JPH08124167A - Method for recording and reproducing optical information and device therefor - Google Patents

Abstract

PURPOSE: To perform a recording and reproducing even in the case a device is made to be high density by performing the recording while making the dimension of a recording mark correspond to multi-valued data and detecting multi- valued data while reducing crosstalk and intercode interference. CONSTITUTION: This device is constituted of a two-dimensional equalization circuit 129 reducing the leak-in of two-dimensional information and an equalization coefficient learning circuit 121 for calculating an optimum equalization coefficient to be used in the two-dimensional equalization circuit in a state in which an optical recording medium is loaded in an information recording and reproducing device. Then, at the time of the reproducing of information, positions where marks for equalization coefficient learnings are recorded are detected based on the reproducing signal of pre-pits prepared previously in a learning track recognizing area and an equalization coefficient is calculated by reproducing learning marks with a spot based on the detection values and then the leak-in of the two-dimensional information is reduced by using the calculated equalization coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing method and apparatus for recording / reproducing information on / from an optical recording medium using a laser beam.

[0002]

2. Description of the Related Art An information mark is recorded on an information track by using a laser beam, and an optical change according to the presence or absence of the information mark is detected to improve the recording density of an optical information recording medium for reproducing information. As a method, it is conceivable to narrow the information track spacing (track pitch) and narrow the information mark array spacing (mark pitch) in the light spot scanning direction. However, when the track pitch and the mark pitch are smaller than the diameter of the light spot, when the light spot irradiates one information mark, part of other surrounding information marks is also irradiated at the same time. There arises a problem that signals of surrounding information marks leak into the signal two-dimensionally. This leakage interferes as a noise component and reduces the reproduction accuracy. Therefore, the sizes of the track pitch and the mark pitch are limited by the diameter of the light spot. The diameter of this light spot depends on the wavelength λ and the numerical aperture (NA) of the focusing lens.
Since the value is limited to the value of NA, in a system including a laser of a specific wavelength and a focusing lens, two-dimensional information leakage becomes a major obstacle to high density.

As a means for solving the above problems and reducing the track pitch and the mark pitch, there is a two-dimensional equalization processing method (Japanese Patent Laid-Open No. 02-257474) for canceling the leak component of the information. This conventional example is shown in FIG. In this conventional method, the binary information is D
iscree Block Servo Forma
It is recorded as the presence or absence of a mark on a predetermined grid point on the recording medium according to t (hereinafter abbreviated as DBF). Conventionally,
The DBF is characterized by its ease of tracking signal detection and stability of clock detection of recorded / reproduced data, and can detect all timings by using clock pits written on the disc, as shown in FIG. Marks can be recorded on such two-dimensional grid points. At the time of information reproduction, based on the reproduction signals on the grid points on track i-1, track i and track i + 1,
Using the signal processing circuit as shown in FIG. 4, information leaks from the reproduction signal of the target track i from the adjacent track (hereinafter referred to as crosstalk) and information leaks on the track i (hereinafter intersymbol interference). Call)). By using this technique, even if the mark pitch and the track pitch are made small, there is no influence of crosstalk or intersymbol interference, and high-density recording / reproducing is possible.

On the other hand, as another method for improving the recording density of an optical information recording medium, a multi-valued recording / reproducing system in which the size of a recording mark is changed and recorded / reproduced in accordance with multi-valued data (Japanese Patent Laid-Open No. 63-63). No. 302426). This conventional example is shown in FIG. In this conventional method, since the area of the recording mark is changed to record the information, it is possible to perform recording of multiple bits on the recording element having a constant size. This enables high-density recording / reproduction without reducing the spot diameter during reproduction or reducing the mark pitch or track pitch.

[0005]

As described above, in the method of reducing the track pitch and the mark pitch, crosstalk and intersymbol interference pose problems.
If the signal processing described in Japanese Patent No. 257474 is used, it is possible to perform high-density recording / reproduction without being affected by crosstalk or intersymbol interference. However, even if this technique is used, it is not possible to reproduce a high-frequency signal above the cut-off spatial frequency (2NA / λ) of the optical disk device, and therefore recording / reproduction cannot be performed at a mark pitch below λ / 4NA. Further, if the track pitch is made too small, crosstalk will increase significantly, and even if the above signal processing is used, crosstalk cannot be reduced sufficiently. Thus, there is a limit to the track pitch and mark pitch that can be realized in a system provided with a laser of a specific wavelength and a focusing lens, and ultra-high density recording / reproducing can be realized even by using the method described in Japanese Patent Laid-Open No. 02-257474. Can not.

On the other hand, recording / reproducing is performed by changing the area of the recording mark corresponding to multi-valued data.
In the multi-valued recording / reproducing method described in Japanese Patent No. 26, since multi-bit recording can be performed on a recording element having a fixed size, high-density recording / reproducing is possible without reducing the mark pitch or track pitch. However, in the conventional method described in Japanese Patent Laid-Open No. Sho 63-302426, it is necessary to provide a mark-to-mark distance such that intersymbol interference from the spot scanning direction and crosstalk from adjacent tracks does not occur during information reproduction. For example, it is necessary to provide a distance in the spot scanning direction so that the maximum marks do not interfere with each other, and the mark pitch becomes larger than that in the conventional binary recording in which the mark pitch is reduced to increase the density. . As a result, the effect of increasing the density due to the multi-value is canceled by decreasing the density by providing the marks, and high density recording / reproduction cannot be realized even by using this conventional method.

An object of the present invention is to provide an ultra high density recording medium and an information recording / reproducing apparatus capable of performing multi-valued recording / reproducing at a mark pitch and a track pitch which are equal to or smaller than those of the conventional one.

[0008]

The above-mentioned problems are caused by changing the size of the recording mark to two or more types corresponding to multi-valued data by irradiating a laser beam on a predetermined lattice point of the optical information recording medium. An area is provided on the recording medium for detecting the amount of leakage of information from the grid point that is two-dimensionally closest to the grid point for recording and reproduction, and the grid point in the area is provided. Based on the detection value obtained by recording the mark group on the top and scanning the mark group with the light spot in advance, the crosstalk amount from the adjacent track to the target track and the target track The inter-symbol interference between adjacent grid points is learned, and the cross-talk from the adjacent track is reduced based on the cross-talk learned using signal processing during information reproduction. Purpose based on quantity By reducing the inter-symbol interference on the rack, it is possible to solve the above problems by reducing the information leakage of from lattice points adjacent two-dimensionally.

The above solving means will be described in detail below.

The multilevel recording / reproducing method of the present invention will be described below. In the information recording / reproducing system according to the present invention, the size of the mark is recorded on the predetermined grid point of the optical information recording medium by changing the size of the mark into two or more types corresponding to multi-valued data. FIG. 1A shows data "0" for 2 bits.
An example of recording 0 ”,“ 01 ”,“ 10 ”, and“ 11 ”by changing the size of the mark to four types is shown.“ 00 ”is recorded by not recording the mark at the grid point, By recording a mark with a diameter of W1 at a point, "01" is recorded, and by recording a mark with a diameter of W2 at a grid point, "1" is recorded.
"0" is recorded and "11" is recorded by recording a mark having a diameter of W3 at the lattice point.

At the time of reproducing information, the signal amplitude on the grid points is modulated according to the mark diameters 0 to W3 recorded on the grid points. For each mark diameter 0 to W3, for example, when no mark is recorded at the grid point, the reproduction signal amplitude on the grid point is 0, and when the mark having the diameter W1 is recorded at the grid point. Has a reproduction signal amplitude of 1 on the grid point, and when a mark having a diameter of W2 is recorded at the grid point, the reproduction signal amplitude on the grid point is 2 and the diameter of the grid point is W3.
When the mark is recorded, the reproduction signal amplitude on the lattice point may be set to 3. By doing this, if the reproduction signal amplitude on the lattice point is 0, "00"
If the reproduction signal amplitude on the grid point is 1, then "01"
If the amplitude of the reproduced signal on the grid point is 2, then "10"
If the amplitude of the reproduced signal on the grid is 3, then "11"
The original data can be played back with.

However, in the information recording method according to the present invention, since the lattice point interval (mark pitch) in the light spot scanning direction and the lattice point interval (track pitch) in the adjacent track direction are smaller than the light spot diameter, the light spot When one illuminates one mark, it also illuminates some of the other marks around it. Therefore, the signals of the surrounding information marks leak into the signals of the information marks to be reproduced two-dimensionally and the accuracy of reproduction is lowered. Therefore, the following processing is performed during reproduction to reduce crosstalk from adjacent tracks and intersymbol interference from the spot scanning direction, which is a two-dimensional information leak. Hereinafter, a signal processing method for reducing crosstalk and intersymbol interference will be described.

First, crosstalk from adjacent tracks and intersymbol interference on the tracks for reproduction will be described. When a light spot scans an arbitrary track, there are 0 to 8 adjacent lattice points around a certain lattice point, and 0 to 8 depending on whether there is an information mark or not.
There are adjacent information marks. When a light spot irradiates a target lattice point, if there is a mark on the adjacent lattice point, the information mark is also partially irradiated, so that information leaks from the adjacent lattice point.

FIG. 3 concretely illustrates the leakage of these information. a to h represent the degree of information leakage (hereinafter referred to as interference coefficient) from the adjacent eight grid points to the target grid point, and in the example shown in FIG. 3, the interference coefficient is as follows. Desired.

[0015]

[Equation 1]

However, S '(i, p) is a lattice point (i, p)
It is assumed that the reproduction signal level is at the position, and that there is a sufficient space between each mark so that each mark can be regarded as isolated.

As will be described later in detail, the value of the interference coefficient is substantially constant even when the mark diameter is changed from W1 to W3, and may be considered independent of the mark diameter. If this condition is satisfied, the reproduced signal S ′ (i, j) that has received interference from the adjacent information mark can be expressed as follows using the interference coefficients a to h shown in FIG.

[0018]

[Equation 2]

Here, S (i, j) is a reproduction signal level when an information mark is independently present at a lattice point (i, j) and no adjacent information mark is present (hereinafter referred to as an isolated signal). As mentioned above, the isolated signal is modulated by the size of the mark diameter. Therefore, the mark diameter to be recorded is, for example, W1 where the isolated signal is 1, and 2 when the isolated signal is
It is preferable to set the diameter such that W2 becomes W2 and the diameter where the isolated signal becomes 3 as W3.

In the signal processing according to the present invention, a signal S ″ (i, j) in which the leakage of two-dimensional information is reduced is obtained based on the reproduction signal represented by the equation (2). , J), a signal processing method for obtaining a signal with reduced crosstalk and intersymbol interference (hereinafter referred to as two-dimensional equalization processing) is shown in the interference coefficient shown in FIG. Assuming that be, f = gd, and h = ge are satisfied, it is possible to reduce the crosstalk by performing the calculation of Expression 3.

[0021]

(Equation 3)

Further, intersymbol interference can be reduced by carrying out the following calculation based on the result of the equation (3).

[0023]

[Equation 4]

The above equation (4) shows an example in which the calculation is performed based on the signals on the four lattice points that are closest to the target lattice point in the spot scanning direction. However, in the calculation for reducing the intersymbol interference, the calculation is performed on the adjacent lattice points. The number of signals is not limited to four.

By the way, in an actual optical disk device, the recording mark shape and position change due to changes in the spot shape, recording power, recording clock timing, focus and tracking during recording, and the optical spot shape during reproduction,
The amount of crosstalk and the amount of intersymbol interference fluctuate due to fluctuations in tracking, focus, and sampling clock timing. Even if these fluctuation factors occur, it is necessary to adaptively change the equalization coefficient used for two-dimensional equalization in order to effectively reduce crosstalk and intersymbol interference.
For this purpose, the value of the interference coefficient shown in FIG. 3 is measured with the optical recording medium mounted in an actual optical disk device. The optimum equalization coefficient can be calculated by obtaining the equalization coefficient from the interference coefficient value obtained as a result of the measurement.

For this purpose, a predetermined mark row pattern
Are recorded in advance at a predetermined position on the optical recording medium. Before the information is reproduced, this mark sequence pattern is reproduced with an optical spot, and the amount of information leakage is learned based on the reproduced signal. As described above, the value of the interference coefficient is independent of the mark diameter, and a = bd, c = be, f = g between the interference coefficients.
If d and h = ge are satisfied, it is possible to reduce the leakage of two-dimensional information by performing the calculations of Expressions 3 and 4. At this time, the equalization coefficients are −b and −g in the equation 4, (1-de), −d, −e, d × in the equation 4.
d, e × e. Therefore, the interference coefficient is b,
It is sufficient to learn d, e, and g, and the equalization coefficient may be calculated based on this learned value. Below, b and g are referred to as crosstalk coefficients from adjacent tracks, and d and e
Is called the intersymbol interference coefficient on the track.

[0027]

In the information recording / reproducing system according to the present invention, the size of the mark is recorded on the predetermined grid points of the optical information recording medium by changing the size of the mark into two or more types corresponding to multi-valued data. For example, as shown in FIG. 1A, 2-bit data “00”, “01”, “10”, and “11” are recorded by changing the mark size into four types of 0 to W3. Then, at the time of reproducing information, the signal amplitude on the grid point is modulated according to the mark diameters 0 to W3 recorded on the grid point.
That is, when the reproduction signal amplitude on the lattice point is 0, "0
0 ", and if the reproduction signal amplitude on the grid point is 1, then" 0 "
1 ", and if the reproduction signal amplitude on the grid point is 2, then" 1 "
0 ", and if the reproduction signal amplitude on the grid point is 3, then" 1 "
The original data can be reproduced by setting it to 1 ".

However, in the information recording method according to the present invention, the grid point interval (mark pitch) in the light spot scanning direction and the grid point interval (track pitch) in the adjacent track direction are smaller than the light spot diameter. When one illuminates one mark, it also illuminates some of the other marks around it. Therefore, the signals of the surrounding information marks leak into the signals of the information marks to be reproduced two-dimensionally and the accuracy of reproduction is lowered. Therefore, signal processing is performed during reproduction to reduce crosstalk from adjacent tracks and intersymbol interference from the spot scanning direction, which is a two-dimensional information leak.
In an actual optical disc device, the recording mark shape and position change due to changes in spot shape, recording power, recording clock timing, focus, and tracking during recording, and changes in optical spot shape, tracking, focus, and sampling clock timing during reproduction. As a result, the amount of crosstalk and the amount of intersymbol interference vary. In the information recording / reproducing system of the present invention, in order to effectively reduce the crosstalk and the intersymbol interference even when these fluctuation factors occur, the method described in the means for solving the above problems is used for the optical disc apparatus. The optimal equalization coefficient is learned with the optical recording medium mounted on the optical disc, and two-dimensional equalization processing is performed based on the equalization coefficient obtained as a result of this learning.

However, in the case of performing the two-dimensional equalization processing, the value of the interference coefficient is substantially constant even when the mark diameter is changed to W1 to W3, and a = bd, c = be, f =
It is necessary that gd and h = ge are substantially satisfied. Hereinafter, it will be shown in FIG. 4 that this condition is substantially satisfied in the optical disk device. FIG. 4 shows a result of simulating a reproduction signal waveform obtained by reproducing an isolated mark and an interference coefficient obtained from the reproduction waveform. In the simulation, the journal of optical society of america, which simulates the optical disk reproduction process, taking into consideration the light diffraction and the numerical aperture of the aperture lens 6
9, No. 1 (1979) Item 4 to Item 24 (J. Opt. Soc. Am., Vol. 69, No. 9).
1, January (1979), PP4-24) Hopkins diffraction calculation was used. Light source wavelength is 780n
m, and the numerical aperture of the aperture lens is assumed to be 0.55.

The left view of FIG. 4A shows a mark of W1 = 0.34 μm and W2 = 0.50 μm recorded on the magneto-optical medium.
The case where a mark of m and a mark of W3 = 0.64 μm are reproduced is shown. On the grid point where the mark is recorded, the reproduction signal level is 1 for the mark of W1, 2 for the mark of W2, and W3.
Each mark diameter was determined so that the mark of 3 was obtained.
The relationship between the inter-lattice point distance and the interference coefficient value is calculated from the reproduced signal level as shown in the right figure. Mark diameter is 0.34
It can be seen that the interference coefficient value is substantially constant even when it is changed from μm to 0.64 μm. Further, assuming that the track pitch and the mark pitch are both 0.6 μm, it can be seen from the value of the lattice point spacing of 0.6 μm that b = d = e = g = 0.2. At this time, the distance between adjacent grid points in the diagonal direction is 0.85 μm, and it can be seen from the value of the grid point distance of 0.85 μm that a = c = f = h = 0.04. Thus, among the interference coefficients, a = bd, c = be, f = gd,
It can be seen that h = ge approximately holds. These relationships are
It is almost true even when disturbance occurs in the recording / reproducing system.

Based on this, the effect of using the information recording / reproducing system according to the present invention will be described below. FIG. 5A shows a result of simulating a reproduction signal obtained when the four-valued recording / reproduction shown in FIG. 1A is performed. The light source wavelength was 780 nm, the aperture lens numerical aperture was 0.55, and the recording medium was a magneto-optical medium. The mark pitch was 0.75 μm, the track pitch was 0.75 μm, the mark diameter W1 was 0.34 μm, W2 was 0.50 μm, and W3 was 0.64 μm. The simulation results are displayed as an eye pattern centered on the grid point. FIG. 5B shows the result when the two-dimensional equalization processing by the equations 3 and 4 is performed based on the reproduction signal shown in FIG. The equalization coefficient used for equalization was obtained by simulation based on the method described in the above means. By performing the two-dimensional equalization using the learned equalization coefficient, it can be seen that the two-dimensional information leakage can be significantly reduced and the eye opening at the grid point position is sufficiently large. At the time of reproducing the calculated information, three slice levels are provided, four values are judged at the positions between the lattice points, and the data of 2 bits is reproduced. Converting the S / N after equalization from the S / N of the current medium based on this result, the S / N for one eye opening is 22d.
It was found that B was obtained and a sufficient S / N was obtained. As described above, by using the information recording / reproducing system according to the present invention, recording / reproducing can be performed under the above conditions, and at this time, recording density 8 times that of the first-generation magneto-optical disk can be realized.

[0032]

EXAMPLE An information recording / reproducing apparatus and an optical information recording medium according to the present invention will be described below.

In the information recording / reproducing system according to the present invention, the size of the mark is recorded on the predetermined grid points of the optical information recording medium by changing the size of the mark into two or more types corresponding to multi-valued data. At the time of reproduction, the optimum equalization coefficient is learned with the optical recording medium mounted on the optical disk device, and the two-dimensional etc. for reducing leakage of two-dimensional information based on the equalization coefficient obtained as a result of this learning. After performing the conversion process, a multilevel signal is detected.

The first embodiment of the present invention will be described below.

FIG. 7 is a schematic diagram of an information recording / reproducing apparatus according to the present invention when a magneto-optical disk is used as an optical recording medium. In this apparatus, an optical recording medium 100 provided with a wobble mark and a clock mark for performing sample servo was used. The multi-spots 101 to 103 are used for recording information on the optical recording medium 100 and reproducing the recorded information. The optical head 104 is used for narrowing down the multi-spot onto the optical recording medium 100 and controlling the positioning of the light spot. Further, a synchronization signal generator 111 that generates a signal synchronized with the rotation of the optical recording medium 100, a servo mark on the optical recording medium is detected based on the synchronization signal generated by the synchronization signal generator 111, and an optical spot positioning circuit 116, A data control circuit 119 which outputs multi-valued user data to be recorded at the time of information recording and outputs recorded data by multi-valued detection and demodulation of a reproduction signal at the time of information reproduction, and a modulation signal output from the data control circuit A laser driving circuit 123 that modulates the intensity of the light spot based on the above, and records the modulated data on the optical recording medium 100, and the light spots 101 to 103.
A reproduction data synchronization circuit 125 for performing analog-digital conversion (hereinafter referred to as A / D conversion) on the reproduction signals of three adjacent tracks reproduced by the above, correcting the timing deviation between the spots, and outputting. A two-dimensional equalization circuit 129 for reducing the leakage of two-dimensional information based on the output signal of the circuit, and an optimum equalization coefficient used in the two-dimensional equalization circuit with the optical recording medium mounted in the information recording / reproducing apparatus. The equalization coefficient learning circuit 121 for obtaining

FIG. 2 shows an example of the information recording medium used in this embodiment. FIG. 2 shows an example of recording information by performing spot positioning at a 1/2 pitch as in the related art. The conventional positioning of the spot at a 1/2 pitch can be realized by switching the polarity of the conventional servo signal, for example.
By using the means described in a known example (Japanese Patent Publication No. 58-021336), spot 101 and spot 10
Positioning of 3 and automatic focusing of the spots 101 to 103 can be realized. This information recording medium has the conventional concept of a sector like the medium according to the conventional sample servo system, but the learning track recognition area and the equalization coefficient learning area for obtaining the optimum equalization coefficient at the time of equalization are set to the sector. The feature is that it is provided at the beginning of.

At the time of information recording, first, the position where the equalization coefficient learning mark is recorded is detected based on the prepit reproduction signal prepared in advance in the learning track recognition area, and the equalization coefficient learning area is determined based on the detected value. A learning mark is recorded at the determined grid point position, and then user data is recorded in the data storage area.

At the time of information reproduction, the position where the equalization coefficient learning mark is recorded is detected based on the prepit reproduction signal prepared in advance in the learning track recognition area, and the learning mark is reproduced as a spot based on the detected value. Then, the equalization coefficient is calculated, and the calculated equalization coefficient is used to perform a two-dimensional equalization process for reducing leakage of two-dimensional information.

In the above, the writable magneto-optical medium has been described as an example. The invention of the present application is also applicable to a so-called ROM disk in which information is formed by uneven pits,
In this case, the learning track recognition area can be omitted, and the wobble marks 151 and 152, the clock mark 153, the learning marks 154, 155 and 156, and the data can be formed by the uneven pits.

Next, the information recording apparatus and medium according to the present invention will be described. Hereinafter, the synchronization signal generator 1 shown in FIG.
11 will be described. The sync signal generator 111 is a component of the recording / reproducing apparatus shown in FIG. 7, and generates a signal synchronized with the reproduction signal of the clock mark 153 obtained from each spot. The synchronization signal generator 111 has three PLLs.
It consists of circuits 200-202. The total light amount signal 105 obtained from the light spot 101, the total light amount signal 106 obtained from the light spot 102, and the total light amount signal 107 obtained from the light spot 103 are first of all three PLL circuits 200 in the synchronization signal generator 111. It is input to 201 and 202. Each of the PLL circuits 200 to 202 detects the signal of the clock mark included in the total light amount signal, and the optical recording medium 1
Clock signals 112 to 114 synchronized with the rotation of 00, and sample and hold signals 139 to 14 for clock marks.
1 is generated. The period of the clock signals 112 to 114 is
For example, it may correspond to the lattice point spacing T in the optical spot scanning direction on the optical recording medium shown in FIG. These clock signals 112 to 114 are output signals of the synchronization signal generator 111. However, the PLL circuit 201 also outputs the wobble mark sample hold signals 142 and 143 used in the above-described light spot positioning circuit 116. These sample and hold signals 142 and 143 are also output signals of the synchronization signal generator 111.

The information recording circuit shown in FIG. 9 will be described below. The information recording circuit is composed of the equalization coefficient learning circuit 121, the data modulation circuit, and the laser drive circuit in the recording / reproducing apparatus shown in FIG. At the time of recording information, the spot 102 has the learning track identification marks 154 to 156 recorded in the learning address area as shown in FIG.
To play. The total light amount signal 106 including the reproduction signal of the identification mark group is input to the equalization coefficient learning circuit 121.
The equalization coefficient learning circuit 121 includes a learning track identification circuit 21.
0 and a learning mark recording signal generation circuit 212. The total light amount signal 106 is first level sliced and binarized by the learning track identification circuit 210. The learning track identification circuit 210 determines the position where the learning mark is to be recorded, based on this binarized signal. Specifically, as shown in FIG. 2, there are three types of recording positions of the identification marks 154 to 156 in the spot scanning direction, m + T, m + 3T, and m + 5T. The learning mark recording circuit uses the clock signal 113 and the clock mark. 2 based on the sample and hold signal 140
It is determined which of these recording positions the pulse position obtained as a result of the digitization corresponds to. When recognizing that the pulse position is m + T, the track identification result signal 211 which is a 2-bit digital signal is output as 00, and when recognizing it as m + 3T, the track identification result signal 211 is output as 01 and is recognized as m + 5T. Then, the track identification result signal 211 is output as 10. This signal is held until the next track identification is performed. However, the learning track identification circuit 210 has a built-in counter, which counts according to the clock signal 113 and is reset when the pulse of the clock mark sample hold signal 140 is input. The learning track identification circuit 210 starts its operation when the value of this counter is the counter value m corresponding to the start position of the learning track recognition area, and ends the operation when it is the counter value n-1 corresponding to the end position.

The learning mark recording signal generation circuit 212 outputs a learning mark recording signal 122 for recording a learning mark based on the track identification result signal 211, the clock signal 113 and the clock mark sample hold signal 140. When the value of the track identification result signal 211 is 00, a pulse is output at the p + T grid point position, and when the value of the track identification result signal 211 is 01, a pulse is output at the p + 4T position and the track identification result signal is If the value of 211 is 10, a pulse is output at the position of p + 7T. The learning mark recording signal 122 is input to the laser driving circuit 123, the laser driving circuit 123 outputs a recording pulse 124 according to the learning mark recording signal 122, and the intensity of the light spot 102 is modulated according to the recording pulse 124. A learning mark 157, a learning mark 158, or a learning mark 159 is recorded in the equalization coefficient learning area on the optical recording medium. However, the learning mark recording signal generation circuit 212 has a built-in counter, counts according to the clock signal 113, and is reset when the pulse of the clock mark sample hold signal 140 is input. The learning mark recording signal generating circuit 212 starts its operation when the value of this counter is the counter value p corresponding to the start position of the equalization coefficient learning area, and ends the operation when it is the counter value q-1 corresponding to the end position.

By using the circuit as described above, it is possible to record a mark for learning the equalization coefficient at a predetermined position in the equalization coefficient learning area as shown in FIG. It is desirable to record the learning marks with two-dimensional intervals so that they do not interfere with each other during learning. Assuming that the learning mark diameter is W, the light source wavelength is λ, and the aperture lens numerical aperture is NA, for example, the learning marks may be arranged with a center-to-center distance of (W + λ / NA) or more.

The data to be recorded is recorded after the above-mentioned learning mark recording is completed. As shown in FIG. 9, the user data 118 to be recorded is the data control circuit 11
9 and the user data 118 is input to the data control circuit 1
The modulation circuit 213 in 19 multi-values. However, the data control circuit 119 incorporates a counter, which counts according to the clock signal 113 and is reset when the pulse of the clock mark sample hold signal 140 is input. The data control circuit 119 starts operation when the value of this counter becomes q or more. The multi-valued modulation data 120 is input to the laser driving circuit 123, the laser driving circuit 123 modulates the intensity of the spot 102 based on the modulation data 120, and the recording mark 160 is recorded in the data storage area on the optical recording medium. . The recording marks 160 are grid points q, q + T, q + in the data storage area.
2T. ． ． ． Recorded above. As a result, it is possible to record on the predetermined grid points of the optical information recording medium while changing the size of the mark into two or more types corresponding to multi-valued data. FIGS. 1A and 2 show an example in which 2-bit data "00", "01", "10", and "11" are recorded by changing the mark size to four types. "00" is recorded by not recording the mark at the grid point, and "0" is recorded by recording the mark with the diameter W1 at the grid point.
"1" is recorded, a mark having a diameter of W2 is recorded at a grid point to record "10", and a mark having a diameter of W3 is recorded at a grid point to record "11". ~ W3
Is, for example, when no mark is recorded on the grid point, the reproduction signal amplitude on the grid point is 0, and when a mark having a diameter W1 is recorded on the grid point, the reproduction signal amplitude is 0 on the grid point. The reproduction signal amplitude is 1, and when the mark having the diameter W2 is recorded at the lattice point, the reproduction signal amplitude on the lattice point is 2, and the mark having the diameter W3 is recorded at the lattice point. In this case, the reproduction signal amplitude on the grid point may be set to 3.

In the above description, the magneto-optical recording method in which rewriting is possible is mainly described as an example. In the above, since both the learning mark and the data are formed as a magneto-optical domain, the recording conditions are the same and the equalization coefficient can be easily compensated. However, by adjusting the conditions, it is possible to record the learning mark in advance with another structure such as an uneven pit. In this case, the learning track identification mark is unnecessary, and the structure for recording the learning mark can be omitted from the device structure.

In the following, a method and apparatus for reproducing the data recorded in the data storage area by reproducing the equalization coefficient learning mark in the learning area during information reproduction to learn the equalization coefficient will be described.

First, the timing shift correction circuit shown in FIG. 10 will be described. The timing shift correction circuit is shown in Fig. 7.
It is a constituent element of the information recording / reproducing apparatus of the present invention shown in FIG. 2 and is used for correcting the timing deviation between spots at the time of reproducing information. The timing deviation correction circuit 125 includes A / D converters 220 to 222 and an offset amount difference circuit 2.
26-228 and first-in / first-out memory circuits (FIFO circuits) 231-232.
The A / D converter and the offset amount difference circuit are connected to the spot 10
1 to 1 to 103 for magneto-optical signals obtained from 1 to 103
They are provided one by one. One FIFO circuit is provided for each of the magneto-optical signals 109 and 110 obtained from the spots 102 and 103. In addition, each A / D converter, offset amount difference circuit, and FIFO circuit has a built-in counter. The counter counts according to the respective clock signals input, and is reset when the pulse of the clock mark sample hold signal is input. The A / D converter and the offset amount difference circuit start operation when the value of this counter reaches the counter value n corresponding to the position of the offset detection area, and the counter value r corresponding to the end position of the data storage area.
Works up to. In particular, two counters are prepared in the FIFO circuits 231 and 232, and the FIFO circuit 231 starts its operation when the counter value counted according to the clock 113 reaches n, and operates until the counter value counted according to the clock 112 reaches r. Similarly, the FIFO
The circuit 232 starts its operation when the counter value counted according to the clock 114 reaches n, and operates until the counter value counted according to the clock 112 reaches r.

The magneto-optical signal 108 input from the spot 101 is first input to the A / D converter 220, and the magneto-optical signal at the lattice point position is digitized. The digitized magneto-optical signal is input to the offset amount difference circuit 226 as a digital reproduction signal 223. The offset amount difference circuit 226 detects an offset component included in the signal component, and outputs a difference value between the offset amount and the input digital reproduction signal. As the offset amount, a value obtained by reproducing the offset learning area shown in FIG. 2 with a spot is used. Specifically, first, the digital reproduction signal 223 obtained by the counter value n is held as an offset amount, and thereafter, the difference value between the offset amount and the digital reproduction signal 223 is output. This difference value becomes the output signal of the timing shift correction circuit 125 as the synchronous reproduction signal 126.
Further, in the present embodiment, the case where the offset amount detection area is composed of one grid point is shown as shown in FIG. 2, but two or more grid points may be arranged in the offset amount detection area. When the offset amount is detected, the offset amount detection accuracy can be improved by setting the average value of two or more grid point signals as the offset amount.

The magneto-optical signal 109 input from the spot 102 is first input to the A / D converter 221, and the magneto-optical signal at the lattice point position is digitized. The digitized magneto-optical signal is input to the offset amount difference circuit 227 as a digital reproduction signal 224. The offset amount difference circuit 227 detects an offset component included in the signal component, and outputs a difference value 229 between the offset amount and the digital reproduction signal 224 input. The difference value 229 output from the offset amount difference circuit 227 is the FIFO
The signal is input to the circuit 231 and is F based on the clock signal 113.
It is stored in the IFO circuit.

The magneto-optical signal 110 input from the spot 103 is also processed in the same manner as the magneto-optical signal 109 described above. First, it is input to the A / D converter 222,
The magneto-optical signal at the lattice point position is digitized. The digitized magneto-optical signal is input to the offset amount difference circuit 228 as a digital reproduction signal 225. The offset amount difference circuit 228 detects an offset component included in the signal component and outputs a difference value 230 between the offset amount and the digital reproduction signal 225 input. The difference value 230 output from the offset amount difference circuit 228 is F
It is input to the IFO circuit 232 and stored in the FIFO circuit based on the clock signal 114.

Difference value 2 stored in the FIFO circuit 231
29 and the difference value 23 stored in the FIFO circuit 232.
0 is read based on the clock signal 112, and these difference values are output signals of the timing shift correction circuit 125 as the synchronous reproduction signals 127 and 128. At this time, the synchronous reproduction signals 127 and 128 are read from the FIFO circuit so as to correct the timing deviation of the magneto-optical signals 108 to 110 due to the spot interval with respect to the adjacent track direction, and as a result, the synchronous reproduction signals 126 to 128 are read. 128 is a signal synchronized with each other in the direction of adjacent tracks. By the way, FIG. 5A shows a result of simulating a reproduction signal obtained when the four-valued recording and reproduction as shown in FIG. 1A is performed. The light source wavelength was 780 nm, the aperture lens numerical aperture was 0.55, and the recording medium was a magneto-optical medium. The mark pitch was 0.75 μm, the track pitch was 0.75 μm, the mark diameter W1 was 0.34 μm, W2 was 0.50 μm, and W3 was 0.64 μm. The simulation results are displayed as an eye pattern centered on the grid point. The magneto-optical signals 108 to 110 are, for example, as shown in FIG.
This corresponds to the eye pattern signal shown in (a), and the lattice point synchronization signals 126 to 128 correspond to the signals at the lattice point positions of the eye pattern shown in FIG. 5 (a). Originally, when the reproduction signal amplitude at the grid point position is 0, it is set to "00", when the reproduction signal amplitude on the grid point is 1, it is set to "01", and when the reproduction signal amplitude on the grid point is 2. The original data can be reproduced by setting "10" and setting it to "11" when the reproduction signal amplitude on the lattice point is 3. However, in the information recording method according to the present invention, since the lattice point spacing (mark pitch) in the light spot scanning direction and the lattice point spacing (track pitch) in the adjacent track direction are smaller than the light spot diameter, one light spot is used. When a mark is illuminated, some of the other marks around it are also illuminated at the same time. Therefore, the signals of the surrounding information marks leak into the signals of the information marks to be reproduced two-dimensionally and the accuracy of reproduction is lowered. Therefore, the following processing is performed during reproduction to reduce crosstalk from adjacent tracks and intersymbol interference from the spot scanning direction, which is a two-dimensional information leak. Hereinafter, a signal processing method for reducing crosstalk and intersymbol interference will be described.

First, the equalization coefficient learning circuit 121 used during reproduction shown in FIG. 11 will be described. In an actual optical disc device, the recording mark shape and position change due to changes in spot shape, recording power, recording clock timing, focus, and tracking during recording, and changes in optical spot shape, tracking, focus, and sampling clock timing during reproduction. As a result, the amount of crosstalk and the amount of intersymbol interference fluctuate. Even if these fluctuation factors occur, it is necessary to adaptively change the equalization coefficient used for two-dimensional equalization in order to effectively reduce crosstalk and intersymbol interference. For this purpose, the value of the interference coefficient shown in FIG. 3 is measured with the optical recording medium mounted in an actual optical disk device. The optimum equalization coefficient can be calculated by obtaining the equalization coefficient from the interference coefficient value obtained as a result of the measurement.

The equalization coefficient learning circuit 121 is a constituent element of the recording / reproducing apparatus shown in FIG. 1, and is used for obtaining an optimum equalization coefficient for reducing the leakage of two-dimensional information. The equalization coefficient learning circuit 121 is composed of a learning track identification circuit used also at the time of recording information, an information leakage amount detection circuit, and an equalization coefficient calculation circuit. The method of obtaining the equalization coefficient is described in detail in the means for solving the problem. A circuit that realizes the means will be described below.

First, the crosstalk amounts b and g, which are the leak amounts of information from the adjacent tracks shown in FIG. 3, are obtained, and the equalization coefficient for reducing the crosstalk is calculated based on the crosstalk amounts. The means will be described. In order to calculate the crosstalk amount, it is necessary to know at which grid point in the equalization coefficient learning area the equalization coefficient learning marks 157 to 159 shown in FIG. 2 are recorded. In this case, the recording position of the equalization coefficient learning mark can be detected by reproducing the learning track identification marks 154 to 156 recorded in the learning track recognition area using the light spots 101 to 103. Spot 101 as shown in FIG.
The total light amount signal 105 obtained from the above is subjected to level slicing and binarized by the learning track identification circuit 250.
The learning track identification circuit 250 detects the position where the learning mark is recorded based on the binarized signal.

Specifically, as shown in FIG. 2, the recording positions of the identification marks 154 to 156 in the spot scanning direction are:
There are three types, m + T, m + 3T, and m + 5T, and the learning mark recording circuit 250 determines which of these recording positions the pulse position obtained as a result of binarization based on the clock signal 112 and the clock mark sample hold signal 139. Ask if it corresponds. When recognizing that the pulse position is m + T, the track identification result signal 253 which is a 2-bit digital signal is output as 00, and when recognizing it as m + 3T, the track identification result signal 253 is output as 01,
When it is recognized as m + 5T, the track identification result signal 25
3 is output as 10. This signal is held until the next track identification is performed. However, the learning track identification circuit 250 has a built-in counter, counts according to the clock signal 112, and is reset when the pulse of the clock mark sample hold signal 139 is input. The learning track identification circuit 250 starts the operation when the value of this counter is the counter value m corresponding to the head position of the learning track recognition area, and ends the operation when the counter value n-1 corresponds to the tail position. Similarly, the total light amount signal 107 obtained from the spot 103 is level-sliced and binarized by the learning track identification circuit 251. The learning track identification circuit 251 detects the position where the learning mark is recorded based on the binarized signal by the same means. The detected result is output as a track identification result signal 254 and held until the next track identification is performed. However, the learning track identification circuit 251 includes a counter, which counts according to the clock signal 114, and the clock mark sample hold signal 141.
When the pulse of is input, it is reset. The learning track identifying circuit 251 starts the operation when the value of this counter is the counter value m corresponding to the head position of the learning track recognition area, and ends the operation when the counter value n-1 corresponds to the tail position.

The crosstalk amount detection circuit 256 uses the synchronous reproduction signal 12 obtained from the timing deviation correction circuit 125.
6, a synchronized reproduction signal 127, and a learning track identification circuit 2
The crosstalk amount b shown in FIG. 3 is detected based on the track identification result signal 253 which is the output signal of 50. However,
The crosstalk amount detection circuit 256 incorporates a counter, which counts according to the clock signal 112 and is reset when the pulse of the clock mark sample hold signal 139 is input. The crosstalk amount detection circuit 256 starts its operation when the value of this counter is the counter value p corresponding to the head position of the equalization coefficient learning area, and ends the operation when the counter value q-1 corresponds to the tail position.

The following description will be given based on the example shown in FIG. 2 in order to give a concrete description. That is, the light spot 101 traces on the track i-1, and the light spot 102
Will be tracked on the track i, and the light spot 103 will be tracked on the track i + 1. in this case,
As a result of the learning track recognition, the track identification result signal 253 becomes 00. At this time, the crosstalk amount detection circuit 256 knows that the learning mark for detecting the crosstalk amount b is recorded at the lattice point p + T position. Therefore, the lattice point (i-1, p +) is determined based on the synchronous reproduction signal 126.
The grid point signal S ′ (i−1, p + T) at the T) position is sampled and held, and the grid point signal S ′ (i, p) obtained at the grid point (i, p + T) based on the synchronous reproduction signal 127 is sampled.
+ T) is sample-held. When S ′ (i−1, p + T) is larger than the half value of the isolated signal amplitude, the crosstalk amount detection circuit 256 outputs S ′ (i, p + T) and S ′.
Ratio of (i-1, p + T), S '(i, p + T) / S'
Output (i-1, p + T). On the other hand, S '(i-1,
p + T) is smaller than the half value of the isolated signal amplitude,
Outputs 0. The crosstalk amount output signal 260 represents the crosstalk amount b from the adjacent track.

Similarly, the crosstalk amount g in FIG. 3 can be obtained. Crosstalk amount detection circuit 25
7 detects the crosstalk amount g shown in FIG. 3 based on the synchronous reproduction signal 127 and the synchronous reproduction signal 128 obtained from the timing shift correction circuit 125 and the track identification result signal 254 which is the output signal of the learning track identification circuit 251. To do. However, the crosstalk amount detection circuit 257 has a built-in counter, which counts according to the clock signal 112 and outputs the clock mark sample hold signal 13
It is reset when 9 pulses are input. The crosstalk amount detection circuit 257 starts its operation when the value of this counter is the counter value p corresponding to the start position of the equalization coefficient learning area, and ends the operation when it is the counter value q-1 corresponding to the end position. In order to make a concrete description, description will be made based on the example shown in FIG. That is, the case where the light spot 101 tracks the track i−1, the light spot 102 tracks the track i, and the light spot 103 tracks the track i + 1 will be described as an example. In this case, the track identification result signal 254 becomes 10 as a result of the learning track recognition. At this time, the crosstalk amount detection circuit 257 detects that the learning mark for detecting the crosstalk amount g is the lattice point p +.
Since it is known that the data is recorded at the 7T position, the grid point signal S ′ (i + 1, p + 7T) at the grid point (i + 1, p + 7T) is sampled and held based on the synchronous reproduction signal 128, and the grid is reproduced based on the synchronous reproduction signal 127. Point (i,
The lattice point signal S '(i, p + 7T) obtained by p + 7T)
Sample hold. Crosstalk amount detection circuit 25
6 is S '(i, p + 7T) and S'when S' (i + 1, p + 7T) is larger than the half value of the isolated signal amplitude.
Ratio of (i + 1, p + 7T), S '(i, p + 7T) /
S '(i + 1, p + 7T) is output. On the other hand, S '(i
0 is output when (+1, p + 7T) is smaller than the half value of the isolated signal amplitude. The crosstalk amount output signal 26
1 represents the crosstalk amount g from the adjacent track. As described above, when the crosstalk amount from the adjacent tracks is obtained, it is determined whether the lattice point signals obtained from the spots at both ends are larger or smaller than half the value of the isolated signal at the recording position of the learning mark. This is to determine whether or not a mark has already been recorded on the track adjacent to the target track. When the mark is recorded on the adjacent track, crosstalk from the adjacent track becomes a problem during reproduction. However, if the mark is not yet recorded on the adjacent track, crosstalk during reproduction does not occur. That is, the amount of crosstalk is zero. When the mark is not recorded on the adjacent track, the learning mark is not recorded in the equalization coefficient learning area. In this case, if the crosstalk amount is obtained without judging whether or not a mark has already been recorded on the track adjacent to the target track, the grid point signals at the learning recording mark positions obtained from the spots on both ends are obtained. As the learning value of the crosstalk amount becomes close to 0, the optimum equalization coefficient cannot be calculated.

Next, the intersymbol interference amounts d and e, which are the information leakage amounts from the target track shown in FIG. 3, are obtained, and the intersymbol interference amount is reduced based on the intersymbol interference amount. The means for calculating the equalization coefficient will be described. In order to calculate the intersymbol interference amount, the learning marks 157 to 15 shown in FIG. 2 are used as in the case of detecting the crosstalk amount described above.
It is necessary to know at which grid point 9 is recorded in the equalization coefficient learning area. This is the learning track identification marks 154 to 156 recorded in the learning track recognition area.
Is reproduced using the light spot 102, the recording position of the learning mark can be detected. The total light amount signal 106 obtained from the spot 102 is level-sliced and binarized by the learning track identification circuit 252. The learning track identifying circuit 252 detects the position where the learning mark is recorded by the above-mentioned means based on the binarized signal. The detected result is output as a track identification result signal 255 and held until the next track identification is performed. However, the learning track identification circuit 252 has a built-in counter,
The counter counts according to the clock signal 113,
It is reset when the pulse of the clock mark sample hold signal 140 is input. The learning track identification circuit 252 starts its operation at the counter value m corresponding to the head position of the learning track recognition area, and ends the operation at the counter value n-1 corresponding to the tail position.

Intersymbol interference amount detection circuits 258 and 259
Detects the intersymbol interference amounts d and e shown in FIG. 3 based on the synchronous reproduction signal 127 obtained from the timing deviation correction circuit 125 and the track identification result signal 255 which is the output signal of the learning track identification circuit 250. However, the intersymbol interference amount detection circuits 258 and 259 have a built-in counter,
The counter counts according to the clock signal 112,
It is reset when the pulse of the clock mark sample hold signal 139 is input. The intersymbol interference amount detection circuits 258 and 259 start the operation at the counter value p corresponding to the start position of the equalization coefficient learning area, and end the operation at the counter value q-1 corresponding to the end position. In the following, in order to give a specific description, description will be given based on the example shown in FIG. That is, the case where the light spot 101 tracks the track i−1, the light spot 102 tracks the track i, and the light spot 103 tracks the track i + 1 will be described as an example. In this case, the track identification result signal 255 is 01 as a result of the learning track recognition. At this time, the intersymbol interference amount detection circuit 258 knows that the learning mark for detecting the intersymbol interference amount d is recorded at the lattice point p + 4T position. Therefore, based on the synchronous reproduction signal 127, the lattice point (i, p + 4T). ) Position grid point signal S '(i,
p + 4T) is sampled and held, and a grid point signal S ′ (i, p +) obtained at a grid point (i, p + 5T) is obtained.
5T) is sample-held. The intersymbol interference amount detection circuit 258 uses S ′ (i, p + 4T) and S ′ (i, p + 5).
Ratio of T), S '(i, p + 5T) / S' (i, p + 4
T) is output. The intersymbol interference amount output signal 262 represents the intersymbol interference amount d on the target track.

Similarly, the intersymbol interference amount e in FIG.
Can be requested. Intersymbol interference amount detection circuit 259
Since the track identification result signal 255 is 01, it knows that the learning mark for detecting the intersymbol interference amount e is recorded at the lattice point p + 4T position. At this time, the grid point (i, p + 3T) is based on the synchronous reproduction signal 127.
The grid point signal S '(i, p + 3T) at the position is sampled and held, and the grid point signal S' (i, p + 4T) obtained at the grid point (i, p + 4T) is sampled and held. The intersymbol interference amount detection circuit 259 uses the S ′ (i, p + 3
Ratio of T) to S '(i, p + 4T), S' (i, p + 3
T) / S '(i, p + 4T) is output. The intersymbol interference amount output signal 263 represents the intersymbol interference amount e on the target track.

The circuit for calculating the equalization coefficient used for equalization based on the crosstalk amounts b and g and the intersymbol interference amounts d and e obtained by the above means will be described below.
The equalization coefficient calculation circuit 264 calculates and outputs an equalization coefficient for reducing crosstalk based on the crosstalk amount output signal 260. Specifically, when the value of the crosstalk output signal 260 is b, −b is output as the equalization coefficient 130. Similarly, the equalization coefficient calculation circuit 266 calculates and outputs an equalization coefficient for reducing crosstalk based on the crosstalk amount output signal 261. In particular,
When the value of the crosstalk amount output signal 261 is g, -g is output as the equalization coefficient 132. Further, the equalization coefficient calculation circuit 265 outputs the equalization coefficient 131 for reducing crosstalk, but it always outputs 1 when the equalization is performed using three spots.

The equalization coefficient calculation circuits 267 and 268 calculate and output equalization coefficients for reducing intersymbol interference based on the intersymbol interference amount output signal 262. Specifically, when the value of the intersymbol interference amount output signal 262 is d, the equalization coefficient calculation circuit 267 outputs d × d as the equalization coefficient 133, and the equalization coefficient calculation circuit 268 outputs −d. Equalization coefficient 13
Output as 4. Similarly, the equalization coefficient calculation circuits 270 and 271 use equalization coefficients for reducing intersymbol interference,
It is calculated and output based on the intersymbol interference amount output signal 263. Specifically, the value of the intersymbol interference amount output signal 263 is e
, The equalization coefficient calculation circuit 270 outputs −e as the equalization coefficient 136, and the equalization coefficient calculation circuit 271 outputs e ×.
e is output as the equalization coefficient 137. Further, the equalization coefficient calculation circuit 269 calculates and outputs an equalization coefficient for reducing intersymbol interference based on the intersymbol interference amount output signal 262 and the intersymbol interference amount output signal 263. Specifically, when the value of the intersymbol interference amount output signal 262 is d and the value of the intersymbol interference amount output signal 263 is e, (1-de) is output as the equalization coefficient 135. These equalization coefficients 130 to 1
37 becomes the output signal of the equalization coefficient learning circuit 121, and the value of the equalization coefficient is held until the next learning is performed.

A circuit for realizing the two-dimensional equalization processing for reducing the two-dimensional information leakage will be described below. In the two-dimensional equalization processing according to the present invention, the crosstalk from the adjacent track is reduced by performing the calculation of the equation 3 described in the means for solving the problem, and the calculation of the equation 4 is performed to further reduce the crosstalk on the target track. To reduce intersymbol interference. FIG. 12 shows a two-dimensional equalization circuit 129 for realizing the calculations of Expressions 3 and 4. The two-dimensional equalization circuit 129 uses the equalization coefficient 1 output from the equalization coefficient learning circuit 121.
The leakage of the two-dimensional information included in the synchronous reproduction signal 127 is reduced based on 30 to 137 and the synchronous reproduction signals 126 to 128 which are signals at the lattice point positions of the magneto-optical signal. The synchronized reproduction signal after equalization is output as an equalized signal 138. The two-dimensional equalization circuit 129 includes a crosstalk reduction circuit 340 and an intersymbol interference reduction circuit 341. The crosstalk reduction circuit 340 includes delay circuits 290 to 292, gain adjustment circuits 297 to 299, and an adder 305. The intersymbol interference reduction circuit 341 includes delay circuits 293 to 296, gain adjustment circuits 300 to 304, and an adder 306 to. 309.

In the following, the crosstalk reduction circuit 340 that implements equation 3 will be described. Delay circuits 290-29
6 is controlled by the clock signal 112 and delays the input signal by the time T and outputs the delayed signal. Timing deviation correction circuit 125
The synchronous reproduction signals 126 to 128 input from the first are input to the delay circuits 290 to 292. Gain adjustment circuit 29
7 to 299 output signals 313 to 315 obtained by multiplying the input signals 310 to 312 by the equalization coefficients 130 to 132 used to reduce the crosstalk input from the equalization coefficient output circuit 121. Signals 313-3
15 is input to the adder 305, and after addition, the signal 3
It is output as 16. The signal 316 corresponds to the sync reproduction signal 127 in which the crosstalk from the adjacent track is reduced.

The intersymbol interference reduction circuit 341 for carrying out the equation 4 will be described below. Intersymbol interference reduction circuit 34
1 reduces intersymbol interference based on the signal 316 and the equalization coefficients 133 to 137. The signal 317 becomes a signal delayed by time T from the signal 316 by passing through the delay circuit 293, and the signal 318 becomes a signal delayed by time 2T from the signal 316 by passing through the delay circuits 293 to 294. Becomes a signal delayed by 3T with respect to the signal 316 by passing through the delay circuits 293 to 295, and the signal 320 becomes a signal delayed by 4T with respect to the signal 316 by passing through the delay circuits 293 to 296. The gain adjusting circuits 300 to 304 output signals 316 to 320.
And a signal 32 obtained by multiplying the equalization coefficients 133 to 137, respectively.
1 to 325 are output. The signals 321 to 325 are adders 3
06-309 to produce the equalized signal 138. The equalized signal 138 corresponds to the synchronous reproduction signal 127 in which the crosstalk from the adjacent track and the intersymbol interference on the target track are reduced, and becomes the output signal of the two-dimensional equalization circuit 129. This equalized signal 138 is, for example, as shown in FIG.
This corresponds to the signal at the grid point position of the eye pattern shown in (b). FIG. 5B shows the result when the two-dimensional equalization processing by the equations 3 and 4 is performed based on the reproduction signal shown in FIG. The equalization coefficient used for equalization was obtained by simulation based on the method described in the above means. By performing the two-dimensional equalization using the learned equalization coefficient, it can be seen that the two-dimensional information leakage can be significantly reduced and that each eye opening at the grid point position opens sufficiently large. When the S / N after equalization is converted from the S / N of the current medium, the S / N for one eye opening is 22 dB, which is a sufficient S / N. Further, the two-dimensional equalization circuit 129 is a simple type equalization circuit that has been conventionally used, but two-dimensional information leakage is performed using the optimum equalization coefficient obtained as a result of the above learning. It is characterized in that it is reduced. Since the calculation of the equalization coefficient can be performed in a shorter time than the case where the equalization coefficient is obtained by using the conventional least square error method, it is possible to cope with random access at high speed.

The data control circuit 119 used during reproduction shown in FIG. 13 will be described below. Data control circuit 1
Reference numeral 19 denotes user data 118 by converting the equalized signal 138 input from the two-dimensional equalization circuit 129 into four values and demodulating the same.
Play and output. The data control circuit 119 includes a comparator 350 and a demodulation circuit 352. Post-equalization signal 13
8 is input to the comparator 350 and is quaternarized. The comparison result signal 351 is input to the demodulation circuit 352 and demodulated. The demodulation circuit 352 outputs a demodulation signal, and this signal becomes the user data 118.

As described above, by using the information recording / reproducing system according to the present invention, recording / reproducing can be performed under the super high density recording condition, and at this time, recording density 8 times higher than that of the first generation magneto-optical disk can be realized. it can.

In the above embodiment, the learning track recognition area is provided in front of the equalization coefficient learning area for the purpose of recording / reproducing the equalization coefficient learning mark at a predetermined grid point in the equalization coefficient learning area. Alternatively, the recording / reproducing position of the equalization coefficient learning mark may be detected based on the track address provided at the beginning of the sector. For example, in FIG. 2, the track address is reproduced at the spot 102, and if the least significant 2 bits of the track address are 00, the learning mark is recorded at the lattice point position of p + T, and the least significant 2 of the track address is recorded.
If the bit is 01, the learning mark may be recorded at the p + 4T lattice point position, and if the least significant 2 bits of the track address are 10, the learning mark may be recorded at the p + 7T lattice point position. Thus, if the recording position of the learning mark is known, the actual recording of the learning mark may be performed by using the device described in the above embodiment. At the time of reproducing information, for example, in FIG. 2, the track address is reproduced by a spot, and if the least significant 2 bits of the track address are 00, it can be recognized that p + T is the recording position of the learning mark, and the least significant 2 of the track address
If the bit is 01, p + 4T can be recognized as the recording position of the learning mark, and if the least significant 2 bits of the track address are 10, p + 7T can be recognized as the recording position of the learning mark. If the recording position of the learning mark is known in this way, the apparatus described in the above embodiment may be used for actual learning of the equalization coefficient.

In the above embodiment, the case where the equalization coefficient is learned for each sector has been described. However, for example, tracks for equalization coefficient learning are provided at the outer peripheral portion, the middle peripheral portion, and the inner peripheral portion of the disk. The equalization coefficient may be learned for each of the outer peripheral portion, the middle peripheral portion, and the inner peripheral portion.

The second embodiment of the present invention will be described below.

In the first embodiment, the case of using the magneto-optical medium has been described, but in the second embodiment shown below, the case of using the ROM medium will be described. ROM
As a medium, a reproduction signal having a higher S / N than that of a magneto-optical medium can be obtained. The higher the S / N of the reproduction signal, the more the multi-valued level can be increased, so that higher density can be realized. FIG. 1B shows data “000” and “00” for 3 bits.
1 "," 010 "," 011 "," 100 "," 10 "
An example of recording 1 "," 110 ", and" 111 "by changing the size of the mark to eight kinds." 000 "is recorded by not recording the mark at the grid point, and the diameter is set at the grid point. By recording the mark X1, "001" is recorded,
By recording marks with a diameter of X2 at the grid points, "010"
, "011" is recorded by recording a mark with a diameter of X3 at a grid point, "100" is recorded by recording a mark with a diameter of X4 at a grid point, and a diameter of X5 is recorded at a grid point. "101" is recorded by recording the mark with the diameter of X6, "110" is recorded with the mark with the diameter of X6 at the lattice point, and "11" is recorded by recording the mark with the diameter of X7 at the lattice point.
In general, an optical disc has maximum and minimum mark diameters that can be recorded. Therefore, it is necessary to reduce the mark diameter increments when increasing the number of multivalues.
Corresponding to the maximum and minimum mark diameter that can be recorded,
Since the maximum value and the minimum value of the reproduction signal at the time of reproduction are determined, when increasing the number of multiple values, each detection level (for example, FIG.
The vertical eye opening amplitude shown in 1) becomes small. That is, more sophisticated mark diameter control during recording and higher S / N during reproduction are required.

For example, in a ROM medium in which signals are recorded by phase pits, it is possible to control the mark diameter at the time of recording at a higher level than that of the magneto-optical medium, and a higher S / N at the time of reproduction can be obtained. The above eight-value recording becomes possible.
However, even with a magneto-optical medium, if the mark diameter can be controlled at a higher level during recording and a higher S / N ratio at the time of reproduction can be obtained, the above-described 8-value recording can be similarly performed. Each mark diameter 0
X7 has a reproduction signal amplitude of 0 on the grid point when no pit is recorded on the grid point during cutting, and a pit with a diameter of X1 on the grid point. When the pit with a diameter of X2 is recorded at the grid point, the reproduction signal amplitude at the point is Y, and the reproduction signal amplitude at the grid point is (Z + Y), and the pit with a diameter of X3 is at the grid point. , The reproduction signal amplitude on the grid point is (2Z + Y), and the diameter is X at the grid point.
When 4 pits are recorded, the reproduction signal amplitude on the grid point is (3Z + Y), and when pits with a diameter of X5 are recorded on the grid point, the reproduction signal on the grid point is The amplitude is (4Z + Y), and when a pit with a diameter of X6 is recorded at the grid point, the reproduction signal amplitude on the grid point is (5Z + Y), and a pit with a diameter of X7 is recorded at the grid point. If so, the reproduction signal amplitude on the grid point may be determined to be (6Z + Y).

The information reproducing apparatus in the second embodiment will be described below. In the case of the ROM medium, the information is recorded in advance in the medium in a concavo-convex shape, so that the information recording circuit as described in the first embodiment is not necessary.

First, in the information recording medium, pits having a diameter of 0 to X7 may be formed in the data storage area shown in FIG. 2. The servo area, the learning track recognition area, the offset amount recognition area, and the equalization coefficient. The areas are similar. However, each pit is formed in advance in the learning track recognition area and the equalization coefficient learning area. Further, the information reproducing circuit may be partially modified from the circuit shown in the first embodiment. The first is RO
Since the signal of the information pit is given by the total light amount signal in the M medium, it is necessary to replace the magneto-optical signal shown in the first embodiment with the total light amount signal. The second is to use linearized signal processing in signal processing when reducing crosstalk and intersymbol interference. This linearized signal processing will be described below.

FIG. 6A shows a result of simulating a reproduction signal obtained when the 8-value recording / reproduction as shown in FIG. 1B is performed. It is assumed that the light source wavelength is 780 nm, the aperture lens numerical aperture is 0.55, and the recording medium is a ROM medium. The pit pitch is 0.69 μm, the track pitch is 0.69 μm, and the minimum pit diameter X1 is 0.25.
2 μm, maximum pit diameter X2 was 0.480 μm, pit diameter step was 0.038 μm, and pit depth was 0.156 μm. The simulation results are displayed as an eye pattern centered on the grid point. FIG. 6A shows a signal before the equalization process. Due to the crosstalk and intersymbol interference, the vertical eye opening on the grid point is collapsed and the data cannot be detected. Therefore, when the signal shown in FIG. 6A is subjected to equalization processing for reducing crosstalk and intersymbol interference as in the magneto-optical medium, the signal shown in FIG. 6B is obtained. In this case, the eye opening is improved where the degree of modulation is small, but the eye opening is not improved where the degree of modulation is large. This is because, when the pits are recorded adjacent to each other on the ROM medium, only a modulation degree smaller than the original modulation degree can be obtained as the modulation degree during reproduction increases.
This is shown in FIG. 6 (c). The horizontal axis represents the modulation degree that should originally be obtained (hereinafter referred to as the linear signal modulation degree), and the vertical axis represents the modulation degree that is actually obtained (hereinafter referred to as the non-linear signal modulation degree). For example, the linear signal modulation degree and the non-linear signal modulation degree are the same near a modulation degree of 20%, but when the linear signal modulation degree increases to 80%, the non-linear modulation degree decreases to 70%. The reason why the eye opening at a small modulation degree as shown in FIG. 6B is improved, but the eye opening at a large modulation degree is not improved can be explained by such a non-linear characteristic during reproduction.

In the present invention, the non-linear characteristic at the time of reproduction shown in FIG. 6C is utilized to correct the deterioration of the non-linear signal modulation degree at a large modulation degree, and the eye opening at a large modulation degree is opened. Improve. Specifically, since the nonlinear characteristic at the time of reproduction shown in FIG. 6C can be approximated by a higher-order function, the linear signal modulation degree is first calculated based on the nonlinear signal modulation degree using this function (linearization Signal processing). Signal processing for reducing crosstalk and intersymbol interference is performed on the basis of the calculated linear signal modulation degree. Figure 6
(D) shows a case where linearized signal processing is used before the equalization processing. Compared to FIG. 6B, the eye vertical aperture is improved in a place where the degree of modulation is large. When the S / N after equalization is converted from the S / N of the current medium, the S / N for one eye opening is 22 dB, which is a sufficient S / N. in this way,
In the second embodiment, if the above-mentioned linearized signal processing is used before the two-dimensional equalization processing, recording / reproduction can be performed under ultra-high density recording conditions. At this time, the recording density is 6 times that of the first-generation CD-ROM. Can be realized.

In the above embodiment, the case where the magneto-optical disk or the ROM medium is used has been described, but the recording / reproducing system according to the present invention may be a recording medium, for example, a write-once medium or a phase change medium. In these media, since the reproduction signal of the information mark is given by the total light amount signal, the ROM
The information recording / reproducing device can be easily realized by the same device as that using.

[0079]

The present invention has devised means for performing a multi-valued recording / reproducing system by narrowing the track pitch and the mark pitch as compared with the prior art. At the time of reproduction, two-dimensional information leakage from adjacent marks becomes a problem, but it is necessary to reduce this leakage by adaptively performing two-dimensional equalization based on the equalization coefficient obtained as a result of learning. You can As a result, multi-valued signals can be detected accurately even when the track pitch and mark pitch are reduced, and recording and reproduction are possible even when the density is increased.

[Brief description of drawings]

FIG. 1 is a plan view showing the principle of an information recording / reproducing system according to the present invention.

FIG. 2 is a plan view showing an embodiment of an information recording system for an optical disc according to the present invention.

FIG. 3 is a plan view for explaining an information leak amount in the information recording / reproducing apparatus according to the present invention.

FIG. 4 is a graph showing the effect of the information recording / reproducing system according to the present invention.

FIG. 5 is a graph showing the effect of the information recording / reproducing system according to the present invention.

FIG. 6 is a graph showing the effect of the information recording / reproducing system according to the present invention.

FIG. 7 is a block diagram showing an outline of an information recording / reproducing apparatus according to the present invention.

FIG. 8 is a block diagram showing an embodiment of a synchronization signal generator that constitutes an information recording / reproducing apparatus according to the present invention.

FIG. 9 is a block diagram showing an embodiment of an information recording circuit which constitutes an information recording / reproducing apparatus according to the present invention.

FIG. 10 is a block diagram showing an embodiment of a reproduction data synchronizing circuit which constitutes an information recording / reproducing apparatus according to the present invention.

FIG. 11 is a block diagram showing an embodiment of an equalization coefficient learning circuit which constitutes an information recording / reproducing apparatus according to the present invention.

FIG. 12 is a block diagram showing an embodiment of a two-dimensional equalization circuit which constitutes the information recording / reproducing apparatus according to the present invention.

FIG. 13 is a block diagram showing an embodiment of a data control circuit constituting the information recording / reproducing apparatus according to the present invention.

FIG. 14 is an explanatory diagram showing a conventional technique.

FIG. 15 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

100 optical recording medium, 101-103 optical spots, 1
04 optical head, 105-107 total light amount signal, 108
~ 110 magneto-optical signal, 111 synchronization signal generator, 11
2 to 114 clock signal, 116 light spot positioning circuit, 117 actuator control signal, 118 user data, 119 data control circuit, 120 modulation data, 121 equalization coefficient learning circuit, 122 learning mark recording signal, 123 laser driving circuit, 124 recording Pulse, 125 reproduction data synchronization circuit, 126 to 128 synchronization reproduction signal, 129 two-dimensional equalization circuit, 130 to 137
Equalization coefficient, 138 Signal after equalization, 139 to 141 Sample and hold signal for clock mark, 142 to 143
Sample hold signal for wobble mark, 150 lattice points, 151 wobble mark A, 152 wobble mark B, 153 clock mark, 154 to 156 learning track identification mark, 157 to 159 equalization coefficient learning mark, 160 information mark, 161 track, 20
0-202 PLL circuit, 210 learning track identification circuit, 211 track identification result signal, 212 learning mark recording signal generation circuit, 213 modulation circuit, 220-22
2 A / D converter, 223-225 digital reproduction signal, 226-228 offset amount difference circuit, 229-
230 difference value, 231-232 first-in first-out circuit, 250-252 learning track identification circuit, 253-255 track identification result signal, 256-
257 crosstalk amount detection circuit, 258 to 259 intersymbol interference amount detection circuit, 260 to 161 crosstalk amount, 262 to 263 intersymbol interference amount, 264 to 271
Equalization coefficient calculation circuit, 290 to 296 delay circuit, 297
-304 Gain adjustment circuit, 305-309 Adder, 3
10-328 signal in two-dimensional equalization circuit, 350 comparator, 351 comparison result signal, 352 demodulation circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Maeda 1-280, Higashi Koikekubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd.

Claims (11)

[Claims] 1. An information mark is recorded on a predetermined lattice point of an optical information recording medium by laser light irradiation, and an optical change due to the information mark is detected by using at least two or more light spots. In the optical information recording / reproducing method for reproducing information, the size of the recording mark is recorded by changing the size of the recording mark into two or more types corresponding to multi-valued data, and the information mark is obtained by scanning the information mark with a light spot. An optical information recording / reproducing method characterized by performing signal processing on a reproduced signal to reduce crosstalk and intersymbol interference and detecting multi-valued data. 2. A recording medium is provided with an area for detecting the amount of leakage of information from the four lattice points that are two-dimensionally most adjacent to the lattice point for reproduction. A mark group is recorded on predetermined grid points of and the amount of information leaked from the four closest grid points is learned based on the detection value obtained by scanning the mark group with an optical spot in advance. Incidentally, at the time of information reproduction, an equalization coefficient for reducing crosstalk from an adjacent track and intersymbol interference on the track for reproduction is calculated based on the learned leakage amount of the information, Signal processing is performed on a reproduction signal obtained by scanning the information mark with a light spot using an equalization coefficient,
2. The optical information recording / reproducing method according to claim 1, wherein the crosstalk and the intersymbol interference are reduced to detect multilevel data. 3. An optical head for irradiating a laser light spot on an information recording medium to record information and for irradiating a laser light spot on each of three adjacent tracks to generate a reproduction signal, and an optical recording from the reproduction signal. Synchronization signal generating means for generating a signal synchronized with the rotation of the medium; data control means for outputting a multilevel modulation signal from the data to be recorded at the time of recording information and demodulating the multilevel reproduction signal at the time of reproducing the information; Laser driving means for modulating the intensity of the light spot based on the modulation signal output from the control means, and reproduction data synchronizing means for correcting the timing deviation of the reproduction signals from the three adjacent tracks reproduced by the three light spots. , Reducing the crosstalk by performing arithmetic processing on the reproduction signals obtained from three adjacent information tracks by using the equalization coefficient. The optical information recording and reproducing apparatus which comprises a two-dimensional equalizing means for reducing the serial intersymbol interference amount. 4. A means for recording a mark group on a predetermined lattice point of an equalization coefficient learning area of an optical information recording medium, and a mark group in the equalization coefficient learning area of the optical recording medium are scanned with three spots. On the basis of the reproduction signal obtained in this way, the amount of information leakage from the four lattice points that are two-dimensionally most adjacent to the lattice point intended for reproduction is detected, and the information is adjoined based on the detected value. It further comprises an equalization coefficient for reducing crosstalk from the track and an equalization coefficient learning means for calculating the equalization coefficient for reducing the intersymbol interference amount on the track for reproduction. The optical information recording / reproducing apparatus according to claim 3. 5. The determination means further comprises means for determining whether or not a mark is already recorded on the adjacent track based on the crosstalk amount from the adjacent track detected by the equalization coefficient learning means. 5. The optical information recording / reproducing apparatus according to claim 4, wherein the equalization coefficient calculation method for reducing crosstalk is changed according to the result. 6. A mark group is provided on a predetermined grid point in order to detect the amount of information leaked from the four grid points that are two-dimensionally most adjacent to the grid point for the purpose of reproducing information. An optical information recording medium comprising an equalization coefficient learning area to be recorded. 7. The equalization coefficient learning area is provided in a portion before a data area of a sector, and a position for recording or reproducing a mark in the equalization coefficient learning area in a portion further before the equalization coefficient learning area. 7. The optical information recording medium according to claim 6, further comprising a recognition area provided with a mark for indicating. 8. The optical information recording medium according to claim 6, wherein the equalization coefficient learning area is provided in a dedicated track. 9. An optical disk medium for optically recording and reproducing information, wherein a track of the optical disk medium is divided into a plurality of unit areas, and the unit areas are servo areas in which servo marks are recorded, and at the time of data reproduction. An equalization coefficient learning area in which a learning mark for setting the equalization condition is recorded,
And an optical disk medium in which a data storage area for recording multi-valued data by data marks of a plurality of sizes is sequentially arranged. 10. The optical disk medium according to claim 9, wherein the servo mark, the learning mark, and the data mark are formed by substantially circular concave and convex pits. 11. The optical disk medium according to claim 9, wherein the servo mark and the learning mark are marks of the same size and form a predetermined array pattern.