JPH02208848A - Optical head device - Google Patents

Abstract

PURPOSE:To reduce the installation space by winding and fixing one or more coil around a branch yoke part formed by a bias magnetic field yoke and forming a bias magnetic field coil. CONSTITUTION:A bias magnetic field generating device 26 is provided on an outer circumferential part of a cover 23, and individual five ends of the yoke 24 formed of an approximately Z-shaped ferromagnetic body are wound and fixed with the bias coil 32 and fixed, for instance, with a screw as shown as 25 to an optical member supporting part 7 or fixed with an adhesive, etc. The other end of the yoke 24 is extended to the vicinity of a hole 29 for a beam of light as a laser light passing part provided to the cover 23 and also to the vicinity of an objective lens 3, where a bias magnetic field generating part 24a is provided in order to generate a bias magnetic field in this part. By this method, the subject device can be reduced in thickness, space, and weight.

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 a direction opposite 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. 3 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. 3, the bias magnet 47 has a size that covers the recording area of the magneto-optical disk 43 in the radial direction, and is fixed to the upper cover 42 of the apparatus. 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 upper lid. The problem of installing and removing such 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.

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

In the conventional example shown in FIG. 3, 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 miniaturize, and weighs very little. The problem is that it becomes

[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 drive device for moving an optical system for irradiating light onto an information recording medium relative to a base, in the vicinity of the optical system of the optical system drive device,
A bias magnetic field yoke is formed between the information recording medium and the optical system, and the bias magnetic field yoke forms at least one branch yoke portion along the outer periphery of the optical system drive device. An optical head device characterized in that a bias magnetic field coil is formed by winding and fixing at least one coil around the branch yoke portion.

[Example] Hereinafter, an example of the present invention will be described specifically and in detail based on the drawings. FIG. 1 is a perspective view showing an optical head device of the present invention. As shown in FIG. 1, 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 3 are mounted to the optical member support section. It has an objective lens drive device that drives in the focus direction (C direction) and the tracking direction (six directions), and the objective lens drive device is connected to the cover 2.
Protected by 3. 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.

A bias magnetic field generator 26 is provided on the outer periphery of the cover 23. In this embodiment, a bias coil 32 is wound and fixed at each end of a yoke 24 formed of a ferromagnetic material in a substantially O-shaped shape at five locations, and is fixed to the optical member support 7 with screws 25, for example. or fixed with adhesive, etc.

The other end of the yoke 24 extends to the vicinity of the beam hole 29, which is a laser beam passage portion provided in the cover 23, and to the vicinity of the objective lens 3, and a bias magnetic field generating portion 24a is arranged to generate a bias magnetic field at this portion. is the provision. In this example, the shape of this 24a is a continuous ellipse. An opposing yoke 27 for concentrating a bias magnetic field and aligning the direction of the magnetic field is provided at a position facing the objective lens 3 and the bias magnetic field generating section 24a with the magneto-optical recording medium 28 in between.

The opposing yoke 27 is longer in the direction A in the figure by the amount of sliding movement of the entire optical head device.

Next, another embodiment according to the present invention will be described.

The present invention can be modified in various ways other than the embodiments described above, and the present invention includes such modifications as long as they do not depart from the scope of the claims. In order to support the objective lens so that it can move vertically in the focusing direction and the tracking direction, there is a support method in which the objective lens is slid up and down and rotated left and right using a support shaft and a bearing. The method of supporting the objective lens is not particularly limited, and may be supported by a leaf spring or wire, or by a hinge.

The opposing yoke 27 is a plate-shaped ferromagnetic material in the embodiment shown in FIG. , trapezoid (0), etc.

Further, the opposing yoke 27 may not be provided.

The shape of the bias magnetic field generating portion of the yoke formed near the objective lens is also not limited to this.

For example, as shown in FIG.
The magnetic field can be further concentrated by moving it closer to

In the figure, the shape of the bias magnetic field generating section 24b is approximately elliptical, but the shape is not limited thereto, such as approximately circular, rectangular, or rectangular.

The number of bias coils 32 does not need to be one for each yoke, and may be wound around and fixed to a plurality of side yokes.

In the embodiment shown in FIG. 1, the bias coil, yoke and cover 2
3 may be close to each other, that is, may have an adverse magnetic effect on the objective lens drive device provided within the cover. Therefore, at least a portion of the cover 23, for example, the portion between the cover 23 and the bias magnetic field generator 26, or the entire cover may be magnetically shielded by using a strong JFI material.

Furthermore, although the yoke 24 is fixed to the optical member support section 7 with screws 25, the present invention is not limited thereto.

[Effects of the Invention] As explained above, a magnetic yoke of ferromagnetic material is formed near the objective lens of the objective lens driving device, near the laser beam passage part, and between the information recording medium, and the outer periphery of the objective lens driving device The bias magnetic field generator is formed by winding and fixing a coil around each branch yoke, which has at least one branch yoke along the yoke.The device, which used to be complicated and large, has been made smaller with a simple mechanism. Thinner, space-saving,
It is possible to provide a magneto-optical recording device with better performance due to its reduced weight.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an optical head device of the present invention, FIG. 2 is a view showing a modification of the yoke, and FIG. 3 is a view showing a conventional magneto-optical recording device. 3...Objective lens 24...Yoke 24a...Bias magnetic field generating section 32...Bias coil

Claims (1)

[Claims] (1) In an optical head device having an optical system drive device for moving an optical system for irradiating light onto an information recording medium with respect to a base, in the vicinity of the optical system of the optical system drive device, and in the vicinity of the information recording medium, A bias magnetic field yoke is formed between the medium and the optical system, and the bias magnetic field yoke forms at least one branch yoke part along the outer periphery of the optical system drive device, and the branch yoke part 1. An optical head device characterized in that a bias magnetic field coil is formed by winding and fixing at least one coil to a coil.