JPH10261233A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a tilt from a low frequency to a high frequency and to control tilt correction with stable drive sensitivity and controllable property regardless of a position of a movable body in the focusing and tracking directions by respectively arranging a yoke and a permanent magnet on the positions containing the centroid of the movable body and becoming symmetric for a plane perpendicular to the radial direction. SOLUTION: In this objective lens driving device, the tilt is detected by a light quantity of light received by light receiving parts 4b, 4c of a tilt detector after the light emitted from the light emission part of the tilt detector is reflected by a disk 13. When a relative angle between an optical axis of an objective lens 1 and the disk 13 is tilted, by respectively inputting different signals generated by the light receiving parts 4b, 4c to a differential amplifier, and taking a difference between them, a tilt detection signal is generated. This tilt detection signal is energized through tilt coils 9a-9d, and tilt drive is performed, and the tilt is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device for an apparatus for optically recording or reproducing information on a disk-shaped recording medium.

[0002]

2. Description of the Related Art An objective lens driving device is used to correct a focusing deviation due to a vertical movement of a disk-shaped recording medium (hereinafter referred to as a disk) such as a compact disk, a tracking deviation due to eccentricity, and a relative inclination between a disk and an objective lens. Then, the objective lens is driven in three directions: a direction perpendicular to the disk (hereinafter, referred to as a focusing direction), a radial direction of the disk (hereinafter, referred to as a tracking direction), and a rotational direction around the tangential direction of the disk (hereinafter, referred to as a tilt direction).

In the optical information recording / reproducing apparatus including the above-described objective lens driving device, if a tilt which is a relative inclination of the optical axis of the objective lens with respect to the disk surface occurs, an optical aberration occurs and the recording / reproducing is performed. This causes deterioration of the signal at the time.

For this reason, in a conventional optical recording / reproducing apparatus, D
A tilt correction control device for tilting the entire optical pickup by a tilt motor such as a C motor and performing tilt correction has been attached.

Further, as an example of an objective lens driving device for detecting a tilt which is a relative angle between a disk and an objective lens and correcting the tilt at a high speed, as disclosed in Japanese Patent Application Laid-Open No. 6-162540, There is a method in which a drive current flowing through a plurality of focusing coils fixed to a movable body is adjusted based on a detection signal that detects a tilt to perform tilt correction.

Further, as disclosed in Japanese Patent Application Laid-Open No. 7-240031, at least one permanent magnet is fixed to a movable body, and the current flowing through at least two focusing coils fixed to a fixed base is adjusted. In some cases, tilt correction is performed.

The above-mentioned Japanese Unexamined Patent Publication No. 7-240031 will be described with reference to FIGS. 9, 10 and 11. FIG.

FIG. 9 is a schematic view of an essential part when the movable body is located at a neutral position for explaining the operation of the objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 7-240031, and FIG.
FIG. 11 is a schematic diagram of a main part when the movable body moves in a tracking direction from a neutral position for explaining the operation of the objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 7-240031.
FIG. 4 is a magnetic flux density distribution diagram in a tracking direction of a magnetic gap portion between a permanent magnet and an opposing yoke for explaining the operation of the objective lens driving device disclosed in Japanese Unexamined Patent Publication (Kokai) No. H11-15095.

9 and 10, reference numeral 101 denotes an objective lens, 102 denotes a lens holder for holding the objective lens 101, 103a and 103b denote permanent magnets fixed to the lens holder 102, and Ha and Hb denote permanent magnets 103a and 103.
b, magnetization directions of 105a to 105d are opposite yokes, 1
06a to 106d are tracking coils, 107a to 1
07d is a focusing coil, 104 is a tilt detector, 104a is a light emitting unit of the tilt detector 104, 104b,
104c is a light receiving portion of the tilt detector 104, T is a tracking direction, and K is a tangential direction. The movable body is an objective lens 101, a lens holder 102, a permanent magnet 103a,
103b and a tilt detector 104.

Further, x is an axis representing the position in the tracking direction T, and FIG. 9 shows the positional relationship between the movable body and the opposing yokes 105a to 105d when the movable body is located at the neutral position. Represents the movable body and the opposing yoke 105 when the movable body moves in the tracking direction T from the neutral position.
It shows the positional relationship with a to 105d.

In FIG. 11, x is an axis representing the position in the tracking direction T shown in FIGS.
B0 is the magnetic flux density distribution of the component in the direction K on the axis x when the movable body and the opposed yokes 105a and 105b have the positional relationship shown in FIG. 9, and B1 is the movable body and the opposed yokes 105a and 105b.
5b is the magnetic flux density distribution of the component in the direction K on the axis x when the positional relationship is shown in FIG.

According to the configuration disclosed in Japanese Patent Application Laid-Open No. 7-240031, when the movable body is as shown in FIG. 9, the magnetic flux density distribution is as shown by B0, whereas when the movable body is as shown in FIG. The distribution is as shown by B1, and is a distribution shifted in the moving direction of the movable body.

Therefore, since the relative position fluctuation between the point of application of the driving force and the movable body is suppressed, the tilt drive sensitivity fluctuation due to the position of the movable body is suppressed, and the generation of an unnecessary rotational moment due to the movement of the movable body. It can be suppressed.

[0014]

In an optical recording / reproducing apparatus using a disk, in order to improve the recording capacity, it is necessary to use an objective lens having a high aperture ratio to perform recording / reproducing with a smaller diameter condensing spot. is increasing. In this case, the degree of aberration due to the tilt, which is the relative inclination of the optical axis of the objective lens with respect to the disk, increases in proportion to the cube of the aperture ratio. In positioning the optical axis, more precise positioning is required.

However, the means for correcting the tilt of the entire optical head by using a DC motor or the like as described above can correct only a low-frequency angle shift, and it is difficult to reduce the aberration. It is very difficult to match the center of rotation during tilt correction with the principal point of the objective lens due to the lack of space. There is a problem that the displacement is large, and therefore, the size is increased by adding some adjustment means.

The above-mentioned problem is described in Japanese Patent Laid-Open No. 6-162.
As disclosed in Japanese Patent Publication No. 540, a tilt which is a relative angle between a disk and an objective lens is detected, and a drive current flowing through a plurality of focusing coils fixed to a movable body is adjusted based on the detected signal to tilt the disk. If the correction is performed, it is possible to correct a tilt from a low frequency to a high frequency.

However, in the configuration disclosed in JP-A-6-162540, the magnetic circuit is fixed.
For example, as the movable body moves in the tracking direction, the positions of the plurality of focusing coils with respect to the magnetic flux density distribution of the magnetic circuit change, and the amount of magnetic flux linked to each focusing coil changes.

Accordingly, the drive sensitivity in the tilt correction direction fluctuates depending on the position of the movable body, and there is a problem that the stability of control is deteriorated.

Further, since the positions of the plurality of focusing coils or tracking coils with respect to the magnetic circuit vary with the movement of the movable body, the relative position between the point of application of the driving force and the movable body varies.

Therefore, when a rotational moment is applied to the movable body by the focusing drive or the tracking drive, the optical axis is tilted, and an unstable offset is always added to the tilt correction direction, and the control accuracy in the tilt correction control is reduced. There was a problem of deterioration.

Regarding the above-mentioned problem in the configuration disclosed in JP-A-6-162540, see JP-A-7-2.
In the configuration disclosed in Japanese Patent No. 40031, at least one permanent magnet is fixed to a movable body, and a current flowing through at least two focusing coils fixed to a fixed base is adjusted, thereby tilting according to the position of the movable body. In addition to suppressing the fluctuation of the drive sensitivity, it is possible to suppress the generation of unnecessary rotational moment due to the movement of the movable body.

However, as shown in FIGS. 9 and 10, focusing coils 107a and 107b and tracking coil 106 are mounted on opposed yokes 105a and 105b.
a and 106b, so that two opposed yokes 105
A space for the winding is always required between a and 105b. In order to obtain a sufficient drive sensitivity, it is necessary to secure a sufficient coil space.
The space between 105b must be large. Therefore, one for each of the two opposing yokes 105a and 105b.
In the configuration of the three permanent magnets 103a, for example, when the movable body moves in the tracking direction T as shown in FIG.
7a and the tracking coil 10
The change rate of the increase of the magnetic flux linked to the focusing coil 107b and the focusing coil 107b increases. For this reason, the point of action of the driving force moves more than the moving amount of the movable body. Therefore, the rotational drive sensitivity varies depending on the position of the movable body, and thus the stability of control is deteriorated. Also, the rotational moment is applied to the movable body, causing the optical axis to tilt, and the optical axis is always unstable in the tilt correction direction. There is a problem that the offset is added and the control accuracy in the tilt correction control is deteriorated.

Further, there is a problem that the amount of magnetic flux is reduced due to the space between the opposed yokes 105a and 105b, and the drive sensitivity in the focusing direction F and the tracking direction T is deteriorated.

In view of the above problems of the conventional objective lens driving device, the present invention corrects the tilt from low frequency to high frequency, and provides the driving sensitivity and the sensitivity regardless of the position of the movable body in the focusing direction and the tracking direction. An object of the present invention is to provide an objective lens driving device capable of performing tilt correction control with stable controllability.

[0025]

In order to solve the above-mentioned problems, an objective lens driving apparatus according to the present invention comprises an objective lens for recording or reproducing optical information on a disk-shaped recording medium, and a lens for holding the objective lens. A movable body having two or more permanent magnets having a direction of magnetization in a tangential direction perpendicular to the optical axis direction of the holder and the objective lens and perpendicular to the radial direction of the disc-shaped recording medium, and fixed to the lens holder. When,
A rod-shaped support member that movably supports the movable body in the optical axis direction of the objective lens or in a radial direction of the disk-shaped recording medium, a fixed base that fixes the rod-shaped support member, and that is fixed to the fixed base. And a yoke made of a magnetic material disposed at a position facing each of the two or more permanent magnets along the direction of the magnetization, and wound around each of the yokes using the optical axis direction as a winding axis. Focusing drive coil, a tracking drive coil wound around each yoke with the radial direction as a winding axis, and a tilt drive coil wound around each yoke with the optical axis direction as a winding axis. And the yoke and the permanent magnet are disposed at positions substantially including the center of gravity of the movable body and substantially symmetric with respect to a plane perpendicular to the radial direction.

Since the permanent magnets are arranged at positions opposed to the two opposing yokes, the shift amount of the driving action point during the movement of the movable body can be reduced even if the distance between the two opposing yokes becomes large in order to secure the coil space. Can be optimized.

Accordingly, even when the movable body is driven in the focusing direction and the tracking direction at the same time, the center of gravity of the movable body and the point of application of the focusing driving force and the tracking driving force can always be matched.

Accordingly, no unnecessary rotational moment is generated when the movable body is moved, so that the optical axis of the objective lens does not tilt, and an unstable tilt offset is not added in the tilt correction direction. Deterioration can be eliminated.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a configuration of an objective lens driving device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a main portion of the objective lens driving device according to an embodiment of the present invention when there is no tilt. FIG. 3 is a schematic diagram of a main part of the objective lens driving device according to the embodiment of the present invention when tilt occurs. FIG. 4 is a diagram of a tilt correction control circuit of the objective lens driving device according to the embodiment of the present invention. FIG. 5 is a circuit configuration diagram, and FIG. 5 is a schematic diagram of a main part for describing the operation of the objective lens driving device according to one embodiment of the present invention.

In FIG. 1, FIG. 2, FIG. 3 and FIG.
3 is a disk, T is a tracking direction parallel to the radial direction of the disk 13, A and B are directions in the tracking direction T, F is a focusing direction perpendicular to the disk 13, K is perpendicular to the focusing direction F and the tracking direction T. Directions, 1 is an objective lens, J is the optical axis of the objective lens 1, 2 is a lens holder on which the objective lens 1 is mounted, and 3a to 3d are symmetrical with respect to a plane including the optical axis J and perpendicular to the tracking direction T. Permanent magnets arranged and fixed on the lens holder 2 two by two, and Ha to Hd are permanent magnets 3a to
The direction of magnetization 3d, 4 is a tilt detector provided on the lens holder 2, 4a is a light emitting section of the tilt detector 4, 4b, 4
c denotes a light receiving unit arranged in the tracking direction T with the light emitting unit 4a interposed therebetween. Light emitted from the light emitting unit 4a is reflected by the disc and received by the light receiving units 4b and 4c. Can occur.

Therefore, the objective lens 1, the lens holder 2,
A movable body is constituted by the permanent magnets 3a to 3d and the tilt detector 4. 6a to 6d are bobbins formed by resin-molding flat opposing yokes 5a to 5d made of a magnetic material; 7a to 7d are tracking coils wound around the bobbins 6a to 6d in the tracking direction T; 8a to 8d are focusing coils having winding axes in the focusing direction F and wound on bobbins 6a to 6d, respectively, and 9a to 9d are winding coils in the focusing direction F.
The tilt coils are wound around bobbins 6a to 6d, respectively, and the tilt coils 9a to 9d are connected in series. 10a to 10d are wire members formed of a conductive material which are substantially parallel bar-shaped support members having an axis in the direction K. One end of each of the wire members 10a to 10d is connected to the lens holder 2. ing. 1
Reference numeral 1 denotes a suspension holder to which the other ends of the wire members 10a to 10d are connected, and 12 denotes a bobbin 6a.
6d and a fixing base for fixing the suspension holder 11. Therefore, the movable body is a wire member 10a-1.
By 0d, the fixed base 12 is supported movably in the focusing direction F, the tracking direction T, and the rotation direction around the direction K.

In FIG. 4, reference numeral 14 denotes a tilt detector 4
Is a differential amplifier that takes the difference between the light detection signals from the light receiving sections 4b and 4c, and outputs the tilt coils 9a to 9c.
d is energized.

In FIG. 5, Ia to Id are disks 13
When the relative angle between the tilt coil 4 and the tilt detector 4 becomes, for example, the state shown in FIG. 3, the direction of the current flowing through the tilt coils 9a to 9d, and M indicates the current flowing in the direction of Ia to Id through the tilt coils 9a to 9d Sometimes the direction of the moment received by the movable body.

S is the wire members 10a to 10d
Is a quadrangular centroid composed of four points supporting the movable body, that is, a support center, and P1 is a midpoint of a line segment connecting centroids of the magnetic pole surfaces of the permanent magnets 3a, 3b, ie, the permanent magnets 3a, 3b.
, P2 (not shown) are permanent magnets 3c, 3d
The midpoint of the line connecting the centroids of the magnetic pole faces, ie, the permanent magnet 3
c, 3d, the center of gravity of the movable body and the support center S
And the drive centers P1 and P2 are on the same straight line, and the same straight line is orthogonal to the optical axis J.

Next, the operation of the embodiment will be described.

FIG. 6 is a schematic view of an essential part for explaining the operation when the movable body of the objective lens driving device according to the embodiment of the present invention is located at the neutral position, and FIG. 7 is a diagram illustrating the operation of the embodiment of the present invention. FIG. 8 is a schematic view of an essential part for describing an operation when a movable body of the objective lens driving device moves from a neutral position in a tracking direction. FIG. 8 is tracking for explaining an operation of the objective lens driving device according to an embodiment of the present invention. It is a magnetic flux density distribution figure in the direction.

First, the driving in the tracking direction T is performed by making the magnetic flux generated by the permanent magnets 3a to 3d fixed to the lens holder 2 to which the objective lens 1 is attached orthogonal to the current flowing through the tracking coils 7a to 7d. Upon receiving the obtained electromagnetic force, the lens holder 2 moves the wire member 1
Obtained by substantially translating in the tracking direction T supported by 0a to 10d.

The driving in the focusing direction F is obtained by the magnetic flux generated by the permanent magnets 3a to 3d fixed to the lens holder 2 on which the objective lens 1 is mounted, being orthogonal to the current flowing through the focusing coils 8a to 8d. The lens holder 2 is supported by the wire members 10a to 10d under the electromagnetic force and is substantially translated in the focusing direction F.

Next, a tilt drive which is a drive in the rotation direction around the direction K will be described.

First, tilt detection is performed as follows. When the optical axis J of the objective lens 1 and the disk 13 are perpendicular to each other, as shown in FIG.
The amount of light received by the light receiving units 4b and 4c after the light emitted from a is reflected by the disk 13 is equal between the light receiving units 4b and 4c. However, when the relative angle between the optical axis J of the objective lens 1 and the disk 13 is inclined as shown in FIG.
The amount of light received by the light receiving unit 4c is larger than the amount of light received by b. Therefore, as shown in FIG. 4, the signals generated in the light receiving portions 4b and 4c are
, And a difference is obtained to generate a tilt detection signal.

Next, the tilt drive, which is a drive in the rotational direction around the direction K, is performed as follows. As shown in FIG. 4, when the tilt detection signal is input to the tilt coils 9a to 9d, the tilt coils 9a to 9d are connected in series,
The direction of the flowing current is the direction of Ia to Id shown in FIG. 5A. Therefore, the permanent magnets 3a to 3d are
Since the reaction force generated in 9d is received, a rotational moment in the direction of M is generated in the movable body.

As described above, the relative angle between the disk 13 and the movable body is detected by the tilt detector 4, and a tilt detection signal corresponding to the amount of tilt is supplied to the tilt coils 9a to 9d. The tilt of the lens 1 with respect to the optical axis J is corrected.

Further, the tilt drive when the movable body moves in the tracking direction T will be described.

6 and 7, T is a tracking direction parallel to the radial direction of the disk 13, A and B are directions in the tracking direction T, K is a focusing direction F
And a direction perpendicular to the tracking direction T, 1 is an objective lens, 2 is a lens holder, 3a to 3d are permanent magnets,
Ha to Hd are directions of magnetization of the permanent magnets 3a to 3d, 4 is a tilt detector, 4a is a light emitting unit of the tilt detector 4, 4b, 4
c is a light receiving portion, 5a to 5d are opposing yokes, 7a to 7d are tracking coils, 8a to 8d are focusing coils, and 9a to 9d are tilt coils. In FIG. 8, x is the tracking direction T shown in FIGS.
B0 is the movable body and the opposing yoke 5
a and 5b are in the positional relationship shown in FIG. 6, the component magnetic flux density distribution in the direction K on the axis x, and B1 is when the movable body and the opposed yokes 5a and 5b are in the positional relationship shown in FIG. Is the magnetic flux density distribution of the component in the direction K on the axis x of the graph.

First, when the movable body is located at the neutral position as shown in FIG. 6, the center lines of the permanent magnet 3a and the opposing yoke 5a and the permanent magnet 3b and the opposing yoke 5b in the tracking direction T coincide with each other. Thus, the magnetic flux density distribution is symmetrical as shown by B0 in FIG. On the other hand, when the movable body moves in the tracking direction, for example, the direction A as shown in FIG. 7, the magnets 3a and 3b move, so that the magnetic flux density distribution also changes and becomes B1 in FIG. Is shifted to the direction A of the tracking direction T and becomes a biased distribution. At this time, since the shift amount of the distribution coincides with the movement amount of the movable portion, the point of application of the driving force of the focusing drive and the tracking drive acts substantially on the center of gravity. Therefore, regarding the focusing drive and the tracking drive, the center of gravity can be driven regardless of the position of the movable body. The same applies to the tilt drive, since the moment acting on the permanent magnet 3a and the permanent magnet 3b is always equal regardless of the position of the movable body, the drive in the rotational direction always rotates around a fixed axis.

As described above, in one embodiment, the opposing yokes 5a, 5b, the tilt coils 9a, 9b, and the permanent magnets 3a, 3b are substantially on a plane including the center of gravity of the movable body and perpendicular to the tracking direction T. They are arranged at symmetrical positions.

The effect obtained by the above configuration is as follows. First, the movement of the movable body also moves the permanent magnets 3a to 3d to shift the magnetic flux density distribution by the same amount as the movement of the movable body. The center of gravity can be driven regardless of the position of the movable body.

Therefore, unnecessary resonance does not occur at the time of focusing drive and tracking drive, and unnecessary rotational moment is not applied to the movable body, so that the movable body moves in the focusing direction F and the tracking direction T. No tilt occurs. This enables high-precision focusing control, tracking control,
It is possible to realize tilt correction control.

Further, since the moment acting on the permanent magnet 3a and the permanent magnet 3b is always the same regardless of the position of the movable body, the driving in the rotating direction always rotates about a fixed axis. , Crosstalk in the focusing direction F and the tracking direction T can be minimized. Accordingly, disturbance to the focusing control and the tracking control by the tilt correction control can be suppressed, and stable control can be performed.

Further, since the permanent magnet 3a can be disposed in front of the opposing yoke 5a and the permanent magnet 3b can be disposed in front of the opposing yoke 5b in a magnetically efficient manner, the space between the opposing yokes 5a and 5b can be obtained. Is large, the driving sensitivity in the focusing direction F and the tracking direction T does not deteriorate.

Further, since the support center, the drive center, and the center of gravity of the movable body are on the same straight line, the center of gravity support and the drive of the center of gravity can be performed at any position of the movable body in the focusing drive, the tracking drive, and the tilt drive. Become.

Accordingly, it is possible to suppress crosstalk between the three directions of the focusing direction F, the tracking direction T, and the rotation direction K, and the optical axis J of the objective lens 1 is orthogonal to the same straight line. Therefore, crosstalk in the focusing direction F and the tracking direction T due to the tilt drive can be minimized. Thereby, stable focusing control, tracking control, and tilt correction control can be performed.

The tilt detecting means of the present invention is a detector in which the reflection type optical sensor is mounted on the movable portion in the above-described embodiment. However, the present invention is not limited to this. Any means can be used as long as it can detect the relative angle of the optical axis.

If a part of the recording / reproducing light beam is used instead of the light emitting portion of the tilt detector, the same effect can be obtained, and further, the weight and simplification can be realized. In the embodiment, two yokes, two permanent magnets, and two tilt drive coils are respectively connected to the opposing yokes 5.
a, 5b, permanent magnets 3a, 3b, tilt coils 9a, 9
Although described as b, the same applies to the opposing yokes 5c and 5d and the permanent magnets 3c and 3d tilt coils 9c and 9d. Therefore, in the present embodiment, two pairs of symmetrically arranged yokes, permanent magnets, and tilt drive coils are provided, but the same effect can be obtained by providing only one pair or three or more pairs.

Further, although the direction of gravity is not specifically discussed in the present embodiment, a similar effect can be obtained regardless of the direction of gravity.

The same effect can be obtained regardless of the cross-sectional shape of the wire members 10a to 10d, which are the rod-shaped support members of the present invention, are circular, substantially polygonal, or elliptical.

In the above-described embodiment, the rod-shaped support member of the present invention is not limited to the four-wire support mechanism in which the movable portion is supported by the four rod-shaped support members, but a support mechanism using a parallel leaf spring and a resin hinge. The same effect can be achieved with another support mechanism such as a support mechanism.

[0059]

As described above, according to the present invention, regarding the focusing drive and the tracking drive, the center of gravity can be driven irrespective of the position of the movable body, and tilt occurs due to the movement of the movable body in the focusing direction and the tracking direction. do not do. This makes it possible to realize highly accurate focusing control, tracking control, and tilt correction control.

Further, crosstalk in the focusing direction F and the tracking direction T due to driving in the rotation direction can be minimized. Accordingly, disturbance to the focusing control and the tracking control by the tilt correction control can be suppressed, and stable control can be performed.

Further, since the permanent magnets can be disposed magnetically efficiently in front of the opposing yokes, the driving sensitivity in the focusing direction and the tracking direction deteriorates even if the space between the two opposing yokes is large. I will not do it.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram of a main part of the objective lens driving device according to an embodiment of the present invention when the tilt detector has no tilt;

FIG. 3 is a schematic diagram of a main part when a tilt of a tilt detector of the objective lens driving device according to the embodiment of the present invention occurs;

FIG. 4 is a circuit configuration diagram of a tilt correction control circuit of the objective lens driving device according to one embodiment of the present invention.

FIG. 5 is a schematic diagram of a main part for describing an operation of the objective lens driving device according to the embodiment of the present invention;

FIG. 6 is a schematic diagram of a main part when the movable body of the objective lens driving device according to the embodiment of the present invention is located at a neutral position.

FIG. 7 is a schematic diagram of main parts when the movable body of the objective lens driving device according to the embodiment of the present invention has moved in the tracking direction from the neutral position.

FIG. 8 is a magnetic flux density distribution diagram in a tracking direction for explaining the operation of the objective lens driving device according to one embodiment of the present invention;

FIG. 9 is a schematic diagram of a main part when the movable body is located at a neutral position for describing the operation of the objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 7-240031.

FIG. 10 is a schematic diagram of a main part when the movable body moves in a tracking direction from a neutral position for explaining the operation of the objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 7-240031.

FIG. 11 is a magnetic flux density distribution diagram in a tracking direction for explaining the operation of the objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 7-240031.

[Explanation of symbols]

T Tracking direction A, B Tracking direction T direction F Focusing direction K direction K J Optical axis Ia-Id Direction of current flowing in tilt coils 9a-9d M Direction of moment received by movable body Ha-Hd Permanent magnets 3a-3d Direction of magnetization S Support center P1 Drive center of permanent magnets 3a, 3b P2 Drive center of permanent magnets 3c, 3d 1 Objective lens 2 Lens holders 3a to 3d Permanent magnet 4 Tilt detector 4a Light emitting units 4b, 4c of tilt detector 4 Light receiving unit 5a to 5d of tilt detector 4 Opposite yoke 6a to 6e Bobbin 7a to 7d Tracking coil 8a to 8d Focusing coil 9a to 9d Tilt coil 10a to 10d Wire member 11 Suspension holder 12 Fixed base 13 Disk 14 Differential amplifier 101 Objective lens 102 Lens holder 103a, 103b Permanent magnet 104 Tilt detection Vessel 105 fixed base 105a~105d opposing yoke portion 106a~106d tracking coils 107a~107d focusing coil 108a~108d wire member 109 support member 110 disk

Claims (7)

[Claims] 1. An objective lens for recording or reproducing optical information on or from a disc-shaped recording medium, a lens holder for holding the objective lens, and a radius of the disc-shaped recording medium perpendicular to the optical axis direction of the objective lens. A movable body having a direction of magnetization in a tangential direction perpendicular to the direction and having two or more permanent magnets fixed to the lens holder, and moving the movable body in the optical axis direction of the objective lens or the disc-shaped recording medium. A rod-shaped support member movably supporting in a radial direction, a fixed base for fixing the rod-shaped support member, and a direction of the magnetization with respect to each of the two or more permanent magnets fixed to the fixed base. A yoke made of a magnetic material disposed at a position facing along the axis, a focusing drive coil wound around each yoke with the optical axis direction as a winding axis, and a winding axis in the radial direction. A tracking drive coil wound around each of the yokes, and a tilt drive coil wound around each of the yokes with the optical axis direction as a winding axis, wherein the yoke and the permanent magnet are each a movable body. An objective lens driving device, wherein the objective lens driving device is arranged at a position substantially including the center of gravity of the above and substantially symmetric with respect to a plane perpendicular to the radial direction. 2. The method according to claim 1, wherein the two or more permanent magnets include at least one pair of permanent magnets each including two permanent magnets disposed at positions substantially symmetric with respect to the plane. 2. The objective lens driving device according to claim 1, wherein the magnetization directions of the two permanent magnets forming each pair are opposite to each other. 3. The objective lens drive according to claim 1, wherein a distance between the two permanent magnets constituting each pair is greater than a distance between the opposing yokes. apparatus. 4. The height of the two permanent magnets constituting each pair in the optical axis direction is smaller than the height of the opposing yokes in the optical axis direction. 3. The objective lens driving device according to any one of 3. 5. A plurality of said bar-shaped support members are arranged, and said plurality of bar-shaped support members and a center of a line segment consisting of a plurality of points for supporting said movable portion or a polygonal centroid and said pair The center of the line segment connecting the centroids of the magnetic pole surfaces of the two permanent magnets and the center of gravity of the movable part are substantially on the same straight line perpendicular to the optical axis and perpendicular to the radial direction. The objective lens driving device according to claim 1, wherein the objective lens driving device is provided. 6. A plurality of said bar-shaped support members are arranged, and said plurality of bar-shaped support members support a center of a line segment consisting of a plurality of points for supporting said movable portion or a polygonal centroid and said pair of pairs. The center of the line segment connecting the centroids of the magnetic pole surfaces of the two permanent magnets and the center of gravity of the movable part are substantially on the same straight line perpendicular to the optical axis and perpendicular to the radial direction. 5. The objective lens driving device according to claim 1, wherein the collinear line and the optical axis are substantially orthogonal to each other. 6. 7. The objective lens driving device according to claim 1, further comprising means for detecting a relative angle between the disc-shaped recording medium and an optical axis of the objective lens as tilt detecting means. .