JPH11232668A - Objective lens-driving apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens-driving apparatus which prevents an objective lens from being inclined to an optical disk even when moving in a focus and a tracking directions. SOLUTION: Focus coils 13A, 13B, magnets 15a, 15b and a yoke 14 are constituted so that a driving force for a focusing operation is generated to parts 13a, 13b of the focus coils 13A, 13B arranged in a nearly orthogonal direction to a tracking direction, and moreover, the center of the generated driving force in the focusing direction is located on a line passing a center position where a movable part is supported (or center of gravity of the movable part).

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, JP-A-8-26386.
No. 0 is known. This objective lens driving device is configured as shown in FIG. FIG. 7 is a front view of a conventional objective lens driving device, FIG. 8 is a front view when the objective lens is moved in the tracking direction, and FIG. 9 shows the relative positions of the magnet and the focus coil when FIG. FIG. 10 is a side view showing the relative positions of the magnet and the focus coil when FIG. 8 is viewed from the E direction. As shown in FIGS. 7 and 8, the objective lens driving device includes a bobbin 2 holding an objective lens 1, a focus coil 3, tracking coils 6 a and 6 b, a magnetic flux generating unit including magnets 5 a and 5 b and a yoke 4. And driving means for supplying current to the focus coil and the tracking coil for driving and displacing the objective lens 1 in the focusing direction (the optical axis direction of the objective lens) and the tracking direction (the direction perpendicular to the optical axis of the objective lens). (Not shown), a plurality of elastic support members 7a for supporting the bobbin 2,
7b, a support holder 9 and a fixed part substrate 10 attached to the support holder 9 and to which one ends of the elastic support members 7a and 7b are fixed. Note that the support holder 9 and the elastic support members 7a and 7b constitute a fixed portion.

In this objective lens driving device, an electromagnetic force acts in the focusing direction by flowing a current in the forward or reverse direction to the focus coil 3 during focus control, and the objective lens 1 responds to the surface deflection of the recording surface of the optical disk. Is operated in the direction of the optical axis, that is, in the direction perpendicular to the plane of the paper of FIG. 7, so that the spot of the light beam follows the recording surface of the optical disk. At the time of tracking control, an electromagnetic force acts to move the objective lens 1 in the radial direction of the optical disk by flowing a current in the forward or reverse direction to each of the tracking coils 6a and 6b. The spot of the light beam is made to follow.

In recent years, there has been a tendency to use an objective lens having a large numerical aperture in order to increase the recording density of an optical disk device. Therefore, strict accuracy is required for the relative angle shift amount between the objective lens and the optical disk. In particular, the tilt angle of the objective lens changes with respect to the initial tilt angle of the objective lens even while the objective lens is moving up, down, left, and right, following the surface deviation of the optical disk and the meandering and eccentricity of the track on the optical disk. It is required to suppress the inclination of the objective lens so as not to prevent the inclination. 7 illustrates the relative positional relationship between the focus coil 3 and the magnets 5a and 5b when the assembly accuracy and component accuracy of each component of the objective lens driving device illustrated in FIG. 7 are ideal and there is no displacement in the tracking direction. It is shown in FIG. In this case, the driving force in the focusing direction acting on the focus coil 3 generated by the action of the current flowing through the focus coil 3 and the magnetic flux in the magnetic flux generating unit composed of the magnets 5a, 5b and the yoke 4, that is, as shown in FIG. The center P of the driving force in the perpendicular direction and the support center (or the center of gravity of the movable portion) G mainly determined by the mounting accuracy or component accuracy of the elastic support members 7a and 7b.
And the relative positions are almost the same. In this state, even if the objective lens is operated in the focusing direction, the objective lens hardly tilts.

On the other hand, when the objective lens driving device shown in FIG. 7 is displaced DC-directionally in the tracking direction, that is, when the objective lens 1 is largely displaced in one direction as shown in FIG. Then, the position of the center of gravity G of the movable portion including the focus coil 3 and the tracking coils 6a and 6b is different. Alternatively, the center P of the driving force in the focusing direction does not coincide with the support center (or center of gravity) G of the movable part due to the assembling accuracy and the accuracy of the components. FIG. 10 shows the relative positional relationship between the focus coil 3 and the magnets 5a and 5b at this time. As shown in FIGS. 8 and 10, when the center P of the driving force in the focusing direction does not coincide with the support center (or the center of gravity) G of the movable portion, the driving force in the focusing direction is generated at substantially the center of the magnets 5a and 5b. ,
The center P of the driving force in the focusing direction is generated at a position shifted by y from the support center (or the center of gravity) G of the movable portion. When the objective lens 1 is operated in the focusing direction in this state, the center P of the driving force in the focusing direction is a rotational torque (P × y, where y is the distance between P and G) that tilts the objective lens 1 in the radial direction of the optical disk. Will also occur at the same time. Therefore, the objective lens 1 is inclined in the radial direction of the optical disk, that is, in the tracking direction. Even if the assembling accuracy is improved and the center P of the driving force in the focusing direction coincides with the support center (or center of gravity) G of the movable portion, the objective lens 1 is displaced DC in the tracking direction and the focusing direction is maintained. Is operated, the focus coil 3 is fixed integrally with the movable portion, and the portion generating the driving force in the focusing direction is in the tracking direction (perpendicular to the longitudinal direction of the elastic support member).
The center P of the driving force in the focusing direction is generated at a position displaced from the support center (or the center of gravity) G of the movable portion together with the tracking operation, and the objective lens 1 is moved along with the focusing operation. Lean. In particular, in the case of a small and thin objective lens driving device, since the distance between the elastic support members supporting both ends of the movable portion cannot be made large, the inclination angle of the objective lens 1 with respect to the rotational torque generated by the focusing operation becomes large,
The inclination angle of the objective lens 1 cannot be suppressed to a small value unless the accuracy of mounting the magnetic flux generating section and the like and the accuracy of individual parts are remarkably improved and the tracking operation range is extremely reduced.

[0006]

As described above, in the configuration of the conventional objective lens driving apparatus described above, if the inclination angle of the objective lens 1 during operation is suppressed to be small, the precision of parts and the precision of assembly can be drastically improved. In addition, there is a need for a means for generating a correction torque so that the objective lens 1 does not tilt when the objective lens 1 is operated in the tracking direction, and it is not possible to simultaneously satisfy the requirements for a thin, compact, and low-cost objective lens driving device. . SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an objective lens driving device capable of suppressing the tilt angle of the objective lens even when performing a focusing operation with the objective lens displaced in the tracking direction. And

[0007]

In order to solve the above-mentioned problems, an objective lens driving apparatus according to the present invention comprises an objective lens for condensing a light beam on an optical disk and an objective lens for driving the objective lens in the optical axis direction. A movable portion including a focus coil for generating a force for driving the objective lens in a tracking direction, a tracking coil for generating a force for driving the objective lens in a tracking direction, and a bobbin for holding the objective lens, the focus coil, and the tracking coil. An elastic support member for movably supporting the unit in the tracking direction and the focus direction, and a magnetic flux generation unit for generating a magnetic flux passing through the focus coil and the tracking coil, for driving the objective lens in the optical axis direction. The driving force is mainly generated in the coil part in the direction orthogonal to the tracking direction of the focus coil. Focusing coil and the magnetic flux generating unit is arranged to.

Further, the magnetic flux generating section is configured so that the main magnetic flux acting on the coil portion in the direction orthogonal to the tracking direction of the focus coil is parallel to the tracking direction. In a preferred embodiment, a tracking coil magnetic flux generator and a focus coil magnetic flux generator are separately provided. Further, the portion substantially parallel to the longitudinal direction of the elastic support member of the focus coil is disposed so as to pass through the support center of the movable portion of the elastic support member. Furthermore, the coil part of the focus coil orthogonal to the tracking direction is disposed so as to pass through the center of gravity of the movable part.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the objective lens driving device according to the present invention will be described below with reference to the drawings. First, a first embodiment of the objective lens driving device according to the present invention will be described with reference to FIGS. FIG. 1 is a front view showing a first embodiment of an objective lens driving device according to the present invention, FIG. 2 is a front view when the objective lens shown in FIG. 1 is moved in the tracking direction, and FIG. 3 is A in FIG. FIG. 4 is a cross-sectional view taken along line BB ′ of FIG. 1, and FIG.
It is C 'sectional drawing. In FIG. 1, an objective lens 11 is attached to a bobbin 12, and a pair of focus coils 13A and 13B are arranged at a central portion thereof.
The focus coils 13A and 13B are composed of two air-core coils having a rectangular cross section, and are adhered and fixed to the bobbin 12 such that the longitudinal components 13a and 13b face each other. The focus coils 13A, 13
B, a pair of opposed longitudinal component parts 13a, 13b
Extend in a direction perpendicular to the disk radial direction or the tracking direction. In the support structure of the movable portion in FIG. 1, the elastic support center of the entire movable portion, that is, the elastic support members 21a and 21a,
It is arranged so as to pass through the center between 1b or near the center of gravity. The winding directions of the focus coils 13A and 13B are wound such that the directions of currents flowing through the opposed longitudinal components 13a and 13b are the same. In order to generate a driving force in the focusing direction, a magnetic flux is sandwiched between a pair of opposed longitudinal component portions 13a and 13b, and a magnetic flux is substantially perpendicular to the pair of longitudinal component portions 13a and 13b of the focus coils 13A and 13B. A magnetic flux generating unit including magnets 15a and 15b and a yoke 14 operatively arranged is arranged. The focus coils 13A and 13B are
a, 15b and the yoke 14 so that the focus coils 13A, 13B
Longitudinal components 13a, 13b and magnets 15a, 1
5b, or the distance between the yoke 14 and the longitudinal component outside the focus coils 13A and 13B, which is necessary to operate at least in the tracking direction (or the disk radial direction), about 0.5 mm to 1 mm. The focus coils 13A and 13B do not come into contact with the magnets 15a and 15b and the yoke 14 even when the tracking operation is performed.

On the other hand, outside the bobbin 12, tracking coils 16a and 16b are arranged, respectively. The magnetic flux generating part composed of the magnets 18a and 18b and the yoke 17a is arranged close to the tracking coil 16a, and the magnetic flux generating part composed of the magnets 18c and 18d and the yoke 17b is arranged close to the tracking coil 16b. ing. These magnetic flux generators are arranged to generate a driving force in the tracking direction, and have a configuration capable of performing a tracking operation.

As is apparent from FIG. 3, the tracking coils 16a, 16b and the magnets 18a, 18b, 18
The magnetic flux generating portion for tracking operation composed of c and 18d and the yokes 17a and 17b has a relationship of a small coil and a large magnet, and the rotational moment generated in the tracking coils 16a and 16b by the focusing operation in the radial direction of the optical disk. Is configured to be extremely small. Further, a movable portion including the objective lens 11, the bobbin 12, the focus coils 13A and 13B, the tracking coils 16a and 16b,
It is elastically supported by four elastic support members 21a and 21b. That is, one end of each of the elastic support members 21a and 21b is physically and electrically coupled to the relay board 22 disposed on the movable portion by soldering or the like, and the other end passes through the inside of the support holder 19 forming the fixed portion. Thus, it is physically and electrically coupled to the fixed part substrate 20. The four elastic support members 21a and 21b are made of a conductive material, and are respectively provided with focus coils 13A and 13B and tracking coils 16a and 16b via a relay board 22 disposed on the movable portion. Is electrically coupled to Therefore,
The focus coils 13A, 13B, the tracking coils 16a, 16
b is configured to be energizable.

The tilt angle of the objective lens 1 when operating in the focusing direction in the above configuration will be described.
In FIG. 4, when a current is applied to the focus coils 13A and 13B via elastic support members 21a and 21b made of a conductive material, the portions of the focus coils 13A and 13B in which the longitudinal components 13a and 13b are opposed to each other. Since the current flows in the same direction, the current flowing through this portion and the magnets 15a, 1
Longitudinal component 13 of focus coils 13A and 13B generated from a magnetic flux generating portion composed of 5b and yoke 14
Due to the electromagnetic action of the magnetic flux flowing in a direction substantially orthogonal to a and 13b, the longitudinal direction components 13a and 13b of the focus coils 13A and 13B have a driving force P in the focusing direction.
That is, in FIG. 1, a driving force P is generated in a direction orthogonal to the paper surface. The focus coils 13A, 1A,
The longitudinal components 13a and 13b, which are substantially parallel to the longitudinal directions of the elastic support members 21a and 21b of 3B, pass through the support center (or the center of gravity) of the movable part and pass through the elastic support members 21a and 21b.
Are located on a straight line that is substantially parallel to the longitudinal direction of the optical disk. Therefore, almost no rotational torque is generated to tilt the objective lens 11 in the radial direction of the optical disk. Therefore, the objective lens 11 hardly tilts in the radial direction of the optical disc.

On the other hand, due to the accuracy of each component constituting the objective lens driving device and the assembling accuracy of those components, the objective lens driving device according to the present invention also has the same structure as the longitudinal direction of the elastic support members 21a and 21b of the focus coils 13A and 13B. The substantially parallel portions 13a and 13b are
It does not always coincide with the center of the magnetic gap of the magnetic flux generating portion composed of the a, 15b and the yoke.
As shown in FIG. 2, when the objective lens 11 is displaced in the tracking direction, the support center (or the center of gravity) of the movable part is located at the center of the magnetic gap of the magnetic flux generating part composed of the magnets 15a, 15b and the yoke 14. Will no longer be located. FIG. 5 is a cross-sectional view taken along the line CC 'of FIG. 2, and shows the relationship between the magnets 15a and 15b, the yoke 14, and the focus coils 13A and 13B in this state.
As shown in FIGS. 2 and 5, when the objective lens 11 is displaced in the tracking direction, the entire movable portion is displaced in the same direction, but the magnetic flux generating portion constituted by the magnets 15a and 15b and the yoke 14 is not displaced. Therefore, as a result, the focusing direction driving force generating portion 13c of the focus coils 13A and 13B moves in the magnetic gap in the magnetic flux generating portion. Focus coils 13A, 13
When a current is supplied to B, the yoke 14 and the magnets 15a, 1
The driving force P is generated in the focusing direction driving force generating portion 13c by the magnetic flux from the magnetic flux generating portion composed of 5b. However, the width of the longitudinal component portions 13a and 13b of the focus coils 13A and 13B, that is, the length in the direction orthogonal to the longitudinal component portions 13a and 13b, is small.
In addition, since the magnetic gap of the magnetic flux generating portion, that is, the magnetic flux density distribution between the magnets 15a and 15b is substantially the same, there is almost no change between the widths of the longitudinal components 13a and 13b of the focus coils 13A and 13B. Therefore, the force P generated between the longitudinal component portions 13a and 13b of the opposed focus coils 13A and 13B is substantially the same, and as a result, as shown in FIG. 5, the portion 13a that generates the driving force P in the focusing direction. , 13b are located on a straight line passing through the support center (or center of gravity) G of the movable part. Therefore, almost no rotational torque is generated for tilting the objective lens 11 in the radial direction of the optical disk, and the objective lens 11 does not tilt in the radial direction of the optical disk even when displaced in the tracking direction.

In this embodiment, the longitudinal components 13a and 13b are provided on the focus coils 13A and 13B, and the longitudinal components 13a and 13b are arranged in parallel with the radial direction of the disk, that is, the direction orthogonal to the tracking direction. Thereby, the focus coil 13A,
Even if 13B moves between the magnetic gaps of the magnetic flux generating portions, that is, between the two magnets 15a and 15b, the center P of the focusing driving force is changed to the longitudinal component portions 13a and 13b.
It can be made to work near the contact portion of b. The center of gravity G of the movable portion is near the contact portion between the two longitudinal component portions 13a and 13b at the longitudinal center of the longitudinal component portions 13a and 13b of the coils 13A and 13B. For this reason,
Since the center P of the focusing driving force and the center of gravity G of the movable portion are substantially at the same position even when the focus coils 13A and 13B move in the tracking direction, no rotational force is applied to the focus coils 13A and 13B by the focusing operation. Therefore, the objective lens 11 hardly tilts.

FIG. 6 is a front view showing a second embodiment of the objective lens driving device according to the present invention. In the figure, two focus coils 33A and 33B are respectively connected to bobbins 32.
Are located on both sides. Each focus carp 33A, 3
3B has a dedicated magnetic flux generator, ie, the focus coil 33A has a magnet 35a and a yoke 34a.
The focus coil 33B is provided with a magnetic flux generating unit including a magnet 35b and a yoke 34b. Focusing direction driving force generator 33
Similarly to the first embodiment, a and 33b are portions substantially parallel to the longitudinal direction of the elastic support members 21a and 21b, and the combined force of the driving force in the focusing direction generated at these two places. The center is configured to act on a position passing through the support center (or center of gravity) of the movable part. Further, the tracking coils 36a and 36b are arranged inside the bobbin 32, and a dedicated magnetic flux generating unit including the magnets 38a and 38b and the yoke 37 is provided. The magnetic flux generator is arranged so as to act on the tracking coils 36a and 36b. Tracking coil 36
As in the first embodiment, the relationship between the small coils a and 36b and the magnets 38a and 38b is a relationship between a small coil and a large magnet as shown in FIG. 3, and the optical disc generated in the tracking coils 36a and 36b by the focusing operation. The rotational moment in the radial direction is designed to be extremely small. Therefore, in the second embodiment, as in the first embodiment, even if the objective lens 11 is displaced in the focusing direction and the tracking direction, the objective lens 11 does not tilt in the radial direction of the optical disc.

The conventional focus coil 3 shown in FIG. 7 is wound in parallel with the tracking direction. When the center of gravity G of the movable portion including the focus coil 3 is moved by the tracking operation, the center P of the driving force in the focusing direction is a magnet P. Since it moves to the center of the focus coil 3 within the width of 5a, 5b, the position of the center of gravity G and the center P position of the driving force in the focusing direction become different as shown in FIG. Although the objective lens 1 is rotated, in the embodiment of the present invention, the focus coils 13A, 13B, 33A, and 33B are wound in a direction perpendicular to the tracking direction, and the magnetic flux is substantially perpendicular to the tracking direction. Parts 13a, 13b, 33
a, 33b, the focus coils 13A, 13A
Even if B, 33A and 33B move in the tracking direction, the position of the center of gravity G of the movable portion including the focus coils 13A, 13B, 33A and 33B and the position of the center P of the driving force in the focusing direction hardly change.

Although the first and second embodiments of the present invention have been described above, the present invention is not limited to this, and the center P of the driving force in the focusing direction passes through the center (or the center of gravity) of the movable part. And the focus coil 13A,
13B, 33A, and 33B, are located in a direction perpendicular to the tracking direction (in the embodiment, the elastic support members 21a,
(It is located on a straight line substantially parallel to the longitudinal direction of 21b)
Any configuration may be used as long as the magnetic flux passes through the coil portion to generate the driving force in the focusing direction, and another configuration may be used. In each embodiment, the tracking coil 16
a, 16b 36a, 36b and magnets 18a, 18
b, 18c, 18d, 38a, 38b and yoke 17
As shown in FIG. 3, the magnetic flux generating section composed of a, 17b, and 37 is of a flat facing type, but generates a driving force in the tracking direction and rotates the objective lens 11 in the radial direction of the optical disk. Any configuration may be used as long as the configuration does not easily generate torque.

[0018]

As described above, the objective lens driving device according to the present invention has an effect that the objective lens is hardly inclined with respect to the optical disk even when the focusing operation is performed by operating the objective lens in the tracking direction.

Further, in the present invention, there is no need to arrange a special mechanism or means for suppressing the inclination angle of the objective lens with respect to the optical disk.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of an objective lens driving device according to the present invention.

FIG. 2 is a front view when the objective lens shown in FIG. 1 is moved in a tracking direction.

FIG. 3 is a sectional view taken along line AA ′ of FIG. 1;

FIG. 4 is a sectional view taken along line BB ′ of FIG. 1;

FIG. 5 is a sectional view taken along the line CC ′ of FIG. 2;

FIG. 6 is a front view showing a second embodiment of the objective lens driving device according to the present invention.

FIG. 7 is a front view of a conventional objective lens driving device.

FIG. 8 is a front view when the objective lens is moved in the tracking direction in FIG.

FIG. 9 is a side view showing the relative positions of the magnet and the focus coil when FIG. 7 is viewed from the direction D.

FIG. 10 is a side view showing the relative positions of the magnet and the focus coil when FIG. 8 is viewed from the direction E.

[Explanation of symbols]

11: Objective lens, 12: Bobbin, 13A, 13B, 3
3A, 33B: Focus coil, 13a, 13b, 3
3a33b: a component substantially orthogonal to the tracking direction of the focus coil, 14, 17a, 17b, 34a, 34
b ... Yoke, 15a, 15b, 18a, 18b, 18
c, 18d, 35a, 35b, 38a, 38b ... magnet, 16a, 16b, 36a, 36b ... tracking coil, 19 ... support holder, 20 ... fixed part substrate, 21
a, 21b: elastic support members; 22, 42: relay boards.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Video Information Media Division (72) Inventor Shinya Fujimori Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa 292 Hitachi Multimedia Systems Development Division, Hitachi, Ltd. (72) Inventor Nobuyuki Maeda 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Multimedia Systems Development Division, Hitachi, Ltd. (72) Inventor Seiichi Kato Ibaraki 502, Kandachi-cho, Tsuchiura-shi

Claims (9)

[Claims] 1. An objective lens for condensing a light beam on an optical disk, a focus coil for generating a force for driving the objective lens in the optical axis direction, and a focus coil for driving the objective lens in a tracking direction. A movable part comprising a tracking coil for generating a force, a bobbin holding the objective lens, the focus coil and the tracking coil, and an elastic support for movably supporting the movable part in a tracking direction and a focus direction. A member, comprising a magnetic flux generating unit that generates a magnetic flux passing through the focus coil and the tracking coil,
The focus coil and the magnetic flux generator are arranged such that a driving force for driving the objective lens in an optical axis direction is mainly generated in a coil portion in a direction orthogonal to a tracking direction of the focus coil. Objective lens driving device. 2. The objective lens driving device according to claim 1, wherein the magnetic flux generator is configured so that a main magnetic flux acting on the coil portion of the focus coil is parallel to a tracking direction. . 3. The magnetic flux generating section includes a first magnetic flux generating section for generating a magnetic flux acting on the tracking coil, and a second magnetic flux generating section for generating a magnetic flux acting on the focus coil. The objective lens driving device according to claim 1, wherein: 4. The objective lens driving device according to claim 1, wherein said coil portion in a direction orthogonal to a tracking direction of said focus coil is disposed so as to pass through a support center of said elastic support member. 5. The objective lens driving device according to claim 1, wherein said coil portion of said focus coil is disposed so as to pass substantially through the center of gravity of said movable portion. 6. The focus coil comprises first and second focus coils, and a coil portion orthogonal to a tracking direction of the first and second coils is arranged adjacently, and the adjacent coils 2. The objective lens driving device according to claim 1, wherein the magnetic flux generating unit is arranged at a portion so as to generate a driving force for operating the objective lens in an optical axis direction. 7. The tracking coil according to claim 1, wherein said tracking coil comprises first and second tracking coils, and is disposed outside said first and second focus coils. And a second tracking coil magnetic flux generator, wherein the first and second tracking coil magnetic flux generators generate the magnetic flux in a direction orthogonal to the tracking direction. 7. The objective lens driving device according to claim 6, wherein the objective lens driving device is disposed near the tracking coil. 8. The focus coil includes first and second focus coils, the first and second coils are arranged separately in a tracking direction, and the first and second coils are disposed in the magnetic flux generating unit. The first and second focusing magnetic flux generating units provide a magnetic flux in a tracking direction to the coil portion in a direction orthogonal to the tracking direction of the first and second focusing coils. 2. The objective lens driving device according to claim 1, wherein the objective lens driving device is arranged near the first focus coil and the second focus coil so as to cause the generation. 9. The tracking coil includes first and second tracking coils, and the first and second tracking coils are disposed inside the first and second focus coils. A magnetic flux generating section for a tracking coil provided in the section, and disposed near the first and second tracking coils so as to generate a magnetic flux in a direction orthogonal to a tracking direction in the magnetic flux generating section for tracking. The objective lens driving device according to claim 8, wherein