JP2001023304A - Record compensating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a record compensating device by which an asymmetry quantity is correctly detected even when a recording medium with improved high density recording conversion is used and by which recording compensation is executed with respect to a reproduced signal having asymmetry. SOLUTION: The recording compensating device 100 is provided with a recording and reproducing device 101 for recording information on a recording medium or reproducing information recorded in the recording medium, a DC controller 102 for making a reproduced signal a multilevel discrete signal through the use of a partial response system and making a DC component in the high frequency area of the multilevel discrete signal be zero, a level detector 103 for detecting the top level and the bottom level of the multilevel discrete signal where the DC component in the high frequency area is made to be zero and an asymmetry detector 104 for obtaining the respective absolute values of the top and the bottom levels in the multilevel discrete signal, subtracting the absolute value of the bottom level from the absolute value of the top level and detecting the asymmetry quantity ΔL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 in particular, has a feature of performing recording compensation on a reproduced signal having asymmetry.

[0002]

2. Description of the Related Art Disk-shaped magnetic recording media and optical recording media (hereinafter, simply referred to as "recording media") have been used for high-density recording with the recent tendency that the amount of information handled at a time is increasing. With this, the amount of information that can be recorded on one recording medium is being increased. 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.

FIG. 3 is a diagram showing a relationship between a reproduction 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 also 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 with low light reflectance, 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 having a high light reflectance. When this optical disc is reproduced, a reproduced signal as shown in FIG. 3A is obtained.

When different lasers are irradiated onto the optical disk surface in this way, some heat is accumulated at the end of the recording mark. This phenomenon is called a heat storage phenomenon. The heat storage phenomenon distorts the original shape of the recording mark, and thus slightly shifts the edge of the recording mark. Even when 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, the width of the recording mark itself and the interval between the recording marks become smaller as the recording medium becomes higher in density, so that the edges of the recording marks tend to fluctuate even though they are 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] 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 errors tend 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.

Referring to FIG. 3B showing the waveform of a reproduced signal in which asymmetry has occurred, the horizontal line shown by a solid line is set as a slice level S in the waveform of the reproduced signal shown here. Is “0” depending on whether is above or below the slice level S
When the determination of “1” is made, a sampling point below the slice level S may come over the slice level S depending on an error, and the determination may be erroneous. 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 indicated by a solid line, the waveform of the reproduced signal is represented by the slice level S.
By correcting the asymmetry so as to have a vertically symmetrical waveform with respect to, the occurrence rate of erroneous determination can be suppressed.

Therefore, the ordinary recording compensator has a function of correcting asymmetry as described above. Therefore, next, a conventional recording compensating apparatus 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 reproduction signal obtained by reproducing information recorded on a recording medium, and obtains the obtained reproduction. This device corrects the asymmetry of the signal.

As shown in FIG. 6, a recording compensating apparatus 200 is a recording / reproducing apparatus 201 for recording information on a recording medium by a light beam or reproducing information recorded on the recording medium.
And a signal reproduced from the recording / reproducing apparatus 201 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 an asymmetry detector 203 for detecting an asymmetry amount ΔL from each level of the multi-valued discrete signal X detected from the above.

The recording compensator 200 uses the asymmetry amount Δ detected by the asymmetry detector 203.
In order to reduce L, the recording power is adjusted by adjusting the laser power which is the output of the light beam emitted from the recording / reproducing device 201 (not shown). Note that each level of a multi-valued discrete signal means, for example, a top level, a center level, and a bottom level when a partial response method that can obtain a ternary discrete signal is used.

Next, the operation of the recording compensator 200 configured as described above will be described. Recording / reproducing device 201
Records information on a recording medium and reproduces the recorded information. Also, to reduce the amount of asymmetry,
Here, the laser power, which is the output of a light beam (not shown), can be adjusted during recording.

The level detector 202 is connected to the recording / reproducing device 20.
The value of each level is detected with respect to the reproduction signal reproduced by 1. For example, when a partial response system that can obtain 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.

The asymmetry detector 203 calculates the following equation (1) from each level value detected by the level detector 202.
To obtain the asymmetry amount ΔL. ΔL = LC− (LT + LB) / 2 (1) In the conventional recording compensation device 200, the asymmetry amount ΔL calculated by the asymmetry detector 203 is fed back to the recording / reproducing device 201, and the asymmetry amount is recorded when information is recorded. The asymmetry was corrected by adjusting the laser power so as to reduce ΔL.

[0013]

However, if the asymmetry correction method described above is used, the center level of the multi-valued discrete signal obtained by using the partial response method is determined as can be seen from equation (1). If not used, the amount of asymmetry could not be determined. However, as recording density of a recording medium increases, asymmetry tends 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.

Therefore, the present invention has been made in view of the above points, and an object of the present invention is to accurately detect the asymmetry amount even when using a recording medium with high recording density. It is another object of the present invention to provide a recording compensator capable of performing recording compensation for a reproduced signal having asymmetry.

[0015]

According to a first aspect of the present invention, there is provided a recording compensating apparatus for reproducing at least information recorded on a magnetic recording medium or an optical recording medium. A reproducing device or an optical recording / reproducing device, and a reproduction 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 high frequency of the multi-valued discrete signal is used. DC component control means for setting a DC component in a region to 0; level detection means for obtaining a top level and a bottom level of the multi-valued discrete signal in which the DC component in a high frequency region is set to 0 by the DC component control means; An asymmetry for obtaining an asymmetry amount of the reproduction signal based on a top level and a bottom level of the multi-valued discrete signal detected by a level detection means; And a bird detecting means, wherein the magnetic recording medium or the optical disc is reproduced by the magnetic recording / reproducing apparatus or the optical recording / reproducing apparatus so as to reduce the asymmetry amount obtained by the asymmetry detecting means. When information is recorded on a recording medium, asymmetry is corrected.

According to a second aspect of the present invention, at least a magnetic recording / reproducing apparatus or an optical recording / reproducing apparatus for reproducing information recorded on a magnetic recording medium or an optical recording medium; DC component control means for converting a reproduced signal reproduced by the reproducing device or the optical recording / reproducing device 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 Level detecting means for obtaining an arbitrary plurality of levels in the multi-valued discrete signal in which the DC component in a high frequency region is set to 0 by the DC component controlling means; and the multi-level discrete signal detected by the level detecting means. An asymmetry detecting means for obtaining an asymmetry amount of the reproduced signal based on a plurality of levels in the discrete signal of the value. A is, so as to reduce the asymmetry amount obtained by the asymmetry detection means,
When information is recorded on the magnetic recording medium or the optical recording medium by the magnetic recording / reproducing device or the optical recording / reproducing device, correction of asymmetry is performed.

According to a third aspect of the present invention, in the recording compensating apparatus according to the second aspect, priorities are assigned to the plurality of asymmetry amounts obtained by the asymmetry detection means, It is preferable to perform asymmetry correction when information is recorded 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 amount of asymmetry having priority. It is an embodiment.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The embodiment described here is merely an example, and the present invention is not necessarily limited to this embodiment.

(Embodiment 1) An example of a recording compensation apparatus according to the present invention will be described as a first embodiment with reference to the drawings. FIG. 1 shows a recording compensation device 1 according to the present embodiment.
00 is a block diagram showing a configuration of the recording compensation apparatus 100. The recording compensation apparatus 100 detects the asymmetry of a reproduction signal obtained by reproducing information recorded on a recording medium, and corrects the asymmetry of the obtained reproduction signal. Compensation device.

As shown in FIG. 1, the recording compensating apparatus 100 records information on a recording medium using a light beam,
Recording / reproducing apparatus 10 for reproducing information recorded on a recording medium
1 and a signal reproduced from the recording / reproducing apparatus 101 as a multi-valued discrete signal A using a partial response method, and a direct current (Direct) for setting a DC component of the multi-valued discrete signal A in a high frequency region to 0. Current,
Hereinafter, it is referred to as “DC”. 2) 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. An asymmetry detector 104 for determining the absolute value of each of the top level and the bottom level of the multi-level discrete signal A, subtracting the absolute value of the bottom level from the absolute value of the top level, and detecting the asymmetry amount ΔL. ing.

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 the discrete signal and the error signal, and a threshold value of 0.
And a decision unit 502 that sets an output signal of the adder 501 to -1 when the output signal is larger than the threshold value and 1 when the output signal is smaller than the threshold value, and an error signal that generates an error signal from the output of the decision unit 502 And a generation circuit 503.

Although 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, the signal in the high frequency region has asymmetry, so that it is determined at the threshold 0 level. The error signal will have either a positive or negative value. For example, FIG.
In the case where the DC component of the signal in the high frequency region is shifted to the positive side as in the case of, the number of times -1 is output from the decision unit increases, and the error signal output from the error signal generation circuit 503 has a negative value. have. 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.

The DC component of the signal in the high frequency region is
In the multi-valued discrete signal A adjusted to the above, 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)

The recording compensating apparatus 100 outputs the light beam emitted 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 laser power is adjusted to compensate for recording.

As can be seen from the above equation (2), the recording compensating apparatus 100 according to the present embodiment
The asymmetry amount ΔL can be calculated without using the center level of the multi-valued discrete signal A obtained using the partial response method. That is, since the recording compensating apparatus 100 can calculate the asymmetry amount ΔL regardless of the center level, the asymmetry amount can always be accurately detected and corrected, which is very preferable.

(Embodiment 2) In the above-described first embodiment, the recording compensator in the case where the discrete signal has three values has been described.
That is, a recording compensation device in the case of a plurality of arbitrarily set values will be described as a second embodiment with reference to the drawings. The same members and configurations as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 4 shows a recording compensation device 60 according to the present embodiment.
0 is a block diagram showing the configuration of the recording compensating device 6.
Reference numeral 00 denotes a recording compensating device that corrects the asymmetry of the obtained reproduced signal, similarly to the recording compensating device 100 described above.

As shown in FIG. 4, the recording compensating apparatus 600 converts a signal reproduced by the recording / reproducing apparatus 101 and a multi-valued discrete signal B using a partial response method into a multi-valued discrete signal B. And a DC controller 102 that sets the DC component in the high frequency region of the discrete signal B to 0, and a multi-valued discrete signal B in which the DC component is 0 in the high frequency region. A level detector 603 for detecting all remaining levels excluding the center level among the existing levels;
Multi-valued discrete signal B detected by level detector 603
And an asymmetry detector 604 for detecting the asymmetry amount ΔL by using all the levels in.

For example, if a quinary discrete signal as shown in FIG. 5 is obtained using a high-order partial response system, the level detector 603 has a middle level in addition to the top level (LT) and the bottom level (LB). Level (LM), (L
N) is 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 the equations (3) and (4).
Is calculated by ΔL1 = | LT | − | LB | (3) ΔL2 = | LM | − | LN | (4)

In the recording compensator 600, the asymmetry detector 104 first roughly corrects the asymmetry with the asymmetry amount ΔL1 obtained by the above equation (3), and then calculates the asymmetry by the above equation (4). The recording / reproducing apparatus 1 (not shown) is used to reduce the overall asymmetry amount by performing a procedure of finely correcting the asymmetry with the obtained asymmetry amount ΔL2.
The recording power is adjusted by adjusting the laser power, which is the output of the light beam emitted by the light emitting device 01.

As can be seen from the above equations (3) and (4), in the recording compensating apparatus 600 according to the present embodiment, the center level of the quinary discrete signal B obtained by using the partial response method is set. It is possible to calculate the asymmetry amount without using it. That is, in the recording compensator 600, the asymmetry amount Δ
Since L1 and ΔL2 can be calculated, accurate asymmetry amount detection and correction can always be performed even when a recording medium with high-density recording is used, which is very suitable.

Although the second embodiment uses the partial response system which is a quinary discrete signal, a higher-order partial response system is used.
Even in the case of a discrete signal having more than five values, the asymmetry is corrected in order from the asymmetry amount obtained from the level with the largest absolute value, as in the case of the second embodiment. By doing so, accurate recording compensation can be performed.

Although not described in detail here, this recording correction device is configured to give a priority to the asymmetry amount obtained by the asymmetry detecting means and correct the asymmetry so as to reduce the asymmetry amount according to the priority. It is also conceivable to construct 600. in this case,
Even when a recording medium with high 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]

As described above, according to the recording compensating apparatus according to the first aspect of the present invention, when the information is recorded on the recording medium, the asymmetry is reduced so that the asymmetry amount obtained by the asymmetry detecting means is reduced. With the function to perform correction, it is possible to accurately detect and correct the amount of asymmetry without using the center level of multi-valued discrete signals. Since the DC component is set to 0, the asymmetry amount can be obtained without using the center level, so that accurate recording compensation can be performed.

According to a second aspect of the present invention, there is provided a recording compensating apparatus having a function of correcting asymmetry at the time of data recording so as to reduce a plurality of asymmetry amounts obtained by the asymmetry detecting means. So
Even when high-density recording has progressed, accurate asymmetry amount detection and correction can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a recording compensation device according to a first embodiment 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 showing a configuration of a recording compensation device according to Embodiment 2 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 compensation 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 Equipment 603 Level detector 604 Asymmetry detector

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5D031 AA01 AA04 CC01 DD01 DD10 EE01 EE08 HH11 5D044 BC01 BC02 CC01 CC04 FG01 FG06 FG16 GK11 GK14 GL02 GL31 5D090 AA01 CC04 DD03 DD05 EE01 EE14 EE15 EE17 FF

Claims (3)

[Claims] At least a magnetic recording / reproducing device or an optical recording / reproducing device for reproducing information recorded on a magnetic recording medium or an optical recording medium; and a reproducing signal reproduced by the magnetic recording / reproducing device or the optical recording / reproducing device. Is a multi-valued discrete signal using a partial response method, DC component control means for setting the DC component in the high frequency region of the multi-valued discrete signal to 0, DC component in the high frequency region by the DC component control means Level detection means for obtaining a top level and a bottom level of the multi-valued discrete signal, where 0 is set to 0; and using the top level and the bottom level of the multi-valued discrete signal detected by the level detection means, An asymmetry detecting means for obtaining an amount of asymmetry as a signal distortion, wherein the asymmetry detecting means comprises: To reduce the amount of asymmetry determined by the output unit, 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, performing asymmetry correction, A recording compensation device characterized by the above-mentioned. 2. A magnetic recording / reproducing apparatus or optical recording / reproducing apparatus for reproducing information recorded on at least a magnetic recording medium or an optical recording medium, and a reproduction signal reproduced by the magnetic recording / reproducing apparatus or the optical recording / reproducing apparatus. Is a multi-valued discrete signal using a partial response method, DC component control means for setting the DC component in the high frequency region of the multi-valued discrete signal to 0, DC component in the high frequency region by the DC component control means A level detection means for obtaining a value for each of a plurality of levels, which is set in advance for the multi-valued discrete signal having a value of 0, and using the value of the level detected by the level detection means, An asymmetry detecting means for obtaining an amount of asymmetry which is a signal distortion, wherein the asymmetry detecting means comprises: Correcting the asymmetry when the magnetic recording / reproducing apparatus or the optical recording / reproducing apparatus records information on the magnetic recording medium or the optical recording medium so as to reduce the amount of asymmetry obtained. , Recording compensator. 3. The recording compensation apparatus according to claim 2, wherein priorities are given to the plurality of asymmetry amounts obtained by said asymmetry detection means, and the amount of asymmetry having these priorities is reduced. And correcting asymmetry when information is recorded on the magnetic recording medium or the optical recording medium by the magnetic recording / reproducing device or the optical recording / reproducing device.