JPH09115158A - Biaxial actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxial actuator with which exact tracking is executed by setting a dynamic skew of a desired quantity with decreased variations. SOLUTION: This biaxial actuator has a lens holder 12 for supporting an objective lens 11 movably in a focusing direction and a tracking direction, a magnet 16 and yoke 15 disposed in a stationary part 13 or a moving part including the objective lens and a tracking coil 18 and focusing coil 17 disposed to face the magnet 16 and yoke 15. In such a case, the magnet 16 is disposed adjustably in the vertical direction, i.e., the optical axis direction of the objective lens 11.

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 and / or reproducing a signal on, for example, an optical disc.

[0002]

2. Description of the Related Art Conventionally, reproduction or recording of an information signal on an optical disc, for example, a so-called compact disc (CD) or a magneto-optical disc is performed by using an optical pickup. 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 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 perpendicular to the optical axis of the objective lens is adjusted so that the position of the spot on the optical disk of the light beam emitted from the semiconductor laser follows the eccentricity of the optical disk or the meandering of the track formed on the optical disk. Is 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 holding member to which the objective lens is attached, a plurality of elastic support members, and a drive unit that generates a driving force. The holding member includes a plurality of elastic support members with respect to the fixed portion, and a position in the optical axis direction of the objective lens, that is, a focus position and a position in a direction orthogonal to the optical axis of the objective lens
That is, the tracking position is adjustably supported. 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 the plan view of FIG. 7, a biaxial actuator 1 includes an objective lens 2, a holding member 3 that holds the objective lens 2, and a fixing portion 4 that movably supports the holding member 3 in the biaxial directions, that is, the focusing direction and the tracking direction. And have.

The holding member 3 is supported by a wire 5 stretched between the fixing member 4 and the holding member 3 so as to be movable in two directions perpendicular to each other, that is, a tracking direction indicated by reference numeral Trk and a focusing direction perpendicular to the paper surface. Has been done.

A coil unit 6 having a focusing coil and a tracking coil is attached to the holding member 3. A yoke 7 having a substantially U-shaped cross section and having an open upper portion is attached to the fixed portion 4 so as to sandwich the coil unit 6 from both sides. In this case, a magnet 8 is provided on the inner surface on the right side so as to face the coil unit 6.

As a result, when the tracking coil of the coil unit 6 is energized, the magnetic flux generated in this coil interacts with the magnetic flux generated by the yoke 7 attached to the fixed portion 4 and the magnet 8 attached thereto. The entire holding member 3 is moved in the tracking direction indicated by the arrow Trk. When the focusing coil of the coil unit 6 is energized, the entire holding member 3 is similarly moved in the focusing direction perpendicular to the paper surface.

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 7 and the magnet 8. This causes the holding member 3 to move in the tracking direction Trk and the focusing direction. Thus, the objective lens 2 attached to the holding member 3 is appropriately moved in the focusing direction and the tracking direction.

By carrying out focusing and tracking in this way, the light beam from the light source of the optical pickup irradiates the signal recording surface of the optical disk through the objective lens 2, and the signal recording surface of the optical disk is irradiated. The return light again enters the photodetector of the optical pickup via the objective lens 2. Thus, the information signal recorded on the signal recording surface of the optical disc is read.

[0011]

By the way, in the biaxial actuator 1 having such a structure, the objective lens 2 is used.
If the height (position in the optical axis direction) of the movable portion (holding member) with respect to the fixed portion 4 or the position of the magnetic circuit formed by the yoke 7 and the magnet 8 shifts with respect to the optical axis direction of the objective lens 2 for tracking. Radial skew occurs when the field of view is shaken. This radial skew causes a deviation of the optical axis of the objective lens 2, and there is a problem that accurate reading of information from the optical disk cannot be performed.

Therefore, conventionally, when assembling the biaxial actuator 1, the height of the movable portion, the yoke 7 and the magnet 8 are set.
By increasing the mounting accuracy of the above to the fixing portion 4, the occurrence of radial skew is suppressed as much as possible.
However, it is difficult to suppress variations in the height of the movable portion and the mounting positions of the yoke 7 and the magnet, and a radial skew of about ± 0.4 degrees occurs. Further, since the automatic sagging as a sag of the movable part during use occurs, the height shift of the movable part is inevitable, and the automatic sagging of the movable part also causes a dynamic skew.

Further, there is a problem that it is difficult to obtain optimum optical characteristics because the dynamic skew generated by the biaxial actuator varies. On the other hand, there is a demand for further miniaturization of the optical pickup and the biaxial actuator in the future, and the influence of the dynamic skew due to the above-mentioned variation in the mounting accuracy tends to increase more and more.

In view of the above points, an object of the present invention is to provide a biaxial actuator in which a desired amount of dynamic skew with a small variation is set to perform accurate tracking movement. There is.

[0015]

According to the present invention, the above object is to provide a holding member for holding an objective lens movably in a focusing direction and a tracking direction, and a fixed portion or a movable portion including an objective lens. And a tracking coil and a focusing coil provided so as to face the magnet and the yoke, and the magnet is adjustable in the vertical direction, that is, in the optical axis direction of the objective lens. Achieved by a biaxial actuator, which is arranged.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
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 for an optical pickup according to the present invention. FIG.
In the two-axis actuator 10, the objective lens 11
The biaxial actuator 10 of the optical pickup includes an objective lens 11, a lens holder 12 as a holding member for holding the objective lens 11, and the lens holder 12 in biaxial directions, that is, a focusing direction and a tracking direction. The fixed part 13 which supports so that movement is possible is included.

The lens holder 12 has a leaf spring 14 stretched between the fixed portion 13 and the fixed portion 13.
Are movably supported in two directions perpendicular to each other, that is, a tracking direction indicated by an arrow Trk and a focusing direction indicated by an arrow Fcs.

Further, in the hollow portion provided in the center of the lens holder 12, a fixed portion 13 is mounted,
Moreover, a yoke 15 having a substantially U-shaped cross section and having an open upper portion is fitted therein. Then, one end 15 of the yoke 15
A magnet 16 is attached to the inner surface of a.
The open upper part of the yoke 15 is closed by a cover 15c.

Further, a focusing coil 17 is attached to the lens holder 12 so as to surround the end portion 15a of the yoke 15 and the magnet 16 in the horizontal direction. Further, the focusing coil 1 is provided between the other end 15b of the yoke 15 and the magnet 16.
Two tracking coils 18 formed by winding the focusing coil 17 in a direction perpendicular to the winding direction of the focusing coil 17 are provided on the outer side of 7.

As a result, when the tracking coil 18 is energized, the magnetic field generated by this coil acts on the magnet 16 and the yoke 15,
The entire lens holder 12 is moved in the tracking direction Trk. Also, the focusing coil 1
When electricity is applied to 7, the entire lens holder 12 is similarly moved in the focusing direction Fcs.

Further, as shown by the arrow X in FIG. 2, the magnet 16 is configured to be adjustable with respect to the end portion 15a of the yoke 15 in the vertical direction, that is, the optical axis direction of the objective lens 11. . For example, the cover 15c in FIG.
Is formed so that the lower surface thereof has a sufficient height when mounted on the yoke 15. Further, as long as the magnetic field formed by the magnet 16 is not extremely disturbed, this may be omitted so as not to obstruct the movement of the magnet 16 in the vertical direction. As a result, as shown in FIG. 3, when the magnet 16 is arranged so that the centers thereof coincide with the tracking coil 18, the center C of the driving force when the tracking coil 18 is energized is C. Is
It is almost in the center. Since the center C of the driving force coincides with the center of the tracking coil 18, the lens holder 12 and the objective lens 11 do not generate a radial skew when the visual field is swung, as indicated by an arrow in FIG. .

From this state, when the magnet 16 is moved upward and adjusted as shown in FIG. 4, the center C of the driving force when the tracking coil 18 is energized is located slightly above. Therefore, the center C of this driving force
Is located above the center of the tracking coil 18, the lens holder 12 and the objective lens 11 receive a moment by this driving force, and as shown by the arrow in FIG. Radial skew occurs. On the other hand, as shown in FIG. 5, when the magnet 16 is moved downward and adjusted, the center C of the driving force when the tracking coil 18 is energized is positioned slightly downward. Therefore, the center C of this driving force
Is located below the center of the tracking coil 18, the lens holder 12 and the objective lens 11 receive a moment by this driving force, and as shown by the arrow in FIG. Radial skew occurs.

The biaxial actuator 10 for the optical pickup according to the present embodiment is configured as described above, and the light from the light source of the optical pickup (not shown) is passed through the objective lens 11 to the optical disk (not shown). An image is formed on the signal recording surface of. Then, the return light from the signal recording surface of the optical disc passes through the objective lens 11 again and is incident on the photodetection section of the optical pickup (not shown). As a result, the information recorded on the signal recording surface of the optical disc is read. At that time, focusing and tracking of the objective lens 11 are performed by appropriately controlling the energization of the focusing coil 17 and the tracking coil 18 attached to the lens holder 12.

In this case, the lens holder 1 which is a movable part
When the mounting height of the second member 2 with respect to the fixed portion 13 is deviated, automatic sagging of the holding member 12 occurs, or the vertical mounting position of the magnet 16 with respect to the tracking coil 18 is deviated, Adjustment is performed by the method as shown in FIG. Even if the center C of the driving force and the center of the tracking coil 17 coincide with each other, the center of gravity of the lens holder 12 deviates from the center of the tracking coil 18 due to the deviation therebetween. Therefore, radial skew occurs due to the field of view of the objective lens 11 caused by tracking.

In this case, the magnet 16 is vertically adjusted with respect to the end portion 15a of the yoke 15 as shown in FIG. 4 or FIG. Coil 18
By moving the lens holder 12 near the center of the lens holder 12 from the center of the
The generation of radial skew due to the swing of the visual field is suppressed. When the optical characteristics of the objective lens 11 at the time of tracking are optimized when there is a constant radial skew, the above-mentioned constant radial skew can be obtained by vertically adjusting the end portion 15a of the yoke 15 of the magnet 16. Is adjusted and fixed there.

Thus, during tracking, the magnet 16 is vertically adjusted so that the radial skew due to the field swing of the objective lens becomes zero or a predetermined value, so that the objective lens 11 is accurately tracked. become.

By thus vertically adjusting the magnet, the vertical positions of the magnetic circuit including the yoke and the magnet and the tracking coil and the focusing coil can be adjusted appropriately. Therefore, by adjusting the magnet up and down, a desired dynamic skew is set in order to compensate for the optical characteristics of the biaxial actuator, that is, the jitter deterioration when the field of view of the objective lens is deviated, and the mounting height of the movable portion to the fixed portion is increased. Variations in the mounting position of the sheath magnet are reduced, and accurate tracking is performed.

FIG. 6 shows a second embodiment of a biaxial actuator for an optical pickup according to the present invention.
In FIG. 6, the biaxial actuator 20 includes an objective lens 21 and a holding member 2 that holds the objective lens 21.
2 and a fixing portion 23 that supports the holding member 22 so as to be movable in two axial directions, that is, the focusing direction and the tracking direction. The holding member 22 is the fixed portion 2
3 is supported by a leaf spring 24 stretched between the fixed portion 23 and the fixed portion 23 so as to be movable in two directions perpendicular to each other, that is, a tracking direction Trk and a focusing direction. Here, the objective lens 21 and the holding member 2
2, the fixed portion 23 and the leaf spring 24 have the same configuration as the biaxial actuator 10 of FIG. 1 and have the same operation, but have different configurations in the following points.

That is, when the holding member 22 which is a movable portion is assembled to the fixed portion 23, the height deviation from the fixed portion 23 due to the automatic sagging of the movable portion is corrected with respect to the fixed portion 23. Relatively up and down, that is, the objective lens 21
It is adjustable with respect to the optical axis direction. It should be noted that the height adjustment of the holding member 22 with respect to the fixed portion 23 may be performed relatively, and in practice, the fixed portion 23 itself may be adjusted in height as shown by the arrow Y. is there.

According to this structure, the height of the movable portion, that is, the holding member 22 is adjusted with respect to the fixed portion 23, so that the tracking coil (not shown) attached to the holding member 22 is The magnet (not shown) fixed to the fixed portion 23 is indirectly adjusted in the vertical direction. Therefore, as in the case of the biaxial actuator 10 shown in FIG. 1, the magnet is vertically adjusted with respect to the tracking coil. Thus, according to the biaxial actuator 20, the holding member 22 is fixed to the fixed portion 2.
By adjusting the height of the magnet 3 and assembling it, the magnet is adjusted up and down, so that the radial skew due to the field swing of the objective lens 21 becomes zero or a predetermined value during tracking. Lens 21
Will be tracked accurately.

In the above embodiment, the yoke 15 and the magnet 16 are fixed to the fixing portions 13 and 23, and the focusing coil 17 and the tracking coil 18 are attached to the lens holders 12 and 22. However, the present invention can be applied to a so-called moving magnet type biaxial actuator in which the magnet is attached to the support member and the focusing coil and the tracking coil are attached to the fixed portion. That is clear.

[0033]

As described above, according to the present invention, it is possible to set a desired amount of dynamic skew with little variation in the biaxial actuator, and accurate tracking movement is performed.

[Brief description of the 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.

FIG. 2 is a schematic sectional view of a main part of the biaxial actuator of FIG.

FIG. 3 is a schematic diagram showing a relationship between a tracking coil and a magnet in the biaxial actuator of FIG.

FIG. 4 is a schematic diagram showing a relationship between the tracking coil of FIG. 3 and a magnet whose movement is adjusted upward.

5 is a schematic diagram showing a relationship between the tracking coil of FIG. 3 and a magnet whose movement is adjusted downward.

FIG. 6 is a schematic side view showing a second embodiment of a biaxial actuator according to the present invention.

FIG. 7 is a schematic plane view showing an overall configuration of an example of a conventional biaxial actuator for an optical pickup.

[Explanation of symbols]

 10 Biaxial Actuator 11 Objective Lens 12 Supporting Member 13 Fixing Part 14 Leaf Spring 15 Yoke 16 Magnet 17 Focusing Coil 18 Tracking Coil 20 Biaxial Actuator 21 Objective Lens 22 Supporting Member 23 Fixing Part 24 Leaf Spring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Okuma 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (3)

[Claims] 1. A holding member for holding an objective lens movably in a focusing direction and a tracking direction, a magnet and a yoke arranged in a fixed portion or a movable portion including an objective lens, and a magnet and a yoke which face the magnet and the yoke. A biaxial actuator comprising the tracking coil and the focusing coil provided as described above, wherein the magnet is arranged so as to be adjustable in the vertical direction, that is, the optical axis direction of the objective lens. 2. The biaxial actuator according to claim 1, wherein the vertical adjustment of the magnet is performed by vertically adjusting the magnet with respect to the yoke. 3. The biaxial actuator according to claim 1, wherein the vertical adjustment of the magnet is performed by adjusting the height of the movable portion with respect to the fixed portion.