JPH03187024A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To control the movement of an objective lens due to inclination of a bobbin by supporting a member to be detected in a required position of the lens bobbin to which the objective lens is attached. CONSTITUTION:A lens bobbin 6 to which an objective lens 2 is attached is supported by a pair of flexible and elastic supporting arms 5 parallel with each other and is freely moved in directions of two orthogonal axes, namely, the direction of the optical axis of the lens 2 as the focusing direction and the direction of an arrow M orthogonal to the direction of the optical axis of the lens as the tracking direction through corresponding voice coils. The bobbin 6 is provided with a member 12 to be detected on the side and in the vicinity of the lens 2, and not only movement in orthogonal directions of the bobbin 6 but also inclination due to pitching DELTAP of the bobbin 6 is optically detected by a light emitting element and a light receiving element 14 provided in the direction orthogonal to the member 12, and the movement of the objective lens due to inclination of the bobbin for quick seek is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an objective lens drive device used in an optical pickup device that writes and/or reads information signals to and from an optical disk, magneto-optical disk, or the like.

B0 Summary of the Invention The present invention is used in an optical pickup device for writing and/or reading information signals on an optical disk, a magneto-optical disk, etc. In an objective lens drive device having a lens bobbin, a member to be detected is attached to the lens bobbin so as to be approximately on the side of the objective lens, and the optical axis of the objective lens of the member to be detected is determined using a position detection means. By detecting the displacement in the direction perpendicular to the direction, it is possible to detect the lateral movement of the objective lens due to the tilt of the lens bobbin. When the objective lens is displaced in a direction perpendicular to the optical axis of the objective lens, the movement of the objective lens is minimized.

BACKGROUND OF THE INVENTION Conventionally, disk devices have been proposed that record and/or reproduce information signals using disk-shaped recording media such as so-called optical disks and magneto-optical disks. Such a disk device includes a rotation operation mechanism that holds and rotates the disk-shaped recording medium, and a light beam that is focused and irradiated onto the disk-shaped recording medium to transmit an information signal to the disk-shaped recording medium. and an optical pickup device that performs writing and/or continuous output.

The optical pickup 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 toward the disk-shaped recording medium, and focuses it on the disk-shaped recording medium, and other components. and an optical device. The optical pickup device is supported so as to be movable in the radial direction of the disk-shaped recording medium over the inner and outer peripheries of the disk-shaped recording medium. That is, the disk device rotates the disk-shaped recording medium and moves the optical pickup device across the inner and outer peripheries of the disk-shaped recording medium, so that the optical pickup device rotates the disk-shaped recording medium and moves the optical pickup device over substantially the entire surface of the disk-shaped recording medium. It is configured to be able to irradiate a light beam.

By the way, when the disk-shaped recording medium is rotated by the rotational operation mechanism, it may cause core wobbling due to so-called surface wobbling or eccentricity.

Therefore, in order to always focus the light beam well on the recording track formed on the signal recording surface of the disk-shaped recording medium, the optical pickup device places the objective lens on the disk-shaped recording medium. It is equipped with an objective lens drive device that moves and operates to follow the objective lens.

The objective lens drive device movably supports the objective lens via a lens bobbin, and moves the lens bobbin in two axial directions: a direction perpendicular to the signal recording surface and a radial direction of the disk-shaped recording medium. configured to operate. Note that the direction perpendicular to the signal recording surface substantially coincides with the optical axis direction of the objective lens, and the radial direction of the disk-shaped recording medium is a lateral direction of the objective lens.

As this objective lens driving device, as shown in FIG.
It has been proposed that a lens bobbin 102 to which an objective lens 101 is attached is supported by a base 104 via two pairs of support arms 103. The support arm 10
3 is made of a member having appropriate flexibility and elasticity, such as a temporary spring or steel wire. The lens bobbin 102 is connected to the objective lens 101 indicated by arrow f in FIG.
The objective lens 101 is supported so as to be displaceable in two axial directions: the optical axis direction, that is, the focus direction, and the lateral direction perpendicular to the optical axis of the objective lens 101, that is, the tracking direction, indicated by the arrow in FIG.

This objective lens drive device includes a focus coil 105, a tracking coil 106, and a magnet 107 that constitute a magnetic circuit in order to move and operate the lens bobbin 102.

The above focus coil 105 and tracking coil 1
06 is attached to the outer side of the lens bobbin 102. The magnet 107 is placed on the base 10 so as to face each of the coils 105 and 106.
It is attached to 4.

In this objective lens drive device, the lens bobbin 102 is moved in the focus direction by supplying a focus drive current to the focus coil 105. In addition, the tracking coil 106
By supplying a tracking drive current to the lens bobbin 102, the lens bobbin 102 is moved in the tracking direction.

D0 invention tries to solve! ! By the way, in the objective lens driving device as described above, when the acceleration in the radial direction of the disk-shaped recording medium of the optical pickup device becomes large when performing a so-called high-speed seek, the lens bobbin 102 moves toward the base. 10
4, there is a risk of movement in the tracking direction. When the lens bobbin 102 moves in the tracking direction relative to the base 104 in this way, even when the optical pickup device is stopped,
There is a risk that the vibration of the lens bobbin 102 relative to the base 104 may continue.

When the lens bobbin 102 vibrates with respect to the base 104, information signals cannot be written and/or read from the disk-shaped recording medium properly. That is, after the optical pickup device is moved at high speed in the trunking direction, the lens bobbin 1
Since writing and/or reading of information signals cannot be performed until the vibration to the base 104 of 02 subsides, it is not possible to shorten the so-called access time even if the moving operation of the optical pick amplifier device is made faster. .

Conventionally, in order to restrict the vibration of the lens bobbin 102 as described above, as shown in FIG.
An objective lens driving device has been proposed that includes a position sensor 10B that detects the amount of movement of the object with respect to the base 104.

The position sensor 08 includes, for example, a light emitting element 109 such as a light emitting diode supported on the base 104, and a light emitting element 109 mounted on the base 104 via one end 102a of the lens bobbin 102. A light receiving element 110, such as a photodiode, that receives a light beam from the outside. In this position sensor 10B, when the lens bobbin 102 moves relative to the base 104, one end 102a of the lens bobbin 102 moves in the light beam emitted from the light emitting element 109, and the light receiving element 1
The output of 10 is configured to change. Therefore, in this position sensor 108, the light receiving element 1
Based on the output of 10, the movement of the lens bobbin 1°2 relative to the base body 104 can be detected.

In the objective lens drive device equipped with such a position sensor lO8, °ζ supplies a drive current to the tracking coil 106 based on the detection output obtained by the position sensor 108 when the optical pickup device is moved at high speed. By doing so, the lens bobbin 102
The above-mentioned base l.

4 can be restricted.

However, when the optical pickup device is moved at high speed, the lens bobbin 102 may tilt in the moving direction of the optical pick amplifier device, that is, pitch, as shown in FIG. This pitching is caused by this lens bobbin 1 of the lens bobbin 102.
This is a rotation around the center of gravity g of 02. When this pitching occurs, the objective lens 101 moves on a circular trajectory centered on the center of gravity g.
1 causes the beam spot formed on the disc-shaped recording medium to move, making it impossible to write and/or read information signals to and from the disc-shaped recording medium in a satisfactory manner.

The position sensor 10 cannot detect such pitching, that is, when the lens bobbin 102 pitches in the counterclockwise direction as indicated by p on the right in FIG. moves to the left in FIG. 9 as indicated by arrow a in FIG. 9, and forms a beam spot b1 on the disk-shaped recording medium. This beam spot b is formed to the left in FIG. 9 of the beam spot b when the lens bobbin 102 is not pitched.

At this time, since the one end 102a of the lens bobbin 102 is located on the side opposite to the objective lens 101 via the center of gravity g, the one end 102a of the lens bobbin 102 It moves to the right in FIG. 9, as shown by right C in the figure.

Therefore, when attempting to return the one end portion 102a to the central position relative to the position sensor 10B by supplying a drive current based on the detection output of the light receiving element 110 to the tracking coil 106, the lens bobbin 102
A movement operation is performed to the left in FIG. 9 as indicated by arrow a in the figure. Then, the beam spot b1 is located on the lens bobbin 10.
Beam spot b when 2 does not cause pitching
moved further away from one another.

In this way, in the objective lens driving device that uses the position sensor 108 as described above to restrict the movement of the lens bobbin 102 during seek, when pitching occurs in the lens bobbin 102, the beam spot b1 It is not possible to suppress the movement of the beam on the disk-shaped recording medium, and there is a possibility that the movement of the beam sub-board (b+) 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 are provided on both sides of the lens and the Jf hinge 102, as shown in FIG. You can also do this. However, even in the objective lens drive device configured in this way, even if the lens bobbin 102 pitches, the position sensors 11
No change occurs in the detection output of 1, and this pitching cannot be detected.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned circumstances, and is an objective lens that can reduce movement of the objective lens even when the movement of the objective lens is caused by tilting of the lens bobbin during so-called high-speed seek. The purpose is to provide a driving device.

80 Means for Solving Problems In order to solve the above-mentioned v4 problem and achieve the above object, an objective lens driving device according to the present invention is provided with an objective lens attached thereto, and an optical axis direction of the objective lens and the optical axis direction. a lens bobbin that is supported so as to be displaceable in two axes perpendicular to the axial direction, and is operable to move in these two axes; and a detected member that is located approximately to the side of the objective lens and supported by the lens bobbin. and a position detection means for detecting displacement of the detected member in a direction perpendicular to the optical axis direction.

11 Effects In the objective lens drive device according to the present invention, the position detection means is configured to detect the detection member located approximately to the side of the objective lens and supported by the lens bobbin in a direction perpendicular to the optical axis direction of the objective lens. Since the displacement is detected, a similar detection signal is generated when the objective lens moves in one direction due to the movement of the lens bobbin in one direction, and when the objective lens moves in one direction due to the tilt of the lens bobbin. Output.

G. Examples Specific examples of the present invention will be described below with reference to the drawings.

The objective lens driving device according to the present invention is a device used in an optical pickup device that writes and/or reads information signals to and from a disk-shaped recording medium such as an optical disk or a magneto-optical disk, This is a device that moves an objective lens that focuses a light beam emitted from a constituent optical block onto the disk-shaped recording medium in two predetermined axial directions.

The optical block section includes a light source such as a laser diode that emits the light beam, a plurality of optical devices that guide the light beam emitted from the light source to the objective lens, and a plurality of optical devices that direct reflected light from the disk-shaped recording medium. It is configured to include a built-in light receiving element such as a photodiode for detection through the sensor.

As shown in FIGS. 1 and 2, this objective lens driving device has a base l, on which a lens bobbin 3, on which an objective lens 2 is attached, is displaced in two axial directions. Constructed with support possible.

The base l is formed of a material such as a metal having high magnetic permeability into a substantially rectangular plate shape. On this base I, a support plate part 4 is vertically provided on the rear side.

Two pairs of rod-shaped support arms 5 are attached to the support plate portion 4 at their proximal ends.

These support arms 5 are formed of steel wire or the like having appropriate flexibility and elasticity, and extend toward the front side of the base 1 so as to be parallel to the base 1. . The lens bobbin 3 is supported on the distal end side of these support arms 5.

The lens bobbin 3 is made of a material such as synthetic resin and has a substantially rectangular shape, and a pair of support arm attachment portions 6 are attached to both sides thereof. The distal ends of each of the support arms 5 are attached to the support arm attachment portions 6 in pairs.

Further, the lens bobbin 3 is provided with an objective lens mounting hole 3a to 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 l.

The objective lens 3 is attached so as to close the opening of the hole 3a on the side opposite to the side facing the base 1.

As shown in FIG. 2, the base l is provided with a light beam entrance hole 1a corresponding to the hole 3a for mounting the objective lens. The light beam entrance hole 1a is formed so that the light beam emitted from the optical block portion (not shown) disposed on the opposite side of the base 1 to the side on which the lens bobbin 3 is supported passes through the light beam entrance hole 1a. It is installed through the. The light beam passing through the light beam entrance hole 1a enters the objective lens 2 through the objective lens mounting hole 3a.

This objective lens driving device moves the lens bobbin 3 in the direction of the optical axis A of the objective lens 2 indicated by arrow F in FIGS. 1 and 2, that is, in the focus direction and The objective lens 2 is provided with a magnetic circuit for driving displacement in two axes directions perpendicular to the optical axis A of the objective lens 2, that is, the tracking direction, as indicated by the arrow below. This magnetic circuit includes a focus coil 7 and a plurality of tracking coils 8 attached to the lens bobbin 3, and the base 1.
a pair of outer and inner magnetic yokes provided thereon9.
10, and a pair of magnets 11 attached to the outer magnetic yoke 9.

The focus coil 7 is wound around the lens bobbin 3. Further, each of the tracking coils 8 is wound into a substantially rectangular shape, and is overlapped with the focus coil 7 to form a predetermined four
pasted in place.

Each pair of magnetic yokes 9.10 is formed into a rectangular plate shape from the same material as the base 1, and
It is suspended above. The outer magnetic yoke 9 is provided 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. and,
The inner magnetic yoke 10 is mounted on the lens bobbin 3 at the front and rear positions of the hole 3a, and in a pair of magnetic yoke insertion holes 3b drilled parallel to the hole 3a. Provision is made for corresponding insertion.

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

With the magnetic circuit configured in this way, the lens bobbin 3 is operated to move in the focus direction by supplying a predetermined drive current to the focus coil,
Further, by supplying a predetermined drive current to the tracking coil, the tracking coil is operated to move in the tracking direction.

Note that when writing and/or reading information signals to and from the disk-shaped recording medium, each of the drive currents is as follows:
The signal is supplied based on a focus error signal and a tracking error signal generated from the light detection output of a light receiving element built into the optical block section. Further, the objective lens driving device is used so that the tracking direction coincides with the radial direction of the disk-shaped recording medium, and is supported so as to be movable in the radial direction of the disk-shaped recording medium.

By the way, this objective lens drive device is provided with a detection mechanism for detecting the inclination of the lens bobbin 3 with respect to the base 1 and the displacement in the tracking direction.

This 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 the pitching caused by the movement of the objective lens drive device in the radial direction of the disk-shaped recording medium, that is, the fourth
As shown by arrow P in the figure, the center of gravity G of the lens bobbin 3
This is rotation around an axis parallel to each support arm 5 through . This pitching rotation axis is perpendicular to both the focusing direction and the tracking direction. Note that the center of gravity G is located on the optical axis A of the objective lens 2.

The detected member 12 is formed into a thin frame shape from a material such as metal or synthetic resin, and is attached to and supported by the lens bobbin 3. The detected member 12 has a rod-shaped detected portion 12a parallel to the optical axis A of the objective lens 2, and the detected portion 12a is placed on the side of the objective lens 2 above the It is attached to the objective lens 2 in a direction perpendicular to the optical axis A of the objective lens 2.

The light emitting element 13 and the light receiving element 14 are supported on the base 1 by support members 15 and 16, respectively. These light emitting elements 13 and light receiving elements 14 are connected to the detected portion 1
They face each other in a direction parallel to the pitching axis of the lens bobbin 3 via 2a. The light emitting element 13
is composed of a laser diode, an LED, etc., and irradiates the light receiving element 14 with a light beam via the detected portion 12a. The light receiving element 14 is composed of a photodiode or the like, and as shown in FIG.
4 a and I 4 b, and each independent first light receiving surface corresponds to the first and second light receiving surfaces 14a and 14b.
and a second photodetection output. These first and second light receiving surfaces 14a and 14b are arranged adjacent to each other in the tracking direction. A boundary line 14C where the first and second light-receiving surfaces 14a and 14b touch each other is parallel to the focus direction, that is, to the detected portion 12a.

Then, the light emitting element 13 and the light receiving element 14 are directed to the detected portion 1 by the light beam emitted from the light emitting element 13 when the lens bobbin 3 is not displaced in the tracking direction and is not pitching.
2a is arranged so that its shadow is formed on the boundary line 14c. Therefore, when the detected portion 12a is displaced in the tracking direction with respect to the base 1,
The shadow of the detected portion 12a caused by the light beam emitted from the light emitting element 13 is formed by the first and second light receiving surfaces 14a.
, 14b. That is, this detection mechanism is configured to be able to detect the displacement of the detected portion 12a with respect to the base l in the direction perpendicular to the optical axis A by comparing the first and second photodetection outputs. has been done.

In the objective lens drive device according to the present invention configured as described above, when the objective lens drive device is operated to move at high speed in the radial direction of the disk-shaped recording medium for so-called high-speed seek or the like, Above lens bobbin 3
is displaced and driven in the tracking direction based on the first and second light detection outputs obtained from the light receiving element 14,
The displacement of the objective lens 2 with respect to the base 1 is reduced.

That is, by moving this objective lens drive device in the radial direction of the disk-shaped recording medium, the lens bobbin 3 is moved in the fourth direction in the tracking direction with respect to the base 1, as shown in FIG. When the lens bobbin 3 is displaced to one side as shown by the arrow ΔT in the figure, the lens bobbin 3 is moved to the fourth position.
If a driving current is supplied to the tracking coil 8 that causes the tracking coil 8 to be displaced to the other side as indicated by an arrow M in the figure, the displacement of the lens bobbin 3 with respect to the base l, that is, the displacement of the objective lens 2 from the base The displacement with respect to l can be reduced.

When the lens bobbin 3 is displaced in the tracking direction with respect to the base 1, the detected portion 12a moves in the same direction by the same distance as the objective lens 2. The first and second photodetection outputs become signals having different signal levels. Here, the difference in signal level between the first and second photodetection outputs has a polarity corresponding to the displacement of the lens bobbin 3 in the tracking direction. That is, the signal level of the first photodetection output is Ll, the signal level of the second photodetection output is L1, and when the lens bobbin 3 is displaced to one side with respect to the base 1, If the difference between these signal levels, -Lo, is positive, then the lens bobbin 3
is displaced to the other side with respect to the base 1, the difference L1 Ll between these signal levels is negative.

Therefore, the difference t in the signal level of each of these photodetection outputs,
, t, and z, it is possible to always drive the lens bobbin 3 in the direction opposite to the displacement caused by the movement of the objective lens drive device. can.

Further, as the objective lens driving device is operated to move in the radial direction of the disk-shaped recording medium, the lens bobbin 3 is moved in the clockwise direction as shown by the arrow ΔP in FIG. When pitching occurs, the objective lens 2 is displaced to one side with respect to the base 1 in response to the pitching of the lens bobbin 3. At this time, if a drive current is supplied to the tracking coil 8 to displace the lens bobbin 3 to the other side as indicated by arrow M in FIG. 4, the displacement of the objective lens 2 with respect to the base l is It can be reduced.

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

That is, the distance between the center of gravity G and the objective lens 2 is r
, since the center of gravity G is on the road light distribution axis A, when the lens bobbin 3 pitches by Δθ, the amount of movement ΔX of the objective lens 2 in the tracking direction is ΔX+' ir+SinΔθ, and the distance between the center of gravity G and the detected part 12a in the tracking direction is r
! , the distance in the focus direction is r, and r
, when SinΔθ is sufficiently smaller than the distance r between the center of gravity G and the objective lens 2, the detected part 1
Movement amount ΔX of 2a in the above tracking direction! is ΔXs "irs TanΔθ. If Δθ is sufficiently small, then SinΔθ"; TanΔθ. Therefore, if rl=rs, then ΔX, ξΔx2.

Therefore, the difference in signal level of each of the above photodetection outputs is -
By supplying the driving current based on L2 to the tracking coil 8, the lens bobbin 3 always
The objective lens 2 is displaced in a direction opposite to the displacement caused by the pitching.

In this way, in the objective lens driving device according to the present invention, the displacement of the objective lens 2 with respect to the base l due to the movement operation of the objective lens driving device in the radial direction of the disk-shaped recording medium is suppressed to a minimum. be able to. Therefore, the occurrence of vibration of the objective lens 2 relative to the base 1 during so-called high-speed seek is suppressed, and writing and/or reading of information signals after the end of the seek can be started quickly.

H1 Effects of the Invention As described above, in the objective lens driving device according to the present invention, the position detection means detects the light of the objective lens of the member to be detected, which is located approximately to the side of the objective lens and supported by the lens bobbin. Detects displacement in the direction perpendicular to the axial direction.

Therefore, the position detection means outputs the same detection signal when the objective lens is moved by the movement of the lens bobbin and when it is moved by the inclination of the lens bobbin.

Therefore, if the lens bobbin is moved in a direction perpendicular to the optical axis direction of the objective lens based on the output signal of the position detection means, the objective lens is moved and the lens bobbin is tilted due to the movement of the lens bobbin. It is possible to restrict both movement of the objective lens.

That is, the present invention can provide an objective lens drive device that can reduce the movement of the objective lens even when the lens bobbin is tilted during so-called high-speed seek.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an objective lens driving device according to the present invention, FIG. 2 is a longitudinal sectional view showing the configuration of the objective lens driving device, and FIG. 3 is a perspective view showing the configuration of the objective lens driving device. FIG. 2 is an enlarged front view of main parts showing the configuration of a detecting means. FIG. 4 is a front view showing a state in which the lens bobbin of the objective lens driving device is displaced in the tracking direction with respect to the base, and FIG. 5 is a front view showing a state in which the lens bobbin of the objective lens driving device has 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 the configuration of a conventional objective lens driving device. FIG. 8 is a partially cutaway front view showing the configuration of a conventional objective lens drive device equipped with a position sensor for detecting movement of a lens bobbin, and FIG. FIG. 2 is a partially cutaway front view showing a state in which the lens bobbin of the objective lens drive device is tilted. FIG. 10 is a partially cutaway front view showing another configuration of a conventional objective lens drive device equipped with a position sensor for detecting movement of a lens bobbin, and FIG. 11 is a front view showing the structure shown in FIG. 10 above. FIG. 3 is a partially cutaway front view showing a state in which the lens bobbin of a conventional objective lens drive device is tilted. objective lens

Claims (1)

[Claims] An objective lens is attached and supported so as to be displaceable in two axes, an optical axis direction of the objective lens and a direction orthogonal to the optical axis direction, and can be moved in these two axes directions. a lens bobbin; a member to be detected located substantially to the side of the objective lens and supported by the lens bobbin; and a position detection means for detecting displacement of the member to be detected in a direction perpendicular to the optical axis direction. Objective lens drive device.