JPH01178106A - Magnetic field device for magneto-optical disk - Google Patents

Abstract

PURPOSE:To attain high speed switching with a large magnetic field by providing plural 1st coils connected in parallel with the arm of U-shaped high permeability magnetic substance and the 2nd coil passing a laser beam through the center via the hollow and generating a magnetic field in the same direction as that of the 1st coil. CONSTITUTION:The hollow part 12 to irradiate a magneto-optical disk 5 with a laser beam L from the outer face of an arm 11A is provided at the tip of the 1st arm 11A of the high permeability magnetic substance 1 and a coil 3 is provided in spiral to the inner circumference of the arm of the hollow 12. Moreover, plural coils 2A-2E are connected in parallel to the 2nd arm 11B and the folded leg of the high permeability magnetic substance 1, the coils 2A-2E, and 3 are excited by a magnetic field generating current modulation circuit 4 and connected to generate a magnetic field to the magneto-optical disk 5 perpendicularly in the same direction. Thus, high speed switching at a larger magnetic field is attained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic field applying device for a magneto-optical disk.

[Conventional technology]

In conventional magnetic field application devices for magneto-optical disks, when erasing recorded information on a magneto-optical disk, an external magnetic field is applied with the opposite polarity to that during recording, and a laser beam is uniformly irradiated onto the recording medium. - Bulk deletion is being performed.

That is, the magnetization state of the recording medium is returned to the initial state before recording by applying an external magnetic field.

Here, as the external magnetic field applying means, there are, for example, a method using an air-core coil, a method using an electromagnet, or a method using a permanent magnet.

In this magnetic field applying means, an applied magnetic field of several hundreds of steps or more is usually required during recording and erasing, so when an air-core coil is used, the coil becomes large.
Along with this, there is a drawback that the magnetic field switching speed becomes slow and the required applied magnetic field cannot be obtained unless the distance between the recording medium and the coil is made sufficiently close.

Also, when using an electromagnet, the magnetic field applying means becomes larger,
The disadvantage is that the magnetic field switching speed is slow due to the large inductance of the coil.

Furthermore, when permanent magnets are used, a complicated mechanism is required to switch the magnetic field using a mechanical drive means, and the magnetic field switching speed is also slow in this case.

As mentioned above, since the magnetic field switching speed is slow with any conventional external magnetic field applying means, the aforementioned batch erasing method is used for erasing, and when recording, laser power is applied while a constant magnetic field is applied. A method of high-speed modulation is used.

[Problem that the invention seeks to solve]

The above-mentioned conventional magnetic field applying device for magneto-optical disks has a slow magnetic field switching speed and uses a batch erasing method, so it has a so-called override function that overwrites new information at high speed on a magneto-optical disk on which information has already been recorded. The problem is that it is difficult to provide

An object of the present invention is to provide a magnetic field application device for a magneto-optical disk that can switch a large magnetic field at high speed and has an override function.

[Means for solving problems]

A magnetic field applying device for a magneto-optical disk according to the present invention is provided with a U-shaped arm that is folded back on the outer side of a peripheral portion of a magneto-optical disk and includes first and second arm portions whose inner surfaces face the upper and lower surfaces of the magneto-optical disk, respectively. a high magnetic permeability magnetic body in the shape of a letter; and a hollow portion provided at the tip of at least one of the first and second arm portions for irradiating the magneto-optical disk with a laser beam from the outer surface side of the arm portion. , a plurality of parallel-connected first coils provided in the high permeability magnetic material and generating a magnetic field in the same direction with respect to the magneto-optical disk; It has a second coil that generates a magnetic field simultaneously and in the same direction as the first coil.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention.

The high magnetic permeability magnetic body 1 is folded back outside the periphery of the magneto-optical disk 5, and includes first and second arm portions 11A and IIB whose inner surfaces face the upper and lower surfaces of the magneto-optical disk 5, respectively, and has a U-shape. formed into a shape.

Here, the high permeability magnetic material includes ferrite (MnZn,
NiZn, etc.), permalloy (NiFu), sendust, amorphous (CoZr.

FeCoZr, CoNb, CoTa, CoHf, etc.),
Iron core etc. are used.

A hollow portion 12 is provided at the tip of the first arm portion 11A of the high magnetic permeability magnetic body 1 for irradiating the magneto-optical disk 5 with a laser beam L from the outer surface side of the arm portion 11A. A coil 3 is provided in a spiral shape around the inner surface of the arm portion of the hollow portion 12. The inner diameters of the hollow portion 12 and the coil 3 are set to a size that allows the laser beam to pass therethrough and allows the lens to move in the track direction by tracking.

Further, a plurality of coils 2A to 2E are connected in parallel to the second arm portion 11B and the folded leg portion of the high permeability magnetic body 1, and these coils 2A to 2B are connected in parallel.
and 3 are driven by a magnetic field generation current modulation circuit 4 and are connected perpendicularly to the magneto-optical disk 5 so as to generate magnetic fields simultaneously and in the same direction.

The wire diameter of these coils 2A to 2E, 3 is, for example, 150 μm.
A drive current of several tens of mA to 1.0 mA is used. OA is appropriate.

With the magnetic field applying means configured in this way, the magnetic field can be focused, and since the coils 2A to 28 are connected in parallel, it is easy to reduce the inductance of the winding to 1 μH or less. At a position several llff1 away from the inner surface of the magnetic material 1, a magnetic field of several hundred Oersteds can be easily switched at a high speed of several MHz.

FIG. 2 is a block diagram of the peripheral system of a magneto-optical recording and reproducing apparatus to which the embodiment of FIG. 1 is applied. I did it.

1 and 2, the output current IA of the magnetic field generation current modulation circuit 4 flows through the coils 2A to 2E and 3, and upward and downward magnetic fields are alternately applied to the magnetic medium 52 of the magneto-optical disk 5.

The magneto-optical head 7 is the same as the conventional one and has the following configuration.

71 is a linearly polarized laser light source, for example, a semiconductor laser is used. 73A to 73° are beam splitters. A condensing lens 72 for the laser beam L is supported by an actuator 72A. The focus error and tracking error signals are inputted to the servo control circuits 8A and 8B by the respective light receiving elements 75B and 75c for detecting fourth error signals, respectively, and are turned into servo signals and fed back to the actuator 72a. Ru.

After passing through the polarizing filter 74, the reproduced signal is detected by the reproduced signal light receiving element 75A, and then sent to the reproduced signal amplification circuit 9.
is amplified by A Durham Thomson prism is used as the polarizing filter 74, and the light receiving element 7 for detecting the reproduced signal is used.
A PIN photodiode was used as the 5A.

A laser light source modulation circuit 6 is used to modulate the laser light source 71, and the power of the laser light is modulated during recording, erasing, and reproduction.

A TbFeCo film was further formed to a thickness of 800mm on SiN formed by sputtering on a plastic substrate 51 with a diameter of 120mm as the magneto-optical disk 5, and SiN was further formed on this TbFeCo film. I used a disc. This board 51 has a track pitch of 1.6 in advance.
A groove of 700 μm in depth was formed and used as a so-called pre-group substrate.

FIGS. 3(a) to 3(c) show waveform diagrams in the recording operation mode.

Constant strength P that can raise the recording medium above the Curie temperature
An external magnetic field corresponding to the recording pattern is applied by passing a modulating current IA as shown in FIG. During the cooling process accompanying the running of the recording medium, a recording magnetization state as shown in FIG. 3(c) is realized corresponding to the direction of the applied magnetic field.

First, while irradiating the laser beam L with a constant intensity of 4 mW onto the 5 surface of the magneto-optical disk at a linear velocity of 9 m/sec, a coil 2°3 of the external magnetic field application means was applied with a constant intensity of 200 MHz at IMHz.
mA modulator. When a current was applied, good recording was made. When a recording magnetic field of 0.5 MHz was newly applied to this recording track under the same conditions, recording corresponding to this recording magnetic field was possible, and no residual trace of the previously recorded signal was observed.

〔Effect of the invention〕

As explained above, the present invention provides a first disk whose inner surface faces each of the upper and lower surfaces of the magneto-optical disk. A plurality of first coils connected in parallel are connected to a U-shaped arm made of a high magnetic permeability magnetic material with a second arm, and a laser beam passes through the center through a hollow part to connect the first coil and the first coil. By providing a second coil that generates a magnetic field in the same direction, the magnetic flux can be used efficiently and the inductance can be reduced, allowing high-speed switching of large magnetic fields and providing an override function. be.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
FIG. 3 is a block diagram of a peripheral system of a magneto-optical recording/reproducing apparatus to which the embodiment shown in the figure is applied, and FIG. 3 is a waveform diagram in the recording operation mode of the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1... High permeability magnetic material, 2A to 2E, 3... Coil, '4... Magnetic field generation current modulation circuit, 5... Magneto-optical disk, 6... Laser light source modulation circuit, 7.・・Magneto-optical head, 8A, 8B・・Servo control circuit, 9・
...Amplifier circuit, 11A11B...Arm part, 12...
- Hollow part, 51... Substrate, 52... Magnetic medium, 71
...Laser light source, 72...Condensing lens, 72A
... Actuator, 73A-73c... Beam splitter, 74... Polarizing filter, 75A-75c...
··Light receiving element.

Claims (1)

[Claims] a U-shaped high permeability magnetic body that is folded back on the outside of the periphery of the magneto-optical disk and has first and second arm portions whose inner surfaces face the upper and lower surfaces of the magneto-optical disk, respectively;
a hollow portion provided at the tip of at least one of the first and second arm portions for irradiating the magneto-optical disk with a laser beam from the outer surface side of the arm portion; and a hollow portion provided in the high permeability magnetic material. a plurality of parallel-connected first coils that generate a magnetic field in the same direction with respect to the magneto-optical disk; and a plurality of first coils that are provided around the inner surface of the arm part of the hollow part and generate a magnetic field simultaneously and in the same direction as the first coils. 1. A magnetic field applying device for a magneto-optical disk, comprising: a second coil that generates .