JP2805651B2 - Objective lens drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used in an optical pickup device for recording and / or reproducing information signals on an optical disk, a magneto-optical disk, or the like.

B. Summary of the Invention The present invention is an objective lens driving device used in an optical pickup device for recording and / or reproducing information signals on an optical disk, a magneto-optical disk, or the like. A lens bobbin supported so as to be displaceable in a direction parallel to the axial direction and a direction perpendicular to the optical axis direction, and detects a displacement of the lens bobbin in a direction substantially perpendicular to the optical axis of the objective lens of the lens bobbin; To be detected is provided. The detected member has a detected portion parallel to the optical axis of the objective lens, and is attached to the lens bobbin at a position closer to the objective lens than the center of gravity of the lens bobbin including the objective lens.

Then, the displacement of the lens bobbin is detected by detecting the displacement of the detected portion by the position detecting means.

C. Prior Art Conventionally, a disk device that records and / or reproduces an information signal on a disk-shaped recording medium such as an optical disk or a magneto-optical disk has been proposed. This type of disk device
A rotation operation mechanism that holds and rotates a disk-shaped recording medium, and an optical pickup that condenses and irradiates a light beam onto the disk-shaped recording medium to record and / or reproduce information signals on the disk-shaped recording medium Device.

The optical pickup device used in the disk device includes a light source such as a laser diode that emits a light beam, an objective lens that guides the light beam emitted from the light source to the disk-shaped recording medium and focuses the light beam on the disk-shaped recording medium, and And other optical devices. This optical pickup device is movably supported over the inner and outer peripheries of a disk-shaped recording medium. That is, the disk device can irradiate the light beam over substantially the entire surface of the disk-shaped recording medium by rotating the disk-shaped recording medium and moving the optical pickup device over the inner and outer peripheries of the disk-shaped recording medium. It is configured as follows.

By the way, when the disk-shaped recording medium is rotated by the rotation operation mechanism, the disk-shaped recording medium may fluctuate due to surface shake or eccentricity. Therefore, the optical pickup device moves the objective lens in a direction parallel to the optical axis of the objective lens and with the optical axis of the objective lens so that the light beam follows a recording track formed in a signal recording area of the disk-shaped recording medium. An objective lens driving device is provided which is operated to move in two orthogonal directions.

The objective lens driving device displaceably supports the objective lens via a lens bobbin, and displaces the lens bobbin in a direction parallel to the optical axis of the objective lens and in a direction perpendicular to the optical axis of the objective lens. The lens is driven and displaced in two axial directions.

As shown in FIG. 7, a lens bobbin 102 to which an objective lens 101 is attached is used as the objective lens driving device.
Are supported by a base 104 via two pairs of support arms 103. The support arm 103 is made of a member having appropriate flexibility and elasticity, such as a leaf spring or a steel wire. The lens bobbin 102 has a focus direction parallel to the optical axis of the objective lens 101 indicated by an arrow f in FIG. 7 and an objective lens indicated by an arrow t in FIG.
Tracking direction 2 which is a direction orthogonal to the optical axis of 101
It is supported so as to be displaceable in the axial direction.

The objective lens driving device includes a magnetic circuit unit as driving means for driving and displacing the lens bobbin 102. This magnetic circuit section includes a focus coil 105, a tracking coil 1
06 and a magnet 107. The focus coil 105 and the tracking coil 106 are mounted on the outer peripheral surface of the lens bobbin 102. The magnet 107 is connected to each coil 10
It is attached to the base 104 so as to face 5,106.

When a focus drive current is supplied to the focus coil 105, the objective lens driving device
Is moved in the focus direction. When a tracking drive current is supplied to the tracking coil 106,
The lens bobbin 102 is operated to move in the tracking direction.

D. Problems to be Solved by the Invention Meanwhile, in the objective lens driving device configured as described above, the optical pickup device to which the objective lens driving device is attached is operated at high speed in the radial direction of the disk recording medium. When the moving speed becomes faster, such as during high-speed seek,
There is a possibility that the lens bobbin 102 moves in the tracking direction with respect to the base 104 due to the acceleration. Even when the lens bobbin 102 moves in the tracking direction with respect to the base 104 and the optical pickup device is stopped, the lens bobbin
There is a possibility that the inertia force causes the base 104 to generate vibrations that repeat displacement.

When the lens bobbin 102 is vibrating with respect to the base 104, focus control and tracking control of the objective lens cannot be performed, and recording and / or reproduction of information signals on the disk-shaped recording medium cannot be performed accurately. . After the optical pickup device is moved at a high speed, the information signal cannot be recorded and / or reproduced until the vibration of the lens bobbin 102 with respect to the base 104 is stopped. It has become difficult to shorten the access time until signal recording and / or reproduction is performed.

In order to restrict the vibration of the lens bobbin 102 as described above, as shown in FIG. 8, an objective lens driving device including a position sensor 108 for detecting the amount of movement of the lens bobbin 102 with respect to the base 104 has been proposed. . The position sensor 108 includes, for example, a light emitting element 109 such as a light emitting diode supported on the base 104, and a lens bobbin 102 mounted on the base 104.
And a light receiving element 110 such as a photodiode for receiving a light beam from the light emitting element 109 via one end 102a of the light emitting element. The position sensor 108 includes a lens bobbin 102 and a base 104.
, One end 102a of the lens bobbin 102 moves in the light beam from the light emitting element 109, and the light receiving element 110
Is configured to change. In the position sensor 108, the amount of movement of the lens bobbin 102 with respect to the base 104 is detected based on the output of the light receiving element 110.

The objective lens driving device equipped with such a position sensor 108, when the optical pickup device is moved at high speed,
By supplying a driving current based on the detection output detected by the position sensor 108 to the tracking coil 106,
The movement of the lens bobbin 102 with respect to the base 104 can be restricted.

However, when the optical pickup device is moved at a high speed, the lens bobbin 102 may tilt in the moving direction of the optical pickup device, that is, pitch, as shown in FIG. This pitching is a rotation of the lens bobbin 102 about its center of gravity g. When this pitching occurs, the objective lens 101 moves on the circumference around the center of gravity g, so that the beam spot of the light beam applied to the disk-shaped recording medium via the objective lens 101 moves, and Recording and / or reproduction of a good information signal on a recording medium cannot be performed.

Then, the position sensor 108 cannot detect such pitching. That is, the lens bobbin 102
When pitching occurs counterclockwise in the direction of arrow p in FIG. 9, the objective lens 101 moves to the left in the direction of arrow a in FIG.
To form This beam spot b1 is
Beam spot b0 when 2 is not pitching
9 is formed on the left side in FIG.

At this time, since one end portion 102a of the lens bobbin 102 is located on the side facing the objective lens 101 via the center of gravity g, the lens bobbin 102 moves rightward in the direction of arrow c in FIG. I do.

Therefore, a driving current based on the detection output of the light receiving element 110 is supplied to the tracking coil 106 to supply the lens bobbin 102
The lens bobbin 102 is moved leftward in the direction of arrow a in FIG. Then, beam spot b1
Is moved further away from the beam spot b0 when the lens bobbin 102 is not pitched.

In the objective lens driving device in which the movement of the lens bobbin 102 at the time of seeking is restricted by using the position sensor 108 as described above, when pitching occurs in the lens bobbin 102, the beam spot b1 on the disk-shaped recording medium D Cannot be suppressed, but rather the movement of the beam spot b1 may be increased.

In order to detect the movement of the lens bobbin 102 in the tracking direction with respect to the base 104, a pair of position sensors 111 may be provided on opposite sides of the lens bobbin 102 as shown in FIG. . In the objective lens driving device configured as described above, as shown in FIG. 11, even if the lens bobbin 102 is pitched, the detection output of each position sensor 111 does not change, and this pitching cannot be detected.

Therefore, the present invention has been proposed in view of the above-described situation, and is intended to move the objective lens even when the lens bobbin is tilted during a high-speed seek operation in which the optical pickup device is operated at a high speed. It is an object of the present invention to provide an objective lens driving device which makes it possible to make recording and / or reproduction of an information signal prompt without reducing the size of the objective lens.

E. Means for Solving the Problems The objective lens driving device according to the present invention has a lens bobbin having an objective lens mounted on the upper surface side and a base end side as a base in order to achieve the above-described object. The lens bobbin is supported such that the center of gravity of the lens bobbin including the objective lens is fixed substantially at the center of the lens bobbin, and the lens bobbin is moved in a direction parallel to the optical axis direction of the objective lens and the light. Four supporting members that support the lens bobbin so as to be displaceable in a direction perpendicular to the axial direction, and driving means for moving the lens bobbin in a direction parallel to the optical axis direction of the objective lens and in a direction perpendicular to the optical axis direction, A test object attached to the lens bobbin having a detection part parallel to the optical axis of the objective lens, which is located on the side of the same height as the objective lens above the center of gravity of the lens bobbin. And the member is made and a position detecting means for detecting a direction of displacement perpendicular to the optical axis of the objective lens of the part to be detected.

F. Function In the objective lens driving device according to the present invention, when the lens bobbin is rotated around the center of gravity, the detected portion of the detected member attached to the lens bobbin is rotated around the center of gravity of the lens bobbin. . Since the detected portion is located closer to the objective lens than the center of gravity of the lens bobbin, when the lens bobbin is turned around the center of gravity, it tilts in a direction corresponding to the turning direction.

G. Examples Hereinafter, specific examples of the present invention will be described with reference to the drawings.

The objective lens driving device according to the present invention is used for an optical pickup device that records and / or reproduces an information signal on a disk-shaped recording medium such as an optical disk or a magneto-optical disk. The objective lens for condensing the light beam emitted from the optical block section on the disk-shaped recording medium is moved in a direction parallel to the optical axis of the objective lens and in two axial directions orthogonal to the optical axis of the objective lens. Device.

The optical block unit constituting the optical pickup device includes a light source such as a laser diode that irradiates a light beam irradiating the disk-shaped recording medium, a plurality of optical devices for guiding the light beam emitted from the light source to an objective lens, and a disk-shaped recording medium. A light receiving element such as a photodiode for detecting reflected light from a medium via an optical device is incorporated.

As shown in FIGS. 1 and 2, the objective lens driving device used in this optical pickup device includes a base 1 and a lens bobbin 3 on which an objective lens 2 is mounted. It is supported so as to be displaceable in a direction parallel to the optical axis of the lens 2 and in two axial directions orthogonal to the optical axis of the objective lens 2.

The base 1 is formed in a plate shape from a metal material having a high magnetic permeability or the like. On the rear side of the base 1, a support plate 4 is formed upright. The base ends of two pairs of support arms 5 formed in a rod shape are attached to the support plate 4.

Each support arm 5 cantilevered by the support plate 4 is formed of a metal wire such as a steel wire having appropriate flexibility and elasticity, and is formed on the base 1 so as to be parallel to the base 1. It extends toward the front side. The lens bobbin 3 is supported on the tip side of the support arm 5.

The lens bobbin 3 is formed in a substantially rectangular shape by molding a synthetic resin, and is provided with a pair of support arm attachment portions 6 on both sides. The distal end side of each support arm 5 is attached to each support arm attachment portion 6 in a pair-wise manner.

The lens bobbin 3 is provided with an objective lens mounting hole 3a in which the objective lens 2 is mounted. The objective lens mounting hole 3a is provided through the lens bobbin 3 in a direction perpendicular to the base 1. The objective lens 3
The objective lens mounting hole 3a is mounted so as to close the opening on the upper surface side opposite to the side facing the base 1.

As shown in FIG. 2, the base 1 is provided with a light beam incident hole 1a so as to communicate with the objective lens mounting hole 3a. The light beam entrance hole 1a is provided so that a light beam emitted from an optical block (not shown) disposed on the side opposite to the side on which the lens bobbin 3 of the base 1 is supported passes.
It is provided through the base 1. The light beam that has passed through the light beam entrance hole 1a enters the objective lens 2 via the objective lens attachment hole 3a.

This objective lens driving device includes a lens bobbin 3
The direction of the optical axis A of the objective lens 2 indicated by an arrow F in FIGS. 2 and 3, ie, the focus direction, and the direction orthogonal to the optical axis A of the objective lens 2 indicated by an arrow T in FIGS. And a magnetic circuit unit which constitutes a driving unit for driving displacement in two axial directions. The magnetic circuit unit includes a focus coil 7 and a plurality of tracking coils 8 attached to the lens bobbin 3, and a first primary coil.
A pair of outer and inner magnetic yokes 9, 10 provided above
And a pair of magnets 11 attached to the outer magnetic yoke 9.

The focus coil 7 is wound around the lens bobbin 3 in the circumferential direction. Also, each tracking coil 8
Each of them is wound in a substantially rectangular shape, and is adhered to predetermined four locations so as to be superimposed on the focus coil 7.

Each of the pair of magnetic yokes 9 and 10 is formed in a rectangular plate shape from the same material as the base 1, and is provided so as to be erected on the base 1. The outer magnetic yoke 9 is disposed on the front side and the rear side of the lens bobbin 3 so as to face each other with the lens bobbin 3 interposed therebetween. Inner magnetic yoke 10
Are inserted into a pair of magnetic yoke insertion holes 3b formed in the lens bobbin 3 in front of and behind the objective lens mounting hole 3a and parallel to the objective lens mounting hole 3a.

The pair of magnets 11 are attached to opposing surfaces of the pair of outer yokes 9, and are located on the front side and the rear side of the lens bobbin 3. That is, these magnets 11
A magnetic gap is formed between the magnetic coil and each inner magnetic yoke 10, and the focus coil 7 and the tracking coil 8 are located in these magnetic gaps.

With the magnetic circuit unit configured as described above, the lens bobbin 3 is moved in the focus direction by supplying a predetermined drive current to the focus coil, and a predetermined drive current is supplied to the tracking coil. Is operated in the tracking direction.

When recording and / or reproducing information signals from / to the disk-shaped recording medium, each drive current includes a focus error signal generated based on a detection output of a light-receiving element built in the optical block unit and a drive signal. It is supplied according to the tracking error signal. Further, the objective lens driving device is used in such a manner that the tracking direction coincides with the radial direction of the disk-shaped recording medium, and is movably supported in the radial direction of the disk-shaped recording medium.

By the way, the objective lens driving device includes a lens bobbin 3
There is provided a detection mechanism for detecting the tilt of the base 1 with respect to the base 1 and the displacement in the tracking direction. The detection mechanism includes a member to be detected 12 attached to the lens bobbin 3.
And a light emitting element 13 and a light receiving element 14 serving as position detecting means.

The inclination of the lens bobbin 3 detected by this detection mechanism is caused by pitching due to the radial movement of the disk-shaped recording medium of the objective lens driving device, that is, the arrow P in FIG.
The rotation is about an axis parallel to each support arm 5 through the center of gravity G of the lens bobbin 3 in the direction. The rotation axis of the pitching is orthogonal to both the focus direction and the tracking direction. The center of gravity G of the lens bobbin 3 including the objective lens 2 is on the optical axis A of the objective lens 2.

The detected member 12 is formed in a thin frame shape from metal, synthetic resin, or the like, and is attached to the lens bobbin 3. The detected member 12 includes a bar-shaped detected portion 12a parallel to the optical axis A of the objective lens 2, and the detected portion 12a is connected to the center of gravity G of the lens bobbin 3 and the objective lens 2 as shown in FIG. And is mounted on the side of the objective lens 2, that is, in a direction perpendicular to the optical axis A of the objective lens 2 with respect to the objective lens 2.

Light-emitting element 13 and light-receiving element 14 constituting position detecting means
Are supported on the base 1 via support members 15 and 16, respectively. The light emitting element 13 and the light receiving element 14 are opposed to each other in a direction parallel to the pitching axis of the lens bobbin 3 with the detected portion 12a interposed therebetween. The light emitting element 13 is composed of a laser diode, an LED, or the like, and the detected part 12a is
Irradiate a light beam through the. The light receiving element 14 is composed of a photodiode or the like, and includes first and second light receiving surfaces 14a and 14b, as shown in FIG.
It is configured to obtain first and second detection outputs from 4a and 14b, respectively. These first and second light receiving surfaces 14a, 14
b is arranged adjacent to the tracking direction. The boundary 14c where the first and second light receiving surfaces 14a and 14b are in contact with each other is set in the focus direction, that is, parallel to the detected portion 12a.

When the lens bobbin 3 is not displaced in the tracking direction and the pitching does not occur, the light-emitting element 13 and the light-receiving element 14 have the boundary of the shadow of the detected portion 12a due to the light beam emitted from the light-emitting element 13. It is arranged to be formed on 14c. Therefore, the detected part 12
When “a” is displaced in the tracking direction with respect to the base 1, the detection target is a light beam emitted from the light emitting element 13.
The shadow of 12a moves to one of the first and second light receiving surfaces 14a and 14b. The detection mechanism detects a displacement of the detected portion 12a with respect to the base 1 in a direction orthogonal to the optical axis A of the objective lens 2 by comparing the first and second detection outputs.

The objective lens driving device according to the present invention configured as described above can be used when the optical pickup device to which the objective lens driving device is attached is moved at a high speed in the radial direction of the disc-shaped recording medium at a high speed seek. The bobbin 3 is driven to be displaced in the tracking direction based on the first and second detection outputs obtained from the light receiving element 14, so that the displacement of the objective lens 2 with respect to the base 1 is suppressed.

That is, when the objective lens driving device is moved in the radial direction of the disk-shaped recording medium, the lens bobbin 3 moves in the tracking direction with respect to the base 1 as shown in FIG. When the lens bobbin 3 is displaced in one direction in the ΔT direction, a drive current for displacing the lens bobbin 3 in the other direction indicated by the arrow M in FIG.
The displacement of the lens bobbin 3 with respect to the base 1, that is, the displacement of the objective lens 2 with respect to the base 1 can be suppressed.

When the lens bobbin 3 is displaced in the tracking direction with respect to the base 1, the detected part 12a moves in the same direction by the same distance as the objective lens 2, so that the first and second parts obtained from the light receiving element 14 are obtained. The detection outputs are signals of different signal levels. Here, the difference between the signal levels of the first and second detection outputs has a polarity corresponding to the displacement of the lens bobbin 3 in the tracking direction. That is, when the signal level of the first detection output is L ₁ and the signal level of the second detection output is L ₂ , when the lens bobbin 3 is displaced in one direction with respect to the base 1, the difference between these signal levels is obtained. Assuming that L ₁ -L ₂ is positive, when the lens bobbin 3 is displaced toward the other side with respect to the base 1, the difference L ₁ -L ₂ between these signal levels is negative.

Accordingly, the difference L ₁ −
If supply a drive current to the tracking coil 8 based on the L ₂ difference, the lens bobbin 3, always, the displacement caused by the objective lens driving device is moving operation can be displaced driven in the reverse direction.

When the objective lens driving device is moved in the radial direction of the disk-shaped recording medium, as shown in FIG. 5, the lens bobbin 3 is pitched in the clockwise direction indicated by the arrow ΔP in FIG. The objective lens 2 is displaced in one direction with respect to the base 1 in accordance with the pitching of the lens bobbin 3. At this time, if a drive current for displacing the lens bobbin 3 in the direction indicated by the arrow M in FIG. 4 is supplied to the tracking coil 8, the displacement of the objective lens 2 with respect to the base 1 can be suppressed.

When pitching occurs in the lens bobbin 3, the detected portion 12a is moved by a distance determined by the positional relationship between the detected portion 12a, the center of gravity G of the lens bobbin 3, and the objective lens 2, as shown in FIG. You.

That is, when the distance between the center of gravity G and the objective lens 2 of the lens bobbin 3 and r _1, the center of gravity G from that on the optical axis A of the objective lens 2, when the lens bobbin 3 is caused pitting only Δθ is movement amount [Delta] x ₁ in the tracking direction of the objective lens 2 becomes Δx ₁ ≒ _r1 S _in Δθ. Then, the center of gravity G of the lens bobbin 3 and the detected portion 12
The distance in the tracking direction between a and r
₂ , let r _s be the distance in the focus direction and r ₃ S _in Δθ
Is sufficiently smaller than the distance r ₁ between the center of gravity G and the objective lens 2, the moving amount Δx ₂ of the detected portion 12 a in the tracking direction becomes Δx ₂ ≒ r _s T _an Δθ. If it is sufficiently small Δθ, because it is SinΔθ ≒ TanΔθ, if r ₁ = r _s, a Δx ₁ ≒ Δx _2.

Accordingly, the drive current based on the difference L ₁ −L ₂ between the signal levels of the respective detection outputs is supplied to the tracking coil 8 so that the lens bobbin 3 always moves the objective lens 2 in the direction opposite to the displacement caused by pitching. Displacement drive is performed to cause displacement.

In this manner, the objective lens driving device according to the present invention can reduce the displacement of the objective lens 2 with respect to the base 1 due to the radial movement of the disk-shaped recording medium. Therefore, the vibration of the objective lens 2 with respect to the base 1 which occurs at the time of high-speed seek or the like can be suppressed, and the recording and / or reproduction of the information signal after the end of the seek can be quickly started.

H. Effects of the Invention As described above, the objective lens driving device according to the present invention includes:
The position of the detection target, which is attached to the lens bobbin and is displaced integrally with the lens bobbin in a direction orthogonal to the optical axis of the objective lens, is detected, and the displacement of the lens bobbin is controlled according to the detection output. Therefore, displacement of the lens bobbin can be suppressed, and focus and tracking control of the objective lens can be performed quickly and accurately.

In particular, the detection target portion of the detection target member attached to the lens bobbin is located on the side substantially at the same height as the objective lens above the center of gravity of the lens bobbin, and is mounted parallel to the optical axis of the objective lens. Therefore, when the lens bobbin is rotated about the center of gravity, the direction of rotation of the lens bobbin can be detected, and the direction of displacing the lens bobbin can be accurately controlled based on the output signal of the position detecting means. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an objective lens driving device according to the present invention, FIG. 2 is a longitudinal sectional view of the objective lens driving device, and FIG. It is a principal part enlarged front view shown. FIG. 4 is a front view showing a state where the lens bobbin of the objective lens driving device is displaced in the tracking direction with respect to the base. FIG. 5 is a diagram showing a state where the lens bobbin of the objective lens driving device is pitched. FIG. FIG. 6 is an enlarged front view for explaining the positional relationship between the center of gravity of the lens bobbin, the objective lens and the detected member in the objective lens driving device. FIG. 7 is a perspective view showing a conventional objective lens driving device. FIG. 8 is a partially cutaway front view showing a conventional objective lens driving device provided with a position sensor for detecting the movement of a lens bobbin, and FIG. 9 is a lens of the conventional objective lens driving device shown in FIG. It is a partially broken front view showing the state where the bobbin was inclined. FIG. 10 is a partially cutaway front view showing another example of a conventional objective lens driving device provided with a position sensor for detecting the movement of a lens bobbin, and FIG. 11 is a conventional objective lens shown in FIG. It is a partially broken front view showing the state where the lens bobbin of the drive device was inclined. 2 ... Objective lens, 3 ... Lens bobbin, 12 ... Detected member, 12a ... Detected portion, 13 ... Light emitting element, 14 ... Light receiving element.

Claims (1)

(57) [Claims] 1. A lens bobbin having an objective lens mounted on an upper surface thereof, a base end portion being fixed to a base, and a center of gravity of the lens bobbin including the objective lens being positioned substantially at the center of the lens bobbin. And four supporting members for supporting the lens bobbin so as to be displaceable in a direction parallel to the optical axis direction of the objective lens and in a direction orthogonal to the optical axis direction. Driving means for moving and operating in a direction parallel to the optical axis direction of the lens and in a direction orthogonal to the optical axis direction; and the objective positioned at the same height as the objective lens above the center of gravity of the lens bobbin. A detection member having a detection portion parallel to the optical axis of the lens and attached to the lens bobbin; and a position for detecting a displacement of the detection portion in a direction orthogonal to an optical axis direction of the objective lens. An objective lens driving device comprising: a position detection unit.