JP2000242942A - Supporting structure for optical head actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supporting structure for making difficult the generation of any radial tilt at the time of the movement of a lens holder to a tracking direction or a focusing direction, and for suppressing the movement of laser beam spots on a recording medium in the rotation of an objective lens for the purpose of the correc tion of aberration due to the inclination of an optical axis. SOLUTION: In the supporting structure of an optical head actuator, a lens holder 4 for holding an objective lens 5 is constituted so as to be driven to a tracking direction and a focusing direction to a discoid recording medium by an electromagnetic driving means, and so as to be suspended and supported through four elastic supporting members 3A and 3B extended to an almost tangential direction to the discoid recording medium as a whole. In this case, the four elastic supporting members 3A and 3B having almost the same length are arranged as pairs to the tracking direction while an almost parallel relation is maintained to the focusing direction, and when the two elastic supporting members near the discoid recording medium are defined as the first elastic supporting members, and the other two are defined as the second elastic supporting members, the interval of the first elastic supporting members is made different from the interval of the second elastic supporting members.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compact disc (CD) and a digital versatile disc (DVD).
The present invention relates to a support structure for an optical head actuator for recording and reproducing information on and from a recording medium such as an optical disk such as an optical disk and a magneto-optical disk such as a mini disk (MD).

[0002]

2. Description of the Related Art As a conventional optical head actuator, for example, there is one shown in a perspective view in FIG.
Such an optical head actuator adopts a moving coil method as a driving method, and a supporting structure includes:
This is a so-called four-wire supporting type. That is, this optical head actuator is, for example, Cu-B
Four elastic members 3 made of e-alloy, Cu-P alloy, or the like are protruded from the support member 1A from, for example, positions near the vertices of a rectangle separated by a predetermined distance. Numeral 3 extends toward the lens holder 4 and suspends and supports the lens holder 4 at its free end so that the objective lens 5 held by the lens holder 4 is
It has a structure that can move in the focusing direction (Z-axis direction) and the tracking direction (Y-axis direction).

In such an optical head actuator, a drive device for moving the objective lens 5 in a tracking direction and a focusing direction is provided as shown in FIG. This objective lens driving device is disposed on the base member 1B side to which the support member 1A is fixed.
For example, a driving permanent magnet made of Nd-Fe-B alloy or the like
2, a tracking coil 6 and a focusing coil 7 disposed on the lens holder 4 side.

That is, the two driving permanent magnets 2 are arranged to face each other with a gap therebetween, and the respective magnetic poles on the back side are
For example, iron (Fe), nickel (Ni), cobalt (C
o) or an alloy containing them, or ferrite, and are connected by a soft magnetic yoke 8 having a substantially U-shape. Then, a tracking coil 6 for driving the objective lens 5 in the radial direction and a focus on the information pit surface of the disk are provided for the purpose of positioning the optical axis on the center line of a predetermined information pit of the disk (not shown). A focusing coil 7 for driving the objective lens 5 in the focusing direction is wound around a bobbin 9 made of resin or the like for the purpose of causing the objective lens 5 to move between the facing magnetic poles of the two driving permanent magnets 2. , The bobbin 9 is fitted and fixed to the lens holder 4.

According to such a configuration, when the tracking coil 6 is energized, the interaction between the current flowing in the Z-axis direction and the magnetic field oriented in the X-axis direction by the driving permanent magnet 2 causes the tracking coil 6 to be driven. Is applied with a force in the Y-axis direction. As a result, the force in the Y-axis direction can displace the lens holder 4 and thus the objective lens 5 in the Y-axis direction, that is, in the radial direction of the disk.

Similarly, when the focusing coil 7 is energized, the interaction between the current flowing in the Y-axis direction and the magnetic field oriented in the X-axis direction by the driving permanent magnet 2 causes the focusing coil 7 to pass through the Z-axis. Directional force acts, and as a result, the force can displace the lens holder 4 and thus the objective lens 5 in the Z-axis direction, that is, the focusing direction orthogonal to the recording surface of the disk.

[0007]

The above-described conventional support structure for an optical head actuator does not have a sliding shaft like a shaft sliding type optical head actuator which is another typical support structure. No friction occurs with the sliding shaft when the lens holder is displaced, so that smooth and high-resolution driving is possible. However, on the other hand, since there is no stable guide like the shaft, the structure is liable to rotate around the axis in the tangential direction, that is, radial tilt.

That is, for example, if the center of the driving force of the tracking coil 6 and / or the focusing coil 7 or the center of gravity of the entire lens holder 4 including the objective lens 5 is shifted from the center of support of the elastic support member 3,
The interaction between the driving force or gravity in the tracking direction or the focusing direction and the restoring force of the elastic support member generates a rotational moment, and the four elastic support members 3 are twisted around the axis in the tangential direction. 4 rotates. In the case of the moving coil system, the center of the driving force in the tracking direction and the focusing direction and the center of gravity of the entire lens holder 4 coincide with the support center of the elastic support member 3 at the neutral position where the driving force does not act on the lens holder 4. However, if the lens holder 4 is moved from the neutral position by applying a driving force in the tracking direction or the focusing direction, the relative positions of the tracking coil 6 and the focusing coil 7 with respect to the driving permanent magnet 2 change. The applied magnetic field also moves in the tracking coil 6 and the focusing coil 7, and the position of the center of these driving forces changes in the lens holder 4. For this reason, even in such a case, an interaction between the driving force in the tracking direction or the focusing direction and the restoring force of the elastic support member 3 generates a rotational moment, and the four elastic support members 3 move in the axial direction in the tangential direction. Twist around,
The lens holder 4 and the objective lens 5 will rotate.

In addition, due to the deformation or fixation of the disk-shaped recording medium, such as warpage, the medium surface is often inclined in the radial direction with respect to the optical axis of the objective lens.

As described above, when the objective lens 5 rotates, the optical axis is tilted, and various aberrations such as coma occur on the wavefront of the laser light applied to the disk-shaped recording medium. A side rope is generated in the spot and crosstalk from the adjacent track is likely to occur,
Problems such as the occurrence of a track offset and the inability to perform proper track control, and the reduction of the reflection intensity and the reduction of the information reading signal level occur, resulting in a reduction in the S / N ratio as the performance of the optical head. Will occur.

To cope with such a problem, Japanese Patent Application Laid-Open No. 9-231595 proposes an optical head actuator having a structure in which a tilt correcting means is provided in the lens holder 4. For example, as shown in FIG. 7, a pair of tilt correction coils 60 are provided on a side surface 4b of the lens holder 4 opposed in the Y-axis direction. Correspondingly, a side yoke 80 as a magnetic path guide is formed in each of the magnetic poles on the back side, so that the tilt correcting permanent magnets 20 of opposite polarities are symmetrical in the magnetic field application direction in the figure. It is arranged. In such an optical head actuator, the lens holder 4 is supported in parallel with the X axis by applying a tilt drive signal so that the current directions of the wires at the symmetric positions in the right and left tilt correction coils 60 become the same. Since the lens can be driven to rotate around the center, and thus the objective lens 5 can be rotated, the aberration caused in the light beam for various reasons described above is corrected to solve the problem caused by the aberration. Things.

However, when the objective lens 5 is rotated about the support center as described above, the rear principal plane of the objective lens 5 is closer to the disk-shaped recording medium than the center of rotation, and as shown in FIG. In accordance with the rotation, the spot position of the laser beam formed on the disc is changed to To.
From Ty to Ty, that is, it moves by Δty in the radial direction.

The movement amount of the spot of the laser beam Δty
Is large enough to jump over a plurality of tracks depending on the degree of correction. In order to return the spot position of the laser beam, a tracking error signal generated due to the rotation operation of the objective lens 5 is detected. In accordance with the magnitude of the tracking error signal, a driving current is supplied to the tracking coil 6 by the tracking servo circuit to move the objective lens 5 in the tracking direction.

As a result, a time lag occurs between the movement of the spot position of the laser beam and the actual tracking operation starting from the detection of the tracking error signal, which delays the operation, and acts as a disturbance to the tracking servo operation. And the control operation becomes unstable, for example, the servo gain of the control circuit becomes insufficient.

An object of the present invention is to provide a support structure for an optical head actuator which can solve the above-mentioned problems of the prior art, and to provide a radial structure for moving a lens holder in a tracking direction or a focusing direction. While providing a support structure that is unlikely to cause tilt,
Provide a support structure that suppresses the movement of a laser beam spot on a recording medium during the rotation operation of an objective lens for the purpose of correcting aberrations caused by an optical axis inclination such as an inclination of an objective lens and a warp of a disk-shaped recording medium. It is assumed that.

[0016]

Means for Solving the Problems As a result of earnest studies to achieve the above-mentioned objects, the inventors have conceived of an invention having the following contents as its gist. That is, the support structure of the optical head actuator according to the present invention is such that the lens holder holding the objective lens can be driven in the tracking direction and the focusing direction with respect to the disk-shaped recording medium by the electromagnetic drive means with respect to the support member. The support structure of an optical head actuator suspended and supported via four elastic support members extending in a substantially tangential direction with respect to the linear recording medium has substantially the same length and is substantially in the focus direction. While maintaining the parallel relationship, the four elastic support members arranged in pairs in the tracking direction are used as two first elastic support members near the disk-shaped recording medium, and the other two are used as the first elastic support members. When the second elastic support member is used, each tracking direction of the first elastic support member and the second elastic support member In which characterized in that a difference in distance.

In the supporting structure of the optical head actuator according to the present invention, it is desirable that the distance between the first elastic supporting members in the tracking direction is larger than the distance between the second elastic supporting members in the tracking direction. In this case, it is a preferred embodiment that the tangential rotation axis of the lens holder by the four elastic support members is positioned on the rear main plane of the objective lens.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the present invention.
FIG. 2 is a perspective view showing the embodiment, and FIG. 2 is an operation explanatory diagram. 1 and 2, the same parts as those in the conventional example are denoted by the same reference numerals.

The optical head actuator shown here is a so-called four-wire supporting type moving coil system similar to that described in the conventional example, and the supporting member 1A fixed to the base member 1B includes, for example, Cu. −
Four linear elastic support members made of a Be alloy, a Cu-P alloy, or the like, that is, first elastic support members 3A, 3A and second elastic support members 3B, 3B are located at predetermined intervals. Each elastic member is protruded and extends toward the lens holder 4. The free end of the elastic member suspends and supports the lens holder 4 so that the objective lens 5 held by the lens holder 4 is focused. The structure is such that it can move in the direction (Z-axis direction) and the tracking direction (Y-axis direction).

That is, the first elastic support members 3A, 3A
The pair of 3A and the pair of second elastic support members 3B and 3B
Have substantially the same length, and each has a tracking direction (Y
In the focusing direction (Z-axis direction), which is substantially parallel to the optical axis of the objective lens 5, and maintains the tangential direction (X-axis) of the disc-shaped recording medium (not shown). Direction). One end of each elastic support member includes a first elastic support member 3A of the disc-shaped recording medium closer, the distance L ₁ between 3A is a second elastic support member 3B of the base member 1B closer, than the distance L ₂ between 3B Is formed so as to form four vertices of an equilateral trapezoid on the support 1A so that the lens holder 4 is suspended and supported on the free end sides of the first and second elastic support members. I have.

In such an optical head actuator, a driving device for moving the objective lens 5 in the focusing direction and the tracking direction is provided. This objective lens driving device includes, for example, Nd-F disposed on the base member 1B side to which the support member 1A is fixed.
It comprises a driving permanent magnet 2 made of e-B alloy or the like, a tracking coil 6 and a focusing coil 7 arranged on the lens holder 4 side.

That is, the two driving permanent magnets 2 are arranged to face each other with a gap therebetween, and the respective magnetic poles on the back side are
For example, iron (Fe), nickel (Ni), cobalt (C
o) or an alloy containing them, or ferrite, and are connected by a soft magnetic yoke 8 having a substantially U-shape. Then, a tracking coil 6 for driving the objective lens 5 in the radial direction and a focus on the information pit surface of the disk are provided for the purpose of positioning the optical axis on the center line of a predetermined information pit of the disk (not shown). A focusing coil 7 for driving the objective lens 5 in the focusing direction is wound around a bobbin 9 made of resin or the like for the purpose of causing the objective lens 5 to move between the facing magnetic poles of the two driving permanent magnets 2. , The bobbin 9 is fitted and fixed to the lens holder 4.

According to such a configuration, when the tracking coil 6 is energized, the interaction between the current flowing in the Z-axis direction and the magnetic field oriented in the X-axis direction by the driving permanent magnet 2 causes the tracking coil 6 to move. Is applied with a force in the Y-axis direction. As a result, the force in the Y-axis direction can displace the lens holder 4 and thus the objective lens 5 in the Y-axis direction, that is, in the radial direction of the disk.

Similarly, when the focusing coil 7 is energized, the Z-axis is applied to the focusing coil 7 by the interaction between the current flowing in the Y-axis direction and the magnetic field oriented in the X-axis direction by the driving permanent magnet 2. Directional force acts, and as a result, the force can displace the lens holder 4 and thus the objective lens 5 in the Z-axis direction, that is, the focusing direction orthogonal to the recording surface of the disk.

[0025] In the support structure of the optical head actuator according to the present invention as described above, the pair of first elastic supporting member 3A, 3A distance, i.e. the distance L ₁ in the tracking direction, a second elastic support of the pair Member 3B, 3B
, That is, a difference from the distance L _{2 in the} tracking direction. In this embodiment, L ₁ > L ₂ is set. According to such a structure, as shown in FIG. 2, the rotation center of the lens holder 4 with respect to the torque around the axis in the tangential direction is at the position indicated by O, and the first elastic support members 3A, 3A and the second Since the elastic support members 3B and 3B are located on the circumference of the virtual circle C centered on the central axis O, the first elastic support members 3A and 3A and the second elastic support member 3B , 3B become longer and the first distance to rotation about an axis in the tangential direction increases.
Elastic support members 3A, 3A and second elastic support member 3
The restoring torque by B and 3B can be increased, and as a result, radial tilt can be suppressed.

Further, the first elastic support member 3A as described above, the distance L ₁ of 3A second elastic support member 3B, 3B
If set larger than the distance L ₂ of the first elastic support member 3A for the driving force in the tracking direction and focus direction, 3A and second resilient supporting member 3B, 3
Even if the support center Q by B is on the side farther away from the disk-shaped recording medium than the rear main plane of the objective lens 5, the center axis O for rotation in the tangential direction is equal to the first and second elastic support members. Since this is the center of the virtual circle C on the circumference, the center axis O of rotation can be made closer to the rear main plane of the objective lens 5. For this reason, when the lens holder 4 is rotated around the axis in the tangential direction by tilt correction means or other means, the movement of the spot position of the laser beam formed on the disk-shaped recording medium in the track width direction is reduced. be able to.

Furthermore, the first elastic support member 3A, the distance L ₁ of 3A second elastic support member 3B, by suitably large relative distance L ₂ of 3B, as shown in FIG. 3, the lens The rotation center O of the holder 4 can be positioned on the rear main plane H of the objective lens 5. Tilt correcting means (not shown) is provided and operated on the lens holder 4 to operate the lens holder 4. Is rotated around the axis in the tangential direction, it becomes difficult for the spot position of the laser beam passing through the objective lens 5 to move in the track width direction, so that the center T of the predetermined track on the information recording surface D of the disk is changed.
o can be reliably captured. In this embodiment, although the interval L ₁ of the first elastic support member closer to the disc-shaped recording medium, is set larger than the distance L ₂ of the second elastic support member, conversely, the second elastic support even if the distance L ₂ of the member is set larger than the interval L ₁ of the first elastic support member, it is possible to obtain an effect of hardly occurs radial tilt.

The above-described supporting structure is an application of the present invention to a moving coil type optical head actuator. However, the present invention is not limited to such a type, and the driving permanent magnet 2 as shown in FIG. Needless to say, the present invention can be applied to a moving magnet type optical head actuator in which a focusing coil and a tracking coil are provided on the base member 1B side on the holder 4 side.

[0029]

By providing a difference between the interval between the pair of first elastic support members and the interval between the pair of second elastic support members, rotation about the axis in a tangential direction with respect to the disk-shaped recording medium is achieved. The first elastic support member and the second
The restoring torque by the elastic support member can be increased, and as a result, radial tilt can be hardly generated, and stable suspension support can be achieved. By increasing the distance L ₁ between the first elastic support member than the distance L ₂ of the second elastic support member, since the tangential direction of the rotation axis of the lens holder is disc-shaped recording medium toward the rear side principal When the lens holder is rotated around the axis in the tangential direction, the movement of the spot position of the laser beam formed on the disk-shaped recording medium in the track width direction can be reduced when the lens holder is rotated about the axis in the tangential direction. it can.
Furthermore, by appropriately expanding the distance L ₁ of the first elastic support member with respect to the spacing L ₂ of the second elastic support member,
Since the rotation center O of the lens holder 4 can be formed so as to be located on the rear main plane H of the objective lens 5, when the lens holder is rotated around the axis in the tangential direction, the rotation of the lens holder 4 on the disk-shaped recording medium is stopped. , The amount of movement of the spot position of the laser beam formed in the direction of the track width can be further reduced. Therefore, a stable tracking servo operation can be performed and the aberration is small, so that an optical signal can be detected with a high S / N ratio.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory diagram in another embodiment of the present invention.

FIG. 4 is a plan view showing still another embodiment of the present invention.

FIG. 5 is a perspective view showing a conventional example.

FIG. 6 is a perspective view of a main part showing a conventional example.

FIG. 7 is a diagram showing a conventional example.

FIG. 8 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

 1A Supporting Member 1B Base Member 2 Driving Permanent Magnet 3A First Elastic Supporting Member 3B Second Elastic Supporting Member 4 Lens Holder 5 Objective Lens 6 Tracking Coil 7 Focusing Coil 8 Soft Magnetic Yoke

Claims (3)

[Claims] 1. A lens holder for holding an objective lens, which can be driven in a tracking direction and a focusing direction with respect to a disk-shaped recording medium by an electromagnetic driving means with respect to a supporting member, and which is substantially tangential with respect to the disk-shaped recording medium as a whole. In a supporting structure of an optical head actuator suspended and supported via four elastic supporting members extending in a primary direction, the optical head actuator has a substantially same length and a tracking direction while maintaining a substantially parallel relationship in a focusing direction. In the case where the four elastic supporting members arranged in pairs are used as two elastic supporting members near the disk-shaped recording medium as the first elastic supporting member and the other two as the second elastic supporting members. An optical head, characterized in that a difference is provided between the first elastic support member and the second elastic support member in the respective tracking directions. The support structure of the actuator. 2. The support structure for an optical head actuator according to claim 1, wherein the distance between the first elastic support members in the tracking direction is larger than the distance between the second elastic support members in the tracking direction. . 3. The optical head according to claim 2, wherein a rotation axis in a tangential direction of the lens holder by the four elastic support members is positioned on a rear main plane of the objective lens. Actuator support structure.