JPH0242632A - Objective lens drive device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device, and more particularly to an objective lens driving device in an optical recording/reproducing device such as an optical disk device.

BACKGROUND OF THE INVENTION In recent years, objective lens drive devices have been used in optical recording and reproducing systems that record information on a recording medium and reproduce information recorded on the recording medium by irradiating a spot of laser light onto the surface of an optical recording medium. The practical application of this device is being actively carried out.

A conventional objective lens driving device will be described below with reference to the drawings. FIG. 5 is an exploded perspective view of a conventional objective lens driving device, and FIG. 6 is a perspective view of the objective lens driving device.

In FIG. 5, a cylindrical objective lens holder 1 has a ball bearing 2 inserted at the center of its cylindrical surface, and a shaft 4 held in the optical axis direction by the ball bearing 2 and an intermediate member 3. It is rotatably supported by. The plate-shaped elastic bodies 5a and 5b provided in parallel have one end fixed to a support 11 fixed to the base lO, and the other end fixed to the intermediate member 3, and the above-mentioned ball bearing 2 and shaft 4, the objective lens holder 1 is supported so as to be translatable in the optical axis direction. An objective lens 7 is fixed to the objective lens holder 1 at a position away from the insertion hole of the ball bearing 2, which focuses the laser beam onto the information recording medium surface. A focusing coil 8 is wound around the outer periphery of the objective lens holder 1, and a tracking coil 9 is fixed onto the focusing coil 8.

The base 10 includes a support 13 on which a tracking permanent magnet 12 is attached so as to face the tracking coil 9, and a focusing permanent magnet 13 on which a yoke 14, 15 is attached on the upper end to face the focusing coil 8. magnet,
16.17 is fixed. Further, the base 10 is provided with a through hole 18 corresponding to the movable range of the objective lens 7 during tracking drive.

FIGS. 7(a) and 7(b) are schematic diagrams illustrating tracking control of the objective lens driving device, and FIG. 7(a)
7 shows a state in which the objective lens holder 1 is located at the neutral point, and FIG. 7 (°C) shows a state in which the objective lens holder 1 is under tracking control.

Tracking control is performed by rotating the objective lens holder 1 about the axis 4 using electromagnetic force generated by a current flowing through the tracking coil 9 and a magnetic field generated by the tracking permanent magnet 12. Figure 7 [with]
The displacement angle θ of the objective lens holder 1 shown in is determined by the relative displacement distance between the objective lens 7 and the desired laser beam irradiation position on the information recording medium.

FIG. 8 is a schematic diagram illustrating focus control of the objective lens driving device. FIG. 8(a) shows a state where the objective lens holder l is located at a neutral point, and FIG. 8(b) shows a state where the objective lens holder l is located at a neutral point. A state in which the lens holder 1 is under focus control is shown.

Focus control is performed using a current flowing through the focusing coil 8, the focusing permanent magnets 16 and 17, and the yokes 14 and 15.
This is done by moving the objective lens holder 1 in the optical axis direction of the objective lens 7 using the electromagnetic force generated by the magnetic field generated by the magnetic field. The displacement X of the objective lens holder 1 shown in FIG. 8(b) is determined by the relative defocus distance between the objective lens 7 and the information recording medium in the optical axis direction.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the objective lens holder is supported by the intermediate member via the ball bearing and the shaft, so that the fixed part and the movable part of the ball bearing itself are Due to the influence of the gap between the lenses, there has been a problem in that unnecessary resonance occurs when performing focus control.

To solve this problem, the intermediate member is equipped with a means for generating a load (hereinafter referred to as preload) that acts mutually on the fixed part and moving part of the ball bearing, and the fixed part and moving part of the ball bearing itself are It is possible to consider means to eliminate the gap between the two parts.

However, with such means, the frictional force in the rotational direction between the fixed part and the moving part of the ball bearing increases in proportion to the magnitude of the preload. Therefore, there is a problem in that the driving force of the objective lens holder in the tracking direction due to electromagnetic force is reduced due to its friction coefficient, making it difficult to perform highly accurate tracking control.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide an objective lens drive device that realizes highly accurate tracking control and focus control.

Means for Solving the Problems In order to achieve the above objects, the objective lens driving device of the present invention includes an objective lens holder holding an objective lens, and a direction perpendicular to the optical axis of the objective lens. , has a structure consisting of an elastic support member that supports rotationally.

Operation The objective lens driving device of the present invention moves the objective lens holder in a direction perpendicular to the optical axis of the objective lens and parallel to the optical axis of the objective lens by twisting the first elastic support member directly attached to the intermediate member. Tracking control is achieved by rotating the objective lens holder with respect to its rotation center passing through the center of gravity of the objective lens holder.

Example Below, regarding an example of the objective lens driving device of the present invention,
This will be explained with reference to the drawings. FIG. 1 is an exploded perspective view of an objective lens driving device in an embodiment of the present invention. FIG. 2 is a perspective view of the objective lens driving device.

In FIG. 1, l is a leaf spring for tracking, 2 is an intermediate member, 3 is an objective lens holder, 6 is an objective lens, and 16
1 is the optical axis of the objective lens, and 17 is a holding member for the leaf spring 1. A fixing surface 14 of the leaf spring 1 is fixed to a fixing surface 4 of the intermediate member 2 that is parallel to the optical axis 6.

The fixed surface 15 of the leaf spring 1 is connected to the optical axis 1 of the objective lens holder 3.
A fixed plane 5 parallel to 6 and including the center of gravity of the objective lens holder 3
is fixed. Therefore, the objective lens holder 3 is supported so as to be rotatable in a direction perpendicular to the optical axis 16 by twisting the plate spring 1.

7 is a focusing leaf spring, and 9 is a magnetic yoke which also serves as a base support member. One end of the temporary spring 7 is fixed to a fixing surface 8 perpendicular to the optical axis 16 of the intermediate member 2. The other end of the leaf spring 7 is fixed to a fixed surface 10 of the magnetic yoke 9.

Therefore, the objective lens holder 3 is supported so as to be able to translate in a direction parallel to the optical axis 16 by bending the leaf spring 7.

11 is a focusing coil, 12 is a tracking coil, and 13 is a permanent magnet. The focusing coil 11 is wound around the outer circumference of the objective lens holder 3, and the tracking coil 12 is fixed to the objective lens holder 3. The permanent magnet 13 is fixed to the magnetic yoke 9 so as to face the focusing coil 11 and the tracking coil 12.

Regarding the objective lens drive device configured as above,
The operation will be explained below.

FIGS. 3(a) and 3(b) are schematic diagrams illustrating tracking control of the objective lens driving device, and FIG. 3(a)
3(b) shows a state in which the objective lens holder 3 is located at a neutral point, and FIG. 3(b) shows a state in which the objective lens holder 3 is under tracking control.

In tracking control, the objective lens holder 3 is rotated in a direction perpendicular to the optical axis 16 of the objective lens 6 using an electromagnetic force generated by a current flowing through the tracking coil 12 and a magnetic field generated by the permanent magnet 13 and the magnetic yoke 9. It is done by letting The displacement angle θ of the objective lens holder 3 shown in FIG. 3(b) is determined by the relative displacement distance between the objective lens 6 and the desired laser beam irradiation position on the information recording medium.

FIGS. 4(a) and 4(b) are schematic diagrams illustrating focus control of the objective lens driving device, and FIG. 4(a) shows a state in which the objective lens holder 3 is located at a neutral point, and FIG. 4
Figure (b) shows a state in which the objective lens holder 3 is under focus control.

Focus control moves the objective lens holder 3 in a direction parallel to the optical axis 16 of the objective lens 6 using electromagnetic force generated by a current flowing through the focusing coil 11 and a magnetic field generated by the permanent magnet 13 and the magnetic yoke 9. It is done from time to time. The displacement X of the objective lens holder 3 shown in FIG. 4(b) is determined by the relative defocus distance between the objective lens 6 and the information recording medium in the direction of the optical axis 16.

As described above, according to this embodiment, since the objective lens holder is rotatably supported by the intermediate member via the leaf spring, the objective lens holder 3 and the intermediate member 2 are in a continuous system. Highly accurate tracking control and focus control are realized.

Effects of the Invention As described above, the present invention enables highly accurate focus control and tracking control by supporting the objective lens holder so as to be rotatable in a direction perpendicular to the optical axis of the objective lens by twisting a leaf spring. This makes it possible to realize an excellent objective lens driving device that can perform the following operations.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of an objective lens drive device in an embodiment of the present invention, FIG. 2 is a perspective view of the objective lens drive device, and FIG. 3 is a diagram for explaining tracking control of the objective lens drive device. A plan view, FIG. 4 is a plan view for explaining focus control of the objective lens driving device, and FIG.
The figure is an exploded perspective view of a conventional objective lens drive device, FIG. 6 is a perspective view of a conventional objective lens drive device, FIG. 7 is a plan view for explaining tracking control of the conventional objective lens drive device, and FIG. The figure is a plan view for explaining focus control of a conventional objective lens drive device. 1... Tracking leaf spring, 2...
Intermediate member, 3...Objective lens holder, 6...
...Objective lens, 7...Focus plate spring, 9...Magnetic yoke, 11...Focusing coil, 12...Tracking coil, 13...Permanent magnet. Name of agent: Patent attorney Shigetaka Awano Haka 1 person draft/Z Figure diagram Figure diagram cause/4

Claims (1)

[Claims] an objective lens holder holding an objective lens; and a first elastic member that supports the objective lens holder so as to be rotatable in a direction perpendicular to the optical axis of the objective lens with a rotation center passing through the center of gravity of the objective lens holder. a support member, an intermediate member that holds the first elastic support member, a second elastic support member that supports the objective lens holder movably in the optical axis direction via the intermediate member; a base support member that supports the objective lens holder via one elastic support member, the intermediate member, and the second elastic support member; and a first drive means that drives the objective lens in the optical axis direction. and second driving means for driving the objective lens in a direction perpendicular to the optical axis direction.