Abstract: In a partial-response maximum-likelihood (PRML) signal detection and processing technique, reduction of data detection error events caused due to medium noise is achieved. For a PRML detection data result obtained after PRML data demodulation, a code error event that depends on a signal distance, and which has a high frequency of occurrences, is noticed and its occurrence probability is estimated. A locally-existing medium noise quantity is estimated from preceding and subsequent code patterns of the PRML detection data result. Based on this, the occurrence probability of the error event is compensated to improve the detection precision. As a result, data modulation with reliability higher than conventional maximum likelihood detection can be realized with a simple circuit structure.

Abstract: A magnetic recording system having a magnetic-recording medium with data sectors wherein a preamble pattern of a prescribed cycle is recorded, the preamble pattern having the cycle of a predetermined T, wherein T represents a minimum duration of a data-recorded bits in the data sectors. The system includes a magnetic head to reproduce the preamble pattern and a signal-processing circuit to process data to be recorded in and reproduced from the data sectors. The signal-processing circuit including (i) a sampler for sampling a signal reproduced from the preamble pattern and (ii) a corrector for correcting the amplitude by using maximum and minimum amplitude values in each cycle of the preamble pattern sampled by the sampler.

Abstract: When jitter-like noise is prominent, sampling-phase control and amplitude control in a preamble pattern region is affected. It is possible to reduce effects of jitter-like noise without increasing the length of the preamble pattern. By altering a preamble pattern from that of a conventional 4T-cycle to 6T-cycle or over, amplitude data at a peak point of a reproduced signal, which is less affected by jitter-like noise, is utilized. Thus, the stability of the amplitude control can be improved. As to the phase control, a shift of the sampling timing is estimated by sample data of one cycle of the preamble pattern, and an acquisition procedure of the timing control is made faster.

Abstract: An error correction method is provided as follows: handling a 2-event error generated very frequently as an object of correction; sequentially finding CRC data for a generated event of an error handled as the defined object of correction at any arbitrary bit position of reproduced data by implementation of a cyclic-replacement process; carrying out an exclusive-addition process of the CRC data to CRC data of the reproduced data in order to virtually carry out a tentative-correction process on a 1-event error at a first bit position; further finding CRC data generated after the tentative-correction process in order to detect a 1-event error at a second bit position; and correcting the 1-event error completing the tentative-correction process at the first position and the 1-event error at the second bit position.

Abstract: A method of recording information on an information medium, especially on an optical recording medium with light. It has been hard to determine optimum power accurately due to the influence of the linearity and the mark length dependence on rewrite deterioration when a write parameter calibration on a phase change optical disk is performed by a conventional asymmetry method prior to information recording. According to the present invention, a single pattern or a random pattern is recorded on an information medium, and the difference between the clock and the data edge is detected using a reproduced signal. On the basis of this difference, the threshold power of the recording is determined and multiplied by a constant to optimize the recording power.

Abstract: In the PRML signal processing technique, reduction of data detection error events caused due to medium noise that occurs depending on a recording code data pattern is realized by using simple means. With respect to a detection data result obtained after PRML data demodulation, a code error event that depends on a signal distance and has a high frequency of occurrence is noticed and its occurrence probability is estimated. At this time, a locally existing medium noise quantity is estimated from preceding and subsequent code patterns of the PRML detection data result. Thereby the occurrence probability of the error event is compensated to improve the detection precision. As a result, data modulation with reliability higher than conventional maximum likelihood detection can be realized with a simple circuit structure.

Abstract: An information recording method for recording information by irradiating an information recording medium with light, including steps of providing the information recording medium with a physical identification field (PID) and a data field, and utilizing a head amplifier for amplifying a detection signal in the PID field with a first gain and amplifying a detection signal in the data field with a second gain different from the first gain to record the information to the data field.

Abstract: When jitter-like noise is prominent, sampling-phase control and amplitude control in a preamble pattern region is affected.. The object of the present invention is to provide a means to reduce effects of jitter-like noise without increasing the length of the preamble pattern. By altering a preamble pattern from that of conventional 4T-cycle to 6T-cycle or over, amplitude data at a peak point of a reproduced signal which is less affected by jitter-like noise is utilized. Thus, stability of the amplitude control can be improved. As to the phase control, a shift of the sampling timing is estimated by sample data of one cycle of the preamble pattern, and an acquisition procedure of the timing control is made faster.

Abstract: An optical disk device including a head amplifier for recording/reproducing a signal onto/from a disk. In DVD-RAM disks, the signal level differs depending on whether the section is the PID area or the data field. The highest level in the PID area is a mirror level, whereas the highest level in the data field is a land/groove level. The gain of the head amplifier is limited so that the mirror level will not exceed the dynamic range of the head amplifier. Therefore, the head amplifier needs to assure a sufficient signal quality and send such a signal to a subsequent processing circuit. The signal is amplified with different suitable gains respectively for the PID area and the data field. Or an offset voltage corresponding to a difference between the mirror level and the land/groove level is applied to the PID area. As a result, the gain for the signal of the data field can be increased.

Abstract: To effectively suppress a signal in a low frequency region in which the medium noise and the signal distortion are concentrated, and in order to effectively utilize a detected component of the reproduced signal in the low frequency region, a target of partial response equalization to the perpendicularly recorded/reproduced signal is set so that the low-frequency component around the direct current is suppressed to a regulated quantity for both the effective suppression and the effective utilization. Accordingly, a maximum-likelihood decoding process is carried out through the target of partial response equalization. Reliability of data detection is made higher and a signal-to-noise ratio is improved, so that the noise from the recording medium can be reduced more and it is possible to provide a high-density magnetic recording/reproducing apparatus.

Abstract: An optical disc apparatus prevents erroneous compensation of tilt and minimizes distortion of waveform of the optical and electrical transmitter channel as a whole. For this purpose, a group delay compensator that assures flat frequency characteristic of the gain and can adjust frequency characteristic of group delay is provided to the electrical transmitter of the optical disc apparatus including tilt controller and settings of tilt and group delay are optimized, in the adjustment, to provide minimum jitter of the reproduced signal or minimum code error of data obtained from the reproduced signal.

Abstract: A reproduced signal 104 is sampled with a half-frequency clock signal to set two threshold levels 107, 108 for a sub-sampled data string 105, and the sub-sampled data string 105 is determined to be at three levels to produce an intermediate value data string 109. A modulo-2 operation is performed on the intermediate data string 109 to determine the data of the sub-sampled data string 105, and the data of a non-sampled data string 106 are decided with the state transition of the sub-sampled data string 105 to acquire reproduced data 112.

Abstract: A reproduced signal 104 is sampled with a half-frequency clock signal to set two threshold levels 107, 108 for a sub-sampled data string 105, and the sub-sampled data string 105 is determined to be at three levels to produce an intermediate value data string 109. A modulo-2 operation is performed on the intermediate data string 109 to determine the data of the sub-sampled data string 105, and the data of a non-sampled data string 106 are decided with the state transition of the sub-sampled data string 105 to acquire reproduced data 112.

Abstract: A super high density optical disk apparatus is obtained by using an exchangeable recording medium having a recording capacity of at least 1.5 Gb/in.sup.2 in an optical recording and reading apparatus for recording or reading at least using a laser beam or by using one of means which can record on a recording medium only once and means which can record at least two times repeatedly as recording means to be used.

Abstract: An optical disk recording/reproducing apparatus includes at least a focus shift mechanism for controlling a lens to focus a laser beam on a disk so as to form a beam spot on the disk, a reproduced signal evaluator for evaluating the quality of the reproduced signal on the basis of the output from a reproduced signal detector, a controller for setting the operation target point of the focus shift mechanism, where the best quality of the reproduced signal is attained, on the basis of the output from the reproduced signal evaluator, and an offset generator circuit for outputting a focus offset signal in response to a command from the controller. The operation target point of the focus shift mechanism is set to the optimal point where the jitter in the reproduced signal is rendered minimum.

Abstract: An optical disk apparatus is capable of recording, reproduction and erasure by a laser beam. The user data is recorded in a RAM area on an optical disk by a recording device including a modulation encoder and a recording waveform generator. At the time of reproduction, the data in the RAM/ROM area is detected by a reproduction device to thereby demodulate the user data.

Abstract: A super high density optical disk apparatus is obtained by using an exchangeable recording medium having a recording capacity of at least 1.5 Gb/in.sup.2 in an optical recording and reading apparatus for recording or reading at least using a laser beam or by using one of an element which can record on a recording medium only once and another element which can record at least two times repeatedly as recording elements to be used.

Abstract: An optical disk device which uses a light spot for reproducing data, including photodetector, a decoder, and a non-linear equalizer provided between the photodetector and the decoder for correcting non-linear distortions in a reproduced signal from an optical disk. The non-linear equalizer includes a linear equalizer and a decision feedback equalizer provided after the linear equalizer. The non-linear equalizer includes a detector for detecting a signal on the basis of the output of the linear equalizer with the output of the detector being input to the decision feedback equalizer, the output of which is input to the detector along with the output of the linear equalizer in an additive manner.

Abstract: An optical recording control method determines an optimum recording laser power by effecting a test recording before information to be recorded is recorded on a disk. The recording laser power is formed of a plurality of powers. A relationship among the plurality of laser powers is regulated by power level ratios between respective powers, whereby a power used when a laser light is radiated on the disk can be controlled to be constant independent of an ambient temperature and a structure of a disk. Therefore, accurate recording marks can be formed on the disk.

Abstract: An information reproducing apparatus is capable of stably and correctly binarizing a signal reproduced from a recording medium, such as an optical disk, even if the reproduced signal contains a fluctuation of its low frequency component. The reproduced signal is replaced by an AC signal in a period other than a period during which the reproduced signal is to be demodulated so that DC fluctuation of the reproduced signal is reduced to thereby stably and correctly binarize the reproduced signal.