JPH05282728A - Magnetic field modulation system magnetooptic disk device - Google Patents

Abstract

PURPOSE:To accurately record information and enable higher-density recording by the magnetic field modulation system magnetooptic disk device by making a range wherein the direction of magnetism is not determined on the recording film of a disk extremely small and reducing places where recording contents are unclear. CONSTITUTION:When the direction of an external magnetic field 3 is inverted, the disk 1 is irradiated with a light beam 2 having larger light power than usual from the start to the end of the inversion of the magnetic field 3 so that the light beam 2 has maximum light power at the point of time when the intensity of the magnetic field becomes zero, thereby decreasing the places where the magnetism direction is not clear on the recording film 1b of the disk 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field modulation type magneto-optical disk device for irradiating a disk to which a modulating magnetic field is applied with a light beam to record information, and particularly to forming an appropriate recording magnetic domain on the disk. It is about technology.

[0002]

2. Description of the Related Art Conventionally, in a magneto-optical disk device,
An extremely large recording capacity is realized compared to other devices. This is mainly due to its recording density, and the high-density recording makes it possible to access the recording location at high speed. Further, since the recording / reproducing is performed in a non-contact manner, there is an advantage that mechanical deterioration is extremely small.

Various recording methods have been proposed and put to practical use in order to perform the above-mentioned large-capacity and non-contact recording, and one of them is a magnetic field modulation method. In this recording method, an external magnetic field modulated according to a recording signal consisting of 1 and 0 is generated, this external magnetic field is applied to the recording film of the disk, and a constant strength is applied to a recording portion on the recording film. By irradiating a light beam, the recording portion is magnetized in the same direction as the external magnetic field and the signalized information is recorded.

A general magnetic field modulation type magneto-optical disk recording apparatus will be described with reference to FIG. In the figure, a disk 1 including a substrate layer 1a, a recording film 1b, and a protective layer 1c is rotated about a line bb 'by a rotation mechanism such as a motor (not shown). An optical head 20 for irradiating the light beam 2 is provided on the lower side of the disk 1 and a magnetic head 30 for generating the external magnetic field 3 is provided on the upper side at positions facing each other.

The optical head 20 is composed of lenses such as a pickup lens 201 and a condenser lens 202, and optical system members such as a semiconductor laser 215 and light receiving elements 216 and 217. Further, from the light receiving elements 216 and 217. A differential amplifier 221 that receives a light reception signal and outputs a reproduction signal to the outside, a lens driving mechanism 222 that minutely drives the pickup lens 201, and the like are provided. Also,
The magnetic head 30 is composed of a core 301 and a coil 302, and the coil 302 is connected to a magnetic field modulation circuit 40 that energizes in accordance with the recording signal.

With the above structure, when information is recorded on the disc 1, the light beam 2 emitted from the semiconductor laser 215 of the optical head 20 is shaped by the collimator lens 205 and then picked up by the pickup lens 201. The light is focused on the recording film 1b. A portion of the recording film 1b irradiated with the light beam 2 (hereinafter, a recording portion) is heated to a Curie temperature or higher, and the coercive force of the portion is made zero. At this time, the external magnetic field 3 generated from the magnetic head 30 is applied to the recording film 1b, and the temperature of the recording film 1b is lowered while the external magnetic field 3 is applied, so that the recording portion is exposed to the external magnetic field. It is magnetized in the same direction as 3 to record signalized information. The direction of the external magnetic field 3 is controlled by the magnetic field modulation circuit 40 switching the energization direction to the coil 302.

On the other hand, when reproducing information recorded on the disk 1, a light beam 2 having a weaker optical power than that at the time of recording is emitted from the semiconductor laser 215, and the light beam 2 is the same as at the time of recording. The light is shaped by the lens 205, and is further focused by the lens 201 on the recording film 1b.

Then, the light beam 2 is reflected on the recording film 1b and returns to the inside of the optical head 20, and the half mirror 2
The light is guided to the light receiving elements 216 and 217 by the polarization beam splitter 214 via the 12 and 1/2 wavelength plates 213.
The outputs of the light receiving elements 216 and 217 are supplied to the differential amplifier 2
By analyzing at 21, the reproduced signal is output. During reproduction, the magnetic field 3 is not generated, the light beam 2 is projected from the optical head 20, and the reflected beam reflected by the recording film 1b is received to optically record the recording magnetic domain on the recording film 1b. Read and reproduce information.

FIG. 4 shows the correlation between the light beam 2, the magnetic field 3, the shape of the recording magnetic domain, and the reproduction signal at the time of recording as described above.
Shown in. In the figure, (a) is a recording signal output to the magnetic field modulation circuit 40, (b) is a magnetic field generated from the magnetic head 30, (c) is the optical power of the light beam of the optical head 20, and (d) is The shape of the recording magnetic domain formed in the recording film 1b,
(E) shows the waveforms of reproduction signals reproduced by reading the recorded magnetic domains.

As shown in FIG. 1A, when a recording signal consisting of 1 and 0 is output to the magnetic field modulation circuit 40, the magnetic field 3 generated from the magnetic head 30 according to 1 or 0 of the signal is generated. It is modulated to + Ha or −Ha and the magnetic field direction is inverted as shown in FIG. On the other hand, the optical power of the light beam 2 emitted from the optical head 20 is maintained at a constant intensity of, for example, W1 level during the recording operation as shown in FIG.

Due to the action of the light beam 2 and the magnetic field 3 described above, the recording film 1b has A1 to A5 as shown in FIG.
Recording magnetic domains are formed. A1, A3 and 45 are 0 of the recording signal, A2 and A4 are 1 of the recording signal,
These are corresponding recording magnetic domains. Then, signals reproduced by optically reading these recording magnetic domains are shown in FIG.
It is a waveform diagram shown in.

[0012]

However, in the magnetic field modulation at the time of recording as described above, at the time of reversal of the magnetic field 3, due to the influence of the inductance of the coil 302, the magnetic field 3 is saturated. T2 time is required, and after T1 time from the start of inversion, the magnetic field 3 becomes zero. When a recording magnetic domain is formed in a state where the external magnetic field 3 is zero or very close to zero, the magnetization direction in the magnetic domain becomes unstable, and as shown in FIG. Near the boundary,
A part such as B1 to B4 in which the magnetization direction is unclear occurs.

If there is such a portion where the magnetization direction is not uniform, the reproduced signal when the recording film 1b is read is as shown in FIG.
As shown in (e), the waveform is output as a waveform with a blunt edge as compared with the recording signal of FIG. 4A, which is the original signal, and jitter is likely to occur, which may cause a read error.

The present invention has been made in order to solve the above-mentioned problems, and makes the area where the magnetization direction is not defined extremely small on the recording film of the disk, and reduces the unclear portion of the recorded content. Accordingly, it is an object of the present invention to provide a magnetic field modulation type magneto-optical disk device in which information can be accurately recorded and which enables high-density recording.

[0015]

In order to achieve the above object, a magneto-optical disk device of the present invention applies an optical head for irradiating a disk for recording signalized information with a light beam, and an optical head for applying the light beam to the disk. A magnetic head that generates a magnetic field and a magnetic field modulation circuit that reverses the magnetic field according to the signaled information are provided, and the optical power of the light beam is maximized when the magnetic field intensity becomes zero when the magnetic field is reversed. As described above, an optical modulation circuit for increasing the optical power from the normal level is provided from the start to the end of the reversal of the magnetic field.

[0016]

According to the above structure, in the magneto-optical disk apparatus of the magnetic field modulation system which irradiates the recording film of the disk with the light beam to record information under the action of the modulation magnetic field, the direction of the magnetic field is changed according to the recording signal. At the time of reversal, a light beam with an optical power larger than usual is used by the optical modulation circuit from the start of the reversal of the magnetic field to the end of the reversal so that the light power of the light beam becomes maximum at the time when the magnetic field strength becomes zero. By irradiating the disc with a magnetic field and reducing the number of unclear magnetization directions on the recording film of the disc, it is possible to form recording areas corresponding to recording signals so that the boundaries between them become clear. It will be possible.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magneto-optical disk device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a recording section of a magnetic field modulation type magneto-optical disk device according to the present embodiment, and FIG. 2 shows a relationship between various signals and recording magnetic domains in the recording section shown in FIG. .. In FIG.
(A) is a recording signal output to the magnetic field modulation circuit 40,
(B) is the magnetic field generated from the magnetic head 30, (c) is the optical power of the light beam of the optical head 20, (d) is the shape of the recording magnetic domain formed in the recording film 1b, and (e) is the recording magnetic domain. The waveforms of reproduction signals reproduced by reading and are shown in FIG.

In FIG. 1, the substrate layer 1a, the recording film 1b,
And a protective layer 1c for recording signalized information (hereinafter referred to as recording signal) consisting of 1 and 0.
However, due to a rotating mechanism such as a spindle motor not shown,
It is rotated about the line aa '. That disk 1
An optical head (optical pickup) 20 for irradiating the recording film 1b with the light beam 2 is disposed below the. Further, the optical head 20 with the disk 1 sandwiched therebetween
A magnetic head (magnetic field generator) 30 for generating a magnetic field 3 for magnetizing the recording film 1b at a position opposed to
Is provided. This magnetic head 30 has a core 301
And the coil 302, and further, the coil 3
A magnetic field modulation circuit (current generator) 40 that is energized in accordance with the recording signal is connected to 02.

On the other hand, the optical head 20 includes lenses such as a pickup lens 201, condenser lenses 202 and 203, a cylindrical lens 204, a collimator lens 205, a half mirror 212, a half-wave plate 213, a polarization beam splitter 214, and the like. The semiconductor laser 215 and the optical system members such as the light receiving elements 216 and 217 are provided. Further, the differential amplifier 221 which is connected to the light receiving elements 216 and 217 and outputs a reproduction signal to the outside, and the pickup lens 201 are minute. It has a lens driving circuit 222 for driving. The semiconductor laser 215 is connected to an optical modulation circuit 50 that modulates the light beam 2 according to a recording signal.

An information recording operation with the above configuration will be described. When a recording signal generated by a recording signal generator (not shown) is output to the magnetic field modulation circuit 40, the magnetic field modulation circuit 40 causes the coil 3 to respond to the recording signal.
Switch the energizing direction to 02. By controlling the energizing direction, the external magnetic field 3 generated from the magnetic head 30 is modulated, that is, the direction of the magnetic field is changed to the upper or lower direction in the figure. 2 is irradiated on the recording film 1b to record signalized information.

On the other hand, in the optical head 20, after the light beam 2 emitted from the semiconductor laser 214 is shaped into a cylindrical closed beam by the collimator lens 205, it passes through the half mirror 212 as it is, and the pickup lens 201. Thus, the light is focused in a spot on the recording film 1b of the disc 1. A portion of the recording film 1b irradiated with the light beam 2 (hereinafter, a recording portion) is heated to a Curie temperature or higher, so that the coercive force of the portion is made zero. At this time, an external magnetic field 3 generated from a magnetic head 30 described later is applied to the recording film 1b,
By lowering the temperature of the recording film 1b with the external magnetic field 3 still acting, the recording portion is magnetized in the same direction as the external magnetic field 3.

Further, in the above-mentioned conventional example, the light beam 2
The optical power of the light beam was constant at the W1 level, but in the present embodiment, the optical power of the light beam 2 is changed by the optical modulation circuit 40 according to the recording signal so as to draw the waveform shown in FIG. Is modulated. This optical modulation is performed by the optical modulation circuit 50 receiving a recording signal similarly to the magnetic field modulation circuit 40, and thereby controlling the drive current to the semiconductor laser 215. That is, when the magnetic field of FIG. 2B is saturated in + Ha or −Ha, the normal W1
The light beam is emitted with a level of optical power, but the magnetic field 3
When the magnetic field intensity is reversed, the optical power is gradually increased until the time T1 after the start of the reversal at which the magnetic field intensity becomes zero, and when the magnetic field intensity becomes zero, the optical power reaches the maximum level W2. After that, the optical power is gradually reduced until the time T2 when the inversion ends.

As described above, when the external magnetic field 3 applied to the recording film 1b becomes weaker, the light beam 2 having an optical power of W2 larger than the normal W1 is irradiated, so as shown in FIG. 2 (d). As described above, clearly magnetized recording magnetic domains A1 to A5 are formed in the recording film 1b, and the magnetization directions are unclear even at the boundaries between the recording magnetic domains B1 to B4.
The area is markedly smaller than that of the conventional example shown in FIG.

When the area of B1 to B4 is large, the reproduction signal when the recording film 1b is read is as shown in FIG.
As shown in (e), as compared with the recording signal of FIG. 4A, which is the original signal, the waveform is output as a blunt edge, and jitter is likely to occur, which may cause a read error. In this embodiment, since the recording film 1b is properly magnetized, the dullness of the edge of the reproduction signal is reduced and the frequency of read errors is extremely reduced, as shown in FIG. 2 (e).

Regarding the magnitude of the optical power W2 shown in FIG. 2B in the above embodiment, the kind of the recording film 1b, the performance and scale of the semiconductor laser 215 or the magnetic head 40, etc. are taken into consideration. A proper value may be set.

[0026]

As described above, according to the present invention, when the direction of the external magnetic field applied to the recording film of the disk is reversed according to the recording signal, the intensity of the magnetic field becomes zero when the intensity of the magnetic field becomes zero. In order to maximize the optical power, a light beam with a larger optical power than usual from the start of inversion to the end of inversion
Irradiate the recording film of the disc. As a result, the destabilization of the magnetization of the recording magnetic domain due to the decrease in the strength of the external magnetic field is reduced, and the area where the magnetization direction is not determined can be made extremely small, and the recording areas corresponding to the recording signals are clearly demarcated from each other. It is possible to realize a magneto-optical disk device in which information can be accurately recorded and recording can be performed with higher density.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a recording unit of a magneto-optical disk device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between various signals and recording magnetic domains in the recording section according to the present embodiment.

FIG. 3 is a configuration diagram of a recording unit of a magneto-optical disk device according to a conventional example.

FIG. 4 is a diagram showing a relationship between various signals and recording magnetic domains in a recording section according to the conventional example.

[Explanation of symbols]

 1 disk 1b recording film 2 light beam 3 external magnetic field (modulating magnetic field) 20 optical head 30 magnetic head 40 magnetic field modulation circuit 50 optical modulation circuit

Claims (1)

[Claims] 1. An optical head for irradiating a disk for recording signalized information with a light beam, a magnetic head for generating a magnetic field applied to the disk, and a magnetic field for inverting the magnetic field according to the signaled information. In a magnetic field modulation type magneto-optical disk device, comprising: a modulation circuit, irradiating the disk with the light beam under the action of the magnetic field, the light beam is generated when the magnetic field is reversed. An optical modulation circuit characterized by comprising an optical modulator circuit for increasing the optical power from the normal optical power from the start of magnetic field inversion to the end of inversion so that the optical power becomes maximum when the magnetic field strength becomes zero. Magnetic disk device.