JP2001351258A - Drive device for optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively constitute an optical system driving device, in which the undesirable torque hardly occurs. SOLUTION: A leaking magnetic field, which is generated in the direction shown by arrow A leaks from a rising part 15b through a rising part 15a is indicated by arrow B. Thus, a magnetic field which is generated in a part 6a and is added in the direction shown by arrow C is reduced, and a force which is generated in a direction different from the direction which should be originally driven by a focusing coil 6 is reduced. Consequently, resonance which is generated in a system consisting of wires 3a-3d, and a lens holder 5 is prevented or is reduced down to a negligible level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to information recording and / or
Also, the present invention relates to an optical system driving device provided in an optical recording / reproducing device that performs reproduction optically.

[0002]

2. Description of the Related Art In a conventional optical system driving device as shown in FIG. 6, a lens holder 102 to which a lens 101 is fixed is provided.
Is supported by a support member (not shown) so as to be movable in a substantially vertical direction (Z direction) and a substantially radial direction (X direction) of a disc-shaped recording medium (for example, an optical disk).

A bobbin 103 is mounted on a lens holder 101. A focus coil 104 is wound around the bobbin 103 around the Z direction, and a tracking coil 105 is fixed.

Further, in order to apply a magnetic field to the focus coil 104 and the tracking coil 105, the magnet 10
6 and a yoke 107 made of a magnetic material.

[0005] In such an optical system driving device, a magnetic field is applied in a direction indicated by an arrow a, for example, in a magnetic gap between the magnet 106 and the rising portion 107a of the yoke 107. As a result, the magnet 106 and the starter 10
7a of the focus coil 104 located between
04a receives a force in the direction shown by the arrow b, and the lens holder 102 is driven in the Z direction.

However, a magnetic field leaks from the rising portion 107b of the yoke 107 as shown by the arrow c. If the yoke 107 is significantly larger and thicker than the magnet 106, the leakage of the magnetic field becomes smaller, but it is necessary to secure a sufficient size and thickness of the yoke 107 from the viewpoint of miniaturization of the device. As a result, the influence of the leakage of the magnetic field cannot be ignored.

Since the focus coil 104 is wound around the magnet 106 with the Z direction as an axis, the rising portion 107
The direction of the current flowing through the portion 104b of the focus coil 104 located on the side opposite to the portion b is exactly opposite to the direction of the current flowing through the portion 104a.

Since the direction a of the magnetic field applied between the magnet 106 and the rising portion 107a is the same as the direction c of the magnetic field leaking from the rising portion 107b, the force acting on the portion 104b by the magnetic field in the direction of arrow c Is exactly opposite to the direction b of the force acting on the portion 104a, as shown by the arrow d. As a result, the arrow e is displayed on the lens holder 102.
Is applied, the support member excites resonance of the rotational moment, and accurate focus control becomes difficult.

In order to prevent the generation of such a rotational moment, the optical system driving device disclosed in Japanese Patent Application Laid-Open No. 7-182669 is provided with a tracking coil opposed to the portion 104b of FIG. The magnetic circuit further includes a magnet, and a magnetic circuit configured by the tracking coil and the magnet generates a magnetic field that cancels a magnetic field generated in a direction indicated by an arrow c in FIG.

[0010]

However, the optical system driving device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-182669 requires one more magnet, which is a relatively expensive component. There is an inconvenience.

An object of the present invention is to provide an inexpensive optical system driving device which hardly generates an undesired rotational moment.

[0012]

According to the first aspect of the present invention, there is provided an optical system driving device, comprising: a conductive elastic member; a fixing member for fixing the conductive elastic member; and a movable member by the conductive elastic member. A movable member having an objective lens and a driving coil supported thereon, wherein the fixed member includes a magnet, a first yoke that forms a magnetic circuit for applying a magnetic field to the driving coil together with the magnet, and the driving device. And a second yoke for reducing the influence of a magnetic field that generates a force in a direction different from the direction intended for the use coil.

According to the optical system driving device of the first aspect,
Since the influence of the force generated in a direction different from the intended direction is reduced by the second yoke, which is less expensive than the magnet, an optical system driving device that hardly generates an undesired rotational moment can be configured at low cost. it can.

According to a second aspect of the present invention, in the optical system driving device, the second yoke is magnetically separated from the first yoke. This further reduces the influence of a magnetic field that causes a force generated in a direction different from the intended direction, thereby further reducing the possibility of generating an undesirable rotational moment.

According to a third aspect of the present invention, in the optical system driving device, the second yoke is also used as a yoke connecting an open end of the first yoke.
Thereby, the magnetic field leaking from the open end of the first yoke can be suppressed. As a result, the magnetic field can be effectively used, and the driving force of the optical system device can be further increased.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical system driving device according to the present invention will be described in detail with reference to the drawings. FIG.
FIG. 2 is a perspective view of a first embodiment of the optical system driving device according to the present invention, and FIG.
FIG. 3 is an exploded perspective view of the first embodiment, and FIG. 3 is a sectional view of a main part of the first embodiment of the optical system driving device according to the present invention.

In such an optical system driving device, a holding member 2 for holding the lens 1, four wires 3a to 3d each having one end fixed to the holding member 2, and the holding member 2 can be moved. And fixing members 4 for fixing the other ends of the wires 3a to 3d as described above.

The holding member 2 includes a lens holder 5 to which the lens 1 is fixed, a focus coil 6 for driving, and tracking coils 7a and 7b fixed to the lens holder 5.
And a bobbin 8 having

The wires 3a to 3d are, for example, 0.1 mm in diameter.
It is a beryllium copper wire of 0 mm. The fixing member 4
Magnetic body (for example, iron) yoke 10 to which magnet 9 is fixed
And a first spring receiver 1 superposed on the yoke 10 and having a surface on which the other ends of the wires 3a and 3b are arranged.
1, a second spring receiver 12 having a first surface superposed on the surface of the first spring receiver 11 and a second surface on which the other ends of the wires 3c and 3d are arranged, and a second surface of the second arrangement member And a third spring support 13 having a surface superposed on the third spring support 13.

With such a configuration, the lens holder 5
Are perpendicular to the surface of an optically recordable and / or reproducible disc-shaped medium (for example, an optical disk) (not shown) by four wires 3a to 3d (Z direction in a three-dimensional coordinate system) and It is movably supported in the radial direction (X direction).

The focus coil 6 is wound around a bobbin 8, and tracking coils 7a and 7b are fixed thereto. Here, instead of fixing the focus coil 6 directly to the lens holder 5 as an air-core coil, by winding the bobbin 8, it is possible to prevent the deformation of the focus coil 6 from interfering with the inner magnet 9. .

At both ends of the bobbin 8, reference pins 8a and 8b for positioning are provided, and receiving portions 5a and 5 of the lens holder 5 are provided.
b, the displacement of the magnet 9, the focus coil 6, and the tracking coils 7a and 7b can be minimized.

The four wires 3a-3d are shown in FIGS.
As shown in (1), it is sandwiched and fixed by the first to third spring supports 11-13.

When the first to third spring supports 11-13 are fixed, spaces are formed around the wires 3a to 3d, and the spaces are filled with gel (for example, silicon gel), so that damping is surely performed. The effect is obtained.

The space is filled with silicon by filling holes 1 formed by the first and second spring supports 11 and 12.
4a to 14d (only 14a, 14c and 14d are shown in FIG. 1).

The magnet 9 is provided at the rising portion 10a of the yoke 10.
Fixed to The yoke 10 also has another rising portion 10b facing the magnet 9a.

The focus coil 6 is wound around the magnet 9 with the Z direction as an axis, and includes a portion 6a located on the side facing the rising portion 10a, a magnet 106 and a rising portion 107.
a and 6b located between the two.

The optical system driving device is a magnetic material (for example, made of iron)
The yoke 15 further includes a rising portion 15a disposed between the rising portion 10a and one surface of the portion 6a, and a rising portion disposed opposite to the other surface of the portion 6a. And a portion 15b. In addition, the starting unit 10
a and the rising portion 15a are in surface contact.

The operation of the thus configured optical system driving device will be described. Laser light emitted from an optical system (not shown) is reflected by a mirror (not shown) arranged below the lens 1 and forms a spot on a medium (not shown) by the lens 1. Light reflected from the medium is again transmitted to the lens 1
And returned to the optical system via mirror, focus error,
A tracking error and a recording signal are detected. When a focus error and / or a tracking error is detected, the focus coil 6 is connected through the wires 3a to 3d.
The lens holder 5 is driven in a predetermined direction by passing a current through the tracking coils 7a and 7b. Thus, the lens 1 and the lens holder 2 having the same
Is subjected to focus control and tracking control.

In this embodiment, since the magnetic flux of the yoke 15 passes more easily than air, the leakage magnetic field generated in the direction shown by the arrow A rises from the rising portion 15a as shown by the arrow B. It leaks through the raising part 15b. As a result, the magnetic field applied to the portion 6a in the direction indicated by the arrow C is reduced, and the force generated by the focus coil 6 in a direction different from the direction in which the focus coil 6 should be driven is reduced. As a result, resonance occurring in the system including the wires 3a to 3d and the lens holder 5 can be prevented or reduced to a negligible level.

FIG. 4 is a sectional view of a main part of a second embodiment of the optical system driving device according to the present invention. In the present embodiment, one rising portion 21a of the yoke 21 and the yoke 22
A plate 23 made of a non-magnetic material (for example, synthetic resin) is interposed between one of the rising portions 22a. Also, one rising portion 22a of the yoke 22 and the other rising portion 2
2b is connected not above but below the portion 24a of the focus coil 24.

According to the present embodiment, the starting section 21a
The yoke 21 and the yoke 22 are magnetically separated from each other by interposing the plate 23 between the yoke 21 and the rising portion 22a.
There is no possibility of leakage to the side of 4a, and it is possible to effectively prevent an undesired magnetic field from being applied to the portion 24a.

Since the rising portion 22a and the other rising portion 22b are connected above the portion 24a, the yoke 22 is attached to the device after the device is assembled with parts other than the yoke 22. be able to.

FIG. 5 is a sectional view of a main part of an optical system driving device according to a third embodiment of the present invention. In the present embodiment, the upper ends of the rising portions 31 a and 31 b of the yoke 31 are respectively in contact with
A yoke 33 that surrounds 2a together with the rising portion 32b is provided.

According to the present embodiment, since the open portion of the yoke 31 is surrounded by the yoke 33, the magnetic field applied from the magnet 34 in the direction of the rising portion 31a as shown by the arrow D rises. By returning from the portion 31a to the rising portion 31b through the yoke 33, the leakage of the magnetic field can be reduced. As a result, the magnetic field applied from the magnet 34 in the direction of the rising portion 31a as shown by the arrow D can be increased, and the performance of the device is improved. By configuring the yoke 31 and the yoke 33 integrally, the apparatus can be made more inexpensive.

The present invention is not limited to the above embodiment, and many modifications and variations are possible. For example, the yoke can be formed in various shapes such as a shape having a protrusion for positioning the two yokes. In the first embodiment, the rising portion 15 of the yoke 15 is used.
a, 15b may be connected above the portion 6a, and in the second embodiment, the rising portions 22a,
22b may be connected below portion 24a.

[0037]

According to the present invention, the influence of a force generated in a direction different from the intended direction is reduced by a yoke which is less expensive than a magnet, so that an optical system drive which hardly generates an undesired rotational moment is produced. The device can be constructed inexpensively.

Further, by magnetically separating the yoke, the influence of a magnetic field which causes a force generated in a direction different from the intended direction is further reduced, so that the possibility of generating an undesirable rotational moment is further reduced. .

Further, by using the second yoke also as a yoke connecting the open end of the first yoke, it is possible to suppress a magnetic field leaking from the open end of the first yoke. As a result, the magnetic field can be effectively used, and the driving force of the optical system device can be further increased.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical system driving device according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the first embodiment of the optical system driving device according to the present invention.

FIG. 3 is a sectional view of a main part of a first embodiment of the optical system driving device according to the present invention.

FIG. 4 is a sectional view of a main part of an optical system driving device according to a second embodiment of the present invention.

FIG. 5 is a sectional view of an essential part of an optical system driving device according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a main part of a conventional optical system driving device.

[Explanation of symbols]

1, 101 lens 2 holding member 3a, 3b, 3c, 3d wire 4 fixing member 5, 102 lens holder 5a, 5b receiving portion 6, 24, 32, 104 focus coil 6a, 6b, 24a, 32a, 104a, 104b portion 7a , 7b, 105 Tracking coil 8, 103 Bobbin 8a, 8b Reference pin 9, 25, 34, 106 Magnet 10, 15, 21, 31, 33, 107 Yoke 10a, 10b, 15a, 15b, 21a, 22a, 2
2b, 31a, 31b, 107a, 107b Rising section 11 1st spring support 12 2nd spring support 13 3rd spring support 14a, 14b, 14c, 14d Filling hole 23 Plate

Claims (3)

[Claims] 1. A conductive elastic member, a fixing member for fixing the conductive elastic member, and a movable member movably supported by the conductive elastic member and having an objective lens and a driving coil. A fixing member includes: a magnet; a first yoke that forms a magnetic circuit for applying a magnetic field to the driving coil together with the magnet; and a magnetic field that generates a force in a direction different from an intended direction of the driving coil. An optical system driving device, comprising: a second yoke for reducing light. 2. The optical system driving device according to claim 1, wherein said second yoke is magnetically separated from said first yoke. 3. The optical system driving device according to claim 1, wherein said second yoke also serves as a yoke for connecting an open end of said first yoke.