JPS61122902A - Bias magnetic field impressing device - Google Patents

Abstract

PURPOSE:To impress a bias magnetic field which is of a small constitution, little in a quantity of the power consumption and equal only to the necessary area by installing a coil for generating a bias magnetic field round the pick-up lens. CONSTITUTION:A coil 107b for generating a bias magnetic field is installed round an objective lens of the actuator 105 of the pick-up, and a bias magnetic field for recording and deleting to vertically-magnetized disk-shaped recording media occurs without using an electromagnet, etc., shifted by a large fixed coil or an exclusive-use shifting device. By the small and little power consumption constitution, the bias magnetic field can be impressed equally to the necessary area only.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for applying a bias magnetic field to a disk-shaped recording medium in a perpendicular magnetization type magneto-optical recording system.

7゜Conventionally, there are two types of bias magnetic field application methods used in perpendicular magnetization type magneto-optical recording devices: a bias magnetic field moving type and a fixed type. Since the rad (for applying a bias magnetic field) must be moved in the radial direction of the disk in accordance with the magnetic field, the moving mechanism becomes complicated, resulting in an increase in the size of the magnetic recording device.

As a prior art, a fixed bias magnetic field applying device as shown in FIGS.
(See Publication No. 505).

In the system shown in FIG. 1, a large coil 4 is installed around the outer periphery of the disk 2, and a bias magnetic field is applied over the entire area of the disk 2. This has the advantage that it does not require a complicated Wh transfer mechanism compared to a method using a moving head, but it requires a large amount of power to obtain the magnetic field strength necessary to record or erase information on the disk, and the coil Many problems have arisen, such as heat generation, an increase in the size of the power supply, and the difficulty in obtaining a negative magnetic field strength. Figure 4 shows what has been done to improve these problems. Permanent magnets 5 are arranged in parallel in the radial direction of the disk 2 as means for generating a bias magnetic field, and the motor 6
By rotating the permanent magnet 5 to adjust the desired magnetic field strength and direction, this method attempts to eliminate the power loss caused by the head moving mechanism and large coil, which are the problems of the prior art. It requires a large permanent magnet and a mechanical part to rotate the permanent magnet, etc.
There are still unresolved problems, and there is room for improvement as a practical bias magnetic field application method.

- In view of the above-mentioned problem of the bias magnetic field application method of the conventional perpendicular magnetization type magneto-optical arrangement and device, the present invention provides a method for applying a bias magnetic field using a large coil, etc., without requiring a special moving mechanism for the head, etc. for the bias magnetic field. It is an object of the present invention to provide a practical bias magnetic field applying device that generates a homogeneous bias magnetic field with a minimum configuration without causing large power loss.

The present invention makes it possible to obtain maximum efficiency with a minimum configuration by providing a coil for generating a large magnetic field of 1<ia around a perpendicular magnetization type magneto-optical recording or erasing pickup lens. It is.

The present invention will be specifically explained below using examples.

FIG. 1 is an explanatory schematic exploded perspective view showing an embodiment of the present invention, in which 10B is a disk-shaped magnetic recording body (hereinafter simply referred to as disk) having magnetic anisotropy perpendicular to the film surface; 105;
g: t: an actuator section of a pickup equipped with a focusing and tracking mechanism; 107 is a bias magnetic field generating section;

101 is a semiconductor laser light generator, 102 is a collimator,
103 is a shaped prism, 104 is a total reflection prism, the laser beam emitted from the semiconductor laser light emitter 101 is received by the collimator lens 102, and the shaped prism 1
03, the half prism 108
The light is reflected into the actuator 105 by the total reflection prism 104, and is focused into a spot light by the objective lens in the actuator 105, and is focused on the disk 10.
B is irradiated to perform recording, erasing, or reproduction.

The light reflected by disk 10B is totally reflected prism 1
04, a portion of the light is reflected by the other surface of the half prism 108, and the light is focused by a lens 11G and converted into a signal by an APD (avalanche, photodiode) 111.

On the other hand, a part of the light that has passed through the half prism 108 is totally reflected on the other surface of the prism 108, and the critical angle prism 1
12 and enters a four-part detector 113, where it becomes a tracking signal and a focusing signal.

In the series of actions described above, the bias magnetic field generating section 10
7 generates a bias magnetic field when recording or erasing on a disk, and as shown in FIG. 2, a yoke 107a
And coil! 07b, the coil is fitted into the yoke or fixed by adhesive, and is attached to the upper part of the actuator section 105.

As is clear from Figure 1, the yoke IQ7a has a through hole 107d in the center, and is provided with a concave groove having a U-shaped radial cross section, and a donut-shaped annular coil is placed in the concave groove. 1G7b is fitted.

FIG. 3 shows a cross section of the main parts of the actuator section 105 and the bias magnetic field generating section 107.
The yoke 107a of No. 07 is attached by well-known fixing means such as fitting, screwing, or adhesion.

107b is a coil for generating a bias magnetic field inside the yoke;
The arrows indicate the distribution state of the magnetic field with respect to the disk 10B. As can be seen from this figure, the bias magnetic field generation coil 1
By arranging 07b around the objective lens +08a on the top of the actuator of the big-up, it is possible to apply a bias magnetic field only to the area necessary for the recording or erasing action during recording or erasing, so the coil can be made smaller. Problems such as heat generation and enlargement of the power supply do not occur.

Therefore, the number of components can be kept to a minimum, and a compact bias magnetic field applying device can be obtained without taking up much space.

In addition, if a strong bias magnetic field is required.

By arranging another bias magnetic field generating coil facing each other with the disk in between, a compact and highly efficient bias magnetic field applying device can be obtained.

According to the present invention, compared to the bias magnetic field applying device of the conventional perpendicular magnetization type magneto-optical recording device, a large coil is not required, power consumption is low, and a uniform bias magnetic field is applied only to the area where the bias magnetic field is required. Because it can apply voltage, the number of products per shot is small, and it is compact and does not take up much space.
This has the effect that a heis magnetic field applying device can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory schematic exploded perspective view showing an embodiment of the present invention;
FIG. 2 is an exploded perspective view of the bias magnetic field generating section, and FIG. 3 is a sectional view of essential parts of the actuator section and the bias magnetic field generating section. FIG. 4 and FIG. 5 are explanatory diagrams of main parts showing the prior art, respectively. 10B... Disc-shaped recording medium 105... Actuator 105a... Objective lens IQ7b... Bias magnetic field generation coil 107a...
・Yoke Figure 8

Claims (2)

[Claims] (1) A bias magnetic field applying device in a perpendicular magnetization type magneto-optical recording device, characterized in that a coil for generating a bias magnetic field is provided around an objective lens of an actuator of a pickup facing a disk-shaped recording medium. (2) The bias magnetic field generating coil is a ring-shaped coil that is housed in a groove of a yoke that has a through hole in the center and has a U-shaped radial cross section. A bias magnetic field applying device according to claim 1.