JPH11232723A - Method, medium, and device for information recording, and information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the recording density of an information signal by arranging a 1st and a 2nd segment of a specific recording area adjacently on a signal track and recording pieces of information in the 1st and 2nd segments with a couple of magnetic walls representing information with their positions at a constant interval. SOLUTION: An array of magnetized areas is formed on the signal track 41, and at the border parts between the magnetized areas and precedent and following magnetized areas, 1st and 2nd magnetic walls Qf01 to Qf16 and Qr01 to Qr16 are formed as information marks in array in the 1st and 2nd segments Sf01 to Sr01. The 1st magnetic walls Qf01 to Qf16 and 2nd magnetic walls Qr01 to Qr16 form couples respectively, the couples of the magnetic walls correspond to pieces of data constituting the information signal, and the intervals Lq between the couples of the 1st magnetic walls Qf01 to Qf16 and 2nd magnetic walls Qr01 to Qr16 are constant. Consequently, even when the formation intervals of the magnetic walls are smaller than the diameter of a light spot, information can be reproduced and the recording density can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording method for recording information, an information recording medium, an information recording device, and an information reproducing device.

[0002]

2. Description of the Related Art Hitherto, several methods for recording an information signal at a high density on an information recording medium have been known, and among them, optical recording and magnetic recording are widely and generally used. In such a method, the recording density of an information signal is limited by the limit of miniaturization of an information signal mark that can be recorded as an information signal on a recording medium and the detection resolution of the information signal mark in the recorded information.

[0003] This will be described with reference to an example in which an information signal is recorded on an optical recording medium and reproduced. FIG. 7 shows a state of recording an information signal on an optical recording medium, and FIG. 8 shows a state of reproducing an information signal from the optical recording medium. Each drawing is a partially enlarged view of a recording portion or a reproduction portion of the information signal of the optical recording medium, (a) is a side sectional view, and (b) is a diagram viewed from a lower surface direction. First, the optical recording medium 50 is a substrate 5 made of a transparent material.
1 and a signal track 52 formed on the substrate. The signal track 52 is composed of layers of an organic dye material, a phase change material, a magnetic material, and the like.

When an information signal is to be recorded, the optical recording medium 50 is moved by the optical recording apparatus in the direction indicated by the arrow A as shown in FIG. A power recording light beam converges on a minute light spot 54 and is irradiated. When the light spot 54 is scanned on the signal track 52 in this manner, the temperature of the irradiated portion of the light spot 54 on the signal track 52 rises,
As a result, the surface shape changes to form a concave portion or cause a phase change (for example, a phase change between a crystal and an amorphous phase). Further, the signal track 52 is formed of a layer of a magnetic material,
If a magnetic field is applied simultaneously with the irradiation of the recording light beam, the magnetization state of the irradiated portion of the light spot 54 changes. As the optical recording medium 50 moves, a row of information signal marks 53 is partially formed on the signal track 52 due to the above state change. Here, as an information recording method, assuming that an information signal is composed of a plurality of data and each data is either “0” or “1”, for example, the front end and the rear end of each information signal mark 53 are simply A mark edge recording method is used in which "1" is made correspondent and the other is made to correspond to "0".

When an information signal is reproduced, as shown in FIG. 8, the optical recording medium 50 is moved by the optical reproducing apparatus in the direction indicated by the arrow A in the same manner as during recording, and at the same time, the signal track 52 is read.
A low-power light beam for reproduction is converged on a minute light spot 55 and irradiated. The light spot 55 is the optical recording medium 50
Scans a row of recorded information signal marks 53 as the light beam moves, and the information signal marks 53 are formed by partial state changes. It changes with the signal mark 53. Therefore, if the reflected light of the reproducing light beam is detected by the optical sensor, a change in the detection signal causes the information signal mark 53 to change.
Can be detected, and the information signal recorded by the recording method can be reproduced.

Here, the diameter of the light spot 55 of the reproducing light beam generally becomes smaller as the wavelength of the light becomes shorter or the NA (Numerical Apert) of the lens for converging the light wavelength.
ure) is larger and smaller. The detection resolution is about 0.4 times the diameter of the light spot of the reproducing light beam. As an example, assuming that the wavelength of the reproducing light beam is 635 nm and the NA of the lens is 0.6, the diameter of the light spot 55 is about 0.9 μm, and the detection resolution at this time is 0.36 μm.
m. Here, the length L of the information signal mark shown in FIG.
Assuming that the length of the shortest distance between m and the information signal mark interval Ls is a length corresponding to the basic period (clock) of data, and is 0.36 μm, which is equal to the detection resolution, the linear recording density is 0.36 μm / bit. Become.

[0007]

By the way, in order to increase the recording density of the information signal, the information signal mark 53 is made finer and the light spot 55 of the reproducing light beam is made smaller to improve the detection resolution. There is a need. For this purpose, methods of shortening the wavelength of the reproducing light beam and increasing the NA of a lens for converging the light beam have been attempted. However, the wavelength of a semiconductor laser, which is the light source, is limited due to its constituent materials and structural problems, and the practical NA of a lens is limited due to manufacturing and design problems of an optical regenerator. There is. For this reason, it is difficult to make the light spot 55 of the reproducing light beam much smaller than before, and there is a limit to the improvement of the detection resolution.

In this situation, not only optical recording but also information signal marks are recorded on a magnetic recording medium using a magnetic head by a change in magnetization state, and information signals are reproduced by detecting magnetic flux generated from the information signal marks. The same applies to a magnetic recording / reproducing apparatus that performs the above. The detection resolution in this case depends on the length of the magnetic flux detection gap provided in a part of the magnetic path of the magnetic head, and it has been difficult to detect an information signal mark that is sufficiently short compared to that. As described above, in the related art, there is a limit in improving the resolution of the detection of the information signal mark by making the gap of the light spot or the magnetic head, which is the detection portion, smaller, and the recording density of the information signal is further increased. It was difficult.

The present invention has been made in consideration of the above-described conventional problems, and has as its object to provide an information recording method, an information recording medium, an information recording device, and an information reproducing device that can further increase the recording density of an information signal. .

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to arrange a first segment and a second segment of a predetermined recording area adjacent to each other on a signal track of an information recording medium, so that each information is recorded. Is recorded in the first segment and the second segment by a pair of domain walls representing information by their positions at regular intervals.

Further, the object of the present invention is achieved by an information recording medium on which information is recorded by the above information recording method.

Still another object of the present invention is an information recording apparatus for recording information on an information recording medium in which a first segment and a second segment of a predetermined recording area are arranged adjacently on a signal track. The information recording apparatus is characterized in that the information recording apparatus has means for recording each information in the first segment and the second segment at a fixed interval by a pair of domain walls representing information by their positions. .

[0013] It is another object of the present invention to provide an information recording medium in which a first segment and a second segment of a predetermined recording area are arranged adjacent to each other on a signal track. And an information reproducing apparatus for reproducing information recorded by a pair of domain walls representing information by their positions in a second segment at a constant interval, and means for moving a domain wall recorded on the signal track. Means for detecting the movement of the domain wall, means for extracting only the movement of the domain wall contributing to the reproduction of information among the detected movements of the domain wall, and means for determining recording information from the output of the extracting means. This is achieved by an information reproducing apparatus characterized in that:

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, an information recording method according to the present embodiment will be described with reference to FIGS. FIG.
FIG. 2 is a partially enlarged view showing a configuration of a magneto-optical recording medium. FIG.
1A is a side sectional view, and FIG. 1B is a view seen from a lower surface direction. In FIG. 1, a magneto-optical recording medium 1 includes a substrate 40 made of a transparent material such as polycarbonate, and a band-like signal track 41 formed on the substrate 40.
The magneto-optical recording medium 1 has, for example, a disk shape, and the signal tracks 41 are spirally formed on the disk. In the signal track 41, first segments Sf01, Sf02, Sf03,... And second segments Sr01, Sr02, S0r3,. Is provided. Here, the first segment Sf01 and the second segment Sr01, the first segment Sf02 and the second segment Sr02, the first segment S
f03 and the second segments Sr03,... make a pair, respectively. Also, as described later, the first segment and the second segment
A 32-bit information signal can be recorded in a pair of segments consisting of the above-mentioned segments.

FIG. 2 shows a detailed configuration of a part of the signal track 41. FIG. 2A is a side sectional view, and FIG. 2B is a view seen from a lower surface direction. The signal track 41 has a configuration in which three magnetic layers made of a magnetic material, that is, a domain wall displacement layer 42, a switching layer 43, and a magnetic recording layer 44 are stacked. The domain wall motion layer 42 is a perpendicular magnetization film having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer 44, and the switching layer 43 is a film of a magnetic material having a lower Curie temperature than the domain wall motion layer 42 and the magnetic recording layer 44. The recording layer 44 is a perpendicular magnetization film. The signal track 41 and the regions on both sides thereof are not magnetically coupled at least in the domain wall motion layer 42.

In the signal track 41, a row of magnetized regions having an upward or downward magnetization is formed as shown by a vertical arrow in the figure, and information is provided at a boundary between the magnetized region and the preceding and succeeding magnetized regions. First domain walls Qf01, Qf0 as signal marks
,..., Qf16 are assigned to the first segment Sf01 and to the second segment Sf01.
, Qr16 are formed in a line in the second segment Sr01. These domain walls are exchange-coupled between the domain wall displacement layer 42, the switching layer 43, and the magnetic recording layer 44.

Here, the first domain wall Qf01 formed in the first segment Sf01 and the second domain wall Qr01 formed in the second segment Sr01 form a pair. The first domain wall Qfxx formed and the second
The second domain wall Qrxx (where xx is 01 to 16) formed in the segment Sr01 of FIG. Each of these 16 domain wall pairs corresponds to each of a plurality of data constituting an information signal. The distance Lq between the first domain wall Qfxx and the second domain wall Qrxx forming a pair is all constant. Further, another first segment S (not shown)
f02, Sf03,..., second segments Sr02, Sr03,
Similarly, 16 domain walls as information signal marks are formed in each of the..., And the first domain wall formed in the first segment and the second domain wall formed in the second segment form a pair. ing.

Next, a method for associating data with a pair of domain walls will be described. FIG. 3 shows an enlarged part of each of the first segment Sf01 and the second segment Sr01. Here, P ₁ , P ₂ , P ₃ , P
₄ is a position where a predetermined domain wall is to be formed,
These are arranged at a fixed cycle. The position of the domain wall to be formed among the positions P ₁ , P ₂ , P ₃ , and P ₄ is determined by the corresponding data. For example, where a respective data 2 bits constituting an information signal, the recording position of the magnetic domain wall corresponding to the data "00" is P _1. Similarly recording position of the magnetic domain wall corresponding to the data "01" is a recording position of the magnetic domain wall corresponding to P _2, the data "10" is the recording position of the magnetic domain wall corresponding to P _3, data "11" is a P _4.

The first domain wall Qfxx and the second domain wall Qrxx forming a pair correspond to the same data and are formed at the same position. In the example shown in FIG. 3, the first domain wall Qf01 and the second
Of domain wall Qr01 is formed at a position P ₁ corresponds to "00". Similarly, the first domain wall Qf02 and the second domain wall Qr02
Corresponds to “10” at a position P ₃ , and the first domain wall Qf03 and the second domain wall Qr03 correspond to “01” at a position P ₂ ,
Of domain wall Qf04 the second domain wall Qr04 are formed respectively at positions P ₄ corresponds to "11". In this way, the pair of segments composed of the first segment Sf01 and the second segment Sr01 has three pairs of domain wall pairs.
It is possible to record 2-bit data. Also,
Similarly, 32-bit data can be recorded in other segment pairs.

Here, the domain wall formation interval is set to 0.075 on average.
Assuming that the length of one segment is 1.2 μm, the linear recording density is 0.075 μm / bit.
According to the domain wall displacement reproducing method described later, the information signal can be reproduced even when the domain wall formation interval is sufficiently smaller than the diameter of the light spot of the reproducing light beam. The magneto-optical recording medium 1 is used as a reference for time when an information signal is recorded by a magneto-optical recording device described later or when the information signal is reproduced by a magneto-optical reproducing device, separately from the illustrated information signal marks. Signal (for example, a clock signal of a fixed frequency synchronized with the information signal), a position signal for detecting a start position and an end position of each segment, and a temperature of a signal track formed by irradiation of a reproduction light beam. A domain wall or the like, which is a control signal mark for detecting and controlling the length of the region where the height has risen, is recorded. Such a timing signal, a position signal, a control signal mark, and the like are to be recorded simultaneously with the information signal when recording the information signal, or are recorded in advance when the magneto-optical recording medium 1 is manufactured. In the present embodiment, each data constituting the information signal is recorded by a pair of a first domain wall and a second domain wall formed at a predetermined interval, and
A first domain wall corresponding to data constituting an information signal and a second domain wall;
A first domain wall or a second domain wall corresponding to other data constituting an information signal is recorded between the domain walls.

Next, a magneto-optical recording apparatus for recording an information signal on the magneto-optical recording medium 1 of FIG. 1 and its recording operation will be described. FIG. 4 shows a schematic configuration of the magneto-optical recording device according to the present embodiment. The magneto-optical recording medium 1 has a disk shape and is driven to rotate by a spindle motor 2. A magnetic head 3 for applying a magnetic field to the signal track 41 is disposed on the upper surface side (the side on which the signal track 41 is provided) of the magneto-optical recording medium 1, and the magnetic head 3 is located on the lower surface side of the magneto-optical recording medium 1. An optical head 4 that converges and irradiates a reproducing light beam and a recording light beam onto a signal track 41 through a substrate 40 of the magneto-optical recording medium 1 is disposed.

The magnetic head 3 comprises a core and a coil (not shown) wound around the core, and a magnetic head drive circuit 5 is connected to the coil. Further, a memory element 6 and a recording signal generation circuit 7 are sequentially connected to the magnetic head drive circuit 5. The optical head 4 has a laser light source 8,
The optical sensor 9 includes an optical system (not shown) such as an objective lens, an actuator (not shown) for driving the objective lens, and the like. 11 are connected. A position signal detection circuit 12 and a timing signal detection circuit 13 are connected to the amplifier circuit 11.

When recording an information signal, first, the magneto-optical recording medium 1 is rotationally driven by the spindle motor 2,
The magnetic head 3 and the optical head 4 scan on signal tracks of the magneto-optical recording medium 1. Next, by supplying a reproduction DC current to the laser light source 8 of the optical head 4 from the laser drive circuit 10, the laser light source 8 is turned on, and a reproduction light beam having a constant intensity and a low power is transmitted through the substrate 40. Then, the signal track 41 is converged on a light spot and irradiated. At this time, an actuator of the optical head 4 is driven by a servo control circuit (not shown), and focusing control and tracking control are performed so that the reproducing light beam accurately converges on the signal track 41 of the magneto-optical recording medium 1 and performs tracking scanning. .

The light reflected from the medium of the reproducing light beam is detected as an electric signal by the optical sensor 9, and the detected signal is amplified by the amplifier circuit 11. The position signal detection circuit 12 detects a position signal representing the start position and the end position of the segment recorded on the magneto-optical recording medium 1 from the output signal of the amplifier circuit 11 and sends it to the memory element 6. Further, the timing signal detection circuit 13 detects a clock signal of a constant frequency, which is a timing signal recorded on the magneto-optical recording medium 1, from the output signal of the amplification circuit 11, and sends it to the memory element 6 and the recording signal generation circuit 7. I do.

Next, an information signal to be recorded is input from the input terminal T ₁ , and the recording signal generation circuit 7 synchronizes with the clock signal and changes at a timing corresponding to each of the two bits of data constituting the information signal. A signal is generated and output to the memory element 6. The memory element 6 once stores data to be recorded in at least one segment pair, that is, a recording signal corresponding to 32 bits, and then refers to a position signal and a clock signal corresponding to the start position and end position of the segment, The recording signal corresponding to 32 bits is repeatedly output to the magnetic head driving circuit 5 twice at predetermined time intervals. Thereafter, similarly, a recording signal corresponding to 32 bits is repeatedly output twice each. The product of the time interval of this repetition and the linear velocity of the magneto-optical recording medium 1 is assumed to be equal to the interval Lq between the first domain wall and the second domain wall.

The magnetic head drive circuit 5 supplies a current that changes in accordance with the input recording signal to the coil of the magnetic head 3 so that the magnetic head 3 moves upward or at a timing corresponding to the data constituting the information signal. A recording magnetic field that changes in the downward direction is generated, and the signal track 4 of the magneto-optical recording medium 1 is generated.
1 vertically. At the same time, the current supplied from the laser drive circuit 10 to the laser light source 8 of the optical head 4 is switched to a direct current for recording or a pulse current synchronized with a clock signal, and is turned on in a fixed intensity or in a pulse form for high power recording. The light beam passes through the substrate 40 and passes through the signal track 4.
The light is converged on a light spot and irradiated. Also in this case, the servo control circuit performs focusing control and tracking control so that the recording light beam accurately converges on the signal track 41 of the magneto-optical recording medium 1 and performs tracking scanning.

Here, at the portion of the signal track 41 where the recording light beam is irradiated, the magnetic recording layer 44 rises above the Curie temperature Tc of the material constituting it, and the magnetization disappears. After that, as the magneto-optical recording medium 1 rotates, the magnetic recording layer 4 moves away from the recording light beam irradiation site.
When the temperature falls below Tc in the process, the direction of the magnetization is oriented in the direction of the magnetic field applied by the magnetic head 3, and is further fixed as the temperature decreases to near room temperature to form a magnetized region. Is done. Then, by switching the direction of the applied magnetic field, a domain wall is formed at the boundary with the immediately preceding magnetization region having the reverse magnetization. The domain wall formed on the magnetic recording layer 44 is also transferred to the domain wall moving layer 42 via the switching layer 43.

As the magneto-optical recording medium 1 rotates, first, the second domain walls Qr01, Qr02,..., Qr16 are sequentially formed in the state shown in FIG. Each of these domain walls has a position P ₁ , P ₂ , P ₃ ,.
It is formed on one of P _4. Further, by successively repeating the recording signal, the second domain walls Qr01, Qr0 are formed.
,..., Qf16 are sequentially formed at predetermined intervals Lq from the first domain walls Qf01, Qf02,. In this manner, information is recorded by forming the first domain wall and the second domain wall corresponding to 32-bit data in the first segment and the second segment, respectively.

A recording method of irradiating a magneto-optical recording medium with a recording light beam and applying a magnetic field modulated by an information signal to be recorded as described above generally employs a magnetic field modulation method. This is called a recording method. According to the magnetic field modulation recording method, the interval between the domain wall and the subsequent domain wall is equal to the product of the time interval of switching the applied magnetic field and the linear velocity of the magneto-optical recording medium, and is equal to the size of the light spot of the recording light beam. Does not depend, the domain wall can be formed at an interval sufficiently shorter than the diameter of the light spot.

Next, a magneto-optical reproducing apparatus for reproducing an information signal from a magneto-optical recording medium and its reproducing operation will be described.
FIG. 5 shows a schematic configuration of the magneto-optical reproducing device according to the present embodiment. The magneto-optical recording medium 1 is driven to rotate by a spindle motor 20. On the lower surface side of the magneto-optical recording medium 1, an optical head 21 for converging and irradiating a reproduction light beam onto a signal track 41 through a substrate 41 is arranged. The optical head 21 includes a laser light source 22, an optical sensor 23, an optical system such as an objective lens, an actuator (not shown) for driving the objective lens, and the like. Is connected to an amplifier circuit 25. The laser drive circuit 24 and the amplifier circuit 25 include:
A signal extraction circuit 26, a position signal detection circuit 27, a timing signal detection circuit 28, a control signal detection circuit 29, an information signal reproduction circuit 30, a comparison circuit 31, and a target value setting means 32 are connected.

As a method of reproducing the information signal, a domain wall displacement reproducing method proposed by the present applicant in Japanese Patent Application Laid-Open No. 6-290496 is used. Hereinafter, details of the operation of reproducing the information signal will be described. When reproducing an information signal, first,
The magneto-optical recording medium 1 is rotationally driven by the spindle motor 20, and the optical head 21 scans over the signal tracks of the magneto-optical recording medium 1. Next, the laser light source 22 is turned on by supplying a direct current for reproduction from the laser drive circuit 24 to the laser light source 22 of the optical head 21, and the light beam for reproduction having a constant intensity and a low power is transmitted through the substrate 40. The signal track 41 is converged on a light spot and irradiated. At the time of information reproduction as well as at the time of recording, the focusing control and the tracking control are performed so that the reproducing light beam converges on the signal track 41 of the magneto-optical recording medium 1 and performs the following scanning.

The reflected light of the reproducing light beam is detected as an electric signal by the optical sensor 23, and the detected signal is amplified by the amplifier circuit 25. The position signal detection circuit 27 detects a position signal representing the start position and the end position of the segment recorded on the magneto-optical recording medium 1 from the output signal of the amplification circuit 25, and sends it to the signal extraction circuit 26. Further, the timing signal detection circuit 28 detects a clock signal of a constant frequency, which is a timing signal recorded on the magneto-optical recording medium 1, from the output signal of the amplification circuit 25, and sends it to the information signal reproduction circuit 30.

FIG. 6 is a diagram for explaining the principle of signal reproduction by the domain wall motion reproduction method of the present embodiment. FIG.
FIG. 6A is an enlarged sectional view of a portion of the magneto-optical recording medium 1 irradiated with a reproducing light beam, and FIG. The reproduction light beam is applied to the substrate 40 of the magneto-optical recording medium 1.
Is transmitted to the signal track 41 so as to converge on a minute light spot 45. The diameter of the light spot 45 is
For example, it is 0.9 μm. The light spot 45 of the reproducing light beam scans the signal track 41 as the magneto-optical recording medium 1 moves in the direction of arrow A. When the light spot 45 is scanned on the signal track 41 in this manner, the signal track 41 is heated by the irradiation of the reproducing light beam, and the position Xp is shifted from the center of the light spot 45 in the moving direction of the magneto-optical recording medium 1. A temperature distribution having a peak at is formed. Here, reference numeral 46 denotes an isotherm indicating a region where the temperature of the switching layer 43 has reached Ts which is a temperature near the Curie temperature. The front end of the region where the temperature of the signal track 41 is equal to or higher than Ts is the position Xf, and the rear end is the position Xr. It is.

With the rotation of the magneto-optical recording medium 1, the temperature of the signal track 41 rises above the temperature Ts at the position Xf in the process of passing through the irradiation area of the light spot 45,
After reaching the peak at the position Xp, it starts to fall, and again falls below the temperature Ts at the position Xr. At a position distant from the light spot 45 of the reproducing light beam, the temperature of the signal track 41 is sufficiently low. At this position, the domain wall displacement layer 42, the switching layer 43, and the magnetic recording layer 44 are exchange-coupled to each other, The domain wall formed on the recording layer 44 is also transferred to the switching layer 43 and the domain wall moving layer 42. Further, since the temperature distribution in the surrounding area is substantially uniform, no driving force for moving the domain wall transferred to the domain wall moving layer 42 acts, and thus the domain wall is fixed.

However, since the temperature between the position Xf and the position Xr of the switching layer 43 is higher than Ts and the magnetization has disappeared, the domain wall displacement layer 42 and the switching layer 4
3. The magnetic recording layers 44 are not exchange-coupled with each other. For this reason, the domain wall reaching position Xf (Qf01 in FIG. 6)
) Are no longer constrained by the exchange coupling force in the domain wall displacement layer 42, while they are driven by the temperature gradient. Further, since the domain wall motion layer 42 is not magnetically coupled to the regions on both sides of the signal track 41, the domain wall moves at a high speed from the position Xf to the position Xp where the temperature is high and the domain wall energy is low in the domain wall motion layer 42. Start. With the movement of the domain wall, a magnetized region R _fex having magnetization in one direction (upward in the illustrated example) is formed while extending. Here, the movement of the domain wall starting at Xf is referred to as a first movement. Since the magnetic recording layer 44 is made of a material having a small domain wall mobility, the magnetic domain layer does not move in the magnetic recording layer 44.

On the other hand, at the position Xr, the switching layer 4
3, the magnetization is generated again, so that the domain wall displacement layer 42, the switching layer 43, and the magnetic recording layer 44 are exchange-coupled to each other.
As a result, the domain wall (Qr01 in FIG. 6) in the magnetic recording layer 44 that has reached the position Xr is transferred to the domain wall moving layer 42 via the switching layer 43. Further, when the magnetization region following the domain wall is transferred to the domain wall motion layer 42, the domain wall motion layer 4
2, a new magnetic domain wall (Qr01 'in FIG. 6) is formed facing the transferred magnetic domain wall (Qr01). This domain wall receives a driving force due to the temperature gradient, and the position X
It starts moving at a high speed from r to a position Xp where the temperature is high and the domain wall energy is low.

With the movement of the domain wall, a magnetized region R _rex having a magnetization in one direction (upward in the illustrated example) is formed while extending. Such a movement of the domain wall starting at Xr is referred to as a second movement here (actual movement is a newly formed domain wall Qr01 ', but hereinafter, for convenience, the "domain wall Qr01 moves.""). As described above, the first domain wall Qfxx and the second domain wall Qrxx (where xx is 01 to 16) successively cause the first movement each time the position Xf is reached, and the second movement each time the position Xr is reached. Is generated. Here, as described above, the paired first domain wall Qfx
The intervals Lq between x and the second domain wall Qrxx are all formed to be constant. Further, the distance between the position Xf and the position Xr, that is, the length of the region where the temperature of the signal track is equal to or higher than Ts is controlled to be substantially equal to the distance Lq by a method described later. Thereby, the first domain wall Qfxx
Movement at the position Xf of the second position and the second movement
The second movement of the domain wall Qrxx at the position Xr occurs substantially simultaneously.

Further, the elongated magnetized region R resulting from the second movement of the second domain wall Qrxx paired with the elongated magnetized region R _fex resulting from the first movement of the first domain wall Qfxx.
Each domain wall is formed so as to have the same direction of magnetization as _rex . Therefore, the moved first domain wall Qfxx and the second
The magnetic walls Qrxx collide near the position Xp and simultaneously cancel and disappear. As a result, the magnetized regions R _fex and R _rex are integrated at the irradiation spot of the light spot 45 of the reproducing light beam. The length of the integrated magnetized region is substantially equal to the distance Lq between the first domain wall Qfxx and the second domain wall Qrxx. The polarization plane of the reflected light of the reproducing beam from the magnetized regions R _fex and R _rex is due to the magneto-optical effect (Kerr effect).
It rotates according to the direction of magnetization of the magnetization regions R _fex and R _rex . The rotation of the polarization plane is converted into a change in light intensity by the optical system of the optical head 21, and further detected and output as an electric signal by the optical sensor 23.

Here, a magnetic recording layer 44 is provided between the first domain wall Qf01 and the second domain wall Qr01 forming a pair to be detected.
, The second domain walls Qr02, Qr03, Qr04,.
Although r16 is formed, these domain walls are not transferred to the domain wall movement layer 42 due to the disappearance of the magnetization of the switching layer 43, and do not affect the detection of the movement of the domain wall. In this way, the first domain wall Qfxx is successively shifted to the position X.
When f reaches f, a first movement occurs in the domain wall motion layer 42, and at the same time, the second domain wall Qrxx successively reaches the position Xr to cause a second movement in the domain wall motion layer 42. Also,
Each time, integrated magnetized regions having upward and downward magnetizations are alternately formed, and a detection signal including a corresponding signal change is output from the optical head 21. The timing of the change of the output signal changes according to the formation position of each domain wall pair, that is, the data constituting the information signal.

Incidentally, as described above, the first domain wall Qfxx
Not only causes a first movement at position Xf,
When the position Xr is reached, a second movement occurs. Similarly, the second domain wall Qrxx not only causes the second movement at the position Xr, but also performs the first movement when reaching the position Xf. The detection signal of the optical head 21 includes the first
Movement of the domain wall Qfxx of the second domain and the first movement of the domain wall Qrxx of the second domain.
The change of the signal corresponding to the movement of is included.

In this embodiment, an information signal is reproduced from the detection signal by the following method. The detection signal is first amplified by an amplifier circuit 25, and the output signal is sent to a signal extraction circuit 26, a position signal detection circuit 27, a timing signal detection circuit 28, and a control signal detection circuit 29. The position signal detection circuit 27 detects a position signal representing the start position and the end position of the segment recorded on the magneto-optical recording medium 1 from the output signal of the amplification circuit 25, and sends it to the signal extraction circuit 26. Further, the timing signal detection circuit 2
8 detects a clock signal of a constant frequency, which is a timing signal recorded on the magneto-optical recording medium 1, from the output signal of the amplifier circuit 25 and sends it to the information signal reproducing circuit 30. The signal extraction circuit 26 refers to the input position signal, and
5 from the detection signal input from the first domain wall Qfxx.
And only the signal change corresponding to the second movement of the second domain wall Qrxx is extracted.

More specifically, the position Xf, which is the front end of the area where the temperature formed on the signal track 41 is equal to or higher than Ts, is from the start position (right end in FIG. 6) to the end position (left end) of the first segment Sf01. , And at the same time, the position Xr at the rear end of the region where the temperature is equal to or higher than Ts is set to the second segment Sr01.
Only the detection signal during the scanning period from the head position to the end position is selectively extracted and output. The detection signal in this period includes the first movement of the first domain wall Qfxx and the second domain wall Qrx
x includes all signal changes corresponding to the second movement of the first domain wall Qfxx and the second movement and the second domain wall Qrx of the first domain wall Qfxx.
The signal change corresponding to the first movement of x is not included. Since the detection signals in the other periods include a change in the signal corresponding to the second movement of the first domain wall Qfxx and the first movement of the second domain wall Qrxx, these are removed.

Next, the signal extracting circuit 26 sends out the extracted signal to the information signal reproducing circuit 30. Information signal reproduction circuit 3
0 indicates a timing of a signal change corresponding to the first movement of the first domain wall Qfxx included in the signal input from the signal extraction circuit 26 and the simultaneously generated second movement of the second domain wall Qrxx. The clock signal input from the detection circuit 28 is compared, and based on the comparison result, the formation positions of the first domain wall Qfxx and the second domain wall Qrxx are changed to the positions P ₁ , P ₂ , P ₃ , P shown in FIG. It is determined whether it is one of _four . Determination result to generate the data "00" of 2 bits corresponding thereto when the position P _1. Similarly, if the determination results are P ₂ , P ₃ , and P ₄ , the data “01”, “1”
Thus, the information signal reproducing circuit 30 reproduces a 32-bit information signal from the pair of 16 domain walls formed in the pair of the first segment and the second segment. Then, the signal is output from the output terminal T2.

Next, the signal track 4 of the magneto-optical recording medium 1
In FIG. 1, the position Xf at which the domain wall starts the first movement and the second position
Is the distance between the positions Xr at which the movements start, that is, the temperature is Ts
A method of controlling the length of the above-described region so as to substantially match the interval Lq between the first domain wall Qfxx and the second domain wall Qrxx forming a pair will be described. The distance between the position Xf and the position Xr depends on the irradiation intensity of the reproducing light beam, and the larger the light intensity, the wider the area where the temperature becomes Ts or higher, so that the distance between the position Xf and the position Xr increases. Conversely, the smaller the light intensity, the smaller the distance between the position Xf and the position Xr. By using this to adjust the intensity of the reproducing light beam, it is possible to control the distance between the position Xf and the position Xr to be a predetermined value.

For use in such control, a domain wall serving as a control signal mark is previously formed on the magneto-optical recording medium 1 separately from the information signal, and the position Xf is determined by detecting the domain wall serving as the control signal mark. The actual distance between the positions Xr is detected. For example, such a control signal mark may be separated from the information signal to facilitate detection.
A single magnetic domain wall or a group of several or less magnetic domains formed at least with the distance Lq or more from the magnetic domain wall serving as an information signal mark or another control signal mark. When the domain wall, which is the control signal mark, reaches the position Xf, a first movement occurs, and a change in the signal corresponding to the first movement is detected.

Further, when the magneto-optical recording medium 1 rotates and the domain wall serving as the control signal mark reaches the position Xr, a second movement occurs. The signal detected by the optical sensor 23 of the optical head 21 includes a signal change corresponding to the movement of the domain wall as the information signal mark and a signal change corresponding to the movement of the domain wall as the control signal mark. I have. This detection signal is amplified by the amplification circuit 25 and input to the control signal detection circuit 29. The control signal detection circuit 29
A change in a signal corresponding to the first movement and the second movement of the domain wall, which is a control signal mark included in the input detection circuit, is detected. Further, a time difference between the first movement and the second movement of the domain wall is measured, and a signal corresponding to the result is compared with a comparison circuit 31.
To send to. Here, since this time difference is the time required for the magneto-optical recording medium 1 to move from the position Xf to the position Xr, the product of this time difference and the linear velocity of the magneto-optical recording medium 1 is the position Xf of the signal track 41. And the position Xr.

On the other hand, the target value setting means 32 comprises a first domain wall Qfxx of the magneto-optical recording medium 1 and a second domain wall Q paired therewith.
A signal corresponding to the interval Lq of rxx is set as a control target value and sent to the comparison circuit 31. The comparison circuit 31 compares the input signal corresponding to the time difference with the signal corresponding to the distance Lq, which is the target value, and sends a control signal based on the comparison result to the laser drive circuit 24. The laser drive circuit 24 adjusts the drive current to the laser light source 22 according to the control signal, and adjusts the irradiation intensity of the reproducing light beam, so that the distance between the position Xf and the position Xr in the signal track 41 becomes equal to the distance Lq. Is controlled so as to substantially match.

If the magneto-optical recording medium is prepared so that the intervals Lq are the same in all the magneto-optical recording media, the target value setting means 32 stores a value corresponding to the interval Lq in the inside thereof in advance. What is necessary is just to memorize. If the interval Lq is different for each type of magneto-optical recording medium, it is recorded as readable information on a part of the magneto-optical recording medium, and the target value setting means 32 reads the information, and as a result, Set the target value based on
Alternatively, the type of the magneto-optical recording medium may be determined from a cartridge or the like of the magneto-optical recording medium, and a value stored in advance for each type may be set as the target value.

Since the temperature distribution in the signal track varies with time due to a change in ambient temperature or the like, the domain walls serving as the control signal marks are formed at a plurality of locations on the magneto-optical recording medium at a constant period, and at least information is recorded. It is desirable to repeat the above control operation periodically during signal reproduction. Further, in the above embodiment, the signal track 41 of the magneto-optical recording medium 1 is heated by irradiation of the reproducing light beam to form a region where the temperature is increased.
A heating means, for example, a heating light beam irradiation means may be provided separately from the reproduction light beam to heat the signal track 41. In this case, it is possible to control the distance between the position Xf and the position Xr on the signal track 41 so as to substantially coincide with the interval Lq by controlling the heating means with a control signal from the comparison circuit.

Furthermore, in the above embodiments, magneto-optical recording and magneto-optical reproduction using light and magnetism are taken as an example, but the present invention is not limited to this, and can be used in other systems. For example, the present invention can be used for magnetic recording or magnetic reproduction for magnetically recording or reproducing. In this case, the information signal may be recorded by applying a magnetic field to the magnetic recording medium with a magnetic head, and the temperature of the signal track may be partially reduced by irradiating the magnetic recording medium with a heating light beam. The information can be reproduced by moving the domain wall by raising the magnetic field and detecting the resulting magnetic flux generated by the elongated magnetized region as an electric signal by a magnetic head having a coil and a magnetoresistive element.

[0051]

As described above, according to the present invention, each piece of information is recorded on a pair of first and second segments by a pair of magnetic domain walls representing information by a position at a fixed interval. Therefore, when information is reproduced, a signal is detected from the magnetized region elongated by the movement of the domain wall, so that the detection resolution is not limited to the size of the reproducing light spot which is a detection part, and the interval between the domain wall formation is smaller than the diameter of the light spot. Even when the size is small, information can be reproduced, and the recording density can be greatly increased as compared with conventional optical recording or magnetic recording.

Even when the information is recorded in pairs in the first and second segments, the information is formed at a predetermined interval only by using a single detecting means (light spot for reproduction). Even if a large number of domain walls of other information are recorded between the domain walls, the information by the pair of domain walls can be easily detected without being affected by the domain walls. In addition, when information is recorded by only one domain wall, when information is reproduced, the first movement of the domain wall indicating information and the second movement of the domain wall of other information occur in an irregular time relationship, or at the same time. However, in the present invention, since each piece of information is recorded by a pair of domain walls formed at regular intervals in the present invention, the first pair forming the pair at the time of reproducing the information is recorded. The first movement and the second movement of the domain wall and the second domain wall occur regularly, and only the first movement of the first domain wall and the second movement of the second domain wall necessary for reproducing information are performed. Can be easily extracted, and the information can be reproduced with high reliability.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magneto-optical recording medium used in the information recording method of the present invention.

FIG. 2 is a diagram showing a state where information is recorded on a signal track of a recording medium by the information recording method according to the present invention.

FIG. 3 is a diagram for explaining the information recording method of the present invention in detail.

FIG. 4 is a diagram illustrating a configuration of an embodiment of an information recording device of the present invention.

FIG. 5 is a diagram showing a configuration of an embodiment of an information reproducing apparatus of the present invention.

FIG. 6 is a diagram for explaining the principle of reproduction of the information reproducing apparatus of the present invention.

FIG. 7 is a diagram for explaining a mode of recording an information signal on a conventional information recording medium.

FIG. 8 is a diagram for explaining a mode of reproducing an information signal on a conventional information recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical recording medium 3 Magnetic head 4, 21 Optical head 5 Magnetic head drive circuit 6 Memory element 7 Recording signal generation circuit 8, 22 Laser light source 9, 23 Optical sensor 10, 24 Laser drive circuit 11, 25 Amplification circuit 12, 27 Position signal detection circuit 13, 28 Timing signal detection circuit 26 Signal extraction circuit 29 Control signal detection circuit 30 Information signal reproduction circuit 31 Comparison circuit 32 Target value setting means 40 Substrate 41 Signal track 42 Domain wall moving layer 43 Switching layer 44 Magnetic recording layer

Claims (5)

[Claims] 1. A first segment and a second segment of a predetermined recording area are arranged adjacent to each other on a signal track of an information recording medium, and each piece of information is stored in the first segment and the second segment.
The information recording method is characterized in that the information is recorded in a segment of a plurality of segments by a pair of domain walls at a predetermined interval, the information being represented by its position. 2. An information recording medium on which information is recorded by the information recording method according to claim 1. 3. A first recording area of a predetermined recording area on a signal track.
An information recording apparatus for recording information on an information recording medium in which a segment and a second segment are arranged adjacent to each other,
An information recording apparatus, comprising: means for recording each piece of information in said first segment and said second segment at regular intervals by a pair of domain walls representing information by their positions. 4. A first recording area of a predetermined recording area on a signal track.
And an information recording medium in which a second segment and a second segment are arranged adjacent to each other, a pair of magnetic domain walls each representing information by the positions of the first segment and the second segment at regular intervals. An information reproducing apparatus for reproducing recorded information, comprising: means for moving a domain wall recorded on the signal track; means for detecting the movement of the domain wall; and reproducing information from the detected movement of the domain wall. An information reproducing apparatus, comprising: means for extracting only the movement of the domain wall which contributes to the above, and means for determining the record information from the output of the extracting means. 5. The apparatus according to claim 4, further comprising means for controlling a distance between positions at which the pair of domain walls representing each piece of information starts to move so as to substantially correspond to an interval between the pair of domain walls. An information reproducing apparatus according to claim 1.