Abstract: The present invention realizes stable and more proper data reproduction even when a reproduced signal varies locally due to a noise or includes a steady distortion. In a data reproduction control method and apparatus, and an optical disk unit that adjust sampled values, in sampling a signal reproduced from a recording medium recorded with data, the frequencies of the levels of quantized data are counted, a histogram of the frequencies of the levels is created based on the counting results, and more accurate reproduced data is obtained by means of a distribution of the frequencies of the levels in the histogram.

Abstract: The present invention provides highly reliable PLL without influence of variations in amplitude of a reproduced signal or variations in inclination of an edge. An information-reproducing apparatus according to the present invention includes a unit for detecting a phase difference between a reproduced signal and a reproducing clock signal, a PLL circuit for regulating a frequency of the reproducing clock signal to compensate for the detected phase difference, a unit for detecting a state of the PLL circuit, and a unit for regulating a loop gain of the PLL circuit corresponding to the detected state.

Abstract: A method and an apparatus are provided which are capable of evaluating a state of a signal with a fewer number of samples compared with an error rate. A reproducing signal obtained from a magneto-optical disk is subjected to maximum-likelihood decode in a maximum-likelihood decoder, paths coupling with each other in the maximum-likelihood decode is detected by an evaluation index generation unit and, at the same time, a difference of likelihoods (path metrics) of those paths is obtained to adjust a parameter of a recording and reproducing signal or a control signal of an optical pickup based on the likelihood difference. The parameter is, for example, auto-tracking, a gain of an auto-focusing loop, or an offset value, or a gain value of a reproducing signal, a recording power, or a reproducing power intensity.

Abstract: An optical disk device has reproduction signal detecting section, each of which detects a reproduction signal corresponding to a reflective wave of an optical disk, a first offset controller, which offsets the reproduction signal with a first offset value F1, an A/D converting circuit, which A/D converts the offset reproduction signal, and a second offset controller, which offsets the converted digital reproduction signal with a second offset value F2, and a decoder, which viterbi decodes the offset digital reproduction signal and outputs decoded data B. Because an offset is performed with each exclusive value to A/D conversion and viterbi decoding, it is possible to obtain high identification accuracy with nonlinear characteristic eliminated.

Abstract: An object of the present invention is, relating to data demodulation from an optical recording medium, to vary a data demodulation process rate according to a reproduction state, thereby reducing power consumption while maintaining a reading performance in a favorable state.

Abstract: A nonlinearity compensation circuit is disclosed which includes an inverse hyperbolic function generation circuit for converting differential currents corresponding to input signals in+ and in− into differential voltages which increase in proportion to an inverse hyperbolic function, an offset provision circuit for providing an offset corresponding to control signals c+ and c− to the differential voltages outputted from the inverse hyperbolic function generation circuit and a hyperbolic function generation circuit for converting the differential voltages to which the offset has been provided by the offset provision circuit into signals which increase in proportion to a hyperbolic function and outputting the resulting signals as output signals out+ and out−. Consequently, compensation for the nonlinearity such as second order distortion can be performed for the read signal from a recording medium.

Abstract: The hold registers (102) receive a hold register enable signal (HRE), and when reading one kind signal of header field data, the hold register enable signal (HRE) is High and the registers (96) store newly renewed values of filter coefficients, and when reading a different kind signal of recording field data, the hold register enable signal (HRE) is Low and the hold registers (102) hold the last stored header field contents of the registers (96). Then, when a header field of the next sector is detected (g1, g2), the contents held in the hold registers (102) are taken and preset to the registers (96). Thus, even in the case where intermittent reproduction signal having different kind of formats is processed in playback, the continuous adaptive equalization can be realized over the different kinds of reproduction signals in quality.

Abstract: The present invention relates to an optical disk device and can be applied to, for example, a reproduction system of a phase-change-type optical disk device handling high density recording in order to improve the detection accuracy of specific patterns, such as a synchronizing pattern, without increasing the redundancy of the format. A specific pattern is detected by using NRZI data D1R that is obtained by signal processing of a reproduction signal DRF, and has been NRAI-modulated from pulse-position-modulated data D2R.

Abstract: A signal can be detected based on a level slice system and detection delay time can be reduced by setting the recording density of a header field in a linear direction lower (coarse) than that of a user data recording field. Further, a signal can be detected based on the level slice system and detection delay time can be reduced by using a mark position form having a large detection margin as an information recording system of the header field. A readout error of a sector number due to a detection error is compensated for by recording address marks AM for attaining byte synchronization of the header field in both of a head portion and tail portion of information recorded in the header field.

Abstract: A signal of a run-length-limited code is reproduced from a recording medium. The reproduced signal is sampled to generate a sampling-resultant signal. An odd-sample signal and an even-sample signal are generated in response to the sampling-resultant signal. A first transversal filter subjects the odd-sample signal to first partial-response waveform equalization to generate an equalization-resultant odd-sample signal. The first partial-response waveform equalization depends on first tap coefficients. The first tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant odd-sample signal. A second transversal filter subjects the even-sample signal to second partial-response waveform equalization to generate an equalization-resultant even-sample signal. The second partial-response waveform equalization depends on second tap coefficients. The second tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant even-sample signal.

Abstract: A data reproduction apparatus that employs an expected value generation unit that employs a maximum likelihood decoding algorithm, thereby an expected value is correctly determined from a histogram of sampled values of a signal to be reproduced, even when an offset arises in the signal to be reproduced, the offset being removed from the sampled values used in generating a histogram that is used to determine the expected value.

Abstract: Signal quality evaluation is performed using a predetermined reproduction signal, a first pattern corresponding to a signal waveform pattern of the reproduction signal, and a given pattern corresponding to the signal waveform pattern of the reproduction signal and being different from the first pattern.

Abstract: An information reproducing apparatus includes: a light emitting device that emits a light beam to the recording medium; a detecting device that detects the light beam reflected by the recording medium, and that generates a detection signal including a first component and a second component which have different middle levels; a sampling device that samples the first component and the second component included in the generated detection signal; an extraction device that extracts a first sampling value closest to the middle level of the first component from the first component, and that extracts a second sampling value closest to the middle level of the second component from the second component; a signal generation device that generates a first middle level signal by using the extracted first sampling value, and that generates a second middle level signal by using the extracted second sampling value; a compensation device that shifts the first component and the second component such that both the first middle l

Abstract: An information recording medium of this invention has a plurality of sector fields that record data, and each sector field has an identification information area (recording type area). The identification information area records one of first identification information indicating that data recorded in the sector field has high integrity, and second identification information indicating that data has low integrity.

Abstract: In a data recording apparatus, values of parity bits to be additionally provided every one predetermined length block in data obtained by demodulating the original data are determined so as to satisfy a part of or an entire the predetermined run length limitation rule in ranges of a current predetermined length block, the plurality of parity bits, and a next predetermined length block that is positioned next to the current block. The parity bits having the values are additionally provided to the current block.

Abstract: A defect detection device for detecting a defect of data recorded on a recording medium includes a waveform state detection part generating information representing a state of a waveform of a reproduced signal from the recording medium based on soft decision results obtained in process of reproducing the data in accordance with a maximum likelihood decoding algorithm corresponding to partial response, and a defect determination part determining the defect of the recorded data based on the information generated in said waveform state detection part.

Abstract: In a digital data reproduction apparatus for demodulating digital data from an optical recording medium, PRML (Partial Response Maximum Likelihood) signal processing effective to high-density recording/reproduction is carried out by using a half rate processing offset control means which performs data demodulation using half of the channel bit frequency, a half rate processing phase sync control means, a half rate processing adaptive equalization means, and a half rate processing maximum likelihood decoder, and the digital data recorded on the optical recording medium are reproduced while restoring signal components which are missing in the time direction, by linear interpolation or Nyquist interpolation. Therefore, digital data reproduction performance is improved, and power consumption is reduced.

Abstract: A sampled amplitude read channel is disclosed for reading data recorded on a disk storage medium by detecting an estimated data sequence from a sequence of read signal sample values generated by an analog read signal emanating from a read head positioned over the disk storage medium. A sampling device samples the analog read signal to generate the read signal sample values, and a discrete-time equalizer equalizes the read signal sample values according to an asymmetric partial response target comprising a dipulse response of the form: (. . . , 0, 0,+X0,+X1,−X2,−X3,−X4, 0, 0, . . . ) where X0−X4 are non-zero to thereby generate equalized sample values. In the embodiments disclosed herein, X0−X4 are 2,2,1,2,1 respectively. A discrete-time sequence detector detects the estimated data sequence from the equalized sample values.

Abstract: A waveform equalizer, which has a partial response characteristic represented in the form of PR (a, b, c, b, a) which is a quaternary transfer function characteristic, is made up an analog filter, an ADC (analog/digital converter), and an FIR filter, for providing matching with the frequency characteristic of a read back waveform read from a recording medium. Such signal processor characteristic approximation to the regenerative signal characteristic makes it possible to easily achieve equalization without particularly emphasizing the regenerative signal, thereby achieving a reduced circuit scale.

Abstract: The optical disk apparatus is provided with a Viterbi decoder and an expected value correction circuit. The branch metric operation unit calculates first, second and third errors between sampling data and expected values, and outputs them to the expected value correction circuit. The expected value correction circuit extracts the sampling data in a region where its variation is small based on the first, second and third errors, calculates the average values of the extracted sampling data to correct the first, second and third expected values, and outputs the corrected expected values to the branch metric operation unit. The Viterbi decoder performs Viterbi decoding of the sampling data based on the first, second and third corrected expected values. Thus, high-precision Viterbi decoding is permitted even if the amplitude value of the reproduction signal varies.

Abstract: A PLL (phase-locked loop) circuit is configured with a phase-error detection circuit comprises the following: a provisional judge circuit for provisionally judging a data signal being input to an A/D converter into three levels of 1, 0, and −1; a pattern detector which, among data signals being input in accordance with a result of the provisional judgment, checks a transition pattern ranging from a data signal that precedes one clock cycle to the actually present data signal, and then, when a specific pattern is detected, instructs a selector to select output data from the A/D converter; and the selector which, in compliance with instruction from the pattern detector, selects phase-error data from data signals output from the A/D converter, and then converts the selected phase-error data into an electric current before externally delivering it as an error-current.

Abstract: In a data reproducing apparatus, a monitor edge sample value is generated based on a second sample value at a trailing edge of the reproduction signal and a change amount of the monitor edge sample value is generated as an offset amount in a first processing part. Then, the offset amount is supplied to a second processing part where the second sample value is obtained by sampling the reproduction signal at the trailing edge. Then, the second processing part restores data based on the reproduction signal and the offset amount.

Abstract: A clock adjustment device for a data reproduction apparatus includes an edge detection part detecting an edge of a reproduced signal corresponding to a predetermined synchronization pattern based on a state of change of sampled values obtained in synchronism with a clock signal from the reproduced signal, a timing signal output part outputting a timing signal in a given cycle determined by the synchronization pattern from a timing at which the edge of the reproduced signal is detected, and a phase adjustment part adjusting a phase of the clock signal when the edge of the reproduced signal is detected and every time the timing signal is output.

Abstract: A Fuzzy Inference System (FIS) algorithm capable of discriminating among various disc types including double-layer DVD, single-layer DVD, CD-ROM/CD-Audio, CD-R, and CD-RW is used to identify disc type in an optical drive. This FIS optical disc determination algorithm relies on the physical properties of the reflecting layer of an optical disc, using a DVD and CD photo diode outputs, to discriminate among several disc types. Focus error and quad sum data from both DVD and CD lasers is provided as eight inputs to a nineteen rule Sugeno FIS which outputs a value corresponding to drive type.

Abstract: A data reproduction apparatus includes first and second sampling parts which sample a reproduced signal from a recording medium in synchronism with first and second clock signals synchronizing respectively with leading and trailing edges of the reproduced signal and output leading and trailing sampled values, respectively, and a combination part which generates combined sampled values based on the leading and trailing sampled values. Recorded data is reproduced based on transition states of the combined sampled values output from the combination part in accordance with a maximum likelihood decoding technique corresponding to a predetermined partial response waveform.

Abstract: A data restoring apparatus of an optical disk reproducing system restores data recorded on an optical disk from an RF signal read from the optical disk.

Abstract: An waveform equalizer equalizes the signal reproduced from an optical disc to remove reproduction waveform distortion with a frequency characteristic controlled. A binary coder and a PLL circuit generate a bit clock. An a/d converter a/d-converts the equalized signal in response to the bit clock. A Viterbi decoder including metric operation decodes the output of the a/d converter in response to the bit clock to output a bit stream. The metric operation generates a metric operation result from an output of the a/d-converter and prediction data. The Viterbi decoder Viterbi-decodes the output of the a/d converter through the metric operation according to prediction data. An operating circuit operates an equalizing error from the output of a/d converter and a waveform equalizing target. A coefficient generator controls the frequency characteristic according to the equalizing error to minimize the equalizing error.

Abstract: In a digital recorded data reproduction which applies PRML signal processing, it is an object to enhance a reproduction signal quality and a playability for an abnormal signal by an offset correction and a phase,-interpolation-type digital phase-locked loop.

Abstract: A signal is reproduced from a recording medium. The reproduced signal is sampled in response to a clock signal to get a sampling-resultant signal. A transversal filter includes a delay line having taps and delaying the sampling-resultant signal, multipliers for multiplying only alternate ones among signals appearing at the taps by tap coefficients to get multiplication results, and an adder for adding the multiplication results into a filtering-resultant signal. A temporary decision device operates for calculating a temporary decision value of the filtering-resultant signal according to a temporary decision procedure, for calculating a difference between the temporary decision value of the filtering-resultant signal and an actual value thereof, and for generating an error signal in response to the calculated difference. The tap coefficients used in the transversal filter are controlled in response to the error signal and the reproduced signal to minimize the error signal.

Abstract: The present invention provides an apparatus and a method for precisely and adequately evaluating actual quality of reproduced data whenever applying a maximum likelihood decoder for converting signal reproduced from a recording medium into binary signal. Based on data arrays of a pair of binary data outputted from a “Viterbi” decoder, SAM values are secured by selecting any of path-metric differential values (00) and (11) being the difference between a pair of values compared when renewing path-metric values PMM (00) and (11) outputted from the “Viterbi” decoder. The minimum SAM value for an ideally-reproduced signal is outputted from a constant generating circuit. If the SAM values are verified as valid, and yet, if the SAM values coincide with the equation “input SAM values”≦“data value outputted from the constant generating circuit”, then squared values outputted from a square circuit are averaged by an averaging circuit.

Abstract: A data processing apparatus having a partial response forward equalizer (filter) with sufficient number of taps to result in 7-tap target response, designed by jointly optimizing the target response and the target coefficients to maximize an appropriate signal-to-noise ratio (SNR) at the detector input, followed by a new post-processing scheme enhances performance of the threshold based bit-by-bit detector designed for the d=2 optical channels. The resulting performance of the proposed scheme over a range of channel densities of 4.5 and below (used on EFM/EFMPlus coded channels for CD/DVD), is close to maximum-likelihood bound (MLB), and it is better than that of other schemes at channel densities of 4.5 and higher. Advantageously, the detector of the invention is simple in structure compared to conventional partial response Viterbi detector schemes. By processing the detected data in accordance with a set of data correction rules, the invention provides advantageous enhanced detection capacity.

Abstract: In a DVD-R on which information is to be recorded by an information recording apparatus, prior to the recording of the information therein, there are recorded in advance at least identification information for identifying the information recording apparatus for recording the information onto the DVD-R, and recording parameter information containing optimization information for optimizing a recording state in the record processing executed by the information recording apparatus specified by the identification information. Furthermore, the information recording apparatus reads the recording parameter information at the execution of record processing to use it for the record processing.

Abstract: An optical recording medium for accurately deriving the address information or the disc rotation control information despite narrow track pitch and for recording signals to a high density, and a method and apparatus for recording and/or reproducing such optical recording medium. The optical recording medium has a wobbled groove and pits formed at a pre-set interval in an area between turns of the wobbled groove. The recording/reproducing method includes controlling rotation of the optical recording medium by a wobbled signal from the groove and detecting the position on the optical recording medium of a recording signal by pit signals detected from the pits. The recording/reproducing apparatus includes a detection device for detecting the wobbled signal from the groove and a detection device for detecting pit signals from the pits.

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: A maximum mark length detector comprising a total value register for storing a total value Lsum of measured mark lengths; a measured value register for storing a measured value of a mark length; an arithmetic unit for computing the sum Lp of a current measured value Lk and a previously measured value PLk stored in the measured value register and subtracting a maximum value Lmax from the total value Lsum when the total value Lsum reaches the measured maximum value Lmax; a counter to count the number of times the subtraction is performed; and a comparator for completing the detection when a count value C of the counter reaches a predetermined value.

Abstract: The present invention provides digital read channel circuitry for an optical disk reader. An RF signal corresponding to a track on the optical disk is sampled to provide digital samples corresponding to the RF signal. The samples are taken at a rate that may differ from the channel bit rate of the RF signal. The digital samples are then processed to provide data at the channel bit rate. Multiple digital read channels may be used to read multiple tracks of an optical disk simultaneously. The multiple RF signals may be sampled based on a sample clock common to the multiple digital read channels.

Abstract: Even with an asymmetric reproduction waveform, or under the noisy environment, an accurate equalizing error is found and temporary judgment value for adaptively controlling the coefficient of FIR filter is accurately outputted. A waveform equalizer for equalizing a waveform of a reproduction signal obtained by reproducing marks and non-marks recorded on a recording medium is provided. The equalizer includes: a detector which detects asymmetry of the reproduction signal arising from physical profiles of the marks and non-marks and outputs a detection signal representing asymmetric amount; a discriminator which discriminates the marks and non-marks based on the reproduction signal to output a discriminated signal; and a selector which calculates a first and second coefficient multiplied by the reproduction signal of the marks and non-marks based on the detection signal, which are different. The selector selects one of the first and second coefficients based on the discriminating signal.

Abstract: An optical disk system comprises an optical disk device and control circuitry. The optical disk device stores user data and transfers an analog signal representing the user data to the control circuitry. The control circuitry sub-samples the analog signal to generate a sub-sampled signal. The control circuitry up-samples and re-times the sub-sampled signal using a control signal to generate an up-sampled and re-timed signal. A digital feedback loop in the control circuitry generates the control signal.

Abstract: A method is disclosed for compensating for intersymbol interference on an optical disc. The method includes measuring an intersymbol linear transfer function. The intersymbol linear transfer function substantially describes a linear portion of the effect of intersymbol interference on an optically detected read signal from an optical disc. A partial response target frequency response is divided by the intersymbol linear transfer function to obtain a linear equalization filter response. A read signal from the optical disc is convolved with the linear equalization filter response. This results in the read signal being equalized and containing a controlled partial-response target intersymbol interference. There is also disclosed a method of compensating utilizing a decision feedback equalizer where the target frequency response is either a partial-response or a zero-forcing response.

Abstract: An information recording and reproducing method is provided with an information recording method of optically recording digital data onto an information recording medium such as an optical disc etc., by forming a pit having a shape corresponding to the digital data, and an information reproducing method of optically reproducing the recorded digital data from the information recording medium.

Abstract: A decoding technique is disclosed for proving inexpensively a read channel circuit which has an error correction function and is applicable to high channel frequencies. In this read channel circuit, generating a reference slice level signal and a plurality of slice level signals which are different from the reference slice level signal, converting the playback signal into a plurality of binary signals synchronized with a channel clock according to each of the slice level signals, selecting two binary signals, measuring the phase distance between the two binary signals, judging the polarity of an inverted edge of a reference binary signal, and generating an error correction signal on the basis of the phase distance and the polarity of the inverted edge of the reference binary signal, whereby any error in the playback signal can be eliminated.

Abstract: An arrangement for generating an error signal representing the differences between an input signal voltage level (xpk, xnk) and an estimated value (rp, rn) for the input signal voltage level comprises first (T1, T2) and second (T5, T6) transconductors and a differencing circuit (T3, T4, T7, T8) which forms the modulus of the difference between the outputs of the transconductors. The error signal is converted into a probability signal by subtracting the error signal from a constant signal (408) to produce a signal at the output (407) which is a maximum when the input voltage level and estimated voltage level are equal.

Abstract: Apparatus for generating estimates of valid input signal values at sampling instants comprises a first data slicer (3) for slicing the input signal at a given level, data sequence detectors (205, 207) for detecting given data sequences in the input signal, second (301) and third (302) data slicers for slicing the input signal at signal values estimated for a given data bit of the given data sequences, memory elements (303, 304, 305; 306, 307, 308) for storing the outputs of the second (301) and third (302) data slicers when slicing the given data bit, and incrementing means (309, 311; 310, 312) for increasing or decreasing the estimated values depending on whether the stored outputs indicate the input signal value was above or below the estimated value when the given data bit was sliced by the second (301) or third (302) data slicer.

Abstract: A first signal is read from a first track of a recording medium. A second signal is read from a second track of the recording medium which neighbors the first track. A filter processes the second signal into a filtering-resultant signal according to a controllable filtering characteristic. A first subtracter operates for subtracting the filtering-resultant signal from the first signal to generate a subtraction-resultant signal. A peak detector generates peak-point information representing a timing at which the level represented by the first signal peaks. A temporary decision circuit implements a temporary decision about the subtraction-resultant signal. A second subtracter generates an error signal indicative of a difference between the subtraction-resultant signal and a signal representative of the result of the temporary decision at a timing equal to the timing represented by the peak-point information. The filtering characteristic of the filter is controlled in response to the error signal.

Abstract: An optical information recording medium (1) is composed of a pit recording area (2), wherein various control information is recorded by a prepit, and an user recording area (3) having a guide groove formed in a groove format, and a phase depth for the prepit and the groove are approximately the same that the phase depth is less than or equal to &lgr;/10, wherein &lgr; is a wavelength for reproducing light source. A recording/reproducing apparatus (4) for the optical information recording medium (1) is composed of decoding means (12) for decoding information by detecting a tangential push-pull reproduced signal from the prepit recording area (2) and detecting an aggregated signal from the user recording area (3).

Abstract: In an information reproducing apparatus employing a maximum likelihood decoding method such as Viterbi decoding, there is a problem such that power consumption increases because a maximum likelihood decoding circuit is complicated, and many circuit elements must be used. A clock output control means is provided on a read clock transmission line of a maximum likelihood decoder, and no read clock is supplied to the maximum likelihood decoder in operation modes other than a specific operation mode when an input data is decoded by a Viterbi decoder, and thereby, it is possible to greatly reduce a power consumption. More specifically, in operation modes other than the read mode, the supply of read clock is stopped by the clock output control means based on a control signal from a controller for controlling an operation mode such as decoding or the like.

Abstract: A sample of an information signal is periodically generated in response to a sampling clock signal. A level relation between successive ones of the information-signal samples is detected. A peak-corresponding sample is detected among the information-signal samples in response to the detected level relation and in response to a prescribed level range containing a “0” level. A level represented by the detected peak-corresponding sample is outside the prescribed level range. Calculation is made regarding a level difference between information-signal samples immediately preceding and immediately following the detected peak-corresponding sample. A phase error signal is generated in response to the calculated level difference. The sampling clock signal is controlled in response to the phase error signal to lock the sampling clock signal in phase with the information signal.

Abstract: A signal of a run-length-limited code is reproduced from a recording medium. A transversal filter subjects the reproduced signal to a partial-response waveform equalization responsive to tap coefficients. Detection is made as to whether or not the reproduced signal corresponds to a peak point. Peak-point information is generated in response to a result of the detection. A delay circuit outputs at least three successive samples of the peak-point information. A temporary decision device operates for calculating a temporary decision value of the equalization-resultant signal on the basis of the successive samples of the peak-point information. A difference between the temporary decision value of the equalization-resultant signal and an actual value thereof is calculated, and an error signal is generated in response to the calculated difference. The tap coefficients of the transversal filter are controlled in response to the error signal so as to minimize the error signal.

Abstract: On an optical disk, information is recorded at a track pitch of TP &mgr;m/track and a bit pitch of BP &mgr;m/bit on the basis of a modulation code with a minimum run of D and a code rate of R. By using a light source whose wavelength is &lgr; &mgr;m and an objective lens whose numerical aperture is NA, the information is reproduced from the optical disk by a PRML scheme. The optical disk fulfills the following conditions: TP>&lgr;/(2NA) BP>{1/(2(D+1)R)}·{&lgr;/(2NA)} TP·BP≦0.135(&lgr;/NA)2 0.361≦BP/TP<1/{(D+1)R}.

Abstract: A disk memory device comprises a head which reads a read-out signal from a disk, an amplifier which amplifies an analog signal waveform of the read-out signal read from the head, a filter which decreases a noise of the read-out signal output from the amplifier, an A/D converter which converts the read-out signal of which noise is decreased by the filter into a digital signal including a waveform distortion component, and a neural network type signal processing circuit which detects a binarized data from the digital signal.