JP2001167458A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driving device capable of improving the tracking driving sensitivity and restraining the generation of a tilt when a movable part performs tracking operation and focusing operation. SOLUTION: The device is provided with a magnet, which has a nearly rectangular focusing coil and a nearly rectangular tracking coil which are fixed to a lens holder in order to drive a lens holder holding an objective lens and which are arranged on the same flat surface, in which inverse magnetic poles are respectively and oppositely arranged in the winding parts of two sides orthogonal to the focusing direction of the focusing coil and in which inverse magnetic poles are respectively and oppositely arranged in the winding parts of two sides orthogonal to the tracking direction of the tracking coil.

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, and more particularly to an objective lens driving device in a device for irradiating a disk-shaped recording medium with a light spot to optically record and reproduce information.

[0002]

2. Description of the Related Art An objective lens driving device irradiates a disc-shaped information recording medium (hereinafter, referred to as a disc) such as a compact disc with a light beam spot, and records / reproduces information represented by a pit array on a recording surface of the disc. Used in an optical disk drive device that performs The objective lens driving device drives the objective lens so that the light beam spot is accurately irradiated on a predetermined position on the disk. Focusing deviation and tracking deviation occur between the pit train on the normally rotating disk and the light beam spot. The focusing deviation occurs due to the runout of the disk, and the tracking deviation occurs due to the eccentricity of the disk. In order to correct these deviations, the objective lens driving device drives the objective lens in a direction perpendicular to the disk surface (hereinafter, referred to as a focusing direction) and in a radial direction of the disk (hereinafter, referred to as a tracking direction) so that an appropriate lens is always obtained. The light beam spot is controlled so as to accurately trace the pit row.

In a CD-ROM drive, a DVD-ROM drive, and the like used in connection with a personal computer, an increase in data transfer speed is required in accordance with an improvement in computer processing performance. Therefore, by increasing the rotation speed of the disk, the data transfer speed is increased to realize high-speed recording and reproduction. As the rotation speed of the disk increases, it is necessary to control the objective lens at a higher speed in order to cope with vibrations due to surface fluctuation and eccentricity that change at a high speed. Therefore, a high acceleration sensitivity is required for the objective lens driving device. The acceleration sensitivity is defined by a ratio between a current supplied to the objective lens driving device and an acceleration during movement of the objective lens. It is known that the acceleration sensitivity required for the objective lens driving device is proportional to the square of the disk rotation speed.

In order to improve the acceleration sensitivity of the objective lens driving device, the weight of the movable part on which the objective lens is mounted is reduced, and the magnetic circuit for generating the driving force is improved. Hereinafter, a conventional objective lens driving device will be described with reference to the drawings.

FIG. 12 is a perspective view of a main part of a conventional objective lens driving device. In FIG. 12, the objective lens 10
1 and the printed coil substrate 104 are the lens holder 102
And constitutes the movable portion 100. Suspension wires 103a, 103b, 103c and 103c
Is connected to one end of another suspension wire 103d which is below the
, And the other end is fixed to the wire holder 111. The wire holder 111 is fixed to the base 110. Two yoke bases 107 on a base 110
a and 107b are provided to face each other. A magnet 1 is provided on each of the opposing surfaces of the yoke bases 107a and 107b.
08a and 108b are provided to form a magnetic circuit. The printed coil board 104 is disposed between the magnets 108a and 108b.

FIG. 13 is a view taken from the direction of arrow V in FIG.
Printed coil substrate 104 and magnets 108a, 10
It is a top view of 8b. In FIG. 13, one focusing coil 105 and 4
Two tracking coils 116 to 119 are provided. An arrow Fo in the drawing indicates a moving direction of the printed coil substrate 104 during the focusing operation (hereinafter, referred to as a focusing direction), and an arrow Tk indicates the same moving direction during the tracking operation (hereinafter, referred to as a tracking direction).

[0007] Referring to FIG.
A focusing coil 105 having a substantially rectangular shape is provided at the center of the focusing coil 4. A current (hereinafter, referred to as a current If) flows through the focusing coil 105 in a direction indicated by an arrow If. Two substantially rectangular tracking coils 116 and 117 are provided on the left side of the focusing coil 105, and two substantially rectangular tracking coils 118 and 119 are provided on the right side. Four tracking coils 116-1
Reference numeral 19 is connected so that a current (hereinafter, referred to as a current It) flows in a direction indicated by an arrow It. The printed coil board 104 is composed of one layer or a plurality of layers. In the case of a plurality of layers, the focusing coil 105 and the tracking coils 116 to 119 are connected so that current flows in the same direction in the coils of each layer.

In FIG. 12 and FIG.
8a and 108b have tracking coils 116 and 117 and tracking coils 118 and 1
The dimensions are determined so as to be at the center of 19. The vertical dimensions of the magnets 108a and 108b are determined by the focusing coil 105 and the tracking coils 116 to 119.
Is made larger than the vertical dimension. Magnet 108
A and 108b are magnetized to have one magnetic pole (for example, N pole) on the surface facing the printed coil substrate 104 and the other magnetic pole (for example, S pole) on the opposite surface.
In FIG. 13, in the upper halves of the magnets 108a and 108b separated by the horizontal dotted magnetized boundary line MB, the magnetic force lines pass from the front to the back of the paper, and in the lower half, the magnetic force lines from the back to the front in the paper. Passes. Magnetization boundary line MB
Indicates that the state of magnetization is reversed across this boundary line. Magnet 108a and magnet 10
8b is magnetized so that the opposite magnetic poles face each other with the printed coil substrate 104 interposed therebetween.

When a current If is applied to the focusing coil 105, the winding portion 105a of the focusing coil 105 having two sides perpendicular to the focusing direction Fo receives an electromagnetic force in the focusing direction Fo according to Fleming's law.
As a result, the movable unit 100 is driven in the focusing direction Fo. Winding portions 116a to 119 of the tracking coils 116 to 119 on two sides perpendicular to the tracking direction Tk.
a, 116b to 119b, the winding portions 116b to 119b on the side closer to the focusing coil 105 are placed in the magnetic field of the magnets 108a and 108b. When a current It flows through the tracking coils 116 to 119, the movable portion 100 is driven in the tracking direction Tk by receiving an electromagnetic force in the tracking direction Tk according to Fleming's law. Two opposing magnets 108a, 10
By arranging the printed coil substrate 104 in the magnetic field having a high magnetic flux density formed by 8b, the focusing drive sensitivity and the tracking drive sensitivity are improved. Here, the focusing drive sensitivity is the focusing coil 1
05, and the ratio (LF / If) of the moving amount LF of the movable portion 100 in the focusing direction Fo, and the tracking drive sensitivity is determined by the tracking coil 11.
It is defined by the ratio (LT / It) between the current It flowing through 6 to 119 and the moving amount LT of the movable section 100 in the tracking direction Tk.

[0010]

In the above configuration, with respect to the focusing coil 105, the winding portions 105a on two sides of the four sides generate a driving force in the focusing direction Fo. In the tracking coils 116 to 119,
Only one of the winding portions 116b to 119b on one side generates a driving force in the tracking direction Tk. Therefore, there is a problem that the tracking drive sensitivity is lower than the focusing drive sensitivity, and the movable unit 100 cannot obtain sufficient acceleration sensitivity for performing high-speed recording and reproduction. The acceleration sensitivity is obtained by calculating the ratio α / acceleration when the movable unit 100 moves in the tracking direction or the focusing direction to the ratio α /
It is defined as It or α / If. Further, there is a problem that a tilt (tilt) occurs in the movable portion 106 due to a moment due to a portion of the tracking coils 116 to 119 that does not contribute to the generation of the driving force in the tracking direction (hereinafter, referred to as an invalid portion). This tilt will be described with reference to FIGS.

FIGS. 14A and 14B show the printed coil board 104 and the magnets 108a and 108b in FIG.
FIG. 5 is a plan view seen from the direction of arrow V of FIG. In the figure, the focusing direction F of each of the tracking coils 116 to 119 placed in the magnetic field of the magnets 108a and 108b.
Invalid portions 116c, 117c and 118 on two sides perpendicular to o
c, 119c, 116d, 117d, 118d, 119
d is shown hatched. Invalid part 116c-11
Focusing direction F acting on 9c, 116d to 119d
o The center point O of the printed coil substrate 104 due to the electromagnetic force
The surrounding moments are indicated by arrows N1 and N2.

FIG. 14A shows a tracking coil 1.
16 shows a state in which the current It flows through 16 to 119, and the printed coil board 104 has moved by the distance X in the tracking direction Tk with respect to the magnet 108a. For simplicity, it is assumed that the area ratios of the invalid portions 116c, 117c, 116d, and 117d and the invalid portions 118c, 119c, 118d, and 119d are 2: 1. Also, the respective electromagnetic force action points of the two invalid parts which are point-symmetric with respect to the center point O,
It is assumed that the distance to the center point O is substantially equal. In the figure, the coefficient of the letter “e” indicates the magnitude of the electromagnetic force, and the arrow indicates the direction. Tracking coil 116
In the above, the upper and lower invalid portions 116c and 116d receive the electromagnetic force 2e of the same strength in opposite directions, and thus cancel each other. Also in the tracking coil 117, the upper and lower invalid portions 117c and 117d receive the electromagnetic force 2e having the same strength in opposite directions and cancel each other. Similarly, in the tracking coils 118 and 119, the invalid portions 118c and 118d, 119c and 11
9d receive the same strength of electromagnetic force e in opposite directions and therefore cancel each other. As a result, the clockwise moment N1 and the counterclockwise moment N2 of the center point O become the same, and the difference N becomes zero.

Next, as shown in FIG. 14B, a case where the printed coil board 104 moves by the distance X in the tracking direction Tk and at the same time moves by the distance Y in the focusing direction Fo by the focusing current If will be described. In this case, each of the tracking coils 116 to 11
9 invalid portions 116c to 119c, 116d to 119d
A difference occurs in the density of the magnetic flux passing through the. The reason is that the magnetic flux density in the focusing direction Fo of the magnetic field by the magnets 108a and 108b is maximum near the central portion CP (indicated by a one-dot chain line) of each magnetic pole, and the dotted magnetized boundary line ML and the end portion E
This is because it has a non-uniform distribution that is minimized in the vicinity.

The case where the printed coil board 104 is displaced as shown in FIG. 14B will be described using specific numerical values. The invalid portions 116c and 118c of the tracking coils 116 and 118 are
8b approaches the end E where the magnetic flux density is small. As a result, the electromagnetic force is reduced by 20% to 1.6e and 0.8e, respectively. The inactive portions 116d and 118d of the tracking coils 116 and 118 are
8a and 108b approach the central portion CP where the magnetic flux density is large. Therefore, the electromagnetic force increases by 20% to 2.4e, respectively.
It is assumed that 1.2e has been reached. Tracking coil 117,
The invalid portions 117c and 119c of 119 are magnets 1
08a and 108b approach the magnetization boundary line ML where the magnetic flux density is small. This reduces the electromagnetic force by 20% each,
Let it be 1.6e and 0.8e. The ineffective portions 117d and 119d of the tracking coils 117 and 119 approach the central portion CP where the magnetic flux densities of the magnets 108a and 108b are large. As a result, the electromagnetic force is 20% each
It is assumed that they increase to 2.4e and 1.2e. As a result, the difference N between the clockwise moment N1 and the counterclockwise moment N2 of the center point O is N1-N2 = -2.4e, and the counterclockwise moment N
Occurs. Due to the moment N, a tilt in the radial direction of the disk (hereinafter referred to as radial tilt) occurs in the movable portion 100. Due to this radial tilt, there is a problem that an aberration is generated in a light beam spot irradiated on a recording surface of a disk, which adversely affects accurate recording and reproduction of signals.

The present invention solves the above-mentioned conventional problems,
It is an object of the present invention to provide an objective lens driving device having high driving sensitivity and capable of suppressing occurrence of radial tilt of a movable portion.

[0016]

According to the present invention, there is provided an objective lens driving apparatus comprising: an objective lens for converging a light beam for recording or reproducing information on a disk to the disk; a lens holder for holding the objective lens; A support member that movably supports a lens holder in a focusing direction in an optical axis direction of the objective lens and a tracking direction in a radial direction of the disc, attached to the lens holder;
A coil unit having at least one focusing coil and at least one tracking coil having a winding axis perpendicular to a plane including the focusing direction and the tracking direction, and a coil unit arranged opposite to the coil unit, and supplying a current to the coil unit. Opposite magnetic poles oppose each of the two winding portions that receive electromagnetic force in the focusing direction of the focusing coil when flowing, and receive electromagnetic force in the tracking direction of the tracking coil.
A magnet unit having a plurality of magnets arranged such that opposite magnetic poles face each of the two winding units.

According to the present invention, since the magnetic poles of the magnets face all the winding portions of the sides effective for generating the respective driving forces of the tracking coils, only a part of the effective sides of each tracking coil is provided. Driving force is increased and higher driving sensitivity is obtained as compared with the conventional one not facing the magnetic pole. The moment around the center of the focusing coil due to the electromagnetic force applied to the winding portion on the side perpendicular to the focusing direction of the tracking coil, that is, the ineffective portion that does not contribute to the driving force is canceled out, and the tilt of the movable portion disk in the radial direction is suppressed. Thus, stable signal recording and reproduction can be performed even under high-speed driving.

According to another aspect of the present invention, there is provided an objective lens driving device which converges a light beam for recording or reproducing information on a disk to a recording surface of the disk, a lens holder for holding the objective lens, A supporting member that supports the lens holder so as to be movable in a focusing direction in an optical axis direction of the objective lens and in a tracking direction in a radial direction of the disk, and a substrate attached to the lens holder; A focusing coil formed, and at least two tracking coils respectively symmetrical to a center line parallel to the tracking direction of the focusing coil and aligned in a direction perpendicular to the center line on both sides of the focusing coil on the substrate. While facing the coil portion, and the focusing coil, A first magnet having a magnetic pole whose edge parallel to the focusing direction faces a half area of the tracking coil through the center of the tracking coil and faces a winding portion intersecting the focusing direction of the focusing coil; and A magnet unit including a second magnet having a magnetic pole opposed to a remaining half area of the tracking coil and opposed to a winding part intersecting a tracking direction of the tracking coil;

According to the present invention, the magnetic poles of the magnet provided opposite to the substantially rectangular focusing coil and the substantially rectangular tracking coil disposed on the same plane are driven in the respective driving directions of the focusing coil and the tracking coil. It is formed at a position facing all the windings that generate a force. As a result, a high drive sensitivity is obtained, the tracking capability of the objective lens is increased, and high-speed recording and reproduction can be performed.
In addition, the moment around the center point of the printed coil board due to the electromagnetic force that is applied to the winding part of the side perpendicular to the focusing direction of the tracking coil, that is, the ineffective part that does not contribute to the generation of the driving force, is canceled, and the radial tilt of the movable part is suppressed Is done. As a result, stable recording and reproduction can be performed even during high-speed driving. Further, the radial tilt can be controlled by providing a plurality of focusing coils in the tracking direction and changing the current direction and the current value of some of them.

An objective lens driving device according to another aspect of the present invention is an objective lens for converging a light beam for recording or reproducing information on a disk to the disk, a lens holder for holding the objective lens, and the lens holder. A support member for movably supporting the focusing direction in the optical axis direction of the objective lens and the tracking direction in the radial direction of the disk; a center line formed on the substrate attached to the lens holder and parallel to the focusing direction of the substrate. A first magnet having a focusing coil asymmetrical with respect to a coil part having a tracking coil asymmetrical with respect to the center line, two magnetic poles on a surface opposed to the focusing coil, and the first magnet Is arranged on the same surface as the first magnet adjacent to the first magnet, and Boundary comprises a magnet unit having a second magnet passing through the center of the tracking coils in the focusing direction.

According to the present invention, since the driving force acts on all of the winding portions on the two sides of each tracking coil, high acceleration sensitivity can be obtained. As a result, the tracking capability of the objective lens during tracking and focusing is enhanced, and high-speed recording and reproduction can be performed. The moment around the center point generated by the electromagnetic force applied to the wound portion of the side perpendicular to the focusing direction of the tracking coil, that is, the ineffective portion where the driving force does not act is also canceled, and the radial tilt of the movable portion is suppressed. This enables stable recording and reproduction of signals even at the time of high-speed driving. By making the focusing coil asymmetrical with respect to the center line of the substrate, the focusing coil can be lengthened in the tracking direction. Thereby, the area of the winding portion of the effective portion perpendicular to the focusing direction increases, and the area of the invalid portion perpendicular to the tracking direction decreases. Therefore, the ratio of the effective portion in the entire focusing coil is increased, and the acceleration sensitivity is further improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to FIGS. 1 to 11B. In each of the drawings, the same reference numerals are used for the same elements.

<< First Embodiment >> FIG. 1 is a perspective view of a main part of an objective lens driving device according to a first embodiment of the present invention. FIG. 2A is a plan view of the printed coil board 4a and the magnet 8a of the objective lens driving device according to the first embodiment viewed from the direction of the arrow V in FIG. FIG. 2B is a plan view of the magnet 8b. FIGS. 3A and 3B are plan views of the printed coil board 4a and the magnet 8a showing the operation of the objective lens driving device of the first embodiment. FIG. 4 shows the first
FIG. 2 is a side view showing the magnetic flux density between magnets 8a and 8b of the objective lens driving device according to the embodiment, as viewed from the direction of arrow W in FIG. FIGS. 5A and 5B are plan views showing another configuration example of the magnet 8a in the objective lens driving device of the first embodiment.

In FIG. 1, the objective lens 1, the printed coil boards 4a and 4b, and the relay printed boards 9a and 9b are fixed to the lens holder 2 to form a movable section 50.
The printed coil boards 4a and 4b are connected to the relay printed board 9
a, 9b. Each coil provided on the printed coil boards 4a and 4b, which will be described in detail later, includes relay printed boards 9a and 9b, suspension wires 3a, 3b and 3c, and suspension wires 3c.
Is connected to a drive circuit (not shown) via another suspension wire 3d which is not shown in FIG. The movable part 50 includes the suspension wires 3a to 3d.
The driving current for driving the movable portion 50 is supplied to each coil via the suspension wires 3a to 3d.
One ends of the suspension wires 3a, 3b, 3c, 3d are fixed to the relay printed boards 9a, 9b, and the other ends are fixed to the wire holder 11. The wire holder 11 is fixed to the base 10. The yoke bases 7a and 7b are fixed to the base 10 at a predetermined interval substantially perpendicular to the surface of the base 10. The yoke base 7a has two yoke base plates 17 and 18 facing each other at a predetermined interval.
Plate-shaped magnets 8a and 8b are attached to the inner surfaces of the yoke base plates 17 and 18, respectively. The yoke base 7b also has yoke base plates 19 and 20 substantially similar to the yoke base 7a, and has magnets 8c and 8d attached to the respective inner surfaces. Yoke base 7a
The objective lens 1 of the movable section 50 is disposed between the movable lens 7 and the movable lens 7b. The printed coil board 4a of the movable section 50 is inserted between the magnets 8a and 8b, and the printed coil board 4b is inserted between the magnets 8c and 8d.

FIG. 2A is a plan view of the printed coil board 4a and the magnet 8a viewed from a direction perpendicular to the printed coil board 4a (the direction of the arrow V in FIG. 1). In FIGS. 1 and 2, the direction in which the movable section 50 moves during the focusing operation is indicated by an arrow Fo.
called o. The direction in which the movable section 50 moves during the tracking operation is indicated by an arrow Tk, and is hereinafter referred to as a tracking direction Tk. In FIG. 2, a substantially rectangular focusing coil 5a having a winding axis perpendicular to a plane including the focusing direction Fo and the tracking direction Tk is provided at the center of the printed coil substrate 4a.

On the left side of the focusing coil 5a, two substantially rectangular tracking coils 4 having similar winding axes are provided.
6, 47 are provided vertically. Similarly, on the right side of the focusing coil 5a, two substantially rectangular tracking coils 48 and 49 are provided vertically. The focusing coil 5a and the tracking coils 46 to 49 are not limited to rectangles, but may be circles or polygons. Focusing coil 5a, tracking coils 46-4
9 is formed integrally on the printed coil board 4a. The four tracking coils 46 to 49 are connected in series so that a tracking current (hereinafter, referred to as tracking current It) flows in a direction indicated by an arrow It in FIG. The printed coil substrate 4a is composed of one layer or a plurality of layers.
a and the tracking coils 46 to 49 are connected in series between the respective layers so that current flows in the coils of the respective layers in the same direction.

The magnet 8a is connected to the printed coil board 4
3 has one magnetic pole (for example, north pole) on one part of the surface facing the surface a, and has the other magnetic pole (for example, south pole) in the other part.
It is composed of an aggregate of two two-pole magnetized magnets 8a1, 8a2 and 8a2. The vertical and horizontal dimensions of the magnet 8a are the focusing coil 5a, the tracking coil 4
The size of the region including 6 to 49 is larger. The magnetic pole of the magnet 8a1 has two winding portions 5a1 perpendicular to the focusing direction Fo of the focusing coil 5a,
It is arranged so that the magnetic flux density is increased at the portion 5a2. The magnetic pole of the magnet 8a2 is connected to the winding part 4 perpendicular to the tracking direction Tk of each of the tracking coils 46 to 49.
They are arranged so that the magnetic flux density is increased in the portions 6a to 49a. When the printed coil board 4a is at the initial position, the left boundary between the magnets 8a1 and 8a2 passes through the center of the tracking coils 46 and 47, and the magnet 8a
The right boundary between 1 and 8a2 is the tracking coil 48, 4
Pass through the center of 9.

The winding portions 46a, 47a of the tracking coils 46, 47 on the sides perpendicular to the tracking direction Tk face the magnetic poles of the magnet 8a2. Winding part 46b, 4
7b faces the magnetic pole of the magnet 8a1. The relationship between the tracking coils 48, 49 and the magnets 8a1, 8a2 is the same as described above. As shown in FIG. 2 (b), the magnet 8b shown in FIG. 1 has three two-pole magnetized magnets 8 having magnetic poles opposite to the corresponding magnetic poles of the magnet 8a on a plane facing the printed coil board 4a.
It is composed of an aggregate of b1, 8b2 and 8b2. Due to the respective opposed magnetic poles of the magnets 8a, 8b, the density of the magnetic flux passing vertically through the printed coil board 4a placed between the magnets 8a, 8b is high. The detailed structures of the printed coil board 4b and the magnets 8c and 8d shown in FIG.
The description is omitted because it is the same as that described above.

A current in a direction indicated by an arrow If (hereinafter referred to as a focusing current If) is applied to the focusing coil 5a.
Is supplied, the winding portions 5a1 and 5a2 on two sides perpendicular to the focusing direction Fo receive an electromagnetic force in the focusing direction Fo according to Fleming's law. As a result, the movable section 50 is driven in the focusing direction Fo. When the tracking current It is supplied to the tracking coils 46 to 49, the winding portions 4 on two sides perpendicular to the tracking direction Tk
6a to 49a and 46b to 49b are in the tracking direction Tk.
The movable portion 50 is driven in the tracking direction Tk. In the magnetic circuit configuration of FIG. 1, winding portions 46 a to 49 a and 46 on two sides of each of the tracking coils 46 to 49 are provided.
b to 49b all contribute to the generation of the driving force. Therefore, the acceleration sensitivity of the objective lens driving device is large, and the focusing and tracking follow-up capabilities of the objective lens are increased, so that high-speed recording and reproduction can be performed.

Further, in the objective lens driving device of the first embodiment, as described in detail below, the occurrence of radial tilt in the movable portion 50 is suppressed. FIG. 3 (a), FIG.
(B) is a plan view of the printed coil board 4a and the magnet 8a showing a moment in the movable portion 50 due to an ineffective portion (hatched portion) that does not contribute to the generation of the tracking driving force of the tracking coils 46 to 49. The winding portions (hatch portions) on two sides perpendicular to the focusing direction Fo of the tracking coils 46 to 49 placed in the magnetic fields of the magnets 8a and 8b are in the focusing direction F.
The electromagnetic force applied to o is f or 2f. The moments around the center point O of the printed coil board 4a due to the electromagnetic force f or 2f are shown by arrows M1 and M2. FIG. 3A shows a state in which the movable section 50 has moved by the distance LT in the tracking direction Tk due to the tracking current It.

For simplicity, it is assumed that the area of the wound portion of the ineffective portion of each of the tracking coils 46 to 49 in the magnetic field of the magnets 8a and 8b is as follows. That is,
The ratio of the area of each of the winding portions 46c, 46e, 47c, and 47e to the area of each of the winding portions 46d, 46f, 47d, and 47f is 1: 2. The winding portions 48c, 48e, 49c, 4
9e and the winding portions 48d, 48f, 49d, 49
The ratio of each area of f is 1: 2. It is assumed that the distance between the point of application of the electromagnetic force of the winding portion of each invalid portion symmetrical to the center point O and the center point O is substantially equal. The left winding part 46c-49 of the upper and lower invalid part of each of the tracking coils 46-49.
In c, 46e to 49e, the electromagnetic forces f having the same magnitude in opposite directions are canceled out. The right winding portion 46d of the upper and lower invalid portions of the tracking coils 46 to 49
At 49d and 46f to 49f, the electromagnetic forces 2f of the same magnitude in opposite directions are received, so that they are canceled out. Therefore, the magnitudes of the clockwise moment M1 and the counterclockwise moment M2 around the center point O are equal, and the total moment M is zero.

FIG. 3B shows a state in which the movable portion 50 has moved a distance LT in the tracking direction Tk, and at the same time has moved a distance LF in the focusing direction Fo by the focusing current If. FIG. 4 is a side view showing the distribution of the lines of magnetic force between the magnets 8a and 8b, viewed from the direction of the arrow W in FIG. In FIG. 4, each arrow g indicates the direction of the line of magnetic force, and the length of each arrow g indicates the magnitude of the magnetic flux density. The envelope G of the arrow g indicates a change in the density of the magnetic flux passing through the printed coil board 4a. As shown by the envelope G, the strength of the magnetic field between the magnets 8a2 and 8b2 is not uniform, and the magnetic flux density becomes maximum near the center C of each magnetic pole, and becomes minimum near the magnetization boundary line MB and near the end E. Become. In the state shown in FIG. 3A in which the printed coil substrate 4a has not moved in the focusing direction Fo, the winding portions 46c to 49c and 46e to 49e of the tracking coils 46 to 49 are provided.
e are both located in the magnetic field at portions having substantially the same magnetic flux density. Similarly, the winding portions 46d to 49d
Both d and 46f to 49f are located at portions having substantially the same magnetic flux density. Therefore, the respective electromagnetic forces received by the tracking coils 46 to 49 are also equal.

As shown in FIG. 3B, when the printed coil board 4a moves in the focusing direction Fo, the lower winding portions 46e to 4e of the tracking coils 46 to 49 move.
9e and 46f to 49f approach the center C where the magnetic flux density is high. Therefore, the electromagnetic force applied to the winding portions 46e to 49e and 46f to 49f increases. On the other hand, the winding parts 46c, 46d, 48c, 4 of the tracking coils 46, 48, 4
8d approaches the end E having a low magnetic flux density, so that the electromagnetic force received is small. Further, the winding portions 47c, 47d, 49c, 49d of the tracking coils 47, 49 are provided at the magnetized boundary line M.
As it approaches B, the electromagnetic force it receives becomes smaller.

For the sake of simplicity, the winding portions 46c to 49c of the tracking coils 46 to 49 in FIG.
The density of the magnetic flux passing through 6d to 49d decreases by 20%, and the winding portion 4
It is assumed that the density of the magnetic flux passing through 6e to 49e and 46f to 49f increases by 20%. Winding portions 46c to 46f, 47c to 47f, 48c to 48 of the tracking coils 46 to 49
f, the direction of the electromagnetic force received by 49c to 49f is indicated by an arrow, and the magnitude of the electromagnetic force is indicated by the coefficient of the letter “f” added near each arrow. As can be seen from FIG.
The electromagnetic forces applied to the respective ineffective winding portions cancel each other out by the tracking coils 46 to 49. Therefore, the moments M1 and M2 around the center point O of the printed coil board 4a are equal, and the total moment M is zero. That is, FIG.
No moment is generated unlike the conventional example shown in FIG. Therefore, no radial tilt of the movable portion 50 occurs, and the spot irradiated on the disk surface does not cause aberration. This enables high-speed and accurate recording and reproduction.

Even if the configuration of each element in the present embodiment is modified as follows, it is included in the scope of the present embodiment. (1) Printed coil substrates 4a and 4 in which focusing coil 5a and tracking coils 46 to 49 are integrated
Instead of using b, a thin focusing coil and a tracking coil formed by winding an enamel wire or the like may be attached to the lens holder 2. (2) As shown in FIG. 5A, the magnet 8a is
It may be constituted by an aggregate of two single-pole magnetized magnets 8a3 and four single-pole magnetized magnets 8a4 magnetized so that one magnetic pole of N or S is formed on the plane facing the printed coil substrate 4a. . Also, as shown in FIG.
An integrated multi-pole magnetized magnet 8a5 having six magnetic poles on a plane facing the printed coil board 4a may be used as the magnets 8a to 8d so that the same magnetic poles adjacent to the magnet are shared. A dotted line MB in the drawing indicates a magnetization boundary line. With this configuration, the number of parts is reduced and the assembling work is simplified.

(3) In the configuration of FIG. 1, a strong magnetic circuit is realized by using two magnets 8a and 8b.
However, in an optical disk drive that requires cost reduction, an opposing yoke (not shown) is used instead of the magnet 8b.
May be arranged. As a result, the number of parts is reduced, and an objective lens driving device that is low in cost and does not cause radial tilt of the movable unit 50 can be obtained.

(4) In the configuration shown in FIG. 1, the printed coil boards 4a and 4b are fixed to the lens holder 2 at both ends. A space is provided between the printed coil board 4a and the objective lens 1 for disposing the yoke base plate 18 and the magnet 8b. The size of the magnet 8b may be reduced by using only the magnet 8b1 having two magnetic poles in the focusing direction Fo. In addition, by reducing this space, the lens holder 2 can be reduced in size and weight, and acceleration sensitivity can be improved. At this time, the magnet 8b1 is
Focusing coil 5a and each tracking coil 46
To 49, which are perpendicular to the tracking direction Tk and have a size facing the winding portion on the side close to the focusing coil 5a. Thereby, the magnet 8b1 also contributes to the tracking drive. In the objective lens driving device shown in FIG. 1, a first device including a printed coil substrate 4a and magnets 8a and 8b is provided.
Drive unit, the printed coil board 4b and the magnet 8
Second driving units including c and 8d are arranged on both sides of the objective lens 1. In this embodiment, either one of the first and second driving units may be omitted, and even in such a case, the operation and effect of this embodiment can be obtained.

According to this embodiment, the magnets 8a, 8b
The focusing coil 5a and the tracking coil 4
Since the size is set so as to face all of the winding portions 6 to 49, the driving force is large and high driving sensitivity is obtained. The focusing direction Fo of the tracking coils 46 to 49 is
The moment around the center point O of the printed coil board 4a due to the electromagnetic force applied to the winding part on the side perpendicular to the side is canceled. Accordingly, the radial tilt of the movable unit 50 is suppressed, and stable recording and reproduction can be performed even during high-speed driving.

<Second Embodiment> In a second embodiment of the present invention, the arrangement of the focusing coil 5a and the tracking coils 46 to 49 of the printed coil board 4a and the arrangement of the magnetic poles of the magnet 8a in the first embodiment are changed. Things. The other configuration is substantially the same as that of the first embodiment, and a duplicate description will be omitted.

FIG. 6 is a plan view similar to FIG. 2A showing the printed coil board 24a and the magnet 28 of the objective lens driving device according to the second embodiment of the present invention.

As shown in FIG. 6, the printed coil substrate 2
Two substantially rectangular tracking coils 26 and 27 are vertically arranged at the center of 4a. Tracking coil 26,
27, focusing coils 30 and 31 each having a substantially rectangular shape.
Are arranged respectively. Two tracking coils 2
Reference numerals 6 and 27 are connected in series so that a current flows in a direction indicated by an arrow It. Focusing coils 30, 31
Are connected in series such that current flows in the direction indicated by arrow If. Magnet 2 constituting magnet 28
8a1 and 28a2 are winding portions 26a, 2a of the tracking coils 26, 27 on two sides perpendicular to the tracking direction Tk.
6b and the winding portions 27a and 27b are configured such that mutually opposite magnetic poles come to the positions thereof. Also, the magnet 28a
1, 28a2 are wound portions 30a of two sides perpendicular to the focusing direction Fo of the focusing coils 30, 31;
It is configured such that magnetic poles opposite to each other come to the position of 30b and the winding portions 31a and 31b. As shown in FIG. 6, the two magnets 28a1, 2
8a2. The magnetization boundary is indicated by a dotted line MB. The magnet 28 may be composed of an aggregate of four single-pole magnetized magnets. Further, it may be constituted by one four-pole magnetized magnet having four magnetic poles on the same plane (not shown).

In the second embodiment, similarly to the first embodiment, the winding portions 26a,
Since 6b, 27a and 27b all receive the driving force, high acceleration sensitivity can be obtained during tracking driving. Also,
Since the two focusing coils 30 and 31 are provided, acceleration sensitivity during focusing driving is improved. As a result, the tracking ability of the objective lens during focusing and tracking is enhanced, and high-speed recording and reproduction can be performed. Further, the moment around the coil center point O generated by the electromagnetic force applied to the winding portions 26c, 26d, 27c, 27d of the sides perpendicular to the focusing direction of the tracking coils 26, 27 is canceled, and the radial direction of the movable portion 50 in the radial direction is cancelled. Tilt is suppressed. Since the focusing coils 30 and 31 are larger than the tracking coils 26 and 27, a large driving force can be obtained in the focusing direction.

The objective lens driving device of the second embodiment has high driving sensitivity due to the improvement of acceleration sensitivity. In addition, the radial tilt of the movable section 50 is suppressed, and stable recording and reproduction can be performed even during high-speed driving. Printed coil board 24
Since the number of magnetic poles of the magnet 28 facing a is four,
Less than six in the first embodiment. Therefore, the structure of the magnet is simplified, and the device is inexpensive.

<< Third Embodiment >> In the third embodiment, the tracking coils 46 to 49 of the printed coil board 4a and the magnet 8a in the first embodiment are changed.
The rest of the configuration is the same as that of the first embodiment, and a duplicate description will be omitted.

FIG. 7A is a plan view similar to FIG. 2A showing the printed coil board 34a and the magnet 38 in the objective lens driving device according to the third embodiment of the present invention. As shown in FIG. 7A, the printed coil substrate 3
A substantially rectangular focusing coil 35a is provided at the center of 4a. Substantially rectangular tracking coils 36 and 37 are provided on both sides of the focusing coil 35a. The two tracking coils 36 and 37 are connected in series so that a current flows in a direction indicated by an arrow It.

The magnet 38 comprises three two-pole magnetized magnets 38a1, 38a2 and 38a3. The magnetized boundary line of each magnet is indicated by a dotted line MB. The magnets 38a1 are provided with winding portions 35b, 35 on two sides perpendicular to the focusing direction Fo of the focusing coil 35a.
There are mutually opposite magnetic poles at position c. Magnet 38a
2 and 38a3 are winding portions 36a, 36 of two sides perpendicular to the tracking direction Tk of the tracking coils 36, 37.
The b, 37a, and 37b have mutually opposite magnetic poles at the center. The three magnets 38a1, 3a shown in FIG.
Instead of the combination of 8a2 and 38a3, the magnet 38 may be composed of an aggregate of six single-pole magnetized magnets. Further, as shown in FIG. 7B, two L-shaped one-pole magnetized magnets 71 are provided.
And two rod-shaped one-pole magnetized magnets 72.

According to the magnetic circuit configuration of FIG. 7A, the winding portions 36a, 36b, 37a, 37b on two sides effective for tracking drive of the tracking coils 36, 37 all receive the driving force. High acceleration sensitivity. Therefore, the objective lens 1 has a high tracking ability during focusing and tracking, and high-speed recording and reproduction can be performed. The moment around the coil center O due to the electromagnetic force applied to the winding portions 36c, 37c of the sides perpendicular to the focusing direction Fo of the tracking coils 36, 37, ie, the ineffective portion, is canceled out, and the radial tilt of the movable portion 50 is suppressed.

According to the third embodiment, since the tracking coils 36 and 37 are long in the focusing direction, the winding portions 36a and 36 of the effective portion perpendicular to the tracking direction Tk are used.
b, 37a, 37b are long, and the lengths of the winding portions 36c, 37c of the ineffective portion perpendicular to the focusing direction Fo are short.
Since the ratio of the effective portion in the tracking coils 36 and 37 is large, the acceleration sensitivity at the time of tracking drive is high. Since the tracking coils 36 and 37 are not divided into two like the tracking coils 46 to 49 in FIG. 2, the configuration is simple and the thickness can be reduced. Therefore, the objective lens driving device of the third embodiment is suitable for a thin optical disk drive for a notebook PC or the like.

<< Fourth Embodiment >> FIG. 8 is a perspective view of a main part of an objective lens driving device according to a fourth embodiment of the present invention. In the figure, a printed coil substrate 4 having coils of the same shape
Reference numerals a and b are fixed to both side surfaces of a lens holder 2 supporting the objective lens 1. Printed coil boards 4a, 4b
Are connected by relay printed circuit boards 9a and 9b.
The outer surface of the printed coil board 4a is connected to the yoke base 7a.
Is opposed to the magnet 8a attached at a predetermined gap. Similarly, the outer surface of the printed coil board 4b faces the magnet 8b attached to the yoke base 7b while keeping a predetermined gap. The yoke bases 7a, 7b are fixed to the base 10. The printed coil boards 4a and 4b and the magnet 8a are the same as those shown in FIG.

According to the magnetic circuit configuration of the fourth embodiment, FIG.
As in the first embodiment shown in FIG.
The winding portions 46a to 49a and 46b to 49b on the two sides of 49 all receive the driving force. Therefore, the tracking capability of the objective lens 1 is high, and high-speed recording and reproduction can be performed. The moment around the center O due to the electromagnetic force applied to the wound portion of the tracking coils 46 to 49 on the side perpendicular to the focusing direction Fo, that is, the ineffective portion not involved in driving is also canceled, and the radial tilt of the movable portion 50 is suppressed.

In the fourth embodiment, two magnets 8a,
8c. Therefore, the number of magnets
It is halved compared to the four in the third embodiment. This is effective when cost reduction is required. In the configuration of the first embodiment, the print coils 4a, 4a,
The distance between b and the objective lens 1 is large. Therefore, depending on the shape of the lens holder 2, the rigidity may be reduced and the resonance frequency of the driving unit 50 may be reduced. In the fourth embodiment, as shown in FIG.
Since the distance between the lens 4b and the objective lens is short, the resonance frequency can be sufficiently increased regardless of the shape of the lens holder 1.
Therefore, a material having a low specific gravity and a low rigidity can be selected as the material of the lens holder 2. As a result, the weight of the movable section 50 can be reduced, and an objective lens driving device having high acceleration sensitivity can be realized.

Fifth Embodiment In the fifth embodiment, the configuration of the focusing coil and the tracking coil of the printed coil board 4a and the arrangement of the magnetic poles of the magnet 8a in the first embodiment are changed. The rest of the configuration is the same as that of the first embodiment, and a duplicate description will be omitted. FIG. 9 is a plan view similar to FIG. 2A showing a printed coil board 64a and a magnet 68a in a fifth embodiment of the objective lens driving device according to the fifth embodiment of the present invention. In FIG. 9, two substantially rectangular tracking coils 66a are provided vertically at the left end of the printed coil board 64a. One substantially rectangular focusing coil 65a is provided in another portion of the printed coil board 64a. The tracking coil 66a and the focusing coil 65a are asymmetric with respect to a center line parallel to the focusing direction of the printed coil board 64a. Two tracking coils 66
a is connected in series so that a current flows in the direction shown by the arrow It.

The magnet 68a has two magnets 68.
a1 and 68a2. The magnet 68a1 is configured such that magnetic poles opposite to each other face winding portions 65a1 and 65a2 on two sides perpendicular to the focusing direction Fo of the focusing coil 65a. The magnets 68a2 are configured such that opposite magnetic poles face the respective winding portions 66a1 of the tracking coils 66a perpendicular to the tracking direction Tk. Magnet 68a
May be constituted by an assembly in which four single-pole magnetized magnets are combined, in addition to the combination of two two-pole magnetized magnets shown in FIG. Further, it may be constituted by one four-pole magnetized magnet having four magnetic poles on the same plane.

The printed coil board 64a corresponds to the printed coil board 4a of FIG. The magnet 68a corresponds to the magnet 8a in FIG. In the objective lens driving device of the fifth embodiment, the magnets and the printed coil boards corresponding to the magnets 8b to 8d and the printed coil board 4b in FIG. 1 are the same as the printed coil board 64a and the magnet 68a shown in FIG. ° Equivalent to rotated. With the above configuration, both magnets 68a and both printed coil substrates 64
a is symmetrical with respect to the optical axis of the objective lens 1. Both focusing coils 65a and both tracking coils 66a
Are supplied with current so that electromagnetic force acts in the same focusing direction Fo and the same tracking direction Tk.

According to the fifth embodiment, since the driving force acts on all the winding portions on the two sides of each tracking coil 66a,
High acceleration sensitivity is obtained. As a result, the tracking capability of the objective lens during tracking and focusing is enhanced, and high-speed recording and reproduction can be performed. Tracking coil 6
The moment around the center point O generated by the electromagnetic force applied to the winding portion of the side perpendicular to the focusing direction Fo of 6a, that is, the ineffective portion where the driving force does not work is also canceled, and the radial tilt of the movable portion 50 is suppressed. This enables stable recording and reproduction of signals even at the time of high-speed driving. Since the focusing coil 65a has winding portions 65a1 and 65a2 long in the tracking direction, the winding portions 65a1 and 65a2 of the effective portion perpendicular to the focusing direction Fo.
Increases, and the area of the invalid portion perpendicular to the tracking direction decreases. Focusing coil 65a
The ratio of the effective portion in the whole increases, and the acceleration sensitivity further improves. This embodiment is particularly applicable to the focusing direction Fo.
It is suitable for an objective lens driving device requiring a high driving sensitivity. The number of magnetic poles of the magnet 68a is four,
Since there are less than six magnets 8a in the embodiment, the magnet 68a is inexpensive.

<< Sixth Embodiment >> FIG. 10 is a perspective view of a main part of an objective lens driving device according to a sixth embodiment of the present invention. The configuration of the present embodiment is similar to the objective lens driving device of the fourth embodiment shown in FIG. What is different is the configuration of the suspension wires 53a to 53d and the printed coil board 54.
a and 54b.

In FIG. 10, the suspension wire 5
One end of each of 3a, 53b, 53c and 53d is fixed to the relay printed circuit boards 9a and 9b, and the other end is
1 is fixed. 6 suspension wires in total
There are four suspension wires 53 in FIG.
a to 53d are visible. The other two invisible suspension wires 53e and 53f are suspension wires 5
In parallel with 3d, the relay printed circuit board 9a and the wire holder 1
It is spread between one. Arrow R indicates printed circuit board 54a,
An axis passing through the center of 54b and perpendicular to the tracking direction Tk, and is hereinafter referred to as an axis R. The rotation direction about the axis R is represented by an arrow Rt. The arrow Rt indicates the movable part 5 including the objective lens 1
1 indicates a tilt in the tracking direction Tk (radial direction of the disc), that is, a radial tilt.

FIGS. 11A and 11B are plan views of the printed coil boards 54a and 54b as viewed from the direction of the axis R. Printed coil substrates 54a and 54b are provided with substantially rectangular tracking coils 56a and 56
b. Substantially rectangular focusing coils 55a and 55b are formed on both sides of the tracking coil 56a of the printed coil board 54a. Substantially rectangular focusing coils 55c and 55d are formed on both sides of the tracking coil 56b of the printed coil board 54b. The focusing coils 55a and 55c are connected via the relay printed circuit board 9a. When the current It flows through the focusing coils 55a and 55c, the focusing coils 55a and 55c
o each focusing coil 5 so as to generate a driving force.
The winding directions of 5a and 55c and the directions of the magnetic poles of magnets 8a and 8c are determined. Similarly, the focusing coils 55b and 55d are connected via the relay printed circuit board 9b. Focusing coils 55b, 55d
When the current If flows through the focusing coil 55b,
The winding directions of the focusing coils 55B and 55d and the directions of the magnetic poles of the magnets 8a and 8b are set so that the driving force of the focusing coils 55B and 55d is generated in the same focusing direction Fo.

The tracking coils 56a and 56b are connected via relay printed circuit boards 9a and 9b. When applying the current It to the tracking coils 56a and 56b,
The winding directions of the tracking coils 56a and 56b and the directions of the magnetic poles of the magnets 8a and 8b are set so that a driving force is generated in the same tracking direction Tk. Of the six suspension wires 53a to 53f, two suspension wires are the focusing coils 55a and 55f.
c is used to supply the drive current. The other two suspension wires are the focusing coils 55b, 55
d is used to supply the drive current. The remaining two suspension wires are used as tracking coils 56a, 56
b is used to supply the drive current.

Next, the operation will be described with reference to FIGS. When driving in the focusing direction Fo, the focusing coils 55a to 55d
, A current in the same direction indicated by an arrow If is passed. Accordingly, the focusing coils 56a to 56d are driven in the same focusing direction Fo, and the focusing operation of the movable unit 51 is performed. When driving in the tracking direction Tk, the tracking coils 56a and 56b
A current in the direction indicated by t is passed. Accordingly, the tracking coils 56a and 56b receive the driving force in the tracking direction Tk, and the tracking operation of the movable unit 51 is performed.

In the first to fifth embodiments, the movable portion 5
No radial tilt of 0 or 51 occurs. However, in the manufacture of the objective lens driving device, there are dimensional errors that cannot be ignored in each element such as the printed coil substrate, the magnet, and the suspension wire. Further, it is inevitable that an assembly error occurs in the assembly process. Radial tilt may occur in the completed objective lens driving device due to a manufacturing error including a dimensional error and an assembly error of each element. Further, the disk may be distorted in the radial direction. This disk distortion causes radial tilt with respect to the objective lens. In the objective lens driving device of the sixth embodiment, the focusing coils 53a,
A current is supplied to the set of 3c and the set of focusing coils 53b and 53d via respective pairs of suspension wires. Therefore, the focusing coil 55
a, 55c and focusing coils 55b, 55
The set of d can be supplied with currents in different directions or currents of different values. In the present embodiment, the radial tilt due to the manufacturing error is detected by the tilt sensor 80 of a known configuration attached to the movable portion 51. Based on the detection result of the tilt sensor 80, for example, the focusing coil 55b shown in FIGS.
The direction of the current If of 55d is changed as shown by the dotted line. As a result, the focusing coils 55b and 55d are driven in the directions indicated by the dotted arrows. As a result, a rotational force acts on the printed coil boards 54a and 54b in the direction indicated by the arrow Rt. As a result, the movable portion 51 rotates in the direction indicated by the arrow Rt in FIG. 10 and tilts in the radial direction. By controlling the current If supplied to the focusing coils 55b and 55d according to the detection output of the tilt sensor 80, it is possible to correct radial tilt caused by manufacturing errors or aging.

According to the sixth embodiment, a driving force is applied to the winding portions on two sides effective for tracking driving of the tracking coils 56a and 56b.
A driving force is applied to the winding portions on two sides effective for the focusing drive of a to 55d. Therefore, the acceleration sensitivity is improved, the tracking capability of the objective lens is increased, and high-speed recording and reproduction can be performed. Further, by individually driving a plurality of focusing coils disposed on the printed coil substrate, radial tilt can be corrected. The same effect can be obtained by arranging a plurality of tracking coils on the printed coil board in the focusing direction and individually driving each of them. As described above, the objective lens driving device of the present embodiment achieves high driving sensitivity and performs tilt control in the radial direction by applying driving currents of different directions and different values to a plurality of focusing coils. Can be. As a result, the inclination of the objective lens 1 with respect to the disk is corrected, so that stable recording and reproduction can always be performed. The rotational force can be applied to the movable section 50 by applying the current If in the same direction to the focusing coils 30 and 31 of the printed coil board 24a shown in FIG. 6, and the tilt control in the radial direction can be performed. .

[0063]

As described in detail in each of the above embodiments, according to the present invention, the magnetic poles of the magnet provided opposite to the substantially rectangular focusing coil and the substantially rectangular tracking coil disposed on the same plane. Are formed at positions facing all the winding portions that generate driving forces in the respective driving directions of the focusing coil and the tracking coil. As a result, a high drive sensitivity is obtained, the tracking capability of the objective lens is increased, and high-speed recording and reproduction can be performed. In addition, the moment around the center point of the printed coil board due to the electromagnetic force that is applied to the winding part of the side perpendicular to the focusing direction of the tracking coil, that is, the ineffective part that does not contribute to the generation of the driving force, is canceled, and the radial tilt of the movable part is suppressed Is done. As a result, stable recording and reproduction can be performed even during high-speed driving. Further, the radial tilt can be controlled by providing a plurality of focusing coils in the tracking direction and changing the current direction and the current value of some of them.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an objective lens driving device according to a first embodiment of the present invention.

2A is a plan view showing the positional relationship between the printed coil board 4a and the magnet 8a of the objective lens driving device of the first embodiment, as viewed from the direction of the arrow V in FIG. 1, and FIG. 2B is a plan view of the magnet 8b.

FIG. 3A illustrates a tracking coil substrate 4a during a tracking operation of the objective lens driving device according to the first embodiment.
FIG. 4B is a plan view showing the positional relationship between the tracking coil substrate 4a and the magnet 8a during the tracking operation and the focusing operation of the objective lens driving device of the first embodiment.

FIG. 4 is a side view showing a magnetic flux density distribution between magnets 8a and 8b in the objective lens driving device of the first embodiment.

5A is a plan view including a printed coil board showing another configuration example of the magnet in the objective lens driving device of the first embodiment. FIG. 5B is a plan view of the magnet in the objective lens driving device of the first embodiment. Plan view including a printed coil board showing another configuration example

FIG. 6 is a plan view of a printed coil board and a magnet of an objective lens driving device according to a second embodiment of the present invention.

7A is a plan view of a printed coil substrate and a magnet of an objective lens driving device according to a third embodiment of the present invention; FIG. 7B is a plan view illustrating another example of the magnet according to the third embodiment;

FIG. 8 is a perspective view of a main part of an objective lens driving device according to a fourth embodiment of the present invention.

FIG. 9 is a plan view of a printed coil board and a magnet of an objective lens driving device according to a fifth embodiment of the present invention.

FIG. 10 is a perspective view of a main part of an objective lens driving device according to a sixth embodiment of the present invention.

FIGS. 11A and 11B are plan views of a printed coil board and a magnet of an objective lens driving device according to a sixth embodiment of the present invention.

FIG. 12 is a perspective view of a main part of a conventional objective lens driving device.

13 is a plan view of a printed coil substrate and a magnet in the conventional objective lens driving device, as viewed from the direction of arrow V in FIG.

14A is a plan view of a print coil and a magnet during a tracking operation in a conventional objective lens driving device. FIG. 14B is a view illustrating positions of a print coil and a magnet during a tracking operation and a focusing operation in the conventional objective lens driving device. Plan view showing the relationship

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3a-3d Suspension wire 4a, 4b Printed coil board 5a Focusing coil 5a1, 5a2 Winding part 7a, 7b Yoke base 8a1 First magnet 8a2, 8a3 Second magnet 8a, 8b, 8c, 8d Magnets 8b1, 8b2, 8b3 Two-pole magnetized magnets 9a, 9b Relay printed circuit board 10 Base 11 Wire holder 17, 18, 19, 20 Yoke base plate 24a Coil unit 26, 27 Tracking coil 28 Magnet unit 28a1 First magnet unit 28a2 Second magnet part 30, 31 Focusing coil 34a Coil part 35a Focusing coil 36, 37 Tracking coil 38 Magnet part 38a1 First magnet 38a2, 38a3 Second Magnets 46 to 49 Tracking coils 46a, 46b, 47a, 47b, 48a, 49a Winding section 50 Moving section 54a Coil section 55a, 55b Focusing coil 56a Tracking coil 65a Focusing coil 66a Tracking coil 68a Magnet section 68a1 First magnet Fo focusing Direction MB, MB1, MB2, MB3 Magnetization boundary line Tk Tracking direction

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Yamamoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5D118 AA13 BA01 BB02 BF02 BF03 DC03 EA02 EC04 EC10 ED05 ED08 EE05 FA29 FB20 5D119 AA09 AA21 BA01 DA01 DA05 JA43

Claims (17)

[Claims] 1. An objective lens for converging a light beam for recording or reproducing information on a disc to the disc, a lens holder holding the objective lens, and a focusing direction of the objective lens in an optical axis direction of the objective lens. At least one focusing coil attached to the lens holder and having a winding axis perpendicular to a plane including the focusing direction and the tracking direction, and at least one focusing coil attached to the lens holder. A coil portion having two tracking coils, and two winding portions disposed opposite to the coil portion and receiving electromagnetic force in a focusing direction of the focusing coil when an electric current is applied to the coil portion. And the tracking core An objective lens driving device comprising: a magnet unit having a plurality of magnets arranged such that opposite magnetic poles are opposed to each of two winding units receiving an electromagnetic force in a tracking direction of the file. 2. The objective lens driving device according to claim 1, wherein the focusing coil and the tracking coil are arranged on the same substrate. 3. The objective lens driving device according to claim 1, wherein the coil unit has a plurality of focusing coils and a plurality of tracking coils smaller than the focusing coils. 4. The coil portion is composed of a plurality of layers, and the focusing coils formed on each layer are connected in series between the layers so that current flows through the focusing coils of each layer in the same direction, and are formed on each layer. 3. The objective lens driving device according to claim 2, wherein the tracking coils are connected in series between the respective layers so that a current flows in the same direction in the tracking coils of the respective layers. 5. The magnet unit according to claim 1, wherein the magnet unit is formed of a single-pole magnetized magnet having an N pole on one surface and an S pole on the other surface. Objective lens driving device. 6. The objective according to claim 1, wherein the magnet portion is formed of an assembly of two-pole magnetized magnets having an N pole on at least a part of one surface and an S pole on another part. Lens drive. 7. The objective according to claim 1, wherein the magnet section is one multi-pole magnetized magnet having at least two or more north poles and two or more south poles on one surface. Lens drive. 8. An objective lens for converging a light beam for recording or reproducing information on a disc to the disc, a lens holder holding the objective lens, and a focusing direction of the objective lens in an optical axis direction of the objective lens. A supporting member movably supporting the disk in a radial tracking direction of the disk, a focusing coil formed at a central portion of the substrate, the focusing coil having at least one layer attached to a lens holder, and focusing on the substrate. On both sides of the coil, a coil unit having at least two tracking coils respectively symmetrical to a center line parallel to the tracking direction of the focusing coil and aligned in a direction perpendicular to the center line, and facing the focusing coil The edge parallel to the focusing direction A first magnet having a magnetic pole facing a half of the tracking coil through a center of the tracking coil and facing a winding portion intersecting a focusing direction of the focusing coil, and a remaining half of the tracking coil An objective lens driving device including a magnet portion including a second magnet having a magnetic pole facing a winding portion that faces a region of the tracking coil and intersects a tracking direction of the tracking coil. 9. The objective lens driving device according to claim 8, wherein a center line parallel to the tracking direction of the focusing coil is located on a boundary between the first and second magnets. 10. The objective lens according to claim 1, wherein the coil unit has a rectangular focusing coil having two sides substantially parallel to the focusing direction and a rectangular tracking coil having two sides substantially parallel to the tracking direction. Drive. 11. The magnet unit includes a first magnet having two magnetic poles on a surface, and a second magnet having two magnetic poles on the surface in an arrangement opposite to that of the first magnet. Two winding portions of the coil portion, which receive electromagnetic force in the respective focusing directions of the plurality of focusing coils, are disposed so as to face opposite magnetic poles of the first and second magnets, respectively. The two winding portions of the tracking coil receiving electromagnetic force in the respective tracking directions are disposed so as to face opposite magnetic poles on both sides of the boundary between the first and second magnets. The objective lens driving device according to claim 1, wherein 12. The first magnet having two magnetic poles on a surface thereof, the magnet unit being disposed on both sides of the first magnet on the same surface as the surface of the first magnet,
And two second magnets having a magnetized boundary line substantially orthogonal to the magnetized boundary line of the first magnet, wherein a focusing coil of the coil unit is provided at a magnetic pole of the first magnet. 2. The objective lens driving device according to claim 1, wherein the at least two tracking coils are disposed so as to face each other, and each of the at least two tracking coils faces the magnetic pole of the second magnet. 13. The objective lens driving device according to claim 12, wherein the tracking coil is long in a direction along a magnetization boundary of the second magnet. 14. An objective lens for converging a light beam for recording or reproducing information on a disk to the disk, a lens holder for holding the objective lens, and a focusing direction of the lens holder in an optical axis direction of the objective lens. A supporting member movably supporting in a radial tracking direction of the disk, a focusing coil formed on at least one substrate attached to the lens holder, and asymmetric with respect to a center line parallel to the focusing direction of the substrate. A coil unit having a tracking coil asymmetric with respect to the center line;
And a first magnet having two magnetic poles facing the focusing coil on a surface, and being disposed on the same surface as the first magnet adjacent to the first magnet, and having a boundary between the first magnet and the first magnet. An objective lens driving device including a magnet unit having a second magnet passing through the center of the tracking coil in a focusing direction. 15. The apparatus according to claim 15, further comprising two coil units, wherein the two coil units are arranged such that a focusing coil and a tracking coil of each coil unit are symmetric with respect to an optical axis of the objective lens. The objective lens driving device according to claim 14, wherein: 16. The coil unit faces at least one of the first and second magnets, and at least two coils are supplied with currents of different directions and values from separate current supply lines.
2. The objective lens driving device according to claim 1, comprising: one focusing coil; and a tracking coil facing a boundary between the first and second magnets. 3. 17. The objective lens driving device according to claim 16, wherein a current is supplied to the at least two focusing coils via a support member of the lens holder.