JPH05189825A - Lens actuator and magneto-optical disk apparatus with it - Google Patents

Abstract

PURPOSE:To constitute a lens actuator for a magneto-optical disk apparatus wherein an auxiliary magnetic field and a recording magnetic field are given to a disk medium provided with two layers of magnetic layers and a piece of information is overwritten and recorded in such a way that the sufficient magnetic field of the actuator is obtained on the face of the medium and that the actuator is small-sized and at low costs. CONSTITUTION:An object lens 1 and a permanent magnet 2 which gives an auxiliary magnetic field are arranged and held on a holding member 3 which can be moved to a focusing direction and to a traveling direction with reference to a sliding shaft 6; its center of gravity is made to nearly coincide with the center of rotation; the distance between the face of a medium and the permanent magnet 2 is made definite. Thereby, an inessential resonance is not generated in the tracking direction. When one part of a magnetic circuit for an actuator is used also as the permanent magnet for auxiliary magnetic field use, an apparatus can be made small-sized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens actuator and a magneto-optical disk device having the same.

[0002]

2. Description of the Related Art Conventionally, recording is performed by irradiating a disk medium with a laser beam to raise the medium temperature and at the same time applying a bias magnetic field to form a reversed magnetic domain in the magnetic layer, and the magnetization direction of the magnetic layer is the same. A magnetic head (bias magnetic field generation device) is known in which a permanent magnet is inverted in accordance with a signal to change the polarity facing the disk medium in a magneto-optical disk device that performs erasing by aligning with the same. 63-317903).

In recent years, as disclosed in Japanese Patent Application Laid-Open No. 2-121103, it is possible to overwrite information without using a recording medium having first and second magnetic layers and reversing the bias magnetic field. Possible thermomagnetic recording methods or recording media have been proposed.

[0004]

However, the former method requires a mechanism for reversing the permanent magnet,
There is a drawback that the device becomes large, and in the latter case, a strong magnetic field is required as an auxiliary magnetic field.
In the former magnetic head, the distance between the magnetic head and the medium changes due to surface wobbling due to rotation of the medium,
There is a drawback that a sufficient magnetic field cannot be obtained on the medium surface.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a small-sized lens actuator capable of obtaining a sufficient magnetic field and a magneto-optical disk apparatus having the same.

[0006]

In order to achieve the above object, the present invention provides a disk-shaped recording medium having first and second magnetic layers with a first bias magnetic field to form a first magnetic layer. A lens actuator for a magneto-optical disk device, which aligns magnetization in one direction and then irradiates a laser beam while applying a second bias magnetic field opposite to the first bias magnetic field to perform overwriting recording of information, It has a permanent magnet held by a holding member movable in the optical axis direction of the laser light together with an objective lens for focusing the laser light on the first and second magnetic layers, and the permanent magnet holds the disk-shaped recording medium. To the first bias magnetic field.

Further, the holding member holding the objective lens and the permanent magnet is rotatable in a plane perpendicular to the optical axis of the laser beam, and the objective is made so that its center of gravity and the center of rotation are substantially coincident with each other. The lens and the permanent magnet are arranged.

Further, there is provided a means for generating a driving force for moving the holding member holding the objective lens and the permanent magnet in the radial direction of the disk-shaped recording medium, and the means for generating the driving force has a magnetic circuit. The permanent magnet constitutes a part of the magnetic circuit.

[0009]

According to the above construction, since the permanent magnet and the objective lens follow the surface wobbling of the disk, a stable and strong auxiliary magnetic field can be obtained on the medium surface, and the movable portion holding the permanent magnet and the objective lens can be obtained. Since the center of gravity is substantially coincident with the center of rotation, unnecessary resonance does not occur in the tracking direction. Furthermore, since a part of the magnetic circuit of the tracking actuator is also used as the permanent magnet for the auxiliary magnetic field, the size and cost of the device can be reduced.

[0010]

Embodiments will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which 1 is an objective lens, 2 is a permanent magnet, and 3 is a holding member for holding the objective lens 1 and the permanent magnet 2. The holding member 3 has a bearing 4 at its center, is fitted to a sliding shaft 6 planted in a base 5, is movable in the vertical direction, and is rotatable about the sliding shaft 6. .. A tracking coil 7 and a focusing coil 8 are provided on the lower surface of the holding member 3, and a movable part is mounted so that the coil faces the magnetic circuit 9 arranged on the base 5. The turning force for the holding member 3 is given by the tracking coil 7 and the magnetic circuit 9, and the driving force in the vertical direction is the focusing coil 8.
Is given by the magnetic circuit 9.

FIG. 2 shows the embodiment of FIG. 1 in more detail. The laser light emitted from the optical system 10 is a prism.
The light is reflected in the direction of the objective lens 1 at 11 and is condensed as a light spot on the magneto-optical disk 12 by the objective lens 1.
The reflected light from the magneto-optical disk 12 is again reflected by the objective lens 1,
Returning to the optical system 10 via the prism 11, the focus error signal and the track error signal are detected, and the information signal is reproduced. The focusing coil 8 and the tracking coil 7 are driven by the detected focus error signal and track error signal, and the objective lens 1 moves up and down and the track 13 moves.
Each of them is moved in a direction orthogonal to, and the follow-up control of the light spot is performed with respect to the surface wobbling and eccentricity of the magneto-optical disk 12.

By moving the objective lens 1 in the vertical direction, the permanent magnet 2 held by the holding member 3 moves in the vertical direction together with the objective lens, and the distance between the magneto-optical disk 12 and the permanent magnet 2 is kept constant. Therefore, a stable and strong magnetic field can be applied to the magneto-optical disk 12. Information is recorded and reproduced by using the magnetic field of the permanent magnet 2 as an auxiliary magnetic field and the magnetic field of the magnetic head (permanent magnet) 14 installed above the objective lens 1 as a recording magnetic field.

Further, in this embodiment, the installation positions of the permanent magnet 2 and the objective lens 1 are determined so that the center of gravity of the holding member 3 holding the permanent magnet 2 and the objective lens 1 coincides with the sliding axis 6. Since the permanent magnet 2 acts as a balancer for the objective lens 1, unnecessary resonance in the tracking direction can be suppressed.

FIG. 3 shows another embodiment of the present invention, in which the objective lens 1 and the tracking yoke 24 are supported by the leaf spring 20 and are movable in the direction orthogonal to the track 13. The tracking force of the objective lens 1 is controlled by the driving force generated by the tracking yoke 24 and the permanent magnet 21. Further, all of these members are supported by the leaf spring 28, and the focusing yoke 27 and the focusing coil 25 are provided.
Also, the driving force generated by the permanent magnets 26 moves up and down to perform focusing control. permanent magnet
21 is as close to the magneto-optical disk 12 as possible,
Similar to the embodiment of FIG. 2, as the objective lens 1 moves up and down, the permanent magnet 21 also moves up and down, and the distance between the magneto-optical disk 12 and the permanent magnet 21 is kept constant, so that a stable and strong magnetic field is obtained. Can be applied to the magneto-optical disk 12.

FIG. 4 shows how information is recorded on a two-layer magneto-optical disc that can be overwritten. The reference medium layer 12a is generated by the auxiliary magnetic field generated by the permanent magnet 2.
Are aligned upward, and only the magnetization of the portion strongly irradiated with the laser beam focused by the objective lens 1 is inverted downward by the magnetic field of the magnetic head 14. Reference medium layer
The magnetization of 12a is transferred to the storage medium layer 12b during the cooling process of the medium. Information is reproduced by changing the polarization direction of reflected light from the storage medium layer 12b (Kerr effect).

FIG. 5 shows still another embodiment of the present invention, which is an example applied to a disk device capable of double-sided recording and reproduction. The double-sided disc 30 has a reference medium layer 30a for each side.
And a storage medium layer 30b. Then, the heads (actuators) 31 and 32 are arranged so that the auxiliary magnetic field on one surface becomes the recording magnetic field on the other surface. With such a configuration, it is possible to realize an extremely miniaturized disk device capable of double-sided recording / reproduction.

[0017]

As described above, according to the present invention,
Since the permanent magnet moves together with the objective lens while following the surface deviation of the disk, a stable and strong auxiliary magnetic field can be obtained on the medium surface, and the actuator and further the magneto-optical disk device can be miniaturized. Further, since the permanent magnet and the objective lens are arranged on both sides of the sliding shaft so that the center of gravity of the movable part thereof substantially coincides with the center of rotation, unnecessary resonance does not occur in the tracking direction. Furthermore, since a part of the magnetic circuit of the tracking actuator is also used as the permanent magnet for the auxiliary magnetic field, the device can be made smaller and the cost can be reduced.

Further, in the case of being applied to a disk device capable of double-sided recording / reproducing, the magnetic field of the permanent magnet for the auxiliary magnetic field provided on the head on each surface is used as the recording magnetic field on the other surface, so that it is small and inexpensive. The device can be configured.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a more specific configuration of FIG.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is an explanatory diagram of an information recording operation in an overwritable dual-layer magneto-optical disk.

FIG. 5 is a layout view of heads in a disk device capable of double-sided recording / reproducing according to still another embodiment of the present invention.

[Explanation of symbols]

1 ... Objective lens, 2,21 ... Permanent magnet, 3 ... Holding member, 6 ... Sliding shaft, 7,23 ... Tracking coil,
8,25 Focusing coil, 9 Magnetic circuit, 1
2… Magneto-optical disk, 14… Magnetic head, 30… Double-sided disk, 31,32… Actuator.

Claims (5)

[Claims] 1. A first bias magnetic field is applied to a disk-shaped recording medium having first and second magnetic layers to align the magnetization of the first magnetic layer in one direction, and then the first bias magnetic field is applied. A lens actuator of a magneto-optical disk device for irradiating a laser beam while applying a second bias magnetic field opposite to the above, and performing overwriting recording of information, the laser beam being applied to the first and second magnetic layers. A permanent magnet held by a holding member that is movable in the optical axis direction of the laser beam together with an objective lens for condensing, and the first bias magnetic field is applied to the disk-shaped recording medium by the permanent magnet. Lens actuator. 2. The holding member holding the objective lens and the permanent magnet is rotatable in a plane perpendicular to the optical axis of the laser light, and the center of gravity thereof and the center of rotation are substantially coincident with each other. The lens actuator according to claim 1, further comprising an objective lens and a permanent magnet. 3. A means for generating a driving force for moving a holding member holding an objective lens and a permanent magnet in a radial direction of a disk-shaped recording medium, and the means for generating the driving force has a magnetic circuit. 2. The lens actuator according to claim 1, wherein the permanent magnet constitutes a part of the magnetic circuit. 4. A magneto-optical disk device comprising any one of claims 1, 2 and 3. 5. A first bias magnetic field is applied to a disk-shaped recording medium having first and second magnetized layers on both the first and second sides, respectively, so that the magnetizations of the first magnetized layer are aligned in one direction. Then, in a magneto-optical disk device for irradiating laser light while applying a second bias magnetic field opposite to the first bias magnetic field to perform overwriting recording of information, 2. The first and second lens actuators according to claim 1, which are opposed to the second surface, respectively, the permanent magnet in the first lens actuator applies a first bias magnetic field to the magnetization layer of the first surface. And a second bias magnetic field is applied to the magnetic layer of the second surface, and a permanent magnet in the second lens actuator applies a first bias magnetic field to the magnetic layer of the second surface and the first magnetic field. Face An optical disk device, wherein a second bias magnetic field is applied to the magnetic layer.