Abstract: The present invention provides an information reproducing apparatus capable of preventing occurrence of erroneous detection as if a recording pit longer than the longest pit in the standard exists on an optical disk even in the case where the difference between frequency of a reproduction signal and frequency of a reproduction clock signal becomes large. When the difference between frequency of a detection signal Sp detected from an optical disk DK and frequency of a reproduction clock signal Scl becomes large, for example, the gain of a high frequency band corresponding to a recording pit length in the range of 2T to 4T is emphasized more than normal one by an equalizer 2, and the resultant is used for detecting a longest-pit-length error.

Abstract: A reproducing device is provided with a beam irradiating means, which irradiates one track on a recording medium with a main beam and irradiates a position deviated from the irradiation position of the main beam with a sub beam; a main signal detecting means for outputting a main reproduction signal based on the main beam; a sub signal detecting means, which is divided by a dividing line along the tangent line direction of the one track, has a plurality of light receiving parts including a first light receiving part on a side close to the one track, and outputs a plurality of sub reproduction signal corresponding to detection light from the plurality of light receiving parts; a delaying means for relatively delaying the main reproduction signal and the sub reproduction signal; a delay quantity setting means for setting a delay quantity; and a crosstalk canceller for removing crosstalk from the delayed main reproduction signal.

Abstract: The present invention provides an information reproducing apparatus capable of preventing occurrence of erroneous detection as if a recording pit longer than the longest pit in the standard exists on an optical disk even in the case where the difference between frequency of a reproduction signal and frequency of a reproduction clock signal becomes large. When the difference between frequency of a detection signal Sp detected from an optical disk DK and frequency of a reproduction clock signal Scl becomes large, for example, the gain of a high frequency band corresponding to a recording pit length in the range of 2T to 4T is emphasized more than normal one by an equalizer 2, and the resultant is used for detecting a longest-pit-length error.

Abstract: A waveform equalizer is designed to perform high frequency enhancement on a read signal without increasing inter symbol interference even when the shortest run length of the read signal is not greater than twice the clock period of the channel clock signal. An addition value of weighted values of signal levels of an amplitude limited read signal obtained by limiting the amplitude of the read signal, where the signal levels are at first and second points of time, is added to a signal level at an intermediate timing of the first and second points of time, and a result of the addition is outputted as an equalization corrected read signal.

Abstract: It is an object to provide a recorded information reproducing apparatus that allows to eliminate crosstalk from an adjacent track correctly, even from a recording medium having both a recorded area in which information data are recorded and an unrecorded area. In order to detect a crosstalk component from an adjacent track based on a correlation between a main read signal read from a main track and a sub read signal read from an adjacent track, the relative phase between the sub read signal and the main read signal is shifted.

Abstract: The object of the present invention is to provide a data recording method and optic recording medium that is capable of reproducing address data accurately by reducing the correlation of address data between adjacent tracks, reducing the effect of cross-talk between adjacent tracks on the recording clock and by making it possible to apply a cross-talk canceller to the wobble signal. The data-recording method of recording data while controlling the correlation between a first data string and a second data string that are contained in recording data, and is provided with a selecting process of selecting inversion/no inversion of first data string such that the correlation between first data string and second data string is reduced; and a recording process of recording first data string according to selected inversion/no inversion polarity, and recording control code that indicates whether inversion/no inversion was selected for first data string.

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 pick up irradiates light beams at specified intervals in the tangential direction of the main track to be reproduced and both of adjacent tracks on a disk 10 on which tracks are formed. A CTC unit 15 uses the delay amount ?d of the respective sample-value series corresponding to the reproduction signal RFm from the main track and reproduction signals RF1, RF2 from both adjacent tracks to correct the delay, then outputs a CTC output signal from which the cross-talk component has been removed. In addition, when adjusting the delay, the CPU 17 applies a disturbance to the control signal for the actuator of the servo-control unit 18 and changes the delay amount ?d within a specified range of change. At this time, the CPU 17 sets the delay amount ?d, which minimizes the jitter value found by the jitter detection unit 16 according to the CTC output signal, for the CTC unit 15. This makes it possible to set the optimum delay amount ?d when adjusting the delay, even when there is little steady cross-talk.

Abstract: A data-reproduction apparatus in which an RF signal that is input from a disk to an A/D converter via a pick-up and RF signal generator is sampled according to a sampling clock from a clock generator and converted to a sample-value series. This sample-value series is input to a phase-correction unit via a delay element, and its phase is corrected based on a phase-error signal from a phase-detection unit, then it is demodulated by a demodulator to become user data. On the other hand, the sample-value series, whose phase has been corrected, is input to a phase-detection unit where the phase error is detected, and a generated phase-error signal is then supplied to both the phase-correction unit and the clock generator. In this way a first PLL is followed by a second PLL, which makes it possible to easily widen the bandwidth of the second PLL without including a delay element in the loop.

Abstract: In a cross-talk canceller (CTC) that removes the cross-talk from the adjacent tracks that is contained in the reproduction signal from the main track, a sample-value series S1? for the reproduction signal from the adjacent track is input to a correlation-detection unit to find its correlation with the signal pattern of the signal output from the CTC that is detected by a pattern-detection unit, and then it passes through one of the correction-coefficient units that is connected by the switch and then integrated by the integrator, and the tap coefficient used by the variable filter of the CTC is obtained to a narrow control frequency zone.

Abstract: An information playback apparatus of the present invention is provided with: a first detecting unit for supplying a difference between respective output signals optically obtained by a pair of detectors for reading the information of the first track; a second detecting unit for supplying a difference between respective output signals optically obtained by a pair of detectors for reading the information of the second track adjacent to the first track; a first demodulating unit for demodulating a detected signal supplied from the first detecting unit, a second demodulating unit for demodulating a detected signal supplied from the second detecting unit. A coefficient controlling unit extracts the crosstalk caused by the second track, which is included in a demodulation signal obtained by the first demodulating unit, from the same signal and controls a coefficient based on the extracted crosstalk, and cancels the crosstalk by the calculated coefficient.

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 defect on a DVD-RAM is detected by using a track error signal TE and an RF signal before the decoding thereof, which are used for the position control of an optical pickup. Because the defect detection is performed by using the track error signal TE and the RF signal before the decoding thereof, even if the verification and reproduction of information are not performed, it is possible to make or update a defect list and increase the accuracy of the defect detection. It is possible to extract only information about the defect which is the obstacle of the information recording realistically and collect it on the defect list.

Abstract: A waveform equalizer is designed to perform high frequency enhancement on a read signal without increasing inter symbol interference even when the shortest run length of the read signal is not greater than twice the clock period of the channel clock signal. An addition value of weighted values of signal levels of an amplitude limited read signal obtained by limiting the amplitude of the read signal, where the signal levels are at first and second points of time, is added to a signal level at an intermediate timing of the first and second points of time, and a result of the addition is outputted as an equalization corrected read signal.

Abstract: A waveform equalizer is designed to perform high frequency enhancement on a read signal without increasing inter symbol interference even when the shortest run length of the read signal is not greater than twice the clock period of the channel clock signal. An addition value of weighted values of signal levels of an amplitude limited read signal obtained by limiting the amplitude of the read signal, where the signal levels are at first and second points of time, is added to a signal level at an intermediate timing of the first and second points of time, and a result of the addition is outputted as an equalization corrected read 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: In the case of delaying any one of the detected signals, which are optically obtained from a plurality of trucks, in which the information are respectively recorded under a state that the DC component is removed, a zero cross waveform is extracted from a main detected signal, which is obtained from a main truck. Then, a sub detected signal obtained from a sub truck is held at a timing at which this zero cross waveform is extracted. Further, a sub detected signal, which has been held during a predetermined time frame, is averaged. Moreover, delay amounts with respect to the sub detected signal and the main detected signal are calculated by comparing a waveform of the averaged sub detected signal and the zero cross waveform. Then, the present sub detected signal and the main detected signal are delayed by the calculated delay amounts.

Abstract: There is disclosed a crosstalk removal apparatus in which a main track, one adjacent track, and the other adjacent track in a disk with the tracks formed therein are irradiated with light beams at predetermined intervals in a tangent direction by a pickup. A CTC unit uses delay amounts of respective sample value series corresponding to a reproduction signal of the main track and those of the adjacent tracks to correct delays, and outputs a CTC output signal from which a crosstalk component is removed. A wobble signal detector detects wobble signals of the respective tracks based on a push-pull output of the disk, and a delay circuit controller obtains optimum delay amounts based on a phase relation of the respective wobble signals and sets the delay amounts in the CTC unit.

Abstract: A tracking controller capable of conducting a correct tracking control even if a recording track is formed with a narrow track pitch on a recording disk. The tracking controller calculates an error value between a read signal read from a recording track intended for reading and a predetermined value, a first coefficient from a correlation between a read signal read from a recording track adjacent to the recording track intended for reading on the inner peripheral side of the disk and the error value, and a second coefficient from a correlation between a read signal read a recording track adjacent to the recording track intended for reading on the outer peripheral side of the disk and the error value. A difference between the first and second coefficients is calculated as a tracking offset which is subtracted from a tracking error to correct a tracking offset.

Abstract: It is an object to provide a recorded information reproducing apparatus that allows to eliminate crosstalk from an adjacent track correctly, even from a recording medium having both a recorded area in which information data are recorded and an unrecorded area. In order to detect a crosstalk component from an adjacent track based on a correlation between a main read signal read from a main track and a sub read signal read from an adjacent track, the relative phase between the sub read signal and the main read signal is shifted.