JPH09138959A - Biaxial actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the manufacture of the biaxial actuator by supporting a lens holder for supporting an objective lens with elastic supporting members and disposing these individual elastic supporting members on the same plane. SOLUTION: One pair of elastic supporting members 13a and 13b and the other one pair 13c and 13d are disposed in the same plane, and one end of each individual elastic supporting member is fixed integrally with a fixed part 14, while the other end is fixed integrally with the lens holder 11. The elastic supporting members 13a and 13b and then 13c and 13d are separated from each other to move individually. Individual connecting terminals of a coil bobbin are electrically connected to feeder lands provided fixedly under their exposed state on an upper surface of a side periphery of the lens holder 11 by the other end side of the elastic supporting members 13a, 13b, 13c and 13d. A driving current is supplied via the individual elastic supporting members to the coil bobbin from the fixed part 14, so that the connection by a flexible substrate is unnucessitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxial actuator for an optical pickup used for recording / reproducing signals of a CD (compact disc), a magneto-optical disc, an information recording medium for data storage and the like. is there.

[0002]

2. Description of the Related Art Conventionally, an optical pickup is used to reproduce or record an information signal on an information recording medium such as an optical disk, for example, a so-called compact disk (CD) or a magneto-optical disk. This optical pickup includes a semiconductor laser as a light source, an objective lens, an optical system, and a photodetector.

In this optical pickup, the light beam emitted from the semiconductor laser is focused on the recording surface of the optical disc by the objective lens through the optical system. The return light beam from the optical disc is separated from the light beam emitted from the semiconductor laser by the optical system and guided to the photodetector. The light beam emitted from the semiconductor laser follows the displacement of the optical disk in the direction (focusing direction) orthogonal to the surface direction of the optical disk caused by the warp of the optical disk, etc., and is focused on the recording surface of the optical disk. Thus, the position of the objective lens in the optical axis direction is adjusted. At the same time, a direction (tracking direction) orthogonal to the optical axis of the objective lens so that the position of the spot of the light beam emitted from the semiconductor laser on the optical disc follows the eccentricity of the optical disc and the meandering of the track formed on the optical disc. The position of is adjusted.

The focus position of the light beam emitted from the semiconductor laser and the spot position on the recording surface of the optical disc are adjusted by adjusting the objective lens in the optical axis direction of the objective lens and in the direction orthogonal to the optical axis. It is done by adjusting. An electromagnetically driven actuator is used to adjust the position of the objective lens. This actuator is called an objective lens actuator or a biaxial actuator, and includes a coil bobbin to which the objective lens is attached, a plurality of elastic supporting members, and a driving unit that generates a driving force. This coil bobbin is supported by a plurality of elastic supporting members on the fixed portion so that the position in the optical axis direction of the objective lens, that is, the focus position and the position in the direction orthogonal to the optical axis of the objective lens, that is, the tracking position are adjustable. Has been done. An example of this biaxial actuator will be described below with reference to FIG.

Such a biaxial actuator is constructed, for example, as shown in FIG. In FIG.
The biaxial actuator 1 includes a lens holder 2 having an objective lens 2a attached to a tip thereof, and the lens holder 2
To the coil bobbin 3 attached by adhesion or the like
And

The lens holder 2 has a plurality of elastic supporting members, one end of which is fixed to both sides of the lens holder 2 and the other end of which is fixed to the fixing portion 4, for example, two pairs of elastic supporting members 5a, 5a, and It is supported by 5b and 5b so as to be movable in two directions perpendicular to the fixed portion 4, that is, in the tracking direction indicated by the reference symbol Trk and the focusing direction indicated by the reference symbol Fcs.

Further, the coil bobbin 3 has an opening 3a penetrating in the vertical direction and the opening 3a is formed.
A focusing coil wound so as to surround a and a tracking coil (not shown) provided on the front side of the coil bobbin 3 (on the objective lens side in FIG. 8) are provided. Then, the winding ends of the focusing coil and the tracking coil are connected to the connection pins 3b implanted on the rear side of the coil bobbin 2, respectively. Then, from the power supply means on the device body side (not shown),
By energizing the focusing coil and the tracking coil through the connection pin 3c, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 6 attached to the fixed portion 4 and the magnet 7 attached thereto. It is supposed to do.

According to the biaxial actuator 1 having the above-described structure, when a driving current is supplied to each coil from the outside, the magnetic flux generated in each coil mutually interacts with the magnetic flux generated by the yoke 7 and the magnet 8. This causes the coil bobbin 3 to move in the tracking direction Trk and the focusing direction Fcs. Thus, the objective lens 2a attached to the lens holder 2 is appropriately moved in the focusing direction and the tracking direction.

[0009]

However, in the biaxial actuator 1 having such a configuration, among the plurality of elastic supporting members for supporting the lens holder 2, a pair of elastic supporting members 5a and another pair of elastic supporting members are provided. The supporting member 5b is arranged so as to overlap in the thickness direction of the lens holder 2. For this reason, as shown in FIG. 8, it is necessary to provide a predetermined distance L between the elastic support members 5a and 5b, which is a constraint in reducing the size of the biaxial actuator 1.

Further, since the pair of elastic support members 5a and the other pair of elastic support members 5b are formed of separate leaf springs, the number of leaf springs used as the material is two, which increases the material cost. There was a problem that it would end up. Further, in order to supply a current to the winding ends of the coils for focusing and tracking wound on the coil bobbin 3,
It is necessary to provide a power supply means such as a flexible substrate between the fixed portion side 4 and the fixed portion side 4, and there is a drawback that the number of steps and the manufacturing cost are increased.

In view of the above points, it is an object of the present invention to provide a biaxial actuator which can further reduce the size of the biaxial actuator and which can reduce the number of manufacturing steps and the cost with a simple structure. There is.

[0012]

According to the present invention, there is provided a lens holder for supporting an objective lens, a coil bobbin provided on the lens holder, and a focusing coil wound around the coil bobbin. And along the direction orthogonal to the winding direction of the focusing coil,
A tracking coil wound around the coil bobbin, and at least two pairs of elastic support members that elastically support the lens holder with respect to a fixed portion, and the at least two pairs of elastic support members, This is achieved by biaxial actuators that are arranged substantially coplanar.

According to the above construction, the lens holder for holding the objective lens can be moved in the respective directions by appropriately energizing the focusing coil and the tracking coil forming a part of the magnetic circuit. . The at least two pairs of elastic supporting members supporting the lens holder are arranged on substantially the same plane. Therefore, the lens holder to which one end of these elastic support members is fixed can fix each end of the elastic support member without being large in the thickness direction as in the conventional case. As a result, the biaxial actuator allows the lens holder to be made thin, and accordingly can be made compact.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below are preferable specific examples of the present invention, and therefore, various technically preferable limitations are given,
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows an embodiment of a biaxial actuator according to the present invention, a side view thereof, and FIG. 2 is a plan view of the biaxial actuator. In FIG. 1, a coil bobbin is not shown for convenience of understanding. doing. In these drawings, the biaxial actuator 10 includes a lens holder 11,
Coil bobbin 12, a plurality of elastic support members 13a, 13
b, 13c, 13d, the fixing portion 14, and the yoke 31 are included.

The lens holder 11 is made of synthetic resin, as will be described later, and has a circular opening 11a at one end as shown in FIG. 2, and the objective lens 36 of the optical pickup is accommodated in the opening 11a. It is supposed to do. As a result, the light from the light source passes through the opening 11a and is condensed on the recording surface of the disc-shaped recording medium by the objective lens 36. Further, the return light from the disc-shaped recording medium passes through the aperture 11a. It passes through and is guided to the signal detection side.

Further, the lens holder 11 has a large opening from the vicinity of its center to the other end. As shown in FIG. 2, a cylindrical coil bobbin 12 having a substantially quadrangular cross section is inserted and fixed in the opening 11b. As described above, since the lens holder 12 is not composed of the upper and lower members as in the conventional case, the number of parts can be reduced and the number of steps in the manufacturing process can be reduced.

Further, the lens holder 11 is supported by elastic supporting members 13a, 13b, 13c, 13d so as to be movable in the focusing direction Fcs and the tracking direction Trk. This elastic support member 13
It is preferable that a, 13b, 13c, and 13d have conductivity and also have spring property, and for example, materials such as phosphor bronze, beryllium copper, titanium copper, tin-nickel alloy, and stainless are used. Due to these, in the present embodiment,
It is formed of a thin metal plate, for example, as a leaf spring suspension.

In the case of this embodiment, the elastic support members 13 are, as shown in FIG. 2, elastic support members 13a and 13b arranged outside and elastic support members arranged inside thereof. 13c and 13d. These are a pair of left and right members (a pair of upper and lower members in FIG. 2) with respect to the axial direction along the longitudinal direction of the lens holder, and the pair of elastic support members 13a, 13 are provided.
b and the other pair of elastic support members 13c and 13d are shown in FIG.
As shown in, they are arranged in substantially the same plane. Then, as will be described later, each of the elastic support members 13a, 13
One end of each of b, 13c and 13d is integrally fixed to the fixing portion 14 and the other end thereof is integrally fixed to the lens holder 11, and the elastic support members 13a and 13b and the elastic support members 13c and 13d are different from each other. They are separated from each other and can move independently.

Further, in this biaxial actuator 10, the end of each elastic supporting member 13 on the side of the fixed portion 14 is constructed as follows. For example, as shown in FIG. 2, the elastic support member 13c is bent at two places, and the first bent portion 13c-1 and the second bent portion 13c-.
2 are provided. Then, in association with these bent portions, a first slit portion (gap) 13c-4 extending in the Trk direction shown by an arrow in FIG. 2 and a second slit portion 13c-3 extending in a direction orthogonal to the slit portion are provided. Are formed. Therefore, the elastic support member 13c is capable of displacing each of the slit portions as the lens holder 11 moves in the tracking direction Trk or in the focusing direction Fcs. Furthermore, the elastic support member 1
In these end regions of 3a, 13b, 13c, 13d,
The viscous body 16 acting as a damping material (damper) is applied and cured (see FIG. 6). As a result, damping characteristics are improved with respect to resonance caused by movement of the lens holder 11.

The coil bobbin 12 is formed with an opening 12a into which a magnetic circuit composed of a metal yoke 31 integral with the base 30 shown in FIG. 1 and a permanent magnet 32 attached to the inner surface of the inner yoke 31a is inserted. And the focusing coil 12b and the tracking coil 1
2c (see FIG. 3). The focusing coil 12b is wound along an axis parallel to the optical axis of the objective lens 36 mounted on the coil bobbin 12. The tracking coil 12c is formed by winding the coil into an elliptical shape or a rectangular shape, and is attached to one side surface of the focusing coil 12b. The coil bobbin 12 is a coil 12 for focusing.
With the b and the tracking coil 12c attached, as shown in FIG. 2, it is attached to the opening 12a formed in the lens holder 11.

Here, the base 30 is provided with a pair of yokes 31a and 31b forming the magnetic circuit by bending a part of the base 30 upward, and the one yoke 31a is the other yoke. A permanent magnet 32 attached to the surface facing 31b is provided.
As a result, the pair of yokes 31a and 31b and the permanent magnet 3 are
2, the magnetic circuit is configured. Then, as described above, when the fixing portion 14 is attached to the base, in the gap between the other yoke 31b and the permanent magnet 32,
The focusing coil 12b and the tracking coil 12c attached to the coil bobbin 12 are inserted. At the same time, the one yoke 31a and the permanent magnet 32 are
It will be inserted into the opening of the coil bobbin 12.

Further, in this biaxial actuator 10, a connecting pin 12d is provided so as to project from the rear surface of the coil bobbin 12 (the surface opposite to the objective lens 36). Then, in order to make contact with the connection pin 12d,
The power feeding land portion 11d provided on the side edge portion 11c of the lens holder 11 is configured as follows, for example.
As shown in FIG. 2, the elastic support members 13a, 13
One ends of b, 13c, and 13d are fixed to the fixed portion 14, and the elastic support members 13a and 13b are connected to the power supply terminals 14a and 14b of the fixed portion 14, respectively. The elastic support members 13 c and 13 d are the power supply terminals 1 of the fixed portion 14.
4c and 14d, respectively. This fixing part 1
Currents for focusing drive and tracking drive are externally supplied to the four power supply terminals 14a, 14b, 14c, 14d by connecting a flexible substrate or the like (not shown).

On the other hand, the elastic support members 13a, 13b, 13
As shown in FIG. 3, the other ends of the c and 13d are fixed so as to be exposed on the upper surface of the side edge 11c of the lens holder 11, and the power feeding lands 11d are provided. Then, the connection terminals 12d of the coil bobbin 12 are electrically connected to the power supply lands 11d by soldering or the like, thereby forming power supply means for the coil bobbin 12. Therefore, the driving current is supplied to the coil bobbin 12 from the fixing portion 14 via the elastic supporting members 13a, 13b, 13c, 13d, so that the coil bobbin 12 and the fixing portion 14 are formed using a flexible substrate or the like. No connection is required and the manufacturing process is simplified.

Next, an example of a method of manufacturing the biaxial actuator 10 will be described. First, as shown in FIG. 4, the thin metal plate 41 is attached to each elastic supporting member 13a, 13b, 13c,
The 13d is punched by a means such as a metal press so as to have the above-mentioned shape. Here, preferably, as shown in the drawing, wide portions 13c-5 and 13d-5 are provided at predetermined positions of the elastic support members 13c and 13d so that the viscous body 16 described later can be applied. Here, it is preferable that the metal plate 41 has conductivity, such as phosphor bronze, beryllium copper, titanium copper, tin-nickel alloy, and stainless, and has a spring property. Next, the metal plate 41 is inserted into a predetermined mold, and as shown in FIG. 5, the fixing portion 14 and the lens holder 11 are resin-molded with, for example, polyphenylene sulfide (PPS) or liquid crystal polymer. At this time, at the same time, the power supply terminals 14a,
14b, 14c and 14d are formed. Therefore, it is not necessary to form the lens holder 11 with the upper and lower members as in the conventional case, and the lens holder 11 can be formed by molding once.

Next, as shown in FIG. 6, the main body of the coil bobbin 12 is formed of liquid crystal polymer and the tracking coil and the focusing coil are wound. This coil bobbin 12 is provided with an opening 11b in the lens holder 11.
And is fixed by adhesion or the like, and the acrylic objective lens 36 is inserted in the opening 11a of the lens holder 11.
Attach. Also, the elastic support members 13a, 13b, 13
C and 13d end portions on the fixed portion 14 side and the elastic support member 13
To the wide portions 13c-5 and 13d-5 of c and 13d, a viscous body 16 made of, for example, silicon gel is applied as a damper material. In this case, the elastic support member 13a,
At the ends of the fixed portions 14 of 13b, 13c, 13d on the side of the fixed portion 14, a preferable damping effect can be obtained by applying the viscous body 16 so as to cross the slit (gap) around the bent portion. You can

Further, as shown in FIG. 7, the respective points C1 to C8 of the metal plate 41 are cut. That is, C1, C2
By cutting C7 and C8, necessary portions are cut out from the metal plate 41. And C3, C4, C5, C6, C
By cutting 7, C8, the elastic support members 13a, 1
3b, 13c and 13d are disconnected from each other so that they can move independently of each other, and they can be electrically disconnected from each other. Finally, the base portion 30 of FIG.
The yoke portion 31 is inserted into the opening 11b of the lens holder 11 from below, and the base portion 30 and the fixed portion 14 are fixed to each other. As a result, in the biaxial actuator 10, the fixing portion 14 and the base portion 30 are fixed. The lens holder 11 is elastically supported by the fixing portion 14 via elastic supporting members 13a, 13b, 13c, 13d.

Biaxial actuator 1 according to the present embodiment
0 is configured as described above, and the coil bobbin 12
Currents based on the focus servo signal and the tracking servo signal are respectively supplied to the focusing coil 12b and the tracking coil 12c that are wound around. As a result, the DC magnetic field of the magnetic circuit and the focusing coil 12b and the tracking coil 12
By the alternating magnetic field generated from c, the lens holder 11
That is, the objective lens 36 is driven in the focus direction Fcs and the tracking direction Trk.

Here, in the biaxial actuator 10, a plurality of elastic supporting members 13a, 13b, 13c,
Since all of 13d are arranged in substantially the same plane, the thickness of the lens holder 11 can be reduced and the entire size can be reduced accordingly. Furthermore, a plurality of elastic support members 13a, 1
Since all of 3b, 13c, and 13d are arranged in substantially the same plane, the lens holder 11 can be formed by one-time molding by insert-molding these in a predetermined mold, and the manufacturing process can be reduced. Further, by using these elastic support members as the power feeding means, it is not necessary to connect a flexible substrate or the like to the coil bobbin 12 from the fixed portion 14 side, which is also the case in the related art, so that the manufacturing process can be reduced in this respect as well. .

In the above-described embodiment, each elastic supporting member is fixed to the end of the lens holder 11 on the opposite side of the objective lens, but it may be fixed to a position other than this. For example, the elastic support members 13c and 13d may be fixed to the objective lens side of the lens holder 11. In addition, a bent portion or a slit portion may be provided at a location where these elastic support members are fixed to the lens holder, and a damping material may be applied to these locations.

[0031]

As described above, according to the present invention, the biaxial actuator can be further miniaturized, and the number of manufacturing steps and cost can be reduced by the simple structure.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a preferred embodiment of a biaxial actuator for an optical pickup according to the present invention.

FIG. 2 is a plan view of the biaxial actuator shown in FIG.

3 is a partially enlarged perspective view showing an electrical connecting means of a coil bobbin of the biaxial actuator of FIG.

4 is a schematic plan view showing a part of a manufacturing process of the biaxial actuator of FIG.

5 is a schematic plan view showing a part of the manufacturing process of the biaxial actuator in FIG. 1. FIG.

6 is a schematic plan view showing a part of the manufacturing process of the biaxial actuator of FIG.

7 is a schematic plan view showing a part of the manufacturing process of the biaxial actuator in FIG.

FIG. 8 is a schematic perspective view showing an example of a conventional biaxial actuator.

[Explanation of symbols]

 10 biaxial actuator 11 lens holder 11a opening 11b opening 11d power feeding land 12 coil bobbin 12a opening 12b focusing coil 12c tracking coil 12d connecting pin 13a, 13b, 13c, 13d elastic support member 14 fixing part 16 viscous body 31 yoke part 32 permanent magnet 36 objective lens

Claims (3)

[Claims] 1. A lens holder for supporting an objective lens, a coil bobbin provided on the lens holder, a focusing coil wound around the coil bobbin, and a direction orthogonal to a winding direction of the focusing coil. A tracking coil wound around the coil bobbin, and at least two pairs of elastic support members that elastically support the lens holder with respect to a fixed portion, and at least two pairs of elastic supports. A biaxial actuator, wherein the members are arranged on substantially the same plane. 2. A pair of elastic support members of the at least two pairs of elastic support members have one end fixed to the fixing portion and the other end fixed to both side surfaces of the lens holder. The biaxial according to claim 1, wherein the other elastic supporting member is arranged outside the pair of elastic supporting members in substantially the same plane as the pair of elastic supporting members. Actuator. 3. The biaxial actuator according to claim 1, wherein the elastic support member also serves as a power supply member for supplying power from the fixed portion side to each coil of the coil bobbin.