JPH05114152A - Objective lens actuator - Google Patents

Abstract

PURPOSE:To provide the objective lens actuator of excellent characteristic which can apply stable servo even in the case of deviation of an objective lens from the driving center by resolving the problem that an objective lens actuator used in various optical heads is oscillated in the direction of the optical axis with the driving center as the center. CONSTITUTION:Eight mobile part supporting members 6a to 6h which fix a mobile part are provided, and each member has end stuck to the mobile part and has the other end support by one of bases 7a and 7b facing each other. Mobile part porting members 6a to 6d are stuck to the base 7a but are not fixed to the base 7b to secure an extent of movement in the focusing direction and the tracking direction. Sticking points A, B, C, and D and sticking points E, P, G, and H on the mobile part side are in two parallel faces which are stretched by the axis of the focusing direction and that the tracking direction and are symmetrical with respect to a face I including the centroid of the mobile part. Thus, pitching is suppressed by the moment generated by the elasticity of mobile part supporting members 6a to 6h of metallic wires even when occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens actuator used in an optical head for projecting a light spot on an information track on a disk to optically record, reproduce and erase signals.

[0002]

2. Description of the Related Art In recent years, an objective lens actuator has been used as a drive device for moving an objective lens by following surface deviation and eccentricity of an optical disk.

A conventional objective lens actuator will be described below. FIG. 3 shows an example of a conventional objective lens actuator. In FIG. 3, a U-shaped magnetic circuit is formed by a pair of magnets 1a and 1b and a yoke 2, and a focusing drive coil 5a and a tracking drive coil 5b, which are wound around a bobbin 4 that holds an objective lens 3, A part of 5c is inserted in the gap of the U-shaped magnetic circuit. One end of each of the movable portion support members 6a, 6b, 6c, 6d made of four parallel linear metal wires is fixed to the bobbin 4 and the other end is fixed to the base 7, so that the bobbin 4 can move in the focusing direction and the tracking direction. It is supported so as to be movable in two directions. As a result, when a current is applied to the focusing drive coil 5a, it moves in the focusing direction, and when a current is applied to the tracking drive coils 5b and 5c, it moves in the tracking direction by electromagnetic action.

[0004]

However, in the conventional objective lens actuator, the movable portion support member 6 made of a metal wire is used.
Since the fixed points a to 6d are stretched by the axis in the focusing direction and the axis in the tracking direction and are in the plane including the center of gravity of the movable portion, that is, in the drive center, the so-called vibration of the movable portion having the axis in this plane Pitching occurs, which causes
Especially, when the objective lens 3 is deviated from the driving center, the focus and tracking servo become unstable.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an objective lens actuator which can apply stable servo even when the objective lens is displaced from the driving center.

[0006]

In order to achieve this object, in the objective lens actuator of the present invention, one end is fixed and the other end is supported by a base at a position symmetrical to the driving center on the side surface or the upper surface of the movable portion. It has a structure including a movable portion support member.

[0007]

With this configuration, both sides of the surface including the focusing direction axis and the tracking direction axis and including the center of gravity of the movable portion can be supported by the movable portion support member, and the inside of this surface serves as the axis. Vibration of the movable part can be suppressed.

[0008]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of an objective lens actuator according to the first embodiment of the present invention. The same members as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. There are eight movable part support members 6a to 6h, one end of which is fixed to the movable part and the other end of which is opposed to the base 7.
It is supported by a or 7b. Although the metal wire is fixed to the base on the 7a side, the metal wire is not fixed on the 7b side to secure the movement amount in the focusing direction and the tracking direction.
A, B, C, D, E, F, G and H are metal wire movable part supporting members 6a, 6b, 6c, 6d, 6e, 6f and 6 respectively.
g and 6h are fixed points on the movable part side. A plane which is stretched by an axis in the focusing direction and an axis in the tracking direction and includes the center of gravity of the movable portion is shown as an I plane. A, B, C,
D and E, F, G, H lie in two parallel planes that are symmetrical with respect to the I plane. As a result, even when pitching is about to occur, the momentum generated by the elasticity of the movable portion support members 6a to 6h suppresses pitching.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a second embodiment of the present invention. The difference from FIG. 1 is that there are four movable part support members 6a, 6b, 6c and 6d, and the fixing points on the movable part side are A, B, C and D, respectively. Four
Each of the movable portion support members 6a to 6d of the book has one end fixed to the movable portion and the other end supported by a base 7a or 7b facing each other. The movable portions supporting members 6a and 6b of metal wires are fixed on the base 7a side, but the base 7b side is not fixed, and the movement amount in the tracking direction is secured. A, B,
C and D are all in a plane including the center of gravity of the movable part and parallel to the horizontal driving surface of the objective lens 3, and A, B and C, D
Lie in two parallel planes, each symmetric with respect to the I plane. In this case, there is an advantage that the number of movable part support members can be omitted.

[0010]

As described above, according to the present invention, by providing the movable portion support member, one end of which is fixed at a position symmetrical to the driving center of the side surface or the upper surface of the movable portion and the other end of which is supported by the base, pitching This is to realize an excellent objective lens actuator that does not occur.

[Brief description of drawings]

FIG. 1 is a perspective view of an objective lens actuator according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an objective lens actuator according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a conventional objective lens actuator.

[Explanation of symbols]

1a, 1b Magnet 2 Yoke 3 Objective lens 4 Bobbin 5a Focusing drive coil 5b, 5c Tracking drive coil 6a to 6h Movable part support 7a, 7b Base A to H Movable part side fixing point I Focusing Surface stretched by the axis of the direction and the axis of the tracking direction and including the center of gravity of the moving part

Front page continued (72) Inventor Yutaka Murakami 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshiaki Ikeda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Invention Kenichiro Urairi 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. An objective lens, a lens holder for holding the objective lens, a movable portion composed of a coil or a magnet, and a base portion which is opposed to the objective lens and which forms a magnetic circuit with the coil or the magnet or a coil and a yoke. An objective lens actuator comprising a movable part support member, one end of which is fixed at a position symmetrical to the drive center of the side face or the upper face of the movable part and the other end of which is supported by a base. 2. One end is fixed at eight side surfaces of a lens holder existing in two parallel planes including the center of gravity of the movable portion and symmetrical with respect to a plane parallel to the horizontal driving surface of the objective lens. Item 1. The objective lens actuator according to item 1.