JP2001331956A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driving device capable of attaining miniaturization and a thin shape by remarkably improving all driving sensitivity of triaxial driving of focusing, tracking and tilting. SOLUTION: Driving coil blocks 10a, 10b are disposed on a fixing base 5 symmetrically in the radial direction r of a disk relative to an objective lens 1. Magnets 3a-3d are arranged in a movable body 4 so as to face both side surfaces in the tangent direction t of the recording track of the disk of respective driving coil blocks 10a, 10b. Since the both surfaces of the driving coil blocks 10a, 10b are utilized in focusing driving, tracking driving and radial tilt driving, the effective part of the coil is doubled and driving sensitivity is remarkably improved.

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 for an optical head used in an optical recording / reproducing device or the like. In particular, the present invention relates to a three-axis driven objective lens actuator having a function of correcting an inclination of an optical axis with respect to a disk.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in the technical development of information recording / reproducing apparatuses for higher density, higher speed, thinner and lower cost, and optical information is recorded on a disk-shaped record carrier. Numerous approaches have also been made to a so-called optical disk recording / reproducing apparatus for reproducing.

In the optical disk recording / reproducing apparatus, if a tilt, which is a relative inclination of the optical axis of the objective lens with respect to the disk surface, occurs, an optical aberration is generated, which causes deterioration of a signal at the time of recording / reproducing. For this reason, recently, in order to correct the relative inclination between the disk and the optical axis of the objective lens, in addition to the focusing deviation due to the vertical movement of the surface deflection of the disk and the tracking deviation due to the eccentricity of the recording track,
There has been proposed an objective lens driving device that drives an objective lens in three axes, that is, a focusing direction, a tracking direction, and a rotation direction (hereinafter, a radial tilt direction) around a tangential direction of a recording track of a disk.

A conventional objective lens driving device of this type is disclosed, for example, in Japanese Patent Application Laid-Open No. 9-022537. FIG. 4 is a schematic plan view for explaining the configuration and operation of this conventional example.

Referring to FIG. 4, the configuration will be described. The objective lens 1, the lens holder 2 holding the objective lens 1, and the direction of magnetization in the tangential direction t of the recording track of the disk, symmetrically disposed in the tangential direction t with respect to the objective lens 1, and fixed to the lens holder 2. The movable body 4 is composed of the two magnets 3a and 3b. Parallel ends 4 fixed at one end to the movable body 4 and at the other end to the fixed base 5
The movable body 4 is held on the fixed base 5 via the metal wires 6a to 6d (6c and 6d are not shown because they overlap in the drawing). The drive coil blocks 10a and 10c are spaced apart from the magnets 3a and 3b, respectively, so as to face the magnetic pole surface on one side of the magnet 3a, and the drive coil blocks 10b and 10d are facing the magnetic pole surface on one side of the magnet 3b. Are located. Drive coil blocks 10a-
10d is a focusing drive coil 8a to 8d wound around magnetic yokes 7a to 7d (not shown) and having a winding axis in the optical axis direction L of the objective lens 1, and wound in the radial direction r of the disk. It has tracking drive coils 9 a to 9 d having a rotation axis, and is fixedly mounted on the fixed base 5. In FIG. 4, reference numeral 20 denotes a virtual line on the outer periphery of the disk.

With the above configuration, when driving in the focusing direction is performed, the driving coil block 10a
Focusing drive coils 8a to 8d within 10 to 10d
The current is supplied so that the generated driving forces are all in the same direction. When driving in the tracking direction T, current is supplied to the tracking drive coils 9a to 9d such that the generated driving forces are all in the same direction. On the other hand, when driving in the radial tilt direction RT, the focusing drive coil 8a on one side with respect to the tangent t of the recording track of the disk passing through the optical axis of the objective lens 1 is used.
8b and focusing drive coils 8c and 8d on the other side
At this time, currents that cause the generated driving forces to be opposite to each other are applied while being superimposed on the current for performing the focusing drive.

[0007]

However, in an optical disk recording / reproducing apparatus, recording / reproducing has been increasingly performed with a smaller diameter condensed spot using an objective lens having a high aperture ratio in order to realize a higher density. . In this case, the degree of aberration generated by the tilt, which is the relative inclination of the optical axis of the objective lens with respect to the disk, increases in proportion to the cube of the aperture ratio. Higher precision positioning is required at the optical axis angle.

[0008] In addition to the above, as the speeding up and miniaturization of the apparatus progress, there is a demand for an improvement in the following capability of the objective lens driving apparatus.
It is essential to have a small and powerful drive mechanism.

However, the above-mentioned prior art disclosed in Japanese Patent Application Laid-Open
In order to obtain a tilt correction function corresponding to high density, the objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 22537/2005 obtains a driving coil block of a conventional two-axis objective lens driving device by dividing the driving coil block in the radial direction by a tangent t. Therefore, the effective magnetic flux and the effective coil length are reduced, and the drive sensitivity has to be reduced. Further, since the driving force is obtained by using only one magnetic pole surface of the magnets 3a and 3b and one side surface of the drive coil blocks 10a to 10d, the driving efficiency with respect to the weight of the movable body is deteriorated.

Further, since the focusing drive coils (also used as tilt drive coils) 8a and 8c and 8b and 8d divided by a tangent t passing through the optical axis of the objective lens are adjacent to each other, each divided focusing is performed. The distance between the point of application of the driving force of the drive coil and the tilt rotation axis cannot be increased, so that the radius of curvature with respect to the tilt rotation axis decreases, and it is difficult to obtain a large rotation moment as the tilt driving force.

Further, since there are four drive coil blocks, the cost is increased, and the work of processing the starting and ending of the focusing drive coil and the tracking drive coil wound therearound is difficult, resulting in poor assembling workability. There was a problem.

In order to solve the above-mentioned problems of the conventional objective lens driving apparatus, the present invention has a tilt correction function and dramatically increases the driving sensitivity of all three-axis driving of focusing, tracking and tilting. ,
It is still another object of the present invention to provide an objective lens driving device that can be reduced in size and thickness.

[0013]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention relates to a conventional four-wire suspension type moving magnet type three-axis driven objective lens driving device, and particularly to a magnet and a driving coil block. Are arranged as follows.

That is, the driving means for driving the objective lens in three axes includes a focusing drive coil wound around a yoke made of a magnetic material and having a winding axis in the optical axis direction of the objective lens, and a focusing drive coil in the radial direction of the disk. It comprises a pair of drive coil blocks each provided with a tracking drive coil having a winding axis. The pair of drive coil blocks are arranged symmetrically in the radial direction of the disk with respect to the objective lens, and are fixedly mounted on a fixed base. The magnet fixed to the lens holder has a magnetization direction in the tangential direction of the recording track of the disk, and the same polar face is opposed to both side surfaces of the drive coil block in the tangential direction of the recording track of the disk. The drive coil block is disposed so as to sandwich the drive coil block at a predetermined distance from the drive coil block. A current is supplied to the focusing drive coils in the pair of drive coil blocks so that the generated driving forces are opposite to each other, thereby rotating the disk around the tangential axis of the recording track, that is, in the radial tilt direction. Is driven.

According to the present invention, since the magnets are arranged on both side surfaces of each drive coil block, the drive sensitivity can be improved. For example, in the case of performing the radial tilt drive, since the radial tilt drive is performed using both side surfaces of the focusing drive coil in the drive coil block, the coil effective portion is twice as large as the conventional one, and the drive sensitivity can be dramatically improved. Further, since the drive coil block is disposed at a position distant from the tilt rotation axis, a large rotational moment can be obtained as a tilt driving force.

Further, the objective lens driving device of the present invention preferably has four magnets, and it is preferable that the total center of gravity of these magnets coincides with the center of gravity of the movable body. Thereby, good frequency characteristics without unnecessary resonance can be obtained.

In the objective lens driving device of the present invention, it is preferable that the lens holder, the magnet, the support member, and the fixed base are integrally formed. As a result, the number of parts and the number of assembly steps can be reduced, and the cost can be reduced.

Preferably, the magnets are arranged symmetrically with magnetic poles different from each other with respect to the tangential axis of the recording track of the disk passing through the center of the objective lens. Thereby, the driving force can be improved.

[0019]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1A is a schematic plan view of an objective lens driving device according to Embodiment 1 of the present invention, and FIG. 1B is a side view thereof. Here, the same operation as the conventional example,
The same numbers are given to parts having functions.

The configuration will be described. A movable body 4 having an objective lens 1, a lens holder 2 holding the objective lens 1, and magnets 3 a to 3 d fixed to the lens holder 2 is fixed to a fixed base 5, one end is fixed to the movable body 4, and the other end is fixed to the movable base 4. Four parallel metal wires (support members) fixed to the fixed base 5
6a to 6d (in FIG. 1A, the metal wires 6c, 6d overlap with the metal wires 6a, 6b and are not shown. In FIG. 1B, the metal wires 6b, 6d are not shown because they overlap with the metal wires 6a, 6c). It is elastically supported. And wound around magnetic yokes 7a and 7b (not shown).
A pair of driving coil blocks 10a, 10a having focusing driving coils 8a, 8b having a winding axis in the optical axis direction L of the objective lens 1 and tracking driving coils 9a, 9b having a winding axis in the radial direction r of the disk. 10b is fixedly mounted on the fixed base 5 in a state where it is symmetrically arranged in the radial direction r of the disk with respect to the center of the objective lens 1.
The magnets 3a, 3b and the magnets 3c, 3d fixed to the movable body 4 all have a magnetization direction in the tangential direction t of the recording track of the disk, and the drive coil block 1
The drive coil blocks 10a and 10b are separated by a predetermined distance from the drive coil blocks 10a and 10b, with the N pole faces facing both sides in the tangential direction t of the recording track of each disk of the drive coil blocks 10a and 10b. It is arranged in a sandwiched state. In FIG. 1A, reference numeral 20 denotes a virtual line on the outer periphery of the disk. In the present invention, the disk is not particularly limited, and a known disk having recording tracks formed concentrically or spirally can be used. Also, the radius r of the disk and the tangent t of the recording track
Means the radius of the disk passing through a point on the disk where the optical axis of the objective lens 1 intersects, and the tangent to the recording track at that point.

An optical path connecting the light emitting element and the light receiving element (not shown) to the objective lens 1 is formed by forming a through hole in a region of the fixed base 5 facing the objective lens 1 as in the prior art. This can be ensured by arranging a reflection mirror on the side opposite to the lens 1. Alternatively, it may be ensured by disposing a prism between the objective lens 1 and the fixed base 5 as in a third embodiment described later.

The operation of the objective lens driving device configured as described above will be described below. When driving in the focusing direction (optical axis direction L), current is supplied to each of the focusing drive coils 8a and 8b in the two drive coil blocks 10a and 10b so that the generated driving force is in the same direction. I do. When driving in the tracking direction T, the tracking drive coil 9 is used.
A current is supplied to a and 9b so that the generated driving force is in the same direction. On the other hand, when driving in the radial tilt direction RT, the two drive coil blocks 10a, 10
b, each focusing drive coil 8a, 8b
Currents such that the generated driving forces are opposite to each other are superimposed on the current for performing the focusing drive and applied.

Therefore, according to the first embodiment, the magnets 3a, 3b and the magnets 3c, 3c are provided on both side surfaces so as to sandwich the drive coil blocks 10a, 10b.
d, the driving coil 8 is used in all of the driving of focusing, tracking, and tilting.
a, 8b or both surfaces of the drive coils 9a, 9b can be used for driving, and the drive sensitivity can be improved. For example, in the radial tilt drive, a driving torque in the radial tilt direction RT is generated because both side surfaces of the focusing drive coils 8a and 8b wound around the respective drive coil blocks 10a and 10b in the tangential line t direction are used. The number of coil effective portions to be made is twice as large as that of the conventional one, so that the drive sensitivity can be dramatically improved. Further, the drive coil blocks 10a and 10b are set with a radius r with the objective lens 1 interposed therebetween.
By arranging them apart in the direction, the point of application of the driving force for radial tilt is located at a position away from the tilt rotation axis, so that a large rotational moment can be generated as the tilt driving force.

Further, the drive coil blocks 10a, 10a
Since the number of b is two, it is possible to reduce the number of components and the number of processing steps for starting and ending the coil.

In the first embodiment, by matching the overall center of gravity of the four magnets 3a to 3d with the center of gravity of the movable body 4, unnecessary resonance is prevented from occurring and good frequency characteristics are obtained. Obtainable.

In the first embodiment, the lens holder 2, the four magnets 3a to 3d, the four metal wires 6a to 6d, and the fixed base 5 are integrally formed by insert molding or the like. By doing so, it is possible to provide a three-axis driven objective lens driving device which is excellent in mass productivity with reduced assembly man-hours and reduced assembly variations.

(Embodiment 2) FIG. 2 is a schematic plan view showing the configuration of a movable section 4 and its periphery of an objective lens driving device according to Embodiment 2 of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the second embodiment, the four magnets 3a to 3d fixed to the lens holder 2 are connected to the objective lens 1
The magnetic poles of the two magnets 3c and 3d arranged on one side and the magnetic poles of the two magnets 3a and 3b arranged on the other side with respect to the tangential t-direction axis of the recording track passing through the center of They are installed in opposite directions. That is, unlike the first embodiment, the magnets 3c and 3d are installed such that the surfaces facing the drive coil block 10b are both S poles. As a result, the magnetic path Ga is formed by the magnets 3a, 3c and the yokes 7a, 7b arranged at the center of the drive coil blocks 10a, 10b on one side with respect to the disk radial direction r. On the other hand, a magnetic path Gb is formed on the other side by the magnets 3b, 3d and the yokes 7a, 7b arranged at the centers of the drive coil blocks 10a, 10b. Then, on the radius r passing through the center of the objective lens 1, the directions of the magnetic path Ga and the magnetic path Gb coincide. In this case, it is obvious that the directions of the currents for driving in the focusing direction, the tracking direction, and the radial tilt direction are different from those in the first embodiment.

Therefore, according to the second embodiment, the amount of effective magnetic flux can be increased by forming the magnetic paths Ga and Gb, and as a result, the drive sensitivity can be further increased.

(Embodiment 3) FIG. 3A is a schematic plan view of a main part of an objective lens driving device according to Embodiment 3 of the present invention, and FIG. 3B is a side sectional view passing through the optical axis of the objective lens. . The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As described above, in the objective lens driving device of the present invention, the magnets 3a to 3d for obtaining the driving force and the drive coil blocks 10a and 10b are symmetrical in the radial direction r of the disk with the objective lens 1 interposed therebetween. Placed in the position.
Therefore, it is possible to secure a space in a region between the objective lens 1 and the fixed base 5 and in a region extending in the tangential line t direction from the region without causing interference with the components. Therefore, as shown in FIG. 3A and FIG.
A part of the lower surface of the lens holder 2 between a and 3c is cut out, and the rising prism 11 is set on the fixed base 5.
The rising prism 11 is disposed below the objective lens 1 without contact with the lens holder 2 by making the inclination angle of the bottom surface 2a of the cutout portion of the lens holder 2 substantially coincide with the inclination angle of the upper surface of the rising prism 11. It is possible to do. Therefore, the overall thickness of the optical pickup can be reduced as compared with the conventional configuration in which the reflection mirror is arranged on the lower surface of the fixed base 5. In FIG. 3B, reference numeral 12 denotes a principal ray of a light beam for performing recording and reproduction on the disk.

[0033]

As described above, according to the present invention, since the two surfaces of the focusing drive coil in the drive coil block are used, the effective coil portion is doubled, so that the drive sensitivity can be dramatically improved. Further, since the drive coil block is installed at a position distant from the tilt rotation axis, a large rotational moment as a tilt driving force can be obtained.

Further, by matching the center of gravity of the magnet with the center of gravity of the movable body, it is possible to obtain good frequency characteristics without unnecessary resonance.

Further, by integrally molding the parts, the number of parts and the number of assembling steps can be reduced, and the cost can be reduced.

The driving force can be improved by devising the arrangement of the magnetic poles of the magnet.

Further, by securing a space below the objective lens of the lens holder, the thickness of the apparatus can be reduced.

[Brief description of the drawings]

FIG. 1A is a schematic plan view of an objective lens driving device according to a first embodiment of the present invention, and FIG. 1B is a side view thereof.

FIG. 2 is a schematic plan view of a main part of an objective lens driving device according to a second embodiment of the present invention;

FIG. 3A is a schematic plan view of a main part of an objective lens driving device according to a third embodiment of the present invention, and FIG. 3B is a side sectional view thereof.

FIG. 4 is a schematic plan view of a conventional objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3a, 3b Magnet 4 Movable body 5 Fixed base 6a-6d Metal wire 7a, 7b Yoke 8a, 8b Focusing drive coil 9a, 9b Tracking drive coil 10a, 10b Drive coil block 11 Start-up prism T Tracking Direction F Focusing direction L Optical axis direction (same as F) t Disc tangential direction r Disc radial direction RT Radial tilt direction

Claims (4)

[Claims] A movable body comprising an objective lens for irradiating a laser beam onto a disk having concentric or spiral recording tracks, a lens holder for holding the objective lens, and a magnet fixed to the lens holder; A base, one end of which is fixed to the movable body, and the other end of which is fixed to the fixed base for elastically supporting the movable body; and A driving means for moving in a radial direction and rotating about an axis tangential to a recording track of the disk, wherein the driving means is wound around a yoke made of a magnetic material. Done,
A pair of drive coil blocks each including a focusing drive coil having a winding axis in the optical axis direction of the objective lens and a tracking drive coil having a winding axis in the radial direction of the disc, wherein the pair of drive coils The block is arranged symmetrically in the radial direction of the disk with respect to the objective lens, and is fixed to the fixed base.The magnet fixed to the lens holder has a magnetization direction tangential to a recording track of the disk. Have
The drive coil blocks are arranged so as to sandwich the drive coil block at a predetermined distance from the drive coil block, with the same polar faces facing both sides of the drive coil block in the tangential direction of the recording track of the disk, A current is supplied to the focusing drive coil in the drive coil block so that the generated drive forces are opposite to each other, thereby obtaining a rotational drive force about a tangential axis of a recording track of the disk. Objective lens driving device. 2. The objective lens driving device according to claim 1, wherein the magnet is composed of four magnets, and the overall center of gravity of the four magnets coincides with the center of gravity of the movable body. . 3. The lens holder, the magnet,
The objective lens driving device according to claim 1, wherein the support member and the fixed base are integrally formed. 4. The magnet according to claim 1, wherein the magnet is arranged with respect to a tangential axis of a recording track of the disk passing through the center of the objective lens.
4. The objective lens driving device according to claim 1, wherein the magnetic poles are different from each other and are arranged at symmetric positions.