Fujitsu Corporation

Toru Fujiwara

Masakazu Taguchi

Shigenori Yanagi

Satoshi Furuta

Masaharu Moritsugu

Akira Nanba

Tadashi Sagawa

Akiyoshi Uchida

Takashi Masaki

Katsuhiko Fukuda

Toru Ikeda

Kenichi Hamada

Shigeyuki Yanagi

A defect detection device, apparatus, and method for detecting a defect of data recorded on a recording medium. The defect detection device includes a waveform state detection part generating information representing a state of a waveform of a reproduced signal from the recording medium based on soft decision results obtained in a process of reproducing the data in accordance with a maximum likelihood decoding algorithm corresponding to a partial response. The defect detection device includes a defect determination part determining the defect of the recorded data based on the information generated in the waveform state detection part.

Data defect detection using soft decision result

An apparatus for reproducing data includes a branch metric computation unit and a plurality of parallel computation units. Each parallel computation unit includes path metric computation units that compute path metric values based on branch metric values. Path metric memories store the path metric values to be used in a next following path metric computation, and reliability computation units compute path reliability. Modified-path generating units generate an inverted path that is inverse to a path indicated by an output of the reliability computation units as having low reliability. If any one of the modified-path generating units generates the inverted path, a corresponding one of the path metric computation units stores a path metric value corresponding to the inverted path in a corresponding one of the path metric memories as a path metric value to be used in a next following path metric computation.

Data reproducing apparatus avoiding selection of incorrect path

A defect detection device for detecting a defect of data recorded on a recording medium includes a waveform state detection part generating information representing a state of a waveform of a reproduced signal from the recording medium based on soft decision results obtained in process of reproducing the data in accordance with a maximum likelihood decoding algorithm corresponding to partial response, and a defect determination part determining the defect of the recorded data based on the information generated in said waveform state detection part.

A data reproduction device in conformity to Viterbi decoding includes an inverted-selected path generation part for receiving a selected path and an inverted candidate, selecting and modifying the selected path corresponding to the inverted candidate so as to produce a inverted-selected path that is an inverted version of the selected path, and outputting a number of the inverted-selected paths in parallel, the number corresponding to a number of the inverted candidates selected for the selected path of a predetermined data length and a second candidate data generation part for generating second candidate data from the inverted candidate. The device further includes a data selection part for selecting between the first and the second candidate data based on error detecting results.

Data reproduction device

A data reproducing method reproduces data corresponding to a state-transition pass selected as being most likely according to a Viterbi decoding algorithm from a reproduction signal supplied from a recording medium. The data reproducing method comprises the steps of detecting at least one state of the reproduction signal according to data used for selecting the state-transition pass, calculating an average value of the reproduction signal in the state detected by the step of detecting, and following a fluctuation amount of a direct current component of the reproduction signal according to the average value.

Data reproducing method and device reproducing data according to a Viterbi decoding algorithm using an average value of a reproduction signal

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.

Data reproduction method and apparatus

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.

Data reproduction control method and apparatus, and optical disk unit

A data reproduction system, which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, includes an expected value setting unit for variably setting the expected values used for a calculation of the branch metrics in order to perform a Viterbi detection process without being easily affected by the transient response, offset variation, phase error and nonlinear torsion component of the readout signal. The readout signal is obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values are determined by the partial response waveform, and the sampled value is obtained by sampling the readout signal at a predetermined frequency.

System for reproducing data with increased accuracy by reducing difference between sampled and expected values

A clock matching apparatus for a data reproduction system includes a phase error detection unit which detects a phase error of a clock signal based on samples of a readout signal output by a sampler of the data reconstruction system. A phase-locked loop supplies a phase-matched clock signal to the sampler by compensating for the phase error detected by the phase error detection unit. The phase error detection unit includes an edge detection unit which detects a sampling instant for an edge sample among the samples of the readout signal. A difference unit generates a difference in timing phase between the edge sample and a sync level, the sync level being a reference signal level corresponding to a level of the readout signal at the sampling instants thereof and defined based on a partial-response waveform, the difference in the timing phase being output to the phase-locked loop as the detected phase error.

Clock matching apparatus for a data reproduction system

An optical disk apparatus adapted to a mark edge recording method having a structure such that a data pattern experimentally recorded on an optical disk with one write power is reproduced plural times while changing reproducing conditions (for example, a slice level for binary-coding a reproduced analog signal) and the number of errors is calculated whenever the reproducing process is performed. The thus-structured process is repeated for using a plurality of write powers. An appropriate write power for the optical disk is determined in accordance with the obtained results of the calculations of the number of errors. In a case of a read-only optical disk, a data pattern experimentally and previously recorded on the optical disk is reproduced plural times by changing the reproducing conditions (for example, a slice level for binary-coding a reproduced analog signal), and the number of errors is calculated whenever the reproducing process is performed. In accordance with the obtained results of the calculations of the number of errors, an appropriate reproducing condition for the optical disk is determined.

Optical disk having write power adjustment portion

Optical disk apparatus

A disc apparatus has a cartridge loading/unloading mechanism to perform a loading operation for attaching an optical disc enclosed in a cartridge inserted from an outside to a rotary shaft of a spindle motor and an unloading operation for removing the optical disc from the rotary shaft of the spindle motor and for ejecting the cartridge to the outside. The loading operation of the cartridge loading/unloading mechanism is executed by the rotation of one direction of a load motor. The unloading operation of the cartridge loading/unloading mechanism is executed by the rotation in the reverse direction of the load motor. A drive current of the load motor is turned on or off at a short period, thereby adjusting so as to optimize a drive torque. When an exchangeable optical disc is loaded, a motor is activated, an initialization control is executed during the acceleration, and after a motor rotational speed reached a specific speed, the apparatus enables the writing/reading operations to be executed. When a voice coil motor is driven simultaneously with the spindle motor during the initialization adjustment, the drive current of the spindle motor is limited.

Disk apparatus

A disc-apparatus has a cartridge loading/unloading mechanism to perform a loading operation for attaching an optical disc enclosed in a cartridge inserted from an outside to a rotary shaft of a spindle motor and an unloading operation for removing the optical disc from the rotary shaft of the spindle motor and for ejecting the cartridge to the outside. The loading operation of the cartridge loading/unloading mechanism is executed by the rotation of one direction of a load motor. The unloading operation of the cartridge loading/unloading mechanism is executed by the rotation in the reverse direction of the load motor. A drive current of the load motor is turned on or off at a short period, thereby adjusting so as to optimize a drive torque. When an exchangeable optical disc is loaded, a motor is activated, an initialization control is executed during the acceleration, and after a motor rotational speed reached a specific speed, the apparatus enables the writing/reading operations to be executed. When a voice coil motor is driven simultaneously with the spindle motor during the initialization adjustment, the drive current of the spindle motor is limited.

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Kato, Japan

Toru Fujiwara