JP2020170576A - Optical disk evaluation method, and optical device - Google Patents

Abstract

To provide an optical disk evaluation method and an optical disk device capable of evaluating reliability of data recorded on the optical disk having a high linear density.SOLUTION: In an optical disk evaluation method, a quality evaluation circuit 110 of an optical disk device includes: an error power measurement circuit for measuring an error power between an equalization signal and an expected waveform; a random component measurement circuit for measuring a variance of an amplitude of the equalization signal for each series pattern; and a non-random component measurement circuit for calculating a non-random component power from a difference between the error power and the random component power.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an evaluation method of an optical disk on which data is optically recorded and an optical disk device.

Currently, many types of optical discs such as DVDs and Blu-ray (registered trademark) discs (hereinafter referred to as BDs) are used as information recording media for storing video or data. From the viewpoint of space efficiency when storing data, there are a technique for improving the linear density and a technique for improving the track density as a technique for improving the recording capacity per volume without increasing the cost of the optical disk.

As a technique for improving the linear density, a Partial Response Maximum Likelihood (hereinafter, PRML) signal processing technique is widely used. A binary signal represented by a mark and a space is recorded on the track of the optical disk. When reproducing this binary signal, the detected reproduced signal is band-limited to a low frequency due to the frequency characteristic of the detection by the light beam. This occurs because a plurality of marks and spaces are read out at the same time according to the size of the diffraction limit of the light beam, and is called intersymbol interference. The PRML signal processing technique is one of the most probable decoding techniques for estimating the recorded binary signal by comparing and selecting the expected waveform and the reproduced signal waveform on the premise of intersymbol interference. As the linear density is improved, a PRML signal processing technique in which the width of intersymbol interference is expanded has been used.

Further, as a technique for improving the track density, as shown in Patent Document 1, an optical pickup that divides and detects the reflected light from the optical disk and a signal processing that combines a plurality of reproduced signals that are divided and detected are combined. There is crosstalk reduction technology. By configuring the signal processing that combines a plurality of reproduced signals with an FIR filter, it is possible to equalize the reproduced signal waveform so as to approach the expected waveform in the PRML signal processing technique while reducing crosstalk.

In order to evaluate the reliability of the recording state recorded on the optical disk, as shown in Patent Document 2, an evaluation index based on the PRML signal processing technique is used. As the density is further increased, the influence of the minute distortion of the mark formed on the track on the reproduction by the PRML signal processing technology cannot be ignored. Such distortion has non-linearity such as depending on the pattern of the recorded binary signal, and tends to deteriorate the error rate of the decoding result by the PRML signal processing technique. In the PRML signal processing technology, the expected value signal for decoding is subjected to adaptive correction processing so as to approach the reproduced signal to cope with the non-linearity and the deterioration of the error rate is minimized. In the conventional evaluation index, the measurement is performed in the state after such correction processing is performed so that the correlation with the error rate becomes high. However, under higher density conditions, the effect of non-linearity on the error rate becomes very large, so it is necessary to appropriately evaluate the effect of non-linearity in addition to the evaluation of the random component due to noise, which is a conventional evaluation index. Therefore, these influences cannot be evaluated separately.

BDs or higher density optical discs are also used in storage devices for long-term storage of important data in reliable systems. In the future, further densification is required so that more data can be stored, and multi-value recording technology for increasing the recording line density of optical discs and data with less noise has been developed. In addition, an evaluation index capable of evaluating the reliability of the long-term recording state of the high-density optical disc used in the storage device is also required. Random component evaluation is suitable for situations where the S / N ratio of the playback signal deteriorates due to dirt on the surface of the optical disc during a long storage period, and it is recorded on the track of the optical disc due to frequent playback. Non-linearity evaluation is required in situations where the shape of the marked mark is distorted.

Japanese Patent No. 5927561 International Publication No. 2018/042814

The present disclosure provides an optical disc evaluation method and an optical disc device that enable reliability evaluation of a recording state of data recorded on an optical disc having a high linear density.

The optical disk evaluation method in the present disclosure is an optical disk evaluation method for evaluating the quality of a reproduced signal obtained by reproducing data recorded on a track on the optical disk, and the reproduced signal is equalized so as to approach a predetermined frequency characteristic. An adaptive equalization step for generating an equalization signal, a most likely decoding step for generating a decoding signal from the equalization signal, an expected waveform generation step for generating an expected waveform corresponding to the equalization signal from the decoding signal, and the above. The error power measurement step for measuring the error power of the equalization signal and the expected waveform, and the decoding signal having a width wider than the front-back interference width in the track line direction generated in the reproduction signal in recording and reproduction by laser irradiation on the track. The first random component measurement step for measuring the first random component power which is the dispersion of the amplitude of the equalization signal for each sequence pattern, and the second random component power which is the dispersion of the amplitude of the reproduced signal for each sequence pattern. It is characterized in that it is composed of a second random component measurement step for measuring the above and a daily random component measurement step for calculating a non-random component power from the difference between the error power and the first random component power.

Further, the amount of lack of frequency characteristics of the reproduced signal with respect to the expected waveform may be evaluated from the difference between the first random component power and the second random component power.
Further, the quality of the recording state on the track on the optical disk may be evaluated from the measured value of the non-random component power.
Further, the degree of performance deterioration of the optical disk and the optical disk device may be evaluated from the measured value of the first random component power.
The optical disk device in the present disclosure is an optical disk device that records and reproduces data on a track on an optical disk, and has an optical head that irradiates the track with a laser and detects a reproduction signal from reflected light, and a laser output of the optical head. The reproduction is provided with a recording circuit that records the data on the track by control, a reproduction circuit that reproduces the data from the reproduction signal, and a controller that controls the optical head, the recording circuit, and the reproduction circuit. The circuit consists of an adaptive equalization circuit that generates an equalization signal that equalizes the reproduction signal so as to approach a predetermined frequency characteristic, a most likely decoding circuit that generates a decoding signal from the equalization signal, and the decoding signal. An expected waveform generation circuit that generates an expected waveform corresponding to the equalization signal, an error power measurement circuit that measures the error power between the equalization signal and the expected waveform, and a reproduction signal in recording and reproduction of a track by laser irradiation. A first random component measuring circuit that measures a first random component power that is a dispersion of the amplitude of the equalized signal for each sequence pattern of the decoded signal with a width wider than the front-rear interference width in the track line direction generated in. A second random component measuring circuit that measures a second random component power that is a dispersion of the amplitude of the reproduced signal for each series pattern, and a non-random component power from the difference between the error power and the first random component power. It is characterized by having a daily random component measurement circuit for calculation.
Further, the controller may evaluate the amount of lack of frequency characteristics of the reproduced signal with respect to the expected waveform from the difference between the first random component power and the second random component power.
Further, when the frequency characteristic shortage amount is larger than a predetermined value, the controller may correct the condition of the laser emission waveform when recording the data on the track on the optical disc.
Further, the controller may evaluate the quality of the recording state on the track on the optical disk from the measured value of the non-random component power.
Further, when the non-random component power is larger than a predetermined value, the controller may correct the laser irradiation power when recording the data on the track on the optical disc.
Further, the controller may evaluate the performance deterioration degree of the optical disk and the optical disk device from the measured value of the first random component power.
Further, when the degree of performance deterioration is larger than a predetermined value, the controller may notify the copy of the data to a different optical disk or the replacement of the optical disk device.

The optical disc evaluation method and the optical disc device in the present disclosure enable reliability evaluation of the recording state of data recorded on an optical disc having a high linear density.

The block diagram which shows the structure of the optical disk apparatus in Embodiment 1. A block diagram showing a configuration of a reproduction signal decoding circuit and a quality evaluation circuit according to the first embodiment. Diagram showing the recording status of marks and spaces on tracks The figure which shows the reproduction signal which detected the mark and space recorded on a track The figure which shows the histogram of the error of the equalization signal and the expected waveform The figure which shows the histogram of the amplitude classified by the pattern of the equalization signal The figure which shows the measured value of the quality evaluation circuit The figure which shows the result of having acquired the measured value of the quality evaluation circuit for every track position.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art.

It should be noted that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
[1. Constitution]
FIG. 1 is a configuration diagram of an optical disk device 10 according to the first embodiment. As shown in FIG. 1, the optical disk device 10 includes an optical head 101, a spindle motor 102, a servo controller 103, a recording circuit 104, a modulation circuit 105, an error correction coding circuit 106, a reproduction signal decoding circuit 107, a demodulation circuit 108, and an error. It includes a correction / decoding circuit 109, a quality evaluation circuit 110, an I / F circuit 111, a buffer memory 112, a system controller 113, and a ROM (Read Only Memory) 114.

The optical disk device 10 records and reproduces user data on the optical disk 100. On the optical disk 100, tracks are spirally formed from the inner circumference to the outer circumference. The track consists of a groove track formed by a groove and a land track formed between adjacent groove tracks. User data can be recorded on both the groove track and the land track.

The spindle motor 102 rotates the optical disc 100. By irradiating the optical disc 100 with a light beam, the optical head 101 records user data on the optical disc 100 and reproduces the user data from the optical disc 100.

The servo controller 103 controls the optical head 101 and the spindle motor 102, and controls and scans the optical beam emitted from the optical head 101 onto the optical disc 100 on a track provided on the optical disc 100. Performs movement control to access the track. The servo controller 103 controls the position of the optical head 101 and the rotation speed of the spindle motor 102 so that the optical head 101 scans the optical disc 100 at a predetermined linear velocity.

The I / F circuit 111 receives the user data to be recorded on the optical disk 100 from the host 115 and stores the user data in the buffer memory 112. Further, the I / F circuit 111 sends the user data stored in the buffer memory 112 reproduced from the optical disk 100 to the host 115. User data and the like stored in the buffer memory 112 can be sent to other internal blocks, and conversely, user data and the like received from other internal blocks can be stored in the buffer memory 112.

The error correction coding circuit 106 generates coded data by adding a parity code for error correction to the user data received from the I / F circuit 111.

The modulation circuit 105 receives the coded data from the error correction coding circuit 106 and generates a modulation signal modulated according to a predetermined modulation code.

The recording circuit 104 converts the modulated signal into a recording pulse signal and drives the light beam of the optical head 101. A mark is formed on the optical disk 100 by the heat of the irradiated light beam.

On the other hand, the user data recorded on the optical disk 100 is reproduced by the reproduction signal decoding circuit 107, the demodulation circuit 108, and the error correction decoding circuit 109.

The optical head 101 irradiates the optical disc 100 with a light beam and detects the reflected light from the optical disc 100. The optical head 101 outputs a reproduction signal based on the detected reflected light.

The reproduction signal decoding circuit 107 decodes the reproduction signal to generate a decoding signal. Specifically, the closest expected value waveform is selected from the comparison between the reproduced signal and the expected value waveform, and PRML signal processing is performed to output the pattern signal that is the source of the expected value waveform as a decoding signal. The characteristics of the expected value waveform shall take into account the effect of band limitation due to the frequency characteristics detected by the light beam.

The demodulation circuit 108 demodulates the coded data from the decoded signal according to a predetermined modulation code.

The error correction decoding circuit 109 corrects an error in the demodulated coded data and restores the user data.

The quality evaluation circuit 110 measures the amount of noise added to the reproduced signal and the like. From this measurement result, it is possible to determine the recording state of user data for the track of the optical disk 100 and the output state of the light beam of the light beam of the light head 101.

The ROM 114 is composed of a flash memory. The ROM 114 stores a program for the system controller 113 to control the entire optical disk device 10.

The system controller 113 controls each circuit and controls communication with the host 115 by reading and executing the program stored in the ROM 114. Note that in FIG. 1, for convenience, the arrows indicating the control of each component from the system controller 113 are omitted. The system controller 113 of the optical disk device 10 in the present embodiment controls the operation of each circuit related to the recording and reproduction of user data.

FIG. 2 is a configuration diagram showing details of the reproduction signal decoding circuit 107 and the quality evaluation circuit 110.

The reproduction signal decoding circuit 107 is composed of a preamplifier circuit 200, an A / D conversion circuit 201, a multi-input adaptive equalization filter circuit 202, a most probable decoding circuit 203, and an expected waveform generation circuit 204. The quality evaluation circuit 110 includes an addition circuit 205, an adaptive equalization filter circuit 206, an error measurement circuit 207, a random component measurement circuit 208, and a non-random component measurement circuit 209.

A reproduction signal is input to the preamplifier circuit 200 from the optical head 101. The optical head 101 detects the reflected light from the optical disc 100 by a light receiving unit whose region is divided into three, and outputs three reproduction signals. The preamplifier circuit 200 performs a low-pass filter process for reducing unnecessary high-frequency noise and a gain process for adjusting the amplitude on these reproduced signals.

The A / D conversion circuit 201 converts the reproduction signal output by the preamplifier circuit 200 into a sampled digital reproduction signal. For the sampling timing, a channel clock corresponding to one channel bit period of the modulated signal is used.

The PRML signal processing is realized by the multi-input adaptive equalization filter circuit 202, the most probable decoding circuit 203, and the expected waveform generation circuit 204.

The multi-input adaptive equalization filter circuit 202 is composed of an FIR filter, synthesizes three digital reproduction signals, and outputs an equalization signal equalized so as to have a frequency characteristic close to the expected waveform of PRML signal processing. The multi-input adaptive equalization filter circuit 202 equalizes and also reduces the crosstalk component detected by leaking from the adjacent track.

The most likely decoding circuit 203 selects the expected waveform closest to the equalization signal, and outputs a modulated signal corresponding to the selected expected waveform as a decoding signal.

The expected waveform generation circuit 204 generates an expected waveform corresponding to the decoded signal. The expected waveform is used in the multi-input adaptive equalization filter circuit 202 to adaptively control the coefficients of the FIR filter.

The adder circuit 205 outputs an adder digital reproduction signal obtained by adding three digital reproduction signals.

The adaptive equalization filter circuit 206 is composed of an FIR filter and outputs an addition equalization signal equalized so as to have a frequency characteristic close to the expected waveform of PRML signal processing. Further, unlike the multi-input adaptive equalization filter circuit 202, the adaptive equalization filter circuit 206 does not have the effect of reducing the crosstalk component.

The error measurement circuit 207 calculates the error power between the equalization signal and the expected waveform output by the multi-input adaptive equalization filter circuit 202 and the error power between the addition equalization signal and the expected waveform output by the adaptive equalization filter circuit 206. Measure.

The random component measurement circuit 208 classifies each of the equalization signal, the addition equalization signal, and the addition signal before equalization according to the signal pattern of the predetermined time interval of the decoding signal output by the most likely decoding circuit 203, and signals. Measure the amplitude variance value. This dispersion value indicates the random component power in the noise added to each of the equalization signal, the addition equalization signal, and the addition signal.

The non-random component measuring circuit 209 obtains the difference between the error power measured by the error measuring circuit 207 and the random component power measured by the random component measuring circuit 208. This difference indicates the non-random component power in the noise added to each of the equalization signal and the addition equalization signal.

The system controller 113 acquires the measurement results of the error power, the random component power, and the non-random component power from the quality evaluation circuit 110, records the user data on the track of the optical disk 100, and determines the light beam of the light beam of the optical head 101. Judge the output status.

[2. motion]
Next, the operation of the optical disk device 10 in this embodiment will be described.

First, the operation of recording the data zone of the optical disk 100 on the track by the optical disk device 10 in the present embodiment will be described.

The I / F circuit 111 acquires the user data transmitted from the host 115 and the logical address of the recording destination. The user data is divided into data blocks of a predetermined unit, and each data block is sent to the error correction coding circuit 106.

The error correction coding circuit 106 adds a parity code for correcting an error during reproduction to the user data in data block units to obtain coded data.

The modulation circuit 105 modulates the coded data to which the parity code is added into a modulated signal according to a predetermined modulation code rule.

The recording circuit 104 forms a mark on the track of the optical disc 100 according to the modulated signal. FIG. 3 shows a state of recording as a mark and a space corresponding to the binary modulation signal. Since the section where the value of the modulated signal sequence 301 is 1 is recorded as a mark, light is emitted with the power and time width as shown in the laser emission waveform 302 in the corresponding section. In order to control the shape of the start and end of the mark, the power should be high at the start position and low at the end position. The laser emission waveform 302 forms a recording mark 304 on the track 303. As a result, the modulated signal is recorded in a state defined as binary values such that the portion of the recording mark 304 is 1 and the portion of the space 305 is 0. However, as shown in FIG. 3, under the high linear density condition in which the one-channel bit length is very short with respect to the track width, the lengths of the recording mark 304 and the space 305 formed on the track 303 are modulated. A deviation will occur with respect to the binary pattern of the signal sequence 301. This deviation becomes an error from the expected waveform at the time of reproduction, and appears as a non-random component depending on the pattern of the modulated signal sequence 301.

The system controller 113 controls the above recording operation. The system controller 113 determines a position to be recorded on the optical disc 100, and controls the servo controller 103 to move the optical head 101 to a target position. The error correction coding circuit 106 is operated before reaching the target track. From the point where the target position is reached, the modulation circuit 105 and the recording circuit 104 are operated to perform recording.

Next, the reproduction operation of the optical disk device 10 in the present embodiment will be described.

As shown in FIG. 4, the reproduction signal decoding circuit 107 decodes the reproduction signal output by the optical head 101 by PRML signal processing to generate a decoding signal. The demodulation circuit 108 demodulates the decoded signal according to the modulation code law, and the error correction decoding circuit 109 corrects the error of the demodulated coded data and restores the user data.

The system controller 113 controls the above-mentioned reproduction operation. The system controller 113 controls the servo controller 103 to move the optical head 101 to a target position. When the target position is reached, the reproduction signal decoding circuit 107 and the demodulation circuit 108 are operated, and then the error correction decoding circuit 109 is operated to restore the user data. The restored user data is stored in the buffer memory 112, and the reproduction operation is completed by sending the user data to the host 115 through the I / F circuit 111.

FIG. 4 shows a state when the recorded track as shown in FIG. 3 is reproduced. A recording mark 304 is formed on the track 303, and is detected as a reproduction signal by the optical head 101. The reproduced signal is decoded as a decoded signal 308 by the reproduced signal decoding circuit 107. The equalization signal 306 shown by the solid line is output from the multi-input adaptive equalization filter circuit 202. The expected waveform 307 shown by the broken line is generated by the expected waveform generation circuit 204 from the decoding signal 308.

The error measurement circuit 207 measures the error power W from the difference between the equalization signal 306 and the expected waveform 307. For example, it is measured in a section of length L corresponding to a data block of a predetermined unit. The error power W is calculated by the following formula.

Error power W _a of the difference between the sum equalized signal S _a which is output from the adaptive equalization filter circuit 206 with the expected waveform 307 is also determined in the same manner. The multi-input adaptive equalization filter circuit 202, the effect of cross-talk component is decreased, the direction of W than error power W _a is smaller. It can be evaluated with these crosstalk component amount C which reduces the W _a -W a difference error power. In the recording state shown in FIG. 3, the larger the recording mark 304 on the adjacent track expands in the track width direction, the larger the crosstalk component appears. By controlling the emission power and emission width of the laser emission waveform 302 so that the crosstalk component amount C does not become larger than a predetermined value, it is possible to ensure the quality of the recording state that can be reproduced well.

FIG. 5 shows a histogram of the error between the equalization signal 306 and the expected waveform 307. The same applies to the case of an addition equalization signal. As shown in FIGS. 3 and 4, the error includes not only random components such as laser noise and circuit noise, but also non-random components depending on the pattern of the recorded modulated signal sequence. In particular, it is difficult to record a small mark or space pattern in an appropriate size, and deviation is likely to occur. In addition, small mark and space patterns are reproduced signal components with high frequencies, and there is a trade-off between equalization processing of high frequency bands to approach the expected waveform and reduction processing of random components such as laser noise and circuit noise. It tends to occur, and even if the equalization process is insufficient, the deviation tends to remain. In the histogram of FIG. 5, the error histogram of the pattern A included in the histogram of all the errors is a pattern in which the average value of the errors is almost zero and there is no deviation as described above. On the other hand, in the histogram of the error of the pattern B, it can be said that the average value of the error is not zero and a deviation occurs. Although the average value of the error of pattern B is different, the variance indicating the amount of the random component is not significantly different from that of pattern A. By measuring such a difference, it is possible to quantitatively evaluate the quality of the recording state and the reproduction condition by discriminating the deterioration state.

FIG. 6 shows a histogram that statistically evaluates the amplitude of the equalization signal for each pattern in order to measure the amount of the random component. This also applies to the addition equalization signal and the addition signal. As shown in FIG. 5, the amplitude of the equalization signal itself is statistically evaluated, not the error from the expected waveform. The difference from the expected waveform appears as the difference between the average value of the distribution of each pattern and the expected amplitude value. In FIG. 6, the average value of the distributions of the pattern A and the pattern C has a small difference from the expected amplitude value, and the average value of the distribution of the pattern B has a deviation from the expected amplitude value. The random component corresponds to the variance of each distribution, not to such a deviation of the mean. The random component measurement circuit 208 measures the variance R _p of the distribution for each of the P types of patterns, and calculates the average value of the variances as the random component power R as shown in the following equation.

Random component powers R _a and R _r are similarly obtained for the addition equalization signal S _a output from the adaptive equalization filter circuit 206 and the addition signal S _r before equalization. The difference between the random component power R _a random component power R and addition equalized signal of the equalized signal, it is possible to know the effect of reducing reduction and random components of the crosstalk component in the multi-input adaptive equalization filter. Further, the difference in frequency characteristics between the reproduced signal and the expected waveform can be seen from the difference between the random component power R _r of the added signal before equalization and the random component power R _a of the added equalized signal after equalization. When R _r and R _a are almost the same value, the frequency characteristic of the reproduced signal is close to the expected waveform, and when R _a is larger than R _r , the frequency characteristic of the reproduced signal is larger than the expected waveform. It turns out that it is low. At this time, the influence of random noise is large, and it tends to lead to deterioration of the error rate. The frequency characteristics of the reproduced signal are often caused by the deviation of the recording state between the small mark and the space, or the aberration of the optical head 101. Therefore, it is desirable to optimize the recording conditions for small marks and spaces, and to optimize the servo conditions so that the light condensing state of the optical head 101 is improved.
In the random component measurement circuit 208, in order to properly measure the random component, it is necessary to be able to sufficiently classify the conditions in which the pattern dependence exists. Factors of pattern dependence include thermal interference due to heat propagation during recording on a track and intersymbol interference due to the characteristics of the optical resolution of the optical head 101 during reproduction. When measuring, it is desirable to take the section length which is the sum of the thermal interference width and the intersymbol interference width as a condition for classifying the patterns because both of these effects are included. The length of the optical resolution limit (diffraction limit) is λ / (2 × N) depending on the wavelength λ of the laser of the optical head 101 and the numerical aperture N of the objective lens. For example, when λ is 405 nm and the numerical aperture N is 0.85, the length is 238.2 nm. On the other hand, when the 1-channel bit length is 50 nm, the intersymbol interference width during reproduction is 4.76 channel bits. The width of thermal interference during recording varies depending on the laser emission waveform, but may extend to the same width as intersymbol interference during reproduction. Therefore, in this case, it can be said that the length for classifying the pattern may be 9 channel bit length.
The non-random component measurement circuit 209 calculates the non-random component power D (D = WR) as the difference between the error power W and the random component power R. As the difference between the error power W _a random component power R _a in the addition equalized signal, the nonrandom component power D _a is also calculated. The non-random component power includes the component of the deviation of the amplitude average value for each pattern described above. Therefore, when the deviation of the pattern of small marks and spaces remains unequalizable, or when the random components such as laser noise and circuit noise remain very large and the high frequency band cannot be equalized to the expected waveform. , Non-random component power increases. In the adaptive equalization filter circuit 206, the inability to reduce the crosstalk component affects as insufficient equalization, and the non-random component power becomes large. Although there are multiple factors that increase the non-random component power, the deviation of the recording conditions is generally dominant under the conditions within a certain range in which recording and reproduction on the optical disc are possible. Therefore, when the non-random component power is large, it is necessary to appropriately adjust the conditions of the laser emission waveform 302 for each pattern.
FIG. 8 shows an example of each value measured by the quality evaluation circuit 110. From the difference between the value of the error power W and _{W a,} the cross-talk component amounts C = 0.000273. W accounted crosstalk component about 44% of _a, by a multi-input adaptive equalization filter circuit 202 can also be evaluated as a reduction of cross-talk component. The random component power R after equalization is about 1.4 times larger than the random component power R _r of the added signal before equalization. From this, it can be seen that in the multi-input adaptive equalization filter circuit 202, the random noise component is increased together with the signal component. That is, it can be evaluated that the frequency characteristic of the reproduced signal is lower than the expected waveform, and the signal power is insufficient by about 0.71 times. Further, the non-random component power D is larger than the random component power R. From this, it can be evaluated that there is about 56% of the total error power W that can be improved by further adjusting the deviation of the recording conditions.

The system controller 113 acquires the measurement results of the error power, the random component power, and the non-random component power from the quality evaluation circuit 110, records the user data on the track of the optical disk 100, and determines the light beam of the light beam of the optical head 101. Judge the output status. FIG. 8 shows the measured values of the random component power and the non-random component power at each track position of the optical disk 100. As shown in FIG. 8, there is a section in which the non-random component power is particularly large. In this section, when the user data is recorded, it can be determined that the laser emission power is recorded while being deviated from the predetermined power, and the recording state with distortion is obtained. In addition, there is a section where the random component is large. In this section, it can be determined that when the user data is recorded or reproduced, the deviation of the servo conditions such as the focus state on the track temporarily becomes large, and the random noise component becomes large. Further, when the same optical disc is continuously reproduced and the measurement result is acquired from the quality evaluation circuit 110, the random component power may increase. Since the recording state of the mark on the optical disc is very stable, in such a case, the amount of reflected light can be reduced, such as deterioration of the laser output of the optical head 101, dirt on the lens, or dirt on the surface of the optical disc. It can be determined that it is in a state of bringing it. Based on the above judgment, the reliability can be appropriately ensured by re-recording the user data on a different track for a partially bad section. Further, when a deterioration tendency is observed as a whole, reliability can be ensured without losing user data by exchanging an optical disk device or copying user data to another optical disk.

[3. Effect, etc.]
As described above, in the first embodiment, according to the optical disk 100 and the optical disk device 10, the non-linear error component whose influence increases with increasing density can be evaluated separately. In addition, during a long storage period, the S / N ratio of the reproduced signal deteriorates due to dirt on the surface of the optical disc, or the shape of the mark recorded on the track of the optical disc is distorted due to frequent reproduction. It is possible to evaluate each situation while identifying each situation even if the situation occurs.

The present disclosure is applicable to an optical disc evaluation method and an optical disc device for recording and reproducing data.

10 Optical disk device 100 Optical disk 101 Optical head 102 Spindle motor 103 Servo controller 104 Recording circuit 105 Modulation circuit 106 Error correction coding circuit 107 Reproduction signal decoding circuit 108 Demodulation circuit 109 Error correction decoding circuit 110 Quality evaluation circuit 111 I / F circuit 112 Buffer Memory 113 System controller 114 ROM
115 Host 200 Preamplifier circuit 201 A / D conversion circuit 202 Multi-input adaptive equalization filter circuit 203 Most likely decoding circuit 204 Expected waveform generation circuit 205 Addition circuit 206 Adaptive equalization filter circuit 207 Error measurement circuit 208 Random component measurement circuit 209 Non-random Component measurement circuit 301 Modulation signal series 302 Laser emission waveform 303 Track 304 Recording mark 305 Space 306 Equalization signal 307 Expected waveform 308 Decoding signal

Claims (11)

An optical disc evaluation method for evaluating the quality of a reproduced signal obtained by reproducing data recorded on a track on an optical disc.
An adaptive equalization step of generating an equalized signal obtained by equalizing the reproduced signal so as to approach a predetermined frequency characteristic.
The most probable decoding step of generating a decoding signal from the equalization signal,
An expected waveform generation step of generating an expected waveform corresponding to the equalized signal from the decoded signal, and
An error power measurement step for measuring the error power of the equalization signal and the expected waveform, and
A first random component power that is a dispersion of the amplitude of the equalized signal for each sequence pattern of the decoded signal with a width wider than the front-back interference width in the track line direction generated in the reproduced signal in recording and reproduction by irradiating the track with a laser. The first random component measurement step to measure
A second random component measurement step of measuring the second random component power, which is the dispersion of the amplitude of the reproduced signal for each series pattern,
A daily random component measurement step of calculating the non-random component power from the difference between the error power and the first random component power, and
An optical disc evaluation method characterized by being composed of. The optical disk evaluation method according to claim 1, wherein the amount of lack of frequency characteristics of the reproduced signal with respect to the expected waveform is evaluated from the difference between the first random component power and the second random component power. The optical disc evaluation method according to claim 1, wherein the quality of the recording state on the track on the optical disc is evaluated from the measured value of the non-random component power. The optical disk evaluation method according to claim 1, wherein the performance deterioration degree of the optical disk and the optical disk device is evaluated from the measured value of the first random component power. An optical disk device that records and reproduces data on tracks on an optical disk.
An optical head that irradiates the track with a laser and detects a reproduction signal from the reflected light,
A recording circuit that records the data on the track by controlling the laser output of the optical head, and
A regenerative circuit that reproduces the data from the reproduction signal,
A controller for controlling the optical head, the recording circuit, and the regenerative circuit is provided.
The regenerative circuit
An adaptive equalization circuit that generates an equalization signal that equalizes the reproduced signal so as to approach a predetermined frequency characteristic.
The most probable decoding circuit that generates a decoding signal from the equalization signal,
An expected waveform generation circuit that generates an expected waveform corresponding to the equalized signal from the decoded signal,
An error power measurement circuit that measures the error power of the equalization signal and the expected waveform, and
A first random component power that is a dispersion of the amplitude of the equalized signal for each sequence pattern of the decoded signal with a width wider than the front-back interference width in the track line direction generated in the reproduced signal in recording and reproduction by irradiating the track with a laser. The first random component measurement circuit that measures
A second random component measurement circuit that measures the second random component power, which is the dispersion of the amplitude of the reproduced signal for each series pattern,
A daily random component measurement circuit that calculates non-random component power from the difference between the error power and the first random component power, and
An optical disk device characterized by having. The optical disk device according to claim 5, wherein the controller evaluates an insufficient amount of frequency characteristics of the reproduced signal with respect to the expected waveform from the difference between the first random component power and the second random component power. .. The optical disk device according to claim 6, wherein the controller corrects the condition of the laser emission waveform when recording the data on the track on the optical disk when the frequency characteristic shortage amount is larger than a predetermined amount. The optical disk device according to claim 5, wherein the controller evaluates the quality of the recording state on the track on the optical disk from the measured value of the non-random component power. The optical disk device according to claim 8, wherein the controller corrects the laser irradiation power when recording the data on a track on the optical disk when the non-random component power is larger than a predetermined value. The optical disk device according to claim 5, wherein the controller evaluates the performance deterioration degree of the optical disk and the optical disk device from the measured value of the first random component power. The optical disk device according to claim 10, wherein the controller notifies the copying of the data to a different optical disk or the replacement of the optical disk device when the degree of performance deterioration is greater than a predetermined value.