JPH05298774A - Magneto-optical disk apparatus - Google Patents

Abstract

PURPOSE:To provide a magneto-optical disk apparatus which enhances information density for realizing high density recording on a disk to enable a large capacity recording by converting information to be recorded into a multi-value signal. CONSTITUTION:Information recorded on a disk 1 is converted to a multi-value signal and a magnetic field modulating circuit 40 modulates in a multi-step an external magnetic field 3, in accordance with such multi-value recording signal, generated from a magnetic head 30. Since the disk 1 is irradiated with the light beam 2 while an external magnetic field 3 is impressed to the disk 1, the information represented by the multi-value signal can be recorded on 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 magneto-optical disk device for recording information by irradiating a disk with a light beam under the action of an external magnetic field, and more particularly to a technique for increasing the recording density.

[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 the high recording density, and the high-density recording enables high-speed and random access to the recording location. In addition, the magneto-optical disk used as a recording medium has the advantage that it is replaceable, and that recording / reproducing is performed in a non-contact state with the magneto-optical disk, so that mechanical deterioration is extremely small. There is.

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, the information to be recorded is converted into a binary signal of 1 and 0, an external magnetic field modulated according to the signaled information is generated, and the external magnetic field is applied to the recording film of the disc while the recording film is being recorded. By irradiating the upper recording portion with a light beam having a constant intensity, the recording portion is magnetized in the same direction as the external magnetic field to record signalized information.

In order to record a large amount of information such as image data, it is expected that the recording amount on the magneto-optical disk will be further increased. For example, the track width of the disk will be narrowed. Although it has been proposed to increase the recording density by shortening the wavelength of the light beam, it has not been possible to dramatically improve the recording density.

[0005]

In the conventional magnetic field modulation method as described above, since the recorded information is signalized by the binary value of 1 and 0, it is more redundant than the original information. , A large recording area is required. Therefore,
Even in the same magnetic field modulation method, if the recorded information is signalized by multivalues of three values or more instead of two values, the signalized information can be recorded in a small area, and the recording density of the disc is increased. be able to.

The present invention has been made to solve the above problems, and a magneto-optical disk capable of recording high-density information on a disk by converting recorded information into a multivalued signal. The purpose is to provide a device.

[0007]

In order to achieve the above object, the present invention provides a magneto-optical disk apparatus for recording signalized information on a disk by irradiating the disk with a light beam under the action of an external magnetic field. A multi-step modulating means for modulating the external magnetic field in multi-steps in accordance with multi-level signalized information, and applying the magnetic field modulated in multi-steps by the multi-step modulating means to the disc, The disc is irradiated to record the multilevel signal information on the disc.

[0008]

According to the above construction, the information recorded on the disc is converted into a multi-valued signal, and the external magnetic field is modulated in multi-steps by the multi-step modulating means in accordance with the multi-valued signalized information. Then, by applying the external magnetic field to the disc and irradiating the disc with a light beam, the multilevel signal information is recorded on the disc.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a recording / reproducing unit of the magneto-optical disk device according to the present embodiment. In the figure, a disk 1 composed of a substrate layer 1a, a recording film 1b, and a protective layer 1c is rotated about an aa 'line by a rotation mechanism such as a spindle motor (not shown). An optical head (optical pickup) 20 for irradiating the recording film 1b with the light beam 2 is disposed below the disc 1. Further, a magnetic head 3 for generating a magnetic field 3 for magnetizing the recording film 1b at a position facing the optical head 20 with the disk 1 sandwiched therebetween.
0 is provided. The magnetic head 30 has a core 30.
1 and a coil 302, and the coil 302 is further connected to a magnetic field modulation circuit (current generator) 40 which is energized in accordance with a multi-valued recording signal described later.

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 minutely driven. It has a lens drive circuit 222 that operates.

An information recording operation with the above configuration will be described. In this embodiment, information recorded on the disc 1 is 0, 1, 2,
It is converted into a multi-valued recording signal consisting of five values 3, 4.
Then, when this multi-valued recording signal is input to the magnetic field modulation circuit 40, the magnetic field modulation circuit 40 switches the energization direction and the energization amount to the coil 302 according to the signal. By controlling the energizing direction and the energizing amount in this way, the external magnetic field 3 generated from the magnetic head 30 is modulated, that is, the direction of the magnetic field applied to the disk 1 is changed to the upper or lower direction in the figure. At the same time, the strength of the magnetic field can be changed. When the recording film 1b is irradiated with the light beam 2 under the action of the modulation magnetic field 3 as described later, the recording film is magnetized corresponding to the respective values of 0 to 4 of the multilevel recording signal. , Information is recorded or overwritten.

On the other hand, in the optical head 20, after the light beam 2 emitted from the semiconductor laser 215 is shaped into a cylindrical parallel 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, the external magnetic field 3 generated from the magnetic head 30 is applied to the recording film 1b as described above, and the temperature of the recording film 1b is lowered while the external magnetic field 3 is applied to perform recording. The location is magnetized in the magnetic field direction and magnetic field strength according to the multilevel recording signal.

In reproducing the information recorded on the disc 1, the semiconductor laser 215 emits a light beam 2 having a weaker optical power than that at the time of recording, and the light beam 2 is the same as at the time of recording. The light is shaped by the collimator lens 205 and is condensed by the lens 201 on the recording film 1b. Then, the light beam 2 is reflected on the recording film 1b, 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
A reproduction signal is output by passing the signal through 21. In addition,
When reproducing information, the magnetic field 3 is not generated and the optical head 20
By projecting the light beam 2 from the optical recording medium 1 and receiving the reflected beam reflected by the recording film 1b, the recording magnetic domain on the recording film 1b is optically read and information, that is, a multilevel signal is reproduced.

2A and 2B show various signals in the recording / reproducing section. FIG. 2A is a recording signal input to the magnetic field modulation circuit 40, and FIG. 2B is a signal applied from the magnetic head 30 to the disk 1. The generated magnetic field, (c) shows the recording power (optical power) of the light beam of the optical head 20, and (d) shows the waveform of the reproduction signal reproduced by reading the information recorded on the disk.

0, 1, 2, 3, as shown in FIG.
The multi-valued recording signal composed of five values of 4 is applied to the magnetic field modulation circuit 40.
Is input to the coil 302, a current corresponding to the multi-valued recording signal is applied to the coil 302, so that the magnetic field 3 as shown in FIG. At this time, the light beam 2 is applied to the disk 1 with a power of W level as shown in FIG. 6C in order to raise the temperature of the recording portion of the recording film 1b to the Curie temperature or higher. As a result, a recording magnetic domain magnetized according to the strength of the applied magnetic field 3 is formed on the recording film 1b,
A multilevel recording signal is recorded or overwritten. Then, the recording magnetic domain of the recording film 1b is optically read by the reproducing operation described above, whereby a reproducing signal having a waveform corresponding to the recording signal as shown in FIG.

FIG. 3 is a graph showing the relationship between the strength of the external magnetic field 3 applied to the recording film 1b and the magnitude of the reproduced signal due to the recording magnetic domains formed under the action of the magnetic field 3. In the conventional device, the information to be recorded is converted into binary signalized information consisting of two values of 0 and 1, and H + and H- at which the magnetization of the recording film 1b is completely saturated according to the binary signal.
Information is recorded by using an external magnetic field having a binary intensity of level, but in the present embodiment, the magnetization H is not saturated.
It was configured to be recorded by an external magnetic field of 0 to H4 level. As shown in the figure, since the recording film has a hysteresis due to the magnetization characteristic, the magnitude of the reproduced signal in the external magnetic field of each strength has a range, but the slice level is provided in the reproduced signal to set D0, D1, D2, D3. , D4 can be separated to reproduce individual signals separately. This allows
The recording capacity is 2.5 times that of the conventional binary recording.

As described above, according to the present embodiment, since the information to be recorded on the disc is converted into multi-valued signalized information consisting of 5 values from 0 to 4, it is possible to convert it to binary value as in the conventional case. Redundancy of information is reduced as compared with an apparatus that records by a recording signal, and high-density information can be recorded on a disc. Further, the present invention is not limited to the case of using a five-valued signal as in the above embodiment, but the difference in magnetic field strength corresponding to each signal is made small, and the signalized information having more values is recorded. By doing so, it is possible to further increase the recording capacity of the disc. Since the recording film has a hysteresis characteristic, the strength difference between the external magnetic fields cannot be less than the H limit shown in FIG.

[0018]

As described above, according to the present invention, the information to be recorded on the disc is converted into a multi-valued signal, and the external magnetic field applied to the disc is modulated in multiple steps according to the multi-valued signalized information. Since the information is recorded by the information recording, the redundancy of the recorded information is reduced, the information can be recorded at high density on the disc, and the recording capacity of the disc is increased. Since the high-density recording is realized, the access speed to the recording location can be increased, and the operability of the apparatus can be improved.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram of various signals according to the embodiment.

FIG. 3 is a graph showing the relationship between magnetic field strength and the magnitude of a reproduction signal.

[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

Claims (1)

[Claims] 1. In a magneto-optical disk device for recording signalized information on a disk by irradiating the disk with a light beam under the action of an external magnetic field, the external magnetic field is multistaged in accordance with multilevel signalized information. A multi-step modulating means for modulating is provided, and while applying a magnetic field which is multi-step modulated by the multi-step modulating means to the disc, the optical beam is applied to the disc to record the multi-level signalized information on the disc. A magneto-optical disk device characterized by: