JP2615446B2 - Lens actuator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention focuses on a disc-shaped information recording medium (hereinafter, referred to as a disc) at a desired position using a laser or the like as a light source.
The present invention relates to a lens actuator of an optical recording / reproducing apparatus for recording or reproducing information such as image and audio information.

Conventional technology As a conventional lens actuator, for example,
There is one shown in -168844. FIG. 5 shows a cross-sectional view of this conventional lens actuator.
Is a semiconductor laser, 2 is a laser beam, 3 is a reflection mirror, 4 is an objective lens, 5 is a disk, 6 is a lens barrel, 7 is a tracking drive coil for driving the barrel 6 in its radial direction,
Reference numeral 8 denotes a tracking drive magnetic circuit, 9 denotes a focusing drive coil that drives the lens barrel 6 in the optical axis direction, 10 denotes a focusing drive magnetic circuit, and 11 and 12 denote elastic support members. When a tracking correction current is applied to a tracking drive coil 7 from a tracking error detection circuit (not shown), an electromagnetic force is generated between the lens actuator used in the conventional optical pickup and the tracking drive magnetic circuit 8, and an objective lens 4 moves in the XX direction (radial direction of the lens barrel 6) in the figure until the elastic force of the elastic support members 11 and 12 is balanced, and tracking control is performed. Similarly, the focusing control is performed by the focusing drive coil 9.
Is performed by moving the objective lens 4 in the Z direction by the electromagnetic force between the focusing drive magnetic circuits 10.

However, in the above configuration, since the focusing drive coil 9 and the tracking drive coil 7 are arranged in the ZZ direction of the lens barrel 6, it is difficult to reduce the thickness of the lens actuator. Had the problem that

To solve this problem, as disclosed in Japanese Patent Application Laid-Open No. Sho 58-182141, a lens actuator designed to be thin by using both a focus drive and a tracking drive by a pair of coils has been proposed. However, the lens actuator having such a configuration has a problem that the drive control circuit is complicated.

Further, in the conventional lens actuator, since a pair of coils are arranged very close to each other, there is a problem that the coil rigidity is reduced due to heat generated during the focus / tracking drive, and the frequency characteristics are deteriorated. Had.

Also, as shown in JP-A-57-210456,
There has also been proposed a lens actuator that is made thin by disposing a tracking drive coil directly on a focus drive coil. However, this lens actuator has a problem that undesirable tracking jitter is generated during tracking control because tracking control is performed by eccentric rotation. Further, there is a problem that the efficiency is low because the effective magnetic flux is linked only to one side of the rectangular tracking drive coil.

In view of the problems of the conventional example, the present invention prevents a reduction in coil rigidity due to heat generation without complicating the drive control circuit, and further reduces the efficiency of tracking drive without generating unwanted jitter. An object of the present invention is to realize a thinner lens actuator without doing so.

Means for Solving the Problems The present invention performs focusing control by driving a lens barrel having a lens in the optical axis direction of the lens, and performs tracking control by driving the lens barrel in the direction of a tracking axis orthogonal to the optical axis. A first pair of lenses substantially co-axial with the tracking axis and arranged symmetrically with respect to the optical axis near the center of gravity of the lens barrel. And a first pair of magnetic circuits for generating a magnetic flux interlinking the first pair of coils, and a coil axis parallel to the optical axis direction near the center of gravity of the lens barrel and the tracking. A second pair of coils substantially integrated with the lens barrel and a second pair of magnetic circuits for generating magnetic flux interlinking the second pair of coils, which are arranged at positions symmetrical about an axis. Ingredient In addition, by making the longitudinal direction substantially coincide with a third direction orthogonal to the tracking axis and the optical axis direction, the third direction has great rigidity, and the tracking axis and the optical axis This is a lens actuator in which the lens barrel is held substantially near its center of gravity by a pair of elastic support members that can be elastically displaced in both directions.

According to the present invention, with the above-described configuration, the first pair of coils are arranged coaxially with the tracking control direction and at symmetrical positions with respect to the optical axis of the objective lens. By arranging the coil axis near the center of gravity of the lens barrel so that its coil axis is coaxial with the focus control direction at a symmetrical position on a line orthogonal to the direction, parallel movement of the objective lens can be realized, and unwanted jitter The thickness can be reduced by preventing the occurrence of the problem.

Embodiment FIG. 1 shows an embodiment of a lens actuator according to the present invention.
This will be described with reference to FIG. FIG. 1 is a schematic plan view of one embodiment of the present invention, and FIG. 2 is a schematic front view of one embodiment of the present invention.

In the figure, reference numeral 4 denotes an objective lens, 6 denotes a lens barrel for accommodating the objective lens 4, and 7 denotes a lens barrel which is coaxial with the tracking control direction XX and symmetric with respect to the optical axis of the objective lens 4. It is a first pair of coils wound around the provided bobbin 14. Reference numeral 8 denotes a first magnetic circuit which generates a magnetic flux interlinking the two surfaces of the coil 7 and is fixed to the housing 16 of the entire lens actuator. Reference numeral 9 is provided in the lens barrel 6 so as to be symmetrical with respect to the optical axis in the YY direction orthogonal to the tracking control direction XX, that is, both the distance between the optical axis and the coil center is 1. A second pair of coils wound around the bobbin 13. Reference numeral 10 denotes a second magnetic circuit which generates a magnetic flux linking the two surfaces of the second pair of coils 9 and is fixed to the housing 16. 1
1 'and 12' have elasticity in the XX and ZZ directions,
The elastic support member has high rigidity in the −Y direction. The elastic support members 11 ′ and 12 ′ have one end fixed near the center of gravity of the lens barrel 6 and the other end fixed to the housing 16, similarly to the focus drive coil 9 and the tracking drive coil 7.

The operation of the lens actuator of the present embodiment configured as described above will be described below with reference to FIGS.

FIG. 3 and FIG. 4 are a plan view and a front view, respectively, illustrating the operation center of the driving force according to this embodiment.

First, focus control will be described. When a drive current is supplied from a focus drive circuit (not shown) to the second pair of coils (focus drive coils) 9, an electromagnetic force in the ZZ direction is generated between the second pair of coils 9 and the magnetic circuit 10. Third
FIG, which was displayed in F ₁ and F ₂ in Figure 4. Due to the balance between the electromagnetic forces F ₁ and F ₂ and the elastic force in the ZZ direction of the elastic support members 11 ′ and 12 ′, the objective lens 4 is moved in the ZZ direction and focus control is performed.

 Next, tracking control will be described.

When a tracking drive current is supplied from a tracking control circuit (not shown) to the first pair of coils (tracking drive coils) 7, an electromagnetic force in the XX direction is generated between the first pair of coils 7 and the magnetic circuit 8. 3 and 4 show T ₁ and T ₂
Indicated by The electromagnetic forces F ₁ and T ₂ and the elastic support members 11 ′ and 12 ′
The tracking control is performed by moving the objective lens 4 in the XX direction by balancing with the elastic tension in the XX direction.

As described above, according to the present embodiment, the focus drive coil 9 and the tracking drive coil 7 are independently arranged in a cross shape on the XY plane so as to coincide with the YY direction and the XX direction. Therefore, without complicating the control circuit, preventing the coil rigidity from being reduced due to heat generation, the tracking driving forces T ₁ , T ₂ and the focus driving forces F ₁ , F ₂ all act as translational forces, and Since the action center is located near the center of gravity of the tube 6 and symmetrically with respect to the optical axis, a torsional moment is less likely to occur in the lens barrel 6, and the action centers of the focus driving forces F ₁ and F ₂ are particularly elastic. Support members 11 'and 12'
Are arranged in the Y-Y direction where the rigidity is large. further,
Can be arranged 'and 12' the elastic support member 11 in the vicinity of the center of gravity of the barrel 6, or generates an error in the distance l in Figure 4, or, Anne to the magnitude of the focus driving force F ₁ and F ₂ Even if balance occurs, occurrence of jitter can be prevented, and the thickness of the lens actuator can be reduced.

In this embodiment, the focus magnetic circuit 10 is configured so as to link the magnetic flux only to two surfaces of the focus drive coil 9. Can be further improved.

Effects of the Invention As described above, according to the present invention, the lens actuator can be prevented from lowering in coil stiffness due to heat generation without complicating the drive control circuit, and without generating undesired jitter. Can be reduced in thickness.

[Brief description of the drawings]

1 and 2 are a plan view and a front sectional view showing a first embodiment of the present invention, and FIGS. 3 and 4 are a plan view and a front view showing an operation center of a driving force of the embodiment. FIG. 5 is a structural view of a conventional lens actuator. 4 ... Objective lens, 7 ... Tracking drive coil, 9
... Focus drive coils, 11 ', 12' ... Elastic support members

Claims (1)

(57) [Claims] 1. A lens actuator for performing focusing control by driving a lens barrel having a lens in the direction of the optical axis of the lens, and performing tracking control by driving in a direction of a tracking axis orthogonal to the optical axis. Wherein near the center of gravity of the lens barrel, a first pair of coils substantially integrated with the lens barrel, disposed coaxially with the tracking axis and symmetrically with respect to the optical axis; A first pair of magnetic circuits for generating a magnetic flux interlinking the one pair of coils; and near the center of gravity of the lens barrel, the coil axis is parallel to the optical axis direction and symmetrical with respect to the tracking axis. A second pair of coils disposed substantially integral with the lens barrel, and a second pair of coils generating a magnetic flux interlinking the second pair of coils.
A pair of magnetic circuits, the longitudinal direction of which substantially coincides with the third direction orthogonal to the tracking axis and the optical axis direction. A lens actuator, wherein the lens barrel is held substantially near its center of gravity by a pair of elastic support members that can be elastically displaced in both directions of an axis and the optical axis.