JPH097180A - Information recording medium, device and method for recording information - Google Patents

Abstract

PURPOSE: To prevent the length of a minimum pit from reducing unnecessarily. CONSTITUTION: The digital data are recorded by changing the front edge and the rear edge of the pit to any positions of nine stages of shift positions. Required combinations of 64 (=8×8) pieces of edges among 81 (=9×9) pieces of combinations of edges, are selected, and only the combinations are made to correspond to the real digital data. At this time, such combinations of the edges that the size of the pit becomes small, are eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, an information recording apparatus and a method, and more particularly to an information recording medium capable of recording information without reducing the minimum pit size more than necessary. The present invention relates to an information recording device and method.

[0002]

2. Description of the Related Art The applicant of the present invention is, for example, Japanese Patent Application No. 5-208.
As No. 76, it corresponds to a predetermined shift period that is shorter than the transient period of the reproduction signal defined by the transfer characteristic of the optical detection system that scans with the light beam along the pit row to obtain the reproduction signal corresponding to each pit. It was previously proposed to shift the edge position of the pit in steps within a range corresponding to the digital information to be recorded from a predetermined reference position.

That is, in the above proposal, for example, as shown in FIG. 15, the front edge (left side edge in the figure) and the rear edge (right side edge in the figure) of the pit are each numbered 0 (000). Through 7 (111) are formed at any of eight shift positions.

The pits are at regular intervals (1.67 μm)
And the step width is 0.05 μm,
If the position of the front edge and the rear edge of the pit is the edge position of number 0, the length of the pit is 0.5 μ.
m (minimum), and in the case where both edges are edges of number 7, the pit length is 1.2 μm (maximum).

That is, according to this principle, eight positions can be set by the front edge of one pit, and
Since the positions of eight edges can be taken even by the trailing edge, as shown in FIG. 16, a total of 64 (=
8 × 8) information can be recorded. In FIG. 16, the hexadecimal numbers 00 to 3f are assigned to the combined positions of 64 edges.

The recording information 00 is located at the lower left of the first position on the two-dimensional plane shown in FIG. 16, and both the front edge and the rear edge of the pit are set to the innermost position of number 0. , The smallest pit.

Next, considering where on the two-dimensional plane the pit, which is enlarged by one step to the left or right from the minimum pit size, is located,
Either the leading edge or the trailing edge
Since the pit is one step (0.05 μm) larger than the minimum pit, the pit corresponds to information number 01 or information number 08 as shown in FIG.

Similarly, if the pits are sequentially grouped into the smallest pit, 2 steps, 3 steps, 4 steps, ..., As shown in FIG. In the figure, the pits having the information numbers within the range surrounded by the common line have the same length.

As is apparent from FIG. 18, it is understood that the pits of the same size correspond to the information numbers arranged diagonally in FIG.

[0010]

In order to increase the recording capacity of the disc, it is preferable to reduce the size of the pits as much as possible. However, the smaller the pit, the more difficult it becomes to form the pit with an accurate size and shape. Therefore, in FIG.
The pit of the information number located in the lower left may have a high error rate.

On the contrary, in FIG. 18, if the recording conditions are set so that the pit corresponding to the information number located at the lower left can be read correctly (when the size of the pit is increased),
This time, in FIG. 18, the pit of the information number recorded in the upper right area becomes large and the recording capacity is reduced. Therefore, there is a problem that it is difficult to set the recording condition (pit size).

The present invention has been made in view of such circumstances, and it is an object of the present invention to realize an information recording medium having a small error rate without reducing the recording capacity.

[0013]

According to a first aspect of the present invention, there is provided an information recording medium in which a front edge of a pit is stepwise shifted to an M stage and a rear edge of the pit is stepped to an N stage. The number K of information represented by pits
The number of combinations of the shift position of the front edge of the pit and the shift position of the rear edge of the pit is set to a value smaller than MN.

An information recording apparatus according to a fourth aspect of the present invention selects K combinations smaller than the value MN from MN combinations of a shift position of a front edge of a pit and a shift position of a rear edge of a pit. , And an assigning unit that assigns the selected K combinations to the K pieces of information.

In the information recording method according to the fifth aspect, K combinations smaller than the value MN are selected from MN combinations of the shift positions of the front edge of the pit and the shift positions of the rear edge of the pit. , K selected combinations are assigned to K pieces of information.

[0016]

In the information recording medium according to the present invention, the front edge of the pit is stepwise shifted to the M step and the rear edge is stepped to the N step and is represented by one pit. The number K of pieces of information is set to a value smaller than the number MN of combinations of the shift positions of the front edge and the rear edge of the pit.

According to another aspect of the information recording apparatus of the present invention, the allocating means selects K pieces smaller than the value MN from a combination of MN pieces of shift positions of the front edge and the rear edge of the pit. And the selected K combinations are assigned to the K information.

In the information recording method according to the fifth aspect, K combinations smaller than the value MN are selected from MN combinations of the shift position of the front edge of the pit and the shift position of the rear edge of the pit. Then, the selected K combinations are assigned to the K information.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when the front edge of a pit is stepwise shifted in M steps and the rear edge is stepwise shifted in N steps, the number K of information represented by one pit is K. Is set to a value smaller than the number MN of combinations of the shift position of the front edge of the pit and the shift position of the rear edge of the pit.

For example, as described with reference to FIGS. 15 and 16, when one pit represents 64 pieces (K pieces) of information, as shown in FIG. 1, the shift position of the front edge of the pit is shown. Is 9 (M), and the number of rear edge shift positions is 9 (N). This gives M
K (= 64) is set to a smaller value than N (= 81).

That is, in the present invention, as shown in FIG. 1, the front edge and the rear edge of the pit are stepwise changed to the positions of 9 steps indicated by the numbers 0 to 8. As a result, there are 81 (= 9 × 9) combinations of edge positions, as shown in FIG.

Since it is sufficient to record 6-bit information in one pit, there are 64 combinations of edge positions that are actually used. Therefore, 64 combinations are selected from 81 combinations. At this time, as shown in FIG. 3, a combination in which the pit size becomes small is excluded (a combination in the lower left direction in FIG. 3 is excluded), and a combination in which the pit size becomes as large as possible (a combination in the upper right direction in the figure). ) Should be adopted. In the embodiment of FIG. 3, the lower left 15 and the upper right 2 are excluded.

FIG. 4 shows an example of the structure of a recording device for recording a disc having the above-described format. In this embodiment, the record information from the information source 1 is input to the error correction circuit 2, and the error correction code using the Reed-Solomon code is added as in the case of a normal optical disc. This allows
Similar to the case of a normal compact disc, redundancy is added in advance so that data can be read correctly even if a part of the playback signal is lost due to a disc defect. To be done. In general, since this error correction code is calculated in units of 8 bits, the output of this error correction circuit 2 is also in units of 8 bits.

However, as described above, in this embodiment, since 6-bit information corresponds to one pit, the bit number conversion circuit 3 converts the bit unit from 8 bits to 6 bits. Processing is performed.

That is, for example, three pieces of 8-bit information are collected and stored in a register as a total of 24-bit information, and the 24-bit information stored in this register is divided into four pieces of 6-bit information. Output.

The 6-bit unit data output from the bit number conversion circuit 3 is input to the mapping circuit 4 and is mapped. This mapping will be described later with reference to FIG. 5, but 6-bit data is converted into 4-bit data for each of the first half and the second half of the pit. This 4-bit data defines the shift positions of the front edge and the rear edge of one pit, respectively.

The 8-bit data output from the mapping circuit 4 is input to the edge modulation circuit 8 via the data selector switch 5. The data selector switch 5 also fetches fixed pattern data as a reference signal generated by the fixed pattern generation circuit 6 and supplies it to the edge modulation circuit 8. The fixed pattern generated by the fixed pattern generation circuit 6 is a pattern for eliminating bias fluctuation, a pattern for automatic gain control (AGC), and a pattern for synchronous clock. The timing controller 7 switches the data selector switch 5 to the fixed pattern generation circuit 6 side at a preset fixed cycle, and supplies the fixed pattern to the edge modulation circuit 8 at a fixed cycle. .

The edge modulation circuit 8 modulates the input data by a predetermined modulation method and outputs it to a mastering machine (not shown).

Next, the operation will be described. The digital data output from the information source 1 is added with an error correction code by the error correction circuit 2 and then input to the bit number conversion circuit 3 in units of 8 bits. The bit number conversion circuit 3 converts the 8-bit unit data into 6-bit unit data and outputs the data to the mapping circuit 4. Mapping circuit 4
Generates 8-bit data corresponding to the combination shown in FIG. 3 from the input 6-bit data.

That is, as described with reference to FIG. 1, in the case of this embodiment, the front edge and the rear edge of the pit are changed to any of the nine shift positions indicated by the numbers 0 to 8. To do. Since 4 bits are required to represent 9 levels of information, in this mapping circuit 4,
6-bit data is converted to 8-bit (= 4 + 4) data. Specifically, the mapping circuit 4 is composed of a ROM, and when 6-bit data is input, it outputs 8-bit data corresponding thereto.

FIG. 5 shows an embodiment of mapping for converting this 6-bit data into 8-bit data.
In the figure, points represented by 64 hexadecimal information numbers 00 to 3f correspond to 6-bit data, and the numbers on the horizontal and vertical axes of each point indicate the pits corresponding to the information points. 4 representing the shift position of the front edge and the rear edge of the
It is bit data.

For example, as shown in FIG. 6A, when the 6-bit data is '111111' (3f in hexadecimal), the front edge is the shift position of number 8 (1000), The rear edge is also set to the shift position of number 8 (1000). Therefore, in this case, 8-bit data '10' is added to 6-bit data '11111'.
001000 'will be output.

Further, as shown in FIG. 6B, 6-bit data is '000011' (03 in hexadecimal).
If is input, the shift position of the front edge is the number 8
The shift position of the rear edge is the shift position of number 0 (0000). That is, 8-bit data "10000000" is output with respect to 6-bit data "000011".

In the mapping circuit 4, 8
The data converted into data in units of bits is input to the edge modulation circuit 8.

Further, instead of the data corresponding to the recording information supplied from the mapping circuit 4, the fixed pattern data output from the fixed pattern generation circuit 6 is input to the edge modulation circuit 8 at a constant cycle. . Edge modulation circuit 8
Modulates the input data by a predetermined method and supplies the data to the mastering machine.

In the mastering machine, the master is cut according to the data input from the edge modulation circuit 8. Then, this master is developed to form pits, and then the surface is plated to form a stamper. Then, a large number of replica disks are created from this stamper. Then, on the surface of this replica disc, pit rows formed according to the above-mentioned principle are formed.

Since the pit size formed at this time can be increased to some extent, it is accurately transferred to the replica disc.

The disc (optical disc) formed as described above is reproduced by a reproducing device as shown in FIG. In this embodiment, the optical disk 21 formed as described above is rotated by the spindle motor 22 at a predetermined speed. The optical head 23 irradiates the optical disc 21 with laser light and reproduces the information recorded on the optical disc 21 from the reflected light. The APC circuit 24 controls a laser diode (not shown) incorporated in the optical head 23 so that the intensity of the laser beam output from the APC circuit 24 becomes constant.

Focus tracking servo circuit 25
In accordance with the focus error signal and the tracking error signal output from the optical head 23, the focus control of the objective lens (not shown) incorporated in the optical head 23 and the tracking control are performed.

The RF signal which the optical head 23 reproduces and outputs the information recorded on the optical disk 21 is supplied to the A / D converter 28, the PLL circuit 35 and the spindle servo circuit 26 via the head amplifier 27. It is designed to be. The spindle servo circuit 26 receives the input R
The jitter component of the optical disk 21 is detected from the F signal, and the spindle motor 22 is controlled so that the rotation speed of the optical disk 21 becomes a predetermined speed. In addition, the PLL circuit 3
Reference numeral 5 generates a clock from the input RF signal and outputs it to each circuit.

The A / D converter 28 A / D-converts the RF signal input from the head amplifier 27 and converts the RF signal into digital data in units of 8 bits.
It is output to 9. The bias fluctuation removing circuit 29 outputs data to which the bias fluctuation component is removed based on the reference signal included in the fixed pattern described above to the AGC circuit 30. The AGC circuit 30 removes the gain fluctuation component based on the reference signal included in the fixed pattern. The details of the bias variation removing circuit 29 and the AGC circuit 30 are disclosed in, for example, Japanese Patent Application No. 5-20876 mentioned above.

The equalizer 31 removes the intersymbol interference component of the data input from the AGC circuit 30 and samples the signal V _X obtained by sampling the leading edge of the pit and the signal obtained by sampling the trailing edge. Two V _Y are output to the decoding map circuit 32 as a pair of signals. In the decoding map circuit 32, the reproduction point is developed on the two-dimensional plane with the value of V _X as the X axis and the value of V _Y as the Y axis. Then, the area to which this reproduction point belongs is determined and decoding is performed.
The decoding map circuit 32 outputs the input 8-bit data as 6-bit decoded data. The processing of this decoding map will be described later with reference to FIG.

The output of the decoding map circuit 32 is input to the bit number conversion circuit 33, and the bit number conversion circuit 33 converts the input 6-bit data into 8-bit data. That is, contrary to the case of the bit number conversion circuit 3 in FIG. 4, four sets of 6-bit data are stored, and the stored total 24-bit data is output as three sets of 8-bit data. The error correction circuit 34 corrects an error in the data input from the bit number conversion circuit 33 and outputs it to a circuit (not shown).

The controller 36 including a CPU is
The respective circuits described above are controlled to execute the reproducing operation.

Next, the operation will be described. When instructed to start reproduction, the controller 36 controls the spindle servo circuit 26 and drives the spindle motor 22 to rotate the optical disk 21 at a predetermined speed. Also, by controlling the focus tracking servo circuit 25,
Execute focus control and tracking control. AP
The C circuit 24 applies servo so that the intensity of the laser light output from the optical head 23 is constant.

In this way, the optical head 23 irradiates the optical disc 21 with laser light, receives the reflected light, and outputs the RF corresponding to the recorded information recorded on the optical disc 21.
Output a signal. The head amplifier 27 amplifies this RF signal and supplies it to the PLL circuit 35. PLL circuit 35
Generates a synchronous clock from the input RF signal and outputs it to each circuit.

The A / D converter 28 A / D converts the RF signal input from the head amplifier 27, and outputs it to the bias fluctuation eliminating circuit 29 as 8-bit digital data. The bias fluctuation removing circuit 29 removes the bias fluctuation component from the input data and outputs it to the AGC circuit 30. The AGC circuit 30 removes the gain fluctuation component of the input data and outputs it to the equalizer 31.

After removing the inter-symbol interference component from the input 8-bit data, the equalizer 31 sets the reproduction data of the front edge of the pit as V _X and the reproduction data from the rear edge of the pit as V _Y. The data is output to the decoding map 32.

The decoding map 32 is composed of, for example, a ROM, and has 8-bit data V _X and 8-bit data V _Y.
The 6-bit data defined by is read and output.

That is, the decoding map circuit 32 stores the table shown in FIG. 8 in the built-in ROM.
When the data V _X and V _Y are input, the data V _X
Corresponding to the value of, the coordinate value of the horizontal axis in FIG. 8 is determined,
The coordinate value of the vertical axis in FIG. 8 is determined corresponding to the data V _Y. Then, the data corresponding to the information points in the area to which the reproduction point defined by the horizontal axis and the vertical axis belongs is output. In other words, assuming that the coordinates of the reproduction point are the data corresponding to the closest information point, 6-bit data of the information point is output.

For example, when the reproduction point defined by the data V _X and V _Y is closest to the information number 19, 6-bit data '011001' is output.

The 6-bit unit data output from the decoding map circuit 32 is input to the bit number conversion circuit 33,
It is converted into 8-bit data and input to the error correction circuit 34. The error correction circuit 34 corrects an error in the input data and outputs it.

As described above, since the size of the minimum pit can be prevented from being made smaller than necessary (to some extent), the minimum pit can be accurately formed and read without error. become.

By the way, as described above, the desired 64 combinations are not selected from the 91 combinations, but, for example, as shown in FIG. The shift positions of the front edge and the rear edge can be left at eight levels and the basic pit length of number 0 can be increased.

For example, as shown in FIG. 9, the minimum pit size that can be recorded on the disc is as follows.
It is assumed to be 0.5 μm. Further, in order to prevent interference with adjacent pits, the maximum pit size is also limited, and its value is 1.3 μm.

In this case, as shown in FIG. 9, when the front edge and the rear edge of the pit are changed to eight shift positions, the one-step change width Δ1 is 0. It becomes 057 μm. Δ1 = (1.3−0.5) / (2 × 7) = 0.057μ
m

On the other hand, as shown in FIG. 10, the front edge and the rear edge of one pit are each shifted to any of nine stages, and
When the desired 64 combinations are selected from the one combination, the combination of the edges of the minimum pits is shown in FIG.
As shown in FIG. 5, for example, the front edge is the shift position of number 5 and the rear edge is the shift position of number 0 (hereinafter, this combination is represented as (5,0)).

Since this (5,0) pit is the minimum pit, its length may be set to 0.5 μm. From this minimum pit of (5, 0), the position shifted leftward (forward) in three steps in FIG. 10 becomes the edge of the front edge number 8, and the rear edge (the right edge in FIG. 10) is moved to the right (to the rear). The maximum pit is a pit that is shifted by 8 steps (shift position of number 8), that is, a pit that is increased by 11 steps in total. Therefore, the length of this pit should be 1.3 μm.

From the above, as shown in FIG. 10, the width Δ2 of one step in this case is 0.073 μm as expressed by the following equation. Δ2 = (1.3−0.5) / (3 + 8) = 0.073μ
m

The step width Δ obtained as described above
Comparing 1 and Δ2, Δ2 is obviously larger. In this way, when the size of the minimum pit and the maximum pit is limited, the step width can be made larger, so that the signal-to-noise ratio becomes good and a noise-resistant information recording medium can be realized. it can.

Therefore, the step width Δ2 is set to the step width Δ
If the value may be the same as 1, the minimum pit size can be made larger than 0.5 μm or the maximum pit size can be made smaller than 1.3 μm.

Naturally, similar results can be obtained even when the maximum pit length is 1.3 μm and the minimum pit is a value other than 0.5 μm.

As described above, in the case of the above-mentioned embodiment, although there are a total of 81 combinations of edges of one pit, only 64 combinations actually appear in the data, and the rest. 17 kinds of combination of
Not used as data. Therefore, one of the 17 types of combinations, which is not used as substantial data, can be used for recording information such as a synchronization pattern.

FIG. 11 shows an embodiment in this case. That is, in this embodiment, the combination of the edge positions of (1, 1) is the synchronization pattern.

FIG. 12 shows an example of the structure of a recording device for recording such a synchronization pattern. In this embodiment, a sync pattern generation circuit 51 is provided, and the data selector switch 5 timings either the output of the mapping circuit 4, the output of the fixed pattern generation circuit 6, or the output of the sync pattern generation circuit 51. The signal is selected according to the control signal from the controller 7 and output to the edge modulation circuit 8. Other configurations are the same as those in FIG.

That is, in this embodiment, by switching the data selector switch 5 at a predetermined timing, the sync pattern generated by the sync pattern generating circuit 51 is recorded on the disc. This synchronization pattern is the (1,1) pattern shown in FIG.

The other operations are the same as in FIG.

FIG. 13 shows an example of the structure of a reproducing device for reproducing the optical disc formed by the recording device shown in FIG. In this embodiment, the equalizer 31
The reproduced data V _X of the leading edge and the reproduced data V _{Y of the} trailing edge output by are added by the adder 61, and the addition output (V _X + V _Y ) is input to the level comparison circuit 62. The output of the level comparison circuit 62 is input to the interpolation circuit 63. Other configurations are the same as those in FIG. 7.

[0069] That is, in this embodiment, the adder 61 adds the data V _X and V _Y, and outputs the addition value V _X + V _Y. This V _X + V _Y becomes a signal proportional to the size of the pit. The level comparison circuit 62 compares the added value with a predetermined reference value set in advance, and when the value of the added value is smaller than the reference value, outputs a sync pattern detection signal.

That is, for example, in FIG. 14, V _X +
When a straight line of V _Y = T is shown, it becomes as shown by a broken line. Therefore, if this T is set as a predetermined reference value, the synchronization pattern is smaller than this reference value T, and other data is larger than this reference value T. Therefore, V _X + V _Y
When the added value is smaller than the reference value T, the reproduction value can be determined to be the reproduction value of the synchronization pattern. At this time, the level comparison circuit 62 outputs the synchronization pattern detection signal to the interpolation circuit 63.

However, even when the optical disc 21 has a defect or the like, the level comparison circuit 6
2 may erroneously detect the sync pattern and output a sync pattern detection signal. Therefore, the interpolator 63 determines the periodicity of the sync pattern detection signal. Since the synchronization pattern is generated in a constant cycle, the interpolation circuit 63
When, for example, a sync pattern detection signal is input, it generates a window having the range of the next generation timing in synchronization with this. Then, when the sync pattern detection signal is input in the window, it is determined as a normal sync pattern, and the sync signal synchronized with this is output. The sync pattern detection signal generated outside the window is ignored as being generated due to a defect or the like. Further, when the sync pattern detection signal is not detected in the window, the interpolation circuit 63 compulsorily (pseudo) generates the sync signal in order to ensure the periodicity.

Other operations of the reproducing apparatus of FIG. 13 are shown in FIG.
Since it is the same as the case in 1, the description thereof will be omitted.

Although the present invention has been described above with respect to an optical disk, the present invention can be applied to a magneto-optical disk and other information recording media.

[0074]

As described above, according to the information recording medium of claim 1, the number K of information represented by one pit is
Since the number of combinations of the shift position of the front edge of the pit and the shift position of the rear edge of the pit is set to a value smaller than MN, it is not necessary to reduce the size of the pit more than necessary, and in mastering and stamping, It is possible to reliably transfer the pits and realize an information recording medium with few errors.

When the wavelength of the laser beam for reading information is shortened, it is necessary to reduce the size of the pits in order to increase the recording density.
Even in such a case, it is possible to prevent the minimum pit size from being reduced more than necessary, and as a result, it is possible to improve the recording density.

According to the information recording apparatus of the fourth aspect and the information recording method of the fifth aspect, K combinations smaller than the value MN are selected from the MN combinations, and the selected K is selected. Since each combination is assigned to K pieces of information, it is possible to provide an information recording medium having a high recording density and a low error rate.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of pits of an information recording medium of the present invention.

FIG. 2 is a diagram illustrating a combination of edges of the pits in FIG.

FIG. 3 is a diagram illustrating a combination assigned to information from among combinations of pit edges.

FIG. 4 is a block diagram showing a configuration example of an information recording apparatus of the present invention.

FIG. 5 is a diagram illustrating mapping by a mapping circuit 4 in FIG.

FIG. 6 is a diagram illustrating an edge of a pit formed corresponding to input information.

7 is a block diagram showing a configuration example of a reproducing device for reproducing an optical disc recorded by the recording device of FIG.

FIG. 8 is a diagram for explaining decoding by the decoding map circuit 32 in FIG.

FIG. 9 is a diagram for explaining edge intervals when the bit edge shift position is set to eight levels.

FIG. 10 shows a shift position of a bit edge in 9 steps,
It is a figure explaining the space | interval of the edge at the time of using a predetermined combination of them.

FIG. 11 is a diagram illustrating a synchronization pattern.

FIG. 12 is a block diagram showing a configuration example of a recording device when forming a synchronization pattern.

FIG. 13 is a block diagram showing a configuration example of a reproducing device for reproducing an optical disc having a sync pattern formed thereon.

14 is a diagram for explaining the operation of the level comparison circuit 62 in FIG.

FIG. 15 is a diagram illustrating a shift position of a conventional pit edge.

FIG. 16 is a diagram for explaining the relationship between the position of the edge of a conventional pit and recorded information.

FIG. 17 is a diagram illustrating a position of information of a pit which is larger than the minimum pit by one step.

FIG. 18 is a diagram showing grouping of information on pits larger than the minimum pit.

[Explanation of symbols]

 1 information source 2 error correction circuit 3 pit number conversion circuit 4 mapping circuit 5 data selector switch 6 fixed pattern generation circuit 7 timing controller 8 edge modulation circuit 31 equalizer 32 decoding map circuit 33 bit number conversion circuit 34 error correction circuit

Claims (5)

[Claims] 1. Scanning with a light beam along a row of pits,
Within the range corresponding to a predetermined shift period shorter than the transient period of the reproduction signal specified by the transfer characteristic of the optical detection system for obtaining the reproduction signal corresponding to each pit, the front edge and the rear edge of the pit are In an information recording medium in which information is recorded by shifting the position in steps corresponding to the recording information, the front edge of the pit is shifted in M steps and the rear edge is shifted in N steps in steps. In addition, the number K of information represented by one of the pits is set to a value smaller than the number MN of combinations of the shift positions of the front edge and the rear edge of the pit. Information recording medium. 2. The information recording medium according to claim 1, wherein a combination having a small pit length is selectively excluded from the MN combinations. 3. The information recording medium according to claim 2, wherein one of the excluded combinations of the MN combinations is assigned to a pit for synchronization. 4. Scanning with a light beam along the pit row,
In front of the pit corresponding to the recorded information within a range corresponding to a predetermined shift period shorter than the transient period of the reproduction signal defined by the transfer characteristic of the optical detection system for obtaining the reproduction signal corresponding to each pit. In the information recording apparatus for recording information by shifting the position of the edge of the pit to M steps and the position of the rear edge to N steps in a stepwise manner, a shift position of the front edge of the pit and a rear position of the pit Value MN among the MN combinations of the edge shift positions
An information recording apparatus, comprising: an allocation unit that selects smaller K combinations and allocates the selected K combinations to K information. 5. Scanning with a light beam along the pit row,
In front of the pit corresponding to the recorded information within a range corresponding to a predetermined shift period shorter than the transient period of the reproduction signal defined by the transfer characteristic of the optical detection system for obtaining the reproduction signal corresponding to each pit. The information recording method for recording information by shifting the position of the edge of the pit in M steps and the position of the rear edge in the N step in a stepwise manner. Value MN among the MN combinations of the edge shift positions
An information recording method characterized by selecting smaller K combinations and allocating the selected K combinations to K information.