JPS61287050A - Lens actuator - Google Patents

Abstract

PURPOSE:To prevent the inclination of the optical axis of an objective lens while driving by providing a pair of elastically-supporting component fixed at the rear and front ends of a lens barrel symmetrically about the center of gravity of the lens barrel and the first and second coils disposed in the vicinity of the center of gravity of the lens barrel. CONSTITUTION:When a current is supplied to the pair of focus-drive coils 9, an electromagnetic force in direction Z-Z is generated between a magnetic coil 10 and themselves. Depending on the balance between said force and the elastic tension in direction Z-Z exerted by the elastically-supporting component 11, the objective lens 4 is moved in direction Z-Z and the focus is controlled. When a driving power supply is supplied to a pair of tracking-drive coils 7, an electromagnetic force in direction X-X is generated between a magnetic circuit 8 and said coils. The objective lens 4 moves in the direction X-X to the position where the supporting component 11 balances in the tension, by which the tracking control is executed. Thus the focus control and the tracking control can be executed by the parallel moving of the objective lens, and accordingly the optical axis is prevented from inclining.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses a laser or the like as a light source and focuses it on a desired position on a disc-shaped information recording medium (hereinafter referred to as a disk).
The present invention relates to a lens actuator for an optical recording and reproducing device that records or reproduces information such as images and audio information.

Conventional technology As a conventional lens actuator, for example,
There is one shown in Japanese Patent No.-168844.

FIG. 7 shows a cross-sectional view of this conventional lens actuator, in which 1 is a semiconductor laser, 2 is a laser beam, 3 is a semiconductor laser, and 3 is a laser beam.
4 is a reflecting mirror, 4 is an objective lens, 6 is a disk, 6 is a lens barrel, 7 and 7' are tracking drive coils that drive the lens barrel 6 in its radial direction, 8 and 8' are tracking drive magnetic circuits, and 9 10 indicates a focusing drive coil that drives the lens barrel 6 in its axial direction, 1o a focusing drive magnetic circuit, and 11° and 12 elastic support members. In this conventional optical pickup lens actuator, when a tracking correction current is applied to the tracking drive coil 7, 7' from a tracking error detection circuit (not shown), an electromagnetic force is generated between the tracking and excitation circuits 8, 8'. occurs,
The objective lens 4 moves in the XX direction (radial direction of the fR cylinder 6) in the figure until it balances the elastic force of the elastic support members 11 and 12, and tracking control is performed. Similarly, focusing control is performed by moving the objective lens 4 in two directions by the electromagnetic force between the focusing drive coil 9 and the focusing drive magnetic circuit 10.

Tracking control of this conventional actuator (4,
This is a so-called rocking drive in which the tip of the objective lens 4 is tilted in the XX direction using the center of the elastic support member 11 as a fulcrum.

Problems to be Solved by the Invention However, in the above configuration, the optical axes of the disk 5 and the objective lens 4 are not perpendicular to each other during the tracking control because the tracking control is performed by swinging drive. As a result, asymmetrical aberrations called astigmatism and coma aberration occur in the objective lens 4, which significantly deteriorates the imaging performance of the light beam.

Therefore, various lens actuators have been proposed that do not cause the objective lens 4 to tilt during tracking control.

For example, a lens actuator disclosed in Japanese Unexamined Patent Publication No. 57-210456 attempts to prevent the optical axis of an objective lens from tilting by performing eccentric rotation for tracking control. However, in this conventional example, it is unavoidable that jitter occurs during tracking drive. Furthermore, since there is a gap between the rotating shaft and the bevel bearing, there is a problem in that the optical axis of the objective lens is tilted due to this gap during focus driving.

In addition, vibrations from outside the lens actuator, especially the force acting as a moment around the rotation axis, shake the objective lens, causing the optical axis to tilt due to play between the rotation axis and the bevel bearing. had.

In view of these points, the present invention prevents tilting of the optical axis of an objective lens during focus driving or tracking driving, further prevents optical axis tilting due to vibration of the objective lens due to external vibration, and also prevents tilting of the optical axis of the objective lens during focus driving or tracking driving. An object of the present invention is to provide a lens actuator that prevents occurrence of jitter.

Means for Solving the Problems The present invention provides a pair of elastic support members fixed symmetrically to the front and rear ends of the lens barrel with respect to the center of gravity of the lens barrel having an objective lens, and a pair of elastic support members arranged near the center of gravity of the lens barrel. The lens actuator includes first and second coils.

According to the present invention, with the above-described configuration, the point of application of the driving force during focus drive and tracking drive acts near the center of gravity of the lens barrel, so that bending or twisting moments are less likely to occur in the lens barrel. Furthermore, the pair of elastic support members are arranged symmetrically with respect to the point of application of the driving force described above, so that υ, that is, the elastic tension acting on the lens barrel is symmetrical with respect to the driving force. Therefore, focus control and tracking control are
Since both are performed by moving the objective lens in parallel, the optical axis of the objective lens does not tilt.

Moreover, it does not generate jitter.

Furthermore, since the upper and lower ends of the lens barrel are supported by elastic support members, there is no so-called gap in supporting the objective lens, so that optical axis tilting due to external vibrations does not occur.

Embodiment FIGS. 1 and 2 are a plan view and a front sectional view, respectively, of a lens actuator in a first embodiment of the present invention.

4 is an objective lens, 6 is a lens barrel that houses the objective lens 4, and 7 is provided in the lens barrel 6 so as to be coaxial with the tracking control direction XX direction and symmetrical with respect to the optical axis of the objective lens 4. These are the first pair of coils wound around the bobbin 14. .

A first magnetic circuit 8 generates a magnetic flux interlinking with the surface of the coil 702, and is fixed to the housing 16 of the entire lens actuator. 9 is the tracking control direction x-
The bobbin 13 is installed in the lens barrel 6 so that it is symmetrical about the optical axis in the Y-direction perpendicular to the x direction, that is, the distance between the optical axis and the coil center is l. This is a second pair of wound coils. 1o is a second coil that generates a magnetic flux that interlinks with the two surfaces of the second pair of coils 9.
This magnetic circuit is fixed to the housing 16. 1
1 has elasticity in two directions, XX direction and 2-2 direction, and Y-
It is an elastic support member with high rigidity in the direction, and is fixed to the tip and rear end of the lens barrel 6 at positions symmetrical to the center of gravity of the lens barrel 6 (that is, the distances from the center of gravity are &). ing.

Both ends of the elastic support member 110 at the tip of the lens are connected to the housing 1
6, both ends of the elastic support member 11 at the rear end of the lens are fixed to elastic support member plates 16, respectively. A resilient support member plate 16 is secured to the housing 16.

The operation of the lens actuator of this embodiment configured as described above will be explained below using FIGS. 1 to 4.

3 and 4 are a plan view and a front view for explaining the operation, showing the center of action of the driving force of this embodiment.

First, focus control will be explained. When drive current is supplied to the second pair of coil focus drive coils 9 from a focus control circuit (not shown), an electromagnetic force in the 2-2 direction is generated between the second pair of coil focus drive coils 9 and the magnetic circuit 10. Figures 3 and 4
It is labeled F and F2 on the teeth. This electromagnetic force F,
, F2 and the 2-2 direction elastic tension of the elastic support member 11, the objective lens 4 is moved in the z-2 direction and focus control is performed.

Next, tracking control will be explained.

When a tracking drive current is supplied to the first pair of coils (tracking drive coils) 7 from a tracking control circuit (not shown), an electromagnetic force in the XX direction is generated between the first pair of coils (tracking drive coils) 7 and the magnetic circuit. This electromagnetic force is shown in Figures 3 and 4.
T1. Indicated by T2. This XX direction electromagnetic force T1. T
Tracking control is performed by moving the objective lens 4 in the XX direction to a position where the elastic tension in the XX direction of the elastic support member 11 and the elastic tension of the elastic support member 11 are aligned with each other.

At this time, tracking control and focus control are performed as parallel movement of the objective lens 4, as shown in FIGS.
This will be explained using figures. Figure 5 shows tracking control, Figure 6
The figure is a schematic diagram showing the operation of focus control. 6 schematically represents a lens barrel, and 11 schematically represents an elastic support member.

During tracking control, as shown in FIG. 5, when a tracking driving force of Tjl''2 is applied to the center of gravity of the lens barrel 6, the elastic supports T + T holding members 11 located at the same distance from the center of gravity are all 17. Since an elastic tension ET equal to 12 is generated, the elastic support members 11 at the leading and trailing ends are displaced in the x-x direction by the same amount, ie the objective lens is translated in parallel.

Similarly, during focus control, as shown in FIG. 6, the elastic support members 11 at the front and rear ends are each displaced by the same amount F in the 2-2 direction, causing the objective lens to move in parallel.

As described above, according to the embodiments of the present invention, focus control and tracking control can be performed by parallel movement of the objective lens, and tilting of the optical axis of the objective lens can be prevented.

Furthermore, due to parallel movement, it is possible to prevent undesired jitter from occurring due to tracking control.

Furthermore, there is no gap or play between the bearing and the rotation axis, and since the elastic support member is arranged symmetrically with respect to the center of gravity of the lens barrel, the objective lens is not easily shaken due to external vibrations. No tilting of the optical axis of the lens occurs.

In the embodiment of the present invention, the focus drive coil 9 and the tracking drive coil 7 are coils with a rectangular cross section, but they may also be coils with a circular cross section.

Furthermore, although the focus magnetic circuit 1o is configured to interlink magnetic flux only to two surfaces of the focus drive coil 9,
It may be configured to interlink on three sides.

According to these other embodiments, the efficiency of tracking drive or focus drive can be improved.

As described in detail, according to the present invention, it is possible to prevent the optical axis of the objective lens from tilting during focus driving or tracking driving, and furthermore, even if the objective lens is shaken due to external vibrations, it is possible to prevent the objective lens from tilting. This prevents optical axis tilt from occurring,
In addition, it is possible to provide a lens actuator that prevents jitter from occurring during tracking drive, and to improve the recording and reproducing characteristics of an optical recording and reproducing device.

[Brief explanation of drawings]

1 and 2 are a plan view and a front sectional view showing one embodiment of the present invention, and FIGS. 3 and 4 are a plan view and a front view showing the center of action of the driving force of the same embodiment, and FIGS. 6 and 6 are explanatory diagrams of operations during tracking control and focus control in the same embodiment, and FIG. 7 is a configuration diagram showing a conventional lens actuator. 4... Objective lens, 6... Lens barrel, 7.
...Tracking drive coil, 9...Focus drive coil, 11...Elastic support member. Name of agent Patent attorney Toshio Nakao and one other person proposed
3 Figure 4 Figure 5

Claims (1)

[Claims] A lens barrel having an objective lens; fixed to the front end and rear end of the lens barrel symmetrically with respect to the center of gravity of the lens barrel, and elastically supporting the lens barrel so as to be movable in a focus control direction and a tracking control direction. a first pair of coils coaxial with the tracking control direction, symmetrical with respect to the optical axis of the objective lens, and disposed near the center of gravity of the lens barrel; a first magnetic circuit that generates a magnetic flux that interlinks with the coil; and a first magnetic circuit that is symmetrical with respect to the optical axis of the objective lens on a line orthogonal to the tracking control direction, and whose axis is located near the center of gravity of the lens barrel. A lens actuator comprising: a second pair of coils arranged to match a control direction; and a second magnetic circuit that generates magnetic flux interlinking with the second pair of coils.