JP2647013B2 - Magneto-optical recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording apparatus capable of rewriting information on a magneto-optical recording medium by overwriting.

[0002]

2. Description of the Related Art Hitherto, as a magneto-optical recording apparatus capable of rewriting information by overwriting, an apparatus as shown in FIG.

In FIG. 3, reference numeral 1 denotes a magneto-optical disk. In this embodiment, the magneto-optical disk 1 is constituted by coating a glass substrate 2 with a perpendicularly magnetized film 3. Can be rotated about a central axis 0-0 '.

Reference numeral 4 denotes a perpendicular magnetization film 3 of the magneto-optical disk 1.
FIG. 1 shows an optical head unit for irradiating a laser beam LB. In this example, the optical head unit 4 includes a semiconductor laser element 5 and a lens 6, and the optical head unit 4 is positioned at a predetermined distance from the surface of the magneto-optical disk 1. The optical disk 1 can be moved in the radial direction while maintaining the interval. in this case,
In the optical head unit 4, a laser beam LB of a constant intensity continuously emitted by the semiconductor laser element 5 is locally radiated to the perpendicular magnetization film 3 of the magneto-optical disk 1 through the lens 6, The temperature of the magnetic film 3 can be raised to the Curie point or higher.

Reference numeral 7 denotes a perpendicular magnetization film 3 of the magneto-optical disk 1.
In the present example, the electromagnet 7 is disposed so as to face the optical head unit 4 with the magneto-optical disk 1 interposed therebetween, and the electromagnet 7 is interlocked with the optical head unit 4. Thus, the optical disk 1 can be moved in the radial direction.

In this embodiment, a magnetic field modulation circuit 8 is provided, a recording signal input terminal 9 is connected to the input side of the magnetic field modulation circuit 8, and the output side of the magnetic field modulation circuit 8 is connected to the coil 7A of the electromagnet 7. In the magnetic field modulation circuit 8, a current whose phase is inverted according to the recording signal supplied through the recording signal input terminal 9, for example, when the signal level of the recording signal is a high level “1”, is indicated by an arrow A. The current flowing in the direction indicated by arrow B is supplied to the coil 7A. When the signal level of the recording signal is low level “0”, the current flowing in the direction indicated by arrow B is supplied to the coil 7A.
When the signal level of the recording signal is a high level "1", a magnetic field as shown by an arrow X is generated. When the signal level of the recording signal is a low level "0", a magnetic field as shown by an arrow Y is generated. It is made to be able to do.

In this case, the directions of the magnetic field indicated by the arrow X and the magnetic field indicated by the arrow Y are set to be exactly opposite to each other, but their strengths are equal, and the intensity of the magnetic field indicated by the arrow X and the intensity of the magnetic field indicated by the arrow Y are changed. When Hc and -Hc are respectively taken into consideration in the direction,
| ± Hc | is a strength capable of orienting the magnetization direction of the perpendicular magnetization film 3 of the magneto-optical disk 1 in the direction of the magnetic field.

In the magneto-optical recording apparatus of the present embodiment thus configured, when a recording signal as shown in FIG.
A magnetic field as shown by B is generated, and this magnetic field is applied to the perpendicular magnetization film 3 of the magneto-optical disk 1.

In this case, as shown in FIG. 4C, the perpendicular magnetic film 3 of the magneto-optical disk 1 is irradiated with the laser beam LB having a constant intensity E capable of setting the temperature of the perpendicular magnetic film 3 to the Curie point or higher. On the recording track 3A of the perpendicular magnetic film 3 of the magneto-optical disk 1, recording patterns 10A, 10B, # 10E as schematically shown in FIG. 4D are formed. In this case, the + and-symbols are upward (FIG. 3).
3 shows a state in which magnetization is performed in a direction indicated by an arrow X) and a downward direction (a direction indicated by an arrow Y in FIG. 3).

As described above, in the magneto-optical recording apparatus of this embodiment, the minute portion on the perpendicular magnetization film 3 of the magneto-optical disk 1
Is heated continuously above the Curie point, and when the heated minute portion is moved to the vicinity of the Curie point, the portion near the Curie point is moved in the direction of the magnetic field modulated according to the recording signal. It magnetizes and, when the temperature further drops, keeps the magnetization, and performs magneto-optical recording in units of dimensions smaller than the dimensions of the heated microscopic part. If
Regardless of what information is recorded on the perpendicular magnetization film 3 of the magneto-optical disk 1, new information can be recorded by overwriting.

[0011]

However, in the conventional magneto-optical recording apparatus shown in FIG. 3, the magnetic field applied to the perpendicular magnetization film 3 of the magneto-optical disk 1 changes according to the change in the signal level of the recording signal. 4B, a finite time t ₁ is required as shown in FIG. 4B. During this reversal time t ₁ , the perpendicular magnetization film 3 has an intensity | ± required to orient the magnetization in the magnetic field direction. hc | of spite magnetic field is not applied, since have been made as to a laser beam LB having a constant intensity E are continuously irradiated, the on the recording track 3A corresponding to the magnetic field inversion time t ₁ in Figure 4D As shown in the figure, there is an inconvenience that high-density recording cannot be performed because areas having an increased noise level, which is likely to cause an error during reproduction, so-called noise-up areas 11A, 11B and # 11E are generated.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a magneto-optical recording apparatus capable of performing high-density recording without forming a noise-up area.

[0013]

The magneto-optical recording apparatus of the present invention is, for example, as shown in FIG. 1, a magneto-optical recording apparatus which overwrites an information signal on a magneto-optical recording medium 1. An optical head unit 4 for irradiating the laser beam LB to the laser beam 1, an electromagnet 7 for applying a magnetic field to the magneto-optical recording medium 1, and a coil 7 A of the electromagnet 7 oscillating with a frequency higher than this information signal An oscillation circuit 19 for generating a magnetic field in which the direction of the magnetic field is periodically inverted by a signal and having a peak value larger than the strength required for reversing the magnetization direction of the magneto-optical recording medium 1; An information signal to be recorded on the magnetic recording medium 1 is supplied, and the optical head unit 4 emits a pulse of the laser beam LB according to the signal level of the information signal and the oscillation signal.
And a light modulation circuit 22 for driving the light modulation circuit.
2, the magnetic field generated by the electromagnet 7 is the optical magnetic recording
While the recording medium 1 is strong enough to reverse the magnetization direction, the laser light LB is emitted with a pulse width shorter than this time, and the magnetic field generated by the electromagnet 7 changes the magnetization direction of the magneto-optical recording medium 1. The drive of the optical head unit 4 is stopped while the strength is not sufficient to cause the reversal.

[0014]

[0015]

According to the present invention, when a magnetic field sufficient to reverse the magnetization direction of the magneto-optical recording medium 1 is not applied to the magneto-optical recording medium 1, a laser is applied to the magneto-optical recording medium 1. Since the light LB is not irradiated, a noise-up area is not formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magneto-optical recording apparatus according to the present invention will be described below with reference to FIGS. In FIGS. 1 and 2, parts corresponding to those in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, a resonance circuit 18 is formed by connecting a capacitor 17 in series to the coil 7A of the electromagnet 7, and an oscillation circuit 19 using the coil 7A of the electromagnet 7 as an oscillation coil is provided. In this case, it sets the value C of the capacitor 17 so as to make the resonance frequency f _O of the resonance circuit 18 is twice the frequency 2f _m the highest frequency f _m of the recording signal,
In the electromagnet 7 generates a magnetic field that reverses direction at the frequency 2f _m such as shown in FIG. 2B, to such may supply this magnetic field perpendicular magnetic film 3 of the magneto-optical disk 1. In this case, the peak value of the magnetic field is set to be larger than the intensity | ± Hc | required for orienting the magnetic field direction of the perpendicular magnetization film 3 in the magnetic field direction.

In this embodiment, the oscillation signal obtained from the oscillation circuit 19 is supplied to one input terminal of the matching circuit 21 via the waveform shaping circuit 20. In this case, in the waveform shaping circuit 20, as shown in FIG. 2C, the peak portion of the oscillation signal is flattened and necessary level adjustment is performed.

In this embodiment, the recording signal input terminal 9
Is supplied to the other input terminal of the matching circuit 21. When the signal levels of the recording signal and the oscillation signal are both at a high level or both are at a low level, the matching circuit 21
A high-level signal is obtained at the output side of the optical modulator 22, and this high-level signal is supplied to the optical modulation circuit 22. In this case, in the light modulation circuit 22, only when the high level signal from the matching circuit 21 is supplied, and supplies a pulse-shaped drive current I ₃ corresponding to the high level signal to the semiconductor laser element 5, the semiconductor laser element in 5, the laser beam LB corresponding to the driving current I ₃ in the manner emit light. Here, it is necessary to set the pulse width of the drive current I ₃ , that is, the pulse width of the laser beam LB to a time t ₃ shorter than the time t _{2 at} which the magnetic field has an intensity of | ± Hc | or more.

In this embodiment, the clock signal CK is supplied to the light modulation circuit 22 and the oscillation circuit 19, and the laser light L
Synchronize B with the magnetic field.

In the magneto-optical recording apparatus of the embodiment shown in FIG. 1 constructed as described above, an oscillation signal as shown in FIG. 2C is supplied to one input terminal of the coincidence circuit 21. When a recording signal as shown is supplied to the other input terminal of the matching circuit 21, the output side of the matching circuit 21
As shown in D, an output signal can be obtained such that when the signal levels of the recording signal and the oscillation signal are both at a high level, or when both are at a low level, the signal becomes a high level "1".

Therefore, the light modulation circuit 22 supplies the semiconductor laser device 5 with the output signal of the coincidence circuit 21 as shown in FIG.
A drive current I ₃ as shown in FIG.
_In correspondence with ₃ , the semiconductor laser element 5 emits a laser beam LB as shown in FIG. 2F. On the other hand, in this case, in the electromagnet 7, a magnetic field as shown in FIG. 2B synchronized with the pulsed laser light LB is generated,
Since this magnetic field is supplied to the perpendicular magnetic film 3 of the magneto-optical disk 1, in this embodiment, the perpendicular magnetic film 3
2G show recording patterns 23A, 23B,.
23E are formed.

In this case, during the time when the magnetic field generated by the electromagnet 7 reverses its direction, the strength of the magnetic field is sufficient to direct the magnetization of the perpendicular magnetization film 3 in the direction of the magnetic field.
During the period t ₄ when Hc | does not exist, the drive current I ₃ is not supplied to the semiconductor laser element 5, and during this time, the laser beam LB is
2G, a noise-up area is not formed, and a recording pattern corresponding to the recording signal as shown in FIG. 2G is formed. When this is reproduced, it is shown in FIG. 2H. A reproduced signal without such errors can be obtained.

As described above, in this embodiment, since the noise-up area is not formed on the recording track of the perpendicular magnetization film 3, there is an advantage that good high-density recording can be performed.

Since the laser beam LB is applied in a pulsed manner, there is an advantage that the life of the semiconductor laser element 5 can be extended.

Further, since the pulse width of the laser beam LB is shortened, only the temperature of the perpendicular magnetization film 3 can be increased, so that there is an advantage that the efficiency of heating is improved and the reliability of the protection film is also improved. .

Further, since the heat distribution of the perpendicular magnetization film becomes constant for each pulse of the laser beam LB, the intersymbol interference due to the thermal diffusion at the time of recording can be uniquely obtained, whereby the peak shift,
The advantage is that the main cause of the occurrence of jitter can be eliminated.

Since a magnetic field applied to the perpendicular magnetization film 3 is generated by an oscillation circuit 19 utilizing a resonance circuit 18 composed of the electromagnet 7 and the capacitor 17, a power supply circuit for the electromagnet 7 and the oscillation circuit 19 is provided. In addition, there is an advantage that the design of the power supply circuit can be facilitated, the size of the power supply circuit can be reduced, and the price can be reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0030]

According to the present invention, since the noise-up area is not formed, there is an advantage that good high-density recording can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a magneto-optical recording device of the present invention.

FIG. 2 is a diagram for explaining FIG. 1;

FIG. 3 is a configuration diagram illustrating an example of a conventional magneto-optical recording device.

FIG. 4 is a diagram for explaining FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 3 Perpendicular magnetization film 4 Optical head part 5 Semiconductor laser element 7 Electromagnet 9 Recording signal input terminal 19 Oscillation circuit 21 Matching circuit 22 Optical modulation circuit

Claims (1)

(57) [Claims] 1. A magneto-optical recording apparatus for overwriting an information signal on a magneto-optical recording medium, comprising: an optical head for irradiating the magneto-optical recording medium with a laser beam; An electromagnet for printing a magnetic field, a magnetic field whose direction is periodically inverted by an oscillation signal having a higher frequency than the information signal on the coil of the electromagnet, and the magnetization direction of the magneto-optical recording medium is inverted. An oscillation circuit for generating a magnetic field having a peak value larger than the intensity required for the operation, and an information signal recorded on the magneto-optical recording medium are supplied;
And a light modulation circuit for driving the head unit so as to pulse emitting the laser beam in accordance with the signal level of the information signal and the oscillation signal, the optical modulation circuit, the upper magnetic field generated by the electromagnet
As long as the intensity is sufficient to reverse the magnetization direction of the magneto-optical recording medium, the laser light is emitted with a pulse width shorter than this time, and the magnetic field generated by the electromagnet reverses the magnetization direction of the magneto-optical recording medium. The magneto-optical recording apparatus is characterized in that the drive of the optical head unit is stopped while the intensity is not sufficient to cause the recording.