JP2003045033A - Information recording method, information recording medium, information recorder, information reproducing method and information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information reproducing method capable of reproducing a cell having multi-valued information recorded thereon without erroneous judgment at the time of reproducing it without propagating the influence to the other cell even when a multi-value level is erroneously judged due to a defect or the like. SOLUTION: Without performing uniform recording by N=octal mark, M= quaternary mark for which a multi-value level number is lowered beforehand is recorded for every prescribed number of the cells, three cells for instance, the cell for which the multi-value level number is lowered is reproduced singly and the other cells (the cells of the octal mark) are reproduced on the basis of the level information of the adjacent cells in front and at the back. Thus, the chain of read errors is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording method, an information recording medium, an information recording apparatus, an information reproducing method and an information reproducing apparatus which handle multi-valued information.

[0002]

2. Description of the Related Art Conventionally, in an optical disc, binary digital data is formed on a spiral or concentric track by forming embossed pits (ROM disc) or holes in an inorganic / organic recording film (additional writing). Type discs) ・ Crystal state difference (phase change disc) ・ Magnetization direction difference (magneto-optical disc). When reproducing these recorded data, a laser beam is irradiated onto the track to detect the intensity difference of the reflected light, the polarization direction difference due to the magnetic Kerr effect and the like to obtain a reproduction RF signal. Then, the obtained reproduction RF signal is processed by, for example, a constant threshold value to detect binary data.

In order to increase the recording density of information, a method of recording multi-valued data of three or more values instead of binary data has been considered. However, in optical disks, there are differences in reflectance between various optical disks and Since the level fluctuation and the amplitude fluctuation occur in the reproduction signal due to various factors such as the difference in the reproduction frequency characteristic between the inner circumference side and the outer circumference side in one optical disc, the threshold value for multi-value conversion is fixed. Then, there is a problem that a reproduced signal may be detected with an incorrect value. In particular, when the data is ternary, quaternary, etc., there is a problem that the threshold value becomes plural and the possibility of erroneous detection of multi-valued level data increases.

According to Japanese Patent Application Laid-Open No. 5-54391, in order to solve the above-mentioned problems, a reproduction signal from a recording medium on which multi-level data is recorded is A / D-converted based on a reference clock. When detecting multi-valued level data by comparing the signal level data obtained by A / D conversion with a threshold value, the signal level data obtained by A / D conversion of the reproduction signal is memorized for each predetermined signal unit. The distribution information of the signal level data is obtained for each predetermined signal unit stored in the memory means, and when the signal level data in the signal unit is multivalued, based on the distribution information. The threshold used is set. Further, at that time, it is premised that a format in which the ratio of the level value of the recorded data is determined is adopted.

For example, in a predetermined signal unit such as a reproduction signal in sector unit in the recording format on the optical disc,
The signal level data obtained by A / D converting the reproduced signal is temporarily stored in the memory, and the CPU is used to obtain the occurrence frequency distribution information to obtain an optimum threshold value as a multi-valued reference, and the threshold value is used again. Then, the stored signal level data is multi-valued and data is detected. Therefore, even when the level fluctuation or amplitude fluctuation of the reproduction signal occurs, there is an effect that the possibility of erroneously detecting multi-valued data is reduced and an accurate multi-valued detection operation is realized. Higher recording data density is promoted.

In Japanese Patent Laid-Open No. 54391/1993, in order to cope with fluctuations in a long section such as fluctuations in signal level on the inner and outer circumferences of an optical disc, for example, the threshold for multi-value quantization is optimized in sector units. Moreover, it is premised that the format is restricted so that each multi-valued level including variations can be separated cleanly.

[0007]

By the way, in order to improve the information recording density, a unit of data recording / reproducing (hereinafter referred to as "information cell" or simply "cell") is used together with multi-valued data.
Call) is also required to be small. When the information cell is made smaller so that the reproduction light beam spot includes a plurality of information cells (see the description of FIG. 1 described later), the reproduction signal output level of the information cell is affected by the information cells before and after. Therefore, the output level of the reproduction signal corresponding to the same multi-value level shifts depending on which multi-value level information cell is recorded before and after, and apparently the spread (extension) of each multi-value level becomes large. . Therefore, when data is aggregated in a long section such as a sector unit, adjacent multi-valued levels have overlapping distributions. As will be described in detail later, FIG. 2 shows an example of a reproduction signal level distribution in the case where a multi-value level = 8-value data level is recorded in one information cell and the reproduction light beam spot size includes three information cells. Is. In this example, Levels 1 and 2, Level 2
And 3, and levels 4 and 5 overlap.

The above-mentioned Japanese Patent Laid-Open No. 5-5
Considering the application of the detection method as in the example of Japanese Patent No. 4391, there is a problem that no matter how the threshold value is determined, there is a high possibility that the level of the information cell with respect to the overlapping distribution is erroneously detected. Another problem is that the flexibility of the format is limited.

The present invention provides an information recording method, an information recording medium, an information recording apparatus, an information reproducing method, and an information reproducing apparatus, which can prevent misjudgment when reproducing a cell in which multi-valued information is recorded. The purpose is to do.

That is, it is an object of the present invention to provide an information recording method and an information recording apparatus capable of recording multivalued information that is unlikely to be misjudged when reproducing a cell in which multivalued information is recorded.

Another object of the present invention is to provide an information recording medium on which multi-valued information is recorded, which is less likely to be erroneously determined when reproducing a cell on which multi-valued information is recorded.

It is another object of the present invention to provide an information reproducing method and an information reproducing apparatus capable of reproducing without misjudgment when reproducing a cell in which multi-valued information is recorded.

Further, when reproducing a cell in which multi-valued information is recorded, reproduction can be performed without erroneous judgment, and even if a multi-valued level erroneous judgment occurs due to a defect or the like, its influence is not affected. An object of the present invention is to provide an information reproducing method and an information reproducing device which are not propagated to other cells.

[0014]

The invention according to claim 1 is
An information recording method of recording a mark representing multi-valued information for each cell of an information recording medium, wherein an M-value mark (M is an integer smaller than N is set for an N-value mark (N is an integer of 3 or more) cell. 1) is recorded for each predetermined number of cells.

Therefore, at the time of reproducing, at least the level judgment of the M-value mark can be performed without error, so that the reliability of reproducing the multi-valued information is improved as compared with the case of recording uniformly with the N-value mark. Can be provided.

According to a second aspect of the invention, in the information recording method according to the first aspect, N = 2 representing T bit data, N = 2.
When the ^T, M represents T least significant bits in the data is fixed to 0 or 1 (T-1) bit data M
= 2 ^T-1 .

Therefore, for example, N = 8 values are set as M = 4 values, and since the marks are of a level thinned out from the N value marks, the N value mark and the M value mark are common. In addition to being able to record under the mark system, M
It is possible to provide an information recording method capable of more accurately determining the level of the value mark.

According to a third aspect of the present invention, there is provided an information recording medium in which a mark representing multi-valued information is recorded for each cell, and an M value is set for an N value mark (N is an integer of 3 or more) cell. One cell of the mark (M is an integer smaller than N) is recorded for each predetermined number of cells.

Therefore, at the time of reproduction, at least the level judgment of the M-value mark can be performed without error, so that the reliability of the reproduction of the multi-valued information is improved as compared with the case where the N-value marks are uniformly recorded. A medium can be provided.

According to a fourth aspect of the invention, in the information recording medium according to the third aspect, N = 2 representing T bit data.
When the ^T, M represents T least significant bits in the data is fixed to 0 or 1 (T-1) bit data M
= 2 ^T-1 .

Therefore, for example, M = 4 values are set for N = 8 values, and the N level marks are thinned out, so that the level of the M value marks can be determined more accurately. An information recording medium that can be provided can be provided.

In the information recording medium according to the third or fourth aspect of the invention, the information recording film on which the N-value mark and the M-value mark are recorded is a recordable and erasable phase change material as in the fifth aspect of the invention. An information recording film according to claim 6, an information recording film based on a recordable and erasable magneto-optical material as claimed in claim 6, or an information recording film based on a recordable organic dye as claimed in claim 7. The information recording film may be a recordable metal film as in the invention described in item 8.

According to a ninth aspect of the present invention, there is provided an information recording device for recording a mark representing multi-valued information for each cell of an information recording medium, wherein the input information is a predetermined number of N-level cell level data (N.
Is an integer of 3 or more) and one M-ary cell level data (M is an integer smaller than N), and N-value cell level data converted by the multi-valued level converting means. Recording means for recording an N-value mark and an M-value mark respectively corresponding to the M-value cell level data such that one cell of the M-value mark corresponds to a predetermined number of cells with respect to the cell of the N-value mark. And

Therefore, at the time of reproduction, at least the level judgment of the M-value mark can be performed without error, so that the reliability of reproduction of multi-valued information is improved as compared with the case of recording uniformly with the N-value mark. Can be provided.

According to a tenth aspect of the present invention, in the information recording apparatus according to the ninth aspect, N = N representing T bit data.
When a 2 ^T, M is set to M = 2 ^T-1 becomes a value representative of the T least significant bits in the data is fixed to 0 or 1 (T-1) bit data.

Therefore, for example, N = 8 values are set as M = 4 values, and since the marks are of a level thinned out from the N value marks, the N value mark and the M value mark are common. In addition to being able to record under the mark system, M
It is possible to provide an information recording device capable of more accurately determining the level of a value mark.

According to an eleventh aspect of the present invention, a multi-valued level of the multi-valued information is reproduced from a reproduction signal of the information recording medium according to any one of the third to eighth aspects in which a mark representing the multi-valued information is recorded for each cell. In this method, the multi-level determination level number of the cell is switched from the N value to the M value for each predetermined number of cells, and the multi-level level of the target cell of interest is determined.

Therefore, at least the level of the M-value mark is determined by switching the multi-level determination level number of the cell from the N value to the M value for each predetermined number of cells to determine the multi-level level of the target cell of interest. It is possible to provide an information reproducing method capable of performing the above without error.

According to a twelfth aspect of the present invention, in the information reproducing method according to the eleventh aspect, the multi-value level judgment of the M-value mark in which the multi-value judgment level number is M value is performed on the reproduction signal of the target cell alone. I decided to do it based on.

Therefore, for the M-value mark whose number of levels is lower than that of the N-value mark, the level can be uniquely determined based on the reproduction signal of the target cell alone.

According to a thirteenth aspect of the present invention, in the information reproducing method according to the twelfth aspect, the multi-value level determination of the N-value mark in which the number of multi-value determination levels is N value is performed in the preceding cell preceding the target cell. The judgment is made based on the judgment standard set by referring to the level judgment value of.

Therefore, with respect to the N-value mark, the multilevel level judgment is performed based on the judgment standard which is set by referring to the level judgment value of the preceding cell, so that the reproduction signal output level of the concerned cell is the same as that of the preceding cell. Even when affected, the level determination error can be prevented, and the level determination error for the M value mark for each predetermined number of cells can be performed without error based on a single cell, so that the level determination error due to a defect or the like propagates. Can be prevented for each M value mark,
An information reproducing method capable of preventing a chain of reading errors can be provided.

According to a fourteenth aspect of the present invention, in the information reproducing method according to the twelfth aspect, the multi-valued level judgment of the N-value mark whose multi-valued judgment level number is an N value is continued to the target cell. The judgment is made based on the judgment standard set by referring to the level judgment value of.

Therefore, for the N-value mark, the multilevel level judgment is performed based on the judgment standard set by referring to the level judgment value of the continuation cell, so that the reproduction signal output level of the cell of interest becomes equal to that of the continuation cell. Even when affected, the level determination error can be prevented, and the level determination error for the M value mark for each predetermined number of cells can be performed without error based on a single cell, so that the level determination error due to a defect or the like propagates. Can be prevented for each M value mark,
An information reproducing method capable of preventing a chain of reading errors can be provided.

According to a fifteenth aspect of the present invention, in the information reproducing method according to the twelfth aspect, the multi-value level judgment of the N-value mark in which the multi-value judgment level number is the N value is performed in the preceding cell preceding the target cell. Also, the judgment is made based on the judgment standard set by referring to the level judgment value of the continuing cell to be continued.

Therefore, with respect to the N-value mark, multi-level level judgment is performed based on the judgment standard set by referring to the level judgment values of the preceding cell and the continuing cell, so that the reproduction signal output level of the target cell is It is possible to prevent an error in the level determination even when influenced by the preceding cell and the continuing cell, and for the M value mark for each predetermined number of cells, the level determination can be performed without error based on a single cell.
It is possible to prevent propagation of a level judgment error due to a defect or the like for each M-value mark, and it is possible to provide an information reproducing method capable of preventing a chain of reading errors.

According to a sixteenth aspect of the present invention, in the information reproducing method according to the twelfth aspect, when the predetermined number of cells = 3, the multi-valued level judgment of the N-valued mark whose multi-valued judgment level number is N value is performed. , For the cell of interest continuing to the M-value mark, based on the criterion set by referring to the level determination value of the preceding cell of the M-value mark preceding the cell of interest, for the cell of interest preceding the M-value mark, The determination is made based on the determination standard set with reference to the level determination value of the continued cell of the M-value mark that continues to the target cell.

Therefore, when the predetermined number of cells in which the M-value mark is every 3 cells = 3, the N-value mark has the preceding cell adjacent to the M-value mark and the succeeding cell adjacent to the M-value mark. Therefore, it is possible to provide an information reproducing method capable of performing more appropriate level determination with few errors by referring to the level determination values of the preceding cell and the continuing cell which are adjacent to each other.

According to a seventeenth aspect of the present invention, in the information reproducing method according to the twelfth aspect, when the predetermined number of cells is ≧ 4, the multi-valued level judgment of the N-value mark whose multi-valued judgment level number is N value is performed. , For the cell of interest continuing to the M-value mark, based on the criterion set by referring to the level determination value of the preceding cell of the M-value mark preceding the cell of interest, for the cell of interest preceding the M-value mark, The determination is made based on the criterion set by referring to the level determination value of the continuing cell of the M-value mark that continues to the target cell, and for the target cell that is not continuous to the M-value mark, the preceding cell preceding the target cell and continue The determination is made based on the determination standard set by referring to the level determination value of the continuation cell.

Therefore, when the number of cells of the M-value mark is equal to or larger than 4, the N-value mark having the preceding cell adjacent to the M-value mark and the succeeding cell adjacent to the M-value mark in the N-value mark is For cells, refer to the level judgment value of the adjacent preceding cell or the succeeding cell, and for the cell of the intermediate N-value mark which is not adjacent to the cell of the M-value mark, the preceding cell and the continuing cell of the succeeding cell to the cell are referred to. By referring to the level determination value, it is possible to provide an information reproducing method capable of performing more appropriate level determination with few errors.

According to the eighteenth aspect of the present invention, a multi-valued level of the multi-valued information is reproduced from the reproduction signal of the information recording medium according to any one of the third to eighth aspects in which a mark representing the multi-valued information is recorded for each cell. Is an information reproducing apparatus for judging the above-mentioned, A / D converting means for converting the above-mentioned reproduced signal into digital data, and the number of multi-level judgment levels of said cells from N value to M for every predetermined number of cells.
And a multi-value level determination means for determining the multi-value level of N value or M value for the digital data of the target cell by switching to the value.

Therefore, at least by determining the multi-valued level of the target cell of interest by switching the multi-valued determination level number of cells from the N value to the M value for each predetermined number of cells in the multi-valued level determination means. It is possible to provide an information reproducing apparatus capable of performing the level determination of the M value mark without error.

According to a nineteenth aspect of the present invention, in the information reproducing apparatus according to the eighteenth aspect, the multilevel level judging means is
The multi-value level determination of the M-value mark whose multi-value determination level number is the M value is performed based on the digital data of the target cell alone.

Therefore, the level of the M-value mark whose number of levels is lower than that of the N-value mark can be uniquely determined based on the reproduction signal of the cell of interest alone.

According to a twentieth aspect of the present invention, in the information reproducing apparatus according to the nineteenth aspect, the multivalue level determination means is:
The multi-level level judgment of the N-value mark having the level judgment value holding means for holding the level judgment value of the preceding cell preceding the cell of interest, the multi-value judgment level number being the N value, is carried out by the level judgment value holding means. The judgment is made based on the judgment standard set by referring to the level judgment value of the preceding cell held in the above.

Therefore, in the multi-level level determining means, the multi-level level determination is performed for the N-value mark based on the determination standard set by referring to the level determination value of the preceding cell. Even when the output level is affected by the preceding cell, it is possible to prevent an error in the level determination, and for the M-value mark for each predetermined number of cells, the level determination can be performed without error on the basis of a single cell, so that a defect or the like may occur. It is also possible to prevent the level determination error from propagating for each M value mark, and it is possible to provide an information reproducing apparatus capable of preventing a chain of reading errors.

According to a twenty-first aspect of the present invention, in the information reproducing apparatus according to the nineteenth aspect, the multilevel level judging means is
Digital data holding means for holding the digital data converted by the A / D conversion means, and continuing cell level calculating means for calculating a multi-valued level of a continuing cell continuing to the target cell prior to the calculation of the target cell The multi-valued level judgment of the N-value mark having the multi-valued judgment level number as N value is performed by using the digital data held in the digital data holding means and is calculated by the continuation cell level calculating means. The determination is made based on the determination standard set by referring to the level determination value of the continuation cell.

Therefore, in the multi-level level determination means, the multi-level level determination is performed for the N-value mark based on the determination standard set by referring to the level determination value of the continuing cell, and the reproduced signal of the target cell is obtained. Even when the output level is affected by the continued cells, it is possible to prevent an error in the level determination, and for the M value mark for each predetermined number of cells, the level determination can be performed without error based on a single cell. It is also possible to prevent the level determination error from propagating for each M value mark, and it is possible to provide an information reproducing apparatus capable of preventing a chain of reading errors.

According to a twenty-second aspect of the present invention, in the information reproducing apparatus according to the nineteenth aspect, the multilevel level judging means is
Digital data holding means for holding the digital data converted by the A / D conversion means, level judgment value holding means for holding the level judgment value of the preceding cell preceding the target cell, and prior to the calculation of the target cell The multi-value level judgment of the N-value mark having a multi-value judgment level number of N value is performed by holding the digital data. With reference to the level judgment value of the preceding cell held in the level judgment value holding means and the level judgment value of the continuation cell calculated by the continuation cell level calculation means while using the digital data held in the means, The judgment is made based on the criteria set.

Therefore, the multi-level level determination means performs multi-level level determination on the N-value mark based on the determination criteria set with reference to the level determination values of the preceding cell and the continuing cell, and thereby the target cell Even when the reproduction signal output level of the above is affected by the preceding cell and the continuing cell, the error of the level determination can be prevented, and the level determination of the M value mark for each predetermined number of cells can be performed without error based on a single cell. Therefore, it is possible to prevent the level determination error due to a defect or the like from propagating for each M-value mark.
An information reproducing apparatus capable of preventing a chain of reading errors can be provided.

[0051]

First, the principle of the embodiment of the present invention will be described.

FIG. 1 is an explanatory view showing an example of the information recording / reproducing system of the present invention. An information recording medium having a tracking groove formed on its surface and provided with a recording / erasable recording material records information as marks at predetermined time intervals. The area corresponding to this predetermined time interval is a unit of multi-valued information recording / reproducing called information cell (or simply cell) 1. For example, when an information recording film made of a phase change (PC) material is used as a recording / erasable recording material, the cell 1 is irradiated with a laser beam to adjust the recording and erasing light amounts and their timings, thereby recording marks. , The recording marks of a plurality of reproduction levels are formed. In FIG. 1A, as the multi-valued level, the largest mark is formed from 0 level where no recording mark is formed.
An example in which cell 1 having N value up to the level = 8 values is recorded is shown. That is, in each cell 1, assuming that N = 2 ^T , T = 3 and 8 = 2 ^3, so information of T bits = 3 bits is recorded. If the multi-valued level of each cell 1 can be reproduced as recorded, an ordinary optical disc records with 2 bits, so that the recording capacity of 3 times can be obtained. Further, in order to increase the storage capacity, it is necessary to make the cell 1 small, and if it is made small, as shown in FIG. 1A, the marks of 2-3 cells 1 are included in the reproduction beam diameter. Become.

As the recording / erasable recording material, an information recording film made of a magneto-optical (MO) material can be used in addition to the phase change film. In addition to the above laser light, a cooperative work with a magnetic field from a magnetic head (not shown) can be performed. By this, the shape of the recording mark is changed, and the recording mark of a plurality of reproduction levels is formed. Furthermore, it is also possible to apply a recording material capable of only recording and reproduction, an organic dye or a metal film can be used as a recording material, and by irradiating the cell with laser light and adjusting the recording light quantity and the timing thereof, By changing the shape of the recording mark, recording marks of a plurality of reproduction levels are formed. Similarly, even in a read-only recording medium, recording marks can be formed on the substrate as unevenness called phase pits, and multi-level level recording can be performed by modulating the area of the phase pits or the optical depth of the phase pits. It is possible.

On the premise of recording at such a multi-valued level, the principle of the present invention will be described with an example in which a phase change recording film is used.

Here, an example of multi-valued recording / reproduction by a general rewritable DVD recording device will be shown. Recording / reproducing wavelength λ = 650 nm, numerical aperture NA of objective lens = 0.
65, the diameter of the beam focused on the optical information recording medium (recording medium) is about 0.8 μm. As the optical information recording medium, a rewritable type of phase change material AgInSbTe was used. The recording mark is formed on a groove called a groove, and the interval (track pitch) between adjacent grooves is 0.7.
The groove width was set to about 0.4 μm, and the recording / reproducing linear velocity was set to about 3.5 m / s. The circumferential length of the cell 1 is about 0.6 μm. The erasing power is set to a value that is 0.5 to 0.6 times the recording power. The number of levels N of multilevel information is N = 8 levels.

First, the result of recording and reproducing random information is shown in FIG. In FIG. 2, the vertical axis represents the reproduction level at the center of each cell, that is, the level at which the mark is not recorded (highest) and the level at which the mark is recorded so that the amount of reflected light is the lowest (max). It is normalized by the difference. When the reproduction signal = RF, the reproduction signal (normalized multi-valued signal) = (RF-min) / (max-min) (1)

According to the result shown in FIG. 2, the reproduced signal is not completely divided into 8 values, and the reproduced signal is changed from 0 to 7
When trying to judge the level of, depending on the playback signal,
In some cases, even if the first level is recorded, the second level is reproduced. This is a phenomenon that occurs because the recording marks of the front and rear cells 1 are included in the reproduction beam, and the reproduction level fluctuates depending on the size of the recording marks of the front and rear cells 1.

On the other hand, FIG. 3 separates the data shown in FIG. 2 for each known multi-valued level (horizontal axis in FIG. 3: previous level) of the immediately preceding cell (preceding cell). Things
It shows how the reproduction level of the target cell of interest changes depending on the previous level. According to the result shown in FIG. 2, it was not possible to uniquely determine the multi-valued level from the reproduced signal, but the relation with the multi-valued level of the preceding cell as shown in FIG. It can be seen that the multi-valued level of the cell of interest can be uniquely determined by holding it as a criterion and disassembling it for each previous level of the preceding cell. The "first principle" of the present invention utilizes this principle. "The multi-level level judgment criterion of the cell of interest is prepared for each multi-level data of the previous cell, and the previous cell is determined. By making a decision by switching the decision criterion of the cell of interest after the decision of the multi-valued level, it is possible to prevent a level decision error that occurs in the state of FIG.

Similarly, in FIG. 4, the data shown in FIG. 2 is separated for each multi-valued level (horizontal axis in FIG. 4: rear level) of the cell (continuation cell) immediately after the cell of interest. This shows how the reproduction level of the target cell of interest changes depending on the previous level. The relationship between the preceding cell and the multi-valued level as shown in FIG. 4 is learned in advance, held as a criterion for the multi-valued level, and decomposed into each level after the succeeding cell to uniquely determine the multiplicity of cells of interest. It can be seen that the value level can be determined. The "second principle" of the present invention utilizes this principle,
"Prepare a criterion for judging the multi-valued level of the cell of interest for each multi-valued level data of the cell after one, and switch the judgment criteria of the cell of interest after judging the multi-valued level of the cell after one" As a result, it is possible to prevent a level determination error that occurs in the state of FIG.

Furthermore, when the multi-valued levels of the cells preceding and succeeding the cell of interest (preceding cell and continuing cell) are known, as shown in FIG. It can be seen that the multi-level can be uniquely determined from the reproduced signal without variation. Note that FIG. 5 shows the multi-valued level of the target cell in the case of the rear level = 0 and the front level = 0 to 7. "Third principle" of the present invention
Uses this, "Preparing a standard for multi-level level judgment of the cell of interest for each multi-level level data of the preceding and following cells,
By determining the cell level of the cell before one and the cell level of the cell after one by switching the criterion of the cell of interest ", it is possible to prevent the level determination error that occurs in the state of FIG. (Combination of the first principle and the second principle).

Further, as shown in FIG. 2, even if the reproduction signal cannot be uniquely determined when it is determined to be an 8-level, the multi-value number of the recording marks is reduced as shown in FIGS. 6 (a) and 6 (b). This allows a unique decision. Figure 6
FIG. 6A shows an example in which the least significant bit of T = 3 bits is fixed to 0 to reduce N = 8 values to M = 4 values, and FIG. An example is shown in which N = 8 values are reduced to M = 2 ^T-1 = 4 values by fixing the lower bits to 1. That is, the recording method is not uniform recording with N-valued marks, but an M-valued mark is intervened with respect to the N-valued mark every predetermined number of cells = 3 cells. The "fourth principle" of the present invention utilizes this principle.

Based on the first principle and the like, when the reproduction of the level of the cell of interest is repeated based on the information of the cell immediately before, if the cell immediately before is erroneously read due to a defect or the like, Since there is a possibility that errors will be chained to cells and read one after another, as shown in FIG. 1C, an M-value mark in which the number of multi-valued levels is reduced in advance is recorded for each predetermined number of cells n. However, the cell in which the number of multi-levels is lowered is played back independently, and the other cells (N
The value mark cell is reproduced based on the level information of the adjacent cells before and after, thereby preventing a chain of read errors. In the example shown in FIG. 1, 8 values, 8
Data is recorded as a combination of values, 4 values, 8 values, 8 values, 4
It is reproduced by a combination of values (actually, the four-valued mark cell is recorded with any one of four kinds of “000”, “010”, “100”, and “110”. When reproducing, as shown in FIG. The least significant bit "0" is omitted and reproduced. This effect can prevent chained errors.

Next, several embodiments based on the principle of the above-described embodiments of the present invention will be described.

The first embodiment of the present invention will be described with reference to FIGS. 7 to 9. The present embodiment utilizes the first and fourth principles.

First, an example of the configuration and operation of the information recording / reproducing apparatus used in this embodiment will be described with reference to FIG. Information recording medium 3 by the spindle motor 2
While rotating, the laser beam emitted from the LD (laser diode) 4 is irradiated by the optical head 5 along the track on the information recording medium 3. Information recording medium 3
The reflected light from is detected by a PD (photodetector) 6 and is controlled by an OP amplifier 7 and a servo circuit 8 so that the beam is stably irradiated onto the information track. The reproduction signal a detected by the PD 6 is amplified by the RF amplifier 9 and then converted into digital data c by the digital data conversion means 12 including the sector synchronization detection means 10 and the A / D conversion means 11.

Although not shown in FIG. 7, the digital data c is subjected to the above-described normalization processing so that the value of the reproduced digital data does not change. Figure 1
In FIG. 7, the maximum level is normalized so that it is easy to understand, but in FIG. 7, the digital data is normalized to be an integer value so that the subsequent data processing is easy. When processed as 10-bit digital data, it is normalized by {(RF-min) / (max-min)} × 1024 (2).

This digital data c is detected by the multi-value level determination means 13, converted into cell level data e corresponding to the multi-value level of each cell 1, and the cell data conversion means 14
By converting the cell level data into the reproduction information g, the information is reproduced from the multi-value recorded information recording medium 3.

Further, at the time of recording, the input information h is converted into cell level data e by the multi-valued level conversion means 15, and the recording pulse generation means 16 generates the light quantity and timing signal of the recording and erasing pulses to generate the LD drive circuit 17. To record a recording mark on the information recording medium 3 by the LD 4. The LD 4, the LD drive circuit 17, the recording pulse generating means 16 and the like constitute recording means.

Under this structure, in the present embodiment,
It utilizes the first principle and the fourth principle. When information is recorded on the information recording medium 3, as described above with reference to FIG. 1, N = 8-valued marks are recorded, and the number of levels is reduced by M = 3 for every predetermined number of cells = 3 cells. By recording a four-valued mark and reproducing the information recording medium 3 on which the multi-valued information is recorded based on the first principle, it is possible to prevent an erroneous determination regarding the multi-valued level and to detect a defect or the like. This is to prevent a chain of read errors when the cell level is read incorrectly.

Therefore, as shown in FIG. 8, the multi-level level judging means 13 of the present embodiment has the calculating means 18 for judging the cell level and the cell level data e of the immediately preceding cell.
Cell level holding means (level judgment value holding means) 19 for holding The calculating means 18 stores the table RAM 20 in which the level data of each input digital data (reproduction level) is recorded, and the table RA based on the cell level f immediately before and the value of the digital data c.
The address generating means 21 reads the cell level data e from M20.

Here, as shown in FIG. 9, the table RAM 20 has a previous table area (addresses 0 to 8191) in which cell level data to be judged for each cell level of the immediately preceding cell (preceding cell) is recorded. 4-level table area (addresses 8192-9215) in which cell-level data for 4-level data is recorded
It is composed of and. That is, the cell level data is stored in the address corresponding to the value of the digital data separately for each cell level data of the preceding cell (preceding cell). For example, the cell level data of the preceding cell is stored. Is "2" and the digital data is "131", "2 *"
The cell level data 1 is read by reading the address of 1024 + 131 ". That is, by reading the address of the digital data to which the offset generated from the cell level data of the previous cell is read, The cell level can be generated by changing the cell level judgment standard, and the 3-bit cell level data string reproduced from this one cell is collected by the cell data conversion means 14 to be the reproduction information g of the 8-bit data string. The level of the cell in which the value mark is recorded is determined based on the 4-value table area, which is divided into the previous table area (address 0 to 8191) and the 4-value table area (address 8192 to 9215). Thus, it is possible to switch the multi-value determination level number between 8 and 4. In this way, the table RAM 2
By accessing a predetermined address of 0, the multi-valued level of the cells having different levels is determined.

An information reproducing process example of the present embodiment will be described with reference to the transition diagram shown in FIG. 10 and the flowchart shown in FIG. As shown in FIG. 1, the recording of the multi-valued information on the information recording medium 3 is performed by a four-value mark (lowermost bi
It is assumed that the method of FIG. 6A in which t is fixed to 0 is recorded.

First, the digital data SL of the Nth cell
_N is read (step S1) and the cell level data C is read.
L _N is obtained from the previous table area of the table RAM 20 based on SL _N and the known reproduction level CL _N-1 immediately before the beginning of the information recording (S2). The Nth cell level determined by this processing is held in the cell level holding means 19 and is used for address generation when reproducing the next (N + 1) th cell. Subsequently, the digital data SL _{N + 1} of the (N + 1) th cell is read (S3), and the cell level data CL _{N + 1} is obtained from the previous table area of the table RAM 20 based on SL _{N + 1} and CL _N (S
4). Next, the digital data S of the (N + 2) th cell
Although L _{N + 2} is read (S5), since this is a 4-valued mark cell, the reproduction signal SL _{N + 2} alone from the target cell is stored in the table RAM ₂₀ by switching the multi-value determination level number to M = 4 values. It is obtained from the 4-value table area (S6). The (N + 2) th cell level (four-valued) determined by this processing is held in the cell level holding means 19 and used for address generation when reproducing the next (N + 3) th cell.

After step S7, by repeating the processing of steps S1 to S6 in the same manner, the information recording medium 3 in which 4-level cells (the least significant bit is fixed to 0) are recorded every 3 cells is recorded. The multi-valued level of each cell is determined.

The obtained cell level data e of each cell of 3 bits is 8 bits by the cell data conversion means 14 by omitting the least significant bit of the 4-level cell as shown in FIG.
Is converted into a data string of and becomes reproduction information g.

By the above-described reproduction processing, even if a cell which is reproduced by mistake due to a defect or the like is generated, it can be reproduced without causing a chain of errors.

A second embodiment of the present invention will be described with reference to FIGS. The present embodiment utilizes the second and fourth principles, and generally, when recording multi-valued information on the information recording medium 3, the number of cell levels is reduced to M = A 4-valued mark cell is recorded every 2 cells (thus, N = 8-valued mark cells and M = 4-valued mark cells are alternated ... See FIG. 14), and the information recording medium thus recorded is recorded. By reproducing the information of No. 3 by referring to the level judgment value of the continuing cell, it is possible to prevent a chain of reading errors without causing erroneous detection and even when the cell level is erroneously read due to a defect or the like. It is the one.

Also in the case of the present embodiment, the information recording / reproducing apparatus having the structure as shown in FIG. 7 can be used.
In the present embodiment, multi-value level determination means 13A shown in FIG. 12 is used in place of the multi-value level determination means 13 shown in FIG. This multilevel level determination means 13
A is a digital data holding means 22 for holding the digital data c of the immediately preceding cell (preceding cell), and a four-value operation as a continuation cell level operation means for detecting the cell level of the M = four-value mark. Means 23, a 4-value cell level holding means 24 for holding the cell level data of the 4-value mark detected by the 4-value arithmetic means 23 and outputting it at the time of reproducing the next cell level, and a cell after one cell (continuation). Cell), an eight-value arithmetic means 25 for detecting the cell level of the target cell, a delay means 26 delaying the operation timing of the eight-value arithmetic means 25 by one cell, and four values of these. The switching means 27 is configured to alternately switch between the four-value mark level output by the for-value calculation means 23 and the eight-value mark level output by the for-eight-value calculation means 25 and output.

As in the case of the calculating means 18 shown in FIG. 8, the 4-value arithmetic means 23 generates an address of the table RAM 28 from the table RAM 28 and the digital data c and reads the cell level of the 4-value mark. And an address generating means 29 for issuing the address. Table RAM 28
Is composed of only a four-value table dedicated to four-value marks, as shown in FIG.

The eight-value arithmetic means 25 detects the cell level of the cell of interest by referring to the cell level of the cell (continuation cell) immediately after, and as shown in FIG. Table RAM30 configured by a table after recording the cell level of the target cell for each cell level
And the table RAM 30 based on the digital data c
And an address generating means 31 for reading the cell level data.

With such a configuration, an example of the information reproducing process of the present embodiment will be described with reference to the transition diagram shown in FIG. 14 and the flowchart shown in FIG. Information recording medium 3
As shown in FIG. 14, the recording of the multi-valued information in the four-valued mark is performed for every two cells (the lowest bit is fixed to 0 in FIG. 6A).
Method) is recorded.

First, the digital data SL _N of the _Nth cell is read as the cell of interest (S11), the digital data SL _N is held by the digital data holding means 22, and the digital data of the (N + 1) th cell is continuously read. SL _{N + 1 is} also read (S12). Where (N +
Since the 1) th cell is a 4-valued mark cell, only the digital data SL _{N + 1} obtained by the reproduced signal is used alone in the table RA in the 4-value arithmetic means 23.
Referring to M28, the 4-level cell level data CL
_{N + 1} is read and held in the 4-level cell level holding means 24 (S13). That is, the processing of the continuation cell is executed first. After this arithmetic processing, the digital data holding means 2
Digital data SL of the Nth cell held in 2
_{Based on N} and CL _{N + 1} obtained from the 4-value arithmetic means 23, the 8-value arithmetic means 25 refers to the table RAM 30 to read the 8-value cell level data CL _N and outputs it through the switching means 27 (S14). ). After that, the output is switched to the 4-value side by the switching means 27, and the 4th of the (N + 1) th cell held in the 4-value cell level holding means 24.
The cell level data CL _{N + 1} of the value is output (S1
5). As a result, the cell level data CL _N , CL
_{The N + 1} output order is maintained.

Hereinafter, the (N + 2) th cell, (N + 3)
For the second cell and the like, the same processing as in steps S11 to S15 is repeated to obtain the cell level of each cell of the information recording medium 3 in which the cell of the four-valued mark is recorded every two cells. The cell level data e of 3 bits of each cell is converted into an 8-bit data string by omitting the least significant bit of the 4-level cell by the cell data conversion means 14.
It becomes the reproduction information g.

By the above reproduction processing, even if a cell which is reproduced by mistake due to a defect or the like is generated, it can be reproduced without causing a chain of errors.

A third embodiment of the present invention will be described with reference to FIGS. This embodiment utilizes the third and fourth principles, and roughly, when recording multi-valued information on the information recording medium 3, M = the number of cell levels is reduced. A 4-valued mark cell is recorded every 2 cells (thus, N = 8-valued mark cells and M = 4-valued mark cells are alternated ... See FIG. 18), and the information recording medium thus recorded is recorded. By reproducing the information of No. 3 by referring to the level judgment values of the preceding cell and the continuing cell, erroneous detection does not occur, and even if the cell level is erroneously read due to a defect or the like, a chain of reading errors can be prevented. It was made possible.

Also in the case of the present embodiment, the information recording / reproducing apparatus having the structure as shown in FIG. 7 can be used.
In the present embodiment, multi-value level determination means 13B as shown in FIG. 16 is used instead of the multi-value level determination means 13 shown in FIG. This multilevel level determination means 13
B is a digital data holding unit 33 that holds the digital data c2 of the immediately preceding cell, a digital data holding unit 34 that holds the digital data c1 of the immediately preceding cell,
It is composed of a table RAM 35 storing cell levels, a data RAM 36 corresponding to the cell level holding means 19 for temporarily holding the detected and judged cell level data, and a sequencer 37 for controlling the data RAM 36 and the table RAM 35. There is. In the present embodiment, the sequencer 37 and the table RAM 35 constitute an arithmetic means 38 for determining the cell level.

Here, the table RAM 3 of this embodiment is used.
As shown in FIG. 17, 5 is the immediately preceding cell (preceding cell)
And the front and back table areas (addresses 0 to 65535) in which cell level data to be judged for each cell level of the next cell (continuation cell) are recorded and the four-level table area in which cell level data in the case of four values are recorded (Addresses 65536 to 66559). That is, the cell level data is separated and stored for each cell level data of the preceding cell (preceding cell) and the succeeding cell (continuation cell) at the address corresponding to the value of the digital data. The cell level data of the previous cell is "0", the cell level data of the next cell is "2", and the digital data is "25".
In the case of 9 ", the cell level data 2 is read by reading the address of" 2 * 1024 + 259. "For the cell in which the 4-level mark is recorded, the level is determined based on the 4-level table area. Area (address 0
To 65535) and 4-value table area (address 65536 to 6655)
By being divided into 9) and 9), it is possible to switch the multi-level judgment level number between 8-level and 4-level. By thus accessing the predetermined address of the table RAM 35, the multi-valued level of the cells having different levels is determined.

With such a configuration, an example of the information reproducing process of the present embodiment will be described with reference to the transition diagram shown in FIG. 18 and the flowchart shown in FIG. Information recording medium 3
As shown in FIG. 18, the recording of the multi-valued information to the four-valued mark is performed for every two cells by a four-valued mark (the least significant bit is fixed to 0 in FIG. 6A).
Method) is recorded. The known reproduction level CL _N-1 immediately before the beginning of the information recording is the data RA.
It is assumed to be stored in M36.

First, the digital data SL _N of the cell of the _Nth octal mark as the target cell is read (S21), and the digital data SL _N is stored in the digital data holding means 33.
While being held at, the digital data SL _{N + 1 of} the (N + 1) th cell is also read (S22). Here, since the (N + 1) th cell is a cell of a four-valued mark, this digital data SL obtained by the reproduction signal is obtained.
Using only _{N + 1} alone, the arithmetic means 38 refers to the four-valued table area in the table RAM 35 to read the four-valued cell level data CL _{N + 1} and hold it in the data RAM 36 (S23). After this calculation processing,
The digital data SL _N of the N-th cell held in the digital data holding means 33 and the judged cell level data CL _N-1 , C stored in the data RAM 36.
Table RA in the calculation means 38 based on L _{N + 1}
The 8-level cell level data CL _N is read with reference to M35 and output under the control of the sequencer 37 (S24).
Subsequently, the data RAM is controlled by the sequencer 37.
The 4-level cell level data CL _{N + 1} of the (N + 1) th cell stored in 36 is output (S25). As a result, the output order of the cell level data CL _N and CL _{N + 1} is maintained.

Hereinafter, the (N + 2) th cell, (N + 3)
For the second cell and the like, the same processing as in steps S21 to S25 is repeated to obtain the cell level of each cell of the information recording medium 3 in which the cell of the four-valued mark is recorded every two cells. The cell level data e of 3 bits of each cell is converted into an 8-bit data string by omitting the least significant bit of the 4-level cell by the cell data conversion means 14.
It becomes the reproduction information g.

By the above-described reproduction processing, even if a cell is reproduced by mistake due to a defect or the like, the cell can be reproduced without causing a chain of errors.

A fourth embodiment of the present invention will be described with reference to FIGS. The present embodiment utilizes the first principle, the second principle, and the fourth principle.
In the information recording medium 3, as in the case shown in FIG. 1, quaternary mark cells are recorded every three cells.
Further, the configuration of the information recording / reproducing apparatus is the same as that shown in FIG. 7, and the configuration of the multi-value level determination means 13B is the same as that shown in FIG.
However, in the multi-value level determination means 13B of the present embodiment, the table RAM 35 has a front table area (addresses 0 to 8191) and a four-value table area (addresses 8192 to 9215) as shown in FIG. Rear table area (address 92
16-17407). That is, the table R shown in FIG. 13B is stored in the table RAM shown in FIG.
It is configured to combine AM.

With such a configuration, an example of the information reproducing process of the present embodiment will be described with reference to the transition diagram shown in FIG. 21 and the flowchart shown in FIG. Information recording medium 3
As shown in FIG. 21, the recording of the multi-valued information into the four-valued mark is performed for every three cells (FIG. 6A in which the least significant bit is fixed to 0).
Method) is recorded. This flow chart of cell level detection reads a cell of a 4-level mark by a 4-level table and a cell of an 8-level mark immediately after the 4-level mark cell by a front table based on the cell-level data of the 4-level mark. And 8 immediately before the cell of the 4-level mark
The cell of the value mark is constructed by reading out the table based on the 4-level cell data.

First, the digital data SL _N of the cell of the _Nth octal mark is read (S31), and the cell level data CL _N thereof is SL _N and the known reproduction level CL _N-1 immediately before the head of the information recording. Table R shown in FIG.
Obtained from the previous table area in the AM 35 and output (S3
2). Subsequently, the digital data SL _{N + 1} of the cell of the (N + 1) th octal mark is read (S33), and the digital data SL _{N + 1} is stored in the digital data holding means 33.
The digital data SL _{N + 2 of} the (N + 2) th cell is read while being held at (S34). Where (N +
Since the 2) -th cell is a 4-value mark cell, only the digital data SL _{N + 2} obtained by the reproduction signal is used alone to refer to the 4-value table area in the table RAM 35 shown in FIG. Then, the 4-level cell level data CL _{N + 2} is read out and held in the data RAM 36 (S35). After this calculation processing,
It is held in the digital data holding means 33 (N +
1) Digital data SL _{N + 1} and data R of the _1st cell
Based on the determined cell level data CL _{N + 2} stored in the AM 36, the calculating means 38 refers to the rear table area in the table RAM 35 shown in FIG.
The cell level data CL _{N + 1} of the value is read out and output under the control of the sequencer 37 (S36). Subsequently, under the control of the sequencer 37, the 4-level cell level data CL _{N + 2} of the (N + 2) th cell stored in the data RAM 36 is output (S37). As a result, the output order of the cell level data CL _{N + 1} and CL _{N + 2} is maintained.

Hereinafter, the (N + 3) th cell, (N + 4)
For the second cell and the like, the same processing as in steps S31 to S37 is repeated to obtain the cell level of each cell of the information recording medium 3 in which the cell of the four-valued mark is recorded every three cells. The cell level data e of 3 bits of each cell is converted into an 8-bit data string by omitting the least significant bit of the 4-level cell by the cell data conversion means 14.
It becomes the reproduction information g.

By the above reproduction processing, even if a cell is reproduced by mistake due to a defect or the like, the cell can be reproduced without causing a chain of errors.

The fifth embodiment of the present invention will be described with reference to FIGS. This embodiment utilizes the first principle, the second principle, the third principle, and the fourth principle. It is assumed that the information recording medium 3 has four-valued mark cells recorded every four cells (see FIG. 24).
Further, the configuration of the information recording / reproducing apparatus is the same as that shown in FIG. 7, and the configuration of the multi-value level determination means 13B is the same as that shown in FIG.
However, in the multi-value level determination means 13B of the present embodiment, the table RAM 35 has a front table area (addresses 0 to 8191) and a four-value table area (addresses 8192 to 9215) as shown in FIG. Rear table area (address 92
16 to 17407) and front and back table area (address 17408 to 8294)
3) and are composed of. That is, the table RAM shown in FIG. 9 is combined with the table RAM shown in FIG. 13B and the table RAM shown in FIG.

With such a configuration, an example of the information reproducing process of the present embodiment will be described with reference to the transition diagram shown in FIG. 24 and the flowchart shown in FIG. Information recording medium 3
As shown in FIG. 24, the multi-valued information is recorded in the four-valued mark every four cells (the least significant bit is fixed to 0 in FIG. 6A).
Method) is recorded. This flow chart of cell level detection reads a cell of a 4-level mark by a 4-level table and a cell of an 8-level mark immediately after the 4-level mark cell by a front table based on the cell-level data of the 4-level mark. And 8 immediately before the cell of the 4-level mark
The value mark cell was read based on the 4-value cell data by the table, and the second 8-value mark cell (cells not adjacent to the 4-value mark cell) from the 4-value cell was read by the front table. It consists of reading from the preceding and following tables based on both the cell data and the cell data read from the subsequent table. Here, as shown in FIG. 24, the case where there is a cell with a quaternary mark in the fourth cell from the beginning will be described.

First, the digital data SL _N of the cell of the _Nth octal mark is read (S41), and the cell level data CL _N thereof is SL _N and the known reproduction level CL _N-1 immediately before the head of the information recording. 23 based on the table RAM
It is determined from the previous table area in 35 (S42). The Nth cell level determined by this process is the data RAM
It is stored in S36 (S43) and is used for address generation when reproducing the next (N + 1) th cell. Continuing,
Digital data SL _{N + 1} , SL _{N + 2} , SL of the (N + 1) th, (N + 2) th, and (N + 3) th cells
_{N + 3} is sequentially read (S44, S45, S46). The digital data SL _{N + 1} is held in the digital data holding means 34, and the digital data SL _{N + 2} is held in the digital data holding means 33. here,
Since the (N + 3) th cell is a 4-valued mark cell,
This digital data SL _{N + 3} obtained by the reproduction signal
23, the arithmetic means 38 refers to the 4-value table area in the table RAM 35 shown in FIG. 23 to read the 4-value cell level data CL _{N + 3} , and
The data is stored in the data RAM 36 (S47).

After this processing, digital data holding means 33
It refers to the table area after the table RAM35 shown in FIG. 23 in the calculation unit 38 based on the cell level data CL N _{+ 3} of 4 values that are stored in the data RAM36 digital data SL N _{+ 2} held in this determination has been to Cell level data CL of the (N + 2) th cell
_{N + 2} is read out and stored in the data RAM 36 (S48).

Next, the cell level data CL stored in the data RAM 36 after being judged as the digital data SL _{N +1} held in the digital data holding means 34.
23 in the calculation means 38 based on _N , CL _{N + 2} .
Cell level data CL _{N of the} (N + 1) th cell with reference to the front and rear table areas in the table RAM 35 shown in FIG.
₊₁ is read and output as it is (S49). Then, under the control of the sequencer 37, the cell level data CL _{N + 2} of the (N + 2) th cell stored in the data RAM 36 is output (S50), and the cell level data CL _{N + 3} of the (N + 3) th cell is output ( S5
1). As a result, the cell level data CL _{N + 1} , CL
The output order of _{N + 2} and CL _{N + 3} is maintained.

Hereinafter, the (N + 4) th cell, (N + 5)
For the second cell and the like, the same processing as in steps S41 to S51 is repeated to obtain the cell level of each cell of the information recording medium 3 in which the cell of the four-valued mark is recorded every four cells. The cell level data e of 3 bits of each cell is converted into an 8-bit data string by omitting the least significant bit of the 4-level cell by the cell data conversion means 14.
It becomes the reproduction information g.

By the above-described reproduction processing, even if a cell is reproduced by mistake due to a defect or the like, the cell can be reproduced without causing a chain of errors.

Incidentally, in these embodiments, the case where the information recording medium 3 using the phase change film as a recording / erasable recording material is used has been described as an example, but as described above in the section of the principle of the invention. It can also be applied to an information recording medium for recording on an information recording film made of a magneto-optical material. Further, the present invention is not limited to the rewritable system example using a recording / erasable recording material, but can be applied to a write-once type system using an organic dye or a metal film, which is a recording-only (non-erasable) recording material. . Furthermore, if it is limited to information reproduction,
It is also applicable to a reproduction-only system in which a multi-valued information mark is formed with phase pits having a plurality of depths, for example.

[0105]

According to the first aspect of the present invention, there is provided an information recording method for recording a mark representing multi-valued information for each cell of an information recording medium, wherein an N-valued mark (N is an integer of 3 or more). 1 for the M-value mark (M is an integer less than N) for the cell
Since I tried to record each cell for every predetermined number of cells,
At the time of reproduction, at least the level judgment of the M-value mark can be performed without error, and it is possible to provide an information recording method in which the reliability of reproduction of multi-valued information is improved as compared with the case of recording uniformly with the N-value mark. .

According to the second aspect of the invention, in the information recording method according to the first aspect, when N is N = 2 ^T representing T-bit data, M has a least significant bit of 0 in the T-bit data. Alternatively, a value of M = 2 ^T-1 representing (T-1) bit data fixed to ¹ , for example, N = 8 values, M =
Since it is set as 4 values and the level of the N-value mark is thinned, the N-value mark and the M-value mark can be recorded under a common mark system, and the M-value mark can be recorded. It is possible to provide an information recording method capable of making the mark level determination more accurately.

According to the third aspect of the invention, an information recording medium in which a mark representing multi-valued information is recorded for each cell, and for a cell of an N-value mark (N is an integer of 3 or more),
Since one cell of the M-value mark (M is an integer smaller than N) is recorded for each predetermined number of cells, at least the level of the M-value mark can be determined without error during reproduction. It is possible to provide an information recording medium in which the reliability of reproduction of multivalued information is improved as compared with the case of uniform recording.

According to the fourth aspect of the invention, in the information recording medium of the third aspect, when N is N = 2 ^T representing T bit data, M has a least significant bit of 0 in the T bit data. Alternatively, a value of M = 2 ^T-1 representing (T-1) bit data fixed to ¹ , for example, N = 8 values, M =
Since the mark is set to have four values and has a level thinned out from the N-value mark, it is possible to provide an information recording medium capable of more accurately determining the level of the M-value mark.

According to the invention of claim 5, the effect of the invention of claim 3 or 4 can be obtained with respect to an information recording medium having an information recording film made of a phase change material capable of recording and erasing.

According to the invention of claim 6, it is possible to obtain the effect of the invention of claim 3 or 4 with respect to an information recording medium having an information recording film of a recordable and erasable magneto-optical material.

According to the invention of claim 7, the effect of the invention of claim 3 or 4 can be obtained with respect to an information recording medium having an information recording film of a recordable dye material.

According to the invention described in claim 8, the effect of the invention described in claim 3 or 4 can be obtained with respect to the information recording medium having the information recording film of the recordable metal film.

According to the ninth aspect of the present invention, there is provided an information recording device for recording a mark representing multi-valued information for each cell of an information recording medium, wherein input information is stored in a predetermined number of N-value cell level data (N: Multi-value level conversion means for converting into 3 or more integer) and one M-value cell level data (M is an integer smaller than N), and N converted by this multi-value level conversion means.
An N-value mark and an M-value mark respectively corresponding to the value-cell level data and the M-value cell level data are set such that one cell of the M-value mark corresponds to a predetermined number of cells with respect to the cell of the N-value mark. Recording means for recording, the level judgment of at least the M-value mark can be performed without error during reproduction, and the reliability of reproduction of multi-valued information is higher than that in the case of recording uniformly with N-value marks. An improved information recording device can be provided.

According to the invention of claim 10, claim 9 is provided.
The information recording apparatus according, when the N = 2 ^T representing the T bit data N, M represents T least significant bits in the data is fixed to 0 or 1 (T-1) bit data M = 2 ^T−1 , for example N = 8 values, M
= 4 values, and the mark is a level thinned out from the N-value mark, so that the N-value mark and the M-value mark can be recorded under a common mark system, and M It is possible to provide an information recording device capable of more accurately determining the level of a value mark.

According to the eleventh aspect of the present invention, a mark representing multi-valued information is recorded for each cell, and the multi-valued information is reproduced from the reproduction signal of the information recording medium according to any one of the third to eighth aspects. An information reproducing method for determining a value level, wherein the number of multi-level determination levels of the cell is changed from N value to M for every predetermined number of cells.
Since the multilevel level of the target cell of interest is determined by switching to the value, it is possible to provide an information reproducing method capable of performing at least the level determination of the M-value mark without error.

According to the invention of claim 12, claim 1
In the information reproducing method described in 1, the number of multi-value determination levels is
Since the multi-valued level of the M-value mark to be used as a value is determined based on the reproduction signal of the target cell alone, the M-value mark whose level number is lower than that of the N-value mark is set to the target cell alone. The level can be uniquely determined based on the reproduction signal.

According to the invention of claim 13, claim 1
In the information reproducing method described in 2, the multi-level level judgment is performed for the N-value mark based on the judgment standard set by referring to the level judgment value of the preceding cell. Even if the level is affected by the preceding cell, it is possible to prevent an error in the level determination, and for the M value mark for each predetermined number of cells, the level determination can be performed without error based on a single cell. It is also possible to prevent the determination error from propagating for each M-value mark, and it is possible to provide an information reproducing method capable of preventing a chain of reading errors.

According to the invention of claim 14, claim 1
In the information reproducing method described in 2, the multi-level level judgment is performed for the N-value mark based on the judgment criterion set by referring to the level judgment value of the continuing cell, so that the reproduction signal output level of the target cell is It is possible to prevent an error in the level judgment even when affected by a continuing cell, and for the M value mark for each predetermined number of cells, the level judgment can be performed without error based on a single cell. Can be prevented for each M-value mark, and an information reproducing method capable of preventing a chain of reading errors can be provided.

According to the invention of claim 15, claim 1
In the information reproducing method described in 2, the multi-level level judgment is performed for the N-value mark based on the judgment criterion set by referring to the level judgment values of the preceding cell and the continuing cell, and thereby the reproduced signal of the target cell is obtained. Even when the output level is affected by the preceding cell and the continuing cell, it is possible to prevent the error in the level determination, and for the M value mark for each predetermined number of cells, the level determination can be performed without error based on the single cell. It is possible to prevent propagation of a level judgment error due to a defect or the like for each M-value mark, and it is possible to provide an information reproducing method capable of preventing a chain of reading errors.

According to the invention of claim 16, claim 1
In the information reproducing method described in 2, when the predetermined number of cells in which the M-value mark is every 3 cells = 3, the preceding cell adjacent to the M-value mark with respect to the N-value mark and the succeeding cell adjacent to the M-value mark are adjacent cells. Since it has, and by referring to the level judgment value of each adjacent preceding cell or continuation cell,
It is possible to provide an information reproducing method capable of making more appropriate level determination with few errors.

According to the invention of claim 17, claim 1
In the information reproducing method described in 2, when the M-value mark has a predetermined number of cells ≧ 4, the N-value mark has N preceding cells that are adjacent to each other by an M-value mark and N consecutive cells that are adjacent to each other by an M-value mark. For the value mark cell, the level judgment value of the adjacent preceding cell or the continuing cell is referred to, and for the intermediate N value mark cell that is not adjacent to the M value mark cell, the preceding cell and the continuation of the cell are continued. By referring to the level determination value of the continuation cell, it is possible to provide an information reproducing method capable of performing more appropriate level determination with few errors.

According to the eighteenth aspect of the present invention, a mark representing multi-valued information is recorded for each cell, and the multi-valued information of the multi-valued information is reproduced from the reproduction signal of the information recording medium according to any one of the third to eighth aspects. An information reproducing apparatus for judging a value level, comprising: an A / D converting means for converting the reproduced signal into digital data; and a multi-level judging level number of the cell for every predetermined number of cells.
A multi-value level determining means for determining the multi-value level of the N-value or the M-value for the digital data of the target cell by switching from the value to the M-value, and the multi-value level determining means determines the multi-value of the cell. By changing the number of levels from the N value to the M value for each predetermined number of cells to judge the multi-valued level of the target cell of interest, at least the level of the M value mark can be judged without error. Can be provided.

According to the invention of claim 19, claim 1
8. In the information reproducing apparatus described in 8, the multi-value level determination means performs the multi-value level determination of an M-value mark whose multi-value determination level number is M value based on the digital data of the target cell alone. Therefore, the level of the M-value mark whose number of levels is lower than that of the N-value mark can be uniquely determined based on the reproduction signal of the cell of interest alone.

According to the invention of claim 20, claim 1
In the information reproducing apparatus described in 9, the multi-level level determination means performs multi-level level determination on the N-value mark based on the determination standard set with reference to the level determination value of the preceding cell, thereby the target cell Even if the reproduction signal output level of 1 is affected by the preceding cell, it is possible to prevent an error in the level determination, and for the M value mark for each predetermined number of cells, the level determination can be performed without error based on a single cell. It is possible to prevent propagation of a level determination error due to a defect or the like for each M-value mark, and it is possible to provide an information reproducing apparatus capable of preventing a chain of reading errors.

According to the invention of claim 21, claim 1
9. In the information reproducing apparatus described in 9, the multi-level level determination means performs multi-level level determination on the N-value mark based on the determination standard set by referring to the level determination value of the continuing cell, thereby the target cell Since it is possible to prevent an error in the level determination even when the reproduction signal output level of is affected by the continued cells, and for the M value mark for each predetermined number of cells, the level determination can be performed without error based on a single cell. It is possible to prevent propagation of a level determination error due to a defect or the like for each M-value mark, and it is possible to provide an information reproducing apparatus capable of preventing a chain of reading errors.

According to the invention of claim 22, claim 1
In the information reproducing apparatus described in 9, the multi-level level determination means performs multi-level level determination on the N-value mark based on the determination standard set with reference to the level determination values of the preceding cell and the continuing cell, Even when the reproduction signal output level of the target cell is affected by the preceding cell and the continuing cell, it is possible to prevent an error in the level determination, and regarding the M-value mark for each predetermined number of cells, the level determination is performed as a single cell. Since it can be performed without error based on this, it is possible to prevent propagation of a level determination error due to a defect or the like for each M-value mark, and it is possible to provide an information reproducing apparatus capable of preventing a chain of reading errors.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a mark shape, a reproduction signal, etc. showing an example of an information recording / reproducing system for explaining the principle of an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a level change of a target cell due to the influence of front and rear cells.

FIG. 3 is a characteristic diagram showing a level change of a cell of interest according to a level of a preceding cell.

FIG. 4 is a characteristic diagram showing a level change of a target cell according to a level of a continuing cell.

FIG. 5 is a characteristic diagram showing a level change of a target cell according to levels of a preceding cell and a continuing cell.

FIG. 6 is a characteristic diagram showing a case of four values.

FIG. 7 is a block configuration diagram showing an information recording / reproducing apparatus of a first embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration example of the multi-value level determination means.

FIG. 9 is an explanatory diagram showing an example of data in a table RAM.

FIG. 10 is a transition diagram illustrating a processing example.

FIG. 11 is a flowchart illustrating a processing example.

FIG. 12 is a block diagram showing a configuration example of multi-value level determination means according to a second embodiment of the present invention.

FIG. 13 is an explanatory diagram showing an example of data in a table RAM.

FIG. 14 is a transition diagram illustrating a processing example.

FIG. 15 is a flowchart illustrating a processing example.

FIG. 16 is a block diagram showing a configuration example of multi-value level determination means according to a third embodiment of the present invention.

FIG. 17 is an explanatory diagram showing an example of data in a table RAM.

FIG. 18 is a transition diagram illustrating a processing example.

FIG. 19 is a flowchart illustrating a processing example.

FIG. 20 is a table RAM according to the fourth embodiment of this invention.
It is explanatory drawing which shows the example of data.

FIG. 21 is a transition diagram showing a processing example.

FIG. 22 is a flowchart showing a processing example.

FIG. 23 is a table RAM according to the fifth embodiment of the present invention.
It is explanatory drawing which shows the example of data.

FIG. 24 is a transition diagram showing a processing example.

FIG. 25 is a flowchart illustrating a processing example.

[Explanation of symbols]

1 cell 3 Information recording medium 11 A / D conversion means 13, 13A, 13B multi-level level determination means 15 Multilevel conversion means 16, 17 Recording means 19 level judgment value holding means 22 Digital data holding means 23 Continuation cell level calculation means 24 level judgment value holding means 33 Digital data holding means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 20/10 301 G11B 20/10 301Z 20/12 20/12 (72) Inventor Akihiko Shimizu Ota-ku, Tokyo Nakamagome 1-chome 3-6 F-term in Ricoh Co., Ltd. (reference) 5D029 JA01 JA04 JB11 JC09 5D044 BC04 CC04 DE11 EF10 FG30 5D090 AA01 BB05 BB07 BB10 CC01 CC04 DD01 DD05 EE13 FF12 GG11

Claims (22)

[Claims] 1. An information recording method for recording a mark representing multi-valued information for each cell of an information recording medium, wherein an M-value mark (M Is an integer smaller than N), and one cell of a predetermined number of cells is recorded. Wherein when the N was N = 2 ^T representing the T bit data, M is M = 2 representing the least significant bit in the T-bit data is fixed to 0 or 1 (T-1) bit data
The information recording method according to claim ^{1, wherein the} value is set to ^T-1 . 3. An information recording medium in which a mark representing multi-valued information is recorded for each cell, and an M-value mark (M is greater than N) for an N-value mark (N is an integer of 3 or more) cell. An information recording medium in which one (small integer) cell is recorded for each predetermined number of cells. Wherein when the N was N = 2 ^T representing the T bit data, M is the least significant bit in the T-bit data is fixed to 0 or 1 (T-1) represents a bit data M = 2
The information recording medium according to claim 3, wherein the value is set to ^T-1 . 5. The information recording medium according to claim 3, wherein the N-value mark and the M-value mark are recorded on an information recording film made of a recordable and erasable phase change material. 6. The information recording medium according to claim 3, wherein the N-value mark and the M-value mark are recorded on an information recording film made of a recordable and erasable magneto-optical material. 7. The information recording medium according to claim 3, wherein the N-value mark and the M-value mark are recorded on an information recording film made of a recordable organic dye. 8. The information recording medium according to claim 3, wherein the N-value mark and the M-value mark are recorded on an information recording film made of a recordable metal film. 9. An information recording apparatus for recording a mark representing multi-valued information for each cell of an information recording medium, wherein input information is a predetermined number of N-value cell level data (N is an integer of 3 or more) and one. Corresponding to the M-value cell level data (M is an integer smaller than N) and the N-value cell level data and the M-value cell level data converted by the multi-value level converting means. The N-value mark and the M-value mark that are
An information recording apparatus comprising: a recording unit that records one cell of the value mark so that each cell has a predetermined number of cells. 10. When the N was N = 2 ^T representing the T bit data, M is the least significant bit in the T-bit data is fixed to 0 or 1 (T-1) represents a bit data M = 2
The information recording apparatus according to claim 9, wherein the value is set to ^T-1 . 11. An information reproducing method for judging a multi-level of the multi-valued information from a reproduced signal of the information recording medium according to claim 3, wherein a mark representing the multi-valued information is recorded for each cell. An information reproducing method, wherein the multi-level determination level number of the cell is switched from an N value to an M value for each predetermined number of cells to determine the multi-level level of a target cell of interest. 12. The information reproducing method according to claim 11, wherein the multi-valued level judgment of the M-value mark in which the number of multi-valued judgment levels is M value is performed based on the reproduction signal of the target cell alone. 13. A multi-valued level judgment of an N-valued mark whose multi-valued judgment level number is an N value is performed based on a judgment standard set by referring to a level judgment value of a preceding cell preceding the target cell. 13. The information reproducing method according to claim 12, wherein. 14. The multi-valued level judgment of an N-valued mark having a multi-valued judgment level number as an N value is performed based on a judgment criterion set with reference to a level judgment value of a continuing cell continuing to the target cell. 13. The information reproducing method according to claim 12, wherein. 15. The multi-value level judgment of an N-value mark whose multi-value judgment level number is an N value is set by referring to the level judgment values of the preceding cell preceding the target cell and the continuing cell to be continued. 13. The method according to claim 12, which is performed based on a criterion.
Information reproduction method described. 16. When the predetermined number of cells = 3, the multi-value level judgment of the N-value mark in which the multi-value judgment level number is N value is performed.
The attention cell continuing to the M-value mark is determined based on the criterion set by referring to the level determination value of the preceding cell of the M-value mark preceding the attention cell, and the attention cell preceding the M-value mark is concerned. 13. The information reproducing method according to claim 12, wherein the information reproduction method is performed based on a determination standard set with reference to a level determination value of a continued cell of an M-value mark that continues to a target cell. 17. When the predetermined number of cells ≧ 4, the multi-valued level judgment of an N-valued mark in which the number of multi-valued judgment levels is N-value,
The attention cell continuing to the M-value mark is determined based on the criterion set by referring to the level determination value of the preceding cell of the M-value mark preceding the attention cell, and the attention cell preceding the M-value mark is concerned. It is performed based on the criterion set by referring to the level judgment value of the continuing cell of the M-value mark that continues to the target cell, and for the target cell that does not continue to the M-value mark, the preceding cell preceding the target cell and the continue continue 13. The information reproducing method according to claim 12, wherein the information reproduction method is performed based on a determination standard set by referring to a cell level determination value. 18. An information reproducing apparatus for determining a multi-valued level of the multi-valued information from a reproduction signal of the information recording medium according to claim 3, wherein a mark representing the multi-valued information is recorded for each cell. And A / D conversion means for converting the reproduction signal into digital data, and the multi-value determination level number of the cell is switched from an N value to an M value for each predetermined number of cells, and An information reproducing apparatus, comprising: a multi-value level determination means for determining a multi-value level of N value or M value for digital data. 19. The multi-value level determination means performs the multi-value level determination of an M-value mark in which the number of multi-value determination levels is an M value, based on the digital data of the target cell alone. Information reproduction device. 20. The multi-valued level judgment means has level judgment value holding means for holding the level judgment value of the preceding cell preceding the cell of interest, and the multi-valued judgment level number is an N value mark. 20. The information reproducing apparatus according to claim 19, wherein the multi-valued level determination is performed based on a determination standard set with reference to the level determination value of the preceding cell held in the level determination value holding means. 21. The multi-valued level determination means includes the A /
The digital data holding means holds the digital data converted by the D converting means, and the continuing cell level calculating means for calculating the multi-valued level of the continuing cell continuing to the target cell prior to the calculation of the target cell. The multi-valued level judgment of the N-value mark whose multi-valued judgment level number is the N value uses the digital data held in the digital data holding means and the continuation cell level calculation means calculates the continuation cell level. 20. The information reproducing apparatus according to claim 19, wherein the information reproducing apparatus is performed on the basis of a judgment standard set with reference to a level judgment value. 22. The multi-valued level determination means is the A /
Digital data holding means for holding the digital data converted by the D conversion means, level judgment value holding means for holding the level judgment value of the preceding cell preceding the target cell,
A multi-value of an N-valued mark having a multi-value determination level number as an N value, which has a multi-value level of the multi-value level of the continuation cell that continues to the target cell prior to the calculation of the target cell. The level judgment uses the digital data held in the digital data holding means and the level judgment value of the preceding cell held in the level judgment value holding means and the continuing cell calculated by the continuing cell level calculating means. 20. The information reproducing apparatus according to claim 19, wherein the information reproducing apparatus is performed on the basis of a judgment standard set with reference to the level judgment value of.