JP2001056977A - Method and device for reproducing magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a much higher density by using a magneto-optical recording medium provided with an MAMMOS(magnetic amplifying magneto-optical system) having a magnetic zone expansion layer where the recording magnetic zone of a recording layer is transferred and expanded. SOLUTION: A magneto-optical recording medium is provided, where recording is made by setting the directions of two different-direction magnetization as first and second recording states respectively, so that the minimum recording magnetic zone of the first recording state becomes larger than that of the second recording state, and an alternating magnetic field is applied while scanning the magneto-optical recording medium by a reproducing laser light. In the case of the scanning of the disk by the reproducing laser light, a reproducing external magnetic field is applied by a cycle shorter than the period of time from the entry of the certain point of a recording/reproducing area into a high temperature region to its exit therefrom. A signal expanded and reproduced by a recording mark is detected in a range longer than this recording mark, and information is reproduced by converting the range of the expanded signal detected in the range longer than the recording mark after the detection of the reproduced signal into the length of the recording mark. Since expansion and reproduction are allowed even when the recording magnetic zone is smaller than a heat spot, the length of the recording magnetic zone is set extremely short, and a recording density is further increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing method and a reproducing apparatus for a magneto-optical recording medium of the type in which a recording magnetic domain of a recording layer is transferred to a magnetic domain enlarging reproducing layer, and more particularly, to realize ultra-high density. And a new reproducing method.

[0002]

2. Description of the Related Art A magneto-optical recording medium such as a magneto-optical disk is known as an external memory of a computer or the like. Magneto-optical recording media are used as recording media in the multimedia era because information can be rewritten and large-capacity data such as moving images and sounds can be handled.
It is desired to further increase the storage capacity of such a magneto-optical recording medium.

As a technique for increasing the storage capacity, for example, mark edge recording in which the leading edge and the trailing edge of a recording mark are made to correspond to recording data "1" and information is added to the length of the recording mark and the interval between the recording marks. The scheme is known. According to this recording method, the recording density in the linear direction can be improved to approximately 1.5 times that of the conventional method (mark position method) even if the minimum recording mark has the same size as the conventional method.

As another method of increasing the storage capacity, it has been studied to record information at a high density by miniaturizing a recording mark (recording magnetic domain). In order to perform recording by miniaturizing the recording magnetic domain, it is possible to use an optical pulse magnetic field modulation method in which a magnetic field having a polarity corresponding to a recording signal is applied while irradiating pulsed light in synchronization with a recording clock. According to this method, a minute recording magnetic domain can be formed. However, when a plurality of such minute recording magnetic domains exist in the reproduction light spot, a method of identifying and reproducing them is required.

For discriminating and reading out a plurality of minute recording magnetic domains existing in a reproducing light spot, for example, Journey
nal of Magnetic Society of Japan, Vol. 17 Supplemen
t A technology called magnetic super-resolution (MSR) proposed in No. S1, pp. 201 (1993) can be used.
This technique is a method in which a magnetic mask is formed in a light spot of a magneto-optical recording medium using a temperature distribution, and recording magnetic domains are read from a region called an aperture (aperture) smaller than the light spot. However, in this method, since the effective spot diameter is reduced by forming a magnetic mask, the amount of light that contributes to the reproduction signal output is small. For this reason, the amplitude of the reproduced signal decreases, and it is difficult to obtain a sufficient S / N.

[0006] As a method of avoiding such a problem, for example, Journal of the Japan Society of Applied Magnetics, Vol. 21, No. 10, pp. 1187-1192.
(1997) proposes a magneto-optical recording medium provided with a reproducing layer for reproducing a magnetic domain recorded on the recording layer by magnetically transferring and enlarging the magnetic domain. In this technology, during reproduction, by applying an external magnetic field synchronized with the recording clock alternately, each magnetic domain magnetically transferred to the reproducing layer is enlarged and completely extinguished to the optical spot size, and amplified from the reproducing layer. The information is read out by detecting the signal amplitude obtained. This technology uses MAMMOS (Magnetic Amplifying)
Magneto-Optical System), which solves the above-mentioned problem of the magnetic super-resolution technique relating to a decrease in the amplitude of a reproduction signal.

[0007]

The present invention relates to the above MAM.
It is an object of the present invention to provide a novel recording / reproducing method capable of realizing higher density using a magneto-optical recording medium for MOS and a reproducing apparatus suitable for the method.

[0008]

According to a first aspect of the present invention, a magneto-optical recording medium including a recording layer in which a recording magnetic domain is formed and a magnetic domain expansion reproducing layer is used to reproduce data from the magneto-optical recording medium. A method of reproducing a magneto-optical recording medium, which irradiates light to generate a high-temperature region in a reproduction light spot, transfers a recording magnetic domain to a reproduction layer through the high-temperature region, and enlarges the transferred magnetic domain by applying an external magnetic field, When a disk is scanned with a reproduction laser beam, an external reproduction magnetic field is applied at a period shorter than the time from when a point in a recording / reproducing area enters the high-temperature area to when it leaves the high-temperature area. A method for reproducing a magneto-optical recording medium is provided.

According to a second aspect of the present invention, a signal enlarged and reproduced by a recording mark is detected over a range longer than the recording mark. A playback method is provided.

According to a third aspect of the present invention, a range of an enlarged signal detected over a range longer than the recording mark by the recording mark after detecting the reproduction signal is converted into a length of the recording mark. A method for reproducing a magneto-optical recording medium according to claim 1 or 2 is provided.

In the magneto-optical recording medium used in the reproducing method according to the first, second and third aspects of the present invention, a recording layer in which information is formed as recording magnetic domains and the recording magnetic domains of the recording layer are transferred. And a magnetic domain enlarging / reproducing layer capable of enlarging the transferred magnetic domain by applying an external magnetic field.
This is a magneto-optical recording medium for MMOS. This MAMMOS
The principle of reproduction of a magneto-optical recording medium will be briefly described with reference to FIG.

The reproducing light spot 50 formed on the magneto-optical recording medium by the irradiation of the reproducing light has a light intensity distribution according to a Gaussian distribution. 29, a temperature region based on the temperature distribution as shown in FIG. In the high-temperature region 52 of the reproducing light spot 50, the coercive force of the magnetic domain expansion reproducing layer 3 is further reduced, so that the magnetic layer is easily affected by the leakage magnetic field from the recording layer 5.

When a reproducing external magnetic field having the same polarity as that of the recording magnetic domain is applied to the magneto-optical recording medium having such a temperature distribution, the coercive force of the magnetic domain enlarging reproducing layer 3 is reduced by the leakage magnetic field of the recording layer and the reproducing external magnetic field. Is smaller than the sum, the recording magnetic domains 53 of the recording layer 5 are transferred to the magnetic domain enlarged reproduction layer 3. Next, the magnetic domain 54 transferred to the magnetic domain expansion reproduction layer 3 expands to the size of the reproduction light spot 50 under a reproduction external magnetic field. Therefore, an amplified magneto-optical signal can be detected from the transfer magnetic domain expanded by the magnetic domain expansion reproducing layer 3. As described above, the recording magnetic domain 5
The high-temperature area where the image 3 can be transferred to the reproduction layer 3 is referred to as a “heat spot” in this specification. The structure and principle of the magneto-optical recording medium for MAMMOS are described, for example, in WO
98/02878, which can be referred to.

FIG. 1 shows a method of recording information on the magneto-optical recording medium for MAMMOS and reproducing the recorded information.
This will be described with reference to FIGS. In the reproduction method of the present invention,
An external magnetic field of one bit and one cycle is applied while scanning the magneto-optical recording medium along the track with reproduction light. FIG. 1 shows an example of a pattern of a recording mark (recording magnetic domain) and an application pattern of a reproducing external magnetic field applied to the recording mark. 2 to 9 show how the recording magnetic domain 32 recorded in the track 30 advances with respect to the reproduction light spot 50. FIGS. 2 to 9 conceptually show the case where the heat spot of the reproduction light spot 50 exists at the position of the state 1 shown in FIG.

As described above, the coercive force of the magnetic domain enlarging reproducing layer is reduced in the heat spot formed on the magnetic domain enlarging reproducing layer due to the irradiation of the reproducing light. However, FIG.
As shown in (1), since the recording magnetic domain 32 has not yet entered the heat spot, the recording magnetic domain 32 is not transferred to the magnetic domain enlarged reproduction layer, and the enlarged reproduction signal is not detected.
Further movement of the magneto-optical recording medium with respect to the reproduction light spot causes the recording magnetic domain 32 to be formed in the magnetic domain enlarged reproduction layer as shown in FIGS. 3, 4, 5, 6, and 7. When entering the spot, the recording magnetic domain 32 is transferred to the magnetic domain enlarged reproduction layer. At this time, since an alternating external magnetic field is applied to the magneto-optical recording medium, the recording magnetic domain transferred to the magnetic domain enlarging and reproducing layer expands to the size of the reproducing light spot in the magnetic domain enlarging and reproducing layer, and is amplified from the expanded magnetic domain. The reproduced signal is detected and reproduced according to the MAMMOS reproduction principle.

As shown in FIG. 1, since the heat spot is larger than the recording magnetic domain 32, an expanded signal of 2 bits or more is detected for a 1-bit recording magnetic domain. The recorded information can be reproduced by converting the range of the enlarged signal detected over the range longer than the recording mark into the length of the recording mark.

That is, in the reproducing method of the present invention, if the recording magnetic domain enters the heat spot, the increased signal intensity can be detected by the reproducing principle of the MAMMOS, so that the size of the recording magnetic domain formed on the recording layer is not limited. . Therefore, it is possible to greatly increase the recording density by making the length of the recording magnetic domain in the line direction extremely short and converting the range of the enlarged signal to the length of the recording mark.

According to a fourth aspect of the present invention, a magneto-optical recording medium having a recording layer in which recording magnetic domains are formed and a magnetic domain expansion reproducing layer is used, and reproducing is performed by irradiating the magneto-optical recording medium with reproducing light. In a reproducing method of a magneto-optical recording medium in which a high-temperature region is generated in a light spot, a recording magnetic domain is transferred to a reproducing layer through the high-temperature region, and the transferred magnetic domain is enlarged by applying an external magnetic field, two magnetizations having different directions are used. In the first recording state and the second recording state, respectively.
When reproducing the information by scanning the high-temperature area from the magnetization pattern recorded so that the minimum recording magnetic domain in the recording state is smaller than the minimum recording magnetic domain in the second recording state, the length of the high-temperature area in the scanning direction is reduced. Is reproduced in a state smaller than the minimum magnetic domain of the second recording state.

According to a fifth aspect of the present invention, a magneto-optical recording medium having a recording layer in which recording magnetic domains are formed and a magnetic domain expansion reproducing layer is used, and reproducing is performed by irradiating the magneto-optical recording medium with reproducing light. In a recording method of a magneto-optical recording medium in which a high-temperature region is generated in a light spot, a recording magnetic domain is transferred to a reproducing layer through the high-temperature region, and the transferred magnetic domain is enlarged by application of an external magnetic field, two magnetizations having different directions are used. In the first recording state and the second recording state, respectively.
A recording method for a magneto-optical recording medium, characterized in that recording is performed such that the minimum recording magnetic domain in the recording state is smaller than the minimum recording magnetic domain in the second recording state.

In the recording and reproducing method according to the fourth and fifth aspects of the present invention, reproduction is performed while moving a magneto-optical recording medium having a plurality of recording magnetic domains based on the above-described reproduction principle relative to reproduction light. In this case, it is necessary to prevent two recording magnetic domains from being simultaneously transferred to the reproducing layer. For this purpose, the transfer of the recording magnetic domain formed on the recording layer to the magnetic domain enlarging / reproducing layer occurs through a heat spot, so that the front recording magnetic domain and the rear recording magnetic domain are not simultaneously included in the heat spot. I just need. Therefore, the shortest distance between the front recording magnetic domain and the rear recording magnetic domain, that is, the shortest interval (shortest space length) between the two recording magnetic domains is equal to or longer than the length of the heat spot in the track direction. May be formed. In other words, after forming the recording magnetic domain, the information is recorded so that a space having a dimension equal to or longer than the length of the heat spot in the track direction is always formed. As a result, the recording magnetic domains adjacent in the track direction exist at least with a blank corresponding to the length of the heat spot, so that only one recording magnetic domain can be independently and reliably reproduced. In the present invention, the space means a region defined by recording magnetic domains adjacent to each other in the track direction and having a magnetization in a direction opposite to the recording magnetic domains.

According to a sixth aspect of the present invention, a magneto-optical device comprising: a recording layer in which recording magnetic domains are formed; and a magnetic domain enlarging / reproducing layer in which the recording magnetic domains of the recording layer are transferred and expanded by application of an external magnetic field. In a method for reproducing a recording medium, magneto-optical recording includes a step of shifting a reproduced signal by one or more bits both before and after, or either before or after, and taking a logical product of the reproduced signal and the shifted signal. A method for playing a medium is provided.

According to a seventh aspect of the present invention, a magneto-optical device comprising: a recording layer in which recording magnetic domains are formed; and a magnetic domain enlarging / reproducing layer in which the recording magnetic domains of the recording layer are transferred and enlarged by applying an external magnetic field. In a reproducing apparatus for reproducing a recording medium,
A light source for irradiating light to the magneto-optical recording medium, a magnetic field application device for generating the external magnetic field, a signal detection device for detecting a reproduction signal from the magnetic domain expansion reproduction layer, A reproducing apparatus is provided, comprising: a waveform shifter for shifting, and a logical operation device for calculating a logical product of a reproduced signal and an output of the waveform shifter.

In the reproducing apparatus of the present invention, signals detected from the magneto-optical recording medium can be moved back and forth in time by the waveform shifting apparatus, and the logical product of the signals and the reproduced signal can be obtained.
Such an operation of moving the signals detected from the magneto-optical recording medium back and forth in time and taking the logical product of the signals and the reproduction signal is extremely effective for the reproduction methods of the first and second aspects of the present invention.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a recording / reproducing method according to the present invention and an apparatus suitable for carrying out the recording / reproducing method will be specifically described with reference to the drawings, but the present invention is not limited thereto. .

[0025]

EXAMPLE 1 First, a magneto-optical recording medium for MAMMOS was prepared as a magneto-optical recording medium according to the reproducing method of the present invention. FIG. 28 shows an example of a cross-sectional structure of a magneto-optical recording medium for MAMMOS. The magneto-optical recording medium 100 has a first dielectric layer 2, a magnetic domain expansion reproducing layer 3, a non-magnetic layer 4, a recording layer 5, and a second dielectric layer 6, which are sequentially laminated on a transparent substrate 1.

In the magneto-optical recording medium 100 used in this embodiment, a disk-shaped polycarbonate substrate is used as the transparent substrate 1, silicon nitride is used for the first dielectric layer 2 and the second dielectric layer 6, and the magnetic domain expansion reproducing layer 3 is used. GdFeCo alloy, silicon nitride for the non-magnetic layer 4, and TbFeCo alloy for the recording layer 5, respectively. Each of these layers 2 to 6 was formed by sputtering using a magnetron sputtering apparatus.

The magneto-optical recording medium 100 includes (2,
7) Encode user data using RLL modulation and N
The recording data was recorded so as to correspond to RZI. In the recording of information, a recording laser beam and a recording magnetic field modulated based on an input signal according to encoded information are applied to a magneto-optical recording medium using an optical pulse magnetic field modulation method, and a recording magnetic domain is formed on a track of a recording layer. Was formed. The length of one bit in the track direction was 0.067 μm. FIG. 1 shows an example of a magnetic domain pattern of the recording magnetic domains formed on the recording layer. The numbers above the magnetic domain pattern indicate input information (recorded information).

Next, while rotating the magneto-optical recording medium in which the recording magnetic domains are formed by the recording method at a constant speed, the reproducing laser beam is irradiated at a predetermined power, and
Information was reproduced by applying a reproduction external magnetic field of one bit period at a constant magnetic field intensity. FIG. 1 shows a timing chart of the applied reproduction external magnetic field and the detected reproduction signal. FIG.
As shown in the above, the spot size of the reproducing laser beam is 1.0 μm, and the length of the heat spot where the transfer of the magnetic domain from the recording layer to the magnetic domain enlarged reproducing layer occurs in the direction parallel to the track is about 0.2 μm. there were. The length of the heat spot in the direction parallel to the track was obtained by adjusting in advance based on a method described later.

Next, when a predetermined track of the magneto-optical recording medium is scanned with the reproducing light spot, the recording magnetic domain moves relative to the heat spot formed in the reproducing light spot, as shown in FIGS. Indicated. Each state shown in FIGS. 2 to 9 corresponds to a number shown below the timing chart of the reproduction external magnetic field shown in FIG. That is, FIGS. 2 to 9 conceptually show a case where a heat spot exists at the position indicated by the symbol in FIG. 2 to 9, the direction from the back of the paper to the front is the recording direction, that is, the same direction as the magnetization of the recording magnetic domain.

As shown in FIGS. 1 and 2, in the state, the reproducing external magnetic field is applied with the same polarity as the recording magnetic domain. However, since the recording magnetic domain 32 does not enter the heat spot, the recording magnetic domain 32 No reproduction signal is detected from the magnetic domain enlarged reproduction layer because it is not transferred to the magnetic domain enlarged reproduction layer. As shown in FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, in the state, the state, the state, the state and the state, since a part of the recording magnetic domain 32 enters the heat spot, Such a magnetic domain (part of the recording magnetic domain 32) is transferred to the magnetic domain expansion reproducing layer, and is expanded by a reproducing external magnetic field, so that the aforementioned MAMM
A reproduction signal amplified by the principle of the OS is detected.

Next, as shown in FIG.
Since the recording magnetic domain 32 has not entered the heat spot, the recording magnetic domain 32 is not transferred to the magnetic domain enlarged reproduction layer, and no reproduction signal is detected from the magnetic domain enlarged reproduction layer. That is, if the space (space) between the recording magnetic domain 32 and the next recording magnetic domain 33 is larger than the heat spot, the recording magnetic domain 32 and the recording magnetic domain 33 are transferred to the magnetic domain expansion / reproduction layer even when an external magnetic field is applied in such a space. Instead, it can be detected that the part is the space. In this embodiment, one bit is set to 0.067.
Since (2,7) RLL modulation is used as μm and the recording magnetic domain is formed corresponding to NRZI, the space is 0.2 μm or more, so that the space can be detected.

However, as shown in FIG. 1, since the heat spot is larger than the recording magnetic domain 32, two bits of one bit before and after each recording magnetic domain are detected more than the recording magnetic domain. Therefore, if an enlarged signal is detected, the same information as the recorded information cannot be obtained unless the enlarged signals at both ends are converted to zero. In this embodiment, as means for converting both ends of the enlarged signal to 0, FIG.
As shown in (1), a method of shifting the reproduced signal one bit at a time and taking the logical product of the shifted signal and the reproduced signal was used.

Thus, by reproducing the position information of each recording magnetic domain with the amplified reproduction signal, the reproduction information as shown in the lower part of FIG. 1 is obtained. The recorded information shown in the upper part of FIG. 1 can be reproduced by taking the logical product of.

Here, when the size of the heat spot at the time of reproduction is 0.2 μm and a recording mark is recorded corresponding to NRZI using the (2,7) RLL code, the space becomes 0.2 μm.
μm, and the bit pitch is about 0.133 μm.
The reason for setting the shortest space to 0.2 μm is that in MAMMOS, a recording magnetic domain smaller than a heat spot can be detected by transfer expansion, but the space smaller than the heat spot cannot be detected, so that the space becomes 0.2 μm or more. Because he did.

In the conventional mark position recording method, the space needs to be longer than the length of the heat spot. That is, when the size of the heat spot is 0.2 μm, 1-bit information includes the above (2,
7) If the space is set to 0.2 μm in the same manner as in the case where RLL modulation is used, the bit pitch is only 0.2 μm. Therefore, it can be seen that the recording / reproducing method of the present invention can further increase the amount of recordable information as compared with the conventional mark position recording method.

Next, a method of adjusting the length of the heat spot in the track direction will be described. First, a recording mark having a length of 1 μm in the track direction is recorded on the recording layer, and the magneto-optical recording medium on which the recording mark is recorded is rotated at a linear velocity of 2.5 m / s, as shown in FIG. Next, the recording mark is scanned with the reproducing light spot. here,
Assuming that the length of the heat spot formed by the reproduction light spot in the track direction is about 0.2 μm, the time after the front edge of the recording mark enters the heat spot of the reproduction light spot, and the time after the recording mark The time T required for the edge to advance from the heat spot is calculated as (1 μm +
0.2 μm) /2.5 m / s = 480 ns seconds.

As shown in FIG. 30, when the recording mark is scanned with the reproducing light spot while applying a reproducing magnetic field having the same polarity as the recording mark from just before the recording mark, the heat spot of the reproducing light spot has When the edge F enters, a reproduced signal is detected. Immediately after the detection of the reproduction signal, the polarity of the reproduction magnetic field is inverted, and the above-mentioned time T = 480 ns
When the reproducing magnetic field is reversed and applied again after 460 ns seconds, the trailing edge E of the recording mark in the heat spot
Is included, a reproduced signal is detected. on the other hand,
As shown in FIG. 31, after reversing the polarity of the reproducing magnetic field immediately after detecting the reproducing signal, the reproducing magnetic field is reversed and applied again after 500 seconds longer than the above-mentioned time T = 480 ns. Is not included in the trailing edge E of the recording mark, and no reproduced signal is detected. Therefore,
From the time when the reproduction signal is first detected, the reproduction signal is detected so that the reproduction signal is detected when the reproduction magnetic field H + is applied after 460 ns seconds and the reproduction signal is not detected when the reproduction magnetic field H + is applied after 500 seconds. By controlling the power, the length of the heat spot in the track direction is almost 0.2μ
m. The above is the method of adjusting the length of the heat spot in the track direction.

[Embodiment 2] First, a MAMMOS similar to that of Embodiment 1 was used as a magneto-optical recording medium according to the reproducing method of the present invention.
A magneto-optical recording medium was prepared.

In this magneto-optical recording medium 100, (2,
7) Encode user data using RLL modulation and N
The recording data was recorded so as to correspond to RZI. However,
Recording was performed by forming a recording magnetic domain so as to be shorter by 1/2 bit before and after. That is, the shortest recording magnetic domain corresponds to a length of 2 bits. In the recording of information, a recording laser beam and a recording magnetic field modulated based on an input signal according to encoded information are applied to a magneto-optical recording medium using an optical pulse magnetic field modulation method, and a recording magnetic domain is formed on a track of a recording layer. Was formed. The length of one bit in the track direction is 0.05 μm
And FIG. 10 shows an example of a magnetic domain pattern of the recording magnetic domains formed on the recording layer. The numbers above the magnetic domain pattern indicate input information (recorded information).

Next, while rotating the magneto-optical recording medium in which the recording magnetic domains are formed by the recording method at a constant speed, the reproducing laser beam is irradiated at a predetermined power, and
Information was reproduced by applying a reproduction external magnetic field of one bit period at a constant magnetic field intensity. FIG. 10 shows a timing chart of the applied reproduction external magnetic field and the detected reproduction signal. As shown in FIG. 11, the spot size of the reproduction laser beam is 1.0 μm, and the length of the heat spot in the direction parallel to the track of the heat spot where the magnetic domain is transferred from the recording layer to the magnetic domain enlarged reproduction layer is about 0.1 μm. It was 2 μm. The length of the heat spot in the direction parallel to the track was obtained by adjusting in advance based on the method described in the first embodiment.

Next, when a predetermined track of the magneto-optical recording medium is scanned with the reproducing light spot, the manner in which the recording magnetic domain moves relative to the heat spot formed in the reproducing light spot is shown in FIGS. Indicated. 11 to 18 respectively correspond to the numbers shown below the timing chart of the reproduction external magnetic field shown in FIG. That is, FIGS. 11 to 18 conceptually show the case where the heat spot exists at the positions indicated by in FIG. 10. Also, FIGS.
In, the direction from the back of the paper to the front is the recording direction, that is, the same direction as the magnetization of the recording magnetic domain.

As shown in FIGS. 10 and 11, in the state, the reproducing external magnetic field is applied with the same polarity as the recording magnetic domain. However, since the recording magnetic domain 32 does not enter the heat spot, the recording magnetic domain 32 No reproduction signal is detected from the magnetic domain enlarged reproduction layer because it is not transferred to the magnetic domain enlarged reproduction layer. , FIG. 11, FIG. 12, FIG. 13, FIG. 14, FIG. 15, and FIG.
Since a part of the recording magnetic domain 32 has entered the heat spot, such a magnetic domain (a part of the recording magnetic domain 32) is transferred to the magnetic domain enlarging and reproducing layer, and is expanded by the reproducing external magnetic field. The reproduced signal amplified by the principle is detected.

Next, as shown in FIG. 17, in the state, since the recording magnetic domain 32 does not enter the heat spot, the recording magnetic domain 32 is not transferred to the magnetic domain enlarged reproduction layer, and the reproduction signal is detected from the magnetic domain enlarged reproduction layer. Not done. That is, if the space (space) between the recording magnetic domain 32 and the next recording magnetic domain 33 is larger than the heat spot, the recording magnetic domain 32 and the recording magnetic domain 33 are transferred to the magnetic domain expansion / reproduction layer even when an external magnetic field is applied in such space. Instead, it can be detected that the part is the space. In this embodiment, one bit is set to 0.0
(2,7) RLL modulation is used as 5 μm to form a recording magnetic domain corresponding to NRZI, and recording is performed so that the length before and after the recording magnetic domain is shortened by ビ ッ ト bit.
As described above, the space can be detected.

However, as shown in FIG. 10, since the heat spot is larger than the recording magnetic domain 32, two bits of one bit before and after each recording magnetic domain are detected more than the recording magnetic domain. Therefore, if an enlarged signal is detected, the same information as the recorded information cannot be obtained unless the enlarged signals at both ends are converted to zero. In this embodiment, as a means for converting both ends of the enlarged signal to 0, a method of shifting the reproduced signal one bit at a time as shown in FIG. 10 and taking the logical product of the result and the reproduced signal is used.

Thus, by reproducing the position information of each recording magnetic domain with the amplified reproduction signal, reproduction information as shown in the lower part of FIG. 10 is obtained. The recorded information shown in the upper part of FIG. 1 can be reproduced by taking the logical product of.

Here, the size of the heat spot at the time of reproduction is set to 0.2 μm, and recording marks are formed using (2, 7) RLL code so that the recording magnetic domain is shortened by 1/2 bit before and after corresponding to NRZI. Recording was performed, and the shortest space was 0.2 μm. At this time, the bit pitch is about 0.1 μm. The reason for setting the shortest space to 0.2 μm is that in MAMMOS, a recording magnetic domain smaller than a heat spot can be detected by transfer expansion, but the space smaller than the heat spot cannot be detected, so that the space becomes 0.2 μm or more. Because he did.

In the conventional mark position recording method, the space needs to be longer than the length of the heat spot. That is, when the size of the heat spot is 0.2 μm, 1-bit information includes the above (2,
7) If the space is set to 0.2 μm in the same manner as in the case where RLL modulation is used, the bit pitch is only 0.2 μm. Therefore, it can be seen that the recording / reproducing method of the present invention can further increase the amount of recordable information as compared with the conventional mark position recording method.

When the length of the recording magnetic domain was not shortened as in Example 1, when the length of the heat spot in the direction parallel to the track was 0.2 μm, the bit pitch was 0.133 μm. That is, it is understood that the recording density is increased by recording the recording magnetic domain short and lengthening the shortest space as in the present embodiment. In this embodiment, the front and rear １ ／
Although the recording magnetic domain of one bit in total is shortened for each bit, the direction in which the recording magnetic domain is shortened and the length of the one bit are not limited. In reproduction by MAMMOS, when an external magnetic field is applied when a small magnetic domain is in a heat spot, the reproduction is enlarged. Therefore, the shortest recording magnetic domain need not be zero. Accordingly, if the length of the recording magnetic domain to be shortened is s and the length of the shortest recording magnetic domain before the shortening is m, the recording magnetic domain can be shortened in the range of 0 ≦ s <m.

[Embodiment 3] First, a MAMMOS similar to that of Embodiment 1 was used as a magneto-optical recording medium according to the reproducing method of the present invention.
A magneto-optical recording medium was prepared.

In this magneto-optical recording medium 100, (2,
7) Encode user data using RLL modulation and N
The recording data was recorded so as to correspond to RZ. In the recording of information, a recording laser beam and a recording magnetic field modulated based on an input signal according to encoded information are applied to a magneto-optical recording medium using an optical pulse magnetic field modulation method, and a recording magnetic domain is formed on a track of a recording layer. Was formed. The length of one bit in the track direction was 0.67 μm. FIG. 19 shows an example of a magnetic domain pattern of the recording magnetic domains formed on the recording layer. The numbers above the magnetic domain pattern indicate input information (recorded information).

Next, while rotating the magneto-optical recording medium having the recording magnetic domains formed by the recording method at a constant speed, the reproducing laser light is irradiated at a predetermined power, and
Information was reproduced by applying a reproduction external magnetic field of one bit period at a constant magnetic field intensity. FIG. 19 shows a timing chart of the applied reproduction external magnetic field and the detected reproduction signal. As shown in FIG. 20, the spot size of the reproduction laser beam is 1.0 μm, and the length of the heat spot in the direction parallel to the track where the magnetic domain is transferred from the recording layer to the magnetic domain enlarged reproduction layer is about 0.1 μm. It was 2 μm. The length of the heat spot in the direction parallel to the track was obtained by adjusting in advance based on the method described in the first embodiment.

Next, when a predetermined track of the magneto-optical recording medium is scanned by the reproducing light spot, the recording magnetic domain moves relative to the heat spot formed in the reproducing light spot, as shown in FIGS. Indicated. 20 to 27 respectively correspond to the numbers shown below the timing chart of the reproduction external magnetic field shown in FIG. That is, FIGS. 20 to 27 conceptually show the case where a heat spot exists at the position indicated by in FIG. 19. In addition, FIGS.
In, the direction from the back of the paper to the front is the recording direction, that is, the same direction as the magnetization of the recording magnetic domain.

As shown in FIG. 20, in the state, the external magnetic field for reproduction is applied with the same polarity as that of the recording magnetic domain. However, since the recording magnetic domain 32 does not enter the heat spot, the recording magnetic domain 32 is enlarged and reproduced. No reproduction signal is detected from the magnetic domain expansion reproduction layer without being transferred to the layer. 20, 22, and 2
3, as shown in FIG. 24 and FIG. 25, in the state, the state, the state, the state, and the state, since a part of the recording magnetic domain 32 enters the heat spot, such a magnetic domain (part of the recording magnetic domain 32) is used. ) Is transferred to the magnetic domain expansion reproducing layer, and is expanded by the reproducing external magnetic field.
A reproduction signal amplified by the principle of the OS is detected.

Next, as shown in FIG. 26, in the state, since the recording magnetic domain 32 does not enter the heat spot, the recording magnetic domain 32 is not transferred to the magnetic domain enlarged reproduction layer, and the reproduction signal is detected from the magnetic domain enlarged reproduction layer. Not done. That is, if the space (space) between the recording magnetic domain 32 and the next recording magnetic domain 33 is larger than the heat spot, the recording magnetic domain 32 and the recording magnetic domain 33 are transferred to the magnetic domain expansion / reproduction layer even when an external magnetic field is applied in such space. Instead, it can be detected that the part is the space. In this embodiment, since the size of the heat spot is 0.2 μm, a space having a length of 0.2 μm or more can be detected.

Here, in this embodiment, the recording magnetic domain is formed corresponding to NRZ by using (2, 7) RLL modulation and setting one bit to 0.067 μm, so that the space is 0.13 μm.
m, 0.2 μm, 0.27 μm, 0.34 μm, 0.4
There are only six patterns of μm and 0.47, and a 1-bit magnetic domain is always recorded between these spaces. Therefore, even if the shortest space of 0.13 μm is not detected, all other recording patterns can be reproduced if the other five spaces can be detected.

Since the heat spot is larger than the recording magnetic domain 32 as shown in FIG.
A 2-bit expanded signal is detected for each bit more than the recording magnetic domain. Therefore, if an enlarged signal is detected, the same information as the recorded information cannot be obtained unless the enlarged signals at both ends are converted to zero. In this embodiment, 1
Eleven reproduction patterns were converted to 010 to obtain reproduction information.

Thus, by reproducing the position information of each recording magnetic domain with the amplified reproduction signal, reproduction information as shown in the lower part of FIG. 19 is obtained, and the reproduction pattern of 111 of the reproduction information is converted into 010. By doing so, the recorded information shown in the upper part of FIG. 19 can be reproduced.

Here, when the size of the heat spot at the time of reproduction is 0.2 μm and a recording mark is recorded corresponding to NRZ using the (2, 7) RLL code, the shortest space to be detected is 0.1 μm. 2 μm, and the bit pitch is about 0.133
μm. The reason why the shortest space to be detected is set to 0.2 μm is that the recording domain smaller than the heat spot can be detected by transfer enlargement in MAMMOS, but the space smaller than the heat spot cannot be detected, so that the space becomes 0.2 μm or more. It is because it became.

Also in the conventional mark position recording method, the space needs to be longer than the length of the heat spot. That is, when the size of the heat spot is 0.2 μm, 1-bit information includes the above (2,
7) If the space is set to 0.2 μm in the same manner as in the case where RLL modulation is used, the bit pitch is only 0.2 μm. Therefore, it can be seen that the recording / reproducing method of the present invention can further increase the amount of recordable information as compared with the conventional mark position recording method.

[Embodiment 4] In this embodiment, an example of the structure of an apparatus suitable for the recording / reproducing method described in Embodiments 1 and 2 will be described. FIG. 32 schematically shows a configuration of a recording / reproducing apparatus according to the recording / reproducing method of the present invention. The recording / reproducing apparatus 101 irradiates a laser beam irradiating unit for irradiating the magneto-optical recording medium 100 with pulsed light in a cycle synchronized with the code data, and applies a magnetic field controlled during recording / reproducing to the magneto-optical recording medium 100 And a signal processing system for detecting and processing a signal from the magneto-optical recording medium 100.

In the laser beam irradiation section, the laser 22
Are connected to a laser driving circuit 132 and a recording pulse width / phase adjusting circuit (RC-PPA) 151, and the laser driving circuit 32 is connected to the recording pulse width / phase adjusting circuit 51.
Alternatively, it receives a signal from the reproduction pulse width / phase adjusting circuit 53 and controls the laser pulse width and phase of the laser 22. The recording pulse width / phase adjustment circuit 151 performs
Upon receiving a recording clock from the PLL circuit 39, the first synchronizing signal for adjusting the phase and pulse width of the laser light is generated.

In the magnetic field applying section, the magneto-optical recording medium 10
The magnetic coil 29 for applying a magnetic field to 0 is connected to a magnetic coil drive circuit (M-DRIVE) 34, and has a direct current (DC) magnetic field (continuous magnetic field) and a pulse magnetic field (alternating magnetic field).
Can be applied to the magneto-optical recording medium 100 by switching. At the time of recording, the magnetic coil driving circuit 34 receives the code-converted data from the encoder 303 that converts the recording data into a predetermined code through the phase adjustment circuit (RE-PA) 231 and controls the magnetic coil 29. On the other hand, during reproduction, a reproduction pulse width / phase adjustment circuit (RP-PPA)
The magnetic coil 29 is controlled through 131. A recording / reproducing switch (RC / RP SW) 1 for switching a signal input to the magnetic coil driving circuit 34 between recording and reproducing.
34 is connected to the magnetic coil drive circuit 34.

In the signal processing system, a first polarizing prism 25 is disposed between the laser 22 and the magneto-optical disk 100, and a second polarizing prism 251 and detectors 28 and 281 are disposed beside the first polarizing prism 25. ing. The detectors 28 and 281 are connected to a subtractor 302 and an adder 301 via I / V converters 311 and 312, respectively. The adder 301 is a clock extraction circuit (CSS) 37
Is connected to the PLL circuit 39 via the. Subtractor 30
2 is a sample-and-hold (S / H) circuit 41 for holding a signal in synchronization with a clock, and an A / D conversion circuit 4 for similarly performing analog-to-digital conversion in synchronization with a clock.
It is connected to a decoder 38 via a binary and binary signal processing circuit (BSC) 43.

The light emitted from the laser 22 is collimated by the collimator lens 23, passes through the polarizing prism 25, and is focused on the magneto-optical disk 100 by the objective lens 24. The reflected light from the disc 100 is directed to the polarizing prism 251 by the polarizing prism 25,
After passing through the half-wave plate 26, the light is split in two directions by a polarizing prism 251. The split light is condensed by a detection lens 27 and guided to photodetectors 28 and 281, respectively. Here, pits for generating a tracking error signal and a clock signal are formed on the magneto-optical disk 100 in advance. After the signals indicating the reflected light from the clock signal generation pits are detected by the detectors 28 and 281, the signals are extracted by the clock extraction circuit 37. Next, a data channel clock is generated in PLL circuit 39 connected to clock extraction circuit 37.

In the above apparatus, an alternating magnetic field of one cycle for one bit is applied to the magneto-optical recording medium via the magnetic head driver as a reproduction external magnetic field in synchronization with the PLL circuit 39. The binarized reproduced signal is supplied to a waveform shifter (P
CS) 71 as the shift register
By shifting the data after a bit and performing a logical AND operation with the reproduced signal by the logic circuit 72, a reproduced signal similar to the recording signal can be obtained as shown in FIG. 1 and FIG. Reproduction of information based on the method is realized.

FIG. 33 and FIG. 34 show an example of the waveform shifter and the logic circuit and the waveforms of each part. The input signal S0 is DF
The rising state of the clock is held by F and S
In the example of FIG. 34 which is output to Q as 0 ', S0 rises at the falling edge of the clock, so S0'
The signal is delayed by a half cycle with respect to CK. Next, the negation of the first stage clock is used as the second stage CK, and S0 ′ is set to DF.
Similarly, when input to F, the signal S is delayed by a half cycle with respect to CK.
It is output as 1. That is, S1 is output as a signal one bit behind the clock of S0. Similarly, S2 is output as a signal one bit behind the clock of S0. As described above, by continuously configuring the D-FFs, it is possible to generate a signal shifted by an arbitrary bit. The reproduction based on the reproduction method described in the first and second embodiments is realized by taking the logical product of the signal shifted as the reproduction signal S0 and the reproduction signal.

The recording / reproducing method of the present invention has been described in detail with reference to the first, second, third and fourth embodiments, but the present invention is not limited to these embodiments. . For example, in the first embodiment, the second embodiment, and the third embodiment, even if the (2,7) RLL code is not used, the (1,7) R
Similar reproduction can be performed by another modulation method such as LL.

In the fourth embodiment, the reproduced signal is shifted using the shift register. However, the reproduced signal can be shifted by passing through a delay circuit.
In addition, it is also possible to take a waveform once into a computer and perform it by software.

Further, in the first and second embodiments, the reproduced signal is shifted forward and backward by one bit, but the same reproduction can be performed by two bits before or after. The shift amount may also vary depending on the size of the heat spot, the minimum length of the space, the period of the reproducing external magnetic field, and the like.

In the first, second, and third embodiments, information is recorded using the optical pulse magnetic field recording method. However, the present invention is not limited to this. It is also possible to use a method. Furthermore,
Although a medium having the structure shown in FIG. 28 was used as a magneto-optical recording medium for MAMMOS, it is not limited to this.
No. 8/02878 MAMMO of various structures
A magneto-optical recording medium for S can be used.

[0071]

According to the reproducing method of the present invention, if the space (space) between the recording marks is larger than the heat spot, the presence or absence of the space is detected, and the information recorded by inverting the bits before and after the detection of the recording magnetic domain is inverted. Therefore, the width of the recording mark with respect to the space can be extremely reduced, and the recording density of the magneto-optical recording medium can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a magnetic domain pattern of a recording magnetic domain formed on a recording layer in Example 1, an application pattern of a reproduction external magnetic field, and a detected reproduction signal.

FIG. 2 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 3 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 4 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 5 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 6 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 7 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 8 is a view for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 9 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot;
It is a case of the state of.

FIG. 10 is a diagram showing an example of a magnetic domain pattern of a recording magnetic domain formed on a recording layer in Example 2, an application pattern of a reproducing external magnetic field, and a reproduced signal detected.

FIG. 11 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a case of the state of FIG. 10;

FIG. 12 is a diagram illustrating a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, which is the case in the state of FIG. 10;

FIG. 13 is a diagram illustrating a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a case of FIG.

FIG. 14 is a diagram illustrating a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a state of FIG. 10;

FIG. 15 is a diagram illustrating a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a state of FIG.

FIG. 16 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the state of FIG. 10;

FIG. 17 is a diagram for explaining a manner in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the state of FIG. 10;

FIG. 18 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the case of the state of FIG. 10;

FIG. 19 is a diagram illustrating an example of a magnetic domain pattern of a recording magnetic domain formed in a recording layer, an application pattern of a reproducing external magnetic field, and a detected reproduction signal in Example 3.

FIG. 20 is a diagram illustrating a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a case of FIG. 19;

FIG. 21 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a state of FIG. 19;

FIG. 22 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the case of the state of FIG. 19;

FIG. 23 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the case of the state of FIG. 19;

FIG. 24 is a diagram for explaining a manner in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the state of FIG. 19;

FIG. 25 is a diagram for explaining how a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the state of FIG. 19;

FIG. 26 is a diagram for explaining a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in a state of FIG. 19;

FIG. 27 is a diagram illustrating a state in which a recording magnetic domain moves with respect to a heat spot formed in a reproduction light spot, in the case of the state of FIG. 19;

FIG. 28 is a diagram schematically illustrating a cross-sectional structure of a magneto-optical recording medium used in an example.

FIG. 29 is a diagram for explaining the principle of reproduction of MAMMOS.

FIG. 30 is a diagram for explaining a method of adjusting the length of a heat spot in the track direction, and is a diagram illustrating a state in which a 1 μm recording mark is scanned with a light spot.

FIG. 31 is a diagram for explaining a method of adjusting the length of a heat spot in the track direction, and is a diagram illustrating a reproduction magnetic field when an application timing is changed and a reproduction signal detected thereby.

FIG. 32 is a block diagram of a magneto-optical recording / reproducing apparatus used in Example 3.

FIG. 33 is a diagram illustrating an example of a waveform shift device and a logic circuit in FIG. 20;

FIG. 34 is an explanatory diagram of waveforms of respective parts of the circuit in FIG. 21;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st dielectric layer 3 Magnetic domain expansion reproduction layer 4 Nonmagnetic layer 5 Recording layer 6 2nd dielectric layer 100 Magneto-optical recording medium 101 Recording / reproducing apparatus

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Awano 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell, Ltd. (Reference) 5D075 AA03 CC01 CC11 CC23

Claims (7)

[Claims] 1. A magneto-optical recording medium having a recording layer in which a recording magnetic domain is formed and a magnetic domain enlarging / reproducing layer, and irradiating the magneto-optical recording medium with reproducing light to generate a high-temperature region in a reproducing light spot. In the method of reproducing a magneto-optical recording medium in which a recording magnetic domain is transferred to a reproducing layer through the high-temperature region and the transferred magnetic domain is enlarged by applying an external magnetic field, when the disk is scanned with a reproducing laser beam, A reproducing method for a magneto-optical recording medium, wherein a reproducing external magnetic field is applied at a period shorter than the time from when a certain point enters the high-temperature area to when the point leaves the high-temperature area. 2. The reproducing method for a magneto-optical recording medium according to claim 1, wherein a signal enlarged and reproduced by the recording mark is detected over a range longer than the recording mark. 3. The method according to claim 1, wherein after detecting the reproduction signal, a range of the enlarged signal detected by the recording mark over a range longer than the recording mark is converted into the same length as the recording mark. A method for reproducing a magneto-optical recording medium. 4. Using a magneto-optical recording medium having a recording layer in which a recording magnetic domain is formed and a magnetic domain expansion reproducing layer, irradiating the magneto-optical recording medium with reproducing light to generate a high-temperature region in the reproducing light spot. A method for transferring a recording magnetic domain to a reproducing layer through the high-temperature region, and enlarging the transferred magnetic domain by applying an external magnetic field. ,
When reproducing information by scanning the high-temperature region from a magnetization pattern recorded such that the minimum recording magnetic domain of the first recording state is smaller than the minimum recording magnetic domain of the second recording state as the second recording state, A reproducing method for a magneto-optical recording medium, wherein reproducing is performed in a state where the length of the high-temperature region in the scanning direction is smaller than the minimum magnetic domain of the second recording state. 5. Using a magneto-optical recording medium having a recording layer in which recording magnetic domains are formed and a magnetic domain enlarging and reproducing layer, irradiating the magneto-optical recording medium with reproducing light to generate a high-temperature region in the reproducing light spot. A recording magnetic domain is transferred to the reproducing layer through the high-temperature region, and the transferred magnetic domain is enlarged by applying an external magnetic field. ,
A recording method for a magneto-optical recording medium, wherein recording is performed such that a minimum recording magnetic domain in the first recording state is smaller than a minimum recording magnetic domain in the second recording state as the second recording state. 6. A reproducing method for a magneto-optical recording medium comprising: a recording layer in which a recording magnetic domain is formed; and a magnetic domain expansion reproducing layer in which the recording magnetic domain of the recording layer is transferred and expanded by applying an external magnetic field. Characterized in that the method comprises: shifting one or more bits forward or backward, or either forward or backward, and taking the logical product of the read signal and the shifted signal. . 7. A reproducing apparatus for reproducing a magneto-optical recording medium comprising: a recording layer in which a recording magnetic domain is formed; and a magnetic domain enlarging reproducing layer in which the recording magnetic domain of the recording layer is transferred and expanded by applying an external magnetic field. A light source for irradiating the magneto-optical recording medium with light, a magnetic field application device for generating the external magnetic field, a signal detection device for detecting a reproduction signal from the magnetic domain expansion reproduction layer, and a reproduction signal A reproducing apparatus comprising: a waveform shifter for shifting back and forth; and a logical operation device for calculating a logical product of a reproduced signal and an output of the signal waveform shifter.