JPH06176422A - Magneto-optical disk driving device - Google Patents

Abstract

PURPOSE:To provide a magneto-optical disk driving device small in power consumption and stable in recording characteristics by eliminating the influence of a magnetic field leaked from an objective lens actuator. CONSTITUTION:A magnetic head 11 and an objective lens 25 of an optical head 21 are disposed opposite to each other via a magneto-optical disk 1. The objective lens is equipped with the actuator 41 for automatically focusing a light beam on a recording surface 2 of the magneto-optical disk. The magnetic head is equipped with a recording or erasing coil 13 and a canceling coil 14, and a current in proportion to a current impressed to the actuator is impressed to this canceling coil in the direction of canceling the leakage magnetic field.

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 drive device, and more particularly to means for canceling a leakage magnetic field from an objective lens actuator.

[0002]

2. Description of the Related Art Conventionally, an objective lens for focusing a laser beam on a recording film of a magneto-optical disk to raise the temperature of the recording film to a predetermined temperature and a magnetic field to a temperature rising portion of the recording film to magnetize the portion. A magneto-optical disk drive device is known in which a magnetic head directed in a recording direction or an erasing direction is arranged to face each other with a magneto-optical disk in between.

It is practically impossible to form a magneto-optical disk on a completely flat surface.
There is a warp regardless of size. Further, when the magneto-optical disk is mounted on a driving device and rotationally driven, surface wobbling occurs due to wobbling of the rotating spindle. Therefore, in the objective lens, an autofocus actuator for tracking the surface wobbling or warping to move the objective lens toward or away from the recording film and to always focus a laser beam having a constant spot diameter on the recording film. Are generally provided. As the autofocus actuator, one in which a coil is wound around a drive magnet is generally used because it is lightweight, compact, and has excellent high-speed operability.

In the magneto-optical disk drive device having the above-mentioned structure, the leakage magnetic field from the autofocus actuator is applied to the recording film of the magneto-optical disk, so that the recording magnetic field or the erasing magnetic field generated from the magnetic head is offset, and the offset amount is generated. If it is large, there is a disadvantage that a sufficient recording magnetic field is not generated and stable information cannot be recorded, or that information can be left unerased without generating a sufficient erasing magnetic field. In particular, in a magneto-optical disk having a high magnetic field sensitivity for recording information with a weak recording magnetic field of about 100 (Oe), such inconvenience becomes remarkable. In order to eliminate such an inconvenience, for example, in Japanese Patent Laid-Open No. 3-259,
As described in Japanese Patent No. 444, a magneto-optical disk drive device has been proposed in which a magnet for canceling the leakage magnetic field is arranged on the magnetic head side.

[0005]

However, in the magneto-optical disk drive device described in the above-mentioned known example, since the magnet is used as the means for canceling the leakage magnetic field, the drive magnet generated by the surface wobbling or warping of the magneto-optical disk. It is impossible to cancel the magnetic field variation due to the variation in the distance between the magneto-optical disk and the magneto-optical disk and the magnetic field variation due to the energization of the coil, so that the adverse effect of the leakage magnetic field cannot be completely eliminated.

The present invention has been made in order to solve the deficiency of the above-mentioned prior art, and its purpose is to be able to almost completely cancel the leakage magnetic field from the autofocus actuator including fluctuations, and to reduce consumption. Stable recording with power /
An object of the present invention is to provide a magneto-optical disk drive device capable of erasing.

[0007]

According to the present invention, in order to achieve the above object, an objective lens of an optical head and a magnetic head are arranged to face each other via a magneto-optical disk, and the objective lens has the objective. In a magneto-optical disk drive device equipped with an actuator for autofocusing a light beam emitted from a lens on a recording surface of the magneto-optical disk, a recording or erasing coil in the magnetic head and a leakage magnetic field from the actuator And a cancel coil for canceling the above, and by applying a drive current according to the autofocus current applied to the actuator to the cancel coil, the leakage magnetic field from the actuator is canceled.

[0008]

According to the above construction, not only the DC magnetic field that acts on the recording film from the autofocus actuator, but also the magnetic field fluctuation due to the surface wobbling and warpage of the magneto-optical disk and the magnetic field fluctuation due to the energization of the coil are also included. Since they can be offset, the adverse effect of the leakage magnetic field can be completely eliminated. Therefore, it is possible to reduce the power consumption of the magnetic head and to stabilize the information recording and reduce the unerased portion.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the magneto-optical disk drive device of this example has a structure in which the magnetic head 11 and the objective lens 25 of the optical head 21 are arranged to face each other with the magneto-optical disk 1 interposed therebetween.

The magneto-optical disk 1 is provided with a magneto-optical recording film 3 on one surface of a transparent substrate 2, a magnetic head 11 is arranged on the magneto-optical recording film 3 side, and an optical head 21 is arranged on the transparent substrate 2 side.
Are arranged. On the side of the magneto-optical recording film forming surface of the magneto-optical disk 1, a pre-format pattern such as a pre-pit row in which a guide groove of a light beam or a track address is recorded is formed in a fine concavo-convex shape. For the pattern arrangement, size, formation method, etc.,
Since this is a well-known technique and is not the gist of the present invention, description thereof will be omitted. Further, although the magneto-optical recording film 3 is shown as a single layer in FIG. 1, it may be formed as a laminated body of a plurality of film bodies if necessary. For example, the magneto-optical recording film 3 can be formed from the transparent substrate 2 side by a laminated body of the first enhancing film, the magnetic film, the second enhancing film, and the metal reflecting film. The material of each of these membranes,
Since the film thickness and the film forming method are known techniques and are not the gist of the present invention, the description thereof will be omitted.

As shown in FIG. 2, the magnetic head 11 includes a coil 12 for generating a recording magnetic field or an erasing magnetic field in a center yoke 12a of a yoke 12 whose side surface is formed in a Y-shape.
3 and a cancel coil 14 for canceling the leakage magnetic field from the autofocus actuator are wound. In the magnetic head 11, as shown in FIG. 1, the magnetic field generating surface (the tip portion of the center yoke 12a) can be set to be separated from the magneto-optical recording film forming surface side of the magneto-optical disk 1 by a predetermined distance. Alternatively, the magnetic field generation surface can be brought into direct contact with the magneto-optical recording film formation surface side of the magneto-optical disk 1. As a method of setting the magnetic field generation surface at a predetermined distance from the magneto-optical recording film forming surface side of the magneto-optical disk 1,
A method in which a slider (not shown) attached to the side yoke 12b is brought into contact with the magneto-optical disk 1, a method in which the magnetic head 11 is levitated by an airflow generated by rotationally driving the magneto-optical disk 1, and a support arm (not shown). To hold the magnetic head 11 in place,
Any known method can be adopted.

The optical head 21 comprises a light projecting optical system 21a and a reflecting optical system 21b. Projection optical system 2
Reference numeral 1a denotes a semiconductor laser 22 and a collimator lens 2 for converting diffused light emitted from the semiconductor laser 22 into parallel light.
3, the incident light on the magneto-optical disk 1 and the magneto-optical disk 1
It comprises a beam splitter 24 for separating the reflected light from the beam splitter and an objective lens 25 for focusing the parallel light on the magneto-optical recording film 3 of the magneto-optical disk 1. On the other hand, the reflection optical system 21b
Is the objective lens 25 and the beam splitter 24.
A second beam splitter 27 that guides a part of the reflected light to the light spot control signal detection circuit 26, a half-wave plate 28 that adjusts the changed surface of the reflected light, and a detection lens 29 that collects the reflected light.
And an analyzer 30 for separating the reflected light into an s-polarized component and a p-polarized component, and two photodetectors 31a and 31b arranged on the condensing surface of the detection lens 29. The output terminals of these two photodetectors 31a and 31b are connected to the two input terminals of the differential amplifier 32, and the reproduction signal is taken out from the output terminal of the differential amplifier 32.

The objective lens 25 is mounted on the actuator 41, and the magneto-optical recording is performed so that the incident light is always focused on the magneto-optical recording film 3 by the output signal of the light spot control signal detecting circuit 26. The distance from the membrane 3 is adjusted. 3 and 4, the actuator 41 according to the embodiment is shown.
An example is shown. As shown in these figures, the actuator 41 of the present example is composed of a non-magnetic base 42 and the base 42.
Four drive magnets 43a, 43b, 43c, 43d mounted on the upper part of the drive magnets 43a, 43b, 43c, 43d, a focus coil 44 wound around the outer circumferences of the drive magnets 43b and 43c, and the focus coil 44 are formed integrally with each other. Lens holder 4 with objective lens 25 attached
5, a tracking coil 46 attached to the side surface of the focus coil 44, and a central shaft 47 that holds the lens holder 45 in a vertically movable and rotatable manner.

As shown in FIG. 4, in the actuator 41 of this embodiment, when a drive current is applied to the focus coil 44, a drive force F according to Fleming's left-hand rule is generated between the drive magnets 43a to 43d. As a result, the objective lens 25 moves up or down depending on the direction of the current. Therefore, the light beam emitted from the objective lens 25 can be constantly focused on the magneto-optical recording film 3 by controlling the direction and magnitude of the drive current so as to follow the surface wobbling and the warp of the magneto-optical disk 21. When a drive current is applied to the tracking coil 46, a drive force is generated between the tracking coil 46 and the drive magnet 43a according to Fleming's left-hand rule, and the objective lens 2 is moved according to the direction of the current.
5 turns clockwise or counterclockwise around the central axis 47. Therefore, by controlling the direction and magnitude of the drive current so as to follow the track-off amount, the light beam emitted from the objective lens 25 is always tracked on the track (not shown) preformatted on the transparent substrate 2. it can.

As described above, since the actuator 41 of this embodiment is provided with the drive magnets 43a to 43d and the focus coil 44, as shown in FIG. Drive magnet 43a-
The total leakage magnetic field of the leakage magnetic field H ₁ from 43d and the leakage magnetic field H ₂ generated by energizing the focus coil 44 acts. In addition, the leakage magnetic field strength acting on the recording film 3 of the magneto-optical disk 1 is such that the gap between the drive magnets 43a to 43d and the recording film 3 of the magneto-optical disk 1 varies due to the warp or surface wobbling of the magneto-optical disk 1. Therefore, it varies with time as the magneto-optical disk 1 is rotationally driven.

As shown in FIG. 1, a drive current corresponding to an information signal is applied to the magnetic head drive circuit 1 in the recording magnetic field or erasing magnetic field generating coil 13 constituting the magnetic head 11.
5 is applied. On the other hand, the cancel coil 14 constituting the magnetic head 11 includes a light spot control signal detection circuit 2
Based on the signal obtained in 6, the focus coil 4
A current proportional to the current applied to the current driving circuit 16
Is applied in a direction to cancel the total leakage magnetic field. As a result, the offset of the magnetic field in the information recording section (light beam focusing section) is reduced or eliminated, so that the drive current to be applied to the recording / erasing coil 13 can be reduced. Further, since the recording and erasing of information can be surely performed, the reproduction C / N ratio (carrier to noise ratio) can be improved.

FIG. 5 shows the effect of the magneto-optical disk drive device according to the above embodiment. In the graph of FIG. 5, the magnitude of the recording magnetic field is plotted on the horizontal axis and the C / N ratio of the reproduced signal is plotted on the vertical axis, and the data of the example product is a circle and has no cancel coil. The data of the magneto-optical disk drive (conventional product) is plotted with triangle marks. As is clear from this figure, when information was recorded / reproduced with the conventional product, stable recording could not be performed without applying a recording magnetic field of 120 (Oe) or more. When information is recorded / reproduced with an example product, approximately 70 (O
It can be understood that stable recording can be realized by applying the recording magnetic field of e) or more, and the power consumption can be significantly reduced.

In the above embodiment, the magnetic head 11 is provided with a yoke having a Y-shaped side surface, but the gist of the present invention is not limited to this, and FIG. As shown in, a bottomed cylindrical outer yoke 5
A center yoke 52 is erected at the center of the coil 1 and a coil 1 for generating a recording magnetic field or an erasing magnetic field is formed in the center yoke 52.
It is also possible to use a coil in which 3 and the cancel coil 14 are wound.

[0019]

As described above, according to the present invention,
Since the leakage magnetic field generated from the objective lens actuator is canceled by the cancel coil provided in the magnetic head, the offset amount of the recording magnetic field or the erasing magnetic field on the recording film is reduced, and the power consumption of the magnetic head can be reduced. At the same time, it is possible to stabilize the information recording and reduce the unerased portion.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magneto-optical disk drive device according to an embodiment.

FIG. 2 is a perspective view of a magnetic head according to an embodiment.

FIG. 3 is a perspective view of an objective lens actuator according to an example.

FIG. 4 is an explanatory diagram of a leakage magnetic field that acts on a magneto-optical recording film.

FIG. 5 is a graph showing the effect of the present invention.

FIG. 6 is a perspective view showing another example of a magnetic head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 11 Magnetic head 13 Coil for generating recording magnetic field or erasing magnetic field 14 Canceling coil 15 Magnetic head drive circuit 16 Current drive circuit 21 Optical head 25 Objective lens 26 Light spot control signal detection circuit 41 Objective lens actuator 43a-43d drive Magnet 44 Focus coil

Claims (1)

[Claims] 1. An objective lens of an optical head and a magnetic head are arranged to face each other via a magneto-optical disk, and a light beam emitted from the objective lens is directed to the recording surface of the magneto-optical disk. In a magneto-optical disk drive device provided with an actuator for autofocusing, the magnetic head includes a recording or erasing coil and a cancel coil for canceling a leakage magnetic field from the actuator, and the cancel coil is provided in the actuator. A magneto-optical disk drive device, wherein a leakage magnetic field from the actuator is canceled by applying a drive current according to an applied autofocus current.