JPH10222847A - Information recording medium, information recorder and information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording medium, an information recorder and an information reproducing device capable of increasing linear recording density. SOLUTION: This information recording medium is constituted so that in the information recording medium reproducing information recorded on respective pits by an optical detection system scanning a light beam along a pit line and obtaining a regenerative signal according to respective pits, an edge position of an information pit is shifted from a prescribed reference position in a step shape in the track direction according to digital information to be recorded within the range equivalent to a prescribed shift period smaller than the transient period of the regenerative signal decided according to the transmission characteristic of the optical detection system, and the information pit shifted in the track direction is displaced further in the direction orthogonally intersecting with the track direction, and another digital information is recorded.

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 an information recording medium suitable for recording or reproducing information on or from this information recording medium.
The present invention relates to an information recording device and an information reproducing device.

[0002]

2. Description of the Related Art A sample servo system MO (magneto-optical disk) used in a conventional CAV (constant angular velocity) mode.
In such an optical disc, a servo byte section is periodically provided at a predetermined position of each track, and a clock pit for generating a reference clock and a wobble pit for tracking are formed in the servo byte section. In this case, the groove is modulated at a predetermined frequency to form a wobble, and the address is recorded in the wobble. However, in order to avoid interference with the originally recorded signal (EFM), as shown in FIG. Was modulated at a relatively low frequency. 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 is no clock pit,
As shown in FIG. 10, the length of the recorded pits and the interval between the pits are set to an integral multiple of the period T (0.3 μm) of the reference clock (channel clock) (3T in the case of a CD).
(0.3 μm) to 11 T (3.3 μm), and the pit lengths varied. Then, clock reproduction is performed using this, and recorded information is cut out in pit units.

[0004]

As described above, when an address is recorded by a wobble like an MO, it must be modulated at a relatively low frequency in order to avoid interference with the originally recorded signal (EFM). However, since the modulation frequency band is limited, high-density recording cannot be performed.

[0005] Further, when recording pits have various lengths such as CDs, it is not practical to record signals by wobbling the pits.

[0006] The present invention has been made in view of the above points, and has as its object to provide an information recording medium, an information recording apparatus, and an information reproducing apparatus which can increase the linear recording density.

[0007]

According to the information recording medium of the present invention, information recorded in each pit is recorded by an optical detection system which scans a light beam along a pit row to obtain a reproduction signal corresponding to each pit. In the information recording medium to be reproduced, the edge position of the information pit is determined by a predetermined reference within a range corresponding to a predetermined shift period shorter than a transition period of the reproduction signal determined according to the transfer characteristic of the optical detection system. From the position, the digital pits are shifted stepwise in the track direction according to the digital information to be recorded, and the information pits shifted stepwise in the track direction are further displaced in a direction orthogonal to the track direction to obtain another digital pit. The information is recorded.

According to the information recording apparatus of the present invention, an information recording medium on which an information signal is reproduced by an optical detection system that scans with a light beam along a pit row is reproduced according to the transmission characteristics of the optical detection system. Within a range corresponding to a predetermined shift period shorter than the signal transition period, the edge position of the information pit is shifted stepwise in the track direction from the predetermined reference position, and is shifted stepwise in the track direction. Digital information is recorded by further displacing the information pit in a direction perpendicular to the track direction.

According to another aspect of the present invention, there is provided an information reproducing apparatus for reproducing an information signal on an information recording medium on which an information signal is reproduced by an optical detection system which scans with a light beam along a pit row. The edge position of the information pit is shifted stepwise in the track direction from a predetermined reference position within a range corresponding to a predetermined shift period shorter than the signal transition period, and the information pit is further orthogonal to the track direction. An information reproducing apparatus for reproducing recorded information from an information recording medium on which digital information is recorded by displacing in the direction in which the information pit is displaced in a direction perpendicular to a track direction. Is what you do.

An information recording medium, an information recording apparatus,
According to the information reproducing apparatus, the following operation is performed. First, the arrangement of pits on an information recording medium in which information pits are recorded in a wobble manner will be described. The pits are formed so as to wobble in the radial direction with respect to the center of the track. Each pit is modulated by a predetermined value above and below the track center in the vertical direction (left and right with respect to the track traveling direction). Such a wobble amount is set to a predetermined amount from the center of the track so that the edge position shifted stepwise in the track direction does not move. If such a wobble of a predetermined value in the up-down direction is recorded by a predetermined modulation method, a signal of one or more pits is recorded for each pit, with the wobble in the up direction and the wobble in the down direction corresponding to the signal level, respectively. Will be.

Next, the operation of reproducing the wobbled pits will be described. The optical detection system irradiates a wobbled pit recorded on the information recording medium with a light beam, and reproduces a signal recorded on the information recording medium from the reflected light. The reproduced signal including the signal of the wobbled pit output from the optical detection system is divided into a plurality of divided photodiodes. The overlapping portion and the overlapping portion of the 0th-order diffracted light and the -1st-order diffracted light are detected.

A push-pull signal, which is a difference between signals detected by the plurality of divided photodiodes, is generated as a wobble modulation signal. At this time, the push-pull signal is the modulation signal itself of each pit wobble up and down with respect to the track center. That is, detecting a push-pull signal directly detects a wobble modulation signal. A push-pull signal in the minus direction is obtained at the portion corresponding to the wobble in the downward direction, and a push-pull signal in the plus direction is obtained at the portion corresponding to the wobble in the upward direction. Thus, by detecting the push-pull signal, the signal can be demodulated in accordance with the signal level of the push-pull signal in the minus direction and the push-pull signal in the plus direction. As described above, by using the push-pull signal, the direction of the wobble and the amount of the wobble can be easily detected.

[0013]

The present embodiment will be described below. First, before describing the present embodiment, a recording / reproducing method as a premise thereof will be described. The present applicant has previously described Japanese Patent Application No. 3-167585 in which digital information is recorded by shifting the position of the front or rear edge of an information pit from a predetermined reference position in a stepwise manner in accordance with recording information. Proposed that. According to this recording / reproducing method, it is possible to detect changes in the positions of pits and pit edges with extremely high accuracy, and thus it is possible to record information with minute changes that have been considered impossible before. As a result, it has become possible to realize higher density recording than ever.

In such a recording method, first, a recording signal subjected to PWM modulation is generated in accordance with recording data, and pits corresponding to the length at the time of the zero cross are formed. By doing so, the position of the edge of the pit changes stepwise from the position indicated by the reference clock. According to the amount of change, data of eight levels (3 bits) from 0 to 7 can be recorded for one edge.

In the reproducing method, first, an RF signal reproduced from an information recording medium is greatly amplified to obtain a binary RF signal. Since a clock pit is formed on the disk on which the information is recorded, a reference clock is generated based on the clock pit, and a sawtooth signal is generated in synchronization with the reference clock. Then, the sawtooth wave signal and the binarized RF
The position of the edge of the information pit can be detected by detecting the timing at which the signal crosses.

However, although higher density recording is required than in the previous proposal, in the future proposal, intersymbol interference between adjacent edges may occur, and the recording density will be further increased. Then, there is a disadvantage that accurate reproduction becomes difficult.

In view of such a situation, the present applicant has
As disclosed in Japanese Patent Application No. 5-20876 (refer to Japanese Patent Application Laid-Open No. 6-76303), it is possible to accurately reproduce high-density recording data with a simple configuration, and to enhance nonlinearity without emphasizing noise components. For the purpose of reducing the intersymbol interference, in an information recording medium in which information recorded in each pit is reproduced by an optical detection system that scans with a light beam along a pit row and obtains a reproduction signal corresponding to each pit. ,
Within a range corresponding to a predetermined shift period shorter than the transition period of the reproduction signal determined according to the transfer characteristic of the optical detection system,
An information recording medium in which the edge position of an information pit is shifted stepwise from a predetermined reference position in accordance with digital information to be recorded, and a recording apparatus and a reproducing apparatus for the same have been proposed.

With respect to the information recording medium, the recording apparatus and the reproducing apparatus which are the premise of the present embodiment, the parts related to the present embodiment will be described. FIG.
Shows an example of a basic format of an optical disk to which the information recording medium proposed above is applied. here,
CLV mode, track pitch 1.6 on reflection type optical disc having a diameter of 120 mm (pits are formed on the reflection surface of the light beam by physical recesses or projections)
A pit row is recorded in μm. All information is
The shift amount is recorded as an eight-step shift amount between the leading edge (rising edge) and the trailing edge (falling edge) of the pits arranged at a constant period of 1.67 μm. 1 of this shift amount
The unit shift amount あ る, which is a unit, is set to 0.05 μm.

Since it is possible to record 3-bit information with eight stages of 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 more than twice the current CD system.

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

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.
A rising period t which is a transient period of the signal (reproduced signal) (a period other than the steady state in which the signal is at the 0 level or the saturation level).
r or within a range corresponding to a period shorter than the falling period tf.

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 represented by its transfer function (OTF: Optic).
MTF (Modulation Transfer), which is the absolute value of al Transfer Function
r 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 △
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 pit edge positions are obtained.
7 can be obtained. Thus, at one sample timing in the transition period of the RF signal, the reproduction level L
The condition for detecting 0 to L7 is shift period Ts ≦ transition period (rising period tr or falling period tf).

Here, the sample timing by the sample clock SP is desirably a timing corresponding to the center of the shift period Ts. By using this timing, the reproduction level can be detected over the entire range of the transition period of the RF signal. Becomes

Information to be recorded on the optical disc 1 is cut out in units of 3 bits, and as recording data an and bn, n
Recorded in the third pit. FIG. 5 shows this state. The leading edge of the pit is set to one of eight shift positions 0 to 7 according to the recording data an.
The pitch 各 of each shift position is 0.05 as described above.
μm. As a result, each pit has the recording data an, b
When n is formed on the edge of shift position 0,
The shortest length LP is 0.5 μm.

Returning to FIG. 3, between the data area consisting of four data pits where data is recorded, five servo pits are provided.
A servo area consisting of pits is inserted. 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 P
3 to P5. The front edge on the left side of the educational pit P2 in the figure is set at any one of the eight shift positions M of 0 to 7 and the rear edge on the right side in the figure is also 0 to 7 Are set to any one of the eight shift positions N.

The combination of the leading edge position M and the trailing edge position N 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 educational pit P1 is a dummy in this case. In other words, it is theoretically possible to form the educational data not on both edges of the pit P2 but on both edges of the pit P1. However, in such a case, since the pit adjacent to the left end of the pit P1 is the data pit in the data area, the position of the edge changes corresponding to the data. As a result, the degree of interference with the edge of the educational pit P1, particularly on the edge on the data area side, changes depending on the data value. Therefore, it is difficult to pattern the educational data in a constant state as described later. Therefore, it is preferable that the educational data is formed not at the edges at both ends of the pit P1, but at both edges of the educational pit P2. In this way, the education pit P3 adjacent to the rear end edge of the education pit P2 and the education pit P1 adjacent to the front end edge are both constant (no change) at the edge of (0, 0), and therefore, the education pit P3 is not changed. When the educational data of the pit P2 is read, constant intersymbol interference is always received, and a constant pattern can be obtained.

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

FIG. 6 briefly explains the planar structure of the optical disc 1. Since a 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 adjacent tracks, and as shown in FIG. It is recorded in.

FIG. 7 is a block diagram showing a configuration of an embodiment of an optical disk reproducing apparatus to which the information reproducing apparatus proposed above is applied. The optical disk 1 is rotated by a spindle motor 2. Information is recorded on the optical disc 1 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 the educational pits P1, P2
And reference pits P3 to P5 are formed. It goes without saying that data pits are formed in the data area.

The optical 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. Pickup 3
Are 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. Also, AP
The C 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 using all RF signals.
Clock recovery is performed using only the F signal. 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 at all.

The spindle servo circuit 8 controls the spindle motor 2 to control the optical disc 1 to rotate at a constant angular 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 timing of the rising edge of P, the digital data (reproduction level) indicating 256 levels of 8-bit data is represented by A /
D conversion is performed. 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 programs executed by the CPU, and the like, and performs various processes such as mapping described later.

The two-dimensional decoder 11 decodes the signal supplied from the bias removing 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).

Next, the operation of the above proposed device configured as described above will be described. First, the principle of reading the shift position of the information pit 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 data of the A / D conversion circuit 9 during the shift period of the leading edge and the trailing edge of the n-th pit. (Reproduction level) is Va as shown in FIG.
(N) and Vb (n). This Va (n), Vb
(N) represents the level of the RF signal and can be expressed by the following equation. Va (n) = {rf × an + ga (bn) Vb (n) = {rf × bn + gb (an) Here, {rf is a value obtained by multiplying the unit shift amount} by a constant k,
ga (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 data is to solve this simultaneous equation and obtain the recorded signals an and bn from the observed Va (n) and Vb (n).

The signals an and bn can be regarded as a problem of pattern recognition in a two-dimensional space. That is, the above equation is calculated for all the combinations of (an, bn), and the resulting Va (n) is plotted in the two-dimensional space as the X-axis and Vb (n) as the Y-axis. I do. On this two-dimensional plane, functions ga (bn) and gb (an) representing the influence of intersymbol interference are expressed as positional distortion of information points. That is, the function ga (b
When n) and gb (an) are 0 (when no intersymbol interference occurs), the information point is Va
It will be located at a reference point determined by (n) and Vb (n). However, actually, functions ga (bn) and gb (an) of intersymbol interference, which are simply increasing functions, occur. As a result, the information point is shifted from the reference point.

Since this shift is caused by intersymbol interference, the larger the intersymbol interference, the greater the shift. That is, the smaller the linear density recording (the higher the density), the greater the distortion.

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 as reference points.
Then, information points obtained by reading the data of the data pits are plotted on the RAM, and it is determined that the closest reference point is 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.

As described above, according to the information recording medium proposed above, the information pits are set within a range corresponding to the predetermined shift period shorter than the transition period of the reproduction signal determined according to the transfer function of the optical detection system. Is shifted stepwise from a predetermined reference position in accordance with digital information to be recorded, so that a recording density twice or more as compared with a conventional CD system can be obtained.

Although high-density recording can be performed by the above-mentioned proposal, recording with higher optical density has been required. Therefore, the applicant has shifted the edge position in the track direction according to the above proposal, and applied the means of the present embodiment to the radial direction.

In the present embodiment, in addition to shifting the edge position of the information pit according to the digital information to be recorded in a step-like manner in the track direction according to the above-mentioned proposal, this edge position does not move. In this case, the wobble (meandering) in the radial direction (the direction perpendicular to the track direction) is slightly wobble (meandering) to further record a signal.

Hereinafter, the present embodiment will be described. First, the arrangement of pits on an information recording medium in which information pits are wobbled and recorded in binary according to the present embodiment will be described.
FIG. 1A is a diagram showing wobbled pits. FIG. 1A
As shown in the figure, the pit is located at the track center C indicated by a chain line.
And wobble in the radial direction. In FIG. 1A, each pit is located at the track center C.
An example is shown in which the data is modulated by binary values (1 bit) in the vertical direction (left and right with respect to the track traveling direction). Such wobble amount is, for example, three times from the track center C.
Experiments have shown that by setting the thickness to about 0 nm, the edge position according to the above-mentioned proposal is not moved. Therefore, in the present embodiment, the maximum wobble amount is set to about 30 nm. Modulation by such a binary wobble in the vertical direction is a modulation method with a small DC component.
For example, NRZ (Non Return to Zero)
o) If recording is performed by the modulation method, when the wobble in the upward direction is “1” and the wobble in the downward direction is “0”, “low level” or “high level” completely corresponds to “0” or “1”. Therefore, in FIG. 1A, “0, 1, 0, 0”
Thus, a 1-bit signal is recorded for each pit.

Next, the operation of reproducing the wobbled pits will be described. In FIG. 7, an optical pickup 3 irradiates a laser beam to a wobble pit recorded on the optical disk 1 and reproduces a signal recorded on the optical disk 1 from the reflected light. The RF signal including the wobbled pit signal output from the pickup 3 is amplified by the head amplifier 4 and supplied to the focus tracking servo circuit 5. The multi-segmented photodiode of the focus tracking servo circuit 5 of the diffracted light due to the wobbled pits of the optical disc 1 overlaps the 0th-order diffracted light passing through the objective lens, the + 1st-order diffracted light, and the 0th-order diffracted light and the -1st-order diffracted light. And the respective parts are detected. The multi-segmented photodiode is divided into two (A, B), three (A, B, C), four (A, B, C) by dividing lines parallel to the track direction.
C, D) and the like, and a push-pull signal in an area symmetrical with respect to the center line is used. As the push-pull signal, AB may be used for two divisions, AC may be used for three divisions, and AD may be used for four divisions.

The focus tracking servo circuit 5
A push-pull signal having a different band, which is a difference between signals detected by the multi-division photodiode, is generated as a tracking error signal and a wobble modulation signal. At this time,
The push-pull signal shown in FIG. 1B is the modulation signal itself of each pit wobbled in the vertical direction with respect to the track center C shown in FIG. 1A. That is, the wobble modulation signal is detected by using a push-pull signal having a band different from that of the tracking error signal. In FIG. 1B,
In the portion corresponding to the downward wobble in FIG. 1A, a push-pull signal in the negative direction is obtained, and in the portion corresponding to the upward wobble, a push-pull signal in the positive direction is obtained. Thus, by detecting this push-pull signal, the push-pull signal in the minus direction is set to “0”,
The push-pull signal in the plus direction is made to correspond to “1”,
The signal of “0, 1, 0, 0” can be demodulated. As described above, by using the push-pull signal, the direction of the wobble and the amount of the wobble can be easily detected.

Next, according to the present embodiment, the number of information pits is three.
The arrangement of pits on an information recording medium recorded by wobbling with a value or quinary will be described. FIG. 2A is a diagram showing wobbled pits. As shown in FIG. 2A, the pits are formed so as to wobble in a radial direction with respect to a track center C indicated by a chain line. In FIG. 2A,
As shown by the solid line, an example is shown in which each pit is modulated by three values of the center with respect to the track center C and the upper and lower values in the vertical direction.
Experiments have shown that the wobble amount is set to about 30 nm from the track center C, as described above, so that the edge position according to the above-mentioned proposal does not move. Therefore, in the present embodiment, the maximum wobble amount is set to about 30 nm. If such modulation by three-valued wobble in the center and vertical directions is recorded by the NRZ modulation method, the center wobble is “0, 0”, the upward wobble is “1, 0”, and the downward wobble is “0, 0”. 0,
When "1", each wobble corresponds to a combination of three of the two bits, and therefore, in FIG. 2A, "1, 0,
0, 1, 0, 0, 0, 0 ", and 2 per pit
A signal of three combinations of the bits will be recorded. In this case, “1, 1” of the two bits is not used.

In FIG. 2A, each pit is located at the center with respect to the track center C as shown by a solid line, the upper and lower three values in the vertical direction, and between the center and upper as shown by a dotted line.
An intermediate value may be provided in the vertical direction between the center and the lower side, and modulation may be performed with five values. In this case, since the maximum wobble amount is about 30 nm, an intermediate value is about 15 nm. If the modulation by the wobble of five values in the middle, the up-down direction, and the middle in the up-down direction is recorded by the NRZ modulation method, the wobble at the center is “0, 0, 0” and the wobble in the up direction is “1, 0, 0 ", wobble downward is" 0, 1,
0 ", the upper middle wobble is" 0, 1, 1 "and the lower middle wobble is" 0, 0, 1 ". Since each wobble corresponds to five combinations of 3 bits, the pit Signals of five combinations of three bits per one are recorded. In this case, of the three bits, “1, 0, 1”, “1, 1, 0”, “1, 1, 1”
Is not used.

Next, the operation of reproducing the wobbled pits will be described. In the same manner as described above, the multi-segment photodiode of the focus tracking servo circuit 5 outputs a portion of the diffracted light by the wobbled pits of the optical disc 1 where the 0th-order diffracted light passing through the objective lens overlaps the + 1st-order diffracted light, An overlapping portion of the first-order diffracted light is detected.

The focus tracking servo circuit 5
A push-pull signal which is a difference between signals detected by the multi-division photodiode is generated as a wobble modulation signal.
At this time, the push-pull signal shown in FIG. 2B is at the center with respect to the track center C shown in FIG.
The modulated signal itself of each pit wobbled in three values in the vertical direction. That is, detecting a push-pull signal directly detects a wobble modulation signal.
In FIG. 2B, a push-pull signal in the minus direction is obtained in a portion corresponding to the downward wobble in FIG. 2A, and a push-pull signal in the plus direction is obtained in the portion corresponding to the upward wobble. By detecting this push-pull signal, the push-pull signal in the minus direction is “0, 1”, the push-pull signal in the plus direction is “1, 0”, and the push-pull signal of 0 is “0, 0”. , The signal of “1, 0, 0, 1, 0, 0, 0, 0” can be demodulated.

When the signal is modulated by five values as shown by the dotted line, a middle push-pull signal in the minus direction is obtained in FIG. 2B at a portion corresponding to the middle wobble in the lower direction in FIG. 2A. In the portion corresponding to the middle wobble in the upward direction, a middle push-pull signal in the plus direction is obtained. Thus, by detecting the push-pull signal, the push-pull signal in the minus direction is set to “0,
1, 0, the middle push-pull signal in the minus direction is “0, 0, 1”, the push-pull signal in the plus direction is “1, 0, 0”, and the middle push-pull signal in the plus direction is “0, 1”. , 1 ”, 0, the push-pull signal is“ 0, 0,
A signal wobbled in correspondence with "0" can be demodulated.

As described above, the values wobbled are binary,
The values are not limited to five values, and may be set to multiple values as long as possible. By setting to multiple values, signals can be recorded at a higher density.

In this manner, the pits of the data area formed continuously from the inner circumference to the outer circumference in the predetermined section are wobble in the radial direction over the entire area on the optical disk 1 to record the address information and the signal for rotation control. By doing so, higher density recording can be performed.

The shift of the edge position in the track direction according to the above-mentioned proposal is executed as it is, and the recording capacity is increased by the amount of information recorded by the wobble in the radial direction without any influence on the shift. Can be done.

In the above example, the modulation by the wobble is N
Although an example in which recording is performed using the RZ modulation method has been described, recording may be performed using the NRZI modulation method or another modulation method.

The optical disc 1 as an information recording medium according to this embodiment is recorded on each pit by a pickup 3 as an optical detection system for scanning a light beam along a pit row to obtain a reproduction signal corresponding to each pit. In the optical disc 1 as an information recording medium on which reproduced information is reproduced, a predetermined shift period T shorter than a transition period of a reproduction signal determined according to a transfer characteristic of the pickup 3 as an optical detection system.
Within the range corresponding to s, the edge position of the information pit is shifted stepwise in the track direction from a predetermined reference position in accordance with the digital information to be recorded, and the information pit shifted stepwise in the track direction. Is further displaced in the direction perpendicular to the track direction to record other digital information. In addition to information recording by the track direction shift, there is no effect on the information recording by the track direction shift. In addition, information can be recorded in the radial direction without any further processing, and an information recording medium of high density recording can be obtained.

Further, the information recording medium of this embodiment is:
In the above description, the displacement values are two or more binary, ternary and quinary values on the inner and outer sides with respect to the track center. At least one bit can be recorded.

Further, the information recording apparatus of this embodiment
An information signal is reproduced by an optical pickup 1 serving as an optical detection system that scans with a light beam along a pit row. An optical disc 1 serving as an information recording medium is provided with a reproduction signal determined according to the transfer characteristics of the pickup 3 serving as an optical detection system. The edge position of the information pit is shifted stepwise in the track direction from a predetermined reference position within a range corresponding to a predetermined shift period Ts shorter than the transition period,
Since a laser cutting device (not shown) is provided as recording means for recording digital information by displacing the information pits shifted stepwise in the track direction in a direction perpendicular to the track direction, the apparatus is provided with a laser cutting device. In addition to the information recording by the shift, the information recording by the shift in the track direction can be further recorded in the radial direction without affecting the information recording at all, and high-density recording can be performed.

Further, the information recording apparatus of this embodiment
In the above description, the displacement values are two or more binary, ternary and quinary values on the inner and outer sides with respect to the track center. At least one bit can be recorded.

Further, the information reproducing apparatus of this embodiment
An information signal is reproduced by an optical pickup 1 serving as an optical detection system that scans with a light beam along a pit row. An optical disc 1 serving as an information recording medium is provided with a reproduction signal determined according to the transfer characteristics of the pickup 3 serving as an optical detection system. The edge position of the information pit is shifted stepwise in the track direction from the predetermined reference position within a range corresponding to a predetermined shift period Ts shorter than the transition period, and the information pit is further shifted in a direction orthogonal to the track direction. In an information reproducing apparatus for reproducing recorded information from an information recording medium on which digital information is recorded by displacing the information, a focus tracking servo as reproducing means for reproducing an information signal due to a displacement of an information pit displaced in a direction orthogonal to a track direction. Since the circuit 5 is provided, in addition to the information signal due to the shift in the track direction, Reproducing the information signal further by the displacement in the radial direction without giving any way affect the information signal by click direction of the shift is possible, it is possible to reproduce the high density recorded information signal.

Further, the information reproducing apparatus of this embodiment
In the above description, the focus tracking servo circuit 5 as the reproducing means has a photodetector for forming a far-field image from the optical disc as the information recording medium, and the photodetector is divided by a dividing line parallel to the track direction. Since a push-pull signal having a strength in a region symmetrical with respect to the center line is used, an information signal due to displacement in the radial direction can be reproduced.

[0063]

According to the information recording medium of the present invention, information recorded in each pit is reproduced by an optical detection system which scans the pit array with a light beam to obtain a reproduction signal corresponding to each pit. In the recording medium, the edge position of the information pit is recorded from a predetermined reference position within a range corresponding to a predetermined shift period shorter than a transition period of the reproduction signal determined according to the transfer characteristic of the optical detection system. According to the digital information to be shifted, the digital pits are shifted stepwise in the track direction, and the other information pits shifted stepwise in the track direction are further displaced in a direction perpendicular to the track direction to record other digital information. In this way, in addition to the information recording by the track direction shift, there is no influence on the information recording by the track direction shift. Furthermore it is possible to carry out the radial direction of the information recorded without an effect that it is possible to obtain an information recording medium of high density recording.

Further, in the information recording medium of the present invention, in the above description, the value of the displacement is two or more values on the inner peripheral side and the outer peripheral side with respect to the track center. There is an effect that an information signal of 1 bit or more can be recorded.

Further, the information recording apparatus of the present invention provides a reproduction apparatus which reproduces an information signal by an optical detection system which scans with a light beam along a pit row, in accordance with the transmission characteristics of the optical detection system. Within a range corresponding to a predetermined shift period shorter than the signal transition period, the edge position of the information pit is shifted stepwise in the track direction from the predetermined reference position, and is shifted stepwise in the track direction. Recording means for recording digital information by further displacing the information pits in a direction perpendicular to the track direction, so that in addition to information recording by the track direction shift, information by the track direction shift is provided. Information can be recorded further in the radial direction without affecting recording, and high-density recording can be performed. There is an effect that kill.

Further, in the information recording apparatus of the present invention, in the above description, since the value of the displacement is two or more values on the inner peripheral side and the outer peripheral side with respect to the track center, at least There is an effect that an information signal of 1 bit or more can be recorded.

Also, the information reproducing apparatus of the present invention provides an information recording medium on which an information signal is reproduced by an optical detection system that scans with a light beam along a pit row, in accordance with the transmission characteristics of the optical detection system. The edge position of the information pit is shifted stepwise in the track direction from a predetermined reference position within a range corresponding to a predetermined shift period shorter than the signal transition period, and the information pit is further orthogonal to the track direction. An information reproducing apparatus for reproducing recorded information from an information recording medium on which digital information is recorded by displacing in the direction in which the information pit is displaced in a direction perpendicular to a track direction. Therefore, in addition to the information signal caused by the shift in the track direction, there is no influence on the information signal caused by the shift in the track direction. Further possible while reproducing the information signal by the displacement in the radial direction, an effect that it is possible to reproduce the high density recorded information signal.

In the information reproducing apparatus according to the present invention, the reproducing means has a photodetector for forming a far-field image from an optical disc as the information recording medium, and the photodetector is provided in a track direction. Since a push-pull signal having a strength in a region symmetrical with respect to the center line is used because the push-pull signal is divided by a dividing line parallel to the center line, an effect that an information signal due to displacement in the radial direction can be reproduced is obtained.

[Brief description of the drawings]

FIG. 1 shows a wobbled pit (binary) according to the present embodiment.
FIG. 1A shows a wobbled pit, and FIG. 1B shows a push-pull signal.

FIG. 2 shows wobbled pits (three values,
5A) and a push-pull signal. FIG. 2A shows a wobbled pit, and FIG. 2B shows a push-pull signal.

FIG. 3 is a diagram showing a configuration of a data area and a servo area of a format of an optical disk to which an information recording medium of the above proposal, which is a premise of the present embodiment, is applied.

FIG. 4 is a diagram showing an example of the configuration of information pits in an information recording medium of the previous proposal, which is a premise of the present embodiment.

FIG. 5 is a diagram showing an example of the configuration of information pits in an information recording medium of the earlier proposal which is a premise of the present embodiment.

FIG. 6 is a diagram for explaining a phase between tracks of an information recording medium proposed earlier as a premise of the present embodiment.

FIG. 7 is a block diagram showing a configuration of an optical disk reproducing apparatus to which the previously proposed information reproducing apparatus which is a premise of the present embodiment is applied.

FIG. 8 is a diagram for explaining intersymbol interference between adjacent edges proposed in the previous proposal as a premise of the present embodiment.

FIG. 9 is a view showing a conventional wobbled groove.

FIG. 10 is a diagram showing pits of different lengths in the related art.

[Explanation of symbols]

Ts shift period, tr rise period (transient period), tf fall period (transient period), 1 optical disk (information recording medium), 3 pickup, 7 PLL
Circuit (clock generation means), 9 A / D conversion circuit (level detection means), 10 bias removal means, 11 two-dimensional decoder, 15 controller (judgment means)

Claims (6)

[Claims] 1. An information recording medium on which information recorded in each pit is reproduced by an optical detection system that scans a light beam along a pit row and obtains a reproduction signal corresponding to each pit, wherein: Within a range corresponding to a predetermined shift period shorter than the transition period of the reproduction signal determined according to the transfer characteristic of the reproduction signal, the edge position of the information pit is tracked from the predetermined reference position according to the digital information to be recorded. The information pits shifted stepwise in the track direction are further displaced in a direction perpendicular to the track direction to record other digital information. Information recording medium. 2. The information recording medium according to claim 1, wherein the value of the displacement is two or more values on an inner peripheral side and an outer peripheral side with respect to a track center. 3. An information recording medium on which an information signal is reproduced by an optical detection system that scans with a light beam along a pit row is shorter than a transition period of a reproduction signal determined according to a transfer characteristic of the optical detection system. The edge position of the information pit is shifted stepwise in the track direction from the predetermined reference position within the range corresponding to the predetermined shift period, and the information pit shifted stepwise in the track direction is further moved in the track direction. An information recording apparatus comprising recording means for recording digital information so as to be displaced in a direction perpendicular to the direction. 4. The information recording apparatus according to claim 3, wherein the value of the displacement is two or more values on an inner peripheral side and an outer peripheral side with respect to a track center. 5. An information recording medium on which an information signal is reproduced by an optical detection system that scans with a light beam along a pit row is shorter than a transition period of a reproduction signal determined according to a transfer characteristic of the optical detection system. Within the range corresponding to the predetermined shift period, the edge position of the information pit is shifted stepwise in the track direction from the predetermined reference position, and the information pit is further displaced in the direction perpendicular to the track direction to obtain digital information. An information reproducing apparatus for reproducing recorded information from an information recording medium on which information is recorded, comprising: reproducing means for reproducing an information signal based on a displacement of the information pit displaced in a direction orthogonal to a track direction. apparatus. 6. The information reproducing apparatus according to claim 5, wherein said reproducing means has a photodetector for forming a far-field image from an optical disc as said information recording medium, and said photodetector is arranged in a track direction. An information reproducing apparatus which uses a push-pull signal divided by a parallel dividing line and having an intensity in a region symmetric with respect to a center line.