JPH01171131A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To make an objective lens driving device thinner by setting a focus coil and a tracking coil approximately at the same height, and sandwiching and arranging at least one tracking coil between a focus movable body and a tracking movable body. CONSTITUTION:A focus driving means and a tracking driving means for the driving of an objective lens 6 in a focus direction and a tracking direction are provided. The focus driving means has a focus coil 15 and a magnetic circuit 20 for a focus, and the tracking driving means has a tracking coil 16 and a magnetic circuit 21 for tracking. The focus coil 15 and the tracking coil 16 are set approximately at the same height, at least one tracking coil 16 is sandwiched and arranged between focus movable bodies 10a and 10b and tracking movable bodies 12a and 12b, and the corresponding magnetic circuits 21 for the tracking are arranged on the both sides of a focus movable body 20. Thus, the objective lens driving device can be made thinner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical system that can optically record, reproduce, erase, etc. information by irradiating a recording medium with a light beam such as a laser beam. The present invention relates to an objective lens driving device in an information recording and reproducing device.

[Conventional technology]

As an optical information recording/reproducing apparatus equipped with an objective lens driving device, for example, one having a structure shown in FIG. 3 is known.

In this optical information recording and reproducing apparatus, a magneto-optical disk 1 is rotationally driven by a motor 2, and a laser light source 3a
The laser beam 7 emitted from the mirror 3b is reflected by the mirror 3b, passes through the objective lens 6, and converges on the surface of the disk recording medium 1a built into the magneto-optical disk l, thereby recording, reproducing, or erasing information. It is configured so that it can be done.

Further, an objective lens driving device 4 is provided for driving the objective lens 6 vertically and horizontally to control the convergence position of the laser beam 7 to follow the recording track of the disk recording medium 1a. Furthermore, an optical head 3 housing the above-mentioned optical system, a coil 5 for recording and erasing information, and a linear motor for moving the optical head 3 to access a target track on the surface of the disk recording medium 1a at high speed. 8 etc. are provided.

As shown in FIG. 4, the conventional objective lens driving device 4 incorporated in the above-mentioned optical information recording/reproducing apparatus includes a lens support member 9 that supports an objective lens 6 whose optical axis faces the recording surface of an optical recording medium. is a pair of focus direction movable springs 10a, 1 which are movable only in the direction perpendicular to the recording surface of the optical recording medium, that is, in the focus direction, and form a focus movable body.
It is supported by an intermediate support 11 via 0b.

The intermediate support 11 is movable only in a direction perpendicular to the plane of the recording track of the optical recording medium, that is, in the tracking direction, and is connected to the fixed support 13 via a pair of tracking direction movable springs 12a and 12b forming a tracking movable body.
A pair of left and right support members 14a and 14b planted on the upper surface of
Supported by

A pair of left and right focusing coils 15 and 1 are provided on both sides of the lens supporting member 9 for driving the objective lens 6 supported by the lens supporting member 9 in the focusing direction.
5, and a pair of left and right tracking coils 16 for driving the objective lens 6 in the tracking direction. A portion of the focus coils 15, 15 and the tracking coils 16, 16 are connected to the magnet 1.
7 and a yoke 18, each pair of left and right magnetic circuits 1
9... are arranged within the magnetic gaps 19a..., respectively.

Then, by energizing the focus coils 15, 15 and the tracking coils 16, 16, respectively, the electromagnetic force generated at this time causes the lens support member 9 supporting the objective lens 6 to move in the focus direction and the tracking direction, respectively. Driven to displace.

In another conventional objective lens driving device, as shown in FIG. 5, the magnetic circuit is separately constructed of a focusing magnetic circuit 20 and a tracking magnetic circuit 21. Regarding the other configurations, the same reference numerals are added to the constituent members having the same functions as those of the conventional example shown in FIG. 4, and the explanation thereof will be omitted.

[Problem that the invention seeks to solve]

However, in the former conventional example shown in FIG. 4, parts of both the focus coil 15 and the tracking coil 16 are disposed within one magnetic gap 19a.
It is necessary to have a large gap length. Therefore, the leakage of magnetic flux at the upper and lower ends of the magnetic gap 19a increases as the gap length increases, and the non-uniformity of the magnetic flux density at the upper and lower positions of the magnetic gap 19a becomes significant. As a result, depending on the height of the magnetic gap 19a at which the tracking coil 16 is set, the position (height) at which the resultant force of the tracking driving force acts will vary greatly. There was a problem with this.

In addition, in the latter conventional example shown in FIG. 5, the length of the magnetic gap 21a of the tracking magnetic circuit 21 can be set short, thereby suppressing leakage of magnetic flux and alleviating non-uniformity of magnetic flux density. On the other hand, in order to secure a space for the focusing magnetic circuit 20, the upper and lower focusing direction movable springs 10a and x6b are each divided into two left and right pieces.This reduces workability. In addition, there is a problem in that the length of the lens support member 9 in the tracking direction inevitably becomes large because it is necessary to provide a sufficient distance between the divided focus direction movable blades 10a and 10b on the left and right sides. are doing.

As described above, the conventional objective lens driving device has problems such as significant non-uniformity of the magnetic flux density within the magnetic gap 19a or an increase in the length of the lens support member 9 in the tracking direction. It had

[Means for solving problems]

In order to solve the above problems, an objective lens driving device according to the present invention supports an objective lens by an intermediate support via a focus movable body that is movable only in the focus direction, and supports the intermediate support in the tracking direction. an objective lens driving device supported on a fixed support via a tracking movable body that is movable only in The focus driving means includes a focus coil fixed to both sides in the tracking direction of a lens support member that supports the objective lens, and a focus magnetic circuit provided corresponding to the focus coil and fixed on a fixed support. The trunking drive means consists of:
The lens support member is composed of a tracking coil fixed on both sides of the lens supporting member, which is orthogonal to the plane of the tracking direction, and a tracking magnetic circuit provided corresponding to the tracking coil and fixed on the fixed support. and tracking coils are set at almost the same height, at least one of the tracking coils is disposed between the focus movable body and the tracking movable body, and a corresponding tracking magnetic circuit is arranged. It is characterized by being arranged on both sides of the focus movable body.

The tracking magnetic circuit is supported by a support member provided on the fixed support, or directly supported on the fixed support.

[For production]

With the above configuration, it is possible to reduce the thickness of the objective lens driving device. In addition, since only the tracking coil is disposed within the magnetic air gap of the tracking magnetic circuit, the length of this magnetic air gap can be set short. Therefore, the leakage of magnetic flux from the magnetic air gap is reduced as much as possible, and the magnetic flux Density non-uniformity can be alleviated.

Furthermore, since the effective part of the magnetic flux is made long in the focus direction and has some play in the movable range in the focus direction, the driving force in the tracking direction can be achieved without using the non-uniform part of the magnetic flux density. can be given.

Further, since the focus coil and the tracking coil are set at substantially the same height and force is applied to the center of gravity of the movable part, application of rotational force to the lens support member can be avoided.

In addition, at least one of the tracking coils is disposed between the focus movable body and the tracking movable body, and corresponding tracking magnetic circuits are disposed on both sides of the focus movable body. So,
There is no need to separately form both the focus movable body and the tracking movable body. therefore,
Not only is workability significantly improved, space loss can be eliminated, and structural members such as the lens support member and the intermediate support can also be downsized.

[Example 1] An example of the present invention will be described below based on FIG. For convenience of explanation, components having the same functions as those of the conventional example will be described with the same reference numerals.

As shown in FIGS. 1(a) and 1(b), the objective lens driving device includes rectangular focus coils 15, 15 on both back sides of a lens support member 9 that supports the objective lens 6 in the tracking direction. Fixed. Also,
On both sides of the lens support member 9 in a direction perpendicular to the plane of the tracking direction, flat-shaped tracking coils 16, 16 are fixed vertically, and are connected to the above-mentioned focusing coils 15, 15. The tracking coils 16 and 16 are set at approximately the same height. This allows the objective lens driving device to be made thinner.

Two focusing magnetic circuits 20, 20 each consisting of a set of a magnet 22 and a yoke 23 have magnetic gaps 20a and 20, respectively.
A portion of each of the focus coils 15, 15 is disposed in each of the focus coils 20a, and is provided corresponding to the two focus coils 15, 15, and is fixed on the fixed support 13, respectively. .

On the other hand, the tracking magnetic circuit 21 consisting of a set of a magnet 24 and a yoke 25 has a magnetic gap 21a.
... is incorporated so that a part of the tracking coils 16, 16 are disposed inside, and each tracking coil 1
1 at each end of the tracking direction in 6 and 16.
A total of four tracking magnetic circuits 21...
It is fixed on a fixed support 13.

Focus coils 15, 15 fixed to both sides of the lens support member 9 supporting the objective lens 6 in the tracking direction, and the focus coils 15, 1
Support member 14 on the fixed support 13 provided corresponding to 5
Focusing magnetic circuit 20 fixed by a and 14b
and 20 constitute a focus drive means for driving the lens support member 9 that supports the objective lens 6 in the focus direction.

Additionally, tracking coils 16 and I6 fixed on both sides of the lens support member 9 that are perpendicular to the plane of the tracking direction, and tracking coils 16 and I6 fixed on the fixed support 13 provided corresponding to the tracking coils 16 and 16 The magnetic circuits 21, . . . constitute a tracking drive means for driving the lens support member 9 supporting the objective lens 6 in the tracking direction.

Because of the above configuration, only the flat-shaped tracking coils 16 are provided in the magnetic gaps 21a of the tracking magnetic circuits 21. For this reason, the tracking magnetic circuit 21...
The length of the magnetic gaps 21a... can be set short. Therefore, the leakage of magnetic flux from the magnetic gaps 21a can be suppressed as much as possible to alleviate the non-uniformity of the magnetic flux density. Furthermore, by making the effective part of the magnetic flux long in the focus direction and allowing some play in the movable range in the focus direction, it is possible to apply driving force in the tracking direction without making use of the non-uniform part of the magnetic flux density. becomes.

The lens support member 9 is movable only in the focus direction and is supported by an intermediate support body 11 via a pair of upper and lower focus direction movable springs 10a and 10b which constitute a focus movable body. This intermediate support body 11 is a pair of left and right support members implanted on a fixed support body 13 via a pair of left and right tracking direction movable springs 12a-12b which are movable only in the tracking direction and constitute a trunking movable body. It is supported by 14a and 14b.

Since two of the tracking magnetic circuits 21 are arranged on both sides of the focus direction movable springs 10a and 10b, each focus direction movable spring 10alOb
There is no need to divide and configure it. Therefore, the lens support member 9, intermediate support body 11, etc. attached to the focus direction movable springs 10a and IOb can be configured to be small and compact.

Further, one of the tracking coils 16 is connected to a focus direction movable spring 10 which forms a focus movable body.
a.1.ob and the tracking direction movable springs 12a and 12b forming the tracking movable body, so the tracking direction movable spring 12a
-12b does not need to be divided and configured in the same way.

A light source 26 such as an LED is attached to the intermediate support 11 described above, while a photodetector 27 is attached to the fixed support 13 facing the light source 26. This photodetector 27 is used for detecting displacement during access.

In the above configuration, when the focus coils 15, 15 and the tracking coils 16, 16 are energized, electromagnetic force is generated in each, so that the lens support member 9 that supports the objective lens 6 is displaced and driven in the focus direction and the tracking direction, respectively. will be done.

[Embodiment 2] Another embodiment of the present invention is shown in FIG. In addition, in this embodiment, the same reference numerals are added to the constituent members having the same functions as those shown in the first embodiment, and the explanation thereof will be omitted.

In this second embodiment, as shown in FIG. 2, the tracking magnetic circuits 21 . . . also serve as support members 14a and 14b for the movable springs 12a and 12b in the tracking direction. That is, in this embodiment, the support members 14a and 14b for supporting the tracking direction movable springs 12a and 12b are not formed, and the tracking direction movable springs 12a and 12b directly support the fixed support body 13.
It is of a fixed configuration on top. This makes it possible to reduce the number of parts and further downsize the device.

〔Effect of the invention〕

As described above, in the objective lens driving device according to the present invention, the objective lens is supported by the intermediate support via the focus movable body that is movable only in the focus direction, and the intermediate support is movable only in the tracking direction. In an objective lens driving device that is supported on a fixed support via a tracking movable body and includes a focus drive means and a tracking drive means for driving the objective lens in a focus direction and a tracking direction, the focus drive means includes: A tracking drive means consisting of a focus coil fixed on both sides in the tracking direction of a lens support member that supports an objective lens, and a focus magnetic circuit provided corresponding to the focus coil and fixed on a fixed support. consists of a tracking coil fixed on both sides of the lens support member in a direction perpendicular to the plane of the tracking direction, and a tracking magnetic circuit provided corresponding to the tracking coil and fixed on the fixed support, and The focus coil and the tracking coil are set at approximately the same height, and at least one of the tracking coils is disposed between the focus movable body and the tracking movable body, and a corresponding tracking magnetic field. This configuration has circuits arranged on both sides of the focus movable body.

Thereby, the objective lens driving device can be made thinner. Furthermore, since only the tracking coil is disposed within the magnetic gap of the tracking magnetic circuit, the length of this magnetic gap can be set short. Therefore, leakage of magnetic flux from the magnetic gap can be reduced as much as possible, and non-uniformity in magnetic flux density can be alleviated. Furthermore, by forming the effective part of the magnetic flux long in the focus direction, it is possible to give some play to the movable range in the focus direction, so the tracking direction can be driven without using the non-uniform part of the magnetic flux density. It can give you strength.

Further, since the focus coil and the tracking coil are set at substantially the same height and force is applied to the center of gravity of the movable part, application of rotational force to the lens support member can be avoided. Further, at least one of the tracking coils is disposed between the focus movable body and the tracking movable body, and corresponding tracking magnetic circuits are disposed on both sides of the focus movable body. There is no need to separately form both the focus movable body and the tracking movable body. Therefore, not only the workability is significantly improved, but also space loss can be eliminated and constituent members such as the lens support member and the intermediate support can be downsized.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which FIG. 1(a) is a plan view of the objective lens driving device, FIG. 1(b) is a side view of the objective lens driving device, and FIG. 1(b) is a side view of the objective lens driving device. The figure is a plan view showing another embodiment of the present invention. 3 to 5 show conventional examples, in which FIG. 3 is a schematic configuration explanatory diagram showing an example of an optical information recording/reproducing device equipped with an objective lens driving device, and FIGS. 4 and 5 FIG. 2 is a perspective view showing a conventional objective lens driving device. 6 is an objective lens, 9 is a lens support member, 10a/lOb
is a focus direction movable spring (focus movable body), 11
is the intermediate support, and 12a12b is the intermediate support. Tracking direction movable spring (tracking direction movable body)
, 13 is a fixed support body, 15 is a focusing coil, 16 is a tracking coil, 20 is a focusing magnetic circuit, 2
0a is a magnetic gap, 21 is a tracking magnetic circuit, 21
a is a magnetic gap, 22 is a magnet, 23 is a yoke, 24
is a magnet, and 25 is a yoke. Figure 1 (b) 4th picture Figure 5

Claims (1)

[Claims] 1. The objective lens is supported by an intermediate support via a focus movable body that is movable only in the focusing direction, and the intermediate support is fixed via a tracking movable body that is movable only in the tracking direction. In an objective lens driving device that is supported on a support and includes a focus drive means and a tracking drive means for driving the objective lens in a focus direction and a tracking direction, the focus drive means is a lens that supports the objective lens. The tracking drive means includes a focus coil fixed to both sides of the support member in the tracking direction, and a focusing magnetic circuit provided corresponding to the focus coil and fixed on the fixed support. The tracking coil is made up of a tracking coil fixed on both sides that are orthogonal to the plane, and a tracking magnetic circuit provided corresponding to the tracking coil and fixed on a fixed support, and the above-mentioned focus coil and tracking coil are set at almost the same height, at least one of the tracking coils is disposed between the focus movable body and the tracking movable body, and the corresponding tracking magnetic circuit is connected to the focus movable body. An objective lens drive device characterized in that it is arranged on both sides of the objective lens drive device.