JP2001256691A - Modulating system, recording method, recording device, reproducing method and the reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modulating system of signals, which is capable of recording signals at high density on a magneto-optical recording medium and is capable accurately reproducing the signals recorded to the magneto-optical recording medium with magnetic domain expansion, a recording device, a recording method, a reproducing device and a reproducing method. SOLUTION: Binarized digital signals (a) are so modulated, that '1' or '0' continues in N pieces or larger through the use of N=L/W formed by a basic domain length L, formed at the magneto-optical recording medium and the minimum length W of the domain length changed from the basic domain length L (b). The domain lengths formed at the magneto-optical recording medium are made correspondent, in accordance with the modulated signals (b) and the respective domains are composed of a variable length domain section and a fixed length domain section and the increase of the domain length, by increasing of one piece of the '1' or '0' is executed in the variable length domain section and the signals are recorded at the magneto-optical recording medium. At reproduction, reproducing with the magnetic domain expansion is conducted by impressing the alternating magnetic fields, having the same frequency as the frequency of the recording data modulated in recording.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modulating recording data when recording a signal on a magneto-optical recording medium, a recording apparatus,
The present invention relates to a recording method, a reproducing apparatus for reproducing a signal from a magneto-optical recording medium, and a reproducing method.

[0002]

2. Description of the Related Art Magneto-optical recording media have attracted attention as rewritable, large-capacity, and highly reliable recording media, and have begun to be put to practical use as computer memories and the like. Recently, the recording capacity is 6.0 Gby.
tes's magneto-optical recording medium is AS-MO (Advanced)
d Storage Magneto Optica
l disk) standard and is about to be put to practical use.

[0003] Further, a 14 Gbyte by magnetic domain expansion reproduction method for reproducing signals by enlarging and transferring magnetic domains of a recording layer to a reproduction layer.
A magneto-optical recording medium having a recording capacity of es has also been proposed. When recording a signal on a magneto-optical recording medium using such a magnetic domain expansion reproduction method, mark length recording has been performed. That is, a signal is recorded by determining a domain length corresponding to a continuous length of "1" or "0" and forming a domain on the magneto-optical recording medium. Therefore, when a large number of “1” or “0” continues, a long domain has been formed on the magneto-optical recording medium.

[0004]

However, in the conventional method of recording a signal on a magneto-optical recording medium, the shortest domain length that can be formed on the magneto-optical recording medium is set to 0.1 μm and 0.1 μm.
If “1” or “0” is recorded in a domain having a length of “1”, the length of the domain when recording a signal of “1, 1” or “0, 0” is 0.2 μm, and “ 1,
The length of the domain when recording the signal of “1, 1” or “0, 0, 0” is 0.3 μm. That is, each time "1" or "0" increases by one, the domain length increases in units of 0.1 μm, and it is difficult to record signals at high density.

When a signal is reproduced from a magneto-optical recording medium by a magnetic domain expansion reproduction method, the magnetic domain of the recording layer is transferred and expanded to the reproducing layer, and the expanded magnetic domain is detected by a laser beam. However, when a signal is reproduced from a magneto-optical recording medium having a long domain by the magnetic domain expansion reproduction method, the leakage magnetic field from the center of the long domain is weaker than the edge of the domain. The magnetic domain cannot be transferred to the reproducing layer, and it is difficult to accurately detect the magnetic domain of the recording layer.

Accordingly, the present invention solves such a problem, and a signal modulation system capable of recording a signal at a high density on a magneto-optical recording medium and accurately reproducing a domain recorded signal on the magneto-optical recording medium with magnetic domain expansion. , A recording device, a recording method, a reproducing device, and a reproducing method.

[0007]

The invention according to claim 1 relates to a modulation system of recording data when recording a signal on a magneto-optical recording medium, and a basic domain formed on the magneto-optical recording medium. When the length is L and the minimum length changed from the basic domain length is W, N determined by N = L / W (N is an integer) is a signal “1” or a signal “0”.
Is a modulation method for modulating the recording data as a minimum number of continuous data.

In the modulation method according to the first aspect, when the basic domain length L formed on the magneto-optical recording medium and the minimum length W to be changed from the basic domain length are determined, N = L / W is calculated. I do. Then, by the calculation, N
Is obtained, the recording data is modulated so that the signal "1" or the signal "0" continues N times or more. Therefore, claim 1
According to the invention described in the above, it is possible to modulate the recording data so that at least N “1” or “0” continues,
By setting a small increase in the domain length due to an increase of one "1" or "0", a change in the domain length on the magneto-optical recording medium can be reduced even if the number of bits increases. As a result, high-density signal recording is possible.

According to a second aspect of the present invention, there is provided a recording apparatus for recording a signal on a magneto-optical recording medium, comprising: a modulation circuit;
This is a recording apparatus including a drive signal generation circuit and a magnetic head drive circuit. When the basic domain length formed on the magneto-optical recording medium is L and the minimum length changed from the basic domain length is W, the modulation circuit outputs N determined by N = L / W (N is an integer). The recording data is modulated as the minimum number of consecutive “1” or signal “0”.

The drive signal generation circuit converts N consecutive "1" and N consecutive "0" based on the modulation data modulated by the modulation circuit into the basic domain length L.
, N + 1 consecutive “1” s and N + 1 consecutive “0” s as domain length L + W, and N + 2 consecutive “1s” and N + 2 consecutive “0s” as domain length L
+ 2W,..., N + s consecutive “1” and N
+ S consecutive “0” s are converted to a domain length L + sW (s =
0, 1, 2, 3,...) Respectively, and when the shortest domain length that can be formed on the magneto-optical recording medium is SL, “1” having the shortest domain length SL, It is represented by a set of “0” having a length SL, and n = L /
(2 × SL) (where n is an integer) is based on a domain consisting of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL). A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” for each integral multiple, and a set of “1,” having a domain length determined by SL + s × (W / 2) A drive signal for forming a variable-length domain portion consisting of "0" on the magneto-optical recording medium is generated.

The magnetic head drive circuit drives the magnetic head based on the drive signal generated by the drive signal generation circuit. In the recording apparatus according to the second aspect, when the basic domain length L formed on the magneto-optical recording medium and the minimum length W to be changed from the basic domain length are determined, N = L / W is calculated. Then, by the calculation, N
Is obtained, the recording data is modulated so that the signal "1" or the signal "0" continues N times or more. Then, the modulated recording data is associated with the domain length formed on the magneto-optical recording medium, and the fixed-length domain portion and the variable-length domain portion constitute a domain formed on the magneto-optical recording medium. Then, the domain length is formed on the magneto-optical recording medium by adjusting the increase W of the domain length due to the increase of one “1” or “0” by the variable length domain part.

Therefore, according to the second aspect of the present invention, the increment W of the domain length due to the increase of one "1" or "0" is minutely set, whereby "1"
Alternatively, even if the number of consecutive "0" s increases, the domain length actually formed on the magneto-optical recording medium does not increase rapidly, so that high-density signal recording is possible. Claim 3
Is a recording method for recording a signal on a magneto-optical recording medium, wherein the basic domain length formed on the magneto-optical recording medium is L, and the minimum length changing from the basic domain length is W.
Where N is determined by N = L / W (N is an integer), the first step of modulating the recording data with N being the minimum number of consecutive signals “1” or “0”; , N consecutive “1” and N consecutive “0” are added to the basic domain length L, and N + 1 consecutive “1” and N + 1 consecutive “0” To the domain length L + W, N + 2 consecutive “1” and N + 2 consecutive “0” to the domain length L + 2W,..., N + s consecutive “1” and N + s consecutive “0”. Is the domain length L + sW
(S = 0, 1, 2, 3,...) And the shortest domain length that can be formed on the magneto-optical recording medium is SL.
Is represented by a set of “1” having the shortest domain length SL and “0” having the shortest domain length SL, and n =
L / (2 × SL) (where n is an integer) is based on a domain composed of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL) ), A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” each time an integer multiple of (S / 2) is obtained, and SL + s × (W / 2)
Set of "1,0" with domain length determined by
Generating a drive signal for forming a variable length domain portion comprising a variable length domain portion on the magneto-optical recording medium; and driving the magnetic head based on the drive signal generated in the second step to perform magneto-optical recording. And a third step of recording a signal on a medium.

According to the recording method of the present invention, when the basic domain length L formed on the magneto-optical recording medium and the minimum length W to be changed from the basic domain length are determined, N = L / W is calculated. I do. Then, by the calculation, N
Is obtained, the recording data is modulated so that the signal "1" or the signal "0" continues N times or more. Then, the modulated recording data is associated with the domain length formed on the magneto-optical recording medium, and the fixed-length domain portion and the variable-length domain portion constitute a domain formed on the magneto-optical recording medium. Then, the domain length is formed on the magneto-optical recording medium by adjusting the increase W of the domain length due to the increase of one “1” or “0” by the variable length domain part.

Therefore, according to the third aspect of the present invention, the increment W of the domain length due to the increment of "1" or "0" is set to a small value, whereby "1"
Alternatively, even if the number of consecutive "0" s increases, the domain length actually formed on the magneto-optical recording medium does not increase rapidly, so that high-density signal recording is possible. Claim 4
In the invention according to the invention, when the basic domain length formed on the magneto-optical recording medium is L and the minimum length changed from the basic domain length is W, N determined by N = L / W (N is an integer) The recording data is modulated as the minimum number of consecutive signals “1” or “0”, and based on the modulated data, N consecutive “1” s and N consecutive “0” s are basically used. For the domain length L, add N + 1 consecutive “1” and N + 1 consecutive “0” to the domain length L.
+ W, N + 2 consecutive “1” and N + 2 consecutive “0” are added to the domain length L + 2W,..., N + s
Number of consecutive “1” s and N + s number of consecutive “0s” are defined as domain length L + sW (s = 0, 1, 2, 3,...)
If the shortest domain length that can be formed on the magneto-optical recording medium is SL, the shortest domain length SL
"1" having the shortest domain length SL and "0" having the shortest domain length SL
And is based on a domain consisting of (n−1) sets of “1,0” that is one less than n determined by n = L / (2 × SL) (n is an integer), and the domain length A fixed-length domain portion configured by increasing a domain consisting of a set of “1,0” each time the increment sW of the integer becomes an integral multiple of (2 × SL);
A reproducing apparatus for reproducing a signal from a magneto-optical recording medium on which a signal has been recorded by forming a set of variable-length domain portions consisting of a set of “1,0” having a domain length determined by SL + s × (W / 2) And a drive signal back circuit;
This is a reproducing apparatus including a magnetic head drive circuit.

The drive signal generation circuit generates a drive signal for generating an alternating magnetic field having the same frequency as the modulation data. Further, the magnetic head drive circuit drives the magnetic head based on the drive signal generated by the drive signal generation circuit. In the reproducing apparatus according to the fourth aspect, N determined from the basic domain length L formed on the magneto-optical recording medium and the minimum length W changed from the basic domain length.
Using (= L / W), modulation is performed such that N or more “1” or “0” are continuous, and the modulated recording data is a domain corresponding to “1” and a domain corresponding to “0”. When magnetic domain expansion reproduction is performed from a magneto-optical recording medium recorded in such a manner that are alternately arranged, an alternating magnetic field having the same frequency as the modulated recording data is applied to the magneto-optical recording medium. Then, even when the laser beam is applied to the domain corresponding to “0” existing between the two domains corresponding to “1”, the diameter of the aperture capable of detecting the magnetic domain is made equal to or greater than the shortest domain length SL. By setting, a reproduction signal by magnetic domain expansion reproduction is detected from a domain corresponding to “1” existing on both sides. Further, since the domain formed on the magneto-optical recording medium has a domain length from the shortest domain length SL to twice or less the shortest domain length SL,
The magnetic domains of the recording layer are stably transferred to the reproducing layer.

Therefore, according to the fourth aspect of the present invention, even when a large number of "1" s or "0s" are recorded on a magneto-optical recording medium, the magnetic domains of the recording layer are transferred to the reproducing layer. Transfer can be performed reliably. As a result, accurate signal reproduction is possible. According to a fifth aspect of the present invention, when the basic domain length formed on the magneto-optical recording medium is L and the minimum length changed from the basic domain length is W, N = L / W
(N is an integer), and the recording data is modulated with N being the minimum number of consecutive signals “1” or “0”, and N consecutive “1” s are generated based on the modulated data. And N consecutive “0” in the basic domain length L, N + 1 consecutive “1” and N + 1 consecutive “0” in the domain length L + W, N + 2 consecutive “1” and N + 2 Are assigned to the domain length L + 2W,..., N + s continuous “1” and N + s continuous “0” are assigned to the domain length L + sW (s =
0, 1, 2, 3,...) Respectively, and when the shortest domain length that can be formed on the magneto-optical recording medium is SL, “1” having the shortest domain length SL and the shortest domain length SL It is represented by a set of “0” having SL, and n = L /
(2 × SL) (where n is an integer) is based on a domain consisting of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL). A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” for each integral multiple, and a set of “1,” having a domain length determined by SL + s × (W / 2) A variable length domain portion consisting of "0" and reproducing a signal from a magneto-optical recording medium on which the signal is recorded, wherein a first step of generating an alternating magnetic field having the same frequency as the modulated data is provided. And a second step of driving the magnetic head based on the drive signal generated in the first step to detect a signal from the magneto-optical recording medium.

In the reproducing method according to the fifth aspect, N (= L / W) determined from the basic domain length L formed on the magneto-optical recording medium and the minimum length W changed from the basic domain length. Is modulated so that "1" or "0" is continuous for N or more, and the domain of the modulated recording data is alternately arranged with the domain corresponding to "1" and the domain corresponding to "0". When performing magnetic domain expansion reproduction from a magneto-optical recording medium recorded as described above, an alternating magnetic field having the same frequency as the modulated recording data is applied to the magneto-optical recording medium. Then, even when the laser beam is applied to the domain corresponding to “0” existing between the two domains corresponding to “1”, the diameter of the aperture capable of detecting the magnetic domain is made equal to or greater than the shortest domain length SL. By setting, a reproduction signal by magnetic domain expansion reproduction is detected from a domain corresponding to “1” existing on both sides. Further, since the domain formed on the magneto-optical recording medium has a domain length from the shortest domain length SL to twice or less the shortest domain length SL,
The magnetic domains of the recording layer are stably transferred to the reproducing layer.

Therefore, according to the fifth aspect of the present invention, even when a large number of "1" s or "0s" are recorded on a magneto-optical recording medium, the magnetic domains of the recording layer are transferred to the reproducing layer. Transfer can be performed reliably. As a result, accurate signal reproduction is possible.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. Referring to FIG. 1, a recording apparatus according to the present invention includes an optical pickup 20 and a reproduction signal amplifying circuit 30.
A servo circuit 40, a servo mechanism 50, a spindle motor 60, an external synchronization signal generation circuit 70, a modulation circuit 80, a drive signal generation circuit 90, a magnetic head drive circuit 110, a laser drive circuit 120, Magnetic head 130
And

The optical pickup 20 includes the magneto-optical recording medium 1
The laser light is irradiated to 0, and the reflected light is detected. The reproduction signal amplifier circuit 30 receives the focus error signal, the tracking error signal detected by the optical pickup 20, and the optical signal based on the shape periodically formed on the magneto-optical recording medium 10, and outputs the focus error signal, the tracking error signal, The optical signal is amplified to a predetermined level, the focus error signal and the tracking error signal are output to the servo circuit 40, and the optical signal is output to the external synchronization signal generation circuit 70.

The external synchronizing signal generation circuit 70 generates a timing signal corresponding to the center position of the optical signal based on the input optical signal, so that a predetermined number of periodic signals exist between the generated timing signals. Generate an external synchronization signal. Then, the generated external synchronization signal is transmitted to the servo circuit 40,
And a drive signal generation circuit 90. Servo circuit 4
Numeral 0 controls the servo mechanism 50 to perform focus servo and tracking servo of an objective lens (not shown) in the optical pickup 20 based on the input focus error signal and tracking error signal. Further, the servo circuit 40 rotates the spindle motor 60 at a predetermined rotation speed in synchronization with the input external synchronization signal.

The servo mechanism 50 performs focus servo and tracking servo of the objective lens in the optical pickup 20 based on the control from the servo circuit 40. The spindle motor 60 rotates the magneto-optical recording medium 10 at a predetermined rotation speed. The modulation circuit 80 modulates recording data by a method described later. The drive signal generation circuit 90 generates a drive signal for driving the magnetic head 130 based on the modulated recording data input from the modulation circuit 80 by a method described later. The drive signal generation circuit 90 generates a drive signal for driving a semiconductor laser (not shown) in the optical pickup 20. Then, a drive signal for driving the magnetic head 130 is output to the magnetic head drive circuit 110,
A drive signal for driving a semiconductor laser is supplied to a laser drive circuit 12.
Output to 0.

The magnetic head drive circuit 110 drives the magnetic head 130 based on the input drive signal. The laser drive circuit 120 drives the semiconductor laser based on the input drive signal. The magnetic head 130 applies a magnetic field to the magneto-optical recording medium 10. Referring to FIG. 2, modulation circuit 80
The modulation of the recording data in will be described. The binarized recording data shown in (a) is input to the modulation circuit 80. When the basic domain length formed on the magneto-optical recording medium 10 is L and the minimum length changed from the basic domain length L is W, “1” or “1” is obtained by using N determined by N = L / W. The signal (a) is modulated so that “0” continues N times or more. Assuming that the basic domain length L formed on the magneto-optical recording medium 10 is 0.6 μm and the minimum length W changed from the basic domain length L is 0.04 μm, 0.6 μm
/0.04 μm = 15, and “1” or “0” is 1
A signal (b) is obtained by modulating the signal (a) so that five or more signals are continuous. Assuming that a signal in which 15 “1” or “0” are continuous is 15T, the signal (b) is “0”, 1
"1" for 5T, "0" for 16T, "1" for 16T, ...
Is recording data modulated so as to be arranged. Therefore, the basic domain length L formed on the magneto-optical recording medium 10
Is set to 0.6 μm and the minimum length W to be changed from the basic domain length L is set to 0.04 μm, the signal is modulated so that a signal of 15 T or more is arranged.

The drive signal generation circuit 90 will be described in detail with reference to FIGS. Referring to FIG. 4, drive signal generation circuit 90 includes counter 91 and buffer memory 9.
2, a magnetic head drive signal generation circuit 93, and a laser drive signal generation circuit 94. The counter 91 receives the signal (b) in FIG. 2, counts the number of consecutive “0” or “1” in synchronization with the external synchronization signal (CK), and counts the count value (CV) to drive the magnetic head. The signal is output to the signal generation circuit 93, the switching timing between a signal in which “0” is continuous and a signal in which “1” is continuous is detected, and the timing signal (TS) is output to the buffer memory 92. That is, the signal 3 in which the first 15 “0” s of the signal (b) are continuous is synchronized with the external synchronization signal (CK) to be 0, 1, 2,.
····································· Counts 14 and outputs the count value 14 to the magnetic head drive signal generation circuit 93. Timing 7 is set to 15 of the external synchronization signal (CK).
It is detected in the cycle, and the detected timing 7 is output to the delay circuit 92 as a timing signal (TS). "1"
, A signal 5 having 16 consecutive "0s", and a signal 6 having 16 consecutive "1s" are similarly counted, and timings 8, 9, and 13 are detected.

The buffer memory 92 stores the signal (b) in FIG.
And holds the signal (b) from the counter 91 until a timing signal (TS) for switching between a signal of continuous “0” and a signal of continuous “1” is input, and the timing signal (TS) is When input, a signal in which one “1” or “0” continues is converted to a magnetic head drive signal generation circuit 9.
Output to 3. That is, the buffer memory 92 stores the counter 9
The signal (b) is held from 1 until the timing 7 is input, and when the timing 7 is input, the signal 3 in which 15 “0” s are continuous is output to the magnetic head drive signal generation circuit 93. Hereinafter, similarly, when the timing 8 is input, "1" is set.
Are output to the magnetic head drive signal generation circuit 93, and when the timing 9 is input, the signal 5 of 16 consecutive "0" s is output to the magnetic head drive signal generation circuit 93.
3 and when the timing 13 is input, a signal 6 consisting of 16 consecutive “1” s is output to the magnetic head drive signal generation circuit 9.
3 is output. Therefore, the buffer memory 92 outputs the signal (bb) to the magnetic head drive signal generation circuit 93.

The magnetic head drive signal generation circuit 93 generates a drive signal (GDS) for driving the magnetic head 130 based on the count value (CV) input from the counter 91 and the signal (bb) input from the buffer memory 92. ) Is generated in synchronization with the external synchronization signal (CK). That is, "0"
The component that drives the magnetic head 130 when recording 15 consecutive signals 3 on the magneto-optical recording medium 10 is the drive signal component 14, and the signal 4 having 15 consecutive “1” s is transmitted to the magneto-optical recording medium 10. The component that drives the magnetic head 130 when recording is the drive signal component 15, and the component that drives the magnetic head 130 when recording the signal 5 having 16 consecutive “0” on the magneto-optical recording medium 10 is the drive signal component 15. Component 16.
The drive signal component 17 is a component that drives the magnetic head 130 when recording the signal 6 having 16 consecutive “1” s on the magneto-optical recording medium 10. Here, the drive signal components 14 and 16
Is a component corresponding to signals 3 and 5 in which “0” is continuous, and is a component to which a magnetic field in a fixed direction is applied.

Referring to FIG. 3, drive signal components 15, 17
Generation will be described in detail. According to the modulation method of the present application, at least fifteen “1” s are continuous, so that the domain length corresponding to the signal 4 having fifteen “1s” is determined as the basic domain length L. Therefore, the magneto-optical recording medium 10
Assuming that the shortest domain length SL that can be formed on the substrate is 0.1 μm, the basic domain length L is determined to be 0.6 μm. Then, 0.6 corresponding to signal 4 in which 15 “1” are continuous
The μm domain has three domains D11, D13, D representing “1” having a shortest domain length SL of 0.1 μm.
15 and three domains D12, D14, and D16 representing “0” having the shortest domain length SL of 0.1 μm. The domain representing “1” and the domain representing “0” are D11. , D12, D13, D
14, D15 and D16 are alternately arranged. Therefore, the drive signal component 15 includes a component 151 for forming a domain D11 corresponding to “1” having the shortest domain length of 0.1 μm and a domain 151 corresponding to “0” having the shortest domain length of 0.1 μm. A component 152 for forming D12, a component 153 for forming a domain D13 corresponding to “1” having a shortest domain length of 0.1 μm, and a “0” having a shortest domain length of 0.1 μm.
154 for forming domain D14 corresponding to
And a component 155 for forming a domain D15 corresponding to “1” having a shortest domain length of 0.1 μm;
A component 156 for forming a domain D16 corresponding to “0” having a shortest domain length of 0.1 μm.

The drive signal component 17 is a drive signal component for recording the signal 6 having 16 consecutive “1” s on the magneto-optical recording medium 10. The drive signal component 17 is the signal 4 having the basic 15 continuous “1” s. On the other hand, “1” is increased by one. Due to the increase of one “1”, the domain length formed in the magneto-optical recording medium 10 is longer by 0.04 μm than the basic domain length L of 0.6 μm. Therefore, the domain length of the domain corresponding to the signal 6 in which 16 “1” s are continuous is 0.6.
4 μm. In this case, since the shortest domain length that can be formed on the magneto-optical recording medium 10 is 0.1 μm, the domains D11 and D1 corresponding to the signal 4 in which 15 “1” are continuous
It is impossible to add a domain of 0.04 μm to 2, D13, D14, D15, and D16 to form a domain corresponding to the signal 6 having 16 consecutive “1” s. Therefore,
Two domains D21 and D23 representing “1” having the shortest domain length SL of 0.1 μm, and two domains D2 representing “0” having the shortest domain length SL of 0.1 μm.
2, D24, one domain D25 corresponding to “1” having a domain length of 0.12 μm, and 0.12 μm.
m and a domain D26 corresponding to “0” having a domain length of m, and a domain representing “1” and a domain representing “0” are D21, D22, and D21.
23, D24, D25 and D26 are alternately arranged. Therefore, the drive signal component 17 includes a component 171 for forming the domain D21 corresponding to “1” having the shortest domain length of 0.1 μm and a domain corresponding to “0” having the shortest domain length of 0.1 μm. Component 172 for forming D22, component 173 for forming domain D23 corresponding to “1” having a shortest domain length of 0.1 μm, and component 173 for forming a domain “0” having a shortest domain length of 0.1 μm 174 for forming a domain D24 to be formed and a component 175 for forming a domain D25 corresponding to “1” having a domain length of 0.12 μm.
And a component 176 for forming a domain D26 corresponding to “0” having a domain length of 0.12 μm.

Incidentally, as shown in FIG.
Although the domain D0 of m is formed as a continuous domain, it is formed on the magneto-optical recording medium 10 as a domain in which domains representing "1" and domains representing "0" are alternately arranged. Conventionally, a domain longer than a 0.6 μm domain has a minimum domain length of 0.1 μm.
Although a domain of 0.7 μm is obtained by adding 1 μm, in the present application, a domain longer than 0.6 μm becomes a domain of 0.64 μm, and the increase in the domain length due to the increase of “1” or “0” is slight. Therefore, high-density signal recording is possible.

Referring to FIG. 2 again, laser drive signal generation circuit 94 outputs a drive signal (LDS) for driving the semiconductor laser in optical pickup 20 to an external synchronization signal (C).
Generated in synchronization with K). In this case, since the semiconductor laser is pulse-driven, the semiconductor laser is
Is driven so as to be turned on only during a time period during which a magnetic field is applied.

As described above, the drive signal generation circuit 9
0 is the magnetic head 13 based on the modulated recording data.
A drive signal (GDS) for driving 0 and a drive signal (LDS) for driving the semiconductor laser are generated. In the present application, the domain representing “1” and the domain representing “0” are alternately formed on the magneto-optical recording medium 10, but the domain representing “1” and the domain “0” formed continuously. In order to detect the domain independently, the diameter of the detection window needs to be about the shortest domain length SL. That is, referring to FIG. 5, a domain D1 representing "1", a domain D2 representing "0", and a domain D3 representing "1" are formed continuously, and laser beam LB is applied to domain D1. Is assumed to be irradiated. When the beam diameter of the laser beam LB is Br, the diameter of the detection window AP is r, and the domain length of the domains D1, D2, and D3 is DL, the domains D1, D2, and D3 are detected through the detection window AP. , D
In order to detect D2 and D3 independently, it is necessary to set the diameter r of the detection window AP equal to or smaller than the domain length DL.
This is because a plurality of domains do not exist in the detection window AP, and each domain can be detected independently.

A method for determining the diameter r of the detection window AP will be described with reference to FIG. When the domain D1 is irradiated with a laser beam and an alternating magnetic field is applied to perform domain expansion reproduction, the domain expansion is performed from the time when the front end of the detection window AP approaches the domain D1 until the rear end of the detection window AP passes through the domain D1. A reproduced signal RF1 by the reproduction is detected. Domain D
1 is known in advance, and at what interval the alternating magnetic field is applied to the domain D1, the number r of peaks of the reproduction signal RF1 is measured. Can be determined. That is, domain D
1 is 1.0 μm and the alternating magnetic field is 0.1 μm.
m, and the diameter r of the detection window AP is set to 0.5 μm.
Assuming that m, the detection window AP moves 1.5 μm in the DR1 direction from the time when the front end of the detection window AP approaches the domain D1 until the rear end of the detection window AP passes through the domain D1. Therefore, the diameter r of the detection window AP is 0.5 μm.
If m, 15 peaks appear in the reproduction signal RF1. If the number of peaks is smaller than 15, the diameter r of the detection window AP is smaller than 0.5 μm, and if the number of peaks is larger than 15, the diameter r of the detection window AP is 0.5 μm.
greater than m.

The diameter r of the detection window AP determined by such a method is set to 0.1 μm in the present application. Referring to FIG. 7, a signal having 15 consecutive "1s" corresponds to domain D15, a signal having 16 consecutive "1s" corresponds to domain D16, and a signal having 17 consecutive "1s" corresponds to domain D15. D17
, And a signal in which 19 “1” s are continuous is a domain D1
9 corresponds. In this case, the domain D15 has two pairs of a domain having a domain length of 0.1 μm corresponding to “1” and a domain having a domain length of 0.1 μm corresponding to “0”, and a domain length corresponding to “1”. A set of a 0.1 μm domain and a domain with a domain length of 0.1 μm corresponding to “0” is constituted by one set. Domain D16
Are two pairs of a domain having a domain length of 0.1 μm corresponding to “1” and a domain having a domain length of 0.1 μm corresponding to “0”, and a domain length of 0.12 μm corresponding to “1”.
m domain and domain length 0.12μ corresponding to “0”
A set with m domains is composed of one set. Also,
The domain D17 has a domain length of 0.1 corresponding to “1”.
μm domain and domain length 0.1μ corresponding to “0”
A set of two sets of m domains and one set of a 0.14 μm domain length domain corresponding to “1” and a 0.14 μm domain length domain corresponding to “0” are formed. The domain D19 has two pairs of a domain having a domain length of 0.1 μm corresponding to “1” and a domain having a domain length of 0.1 μm corresponding to “0”, and a domain length of 0 corresponding to “1”. A set of a .18 μm domain and a domain with a domain length of 0.18 μm corresponding to “0” is 1
And a set. Therefore, when the entire domain length is from 0.6 μm to 0.76 μm, which is the basic domain length, two domains are used, one having a fixed domain length corresponding to “1” and the other having a fixed domain length corresponding to “0”. One set includes a domain whose domain length corresponding to “1” is variable and a domain whose domain length corresponding to “0” is variable. Therefore, an area in which two sets of a domain having a fixed domain length corresponding to “1” and a domain having a fixed domain length corresponding to “0” are defined as a fixed-length domain portion 1 and a domain length corresponding to “1” A variable-length domain portion 2 is defined as a region in which a set of a domain in which the variable is variable and a domain in which the domain length corresponding to “0” is variable.

When the entire domain length becomes 0.80 μm, the variable length domain portion 2 is composed of a domain corresponding to “1” of 0.2 μm and a domain corresponding to “0” of 0.2 μm. . Then, since the 0.2 μm domain can be divided into two 0.1 μm domains, like the domain D20, a domain length of 0.1 μm corresponding to “1” and a domain length of 0.1 μm corresponding to “0”. Three sets of 1 μm domains and one set of a 0.1 μm domain length corresponding to “1” and a 0.1 μm domain length corresponding to “0” are formed. Therefore, three sets of “1” are included in the domain D20.
Length domain part 11 composed of a 0.1 μm domain corresponding to “1” and a 0.1 μm domain corresponding to “0”
And a variable-length domain portion 12 including a set of 0.1 μm domains corresponding to “1” and 0.1 μm domains corresponding to “0” exists. And "1" is 2
In the range from 1 to 24, variable-length domain portions 12 whose domain lengths are increased at the same ratio as the variable-length domain portions 2 are added to the fixed-length domain portions 11, and domains D21, D22, D23, D24 is configured.

Since the domain length of a domain corresponding to a signal having 25 continuous "1" s is 1.0 .mu.m, a domain corresponding to a "1" constituting a fixed length domain portion and a "0" are formed similarly to the domain D20. The fixed length domain part is configured by adding one set of the domains corresponding to. That is, every time the domain length of the domain corresponding to “1” or “0” constituting the variable-length domain portion becomes 0.2 μm, the domain corresponding to “1” constituting the fixed-length domain portion becomes “0”.
Is increased by one set with the domain corresponding to.

Accordingly, the domain D15 to the domain D1
Up to 9, the fixed-length domain portion 1 is composed of two sets of a 0.1 μm domain corresponding to “1” and a 0.1 μm domain corresponding to “0”, and 0 corresponding to “1”. .
0.1 to 0.18 μm domain and 0.1 corresponding to “0”
The variable length domain portion 2 is constituted by one set including a domain of about 0.18 μm. Further, from domain D20 to domain D24, a set of a 0.1 μm domain corresponding to “1” and a 0.1 μm domain corresponding to “0” has three pairs.
A fixed-length domain portion 11 is configured as a set, and a set of a 0.1 to 0.18 μm domain corresponding to “1” and a 0.1 to 0.18 μm domain corresponding to “1” is variable in one set. The long domain section 12 is configured. Further, the domain D25 to the domain D29 have a size of 0.1 μm corresponding to “1”.
The fixed-length domain portion is composed of four pairs of a domain of "1" and a domain of 0.1 .mu.m corresponding to "0", and a domain of 0.1 to 0.18 .mu.m corresponding to "1" and corresponding to "1". The variable length domain portion is constituted by one set of 0.1 to 0.18 μm domains.

Then, the number n = 3 obtained by dividing 0.6 μm, which is the basic domain length L formed on the magneto-optical recording medium 10, by 0.1 μm × 2, which is twice the shortest domain length SL, is obtained. One less n-1 = 3-1 = 2 is domain D
A 0.1 μm domain corresponding to “1” and a “0” corresponding to the fixed length domain part 1 from the domain 15 to the domain D19
Each time the domain length of the domain corresponding to “1” or “0” constituting the variable-length domain portion 2 becomes 0.2 μm, the fixed-length domain becomes The number of sets may be increased by one.

In general terms, the basic domain length L
= 2 obtained by dividing the minimum domain length by twice the shortest domain length SL
N-1 less than / (2 × SL) (n is an integer) is the number of pairs of the domain corresponding to “1” and the domain corresponding to “0” of the fixed-length domain part, and The increase sW in the domain length of the domain corresponding to “1” or “0” doubles the shortest domain length SL (2 × S
Every time an integer multiple of L) is reached, the number of pairs of domains corresponding to “1” and domains corresponding to “0” is increased by one. The domain length of the domain corresponding to “1” or “0” in the variable-length domain portion is SL + m × (W / 2) (m =
0, 1, 2, 3,...).

As described above, in the present application, the domain length increased by the increase of “1” or “0” is adjusted to the domain corresponding to “1” and “0” by adjusting the variable length domain part. The corresponding domains are formed alternately. Referring again to FIG. 1, when the magneto-optical recording medium 10 is mounted on the recording apparatus 100, the focus servo of the objective lens (not shown) in the optical pickup 20 to the magneto-optical recording medium 10 as described above. And the tracking servo is turned on. The recording data is modulated by the modulation circuit 80 by the method described above, and the drive signal generation circuit 90 generates a drive signal (GDS) for driving the magnetic head 130 based on the modulated recording data from the modulation circuit 80. It is generated by the method described above and output to the magnetic head drive circuit 110. The drive signal generation circuit 90 generates a drive signal (LDS) for driving a semiconductor laser (not shown) in the optical pickup 20 by the above-described method, and outputs the drive signal to the laser drive circuit 120. The magnetic head drive circuit 110 receives the input drive signal (GDS)
The magnetic head 130 is driven based on the
0 indicates that the magnetic field modulated to the recording data
Is applied. The laser drive circuit 120 drives the semiconductor laser based on the drive signal (LDS), and the optical pickup 20 irradiates the magneto-optical recording medium 10 with pulse light. As a result, the recording data is magnetically modulated and recorded on the magneto-optical recording medium 10.

Referring to FIG. 8, a reproducing apparatus 200 according to the present invention comprises an optical pickup 20 and a reproduced signal amplifying circuit 3.
0, a servo circuit 40, a servo mechanism 50, a spindle motor 60, an external synchronization signal generation circuit 70, a drive signal generation circuit 90, a magnetic head drive circuit 110, a laser drive circuit 120, and a magnetic head 130. , A comparator 140 and a decoder 150.

Optical pickup 20, reproduction signal amplifying circuit 3
0, the servo circuit 40, the servo mechanism 50, the spindle motor 60, and the external synchronization signal generation circuit 70 are the same as those in FIG. The drive signal generation circuit 90 generates a drive signal for driving the magnetic head 130 at the same frequency as the frequency of the modulated data modulated at the time of recording, and outputs the generated drive signal to the magnetic head drive circuit 110. Further, the drive signal generation circuit 90 includes:
A drive signal for driving the semiconductor laser in the optical pickup 20 is generated and output to the laser drive circuit 120.
The comparator 140 compares the reproduced signal detected by the optical pickup 20 and amplified by the reproduced signal amplifier circuit 30 and outputs the signal to the decoder 150. Decoder 150
Decodes the reproduction signal and outputs it as reproduction data.

The drive signal generation circuit 90 includes a magnetic head drive signal generation circuit 93 and a laser drive signal generation circuit 94 shown in FIG. Referring to FIG. 9, magnetic head drive signal generation circuit 93 synchronizes a drive signal (GDSR) for driving magnetic head 130 at the same frequency as the recording data modulated at the time of recording with an external synchronization signal (CK). Generate. The laser drive signal generation circuit 94 generates a drive signal for emitting laser light having a constant intensity.

When a laser beam having a constant intensity is irradiated from the optical pickup 20 to the magneto-optical recording medium 10 by the laser driving circuit 120 and an alternating magnetic field having the same frequency as the recording data modulated at the time of recording is applied from the magnetic head 130. The optical pickup 20 detects the reproduction signal RF. In the magneto-optical recording medium 10, domains having a domain length of 0.1 μm to a domain length of 0.18 μm are formed.
Domains corresponding to “1” and domains corresponding to “0” are formed alternately. Since the diameter r of the laser beam detection window AP is 0.1 μm, the domain D11 corresponding to “1”, the domain D12 corresponding to “0”,
When the detection window AP moves in the order of the domain D13 corresponding to “1”, the detection window AP moves from the domain D11 to the domain D13.
13, a part of the detection window AP is in the domain D1.
Since the detection signal is applied to either the domain D13 or the domain D13, even when the detection window AP passes through the domain D12 corresponding to "0", the reproduction signal is detected by the magnetic domain expansion.
Therefore, the reproduced signal is continuously detected from the time when the front end of the detection window AP approaches the domain D11 to the time when the rear end of the detection window AP approaches the domain D16. Since each domain has a short domain length of 0.1 μm to 0.18 μm, each domain of the recording layer is reliably transferred and expanded to the reproduction layer, and accurate signal reproduction is possible.

The detected reproduction signal RF is amplified by the reproduction signal amplifier circuit 30, then is compared by the comparator 140, and is output to the decoder 150 as a signal (RFD). Although the signal (RFD) is a signal in which fifteen “1,0” are continuous, the decoder 150 recognizes “1,0” as “1” and outputs “1111111111” from the signal (RFD).
11111 "is obtained. After that, it is demodulated and output as reproduction data.

Referring again to FIG. 8, when the magneto-optical recording medium 10 is mounted on the reproducing apparatus 200, the objective lens (not shown) in the optical pickup 20 to the magneto-optical recording medium 10 as described above. The focus servo and tracking servo are turned on. Then, under the control of a control circuit (not shown), the drive signal generation circuit 90 generates a drive signal (GDSR) for driving the magnetic head 130, outputs the drive signal (GDSR) to the magnetic head drive circuit 110, and emits laser light of a predetermined intensity. A driving signal for performing the driving is generated and output to the laser driving circuit 120. Then, the optical pickup 20
Irradiates the magneto-optical recording medium 10 with a laser beam having a predetermined intensity, applies an alternating magnetic field having the same frequency as the recording data modulated during recording to the magneto-optical recording medium 10, and detects a reproduction signal RF due to magnetic domain expansion. You. Thereafter, the detected reproduction signal RF is output as reproduction data via the reproduction signal amplification circuit 30, the comparator 140, and the decoder 150 as described above.

Referring to FIG. 10, a flow chart of the modulation method according to the present invention will be described. When the modulation operation starts, the basic domain length L formed on the magneto-optical recording medium is determined (step S1), and the minimum domain length W to be changed from the basic domain length L is determined (step S2). Then, N = L / W is calculated (step S3), the recording data is modulated with the minimum number of consecutive “1” or “0” as N (step S4), and the modulation operation is completed.

The flowchart of the recording method according to the present invention will be described with reference to FIG. Step S1
Steps up to step S4 are the same as those in the flowchart of the modulation method shown in FIG. After the recording data is modulated, N consecutive “1” s and N consecutive “0” s are generated based on the modulated recording data.
To the basic domain length L, N + 1 consecutive “1” and N + 1 consecutive “0” to the domain length L + W, N
+2 consecutive “1” and N + 2 consecutive “0” to the domain length L + 2W,..., N + s consecutive “1” and N + s consecutive “0” to the domain length L + sW (s = 0, 1, 2, 3,...) (Step S5). A fixed length domain portion and a variable length domain portion are formed for each of the domain lengths L, L + W, L + 2W,..., L + sW, and the fixed length domain portion and the variable length domain portion are formed on the magneto-optical recording medium. A drive signal is generated (step S6).
Thereafter, the magnetic head is driven based on the drive signal generated in step S6, and the signal is recorded on the magneto-optical recording medium (step S7), and the recording operation ends.

Referring to FIG. 12, a flowchart for reproducing a signal from a magneto-optical recording medium on which a signal has been recorded by the recording method according to the present invention will be described. When the reproducing operation starts, a drive signal for generating an alternating magnetic field having the same frequency as the recording data modulated at the time of recording is generated (step S8), and the magnetic head is driven based on the generated drive signal (step S9). ). Then, a magnetic domain expansion signal is detected by the laser beam (step S10), a decoding process is performed, and reproduction data is obtained (step S11), and the reproduction operation ends.

In the above description, the magneto-optical recording medium 10
The basic domain length to be formed is 0.6 μm, and the minimum domain length W to be changed from the basic domain length is 0.04 μm.
Although described as m, this is merely an example and may be changed to any value. However, the minimum length W of the domain length to be changed from the basic domain length needs to be set to a length that can detect a change in the reproduced signal due to an increase of “1” or “0” by one.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a recording apparatus according to the present invention.

FIG. 2 is a diagram illustrating signals in a modulation circuit and a drive signal generation circuit of the recording apparatus illustrated in FIG.

FIG. 3 is a diagram illustrating a method of generating a drive signal when recording a signal in which 15 or 16 consecutive “1” s are recorded.

FIG. 4 is a configuration diagram of a drive signal generation circuit.

FIG. 5: Necessary for detecting each domain independently.
FIG. 4 is a diagram illustrating a relationship between a diameter of a detection window formed by a laser beam and a domain length.

FIG. 6 is a diagram illustrating a method for determining the diameter of a detection window formed by a laser beam.

FIG. 7 is a diagram illustrating a configuration of a domain in the present application.

FIG. 8 is a configuration diagram of a playback device according to the present invention.

FIG. 9 is a diagram showing signals in the reproducing apparatus shown in FIG.

FIG. 10 is a flowchart of a modulation method according to the present invention.

FIG. 11 is a flowchart of a recording method according to the present invention.

FIG. 12 is a flowchart of a reproducing method according to the present invention.

[Explanation of symbols]

1,11 fixed length domain part, 2,12 variable length domain part, 3,4,5,6 signal, 7,8,9,13 timing, 14,15,16,17 drive signal component,
0 magneto-optical recording medium, 20 optical pickup, 30 reproduction signal amplification circuit, 40 servo circuit, 50 servo mechanism, 60 spindle motor, 70 external synchronization signal generation circuit, 80 modulation circuit, 90 drive signal generation circuit, 91
Counter, 92 delay circuit, 93 magnetic head drive signal generation circuit, 94 laser drive signal generation circuit, 100
Recording device, 110 magnetic head drive circuit, 120 laser drive circuit, 130 magnetic head, 140 comparator, 150 decoder

Claims (5)

[Claims] 1. A modulation method for recording data when a signal is recorded on a magneto-optical recording medium, wherein a basic domain length formed on the magneto-optical recording medium is L, and a minimum length changed from the basic domain length is Where N is an integer determined by N = L / W (N is an integer), and the minimum number of consecutive signals “1” or “0” modulates the recording data. 2. A recording apparatus for recording a signal on a magneto-optical recording medium, wherein L is a basic domain length formed on the magneto-optical recording medium, and W is a minimum length changed from the basic domain length. A modulation circuit that modulates the recording data by setting N determined by N = L / W (N is an integer) to a minimum number of consecutive signal “1” or signal “0”; and a modulation modulated by the modulation circuit. Based on the data,
N consecutive “1s” and N consecutive “0s” are defined as the basic domain length L
, N + 1 consecutive “1” s and N + 1 consecutive “0” s as domain length L + W, and N + 2 consecutive “1s” and N + 2 consecutive “0s” as domain length L
+ 2W,..., N + s consecutive “1” and N
+ S consecutive “0” s are converted to a domain length L + sW (s =
0, 1, 2, 3,...), And the shortest domain length that can be formed on the magneto-optical recording medium is SL
Is represented by a set of “1” having the shortest domain length SL and “0” having the shortest domain length SL, and n = L /
(2 × SL) (where n is an integer) is based on a domain consisting of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL). A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” for each integral multiple, and a set of “1,0” having a domain length determined by SL + s × (W / 2) A drive signal generation circuit for generating a drive signal for forming a variable length domain portion comprising "0" on the magneto-optical recording medium; and driving the magnetic head based on the drive signal generated by the drive signal generation circuit Recording apparatus including a magnetic head drive circuit. 3. A recording method for recording a signal on a magneto-optical recording medium, wherein a basic domain length formed on the magneto-optical recording medium is L, and a minimum length changed from the basic domain length is W. A first step of modulating the recording data, wherein N determined by N = L / W (N is an integer) is a minimum number of consecutive signal “1” or signal “0”; Based on the modulated modulation data, N consecutive “1” s and N consecutive “0s” are added to the basic domain length L, and N + 1 consecutive “1s” and N +
One continuous "0" in the domain length L + W, N + 2 continuous "1" and N + 2 consecutive "0" in the domain length L + 2W, ..., N + s continuous "1" and N + s consecutive “0” s are defined as domain length L
+ SW (s = 0, 1, 2, 3,...)
The minimum domain length that can be formed on the magneto-optical recording medium is SL
Is represented by a set of “1” having the shortest domain length SL and “0” having the shortest domain length SL, and n = L /
(2 × SL) (where n is an integer) is based on a domain consisting of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL). A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” for each integral multiple, and a set of “1,0” having a domain length determined by SL + s × (W / 2) A second step of generating a drive signal for forming a variable-length domain portion consisting of "0" on the magneto-optical recording medium; and driving the magnetic head based on the drive signal generated in the second step. And recording a signal on the magneto-optical recording medium. 4. When the basic domain length formed on the magneto-optical recording medium is L and the minimum length changed from the basic domain length is W, N is determined by N = L / W (N is an integer). Is modulated as the minimum number of consecutive signal “1” or signal “0”, and N consecutive “1” and N consecutive “0” are determined based on the modulated data.
Is added to the basic domain length L by N + 1 consecutive “1”.
And N + 1 consecutive “0” are converted to domain length L + W
, N + 2 consecutive “1s” and N + 2 consecutive “0s” in the domain length L + 2W,..., N + s consecutive “1” s and N + s consecutive “0” in the domain length L + sW (S = 0, 1, 2, 3,...), And the shortest domain length that can be formed on the magneto-optical recording medium is SL
Is represented by a set of “1” having the shortest domain length SL and “0” having the shortest domain length SL, and n = L /
(2 × SL) (where n is an integer) is based on a domain consisting of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL). A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” for each integral multiple, and a set of “1,0” having a domain length determined by SL + s × (W / 2) A variable-length domain portion comprising a variable-length domain portion for reproducing a signal from a magneto-optical recording medium on which the signal is recorded, wherein the driving device generates an alternating magnetic field having the same frequency as the modulated data. A reproducing apparatus comprising: a drive signal generation circuit for generating a signal; and a magnetic head drive circuit for driving a magnetic head based on the drive signal generated by the drive signal generation circuit. 5. When the basic domain length formed on the magneto-optical recording medium is L and the minimum length changed from the basic domain length is W, N is determined by N = L / W (N is an integer). Is modulated as the minimum number of consecutive signal “1” or signal “0”, and N consecutive “1” and N consecutive “0” are determined based on the modulated data.
Is added to the basic domain length L by N + 1 consecutive “1”.
And N + 1 consecutive “0” are converted to domain length L + W
, N + 2 consecutive “1s” and N + 2 consecutive “0s” in the domain length L + 2W,..., N + s consecutive “1” s and N + s consecutive “0” in the domain length L + sW (S = 0, 1, 2, 3,...), And the shortest domain length that can be formed on the magneto-optical recording medium is SL
Is represented by a set of “1” having the shortest domain length SL and “0” having the shortest domain length SL, and n = L /
(2 × SL) (where n is an integer) is based on a domain consisting of (n−1) sets of “1,0” which is one less than n, and the increase sW of the domain length is (2 × SL). A fixed-length domain portion configured by increasing the domain consisting of a set of “1,0” for each integral multiple, and a set of “1,0” having a domain length determined by SL + s × (W / 2) A variable-length domain portion consisting of a "0", and reproducing a signal from the magneto-optical recording medium on which the signal is recorded, wherein a first magnetic field having the same frequency as the modulated data is generated. And a second step of driving a magnetic head based on the drive signal generated in the first step to detect a signal from the magneto-optical recording medium.