JPH02208851A - Optical head device - Google Patents

Abstract

PURPOSE:To compress an installing space by supplying a magnetic field to an information recording medium by a permanent magnet provided in the neighborhood of the optical system of a base part and at a side opposite to that of the information recording medium of the optical system. CONSTITUTION:The permanent magnet 34 is provided at an optical member supporting part 7, and is magnetized in the neighborhood of an objective lens 15 in a direction of optical axis. Thereby, the magnetic field generated from the permanent magnet 34 when no current flows on a bias coil 32 transmits the neighborhood of the objective lens, and transmits a yoke part 33, then, is concentrated on an opposite yoke 35. When the current flows on the bias coil 32 through a path (a) and the magnetic field in the direction of the opposite yoke 35 is generated at the yoke part 33, the permanent magnet functions as an auxiliary magnetic field for the magnetic field, then, generates the magnetic field (b), which increases total magnetic field strength. Thus, by providing the permanent magnet to generate the magnetic field in the direction of the optical axis of the objective lens 15 and setting it as an auxiliary magnetic field generating source for the bias coil 32, the miniaturization of the bias coil 32 can be attained. Thereby, it is possible to obtain a magneto-optical recorder suitable for a system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to a magneto-optical recording device that records information on a magneto-optical recording medium, which is an information recording medium, by cooperating a light beam and a magnetic field. The present invention relates to an optical head device.

Here, the magneto-optical recording medium can take various forms such as a disk-like shape and a card-like form, but a disk-like magneto-optical recording medium (hereinafter referred to as a magneto-optical disk) will be explained below as an example.

[Prior Art] A magneto-optical disk is formed by forming a magnetic thin film having an axis of easy magnetization perpendicular to the film surface on a substrate, and records information by changing the magnetization direction of this magnetic thin film. During recording, the magnetization direction of the magnetic thin film is first aligned in one direction, and a laser beam digitally modulated in accordance with an information signal is irradiated while applying a bias magnetic field in the opposite direction to the magnetization direction. Then, the temperature of the area irradiated by the laser beam increases, the coercive force decreases, and the area is magnetized in the opposite direction to the surrounding area due to the influence of the bias magnetic field.
A magnetization pattern corresponding to the information is formed. Information recorded in this manner can be optically read out using the well-known magneto-optic effect by irradiating the medium with a low-power unmodulated beam. Furthermore, recorded information can also be erased by applying a magnetic field in the opposite direction to the bias magnetic field during recording.

FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a conventional magneto-optical recording device. In the example shown in FIG.
has a size that covers the recording area in the radial direction of the magneto-optical disk 43, and is fixed to the upper lid 42 of the device.

With the top lid closed, the bias magnet 47 approaches the magneto-optical disk 43 as shown by the broken line. Although this example has a simple configuration as described above, there is a problem in that the applicable devices are limited to those with an openable and closable top lid. The problem of installing and removing media is very important when considering systemization with other information devices.For example, as an alternative to magnetic disks, there are particular restrictions on the height of the installation space, and it is difficult to open and close the lid. The above-mentioned apparatus, which requires space, could not be used.

[Problem to be Solved by the Invention 1] However, the conventional example described above has the following problems.

In the conventional example shown in FIG. 4, the bias magnet is fixed to the upper lid of the device. For this reason, there is a problem in that applicable devices are limited to those with an upper lid that can be opened and closed. The problem of loading and unloading such media is very important when considering systemization with other information devices. It was not possible to use the above-mentioned device, which required an opening/closing space. Another possibility is to install a bias magnet in the device and provide a mechanism to move the bias magnet away from the insertion path when inserting the magneto-optical recording medium, but this mechanism is complicated, difficult to downsize, and heavy. There is a problem with this.

[Summary of the Invention] The present invention has been made in view of the problems of the prior art described above, and its purpose is to provide a magneto-optical recording device that requires a small installation space and is suitable for systemization with other information devices. There is a particular thing.

The above object can be achieved by an optical head device used in the following magneto-optical recording device.

In an optical head device having an optical system driving device for moving an optical system for irradiating light onto an information recording medium with respect to a base, the optical system is located near the optical system in the base and on the information recording medium side of the optical system. An optical head device characterized in that a permanent magnet magnetized in the optical axis direction of the optical system is provided on the opposite side of the optical system, and the permanent magnet applies a magnetic field to the information recording medium.

[Embodiments] Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 is an exploded perspective view showing the optical head device of the present invention, and FIG. 2 is a perspective view of the optical head device in use.

As shown in the figure, an objective lens holder 12 having a cylindrical shape
is supported by a support shaft 14 through a bearing 13 so as to be slidable in the vertical direction and rotatable around the vertical direction.

Near the bearing 13, an objective lens 15 and a weight 16 having approximately the same weight as the objective lens 15 are attached to maintain the weight balance, and a weight (not shown) at the bottom to maintain the weight balance in the vertical direction. is installed. A focusing coil 17 is wound around the lower outer periphery of the objective lens holder 12, and approximately rectangular tracking coils 18a to 18d (not shown 18b to 18
d) is attached.

The support shaft 14 is fixed to a yoke 19 made of a ferromagnetic material by direct press-fitting or the like. In addition, the yoke 19 has tracking permanent magnets 20a, 20b, 20c, and 20d near the outer periphery of the objective lens holder 12 so as to face the tracking coils 18a to 18d (not shown 18b to 18d).
are each fixed.

Below the tracking permanent magnets 20a to 20d, focusing permanent magnets 21a and 21b are connected to the focusing coil 1.
It is fixed so as to face 7. Tracking permanent magnets 20a to 20d and focusing permanent magnet 21a
, 21b, and an inner yoke 22a extending in the vertical direction as an opposing magnetic pole.

22b is provided near the inner circumference of the objective lens holder 12 and facing the inner circumference.

The focusing permanent magnets 21a, 21b and the tracking permanent magnets 20a to 20d are directly attached to the yoke 19 with an adhesive or the like.

A pin 25a is provided on the upper part of the inner yokes 22a and 22b for positioning the cover 23 and the cover plate 24 made of ferromagnetic material.
, 25b are provided.

The cover plate 24 is made of ferromagnetic material, and the pins 25a, 2
Hole 31a for positioning with the yoke at the position corresponding to 5b
, 31b are provided. The cover plate 24 is integrally formed with the cover 23 made of resin such as polycarbonate or ABS by adhesive or insert molding.

The opening of the cover plate is drawn to provide a yoke portion 33 that serves as a center yoke and for positioning the bias coil A32, which is an air-core coil. By winding and fixing the bias coil A32 here, a bias magnetic field generating device 26 including the cover 23 is configured.

The cover 23 has one or more locking members 28 (in the figure,
A total of 3 locations (including 1 locations not shown) are provided.

The bias magnetic field generator 26 is inserted into the yoke 1 from above in the figure.
At this time, the pins 25a, 25b of the inner yokes 22a, 22b and the positioning hole 31a of the bias magnetic field generator 26 are fixed to the pins 25a, 25b of the inner yokes 22a, 22b.

31b, the cover plate 24 of the bias magnetic field generator 26 is positioned in the A direction and the B direction in the figure. In the vertical C direction, an inner yoke 22a,
The cover plate 24 is positioned by abutting against the cover positioning surface 27, which is the upper end surface of the cover plate 22b. In order to maintain this positioning state, a locking member 28 provided on the cover 23 is locked to the lower surface of the yoke 19.

By the way, as shown in FIG. 2, the optical head device includes an optical member support section 7 containing optical members (not shown) such as a semiconductor laser, a condenser lens, a beam splitter, and a photodetector, and an objective lens 15. The objective lens driving device (not shown) is protected by a cover 23. The entire optical head device is supported by a sliding shaft 10 through a bearing 9 so as to be slidable in the D direction. In other words, the optical system (a movable part on an optical system drive device) has a base part (a non-movable part on an optical system drive device, that is, an optical member support part, etc.) on the cover 23, and the bias magnetic field generating device 26 described above is placed on the cover 23, Cover plate 24, bias coil 3
Consisting of 2. A ferromagnetic opposing yoke 35 is provided at a position facing the bias coil 32 across the opto-electrical recording medium 36, which is an optical information recording medium, in order to concentrate the magnetic field generated by the bias magnetic field generator 26. ing.

The opposing yoke is longer in the direction A in the figure by the amount of sliding movement of the entire optical head device.

Further, a permanent magnet 34 is provided on the optical member support section 7, and a third
As shown in the figure (sectional view), the objective lens 15 is magnetized near the optical path in the optical axis direction. For this reason, bias coil 3
When no current is flowing through the magnet 2, the magnetic field generated by the permanent magnet 34 passes through the vicinity of the objective lens, passes through the yoke portion 33, and is concentrated on the opposing yoke 35.
When a current is passed through the bias coil 32 and a magnetic field is generated in the yoke portion 33 in the direction of the opposing yoke 35, the permanent magnet acts as an auxiliary magnetic field to generate the magnetic field shown in the figure, increasing the overall magnetic field strength.

[Effects of the Invention] As described above, a permanent magnet that generates a magnetic field in the optical axis direction of the objective lens is applied to a member other than the movable part, which is the objective lens holder, in the vicinity of the laser beam path at the bottom of the objective lens of the objective lens drive device. By providing a bias coil and using it as an auxiliary magnetic field generation source for the bias coil, it has become possible to downsize the bias coil, and it has become possible to provide a small and thin magneto-optical recording device.

[Brief explanation of the drawing]

1 and 2 are perspective views showing an optical head device of the present invention, FIG. 3 is a sectional view showing an optical head device of the present invention, and FIG. 4 is a diagram showing a conventional magneto-optical recording device. 15...Objective lens 4...Permanent magnet

Claims (1)

[Claims] (1) In an optical head device having an optical system driving device for moving an optical system for irradiating light onto an information recording medium relative to a base, the information of the optical system in the base and near the optical system. An optical head device characterized in that a permanent magnet magnetized in the optical axis direction of the optical system is provided on the opposite side to the recording medium side, and the permanent magnet applies a magnetic field to the information recording medium.