JP3277585B2 - Information recording medium, its recording device and reproducing device - Google Patents

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 such as an optical disk, and a recording apparatus and a reproducing apparatus suitable for recording or reproducing information on or from the information recording medium.

[0002]

2. Description of the Related Art In an optical disk used in a conventional CAV (constant angular velocity) mode, a servo byte section is periodically provided at a predetermined position of each track, and a clock pit for generating a reference clock is provided in the servo byte section. A wobble pit for tracking is formed. Then, a reference clock (channel clock) is generated corresponding to the clock pit, and information is digitally recorded by a pit having a length that is an integral multiple of the period of the reference clock. For example, in a system used in a CLV (constant linear velocity) mode such as a CD (compact disk), there are no clock pits, but the length and pit interval of the recorded pits are determined by a reference clock (channel clock). ) Period (0.3 μm)
(In the case of a CD, nine types of lengths of about 0.9 μm to 3.3 μm), which are used to perform clock recovery and record information in bit units. Cut out.

On the other hand, in the case of a video disk which is the same optical disk, a video signal is recorded and reproduced with a pit length difference much smaller than that of a CD. Now, this will be described with an example of a signal recorded in a 55-mm radius in the CAV mode. For video discs, the brightest part of the video signal is 9.3 MHz and the darkest part is 7.6 MHz.
This corresponds to 1.075 μm and 1.316 μm, respectively, on a 55 mm radius disk. It is a well-known fact that when a disc recorded in this manner is reproduced, a very beautiful video is reproduced. In this video,
Assuming that the change in brightness of 128 gradations can be expressed,
This means that the pit period is recorded on the disc in detail with 128 or more stages, and is reproduced. That is, a small change in pit length and pit interval of (1.316 μm−1.075 μm) ÷ 128 = 0.002 μm is reflected in the video signal. Despite the fact that such a fine change can be recorded as a change in the pit length, the minimum unit of the pit length change in a CD is 0.3 μm.
The reason for having to increase the value of m is mainly that the recording / reproducing method is not optimal.

The applicant of the present invention has disclosed Japanese Patent Application No. 3-167585 in which the position of the front or rear edge of an information pit is shifted stepwise from a predetermined reference position in accordance with recording information to record digital information. It was suggested earlier.
According to this recording / reproducing method, changes in the pit length and the position of the pit edge can be detected with extremely high accuracy.
It is possible to record information with a small change that has been considered impossible so far, and as a result, it is possible to realize higher density than ever.

FIG. 33 shows the principle of recording information by shifting the position of an edge previously proposed by the present applicant in a stepwise manner. As shown in the figure, a recording signal PWM-modulated according to the recording data (FIG. 33 (B))
Generate Then, a pit (FIG. 33A) corresponding to the length at the time of the 0 cross is formed. In this case, the position of the edge of the pit is determined by the reference clock (FIG. 33).
The position changes stepwise from the position indicated by (C)). According to the amount of change, 8 from 0 to 7 for one edge
Step (3 bit) data can be recorded.

FIG. 34 shows the principle of reproducing the signal recorded in this way. The RF signal (FIG. 34A) reproduced from the information recording medium is greatly amplified and binarized.
An F signal (FIG. 34B) is obtained. Since a clock pit is formed on a disk on which information is recorded, a reference clock (FIG. 34C) is generated based on the clock pit, and a sawtooth signal (FIG. 34) is generated in synchronization with the reference clock.
(D)). The position of the edge of the information pit is detected by detecting the timing at which the sawtooth signal crosses the binary RF signal.

[0007]

However, in the above proposal, there is a problem that intersymbol interference occurs between adjacent edges, and if the recording density is further increased, accurate reproduction becomes difficult.

In order to reduce the influence of the intersymbol interference,
It is conceivable to use an equalizer. For example, the reproduction RF signal is sampled three times with a three-tap equalizer separated by a certain distance Δ, and a linear operation is performed on these three values. The impulse response in this case is h (t) = δ (t) −κ {δ (t + Δ) + δ (t−Δ)}, and the frequency response is as follows. H (f) = 1−2κcos (2πΔf)

By appropriately selecting Δ and κ, it is possible to emphasize the signal components in the high frequency region and reduce the influence of intersymbol interference.

However, since the operation performed is linear, it cannot be perfectly adapted to non-linear intersymbol interference. In addition, if the value of the coupling coefficient κ is increased in order to increase the degree of intersymbol interference elimination, noise components in a high-frequency region are emphasized, which may have an adverse effect.

In the above-mentioned proposal, a saw-tooth wave is generated to detect the position of the edge, and the occurrence timing of the edge is detected from the saw-tooth wave. Therefore, the occurrence timing of the edge is read. Therefore, there has been a problem that the configuration for the measurement is complicated, and it is difficult to accurately detect it.
Furthermore, in the above proposal, no consideration was given to the effects of amplitude fluctuations and bias component fluctuations peculiar to optical disks. For this reason, there is a disadvantage that correct data cannot be read due to these fluctuations.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and it is possible to accurately reproduce high-density data with a simple configuration and to realize a nonlinear recording without emphasizing noise components. It is intended to reduce intersymbol interference.

[0013]

An information recording medium according to the present invention is, for example, as shown in FIGS. 1 and 2, an optical detection system for scanning a light beam along a pit row to obtain a reproduced signal corresponding to each pit. Tachinobo of the reproduced signal determined in accordance with the transfer characteristics
Within a predetermined period that is smaller than the falling period or the falling period ,
The edge position of the information pit is shifted stepwise from a predetermined reference position according to digital information to be recorded.

Further, an educational pit which is inserted into a pit row of information pits and whose edge position is shifted stepwise from a predetermined reference position is added according to educational data set in advance corresponding to the inserted position. .

Further, a reference pit which is inserted into the pit row of the information pits and whose edge position shift amount is set to the minimum value is added.

Further, a reference pit, which is inserted into the pit row of the information pit and in which the shift amount of the edge position is set to the maximum value, is added.

The information recording apparatus according to the present invention is, for example, shown in FIG.
As shown in FIG. 2, on an information recording medium on which recorded information is reproduced by an optical detection system that scans with a light beam along a pit row,
Standing of the reproduced signals that are based on the transfer characteristic of the optical detection system
Recording means for recording digital information by shifting the edge position of the information pit stepwise from a predetermined reference position within a predetermined period shorter than the rising period or the falling period. It is characterized by.

In the information reproducing apparatus according to the present invention, for example, as shown in FIG. 5, a rising period of a reproduced signal determined according to a transfer characteristic of an optical detection system that scans with a light beam along a pit row.
Alternatively, in an information reproducing apparatus that shifts an edge position of an information pit from a predetermined reference position in a step-like manner within a predetermined period shorter than a falling period and reproduces recorded information from an information recording medium on which digital information is recorded. A clock generation means for generating a clock phase-synchronized with the reference position based on a reproduction signal obtained from the optical detection system; and a rising or falling period of the reproduction signal at a timing defined by the clock. And level determining means for determining the recording information corresponding to the shift amount of the edge position of the information pit based on the reproducing level.

Further, the clock generation means generates a clock at a timing corresponding to the center of the shift period.

Further, the clock generation means is provided with a phase shift with respect to the reference position based on a reproduction signal obtained from a reference pit indicating a predetermined reference position recorded in the servo area of the information recording medium via the optical detection system. Generate a clock synchronized with.

Further, the level detecting means is constituted by an A / D conversion circuit for detecting a reproduction level by converting a reproduction signal from analog to digital at a sample timing specified by the clock.

Further, the judging means detects the level of the educational data set in advance according to the insertion position of the information pit into the pit row from the educational pit set as the shift amount of each edge position adjacent in the pit row direction. Each of the edge positions adjacent to each other in the pit row direction of the information pit is determined based on a reference point defined by the reproduction level sequentially detected by the means and an information point defined by the reproduction level sequentially detected from the information pit. The recording information corresponding to the shift amount is determined.

Further, the judging means includes a pair of educational data set in advance according to the insertion position, the pair of educational data detected by the level detecting means from the educational pit set as the shift amount of each of the pair of edge positions. Based on a reference point defined by a reproduction level and an information point defined by a pair of reproduction levels detected from information pits,
A pair of recording information corresponding to each shift amount of a pair of edge positions adjacent to each other in the pit row direction of the information pit is determined.

Further, of the pair of playback levels detected from the education pit in which the pair of education data is set, an address defined by setting one of the playback levels as the upper address and the other as the lower address. Is used as a reference point, and a storage unit is provided at the reference point where the pair of educational data is stored as decoded data, and the determination unit includes a pair of reproduction levels detected from information pits.
An address defined by setting one reproduction level as an upper address and the other reproduction level as a lower address is an information point, and a pair of decoded data stored at an address of the storage means corresponding to this information point is It is determined as record information.

Further, the judging means regards the decoded data stored at the reference point closest to the information point among the decoded data stored at each reference point of the storage means as recording information. judge.

[0026] Further, mapping is performed by using an address of the storage means defined by the reproduction level detected from the educational pit in which the educational data is set as a reference point, and performing mapping processing for storing the educational data as decoded data at this reference point. Means are provided.

Further, the mapping means stores the decoded data stored at the reference point closest to each storage point at each storage point other than the reference point among the storage points of the storage means.

Further, there is provided a bias removing means for subtracting the reproduction level detected from the reference pit having the minimum shift amount of the edge position from the reproduction level detected by the level detection means.

Further, the bias removing means calculates an average value of each value excluding the maximum value and the minimum value among a plurality of reproduction levels detected from the plurality of reference pits whose edge position shift amounts are set to the minimum value. Has a defect removing function of subtracting from a reproduction level.

Further, a gain for adjusting the gain of the reproduction level detected by the level detection means so that the reproduction level detected from the reference pit in which the shift amount of the edge position is set to the maximum value becomes a predetermined target value. Adjusting means is provided.

Further, the gain adjusting means calculates an average value of each value excluding the maximum value and the minimum value among a plurality of reproduction levels detected from the plurality of reference pits in which the shift amount of the edge position is set to the maximum value. It has a defect removal function of adjusting the gain of the reproduction level so as to reach a predetermined target value.

[0032]

In the information recording medium according to the present invention, the rising period of the reproduction signal determined according to the transmission characteristics of the optical detection system.
Alternatively, within a predetermined period shorter than the falling period , the edge position of the information pit is shifted stepwise from a predetermined reference position according to digital information to be recorded.

Therefore, the information reproducing apparatus according to the present invention detects the reproduction level at one sample timing in the rising period or the falling period of the reproduction signal, thereby enabling the shift amount of the edge position of the information pit to be detected. Can be reliably determined, and therefore, high-density information can be accurately reproduced with a simple configuration.

Further, a reproduction level which is sequentially detected from educational pits in which educational data preset according to the insertion position of the information pits in the pit row is set from the educational pits set as the respective shift amounts of the edge positions adjacent in the pit row direction. Recording information corresponding to each shift amount of the edge position adjacent to the information pit in the pit row direction based on the reference point defined by the information pit and the information point defined by the reproduction level sequentially detected from the information pit. By making the determination, non-linear intersymbol interference can be reduced without emphasizing noise components, and accurate decoding can be performed.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a basic format of an optical disk to which the information recording medium of the present invention is applied.

In this embodiment, a reflective type optical disc 1 having a diameter of 120 mm (pits are formed on a light beam reflecting surface by physical concave or convex portions) in a CLV mode, a track pitch of 1.6 μm, and a pit row is formed. Has been recorded.
All pieces of information are recorded as eight-step shift amounts of the leading edge (rising edge) and the trailing edge (falling edge) of the pits arranged at a constant period of 1.67 μm. The unit shift amount Δ, which is one unit of the shift amount, is set to 0.05 μm.

Since it is possible to record 3-bit information with eight-step shift amounts of the edge positions of the pits arranged as described above, the linear recording information density in the pit row direction is 0.28 μm / bit. And 2 of the current CD system
More than twice.

In the CD system, even when the linear velocity is set to the upper limit of 1.2 m / s, EFM (Eight to
By Fourteen Modulation, eight data bits to be recorded are converted into a total of 17 channel bits of 14 information bits and 3 margin bits, which are recorded in pits on the disk. Therefore, taking this EFM modulation into account, the linear recording information density is about 0.6 μm / bit. That is, about
Since the shortest pit of 0.9 μm corresponds to three channel bits, (0.9 ÷ 3) × (17 ÷ 8) = about 0.6 μm / bit.

Here, as shown in FIG.
The edge position of the pit recorded in the pit is shifted stepwise from the reference position at the center of the pit according to the digital information to be recorded.
Δ × 7) is RF determined according to the transfer characteristics of the optical detection system.
It is set within a range corresponding to a period shorter than a rising period tr or a falling period tf which is a transient period of the signal (reproduced signal) (a period other than a steady state in which the signal is at a zero level or a saturation level).

The RF signal is output from a pickup 3 of a reproducing apparatus described later, and a transition period is determined by a transfer characteristic of the pickup 3. Generally, the transfer characteristic of an optical system is determined by its transfer function (OTF; Optical Tr
MTF (Modulation) which is the absolute value of ansfer Function
This MTF is determined depending on the numerical aperture NA of the lens and the wavelength λ of the laser.

In the shift period Ts, the unit shift amount Δ
Is shifted by a unit amount smaller than 0.05 μm, the recording density can be further increased.

The sample clock SP which is phase-synchronized with the reference position of the center of the pit thus recorded,
By performing A / D conversion on the RF signal, reproduction levels L0 to L corresponding to shift amounts 0 to 7 of the pit edge position are obtained.
You can get 7. Thus, at one sample timing in the transition period of the RF signal, the reproduction level L
0 to L7 are detected during the shift period T.
s ≦ transient period (rising period tr or falling period t
f).

Here, the sampling timing by the sample clock SP is desirably the timing corresponding to the center of the shift period Ts. By setting this timing, the reproduction level is detected over the entire range of the transition period of the RF signal. It becomes possible. In this embodiment, a so-called reflection type optical disc 1 in which pits are formed as physical recesses or projections on the reflection surface of a light beam will be described as an example. A so-called MO (Ma) that forms a pit by reversing the magnetization
gneto Optical) It is also applicable to discs and the like.

Information recorded on the optical disk 1 is cut out in units of 3 bits, and is recorded as recorded data an and bn.
Recorded in the n-th pit. FIG. 3 shows this state. The leading edge of the pit is set to one of eight shift positions from 0 to 7 in accordance with the recording data an.
Similarly, the position of the trailing edge is set to one of eight shift positions from 0 to 7 in accordance with the recording data bn. The pitch Δ of each shift position is 0.05 as described above.
μm. As a result, each pit has recorded data an, bn
Are formed at the edge of the shift position 0, the shortest length LP = 0.5 .mu.m.

Returning to FIG. 1, the data recorded 4
A servo area consisting of five pits for servo is inserted between data areas consisting of four data pits. Of the five pits recorded in this servo area,
Two are set as educational pits P1 and P2, and the remaining three are set as reference pits P3 to P5. The front edge on the left side of the educational pit P2 in the figure is set to any position M of eight shift positions from 0 to 7, and the rear edge on the right side in the figure also ranges from 0 to 7. Are set at any one of the eight shift positions N.

The combination of the position M of the leading edge and the position N of the trailing edge of the educational pit P2 is set regularly so as to be different in each servo area. That is, M and N are (0, 0) in the first servo area and (0, 1) in the next servo area. Similarly, (0, 2),
(0, 3),..., (7, 6), (7, 7) are regularly set in combination. Thereby, 64 (=
In 8 × 8) servo areas, combinations of all possible positions of the leading edge and the trailing edge of the educational pit P2 are prepared.

The education pit P1 is a dummy in this case. That is, it is theoretically possible to form the educational data not at the edges at both ends of the pit P2 but at the edges at both ends of the pit P1. However, if you do so,
Since the pit adjacent to the left of the pit P1 is the data pit in the data area, the position of the edge changes according to the data. As a result, the educational pit P1, particularly the degree of interference on the data area side edges varies depending on the value of the data. Therefore, it is difficult to pattern the educational data in a constant state as described later.
Therefore, as in the embodiment, it is preferable that the educational data is formed not at the edges at both ends of the pit P1, but at the edges at both ends of the educational pit P2. In this way, the reference pit P3 adjacent to the trailing edge of the educational pit P2 and the educational pit P1 adjacent to the leading edge are both constant (no change) with their edges remaining at (0,0).
Therefore, when reading the educational data of the educational pit P2,
A constant pattern can always be obtained by receiving constant intersymbol interference.

The reference pits P3 to P5 are pits for obtaining data of reference positions (0, 0) and (7, 7). This reference position data is also theoretically, for example, the pit P
5 can be formed at both edges. However, in this case, as in the case of the education pit, the ratio of interference from the adjacent data area changes depending on the recording data. It is preferable not to form the reference position data at the end edge.

FIG. 4 briefly explains the planar structure of the optical disc 1. Since the signal recorded at a track pitch of 1.6 μm is recorded in the CLV mode,
The phase of the pit position does not match between the adjacent tracks, and as shown in this figure, the pit positions are recorded on the disk with different phases.

FIG. 5 is a block diagram showing the configuration of an embodiment of an optical disk reproducing apparatus to which the information reproducing apparatus of the present invention is applied. The optical disk 1 is rotated by a spindle motor 2. This optical disc 1 includes
Information is recorded based on the principle shown in FIGS. That is, digital information is recorded by shifting at least one of the front edge and the rear edge of the information pit from a predetermined reference position in a stepwise manner. In this optical disc 1, servo areas are formed at regular intervals, and educational pits P1 and P2 and reference pits P3 to P5 are formed. It goes without saying that data pits are formed in the data area.

The pickup 3 irradiates the optical disk 1 with a laser beam and reproduces a signal recorded on the optical disk 1 from the reflected light. The RF signal output from the pickup 3 is amplified by a head amplifier 4 and supplied to a focus tracking servo circuit 5, an APC circuit 6, and a PLL circuit 7. The focus tracking servo circuit 5 generates a focus error signal and a tracking error signal from the input signal, and executes focus control and tracking control in accordance with the error signal. APC circuit 6
Applies a servo so that the power of the laser beam applied to the optical disc 1 becomes constant.

The PLL circuit 7 extracts a clock component from an input signal. A PLL circuit used in a normal CD system or the like reproduces a clock by using all RF signals. In the case of the present embodiment, a clock is reproduced by using only an RF signal in a servo area. That is, since the servo area is not modulated with the recording data, stable clock reproduction can be performed without being affected by the recording data.

FIG. 6 is a block diagram showing a configuration of the PLL circuit 7 for realizing such a function. In this figure,
First, when the servo area pattern determination circuit 171 detects a pattern considered to be a servo area from the RF signal, it generates a servo area detection pulse. Here, the same pattern as the servo area may appear in the data area,
This pulse is not necessarily correct, but for the time being it is assumed that it is correct, the lock detection circuit 172
Supplies this signal to the counter 173 as a reset pulse, and resets the counter 173. If this is a correct servo area, the detection pulse should always be output at the same timing thereafter. The lock detection circuit 172 detects this, and determines whether or not the PLL circuit 7 is in a locked state. If it is not a correct detection pulse, the lock detection is not output even after a certain period of time, so the above operation is repeated until the lock state is achieved.

After the servo area is correctly detected, the counter 173 is reset at the correct timing. By decoding the count value of the counter 173, it is possible to roughly estimate the next timing when the servo area appears. it can. Using this principle, counter 1
From the count value of 73, a timing at which a specific pit present in the servo area appears is generated and supplied to the AND gate 176 as a gate signal.

In order to eliminate the influence from the data recorded on both sides of the servo area, the timing of the gate signal is adjusted so that a pit located at the center of the servo area is selected as much as possible.

Of the signals obtained by differentiating the RF signal by the differentiating circuit 174 and detecting the zero-cross point by the zero-cross detecting circuit,
What passed through the AND gate 176 becomes a phase comparison pulse, which is supplied to the sample and hold circuit 177.

The sample and hold circuit 177 counts the counter 173 by instantaneously sampling and holding the sawtooth wave generated by the sawtooth wave generation circuit 178 based on the output of the counter 173 at the timing when a specific pit appears. A time difference (phase error) between the rising clock and a specific pit existing in the servo area on the optical disk 1 is detected. This phase error signal is applied to the filter 179
Is passed back as a drive voltage of a VCO (Voltage Controlled Oscillator) to form a PLL loop in which a clock always keeps a correct phase relationship with a specific pit existing in a servo area on the optical disk 1.

The output of the counter 173 is decoded by the decoder 181 so that the sample clock SP, the clock A, the clock B, the clock RA, the clock RB, the clock TA, and the clock having a predetermined phase relationship shown in FIG.
TB is generated. These clocks are supplied to an A / D conversion circuit 9, a bias removal circuit 10, and a two-dimensional decoder 11, as shown in FIG.

The spindle servo circuit 8 in FIG.
The spindle motor 2 is controlled so that the drive voltage of the VCO 180 in FIG. 6 always has a constant value, and the optical disk 1 is controlled so as to rotate at a constant linear velocity.

On the other hand, the RF signal output from the head amplifier 4 is input to the A / D conversion circuit 9 and the sample clock S
At the rising edge of P, the digital data (reproduction level) indicating 256 levels of 8-bit levels is A / D
Is converted. The 8-bit data is supplied to the bias removing circuit 10, and after the bias component is removed by the bias removing circuit 10, the data is supplied to the two-dimensional decoder 11 and the controller 15. The controller 15 includes a CPU for performing various operations, a program ROM storing a program to be executed by the CPU, and the like, and executes a mapping process described later.

The two-dimensional decoder 11 decodes the signal supplied from the bias elimination circuit 10 and outputs its output to
It is supplied to an 8-bit conversion circuit 12. The 6-8-bit conversion circuit 12 accumulates four sets of input 6-bit data, converts them into three sets of 8-bit data, and outputs the data to the error correction circuit 1.
Output to 3. The error correction circuit 13 corrects an error in the input data, and outputs the data to the D / A conversion circuit 14.
The D / A conversion circuit 14 converts the input data into an analog signal and outputs it to an analog audio amplifier (not shown).

The two-dimensional decoder 11 is configured, for example, as shown in FIG. That is, the 8-bit reproduction level data supplied from the bias removing circuit 10
Delayed sequentially by 1 and 22. The data output from the first-stage delay circuit 21 and the data delayed by the second-stage delay circuit 22 are output to the RAM 23 as address data. The RAM 23 stores the delay circuit 21
, And reads out the 6-bit decoded data written in the address corresponding to the address data supplied from, and outputs it to the 6-8-bit conversion circuit.

FIG. 8 shows a more detailed configuration example of the bias removing circuit 10 and the two-dimensional decoder 11. That is, in this embodiment, the 8-bit data output from the A / D conversion circuit 9 is supplied to the latch circuits 31 and 32, and the latch circuit 41 constituting the bias removal circuit 10 together with the subtraction circuits 42 and 44. And 43. The subtraction circuit 42 subtracts the data latched by the latch circuit 41 from the data latched by the latch circuit 31, and the subtraction circuit 44 subtracts the data latched by the latch circuit 43 from the data latched by the latch circuit 32. And output each.

The outputs of the subtraction circuits 42 and 44 are
Are supplied as the 8-bit upper address and the 8-bit lower address. The latch circuits 33 and 34 latch the 8-bit training data supplied from the subtracting circuits 42 and 44 at a predetermined timing, and output the latched training data to the controller 15. The controller 15 is pre-programmed to pattern the educational data and map it to the RAM 23.

Next, the operation of the above embodiment will be described. Before that, the principle of reading the shift position of the information pit in this embodiment will be described. Now, assuming that the distance between the pits is sufficiently large and ignoring the intersymbol interference from the adjacent pits, the output of the A / D conversion circuit 9 during the shift period of the leading edge and trailing edge of the n-th pit. The data (reproduction level) is Va (n) and Vb (n) as shown in FIG. This Va (n),
Vb (n) represents the level of the RF signal, and can be expressed by the following equation. Va (n) = Δrf × an + ga (bn) Vb (n) = Δrf × bn + gb (an) where Δrf is a value g obtained by multiplying the unit shift amount Δ by a constant k.
a (bn) and gb (an) are non-linear functions representing the intersymbol interference between two edges, and these values increase as the recording density increases (ie, as the two edges come closer). . The decoding of the data is to solve this simultaneous equation and obtain the recorded signals an and bn from the observed Va (n) and Vb (n). Note that the above nonlinear function is a line spread function (Line
spread function) f, and the line spread function f is determined by the intensity distribution of the light reflected from the reflection surface of the optical disc 1.
PTICS / Vol.26, No.18 / 15 September 1987 P.3961
~ P. 3973 ".

The signals an and bn can be understood as a problem of pattern recognition in a two-dimensional space. That is,
The above equation is calculated for all combinations of (an, bn), and the resulting Va (n) is plotted in a two-dimensional space as, for example, the X-axis and Vb (n) as the Y-axis values. , Va (n) and Vb (n) are represented as information points as shown in FIG. On this two-dimensional plane, a function ga (b) representing the effect of intersymbol interference
n) and gb (an) are expressed as positional distortions of information points. That is, the functions ga (bn) and gb (an)
Is 0 (when no intersymbol interference occurs), the information point is located at the intersection (grid point) (reference point) of the line shown by the broken line in FIG. However, in practice, for example, inter-symbol interference functions gb (an) and ga which are monotonically increasing functions as shown in FIG.
(Bn) occurs. As a result, as shown in FIG.
Information points indicated by black circles in the figure deviate from lattice points (reference points).

Since this shift is caused by intersymbol interference, the larger the intersymbol interference, the greater the shift. FIG. 12 shows this state. That is, FIG.
2 (A) shows the deviation (strain) when the linear recording density is 0.32 μm / bit, and FIGS.
Represents distortion when the linear recording density is 0.36 μm / bit or 0.46 μm / bit, respectively. The smaller the linear recording density (the higher the density)
It is understood that the distortion increases.

That is, the educational data recorded in the educational pit P2 is reproduced, and information points defined by the reproduction level are mapped on the RAM 23 as reference points as indicated by black circles in FIG. . The information points obtained by reading the data of the data pits are stored in the RAM 23.
The above is plotted, and the closest reference point is determined to be the reference point corresponding to the information point. Then, the edge position (an, bn) indicated by the reference point is output as the edge position of the read information point.

Next, the operation of mapping a reference point to the RAM 23 will be described first with reference to the timing chart of FIG.

The pickup 3 reproduces a signal recorded on the optical disk 1 from the optical disk 1. This reproduced RF signal is supplied to the A / D conversion circuit 9 via the head amplifier 4,
A / D conversion is performed at the timing of the rising edge of the sample clock SP (FIG. 13C). The digital data output from the A / D conversion circuit 9 is output to the latch circuits 31, 32, 4
1 and 43 respectively. These latch circuits include a clock A (FIG. 13D) and a clock B (FIG. 13D).
(E)), clock RA (FIG. 13 (H)), clock R
B (FIG. 13 (I)).

The clock A, clock B, clock RA, clock RB, and clock TA shown in FIG.
(F)) and a clock TB (FIG. 13 (G)) are clocks generated by the PLL circuit 7. As apparent from FIG. 13, clock A and clock B are generated immediately after the timing of sampling the leading edge and trailing edge of each pit, respectively. Also, clocks RA and R
B is generated at the timing of latching the reference position data (0, 0) of the reference pit P3 in the servo area.

Therefore, the latch circuits 41 and 43
Has latched the reference position data (0, 0) of the front edge and the rear edge of the reference pit P3 in the previous servo area. When the educational data of the leading edge and the trailing edge of the educational pit P2 are latched by the latch circuits 31 and 32, the latch data of the latch circuit 41 is subtracted from the latch data of the latch circuit 31 by the subtractor. Similarly, the data latched by the latch circuit 43 is subtracted from the data latched by the latch circuit 32.

That is, the subtraction circuits 42 and 44 determine the position M (M is any value from 0 to 7) and the position 0 of the educational pit P2.
Will be output. Further, the subtraction circuit 44 outputs the difference between the level of the position N (N is any value of 0 to 7) and the level of the position 0. in this way,
By subtracting the level at the position 0, the DC component (bias component) of the reproduced signal is removed. The data from which the DC component has been removed is supplied to the latch circuits 33 and 34, respectively. Latch circuit 3
3 and 34 latch the data at the timing when the clocks TA and TB are input, and
Output to That is, the latch circuits 33 and 34 latch the educational data from which the DC component has been removed, and
Will be output.

Of course, the absolute level of the data at each shift position can be latched without subtracting the value of the reference position data (0, 0). However, in such a case, since the absolute level of each shift position changes due to variations in the disc 1 and the optical system, it is difficult to determine each shift position. Therefore, it is preferable to reduce the influence of variations in the disc 1 and the optical system by subtracting the value of the reference position data (0, 0).

The controller 15 sets the educational data input from the latch circuit 33 as the lower address in FIG. 8 and the educational data input from the latch circuit 34 as the upper address in FIG. Are mapped on the RAM 23 with reference to.

When the above mapping operation is performed corresponding to the training data from the 64 servo areas, the 64 reference points are mapped to predetermined storage points on the RAM 23 as shown in FIG. Will be.

Next, the controller 15 calculates the distance between each of the storage points on the RAM 23 and the storage point where the 64 reference points are stored. That is, as shown in FIG. 15, for example, the distance between the storage points m1 to m17 and the storage point mi at which the reference point (0, 7) is stored is calculated. Similarly, the distance between the storage points m1 to m17 and the storage point mj at which the reference point (1, 7) is stored is calculated. Then, in each storage point, the same data as the reference point stored in the closest storage point among the storage points storing the reference point is stored.

Since the number of quantization bits per sample in the A / D conversion circuit 9 is 8 bits, the output has 256 levels. Therefore, the RAM 23 has 256 addresses as the addresses on the horizontal axis and the vertical axis. In other words, the RAM 23 is configured by 256 × 256 storage points. Of these, predetermined memory points are stored in FIG.
The reference point is stored as shown in FIG.

For the other storage points in which the reference point is not stored, the distance from the storage point in which the reference point is already stored is calculated and stored in the storage point of the closest distance. The same data as the reference point is stored in each storage point. For example, in the embodiment of FIG.
Memory points m1 to m9 are closest to storage point mi (reference point (0,7)), and storage points m10 to m17 are closest to storage point mj (reference point (1,7)). Become. Therefore, the reference points (0, 0) are stored at the storage points m1 to m9.
The data of 7) is written. That is, these storage points are set as the area A (0, 7) of the reference point (0, 7). On the other hand, the storage points m10 to m17 have the reference point (1,
The data of 7) is written. That is, these storage points are set to the area A (1, 7) corresponding to the reference point (1, 7).

As described above, the reference point data is written into each of the 256 × 256 storage points, and the area on the RAM 23 corresponding to each reference point is as shown in FIG. . The data of the reference point (i, j) is stored in the storage points included in each area A (i, j).

FIG. 17 is a flowchart showing the mapping process by the controller 15 described above.

First, as described above, the position M of the leading edge and the position N of the trailing edge of the educational pit P2 in each servo area of the optical disc 1 are set to different combinations in each servo area. These educational data (M, N) are regularly set in a predetermined order corresponding to the insertion position in the data area. That is, (0, 0) is set in the first servo area, (0, 1) is set in the next servo area, and (0, 2), (0, 3),. , (7,
6), (7, 7).

Therefore, in step SP1 shown in FIG. 17, the educational data (0, 0) corresponding to the reference position data (0, 0) is detected from the sequentially arriving servo areas, and the first servo area is detected. At this point, the process proceeds to step SP2, where M and N are set to 0, and then proceeds to step SP3. In this step SP3, the education data (0,
The decoded data (0, 0) is stored with the address (memory point) on the RAM 23 designated by (0) as the reference point (0, 0). Similarly, by repeating steps SP3 to SP8 in the same manner, the educational data (0, 1),.
.., (7, 7), the decoded data (0, 1),.
7) is stored.

Thereafter, the process proceeds to step SP9, where the decoded data (i, j) is stored in a storage point other than the reference point (i, j) by the above-described interpolation calculation processing. The above-described mapping process is executed by the controller 15 as an initial setting operation every time a different optical disc 1 is loaded into the reproducing apparatus.

Next, the operation in the data area will be described with reference to the timing chart of FIG. FIG.
The RF signal shown in FIG. 8B is input to the A / D conversion circuit 9 corresponding to the pit row shown in FIG. The level of the leading edge and trailing edge of each pit is the sample clock SP
The sampling is performed in synchronization with the rising edge of FIG. As shown in FIGS. 18A and 18B, the phase of the RF signal changes according to the position of the edge of the pit.
Since the sample clock SP is generated during this edge shift period, the edge shift position can be detected as a change in the level of the RF signal.

The data of the leading edge of the data pit latched by the latch circuit 31 is stored in the RAM 23 after the difference between the level at the position 0 latched by the latch circuit 41 and the subtraction circuit 42 is calculated. (Address on the horizontal axis in FIG. 10). Similarly, the data of the trailing edge of the data pit latched by the latch circuit 32 is subtracted from the level of the position 0 latched by the latch circuit 43 to remove the DC component, and then stored in the RAM 23 in the upper address ( (The address on the vertical axis in FIG. 10). The RAM 23 reads and outputs decoded data stored at an address defined by the horizontal axis and the vertical axis. As the decoded data, the reference point of the educational data by the above-described mapping is written. Therefore, the data (an, bn) of the reference point closest to the information point is selected and output.

The 6-bit decoded data (an, bn) output from the two-dimensional decoder 11 shown in FIG.
) Is supplied to the 6-8-bit conversion circuit 12 and converted into 8-bit data. That is, when an audio signal is recorded on the optical disc 1, for example, the audio signal is subjected to error correction processing in units of 8 bits. However, as described above, in the present embodiment, data is recorded as a basic unit using a total of 6 bits of 3 bits of the leading edge (8-step shift position) and 3 bits of the trailing edge (8-step shift position). You. That is, the data recorded on the optical disc 1 is recorded by converting the data separated by 8 bits into the data separated by 6 bits according to a predetermined method at the time of recording. Therefore,
The 6- to 8-bit conversion circuit 12 reversely converts the data in units of 6 bits into the original data in units of 8 bits. This operates to decode, for example, four sets of data in 6-bit units, and then collectively output three sets of data in 8-bit units. 6-8 bit conversion circuit 1
The data in units of 8 bits inversely transformed by 2 is:
After being supplied to the error correction circuit 13 and correcting the error, it is supplied to the D / A conversion circuit 14, where it is D / A converted, amplified by, for example, an analog audio amplifier (not shown), and reproduced from a speaker or the like. Sound is emitted.

FIG. 19 shows an error rate of data obtained by decoding in the above-described embodiment in a state where the bias removing circuit 10 is not operated. As shown in the figure, as compared with the conventional decoding method using the sawtooth wave (the method described in Japanese Patent Application No. 3-167585 previously proposed by the present applicant), the mapping on the RAM 23 described above is performed. It can be seen that the error rate is smaller when two-dimensional decoding is performed using the reference points thus set. It can also be seen that the effect is higher when the linear recording density is reduced.

In the above-mentioned embodiment, as shown in FIG. 1, the data an and bn are respectively recorded with the leading edge and the trailing edge of one pit as a pair. As shown in (1), data an and bn can be recorded on the opposing edges of adjacent pits. In this case, the education data and the position reference data in the servo area are also recorded at the opposite edges of the two pits, as shown in FIG. In this embodiment, the educational data (M, N) is recorded on the opposite edges of the educational pits P1 and P2, and the position reference data (0, 0) is recorded on the opposite edges of the reference pits P3 and P4. The position reference data (7, 7) is recorded on the opposing edges of the reference pits P4 and P5.

In this case, as shown in FIGS. 18F and 18G, the clock A and the clock B are generated at the rear edge and the front edge of the pit, respectively.

The distance between the information point obtained from the reproduced data and the reference point obtained from the educational data is not stored in the RAM 23 in advance, but can be calculated each time. In this case, it is difficult to make a quick determination. Therefore, it is preferable to write the information in the RAM 23 in advance as in the embodiment.

In the embodiment shown in FIG. 5, the bias removing circuit 10 is arranged between the A / D conversion circuit 9 and the two-dimensional decoder 11.
In addition, a gain adjustment circuit can be inserted. FIG. 22 shows an embodiment in this case. That is, in this embodiment, the output of the subtraction circuit 42 is supplied to the variable gain amplifier 63 and also supplied to the latch circuit 61, and is latched by the clock KA.
The output of the latch circuit 61 is supplied to a subtraction circuit 62, and a difference from a predetermined target amplitude is calculated. Then, the output of the subtraction circuit 62 is supplied to the variable gain amplifier 63.

Similarly, the output of the subtraction circuit 44 is supplied to the variable gain amplifier 66 and the latch circuit 64
Is supplied to Clock KB by latch circuit 64
The data latched at the timing (1) is supplied to a subtraction circuit 65, and after a target amplitude supplied from a circuit (not shown) is subtracted, the data is supplied to a variable gain amplifier 66.

Note that the variable gain amplifiers 63 and 66
M. The outputs of the subtraction circuits 42 and 62 (44 and 65) are input to this ROM as addresses, and data corresponding to the addresses is read.

The output of the variable gain amplifier 63 is R
The output of the variable gain amplifier 66 is supplied to the RAM 23 and the latch circuit 34 while being supplied to the AM 23 and the latch circuit 33.
To be supplied. That is, the gain adjustment circuit 60 is connected to the subsequent stage of the bias removal circuit 10. Other configurations are the same as those in FIGS. 5 and 8.

Next, the embodiment of FIG. 22 will be described with reference to the timing chart of FIG. In the embodiment shown in FIG. 22, unlike the embodiments shown in FIGS. 1 and 13, the education data is arranged at the edges of the education pits P1 and P2 that face each other. Also, the reference pit P
Reference position data (0,0) on opposite edges of 3 and P4
Are recorded, and reference position data (7, 7) is recorded at the opposing edges of the reference pits P4 and P5 (FIG. 23).
(A)).

An RF signal shown in FIG. 23B is obtained corresponding to the educational pits P1 and P2 and the reference pits P3 to P5. This is converted by the A / D conversion circuit 9 at the timing of the sample clock SP shown in FIG.
The data is converted and latched by the latch circuit 31 at the timing of the clock A (FIG. 23D) and latched by the latch circuit 32 at the timing of the clock B (FIG. 23E). Furthermore, the clock RA
The latch is performed by the latch circuit 41 at the timing of FIG. 23 (F), and is latched by the latch circuit 43 at the timing of the clock RB (FIG. 23 (G)).

Then, in the subtraction circuit 42, the output of the latch circuit 41 is subtracted from the output of the latch circuit 31, and in the subtraction circuit 44, the output of the latch circuit 43 is subtracted from the output of the latch circuit 32. In this way,
Data that is not affected by the DC component can be obtained (in FIG. 14, the reference point (0,0) can be arranged at the position of the grid point where the straight line indicated by the broken line intersects).
This is the same as the case described above.

In this embodiment, the latch circuit 6
1, the output of the subtraction circuit 42 is the clock KA (FIG. 2).
3 (H)). That is, the position reference data 7 recorded at the trailing edge of the reference pit P4 is latched in the latch circuit 61. From the output of the latch circuit 61, a preset target amplitude is subtracted in a subtraction circuit 62. Then, the difference is supplied to the variable gain amplifier 63. The variable gain amplifier 63 is connected to the subtraction circuit 42 according to the signal supplied from the subtraction circuit 62.
The gain of the supplied signal is adjusted. That is, thereby, the position of the signal output from the variable gain amplifier 63 in the horizontal axis direction indicated by the reference point (7, 7) in FIG. 10 is set to the target amplitude.

Similarly, in the latch circuit 64, at the timing of the clock KB (FIG. 23 (I)), the subtraction circuit 4
4 is latched. That is, the latch circuit 64 latches the position reference data 7 recorded at the leading edge of the reference pit P5. The data latched by the latch circuit 64 is supplied to the variable gain amplifier 66 after the target amplitude is subtracted in the subtraction circuit 65. The variable gain amplifier 66 adjusts the gain of the signal supplied from the subtraction circuit 44 in accordance with the signal supplied from the subtraction circuit 65. Thereby, the variable gain amplifier 6
In FIG. 10, the signal output from the signal 6 is adjusted so that the position on the vertical axis indicated by the reference point (7, 7) becomes the target amplitude position set in advance.

As described above, by adjusting the gain by the gain adjusting circuit 60, the reference points (7,
The position 7) can always be arranged at a predetermined position.
This makes it possible to read data accurately even when the optical disc 1 locally has characteristic variations.

FIG. 24 shows the output of the variable gain amplifier 63 (or 66). FIG. 7A shows a case where the output of the subtraction circuit 62 is not supplied to the variable gain amplifier 63, and FIG. 7B shows a case where the output is supplied. It can be seen that the level fluctuation is suppressed when the gain is adjusted by the output of the subtraction circuit 62.

FIG. 25 shows a case where the number of C1 errors is measured when the error correction method used in the CD system is applied in the embodiment shown in FIG. In the figure, white circles indicate that the outputs of the latch circuits 41 and 43 are supplied to the subtraction circuits 42 and 44, and the subtraction circuit 6
2 and 65 are not supplied to the variable gain amplifiers 63 and 66. In FIG.
1 and 43 are supplied to subtraction circuits 42 and 44, and outputs of the subtraction circuits 62 and 65 are
3, 66. It can be seen that the latter has a reduced number of errors that occur. Also, it can be seen that the number of errors satisfies the CD standard, even though the recording linear density is twice that of the CD.

As described above, the reproduction data is processed based on the data recorded in the education pits P1 and P2 or the data recorded in the reference pits P3 to P5. If so, it becomes difficult to read accurate data. In order to prevent this, for example, a configuration shown in FIG. 26 can be used. That is, in this embodiment, the latch circuits 31 and 32 in FIG. 22 are replaced by FIFOs 71 and 72, and the latch circuits 41 and 43 are replaced by defect removal circuits 73 and 74. The latch circuits 61 and 64 are replaced by defect removal circuits 82 and 84, and FIFOs 81 and 83 are inserted in front of the variable gain amplifiers 63 and 66. Other configurations are the same as those in FIG.

That is, the defect removal circuit 73 outputs
The data input from the D conversion circuit 9 is stored, for example, for four blocks as shown in FIG. Then, the position reference data (0, 0) in each block is compared, the average of two data excluding the maximum and minimum data is calculated, and the result is used as the position reference data (0, 0). In this manner, even if the value of the position reference data (0, 0) becomes an abnormal value due to dropout or the like, it is prevented that the abnormal value is used as the reference data.

This means that other defect removing circuits 7
The same applies to 4, 82 and 84.

The FIFOs 71, 72, 81, 83 are
Since the defect removal circuits 73, 74, 82, and 84 need to store four blocks of data, the data is delayed by a delay time based on this, and the subtraction circuit 4
2, 44 or variable gain amplifiers 63, 66.

FIG. 28 shows a defect removal circuit 73 (7
4, 82, and 84). In this embodiment, data input from the A / D conversion circuit 9 is sequentially latched by the latch circuits 91 to 94 in synchronization with the clock RA. And the latch circuit 9
The data latched in 1 to 94 are gates 95 to 9
When 8 is turned on, the data is read out to the data bus.
The data on the data bus is stored in the latch circuits 99 to 102.
Then, the data is latched at a predetermined timing in synchronization with the clock output from the controller 104. This controller 1
Reference numeral 04 denotes a microcomputer for performing various operations and a microcomputer including a ROM in which programs used by the CPU are stored in advance.

The data latched by the latch circuits 99 and 100 is supplied to a comparison circuit 103, where the levels are compared. Then, a signal SAB corresponding to the comparison result is supplied to the controller 104. The controller 104 outputs gate control signals EA, EB, EC, and ED to the gates 95 to 98, respectively, to read out predetermined data to the data bus, and to latch the data.
To 102 are generated. Also,
From the signal supplied from the comparison circuit 103, the latch circuit 9
Among the data latched in 1 to 94, the maximum value and the minimum value are determined according to a table as shown in FIG.

That is, the controller 104 outputs a predetermined one of the gate control signals EA to ED at a predetermined timing, and sends the gate control signal to the latch circuits 99 and 100 via the data bus.
Of the data latched by the latch circuits 91 to 94, two predetermined data are respectively latched. Then, the magnitude of the latched data is determined by the comparison circuit 103. By repeating this process several times, the maximum value and the minimum value of the data latched in the latch circuits 91 to 94 are obtained.

In FIG. 29, among the latch data Rn-1 to Rn + 2, the one described on the left in the top row is logic 1 when it is larger than that described on the right, logic 0 when it is smaller, and undefined. In this case, it is indicated by X.
For example, the data Rn-1 latched by the latch circuit 94
Is larger than the data Rn latched by the latch circuit 93, and the data Rn−
1 is the data Rn + 1 latched by the latch circuit 92
When the data Rn-1 latched by the latch circuit 94 is larger than the data Rn + 2 latched by the latch circuit 91, the data Rn-1 latched by the latch circuit 94 becomes the maximum value. Become.

Further, Rn-1 is smaller than Rn, and Rn is smaller than Rn.
If n is greater than Rn and Rn is greater than Rn + 2,
Rn becomes the maximum value.

Similarly, the maximum value and the minimum value are obtained from FIG.

When the controller 104 determines the maximum value and the minimum value among the data Rn-1 to Rn + 2 stored in the latch circuits 91 to 94 from the table shown in FIG. Is read out onto the data bus, and this is latched by the latch circuits 101 and 102. Then, the data latched by the latch circuits 101 and 102 are added by the adder circuit 105, multiplied by a coefficient に よ り by the multiplier circuit 106, supplied to the latch circuit 107, and latched. That is, the latch circuit 107 latches the average value of the two data, excluding the maximum value and the minimum value, of the data Rn-1 to Rn + 2 latched by the latch circuits 91 to 94. This data is supplied to the subtraction circuit 42.

FIG. 30 shows the level change when the defect removal circuits 73, 74, 82, and 84 are used (shown by A in FIG. 26) and when they are not used (shown by B in FIG. 26). Is shown. When the defect removing circuit is not used, it can be seen that the level varies according to the defect caused by dropout or the like. On the other hand, in the case where the defect removing circuit is used, the defect is removed, so that the level variation is suppressed. That is, data can be determined more accurately.

In addition, the minimum distance between the information point obtained by the reproduction data and the reference point set by the education data is:
For example, it can be detected by a configuration as shown in FIG.

In this embodiment, the reproduced RF signal is A
A / D conversion is performed by the / D conversion circuit 50 and the latch circuit 5
It is adapted to be latched by 1 and 52. The latch circuit 51 latches data corresponding to, for example, the leading edge of the pit, and the latch circuit 52 latches data corresponding to the trailing edge. Latch circuit 51
And 52, the data latched by 64 correlators 5
3-1 to 53-64. The correlators 53-1 to 53-64 are supplied with 64 types of educational data, respectively. Then, each of the correlators 53-1 to 53-64
Calculates the correlation between the data supplied from the latch circuits 51 and 52 and the educational data, and outputs the calculation result to the maximum value detector 54. The maximum value detector 54 is, for example, Wi
The maximum data is detected from the 64 data supplied from the correlators 53-1 to 53-64, and is output.

In the above-described embodiment, the case where the CLV mode is set has been described as an example. However, the CAV mode may be set as a matter of course. In this case, by arranging the pits so that the positions of the pits have a phase shift of 90 degrees between adjacent tracks, the influence of crosstalk between adjacent tracks is reduced, and the density is increased in the track direction. Can be realized.

In the above-described embodiment, the RAM 2
In FIG. 3, all the reference points are mapped in correspondence with the educational data, but only a part (for example, 16) of the reference points are mapped by the educational data, and the other reference points are mapped by the educational data. It is also possible to interpolate from the reference point by calculation.

Finally, a description will be given of an embodiment of a recording apparatus for the above-described optical disk 1 having a high recording density. In FIG. 32, an information source 201 digitizes and outputs an audio signal as a signal to be recorded. ECC circuit 202
Adds an error correction code to the digital audio data supplied from the information source 201, and outputs the digital audio data to the conversion circuit 203. The conversion circuit 203 converts the input data into data in units of 3 bits. That is, in this embodiment, the edge position of each pit is set to one of eight positions from 0 to 7. For this reason, 3-bit data is required to specify the position of each edge. The conversion circuit 203 generates the 3-bit data.

The clock information generating circuit 205 generates data necessary for generating a clock necessary for reading data recorded on the optical disk 1. The bias gain information generation circuit 206 generates data indicating a bias point (data indicating a reference point (0, 0), and data indicating that the positions of the leading edge and the trailing edge are both 0).
And data for setting the gain (data indicating the reference point (7, 7), and the positions of the leading edge and the trailing edge are 7
).

The PLL pull-in signal generation circuit 207 includes a PLL
Generates a signal for pulling in. The education data generation circuit 208 sets the edge position (an, bn) to (0,
Data corresponding to the edge positions 0) to (7, 7) is generated. The data output from the clock information generation circuit 205, the bias gain information generation circuit 206, the PLL pull-in signal generation circuit 207, and the education data generation circuit 208 are all supplied to the adder 204, and the conversion circuit 2
03 (time-division multiplexed).

The output of the adder 204 is supplied to the recording edge position calculation circuit 209, and the output of the recording edge position calculation circuit 209 is output to the edge modulation circuit 210. Then, the output of the edge modulation circuit 210 is supplied to the mastering device 211, and the optical disc 1 is created through processes such as cutting, development, plating, transfer, aluminum deposition, and protection film application.

In the above configuration, the edge modulation circuit 21
0 generates a timing signal of a timing corresponding to the data output from the recording edge position calculation circuit 209,
This is output to the mastering device 211.

Here, as shown in FIG. 2, the edge position modulation circuit 210 determines the edge positions of the front end and the rear end of each pit from the reference position at the center of the pit according to the digital information to be recorded. Although a timing signal is generated to shift each of the pits in eight stages, the shift period Ts of the edge position of each pit is determined according to the transfer characteristic of the optical detection system (pickup 3) on the reproducing apparatus side. It is set so as to fall within a range corresponding to a period shorter than the transient period (rising period tr or falling period tf) of the RF signal.

The mastering device 211 cuts the photosensitive film applied on the recording master by a laser beam in synchronization with the timing signal supplied from the edge modulation circuit 210. The cut master is developed,
Plating is applied to create a stamper. Then, the pits formed on the stamper are transferred to a replica, aluminum is deposited on the replica, and a protective film is applied, whereby the optical disc 1 is manufactured. In the manufacturing process of such an optical disc 1, by using the above-described recording method based on the edge position modulation, it is possible to eliminate the influence of the change in the state of the bit that differs for each disc, so that it is always stable and has a high recording density. Can be achieved. That is, a conventional CD is manufactured using the same mastering apparatus as described above, but the state of the bit, particularly the size, changes to a very small amount due to various factors in the manufacturing process. There are many factors that change the bit size in this way, such as fluctuations in the power of the recording laser, changes in the temperature of the developing solution, errors in the developing time, and changes in the temperature during replica production. Very difficult to control. For this reason, in the conventional CD, the minimum step of the change in the bit length is set to 0.3 μm so that the recorded information can be sufficiently decoded even if the bit length changes by a very small amount. However, according to the above-described embodiment, even if the bit size changes due to various factors in the manufacturing process, the change in the RF signal due to this change is embedded in the servo area.
It can be known from the position reference bits of (0, 0) and (7, 7). Further, these effects are eliminated by the bias and gain adjustment circuit described in the above-described embodiment. For this reason, the minimum step of the change in bit length can be made much smaller (for example, 0.05 μm) than in the conventional CD, and high-density recording becomes possible. Further, it is known that not only the variation in the bit size but also the change in the bit shape occurs in the optical disk. The influence of such a change in shape on the RF signal is reflected in the instruction bit RF signal embedded in the servo area. In the above-described embodiment, when information is read out, the calculation is performed based on the reference point defined from these educational bits, so that the influence of the change in the bit shape is removed, and stable information reproduction is possible. Become. further,
A case in which the above-described embodiment is applied to an MO disk system that performs recording by partially reversing the magnetization of a magneto-optical film will be described. When recording information, the MO disk system
The laser power is greatly increased to increase the temperature of the disk, thereby changing the characteristics of magnetic film formation, thereby forming a bit whose magnetization is inverted. When a conventional CD recording method is applied to such an MO disk system, a reproduced signal is distorted due to a so-called heat storage effect, and a margin for reading a digital signal is reduced. That is, if the bit of 0.9 μm is to be recorded immediately after the bit having the maximum length of 3.3 μm is recorded based on the CD recording method, the bit of 3.3 μm is recorded due to the so-called heat storage effect. Because the disk (recording master) is locally heated while
A 0.9 μm bit is formed larger than a desired shape. As a result, the reproduced signal is distorted and the margin for reading the digital signal is reduced. According to the above-described embodiment, since the bit length is distributed between 0.5 and 1.2 μm, the dynamic range of the recorded bit length is low. Also 1.
Since the bits are always formed at a constant interval of 67 μm, the disk is always heated almost the same regardless of the information to be recorded. Therefore, the effect of the heat storage effect is significantly reduced as compared with the CD recording method, and good signal characteristics can be obtained even when recording is performed at a high recording density.

[0127]

As described above, according to the information recording medium of the present invention, the period is shorter than the rising or falling period of the reproduction signal determined according to the transfer characteristics of the optical detection system.
Within a predetermined period, the edge position of the information pit is shifted stepwise from a predetermined reference position according to digital information to be recorded, so that a recording density more than twice as high as that of a conventional CD system can be obtained. Can be

Also, in the information reproducing apparatus for reproducing the information recording medium according to the present invention, the information reproducing apparatus is used for the reproduction signal rising period.
Alternatively, the reproduction level can be detected at one sample timing in the falling period , so that the recording information corresponding to the shift amount of the edge position of the information pit can be reliably determined. , High-density information can be accurately reproduced, the configuration is simplified,
The cost can be reduced.

Further, the reproduction level which is sequentially detected from educational pits in which the educational data set in advance according to the insertion position of the information pits with respect to the pit row is set from the educational pits set as the shift amounts of the edge positions adjacent in the pit row direction. Recording information corresponding to each shift amount of the edge position adjacent to the information pit in the pit row direction based on the reference point defined by the information pit and the information point defined by the reproduction level sequentially detected from the information pit. By making the determination, non-linear intersymbol interference can be reduced without emphasizing the noise component, and the recording density can be further improved, and more accurate decoding can be performed.

Since the reference point is mapped on the storage means, the position of the edge can be determined easily and quickly.

Since the reference points are mapped from the educational pits recorded on the information recording medium, the data can be read accurately without being affected by the variation of the information recording medium.

Further, since a part of the reference point is obtained by calculation from the reference point specified from the educational pit, the number of educational pits to be recorded on the information recording medium can be reduced, and the information recording medium can be accordingly reduced. The capacity can be used effectively.

Since the reference point is stored in the storage point specified by the address corresponding to the reproduction level of the educational pit, the reference point corresponding to the information point can be easily determined. .

The storage point other than the storage point specified by the address corresponding to the reproduction level of the educational pit is stored in the storage point closest to the storage point specified by the address corresponding to the reproduction level of the educational pit. The stored reference points are stored, so that the corresponding reference points can be quickly determined, and decoding can be accurately performed even if the reproduction level is slightly changed by noise.

Further, since the signal corresponding to the reference pit located at the shift position with the smallest edge shift amount is subtracted from the signal reproduced from the information recording medium, it is not affected by the variation of the information recording medium. In addition, data can be read accurately.

Further, since the signal corresponding to the reference pit at the shift position where the edge shift amount is the largest is subtracted from the signal reproduced from the information recording medium, the local characteristic of the information recording medium itself is reduced. Data can be read accurately without being affected by variations.

Further, the signal corresponding to the reference pit at the shift position with the smallest edge shift amount and the signal at the largest shift position are subtracted from the signal reproduced from the information recording medium. The data can be read accurately regardless of individual variations or internal local variations.

Further, since the educational pits are formed, it is possible to accurately reproduce the recorded data without being affected by variations in the characteristics of the information recording medium and the reproducing apparatus.

Further, since the educational data is formed apart from the data pits, the influence of the recorded data on the educational data is reduced.

Since the reference pit having the edge of the shift position with the smallest shift amount is recorded at a predetermined position other than the data pit, even if there is an individual variation, data can be read accurately. An information recording medium capable of performing this can be realized.

Further, since the reference pit having the edge of the shift position having the largest shift amount is recorded at a predetermined position other than the data pit, even if the characteristics are locally varied, the data can be transferred. An information recording medium that can be read accurately can be realized.

Further, since the reference pit having the edge of the shift position with the smallest shift amount and the edge of the shift position with the largest shift amount is recorded at a predetermined position other than the data pits, individual variations and Thus, it is possible to realize an information recording medium capable of accurately reading data regardless of local variations.

Further, according to the information recording apparatus of the present invention, the dynamic range of the length of the pit to be recorded is low, so that the influence of the heat storage effect at the time of recording can be almost neglected, and the high recording density Good signal characteristics can be obtained even when recording is performed by using.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a data area and a servo area of an information recording medium according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of an information pit in an information recording medium of the present invention.

FIG. 3 is a diagram illustrating a configuration example of an information pit in the information recording medium of the present invention.

FIG. 4 is a diagram illustrating a phase between tracks of the information recording medium of the present invention.

FIG. 5 is a block diagram showing a configuration of an embodiment of an optical disc reproducing apparatus to which the information reproducing apparatus of the present invention is applied.

6 is a block diagram illustrating a configuration example of a PLL circuit 7 in the embodiment of FIG.

FIG. 7 is a block diagram showing a configuration example of a two-dimensional decoder 11 in the embodiment of FIG.

8 is a block diagram showing a configuration example of a bias removal circuit 10 and a two-dimensional decoder 11 in the embodiment of FIG.

FIG. 9 is a diagram illustrating intersymbol interference of adjacent edges.

FIG. 10 is a diagram illustrating the principle of mapping of reference points in a RAM 23 of FIG. 8;

FIG. 11 is a diagram illustrating a function indicating the influence of an adjacent edge.

FIG. 12 is a diagram illustrating the relationship between the influence of an adjacent edge and the line density.

FIG. 13 is a timing chart for explaining an operation of a servo area in the embodiment of FIG. 8;

FIG. 14 is a diagram illustrating mapping of reference points in a RAM 23 of FIG. 8;

FIG. 15 is a diagram illustrating mapping of a reference point to another storage point in the RAM 23 of FIG. 8;

FIG. 16 is a diagram illustrating a mapping state of a reference point to all storage points in a RAM 23 of FIG. 8;

FIG. 17 is a flowchart for explaining a procedure of a mapping process by the controller 15 of FIG. 8;

FIG. 18 is a timing chart illustrating an operation in a data area in the embodiment of FIG.

FIG. 19 is a diagram for explaining an error rate realized by the embodiment in FIG. 5;

FIG. 20 is a diagram illustrating another configuration example of the information recording pit.

21 is a diagram illustrating a configuration example of a servo area when the information recording pit is configured as illustrated in FIG. 20;

FIG. 22 is a block diagram showing a configuration of another embodiment of the optical disc reproducing apparatus to which the information reproducing apparatus of the present invention is applied.

FIG. 23 is a timing chart for explaining the operation of the embodiment in FIG. 22;

24 shows variable gain amplifiers 63 and 66 in FIG.
FIG. 6 is a diagram for explaining a change in the output level of FIG.

FIG. 25 is a diagram illustrating an occurrence state of an error realized in the embodiment of FIG. 22;

FIG. 26 is a block diagram showing a configuration of still another embodiment of the optical disc reproducing apparatus to which the information reproducing apparatus of the present invention is applied.

FIG. 27 is a diagram for explaining the operation of the defect removal circuit 73 of FIG. 26;

FIG. 28 is a block diagram illustrating a configuration example of a defect removal circuit 73 in FIG. 26;

FIG. 29 is a diagram of a table explaining an operation in the controller 104 of FIG. 26;

FIG. 30 is a diagram for explaining the influence of defects on the outputs of the variable gain amplifiers 63 and 66 of FIG. 26;

FIG. 31 is a block diagram showing another configuration example for obtaining the minimum distance between the education data and the reproduction data.

FIG. 32 is a block diagram showing a configuration of an embodiment of an optical disk manufacturing apparatus to which the information recording device of the present invention is applied.

FIG. 33 is a diagram illustrating a data recording method in a conventional optical disc.

FIG. 34 is a diagram illustrating a data reproducing method in a conventional optical disc.

[Explanation of symbols]

 Ts: shift period tr: rising period (transient period) tf: falling period (transient period) 1: optical disk (information recording medium) 3: pickup (optical detection system) 7: PLL circuit (clock generation means) 9: A / D conversion circuit (level detecting means) 10 bias removing circuit 11 two-dimensional decoder (determining means) 15 controller (determining means) 21, 22 delay circuit 23 RAM 31, 32, 41, 43 latch circuit 60 Gain adjustment circuits 63 and 66 Gain variable amplifiers 71 and 72 FIFOs 73 and 74 Defect removal circuits 81 and 83 FIFOs 82 and 84 Defect removal circuits

Continuation of the front page (56) References Patent 3068105 (JP, B2) Patent 3147255 (JP, B2) Table 6-507513 (JP, A) US Patent 4,873,680 (US, A) International Publication 93/16467 (WO, A1) H. H. Hopkins, Diffraction action of laser read-out systems for optical video discs, Journal of the Optical Society, United States of America. 69, no. 1, pp. 4-24 Shigeo Kubota, Applative Conditional Requirements to Reproduction Jitter-Free Signals in an Optical Digital Disk System, Applica. 26, No. 18, pp. 3961− 3973 (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/24

Claims (41)

(57) [Claims] 1. An information recording medium on which information recorded in each pit is reproduced by an optical detection system which scans with a light beam along a pit row and obtains a reproduction signal corresponding to each pit, wherein: A predetermined period smaller than a rising period or a falling period of the reproduction signal determined according to the transfer characteristic of the reproduction signal.
In between, the edge position of the information pit from a predetermined reference position, the information recording medium characterized in that shifted stepwise in response to the digital information to be recorded. 2. The information according to claim 1, wherein edge positions of a front end and a rear end of the information pit are shifted stepwise from a predetermined reference position according to digital information to be recorded. recoding media. 3. The information recording medium according to claim 1, wherein the information pit is formed as a physical concave or convex portion on a light beam reflection surface. 4. The information recording medium according to claim 1, wherein said information pits are formed by partial reversal of magnetization of a magneto-optical film. 5. The information recording medium according to claim 1, wherein the information pits are arranged at a constant distance interval when moving relative to the optical detection system at a constant linear velocity. 6. The information pits are arranged at a constant angular interval with respect to a central angle when the optical pits are moved relative to the optical detection system at a constant angular velocity about a predetermined rotation center. 2. The information recording medium according to 1. 7. The information recording medium according to claim 1, wherein the predetermined reference position is set corresponding to a center position of the information pit. 8. The information pit is inserted into a pit row,
2. The information recording apparatus according to claim 1, further comprising an educational pit whose edge position is shifted stepwise from the predetermined reference position in accordance with educational data set in advance corresponding to the insertion position. Medium. 9. A pair of edge positions adjacent to each other in the pit row direction of the educational pit in a stepwise manner from the predetermined reference position according to a pair of educational data set in advance corresponding to the insertion position. 9. The information recording medium according to claim 8, wherein the information recording medium is shifted. 10. As the pair of educational data, all conceivable combinations are set in advance corresponding to the insertion positions, and educational pits corresponding to the educational data of all these combinations are set as pits of the information pit. 10. The information recording medium according to claim 9, wherein the information recording medium is sequentially inserted and arranged at a row insertion position. 11. The educational pit of the educational data is arranged at a position where at least one dummy pit is interposed from the information pit.
The information recording medium according to 9 or 10. 12. When the educational pit is arranged at a position adjacent to the information pit, an edge opposite to an edge facing the information pit is shifted stepwise according to the educational data. The information recording medium according to claim 8, 9 or 10, wherein 13. The information according to claim 1, further comprising a reference pit inserted into a pit row of the information pit, the shift amount of an edge position being set to a minimum value. recoding media. 14. The information recording medium according to claim 13, wherein a shift amount of a pair of edge positions adjacent to each other in the pit row direction of the reference pit is set to a minimum value. 15. The information according to claim 1, further comprising a reference pit inserted into a pit row of the information pit, the shift amount of an edge position being set to a maximum value. recoding media. 16. The information recording medium according to claim 15, wherein a shift amount of a pair of edge positions adjacent to each other in the pit row direction of the reference pit is set to a maximum value. 17. A system according to claim 1, further comprising a pair of reference pits inserted into a pit row of said information pits, wherein a shift amount of each edge position is set to a minimum value and a maximum value. The information recording medium according to 9 or 10. 18. The shift amount of a pair of edge positions adjacent to each other in the pit row direction among the edge positions of the two reference pits is set to a minimum value, and the other pair of adjacent positions in the pit row direction is set to a minimum value. 18. The information recording medium according to claim 17, wherein the shift amounts of the edge positions are set to maximum values. 19. A rising or falling period of a reproduction signal determined on the basis of a transfer characteristic of the optical detection system on an information recording medium on which recorded information is reproduced by an optical detection system that scans with a light beam along a pit row. Predetermined period smaller than
An information recording apparatus comprising: recording means for recording digital information by shifting an edge position of an information pit stepwise from a predetermined reference position within the interval . 20. The recording means, wherein the recording means is inserted into a pit row of the information pit, and an edge position is shifted stepwise from the predetermined reference position in accordance with educational data set in advance corresponding to the insertion position. 20. The information recording apparatus according to claim 19, wherein the recorded educational pit is recorded on the information recording medium. 21. The information recording medium according to claim 19, wherein the recording means records a reference pit inserted into a pit row of the information pit and having a minimum shift amount of an edge position on the information recording medium. Or the information recording device according to 20; 22. The information recording medium according to claim 19, wherein the recording means records a reference pit inserted into a pit row of the information pit and having a maximum shift amount of an edge position on the information recording medium. Or the information recording device according to 20; 23. The recording means for recording on the information recording medium a pair of reference pits which are inserted into a pit row of the information pits and wherein the shift amount of each edge position is set to a minimum value and a maximum value. 21. The method according to claim 19, wherein
An information recording device according to claim 1. 24. Tachinobo of the reproduced signal determined in accordance with the transfer characteristic of the optical detection system along a pit row scanning with a light beam
Within a predetermined period that is smaller than the falling period or the falling period ,
An information reproducing apparatus that shifts an edge position of an information pit from a predetermined reference position in a step-like manner and reproduces recorded information from an information recording medium on which digital information is recorded. A clock generation unit that generates a clock that is phase-synchronized with the reference position; and a level detection unit that detects a reproduction level in a rising period or a falling period of the reproduction signal at a timing defined by the clock. An information reproducing apparatus comprising: a determination unit configured to determine recording information corresponding to a shift amount of an edge position of the information pit based on the reproduction level. 25. The information reproducing apparatus according to claim 24, wherein said clock generating means generates a clock at a timing corresponding to the center of said shift period. 26. The clock generating means according to claim 16, wherein said reference position is determined based on a reproduction signal obtained from a reference pit indicating the predetermined reference position recorded in a servo area of the information recording medium via the optical detection system. 26. The information reproducing apparatus according to claim 24, wherein the information reproducing apparatus generates a clock that is phase-synchronized with respect to. 27. An apparatus according to claim 27, wherein said level detecting means is constituted by an A / D conversion circuit for detecting the reproduction level by performing analog / digital conversion on the reproduction signal at a sample timing defined by the clock. 25. The information reproducing apparatus according to claim 24, wherein: 28. The information according to claim 27, wherein the A / D conversion circuit converts the digital data into digital data having a bit number larger than the bit number indicated by the shift amount of the edge position of the information pit. Playback device. 29. The judging means according to claim 1, wherein the educational data set in advance according to the insertion position of the information pit into the pit row is obtained from an educational pit set as a shift amount of each edge position adjacent in the pit row direction. Based on a reference point defined by a reproduction level sequentially detected by the level detecting means and an information point defined by a reproduction level sequentially detected from the information pit, the information pit is adjacent to the information pit in a pit row direction. 25. The information reproducing apparatus according to claim 24, wherein the recording information corresponding to each shift amount of the edge position is determined. 30. The level detecting unit detects a pair of educational data preset according to the insertion position from an educational pit set as a shift amount of each of the pair of edge positions. A reference point defined by a pair of reproduction levels obtained is learned, and a pit row direction of the information pit is determined based on the reference point and an information point defined by the pair of reproduction levels detected from the information pit. 25. The information reproducing apparatus according to claim 24, wherein a pair of recording information corresponding to a shift amount of each of a pair of edge positions adjacent to the pair is determined. 31. A pair of reproduction levels detected from the educational pits in which the pair of educational data is set are defined by setting one reproduction level as an upper address and the other reproduction level as a lower address. An address is used as a reference point, and the reference point is provided with storage means for storing the pair of educational data as decoded data, and the determination means determines whether one of the pair of reproduction levels detected from the information pit is to be reproduced. An address defined by setting the level as an upper address and the other reproduction level as a lower address is defined as an information point, and a pair of decoded data stored in an address of the storage means corresponding to the information point is recorded information. The information reproducing apparatus according to claim 24, wherein the determination is made as: 32. The decoding means regards the decoded data stored at the reference point closest to the information point among the decoded data stored at each reference point of the storage means as recorded information. 32. The information reproducing apparatus according to claim 31, wherein the information is determined by performing the determination. 33. A mapping process of setting an address of the storage means defined by a reproduction level detected from an educational pit in which the educational data is set as a reference point, and storing the educational data as decoded data at the reference point. 4. The apparatus according to claim 3, further comprising mapping means for performing the mapping.
33. The information reproducing apparatus according to 1 or 32. 34. The mapping means stores decoded data stored in a reference point closest to each of the storage points at each of the storage points other than the reference point among the storage points of the storage means. The information reproducing apparatus according to claim 33, wherein: 35. The information reproducing apparatus according to claim 31, wherein said storage means is constituted by a semiconductor memory which can be written / read at any time. 36. Bias removing means for subtracting a reproduction level detected from a reference pit whose edge position shift amount is set to a minimum value from a reproduction level detected by said level detection means. Claims 24, 25, 26, 27, 28, 29, 30, 31, 3.
The information reproducing apparatus according to 2, 33, 34 or 35. 37. An apparatus according to claim 37, wherein the bias removing unit is configured to calculate an average value of values other than a maximum value and a minimum value among a plurality of reproduction levels detected from a plurality of reference pits in which the shift amount of the edge position is set to the minimum value 37. The information reproducing apparatus according to claim 36, further comprising a defect removing function of subtracting a value from the reproduction level detected by the level detection unit. 38. The gain of the reproduction level detected by the level detection means is adjusted so that the reproduction level detected from the reference pit in which the shift amount of the edge position is set to the maximum value becomes a predetermined target value. 27. The method according to claim 24, further comprising gain adjusting means.
7, 28, 29, 30, 31, 32, 33, 34 or 3
6. The information reproducing apparatus according to 5. 39. An average value of values other than a maximum value and a minimum value among a plurality of reproduction levels detected from a plurality of reference pits in which a shift amount of an edge position is set to a maximum value. 39. The information reproducing apparatus according to claim 38, further comprising a defect removing function of adjusting a gain of a reproduction level detected by said level detecting means so that the value of the reproduction level becomes a predetermined target value. 40. A bias removing means for subtracting a reproduction level detected from a reference pit having a minimum edge position shift amount from a reproduction level detected by said level detection means, and a shift amount of the edge position. Gain adjustment means for adjusting the gain of the reproduction level output from the bias removing means so that the reproduction level detected from the reference pit set to the maximum value becomes a predetermined target value. Claims 24, 25, and 2
6, 27, 28, 29, 30, 31, 32, 33, 34
35. The information reproducing apparatus according to 35. 41. The bias removing means, comprising: a plurality of reproduction levels detected from a plurality of reference pits in which the shift amount of the edge position is set to the minimum value; Is subtracted from the reproduction level detected by the level detection means, and the gain adjustment means has a plurality of reference pits detected from a plurality of reference pits in which the shift amount of the edge position is set to the maximum value. It has a defect removal function of adjusting the gain of the reproduction level detected by the level detection means so that the average value of each of the levels except the maximum value and the minimum value becomes a predetermined target value. Claim 40
An information reproducing apparatus according to claim 1.