JP3602983B2 - Recording compensator - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for recording and reproducing data on a magnetic recording medium and an optical recording medium, and particularly has a feature of performing recording compensation on a reproduction signal having asymmetry.
[0002]
[Prior art]
Disc-shaped magnetic recording media and optical recording media (hereinafter, simply referred to as “recording media”) have recently been increasing in the amount of information to be handled at a time. An attempt is being made to increase the amount of information that can be recorded on a single recording medium. However, a signal obtained when reproducing information recorded on a recording medium on which high-density recording has been advanced by a reproducing device is a signal having non-linear distortion called asymmetry.
This will be described with an example of an optical disk that performs thermal recording using a light beam.
[0003]
FIG. 3 is a diagram showing a relationship between a reproduced signal and a recording mark thermally recorded on a surface of an optical disk by using a laser.
The recording mark is generated by irradiating the surface of the optical disk with a different laser. Erasing is performed in the same manner. In the portion of the recording mark generated by the laser, the surface of the optical disk is in an amorphous state where the light reflectance is low, while between the recording marks, that is, in the portion where no recording mark exists, the original optical disk surface remains as it is. That is, it remains in a crystalline state with high light reflectance. When this optical disc is reproduced, a reproduced signal as shown in FIG. 3A is obtained.
[0004]
When such different lasers are irradiated on the surface of the optical disk, a slight amount of heat is accumulated at the end of the recording mark. This phenomenon is called a heat storage phenomenon. The heat storage phenomenon causes the original shape of the recording mark to be distorted, so that the edge of the recording mark slightly shifts. Even if such an optical disc is reproduced, only a non-linearly distorted reproduction signal as shown in FIG. 3B, that is, a reproduction signal having asymmetry can be obtained. In this asymmetry, as recording density of a recording medium increases, the width of the recording mark itself and the interval between the recording marks become smaller, so that the edge of the recording mark is liable to fluctuate even though it is minute. That is, asymmetry is more likely to occur in a recording medium with higher recording density. Also, in the case of a signal in a high-frequency region where the width of the recording mark and the interval between the recording marks are originally small, asymmetry is likely to occur even in normal cases, but asymmetry is more likely to occur due to the progress of high-density recording.
[0005]
Then, when asymmetry occurs, the center level differs between the signal in the high frequency region and the signal in the low frequency region, so that an error is likely to occur when reading data, which is a problem. That is, even if the asymmetry amount is the same, the influence in the high frequency region where the recording mark is small is large, and therefore the center level is largely shifted, whereas the influence in the low frequency region where the recording mark is large is small. The phenomenon that the level does not shift so much occurs.
[0006]
This will be further described with reference to FIG. 3B showing the waveform of the reproduced signal in which asymmetry has occurred. In the reproduced signal waveform shown here, the horizontal line shown by the solid line is set to the slice level S, and the sampling point is set to the slice level. When determining “0” or “1” depending on whether it is above or below S, the sampling point below the slice level S comes above the slice level S depending on the error, and the determination is incorrect. That happens. Therefore, if the horizontal line indicated by the one-dot chain line in the figure is the slice level T, the above-described erroneous determination will not occur with a slight error. However, since the actual slice level is the slice level S, which is a horizontal line shown by a solid line, the asymmetry is corrected by correcting the asymmetry of the waveform of the reproduced signal so that the waveform is vertically symmetric with respect to the slice level S. The occurrence rate of erroneous determination can be suppressed.
[0007]
Therefore, a normal recording compensating apparatus is provided with a function capable of correcting asymmetry as described above. Therefore, next, a conventional recording compensator 200 having such an asymmetry correction function will be described with reference to the drawings.
FIG. 6 is a block diagram showing the configuration of the recording compensating device 200. The recording compensating device 200 detects the asymmetry of a reproduced signal obtained by reproducing information recorded on a recording medium, and obtains the obtained reproduction. This device corrects the asymmetry of the signal.
[0008]
As shown in FIG. 6, the recording compensating apparatus 200 records information on a recording medium by a light beam or reproduces information recorded on the recording medium, and the recording / reproducing apparatus 201 reproduces the information recorded on the recording medium. The signal is converted into a multi-valued discrete signal X using a partial response method, and a level detector 202 for detecting each level of the multi-valued discrete signal X, and a multi-valued discrete signal X detected by the level detector 202 And an asymmetry detector 203 for detecting the asymmetry amount ΔL from each of the levels.
[0009]
The recording compensator 200 adjusts the laser power, which is the output of the light beam emitted from the recording / reproducing device 201 (not shown), so as to reduce the asymmetry amount ΔL detected by the asymmetry detector 203. This is to compensate for recording.
Note that each level of a multi-valued discrete signal means a top level, a center level, and a bottom level when a partial response method that can obtain a ternary discrete signal is used, for example.
[0010]
Next, the operation of the recording compensation device 200 configured as described above will be described.
The recording / reproducing device 201 records information on a recording medium and reproduces the recorded information. The laser power, which is the output of a light beam (not shown), can be adjusted during recording so as to reduce the amount of asymmetry.
[0011]
The level detector 202 detects the value of each level with respect to the reproduced signal reproduced by the recording / reproducing device 201. For example, when a partial response method capable of obtaining a ternary discrete signal is used, the obtained reproduced signal has a top level (LT), a center level (LC), and a bottom level (LB) as shown in FIG. A discrete signal having three levels is obtained, and the level detector 202 detects the value of each of these levels.
[0012]
The asymmetry detector 203 obtains an asymmetry amount ΔL from the value of each level detected by the level detector 202 by the following equation (1).
ΔL = LC− (LT + LB) / 2 (1)
In the conventional recording compensator 200, the asymmetry amount ΔL calculated by the asymmetry detector 203 is fed back to the recording / reproducing device 201, and the laser power is adjusted so as to reduce the asymmetry amount ΔL at the time of recording information. Had been corrected.
[0013]
[Problems to be solved by the invention]
However, when the above-described asymmetry correction method is used, as can be seen from Expression (1), it is necessary to obtain the asymmetry amount without using the center level of the multi-valued discrete signal obtained using the partial response method. could not.
However, as recording density of a recording medium increases, asymmetry is likely to occur as described above, and the center level of a signal in a high frequency region is different from the center level of a signal in a low frequency region due to asymmetry. Therefore, the amount of asymmetry changes depending on the value of the center level, which causes a problem that the setting of the center level becomes difficult.
[0014]
Therefore, the present invention has been made in view of the above points, and its purpose is to accurately detect the amount of asymmetry even when using a recording medium with high-density recording. An object of the present invention is to provide a recording compensating apparatus capable of performing recording compensation on a reproduced signal having asymmetry.
[0015]
[Means for Solving the Problems]
To achieve the above object, the recording compensator according to claim 1 of the present invention includes a magnetic recording and reproducing apparatus or optical recording and reproducing apparatus for reproducing information recorded on the magnetic recording medium or an optical recording medium, wherein A read signal reproduced by the magnetic recording / reproducing apparatus or the optical recording / reproducing apparatus is converted into a multi-valued discrete signal using a partial response method, and a direct-current component for setting a direct-current component in a high frequency region of the multi-valued discrete signal to 0. Control means, level detection means for obtaining the top level and bottom level of the multi-valued discrete signal output by the DC component control means, and top level and bottom of the multi-valued discrete signal detected by the level detection means from the difference between the absolute value of the level, e Bei and a asymmetry detecting means for determining the amount of asymmetry is the strain of the reproduction signal, to said asymmetry detecting means As to reduce the asymmetry amount obtained, characterized when recording information on the magnetic recording medium or the optical recording medium by the magnetic recording and reproducing apparatus or the optical recording and reproducing apparatus, that, for correcting the asymmetry And
[0016]
Further, the recording compensator according to claim 2 of the present invention includes a magnetic recording and reproducing apparatus or optical recording and reproducing apparatus for reproducing information recorded on the magnetic recording medium or an optical recording medium, the magnetic recording and reproducing apparatus or the DC component control means for converting a reproduced signal reproduced by an optical recording / reproducing apparatus into a multi-valued discrete signal using a partial response method, and setting a DC component in a high frequency region of the multi-valued discrete signal to 0; a level detecting means for obtaining a value of a plurality of levels each, except for the center level from the level of the multi-level discrete signals component control means outputs, using the value of said each level detected by said level detecting means, Center determine the amount of asymmetry is the strain of the plurality of the reproduction signal from the difference of the absolute values for the values of the plurality of levels between a certain level positioned symmetrically as a border E Bei a symmetry detecting means, and said to mitigate the plurality of asymmetry amount determined by the asymmetry detection unit, the magnetic recording and reproducing apparatus or the optical recording and reproducing apparatus by the magnetic recording medium or the optical recording medium When information is recorded in the data, the asymmetry is corrected.
[0017]
The recording compensator according to claim 3 of the present invention, there is provided a recording compensator according to claim 2, giving priority to the plurality of the asymmetry amount determined by the asymmetry detection means, these preferences to reduce the amount of asymmetry having a rank, characterized by the magnetic recording and reproducing apparatus or the optical recording and reproducing apparatus when recording information on the magnetic recording medium or the optical recording medium, by performing the correction of asymmetry, the And
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiment shown here is merely an example, and the present invention is not necessarily limited to this embodiment.
[0019]
(Embodiment 1)
An example of a recording compensation device according to the present invention will be described as a first embodiment with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a recording compensation device 100 according to the present embodiment. The recording compensation device 100 detects asymmetry of a reproduction signal obtained by reproducing information recorded on a recording medium. And a recording compensating device for correcting the asymmetry of the obtained reproduced signal.
[0020]
As shown in FIG. 1, the recording compensating apparatus 100 uses a light beam to record information on a recording medium and reproduces information recorded on the recording medium, and a recording / reproducing apparatus 101 reproduces information from the recording medium. The resulting signal is converted into a multi-valued discrete signal A by using a partial response method, and a direct current (hereinafter, referred to as “DC”) that reduces a DC component of the multi-valued discrete signal A in a high frequency region to zero. The control device 102 and the DC control device 102 detect the top level and the bottom level of the multilevel discrete signal A with the DC component in the high frequency region being 0, and the level detector 103 detects the level. , The absolute values of the top level and the bottom level of the multi-valued discrete signal A are obtained, and the absolute value of the bottom level is calculated from the absolute value of the top level. An asymmetry detector 104 for subtracting and detecting an asymmetry amount ΔL.
[0021]
Here, the DC control device 102 will be briefly described.
The configuration of the DC control device 102 is as shown in the block diagram of FIG. 2. The DC control device 102 includes an adder 501 for adding a discrete signal and an error signal, a threshold value set to 0 level, and an adder 501. Is determined to be -1 if the output signal of the output signal is larger than the threshold value, and 1 if the output signal is smaller than the threshold value, and an error signal generation circuit 503 for generating an error signal from the output of the determiner 502. .
[0022]
The value of the error signal is almost 0 even when the signal in the low frequency region is determined using the threshold of 0 level, but the signal in the high frequency region has asymmetry, so that when the signal is determined at the threshold 0 level, the error signal becomes It will have either a positive or negative value.
For example, when the DC component of the signal in the high frequency region is shifted to the positive side as shown in FIG. 3B, the number of times −1 is output from the determiner increases, and the output from the error signal generation circuit 503 is increased. The error signal has a negative value. By adding this to the multi-valued discrete signal A, the DC component of the signal in the high frequency region can be adjusted to zero.
[0023]
With the multivalued discrete signal A in which the DC component of the signal in the high frequency region is adjusted to 0, the asymmetry amount can be obtained without using the center level.
Assuming that the top level of the multilevel discrete signal A is (LT) and the bottom level is (LB), the asymmetry amount ΔL is calculated by the following equation (2).
ΔL = | LT | − | LB | (2)
[0024]
The recording compensating apparatus 100 outputs the laser beam output from the recording / reproducing apparatus 101 (not shown) so that the asymmetry detector 104 reduces the asymmetry amount ΔL obtained by the above equation (2). The power is adjusted to compensate for the recording.
[0025]
Thus, as can be seen from the above equation (2), in the recording compensating apparatus 100 according to the present embodiment, the asymmetry is performed without using the center level of the multi-valued discrete signal A obtained by using the partial response method. It is possible to calculate the quantity ΔL. That is, the recording compensator 100 can calculate the asymmetry amount ΔL regardless of the center level, so that the asymmetry amount can always be accurately detected and corrected, which is very suitable.
[0026]
(Embodiment 2)
In the above-described first embodiment, the recording compensation apparatus in which the discrete signal is ternary has been described. However, when the discrete signal is other than ternary, that is, when the discrete signal has a plurality of arbitrarily set values. A recording compensation device will be described as a second embodiment with reference to the drawings. Note that the same reference numerals are used for the same members and configurations as in the first embodiment described above, and description thereof is omitted.
FIG. 4 is a block diagram showing a configuration of a recording compensating device 600 according to the present embodiment. This recording compensating device 600 corrects the asymmetry of the obtained reproduced signal, similarly to the above-described recording compensating device 100. It is a recording compensation device.
[0027]
As shown in FIG. 4, the recording compensating apparatus 600 converts the signal reproduced by the recording / reproducing apparatus 101 into a multi-valued discrete signal B using a partial response method. A DC controller 102 that reduces the DC component in the high frequency region of B to 0, and an arbitrary number of multi-valued discrete signals B in which the DC component is 0 in the high frequency region by the DC controller 102 Among the levels, a level detector 603 for detecting all remaining levels excluding the center level, and asymmetry detection for detecting an asymmetry amount ΔL using all levels in the multi-valued discrete signal B detected by the level detector 603 604.
[0028]
For example, if a 5-level discrete signal as shown in FIG. 5 is obtained using a high-order partial response method, the level detector 603 outputs a middle level (LM) in addition to a top level (LT) and a bottom level (LB). ) And (LN) are detected.
The asymmetry detector 604 obtains the asymmetry amount ΔL1 from the level having the largest absolute value on the positive side and the negative side, and then obtains the asymmetry amount ΔL2 from the level having the second largest absolute value on the positive side and the negative side. These asymmetry amounts ΔL1 and ΔL2 are calculated by equations (3) and (4).
ΔL1 = | LT | − | LB | (3)
ΔL2 = | LM | − | LN | (4)
[0029]
In the recording compensator 600, the asymmetry detector 104 first roughly corrects the asymmetry using the asymmetry amount ΔL1 obtained by the above equation (3), and then obtains the asymmetry by the above equation (4). By the procedure of finely correcting the asymmetry with the asymmetry amount ΔL2, the recording is performed by adjusting the laser power, which is the output of the light beam emitted from the recording / reproducing apparatus 101 (not shown), so as to reduce the overall asymmetry amount. Is compensated.
[0030]
Further, as can be understood from the above equations (3) and (4), the recording compensating apparatus 600 according to the present embodiment does not use the center level of the quinary discrete signal B obtained by using the partial response method. It is possible to calculate the asymmetry amount. That is, the recording compensator 600 can calculate the asymmetry amounts ΔL1 and ΔL2 regardless of the center level, so that even when a recording medium with high-density recording is used, detection and correction of the asymmetry amount are always accurate. Can be performed, which is very suitable.
[0031]
Although the second embodiment uses the partial response system which is a quinary discrete signal, a higher order partial response system is used to obtain a discrete signal having more than five values. Even in this case, as in the case of the second embodiment, accurate recording compensation can be performed by correcting the asymmetry in order from the asymmetry amount obtained from the level with the largest absolute value. .
[0032]
Although not described in detail here, the recording correction apparatus 600 is configured to give a priority to the asymmetry amount obtained by the asymmetry detection means and correct the asymmetry so as to reduce the asymmetry amount according to the priority. It is also possible to do. In this case, even when a recording medium with higher recording density is used, the asymmetry amount can be detected and corrected more accurately than in the case described above, which is very preferable.
[0033]
【The invention's effect】
As described above , according to the recording compensation apparatus of the present invention, the amount of asymmetry, which is distortion of a reproduced signal, is obtained from the difference between the absolute values of the top level and the bottom level of a multilevel discrete signal detected by the level detecting means. The asymmetry detection means for obtaining the asymmetry, by correcting the asymmetry at the time of recording information on the recording medium so as to reduce the asymmetry amount obtained by the asymmetry detection means, without using the center level of the multi-valued discrete signal it is possible to also perform the detection and correction of exact asymmetry amount, the DC component of the high frequency range even if the progress in recording density than that in the 0, without using the center level of asymmetry amount Since it can be obtained, accurate recording compensation can be performed.
[0034]
Further , according to the recording compensation device of the present invention, the value of each level detected by the level detection means is used to calculate the difference between the absolute values of the values of a plurality of levels symmetrically positioned around the center level. A center is provided by providing asymmetry detection means for obtaining an amount of asymmetry which is a distortion of a plurality of reproduction signals, and performing asymmetry correction at the time of data recording so as to reduce the plurality of asymmetry amounts obtained by the asymmetry detection means. Since the asymmetry amount can be obtained regardless of the level, accurate asymmetry amount detection and correction can be performed even when high-density recording has progressed.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a recording compensation device according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a DC control device used in the recording compensation device according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a relationship between a reproduction signal and a recording mark obtained when reproducing a recording medium.
FIG. 4 is a block diagram illustrating a configuration of a recording compensation device according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a quinary discrete signal according to Embodiment 2 of the present invention.
FIG. 6 is a block diagram showing a configuration of a conventional recording compensating device in a conventional technique.
FIG. 7 is a diagram showing a ternary discrete signal according to a conventional technique.
[Explanation of symbols]
REFERENCE SIGNS LIST 100 recording compensating device 101 recording / reproducing device 102 DC control device 103 level detector 104 asymmetry detector 200 recording compensating device 201 recording / reproducing device 202 level detector 203 asymmetry detector 501 adder 502 determiner 503 error signal generating circuit 600 recording compensation Device 603 Level detector 604 Asymmetry detector

Claims (3)

A magnetic recording and reproducing apparatus or optical recording and reproducing apparatus for reproducing recorded information on magnetic recording medium or an optical recording medium,
A reproduced signal reproduced by the magnetic recording / reproducing device or the optical recording / reproducing device is converted into a multi-valued discrete signal using a partial response method, and a DC component in which a DC component in a high frequency region of the multi-valued discrete signal is 0 Component control means;
Level detection means for determining the top level and bottom level of the multi-valued discrete signal output by the DC component control means,
Asymmetry detection means for detecting the amount of asymmetry, which is the distortion of the reproduction signal, from the difference between the absolute value of the top level and the bottom level of the multi-valued discrete signal detected by the level detection means,
Bei to give a,
Adapted to reduce the asymmetry amount obtained by the asymmetry detection unit, when recording information on the magnetic recording medium or the optical recording medium by the magnetic recording and reproducing apparatus or the optical recording and reproducing apparatus, the correction of the asymmetry To do,
A recording compensation device characterized by the above-mentioned. A magnetic recording and reproducing apparatus or optical recording and reproducing apparatus for reproducing recorded information on magnetic recording medium or an optical recording medium,
A reproduced signal reproduced by the magnetic recording / reproducing device or the optical recording / reproducing device is converted into a multi-valued discrete signal using a partial response method, and a DC component in which a DC component in a high frequency region of the multi-valued discrete signal is 0 Component control means;
Level detection means for obtaining a value for each of a plurality of levels excluding the center level from the level of the multi-valued discrete signal output by the DC component control means,
A strain of the level have use the value of the each level detected by the detecting means, the absolute value plurality of the reproduction signal from the difference with respect to the values of a plurality of levels between which is positioned symmetrically to the center level as a boundary An asymmetry detecting means for obtaining an asymmetry amount;
Bei to give a,
When recording information on the magnetic recording medium or the optical recording medium by the magnetic recording / reproducing device or the optical recording / reproducing device so as to reduce the plurality of asymmetry amounts obtained by the asymmetry detecting means, Making corrections,
A recording compensation device characterized by the above-mentioned. The recording compensation device according to claim 2,
Giving priority to the plurality of the asymmetry amount determined by the asymmetry detection unit, so as to reduce the amount of asymmetry having these priorities, the magnetic by the magnetic recording and reproducing apparatus or the optical recording and reproducing apparatus When recording information on a recording medium or the optical recording medium, performing asymmetry correction,
A recording compensation device characterized by the above-mentioned.

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