JP2001184796A - Data reproducing system and optical disk device to reproduce data by using the same system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data reproducing system capable of efficiently detecting viterbi even in the case of reproduced waveform containing distortion. SOLUTION: In the data reproducing system to calculate a path metric value based on a branch metric value to be calculated from an expectation value to be determined by partial response waveform and a sampling value and to determine reproduced data based on a comparison and calculation result of the value, the branch metric value is used for calculation of the path metric value by providing a means to perform sampling with prescribed cycles at plural sampling positions by unit of recorded data and a synthetic calculation means to calculate branch metric according to each sampling position from plural sampling values and expectation value from the means to perform sampling, to weigh the value according to the sampling positions, to synthesize the branch metric value according to a prescribed data transition state and to calculate a synthetic branch metric value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data reproducing system for a recording medium applied to a data recording device such as an optical disk device, a magneto-optical disk device or a magnetic disk device. Further, the present invention relates to an optical disk device for reproducing data using the system.

[0002]

2. Description of the Related Art For example, an optical disk recording medium (optical disk, magneto-optical disk) used in an optical disk device is
Due to its large capacity, interchangeability, high reliability, and the like, it is used in various fields such as recording and reproduction of image / image information and code recording for computers. In such an optical disk device, a method of recording and reproducing data with higher accuracy is desired as the recording density increases. As a method of recording and reproducing data with high accuracy on the optical disk recording medium, for example, a recording data signal is modulated into a so-called partial response (PR) waveform and recorded on the optical disk recording medium, while reproduction from the optical disk recording medium is performed. A method has been proposed in which a so-called Viterbi detector (maximum likelihood data detector) detects the most probable data after sampling a signal at a predetermined cycle.

In the conventional PRML system configuration shown in FIG. 1, a reproduced signal is analog-processed by an amplifier (Amp) 50 and a low-pass filter (LPF) 51,
2 and is equalized by an equalizer (EQ) 53. The equalizer 53 may be performed by analog processing or may be performed by both analog and digital. Phase detector (Phase Detect)
(or) 55 to extract a phase error, create a clock (channel clock) whose phase and frequency are adjusted by the PLL 54 based on the phase error, and supply the ADC 52 with a clock for obtaining an optimal sampling value. Although not shown, a similar clock is also supplied to the logic system.

FIG. 2 shows an example of a reproduced waveform and a sampling value. When the ideal signal of PR (1, 1) is sampled at the rising edge of the clock, three levels of "0", "1" and "2" are obtained. PR that satisfies Nyquist conditions
From FIG. 3 showing an example of (1, 1) waveform interference,
It can be understood that there are three levels in PR (1, 1) waveform interference that satisfies the Nyquist condition from an eye pattern for random data of (1, 7) modulation ((1, 7) RLLC).

FIG. 4 shows base data and its expected value in the case of PR (1, 1) as an example. From FIG. 4, in the case of waveform interference satisfying the Nyquist condition by a combination of data transition states, that is, in the case of PR (1, 1) as an example, the combination of transition states and the level expected according to the combination are shown as It is indicated by the expected value Ph. Here, the two combinations of the state transitions S2 to S1 and S1 to S2 do not exist in the (1, 7) RLLC and are not considered in Viterbi detection described later, and thus are deleted.

The Viterbi detection is performed by a branch metric calculation circuit (BM) 56 shown in FIG.
S) 58, a path metric memory (PMM) 57 and a path memory (PM) 59. The branch metric calculation circuit 56 calculates a branch metric for the expected value. The calculation formulas are shown in (1) to (6) below. In the following formula, the branch metric BMn (n =
0, 1, 3, 4, 6, and 7) calculate the square of the difference between the sample value yt at time t and the expected value Ph (h = 0, 1, 3, 4, 6, and 7). Since the branch metric only needs to know its relative size, the absolute value of the difference may be used.

BM0 = (yt-P0) 2 = yt2 (1) BM1 = (yt-P1) 2 = yt2 (2) BM3 = (yt-P3) 2 = (yt-1) 2 (3) BM4 = ( yt-P4) 2 = (yt-1) 2 (4) BM6 = (yt-P6) 2 = (yt-2) 2 (5) BM7 = (yt-P7) 2 = (yt-2) 2 (6) Next, the path metric is calculated by the ACS 58 using the branch metric. From FIG. 5 showing the state transition, the state S
There is only one path from state transitions S3 to S1 for the path to state 1 and state transition S0 to state S2 for the path to state S2. Therefore, it is uniquely calculated from the path metric PM (t-1, 0) of the path metric PM (t-1, 3). Each path metric calculation formula is shown in (7) to (10).

PM (t, 0) = min (PM (t−1,0) + BM0, PM (t−1,1) + BM1) (7) PM (t, 1) = PM (t−1,3) + BM3 (8) PM (t, 2) = PM (t-1,0) + BM4 (9) PM (t, 3) = min (PM (t-1,2) + BM6, PM (t-1,3) + BM7 (10) The magnitude relationship between the elements of PM (t, 0) expressed by the above equation (7) and PM (t, 3) expressed by the equation (10) is expressed by the following equation (7) -1
And (7) -2 and 4 of the formulas (10) -1 and (10) -2
It becomes the condition of the expression.

PM (t-1,0) + BM0 <PM (t-1,1) + BM1 (7) -1 PM (t-1,0) + BM0 ≧ PM (t-1,1) + BM1 (7) − 2 PM (t-1,2) + BM6 <PM (t-1,3) + BM7 (10) -1 PM (t-1,2) + BM6 ≧ PM (t-1,3) + BM7 (10) -2 Those Are classified into four types of merges as shown in FIG. In FIG.
In the case of a state transition from bottom to top, the corresponding path memory D0
The value of D3 is “0”. For example, in the case of a state transition from S1 to S2, the value of D2 is “0”. On the other hand, in the case of a state transition from top to bottom, the values of the corresponding path memories D0 to D3 are “1”. For example, 4 shown in FIG.
A path merge occurs when at least three or more merges are combined from one merge combination. In FIG.
In the case of the above-mentioned PR (1, 1) waveform as an example, it is a condition that a sample value “0” can be taken, a condition that a sample value “1” can be taken, and a condition that a sample value “2” can be taken. Is satisfied. In this case, since the condition is a condition that cannot occur, a merge occurs under the condition and the condition.
Kind. In FIG. 7, by tracking the data to the past so as to converge, the past data can be determined (the point indicated by ●), and the state transition is determined.

FIG. 8 shows the configuration of the path memory. Data selected by the path metric is input to D0 to D3. The input data is determined according to the merge shown in FIG.
In FIG. 8, the shift register SR operates in clock synchronization, but before the SR, the selector Sel. There is, SR
The data to enter is selected. For example, if “1” is input to D3, it is determined from FIG. 6 that the path from S3 to S3 is likely to be correct, and all SRs of D3 are at time t
The data of D3 of −1 is data at time t. On the other hand, D
When "0" is input to 3, the process goes from S2 to S3 according to FIG.
All SRs in D3
Represents the data at D2 at time t-1 as the data at time t.
Such an operation is performed by each SR and Sel. By doing,
Behind the path memory, D0 to D due to path merge
3 are converged to the same data.

The above-described conventional PRML system configuration has been effective in reproducing data using a waveform composed of linear superpositions.

[0012]

In the above-described operation principle of the conventional PRML, the target waveform is a transmission system in which linear superposition is established. That is, it was assumed that the sampling point of the reproduced waveform satisfies the Nyquist condition. However, magnetic disks, optical disks, and the like are no longer concerned with the easiness of magnetization orientation and read spots (apertures) that are increasing in density. Therefore, a nonlinear deviation component is included in the reproduced signal, and as a result, distortion occurs. For example, a medium having a magnetic super-resolution effect (MSR (Magnetic Sup
er Resolution) Medium creates a super-resolution effect by forming a mask using the heat distribution of the light beam, so a non-linear deviation component occurs in the reproduced signal due to the bias of the heat distribution of the light beam moving on the medium. However, a distortion occurs in the reproduced waveform due to the non-linear deviation component. In such a case, there is a problem that sufficient data detection capability cannot be obtained with the conventional PRML.

Therefore, it is required that Viterbi detection be effectively performed even on a reproduced waveform including distortion.
Therefore, a first object of the present invention is to provide a data reproducing system in which Viterbi detection is effectively performed even on a reproduced waveform including distortion. A second object of the present invention is to provide an optical disk device for reproducing data using the system.

[0014]

According to a first aspect of the present invention, there is provided a method for reproducing data from a recording medium on which data is recorded in accordance with a partial response waveform recording signal. The signal is sampled at a predetermined cycle, and a path metric value is calculated based on a branch metric value calculated from an expected value determined by the partial response waveform and the sampling value according to a Viterbi decoding algorithm, and the path metric value is calculated. In a data reproduction system in which reproduction data is determined based on a result of a comparison operation, a plurality of sampling means for sampling at a plurality of sampling positions in a predetermined cycle in a recording data unit, and a plurality of sampling means obtained by the plurality of sampling means Response to each sampling position based on the A combined branch metric value by calculating the calculated branch metric, weighting the branch metric value according to the sampling position, and combining the branch metric value according to a predetermined data transition state. Metric calculation means, and is configured to use the combined branch metric value for calculating a path metric value.

In such a data reproducing system, sampling is performed at a plurality of positions in units of recording data, and the most probable data transition state is extracted from branch metric values of a plurality of sampled sampled values. Therefore, since the data transition state is considered from a plurality of sampling values, the accuracy of extracting the data transition state can be improved. That is, when the sampling position does not satisfy the Nyquist condition, distortion can be corrected from the sampling values at a plurality of positions.

The partial response waveform is, for example, PR (1,1) ML or PR (1,1) in three values and four states.
2, 1) ML, PR (1, 2, 2, 1) ML or P
This is a waveform having a long constraint length such as R (1331) ML. The recording data unit is, for example, a data unit composed of 3 bits indicating a data transition state.

From the viewpoint that the Viterbi decoding algorithm can be applied even when the sampling position does not satisfy the Nyquist condition, according to the present invention, the combined branch metric calculation means includes: First calculating means for calculating a branch metric value for each sampling position; and adding a value obtained by multiplying the branch metric value by a weighting coefficient corresponding to the sampling position in accordance with the data transition state. And a second calculating means for calculating the combined branch metric value.

In such a data reproducing system, first, a first branch metric value in which a data transition state is weighted by a sampling value and an expected value for each sampling position is calculated. Next, a second branch metric value is calculated by adding the first branch metric values calculated at a plurality of positions for each data transition state. Therefore, even when sampling is performed at a plurality of positions, it can be applied to the conventional Viterbi decoding algorithm.

From the viewpoint of more effectively correcting distortion, the present invention is configured such that the weighting coefficient can be variably set. Further, from the viewpoint of sampling at a plurality of sampling positions in a predetermined cycle, the present invention
As described in the above, the plurality of sampling means, using a clock, performs sampling at a plurality of sampling positions in a predetermined cycle, extracts a phase error amount from a plurality of sampling values of a recording data unit, and synchronizes a phase and a frequency. Is performed.

Further, in view of the fact that the expected value is referred to according to the sampling values at a plurality of sampling positions, the present invention provides the following:
It is configured to refer from a reference area in which an expected value according to a combination of a data transition state and a sampling position is stored. Further, from the viewpoint of setting an expected value, the present invention provides, as described in claim 6, a sampling value obtained by sampling a reference signal corresponding to a data pattern composed of the data transition state several times. Is stored in the reference area. Alternatively, according to the present invention, an average value of sampling values obtained by sampling a signal recorded in accordance with a data pattern composed of the data transition state several times is used as the reference area. Is configured to be stored.

In such a data reproducing system, an expected value is set from a signal recorded in accordance with a basic data pattern, so that the expected value includes an expected distortion, and an actual sampling value And the expected value can be reduced, and a more reliable branch metric value can be obtained. Further, from the viewpoint of obtaining a more likely branch metric value from the learned distortion, the present invention sets the average value read from the reference area as an expected value in a register as described in claim 8. It is configured as follows. Further, according to the present invention, as set forth in claim 9, the register is readable and writable by firmware;
It is configured such that a value corrected by the judgment of the firmware can be set.

In such a data reproducing system, by setting the average value in the register as necessary, the average value set in the register is rewritten to a corrected value in accordance with the distortion learned by the firmware. It can be a value. Therefore, the expected value can be dynamically corrected according to the distortion, so that a more effective branch metric value can be obtained in Viterbi detection.

The firmware includes, for example, an MPU (Micro Processing) for controlling a data reproduction system.
Unit). In addition, from the viewpoint of obtaining a more probable branch metric value by using a weighting coefficient, the present invention provides a method as set forth in claim 11, wherein the weighting coefficient is variably set by setting in a register by firmware. It is configured to be able.

In order to solve the above-mentioned second problem, the present invention provides an optical reproducing apparatus for optically reproducing data from a recording medium on which data is optically recorded in accordance with a recording signal of a partial response waveform. The reproduced signal is sampled at a predetermined cycle by an optical head that reads the signal, and a path metric value is calculated based on a branch metric value calculated from the expected value determined by the partial response waveform and the sampling value according to a Viterbi decoding algorithm. And reproducing means for reproducing data based on the result of the comparison operation of the path metric value, wherein the reproducing means comprises: a plurality of sampling means for performing sampling at a plurality of sampling positions at predetermined intervals in units of recording data. And a plurality obtained by the plurality of sampling means. Based on the sampling value and the expected value, a branch metric corresponding to each sampling position is calculated, the branch metric value is weighted according to the sampling position, and the branch metric value is determined according to a predetermined data transition state. And a combined branch metric calculation means for calculating a combined branch metric value by combining the above.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. An optical disc device according to an embodiment to which the present invention is applied is configured, for example, as shown in FIG. This optical disk device is a magneto-optical disk device using a magneto-optical disk as a recording medium.

Referring to FIG. 9, the magneto-optical disk drive includes a magneto-optical disk 10 serving as a recording medium and an optical head 2.
0, amplifier 21, reproducing unit 25, writing unit 26, electromagnet 27, MPU 28, servo unit 2
9 and a motor 30. Data is recorded on the magneto-optical disk 10 in accordance with a predetermined recording rule (partial response PR (1, 1) with a constraint length of 2), and data is reproduced from the magneto-optical disk 10.

The MPU 28 operates as firmware, and in accordance with a data reproduction command and a data write command from an external unit (not shown) supplied through the connector 32 and the interface circuit 31, the reproduction unit 2
5. Control the writing unit 26 and the servo unit 29. The control of the reproduction system unit 25 by the MPU 28 will be described later in detail.

In the above-described magneto-optical disk device, when a data reproducing command is supplied, the optical head 20 optically scans the magneto-optical disk 10, and at this time, a reproduced signal output from the optical head 20 drives the amplifier 21. The signal is supplied to the reproduction system unit 25 via the control unit. The reproduction system unit 25 quantizes the supplied reproduction signal and generates output data from the quantized data according to a maximum likelihood (ML) decoding algorithm (for example, a Viterbi decoding algorithm). This output data is supplied to the MPU 28,
8 to an external unit via an interface circuit 31 and a connector 32.

On the other hand, when the MPU 28 receives the write command together with the recording data from the external unit, the MPU 28 restricts the recording data to a predetermined recording regulation (for example, a partial response P).
R (1, 1)), and supplies the modulated data to the writing unit 26. The writing unit 26 controls the driving of the optical head 20 in accordance with the supplied data, and the MPU 28 controls the electromagnetic field 27 based on the data obtained by modulating the recording data.
As a result, data according to the above-mentioned predetermined recording rule is written on the magneto-optical disk 10.

The servo system unit 29 controlled by the MPU 28 drives the motor 30 to rotate the magneto-optical disk 10 at a predetermined speed,
0 is positioned at the recording / reproducing position of the magneto-optical disk 10. The reproduction system unit 25 shown in FIG.
Can be configured as shown in FIG.

The reproduced signal from the optical head 20 shown in FIG.
Amplifier (Amp) 111 and Filter (LPF) 11
2 to the ADC 113. Also, PLL
From 119, a synchronous clock is generated. The difference from the related art is that a clock is created by the multi-clock (Multi-CLK) circuit 120 for sampling at a plurality of points. The clock tripled by the Multi-CLK circuit 120 is supplied to three equalizers EQ_ by a selector (Selector) 114.
Distribute in parallel to M115, EQ116 and EQ_P117. Three branch metrics BM_M121, BM
122 and BM_P 123 calculate the values of the six branch metrics MB0 to MB7 according to the sample values detected in synchronization with each clock. From FIG. 4, since two of the eight possible combinations of state transitions cannot actually occur, the branch metrics of MB0 to MB7 corresponding to the possible combinations of state transitions are calculated.

As described above, the multi-clock (Multi-CL)
K) By doubling the clock in the circuit 120, 1
It becomes possible to detect sample values at a plurality of points in the clock. In FIG. 10, the Viterbi detection
Branch metric (BM-MIX) circuit 124, AC
S (Add Compare Select) 126, path metric memory (PMM) 125 and path memory (PM) 127. The branch metric calculation in this Viterbi detection is performed by each of BM_M121, BM122 and BM_P
The branch metric value calculated in 123 is weighted. ACS 126, PMM 125 and PM 127 are:
Same as before. The weight calculation for Viterbi detection according to the present invention will be described later.

The multi-clock circuit 120 shown in FIG. 10 can be configured, for example, as shown in FIG. FIG.
In 1 (A), the clock signal of the PLL 119 in FIG. 10 is obtained from (1), and a synthesizer (Synthesize) is obtained.
(r) A double clock signal (2) is supplied by 1201 to a counter (Counter) 1202. Counter 12
02 is a 2-bit counter, starting from 1 and 2, 3
And returns to 1. This counter 1202
The outputs C [0] and C [1] of each bit of three logical circuits not 1203, not 1204 and and 125
As a result, a logical operation is performed on a 2-bit value, resulting in three output signals (a), (b) and (c). FIG. 11B is a diagram showing a time chart of each signal.
(A) corresponds to the sign.

In the first configuration example shown in FIG.
This is an example in which the ADC 113 that operates at a sufficiently high speed in accordance with the tripled clock is used. Multi-clock circuit 1
As the clock signal from 20 to the ADC, a clock signal three times the clock signal (2) shown in FIG. 11B is used. Further, in this configuration example, a triple clock signal is used, but a double or more clock signal may be generated according to a plurality of sampling points using the synthesizer 1201 in FIG.

Next, the branch metric (BM) shown in FIG.
The _MIX) circuit 124 is configured, for example, as shown in FIG. Branch metric (BM_MIX)
The circuit 124 is controlled by the MPU 28 (firmware) shown in FIG.
1, 1242 and 1243 and an adder 1247.

The multiplier 1242 gives a predetermined weight to the branch metrics from BM0 to BM7 calculated according to the sampled values. For example, if the weighting coefficient is K0, each of BM0 to BM7 is multiplied by K0. In multipliers 1241 and 1243, similar processing is performed using weighting coefficients KM and KP. The weighting coefficients KM, K0 and KP are set by the MPU 28 in FIG.

The adder 1247 performs a process of adding the weighted branch metrics calculated by each multiplier for each state transition. This allows the ACS 126
Can obtain the calculation results of the branch metrics of BM0 to BM7 as in the past, and can be applied to the conventional Viterbi detection method.

Further, since the calculation results of the branch metrics of BM0 to BM7 are calculated from three sampling values, it is possible to obtain more accurate results.
Further, the reproduction system unit 25 in FIG. 9 can have a configuration using a plurality of ADCs as shown in FIG. 13, for example. In FIG. 13, the same components as those already described are denoted by the same reference numerals, and description thereof will be omitted. FIG.
In the second configuration example shown in (1), three ADCs are used.

The three ADCs 1131 to 1133 output clock signals (a) and (b) shown in FIGS. 11A and 11B from the multi-clock circuit 120, respectively.
And sampling in synchronization with (c). Further, FIG.
The reproduction system unit 25 can be configured as shown in FIG. 14, for example. 14, the same components as those already described are denoted by the same reference numerals, and description thereof will be omitted. In the third configuration example shown in FIG.
The phase error amount supplied to the LL 119 is calculated from a plurality of sampling values for one recording data. By acquiring the signals from the three equalizers 115 to 117, it is easy to detect that the signal has reached the synchronized level, and thus it is possible to easily extract the phase error amount.

In the first to third configuration examples of the reproduction system unit, when three sampling values are obtained in one channel clock with a triple clock, the three sampling values are supplied to each equalizer by a selector or three ADCs. And performs waveform equalization. The original reproduced signal is the same, and in the original waveform restored by sampling at least twice the frequency of the analog reproduced signal, the time series of the three samplings also has the same partial response characteristics.

In the first to third configuration examples of the reproduction system unit, a configuration in which three equalizers are used for waveform equalization has been described. However, sampling values are supplied serially and equalization is performed by one equalizer. After that, three sampling values are acquired in parallel, and a branch metric can be calculated for each sampling value. Sampling is performed, for example, at three points a, b, and c as shown in FIG.
In FIG. 15, the sampling positions of data transitions 0 to 7 are shown. A branch metric is calculated for three sampling values collected at these sampling positions. In this example, the sampling positions are three points, but the branch metric values at two or more points may be calculated, and may be more.

As described above, by sampling at a plurality of points within one channel clock as compared with the conventional case, the accuracy of the branch metric value according to the data transition can be improved. Next, FIG. 16 shows an example of a data pattern of the reference area and an ideal waveform corresponding to the data pattern. The data pattern shown in FIG. 16 shows the data transition shown in FIG. 15 every three channel clocks,
All combinations are indicated by this data pattern. FIG. 16 shows an ideal waveform corresponding to the data pattern.

Using this data pattern as a reference pattern, a, b and c are used for each data transition in FIG.
The sampling values obtained by sampling several times at the points are averaged and set as an expected value. By setting the expected value in this way, it is possible to set the expected value including the distortion in advance for the reproduced signal having the distortion.
Therefore, branch metric calculation is improved, and correct data detection becomes possible.

FIG. 17 shows an example of a data pattern in the reference area and a waveform having distortion according to the data pattern. In FIG. 17, for example, an expected value is set according to a waveform (thick line) distorted from the ideal waveform. As a result, the data detection capability of the reproduction unit can be improved. As a configuration for setting an expected value for each data transition by the MPU, for example, a configuration shown in FIG. 18 can be used. FIG. 18 is obtained by adding a configuration for setting an expected value for each data transition by the MPU to the first configuration example shown in FIG. In FIG. 18, the same components as those already described are denoted by the same reference numerals, and description thereof will be omitted.

In the fourth configuration example shown in FIG.
9 has the first configuration shown in FIG. 10, and further includes an average number setting register 130, an averaging circuit 1
31, 132 and 133, Controller
140, selectors (Sel.) 141, 142 and 143,
Registers Xa, Xb and Xc, reference area 150
And

In the reference area (VFO area) 150, data transitions 0 to 7 and sampling positions a, b, and c
Registers Xa, Xb, and Xc are set in accordance with the combination of, and the address of each register indicating the combination is assigned. Each register stores the average of the sampling value one clock before. here,
In the registers Xa, Xb, and Xc, X indicates a data transition number, and a, b, and c indicate sampling positions for each data transition shown in FIG.

When the register switching signal, which is one of the control signals received from the MPU 28, is a register read command, the controller 140 writes / writes the registers Xa to Xc.
Switch Read operation to Read state. Furthermore, MPU28
By switching the write / read operation of the registers Xa, Xb, and Xc in accordance with the average value calculation instruction from the CPU, a new average value of the sampling values is obtained.

That is, the controller 140 first sets M
Register X in response to a register read instruction from PU 28
a to Xc are read, the average value one clock before is read from the reference area 150, and the averaging circuits 131 to
The read average value is supplied to 133. Next, when a new average value is obtained from the averaging circuits 131 to 133, the controller 140 sends a Write command to the registers Xa to Xc,
By switching the selectors 141 to 143, new average values are written to the registers Xa to Xc. The written average value becomes the expected value. The expected value learned by repeating such an operation is the most likely expected value. This expected value is determined by the branch metric 121
１２３123 is referred to when calculating a branch metric value.

Each of the averaging circuits 131 to 133 may average the sampling values by the following formula, for example. New Ave = ((n-1) * Old Ave + New Smpl) / n The new average value (New Ave) is a number (n-1) obtained by subtracting 1 from a predetermined average number of old Ave acquired from the reference area 150. , And the result of adding a newly sampled sampling value (new Smpl) is divided by a predetermined average number (n). The average number is specified by the average number setting register 130, and the average number setting register 130 is set by the MPU 28. When the average number is one, the registers Xa to Xc
Newly sampled value (new Smp
l) is stored as an average value.

The MPU 28 has registers Xa to Xc
Is possible, the average value stored in the registers Xa to Xc is read, corrected by an algorithm in consideration of the characteristics of the system, and the expected value can be corrected by writing the value as necessary. . In the first to fourth embodiments, PR (1, 1) ML in three values and four states is shown as an example of the partial response waveform, but PR (1, 2, 1) ML, PR (1, 2,. 2, 1)
The same applies to the case where the constraint length is long, such as ML or PR (1, 3, 3, 1) ML.

The configuration for setting the expected value for each data transition in the fourth embodiment can be applied not only to the first embodiment but also to the second and third embodiments. As described above, even when a nonlinear deviation component is included in the reproduced signal and the sampling point does not satisfy the Nyquist condition, distortion correction can be performed by sampling at a plurality of positions, setting a weighting coefficient, or setting an expected value. Therefore, sufficient data detection capability can be obtained.

In each of the above examples, a data reproducing system for an optical disk recording medium (specifically, a magneto-optical disk) has been described. However, the present invention is not limited to this. It is also applicable to systems.

[0053]

As described above, according to the present invention, the sampling values are acquired at a plurality of sampling positions, and the weighted branch metric values are calculated, whereby the most significant value is obtained. Probable data transition states can be extracted. Therefore, the accuracy of data detection can be improved. Further, the difference between the actual sampling value and the expected value is reduced by changing the expected value or the weighting coefficient according to the characteristics of the reproduction signal (such as the amount of nonlinear deviation) depending on the characteristics of the recording medium and the characteristics of the reproduction system. And more reliable data can be reproduced with higher accuracy.

According to the twelfth aspect of the present invention, the most probable data transition state is extracted by acquiring sampling values at a plurality of sampling positions and calculating a weighted branch metric value. An optical disc device that can reduce the difference between the actual sampled value and the expected value by changing the expected value or the weighting coefficient so as to correct the deviation amount, etc., and reproduce more accurate data with higher accuracy. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a conventional PRML system.

FIG. 2 is a diagram illustrating an example of a reproduction waveform and a sampling value.

FIG. 3 is a diagram illustrating an example of waveform interference satisfying a Nyquist condition.

FIG. 4 is a diagram illustrating an example of base data and its expected value;

FIG. 5 is a state transition diagram.

FIG. 6 is a diagram illustrating types of merge.

FIG. 7 is a diagram illustrating a combination of path merges;

FIG. 8 is a diagram illustrating a configuration of a path memory;

FIG. 9 is a diagram illustrating a configuration example of an optical disc device;

FIG. 10 is a diagram illustrating a first configuration example of a reproduction system unit.

FIG. 11 is a diagram illustrating a configuration example of a multi-clock circuit.

FIG. 12 is a diagram illustrating a configuration example of a BM-MIX circuit;

FIG. 13 is a diagram illustrating a second configuration example of the reproduction system unit.

FIG. 14 is a diagram illustrating a third configuration example of the reproduction system unit.

FIG. 15 is a diagram illustrating an example of data transition and its sampling position.

FIG. 16 is a diagram illustrating an example of a data pattern and an ideal waveform in a reference area.

FIG. 17 is a diagram illustrating an example of a data pattern in a reference area and a waveform having distortion.

FIG. 18 is a diagram illustrating a fourth configuration example of the reproduction system unit.

[Description of Signs] 10 Magneto-optical disk 25 Reproduction system unit 28 MPU 114 Selector 115, 116, 117 Equalizer 120 Multiclock 121, 122, 123 Branch metric calculation 124 Branch metric calculation (weighting calculation) 125 Path metric memory 126 ACS (Add Compare Select) 127 Path Metric

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Claims (12)

[Claims] 1. A reproduction signal from a recording medium on which data is recorded according to a recording signal of a partial response waveform is sampled at a predetermined period, and an expected value determined by the partial response waveform and the sampling value are determined according to a Viterbi decoding algorithm. A path metric value based on the branch metric value calculated from the data, and determining the reproduction data based on a result of the comparison operation of the path metric value. A plurality of sampling means for sampling at the sampling position; a branch metric corresponding to each sampling position is calculated based on a plurality of sampling values and an expected value obtained by the plurality of sampling means; Sampling position Means for calculating a combined branch metric value by combining the branch metric value according to a predetermined data transition state, and calculating the combined branch metric value as a path metric value. A data reproduction system used for the calculation of. 2. The combined branch metric calculating means is obtained by first calculating a branch metric value for each sampling position, and multiplying the branch metric value by a weighting coefficient corresponding to the sampling position. 2. A data reproducing system according to claim 1, further comprising: a second calculating means for calculating a combined branch metric value by adding the calculated values to the data transition state according to the data transition state. 3. The data reproducing system according to claim 1, wherein said weighting coefficient can be set variably. 4. The plurality of sampling units sample at a plurality of sampling positions in a predetermined cycle using a clock, extract a phase error amount from a plurality of sampling values of a recording data unit, and synchronize phase and frequency. 2. The data reproduction system according to claim 1, wherein: 5. The data reproduction system according to claim 1, wherein the expected value is referred to from a reference area storing an expected value corresponding to a combination of a data transition state and a sampling position. 6. The data reproduction according to claim 5, wherein an average value of sampling values obtained by sampling a reference signal corresponding to a data pattern composed of the data transition state several times is stored in the reference area. system. 7. The reference area according to claim 5, wherein an average value of sampling values obtained by sampling a signal recorded according to a data pattern composed of the data transition state several times is stored in the reference area. Data playback system. 8. The data reproduction system according to claim 5, wherein an average value read from said reference area is set as an expected value in a register. 9. The data reproducing system according to claim 8, wherein said register is readable and writable by firmware, and can set a value corrected by the judgment of said firmware. 10. The data reproducing system according to claim 9, wherein the firmware can directly read the sampling value by setting the number of times of sampling to one. 11. The data reproducing system according to claim 3, wherein the weighting coefficient can be variably set by setting in a register by firmware. 12. A reproduction signal is sampled at a predetermined cycle by an optical head for reading a reproduction signal optically from a recording medium on which data is optically recorded in accordance with a recording signal of a partial response waveform, and according to a Viterbi decoding algorithm. Reproducing means for calculating a path metric value based on a branch metric value calculated from an expected value determined by the partial response waveform and the sampling value, and reproducing data based on a comparison calculation result of the path metric value. In the optical disc apparatus having the above, the reproducing means comprises: a plurality of sampling means for sampling at a plurality of sampling positions in a predetermined cycle in a recording data unit; and a plurality of sampling values and an expected value obtained by the plurality of sampling means. Bra according to each sampling position A combined branch metric value by calculating multi-metrics, weighting those branch metric values according to the sampling position, and combining the branch metric values according to a predetermined data transition state. An optical disc device, comprising: arithmetic means, wherein the combined branch metric value is used for calculating a path metric value.