Abstract: A pre-learning section pre-learns whether or not a signal characteristic has been changed by use of at least data in a plurality of data areas, and obtains an optimum equalization coefficient of an adaptive equalizer for the data areas after the signal characteristic has been changed, and then stores the optimum equalization coefficient in a optimum equalization coefficient storage section. On the basis of detection information from a reference information (VFO) area detection section, the optimum equalization coefficient pre-learned in a reference information (VFO) area is preset in the adaptive equalizer, and equalization coefficient learning processing for the adaptive equalizer is started after entering a next data area.

Abstract: There is provided an apparatus which can flexibly cope with both of a signal reproduction process for a region with high recording density and a signal reproduction process for a region with low recording density. The apparatus includes a waveform equalizing circuit which subjects data read out from an optical disk to a waveform equalizing process, a plurality of PRML processors of different classes supplied with an output signal of the waveform equalizing circuit, a switch which selects one of output signals of the plurality of PRML processors and supplies the selected output signal to a decoder, and a controller which controls the switch according to high-density and low-density regions with different recording densities of the optical disk to set a selection state in which a corresponding one of the output signals of the plurality of PRML processors is selected.

Abstract: When an error-correcting code is created for the data stored in a memory and added to the data, even if an error occurs in the data on the memory, the adverse effect of the error will be eliminated. In the present invention, when the data is stored in the memory, an error-correcting code PI is created beforehand using another memory, such as an S-RAM. The error-correcting code PI, together with the data, is written into the memory. After 16 sectors of data and PI have been stored, an error-correcting code PO is created for the data and PI and added to them. When the data is read from the memory, a PI correcting process is carried out each time a PI series is read out. This makes it possible to restore the original data, even if the data is destroyed (or an error occurs) on the memory.

Abstract: A disk apparatus has a reading unit which reads reflection light from a disk and outputting a read signal, an identifying unit which identifies whether the read signal has been modified in accordance with a first modulation rule or has been modulated in accordance with a second modulation rule and outputs an identification signal, an equalizing unit which applies a waveform equalizing process to the read signal, and a decoding unit which carries out likelihood decoding of the waveform equalized read signal according to the modulation rule indicated by the identification signal from the identifying unit, and outputs a reproduction signal.

Abstract: A digital RF signal resulting from A/D conversion of an RF signal reproduced from an optical disk is compared with a plurality of set values, so that a predetermined waveform is detected from the digital RF signal. The wavelength of the detected waveform is measured, and the A/D conversion is controlled based on this wavelength. Comparing the digital RF signal with the plural set values enables high-accuracy waveform detection.

Abstract: A disk apparatus has a reading unit which reads reflection light from a disk and outputting a read signal, an identifying unit which identifies whether the read signal has been modified in accordance with a first modulation rule or has been modulated in accordance with a second modulation rule and outputs an identification signal, an equalizing unit which applies a waveform equalizing process to the read signal, and a decoding unit which carries out likelihood decoding of the waveform equalized read signal according to the modulation rule indicated by the identification signal from the identifying unit, and outputs a reproduction signal.

Abstract: A disk apparatus has an equalizing unit which performs PR equalization for the read signal from the disk based on a plurality of tap coefficients, a decoding unit which performs a decoding process for the equalized read signal, a calculating unit which obtains an ideal signal of the decoded read signal, and compares the ideal signal with the decoded read signal, thereby calculating an error signal E, and a control unit which groups the tap coefficients into at least a first and second coefficient groups which are groups of tap coefficients at symmetrical locations each, and determines tap coefficients of the first coefficient group in a range of a first limit value K1 according to the calculated error signal, determines tap coefficients of the second coefficient group in a range of a second limit value and supplies the determined tap coefficients to the equalizing unit.

Abstract: A recorded stream generator generates a data block stream in synchronism with the phase of a recording clock, from the input data. The recorded stream generator further generates, for each predetermined data unit constituting the data block stream, a data phase reference pulse indicative of the phase of the data unit. An inserting section inserts a VFO signal into a predetermined amount (32 sectors) of the data block stream, the VFO signal having a length of time corresponding to a difference in phase between an wobble address phase signal and a data phase reference pulse. The inserting section thus provides a data stream DST consisting of the VFO signals and the data block streams. An LD uses light beams to record the data stream on an optical disk.

Abstract: A disk device includes a reading section which reads reflected light and outputs a read signal according to the read reflected light, a processing section which calculates an adjustment value from the read signal, performs predetermined processing on the read signal based on the adjustment value, and outputs a process signal, a detecting section which detects a reading defect in the reading section based on the read signal, a determining section which determines signal quality of the process signal output from the processing section, a storage section which stores the adjustment value calculated by the processing section, in a memory area, based on a result output from the determining section, and a controller which, when the detecting section detects the reading defect, performs control so that the adjustment value is read out of the storage section and is supplied to the processing section.

Abstract: A disk apparatus has a reading portion which reads out a plurality of frames stored in a disk and outputs a read signal, a detecting portion which determines that part of the read signal is identical to a frame synchronization code signal or determines that a deviation between a symbol of part of the read signal and a symbol of the frame synchronization code signal is within a certain time range to detect the frame synchronization code signals from the read signal, and a reproducing portion which reproduces the read signal in synchronization with the detected frame synchronization code signals.

Abstract: A sync pattern detection apparatus includes a sync pattern detection unit configured to detect a sync pattern from an input signal, a plurality of sync pattern protection units configured to protect the sync pattern detected by the sync pattern detection unit, a reliability evaluation unit configured to evaluate the reliabilities of a plurality of sync pattern protection situations by the plurality of sync pattern protection units, and a selection unit configured to select a sync pattern protected by a predetermined sync pattern protection unit, on the basis of the reliability evaluation of the plurality of sync pattern protection situations by the reliability evaluation unit.

Abstract: When an error-correcting code is created for the data stored in a memory and added to the data, even if an error occurs in the data on the memory, the adverse effect of the error will be eliminated. In the present invention, when the data is stored in the memory, an error-correcting code PI is created beforehand using another memory, such as an S-RAM. The error-correcting code PI, together with the data, is written into the memory. After 16 sectors of data and PI have been stored, an error-correcting code PO is created for the data and PI and added to them. When the data is read from the memory, a PI correcting process is carried out each time a PI series is read out. This makes it possible to restore the original data, even if the data is destroyed (or an error occurs) on the memory.