measured jitter value C is smaller than the counter jitter value, it is judged that the slice level detected at that time is an optimum slice level.

Abstract: An optical recording apparatus for recording a plurality of information units on an optical storage medium. Each of the information units includes a long run-length sync pattern. The optical recording apparatus includes a recording means for recording the plurality of information units on the optical storage medium and a sync pattern selector for determining the type of each of the long run-length sync patterns. The sync pattern selector determines at least one long run-length sync pattern as a mark when marks with run-lengths longer than a first length threshold do not appear for a time period longer than a first time threshold. The sync pattern selector determines at least one long run-length sync pattern as a space when spaces with run-lengths longer than a second length threshold do not appear for a time period longer than a second time threshold.

Abstract: In a data reproduction method and apparatus of the present invention, a Viterbi detection unit is provided, the Viterbi detection unit having a plurality of detectors each providing a first partial response signal with a first constraint length from a first sequence of samples derived from a first readout signal. One of connection and disconnection of the plurality of detectors in the Viterbi detection unit is selected in response to a timing signal, wherein, when the connection of the plurality of detectors is selected, the Viterbi detection unit provides a second partial response signal with a second constraint length from a second sequence of samples derived from a second readout signal, the second constraint length being different from the first constraint length.

Abstract: An optical disc playback apparatus that performs appropriate waveform equalization according to a difference in characteristics of reproduced signals between land parts and groove parts in an optical disc to which high-density recording is performed using a land/groove recording method. The optical disc playback apparatus includes a reproduction device, an A/D conversion circuit for sampling a reproduced signal to be converted into a multi-bit digital signal, a filter for subjecting the multi-bit digital signal to digital equalization, a filter coefficient learning device for adaptively controlling filter coefficients for the filter corresponding to the land part and the groove part to minimize an equalization error, and a switch signal generation device for generating a signal for switching between land and groove, thereby changing the filter coefficient adaptively to the land or the groove.

Abstract: A data reproducing apparatus and method for improving data detection performance by adjusting decision levels used in a data detector. The data reproducing apparatus includes an equalizer which equalizes an input digital signal, a data detector which detects data from the output of the equalizer based on decision levels, and a level decision unit which detects levels corresponding to the decision levels used in the data detector from the output of the equalizer and feeds back corrected decision levels, which adaptively vary with the output level of the equalizer, to the data detector. Accordingly, the detection performance of the data detector is improved.

Abstract: A method and apparatus for playing compressed audio compact discs in a CD player is provided in which compressed audio data is cached in the local memory of the CD player. If a sufficient amount of compressed audio data is cached in the local memory of the CD player, the CD player can be placed in a reduced power state, reducing the consumption of power by the loader of the CD player. The determination of whether a sufficient amount of compressed audio data is present in the local memory of the CD player is made on the basis of a comparison of the playback time of the unaccessed cached audio and the restart time of the CD player.

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: The optical disk apparatus is provided with a Viterbi decoder and an expected value correction circuit. The branch metric operation unit calculates first, second and third errors between sampling data and expected values, and outputs them to the expected value correction circuit. The expected value correction circuit extracts the sampling data in a region where its variation is small based on the first, second and third errors, calculates the average values of the extracted sampling data to correct the first, second and third expected values, and outputs the corrected expected values to the branch metric operation unit. The Viterbi decoder performs Viterbi decoding of the sampling data based on the first, second and third corrected expected values. Thus, high-precision Viterbi decoding is permitted even if the amplitude value of the reproduction signal varies.

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: Methods and apparatus for recording on DVD-like recording media in which audio content is stored in a high-capacity multi-channel (e.g., six-channel) format are provided. Various channels may use various resolutions. A two-channel audio output may be derived from the multi-channel audio data stream during playback. To facilitate an accurate derivation, the mixing coefficients to be used in generating the derivation can be supplied along with the six-channel audio data.

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: A binarizing device operates for controlling a slice level relative to a DC level of a reproduced signal in response to a slice level control signal to generate a controlling-resultant slice level, and for comparing the reproduced signal with the controlling-resultant slice level to convert the reproduced signal into a binary signal. A signal generating device operates for generating the slice level control signal in response to the binary signal. An offset detecting device operates for detecting an offset in a modulation-resultant-code pattern in response to the binary signal, and for generating code pattern offset information in response to the detected offset. An offset-responsive controlling device operates for implementing one of (1) changing a response characteristic of a loop formed by the binarizing device and the signal generating device and (2) suspending the slice level control by the binarizing device in response to the code pattern offset information.

Abstract: A signal is reproduced from a recording medium. The reproduced signal is sampled in response to a clock signal to get a sampling-resultant signal. A transversal filter includes a delay line having taps and delaying the sampling-resultant signal, multipliers for multiplying only alternate ones among signals appearing at the taps by tap coefficients to get multiplication results, and an adder for adding the multiplication results into a filtering-resultant signal. A temporary decision device operates for calculating a temporary decision value of the filtering-resultant signal according to a temporary decision procedure, for calculating a difference between the temporary decision value of the filtering-resultant signal and an actual value thereof, and for generating an error signal in response to the calculated difference. The tap coefficients used in the transversal filter are controlled in response to the error signal and the reproduced signal to minimize the error signal.

Abstract: A recording medium, such as an optical disk, a recorder for recording data on the recording medium, and a player for playing back the data are described. Music information can be recorded on the recording medium with higher sound quality than that achieved by a conventional compact disk, and the music information can be played back with higher quality than that achieved by the conventional compact disk. Further, the recording medium can be played back through use of a conventional CD player. The recording medium has two recording layers, i.e., layer A and layer B. Conventional CD data are recorded on the layer A, and data for complementing the CD data are recorded on the layer B. The two data sets are merged into a single data set during playback, thereby enabling playback of data in higher quality and resolution than the CD data.

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 present invention provides a method and system for calibration of writing to an optical medium. The method includes: sampling marks in a calibration area of the optical medium; and converting the sampled marks into a digital format utilizing an ADC, the ADC also utilized by a servo control. The present invention provides a controller with an integrated servo and recording processor which allows a single ADC to be used for converting sample marks used in calibrating the writing to an optical media. No separate subsystem for converting sample marks is thus necessary. Less components are required, reducing the cost of manufacturing the controller. With less components, the risk of component failure is reduced as well.

Abstract: A method and apparatus in an optical disk system employing a decision feedback equalization (DFE) technique to provide a boosted signal resolution at a data slicer input while minimizing noise. In one embodiment, an optical equalizer includes a feed forward equalizer (FFE) that equalizes the signal from the optical disk and provides an equalized signal and a feedback equalizer (FBE) that generates a feedback signal. The feedback signal is subtracted from the equalized signal to provide a signal having increased resolution and low noise, which is then applied to a data slicer. In one embodiment, the boost provided by the FFE is lower than in conventional equalizers to minimize noise. As the boost of the FFE is reduced, the number of taps in the FBE is increased to provide optimized system performance.

Abstract: Disclosed herein is a technology that enables stable and high-speed writing and/or reading in an optical disk apparatus. The optical disk apparatus has an optical head that includes a first circuit for driving a laser diode, a second circuit for sampling and holding analog electric signals that are based on reflected laser light from the optical disk, and a third circuit for converting said signals being sampled and held into digital signals. Signals digitized in the optical head are transmitted to the apparatus body side using time-division multiplexing. The first circuit, the second circuit, and the third circuit are constructed on a single substrate or in a single IC.

Abstract: A reproduction signal evaluation method of this invention includes the step of obtaining a reproduction signal from an information recording medium on which digital information is recorded with record marks having different sizes, the step of obtaining the amplitude of a first reproduction signal, of the signals contained in the reproduction signal, which reflects digital information recorded with a record mark having the maximum size, the step of obtaining the amplitude of a second reproduction signal, of the signals contained in the reproduction signal, which reflects digital information recorded with a record mark having the second smallest size, the step of obtaining an evaluation value from the ratio of the amplitudes of the first and second reproduction signals, and the step of evaluating a characteristic of the reproduction signal on the basis of the evaluation value.

Abstract: The invention has an object to provide a disk evaluation apparatus capable of performing a highly reliable disk evaluation even on a recording disk on which information is recorded in high density. Amplitude-limited read sample value sequence are obtained by limiting read sample value sequence to a predetermined amplitude limit value, the read sample value sequence obtained by sampling a read signal read out from the recording disk as timed to a clock having the same frequency as that of a channel clock. Where a gap between a maximum sample value and a minimum sample value of the amplitude-limited read sample value sequence is equivalent to a predetermined distance of high-frequency wavelength, the maximum sample value and the minimum sample value are increased thereby to obtain high-frequency enhanced read sample value sequence enhanced at the high region thereof.

Abstract: Reproduced signals are equalized by the least square technique by using a predetermined number of data samples binarized by a Viterbi decoder. Even when data written on an optical disk is unknown, the data can be equalized in a stable manner and can be reproduced at a low error rate without instability factors such as divergence due to interference.

Abstract: The object of the present invention is to realize reduction of the level jitter generated from a noise component at a signal saturation level or a waveform distortion in a portion except for signal polarity portions (rising edge and falling edge), and good error characteristics. In the present invention, a predetermined upper or lower limit value is set to reproduction signals, the reproduction signals are subjected to a limiter processing for correcting reproduction signals of the upper limit value or more, or the lower limit value or less to the level of the upper limit value or the lower limit value, respectively, the signal subjected to the limiter processing is subjected to a partial response equalizing (PR equalizing) processing, and PR reproduction is performed to improve the level jitter at PR detection time and the error rate at information reproduction time.

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: A method and apparatus in an optical disk system employing a look-ahead data detection technique is described where an optimum detection is achieved with a minimum hardware complexity. In one embodiment, the boundary functions and the corresponding boundary decisions are derived for next state determination using only the minimum distance event pair for each state over the look-ahead samples, thereby reducing the detector hardware significantly relative to the Viterbi counterpart where the most likely occurring path is searched at every state. Depending on the sample quality, the limits for the boundary decisions can be programmable to combat the channel impairments like misequalzation, signal asymmetry, etc.

Abstract: A recording medium, such as a high-density and/or read-only recording medium, such as BD-ROM, which includes copy protection information for preventing illegal copying of the contents recorded on the recording medium, and to methods and apparatuses for forming, recording, and reproducing data on the recording medium.

Abstract: A pit data generation circuit generates a first clock signal synchronized with pit data and a pit synchronization signal from a sum read signal obtained by reading the length of a pit. A division circuit generates a second clock signal by frequency-dividing the first clock signal. The division circuit is reset by the pit synchronization signal, and is capable of adjusting the phase of the second clock signal.

Abstract: An information recording and reproducing apparatus performs information recording and reproducing on an optical disc having a recording track wobbled by a predetermined frequency, such as a DVD-RW.

Abstract: An optical recording medium such as an optical disc and an apparatus for recording/reproducing data on or from the medium are provided. Data of various information such as copy protection information, disc type identification, main disc information or the like is recorded on the side (or peripheral edge) of an optical disc such as a CD, a DVD or a BD. When the optical disc is loaded, data recorded on the side of the optical disc is read and a playback operation is performed according to the read data. Various additional information can be effectively recorded on the side of the optical disc without reducing the recording capacity. When an optical disc is loaded, it is possible to determine the disc type of the optical disc more rapidly. Main information such as copy protection information can be effectively prevented from being easily copied.

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 optical disc device serving as an information memory and reproduction device includes: an A/D converter for performing sampling to an analog signal to convert the analog signal into a first digital signal, which has been offset-adjusted, using an n times higher frequency than that of a channel clock (where n is 2 or a larger integer than 2); and a digital equalizer for digitally performing wave-form equalization of a reproduction signal, which has been converted into the first digital signal, and outputting a second digital signal. In this manner, wave-form equalization is performed to the digital signal which has been A/D converted, so that a small circuit configuration can be obtained. Moreover, oversampling is performed, thus equivalently improving a resolution when A/D conversion is performed.

Abstract: A clock generator in a recorded information reproduction apparatus for reproducing recorded information from a recording medium includes a pickup that produces a reading signal by reading a recording track of the recording medium. The reading signal is sampled by a sampling circuit at timing corresponding to a clock signal to produce a reading sample value sequence. A crosstalk removing circuit removes crosstalk components which are present in recording tracks adjacent to the recording track read by the pickup from the reading sample value sequence and produces a crosstalk-removed reading sample value sequence. A phase detecting circuit detects a phase error existing in the reading signal based on the crosstalk-removed reading sample value sequence. A clock signal generating circuit generates the clock signal based on the phase error.

Abstract: A digital signal recording disc has a first area and a second area. The second area differs from the first area. The first area stores a first-channel digital audio signal and a second-channel digital audio signal. The first-channel digital audio signal results from quantizing a first-channel analog audio signal with a first quantization bit number. The second-channel digital audio signal results from quantizing a second-channel analog audio signal with a second quantization bit number. The second area stores information of the first and second quantization bit numbers.

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 method and apparatus for detecting information recorded as a phase-modulated wobble along a track of an optical disk, whereby a reference phase section is recorded with wobble having a predetermined reference phase and whereby respective polarities of phase integration values obtained by synchronous detection of phase-modulated unit sections following the reference phase section, in a playback wobble signal, are compared with the polarity of a reference phase integration value obtained for the reference phase section, to thereby detect respective bit states expressed by the phase-modulated unit sections.

Abstract: A data recording method for calculating a digital sum value (DSV) corresponding to a proportion of positive data and negative data included in predetermined data ranges, selecting a resync pattern to be inserted between the data ranges according to the DSV, and inserting the selected resync pattern between the data ranges, has a step of selecting a resync pattern that minimizes differences in DSV between the data ranges.

Abstract: A PLL circuit is disclosed which extracts phase difference information of a high S/N ratio from a readout signal uses the phase difference information for PLL control. An A/D converter samples the input signal to produce a digital signal. A pattern string detector identifies a type of an input pattern string formed from a plurality of successive sample values successively outputted from the A/D converter and outputs pattern string identification information which indicates an identification result. A phase difference generator outputs phase difference information which indicates a phase error of the output of the A/D converter based on the pattern string identification information and the output of the A/D converter. A loop filter, a D/A converter and a voltage controlled oscillator generate a clock signal from the phase difference information to control the sampling timing of the A/D converter.

Abstract: A data reproduction apparatus that employs an expected value generation unit that employs a maximum likelihood decoding algorithm, thereby an expected value is correctly determined from a histogram of sampled values of a signal to be reproduced, even when an offset arises in the signal to be reproduced, the offset being removed from the sampled values used in generating a histogram that is used to determine the expected value.

Abstract: The present invention realizes stable and more proper data reproduction even when a reproduced signal varies locally due to a noise or includes a steady distortion. In a data reproduction control method and apparatus, and an optical disk unit that adjust sampled values, in sampling a signal reproduced from a recording medium recorded with data, the frequencies of the levels of quantized data are counted, a histogram of the frequencies of the levels is created based on the counting results, and more accurate reproduced data is obtained by means of a distribution of the frequencies of the levels in the histogram.