JP2842553B2 - Objective lens drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electromagnetic effect of an objective lens for guiding a light beam to an optical recording medium by a tracking coil and a focus coil, and a magnet arranged to face these coils. The present invention relates to an objective lens driving device that drives a light beam to be displaced in a tracking direction and a focus direction on an optical recording medium.

[Conventional technology]

For example, in an optical disk device, generally, focus control for forming a light spot on a disk, and
In order to perform tracking control for causing a light spot to follow a recording track on a disc, the objective lens is driven in an optical axis direction (focus direction) and in a direction perpendicular to the optical axis and the recording track (tracking direction). I have to.

Conventionally, as such an objective lens driving device, for example, JP-A-61-20232, JP-A-61-26945, and JP-A-59-26945.
No. 221836, Japanese Utility Model Publication No. 60-175325 and No. 61-86
There is one disclosed in Japanese Patent No. 823.

FIG. 9 shows an objective lens driving device disclosed in Japanese Patent Application Laid-Open No. 61-26945. The holder 2 holding the objective lens 1 is supported by the main body 4 via eight elastic members 3 so as to be displaceable in the focus direction F and the tracking direction T. A pair of tracking coils 6, 6 wound around the bobbin 5, respectively, are mounted on the holder 2, and a focus coil 7 is wound around the tracking coils 6, 6 and the outer periphery of the holder 2. . Further, permanent magnets 9, 9 are mounted on the main body 4 via yokes 8, 8 so as to face the tracking coils 6 and the focus coils 7. Where the tracking coil
The width of each of the tracking magnets 6 and 6 in the tracking direction T is substantially equal to the width of each of the facing permanent magnets 9 and 9. In this way, in this objective lens driving device, a predetermined current is applied to each of the tracking coils 6, 6 and the focus coil 7, so that the holder 2 is moved in the tracking direction T and the focus direction by the electromagnetic action with the permanent magnets 9, 9. The drive is performed in the direction F. Incidentally, JP-A-61-2023
No. 2 also discloses an objective lens driving device having a tracking coil having a width substantially equal to the width of the permanent magnet as in FIG.

FIG. 10 shows an objective lens driving device disclosed in Japanese Utility Model Laid-Open No. 86823/1986. In this objective lens driving device, the width of the pair of tracking members 6 and 6 is reduced, and these are wound around both ends of the holder 2 so as to face the both ends of the pair of permanent magnets 9 and 9. 9 is basically different from that shown in FIG. 9 in that the inner yokes 10, 10 are provided so as to pass through the holder 2 so as to face the respective permanent magnets 9, 9 via the coils 6, 6 and the focus coil 7. The other configuration is almost the same as that of FIG. Incidentally, Japanese Utility Model Laid-Open No. 60-175325 and Japanese Patent Laid-Open No. 59-221836 also disclose a tracking coil having a small width between the end of the permanent magnet and the inner yoke as in FIG. An objective lens driving device mounted on a holder is disclosed.

[Problems to be solved by the invention]

However, in the objective lens driving device shown in FIG. 9, since the tracking coil 6 is wound around the bobbin 6 and mounted, the weight of the movable portion increases in conjunction with the large coil width. However, there is a problem that the drive sensitivity in the tracking direction and the focus direction is reduced.

In the objective lens driving device shown in FIG. 10, the inner yoke 10 is arranged inside the tracking coil 6 (the tracking coil and the inner yoke cross each other when viewed from the optical axis direction of the objective lens 1). Therefore, there is a problem that the assembling procedure and method are complicated and the cost is increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an objective lens driving device which can solve the above-mentioned disadvantages, can reduce the cost, and can appropriately obtain the driving sensitivity in the tracking direction and the focus direction.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, an objective lens for guiding a light beam to an optical recording medium, a tracking coil, and a focus coil are fixed to a holder, and the objective lens is attached to the tracking coil, the focus coil, and these coils. In an objective lens driving device that drives an optical beam to be displaced in a tracking direction and a focus direction on an optical recording medium by an electromagnetic action with a magnet disposed to face, a tracking coil is wound around an axis parallel to the tracking direction. A wound wound coil, the coil width of which in the tracking direction is smaller than the width of the magnet, which is disposed to face the magnet and is not located inside the wound tracking coil. As described above, a yoke is arranged facing the magnet, The tracking coil and the focus coil are arranged so as to face the same magnetic pole surface of the magnet, and the positional relationship between the tracking coil, the magnet, and the yoke is symmetric with respect to an axis orthogonal to the tracking direction when viewed from the optical axis direction of the objective lens. It is constituted so that it becomes.

〔Example〕

1 to 3 show a first embodiment of the present invention. FIG. 1 is a perspective view, FIG. 2 is an exploded perspective view of a main part,
FIG. 3 shows a partial sectional view. This embodiment shows an objective lens driving device in an optical pickup.
The objective lens 21 is held by a holder 22, and the holder 22 is fixed to a base 24 made of a magnetic agent material via elastic supporting means consisting of four metal wires 23 coated with rubber.
25 is supported so as to be displaceable in the focus direction F and the tracking direction T. In the holder 22, openings 26a and 26b are formed symmetrically with respect to the objective lens 21 in a direction Y orthogonal to the focus direction F and the tracking direction T,
Slits 27a and 27b are formed at the center portions of both end faces 22a and 22b in the focus direction F so as to communicate with the openings 26a and 26b. Also,
Opening end faces 28a, 28b facing the end faces 22a, 22b have slits
Concave portions 29a, 29b are formed opposite to 27a, 27b, and a pair of tracking coils 30a, 30b are mounted on concave portions 29a, 29b through these slits 27a, 27b, and tracking coils 30
a, 30b and the focus coil 3
Wrap 1 The tracking coils 30a and 30b are wound around an axis parallel to the tracking direction T.

Further, a pair of outer yokes 24a, 24b are integrally formed on the base 24 so as to face the end surfaces 22a, 22b of the holder 22, and the permanent magnets 32a, 32b are formed on the surfaces of the outer yokes 24a, 24b facing the holder 22.
b, the pair of inner yokes 24c respectively penetrate the openings 26a, 26b of the holder 22 and face the permanent magnets 32a, 32b so as to be located on both sides of the tracking coils 30a, 30b in the tracking direction T. , 24d, 24e, and 24f are integrally provided to form two sets of magnetic circuits. The tracking coils 30a, 30b are mounted so that their widths in the tracking direction T are sufficiently smaller than those of the permanent magnets 32a, 32b, and are located substantially at the center of the permanent magnets 32a, 32b. Similarly, the width of the focus coil 31 in the focus direction F is smaller than that of the permanent magnets 32a and 32b, so that the focus coil 31 is located substantially at the center of the permanent magnets 32a and 32b. When viewed from the focus direction, the tracking coils 30a, 30b, the permanent magnets 32a, 32b, and the inner yokes 24c, 24d, 24
The position relationship between e and 24f is configured to be symmetric with respect to a direction Y orthogonal to the tracking direction.

In the above configuration, when a required current is supplied to the tracking coils 30a, 30b and the focus coil 31 via the metal wire 23, the holder 22 and the objective lens 21 are moved in the tracking direction by the electromagnetic action of the current and the permanent magnets 32a, 32b. It moves in T and the focus direction F, whereby the tracking control and the focus control of the light beam projected on the optical recording medium through the objective lens 21 can be performed.

According to this embodiment, the positioning of the tracking coils 30a, 30b is performed by the slits 27a, 27b and the recesses 29a, 29b formed in the holder 22, so that the tracking coils 30a, 30b can be easily and accurately performed. Also, the tracking coils 30a, 30
Since the dimension b in the tracking direction T is small, the dimension of the movable portion including the objective lens 21 and the holder 22 in the tracking direction T can be reduced, and the forming of the coils 30a and 30b is not required. Further, inside the wound tracking coils 30a, 30b, inner yokes 24c, 24d, 24e,
24f is not disposed, and when viewed from the focus direction, the wound tracking coils 30a and 30b and the inner yoke 2
Since 4c, 24d, 24e, and 24f do not intersect, assembly of the device is facilitated. Further, since the positional relationship between the tracking coils 30a, 30b, the permanent magnets 32a, 32b and the inner yokes 24c, 24d, 24e, 24f is symmetric with respect to the direction Y orthogonal to the tracking direction, the driving in the tracking direction is performed. The sensitivity becomes good.

4 to 7 show the second to fifth embodiments of the present invention. In these embodiments, members having the same functions as in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. In addition, the elastic support means for holding the holder 22, the fixing member 25, and the base 24 Is not shown in the figure. Hereinafter, the configurations of these embodiments will be briefly described.

The second embodiment shown in FIG.
a and 30b and the corresponding magnetic circuit and objective lens 21
Are arranged axially symmetrically with respect to the optical axis. With such a configuration, the tracking coils 30a, 30a in the direction Y orthogonal to the focus direction F and the tracking direction T,
Even if the dimension of 30b is long, the dimension of the entire movable section in the Y direction can be reduced.

In this embodiment, as shown in FIG. 4, the magnetic circuit on the left side and the magnetic circuit on the right side are displaced with respect to the tracking direction T.
a, the magnet 32a, and the inner yokes 24c, 24d are symmetrically arranged with respect to the direction Y, and the tracking coil 30b, the magnet 32
b, the inner yokes 24e and 24f are arranged symmetrically with respect to the direction Y.

In the third embodiment shown in FIG. 5, the objective lens 21 is mounted so as to be offset, and the portion where the driving force of the tracking coils 30a and 30b does not act is adjusted so that the weight balance of the movable portion is maintained. Is mounted in a direction opposite to the offset direction. With this configuration, the dimension of the movable portion in the Y direction can be reduced.

The fourth embodiment shown in FIG. 6 has two objective lenses 21a and 21a.
b (for example, for light emission and light reception)
The tracking coils 30a are wound. In such a configuration, two sets of magnetic circuits operate on one tracking coil 30, so that
The use efficiency of the device 30 can be improved, and the number of assembling steps such as mounting a coil and soldering a terminal can be reduced.

In the fifth embodiment shown in FIG. 7, a pair of focus coils 31 are provided on both sides of the holder 22 when viewed in the tracking direction T.
a and 31b are mounted, and tracking coils 30a and 30b are mounted on the focuses 31a and 31b, respectively, so as to be driven by four sets of magnetic circuits. Therefore, according to this embodiment, similarly to the fourth embodiment, the utilization efficiency of each coil can be increased, a large driving force can be obtained, and the dimension in the Y direction can be reduced.

FIG. 8 shows a sixth embodiment of the present invention. In this embodiment, the holder 22 for holding the objective lens 21 is not supported by the elastic support means, but is supported by a support shaft 35 provided on the base bottom (not shown).
To be pivotable and slidable in the axial direction with respect to
The objective lens 21 is displaced in the focus direction F by sliding the objective lens 21 in the tracking direction T and in the axial direction by rotation, so that tracking and focus control are performed. Except for this, it is basically the same as the first embodiment.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications or changes can be made.

For example, in the first to fifth embodiments, the elastic support means for supporting the holder so as to be displaceable in the focus and tracking directions is not limited to a metal wire, and is constituted by a leaf spring, a coil spring, or a viscoelastic body of a polymer material. You can also. In addition, in FIG.
A balancer may be provided at a position symmetrical to 21 to keep the weight balance.

〔The invention's effect〕

As described above, according to the present invention, since the yoke is arranged so as not to be located inside the wound tracking coil, the objective lens driving device can be easily assembled and can be manufactured at low cost. Further, since the tracking coil and the focus coil are arranged in a common magnetic gap, downsizing can be achieved. Furthermore, the positional relationship between the tracking coil, magnet, and yoke
The drive sensitivity is improved because the lens is configured to be symmetrical with respect to an axis orthogonal to the tracking direction when viewed from the optical axis direction of the objective lens.

[Brief description of the drawings]

1 to 3 are diagrams showing a first embodiment of the present invention, FIG. 4 is a diagram showing a second embodiment, FIG. 5 is a diagram showing a third embodiment, and FIG. FIG. 7 is a view showing the fifth embodiment, FIG. 8 is a view showing the same as in the sixth embodiment, and FIGS. 9 and 10 are views showing the prior art. 21, 21a, 21b Objective lens 22 Holder 23 Metal wire 24 Base 24a, 24b Outer yoke 24c to 24f Inner yoke 25 Fixed member 26a, 26b Opening 27a, 27b Slit 29a, 29b Concave section 30, 30a, 30b Tracking coil 31, 31a, 31b Focus coil 32a, 32b Permanent magnet 35 Support shaft

Claims (1)

(57) [Claims] An object lens for guiding a light beam to an optical recording medium, a tracking coil, and a focus coil are fixed to a holder, and the objective lens is composed of the tracking coil, the focus coil, and a magnet arranged to face these coils. In an objective lens driving device for driving a light beam to be displaced in a tracking direction and a focusing direction on an optical recording medium by an electromagnetic action, the tracking coil is wound around an axis parallel to the tracking direction. The coil has a coil width in the tracking direction smaller than the width of the magnet, is disposed to face the magnet, and faces the magnet so as not to be located inside the wound tracking coil. The yoke is arranged, and the tracking coil and The focusing coil is disposed to face the same magnetic pole surface of the magnet, and the positional relationship between the tracking coil, the magnet, and the yoke is symmetric with respect to an axis orthogonal to the tracking direction when viewed from the optical axis direction of the objective lens. An objective lens driving device, comprising: