JP2005339711A - Waveform equalization method, information reproduction method, information reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveform equalization method, an information reproduction method, and an information reproducing apparatus which facilitate calculation processing while preventing reduction in capacity. <P>SOLUTION: The waveform equalization method comprises: extracting a clock; quantizing a reproduced signal by the clock; multiplying consecutive quantized data by coefficients; and adding multiplication result when reproducing information by using a multi-valued signal, wherein a waveform interference amount is calculated from a known part out of the quantized data, and the coefficients are obtained from the waveform interference amount. A delay element D delays quantized data by one sample (clock), and a multiplier ×C0 multiplies quantized data by a coefficient C0, and a multiplier ×C1 multiplies quantized data by a coefficient C1, and a multiplier ×C2 multiplies quantized data by a coefficient C2, and an adder Σ adds outputs of all multipliers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reproducing method for recording information on a recording medium or reproducing information from a recording medium, particularly a waveform equalizing method, an information reproducing method, and an information reproducing method for improving recording and reproducing characteristics when information is recorded in multiple values. The present invention relates to an information reproducing apparatus.

Japanese Patent Laid-Open No. 2000-348440 discloses a waveform equalization apparatus and information capable of accurately performing waveform equalization processing even when an extreme noise component or distortion component is included in a generated input sample. A playback device is described.
This is a waveform equalizer that performs waveform equalization processing on an input sample, an ideal response generator that generates an ideal response sample having the same content as an input sample of known content, and an input sample A digital filter that performs waveform equalization processing and generates waveform equalization samples, an information interpreter that interprets the contents of waveform equalization samples and generates interpretation signals, and a period during which input samples with known contents should be input to the digital filter The coefficient determination for setting the filter coefficient of the digital filter in the period based on the input sample actually input to the digital filter in the known sample input period, the ideal response sample, and the interpretation signal generated in the period Department.

In Japanese Patent Laid-Open No. 2003-317256, when reproducing information in which the level of a reproduction signal is multi-valued by modulating the area of a recording mark of an optical information recording medium, intersymbol interference is accurately processed by waveform equalization processing. A multi-value data recording / reproducing apparatus is described for enabling good removal.
This is because the size of the recording mark is changed on the optical information recording medium corresponding to the multi-value data, and at the time of information reproduction, the signal obtained by scanning the recording mark with a light spot is subjected to predetermined signal processing. In a multi-value data detection circuit for detecting multi-value data, a predictor that predicts and predicts the multi-value data, a delay device that delays signal processing by the time required for the prediction determination in the predictor, and a predictive determination of the predictor It has a determiner that performs waveform equalization based on the prediction data as a result to determine multi-value data.

Japanese Patent Application Laid-Open No. 2002-319138 discloses an information recording / reproducing apparatus for accurately reproducing a recorded multi-value information sequence when the multi-value information sequence is recorded at a high density on a recording medium such as an optical disk. Is described.
This reproduces the calibration information of the multi-value information sequence recorded on the optical disc and the user information of the multi-value information sequence, obtains the maximum value of the reproduction signal of each value of the reproduced calibration information by the demodulation circuit, and reproduces each reproduction Determine the waveform equalization processing to make each amplitude outside the range separated by the multi-value data period of each value before and after each maximum value with respect to the signal, and determine the reproduced signal of the user information as described above. A waveform equalization process based on the waveform equalization process is performed.

JP 2000-348440 A JP 2003-317256 A JP 2002-319138 A

In general, when information is recorded in multiple values on an information recording medium, waveform equalization processing for removing waveform interference is performed when information is reproduced from the reproduced signal.
The waveform equalization system number is obtained by recording and reproducing known data in advance, performing a plurality of processes, and changing the output by equalization to be close to the target value. Japanese Patent Laid-Open No. 2002-319138 describes a method for shortening the coefficient calculation.
However, in any of the above prior arts, it is necessary to record a special pattern in order to obtain the waveform equalization coefficient, which causes a reduction in capacity.
Further, in order to periodically update the coefficient, it is necessary to simplify the calculation process as well as the capacity problem.

  Therefore, the main object of the present invention is to provide a waveform equalization method, an information reproduction method, and an information reproduction device that can solve the above capacity reduction problem.

In order to achieve the above object, the present invention uses the fact that waveform equalization has linearity, calculates the amount of interference from a plurality of patterns that can detect the amount of waveform interference, and calculates each coefficient from this amount It was.
Further, the capacity is prevented from being reduced by determining the coefficient using the preamble used for the phase alignment of the sector mark and the clock indicating the sector as the plurality of patterns.

  Specifically, in the first aspect of the present invention, there is provided a reproduction method for reproducing information from a recording medium using a multilevel signal, and when reproducing the information from the recording medium, a clock is extracted, In a waveform equalization method in which a reproduction signal is quantized by a clock and multiplied by a coefficient to each of the continuous quantized data, a waveform interference amount is calculated from a known portion of the quantized data, and the waveform interference amount The coefficient is obtained from the following.

  According to a second aspect of the present invention, in the waveform equalization method according to the first aspect, the waveform interference amount is calculated using a first level L1 and a second level L2 among a plurality of levels at which multilevel recording is performed. It is characterized by doing.

  According to a third aspect of the present invention, in the waveform equalization method according to the second aspect, the first level L1 and the second level L2 are combinations in which a multilevel reproduction signal is maximized and minimized. Features.

  According to a fourth aspect of the present invention, in the waveform equalization method according to any one of the first to third aspects, synchronization in a reproduction signal is performed as known data that is a known part of the quantized data. A signal and a clock phase synchronization signal are used.

  According to a fifth aspect of the present invention, in the waveform equalization method according to any one of the first to fourth aspects, the known data that is a known portion of the quantized data is acquired a plurality of times, and an average process is performed. It is characterized by performing.

  According to a sixth aspect of the present invention, in the waveform equalization method according to the fourth aspect, the coefficient is updated every time the synchronization signal appears.

  According to a seventh aspect of the present invention, there is provided a reproducing apparatus for reproducing information from a recording medium using a multilevel signal, and when reproducing the information from the recording medium, a clock is extracted by a PLL circuit, Synchronously, a reproduction signal is quantized by an AD converter, and the quantized value is input to a circuit that delays a plurality of clocks. The quantized data is multiplied by a coefficient, and an output of the multiplier In the information reproducing apparatus for adding the signals by an adder, a waveform interference amount is calculated from a synchronization signal and a clock phase synchronization signal in the reproduction signal of the quantized data, and the coefficient is obtained from the waveform interference amount. To do.

  According to an eighth aspect of the present invention, there is provided a reproducing method for reproducing information from a recording medium using a multi-level signal, and when reproducing the information from the recording medium, a clock is extracted and synchronized with the clock. In an information reproduction method in which a reproduction signal is quantized, and each of the continuous quantized data is multiplied by a coefficient, the amplitude value of each of the synchronization signal in the reproduction signal and the phase synchronization signal of the clock is detected. The coefficient is obtained from the value.

  According to a ninth aspect of the present invention, there is provided a reproducing apparatus for reproducing information from a recording medium using a multi-level signal, and when reproducing the information from the recording medium, a clock is extracted by a PLL circuit, Synchronously, a reproduction signal is quantized by an AD converter, and the quantized value is input to a circuit that delays a plurality of clocks. The quantized data is multiplied by a coefficient, and an output of the multiplier In the information reproducing apparatus for adding the signals by an adder, the amplitude of the synchronizing signal and the phase synchronizing signal of the clock in the reproduced signal of the quantized data is obtained by a peak hold circuit, and the coefficient is obtained from this amplitude. To do.

  The invention according to claim 10 is a reproducing method for reproducing information from a recording medium using a multi-level signal, and when reproducing the information from the recording medium, a clock is extracted and synchronized with the clock. In the information reproduction method of quantizing a reproduction signal and multiplying each of the continuous quantized data by a coefficient and adding them, when the clock is extracted, the synchronization signal in the reproduction signal and the phase synchronization signal of the clock are Each amplitude value from the quantized value is detected, and when the clock is not synchronized, the amplitude is detected by peak detection of the reproduction signal, and the coefficient is obtained from the amplitude value.

  According to an eleventh aspect of the present invention, there is provided a reproducing apparatus for reproducing information from a recording medium using a multilevel signal, and when reproducing the information from the recording medium, a clock is extracted by a PLL circuit, Synchronously, a reproduction signal is quantized by an AD converter, and the quantized value is input to a circuit that delays a plurality of clocks. The quantized data is multiplied by a coefficient, and an output of the multiplier In the information reproducing device for adding the signals by the adder, when the PLL circuit locks the amplitude of the synchronizing signal in the reproduced signal of the quantized data and the amplitude of the phase synchronizing signal of the clock, the synchronizing signal in the reproduced signal In addition, the phase synchronization signal of the clock is calculated from the quantized value. When the PLL circuit is not locked, the reproduction signal is calculated from the output of the peak hold circuit, and the amplitude is calculated from the amplitude. And obtaining the.

  According to the first aspect of the present invention, there is provided a reproducing method for reproducing information from a recording medium using a multi-level signal, and when reproducing the information from the recording medium, a clock is extracted and reproduced by the clock. In a waveform equalization method of performing signal quantization and multiplying each of the continuous quantized data by a coefficient, a waveform interference amount is calculated from a known portion of the quantized data, and the coefficient is calculated from the waveform interference amount. Therefore, the coefficient can be calculated easily.

  According to a second aspect of the present invention, in the waveform equalization method according to the first aspect, the waveform interference amount is calculated using a first level L1 and a second level L2 among a plurality of levels at which multilevel recording is performed. Therefore, the amount of waveform interference can be easily calculated at any two levels.

  According to a third aspect of the present invention, in the waveform equalization method according to the second aspect, the first level L1 and the second level L2 are combinations in which a multilevel reproduction signal is maximized and minimized. Therefore, stability against noise can be obtained by using the maximum and minimum levels.

  According to a fourth aspect of the present invention, in the waveform equalization method according to any one of the first to third aspects, the known data that is a known part of the quantized data is included in the reproduced signal. Since the synchronization signal and the clock phase synchronization signal are used, new data for coefficient calculation becomes unnecessary.

  According to the invention of claim 5, in the waveform equalization method according to any one of claims 1 to 4, the known data that is a known part of the quantized data is acquired a plurality of times, Since the averaging process is performed, the influence of noise can be reduced.

  According to the sixth aspect of the present invention, in the waveform equalization method according to the fourth aspect, since the coefficient is updated every time the synchronization signal appears, fluctuation due to in-plane variation of the media can be suppressed. it can.

  According to the seventh aspect of the present invention, there is provided a reproducing apparatus for reproducing information from a recording medium using a multilevel signal, and when reproducing the information from the recording medium, a clock is extracted by a PLL circuit, and A reproduction signal is quantized by an AD converter in synchronization with a clock, the quantized value is input to a circuit that delays a plurality of clocks, and the quantized data is multiplied by a coefficient, respectively. In an information reproducing apparatus that adds the outputs of the above-mentioned outputs by an adder, a waveform interference amount is calculated from a synchronization signal and a clock phase synchronization signal in the reproduction signal of the quantized data, and the coefficient is obtained from the waveform interference amount; As a result, the coefficient can be easily calculated.

  According to an eighth aspect of the present invention, there is provided a reproducing method for reproducing information from a recording medium using a multi-level signal, and when reproducing the information from the recording medium, a clock is extracted and synchronized with the clock. Then, in the information reproduction method of performing quantization of the reproduction signal and multiplying each of the continuous quantized data by a coefficient and detecting the amplitude value of each of the synchronization signal in the reproduction signal and the phase synchronization signal of the clock, Since the coefficient is obtained from the amplitude value, the coefficient can be easily obtained even when the clocks are not synchronized.

  According to a ninth aspect of the present invention, there is provided a reproducing apparatus for reproducing information from a recording medium using a multilevel signal, and when reproducing the information from the recording medium, a clock is extracted by a PLL circuit, A reproduction signal is quantized by an AD converter in synchronization with a clock, the quantized value is input to a circuit that delays a plurality of clocks, and the quantized data is multiplied by a coefficient, respectively. In an information reproducing apparatus for adding the outputs of the output signals by an adder, the amplitude of the synchronizing signal and the phase synchronizing signal of the clock in the reproduced signal of the quantized data is obtained by a peak hold circuit, and the coefficient is obtained from the amplitude. Therefore, the coefficient can be easily obtained even when the clocks are not synchronized.

  According to a tenth aspect of the present invention, there is provided a reproducing method for reproducing information from a recording medium using a multi-level signal, and when reproducing the information from the recording medium, a clock is extracted and synchronized with the clock. In the information reproduction method of performing quantization of the reproduction signal and multiplying each of the continuous quantized data by a coefficient and adding the coefficient, the synchronization signal in the reproduction signal and the phase synchronization of the clock are extracted when the clock is extracted. When each amplitude value from the quantized signal is detected and the clock is not synchronized, the amplitude is detected by peak detection of the reproduction signal, and the coefficient is obtained from this amplitude value. When the clocks are not synchronized, an optimum coefficient can be obtained for each of the synchronized cases.

  According to the invention of claim 11, there is provided a reproducing apparatus for reproducing information from a recording medium using a multilevel signal, and when reproducing the information from the recording medium, a clock is extracted by a PLL circuit, and A reproduction signal is quantized by an AD converter in synchronization with a clock, the quantized value is input to a circuit that delays a plurality of clocks, and the quantized data is multiplied by a coefficient, respectively. In the information reproducing apparatus for adding the outputs of the output signals by the adder, when the PLL circuit locks the amplitude of the synchronizing signal in the reproduced signal of the quantized data and the phase synchronizing signal of the clock, The synchronization signal and the phase synchronization signal of the clock are calculated from the quantized values. When the PLL circuit is not locked, the reproduction signal is calculated from the output of the peak hold circuit, Since it was decided to determine the coefficients, if the clock is not synchronized, it is possible to find the optimal coefficient in each case are synchronized.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 shows a reproduction waveform of multilevel recording. The upper stage is the ideal value of the reproduced waveform, and the middle stage is the ideal reproduced clock. The voltage of the reproduced waveform changes to a rectangular waveform at the rising edge of the reproduced clock, and the level can be determined stably at the falling edge of the clock. On the other hand, the actual waveform is as shown in the lower part.

FIG. 2 shows a configuration example of an optical disk device as an information reproducing device. In the present embodiment, an optical disk is described as an example of a recording medium, but the present invention is not limited to the recording method of the medium. That is, the same effect can be obtained with a magneto-optical, write-once medium, and rewritable medium.
FIG. 2 shows the minimum necessary configuration centering on the parts related to the present invention. When a command is sent from an external device (for example, a personal computer) to the optical disk drive, the interface controller 10 receives the command and reports to the controller 11 that the command has been received. The controller 11 interprets this command, causes the optical disc drive to perform the operation requested by the command, and sends a report to the external device through the interface controller 10. When recording information, the information is temporarily stored in the buffer memory 13 from the external device through the interface controller 10 through the digital circuit 12. The digital circuit 12 performs operations such as adding an error correction code, adding a synchronization signal, and converting the data into a modulation code to a multilevel level.

As for the address to be written, information is recorded at an address indicated by reading an address written in advance on the medium. Next, the current is controlled so that an LD (laser diode) on the optical pickup unit 16 emits light so that recording is performed on the optical disk 15 by the analog circuit 14, and recording is performed at a multilevel level.
Also, the light emitted from the LD from the optical pickup unit 16 hits the medium (optical disk 15), and the reflected light is received by a PD (photo detector) and processed by the analog circuit 14 to generate a focus error signal, a tracking error signal, and the like. The servo circuit 17 controls the pickup position and lens position.
At this time, the optical information medium (optical disk 15) usually has a spiral groove or data array. For this reason, it moves from the inner periphery to the outer periphery with the passage of time (for example, from the outer periphery to the inner periphery), and exceeds the range where tracking control is possible.
Therefore, the entire optical pickup unit 16 is moved from the tracking servo signal, and a control called a caliper is performed so that the position of the lens can always be kept close to neutral.

In the case of reproduction, the output of the pickup is quantized by the analog circuit 14 and extracted by using a PLL (phase synchronization circuit: hereinafter also referred to as “PLL circuit”) and the like, and the digital circuit 12 detects synchronization, demodulation, and error. Corrections are made and stored in the buffer memory 13. Thereafter, the information is transferred to the external device through the interface controller 10.
FIG. 3 shows an example of the information array. In the case of multi-level recording, unlike the binary recording, the edge portion of the reproduction signal cannot be correctly extracted, so that the clock cannot be extracted from the edge. Therefore, a clock is extracted using a special mark written as “ClockMark” separately from the information part written as “Data”. The length of Data is set so that the amount of clock fluctuation caused by eccentricity or the like is within the allowable value of the system.
As the clock mark, it is necessary to use a pattern that is not affected by intersymbol interference from the data before and after the clock mark, and to prevent erroneous synchronization even if the position fluctuates.

FIG. 4 shows an example of the clock mark. This is an example of a clock mark of “00700” when information is recorded with eight values, for example, when the amount of reflected light is 0 and when the amount of reflected light is 7. FIG. 4B shows a waveform obtained by differentiating the reproduction signal, and the synchronization position can be detected at this zero cross. A clock can be generated by inputting this synchronization position to a commonly used PLL phase comparator.
FIG. 5 shows an example of the synchronization mark. Similar to the clock mark, for example, when recording information with eight values, an example of a synchronization mark of “00000700” is shown in which the larger reflected light amount is 0 and the smaller light amount is 7. FIG. 5B shows a waveform obtained by differentiating the reproduction signal, and the synchronization position can be detected at this zero cross.
The reason why the synchronization mark is longer than the clock mark is that a fluctuation for recovering a bit slip caused by a defect or the like is larger than the clock mark, and therefore a larger window is required. FIG. 6 shows the arrangement of clock marks and synchronization marks.

FIG. 7 shows an example of the sector mark and preamble. The sector mark A can be detected even in an asynchronous state by using a special pattern that does not exist in the data. Therefore, a mark is composed of a series of 7 and a series of 0.
Preamble B records 0 and 7 alternately in order to pull in the clock phase early and reduce the inversion interval.
FIG. 8 shows an example of a 3-tap waveform equalization circuit. D is a delay element for one sample (clock), xC0 is a multiplier that multiplies the coefficient C0, similarly, xC1 is a multiplier that multiplies the coefficient C1, and xC2 is a multiplier that multiplies the coefficient C2. Yes, Σ is an adder for adding the outputs of all the multipliers.
“3 taps” means that the number of multiplications and the total addition of these is 3, and any number of taps can be similarly performed.

This waveform equalization is considered as follows from previous and subsequent data, and eliminates waveform interference.
In the case of a signal having no waveform interference, the amplitude of the mark at the time of recording is expressed as follows.
_{W n-5, W n-} 4, W n-3, W n-2, W n-1, W n, W n + 1, W n + 2, W n + 3,
W _{n + 4} , W _{n + 5}
At this time, waveform interference occurs because the beam diameter is larger than the mark. When this degree is α, the reproduction signal can be expressed as follows together with the preceding and following signals.
R _n = αW _n-1 + W _n + αW _{n + 1}
The waveform equalization is to remove the W _n−1 and W _{n + 1} components from the reproduction signal.
Similar to _{R n R n-1, R} n + 1 can be expressed as follows.
R _n-1 = αW _n-2 + W _n-1 + αW _n
R _n = αW _n-1 + W _n + αW _{n + 1}
R _{n + 1} = αW _n + W _{n + 1} + αW _{n + 2}
In the case of 3 Tap, waveform equalization is obtained by subtracting αR _n−1 and αR _{n + 1} from R _n .
-ΑR _n-1 + R _n -αR _n-1
= −α ² W _n−2 + (1-2 × α ² ) W _n −α ² W _{n + 2}
Furthermore, as shown in the following formula, the reciprocal of (1-2 × α ² ) is applied so that the term of Wn becomes 1.

Each coefficient of the equation represented by R in the above equation is a waveform equalization factor. At this time, the coefficients of the first and third items in the expression indicated by W are residual errors, and when this value is large, the number of taps may be increased.
In this way, if a reproduction signal having a waveform interference of about α times that of an adjacent sample is R and a true value without waveform interference is W, R can be expressed by a function of W and α.
At this time, if an inverse function is obtained, W can be obtained from R. However, in order to obtain W by an inverse function, it is necessary to use all R from −infinity time to + infinity time, but the processing can be performed with a finite sample in consideration of an allowable value.

Next, this α is calculated. The value of W without waveform interference at level 0 is V0, and the value at 7 is V7. At this time, if the levels 0, 0, 0 are recorded, the reproduction signal R000 is
R000 = αV0 + V0 + αV0
= (1 + 2α) V0
It becomes. Similarly, when levels 7, 7, and 7 are recorded, the reproduction signal R777 is
R777 = αV7 + V7 + αV7
= (1 + 2α) V7
It becomes.
Next, when levels 0, 7, and 0 are recorded, the reproduction signal R070 is
R070 = αV0 + V7 + αV0
= V7 + 2αV0
It becomes.

Next, when levels 7, 0 and 7 are recorded, the reproduction signal R707 is
R707 = αV7 + V0 + αV7
= V0 + 2αV7
It becomes.
Here, the difference between R000 and R777 and the difference between R707 and R070 are taken.
R000−R777 = (1 + 2α) (V0−V7)
R707-R070 = (1-2α) (V0-V7)
Therefore (R000−R777) (1-2α) = (R707−R070) (1 + 2α)
And solving for α,
α = ((R000−R777) − (R707−R070)) / ((R000−R777) + (R707−R070)) / 2
It becomes. Since R000, R777, R070, and R707 are reproduction signals, the code interference amount α can be calculated only from the reproduction signal. This may be any two values other than the combination of 0 and 7 (claims 2 and 3).

The four types of reproduction signals can be obtained from R000 and R777 from the sector mark and R070 and R707 from the preamble without special recording as test data.
Further, since the reproduced signal contains a noise component, the random noise component can be removed by performing averaging processing a plurality of times.
Since the sector mark and the preamble are recorded at a certain period, this calculation can be repeated for each constant period to update the coefficient.

A second embodiment will be described with reference to FIGS.
FIG. 9 shows a waveform equalization circuit in this embodiment. The difference from the circuit shown in FIG. 8 is that a coefficient calculator is provided.
In this method, the four signals R000, R777, R070, and R707 described above are sampled from the input signals by a sequencer (not shown) to obtain each coefficient (claim 7).
When a medium (such as an optical disk) is inserted into the drive or when the power is turned on, the waveform equalization coefficient cannot be obtained. If the PLL is not locked, R000 and R777 can be detected by AD, but R070 and R707 cannot be detected.

Therefore, a method of calculating α using peak hold not related to the clock will be described. As shown in FIG. 10, enable signals 1 and 2 that permit detection of peak hold are generated for sector mark A and preamble B. This signal only needs to be roughly aligned.
The peak of R000 and R777 is detected by the enable signal 1 and held in the L period. Further, the peaks of R070 and R707 are detected by the enable signal 2 and held in the L period.
As shown in FIG. 11, the maximum value and the minimum value of the reproduction signal are held at the respective timings by the peak hold circuit PH based on the enable signal shown in FIG. This is input to an AD converter by a switch or the like, and a value is read by a controller (not shown) to calculate a coefficient (claims 8 and 9).
Further, when the power is turned on or when the medium is loaded, the coefficient is determined by this sample hold, and when the PLL clock is locked, the coefficient can be determined by a sample value based on the clock. The flow at this time is shown in FIG. 12 (claims 10 and 11).

It is a figure which shows the example of the reproduction | regeneration waveform in multi-value recording. It is a block diagram of the recording / reproducing apparatus in 1st Embodiment. It is a figure which shows the example of an arrangement | sequence of data. It is a figure which shows a clock mark and its differential waveform. It is a figure which shows a synchronous mark and its differential waveform. It is a figure which shows the example of arrangement | positioning of the conventional synchronous mark, a clock mark, and data. It is a figure which shows a sector mark and a preamble. It is a figure which shows a waveform equalization circuit. It is a figure which shows the waveform equalization circuit in 2nd Embodiment. It is a figure which shows the relationship between a sector mark, a preamble, and an enable signal. It is a block diagram which determines a coefficient by peak hold. It is a flowchart of coefficient determination.

Explanation of symbols

  15 Optical disc as a recording medium

Claims (11)

A reproduction method for reproducing information from a recording medium using a multilevel signal, wherein when reproducing the information from the recording medium, a clock is extracted, and the reproduced signal is quantized by the clock, and the continuous In the waveform equalization method of multiplying and adding each coefficient to quantized data,
A waveform equalization method, wherein a waveform interference amount is calculated from a known part of the quantized data, and the coefficient is obtained from the waveform interference amount. The waveform equalization method according to claim 1,
A waveform equalization method, wherein the waveform interference amount is calculated using a first level L1 and a second level L2 among a plurality of levels at which multilevel recording is performed. The waveform equalization method according to claim 2,
The waveform equalization method, wherein the first level L1 and the second level L2 are a combination that maximizes and minimizes a multilevel reproduction signal. In the waveform equalization method according to any one of claims 1 to 3,
A waveform equalization method using a synchronization signal in a reproduction signal and a phase synchronization signal of a clock as known data which is a known part of the quantized data. In the waveform equalization method according to any one of claims 1 to 4,
A waveform equalization method characterized in that known data, which is a known part of the quantized data, is acquired a plurality of times and averaged. The waveform equalization method according to claim 4,
A waveform equalizing method, wherein a coefficient is updated every time the synchronization signal appears. A reproduction apparatus for reproducing information from a recording medium using a multilevel signal, wherein when reproducing the information from the recording medium, a clock is extracted by a PLL circuit and is reproduced by an AD converter in synchronization with the clock. Information reproduction in which a signal is quantized, the quantized value is input to a plurality of circuits that delay one clock, the quantized data is multiplied by a coefficient, and the multiplier output is added by an adder. In the device
An information reproducing apparatus, wherein a waveform interference amount is calculated from a synchronization signal and a clock phase synchronization signal in the reproduction signal of the quantized data, and the coefficient is obtained from the waveform interference amount. A reproduction method for reproducing information from a recording medium using a multilevel signal, wherein when reproducing the information from the recording medium, a clock is extracted, and a reproduction signal is quantized in synchronization with the clock, In the information reproduction method for multiplying and adding each coefficient to the continuous quantized data,
An information reproducing method, wherein the amplitude value of each of the synchronizing signal and the clock phase synchronizing signal in the reproduced signal is detected, and the coefficient is obtained from the amplitude value. A reproduction apparatus for reproducing information from a recording medium using a multilevel signal, wherein when reproducing the information from the recording medium, a clock is extracted by a PLL circuit and is reproduced by an AD converter in synchronization with the clock. Information reproduction in which a signal is quantized, the quantized value is input to a plurality of circuits that delay one clock, the quantized data is multiplied by a coefficient, and the multiplier output is added by an adder. In the device
An information reproducing apparatus characterized in that an amplitude of a synchronizing signal and a clock phase synchronizing signal in a reproduced signal of the quantized data is obtained by a peak hold circuit, and the coefficient is obtained from the amplitude. A reproduction method for reproducing information from a recording medium using a multilevel signal, wherein when reproducing the information from the recording medium, a clock is extracted, and a reproduction signal is quantized in synchronization with the clock, In the information reproduction method for multiplying and adding each coefficient to the continuous quantized data,
When the clock is extracted, the respective amplitude values from the quantized values of the synchronization signal and the clock phase synchronization signal in the reproduction signal are detected, and when the clock is not synchronized, the reproduction signal An information reproducing method characterized by detecting an amplitude by detecting a peak and obtaining the coefficient from the amplitude value. A reproduction apparatus for reproducing information from a recording medium using a multilevel signal, wherein when reproducing the information from the recording medium, a clock is extracted by a PLL circuit and is reproduced by an AD converter in synchronization with the clock. Information reproduction in which a signal is quantized, the quantized value is input to a plurality of circuits that delay one clock, the quantized data is multiplied by a coefficient, and the multiplier output is added by an adder. In the device
When the PLL circuit locks the amplitude of the synchronization signal in the reproduction signal of the quantized data and the phase synchronization signal of the clock, the synchronization signal in the reproduction signal and the phase synchronization signal of the clock are quantized. An information reproducing apparatus characterized by calculating from a value and, when the PLL circuit is not locked, calculating a reproduction signal from an output of a peak hold circuit and obtaining the coefficient from the amplitude.

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