JP2751459B2 - Objective lens drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an objective lens which focuses a light beam emitted from a light source on a signal recording surface of an optical disc, for example, in a focus direction and a tracking direction, or in any of these directions. The present invention relates to an objective lens driving device for driving and displacing one side.

[Summary of the Invention]

The present invention relates to an objective lens driving device for driving and displacing an objective lens in a focus direction and a tracking direction, wherein a support on which the objective lens is mounted is moved in a radiation direction at a required angle around a center of gravity separated from a mounting portion of the objective lens. Supported by the movable support member on a plurality of lines extending in the direction of gravity, the support will be supported in the direction of the center of gravity, and the support will cooperate with the coil and the magnetic circuit of the closed magnetic circuit composed of the magnet and the yoke. And the moving operation in the direction parallel to the optical axis of the objective lens, that is, in the focus direction, is performed stably, and the objective lens is rotated about the center of gravity to make the objective lens orthogonal to its optical axis. It is possible to stably move in the direction, that is, the tracking direction.

[Conventional technology]

2. Description of the Related Art Conventionally, an optical pickup is used as a means for irradiating a signal recording surface of an optical disc mounted on a disc rotation driving device and rotating to irradiate a light beam to read an information signal recorded on the optical disc or write a predetermined information signal on the optical disc. The device is used. In this optical pickup device, an objective lens for focusing a light beam emitted from a semiconductor laser as a light source on a signal recording surface of an optical disk is provided in a focus direction and a tracking direction or one of these directions with a magnetic driving force. There is provided an objective lens driving device for performing the driving displacement so that the light beam is focused on the signal recording surface of the optical disk to accurately operate the recording track.

As an objective lens driving device applied to a conventionally used optical pickup device, as shown in FIG. 11, an objective lens (1) is supported and a focus control drive coil (2) and a tracking control drive coil (3) are supported. ) Is mounted between the magnets (6) and (6) opposed to the base (5) and the front left and right sides of the mounting plate (7) planted on the base (5). There has been known a configuration in which a metal support bar (8) having a spring property and supported in a cantilever manner is arranged in a cantilever manner in parallel with the upper and lower parts of the body in a cantilever manner. In this structure, the bobbin (4) is moved by the elastic displacement of the support rod (8) by supplying a drive current to the focus control drive coil (2) or the tracking control drive coil (3). The objective lens (1) supported by (4) is moved in the focus direction and the tracking direction.

[Problems to be solved by the invention]

By the way, in the objective lens driving device configured as described above, the bobbin (4) on which the objective lens (1) is mounted is supported by the support rod (8) parallel to the left and right with respect to the mounting plate (7). , The bobbin (4), the mounting plate (7) and the left and right support rods (8) to form a plane parallel link, so that the bobbin (4) is moved up and down (focus direction).
In order to stably support the support rod (8), the support rod (8) needs to have a strong spring property. If the spring property of the support rod (8) is increased, the bobbin (4) moves smoothly in the lateral direction (tracking direction). There is an inconvenience that cannot be performed.

The present invention has been made in view of such a point, and has an objective lens driving device that can stably support a support on which an objective lens is mounted in a focus direction and can move smoothly in a tracking direction with a simple configuration. The purpose is to provide.

[Means for solving the problem]

In order to achieve the above object, an objective lens driving device according to the present invention includes a support on which an objective lens is mounted, and a center of gravity located away from a mounting portion of the objective lens, which is orthogonal to an optical axis of the objective lens. A movable support member for supporting the support on a plurality of lines extending in a radiation direction at a predetermined angle on a plane to be formed, a magnetic circuit of a closed magnetic circuit including a magnet for generating a magnetic field and a yoke, and cooperation with the magnetic circuit. And a coil for moving the support by moving.

[Action]

With this configuration, the support on which the objective lens is mounted is supported in the direction of the center of gravity by the movable support member, and is rotated about the center of gravity. The support is composed of a magnet and a yoke. The vertical and rotational forces are applied by the cooperation of the coil and the magnetic circuit of the closed magnetic circuit, so that the support moves smoothly in the vertical direction by the movable support member in a stable state without any attractive force from the outside. Alternatively, the objective lens is rotated, so that the objective lens is accurately moved in the forcible direction or the tracking direction.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the drawing, reference numeral (11) denotes an objective lens, which is attached to a support (12). The support (12) is moved vertically and horizontally with respect to the base (14) by a movable support member (13), that is, the objective lens ( It is movably supported in a direction parallel to the optical axis (focus direction) and in a direction perpendicular to the optical axis (tracking direction).

A concave portion (12b) is formed on the lower surface of a portion of the support (12) remote from the lens mounting portion (12a), and a magnetic circuit (15) forming a closed magnetic circuit is provided. This magnetic circuit is composed of a yoke (16) and a magnet piece (17), and the yoke (16) has leg pieces (16b) protruding downward from each corner of the substantially quadrangular plate (16a). The magnet piece (17) is cylindrical and is bisected in the axial direction. The yoke (16) is fixed to the support (12) by projecting its leg (16b) into the recess (12a), and is fixed downward to the center of the plate (16a). A magnetic circuit (15) is formed by fixing a magnet piece (17) to a magnetic pin (18) projecting from the center of the concave portion (12a).

The magnetic circuit (15) configured as described above is fitted to the drive coil (19) fixed to the base (14) to form an electromagnetic drive means.

The drive coil (19) includes four tracking coils (21) wound in a substantially quadrilateral shape on the outer peripheral surface of a focus coil (20) wound in a cylindrical shape, and leg portions of the above-described yoke (16). It is configured by joining corresponding to (16b). Although not shown, lead wires for the drive coil (19) and terminals thereof are provided on the base (14).

In this configuration, the center of the portion where the magnetic circuit (15) is provided becomes the center of gravity of the support (12), and in this example, the support (12) is supported on the base (14). The movable support member (13) is attached at a required angle (a sharp angle, for example, 10 ° to 30 °) from the center of gravity on an extension line in the radiation direction.

The movable support member (13) is composed of a pair of vertically parallel left and right arm portions that support the support body (12) at one end side in the same manner as previously proposed by the present applicant (Japanese Patent Application No. 1-110258). (13
a), (13b) and a connecting portion (13c) connecting the other ends of both arms (13a) and (13b), and both arms (13a) and (13b) are supported. It is fixed to the body (12) on the above-mentioned extension line in the radiation direction, that is, is fixed to the support (12) in an inverted C-shape.
c) is fixed to the mounting portion (14a) of the base (14).

The number of the arm portions of the movable support member (13) is not limited to a pair on the left and right sides, and may be three or more.

The objective lens driving device of this example configured as above is
The support (12) to which the objective lens (11) is attached is the base (14)
The upper and lower and horizontal directions are
It is movably supported in the axial direction, and when a required focus current is supplied to the focus coil (20) of the drive coil (19), the support coil (12) moves up and down in cooperation with the magnetic flux of the magnetic circuit (15). This support is driven and displaced in the direction parallel to the optical axis of the objective lens (11) by the vertical movement of the support member (13), that is, the vertical swing, thereby focusing the light beam. . The tracking coil (21)
When the required tracking current is supplied to the support (12)
, A rotational force acts on the magnetic circuit (15), and as shown in FIG. 3, the respective arms (13a) and (13b) of the support member (13) operate in the lateral direction. That is, by swinging in the horizontal direction, the support (12) is rotated, and the objective lens (11) attached to a portion distant from the center of rotation is driven and displaced in a direction orthogonal to the optical axis. Tracking of the light beam is performed.

In this operation, the support (12) is moved by the movable support member (1).
3) It is supported in the direction of the center of gravity, so that it is stably supported and swings accurately in the vertical direction, and is stably rotated in the horizontal direction around the center of gravity, and the support (12)
The vertical and pivotal forces act on the drive coil (19) in cooperation with the magnetic circuit (15) of the closed magnetic path composed of the yoke (16) and the magnet piece (17). (12a) can be accurately and reliably moved in the vertical and horizontal directions in a stable state without any suction force from the outside, so that focusing and tracking can be performed accurately and reliably.

As the material of the support (12), various materials can be used as long as it is a non-magnetic material, and it is particularly preferable to use a lightweight material.

Further, the magnet (17) of the magnetic circuit (15) is not limited to a two-part cylinder, but may be formed in a continuous cylinder and the magnetization direction may be adjusted.

FIG. 4 shows another embodiment, in which the support (2
2) is made of a heat-resistant and highly rigid synthetic resin such as ABS resin in the shape of a box, and the objective lens (11) is fitted and held on its upper surface with the optical axis up and down. An optical pickup unit including a semiconductor laser as a light source, a beam splitter and a reflection mirror for guiding a light beam from the semiconductor laser to an objective lens, and a photodetector such as a photodetector for detecting a return beam reflected from an optical disk through the beam splitter ( 22) is built-in, and a focus coil (24) is wound around the outer circumference. A tracking coil (25) wound in a substantially rectangular shape at each corner of the focus coil (24) is joined onto this coil (24). And so on.

The yoke (26) is formed as a frame having a size surrounding the support (22) at a required interval, and the focus coil (24) and the tracking coil (2)
A magnet (27) is fixed to face 5), and a magnetic circuit is formed by the magnet (27) and the yoke (26).

The movable support member (28) for supporting the support (22) with respect to the yoke (26) as a base is formed in the same manner as in the above-described embodiment.

In this embodiment thus configured, the support (22) is moved up and down and in the horizontal direction to perform focusing and tracking operations, similarly to the above-described embodiment.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and can be variously modified without departing from the gist of the present invention.

〔The invention's effect〕

As described above, according to the present invention, since the support on which the objective lens is mounted is supported by the movable support member in the direction of the center of gravity, it is stably moved in the focusing direction and the tracking direction, and the support has a yoke. The vertical and rotational forces act by the cooperation of the coil and the magnetic circuit of the closed magnetic path composed of the magnet and the support, so that the support is smoothly driven without the attraction force from the outside and acts on the object. The focusing and tracking of the lens can be performed accurately, and the reliability is significantly improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an example of an objective lens driving device according to the present invention, FIG. 2 is a longitudinal sectional view, FIG.
The figure is a longitudinal sectional view of another example, and FIG. 5 is a perspective view of a conventional example. In the figure, (11) is an objective lens, (12) and (22) are supports,
(13) and (28) are movable support members.

Claims (1)

(57) [Claims] 1. A support on which an objective lens is mounted, and extending in a radiation direction at a predetermined angle on a plane orthogonal to the optical axis of the objective lens, with a center of gravity at a distance from a mounting portion of the objective lens. A movable support member for supporting the support on a plurality of lines; a magnetic circuit of a closed magnetic path composed of a magnet for generating a magnetic field and a yoke; and a movable circuit for moving the support in cooperation with the magnetic circuit. An objective lens driving device including a coil.