JP2000113477A - Objective lens drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driving device securing the fine vibration property while keeping the high acceleration performance, by eliminating the balance weight of a movable part. SOLUTION: The centroidal position F of a focusing coil 3 of this device in the direction of an optical axis of the objective lens is moved to the lower side in the direction of the optical axis of the objective lens 1 than the centroidal position G of the whole movable part. By this arrangement, the centroid G of the whole movable part, a support center P by an elastic supporting member 8 and a center T of the tracking drive force are made to coincide in spite of that the balance weight is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used for an optical disk device.

[0002]

2. Description of the Related Art An example of an objective lens driving device used in an optical disk device is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-128559.
The one described in Japanese Patent Application Laid-Open Publication No. H10-260, 1993 is known. 5 and 6 show the configuration of a basic objective lens driving device. FIG. 5 is a cross-sectional configuration diagram of a conventional objective lens driving device.
FIG. 6 is a top view of the objective lens driving device.

The objective lens 1 is held by a lens holder 2, and a focusing coil 3 is wound around the lens holder 2 in a substantially rectangular shape with the objective lens 1 being substantially at the center.
A tracking coil 4 is attached to the outer surface of the focusing coil 3 in the tangential direction of the optical disk.

[0004] Four parallel linear elastic support members 8 (lower side 8a, upper side 8b) have one ends thereof connected to the lens holder 2.
The other end is fixed to a fixing portion, and the lens holder 2 on which the objective lens 1 is disposed is elastically supported so as to be movable in the focusing direction and the tracking direction.

A magnetic circuit composed of a magnet 6 and a yoke 7 is arranged on a fixed portion to which one end of the elastic support member 8 is fixed, and a driving current flowing through the focusing coil 3 and the tracking coil 4 is supplied from the magnetic circuit. It is arranged to act on the generated magnetic flux.

A balance weight 5 is provided on the lower surface of the lens holder 2.
The center of gravity G of the entire movable part in the optical axis direction of the objective lens 1 is determined by the center T of the driving force generated by the driving current flowing through the tracking coil 4 and the rigidity balance of the four elastic support members 8. It is configured such that the determined support center position P matches.

At the time of focusing control, an electric current is appropriately supplied to the focusing coil 3 in accordance with the deflection of the recording surface of the optical disk, the objective lens 1 is operated in the optical axis direction, and the spot of the light beam is focused on the recording surface of the optical disk. Can be followed.

At the time of tracking control, the tracking coil 4 is controlled in accordance with the eccentricity and meandering of the track of the optical disk.
The objective lens 1 can be operated in a direction perpendicular to the optical axis by supplying an appropriate current to the optical disk so that the spot of the light beam follows the track of the optical disk.

At this time, the center T of the driving force generated in the tracking coil 4, the position G of the center of gravity of the entire movable part, and the support center position P determined by the rigidity balance of the four elastic support members substantially coincide with each other. Further, the movable portion on which the objective lens 1 is disposed does not tilt in the radial direction of the optical disk due to the tracking driving force, and the tracking operation can be performed stably.

[0010]

In recent years, it has been demanded that the objective lens driving device has not only high acceleration characteristics but also good vibration characteristics. For this reason, it is necessary to eliminate waste of the movable portion of the objective lens driving device as much as possible, and to eliminate components that can be removed, thereby reducing the weight of the entire movable portion.

To realize an objective lens driving device having good vibration characteristics, the weight of the movable portion of the objective lens driving device is balanced, and the center of support of the movable portion, the position of the center of gravity of the movable portion, and the focusing drive It is necessary to make the driving center of the force and the tracking driving force substantially coincide with each other in the direction of the driving force.

In general, a balance weight is disposed on the movable portion of the objective lens driving device according to the prior art on the opposite side of the objective lens with respect to the center of gravity of the movable portion, whereby the weight of the movable portion is balanced. . In other words, the center of the focusing driving force, the position of the center of gravity of the movable portion, and the center of support of the movable portion substantially match, and the center of the tracking drive force, the position of the center of gravity of the movable portion, and the center of support of the movable portion substantially coincide. I do. Therefore, unnecessary torque is hardly generated in the movable portion by each driving force, and as a result, a good vibration characteristic is obtained.

However, this balance weight has only a function as a balance weight, and is an inefficient component for obtaining high acceleration characteristics when viewed from the objective lens driving device.

As described above, in the configuration of the conventional objective lens driving device described above, there are inefficient parts having only the function of the balance weight only in the movable part, and the efficiency is low to obtain high acceleration characteristics. There is a disadvantage that it is very difficult to obtain the above acceleration characteristics.

In order to solve the above-mentioned drawbacks, the present invention provides an objective lens driving device which realizes high acceleration characteristics and has good vibration characteristics by eliminating parts having only a function of only a balance weight. It is intended to be.

[0016]

The object of the present invention is to provide an objective lens for condensing a light beam on an optical disk, a focusing coil for driving the objective lens in the optical axis direction,
A tracking coil for driving the objective lens in the radial direction of the optical disc; a movable section including a lens holder for holding the objective lens, the focusing coil, the tracking coil, and the like; and a movable section having one end fixed to the movable section. At least one or more elastic support members for elastically supporting the elastic support member, a fixing portion to which the other end of the elastic support member is fixed, and at least one or more magnets for generating a driving force on the drive coil, The center of gravity of the focusing coil in the direction of the optical axis of the objective lens,
This is achieved by a first means which is set so as to be located on the side opposite to the optical disc with respect to the center of gravity of the entire movable portion.

The above object is also achieved by an objective lens for condensing a light beam on an optical disk, a focusing coil for driving the objective lens wound substantially in a square around the objective lens in the optical axis direction, A tracking coil disposed on each surface of the focusing coil in the tangential direction of the optical disc for driving the objective lens in a radial direction of the optical disc; At least a magnetic circuit comprising a magnet and a yoke, wherein the center of gravity of the focusing coil in the direction of the optical axis of the objective lens is set so as to be located on the side opposite to the optical disc with respect to the center of gravity of the entire movable part. This is achieved by the second means.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram of an objective lens driving device according to a first embodiment of the present invention, and FIG. 2 is a top configuration diagram of the objective lens driving device.

As shown in these figures, the lens holder 2
, An objective lens 1, a focusing coil 3, a tracking coil 4, and the like are arranged. The movable portion (lens holder 2) is supported by a plurality of elastic support members 8, and one end of the elastic support member 8 is connected to the movable portion, and the other end is connected to the fixed portion 9, respectively.

The elastic support member 8 is made of a conductive material,
The fixed part 9 is electrically connected to the focusing coil 3 and the tracking coil 4 disposed on the movable part, respectively.
Via the conductive elastic support member 8 (8a, 8b)
The focusing coil 3 and the tracking coil 4 are energized.

The fixed portion 9 has a magnet 6 and a yoke 7
And a drive current flowing through the focusing coil 3 and the tracking coil 4 is arranged so as to act on a magnetic flux generated from the magnetic circuit.

Here, the position F of the center of gravity of the focusing coil 3 in the direction of the optical axis of the objective lens is the position G of the center of gravity of the entire movable part.
It is located on the lower side in the optical axis direction of the objective lens 1, that is, on the opposite side to the objective lens 1 or on the opposite side to the optical disk.

By appropriately moving the focusing coil 3 downward, the center of gravity G of the entire movable part and the optical axis of the objective lens 1 of the tracking coil 4 can be obtained without the balance weight 5 (see FIG. 5). The center position T in the direction can be substantially matched, and the center of gravity G of the entire movable part can be substantially matched with the support center P determined by the rigidity balance of the elastic support member 8 supporting the movable part.

Therefore, there is no component having only a function as a balance weight, and the movable portion is an aggregate of functional components. Therefore, the entire movable portion can be reduced in weight by the weight of the balance weight, and high acceleration characteristics can be obtained. This is an advantageous configuration.

Next, the operation of the driving device will be described. The objective lens 1 is driven by appropriately supplying a driving current to the focusing coil 3 and the tracking coil 4 to adjust the position with respect to the vertical runout of the optical disc, the meandering of the track, and the eccentricity of the track. Control is performed so that the spot of the focused light beam is always located on the track on the recording surface of the optical disk.

The movable portion of the objective lens driving device has a focusing coil 3 located below the position G of the center of gravity of the entire movable portion.
The center of gravity G of the entire movable part, the support center position P, and the center of the focusing driving force and the center of the tracking driving force T substantially match each other in each driving direction.

Therefore, unnecessary rotational torque for rotating the entire movable portion around its center of gravity is hardly generated for both the focusing driving force and the tracking driving force. As a result, unnecessary vibration is generated. , And good vibration characteristics can be obtained.

FIG. 3 is a sectional view of an objective lens driving device according to a second embodiment of the present invention, and FIG. 4 is a top view of the objective lens driving device. In this embodiment, the objective lens 1 is arranged at a position distant from the center of the movable section in the tangential direction of the optical disc.

Also, the focusing coil 3 disposed at the substantially central portion of the movable portion has its center of gravity F located below the center of gravity G of the entire movable portion, as in the first embodiment. Thus, the entire movable part is balanced without the balance weight. The tracking coil 4 is arranged on the surface of the focusing coil 3.

In this embodiment, as in the first embodiment, there is no component having only a function as a balance weight. In other words, the movable part is an aggregate of functional parts, and the entire movable part can be reduced in weight by the weight of the balance weight, which is advantageous for obtaining high acceleration characteristics and good while realizing high acceleration characteristics. Vibration characteristics can be secured.

[0031]

As described above, according to the present invention, the balance weight is eliminated from the movable portion of the objective lens driving device, and the position of the center of gravity of the focusing coil in the direction of the optical axis of the objective lens is made smaller than the position of the center of gravity of the entire movable portion. By moving downward, the entire movable part is balanced. Therefore, the center of the driving force substantially coincides with the center of gravity of the movable portion, and the entire movable portion can be reduced in weight while maintaining good vibration characteristics without generating unnecessary rotational torque, and high acceleration characteristics are realized. easy.

Further, since the conventional balance weight is deleted, the number of parts can be reduced by the balance weight, so that the number of assembly steps and the cost of parts can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram showing a first embodiment of an objective lens driving device according to the present invention.

FIG. 2 is a top view of the objective lens driving device.

FIG. 3 is a sectional view showing a second embodiment of the objective lens driving device according to the present invention.

FIG. 4 is a top view of the objective lens driving device.

FIG. 5 is a cross-sectional configuration diagram of a conventional objective lens driving device.

FIG. 6 is a top view of the objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Focusing coil 4 Tracking coil 5 Balance weight 6 Magnet 7 Yoke 8 Elastic support member 9 Fixed part

Claims (2)

[Claims] 1. An objective lens for condensing a light beam on an optical disk, a focusing coil for driving the objective lens in an optical axis direction, a tracking coil for driving the objective lens in a radial direction of the optical disk, and the objective lens A movable part comprising a lens holder for holding the focusing coil, the tracking coil, and the like; an elastic support member having one end fixed to the movable part and elastically supporting the movable part; A fixed portion to be fixed, and a magnet for generating a driving force to the drive coil, wherein the center of gravity of the focusing coil in the direction of the optical axis of the objective lens is opposite to the center of gravity of the entire movable portion. 2. An objective lens driving device, wherein: 2. An objective lens for condensing a light beam on an optical disk, a focusing coil for driving the objective lens wound substantially in a quadrangle around the objective lens in the optical axis direction, and the focusing coil A tracking coil disposed on each surface in the tangential direction of the optical disc to drive the objective lens in the radial direction of the optical disc; and a magnet configured to sandwich the effective portion of the tracking coil and the tangential portion of the focusing coil in the optical disc. And a magnetic circuit comprising a yoke, wherein the center of gravity of the focusing coil in the direction of the optical axis of the objective lens is set so as to be located on the side opposite to the optical disc with respect to the center of gravity of the entire movable part. Characteristic objective lens driving device.