JPS61264525A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To stabilize the motion of an objective lens and facilitate controlling it by forming the surface of a magnetic body, which faces a driving means, into a projecting shape. CONSTITUTION:The surface of a magnetic plate 25a which faces a driving means 27 is formed into a circle having the same radius as a radius R of rotation of the magnetic body 25a with rubber members 9 and 11 provided on a pole brace 3 as the center. Since the surface of the magnetic body 25a is formed into the same curvature as the radius R of rotation of the magnetic body 25a, positional relations between the magnetic body 25a and the driving means 27 are scarcely changed whether the magnetic body 25a is placed in the position indicated by a solid line or in the position indicated by a dotted line. Thus, the magnetic body 25a receives always a stable force from the driving means 27.

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 recording/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 f-isk device, @1 to
Information pits with a length of 2 μm to 3 μm are recorded. K, which reads information from this information pit, first focuses a light beam onto a minute spot using an objective lens, and irradiates the information bit with the light beam. At this time, the reflected light or transmitted light from the recording medium changes optically depending on the presence or absence of information bits.
Information is obtained by detecting this change with a photodetector.
A corresponding reproduction signal can be obtained.

In this case, it is important that the minute spot always accurately scans the information bit string on the recording medium, and for this reason, the irradiation position is adjusted by autofocus to correct the focal shift due to warping of the recording medium, etc., and by eccentricity of the recording medium, etc. An auto tracker and king are required to correct the deviation.

In order to realize this autofocus function and autotracking function, K requires a mechanism that moves the objective lens two-dimensionally, that is, in the optical axis direction and in the direction orthogonal to the optical axis. , an objective lens holder having an objective lens and provided on a base so as to be movable in the optical axis direction of the objective lens and in a direction perpendicular to the optical axis; a magnetic body fixed to the objective lens holder;
Some devices are equipped with a driving means that applies a force in the optical axis direction and a force perpendicular to the optical axis to the magnetic body by magnetic action to move the objective lens holder in the optical axis direction and in the direction perpendicular to the optical axis.

FIG. 6 is a perspective view of such a conventional objective lens driving device, and FIG. 7 is a perspective view of this objective lens driving device viewed from direction B.

A support 3 is erected on the base 1, and a mouth-shaped rigid plate 5, 7 is attached to the support 3 with a rubber member 9. Supported by IC. The rigid plate 5.7 is made of a lightweight and highly rigid material such as aluminum, and is connected to the support column 3 by rubber members 9 and 11.
These rigid plates 5, 7 are supported by rubber members 9, 1.
It is movable in both the X and Y directions in the figure using 1 as a fulcrum. An objective lens holder 23 having an objective lens 21 is supported by a rubber member 13.15 and a rubber member 17.19 on the side of the rigid plate 5.7 opposite to the side supported by the pillar 3. A flat magnetic body 25 is fixed to one surface of the square columnar objective lens holder 23 .

A driving means 27 shown in FIG. 8 is provided near the magnetic body 25 and spaced apart from the magnetic body 25 on a side plate 29 fixed to the base 1.

This driving means 27 has a permanent magnet 33 on a magnetic yoke plate 31.
A magnetic core 35 and a coil 3 are provided on all sides of this permanent magnet 33.
7 electromagnets 39a+39b+39e, 39d are provided, and electromagnets 39&, permanent magnets 33. The electromagnets 39m, 39b, 39c are arranged so that the arrangement direction of the electromagnet 39c coincides with the optical axis direction of the objective lens-e21, and the arrangement direction of the electromagnet 39b1, permanent magnet 33, and electromagnet 39d is perpendicular to the optical axis direction. , 39d are provided.

Since the magnetic body 25 is attracted by the permanent magnet 33, forces in two directions are constantly acting on the objective lens holder 23.

When the electromagnets 39m and 39c are operated together, a force is applied to the magnetic plate 25 in the X direction, and the rigid plates 5 and 7 move in the X direction using the rubber members 9 and 11 of the support 3 as fulcrums, and as a result, the objective lens is held. The body 23 also moves in the X direction and focus control is performed.

When the electromagnets 39b and 39d are operated together, Y is generated on the magnetic plate.
When a force in the direction is applied, the rigid plates 5 and 7 move against the arm member 9 of the support column 3.
, 11 as fulcrums in the Y direction, and as a result, the objective lens holder 23 also moves in the Y direction, and tracking control is performed.

[Problems with conventional technology]

However, in such a conventional objective lens driving device, when performing tracking and king control, the magnetic body 25 performs a circular motion around the rubber members 9 and 11 of the support, and the driving means 27 of the magnetic body 25 Since the opposing surfaces were flat as described above, the distance between the magnetic body 25 and the driving means 27 changes as the magnetic body 25 moves, making the movement of the objective lens unstable and making it difficult to control the drive of the objective lens. There was a problem that.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an objective lens driving device in which the movement of the objective lens is stable and the movement of the objective lens is easy to control, in order to solve the above-mentioned problems.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized in that the surface of the magnetic body facing the driving means is formed into a convex shape.

[Embodiments of the invention]

One embodiment of the present invention will be described in detail below based on the drawings. Fig. 1 is a perspective view of an objective lens driving device according to this embodiment, and is the same as the conventional example shown in Figs. 6 to 8. Elements that perform the same function are given the same number.

In this embodiment, the surface of the magnetic plate 25 facing the drive means 27 is formed in a circular shape having the same radius as the rotation radius R of the magnetic body 25m rotating around the rubber members 9 and 11 provided on the support column 3. The other configurations are the same as the conventional example shown in FIG. 6.7.8.

Next, the operation of this embodiment will be explained. As shown in FIG.
1 as a fulcrum, and as a result, the objective lens holder 23 also moves in the X direction. At this time, the member 13
, 15, 17.19, the optical axis of the objective lens 21 is set to the electromagnet 39a.

The objective lens holder 23 is moved in step 5 so that it becomes parallel to the optical axis 39c before operation.

Further, when the electromagnets 39 b t 39 c of the driving means 27 are activated, the rigid plates 5 and 7 move toward the support column 3 as shown in FIG.
It performs a circular motion centering on the rubber member 9.11 provided at , and is moved to the position shown by the dotted line in the figure. Magnetic body 25a
Since the surface of is formed to have the same curvature as the radius of rotation R of the magnetic body 25m, the relationship between the magnetic body 251 and the driving means 27 is constant even when the magnetic body 25m is at the position indicated by the solid line and when the magnetic body 25a is at the position indicated by the dotted line. The positional relationship hardly changes, and therefore the magnetic body 25m always receives a stable force from the driving means 27.

4 and 5 show the shape of the magnetic body 25a according to the second and third embodiments of the present invention, and as shown in these figures, the surface of the magnetic body 25m is shaped like a trapezoid. Alternatively, even if the magnetic body 25 is formed in a triangular shape, a more stable force can be applied from the driving means 27 to the magnetic body 25& compared to the conventional one.

Further, the surface of the magnetic body 25 may be processed not only into a triangular shape and a trapezoidal shape but also into other n-gonal shapes.

〔Effect of the invention〕

As described above in detail, according to the present invention, the movement of the objective lens is stabilized and its control becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an objective lens driving device according to an embodiment of the present invention, FIGS. 2 and 3 are side views and plan views of the objective lens driving device, and FIGS. 4 and 5 are 6 and 7 are perspective views of a conventional objective lens driving device, and FIG. 8 is a perspective view of a driving means. DESCRIPTION OF SYMBOLS 1... Base body, 21... Objective lens, 23... Objective lens holder, 25a... Magnetic body, 27... Drive means. Agent Patent Attorney Jo Taira Yamashita Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) An objective lens holder having an objective lens and provided on a base so as to be movable in the optical axis direction of the objective lens and in a direction perpendicular to the optical axis, and a magnetic body fixed to the objective lens holder. , an objective lens comprising driving means for moving the objective lens holder in the optical axis direction and in the direction perpendicular to the optical axis by applying a force in the optical axis direction and a force perpendicular to the optical axis to the magnetic body by magnetic action. A driving device for an objective lens, characterized in that a surface of the magnetic body facing the driving means is formed into a convex shape. (2) A surface of the magnetic body facing the driving means forms part of a cylinder having a radius substantially the same as a radius of rotation when the magnetic body rotates in a direction perpendicular to the optical axis. An objective lens driving device according to claim 1.