Abstract: A magneto-optic recording medium, which has a multilayered magnetic layer including a recording layer and a reproducing layer, is capable of reproducing a micro mark by utilizing a temperature distribution generated by laser beam irradiation for transferring a domain wall from the recording layer to the reproducing layer and by utilizing the movement of the domain wall. Each of the recording areas is arranged so that the recording area is adjacent to a magnetic partition area of a neighboring track. The recording areas and the magnetic partition areas are arranged alternately in one track, and an edge of a record mark is positioned in the recording area. Preferably, when reproducing information recorded on this magneto-optic recording medium, two neighboring tracks are irradiated with one laser beam for reproduction so that high speed transmission can be performed.

Abstract: A data reproduction device includes an A/D converter quantizing a reproduction signal read from data recorded on a recording medium to produce quantized data based on a sampling clock; a reproduction signal determination unit determining rising and falling parts of the reproduction signal based on the quantized data, and outputting a gate signal corresponding to a result of determining the rising and falling parts; a leading-edge clock generation unit generating a leading-edge clock signal synchronous to a leading edge indicating a rising part of the reproduction signal; a trailingedge clock generation unit generating a trailingedge clock signal synchronous to a trailing edge indicating a falling part of the reproduction signal; a signal switch unit generating the sampling clock by selecting one of the leading-edge clock signal and the trailing-edge clock signal based on a value of the gate signal; and a signal supply unit supplying the sampling clock to the A/D converter, wherein the data reproduction device

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: An information recording method and an apparatus therefor, wherein a recording compensation controlling unit 1 receives data to be recorded and determines whether a pulse timing adjustment is to be performed or not, and instructs an APC 3 to adjust the timing thereby to advance the pulse start timing of laser light and/or to delay the pulse termination timing when the pulse timing adjustment is to be performed. The recording compensation controlling unit 1 determines the pulse timing adjustment corresponding to the presence or absence of a predetermined “space, record mark”, whereby the positional shift quantity of leading and trailing edges is reduced even for the marks having a fine dimension, and the jitter is reduced.

Abstract: In an apparatus for recording and regenerating data, a pass metric is calculated based on a likelihood converted from a previous calculation result iteratively until all pass metrics of the same data recorded many times on a recording medium are calculated, and then data recorded on the recording medium is decoded.

Abstract: An information reproducing element formed by a plurality of transferring portions sandwiching magnetically insulatable regions is arranged so as to face an information recording medium. A plurality of record marks on the information recording medium are mutually insulatedly transferred onto the information reproducing element. A light beam is irradiated onto the information reproducing element. The record marks recorded by high density recording are then reproduced by magneto-optical reproduction or maximum-likelihood detection.

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 auxiliary magnetic layer for generating a reproduction magnetic field which can be positive or negative in accordance with the front and rear edges of a reproduction waveform is provided on the opposite side of the magnetic layer to the substrate for recording and reproducing data. Consequently, a magnetic field which has an advantageous polarity to each of the front and rear edges of the reproduction waveform functions and both edges can have steep inclinations, which enhances the quality of the reproduction signal.

Abstract: 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.

Abstract: A magneto-optical recording medium which is adapted to realize a partial ROM with remarkable facility in providing software. The magneto-optical recording medium comprises a transparent substrate, a volatile magnetic recording layer formed on the transparent substrate and having a Curie temperature approximately equal to or lower than a temperature raisable in a recording/reproducing apparatus of a user, and a nonvolatile magnetic recording layer formed on the volatile magnetic recording layer and having a Curie temperature higher than the temperature raisable in the recording/reproducing apparatus of the user; wherein the nonvolatile magnetic recording layer is not initialized and is retained in a state immediately after manufacture of the medium.

Abstract: A system reproduces data from an optical disk in which a signal obtained by encoding recording data in accordance with a recording rule including a rule corresponding to a partial response class I characteristic has been recorded. The system includes an optical head for reproducing a signal from the optical disk, an analog-to-digital converter for sampling the signal reproduced by the optical head at predetermined timing and for outputting sampling data, a determination unit for determining, based on the sampling data from the analog-to-digital converter, a transition state of data to be reproduced in accordance with a transmission line characteristic of the reproduction system for the optical disk, and a data decision unit for deciding maximum likelihood reproduction data at present timing based on the determination result obtained by the determination unit.

Abstract: A reading method and reading apparatus for a magneto-optical recording medium designed to modulate an applied magnetic field. The magnetic field corresponds to the leading and trailing edges of a reproduction signal so that when reading data a magnetic field may be applied in a direction of steep inclination of the edges of the waveform of the reproduction signal.

Abstract: To provide a magneto-optical reading method of making the inclinations of the front and rear edges of a waveform of a reading signal formed on a magneto-optical recording medium to be read more symmetric by applying a reading magnetic field different in accordance with the direction of a recording magnetic field when reading the recording marks to which recording magnetic fields in different directions are applied for recording because the present ranges of the front and rear edges are previously determined.

Abstract: A data reproduction apparatus assuring compatibility of optical disks capable of reproducing both pit-position recorded data and edge-position recorded data in optical disks by digital operation by using digital values obtained by sampling reproduction signals. A reproduction signal obtained by an optical head is converted into a digital value by a first A/D converter, and on the basis of the converted digital value, pit-position recorded data is recorded by a pit-position detector. Moreover, the reproduction signal obtained by the optical head is converted into digital values by first and second A/D converters, and on the basis of the converted digital values, front edge and rear edge maximum likelihood decoded data of edge-position recorded data are detected by first and second maximum likelihood detectors, and both maximum likelihood decoded data are synthesized by a synthesizer.

Abstract: A magneto-optical recording medium which is adapted to realize a partial ROM with remarkable facility in providing software. The magneto-optical recording medium comprises a transparent substrate, a volatile magnetic recording layer formed on the transparent substrate and having a Curie temperature approximately equal to or lower than a temperature raisable in a recording/reproducing apparatus of a user, and a nonvolatile magnetic recording layer formed on the volatile magnetic recording layer and having a Curie temperature higher than the temperature raisable in the recording/reproducing apparatus of the user; wherein the nonvolatile magnetic recording layer is not initialized and is retained in a state immediately after manufacture of the medium.

Abstract: A magneto-optic disk recording system capable of canceling shifts of the front edge and the rear edge of the record mark due to accumulation of heat. The recording system includes a magneto-optic disk having a record magnetic film, and a magnet for applying a bias magnetic field to the disk in the direction perpendicular thereto. The recording system further includes a laser diode for generating laser beams, an optical head for focusing the laser beam on the disk, a pulse generator for generating square wave pulses with a predetermined period, and a duty ratio controller for alternately increasing and decreasing the duty ratio of the square wave pulses every time data "1" of binary record data is generated. The laser diode is driven by a constant-current circuit for write power. There is connected a switch between the laser diode and the constant-current circuit for write power.

Abstract: A system reproduces data from an optical disk in which a signal obtained by encoding recording data in accordance with a recording rule including a rule corresponding to a partial response class I characteristic has been recorded. The system includes an optical head for reproducing a signal from the optical disk, an analog-to-digital converter for sampling the signal reproduced by the optical head at predetermined timing and for outputting sampling data, a determination unit for determining, based on the sampling data from the analog-to-digital converter, a transition state of data to be reproduced in accordance with a transmission line characteristic of the reproduction system for the optical disk, and a data decision unit for deciding maximum likelihood reproduction data at present timing based on the determination result obtained by the determination unit.

Abstract: An optical recording medium in which a medium identification code is recorded as a nonvolatile mark which is formed through irreversible change of a recording film, such as magnetization characteristic change, deformation and formation of a hole, so as to prevent illegal copying of the optical recording medium, and a recording/reproducing method for the same.

Abstract: A data reproduction apparatus of an optical disk having a maximum likelihood detection system for compensating a stationary edge shift and an edge shift depending on record pattern at the time of reproduction. The edge shift that has not completely been compensated at the time of recording in an optical disk is compensated by controlling an expected value in branch metric calculation of maximum likelihood detection while recognizing the pattern of record data at the time of reproduction. The edge shift amount is measured on the basis of the reproduction signal relative to the VFO area of the optical disk, and an expected value compensation table for showing an optimum expected value in branch metric calculation is selected preliminarily according to the measured amount.

Abstract: A data reproduction apparatus for reproducing data corresponding to front and rear edges of marks is recorded in an optical disk. The apparatus includes an optical head for obtaining a reproduction waveform from the optical disk, an A/D converter for obtaining a real sampling value from the reproduction waveform so as to detect an ascending edge (or a descending edge), an interpolator for obtaining a descending edge (or ascending edge) calculate sampling value through interpolation using the real sampling value, and a maximum likelihood detector for detecting a maximum likelihood signal on the basis of a real sampling value and the interpolated sampling value.