JP2001155358A - Objective lens driving means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens driving means in which the position of a converging beam in the radial direction of an optical disk is unchanged when the inclination of an objective lens is corrected. SOLUTION: On the side face of a lens holder 2 on which the objective lens 1 is mounted, one end of a focus leaf spring 6a, 6b is projectingly provided which consists of an upper and lower pairs of metallic elastic bodies, with the other end projectingly provided on a track holder 7. In addition, the width and the thickness of the pair of focus leaf springs 6a provided upward in the Z-axis direction are made larger than those of the pair of focus leaf springs 6b provided downward, thereby strengthening the rigidity of the focus leaf springs 6a against a rotary motion at the time of inclination correction, and making the center of the rotation of the objective lens 1 coincide with the principal point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device in a recording / reproducing apparatus for recording / reproducing information by irradiating a recording medium with a light beam, and more particularly to an objective mounted with an objective lens for converging light. The present invention relates to a lens driving device.

[0002]

2. Description of the Related Art Hitherto, as a storage / reproduction device for handling a large amount of information, a storage / reproduction device using a light beam which can be reduced in size has been developed. In recent years, a technology for writing information on an optical disk, which is a storage medium, in a higher-density form has been studied in order to meet the demand for further downsizing and increasing the capacity of a storage / reproduction device.

As described above, in order to handle information in a high-density form, it is necessary to form a minute light spot, and an objective lens having a high numerical aperture (NA) has been used. . That is, if an objective lens having a high aperture ratio is used, the diameter of the condensed beam can be reduced, so that a finer light spot can be formed.

On the other hand, when the light spot is miniaturized, optical aberration occurs and crosstalk and jitter occur even when the optical axis of the objective lens is slightly inclined with respect to the recording surface of the optical disk. And good recording / reproducing characteristics cannot be obtained. Further, since the adverse effect due to the inclination of the optical axis becomes more remarkable as the aperture ratio of the objective lens increases, the inclination of the optical axis is reduced in further reducing the size and capacity of the storage / reproduction device. That is a very important issue.

As a conventional technique for solving this problem, there has been proposed an objective lens driving device which corrects the inclination of the optical axis of a condensed beam with respect to an optical disk. This conventional example will be described with reference to the drawings. FIG. 6 is a schematic external perspective view of a conventional objective lens driving device. In the figure, the objective lens driving device has a structure in which a lens holder 52 in which an objective lens 51 is embedded in the center is mounted in a state of being floated from a base 60 by a focus leaf spring 56 and a track leaf spring 58. It is driven by the coils 53a and 53b, the track coil 54, and the tilt coils 55a and 55b.

Incidentally, for easy understanding, the X axis, the Y axis,
A description will be given by introducing an orthogonal coordinate system including the Z axis. In this rectangular coordinate system, the origin is set to a lens holder 52, an objective lens 51,
Focus coils 53a, 53b, track coil 54
The center of gravity of the movable part including the tilt coils 55a and 55b, the Z axis as the optical axis of the objective lens 51, the Y axis direction as the radial direction of the optical disk as the storage medium, and the X axis direction as the direction in contact with the circumferential direction of the optical disk The origin has been moved and shown for easy viewing.

Here, as shown in FIG. 7, the lens holder 52 has concave portions 53 on both side surfaces in the X-axis direction,
It has a substantially rectangular parallelepiped shape having convex portions 55 on both side surfaces in the axial direction, and an objective lens 51 is provided at the center of the upper surface. As shown in FIG. 8, the objective lens 51 is a hemispherical convex lens, and is embedded in a hole formed in the lens holder 52 with its convex side facing down. For this reason, the objective lens 51 can converge the light beam incident from above, reduce the light beam diameter, and irradiate the light beam downward.

A lens holder 52 is provided with a rectangular annular focus coil 5 in recesses 53 formed on both sides in the X-axis direction.
3a and 53b are fixed. This focus coil 5
3a and 53b are inner yokes 63 protruding from the base 60.
The lens holder 52 can be moved in the Z-axis direction by acting on the main magnet 62 fixed to the side surface of the main yoke 61.

[0009] In the lens holder 52, track coils 54 are fixed to concave portions 53 on both side surfaces in the X-axis direction. The track coil 54 works with the main magnet 62 attached to the main yoke 61 to move the lens holder 52 to Y.
It can be moved axially.

The lens holder 52 has protrusions 55 projecting from both sides in the Y-axis direction, and rectangular annular tilt coils 55a and 55b are fixed to the front of the protrusions. The tilt coils 55 a and 55 b are provided so that the penetrating portions thereof extend in the vertical direction, and are inserted into a tilt inner yoke 65 protruding from the base 60, and act with a tilt magnet 66 attached to a side surface of the tilt yoke 64. As a result, a magnetic force in the Z-axis direction is generated. Here, the tilt coils 55a and 55b
They are connected in series, and generate a magnetic force (rotation torque) whose direction is opposite in the Z-axis direction by a combination of the pole direction of the tilt magnet 66 and the winding direction of the tilt coils 55a and 55b.

In the lens holder 52, four focus leaf springs 56 made of a metal elastic body are provided on one side surface of the convex portion 55 so as to protrude in the X-axis direction. The other end protrudes from the track holder 57.

Here, since each focus leaf spring 56 is provided so as to be displaceable in the Z-axis direction, the lens holder 52 is provided.
Can move in the Z-axis direction when it receives the magnetic force of the focus coils 53a and 53b. Since the focus leaf spring 56 is sufficiently long with respect to the movement distance of the lens holder 52 in the Z-axis direction, the movement of the lens holder 52 is approximated not as an arc-shaped movement but as a linear (Z-axis) movement. is there. Further, the lens holder 52 includes a tilt coil 55
When receiving the rotational torques a and 55b, the focus leaf spring 56 is twisted to be able to rotate about the X axis.

The track holder 57 has an elongated plate-like shape, and a track leaf spring 58 made of a metal elastic body is provided at the center of the side surface facing the lens holder 52 so as to be displaceable in the Y-axis direction. The other end of the track leaf spring 58 protrudes from the holder holding portion 59, and the holder holding portion 59 is attached to the main yoke 61. Therefore, when the track holder 57 receives the magnetic force of the track coil 54, it can move in the Y-axis direction, and in conjunction with this movement, the lens holder 52 similarly moves in the Y-axis direction. Since the focus leaf spring 56 is sufficiently long with respect to the movement distance of the lens holder 52 in the Y-axis direction, the movement of the lens holder 52 is not a circular movement but a linear movement (Y
(Axial direction) movement.

As described above, the lens holder 52 is provided with the focus leaf spring 56 and the track leaf spring 58 so that
It is suspended so as to be movable in the axial direction and the Y-axis direction and rotatable around the X-axis, and is easily position-controlled (driven) by a magnetic force.

The base 60 has a rectangular flat plate shape with a hole 70 through which laser light passes, and has a structure in which a main yoke 61, an inner yoke 63, a tilt yoke 64, and a tilt inner yoke 65 are protruded. . Also, base 6
Numeral 0 is made of a magnetic material and manufactured by integral molding.

The objective lens driving device having such a structure is not shown, but the control means for inputting the tilt signal from the tilt detecting means to control the tilt coil 55a,
Power is supplied to 55b. Then, the tilt coils 55a, 55
b generates a magnetic force (rotation torque) opposite to the Z-axis direction, and the lens holder 52
Can be rotated while being twisted to correct the inclination of the light emitted from the objective lens 51 with respect to the optical disk.

More specifically, since the movable portion has a symmetrical structure with respect to the center of rotation, and the torsional rigidity of the four focus leaf springs 56 is equal to the center of rotation, the objective lens 51 is moved to the center of rotation. , The inclination of the emitted light from the objective lens 51 with respect to the optical disk can be corrected.

Here, in the objective lens driving device, the principal point of the objective lens 51 is generally shifted upward in the Z-axis direction with respect to the center of gravity of the movable part as shown in FIG. That is, when designing the objective lens 51, the lens holder 52, and the like, it is necessary to comprehensively determine restrictions due to specifications of the objective lens 51 and restrictions due to stability of control of the lens holder 52, and as a result, This is because the rotation center of the lens holder 52 cannot be matched with the principal point of the objective lens 51.

However, in the conventional objective lens driving device, when the tilt coil is energized and the objective lens is tilted, a phenomenon occurs that the position of the focused beam from the objective lens shifts in the Y-axis direction. Is smaller, there is a problem that good recording / reproducing characteristics cannot be obtained due to the deviation. Further, in order to correct the position of the condensed beam in order to prevent this, it is necessary to supply extra power, which causes new problems such as an increase in heat generation and an increase in power consumption.

[0020]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and in particular, the position of the condensed beam in the radial direction of the optical disk does not shift even if the inclination of the objective lens is corrected. It is an object of the present invention to provide an objective lens driving device.

[0021]

In order to achieve the above object, the objective lens driving device according to the first aspect of the present invention is arranged such that an optical axis is set on a Z axis of a rectangular coordinate system including an X axis, a Y axis and a Z axis. And an objective lens having the objective lens embedded therein, and a plurality of lenses protruding from the lens holder, the lens holder being movable in the Z-axis direction and rotatable around the X-axis. A focus leaf spring, a track holder to which an end of the focus leaf spring opposite to the lens holder is fixed, and a track plate protruding from the track holder and capable of moving the lens holder in the Y-axis direction. A spring, a base to which an end of the track leaf spring opposite to the track holder is fixed, a focus coil for moving the lens holder in the Z-axis direction, and the lens A tracking coil for moving the Y-axis direction holder, and tilt coils for rotating the lens holder about the X-axis, the focus coils,
An objective lens driving device provided with a magnetic circuit for applying a magnetic field to a track coil and a tilt coil, wherein the X-axis moves in the Z-axis direction when the lens holder rotates, whereby the main lens of the objective lens is driven. It is configured to pass through points.

With this arrangement, it is not necessary to correct the position of the objective lens when correcting the inclination between the optical disk and the optical axis emitted from the objective lens. Problems such as an increase in the amount and power consumption can be prevented.

According to a second aspect of the present invention, in the objective lens driving device of the first aspect, the direction of the X axis is a direction in contact with a circumferential direction of an optical disk as a storage medium.

As described above, by simply determining the positional relationship with respect to the optical disk, control means and the like can be simplified, and as a result, an inexpensive objective lens driving device can be obtained.

According to a third aspect of the present invention, in the objective lens driving device according to the first or second aspect, the focus leaf spring is provided on a side surface of the lens holder, and the objective lens, the lens holder, A pair is provided on both sides of the center of gravity of the movable portion including the focus coil, the track coil, and the tilt coil and in the vertical direction of the principal point.
The torsional rigidity of the pair of focus leaf springs in the upward direction around the X axis is higher than the torsional rigidity of the pair of focus leaf springs in the downward direction.

Thus, even when the principal point of the objective lens is different from the center of gravity of the movable portion, the rigidity of the upper focus leaf spring in the optical axis direction against torsion is stronger than that of the lower focus leaf spring. With this setting, the center of rotation can be made to coincide with the principal point, and even if the inclination of the optical axis is corrected, it is possible to prevent the position of the focused beam position from shifting in the radial direction of the optical disk.

According to a fourth aspect of the present invention, in the objective lens driving device according to the third aspect, the pair of upward focusing leaf springs is thicker than the pair of downward focusing leaf springs. It has a wide configuration.

As described above, by changing the shape of the focus leaf spring itself and changing the torsional rigidity, even if the inclination of the objective lens is corrected, it is possible to prevent the position shift of the focused beam.

According to a fifth aspect of the present invention, in the objective lens driving device according to the third or fourth aspect, the pair of focus leaf springs in the upward direction is attached to the track holder so as to open toward the track holder. It has a fixed configuration.

As described above, by changing the mounting structure of the focus leaf spring, the torsional rigidity can be changed with almost no increase in weight due to an increase in plate thickness and the like.

[0031] The invention of claim 6 provides the above-mentioned claims 3-5.
In the objective lens driving device according to any one of the above, the material of the pair of focus leaf springs in the upward direction is a material having a larger shear modulus than the material of the pair of focus leaf springs in the downward direction.

As described above, by changing the material of the focus leaf spring itself, the torsional rigidity can be easily changed, which is effective when the weight and the outer dimensions are limited.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an objective lens driving device according to a first embodiment of the present invention will be described with reference to the drawings. First Embodiment FIG. 1 is a schematic perspective view of an objective lens driving device according to a first embodiment. In the figure,
In the objective lens driving device, a lens holder 2 holding an objective lens 1 in the center is supported by focus leaf springs 6a and 6b and a track leaf spring 8 in a state of being floated from a base 10, and focus coils 3a and 3b are provided. , A track coil 4 and tilt coils 5a and 5b.

As shown in FIGS. 2 and 3, the objective lens driving device is similar to the objective lens driving device in the conventional example described above.
a, a track coil 4 and tilt coils 5a and 5b.

Each of the focus leaf springs 6a and 6b is made of a metal elastic body, and has one end protruding from the projection 5 on the Y-axis side surface of the lens holder 2 and the other end protruding from the track holder 7. . Here, as shown in FIG. 4, the focus leaf spring 6a is protruded near both upper ends of the lens holder 5, and the focus leaf spring 6b is similarly protruded near both lower ends. is there. Further, the width and thickness of the focus leaf spring 6a are formed to be larger than the width and thickness of the focus leaf spring 6b, and the torsional rigidity of the focus leaf spring 6a is made larger than the torsional rigidity of the focus leaf spring 6b. is there.

For this reason, if the tilt coils 5a and 5b try to move in opposite directions by the action of the electromagnetic force,
The lens holder 2 attempts to rotate around the center of gravity of the movable part, but since the torsional rigidity of the focus leaf spring 6a is greater than the focus leaf spring 6b, the focus leaf spring 6
b is twisted from the focus leaf spring 6a, the rotation on the lower surface side of the lens holder 2 becomes larger than the rotation on the upper surface side, and as a result, the center of rotation moves above the center of gravity, and the principal point of the objective lens 1 This rotation center can be matched. Other structures and operations are the same as those of the objective lens driving device in the conventional example.

Next, the operation of the objective lens driving device having the above-described structure will be described. In this objective lens driving device, although not shown, the control means for inputting the tilt signal from the tilt detecting means energizes the tilt coils 5a and 5b. When the tilt coils 5a and 5b are energized, an electromagnetic force in the opposite direction in the Z-axis direction is generated, and the lens holder 2 rotates around the center of rotation so as to twist the focus leaf springs 6a and 6b. The inclination of the emitted light from 1 with respect to the optical disk is corrected.

As shown in FIG. 4, the center of rotation is located at the center of gravity because the torsional rigidity of the pair of upper focus leaf springs 6a around the X axis is greater than that of the pair of lower focus leaf springs 6b. Move to the upper side, the objective lens 1
And the principal point of. For this reason, even if the objective lens driving device corrects the inclination of the objective lens 1, there is no displacement of the condensed beam, so that it is not necessary to correct the position of the condensed beam. Other operations are the same as those of the conventional objective lens driving device.

As described above, in the objective lens driving device according to the first embodiment, the center of rotation coincides with the principal point of the objective lens by changing the torsional rigidity of the focus leaf springs 6a and 6b around the X axis. When correcting the tilt between the optical disc and the optical axis emitted from the objective lens, the phenomenon that the position of the condensed beam from the objective lens shifts in the Y direction even when the tilt coils 5a and 5b are energized and the objective lens is tilted. Therefore, there is no need to correct the position of the objective lens, and there is no need to energize the track coil, thereby preventing problems such as increased heat generation and increased power consumption.

Next, an objective lens driving device according to a second embodiment of the present invention will be described with reference to the drawings. Second Embodiment FIG. 5 is a schematic plan view of an objective lens driving device according to a second embodiment. In the figure,
The objective lens driving device has a basic configuration for supporting the lens holder 2 in a state where the lens holder 2 in which the objective lens 1 is embedded in the center portion is floated from the base 10 by the focus leaf springs 6c and 6d and the track leaf spring 8. It is mounted and driven by a focus coil 3, a track coil 4, and tilt coils 5a and 5b.

In the objective lens driving device according to the first embodiment, the torsional rigidity around the X axis is changed by changing the cross-sectional shape of the focus leaf springs 6a and 6b in the upper and lower pairs in the Z axis direction. In the case where weight reduction is an extremely important selling point of a product, the above-mentioned change in shape may not be recognized.

However, in the objective lens driving device according to the second embodiment, the pair of upper focus leaf springs 6c are mounted so as to open toward the track holder 7 without changing the sectional shape of the focus leaf spring. Thereby, the torsional rigidity around the X axis can be improved,
The same effect as the focus leaf spring 6a of the first embodiment can be obtained.

As described above, the objective lens driving device according to the second embodiment includes the focus leaf spring 6 having the same sectional shape.
Although c and 6d are used, the center of rotation of the lens holder can be made coincident with the principal point of the objective lens 1 by improving the torsional rigidity by attaching the focus leaf spring 6c. This eliminates the need to thicken or widen the shape of the focus leaf spring 6c, thereby making it possible to reduce the weight of the objective lens driving device.

As described above, the objective lens driving device according to the present invention changes the torsional rigidity of the focus leaf spring to correct the inclination of the objective lens about the principal point of the objective lens, thereby condensing light. It is possible to prevent the occurrence of a phenomenon that the beam position shifts in the Y-axis direction, and obtain good recording / reproducing characteristics. In addition, since the displacement in the Y-axis direction can be prevented, it is not necessary to carry out extra power supply for correcting the focused beam position, and new problems such as increased heat generation and increased power consumption are prevented. be able to.

The present invention includes various modifications. For example, as a method for increasing the torsional rigidity of the focus leaf spring, the material itself of the focus leaf spring has a large shear coefficient in addition to the method described above. The same effect can be obtained by using a material. When it is necessary to greatly increase the torsional rigidity of the focus leaf spring, it goes without saying that the above-described means can be used in combination.

[0046]

As described above, the objective lens driving device according to the present invention makes the center of rotation by the inclination correction of the objective lens coincide with the principal point of the objective lens so that the optical disc and the optical axis emitted from the objective lens can be aligned. Even if the objective lens is tilted to correct the tilt, the position of the condensed beam does not shift in the radial direction of the optical disc, so that good recording / reproducing characteristics can be obtained. Furthermore, this eliminates the need for the objective lens driving device to correct the position even when the tilt of the objective lens is corrected, so that the amount of current supplied to the track coil increases, the amount of heat generation increases, and power consumption increases. Problems such as increase can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an objective lens driving device according to a first embodiment.

FIG. 2 is a schematic exploded perspective view of the objective lens driving device according to the first embodiment.

FIG. 3 shows a schematic plan view of the objective lens driving device according to the first embodiment.

FIG. 4 is a schematic cross-sectional view of a main part of the objective lens driving device according to the first embodiment.

FIG. 5 shows a schematic plan view of an objective lens driving device according to a second embodiment.

FIG. 6 is a schematic external perspective view of a conventional objective lens driving device.

FIG. 7 is a schematic exploded perspective view of a conventional objective lens driving device.

FIG. 8 is a schematic cross-sectional view of a main part of a conventional objective lens driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Concave part 3a, 3b Focus coil 4 Track coil 5 Convex part 5a, 5b Tilt coil 6a, 6b, 6c, 6d Focus leaf spring 7 Track holder 8 Track leaf spring 9 Holder holder 10 Base 11 Main yoke Reference Signs List 12 Main magnet 13 Inner yoke 14 Tilt yoke 15 Tilt inner yoke 16 Tilt magnet 20 Hole 51 Objective lens 52 Lens holder 53 Depression 53 Focus coil 54 Track coil 55 Projection 55a, 55b Tilt coil 56 Focus leaf spring 57 Track holder 58 Track plate Spring 59 Holder holder 60 Base 61 Main yoke 62 Main magnet 63 Inner yoke 64 Tilt yoke 65 Tilt inner yoke 66 Tilt magnet 70 Hole

Claims (6)

[Claims] 1. An objective lens whose optical axis coincides with the Z axis of a rectangular coordinate system consisting of an X axis, a Y axis, and a Z axis, a lens holder in which the objective lens is embedded, and a projection provided on the lens holder. A plurality of focus leaf springs capable of moving the lens holder in the Z-axis direction and rotatable around the X-axis; and a track holder to which an end of the focus leaf spring opposite to the lens holder is fixed. A track leaf spring protruding from the track holder and capable of moving the lens holder in the Y-axis direction; a base having a fixed end of the track leaf spring on the side opposite to the track holder; A focus coil for moving the lens holder in the Z-axis direction, a track coil for moving the lens holder in the Y-axis direction, and
An objective lens driving device comprising: a tilt coil that rotates around an axis; and a magnetic circuit that applies a magnetic field to the focus coil, the track coil, and the tilt coil, wherein when the lens holder rotates, the X axis is An objective lens driving device characterized by passing through a principal point of the objective lens. 2. The objective lens driving device according to claim 1, wherein the direction of the X axis is a direction in contact with a circumferential direction of an optical disk as a storage medium. 3. The objective lens driving device according to claim 1, wherein the focus leaf spring is provided on a side surface of the lens holder, the objective lens, the lens holder, the focus coil, the track coil, and the tilt coil. A pair is provided on both sides of the position of the center of gravity of the movable portion and in the vertical direction of the principal point,
An objective lens driving device, wherein the torsional rigidity of the pair of focus leaf springs in the upward direction around the X axis is higher than the torsional rigidity of the pair of focus leaf springs in the downward direction. 4. The objective lens driving device according to claim 3, wherein the pair of upward focusing leaf springs is thicker and wider than the pair of downward focusing leaf springs. Objective lens driving device. 5. The objective lens driving device according to claim 3, wherein the pair of upward focusing leaf springs is fixed to the track holder so as to open toward the track holder. Objective lens driving device. 6. The objective lens driving device according to claim 3, wherein the material of the pair of upward focus leaf springs is more elastically sheared than the material of the pair of downward focus leaf springs. An objective lens driving device comprising a material having a large coefficient.