JP2004146034A - Objective lens driving device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce pitching vibration of a movable part and to improve driving sensitivity in an objective lens driving device for driving an objective lens in a radial tilting direction in addition to a focusing direction and a tracking direction.
SOLUTION: Tracking coils 5R and 5L are mounted on outer surfaces of two focusing coils 4R and 4L. A first magnet 10 and a second magnet 11 are disposed inside the focusing coils 4R and 4L, respectively. The third magnet 12 is disposed so as to face the first magnet 10 and the second magnet 11 with the tracking coils 5R and 5L interposed therebetween. The open end of the first yoke 6 holding the first magnet 10 and the open end of the second yoke 7 holding the second magnet 11 are connected by a bridging yoke 9. Since magnetic flux is formed in the bridging yoke 9, pitching vibration can be suppressed, and drive sensitivity is improved because effective magnetic flux is increased.
[Selection diagram] Fig. 1

Description

The present invention relates to an objective lens driving device, and more particularly, to an objective lens driving device used in a recording / reproducing device of a type that optically records and / or reproduces information by irradiating a disk-shaped recording medium with a light spot. Further, the present invention relates to an optical disk device provided with such an objective lens driving device.

In a conventional objective lens driving device, an objective lens for forming a light spot on a disk recording surface is moved in a direction perpendicular to the disk surface (hereinafter, referred to as a “focusing direction”) and a radial direction of the disk (hereinafter, referred to as a “tracking direction”). To translate. In optical disc devices that support high density, a function to correct optical coma has been added in order to obtain good recording / reproducing characteristics. To achieve this, it is necessary to add a function to the focusing and tracking directions. Therefore, it is required to drive the objective lens in a rotational direction (hereinafter, referred to as a "radial tilting direction") about an axis parallel to a tangential direction of the circumference of the disk (or a recording track on the disk). Such an objective lens driving device is disclosed, for example, in Patent Document 1. Hereinafter, a conventional objective lens driving device will be described with reference to the drawings, taking the prior art disclosed in Patent Document 1 as an example.

FIG. 6 is a perspective view showing the configuration of a conventional objective lens driving device, and FIG. 7 is a plan view showing the arrangement of coils and magnets of the conventional objective lens driving device. 6 and 7, an arrow Fo indicates a focusing direction, an arrow Tr indicates a tracking direction, an arrow Ti indicates a radial tilting direction, and an arrow S indicates a tangential direction (hereinafter referred to as a circumferential direction of a disc (not shown) or a recording track on the disc). , "Circumferential direction").

(4) The focusing coils 54L and 54R and the tracking coil 55 are fixed to the lens holder 52 that holds the objective lens 51, and the movable portion 64 is configured. One end of each of the elastically deformable support members 53a, 53b, 53c, and 53d is fixed to the lens holder 52, and the other end is fixed to the fixed portion 62, so that the movable portion 64 moves in the focusing direction Fo and the tracking direction Tr. It is supported so as to be translatable and rotatable in the radial tilting direction Ti. Further, the fixing portion 62 is fixed to the base 63.

(4) The magnet 58 and the magnet 59 are arranged to face each other, and are attached to the yoke 56a and the yoke 56b, respectively, to configure the magnetic circuit 65R. A focusing coil 54R and a tracking coil 55 are arranged in a magnetic gap between the magnet 58 and the magnet 59. Similarly, the magnet 60 and the magnet 61 are arranged to face each other, and are attached to the yoke 57a and the yoke 57b, respectively, to form a magnetic circuit 65L. The focusing coil 54L and the tracking coil 55 are arranged in a magnetic gap between the magnet 60 and the magnet 61. Driving means is constituted by an interaction between the two magnetic circuits 65R and 65L and currents flowing through the focusing coils 54L and 54R and the tracking coil 55, that is, an electromagnetic force. It should be noted that current is supplied to the focusing coils 54L and 54R and the tracking coil 55 via the support members 53a, 53b, 53c and 53d.

Next, the arrangement of each coil and the magnetic pole of the magnet will be described with reference to FIG. Both the magnet 58 and the magnet 59 are magnetized in the same direction as the arrow S (circumferential direction of the disk) and supply the magnetic flux J1. On the other hand, the magnet 60 and the magnet 61 are magnetized in the direction opposite to the arrow S and supply the magnetic flux J2. By arranging the magnetic circuit 65R and the magnetic circuit 65L close to each other in addition to the main magnetic flux J1 and the magnetic flux J2, the leakage magnetic flux H1 is provided between the yoke 56a and the yoke 57a, and the leakage magnetic flux is provided between the yoke 56b and the yoke 57b. H2 respectively occurs.

The operation of the conventional objective lens driving device configured as described above will be described below with reference to the drawings. In FIG. 7, when a current I1 is applied to the focusing coil 54R, an electromagnetic force in the focusing direction Fo is generated at a portion (point P1) that receives the magnetic flux J1 according to Fleming's law. Similarly, when the current I2 is applied to the focusing coil 54L, an electromagnetic force in the focusing direction Fo is generated at a portion (point P2) that has received the magnetic flux J2. As a result, the movable section 64 is driven in the focusing direction Fo. However, a portion (point P3) receiving the leakage magnetic flux H1 generates an electromagnetic force in a direction opposite to the focusing direction Fo.

駆 動 Regarding the driving in the radial tilting direction Ti, the movable portion 64 is tilted by the moment generated by the difference between the currents I1 and I2, that is, the difference between the electromagnetic forces in the focusing direction Fo received by the focusing coil 54R and the focusing coil 54L.

The operation of generating an electromagnetic force by supplying a current to the tracking coil 55 is the same as the operation by the focusing coils 54R and 54L, and thus the description is omitted.
JP-A-11-283258

In the conventional objective lens driving device configured as described above, an electromagnetic force is generated in a direction opposite to the focusing direction Fo at a portion receiving the leakage magnetic flux H1. Therefore, a rotational vibration around the tracking direction Tr, that is, a so-called pitching vibration is generated in the movable portion 64 including the objective lens 51, so that the aberration of the light spot is deteriorated, and there is a problem that the recording and reproduction are affected.

An object of the present invention is to solve the above-mentioned problems and to provide an objective lens driving device that suppresses pitching vibration and has improved driving sensitivity, and an optical disk device using the same.

In order to achieve the above object, an objective lens driving device of the present invention includes an objective lens for converging a light beam on a disc, a lens holder for holding the objective lens, and a translational movement of the lens holder in a focusing direction and a tracking direction. And a driving means for driving the lens holder in three axes of the focusing direction, the tracking direction, and the radial tilting direction. Here, the driving unit has a winding axis parallel to the optical axis direction of the objective lens, and has two focusing coils wound in a rectangular ring shape, and a winding axis parallel to the circumferential direction of the disk. A tracking coil having an axis and mounted on an outer surface of the focusing coil, a first magnet having a magnetic pole direction parallel to a circumferential direction of the disk, and disposed inside one of the focusing coils; The first magnet has a magnetic pole direction opposite to the first magnet, and faces a second magnet disposed inside the other of the focusing coils while forming a magnetic gap with each of the first magnet and the second magnet. A third magnet and a fourth magnet arranged such that the tracking coil and the focusing coil are located in a magnetic gap, and holding the first magnet outside the magnetic gap. 1 comprises a yoke, a second yoke that holds the second magnet outside of the magnetic gap, and a bridge yoke connecting the open end of the second yoke and the open end of the first yoke.

光 デ ィ ス ク Further, an optical disk device of the present invention includes the above-described objective lens driving device of the present invention.

The objective lens driving device according to the present invention includes a bridging yoke connecting the open end of the first yoke and the open end of the second yoke, so that the crossing yoke intersects the focusing coil between the first yoke and the second yoke. This can prevent the occurrence of leakage magnetic flux. Therefore, pitching vibration of the movable part can be suppressed. Further, since the magnetic utilization efficiency can be increased, the focusing drive sensitivity can be improved.

Further, since the bridging yoke is arranged so as not to interfere with the tracking coil, the tracking drive sensitivity can be improved without reducing the effective length of the tracking coil and without increasing the thickness of the objective lens driving device. Can be.

Further, the optical disk device of the present invention includes the above-described objective lens driving device of the present invention, so that optical coma can be corrected. Quality can be improved.

In the above objective lens driving device of the present invention, it is preferable that the third magnet and the fourth magnet are held by a common third yoke arranged outside the magnetic gap. As a result, generation of leakage magnetic flux can be prevented. Since a closed magnetic flux circuit can be formed together with the bridging yoke, the magnetic utilization efficiency can be improved, and the driving efficiency can be further improved.

In the objective lens driving device of the present invention described above, it is preferable that the third magnet and the fourth magnet are one magnet with two poles. Thereby, a large magnetomotive force can be obtained with a small size.

光 デ ィ ス ク Further, an optical disk device of the present invention includes the above-described objective lens driving device of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of an embodiment of the objective lens driving device of the present invention, and FIG. 2 is a plan view showing the arrangement of coils and magnets in the embodiment of the objective lens driving device of the present invention. FIG. 3 is a perspective view showing a yoke used in the objective lens driving device shown in FIGS. 1 to 3, an arrow Fo indicates a focusing direction, an arrow Tr indicates a tracking direction, an arrow Ti indicates a radial tilting direction, and an arrow S indicates a circumferential direction of a disc (not shown).

レ ン ズ Two focusing coils 4R, 4L and two tracking coils 5R, 5L are attached to the lens holder 2 holding the objective lens 1. The two focusing coils 4R and 4L are used for tilting drive as in the conventional example, and the operation thereof will be described later. The movable part 15 is configured by integrating the objective lens 1, the lens holder 2, the focusing coils 4R and 4L, and the tracking coils 5R and 5L. One end of six elastically deformable linear support members 3a, 3b, 3c, 3d, 3e, 3f (3f is not shown because it is hidden) is fixed to the outer end of the lens holder 2, and the other end is fixed. It is fixed to the unit 13. Thereby, the movable portion 15 is elastically supported by the fixed portion 13 so as to be able to translate in the focusing direction Fo and the tracking direction Tr and to be rotatable in the radial tilting direction Ti. The support members 3a, 3b, 3c, 3d, 3e, and 3f are made of a conductive material such as a beryllium copper alloy or phosphor bronze. Also serves as a means for supplying electricity to 5L. Further, the fixing portion 13 is fixed to the base 14. A magnetic circuit for supplying a magnetic flux to the focusing coils 4R and 4L and the tracking coils 5R and 5L is arranged on the base 14, and the configuration of the magnetic circuit will be further described.

(3) As shown in FIG. 3, the yoke 17 is made of a magnetic material having a substantially “U” shape when viewed along the tracking direction Tr. The first yoke 6, the second yoke 7, and the third yoke 8 are erected on the base 18 of the yoke 17 so as to face each other along the focusing direction Fo. The yoke 17 is fixed to the base 14 at the base 18.

As shown in FIGS. 1 and 2, the first magnet 10 is provided on the surface of the first yoke 6 facing the third yoke 8, and the second magnet 10 is provided on the surface of the second yoke 7 facing the third yoke 8. Each of the magnets 11 is fixed. A third magnet 12 is fixed to a surface of the third yoke 8 on a side facing the first and second yokes 6 and 7. The first and second magnets 10, 11 and the third magnet 12 are separated from each other, and a magnetic gap is formed therebetween.

The two winding coils having a winding axis parallel to the focusing direction Fo and having a winding axis parallel to the circumferential direction of the disc on each outer surface of the two focusing coils 4R and 4L wound in a substantially rectangular annular shape. Are mounted respectively. The first magnet 10 fixed to the first yoke 6 and the second magnet 11 fixed to the second yoke 7 are loosely inserted into the two focusing coils 4R and 4L, respectively. At this time, a part of the focusing coil 4R and the tracking coil 5R are loosely inserted into a magnetic gap formed between the first magnet 10 and the third magnet 12. Further, a part of the focusing coil 4L and the tracking coil 5L are loosely inserted into a magnetic gap formed between the second magnet 11 and the third magnet 12.

Further, a fourth yoke (bridge yoke) 9 is connected and fixed to each open end of the first yoke 6 and the second yoke 7 so as to bridge between the first yoke 6 and the second yoke 7. A magnetic path connecting the first yoke 6 and the second yoke 7 is formed. In FIGS. 1 and 3, the fourth yoke 9 is shown separately from the first yoke 6 and the second yoke 7 in order to make it easier to see the arrangement state of the components. Are arranged in the state shown by the broken line. The fourth yoke 9 is made of a magnetic material similarly to the yoke 17.

Next, the magnetized form of the first magnet 10, the second magnet 11, and the third magnet 12 will be described with reference to FIG. The first magnet 10 has a magnetic pole direction parallel to the circumferential direction S of the disk, and the second magnet 11 has a magnetic pole direction opposite to the first magnet 10. The polarity of the third magnet 12 is divided into two parts so that the surfaces facing the first magnet 10 and the second magnet 11 are opposite to the first magnet 10 and the second magnet 11, respectively. The second magnets 10 and 11 are arranged to face each other. Specifically, one half 12a of the third magnet 12 is magnetized so that the S pole faces the N pole of the first magnet 10, and the N pole faces the S pole of the second magnet 11. Thus, the other half 12b of the third magnet 12 is magnetized. As a result, a magnetic flux K1 is formed in the magnetic gap between the first magnet 10 and one half 12a of the third magnet, and the magnetic flux K1 is formed in the magnetic gap between the second magnet 11 and the other half 12b of the third magnet 12. , A magnetic flux K2 opposite to the magnetic flux K1 is formed. Magnetic fluxes K1 and K2, which are main magnetic fluxes, are supplied to focusing coils 4R and 4L and tracking coils 5R and 5L arranged in the magnetic gap.

Here, the magnetic flux H3 in FIG. 2 corresponds to the leakage magnetic flux H1 in FIG. 7 which has been a problem in the conventional example. In the present embodiment, since the magnetic flux H3 passes through the fourth yoke 9, it does not cross the focusing coils 4R and 4L. Further, the leakage magnetic flux H2 in FIG. 7 of the conventional example corresponds to the magnetic flux H4 flowing through the third magnet 12 and the third yoke 8 in FIG. While the leakage magnetic flux H2 in the conventional example passes through the air, the magnetic flux H4 efficiently passes through the magnetic material in the present embodiment. When the magnetized form shown in FIG. 2 of the present invention is put together, an efficient closed magnetic path that flows in the order of the magnetic flux K1, the magnetic flux H4, the magnetic flux K2, and the magnetic flux H3 is formed, and the magnetic flux H3 is bypassed through the fourth yoke 9. Thus, the leakage flux that intersects with the focusing coil, which has been a conventional problem, is suppressed.

The operation of the embodiment of the objective lens driving device of the present invention configured as described above will be described with reference to the drawings.

In FIG. 2, when a current I3 is applied to the focusing coil 4R, an electromagnetic force in the focusing direction Fo is generated at a portion (point Q1) receiving the magnetic flux K1 according to Fleming's law. Similarly, when the current I4 is applied to the focusing coil 4L, an electromagnetic force in the focusing direction Fo is generated at a portion (point Q2) receiving the magnetic flux K2. As a result, the movable section 15 is driven in the focusing direction Fo. Since the magnetic flux H3 does not intersect with the focusing coils 4R and 4L, unnecessary force unlike the conventional example does not occur.

Regarding the driving in the radial tilting direction Ti, the movable portion 15 is moved by the difference between the current I3 and the current I4, that is, the moment caused by the difference between the electromagnetic force in the focusing direction Fo received by the focusing coil 4R and the focusing coil 4L. It inclines with the circumferential direction (arrow S direction) as the axis. The driving of the movable portion 15 in the focusing direction Fo and the driving in the radial tilting direction Ti are the same as those of the conventional objective lens driving device.

The operation of the objective lens driving device of the present invention is different from the operation of the conventional objective lens driving device in that the magnetic flux H3 is bypassed through the fourth yoke 9 so that focusing between the first yoke 6 and the second yoke 7 is performed. The point is that the magnetic flux that intersects the coils 4R and 4L is eliminated. Therefore, no unnecessary force in the direction opposite to the driving force is generated during driving in the focusing Fo direction. Accordingly, the drive sensitivity is increased, and rotational vibration around the tracking direction Tr, that is, so-called pitching vibration is suppressed.

The operation of generating an electromagnetic force in the tracking direction Tr by flowing a current through the tracking coils 5R and 5L is the same as the operation by the focusing coils 4R and 4L, and thus the description is omitted.

In the present embodiment, the third magnet 12 is one magnet that is magnetized in two poles, and the third magnet 12 is fixed to one third yoke 8. As a result, a magnetic flux H4 that passes through the third yoke 8 and the third magnet 12 is formed, and the generation of a magnetic flux that passes through the air like the leakage magnetic flux H2 shown in FIG. 7 of the conventional example is suppressed. Therefore, since a closed magnetic flux circuit is formed together with the magnetic flux H3 passing through the fourth yoke 9, the generation of leakage magnetic flux is suppressed, the effective magnetic flux is increased, the magnetic utilization efficiency is improved, and the driving efficiency is improved.

In the conventional magnetic flux circuit shown in FIGS. 6 and 7, as one method for suppressing the generation of the leakage magnetic fluxes H1 and H2, as shown in FIG. 4, the open ends of the yokes 56a and 56b are connected to both yokes 56a and 56b. It is conceivable that the first bridge yoke 70R is fixed so as to bridge between them, and the second bridge yoke 70L is fixed to each open end of the yokes 57a and 57b so as to bridge between the two yokes 57a and 57b. As a result, a magnetic flux in a direction opposite to the magnetic flux J1 is formed in the first bridge yoke 70R, and a magnetic flux in a direction opposite to the magnetic flux J2 is formed in the second bridge yoke 70L. Generation of H1 and H2 can be suppressed.

However, when such first and second bridge yokes 70R and 70L are provided, the following problems occur. First, when the tracking coil 55 is driven in the focusing direction Fo, the possibility that the tracking coil 55 collides with the first and second bridge yokes 70R and 70L increases, so that the amount of movement of the movable portion 64 in the focusing direction Fo is limited. You. Second, when the distance from the tracking coil 55 of the first and second bridge yokes 70R and 70L is increased in order to secure the amount of movement of the movable portion 64 in the focusing direction Fo, the thickness of the objective lens driving device (the focusing direction) is increased. Fo size) is increased. Third, in order to secure the amount of movement of the movable section 64 in the focusing direction Fo while suppressing an increase in the thickness of the objective lens driving device, a large effective dimension of the tracking coil 55 (particularly, an effective dimension in the focusing direction Fo) is secured. The driving efficiency in the tracking direction cannot be improved.

In the above-described embodiment of the present invention, the drive efficiency is reduced by causing the magnetic flux H3 to pass through the fourth yoke 9 and passing the magnetic flux H4 through the third yoke 8 and the third magnet 12, thereby suppressing generation of leakage magnetic flux. At the same time, the above-mentioned problem in the case of the configuration as shown in FIG. 4 is solved, and the driving efficiency in the tracking direction is improved.

In the above-described embodiment, the magnet 12 is a single magnet with two poles. However, as shown in FIGS. 6 and 7, two single-pole magnets may be used. Even in this case, the effect of suppressing the pitching vibration of the movable portion 15 does not change. However, using a two-pole magnetized magnet has the advantage that the magnetomotive force in a limited space can be set higher.

In the above-described embodiment, the third yoke 8 is divided into a portion facing the first yoke 6 and a portion facing the second yoke 7 as shown in FIGS. Is also good. Even in this case, the effect of suppressing the pitching vibration of the movable portion 15 does not change. However, there is a possibility that the driving efficiency is reduced due to the generation of the leakage magnetic field.

Further, in the above-described embodiment, two tracking coils 5R and 5L are used so as to pair with the two focusing coils 4R and 4L, respectively. However, as shown in FIGS. It is also possible to use coils.

FIG. 5 is a perspective view of an embodiment of the optical disk device of the present invention using the objective lens driving device configured as described above. The optical disk device includes a spindle motor 22 mounted with a turntable 21 for mounting an optical disk 20 as an information recording medium, an optical pickup 23 mounted with the above-described objective lens driving device, and an optical pickup 23 (not shown in detail) in a tracking direction. A traverse mechanism that moves to Tr is provided. The traverse mechanism is stored and arranged in the tray section 25. When the tray section 25 is inserted into the main body 26, the information recording / reproducing operation is started based on a command signal from the circuit board 27. At the time of recording and reproducing information, the objective lens is driven in the focusing direction and the tracking direction to focus on the information recording position on the optical disk surface. Further, when the optical disk has warpage, it is necessary to control the tilt of the objective lens. When the objective lens driving device described in the above embodiment is applied, the objective lens can be driven and controlled in the radial tilting direction, and optical coma can be corrected.

The optical disc device of the present invention can correct optical coma, so that it is possible to reduce the aberration deterioration of the light spot and to improve the signal quality of recording and reproduction. Therefore, the field of use is wide, and is not particularly limited. For example, it can be used as an optical disk device that requires high density.

The objective lens driving device of the present invention can be used, for example, in the above-described optical disk device.

1 is a perspective view showing a configuration of an embodiment of an objective lens driving device according to the present invention. FIG. 2 is a plan view showing the arrangement of coils and magnets in an embodiment of the objective lens driving device of the present invention. FIG. 2 is a perspective view showing a yoke used in the objective lens driving device shown in FIG. FIG. 2 is a perspective view of an objective lens driving device according to a comparative example that can suppress generation of leakage magnetic flux. Perspective view of an optical disk device using the objective lens driving device of the present invention Perspective view showing the configuration of a conventional objective lens driving device Plan view showing arrangement of coils and magnets in conventional objective lens driving device

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3a, 3b, 3c, 3d, 3e, 3f Support member 4R, 4L Focusing coil 5R, 5L Tracking coil 6 First yoke 7 Second yoke 8 Third yoke 9 Fourth yoke (bridge yoke)
DESCRIPTION OF SYMBOLS 10 1st magnet 11 2nd magnet 12 3rd magnet 13 Fixed part 14 Base 15 Moving part 17 Yoke 18 Base 20 Disk 21 Turntable 22 Spindle motor 23 Optical pickup 25 Tray part 26 Main body 27 Circuit board

Claims (4)

An objective lens that converges the light beam on the disc, a lens holder that holds the objective lens, and the lens holder that is supported by the fixed unit so that it can be translated in the focusing direction and the tracking direction and can be rotated in the radial tilting direction. An objective lens driving device comprising: a supporting unit that drives the lens holder; and a driving unit that drives the lens holder in three axes of the focusing direction, the tracking direction, and the radial tilting direction.
The driving means,
Two focusing coils having a winding axis parallel to the optical axis direction of the objective lens and wound in a substantially rectangular annular shape;
A tracking coil having a winding axis parallel to the circumferential direction of the disk, and mounted on an outer surface of the focusing coil;
A first magnet having a magnetic pole direction parallel to a circumferential direction of the disk, and disposed inside one of the focusing coils;
A second magnet having a magnetic pole direction opposite to the first magnet and disposed inside the other of the focusing coils;
A third magnet and a fourth magnet which face each of the first magnet and the second magnet while forming a magnetic gap, and are arranged so that the tracking coil and the focusing coil are positioned in the magnetic gap;
A first yoke for holding the first magnet outside the magnetic gap;
A second yoke that holds the second magnet outside the magnetic gap;
An objective lens driving device, comprising: a bridging yoke connecting an open end of the first yoke and an open end of the second yoke. The objective lens driving device according to claim 1, wherein the third magnet and the fourth magnet are held by a common third yoke disposed outside the magnetic gap. 2. The objective lens driving device according to claim 1, wherein the third magnet and the fourth magnet are one magnet magnetized with two poles. 3. An optical disk device comprising the objective lens driving device according to claim 1.

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