JPH0772945B2 - Objective lens drive - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device of an apparatus for optically writing or reading information.

2. Description of the Related Art An objective lens driving device drives an objective lens in two axes of a focus direction and a tracking direction in order to correct a focus shift due to vertical movement of a warp of a disk-shaped recording medium such as a compact disc or a tracking shift due to eccentricity. .

A conventional objective lens driving device of this type has a structure as shown in FIG.

That is, in the driving in the tracking direction (Tr), the lens holder 2 to which the objective lens 1 is attached and the second movable portion 3 connected by the leaf springs 4a, 4b, 4c and 4d are magnets 8a and 8c and the magnetic yokes 7a and 7c.
It is obtained by rotating around the shaft 5 by an electrodynamic converter in which the tracking coil 10 is arranged in the air gap of the magnetic circuit.

For driving in the focus direction, the lens holder 2 to which the objective lens 1 is attached is driven by an electrokinetic converter in which the focusing coil 9 is arranged in the air gap of the magnetic circuit composed of the magnets 8a and 8b and the magnetic yokes 7a and 7b. It is obtained by moving via the springs 4a, 4b, 4c, 4d.

In addition, the entire objective lens driving device is access-driven by a motor in the access direction Ad (the same direction as the tracking direction) on the recording medium.

Problems to be Solved by the Invention In the structure as shown in FIG. 4, the lens holder 2 to which the objective lens 1 is attached and the second movable portion 3 are the leaf springs 4a, 4b, 4c, 4.
Since it is connected by d, it becomes difficult for the leaf spring itself to maintain rigidity in the tracking direction when the entire objective lens driving device is moved in the access direction by the motor or due to the impact force in the tracking direction from the outside. , For example, vibrates together with the first movable portion as shown in FIG.

For example, when stainless steel having a width of 3 mm, a length of 14 mm, and a thickness of 0.06 mm is used for the leaf spring, the above resonance occurs at 2300 Hz, and the first movable portion sways in the tracking direction.

In this way, since the leaf spring is weak in the lateral direction, the impact force may cause skipping during movement of the compact disc player, and a recording error may occur during data writing in the data recording system. It was the current situation that a structure for absorbing the impact force had to be separately provided in the system for mounting the device.

Therefore, the present invention provides a stable objective lens driving device that is not affected by such impact force.

Means for Solving the Problems The technical means of the present invention for solving the above problems includes the first and second movable parts so that only the first movable part is movable in the focus direction. In the vicinity of the center of the length of the pair of leaf springs lined up in the tracking direction, connected by four parallel leaf springs of the same shape to increase the rigidity in the tracking direction and strengthen the impact force in this direction. It is configured to use two leaf springs connected to each other.

Operation The effects of this technical means are as follows.

When the objective lens driving device is vibrated in the access direction from the outside, the leaf spring is deformed.However, if the connecting portion is provided in the vicinity of the center of the leaf spring, the leaf spring may be deformed and the connecting portion itself may be deformed. I have to know.

Here, if a wide leaf spring or a rod-shaped rigid body that is strong against bending in the tracking direction is used for this connecting portion, the connecting portion does not cause bending, and therefore the rigidity in the tracking direction becomes very large.

Therefore, it becomes very strong against the impact force in the access direction.

Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 (A) is a plan view of an objective lens driving device according to an embodiment of the present invention, and FIG. 1 (B) is a front portion thereof. In FIG. 1, a lens holder 2 holding a lens 1 and a second movable portion 3 supported by a shaft 5 are connected by leaf springs 14a and 14b.

The movement in the tracking direction (Tr) is caused by the magnetic yokes 7a and 7c.
The magnetic circuit composed of the magnets 8a and 8c and the driving force generated from the coil 10 cause rotational movement about the shaft 5 from the base 11.

Here, the leaf springs 14a and 14b are two leaf springs of the same shape that connect the lens holder 2 and the second movable portion 3, respectively, and the movement in the focus direction (Fo) is caused by the magnetic yokes 7a and 7b and the magnet 8.
The driving force generated from the magnetic circuit focusing coil 9 composed of a and 8b makes it movable via the leaf springs 14a and 14b.

In this way, the first movable part that mounts the objective lens and exerts the driving force in the focus direction and the second movable part that does not move in the focus direction are connected by four leaf springs of the same shape. Therefore, when the objective lens is driven in the focus direction, the deflection of the leaf spring in the focus direction allows the objective lens to translate in the focus direction, and the optical axis of the objective lens and the disk-shaped recording medium do not tilt, so that the Stable characteristics can be maintained.

The leaf springs 14a and 14b each have a shape as shown in FIG. 2 which is connected in the vicinity of the center of the length of the leaf spring, and the connecting portion has a strong shape against bending in the tracking direction. Do not bend as shown. Therefore, the rigidity in the tracking direction becomes very large, and the rigidity in the access direction becomes very strong.

If a leaf spring having the same thickness is used for this connecting portion as shown in FIG. 2 (A), it can be formed by punching, etching, etc., and processing becomes easy. If a rod-shaped rigid body is used for this connecting portion as shown in FIG. 2 (B), the rigidity in the tracking direction becomes greater and the impact force in the access direction becomes stronger.

EFFECTS OF THE INVENTION The present invention provides an objective lens drive device of a type in which drive in the focus direction is obtained by moving a movable part in the focus direction via four parallel leaf springs of the same shape,
By connecting the two leaf springs arranged in the tracking direction in the vicinity of the center of the leaf spring, the rigidity of the leaf spring in the tracking direction becomes very high.

For this reason, the number of parts can be reduced, and at the same time, there is no effect of the movement in the access direction at the time of high-speed access and the impact force in the access direction from the outside. Therefore, the system for mounting the objective lens driving device can be easily designed. Can be done.

[Brief description of drawings]

FIG. 1 (A) is a plan view of an objective lens driving device according to an embodiment of the present invention, FIG. 1 (B) is a front view of the objective lens driving device, and FIGS. 2 (A) and 2 (B) are the same. FIG. 3 is a perspective view of a leaf spring used in the objective lens driving device, FIG. 3 is a plan view of a main part showing the function of the leaf spring, and FIG. 4 (A) is a plan view of a conventional objective lens driving device. ) Is a front view of the same, and FIG. 5 is a plan view of the same main part. 1 ... Lens, 2 ... Lens holder, 3 ... Second movable part, 5 ... Shaft, 6 ... Elastic material, 7a to 7c ... Magnetic yoke,
8a to 8c ... Magnet, 9 ... Focus coil, 10 ... Tracking coil, 11 ... Base, 14a, 14b ... Leaf spring.

Claims (3)

[Claims] 1. An objective lens of an apparatus for optically writing or reading information on a recording medium is arranged in a direction perpendicular to the surface of the recording medium, that is, a focus direction which is an optical axis direction, and a radial direction which is perpendicular to the optical axis. A first movable part composed of the objective lens and a lens holder, and a second movable part rotatably fixed only in the tracking direction by an axis or a pivot. The center of gravity of all the movable parts is located on the shaft or the pivot part, and one or a plurality of members for returning to the original position after the first and second movable parts move in the tracking direction. A spring material, one or more focusing magnetic circuits for driving the first movable portion in the focus direction, and one for driving the first and second movable portions in the tracking direction. Alternatively, the plurality of magnetic circuits for tracking and the first and second movable parts are composed of four parallel leaf springs having the same shape so that only the first movable part can be moved in the focus direction. An objective lens driving device, characterized in that a pair of leaf springs connected to each other and aligned in the tracking direction are joined near the center of the leaf spring length. 2. The objective lens driving device according to claim 1, wherein a pair of leaf springs are connected by a leaf spring having the same thickness. 3. The objective lens driving device according to claim 1, wherein a pair of leaf springs is connected by a rod-shaped rigid body.