Abstract: In a crosstalk canceling system for use in an optical disk signal reproducing apparatus, rough delay units roughly adjust a delay amount of reproduction signals and fine delay units finely adjust a delay amount with high precision, and a delay amount control unit controls the delay amounts of the rough and fine delay units so that the jitter of the reproduction signal is minimized.

Abstract: The invention provides an optical disk medium having a recording spiral formed by connecting groove tracks and land tracks alternately, and permitting detection of a connecting point between a groove track and a land track reliably is provided, and a method of tracking the optical disk medium and an optical disk drive apparatus for driving the optical disk medium. One part of an identification signal area is shifted by a predetermined distance in one radial direction from the center of a groove, while another part of the identification signal area is shifted by the same distance in the opposite radial direction from the center of the groove. A land/groove polarity of a sector is determined by the polarity of a tracking error signal and the order of the polarities during reproduction of an identification signal.

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.

Abstract: Apparatus and method for detecting zero-crossings and correcting asymmetry of an RF signal. The RF signal is first converted into a digital signal having a plurality of samples. Zero-crossings detection is achieved by calculating the differences between neighboring samples, and by determining whether the differences exceed a pre-determined threshold value. Zero-crossings are also detected by comparing the differences to a pre-determined negative threshold value when the differences are negative. If a zero-crossing sample, a sum of the data values of the neighboring samples is used to generate an asymmetry offset value.

Abstract: An information reproducing apparatus method includes the steps of radiating an optical spots to scan information marks recorded on tracks inside a predetermined information recording region, detecting an optical change of the information marks by this scanning operation, executing a signal processing for the reproducing signal so as to reduce inter-symbol interference of an interference amount that varies for each of the information marks, and reproducing the information corresponding to the information mark. The magnitude of the optical change due to the information mark is thereby detected, and a plurality of equalization coefficients used for an equalization processing are calculated for the magnitude of the optical change detected for each information mark. The inter-symbol interference is reduced on the basis of these equalization coefficients.

Abstract: The present invention relates to an apparatus for reading and/or writing data markings of an optical recording medium having data markings arranged along a track and header markings arranged laterally offset with respect to the center of this track. The apparatus has a signal conditioner, a header identification unit and a switch unit driven by the latter. The object of the invention is to enable data and header markings to be read out with the lowest possible error rate. For this purpose, the apparatus according to the invention has a threshold value forming unit and a storage unit with at least two storage locations, in which case, by means of the switching unit, the input of the storage unit can be connected to the output of the threshold value forming unit and the output of the said storage unit can be connected to a threshold value input of the signal conditioner. The apparatus according to the invention is suitable for reading from or writing to optical recording media such as a DVD-RAM, for example.

Abstract: A method of recording a digital signal representing digital data onto a recording medium by changing a position of each edge of each of a plurality of pits in accordance with the digital signal is provided.

Abstract: Optical pickup is provided which includes a first reproduction channel for reproducing a first-type optical disk and a second reproduction channel for reproducing a second-type optical disk. When reproduction is to be performed on a third-type optical disk that is different from the first-type and second-type optical disks but reproducible via each of the first and second reproduction channels, the third-type optical disk is first test-reproduced both via the first reproduction channel and via the second reproduction channel, to thereby detect a jitter value of the information reproduced via the first reproduction channel and a jitter value of the information reproduced via the second reproduction channel. Then, the recorded information of the third-type optical disk is reproduced using one of the first and second reproduction channels that attains the jitter value closer to a predetermined target jitter value.

Abstract: An apparatus operates for recording and reproducing information on and from a recording medium formed with a track and pre-pits. The track has a wobble. The pre-pits are in a predetermined phase relation with the wobble of the track. The apparatus includes a pickup for reproducing a signal from the recording medium. A limiter operates for limiting an amplitude of the signal reproduced by the pickup in response to a limiting level, and thereby processing the signal reproduced by the pickup into a limiting-resultant signal. A filter operates for suppressing components of the limiting-resultant signal, and thereby processing the limiting-resultant signal into a filtering-resultant signal. The components have specified frequencies, and are caused by the pre-pits. The limiting level for the limiter is generated in response to the filtering-resultant signal. A signal caused by the wobble of the groove is extracted from the filtering-resultant signal.

Abstract: The objective of the present invention is to prevent the occurrence of crosstalk between adjacent pregrooves, even if the light beam is applied across the adjacent information recording layers in accordance with the increase in a storage density of the optical disc.

Abstract: The invention provides an optical disk medium having a recording spiral formed by connecting groove tracks and land tracks alternately, and permitting detection of a connecting point between a groove track and a land track reliably is provided, and a method of tracking the optical disk medium and an optical disk drive apparatus for driving the optical disk medium. One part of an identification signal area is shifted by a predetermined distance in one radial direction from the center of a groove, while another part of the identification signal area is shifted by the same distance in the opposite radial direction from the center of the groove. A land/groove polarity of a sector is determined by the polarity of a tracking error signal and the order of the polarities during reproduction of an identification signal.

Abstract: An optical disc is irradiated with a main beam and a pair of side beams, and respected reflected beams of light are detected by a main detector and a pair of side detectors. A first push-pull signal is generated which includes wobble components obtained by a detection signal from the main detector, and second and third push-pull signals are generated using detection signals from the pair of side detectors. The second and third push-pull signals are added by an adder to generate crosstalk components included in the first push-pull signal, and wobble information of the recording track is generated and output using signals obtained by canceling the crosstalk components in the first push-pull signal including wobble signal components in the recording track.

Abstract: A method protecting a header region formed in an optical disc when a signal is written on the optical disc and an apparatus therefor. The method protecting a header region of an optical disc write apparatus comprises detecting the header region from an RF signal detected from the optical disc through a pick up, generating a write clock, generating a write control signal whose state is inverted after the lapse of a predetermined clock by counting the write clock, generating a write stop signal when the write control signal is generated in the header region detected in the detecting of the header region, and controlling the intensity of the write laser beam corresponding to the write control signal. The generating of the write stop signal comprises feeding the write control signal back to the generating of the write control signal to control the write control signal.

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.

Abstract: In an apparatus and a method for correcting asymmetry in an optical disk reproduction system, an analog RF signal is received from an optical diode and an asymmetry-corrected signal is output as a digital EFM signal. The apparatus includes envelope detectors for detecting upper and lower envelopes of the RF signal, a level controller for controlling the level of the sum of the upper envelope and the lower envelope and for outputting signal having the controlled level, and a comparator for comparing the level of the signal output from the level controller with the level of the RF signal and for outputting the comparison result as the digital EFM signal.

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: When subcodes included in a CD format are reproduced, jitter is removed when the subcodes are synchronized with signal data. The data is connected together by using the subcode data to prevent interruptions of sound and pictures. An error correction unit performs error correction processing for signal data reproduced (read) from a CD. A memory stores the signal data whose error is corrected and a data output unit reads out the signal data stored in the memory according to a reference clock. A subcode detection/jitter removal unit detects subcode data reproduced from the CD and outputs the subcode data to the memory in synchronism with outputting of the signal data whose error is corrected by the error correction unit, to thereby remove jitter.

Abstract: A method of recording data on a recording medium includes mapping the data to a set of write symbols wherein each write symbol represents more than one bit of the data. The set of write symbols is defined by defining a set of variable write parameters; generating a plurality of candidate write symbols that specify different values for the variable write parameters; generating a plurality of readout waveforms produced by the plurality of candidate write symbols; analyzing the readout waveforms to determine desired set of readout waveforms; and selecting selected ones of the plurality of candidate write symbols that correspond to the desired readout waveforms to be included in the set of write symbols. The data is written to the medium using the write symbols.

Abstract: A pickup device and an information recording/reproducing apparatus for reproducing information in which crosstalks have been suppressed without causing an erasure or the like of the information which has already been recorded on an information recording medium. The apparatus has a light source 1 for emitting first and second lights whose polarizing directions cross perpendicularly. The first and second lights are transmitted through a grating for merely transmitting the first light and diffracting the second light at a predetermined diffraction efficiency and those lights are converged by an objective lens, thereby forming a laser beam and irradiating it onto an optical disc. At the time of the recording of information, the second light is set to a light-off mode or a low power state and the recording of information is performed by the laser beam caused by the first light.

Abstract: An information recording/reproducing apparatus of the invention is equipped with an objective lens, a light source and a variable optical element having a grating which demonstrates a piezo-electric effect by means of an electric field. The light source emits and irradiates a laser beam onto the grating to generate a 0th order diffraction beam and +/− 1st order diffraction beams in accordance with first order diffraction efficiency, and the objective lens converges the 0th diffraction beam and +/− 1st order diffraction beams which are irradiated onto an information recording medium for the purpose of information recording or information reproducing. By controlling an electric field applied to the grating, the first order diffraction efficiency of the grating is adjusted, whereby light beams are generated which have power levels appropriate for various kinds of information recording media.

Abstract: An error compensation device for a disk signal reproduction apparatus that reads out data from a disk on which the data is recorded along a spiral track, such as a CD, and reproduces a signal. The error compensation device includes a data read unit which reads out data from a disk, a signal memory unit which stores output data of the read unit, a servo control unit which controls the read unit, a microcomputer which controls the servo control unit and the signal memory unit, a storage unit for microcomputer control which controls the control microcomputer, a D/A conversion unit which coverts the output of the signal memory unit, and a signal mute unit which is controlled by the microcomputer. When there is a region from which disk data cannot be reproduced, the storage unit for microcomputer control stores the region as an error region. Signals stored in the signal memory unit are sequentially read out at a reference speed to reproduce the signals.

Abstract: A method is described for optimizing recording conditions for writing information on an optical record carrier. The information is written on the record carrier in the form of optically detectable marks, each mark being written by a pulse series of radiation. A series of test patterns is written on the record carrier (1) for the optimization. A jitter detector (11) measures both the leading-edge and trailing-edge jitter of the read signal. The leading-edge jitter is used to optimize the value of a parameter influencing only the leading part of a pulse series. The trailing-edge jitter is used to optimize a parameter influencing only the trailing part of the pulse series.

Abstract: A writable optical disc has an information writing track, and a guiding track for introducing a laser beam to the information writing track. The guiding track has prepit information recorded thereon, the prepit information including at least address information of the optical disc. The prepit information is recorded on the guiding track at a position where interference of adjacent guiding tracks with the prepit information is prevented. The information writing track is a groove track, and the guiding track is a land track.