JP2006236575A - Apparatus and method for evaluating reproduced signal, reproducing apparatus and method, and recording apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for speedily and adequately evaluating quality of a reproduced signal when using a maximum likelihood decoder for binarizing the signal reproduced from a recording medium. <P>SOLUTION: Based on data arrays of two binary data outputted from a "Viterbi" decoder, SAM values are secured by selecting any of path-metric differential values (00), (11) being the difference between the two values compared when renewing path-metric values PMM (00), (11) outputted from the "Viterbi" decoder. The minimum SAM value for an ideally-reproduced signal is outputted from a constant generating circuit 311, and the difference between the output value and the inputted SAM value is squared by a squaring circuit 312 and supplied to an averaging circuit 315. On the other hand, an output value from the canstant generating circuit 311 is compared with the input SAM value by a comparator 313, and if the SAM values are verified as valid, and if the SAM values coincide with the equation (input SAM values)≤(output of the constant generating circuit 311), then output values of the the squaring circuit are averaged by the averaging circuit 315, and the average value is outputted as the reproduced signal evaluation value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reproduction signal evaluation apparatus and method, a reproduction apparatus and method, and a recording apparatus and method that can appropriately evaluate a reproduction signal reproduced from a recording medium.

  In order to achieve high-density recording in a practical sense in a data storage device, it is necessary to deal with factors such as manufacturing variations of the data storage device, changes with time and temperature changes, and variations in recording media used in the data storage device. Therefore, it is necessary to ensure a certain margin. In the reproduction system, if the data storage device itself has a means for detecting the quality evaluation value of the reproduction signal in real time, the reproduction condition is automatically adjusted based on the evaluation value, and the above margin is substantially increased. Is possible.

  Such evaluation value detection is required to be accurate and at the same time fast. A value having a direct meaning as an evaluation value of the reproduction signal is an error rate of the reproduction data. However, a relatively long time is required to stably measure the error rate. Therefore, conventionally, the jitter of the reproduction signal is often used as the evaluation value of the reproduction signal quality. Jitter is the fluctuation of the difference between the time at which the playback signal crosses the threshold value that serves as a reference for binarizing the playback signal and the time at which the playback signal is discriminated into binary, and is usually expressed as a standard deviation. . Evaluation of a reproduced signal using jitter is originally premised on using threshold detection as a binarization means of the reproduced signal.

  On the other hand, in recent years, with the development of LSI (Large Scale Integrated circuit) technology, it is easy to use a maximum likelihood decoder such as a Viterbi decoder as a binarization means of a reproduction signal for achieving a high recording density. Became. In the maximum likelihood decoder, binarization is performed by detecting the most probable sequence when reproducing a data string recorded with correlation between data.

  However, conventionally, even when such a maximum likelihood decoder is used to binarize the reproduction signal, jitter is still often used as an evaluation value of the reproduction signal quality. In such a combination, the correlation between the evaluation value and the actual error rate becomes low. For this reason, even if the reproduction condition is adjusted based on the jitter, there is a problem that the condition deviates from the condition for minimizing the error rate.

  Accordingly, an object of the present invention is to provide a reproduction signal evaluation apparatus and a reproduction signal evaluation apparatus that perform high-speed and appropriate evaluation of reproduction signal quality when a maximum likelihood decoder is used for binarization of a reproduction signal reproduced from a recording medium. A method, a reproducing apparatus and method, and a recording apparatus and method are provided.

  In order to solve the above-described problem, the present invention provides a reproduction signal evaluation apparatus for evaluating a signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded. Binarized data detecting means for decoding binarized data by decoding a reproduction signal reproduced from a recording medium on which data modulated using one or more modulation codes is recorded by maximum likelihood decoding, and binarization SAM value calculating means for calculating the SAM value based on the detection result by the data detecting means, and selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculating means, and statistically processing the selected SAM value The reproduction signal evaluation device comprises reproduction signal evaluation means for evaluating the reproduction signal by doing so.

  The present invention also provides a reproduction signal evaluation method for evaluating a signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded. A binarized data detecting step for decoding binarized data by decoding a reproduction signal reproduced from a recording medium on which data modulated by using the maximum likelihood decoding is detected, and detection by the binarized data detecting step A SAM value calculating step for calculating a SAM value based on the result, a SAM value within a predetermined range is selected from the SAM value calculated by the SAM calculating step, and the selected SAM value is statistically processed. A reproduction signal evaluation method comprising: a reproduction signal evaluation step for evaluating a reproduction signal.

  According to the present invention, in a reproducing apparatus for reproducing a signal from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded, the minimum run is modulated using a modulation code of 1 or more. Reproduction means for reproducing a signal from a recording medium on which data is recorded, binary data detection means for detecting binary data by decoding a reproduction signal reproduced from the recording medium by the reproduction means by maximum likelihood decoding, and 2 SAM value calculating means for calculating the SAM value based on the detection result by the value data detecting means, and selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculating means, and selecting the selected SAM value A reproduction signal evaluation unit that evaluates a reproduction signal by performing statistical processing, and a reproduction control unit that controls the reproduction unit based on the result of the evaluation by the reproduction signal evaluation unit A reproducing apparatus characterized.

  According to the present invention, in a reproducing method for reproducing a signal from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded, the minimum run is modulated using a modulation code of 1 or more. A reproduction step for reproducing a signal from a recording medium on which data is recorded, and a binarized data detection step for detecting binarized data by decoding the reproduction signal reproduced from the recording medium by the reproduction step by maximum likelihood decoding A SAM value calculation step for calculating a SAM value based on a detection result obtained by the binarized data detection step, and a SAM value having a value within a predetermined range from the SAM value calculated by the SAM calculation step. Based on the result of the evaluation by the reproduction signal evaluation step for evaluating the reproduction signal by statistically processing the selected SAM value and the reproduction signal evaluation step. A reproduction method characterized by comprising the steps of reproduction control for controlling the steps of the feeder playback.

  According to another aspect of the present invention, there is provided a recording apparatus for modulating data using a modulation code having a minimum run of 1 or more and recording the data on a recording medium. A recording means for recording, a reproducing means for reproducing a signal from the recording medium immediately after being recorded on the recording medium by the recording means, and a binary signal obtained by decoding the reproduction signal reproduced from the recording medium by the reproducing means by maximum likelihood decoding Binarized data detecting means for detecting the SAM value, SAM value calculating means for calculating the SAM value based on the detection result by the binarized data detecting means, and a value within a predetermined range from the SAM value calculated by the SAM calculating means. Reproduction signal evaluation means for selecting a SAM value and evaluating the reproduction signal by statistically processing the selected SAM value, and recording based on the evaluation result by the reproduction signal evaluation means A recording apparatus characterized by comprising a recording control means for controlling the stage.

  The present invention also provides a recording method for modulating data using a modulation code having a minimum run of 1 or more and recording the data on a recording medium, and modulating the data using a modulation code having a minimum run of 1 or more. A recording step for recording, a reproduction step for reproducing a signal from the recording medium immediately after being recorded on the recording medium by the recording step, and a reproduction signal reproduced from the recording medium by the reproduction step is decoded by maximum likelihood decoding A binarized data detection step for detecting binarized data, a SAM value calculation step for calculating a SAM value based on a detection result of the binarized data detection step, and a SAM value calculated by the SAM calculation step The SAM value of a value within a predetermined range is selected, and the reproduced signal is evaluated by statistically processing the selected SAM value. And-up, it is a recording method characterized by comprising a recording control step of controlling the recording step based on the evaluation of the results of the step of the reproduced signal evaluation.

  As described above, the present invention detects binary data by decoding a reproduction signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded by maximum likelihood decoding. Since the SAM value calculated within the predetermined range is selected from the SAM values calculated based on the detection result, and the reproduced signal is evaluated by statistically processing the selected SAM value, Evaluation can be performed in substantially real time, and an evaluation value can be obtained with higher accuracy.

  As described above, the present invention detects binary data by decoding a reproduction signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded, by maximum likelihood decoding. Since the SAM value calculated within the predetermined range is selected from the SAM values calculated based on the detection result, and the reproduced signal is evaluated by statistically processing the selected SAM value, The evaluation can be performed in substantially real time, and the evaluation value can be obtained with higher accuracy.

  The first embodiment of the present invention will be described below. In the present invention, an evaluation value suitable for a reproduction system using a maximum likelihood decoder is obtained based on a value called SAM (Sequenced Amplitude Margin). SAM is the difference between the correct path metric and the closest other path metric in the maximum likelihood decoder, eg, Tim Perkins and Zachary A. Keirn, “A Window-Margin-Like Procedure for Evaluating PRML Channel Performance ", IEEE Trans.Magn.Vol.31, No.2, pp1109-1114. Conventionally, the SAM has been obtained by a method of calculating data once captured by a computer with an evaluation system using a storage oscilloscope or the like. In the present invention, the reproduction signal evaluation value is obtained based on the SAM value obtained by performing the SAM calculation in substantially real time by the data recording / reproducing apparatus itself.

  The SAM is a noise margin that is allowed until the maximum likelihood decoder outputs an erroneous binary data sequence. Actually, it is difficult to obtain a completely correct binarized data sequence with a small delay time in the reproduction signal processing process. Therefore, the difference (Mr−Mw) between the degree of probability of the data series determined by the maximum likelihood decoder to be most likely (path metric Mr) and the degree of likelihood of the data series determined to be error (path metric Mw). ) Is a practical SAM value. Usually, in a situation where the reproduction signal quality is to be evaluated, the error rate of the data sequence that the maximum likelihood decoder has determined to be most likely is considered to be small. Therefore, the SAM value obtained by such a method and the SAM in a strict sense are used. The difference from the value is small.

  Next, the maximum likelihood decoder and the SAM calculator according to the first embodiment will be described. In the first embodiment, a Viterbi decoder is used as the maximum likelihood decoder. In the following description, it is assumed that an RLL (1, 7) code (minimum run limit = 1) is used as a modulation code and a PR (1, 2, 1) Viterbi decoder is used as a maximum likelihood decoder.

  FIG. 1 shows a trellis diagram corresponding to a combination of RLL (1, 7) and PR (1, 2, 1). In FIG. 1, a state transition from time k to time k + 1 is shown. The states S00, S01, S10, and S11 are states determined by a combination of data for the past two bits from the present time. The value ak represents binary data, and the value yk represents an ideal reproduction signal.

  FIG. 2 shows an exemplary configuration of the Viterbi decoder 100 based on the trellis diagram of FIG. For example, a reproduction signal reproduced by a reproducing head from a recording medium such as a magneto-optical disk is supplied to the branch metric calculation circuit 105. In the branch metric calculation circuit 105, the metric of the actual reproduction signal for the four types of ideal reproduction signal levels is calculated for each channel bit.

In an actual Viterbi decoder, the Euclidean distance × (−1) between the ideal reproduction signal y _k and the actual reproduction signal z _k is often adopted as a metric. That is, as the branch metric BM (y) for the ideal reproduction signal level y,
BM (y) = − (y−z _k ) ² (1)
Should be calculated.

  On the other hand, the path metric memory 130 stores a path on a trellis selected by a method to be described later, that is, a cumulative value of branch metrics corresponding to a data series pattern. In the path metric memory 130, four values are stored corresponding to the type of state where the path finally arrives. In FIG. 2, four corresponding values are stored in the areas PMM (11), PMM (10), PMM (01), and PMM (00) in the path metric memory 130, respectively. That is, the value of the state S11 is stored in the area PMM (11). Similarly, the value of state S10 is stored in area PMM (10), the value of state S01 is stored in area PMM (01), and the value of state S00 is stored in area PMM (00).

  In the following, the values stored in the areas PMM (11), PMM (10), PMM (01), and PMM (00) are represented as PMM (11), PMM (10), PMM (01), and PMM, respectively. Called (00).

When moving from time k to k + 1, it is stored in each area PMM (11), PMM (10), PMM (01) and PMM (00) of the path metric memory 130 according to the following equations (2) to (5). The updated value is updated. In the equations (2) to (5), the path metric corresponding to the path that finally reaches the state S00 at time k is expressed as PM (00) _k .

PMM (00) _{k + 1} = max {PMM (00) _k + BM (-2), PMM (10) _k + BM (-1)} (2)
PMM (01) _{k + 1} = PMM (00) _k + BM (−1) (3)
PMM (10) _{k + 1} = PMM (11) _k + BM (+1) (4)
PMM (11) _{k + 1} = max {PMM (01) _k + BM (+1), PMM (11) _k + BM (+2)} (5)

  In equations (2) and (5), max {X, Y} indicates that the larger value is selected by comparing X and Y.

  In the configuration of FIG. 2, the branch metrics BM (+2) and BM (+1) obtained by the branch metric calculation circuit 105 by the adders 110A to 110C and 120A to 120C, the comparators 112 and 122, and the selectors 113 and 123 are used. ), BM (-1) and BM (-2), and the values PMM (11), PMM (10), PMM (01) and PMM (00) stored in each area of the path metric memory 130 The calculations of the above formulas (2) to (5) are performed, and the stored contents of the path metric memory 130 are updated.

  For example, Equation (5) indicates that the selector 113 compares the outputs of the adders 110A and 110B with the comparator 112, and the selector 113 selects the outputs of the adders 110A and 110B based on the comparison result. Desired. Similarly, Expression (2) is obtained by comparing the outputs of the adders 120A and 120B by the comparator 122 and selecting the outputs of the adders 120A and 120B by the selector 123 based on the comparison result.

  When PMM (00) and PMM (11) are updated, comparators 112 and 122 select the one with the larger path metric out of the two candidate values. By repeating this selection, all the paths that reach each of the four states share the same path at some point in time. This shared portion is the path that was most likely estimated by the Viterbi decoder 100. Based on the selection results by the comparators 112 and 122, the remaining path is stored in the path memory 140, and binarized data corresponding to the path is output from the path memory 140.

  Note that if the stored contents of the path metric memory 130 are continuously updated according to the above-described equations (2) to (5), the value of the path metric tends to increase overall. For this reason, a mechanism for preventing the overflow of the path metric memory 130 is required. Several methods have been proposed for this mechanism, but since they are not directly related to the essential part of the present invention, description thereof is omitted here.

  In FIG. 2, the outputs of the adders 110 </ b> A and 110 </ b> B are supplied to the comparator 112 and also supplied to the differentiator 111 as described above. The difference unit 111 obtains the difference between the outputs of the adders 110A and 110B, that is, the difference between the values compared by the comparator 112. The difference value obtained by the differentiator 111 is output as a path metric difference (11). Similarly, the outputs of the adders 120A and 120B are supplied to the comparator 122 and also supplied to the difference unit 121, and the difference between the outputs of the adders 120A and 120B, that is, the difference between the values compared by the comparator 122. Is output as the path metric difference (00). These path metric differences (11) and (00) are used for SAM calculation.

  Prior to a specific configuration of the SAM calculation unit, first, an algorithm of the SAM calculation will be described. As described above, the SAM here is the difference between the path metric of the data series that the Viterbi decoder has determined to be most likely and the path metric of the data series that has been determined to be in error. When the 2 bits of the data series output from the Viterbi decoder 100 are 0 → 0, the corresponding state on the trellis should have transitioned from state S00 → S00 or state S10 → S00. For example, when a path that passes through the state S00 is selected, it means that it has been determined whether it has transitioned from the state S00 or from the state S10. At this time, the path metric difference based on this is a path metric difference (00). Similarly, when the data sequence 2 bits is 1 → 1, the path metric difference that is the basis for path selection is the path metric difference (11).

  On the other hand, for example, when the data series 2 bits are 0 → 1, this corresponds to the state transition from state S00 → S01, and the path passing through the state S01 is in the state S00 → S01 → without any choice. S11. Similarly, if the 2 bits of the data series are 1 → 0, the path passes through the states S11 → S10 → S00 with no room for selection. In summary, the SAM value may be output as shown in FIG. 3 according to the data series.

  FIG. 4 shows an exemplary configuration of the SAM calculation unit 200. The path metric difference (11) and the path metric difference (00) output from the Viterbi decoder 100 are input to the two selection input terminals of the selection circuit 212 via the shift registers 210 and 211, respectively. The shift registers 210 and 211 are for compensating for the difference between the timing at which the path metric differences (00) and (11) are calculated and the timing at which the binarized data is output.

  The binarized data output from the path memory 140 of the Viterbi decoder 100 is input to the selection circuit 212 together with the value delayed by one clock by the D-flip flop circuit 213. In the selection circuit 212, the path metric differences (11) and (00) are selected and output as SAM values based on the data series represented by the binarized data according to FIG. 3 described above, and the validity / invalidity of the SAM values is determined. The SAM valid signal shown is output. The SAM valid signal is, for example, a signal that is in the “H (high level)” state when the SAM value is valid and in the “L (low level)” state when the SAM value is invalid.

  By the way, when there is no run restriction on the modulation code used in the recording system or the reproduction system, the SAM value for the ideal signal is constant regardless of the data sequence pattern, and the dispersion of the SAM value increases as the reproduction signal deteriorates. Further, it is known that the average value of the SAM is close to the SAM value for the ideal signal regardless of the degree of deterioration of the reproduction signal. Therefore, in such a system, by calculating the variance or standard deviation of the SAM value as statistical processing, the evaluation in the reproduction system using the maximum likelihood decoder just like the jitter in the reproduction system using threshold detection is performed. Can be handled as a value.

  On the other hand, in a reproduction system using a maximum likelihood decoder corresponding to a modulation code with a run restriction, the SAM value for an ideal signal varies depending on the data pattern. Therefore, even if the variance of the SAM value is calculated, the value cannot be effectively handled as an evaluation value of the reproduction signal quality. Note that the maximum likelihood decoder corresponding to a modulation code having a run limit is substantially only compatible with the minimum run limit.

  According to the present invention, it is possible to obtain a reproduction signal evaluation value by taking out only a limited range of values from the calculated SAM values and performing predetermined statistical processing on them. More specifically, the selection condition for the SAM value is a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal, and an average of the squares of the differences between the minimum value of the SAM value for the ideal reproduction signal and the selected SAM value is calculated. This is obtained and used as a reproduction signal evaluation value.

  FIG. 5 shows an exemplary configuration of an evaluation value calculation circuit 300 that obtains a reproduction evaluation value from the SAM value output from the SAM calculation unit 200. The constant generation circuit 311 generates a minimum SAM value for the ideal reproduction signal. For example, in the Viterbi decoder according to the trellis diagram of FIG. 1, the minimum value of the SAM value for the ideal reproduction signal is 6. The SAM value output from the selection circuit 212 of the SAM calculation unit 200 and the minimum value of the SAM value for the ideal reproduction signal generated by the constant generation circuit 311 are input to one and the other input terminals of the subtractor 310, respectively. Is done.

  The difference value obtained by subtracting the SAM value from the output value of the constant generation circuit 311 output from the subtractor 310 is squared by the squaring circuit 312 and supplied to the averaging circuit 315. The averaging circuit 315 averages the output value of the squaring circuit 312 when the enable signal supplied from the AND circuit 314 is “H”. The average value of the output values of the square circuit 312 is output from the averaging circuit 315 as a reproduction signal evaluation value.

  Note that the averaging circuit 315 may calculate an average value by averaging the output values of the square circuit 312 within a fixed time or a fixed number of samples, or calculate a moving average of the output values of the square circuit 312. You may do it.

  On the other hand, the SAM value and the output value of the constant generation circuit 311 are compared by the comparator 313. The output of the comparator 313 is input to one input terminal of the AND circuit 314. The other input terminal of the AND circuit 314 is supplied with the SAM valid signal output from the selection circuit 212 of the SAM calculation unit 200. As a result of the comparison by the comparator 313, if (SAM value) ≦ (output value of the constant generation circuit 311), the output of the comparator 313 is set to the “H” state, for example.

  Therefore, if the SAM valid signal is a value (“H”) indicating that the SAM value is valid and (SAM value) ≦ (output value of the constant generation circuit 311), the signal is output from the AND circuit 314. The enable signal is set to the “H” state, and the averaging circuit 315 averages the output values of the square circuit 312.

  When the SAM value is larger than the output value of the constant generation circuit 311, the enable signal is in the “L” state, and the output value of the squaring circuit 312 is ignored. Therefore, it is not necessary to perform the square calculation correctly at this time.

  6 and 7 show experimental results comparing the case where the jitter described in the prior art is used as the reproduced signal evaluation value and the case where the value according to the first embodiment of the present invention is used. FIG. 6 shows an example of the correlation between the reproduction signal evaluation value and the bit error rate of the reproduction signal when jitter is used as the reproduction signal evaluation value. FIG. 7 shows an example of the correlation between the reproduced signal evaluation value and the bit error rate of the reproduced signal according to the first embodiment of the present invention.

  The reproduction system used in the experiment uses a magnetic super-resolution magneto-optical disk as a recording medium, and the bit error rate greatly depends on the reproduction laser power. The experiment was performed by examining the correlation between the error rate and the reproduction signal evaluation value while changing the reproduction laser power. 6 and 7, the numerical value written beside the data point indicates the reproduction laser power.

  When the jitter shown in FIG. 6 is the reproduction signal evaluation value, it can be seen that the correlation between the reproduction signal evaluation value and the bit error rate is lower than that in the example of FIG. If the reproduction system is adjusted so that the jitter is minimized, the bit error rate is shifted to the minimum state. On the other hand, in the reproduced signal evaluation value according to the first embodiment of the present invention shown in FIG. 7, the correlation between the reproduced signal evaluation value and the error rate is higher in the entire measurement range than in the example of FIG. I understand. Therefore, the bit error rate can be minimized by adjusting the reproduction system so that the reproduction signal evaluation value is minimized.

  Next, a modification of the first embodiment of the present invention will be described. In this modified example, in the input SAM value, the appearance frequency of a value that is equal to or less than the minimum value of the SAM value for the ideal reproduction signal is input so as to be equal to the appearance frequency of the minimum value of the SAM value for the ideal reproduction signal. The SAM value is multiplied by a coefficient. By performing the same processing as that described with reference to FIG. 5 in the first embodiment, the input SAM value multiplied by the coefficient is used as the corrected new SAM value. A higher correlation with the error rate is obtained.

  FIG. 8 shows an exemplary configuration of the evaluation value calculation circuit 300 'according to this modification. The evaluation value calculation circuit 300 ′ is configured to multiply the input SAM value by a coefficient based on the enable signal with respect to the evaluation value calculation circuit 300 according to the first embodiment described above. In FIG. 8, the same reference numerals are given to the portions common to FIG. 5 described above, and detailed description thereof is omitted.

  The SAM value output from the SAM calculation unit 200 is multiplied by a coefficient by a multiplier 350 and input to the evaluation value calculation circuit 300 ′, and is subtracted in the evaluation value calculation circuit 300 ′ as described with reference to FIG. Are input to the comparator 310 and the comparator 313, respectively.

  The coefficient multiplied by the multiplier 350 with respect to the inputted SAM value is obtained as follows. The coefficient input to the multiplier 350 is controlled by applying feedback so that the frequency at which the averaging process of the output of the square circuit 312 by the averaging circuit 315 is validated by the enable signal becomes constant.

  More specifically, the output of the AND circuit 314 is input to the frequency measurement circuit 351, and the frequency at which the output of the AND circuit 314 is in the “H” state and the averaging circuit 315 is enabled is measured. The measured frequency is supplied to the subtracter 353, and the target frequency output from the constant generation circuit 352 is subtracted from the measured frequency. The target frequency is the appearance frequency of the minimum value of the SAM value for the ideal reproduction signal, and is a value obtained in advance by simulation or the like. The output of the subtracter 353 is supplied to the adder 356 via the low-pass filter 354, and the constant “1” output from the constant generation circuit 355 is added to obtain a coefficient for the multiplier 350.

  9 and 10 show a correlation between an example of the reproduction signal evaluation value and the bit error rate according to the first embodiment described above and a modification of the first embodiment. FIG. 9 shows the experimental results according to the first embodiment described above, in which the SAM value is not corrected according to the modification of the first embodiment. FIG. 10 shows experimental results when the SAM value is corrected according to the modification of the first embodiment. In the experiment, the reproduction system uses the magnetic super-resolution magneto-optical disk and changes the reproduction laser power Pr to obtain the reproduction signal evaluation value and the error rate in the same manner as the experiment shown in FIG. 6 and FIG. It was measured. Furthermore, experimental values under different reproduction conditions are obtained by changing the frequency characteristics of the equalizer of the electric circuit in the reproduction system for the same reproduction laser power.

  9 and 10, the data indicated as “calculation” is the relationship between the reproduction signal evaluation value and the error rate when white noise is added to the ideal reproduction signal by computer simulation. The result obtained by correcting the SAM value shown in FIG. 10 matches well with the computer simulation result, and clearly the correlation between the reproduced signal evaluation value and the error rate than the result obtained without performing the SAM correction shown in FIG. It can be seen that is higher.

  Next, a second embodiment of the present invention will be described. The second embodiment is an example in which the above-described first embodiment and the modification of the first embodiment are applied to a recording / reproducing apparatus. FIG. 11 shows a configuration of an example of a recording / reproducing apparatus according to the second embodiment. This recording / reproducing apparatus includes an encoder 51 that encodes data, a magnetic head 8 that applies a magnetic field to the signal recording surface of the magneto-optical disk 9, and a magnetic field that is modulated by the magnetic head 8 based on data 24 from the encoder 51. And a magnetic field modulation driver 6 for generating.

  The encoder 51 is used in an encoding process at the time of recording, and a data input unit 1 that performs predetermined processing on data input from the outside, and an ID and an error detection code (error detection code) for data 21 from the data input unit 1. ID, EDC encoding unit 2 that encodes EDC), ECC encoding unit 3 that encodes error correction code (ECC) into the data from ID and EDC encoding unit 2, and data from ECC encoding unit 3 22 and a modulation unit 5 that modulates the data 23 from the memory 4 in a predetermined method.

  Data 20 input from an external block (not shown) is input to the data input unit 1. The data 20 is output as data 21 from the data input unit 1 and sent to the ID / EDC encoding unit 2. In the ID / EDC encoding unit 2, an ID recorded on the magneto-optical disk 9 and an EDC signal for checking a reproduction signal during reproduction are added to the data 21.

  The output of the ID and EDC encoding unit 2 is supplied to the ECC encoding unit 3, added with parity for error correction, and is output as data 22. The data 22 is temporarily stored in the memory 4, and the time lag transferred from the external block and processed as described above is absorbed. The signal 23 in which the data 22 has absorbed the time lag due to the processing is read from the memory 4 to the modulation unit 5.

  The signal 23 is modulated by the modulator 5 into a signal 24 for recording on the magneto-optical disk 9 and output. For example, the modulation unit 5 modulates the signal 23 into the signal 24 using a modulation code having a minimum run of 1 or more. The signal 24 is sent to the magnetic field modulation driver 6. The magnetic field modulation driver 6 drives the magnetic field head 8 based on the signal 24 to generate a magnetic field sufficient for recording on the magneto-optical disk 9 and records data on the magneto-optical disk 9.

  The recording / reproducing apparatus also includes a spindle motor 11 that rotationally drives the magneto-optical disk 9, an optical system 10 that collects and irradiates laser light onto the signal recording surface of the magneto-optical disk 9, and receives return light; An RF amplifier unit 33 that amplifies an RF signal from the optical system 10 and a servo circuit 12 that servos the optical system 10 and the spindle motor 11 based on the signal from the RF amplifier unit 33 are provided.

  A signal recorded on the magneto-optical disk 9 is read by the optical system 10 and supplied to the RF amplifier unit 33 as a reproduction signal 34. In the RF amplifier unit 33, an RF signal 35, an ADIP (ADdress In Pre-groove) signal 36 of a wobbling address cut on the magneto-optical disk 9, a focus error, a tracking error, and the like are based on the supplied reproduction signal 34. A servo error signal 37 is generated. These generated signals are sent to the servo circuit 12, the RF signal demodulator 13, and the ADIP signal demodulator 38, respectively.

  The servo circuit 12 controls the optical system 10 and the spindle motor 11 so that the reproduction signal 34 is in an appropriate state. The spindle motor 11 is controlled so that the disk 9 rotates at an appropriate number of rotations.

  The recording / reproducing apparatus further includes a decoder 52 that decodes the RF signal 35 output from the RF amplifier unit 33 and an ADIP signal unit 53 that processes the ADIP signal 36 output from the RF amplifier unit 33. .

   The decoder 52 is used for a decoding process at the time of reproduction. The decoder 52 demodulates the RF signal 35 amplified by the RF amplifier unit 33 and the data 25 from the RF signal demodulator 13. An ID decoding unit 14 that decodes the ID based on the data and a memory 14 that stores data 26 from the RF signal demodulation unit 13 and data 27 from the ID decoding unit 14 are provided.

  The RF signal 35 is demodulated in the RF signal demodulating unit 13 by a process reverse to that of the modulating unit 5. Signals 25 and 26 obtained by demodulating the RF signal 35 by the RF signal demodulator 13 are sent to the ID decoder 14 and the memory 15, respectively.

  The ID decoding unit 14 detects the ID added by the ID and EDC encoding unit 2 from the signal 25 output from the RF signal demodulating unit 13. Based on the detected ID, an address 27 for storing the signal 26 output from the RF signal demodulator 13 in the memory 15 is determined.

  The decoder 52 further includes an ECC decoding unit 16 that decodes the ECC from the data 28 read from the memory 15, and an EDC decoding unit 17 that decodes the EDC from the data 29 output by decoding the ECC from the ECC decoding unit 16. And a data output unit 18 that performs predetermined processing on the data 30 output by decoding the EDC from the EDC decoding unit 17 and outputs the data 31 to the outside.

  The signal 26 output from the RF signal demodulator 13 and temporarily stored in the memory 15 in accordance with the address 27 is read as data 28 to the ECC decoder 16. The data 28 is ECC-decoded by the ECC decoding unit 16, subjected to error correction, and supplied to the EDC decoding unit 17. The EDC decoding unit 17 checks whether the error-corrected data 29 is correct. The data 30 whose data 29 has been checked is sent to the data output unit 18 and transferred as output data 31 to an external block (not shown).

  The ADIP signal unit 53 is used at the time of recording and / or reproduction. The ADIP signal demodulating unit 38 demodulates the ADIP signal output from the RF amplifier unit 33, and the ADIP signal demodulating unit 38 outputs the ADIP signal. And an ADIP decoding unit 39 for decoding ADIP from the demodulated data 40.

  By demodulating the ADIP signal by the ADIP signal demodulator 38, data 40 composed of a data string cut on the disk is obtained. Further, the ADIP decoding unit 39 performs error checking on the data 40 to obtain address information 41. This address information 41 is sent to the MCU unit 42 and used as a reference during recording and reproduction.

  The recording / reproducing apparatus includes a control unit 19 that controls each unit and an MCU unit 42 that controls the control unit 19. The MCU unit 42 issues an instruction 32 to the control unit 19 based on the communication 43 with the external block. The control unit 19 is configured as hardware, and sends a fine timing signal to each block based on the control from the MCU unit 42.

  In the recording / reproducing apparatus described above, the configuration according to the first embodiment of the present invention and the modification of the first embodiment is applied to, for example, the RF signal demodulator 13. That is, the RF signal demodulator 13 includes a Viterbi decoder 100, a SAM calculator 200, and an evaluation value calculator circuit 300. A reproduction signal 34 reproduced from the magneto-optical disk 9 by the optical system 10 is amplified to a predetermined value by the RF amplifier unit 33 to be an RF signal 35 and supplied to the RF signal demodulation unit 13. The RF signal 35 is supplied to the Viterbi decoder 100 and decoded into binary data. The decoded binary data string is stored in the memory 15, for example.

  On the other hand, the path metric differences (00) and (11) obtained in the Viterbi decoder 100 and the binarized data are supplied to the SAM calculation unit 200 to obtain the SAM value and the SAM valid signal. The SAM value and the SAM valid signal are supplied to the evaluation value calculation circuit 300, and the reproduction signal evaluation value is obtained as described above. The reproduction signal evaluation value is supplied to, for example, the control unit 19. The control unit 19 sends a control signal to the servo circuit 12 so that, for example, the laser power (reproduction power) by the optical system 10 is optimized based on the supplied reproduction signal evaluation value.

  This configuration can be applied not only when data is reproduced from the magneto-optical disk 9 but also when data is recorded on the magneto-optical disk 9. At the time of recording, immediately after recording on the magneto-optical disk 9 by the magnetic head 8, the recorded signal is reproduced by the optical system 10, and the reproduced signal evaluation value is obtained as described above. For example, by controlling the magnetic field modulation driver 6 based on the reproduction signal evaluation value, the recording power can be optimized and the recording on the magneto-optical disk 9 can be appropriately controlled.

The control when the present invention is applied at the time of recording and reproduction will be described in more detail. In the following description, the reproduction signal evaluation value calculated based on the SAM value in the first embodiment will be referred to as a SAM value for simplicity. In the second embodiment, a reference value SAM _th for a predetermined SAM is set in advance, and the SAM value obtained during reproduction or recording is compared with this reference value SAM _th . As a result of comparison, among reproduction or recording powers in which the SAM value obtained at the time of reproduction or recording is lower than the reference value SAM _th , a value obtained by multiplying the lowest value power value P _th by a predetermined coefficient is designated as the reproduction power. Or the recording power.

At this time, since the reference value SAM _th is not a SAM value that gives the minimum value of the error rate, the power value P _th also does not give the minimum value of the error rate. However, if you select the appropriate value as the reference value SAM _th, and the selected reference value SAM _th, between the optimum power value P _o which minimizes the error rate, the predetermined relationship, for example, a proportional relationship is I know that there is. Therefore, the optimum power value P _o can be obtained by multiplying the power value P _th obtained based on the reference value SAM _th by a predetermined coefficient. The correspondence relationship between the reference value SAM _th and the power value P _th can be obtained by experiment, for example.

First, control during reproduction will be described. FIG. 12 is a flowchart of an example of processing for setting the reproduction power using the SAM value. In the first step S10, the reproduction power PR is initialized. In the next step S11, the SAM value at the initially set reproduction power PR is measured. In step S12, the measurement result in step S11 is compared with a preset reference value SAM _th . As a result of the comparison, if it is determined that the measured SAM value ≦ reference value SAM _th is not satisfied, that is, if it is determined that SAM value> reference value SAM _th , the process proceeds to step S13, and the reproduction power PR is Will be increased. Then, the process returns to step S11, and the SAM value is measured again with the increased reproduction power PR.

On the other hand, if it is determined in step S12 that the measured SAM value ≦ the reference value SAM _th , the process proceeds to step S14. In step S14, the reproducing power PR when a SAM value ≦ reference value SAM _th in step S12 as the power value PR _th, a value obtained by adding 1 to a predetermined coefficient k to the power value PR _th to (1 + k) Multiply. The multiplication result (1 + k) PR _th is set as the optimum reproduction power PR _o .

In the next step S15, the optimum reproducing power PR _o is set for the optical system 10 by the servo circuit 12, at step S16, the reproduction of data from the magneto-optical disc 9 is started by the optimum reproducing power PR _o.

FIG. 13 shows a measurement result of an example of the SAM value and the error rate with respect to the reproduction power PR. Thus, it can be seen that the SAM value indicated by the black circle (●) and the error rate indicated by the white circle (◯) have a correlation with the reproduction power PR. Here, for example, when the reference value SAM _th is set to 0.7, the corresponding reproduction power PR _th is approximately 2.0 mW. On the other hand, the optimum reproduction power PR _o that minimizes the SAM value is approximately 2.2 mW. Therefore, in this example, the coefficient k = 0.1 can be obtained from (1 + 0.1) × 2.0 mW = 2.2 mW.

Incidentally, at this time, to measure the SAM values waving reproducing power PR, it is also considered a method of obtaining an optimum power value PR _o. This method, however, a fact that time to the optimum power value PR _o is obtained Cal, since it is necessary swung beyond the optimum power value PR _o the reproducing power PR, damaging the optical disk 9 For reasons such as fear, it is not preferable.

  Next, control during recording will be described. FIG. 14 is a flowchart of an example of processing for setting recording power using a SAM value. The flowchart of FIG. 14 is substantially the same as the flowchart of FIG. 12 except that the process of obtaining the SAM value by reproducing data once recorded on the magneto-optical disk 9 (step S21) is added to the flowchart of FIG. .

In the first step S20, the recording power PW is initialized, and in step S21, recording is performed on the magneto-optical disk 9 with the initialized recording power PW. The recorded data is reproduced immediately after, for example, and the SAM value is measured (step S22). In step S23, the measurement result in step S22 is compared with a preset reference value SAM _th . As a result of the comparison, if it is determined that the measured SAM value ≦ the reference value SAM _th is not satisfied, the process proceeds to step S24, and the recording power PW is increased. Then, the process is returned to step S21, recording is performed again with the increased recording power PW, and playback is performed immediately after recording, and the SAM value is measured.

On the other hand, if it is determined in step S23 that the measured SAM value ≦ the reference value SAM _th , the process proceeds to step S25. At step S25, the recording power PW when a SAM value ≦ reference value SAM _th in step S23 as the power value PW _th, multiplied by the value (1 + k) obtained by adding 1 to a predetermined coefficient k to the power value PW _th. The (1 + k) PW _th resulting from this multiplication is taken as the optimum recording power PW _o .

In the next step S26, set the optimum recording power PW _o is the magnetic field modulation driver 6, at step S27, data to the magneto-optical disc 9 recording is started by the optimum recording power PW _o.

FIG. 15 shows a measurement result of an example of the SAM value and the error rate with respect to the recording power PW. Thus, it can be seen that the SAM value indicated by the black circle (●) and the error rate indicated by the white circle (◯) have a correlation with the recording power PW. Here, for example, when the reference value SAM _th is set to 0.6, the corresponding recording power PW _th is approximately 10 mW. On the other hand, the optimum recording power PW _{o at} which the SAM value is minimized is approximately 11 mW. Therefore, in this example, the coefficient k = 0.1 can be obtained from (1 + 0.1) × 10 mW = 11 mW.

  Next explained is the third embodiment of the invention. The third embodiment is an example in which the first embodiment and the modification of the first embodiment are further improved. In the method according to the first embodiment described above, approximately half of the SAM samples that are effective for statistical processing are discarded when the SAM values are selected. That is, as shown in FIG. 5, the SAM value is compared with the constant (minimum value of the SAM value for the ideal reproduction signal) generated by the constant generation circuit 311 when selecting the SAM value. At the following values, processing by the averaging circuit 315 is performed, and a reproduction signal evaluation value is output. Therefore, the SAM sample when the SAM value exceeds the constant is discarded.

  On the other hand, in the configuration according to the modification of the first embodiment shown in FIG. 8 described above, a more accurate SAM evaluation value can be obtained. However, in the configuration of FIG. 8, since the set value of the constant generation circuit 352 depends on the characteristics of the modulation code of the signal to be recorded, this constant is used to change the modulation code in order to cope with the change of the modulation code. It was necessary to set it accordingly.

  A reproduction system that employs a modulation code having a minimum run limit of 1 or more has a characteristic that the SAM value varies depending on the data pattern even when the SAM is calculated for a reproduction signal that is ideally equalized and has no noise. Therefore, in order to evaluate signal degradation due to the effects of equalization errors and noise, a method of simply obtaining the standard deviation of SAM values cannot be taken. Therefore, in the first embodiment and the modification of the first embodiment described above, the reproduction signal is calculated by calculating the SAM value below the minimum value of the SAM with respect to the ideal reproduction signal and the root mean square of the difference between the minimum values. An evaluation value was obtained.

  On the other hand, in the third embodiment, pattern matching of the detected data string is performed, and the SAM is calculated only for the pattern having the minimum SAM in the case of an ideal reproduction waveform. ing.

  FIG. 16 shows a trellis diagram from time k to time k + 5. The SAM value for the ideal reproduction signal at time k + 5 is minimized when the path metric of the thick solid line in FIG. 16 is compared with the path metric of the broken line, or the polarity of the reproduction signal is reversed, that is, FIG. This is a case where the path indicated by is upside down.

First, the SAM calculation method when it is determined that the path indicated by the thick solid line in FIG. 16 is correct will be described. The path metric PMM _{C for} the thick line path and the path metric PMM _{W for the} broken line path from the time k + 2 to the time k + 5 are obtained by Expression (6) and Expression (7), respectively.

Therefore, the SAM value at this time is as shown in Expression (8).

On the other hand, when it is determined that the path indicated by the broken line in FIG. 16 is correct, the path metrics PMM _C and PMM _W may be interchanged in the above formulas (6) and (7). Therefore, the SAM is as shown in Equation (9).

  In either of the formulas (8) and (9), the SAM is obtained based on the data string detected by the maximum likelihood decoder. Therefore, the absolute value of the SAM value is as shown in the formula (10). You can ask for.

  As already described in the first embodiment, the degree of likelihood of the data sequence determined to be most likely by the maximum likelihood decoder and the reliability of the data sequence determined to be erroneous. Strictly speaking, the SAM value obtained from the difference in the degree of likelihood is an approximate value.

Next, conditions for comparing the thick solid line path and the broken line path in FIG. 16 as SAM values will be described. According to FIG. 16, both the thick solid line and the broken line pass through the state S00 at time k + 2. In this case, the data {a _k , a _{k + 1} } is always {0, 0} regardless of which path is selected between time k and time k + 2. Therefore, if {a _k , a _{k + 1} , a _{k + 2} , a _{k + 3} , a _{k + 4} } is {0, 0, ₁ , ₁ , ₁ }, a thick solid line path is selected, and { If it is 0, 0, 0, 1, 1}, it can be seen that a dashed path has been selected.

  When the thick solid line path is selected, the path compared at the time k + 5 may not be a broken line path. However, this is a case where the reproduction waveform is largely distorted and can be normally ignored. The same applies to the case where a dashed path is selected. Further, the case where the polarity of the reproduction signal is opposite to that in the example of FIG. 16 can be considered similarly. Therefore, it is necessary to obtain the following equation (11).

  FIG. 17 shows an example of the configuration for calculating the SAM by the method according to the third embodiment described above. For example, a reproduction signal reproduced by a reproducing head from a recording medium such as a magneto-optical disk is supplied to delay circuits 400, 400,... And given delay, and is also supplied to a maximum likelihood decoder 405. Here, the reproduction signal is assumed to be a multi-bit digital signal that has been A / D (Analog / Digital) converted using a channel clock regenerated by PLL (Phase Locked Loop) or the like.

  The delay circuits 400, 400,... And the delay circuits 406A to 406D represented by “D” in FIG. 17 are one-clock delay elements that give a delay of one clock to the input signal. Each of the delay circuits 400, 400,... Can use, for example, a D flip-flop. The delay circuits 400, 400,... Compensate for the delay of the reproduced signal until binary data is detected by a maximum likelihood decoder 405, which will be described later, and the delay for generating the SAM valid signal. Is. The number of stages of the delay circuits 400, 400,... Is set so that the timing at which the SAM is calculated and the SAM value is output matches the timing at which the SAM valid signal is output.

The reproduction signal given a predetermined delay by the delay circuits 400, 400,... Is supplied to a SAM calculation circuit including delay circuits 401 A and 401 B, a multiplier circuit 402, an adder 403 and an absolute value conversion circuit 404. In the SAM calculation circuit, y _{k + 2} + 2y _{k + 3} + y _{k + 4} is obtained by the delay circuits 401A and 401B, the multiplier circuit 402 and the adder 403 based on the supplied reproduction signal. The output of the adder 403 is supplied to the absolute value conversion circuit 404, and if the calculation result of y _{k + 2} + 2y _{k + 3} + y _{k + 4} is a negative number, it is converted to a positive number.

  Note that the SAM value obtained by the SAM calculation circuit is ½ of the value obtained by the above equation (5), but this is a matter of which bit is regarded as one digit in the digital circuit. There is no difference.

On the other hand, binary data is detected from the reproduction signal supplied to the maximum likelihood decoder 405, for example, based on the configuration of FIG. 2 described above in the first embodiment. The detected binary data is output as it is and supplied to the delay circuits 406A, 406B, 406C, and 406D, and is delayed by 4 clocks. The inputs of the delay circuits 406A, 406B and 406D and the output of the delay circuit 406D are respectively taken out and supplied to the comparators 407 and 408 as data strings {a _k , a _{k + 1} , a _{k + 3} , a _{k + 4} }, respectively. Is done.

In the comparator 407, the data string {a _k , a _{k + 1} , a _{k + 3} , a _{k + 4} } is compared with the data string {0, _{0, 1} , ₁ }. Similarly, in the comparator 408, the data string { _ak , _{ak + 1} , _{ak + 3} , _{ak + 4} } is compared with the data string {1, 1, 0, 0}. The comparison results of the comparators 407 and 408 are supplied to the OR circuit 409, and the output of the OR circuit 409 is output as a SAM valid signal indicating that the SAM value is valid. That is, the data string {a _k , a _{k + 1} , a _{k + 3} , a _{k + 4} } matches either the data string {0, 0, 1, 1} or {1, 1, 0, 0}. Sometimes, the SAM value output from the absolute value circuit 404 described above is valid.

  The standard deviation of the SAM value output from the absolute value circuit 404 can be used as the reproduction signal evaluation value. However, it can be said that it is impractical to accurately calculate the standard deviation using hardware because the circuit scale becomes too large. Hereinafter, a method for calculating a reproduction signal evaluation value in consideration of easy hardware implementation will be described.

  A first method for calculating the reproduction signal evaluation value will be described. In a system in which the change in the average value of the SAM is considered to be small within the assumed range of change in the recording / playback state, the expected average value of the SAM is simply set as a constant, and the square of the difference between this constant and each SAM value is simply set. The calculation result obtained by calculating the average of can be used as the reproduction signal evaluation value.

  FIG. 18 shows an example of the configuration of a reproduction signal evaluation value calculation circuit according to the first method. The SAM value output from the absolute value conversion circuit 404 in FIG. 17 is supplied to the adder 420. On the other hand, in the constant generation circuit 421, the expected average SAM value is generated as a constant. This constant generated by the constant generation circuit 421 is supplied as a negative input to the adder 420, and this constant is subtracted from the SAM value. The output of the adder 420 is supplied to the squaring circuit 422, squared, and supplied to the averaging circuit 423. The averaging circuit 423 averages the output value of the square circuit 422 when the SAM valid signal output from the OR circuit 409 indicates validity. This average value is output as the latest issue quality evaluation value.

  Note that the averaging circuit 423 may calculate an average value of the output values of the square circuit 422 within a fixed time or a fixed number of samples, or may calculate a moving average of the output values of the square circuit 422. .

  A second method for calculating the reproduction signal evaluation value will be described. The second method is a reproduction signal evaluation value calculation method that can be applied when the average value of the SAM cannot be predicted in advance. FIG. 19 shows an example of the configuration of a reproduction signal evaluation calculation circuit according to the second method. Note that, in FIG. 19, the same reference numerals are given to portions common to FIG. 18 described above, and detailed description thereof is omitted. In FIG. 19, the part surrounded by the broken line has the same configuration as that of FIG.

  The SAM value output from the absolute value conversion circuit 404 in FIG. 17 is multiplied by a coefficient by the multiplier 430 and supplied to the adder 420. The coefficient input to the multiplication circuit 430 is controlled by applying feedback so that the average of the difference between the output of the multiplier 430 and the constant generated by the constant generation circuit 421 becomes zero.

  That is, the output of the adder 420 is supplied to the low pass filter 435. The low-pass filter 435 integrates the output of the adder 420 when the SAM valid signal is input as an enable signal and the SAM valid signal indicates the validity of the SAM value. The output of the low pass filter 435 is supplied as a negative input to the adder 436, and the adder 436 subtracts the output of the low pass filter 435 from the constant (+1) generated by the constant generation circuit 437. The output of the adder 436 is used as the coefficient of the multiplier 430.

  By performing such control, the output of the multiplier 430 can be regarded as a standardized SAM so that the average value is substantially equal to the value set as a constant by the constant generation circuit 421. Therefore, the output of the averaging circuit 423 is approximately equal to the standardized SAM variance, and this can be used as a reproduction signal evaluation value.

  Note that the SAM distribution is often a target distribution with respect to an average value such as a Gaussian distribution. Therefore, by utilizing this property, the negative value is converted to (−1) and all the positive values are converted to (+1) at the input unit of the low-pass filter 435, while maintaining the accuracy of the evaluation value equal. The circuit can be simplified.

  The calculation method of the reproduction signal evaluation value and the configuration for performing the calculation according to the third embodiment are the same as those in the first embodiment and the modification of the first embodiment described above. It can be applied to the recording / reproducing apparatus according to the above. That is, it is possible to control reproduction in the recording / reproducing apparatus according to the second embodiment based on the reproduced signal evaluation value obtained by the configuration and method of the third embodiment.

  For example, the configurations of FIG. 17 and FIG. 18 or FIG. 19 according to the third embodiment are applied to the RF signal demodulator in FIG. At the time of reproduction, a reproduction signal 34 reproduced from the magneto-optical disk 9 by the optical system 10 is amplified by the RF amplifier unit 33 to be an RF signal 35 and supplied to the RF signal demodulation unit 13. The RF signal 35 is demodulated by the RF signal demodulator 13 and output as a reproduction signal 26. At this time, the RF signal demodulator 13 performs A / D conversion on the signal obtained by demodulating the RF signal 35 using the channel clock regenerated by the PLL as described above, and the reproduced signal 26 is Suppose that it is output as a multi-bit digital signal.

  This reproduction signal 26 is input to the configuration shown in FIG. A SAM value is obtained based on the input reproduction signal 26. In addition, a SAM valid signal is output based on the binary data sequence obtained by the maximum likelihood decoder 405, and the binary data sequence is stored in the memory 15 as described above. The SAM value and the SAM valid signal are input to the configuration shown in FIG. 18 or FIG. 19, and the reproduction signal evaluation value is obtained as described above. The reproduction signal evaluation value is supplied to, for example, the control unit 19. The control unit 19 sends a control signal to the servo circuit 12 so that, for example, the laser power (reproduction power) by the optical system 10 is optimized based on the supplied reproduction signal evaluation value. The reproduction power can be controlled based on the flowchart of FIG.

  At the time of recording, the recording signal is reproduced by the optical system 10 immediately after recording on the magneto-optical disk 9 by the magnetic head 8, and the reproduction signal evaluation value is obtained as described above. For example, by controlling the magnetic field modulation driver 6 based on the reproduction signal evaluation value, the recording power can be optimized and the recording on the magneto-optical disk 9 can be appropriately controlled. The recording power can be controlled based on the above-described flowchart of FIG.

  In the above description, the present invention has been described so as to be applied to an apparatus that performs recording and reproduction of a magneto-optical disk and a magnetic super-resolution magneto-optical disk. The present invention is also applicable to other devices such as a hard disk device for decoding a reproduction signal using a maximum likelihood decoder.

  As described above, in the present invention, since the reproduction signal evaluation value is obtained using the value compared when the path metric memory is updated, the reproduction signal having a higher correlation with the error rate of the reproduction signal. An evaluation value can be obtained at higher speed.

  Further, by applying the present invention to a recording and / or reproducing apparatus and adjusting the data recording and / or reproducing apparatus based on the reproduction signal evaluation value obtained by the present invention, high-density recording can be performed with higher reliability. Can be realized.

  Furthermore, in the third embodiment of the present invention, the reproduction signal evaluation value is obtained by performing pattern matching on the detected data string. Therefore, there is an effect that a highly reliable reproduction signal evaluation value can be obtained by effectively using more data. Furthermore, since pattern matching is used, the reproduction signal evaluation value can be obtained without depending on the characteristics of the modulation code of the recorded signal.

It is a trellis diagram corresponding to the combination of RLL (1, 7) and PR (1, 2, 1). It is a block diagram which shows the structure of an example of a Viterbi decoder based on the trellis diagram corresponding to the combination of RLL (1, 7) and PR (1, 2, 1). It is a basic diagram which shows the example of the output of a SAM value. It is a block diagram which shows the structure of an example of a SAM calculation part. It is a block diagram which shows the structure of an example of the evaluation value calculation circuit by the 1st Embodiment. It is a basic diagram which shows the correlation of an example of the reproduction signal evaluation value at the time of using jitter as a reproduction signal evaluation value, and a bit error rate. It is a basic diagram which shows the correlation of an example of the reproduction signal evaluation value and bit error rate at the time of using the value by the 1st Embodiment of this invention as a reproduction signal evaluation value. It is a block diagram which shows the structure of an example of the evaluation value calculation circuit by the modification of the 1st Embodiment. It is a basic diagram which shows the correlation of an example of the reproduction signal evaluation value and bit error rate by the 1st Embodiment. It is a basic diagram which shows the correlation of an example of the reproduction signal evaluation value and bit error rate by the modification of the 1st Embodiment. It is a block diagram which shows the structure of an example of the recording / reproducing apparatus applicable to the 1st Embodiment and the modification of the 1st Embodiment. It is a flowchart of an example of the process which sets reproduction | regeneration power using a SAM value. It is a basic diagram which shows the measurement result of an example of SAM value with respect to reproduction power PR, and an error rate. It is a flowchart of an example of the process which sets recording power using a SAM value. It is a basic diagram which shows the measurement result of an example of SAM value with respect to recording power PW, and an error rate. It is a trellis diagram from time k to time k + 5 corresponding to a combination of RLL (1, 7) and PR (1, 2, 1). It is a block diagram which shows the structure of an example which calculates SAM by the method by the 3rd Embodiment. It is a block diagram which shows the structure of an example of the reproduction | regeneration signal evaluation value calculation circuit by the 1st method of the 3rd Embodiment. It is a block diagram which shows a structure of an example of the reproduction signal evaluation value calculation circuit by the 2nd method of the 3rd Embodiment.

Explanation of symbols

100 Viterbi decoder 105 Branch metric calculation circuit 111, 121 Difference unit 130 Path metric memory 140 Path memory 200 SAM calculation unit 212 Selection circuit 300, 300 'Evaluation value calculation circuit 310 Subtractor 311 Constant generation circuit 312 Square circuit 313 Comparator 314 AND circuit 315 Average circuit 350 Multiplier 351 Frequency measurement circuit 352 Constant generation circuit 353 Subtractor 405 Maximum likelihood decoder 404 Absolute value circuit 407, 408 Comparator 421 Constant generation circuit 422 Square circuit 423 Average circuit 435 Low-pass filter 437 Constant generation circuit

Claims (19)

In a reproduction signal evaluation apparatus for evaluating a signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded,
Binarized data detection means for decoding a reproduction signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded, and detecting binarized data by maximum likelihood decoding;
SAM value calculating means for calculating a SAM value based on the detection result by the binarized data detecting means;
Reproduction signal evaluation means for selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculation means, and evaluating the reproduction signal by statistically processing the selected SAM value; A reproduction signal evaluation apparatus comprising: The reproduction signal evaluation apparatus according to claim 1,
The reproduction signal evaluation means includes
Among the SAM values calculated by the SAM value calculating means, the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected, and the minimum SAM value for the ideal reproduction signal is used as the statistical processing. A reproduction signal evaluation apparatus characterized by performing a process of obtaining an average of the square of the difference between the value and the selected SAM value. The reproduction signal evaluation apparatus according to claim 1,
Coefficient multiplication means for multiplying the SAM value input to the reproduction signal evaluation means by a coefficient,
The reproduction signal evaluation means includes
Among the SAM values multiplied by the coefficient by the coefficient multiplication means, the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected, and the SAM value for the ideal reproduction signal is used as the statistical processing. A process for obtaining an average of the square of the difference between the minimum value of the SAM value and the selected SAM value,
The coefficient is controlled so that the frequency at which the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected is equal to the appearance frequency of the minimum value of the SAM value for the ideal reproduction signal. A reproduction signal evaluation apparatus characterized by being configured as described above. The reproduction signal evaluation apparatus according to claim 1,
Path metric difference calculating means for calculating a path metric difference corresponding to the data series indicated by the binarized data,
The SAM value calculation means includes:
A reproduction signal evaluation apparatus, wherein the SAM value is calculated by selecting the path metric difference corresponding to the data series based on the binarized data. In a reproduction signal evaluation method for evaluating a signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded,
A binarized data detection step of decoding binarized data by decoding a reproduction signal reproduced from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded, and detecting binarized data;
A SAM value calculation step of calculating a SAM value based on the detection result of the binarized data detection step;
The reproduction signal evaluation is performed by selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculation step, and evaluating the reproduction signal by statistically processing the selected SAM value. A reproduction signal evaluation method comprising: steps. In a reproducing apparatus for reproducing a signal from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded,
Reproducing means for reproducing a signal from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded;
Binarized data detecting means for decoding the reproduced signal reproduced from the recording medium by the reproducing means by maximum likelihood decoding and detecting binarized data;
SAM value calculating means for calculating a SAM value based on the detection result by the binarized data detecting means;
Reproduction signal evaluation means for selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculation means, and evaluating the reproduction signal by statistically processing the selected SAM value; ,
A reproduction apparatus comprising: reproduction control means for controlling the reproduction means based on the result of the evaluation by the reproduction signal evaluation means. The playback device according to claim 6,
The reproduction signal evaluation means includes
Among the SAM values calculated by the SAM value calculating means, the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected, and the minimum SAM value for the ideal reproduction signal is used as the statistical processing. A reproduction apparatus characterized by performing a process of obtaining an average of squares of differences between values and the selected SAM values. The playback device according to claim 6,
Coefficient multiplication means for multiplying the SAM value input to the reproduction signal evaluation means by a coefficient,
The reproduction signal evaluation means includes
Among the SAM values multiplied by the coefficient by the coefficient multiplication means, the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected, and the SAM value for the ideal reproduction signal is used as the statistical processing. A process for obtaining an average of the square of the difference between the minimum value of the SAM value and the selected SAM value,
The coefficient is controlled so that the frequency at which the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected is equal to the appearance frequency of the minimum value of the SAM value for the ideal reproduction signal. A playback apparatus characterized by being configured as described above. The playback device according to claim 6,
The recording medium is an optical recording medium or a magneto-optical recording medium for reproducing recorded data using light,
The reproduction signal evaluation means evaluates the quality of the reproduction signal when the data recorded on the recording medium with a constant output is reproduced with different reproduction light output, using the SAM value calculated by the SAM value calculation means. A reproduction apparatus characterized in that an optimum reproduction light output for reproducing data recorded on the recording medium is determined based on a result of the evaluation. The playback device according to claim 9, wherein
The optimum reproduction light output is a value obtained by multiplying the reproduction light output that is the lowest among the reproduction light outputs in which the SAM value obtained during the reproduction is equal to or less than a predetermined SAM reference value by a predetermined coefficient. A playback device. The playback device according to claim 6,
Path metric difference calculating means for calculating a path metric difference corresponding to the data series indicated by the binarized data,
The SAM value calculation means includes:
A reproducing apparatus, wherein the SAM value is calculated by selecting the path metric difference corresponding to the data series based on the binarized data. In a reproduction method for reproducing a signal from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded,
A reproduction step of reproducing a signal from a recording medium on which data modulated using a modulation code having a minimum run of 1 or more is recorded;
A binarized data detection step of decoding the reproduction signal reproduced from the recording medium by the reproduction step by maximum likelihood decoding and detecting binarized data;
A SAM value calculation step of calculating a SAM value based on the detection result of the binarized data detection step;
The reproduction signal evaluation is performed by selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculation step, and evaluating the reproduction signal by statistically processing the selected SAM value. Steps,
A reproduction control step of controlling the reproduction step based on the result of the evaluation by the reproduction signal evaluation step. In a recording apparatus for modulating data using a modulation code having a minimum run of 1 or more and recording the data on a recording medium,
Recording means for modulating data using a modulation code having a minimum run of 1 or more and recording the data on a recording medium;
Reproducing means for reproducing a signal from the recording medium immediately after being recorded on the recording medium by the recording means;
Binarized data detecting means for decoding the reproduced signal reproduced from the recording medium by the reproducing means by maximum likelihood decoding and detecting binarized data;
SAM value calculating means for calculating a SAM value based on the detection result by the binarized data detecting means;
Reproduction signal evaluation means for selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculation means, and evaluating the reproduction signal by statistically processing the selected SAM value; ,
And a recording control means for controlling the recording means based on the result of the evaluation by the reproduction signal evaluating means. The recording apparatus according to claim 13.
The reproduction signal evaluation means includes
Among the SAM values calculated by the SAM value calculating means, the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected, and the minimum SAM value for the ideal reproduction signal is used as the statistical processing. A recording apparatus that performs a process of obtaining an average of squares of differences between values and the selected SAM values. The recording apparatus according to claim 13.
Coefficient multiplication means for multiplying the SAM value input to the reproduction signal evaluation means by a coefficient,
The reproduction signal evaluation means includes
Among the SAM values multiplied by the coefficient by the coefficient multiplication means, the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected, and the SAM value for the ideal reproduction signal is used as the statistical processing. A process for obtaining an average of the square of the difference between the minimum value of the SAM value and the selected SAM value,
The coefficient is controlled so that the frequency at which the SAM value having a value equal to or smaller than the minimum value of the SAM value for the ideal reproduction signal is selected is equal to the appearance frequency of the minimum value of the SAM value for the ideal reproduction signal. A recording apparatus characterized by being configured as described above. The recording apparatus according to claim 13.
The recording medium is an optical recording medium or a magneto-optical recording medium for reproducing recorded data using light,
Using the SAM value calculated by the SAM value calculating means, the reproduction signal evaluating means evaluates the quality of the reproduction signal when data recorded on the recording medium with different recording outputs is reproduced, and the result of the evaluation And determining an optimum recording output for recording data on the recording medium. The recording apparatus according to claim 16, wherein
The optimum recording output is a value obtained by multiplying the lowest recording output among the recording outputs in which the SAM value obtained at the time of reproduction is equal to or less than a predetermined SAM reference value by a predetermined coefficient. apparatus. The recording apparatus according to claim 13.
Path metric difference calculating means for calculating a path metric difference corresponding to the data series indicated by the binarized data,
The SAM value calculation means includes:
A recording apparatus, wherein the SAM value is calculated by selecting the path metric difference corresponding to the data series based on the binarized data. In a recording method for recording data on a recording medium by modulating data using a modulation code having a minimum run of 1 or more,
A recording step of modulating data using a modulation code having a minimum run of 1 or more and recording the data on a recording medium;
A reproduction step of reproducing a signal from the recording medium immediately after being recorded on the recording medium by the recording step;
A binarized data detection step of decoding the reproduction signal reproduced from the recording medium by the reproduction step by maximum likelihood decoding and detecting binarized data;
A SAM value calculation step of calculating a SAM value based on the detection result of the binarized data detection step;
The reproduction signal evaluation is performed by selecting the SAM value within a predetermined range from the SAM value calculated by the SAM calculation step, and evaluating the reproduction signal by statistically processing the selected SAM value. Steps,
And a recording control step of controlling the recording step based on a result of the evaluation by the reproduction signal evaluation step.

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