JPH079717B2 - Optical head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to recording and erasing information on a magneto-optical recording medium by the cooperative action of a light beam emitted from an objective lens and an auxiliary magnetic field. The present invention relates to an optical information recording / reproducing apparatus, and more particularly to an optical head apparatus capable of appropriately recording and erasing information by subjecting an optical head apparatus provided with the objective lens to magnetic field shielding processing.

(Prior Art) In recent years, a magneto-optical disk has been used as an information recording medium capable of rewriting a large amount of information.

In order to record information on such a magneto-optical disk, a perpendicular magnetic film is formed on the disk surface, the magnetization direction of the perpendicular magnetic film is aligned in one direction in advance, and a laser is digitally modulated by an information signal. The perpendicular magnetization film is irradiated with a beam to bring the temperature of the irradiation site to the Curie point temperature.

Thus, the coercive force of the perpendicularly magnetized film having the Curie point temperature becomes 0, and the magnetization direction can be easily changed by the external auxiliary magnetic field.

Therefore, when the laser beam is heated to the Curie point temperature while applying a DC bias magnetic field as an auxiliary magnetic field, the magnetization direction at this portion is reversed to the direction of the applied magnetic field. Then, when the irradiation state of the laser beam changes due to the movement of the recording medium, the temperature of the portion again decreases and the coercive force increases, so that the magnetization direction can be maintained and the stable magnetization state can be maintained. In this way, a recording pit string corresponding to the information is formed.

On the other hand, in order to erase the information recorded on the magneto-optical disk, a laser beam is applied to the recording pit portion while tracking on the recording pit row, a DC bias magnetic field in the magnetization direction opposite to the recording pit is applied, and the information is re-recorded. This is done by aligning the magnetization directions of the perpendicularly magnetized films.

By the way, the optical head device conventionally used for recording, reproducing and erasing the above-mentioned information includes semiconductor lasers, condenser lenses, beam splitters, photodetectors, etc., as shown in FIGS. 3 and 4. An optical member support 1 including an optical member (not shown), a focusing permanent magnet 6 and a focusing coil 7 for driving the objective lens 2 in the focus direction, and a tracking permanent magnet for driving in the tracking direction. 8 and a coil 9 for tracking, these objective lens driving devices are protected by a cover 3, and a sliding shaft 5 held by a bearing 4 is provided.
It is possible to move in the access direction (the direction of the arrow in FIG. 3) by driving means such as a linear motor via the.

The objective lens 2, the tracking coil 9, and the focusing coil 7 are attached to an objective lens holding member 10, and the holding member 10 rotates horizontally and vertically about a support shaft 11 fixed to a substrate 12 during driving. To do.

(Problems to be Solved by the Invention) The objective lens 2 is driven by an electromagnetic force generated by the tracking permanent magnet 8, the tracking coil 9, the focusing permanent magnet 6 and the focusing coil 7. However, the leakage magnetic flux generated from the driving means disturbs the auxiliary magnetic field applied to the magneto-optical medium, which adversely affects the recording and erasing of information.

In order to prevent this leakage magnetic flux, the cover 3 is conventionally made of a ferromagnetic material so as to guide the leakage magnetic flux from the driving means to the cover 3, but the objective lens holding member 10 covers the cover 3 during driving. When moved to the 3 side, one end of the tracking coil 9 may collide with the cover 3 to damage the coil, or an erroneous operation may occur in driving the objective lens.

The present invention has been made in view of the above problems of the conventional device, and it is a highly reliable optical head device capable of preventing damage to the coil of the objective lens driving device and eliminating malfunction of driving the objective lens. The purpose is to provide.

(Means for Solving Problems) The problem of the above-mentioned conventional technique is that the objective lens driving device is provided with a ferromagnetic material and is provided with an objective lens driving device having an electromagnetic force generating means composed of the coil and the magnet of the present invention. In the optical head device covered with the magnetic shield cover, the optical head device is characterized in that a non-conductive member having a cushioning property is provided on the inner surface of the magnetic shield cover.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of the apparatus of this embodiment, and FIG. 2 is an exploded perspective view of the apparatus of this embodiment.

In these figures, 20 is a base, and a support shaft 21 is fixed on the base 20, and an objective lens holding member 23 is supported by a bearing 22 so as to be vertically movable and rotatable left and right.
The objective lens 24 and the objective lens 24 are provided on the holding member 23.
A weight 25 is attached to balance the weight against
Further, a focusing coil 25 and a tracking coil 26 are provided below the holding member 23. And
A yoke 27 is fixed on the base 20, and another yoke 28 is fixed around the yoke 27 so as to surround the yoke 27, and a focusing permanent magnet 29 is fixed on the yoke 27. There is. Further, a tracking permanent magnet 30 is fixedly attached to a yoke 31 on the base 20 so as to face the tracking coil 26.

Reference numeral 34 is a neutral point support member for holding the objective lens holding member 23 at the neutral position, and 35 is a support rod for supporting the neutral point support member 34, which is erected on the base 20. .

The objective lens driving device configured as described above is protected by the cover 33, and the cover 33 is made of a ferromagnetic material, and leaks generated by the driving means in the cover 33 when the objective lens is driven. Magnetic flux 35
Acts as a magnetic shield cover to prevent against.

Further, the optical head device of the present embodiment is formed by adhering a non-conductive member 34 such as Mylar tape to the inner upper surface of the cover 33.

This mylar tape has a shock absorbing property against an external impact, and when the objective lens holding member 23 moves to the cover 33 side and the end of the tracking coil 26 collides with the cover 33,
It has a function of softening the impact.

Therefore, even when the objective lens is driven, the tracking coil 26 collides with the cover 33, or at the time of this collision, the objective lens holding member is simultaneously moved in the focusing direction.
Even if the tracking coil 26 rubs and contacts the cover 33 by rotating 23, the coil is not damaged, and the control characteristics when the objective lens is driven are not adversely affected.

In this embodiment, an example in which a mylar tape is used as the non-conductive member has been described, but the application of other materials having the same function is not limited.

Further, in the embodiment, the device in which the objective lens holding member is slidably rotated with respect to the support shaft provided on the base is described, but within the scope of application of the function of the present invention, for example, the objective lens holding member is held. It can also be applied to an optical head device of a type in which members are held by leaf springs, coil springs, elastic wires, various combs and the like.

(Effects of the Invention) As described above, in the optical head device of the present invention, since the non-conductive member having a cushioning property is provided on the inner surface of the magnetic shield cover that covers the objective lens holding member, the objective lens Even if the holding member moves to the side of the magnetic shield cover during driving and the drive coil collides or rubs against the cover, the coil will not be damaged, and therefore malfunctions due to this damage will also occur. Therefore, it is possible to obtain an optical head device having high reliability in driving the objective lens.

[Brief description of drawings]

FIG. 1 is a sectional view of the device of the present invention, FIG. 2 is an exploded perspective view of the device of this embodiment, FIG. 3 is a perspective view of an optical head device of a conventional device, and FIG. 4 is a sectional view of the conventional device. 23 …… Objective lens holding member, 24 …… Objective lens, 33 ……
Cover, 34 ... Non-conductive material.

Claims (1)

[Claims] 1. An optical head device comprising an objective lens driving device having an electromagnetic force generating means composed of a coil and a magnet, the objective lens driving device being covered with a magnetic shield cover made of a ferromagnetic material. An optical head device, wherein a non-conductive member having a cushioning property is provided on the inner surface of the optical head device.