JP2000067443A - Optical head actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make correctable aberrations by linearly moving an objective lens in Y-axis direction and Z-axis direction, rotationally driving the lens around the axis parallel with X-axis and interlocking the objective lens to rotational driving in such a direction where the movement of a light spot in the Y-axis direction on a disk surface arising accompanying the rotational driving of the objective lens is offset. SOLUTION: When a coil 19 for tilt correction is energized, both of a first supporting member 13 and a second supporting member 14 move parallel in the same direction parallel with the Y-axis so as to offset the moving quantity on the basis of a fixing member 12. The ratio ΔT1/ΔT2 of the moving quantity ΔT1 of the first supporting member 13 and the moving quantity ΔT2 of the second supporting member 14 is determined by the relation ΔX1/(ΔX1+ΔX2) between the spacing ΔX1 between a first hinge 16 and a second hinge 17 and the spacing ΔX2 between the second hinge 17 and a third hinge 18. The objective lens 5 is rotated around the axis parallel with the X-axis by the parallel movement of the first supporting member 13 and the second supporting member 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact disc (CD), a digital versatile disc (DV).
The present invention relates to an optical head actuator used for recording and reproducing information on a recording medium such as an optical disk such as D) or 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 FIG. Such an optical head actuator is a so-called 4-wire supporting type moving coil type, and the base member 1B side of the support member 1A is made of, for example, Nd-Fe-B alloy. Drive permanent magnet 2 is provided, and the support member 1A
For example, four elastic members made of a Cu-Be alloy, a Cu-P alloy, or the like, that is, spring members 3 are supported at predetermined intervals such as vertices of a rectangle, for example. The lens holder 4 extends toward the lens holder 4 and supports the lens holder 4 at its free end. The objective lens 5 held by the lens holder 4 is moved in the focus direction (Z axis direction) and the tracking direction (Y direction). Axial direction)
And a movable structure.

As a driving means of the lens holder 4, a driving permanent magnet 2, a tracking coil 6 and a focusing coil 7 are used. In FIG. 6, a main part of such a driving means is shown in detail in a perspective view. It is. The two driving permanent magnets 2 are opposed to each other with a gap therebetween, and the magnetic poles on the back side are made of, for example, iron, nickel, cobalt, an alloy containing them, or ferrite,
The sections are connected by a soft magnetic yoke 8 having a substantially U-shaped cross section. Tracking for driving the objective lens 5 in the track width direction (Y-axis direction) in order to position the optical axis of the objective lens 5 on the center line of a predetermined information pit of a disk (not shown) as a recording medium. Coil 6
And a focusing coil 7 for driving the objective lens 5 in the focusing direction (Z-axis direction) for the purpose of focusing on the information pit surface of the disk are wound around a bobbin 11 made of resin or the like. ing. The bobbin 11 is fitted and fixed to the lens holder 4 such that each coil is located between the opposing magnetic poles of the two driving permanent magnets 2.

When the tracking coil 6 is energized, the current flowing in the Z-axis direction and the X
The interaction with the magnetic field oriented in the axial direction causes a force in the Y-axis direction to act on the tracking coil 6. As a result, the force in the Y-axis direction can displace the lens holder 4 and thus the objective lens 5 in parallel with the track width 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 to occur.
Since a force in the Z-axis direction acts on the casing coil 7, the force in the Z-axis direction is consequently applied to the lens holder 4.
Consequently, the objective lens 5 can be displaced in the Z-axis direction, that is, in the optical axis direction perpendicular to the recording surface of the disk.

The above-described optical head actuator has a suspension support structure using four spring members 3, and therefore, for example, a shaft-sliding type optical head actuator which is another typical support structure is used. Although the lens holder does not generate friction with the shaft when displacing the lens holder, it can be driven smoothly and with high resolution, but because there is no stable guidance like the shaft, around the axis parallel to the X axis The structure is easy to rotate.

For example, if the center of the driving force by the tracking coil 6 or the focusing coil 7 is shifted from the center of gravity of the entire lens holder 4 including the objective lens 5 or the like, or is shifted from the center of support by the spring member 3, the tracking direction is changed. Since a torque is generated between the driving force in the focusing direction and the restoring force of the gravitational force or the elastic member, the lens holder 4 rotates around an axis parallel to the X axis. In the neutral position where no driving force acts on the lens holder 4, the center of the driving force in the tracking direction or the focusing direction coincides with the center of gravity of the entire lens holder 4 or the support center of the elastic member 3. Also, when a driving force is applied in the tracking direction or the focusing direction to move the lens holder 4 from the neutral position, the relative positions of the tracking coil 6 and the focusing coil 7 with respect to the driving permanent magnet 2 are changed. Changes, the position of the center of these driving forces fluctuates in the lens holder 4. Even in such a case, the tracking coil 6
Also, the lens holder 4 may rotate around an axis parallel to the X-axis due to the driving force of the focusing coil 7. Further, the disk surface is often inclined in the radial direction with respect to the optical axis of the optical head due to deformation such as warpage of the disk or a fixing problem.

When such an inclination of the optical axis occurs, the laser
Various aberrations, including coma, are caused on the wavefront of the light. When aberration occurs, side lobes are formed in the spot of laser light applied to the disk surface, and crosstalk from adjacent tracks is likely to occur, or track offset occurs, so that proper track control cannot be performed. In addition, since the information reading signal level is reduced due to the reduction in the reflection intensity of the laser light from the disk surface, the S / N ratio as the performance of the optical head is reduced.

In order to cope with such a problem, for example, in Japanese Patent Laid-Open No. Hei 9-231595, as shown in FIG.
b, a pair of tilt correction coils 60 is provided, and side yokes 80 as magnetic path guides are formed on the magnetic poles on the back sides of the upper and lower sides of the tilt correction coils 60, respectively. There has been proposed an optical head actuator having a configuration in which a magnetic tilt correcting permanent magnet 20 is provided so that the direction of application of a magnetic field is symmetrical in the drawing. In such an optical head actuator, the lens holder 4 is parallelized with the X axis by applying a tilt drive signal so that the current directions of the wires located at symmetric positions in the left and right tilt correction coils 60 are the same. It is intended to solve the problem caused by the aberration by correcting the aberration caused in the light beam due to the various reasons described above because it can be driven to rotate around the center of support and thus the objective lens 5 can be rotated. It is.

[0009]

However, when the objective lens 5 is rotated around the support center as described above,
As shown in FIG. 8, according to the rotation, the spot position of the laser light formed on the disk is approximately T0.
From Ty to Ty in the radial direction. The movement amount Δty of the spot of the laser light often becomes large enough to jump over a plurality of tracks depending on the degree of correction. In order to pull back the spot position of the laser light, a tracking error signal generated due to the rotation of the objective lens 5 is detected, and then a tracking error signal is generated in accordance with the magnitude of the tracking error signal.
Since it is necessary to supply a drive current to the tracking coil 6 by the servo circuit and move the objective lens 5 in the tracking direction, the operation starts from the movement of the spot position of the laser light and the detection of the tracking error signal. A time lag occurs between the actual tracking operation and the operation is delayed. For this reason, the control operation becomes unstable, for example, it acts as a disturbance to the tracking servo operation, or the servo gain of the control circuit becomes insufficient.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to correct aberrations caused by optical axis tilt such as tilt of an objective lens and warpage of a disk. During the rotation of the objective lens, the movement of the spot position of the laser light on the disk is suppressed to stabilize the tracking servo operation, and light capable of detecting an optical signal having a small S / N ratio and a small aberration. An object of the present invention is to provide a head actuator.

[0011]

To achieve the above object, an optical head actuator according to claim 1 of the present invention.
In the XYZ rectangular coordinate system, the objective lens opposes the disk surface disposed substantially parallel to the XY plane, a lens holder for holding the objective lens, and the lens holder as a whole extending substantially in the X-axis direction. A supporting member that is displaceably supported via a plurality of existing spring members, first electromagnetic driving means for moving the lens holder substantially in the Y-axis direction and the Z-axis direction, and a lens holder substantially parallel to the X-axis. A second electromagnetic driving means for rotating and driving around the axis, and in conjunction with the operation of the second electromagnetic driving means, move the light spot in the Y-axis direction of the light spot generated on the disk surface with the rotation of the lens holder. Means for linearly moving the lens holder in such a direction as to cancel each other.

Further, the optical head actuator according to a second aspect of the present invention is provided with an optical head actuator in an XYZ rectangular coordinate system.
An objective lens opposed to a disk surface disposed substantially parallel to the Y plane, a lens holder for holding the objective lens, and a plurality of spring members extending through the lens holder substantially in the X-axis direction as a whole A support that supports as much as possible,
First electromagnetic driving means for moving the lens holder substantially in the Y-axis direction and the Z-axis direction, respectively;
A fixing member having a plane substantially parallel to the plane, and a pair of connections connected to a surface substantially parallel to the YZ plane of the fixing member via a pair of first hinges extending in the Z-axis direction at a predetermined interval. Y and a member arranged between the member and the pair of connecting members.
A first supporting member connected to the pair of connecting members via a pair of second hinges extending in the Z-axis direction near both ends in the axial direction, and a first supporting member between the pair of connecting members. And a second support member connected to a pair of connecting members via a pair of third hinges extending in the Z-axis direction near both ends in the Y-axis direction,
One end of at least one pair of the first spring member and at least one pair of the second spring member constituting the spring member is supported by the first support member and the second support member, respectively, and the other end is a lens. The first spring member is connected to the lens holder, and the connection position between the first spring member and the lens holder is closer to the disk than the connection position between the second spring member and the lens holder. Support members,
A second electromagnetic driving means for moving any of the second support members in the Y-axis direction.

According to the second aspect of the present invention, the position where the first spring member is supported by the first support member and the position where the second spring member is supported by the second support member are substantially parallel to the YZ plane. It is characterized by being formed on the same surface.

According to the second or third aspect of the present invention, the second electromagnetic driving means is provided between the fixed member and the first supporting member, and between the first supporting member and the second supporting member. And between the fixing member and the second support member.

Further, the optical head actuator according to the fifth aspect of the present invention is an optical head actuator comprising: an XYZ orthogonal coordinate system;
An objective lens opposed to the disk surface disposed substantially parallel to the Y plane, a lens holder for holding the objective lens, and a plurality of spring members extending substantially in the X-axis direction as a whole with the lens holder. A support for displaceably supporting, a first electromagnetic driving means for moving the lens holder substantially in the Y-axis direction and the Z-axis direction, and a second driving means for rotating the lens holder about an axis substantially parallel to the X axis. At the same time as the operation of the electromagnetic drive means and the second electromagnetic drive means, a drive signal for canceling the movement of the light spot on the disk surface in the Y-axis direction due to the rotation of the lens holder to the first electromagnetic drive means. And means for supplying the same.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective view showing a main part of a first embodiment of the present invention, and portions similar to those of the conventional example as shown in FIGS. 5 and 6 are omitted for simplification. In FIG. 1, reference numeral 12 denotes XY
In a Z coordinate system, a vertical surface 12a extending in the Y-axis direction and having an L-shaped cross section and substantially parallel to the YZ plane and XY
It has a bottom surface 12b substantially parallel to a plane. The lens holder 4 holding the objective lens 5 (not shown) is connected to a pair of support members 13 and 14 via a plurality of spring members 31a and 31b, which will be described later, and each support member 13 and 14 is connected to a pair of connection members. It is supported so as to be displaceable with respect to the fixed member 12 via the reference numeral 15. That is, the fixing member 12 constitutes a supporting body that displaceably supports the lens holder 4 together with the pair of supporting members 13 and 14 and the pair of connecting members 15.

In this optical head actuator, the permanent magnet 2, the tracking coil 6, and the electromagnetic driving means for linearly moving the lens holder 4 with respect to the fixed member 12 substantially in the Y-axis direction and the Z-axis direction, respectively. The arrangement of a focusing coil 7 (both not shown) is the same as that of the conventional example.

As shown in FIG. 1, a predetermined distance is provided between the vertical surface 12a of the fixing member 12 near both ends in the Y-axis direction and near one end of the pair of connecting members 15 in the X-axis direction. The fixing member 12 and the pair of connecting members 15 are connected via a pair of first hinges 16 extending in the direction of the arrow. The first support member 13 and the second support member 14 are arranged between the pair of connection members 15 at a predetermined interval. The first support member 13 is connected to a pair of connecting members 15 via a pair of second hinges 17 extending in the Z-axis direction in the vicinity of both ends in the Y-axis direction. Are connected to a pair of connecting members 15 via a pair of third hinges 18 extending in the Z-axis direction near both ends in the Y-axis direction. In this manner, the fixing member 12, the first support member 13, and the second support member 14 are arranged so as to be adjacent to each other in the X-axis direction, and the pair of connecting members 15 connect the pair of first hinges 16 to each other. The first support member 1 can rotate around an axis parallel to the Z-axis at the center.
Both the third and second support members 14 can be translated in a direction parallel to the Y axis.

The first hinge 16 in this embodiment,
The second hinge 17 and the third hinge 18 are both Z
It extends continuously in the axial direction, but is not limited to this.
It may be configured to be divided into a plurality of parts at an intermediate position in the axial direction. One end of each of a pair of first spring members 31a extending substantially in the X-axis direction is supported by the first support member 13, and a pair of second spring members 31b extending substantially in the X-axis direction is formed. One end is supported by the second support member 14, and the other end side of the first and second spring members 31a and 31b is connected to the lens holder 4 so as to be suspended and supported. The position where the first spring member 31a is supported by the first support member 13 and the position where the second spring member 31b is supported by the second support member 14 are on the same plane substantially parallel to the YZ plane. The connection position between the lens holder 4 and the first spring member 31a is closer to the disk (upward in FIG. 1) than the connection position between the lens holder 4 and the second spring member 31b. You.

Further, in this optical head actuator, as shown in FIG. 2, the first and second support members 13 and 14 are moved in a direction parallel to the Y axis. Electromagnetic drive means is provided. This electromagnetic drive means is composed of a tilt correction coil 19 disposed on the vertical surface 12a of the fixed member 12, and a tilt correction permanent magnet 21 disposed on the side surface of the first support member 13 opposed thereto. , Both are arranged facing each other with an appropriate gap therebetween. The electromagnetic driving means constituted by such a tilt correction coil 19 and tilt correction permanent magnet 21 is not limited to between the fixed member 12 and the first support member 13 illustrated, Between the second support member 14,
And / or at least one between the fixing member 12 and the second support member 14.

When the tilt correction coil 19 is energized, the first support member 1
The third support member 14 and the second support member 14 are moved in parallel in the same direction parallel to the Y axis so that the movement amounts are different. The ratio ΔT1 / ΔT2 of the movement amount ΔT1 of the first support member 13 and the movement amount ΔT2 of the second support member 14 is equal to the first hinge 16
The distance between the second hinge 17 and the second hinge 17 and the distance between the second hinge 17 and the third hinge 18 are defined as ΔX1 and ΔX2, respectively, and are determined by ΔX1 / (ΔX1 + ΔX2). The parallel movement of the first support member 13 and the second support member 14 allows the objective lens 5 to be rotated around an axis parallel to the X axis. become. Further, these moving directions are opposite to the moving directions of the laser light spot due to the rotation of the objective lens 5, and by appropriately setting ΔX1 and ΔX2,
Since the movement of the objective lens 5 and the movement of the laser light spot can be offset, the movement of the laser light spot on the disk can be effectively suppressed.

The movement of the laser beam spot due to the rotation of the objective lens will be described with reference to FIG. The spot position of the laser light having passed through the objective lens 5 is located at the center T0 of a predetermined track on the information recording surface D of the disk.
The first support member 13 and the second support member 14 are moved in parallel in the Y-axis direction so as to be located close to each other, and the objective lens 5 is moved to the first support member 13 and the second support member 14. The laser light spot is moved in the opposite direction while moving in the same direction, that is, the rotation center O of the objective lens 5 is located near the intersection of the rear principal plane H of the objective lens 5 and the optical axis. To offset the spot movement of the laser light as a whole. In addition, these series of operations do not perform the servo operation after the movement of the laser beam spot, that is, the tracking error signal is detected, but the parallel movement and rotation of the objective lens 5 are simultaneously linked. Therefore, a time lag hardly occurs. Thereby, the tracking servo operation is stabilized, the generated aberration is small, and the detection of the optical signal with a high S / N ratio becomes possible.

FIG. 4 is a block diagram showing the configuration of the second embodiment of the present invention. The optical head actuator in this embodiment also has an XYZ orthogonal coordinate system.
It enables linear movement of the objective lens facing the disk surface disposed substantially parallel to the Y plane in substantially the Y-axis direction and the Z-axis direction, and rotational driving about an axis substantially parallel to the X-axis. In this configuration, the objective lens is linearly moved in conjunction with the rotation drive in such a direction as to offset the movement of the light spot on the disk surface in the Y-axis direction caused by the rotation drive.

In the case of this embodiment, the above-mentioned operation is performed electrically, and the configuration of the optical head actuator is, for example, the same as that of the conventional example described with reference to FIGS. Can be used. To describe the application to an optical head actuator having a conventional structure, a tilt error signal SK corresponding to the inclination of a disk or the like is input to a tilt drive circuit 33, and a correction current based on the tilt error signal SK is used as a tilt current in FIG. The lens holder 4 is rotated about an axis substantially parallel to the X axis by the interaction between the correction current supplied to the correction coil 60 and the magnetic field generated by the tilt correction permanent magnet 20, thereby rotating the objective lens 5. Let it. Tilt error signal S
K is also input to the tracking drive circuit 32 to which the tracking error signal TE is input at the same time, and the drive current based on the tracking error signal TE and the tilt error signal SK is supplied to the tracking coil 6 in FIG.
And the objective lens 5 is moved in the direction opposite to the direction of movement of the laser light spot, so that the movement of the laser light spot accompanying the rotation of the objective lens 5 is offset. Things. Accordingly, also in this embodiment, since the parallel movement and the rotation of the objective lens 5 are operated simultaneously in conjunction with each other, a time lag hardly occurs, and the tracking lens is not used.
Operation is stabilized, the generated aberration is small, and the S / N is high.
It is possible to detect an optical signal having a ratio.

In the first embodiment, each of the spring members 31a and 31b may be formed as two or more pairs of elements. Further, the spring members 31a and 31b need not necessarily be parallel to each other. Also, the extending direction of each spring member is X
It does not need to be parallel to the axis, and may extend in the X-axis direction as a whole toward the lens holder. The technique described above works effectively whether or not each is parallel. Further, the arrangement relationship of the tilt driving permanent magnet and the solenoid coil is not limited to the illustrated one, and the solenoid coil may be disposed on the movable member side and the tilt driving permanent magnet may be disposed on the fixed member side. In the first and second embodiments, the optical head actuator
Needless to say, the method is applicable and effective to both the moving coil type and the moving magnet type. Furthermore, other than the technology described here in the second embodiment,
Of course, it is also possible to apply the present invention to another configuration in which the objective lens 5 is mechanically rotated.

[0026]

As described above, according to the optical head actuator of the present invention, the objective lens is linearly moved substantially in the Y-axis direction and the Z-axis direction, and is rotated about an axis substantially parallel to the X-axis. In addition, the objective lens can be linearly moved in a direction such that the movement of the light spot on the disk surface in the Y-axis direction that is caused by the rotational driving of the objective lens is offset, in conjunction with the rotational driving of the objective lens. The objective lens can be corrected for the aberration caused by the tilt of the optical axis, the warpage of the disk, and the like. Further, since the tracking servo operation can be stabilized by suppressing the movement of the spot position of the laser light on the disk, it is possible to detect an optical signal having a small S / N ratio with little aberration. .

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a configuration of a main part of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a configuration of a main part in FIG. 1;

FIG. 3 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a block circuit diagram showing a configuration of a second embodiment of the present invention.

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

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

FIG. 7 is a schematic view showing a conventional tilt correcting means.

FIG. 8 is a diagram for explaining the operation of the conventional example.

[Explanation of symbols]

 Reference Signs List 4 Lens holder 5 Objective lens 12 Fixing member 13 First supporting member 14 Second supporting member 15 Connecting member 16 First hinge 17 Second hinge 18 Third hinge 19 Tilt correcting coil 21 Tilt correcting permanent magnet 31a, 31b Spring member

Claims (5)

[Claims] In an XYZ orthogonal coordinate system, an objective lens opposed to a disk surface disposed substantially parallel to an XY plane, a lens holder for holding the objective lens, and the lens holder as a whole substantially in the X-axis direction A first electromagnetic driving means for moving the lens holder substantially in the Y-axis direction and the Z-axis direction, respectively;
A second electromagnetic driving means for rotating and rotating about an axis substantially parallel to the axis, and a Y of a light spot generated on the disk surface with the rotation of the lens holder in conjunction with the operation of the second electromagnetic driving means. Means for linearly moving the lens holder in a direction to offset the movement in the axial direction. 2. In an XYZ orthogonal coordinate system, an objective lens opposed to a disk surface disposed substantially parallel to an XY plane, a lens holder for holding the objective lens, and the lens holder as a whole substantially in the X-axis direction. An optical head actuator comprising: a support member that is displaceably supported via a plurality of spring members extending in a direction; and first electromagnetic driving means that moves the lens holder substantially in the Y-axis direction and the Z-axis direction. In the above, the support is substantially fixed to the YZ plane of the fixed member via a pair of first hinges extending in the Z-axis direction at a predetermined interval, and a fixing member having a plane substantially parallel to the YZ plane. A pair of connecting members connected to the parallel surfaces; and a pair of second hinges disposed between the pair of connecting members and extending in the Z-axis direction near both ends in the Y-axis direction. A first support member connected to each of the pair of connection members, and a first support member disposed between the pair of connection members and adjacent to the first support member, and a Z-axis direction near both ends in the Y-axis direction. And a second support member connected to the pair of connecting members via a pair of third hinges extending to the at least one pair of the first spring member and the at least one pair of the spring members. Each end of the second spring member is
While each is supported by the first support member and the second support member, the other end is connected to the lens holder, and the connection position between the first spring member and the lens holder is the second position. A third member is disposed so as to be closer to the disc than the connection position between the spring member and the lens holder, and further moves one of the connecting member, the first support member, and the second support member in the Y-axis direction. An optical head actuator comprising two electromagnetic driving means. 3. The support position of the first spring member by the first support member and the support position of the second spring member by the second support member are formed on the same plane substantially parallel to the YZ plane. The optical head actuator according to claim 2, wherein 4. The apparatus according to claim 1, wherein the second electromagnetic driving means is provided between the fixing member and the first supporting member, between the first supporting member and the second supporting member, and between the fixing member and the second supporting member. 4. The optical head actuator according to claim 2, wherein the optical head actuator is provided at any position between the second support member and the second support member. 5. In an XYZ orthogonal coordinate system, an objective lens opposed to a disk surface disposed substantially parallel to an XY plane, a lens holder for holding the objective lens, and the lens holder as a whole substantially in the X-axis direction. A first electromagnetic driving means for moving the lens holder substantially in the Y-axis direction and the Z-axis direction, respectively;
A second electromagnetic driving means for rotationally driving about an axis substantially parallel to the axis, and a movement of the light spot on the disk surface in the Y-axis direction accompanying the rotation of the lens holder simultaneously with the operation of the second electromagnetic driving means And a means for supplying a drive signal to the first electromagnetic drive means to cancel the drive signal.