JPH04205925A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To reduce the size and weight of an objective lens driving section by forming the part on the outer side of coils for driving a lens holding body smaller than the parts on the inner side thereof. CONSTITUTION:This device has the rectangular parallelepiped-shaped lens holding body 103 holding the objective lens 101, the wire-shaped supporting members 103a to 103d which support the lens holding body 102 at four points, a fixing part 104 which fixes and supports the wire-shaped supporting members 103a to 103d, and the coils 7A to 7D for driving the holding body between the lens holding body 102 and the fixing part 104. The parts 9a to 9d in proximity to the wire-shaped supporting members 103a to 103d of the coils 7A to 7D for driving the holding body are formed shorter than the parts constituting the opposite sides thereof. Then, the spacings between the two wire-shaped supporting members 103a and 103b, 103c and 103d fixed to the projecting parts of the movable parts on both sides of the coils 7A to 7D are shortened. The size and weight of the objective lens driving device are reduced in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an objective lens driving device of an optical head,
The present invention relates to an objective lens driving device for an optical head used in an optical disk device.

[Prior Art] A conventional example of this type of objective lens driving device will be described with reference to FIGS. 8 to 11.

FIG. 8 is a perspective view of a conventional example.

The objective lens drive device shown in FIG.
01, and a cubic lens holder 102 that holds the objective lens 101.

Of these, the lens holder 102 has two protrusions 110 on both sides thereof, as shown in FIG. Two yoke housing holes 111a and 111b for yokes are bored parallel to and symmetrical to the optical axis of the objective lens 101, each having a rectangular cross section.

The objective lens driving device further includes wire-like support members 103a, 103b, j03c, and 103d that are fixed to the protrusion 110 and support the lens holder 102 at four points, and these wire-like support members 103a, 103b, and 103c10.
3d and a thick plate-shaped fixing part 104 supporting them.

This fixed part 104 includes four yokes 106a, 106b, 106c, which are parallel to the optical axis of the objective lens 101, respectively.
106c and 106d, and a yoke support member 106e that fixedly supports them and projects from the fixing portion 104. The inner yokes 106a and 106b are located in the two yoke storage holes 111a of the lens holder 102,
111b. The yoke 106C is arranged outside the hole of the lens holder 102 so that its surface faces the yoke 106a, and the yoke 106d is arranged outside the lens holder 102 so that its surface faces the yoke 106b.
It is located outside of the 2nd hole.

The yokes 106a and 106b, and the yokes 106C and 106d are symmetrical and parallel to the optical axis of the objective lens 101.

The magnet 105a is connected to the yoke 106a and the yoke 106.
C and is fixed to the yoke 106c.

Moreover, the mag foot 105b is connected to the yoke 106b and the yoke 1.
06d, and is fixed to the yoke 106d. The rectangular coils 107A and 107B are mounted on the lens holder 102 between the yoke 106a and the magnet 105a so as to be adjacent to each other on the same plane. The rectangular coils 107C and 107D are mounted on the lens holder 102 between the yoke 106b and the magnet 105b so as to be adjacent to each other on the same plane.

Square coils 107A, 107B and square coil 1
0.7C107D are symmetrical and parallel to each other with respect to the optical axis of the objective lens 101.

FIG. 10(a) shows the objective lens 101. Lens holder 1
02. Wire-shaped support members 103a, 103b, 103c
, 103d, rectangular coils 107A, 107B, 10
This shows the positional relationship between 7C and 107D. 10th
Figure (b) shows them viewed from the side. The length of the lens holder 102 in the optical axis direction of the objective lens 101 is larger than the length of the rectangular coil 107A, etc. in the optical axis direction.

Here, the driving principle of this device will be explained based on FIG. 11.

Magnet 105a, yoke 106a, 106C
constitutes a magnetic circuit, and the lines of magnetic force of the magnetic circuit are perpendicular to the plane of the paper and are within the dotted line range in the figure. Portions 108a and 108b forming one side of the coil are rectangular coil 1.
This is a part of 07A and 107B that forms adjacent sides. Portions 108a and 108b forming one side of the coil are within the range of the magnetic lines of force of the magnetic circuit. In the coil 107A, a portion 109a forming one side of the coil, which is the opposite side to a portion 108a forming one side of the coil, is attached sufficiently away from the magnetic circuit. Rectangular coils 1 that are symmetrical and parallel to each other with respect to the optical axis of the objective lens 101
07C, 107D, etc. have a similar configuration.

Rectangular coils 107A, 107B, 107c.

When power is applied to 107D, the portion 108. which forms one side of the magnetic circuit and coil described above. a, 108b, 108c, 10
An electromagnetic force is generated by the electromagnetic interaction with the lens holder 8d, and this becomes a driving force for the lens holder 102. The electromagnetic force caused by this interaction is known as Fleming's law, and is expressed as "electromagnetic force = magnetic flux density x length of electric wire x current x number of turns." The electromagnetic force, that is, the driving force of the lens holder 102 is The part 108 a.

It is proportional to the lengths of 108b, 108c, and 108d.

Portions 108a, 108b, 108c forming one side of the coil
, 108d forming one side of the coil opposite to 108d.
9a, 109b, 109c, and 109d have a current direction opposite to that of the portion 108a forming one side of the coil, but are sufficiently far away from the magnetic circuit so that they do not contribute to electromagnetic interaction.

When the lens holder 102 is displaced by this driving force, the wire-shaped support members 103a and 103b.

103c and 103d generate an elastic repulsion force proportional to their displacement. The lens holder 102 comes to rest at a position where the driving force and its repulsive force are balanced. Therefore, the lens holder 102
The positioning of the rectangular coils 107A, 107B, 1
Increase or decrease the current flowing through 07C and 107D to adjust the lens holder 10.
It is controlled by adjusting the displacement of 2.

[Problem to be solved by the invention]

In the above-mentioned conventional objective lens drive device, in response to the recent demand for miniaturization of the device, if the shape is miniaturized as it is, the coil becomes smaller and the portions 108a and 1 forming one side of the coil become smaller.
08b, 108c, and 108d become smaller, which causes a problem in that the driving force of the lens holder 102 decreases as shown in the above-mentioned equation. Furthermore, when the portions 109a, 109b, 109c, and 109d forming one side of the coil approach the center of the magnetic circuit described above, the lens holder 1
A force in the opposite direction to the driving force of 02 is generated, reducing the driving force, and in addition, there is a risk that secondary resonance such as rolling may occur.

As described above, it has been difficult for conventional objective lens driving devices to meet the demands for smaller and lighter devices.

[Object of the Invention] The present invention improves the disadvantages of the conventional example, and provides an objective lens drive that makes it possible to further reduce the size and weight of an optical disk device by reducing the size and weight of the objective lens drive device. Its purpose is to provide equipment.

Means for Solving Problem C] The present invention includes a rectangular parallelepiped lens holder that holds an objective lens, and wire-shaped support members that support the lens holder at four points. The lens holder is provided with a fixing part that firmly supports the lens holder, and a holder driving coil is provided between the lens holder and the fixing part.

In general, the portion of the holder driving coil that is close to the wire-shaped support member is formed shorter than the portion that forms the opposite side.

This aims to achieve the above-mentioned purpose.

[Effect]

In the present invention, the part forming one side of the holder driving coil near the wire-shaped support member described above is shorter than the part forming the opposite side, so that the coil is fixed to the protrusion of the movable part by sandwiching the coil. The distance between the two wire-shaped support members can be reduced.

[Example] Next, an example of the present invention will be described based on FIGS. 1 to 7.

Here, the same reference numerals are used for the same or equivalent parts as in the conventional example described above.

The objective lens driving device shown in FIG. 1 has rectangular coils 107A, 107B, 107C, and
Coils 7A, 7B, 7C, and 7D are provided in place of D, and a lens holder 2 is provided in place of lens holder 102. FIG. 2 is a perspective view showing the shape of the lens holder 2. FIG. In addition, Fig. 3 Nioiite, ril 7A, 7B, 7C
, 7D are the parts 9a, 9b, 9c, 9 that form one side of the coil that are opposite sides of the parts 8a, 8b, 8c, and 8d that are within the range of the magnetic lines of force of the magnetic circuit.
It is made so that d is small.

Next, using FIG. 4, the shape of the lens holder 2 and the positional relationship between it and 103a, 103b, 103c, and 103d will be outlined.

FIG. 4(a) shows a wire-like support member 10 attached to the lens holder 2.
3a, 103b, 103c, 103d and coils 7A, 7
It is a perspective view showing the situation when B, 7C, 7D, etc. are attached.

Moreover, FIG. 4(b) shows them when viewed from the side. Here, a portion 9a forming one side of the coil 7A
, 9b, 9c, and 9d form one side of the coil 8a, 8
b, 8c, and 8d, the wire-like support members 103a and 103b, 103c and 103d
The length of the lens holder 2 in the optical axis direction of the objective lens 101 is made the same as the length of the coil 7A, etc. in the optical axis direction.

The positional relationship between the coils 7a, 7b, 7c, and 7d and the magnetic circuit will be explained using FIG. 5. A portion 8a forming one side of the coil within the range of magnetic lines of force of the magnetic circuit.

Portions 9a, 9b, 9c, and 9d forming one side of the coil corresponding to the opposite side are sufficiently apart from 8b, 8c, and 8d. Therefore, the lens holder 2 is not easily affected by the parts 9a, 9b, 9c, and 9d forming one side of the coil that weaken the driving force, and a sufficient movable range of the lens holder 2 is obtained.

Here, in order to obtain the same driving force as the conventional objective lens driving device described above, if the length of the magnet 105a etc. and the portion 8a forming one side of the coil is made the same length, the conventional objective lens driving device In this example, the length of the lens holder I02 in the optical axis direction of the objective lens 101 is longer than the portion 8a forming one side of the coil.
The length of the lens holder 2 in the optical axis direction of the objective lens 101 can be made the same length as the portion 8a forming one side of the coil, making the lens holder 2 smaller and lighter than the conventional one. Therefore, control with sufficient responsiveness becomes possible.

The same effect can be obtained even if the shapes of the coils 7C and 7D are as shown in the conventional example.

In addition, the shapes of the coils 7A, 7B, etc. are in addition to those described above.
Similar effects can be obtained with the shapes shown in FIGS. 6 and 7.

〔Effect of the invention〕

Since the present invention is configured and functions as described above, by making the outer part of the coil smaller than the inner part, the movable part can be made smaller and lighter, and therefore, To create an optical disk device that is smaller and lighter than conventional ones. I can do two things. Also, in addition to that,
The responsiveness of the moving parts has been improved, making it possible to provide equipment with even higher performance.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2 is a perspective view of a lens holder of the embodiment, Fig. 3 is a plan view showing the shape of the coil of the embodiment, and Fig. 4 ( a) and (b) are a perspective view and a side view showing the positional relationship between the lens holder and the wire-shaped support member in the example, and FIG. 5 is a plan view showing the positional relationship between the coil and the magnetic circuit in the example. 6 and 7 are plan views illustrating the shape of the coil, FIG. 8 is a perspective view showing a conventional example, FIG. 9 is a perspective view of the lens holder of the conventional example, and FIGS. 10 (a) and (b). ) is a perspective view and a side view showing the positional relationship between the lens holder and the wire-shaped support member in the conventional example, and
FIG. 1 is a plan view showing the driving principle of the conventional example. 7A, 7B, 7C, ID-- Coil, 8a, 8b
, 8c, 8d... part forming one side of the coil, 9
a, 9b, 9c, 9d... Part forming one side of the coil, 101... Objective lens, 102...
...Lens holder, 103a, 103b, 103c, 1
03d...Wire-shaped support member, 104...
··Fixed part. Applicant Nihon Denki Co., Ltd. Agent Patent Attorney Isamu Takahashi Figures 1 and 4 Figure 2 Figure 3 Figure 4 (b) (a) Figure 5@--] Figure 6 Figure 7 Figure 8 Figure 9

Claims (2)

[Claims] (1) A rectangular parallelepiped lens holder for holding an objective lens, wire-shaped support members for supporting the lens holder at four points, and a fixing part for firmly supporting the wire-shaped support members; In an objective lens driving device comprising a holder driving coil between a lens holder and the fixing part, a portion of the holder driving coil that is closer to the wire-shaped support member is longer than a portion forming the opposite side thereof. An objective lens drive device characterized by being short. (2) An objective lens driving device characterized in that a portion of the holder driving coil that is close to the wire-shaped support member is formed to become smaller as it approaches the wire-shaped support member.