JPH11185266A - Biaxial actuator, optical pickup and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin structure with a simple constitution and to prevent the optical axis falling of an objective lens especially during tracking. SOLUTION: This actuator 30 is provided with a holding member 31 for holding an objective lens 22 to be moved in a biaxial direction, magnets 33 and 34 arranged in movable parts including the objective lens 22 and the holding member 31, focussing and tracking coils 37 and 36 arranged in fixed parts so as to face the magnets 33 and 34, and a yoke 38 related to the magnets 33 and 34 and the coils 36 and 37. Of the magnets 33 and 34, tracking magnets 33 are attached to both side faces in the tracking direction of the holding member 31, and tracking yokes 38a and 38b are arranged in the outside so as to face the tracking magnet 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-axis actuator for an optical pickup used in an optical disk device for recording and reproducing signals on an information recording medium such as an optical disk, an optical pickup, and an optical disk device.

[0002]

2. Description of the Related Art Conventionally, reproduction or recording of 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 (MO) has been performed.
This is performed using an optical pickup. This optical pickup has a semiconductor laser as a light source, an objective lens,
It includes 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 disk 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.

A light beam emitted from a semiconductor laser is
The position of the objective lens in the optical axis direction is adjusted so that it is focused on the recording surface of the optical disk by following the displacement of the optical disk in the direction orthogonal to the surface direction of the optical disk that occurs due to the warp of the optical disk. Is done. 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 in-focus position of the light beam emitted from the semiconductor laser and the spot position on the recording surface of the optical disk are adjusted by adjusting the position of the objective lens in the direction of the optical axis of the objective lens and in the direction perpendicular to the optical axis. Done by An electromagnetically driven actuator is used to adjust the position of the objective lens.

[0004] The actuator is called an objective lens actuator or a biaxial actuator, and includes a bobbin to which an objective lens is attached, a plurality of elastic support members, and a drive unit for generating a driving force. The bobbin is supported by the plurality of elastic support members such that the position in the optical axis direction of the objective lens, that is, the focusing position, and the position in the direction orthogonal to the optical axis of the objective lens, that is, the tracking position, are adjustable with respect to the fixed portion. ing. Such a biaxial actuator is configured, for example, as shown in the plan view of FIG. The biaxial actuator 1 includes an objective lens 2 and
A holding member 3 for holding the objective lens 2 and a fixing portion 4 for supporting the holding member 3 movably in two axial directions, that is, in a focusing direction and a tracking direction.

The holding member 3 is moved in two directions perpendicular to each other by a wire 5
It is movably supported in a tracking direction indicated by rk and a focusing direction perpendicular to the paper surface. A coil unit 6 on which a focusing coil and a tracking coil are formed is attached to the holding member 3. A yoke 7 whose cross section is substantially U-shaped and whose upper part is open 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 right inner surface so as to face the coil unit 6.

Accordingly, when the tracking coil of the coil unit 6 is energized, the magnetic flux generated in the coil interacts with the magnetic flux generated by the yoke 7 attached to the fixed part 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 plane of the drawing. 2 configured in this way
According to the shaft actuator 1, when a driving voltage is supplied to each coil from the outside, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 7 and the magnet 8, and the holding member 3 moves in the tracking direction. Moved with respect to Trk and focusing direction.

As a result, the objective lens 2 attached to the holding member 3 is appropriately moved in the focusing direction and the tracking direction. By performing focusing and tracking in this manner, the light beam from the light source of the optical pickup is irradiated onto the signal recording surface of the optical disk via the objective lens 2, and the return light from the signal recording surface of the optical disk is generated. ,
The light again enters the optical detector 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.

[0008]

However, in the biaxial actuator 1 having such a configuration, the coil unit 6 having the focusing coil and the tracking coil is provided on the holding member 3 for holding the objective lens 2. The U-shaped yoke 7 is mounted on the fixing portion 4 so as to sandwich each coil of the coil unit.
Are arranged. For this reason, since the lower end portion of the yoke 7 is located immediately below the holding member 3, when the holding member 3 moves in the focusing direction, the yoke 7 is moved so that the holding member 3 does not interfere with the yoke 7. Allowance is given to the distance to the lower end. Therefore, there is a problem that it becomes an obstacle to thinning the entire biaxial actuator 1.

Further, since the center of gravity of the entire movable portion including the objective lens 2, the holding member 3, and the coil unit 6 is deviated from the center of the driving force received by each coil of the coil unit 6, the holding force is maintained. Member 3 and objective lens 2
Will be affected by the rotational moment. Therefore, during focusing or tracking, the objective lens 2
This causes a problem that the optical performance of the optical pickup and the optical disc device is deteriorated because the optical axis is particularly tilted during tracking. On the other hand, a method of adding a balance weight to the holding member 3 is also conceivable, but in this case, the number of parts increases, the parts cost and the assembly cost increase, and the weight of the entire movable part increases. As a result, there is a problem that the drive response of the movable part and the objective lens 2 in the focusing direction and the tracking direction is reduced.

In view of the above, the present invention provides a two-axis actuator which can be made thin with a simple structure and which can prevent the optical axis of the objective lens from being tilted particularly during tracking. It is an object to provide an optical pickup and an optical disk device.

[0011]

According to the present invention, there is provided a holding member for holding an objective lens movably in two axial directions, and a movable portion including the objective lens and the holding member. A two-axis actuator comprising: a magnet; a focusing coil and a tracking coil disposed on a fixed portion so as to face the magnet; and a yoke associated with the magnet and each coil. Among them, the tracking magnet is attached to both sides with respect to the tracking direction of the holding member, and among the yokes, the tracking yoke is disposed outside so as to face the tracking magnet. Achieved.

Further, according to the present invention, there is provided an object lens for irradiating a light beam emitted from the light source so as to be focused on a signal recording surface of a rotationally driven optical disk; An optical pickup comprising: a photodetector on which a return light beam from a signal recording surface of an optical disc is incident; and a biaxial actuator for supporting the objective lens so as to be movable in biaxial directions, wherein the biaxial actuator is A holding member for holding the objective lens movably in two axial directions, a magnet provided on a movable portion including the objective lens and the holding member, and a magnet provided on a fixed portion facing the magnet. A focusing coil and a tracking coil; and a yoke associated with the magnet and each coil. Together are attached to both sides with respect to the tracking direction of the holding member, the tracking yoke is achieved by being disposed outside so as to face the tracking magnets.

Further, according to the present invention, there is provided, according to the present invention, a driving means for driving an optical disc to rotate, and irradiating the rotating optical disc with light through an objective lens, and a signal recording surface from the optical disc. An optical pickup that detects return light via the objective lens, a two-axis actuator that supports the objective lens movably in two axial directions, and a detection signal from the optical pickup,
An optical disc device comprising: a signal processing circuit that generates a reproduction signal; and a servo circuit that moves the objective lens in biaxial directions based on a detection signal from the optical pickup, wherein the biaxial actuator includes: A holding member for holding the objective lens movably in two axial directions, a magnet provided on a movable portion including the objective lens and the holding member, and a focusing member provided on a fixed portion to face the magnet A coil for tracking and a coil for tracking, and a yoke associated with the magnet and each coil.Further, tracking magnets are attached to both sides in the tracking direction of the holding member, and the tracking yoke is provided. ,
This is attained by being disposed outside so as to face the tracking magnet.

[0014] According to the above configuration, when the focusing coil or the tracking coil provided in the fixed portion is energized, the magnetic flux generated in these coils is reduced.
Interacting with the magnetic flux of the magnet and the yoke attached to the holding member, the holding member and the objective lens are moved along the focusing direction or the tracking direction, and focusing or tracking of the objective lens is performed. Here, the tracking yoke is attached to the holding member so as to protrude outward from the tracking magnet attached to both side surfaces of the holding member, or is attached to the fixed portion as an iron core of a corresponding tracking coil. Therefore, the yoke does not exist even directly below the holding member. Therefore, even when the holding member moves in the focusing direction, the holding member does not interfere with the yoke, so that the two-axis actuator is configured to be thin, and the optical pickup and the optical disk device are also thin. Be composed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows a basic configuration of an embodiment of an optical disk device incorporating a biaxial actuator according to the present invention. The optical disk device 10 includes an optical disk 1
Spindle motor 1 as a driving means for rotationally driving the motor 1
2. An optical pickup 20 for irradiating a signal recording surface of a rotating optical disk 11 with a light beam to record a signal and reproducing a recorded signal by a return light beam from the signal recording surface, and a control unit 13 for controlling these. It has. The control unit 13 includes an optical disk controller 14, a signal demodulator 15, an error correction circuit 16, an interface 17, a head access control unit 18, and a servo circuit 19.

The optical disk controller 14 controls the drive of the spindle motor 12 at a predetermined rotation speed. The signal demodulator 15 demodulates the recording signal from the optical pickup 20, corrects the error, and sends the signal to an external computer or the like via the interface 17. Thus, an external computer or the like can receive a signal recorded on the optical disk 11 as a reproduction signal. The head access control unit 18 moves the optical pickup 20 to a predetermined recording track on the optical disk 11, for example, by a track jump or the like. The servo circuit 19 moves the objective lens held by the biaxial actuator of the optical pickup 20 in the focusing direction and the tracking direction at the moved predetermined position.

FIG. 2 shows a configuration of the optical pickup 20 incorporated in the optical disk device 10. This optical pickup 20 includes a light emitting / receiving element 21 and an objective lens 22. The light receiving and emitting element 21 is configured by integrating a semiconductor laser element as a light emitting element and a photodetector as a light receiving element. The objective lens 22
A convex lens, which emits a light beam from the light receiving / emitting element 21;
An image is formed on a desired track on the signal recording surface of the optical disk 11 that is driven to rotate. Further, the objective lens 22 is movably supported in a biaxial direction, that is, a tracking direction and a focusing direction, by a biaxial actuator according to the present invention described in detail below.

FIG. 3 and FIG.
1 shows an embodiment of a two-axis actuator according to the present invention incorporated in an optical pickup 20. This 2
The axis actuator 30 includes a lens holder 31 as a holding member for holding the objective lens 22, and a fixing portion 32 that supports the lens holder 31 movably in two axial directions, that is, a focusing direction and a tracking direction. The lens holder 31 is moved in two directions perpendicular to each other, that is, in the tracking direction indicated by the arrow Trk and the focusing direction indicated by the arrow Fcs by the leaf spring 33 stretched between the fixed part 32 and the fixed part 32. It is movably supported.

Further, tracking magnets 34 are attached to both end faces of the lens holder 31 with respect to the tracking direction. Further, a focusing magnet 35 is attached to an end surface of the lens holder 31 on the fixing portion 32 side. In the illustrated case, the tracking magnet 34 and the focusing magnet 35 are fixedly held by the lens holder 31 by insert molding or the like.

On the other hand, outside the tracking magnet 34, these tracking magnets 34
, The tracking coil 36 is fixedly arranged. Furthermore, focusing magnet 3
The focusing coil 37 is fixedly disposed on the side of the fixing portion 32 of the fourth. These tracking coils 3
The focusing coil 6 and the focusing coil 37 are fitted to a flat plate-like base 38 and iron cores 38a, 38b, 38c raised from the base 38. The base 38 is made of a magnetic material such as iron, and is provided with a cutout portion below the lens holder 31 to avoid interference with the lens holder 31.

The biaxial actuator 10 is configured as described above. When reproducing the optical disk 11, the semiconductor laser element of the light emitting / receiving element 21 of the optical pickup 20 emits light. Objective lens 2
The light is focused on the signal recording surface of the optical disk 11 via the optical disk 2. The return light from the optical disk 11 is again transmitted to the objective lens 2.
The light is incident on the photodetector of the light receiving / emitting element 21 through 2. Thus, a reproduction signal, a focusing error signal, and a tracking error signal relating to the optical disk 11 are detected based on the detection signal from the photodetector, and the optical disk 1
1 is reproduced.

At this time, the servo circuit 19 controls the drive current to the tracking coil and the focusing coil of the biaxial actuator 30 based on the focusing error signal and the tracking error signal, so that the tracking and focusing of the objective lens 22 are performed. Is performed. That is, currents based on the focusing servo signal and the tracking servo signal are supplied to the focusing coil and the tracking coil of the two-axis actuator 30, respectively.

Thus, the magnetic flux generated from the focusing coil and the tracking coil and the magnet 3
Due to the interaction between the magnets 34 and 35 and the magnetic fluxes, the magnets 34 and 35 generate driving forces in the focusing direction and the tracking direction, respectively, and the lens holder 31, that is, the objective lens 22 is moved in the focusing direction Fcs.
And in the tracking direction Trk. in this case,
The tracking magnet 34 is attached to the lens holder 3 such that the center of gravity of the tracking magnet 34 substantially coincides with the center of gravity of the entire movable part including the objective lens 22 and the lens holder 31. Since the point of action of the driving force at the time of tracking substantially coincides with the center of gravity of the movable portion, no rotational moment acts on the lens holder 32 and the objective lens 22, so that the light of the objective lens 22 There is no such thing as axis falling.

FIG. 5 shows the tracking coil described above.
14 shows a modification of the arrangement of the tracking yoke and the tracking magnet. In this case, the tracking yoke 39 is configured to protrude outwardly in a substantially U-shape in the drawing from the tracking magnet 34 attached to the lens holder 31, and the tip thereof is fitted into the tracking coil 36. ing. According to such a configuration, when a drive current flows through the tracking coil 36, the magnetic field generated in the tracking coil 36 interacts with the magnetic field generated by the tracking magnet 34 and the tracking yoke 39, and thus the tracking yoke 39 The driving force in the tracking direction acts on the tip portion of 39. Also in this case, since the yoke does not exist in the lower part of the lens holder 31,
The lens holder 31 does not interfere with the yoke during focusing.

In the above-described embodiment, the leaf spring 33 is described as being stretched between the lens holder 31 and the fixing part 32.
Obviously, the fixing portion 32 may be integrally formed with the fixing portion 32 by insert formation or the like. In the above-described embodiment, the optical disk device 10 and the optical pickup 20 are exemplifications, and the present invention can be applied to an optical disk device having another configuration or a biaxial actuator used in an optical pickup.

[0027]

As described above, according to the present invention, a thin structure can be realized with a simple structure.
In particular, it is possible to prevent the optical axis of the objective lens from being tilted during tracking.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device incorporating a two-axis actuator according to the present invention.

FIG. 2 is a schematic diagram showing a configuration of an optical pickup in the optical disk device of FIG. 1;

FIG. 3 is a schematic perspective view showing a configuration of an embodiment of a biaxial actuator in the optical disk device of FIG. 1;

FIG. 4 is a schematic plan view of the biaxial actuator of FIG. 3;

FIG. 5 is a schematic sectional view showing a modification of the biaxial actuator of FIG. 3;

FIG. 6 is a schematic plan view showing the overall configuration of an example of a conventional two-axis actuator for an optical pickup.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Optical disk apparatus, 11 ... Optical disk apparatus, 12 ... Spindle motor, 13 ... Control part,
14 ... optical disk controller, 15 ... signal demodulator, 16 ... error correction circuit, 17 ... interface, 18 ... head access control unit, 19 ...
Servo circuit, 20 ... Optical pickup, 21 ...
Light receiving / emitting element, 22 ... objective lens, 30 ... biaxial actuator, 31 ... lens holder, 32 ...
Fixed part, 33: leaf spring, 34: tracking magnet, 35: focusing magnet,
36: tracking coil, 37: focusing coil, 38: base, 39: yoke

Claims (6)

[Claims] 1. A holding member for holding an objective lens movably in two axial directions, a magnet provided on a movable part including the objective lens and the holding member, and a magnet provided on a fixed part facing the magnet. A biaxial actuator comprising a focusing coil and a tracking coil provided therein, and a yoke associated with the magnet and each coil, wherein tracking magnets are attached to both side surfaces in a tracking direction of the holding member. A two-axis actuator, wherein a tracking yoke is disposed outside so as to face the tracking magnet. 2. The biaxial actuator according to claim 1, wherein the tracking yoke is attached to the holding member so as to protrude outward from each of the corresponding tracking magnets. 3. The two-axis actuator according to claim 1, wherein the tracking yoke is attached to the fixed portion as an iron core of each of the corresponding tracking coils. 4. The two-axis actuator according to claim 1, wherein the two tracking magnets are disposed such that their centers of gravity substantially coincide with the centers of gravity of the movable parts. 5. A light source, an objective lens for irradiating a light beam emitted from the light source so as to focus on a signal recording surface of a rotationally driven optical disk, and a return light beam from the signal recording surface of the optical disk An optical pickup, comprising: a photodetector on which the objective lens is incident; and a biaxial actuator that supports the objective lens movably in the biaxial directions, wherein the biaxial actuator moves the objective lens in the biaxial directions. A holding member for holding the object, a magnet disposed on a movable portion including the objective lens and the holding member, a focusing coil and a tracking coil disposed on a fixed portion to face the magnet, A magnet and a yoke associated with each coil; and a tracking magnet for tracking the holding member. Together are attached to both sides with respect to, tracking yoke, the optical pickup being characterized in that disposed on the outside so as to face the tracking magnets. 6. A driving means for driving an optical disc to rotate, and irradiating the rotating optical disc with light through an objective lens, and detecting return light from a signal recording surface from the optical disc through the objective lens. An optical pickup, a biaxial actuator that supports the objective lens so as to be movable in two axial directions, a signal processing circuit that generates a reproduction signal based on a detection signal from the optical pickup, and a detection from the optical pickup An optical disc device comprising: a servo circuit that moves the objective lens in two axial directions based on a signal, wherein the biaxial actuator holds the objective lens so as to be movable in two axial directions; A magnet disposed on a movable part including the objective lens and the holding member, and a fixed part facing the magnet. It is provided with a focusing coil and a tracking coil provided, and a yoke associated with the magnet and each coil.Furthermore, tracking magnets are attached to both sides with respect to the tracking direction of the holding member, An optical disk device, wherein a tracking yoke is disposed outside so as to face the tracking magnet.