JPS61264523A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To obtain a small-sized and light-weight objective lens driving device which is easy to assemble and has a high reliability, by providing a driving means on a base. CONSTITUTION:A permanent magnet 33a is attached to a magnetic yoke plate 31, and magnets 39a-39d consisting of magnetic cores 35 and coils 37 are attached to the magnetic yoke plate 31 on four sides of the permanent magnet 33a. Meanwhile, magnetic plates 27a and 27b are attached to an objective lens holding member 1, and the magnetic yoke plate 31 is attached to a base 11 so that the permanent magnet 33a is near and opposite to the magnetic plate 27a. If electromagnets 39a and 39c are excited in directions opposite to each other, a driving force in the Z direction is allowed to act upon the objective lens holding member 1 besides the attraction by the cooperation between lines of the magnetic force of them and those of the permanent magnet 33; and if electromagnets 39b and 39d are excited in directions opposite to each other, a driving force in the Y direction is allowed to act upon the objective lens holding member 1 similarly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a driving device for an objective lens used in an optical information writing/reproducing device or the like.

[Conventional technology]

Generally, in an optical disk device, a magneto-optical disk device, a digital audio device, etc., tracking control and focus control are performed on an objective lens to read information recorded on a recording medium.

For example, in an optical disk device, the recording medium has a width of 1 to 2 μm.
m, and information pits with a length of 1 to 3 μm are recorded. To read information from this information pit, first a light beam is focused onto a minute switch using an objective lens, and is irradiated onto the information pit. At this time, the reflected light or transmitted light from the recording medium changes optically depending on the presence or absence of information pits, and by detecting this change with a photodetector, a reproduced signal corresponding to the information pits can be obtained.

In this case, it is important that the minute spots always accurately scan the information pit row on the recording medium, and for this reason, the irradiation position is adjusted by autofocus to correct the focus shift caused by the warping of the recording medium, etc., and by adjusting the eccentricity of the recording medium, etc. Auto-tracking is required to correct the deviation.

In order to realize this autofocus function and autotracking function, a mechanism is required to move the objective lens two-dimensionally, that is, in the optical axis direction and in a direction orthogonal to the optical axis. Conventionally, such an objective lens driving device is required. In some cases, tracking is performed by rotating the objective lens along the support shaft, and autofocus is performed by sliding the objective lens along the support shaft.

FIGS. 4 and 5 are a plan view and a side view of this conventional objective lens driving device.

The objective lens holding member 1 is composed of a disk-shaped plate part 3, an outer cylindrical part 5, and an inner cylindrical part 7, and the upper part of a support shaft 9 passes through a bearing hole of the inner cylindrical part 7.

The lower part of the support shaft 9 is fixedly supported by a base 11.

The objective lens holding member 1 is supported rotatably around the support shaft 9 and slidably along the support shaft 9.

A pair of through holes are provided in the plate portion 3 of the objective lens holding member 1 at positions symmetrical about the support shaft 9, and the tips of a pair of yokes 13m and 13b are inserted into these through holes. A pair of through holes are also provided at positions symmetrical to the X-axis, and an objective lens 15 is fitted into one of the through holes, and a balancer 17° is fitted into the other through hole for fixed support.

A focus coil 19 is wound around the outer periphery of the outer cylindrical portion 5 of the objective lens holding member 1.
On the surface of 90, four tracking coils 21a are located symmetrically with respect to the support shaft 9.

21b, 21c, and 21d are bonded. Yokes 23m and 23b are integrally formed on the base 11 at positions spaced apart from the objective lens holding member and symmetrical with respect to the support shaft 9.

A magnetic circuit is constituted by permanent magnets 25 m * 25 b provided between the yokes 13 m and 13 b and the base 11 .

Next, the operation of this objective lens driving device will be explained.

A magnetic field is formed in the magnetic circuit made up of permanent magnets 25m and 25b, and when electric power is applied to the focus coil 19, forces in two directions are applied to the objective lens holding member 1. Focusing is performed by sliding the lens along the lens.

Also tracking coils 21m, 21b, 21c.

When a current is applied to 21d, the objective lens holding member 1 rotates around the support shaft 9, and tracking is performed.

[Problems with conventional technology]

In such an objective lens drive device, there is a focus coil within the same magnetic field. Since both the twin and the tracking coils can be placed, the shed is lightweight, but the four tracking coils are positioned at predetermined positions on the surface of the focus coil and attached by gluing, making the mounting process very troublesome. Also, since it is attached only by gluing, the strength of the attachment may be insufficient. Furthermore, since there is a coil in the movable part, at least four lead wires have to be taken out from the movable part, two for focusing and two for tracking, making handling difficult and the lead wires getting caught somewhere along the way. However, there was a problem that the movement became slow and the wire broke.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by providing an objective lens driving device that is easy to assemble, has high reliability, and is small and lightweight.

[Summary of the invention]

In order to achieve the above object, the present invention fixes a support shaft to a base, and provides an objective lens holding member on the support shaft that is slidable on the support shaft and rotatable around the support shaft. An objective lens is provided on the objective lens holding member so as to be spaced apart from the axis so that its optical axis is substantially parallel to the support axis, and a magnetic material is fixed around the objective lens holding member, and the magnetic material is a driving means for moving the objective lens holding member in the direction of the support axis by applying a force in the direction of the support axis to the body, and rotating the objective lens holding member around the support axis by applying a force in the direction of the support axis to the magnetic body; This is a driving device for an objective lens provided on the base.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below based on the drawings.

1 and 2 are a plan view and a side view of an objective lens driving device according to an embodiment of the present invention.

The objective lens holding member 1 consists of a disk-shaped plate part 3, an outer cylindrical part 5, and an inner cylindrical part 7, and the upper part of the support shaft 9 passes through the bearing hole of the inner cylindrical part 70. The lower part of the support shaft 9 is fixedly supported by a base 11. The objective lens holding member 1 is supported rotatably around a support shaft 9 and slidably along the support shaft 9.

An objective lens 15 and a balancer 17 are fixedly supported on the plate portion 3 of the objective lens holding member 1 at symmetrical positions with respect to the X-axis. Also, on the outside of the cylindrical part 5 outside the objective lens holding member, magnetic plates 27m and 27b are placed at symmetrical positions around the support shaft 9.
is fixed.

Objective lens driving means 29 m + 29 b is fixedly supported on a part of the base 11 at a position facing the magnetic plates 27 m and 27 bK.

FIG. 3 is a perspective view of the objective lens driving means 29&. In the figure, a permanent magnet 33m is attached to the base of the magnetic yoke, and magnets 39a consisting of a magnetic core 35 and a coil 37 are arranged on all sides of this permanent magnet 33&.

39b, 39c, and 39d are attached to the magnetic yoke plate 31. On the other hand, as described above, the objective lens holding member 1
Magnetic plates 27m and 27b are attached to the magnetic plate 27.
The magnetic yoke plate 31 is attached to the base 11 so that the permanent magnets 33 & are closely opposed to each other.

The magnetic plates 27m and 27b are attracted by permanent magnets 33a and 33b. Also, the electromagnets 39m and 39c are in two directions,
The electromagnets 39b and 39d are arranged in the Y direction. Therefore, if the electromagnets 39m and 39c are excited in opposite directions,
Due to the cooperation between these lines of magnetic force and the lines of magnetic force of the permanent magnet 33, in addition to the above-mentioned attractive force, a driving force is generated in two directions, and if the electromagnets 39b and 39d are excited in opposite directions, a driving force is also generated in the Y direction. can be made to act on the objective lens holding member 1. Therefore, tracking control and focusing control of the objective lens 15 can be performed by controlling the direction and magnitude of excitation of these electromagnets.

〔Effect of the invention〕

As described in detail above, according to the present invention, since the driving means can be provided on the base, it is possible to provide an objective lens driving device that is easy to assemble, has high reliability, and is small and lightweight.

[Brief explanation of the drawing]

1 and 2 are a plan view and a side view of an objective lens driving device according to an embodiment of the present invention, FIG. 3 is a perspective view of a driving means, and FIGS. 4 and 5 are a conventional one. FIG. 2 is a plan view and a side view of an objective lens driving device. 1... Objective lens support member, 9... Support shaft, 11...
・Base, 15...Objective lens, 27a, 27b...
・Magnetic plates, 29a, 29b''-driving means. 39c 39d 4th flash Figure 5

Claims (2)

[Claims] (1) A support shaft is fixed to a base, and an objective lens holding member is provided on the support shaft so as to be able to slide on the support shaft and rotatable around the support shaft, and to hold the objective lens at a distance from the support shaft. An objective lens is provided on the objective lens holding member so that the optical axis is approximately parallel to the support axis, a magnetic material is fixed around the objective lens holding member, and magnetic interaction causes the magnetic material to move in the direction of the support axis. The base is provided with driving means for applying a force to move the objective lens holding member in the direction of the supporting axis and applying a force around the supporting axis to the magnetic body to rotate the objective lens holding member about the supporting axis. Objective lens drive device. (2) The objective lens driving device according to claim 1, wherein the driving means comprises a permanent magnet and electromagnets provided on all sides of the permanent magnet in the direction of the spindle and in the direction orthogonal to the spindle.