JPH08180439A - Biaxial actuator - Google Patents

Abstract

(57) [Summary] [Object] To provide a biaxial actuator having a simple structure and capable of reducing the inclination of the lens holder due to the warp of the elastic supporting member. [Structure] Lens holder 11 for supporting an objective lens
And two pairs of elastic support members 13a arranged side by side in the focusing direction on both sides of the lens holder for elastically supporting the lens holder with respect to the fixed portion 14.
13b, 13c and 13d, a coil bobbin 12 provided on the lens holder, a focusing coil 12b wound around the coil bobbin, and a tracking coil 12 wound around the coil bobbin.
c, and elastic supporting members 13a, 13a arranged side by side in the focusing direction on both sides of the lens holder.
By disposing b and 13c and 13d so that the warp directions thereof are opposite to each other, the biaxial actuator 1
Configure 0.

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 an information recording medium for CD, MD, etc. and data storage.

[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 an optical pickup, a light beam emitted from a semiconductor laser is focused on a recording surface of an optical disc by an objective lens via an 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 is guided to the photodetector. The light beam emitted from the semiconductor laser follows the displacement of the optical disc in the direction orthogonal to the surface direction of the optical disc caused by the warp of the optical disc, etc., and is focused on the recording surface of the optical disc. The position of the objective lens in the optical axis direction is adjusted. At the same time, the position in the direction orthogonal to the optical axis of the objective lens is adjusted 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. To be done.

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 bobbin to which the objective lens is attached, a plurality of elastic supporting members, and a drive unit that generates a driving force.
The bobbin is supported by a plurality of elastic supporting members with respect to the fixed portion such 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. ing. 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. 8, the biaxial actuator 1 has a lens holder 2 to which an objective lens 2a is attached at the tip, and a coil bobbin 3 attached to the lens holder 2 by adhesion or the like.

The lens holder 2 has two ends perpendicular to the fixed portion 4 by two pairs of elastic supporting members 5 having one end on both sides of the lens holder 2 and the other end fixed to the fixed portion 4. Direction, that is, the tracking direction indicated by the reference symbol Trk and the focusing direction indicated by the reference symbol Fcs are movably supported.

Further, the coil bobbin 3 is wound with a focusing coil and a tracking coil (not shown). By energizing the focusing coil and the tracking coil, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 6 integrally attached to the fixed portion 4 and the magnet 7 attached thereto. It has become.

Further, the elastic support member 5 is formed of an elastic body and is fixed between the lens holder 2 and the fixing portion 4 so as to be parallel to each other.

According to the biaxial actuator 1 having the above-described structure, the driving voltage is supplied to each coil from the outside, so that the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 6 and the magnet 7. 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.

[0010]

However, in the biaxial actuator 1 having such a structure, the elastic supporting member 5 is formed by pressing the plate member 5a for the first time as shown in FIG. 9, for example. Punch out the unnecessary part 5b,
Further, in the second press working, the unnecessary portion 5c is punched out to be formed as a region sandwiched between the portions 5b and 5c. For this reason, the elastic support member 5 has the structure shown in FIG.
As shown in (1), there is a warp due to punching during press molding. When the tip of the elastic support member 5 is separated from the plate member 5a, this warp is displaced by the distance d in the punching direction.

Therefore, when the elastic supporting member 5 thus formed is incorporated in the biaxial actuator 1,
Since the elastic support members 5 are arranged side by side in the focusing direction as shown in FIG. 11, both elastic support members 5 have a warp in the same direction. Therefore, in the biaxial actuator 1, the movable portion assembly including the lens holder 2 and the coil bobbin 3 is provided on both sides of the movable portion assembly with the upper and lower elastic support members 5 relative to the fixed portion 4 in the biaxial direction, that is, the focusing direction. Although it is movably supported in the tracking direction, there is a problem in that the movable portion assembly is inclined in the focusing direction by the amount of the warp due to the warp of the elastic support member 5 described above.

Further, since the surface of the elastic support member 5 is not particularly treated, when an oxide film is formed on the surface, the solderability is deteriorated and the surface is discolored, so that the vibration characteristic is increased. Then, there is a problem that the damping characteristic may be deteriorated. Therefore, it is conceivable to plate the surface of the elastic support member 5, but the plating process is costly and
There is also a problem that it is difficult to obtain high accuracy.

Further, as shown in FIG. 13, the lens holder 2 and the fixing portion 4 are vertically divided into two parts, and an elastic supporting member above the upper portion 2U of the lens holder 2 and the upper portion 4U of the fixing portion 4 is provided. 5U is outsert-molded, the lower elastic support member 5L is outsert-molded to the lower portion 2L of the lens holder 2 and the lower portion 4L of the fixed portion 4, and then the upper portion and the lower portion are joined to each other, whereby When the fixing portion 4 and the elastic support member 5 are integrally formed, the upper and lower elastic support members 5U and 5L are provided.
Will be manufactured as separate parts.

Therefore, the upper and lower elastic support members 5U, 5L
Since they are formed by using separate molds, they have their own dimensional variation, which causes a difference in dimensional variation. Thus, the vibration characteristics are adversely affected. Also, the upper and lower elastic support members 5
Since U and 5L are formed using separate molds, respectively, they will be manufactured on different lead frames,
It was not possible to mold the upper and lower elastic support members 5U and 5L with one lead frame.

In view of the above points, an object of the present invention is to provide a biaxial actuator having a simple structure and capable of reducing the inclination of the lens holder due to the warp of the elastic supporting member.

[0016]

According to the present invention, the above object is to provide a lens holder for supporting an objective lens and both sides of the lens holder for elastically supporting the lens holder with respect to a fixed portion. A plurality of elastic supporting members arranged side by side in the focusing direction, a coil bobbin provided in the lens holder, a focusing coil wound around the coil bobbin, and a coil bobbin wound around the coil bobbin. A plurality of elastic supporting members, which are provided side by side in the focusing direction on both sides of the lens holder, have warping directions opposite to each other. Is achieved by a biaxial actuator, which is provided as described above.

In the biaxial actuator according to the present invention, preferably, the elastic support member is formed by press working, and the elastic support members are arranged so that the warping directions by punching during the press working are opposite to each other. ing.

In the biaxial actuator according to the present invention, preferably, the elastic supporting member on the upper side in the focusing direction has a convex warp upward, and the elastic supporting member on the lower side in the focusing direction is lower. It has a convex warp toward.

In the biaxial actuator according to the present invention, preferably, the elastic supporting member on the upper side in the focusing direction has a convex warp downward, and the elastic supporting member on the lower side in the focusing direction is upward. It has a convex warp toward.

In the biaxial actuator according to the present invention, the elastic supporting member is preferably glycoat-treated.

In the biaxial actuator according to the present invention, preferably, the upper elastic supporting member in the focusing direction and the lower elastic supporting member in the focusing direction have the same shape.

[0022]

According to the above construction, since the lens holder for holding the objective lens is supported by the elastic supporting member, the focusing coil or the tracking coil is energized to resist the tension of the elastic supporting member. Then, the lens holder is moved along the focusing direction or the tracking direction, and the objective lens is focused or tracked.

Since the elastic supporting members arranged vertically in the focusing direction are arranged so that the warping directions thereof are opposite to each other, the deviations in the focusing direction due to the warping cancel each other. It will be. Therefore, the lens holder supported by the elastic support member does not tilt due to the warp of the elastic support member.

If the elastic supporting members are formed by press working and are arranged so that the warping directions due to punching during the press working are opposite to each other, the elastic supporting members by press working are provided. The warpages of the members cancel each other out.

The upper elastic support member in the focusing direction has a convex warp upward or downward, and the lower elastic support member in the focusing direction has a convex warp downward or upward. In the case of the above, the upward and downward shifts in the focusing direction due to this warp cancel each other out.

Further, when the elastic supporting member is subjected to the glycoat treatment, the surface of the elastic supporting member can be covered easily and at low cost. As a result, surface oxidation is prevented, solderability is improved, and deterioration of vibration characteristics due to discoloration is prevented.

When the upper elastic supporting member in the focusing direction and the lower elastic supporting member in the focusing direction are formed in the same shape, the upper and lower elastic supporting members are formed by one type of mold. It will be formed as one lead frame.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to FIGS. In addition, since the Examples described below are preferred specific examples of the present invention, various technically preferable limitations are given. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

1 to 3 show an embodiment of a biaxial actuator according to the present invention. 1 to 3, 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.

As shown in FIG. 3, the lens holder 11 is divided into an upper portion 11U and a lower portion 11L by a horizontal dividing line, and they are adhered to each other with an adhesive. Further, the lens holder 11 has a structure shown in FIG.
As shown in, the opening 1 in which the coil bobbin is attached
1a is formed, and a recess 11b to which the objective lens is attached is also formed. A hole through which the light beam emitted from the semiconductor laser or the return light beam from the recording surface of the optical disk passes is formed on the bottom surface of the recess 11b. In the concave portion 11b of the lens holder 11,
The objective lens 11c is attached by adhesion or the like.

Further, the lens holder 11 is supported by the elastic supporting members 13a, 13b, 13c, 13d so as to be movable in the focusing direction Fcs and the tracking direction Trk.

The coil bobbin 12 is formed with an opening 12a into which a magnetic circuit composed of a yoke 31 integral with the base and a magnet 32 attached to the inner side surface of the inner yoke 31a is inserted, and a focusing coil 12b. And a tracking coil 12c. The focusing coil 12b is wound around the coil bobbin 12 along an axis parallel to the optical axis of the objective lens 11c. In addition, the tracking coil 12
The c is formed by winding a coil in an elliptical shape or a rectangular shape, and is attached to one side surface of the focusing coil 12b. The upper surface of the coil bobbin 12 is covered with the yoke bridge 36. The yoke bridge 36, together with the yoke portion of the magnetic circuit,
It may constitute a closed magnetic circuit. Coil bobbin 1
2 is attached to the opening formed in the lens holder 11 with the focusing coil 12b and the tracking coil 12c attached.

The elastic support members 13a, 13b, 13
It is preferable that c and 13d have conductivity and have spring property, and for example, phosphor bronze, beryllium copper, titanium copper, tin-nickel alloy, stainless steel, or the like is used. Due to these, in the present embodiment, for example, a leaf spring suspension is formed by thin sheet metal, and is fixed between the lens holder 11 and the fixing portion 14 so as to be parallel to each other. As a result, the elastic support members 13a, 13b, 13c, 13d supply the drive current from the external current supply means (not shown) to the focusing coil 12b and the tracking coil 12c wound around the coil bobbin 12. It may be configured as follows.

Further, the elastic support members 13a, 13b, 1
A viscous body 16 acting as a damper is applied to the end regions 15 of 3c and 13d and hardened. The lens holder 11 and the fixing portion 14 are four elastic support members 13
a, 13b, 13c, 13d are connected,
The fixed portion 14 is attached to the adjustment plate 30. The adjusting plate 30 is for adjusting the fixing position of the fixing portion 14 when the biaxial actuator 10 is assembled. The adjusting plate 30 is fixed to the base 31 formed integrally with the yoke by soldering or the like.

The adjustment plate 30 is attached to the base 31 with respect to the rising portions 30a extending upward from both sides near the rear end of the adjustment plate 30 with respect to the rising portions extending upward from both sides of the rear end of the base 31. It is done by soldering. Here, the base 31 is provided with a pair of yokes 31a and 31b forming the magnetic circuit by bending the ends of the base 31 on the objective lens side upward, respectively, and the opposing yoke 31b of the inner yoke 31a. Permanent magnet 3 mounted on the inner surface facing the
2 is provided. Thereby, the pair of yokes 31
A magnetic circuit is configured by a and 31b and the permanent magnet 32. Then, as described above, the fixing portion 14 is fixed to the base 3
1, the opposing yoke 31b and the permanent magnet 3 are attached.
The focusing coil 12b and the tracking coil 12c attached to the coil bobbin 12 are inserted into the gap between the two. At the same time, the inner yoke 31a
And the permanent magnet 32, the opening 12a of the coil bobbin 12
Will be inserted inside.

The elastic support members 13a, 13b, 13
Since c and 13d are formed by punching the lead frame 13e made of a plate member by press working, as shown in FIG. 4, it has a warp due to punching at the time of press molding. This warpage causes the tips of the elastic support members 13a, 13b, 13c, 13d to be displaced by the distance d in the punching direction.

The elastic support members 13a, 13b, 13c, 13d thus formed are arranged side by side in the focusing direction as shown in FIG. That is,
Elastic support member 13 above in the focusing direction
The a and 13c are arranged so as to be convex upward, and the elastic support members 13b and 13d on the lower side in the focusing direction are arranged so as to be convex downward. Thereby, the upper elastic support member 13
The a and 13c have a warp in the opposite direction to the elastic support members 13b and 13d below, and the deviation due to the warp cancels each other.

Therefore, as shown in FIG. 6, when assembled as the biaxial actuator 10, the movable part assembly including the lens holder 11 and the coil bobbin 12 has two upper and lower elastic support members 13a, 1 on both sides thereof.
3b, 13c, 13d to the fixed portion 14,
The movable portion assembly is movably supported in the biaxial direction, that is, the focusing direction and the tracking direction, and the movable portion assembly is offset by the above-mentioned warping of the elastic support members 13a, 13b, 13c, 13d.
Inclination due to warpage during press molding of 13b, 13c, 13d is eliminated.

Further, each elastic supporting member 13a, 13b, 1
The surfaces of 3c and 13d are subjected to glycoat treatment. This will prevent surface oxidation and discoloration. This glycoat treatment is performed on the completed elastic supporting members 13a, 13b, 13c, 13d, or after rolling the plate member that is the material of the lead frame 13e or at the time of manufacturing the elastic supporting member, or after press molding. This is performed on the plate member 13e.

Here, the glycoat treatment is specifically as follows.
The surfaces of the elastic support members 13a, 13b, 13c, 13d are polished, immersed in an aqueous hydrochloric acid solution, washed with water, and dried to be treated with a glycoat T containing alkylimidazole as a main component. Thereby, the elastic support members 13a,
On the surfaces of 13b, 13c and 13d, a monomolecular film of alkylimidazole having a thickness of, for example, about 0.2 micron is formed. This film is formed at low cost as compared with, for example, a plating process, and is easily removed by post flux. As a result, since the surfaces of the elastic support members 13a, 13b, 13c, 13d are covered with the film by the glycoat treatment, oxidation and discoloration of the surface are prevented, solderability is improved, and vibration characteristics are deteriorated. Is blocked.

Further, the elastic support members 13a, 13b, 1
In 3c and 13d, upper elastic members 13a and 13c in the focusing direction and lower elastic members 13b and 13d in the focusing direction are formed in the same shape. Therefore, the elastic support members 13a, 13b,
As shown in FIG. 7, 13c and 13d are formed on the same lead frame 13e. Then, each elastic member 13a, 13b, 13 of the lead frame 13e
The upper part 11U and the lower part 11L of the lens holder 11 and the upper part 14U and the lower part 14L of the fixed part 14 are outsert-molded with respect to c and 13d.
Therefore, on one lead frame 13e, an upper part including the upper part 11U of the lens holder 11, the upper part 14U of the fixing part 14 and the elastic supporting members 13a and 13c, the lower part 11L of the lens holder 11, the lower part 14L of the fixing part 14 and A lower part including the elastic support members 13b and 13d is configured. Thus, by removing the upper part and the lower part from the lead frame 13e and joining them together, the biaxial actuator 10 is assembled.

Biaxial actuator 10 according to the present embodiment
Is configured as described above, and currents based on the focus servo signal and the tracking servo signal are supplied to the focusing coil 12b and the tracking coil 12c wound around the coil bobbin 12, respectively. Thereby, the DC magnetic field of the magnetic circuit, the focusing coil 12b, and the tracking coil 12c.
The lens holder 11, that is, the objective lens 11c is driven in the focus direction Fcs and the tracking direction Trk by the alternating magnetic field generated by

Further, as a damper, the elastic support member 13 is used.
The viscous body 16 is applied to the end regions 15 of the a, 13b, 13c, and 13d on the side of the fixed portion 14 and hardened. Thereby, the elastic support members 13a, 13b, 13c, 13d
Will be respectively damped in the end regions 15.

Furthermore, the upper elastic support members 13a, 13
Since c has a warp in the opposite direction with respect to the elastic support members 13b and 13d below, the deviation due to the warp cancels each other. Therefore, the lens holder 1
The moving part assembly consisting of the coil bobbin 12
The elastic support members 13a, 13b, 13c, 13d described above
Of the elastic support members 13a, 13b,
Inclination due to warpage during press molding of 13c and 13d is prevented. As a result, the inclination of the objective lens 11a attached to the lens holder 11 is eliminated, so that highly accurate recording or reproducing of the optical disc becomes possible.

As described above, in the above-described embodiment, the deviations in the focusing direction due to the warp of the elastic support members arranged in the focusing direction cancel each other out.
The lens holder supported by the elastic support member does not tilt due to the warp of the elastic support member.
Therefore, the lens holder, the movable part assembly including the coil bobbin, and the objective lens are properly held without tilting. Thus, recording or reproduction of the optical disc can be performed with high accuracy and reliability.

Further, when the elastic supporting member is subjected to the glycoat treatment, the surface of the elastic supporting member is covered easily and at low cost. As a result, surface oxidation is prevented, solderability is improved, and deterioration of vibration characteristics due to discoloration is prevented.

When the upper elastic supporting member in the focusing direction and the lower elastic supporting member in the focusing direction are formed in the same shape, the upper and lower elastic supporting members are formed by one type of mold. Will be formed. Therefore, since there is no difference in dimensional variation between the upper and lower elastic support members, the vibration characteristic is improved. Further, since only one type of die is required to form the upper and lower elastic support members, the die cost can be reduced. Furthermore, since the upper and lower elastic support members are formed in one lead frame, parts management becomes easy,
Costs will be reduced.

In this embodiment, two pairs of elastic support members are provided on both sides of the lens holder, one pair along the focusing direction. However, the present invention is not limited to this, and the present invention can also be applied to a case where a plurality of elastic supporting members are provided on both sides of the lens holder along the focusing direction, preferably a plurality of pairs.

[0049]

As described above, according to the present invention, it is possible to provide a biaxial actuator having a simple structure and capable of reducing the inclination of the lens holder due to the warp of the elastic supporting member.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing the overall configuration of an embodiment of a biaxial actuator for an optical pickup according to the present invention as seen from the front.

FIG. 2 is a schematic perspective view showing the biaxial actuator of FIG. 1 as viewed from the rear.

FIG. 3 is an exploded perspective view of the biaxial actuator of FIG.

4 is an enlarged perspective view around a damping member of the biaxial actuator of FIG.

5 is a schematic side view showing a moving state in the focusing direction in the biaxial actuator of FIG.

6 is a schematic plan view showing a movement state in a tracking direction in the biaxial actuator of FIG.

FIG. 7 is a schematic perspective view showing a part of the manufacturing process of the mold part of the biaxial actuator of FIG.

FIG. 8 is a schematic perspective view showing an entire configuration of an example of a conventional biaxial actuator for an optical pickup.

9 is a schematic plan view showing pressing of an elastic support member in the biaxial actuator of FIG.

10 is a side view and a plan view showing a warp of an elastic support member in the biaxial actuator of FIG.

11 is a schematic side view showing an arrangement state of elastic support members in the biaxial actuator of FIG.

FIG. 12 is a schematic side view showing the inclination of the lens holder due to the warp of the elastic support member in the biaxial actuator of FIG.

13 is a schematic perspective view showing a state where the elastic support member, the lens holder, and the fixing portion in the biaxial actuator of FIG. 8 are being assembled.

[Explanation of symbols]

 10 Biaxial Actuator 11 Lens Holder 11a Opening 11b Recess 11c Objective Lens 12 Coil Bobbin 12a Opening 12b Focusing Coil 12c Tracking Coil 13a, 13b, 13c, 13d Elastic Supporting Member 14 Fixing Part 15 End Region 16 Viscous Body

Front page continuation (72) Inventor Hideo Okuma 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (6)

[Claims] 1. A lens holder for supporting an objective lens, and a plurality of elastic supports arranged side by side in the focusing direction on both sides of the lens holder for elastically supporting the lens holder with respect to a fixed portion. A member, a coil bobbin provided on the lens holder, a focusing coil wound on the coil bobbin, and a tracking coil wound on the coil bobbin, and both sides of the lens holder are provided. In the biaxial actuator, the plurality of elastic supporting members arranged side by side in the focusing direction are provided so that the warping directions caused by the processing at the time of manufacturing are opposite to each other. . 2. The elastic supporting member is formed by press working, and is arranged so that warp directions due to punching during the press working are opposite to each other. The biaxial actuator according to 1. 3. The elastic support member on the upper side in the focusing direction has a convex warp upward, and the elastic support member on the lower side in the focusing direction has a convex warp downward. The biaxial actuator according to claim 1 or 2, characterized by having. 4. The elastic support member on the upper side in the focusing direction has a convex warp downward, and the elastic support member on the lower side in the focusing direction shows a convex warp upward. The biaxial actuator according to claim 1 or 2, characterized by having. 5. The biaxial actuator according to claim 1, wherein the elastic support member is subjected to a glycoat treatment. 6. The elastic supporting member on the upper side in the focusing direction and the elastic supporting member on the lower side in the focusing direction are formed in the same shape as each other. Biaxial actuator.