JP2000285490A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the driving sensitivity of a moving magnet type three axial driving objective lens driving device in a four wire suspension type, and to make this device compact, thin and inexpensive. SOLUTION: Magnets 3a and 3b are symmetrically arranged in a disk radial direction (r) at the center of an objective lens 1 so that the surface magnetic fields of both polar faces of the magnets, and the valid magnetic field areas can be made twice as large as those in a conventional manner. Thus, the driving sensitivity of this objective lens driving device can be sharply improved. Also, the arrangement constitution of the objective lens 1 and driving parts is devised so that this objective lens driving device can be made compact, thin and inexpensive.

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 provided in an optical pickup for irradiating a recording medium with a laser beam through an objective lens to optically record, reproduce, or erase information. In particular, the present invention relates to a three-axis driven objective lens driving device having a function of correcting the inclination of the optical axis with respect to the disk.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable technological progress in information recording / reproducing apparatuses, such as higher density, higher speed, thinner, lower cost, and so-called optical disk recording for optically recording / reproducing information on a disk. Many efforts have been made even for playback devices.

In the above optical disk recording / reproducing apparatus,
When 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 occurs, which causes deterioration of a signal during recording and reproduction. For this reason, recently, regarding the objective lens driving device, in order to correct the relative tilt between the disk and the objective lens optical axis, in addition to the focusing deviation due to the vertical movement of the disk runout and the tracking deviation due to the eccentricity, etc. A device that drives three axes in a rotation direction (hereinafter referred to as a radial tilt direction) has been proposed.

As a conventional objective lens driving device of this kind, there is one disclosed in Japanese Patent Application Laid-Open No. 9-022537, for example. FIG. 6 is a schematic plan view for describing the configuration and operation of JP-A-9-022537.

Referring to FIG. 6, the structure will be described. An objective lens 1 and a lens holder 2 for holding the objective lens 1 are described.
A movable body 4 having two magnets 3a and 3b which have a direction of magnetization in the tangential direction t of the disk and are symmetrically arranged about the objective lens 1 in the tangential direction t of the disk and fixed to the lens holder 2; A base 5 and four parallel metal wires 6a to 6d (one not shown because 6c and 6d overlap in the figure), one end of which is fixed to the movable body 4 and the other end of which is fixed to the fixed base 5; Drive coil blocks 10a and 10c are arranged for the magnet 3a and drive coil blocks 10b and 10d are arranged for the magnet 3b in the vicinity of the magnetic pole faces on one side of the magnets 3a and 3b, respectively.
The drive coil blocks 10a to 10d are wound around magnetic yokes 7a to 7d (not shown) and have focusing drive coils 8a to 8d having a winding axis in the optical axis direction L of the objective lens 1 and a radial direction r of the disk. And tracking drive coils 9 a to 9 d having a winding axis.

[0006] With the above configuration, the drive coil blocks 10a to 10a are used for ordinary focusing drive.
The current is supplied so that the driving forces generated in the focusing driving coils 8a to 8d in the direction d are all in the same direction (the same applies to the tracking driving).
In the drive of T, currents such that the driving forces generated in the focusing drive coils 8a, 8b and 8c, 8d divided by the tangent of the disk passing through the center of the objective lens 1 are opposite to each other are separately applied and superimposed. This is achieved by:

[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 associated with 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. More precise positioning at the optical axis angle is required.

[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
Japanese Patent Publication No. 022537 discloses that a drive coil block is provided with a tilt correction function for increasing the density.
Since the shaft objective lens driving device is divided into two parts, the effective magnetic flux and the effective coil length are reduced, so that the drive sensitivity must be reduced. Further, since only one magnetic pole surface of the magnet is used, the driving efficiency with respect to the movable weight is deteriorated.

Further, the focusing drive coil (also used as a tilt drive coil) is divided into two parts by a disk tangent passing through the center of the objective lens and is adjacent to each other, so that the driving center point of each divided focusing drive coil is provided. However, there is a problem that a radius of curvature with respect to the tilt rotation axis becomes small, and it is difficult to obtain a large rotation moment as a tilt driving force.

In view of the above-mentioned problems of the conventional objective lens driving device, the present invention has a tilt correction function and has three functions of focusing, tracking, and tilting.
It is an object of the present invention to provide an objective lens driving device capable of drastically increasing the driving sensitivity of all shaft drives and further reducing the size and thickness.

[0012]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and achieves the object. The present invention relates to a conventional four-wire suspension type moving magnet type three-axis driven objective lens driving apparatus. In particular, the arrangement of the magnet and the drive coil block is configured as follows.

That is, a magnet having a direction of magnetization in the tangential direction of the disk is fixed to the movable body symmetrically in the radial direction of the disk with the objective lens as the center. 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 tracking drive coil having a winding axis in a radial direction of the disk are provided near the pole side. A drive coil block having the following arrangement is arranged and fixed on a fixed base.

In addition, current is supplied so that the driving force generated in the focusing drive coils in the four drive coil blocks is opposite to each other with respect to the radial direction of the disk around the objective lens. This has the function of obtaining driving means in the direction of rotation about the tangential direction of the disk, that is, in the radial tilt direction.

According to the present invention, since the magnetic flux on both the N-pole side and the S-pole side of the magnet is used, the effective magnetic field area is twice as large as the conventional one, and the driving sensitivity can be greatly 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, with respect to a plane configuration perpendicular to the optical axis of the objective lens, the center of the objective lens is formed at a position separated from a straight line connecting the centers of the two magnets. That is, the apparatus can be made thinner by separating the objective lens from the driving unit.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a schematic plan view of a three-axis driven objective lens driving device according to Embodiment 1 of the present invention. Here, parts having the same functions and functions as those of the conventional example are given the same numbers.

Referring to FIG. 1, the structure will be described. An objective lens 1 and a lens holder 2 for holding the objective lens 1
A movable body 4 having two magnets 3a and 3b fixed in the radial direction r of the disk with the direction of magnetization in the tangential direction t of the disk and centered on the objective lens 1 and fixed to the lens holder 2; A base 5 and four parallel metal wires 6a to 6d (one not shown because 6c and 6d overlap in the figure), one end of which is fixed to the movable body 4 and the other end of which is fixed to the fixed base 5; Drive coil blocks 10a and 10b are provided near the magnets 3a and 3b in the vicinity of the N pole side and the S pole side of the magnets 3a and 3b, respectively.
, Drive coil blocks 10c and 10d are arranged. The drive coil blocks 10a to 10d are wound around magnetic yokes 7a to 7d (not shown) and have focusing drive coils 8a to 8d having a winding axis in the optical axis direction L of the objective lens 1 and a radial direction r of the disk. And tracking drive coils 9 a to 9 d having a winding axis.

With the above configuration, the driving coil blocks 10a to 10a are used for ordinary focusing driving.
The current is supplied so that the driving forces generated in the focusing driving coils 8a to 8d in the direction d are all in the same direction (the same applies to the tracking driving).
Regarding the driving of T, a current such that the driving forces generated in the respective focusing driving coils 8a, 8b and 8c, 8d symmetrically arranged in the radial direction r of the disk around the objective lens 1 are opposite to each other. This is realized by applying and superimposing.

Therefore, the effect obtained in the first embodiment is that the effective magnetic field area is twice as large as the conventional one because the magnetic fluxes on both the N pole side and the S pole side of each of the magnets 3a and 3b are used. Can be increased. Further, since the drive center of the tilt is located at a position distant from the tilt rotation axis, a large rotational moment as a tilt drive force can be generated.

In the first embodiment, the configuration is such that the center of gravity of the movable body 4 is located on the line connecting the centers of gravity of the two magnets 3a and 3b, that is, by matching the drive center with the center of gravity of the movable body, unnecessary resonance is generated. The occurrence is prevented and good frequency characteristics are obtained.

In the first embodiment, the lens holder 2, the two magnets 3a and 3b, the four metal wires 6a to 6d, and the fixed base 5 are integrally formed by insert molding or the like. With this configuration, 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 man-hours.

(Embodiment 2) FIG. 2 is a schematic plan view of a main part according to Embodiment 2 of the present invention.

Only the components different from those in the first embodiment (FIG. 1) will be described. The polarities of the magnets 3a and 3b are opposite to each other, and the drive coil blocks 10a to 10b
A magnetic path G is formed by causing the magnetic flux to flow in the same direction with the yokes 7a to 7d in the figure located at the center of d. In this case, it goes without saying that the direction of the drive current is different from that of the first embodiment.

Therefore, the effect obtained in the second embodiment is that the effective magnetic flux can be increased by forming the magnetic path, and the driving sensitivity can be further increased.

(Embodiment 3) FIG. 3 is a schematic plan view (1) and a side view (2) of a main part according to Embodiment 3 of the present invention. Only components different from those of the first embodiment will be described. As shown in the plan view of FIG. 3A, the center of the objective lens 1 is located at a position D1 away from the straight line connecting the centers of the magnets 3a and 3b, that is, the objective lens 1 is separated from the driving unit. This secures a space below the objective lens 1. Therefore, the rising mirror 11 can be installed as shown in the side view of FIG. 3B, and the entire optical pickup can be made thinner.

(Embodiment 4) FIG. 4 is a schematic plan view of a main part according to Embodiment 4 of the present invention.

Only components different from those of the third embodiment will be described. A configuration in which the distance D2 between the magnets 3a and 3b in the disk radial direction is smaller than the outer diameter D3 of the objective lens 1, that is, the magnet 3 is smaller than the third embodiment described above.
The distance between installation of a and 3b is shortened.

Therefore, in the case of this configuration, the metal wires 6a, 6b
Can be reduced, so that the width direction of the objective lens driving device can be reduced. Further, since the width of the lens holder 2 is also reduced, the weight of the movable body 4 can be reduced, and the driving sensitivity can be further improved.

(Embodiment 5) FIG. 5 is a schematic plan view of a main part according to a fifth embodiment of the present invention.

Only the components different from those of the fourth embodiment will be described. A configuration in which the drive coil blocks 10a and 10c are opposed to each other only on the magnetic pole surfaces of the magnets 3a and 3b on the objective lens 1 side, that is, two drive coil blocks are used.
I use them individually. In this case, the drive coil block 10
Since the center of the coil on the surface of each of the magnets 3a, 3c facing the magnets 3a, 3b is the drive center S, the magnets 3a, 3b
The movable body 4 also serves as a balance weight.

Therefore, the effective magnetic field area is reduced to half of that of the first to fourth embodiments, but the weight of the movable body 4 can be remarkably reduced, so that the reduction of the drive sensitivity relatively stops slightly. Further, the distance between the metal wires 6a and 6b can be minimized, and the width of the device can be reduced. Further, since the number of drive coil blocks is halved, it is advantageous in reducing the number of parts and in line processing.

[0034]

As described above, according to the present invention, since the magnetic flux on both the N-pole side and the S-pole side of the magnet is used, the effective magnetic field area is twice as large as that of the prior art, and the driving sensitivity is dramatically improved. be able to. 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, with respect to the plane configuration perpendicular to the optical axis of the objective lens, the center of the objective lens is formed at a position separated from a straight line connecting the centers of the two magnets. That is, by separating the objective lens from the drive unit, a space below the objective lens is secured and the device can be made thinner.

Further, it is possible to further improve the driving force, reduce the size, and reduce the cost by devising the polarity arrangement of the magnets and optimizing the distance between the magnets.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a three-axis driven objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a schematic plan view of a main part according to a second embodiment of the present invention.

FIG. 3 is a plan view 3 (1) and a side view 3 (2) of a main part according to a third embodiment of the present invention.

FIG. 4 is a schematic plan view of a main part according to a fourth embodiment of the present invention.

FIG. 5 is a schematic plan view according to a fifth embodiment of the present invention.

FIG. 6 is a schematic plan view for explaining the configuration and operation 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-7d Yoke 8a-8d Focusing drive coil 9a-9d Tracking drive coil 10a-10d Drive coil block 11 Start-up mirror 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

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hideji Iwasaki 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D118 AA01 AA02 AA13 AA23 BA01 BB02 BF02 BF03 CD02 CD03 DC03 EA03 EB15 ED05 ED07 ED08 EE06 EF09 FA29 FB08 FB20

Claims (7)

[Claims] An object lens for irradiating a laser beam to a disc, a movable body having a lens holder for holding the objective lens and a magnet fixed to the lens holder, a fixed base, and one end of the movable body. A support means comprising four parallel metal wires fixed to each other and fixed to the fixed base at the other end; and adding the movable body in the optical axis direction of the objective lens and in the radial direction of the disk. In a three-axis driving objective lens driving device having a driving means capable of moving in a rotation direction about the tangential direction of the disk, the magnet fixed to the movable body changes the direction of magnetization in the tangential direction of the disk. The two magnets are arranged symmetrically in the radial direction of the disk around the objective lens. A drive coil block wound around a yoke made of a body and having 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 a radial direction of the disk is arranged. The driving force generated in the focusing drive coils in the four drive coil blocks is fixed to the fixed base so that the driving forces are opposite to each other with respect to the radial direction of the disk around the objective lens. A three-axis objective lens driving device, characterized in that a current is supplied to the motor to obtain driving means in a rotational direction about a tangential direction of the disk. 2. The three-axis objective lens driving device according to claim 1, wherein the center of gravity of the movable body is located on a straight line connecting the centers of gravity of the two magnets. 3. A lens holder, two magnets,
3. The three-axis objective lens driving device according to claim 1, wherein the four metal wires and the fixed base are integrally formed by insert molding or the like. 4. The three-axis objective lens driving device according to claim 1, wherein the two magnets are arranged with polarities opposite to each other with respect to a tangential direction of the disk. 5. The apparatus according to claim 1, wherein the center of the objective lens is located away from a straight line connecting the centers of the two magnets with respect to a plane configuration of a plane perpendicular to the optical axis of the objective lens. Axis driven objective lens drive. 6. The three-axis objective lens driving device according to claim 5, wherein a distance between the two magnets in the disk radial direction is smaller than an outer diameter of the objective lens. 7. The three-axis driven objective lens driving device according to claim 5, wherein the drive coil blocks are opposed to each other only on the magnetic pole surfaces of the two magnets on the objective lens side.