JPH01155504A - Controller for external magnetic field of magneto-optical disk device - Google Patents

Abstract

PURPOSE:To eliminate the needs for adjusting the alignment of an optical spot and a magnetic head and to attain the impression of the magnetic field of a prescribed strength even if an aberration occurs by providing an optical detector detecting the aberration of the optical spot and providing an actuator which makes the magnetic head to follow the optical spot by means of the detection signal. CONSTITUTION:The optical detector 7 detects the aberration of the optical spot 12 and the magnetic head 8. The actuator 9 shifts the magnetic head 8 in a shifted direction by the detection signal and the detection signal is outputted accompanied by the aberration of the optical spot 12. Since the actuator 9 shifts the magnetic head 8 in the direction until it coincides with the optical spot, the optical spot 12 and the magnetic head 8 are prevented from being relatively shifted. Thus, the magnetic field of the prescribed strength can always be impressed on a part where the optical spot of a recording film 13 is projected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical disk device, and relates to a particularly stable recording and
The present invention relates to an external magnetic field control device that performs erasing.

[Conventional technology]

A magneto-optical disk device records and erases information by reversing the direction of magnetization of a recording film on a disk surface upward or downward. Recording is performed by raising the temperature of the recording film by irradiating it with a light spot, causing it to lose magnetization, and then, when it cools down, to generate magnetization in the direction of a magnetic field applied from the outside. Erasing is performed by raising the temperature of the recording film by irradiating it with a light spot, causing it to lose magnetization, and then, when it cools down, changing the direction of the applied magnetic field opposite to that during recording to restore the original direction of magnetization.

In a device that uses a permanent magnet as an external magnetic field, it is necessary to reverse the direction of the magnetic field during recording and erasing, and recording and erasing cannot be performed simultaneously.

Therefore, as an override magneto-optical device that can perform recording and erasing at the same time, it is a device consisting of a magnetic head with two magnets that generate magnetic fields in two directions and an optical head that focuses two or more light spots. is published in 1986-
196446.

This is done by focusing the erasing light spot on the position of the magnet that generates the magnetic field in the erasing direction, and focusing the recording light spot on the position of the magnet that generates the magnetic field in the recording direction.
Record erasure is performed at the same time. The conventional device described above is composed of an optical head and a magnetic head attached to an arm.

The optical head and the magnetic head are arranged to sandwich the magneto-optical disk, and move together in the radial direction of the disk. However, the distance between two or more light spots that can be focused on the disk by a common optical system is within about 100 μm. Therefore, the positional accuracy of the two magnets and two spots is 50μ
It is considered to be less than m. In order to perform stable record erasing,
It is necessary to keep the intensity of the externally applied magnetic field constant at the position of the magneto-optical recording film where the light spot is irradiated.

However, since the disk changes in the vertical direction as it rotates, the strength of the magnetic field applied to the recording film on the disk changes. Regarding this point, in order to maintain a constant magnetic field strength at the optical spot position on the disk, we detect the positional fluctuation in the optical axis direction of the aperture lens that moves with the disk fluctuation, and adjust the drive current of the external magnetic field accordingly. An optical recording/reproducing device having a control function was proposed in Japanese Patent Laid-Open No. 60-630.

[Problem that the invention seeks to solve]

In the first prior art magneto-optical recording device, a first optical spot is focused on a portion of the magnet having a first magnetic field direction of the magnetic head, and a first optical spot is focused on a portion of the magnet having a second magnetic field direction. Focus two light spots. As mentioned above, the positional accuracy between the two magnets and the two spots is thought to be less than 50 μm, and the optical spot is easily misaligned due to temperature changes, etc., so if there is no alignment mechanism between the optical spot and the magnetic head, the two There was a problem in that it was difficult to focus the light spot on the position of each magnet6.The second conventional technology described above constantly focuses the magnetic field in response to the positional changes in the optical axis direction of the disk and the aperture lens linked thereto. The intensity of the magnetic head is controlled to be constant, but no consideration is given to the case where the optical head changes its position in the direction perpendicular to the optical axis. , there was a problem that the magnetic field strength changed.

An object of the present invention is to provide an external magnetic field control device for a magneto-optical disk that does not require alignment adjustment between a light spot and a magnetic head and can apply a magnetic field of constant strength even if the light spot is misaligned. purpose.

[Means for solving problems]

A magneto-optical disk device is provided with a photodetector for detecting a shift in the position of a light spot, and further provided with an actuator that causes a magnetic head to follow the light spot based on a detection signal from the photodetector.

[Effect]

The photodetector detects the misalignment between the optical spot and the magnetic head. The actuator moves the magnetic head in a shifted direction based on the detection signal. Therefore, as the optical spot shifts, a detection signal is output, and the actuator moves the magnetic head in that direction until it coincides with the optical spot, so that the optical spot and the magnetic head do not shift relative to each other.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a schematic diagram of a portion related to the present invention of a magneto-optical disk device using an external magnetic field control device of the present invention.

4 indicates an optical head. Light 11 from a light source 1 is turned into parallel light by a coupling lens 2 and focused onto a disk 5 by a focus lens 3 to form a light spot 12.

A magnetic head 8 is placed on the other side of the optical head 4 across the disk 5. The magnetic head 8 includes a magnet 6 and a photodetector 7 arranged around it. The magnetic head 8 is moved by an actuator 9. The disk 5 has a magneto-optical recording film 13
The light transmittance of this recording film 13 is, for example, about 70%. After the light 11 becomes a light spot 12, 30% of the light is reflected and returns to the optical head 4, where it is used for automatic focus control, tracking control, and signal detection, and the remaining 70% of the light passes through the disk 5. The light spreads and reaches the surface of the photodetector 7.

FIG. 2 is a diagram for explaining the arrangement of the photodetector 7,
This is a view from the disk 5 side. The photodetector 7 is composed of four light receiving elements 21, 22, 23 and 24, and a magnet 6.
arranged around. A circle 10 is a light beam on the photodetector 7 surface. The circuit 25 outputs a detection signal 28 from the outputs of the light receiving elements 21 and 23, and the circuit 26 outputs a detection signal 29 from the outputs of the light receiving elements 22 and 24. When the light spot 12 is directly below the magnet 6 as shown in FIG. 1, the light beam 10 is located at the center of the photodetector 7 as shown in FIG. 2, and the light receiving elements 21, 22, 23, and 24 are receive a certain amount of light. Therefore, the detection signals 28 and 29 become 0 level. In FIG. 1, when the light spot 12 shifts in the direction within the paper plane, the light flux [0] shifts toward the light receiving element 22 as shown in FIG. 3 (A), the amount of light received by the light receiving element 22 increases, and the light receiving line Child 2
4, the amount of light received decreases. Therefore, the detection signal 29 is at level 10. The actuator 9 moves the magnetic head 8 in the direction within the paper plane in response to the 10 level of the detection signal 39 until the detection signal 29 reaches the 0 level. In Figure 1, if 12 is shifted perpendicularly to the paper surface, the optical spora]
), the light beam 10 shifts toward the light receiving element 23, the amount of light received by the light receiving element 23 increases, and the amount of light received by the light receiving element 24 decreases. Therefore, the detection signal 28 becomes one level. The actuator 9 moves the magnetic head in a direction perpendicular to the plane of the paper until the detection signal 28 reaches the 0 level. As described above, the magnetic head can be positioned directly above the optical spot 12. Therefore, a magnetic field of constant strength is always applied to the portion of the recording film 13 that is irradiated with the light spot, resulting in stable recording.

Can be erased.

In a magneto-optical disk device, during initial adjustment, the optical spot 12
It is necessary to align the magnetic head 8 with the magnetic head 8. Furthermore, after the initial adjustment, there is a possibility that the optical spot 12 and the magnetic head 8 will be misaligned due to temperature changes or the like. According to the present invention, the photodetector 7 detects the positional deviation between the optical spot and the magnetic head 8, and the actuator 9 detects the positional deviation between the optical spot and the magnetic head 8.
Initial stage? J! This eliminates the need for four-dimensional adjustment, and enables a magneto-optical disk device that is stable against temperature changes.

〔Effect of the invention〕

According to the present invention, since the magnet can be moved to the focusing position on the optical spot 1, there is an effect that the magnetic field strength with respect to the spot is always constant.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a portion related to the present invention of a magneto-optical disk device using an external magnetic field control device of the present invention. Second
The figure shows the arrangement of photodetectors. FIG. 3 is a diagram showing a method for detecting the position of a light spot. DESCRIPTION OF SYMBOLS 1... Light source, 4... Optical head, 5... Magneto-optical disk, 6... Permanent magnet, 7... Photodetector, 8...
Magnetic head, 9... Actuator, 12... Optical spot, 13... Magneto-optical recording film, ]0... Luminous flux, 2
8.29...Detection signal. Kaya 3 → Mehato Susu Φ Se Drop

Claims (1)

[Claims] 1. In a magneto-optical disk device having an optical head that forms a light spot on the information recording surface of a magneto-optical disk and a magnetic head that applies a magnetic field to the disk, a photodetector that detects a change in the position of the light spot; 1. An external magnetic field control device for a magneto-optical disk drive, comprising an actuator that causes the magnetic head to follow positional changes.