Optical pickup actuator for driving an objective lens

This application claims the benefit of Korean Patent Application No. 10-2006-0018519, filed on Feb. 25, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

1. Field of the Invention

The present invention relates to an optical pickup actuator used for an optical recording and reproducing apparatus. More particularly, to a slim-type 3-axis driving optical pickup actuator using a fine pattern coil (FPC).

2. Description of the Related Art

A conventional optical pickup is used for an optical recording and reproducing apparatus and performs recording and/or reproduction of information in a non-contact manner with respect to an optical disk (i.e., an information storage medium). The optical pickup requires an optical pickup actuator capable of driving an objective lens in a track direction, a focus direction, and/or a tilt direction to form an optical spot at a correct position on the optical disk.

As high density optical disks become popular, the optical pickup and optical pickup actuator tend to be compact and light. In particular, for the optical pickup actuator to perform the recording/reproducing of information with respect to the high density optical disk, 3-axis driving, i.e. driving in the track direction, the focus direction, and the tilt direction, is necessary. Also, to make the optical pickup compact and light, the size of the optical pickup actuator needs to be small. Accordingly, an optical pickup actuator using a fine pattern coil capable of driving in three axes is needed.

FIGS. 1-3 illustrates a conventional optical pickup actuator using a fine pattern coil. As shown in FIG. 1 , the conventional optical pickup actuator includes a base 1 , a blade 5 supported by a suspension 3 and installed on the base 1 to be capable of moving, a magnetic circuit 10 dividedly installed on the blade 5 and the base 1 , and a stopper 9 restricting a driving height during the driving of the blade 5 .

An objective lens 7 is installed on the blade 5 . As the blade 5 is driven by a driving force through the magnetic circuit 10 , the objective lens 7 is driven in the track direction, the focus direction, and the tilt direction.

Thus, the magnetic circuit 10 includes a fine pattern coil 11 fixed to the blade 5 , a pair of magnets 15 arranged to face each other with respect to the fine pattern coil 11 interposed therebetween, and a yoke 17 fixing the magnet 15 to the base 1 and forming a magnetic path. The magnets 15 are 2-pole magnetized permanent magnets. In FIGS. 1-3 , the magnets 15 are illustrated as being surface polarized to the left and right.

The fine pattern coil 11 is divided into focus coils 12 a and 12 b and a track coil 13 according to the direction to drive the blade 5 . The focus coil includes first and second focus coils 12 a and 12 b which are separated from a polarization line 15 a of the magnet 15 that is polarized to the left and right. Thus, when current is applied, the focus coils 12 a and 12 b make the fine pattern coil 11 and the blade 5 driven in a Y-axis direction. To this end, the first and second focus coils 12 a and 12 b are arranged such that a part of the focus coils 12 a and 12 b parallel to the X-axis direction faces the magnet 15 , and contribute to the driving in the focus direction. Thus, the other part (the lower portion in the drawing) of the focus coils 12 a and 12 b does not face the magnet 15 to prevent the offset of a driving force.

The track coil 13 is arranged in front of the polarization line 15 a of the magnet 15 and drives the blade 5 in the X-axis direction when current is applied to the track coil 13 . The track coil 13 is arranged such that a part of the track coil 13 parallel to a Y-axis direction faces the magnet 15 , and contribute to the driving in the tracking direction.

In the conventional optical pickup actuator using a fine pattern coil configured as above, as shown in FIG. 3 , when magnetic poles of the magnet 15 are arranged, an N pole and an S pole are respectively arranged in the left and right sides with respect to the polarization line 15 a . When current is applied to the focus coils 12 a and 12 b in a direction indicated by arrows (→), the blade 5 is driven in a direction indicated by arrow (→).

In the above conventional optical pickup actuator, tilt driving is performed, not by including an additional tilt coil, but instead by using the first and second focus coils 12 a and 12 b . That is, input/output ports of current with respect to each of the first and second focus coils 12 a and 12 b are independently configured. Current of a different direction or intensity is applied to the input/output ports. Thus, the focus driving and tilt driving are performed using a difference in the driving forces.

Thus, since the conventional optical pickup actuator includes a structure to perform both focus driving and tilt driving using the first and second focus coils 12 a and 12 b , a drive circuit is complicated and a correction error may be generated when the driving to correct a focus error and the driving to correct a tilt error are simultaneously performed. Also, in the arrangement of the first and second focus coils 12 a and 12 b and the magnet 15 , since only the upper portions of the first and second focus coils 12 a and 12 b are used, a magnetic force is weak.

Accordingly, it is an aspect of the present invention to provide an optical actuator using a fine pattern coil which increases a magnetic driving force by improving the arrangement structure between the focus coil and the magnet and reduce a drive error by configuring an independent tilt coil.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

The foregoing and/or other aspects of the present invention are achieved by providing an optical pickup actuator including a base, a blade having an objective lens mounted thereon, a plurality of suspensions supporting the blade to be movable with respect to the base and providing an electroconductive path, and a magnetic circuit driving the blade according to a driving signal applied through the respective suspensions, wherein the magnetic circuit includes a magnet fixed to the base, and a fine pattern coil installed on the blade at a position facing the magnet, and having a track pattern coil, a focus pattern coil, and a tilt pattern coil, independently driven by current applied through the suspensions and providing driving forces in a track direction, a focus direction, and a tilt direction of the blade.

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a plan view of a conventional optical pickup actuator;

FIG. 2 is a cross-sectional view of a part of the conventional optical pickup actuator of FIG. 1 ;

FIG. 3 is a view of the arrangement of the fine pattern coil and the magnet of the conventional optical pickup actuator shown in FIG. 1 and a driving direction according to the direction of current;

FIG. 4 is a perspective view of an optical pickup actuator according to an embodiment of the present invention;

FIG. 5 is a plan view of the optical pickup actuator of FIG. 4 ;

FIG. 6 is a cross-sectional view of a part of the optical pickup actuator of FIG. 4 ;

FIGS. 7-9 are views illustrating the arrangements of magnetic poles of magnets according to embodiments of the present invention;

FIG. 10 is a view illustrating the arrangement of the fine pattern coil and the magnet of FIG. 4 and a driving direction according to the direction of current; and

FIGS. 11A and 11B are view illustrating the arrangements of coils and electrodes on different layers of the fine pattern coil.

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.

FIGS. 4 and 5 are a perspective view and a plan view of an optical pickup actuator according to an embodiment of the present invention. FIG. 6 is a cross-sectional view of a major part of the optical pickup actuator of FIG. 4 . As shown in FIGS. 4-6 , an optical pickup actuator according to an embodiment of the present invention comprises a base 31 , a blade 35 on which an objective lens 37 is mounted, a plurality of suspensions 33 supporting the blade 35 to be movable with respect to the base 31 , and a magnetic circuit 40 driving the blade 35 . The suspensions 33 provide electroconductive paths through which current is applied to a fine pattern coil 41 which constitutes the magnetic circuit 40 . Thus, in this embodiment of the present invention, the suspensions 33 are six suspension wires, for example, as shown in FIG. 4 . However, the present invention is not limited hereto, and may vary as necessary.

The base 31 is installed to be movable in a radial direction of an optical recording medium with respect to an optical information recording/reproducing apparatus. The base 31 comprises a holder 31 a to support an end of the suspensions 33 . As the blade 35 is operated by a driving force through the magnetic circuit 40 , the objective lens 37 is independently driven in a track direction, a focus direction, and a tilt direction (i.e., 3-axis driving).

Thus, the magnetic circuit 40 comprises a magnet 45 fixed to the base 31 and a fine pattern coil 41 installed at a position facing the magnet 45 of the blade 35 . According to an embodiment of the present invention, the fine pattern coil 41 is directly formed on the blade 35 by insert molding or assembly, for example. As the fine pattern coil 41 is formed as described later, an electrode 410 of FIG. 10 and the suspensions 33 can be directly and electrically connected.

The magnet 45 comprises first and second magnets 45 a and 45 b arranged to face each other with respect to the fine pattern coil 41 interposed therebetween. In this case, since a magnetic driving force between the fine pattern coil 41 and the magnet 45 is increased, more accurate driving control is available. Further, a yoke 47 which fixes the magnet 45 to the base 31 and forms a magnetic path is provided. The arrangement of magnetic poles of the magnet 45 according to an embodiment of the present invention will be described with reference to FIGS. 7-9 .

FIG. 7 is a view illustrating the arrangement of magnetic poles of a magnet according to an embodiment of the present invention. As shown in FIG. 7 , a magnet 451 , according to an embodiment of the present invention, is a magnet which is 4-pole magnetized and surface divided for example. That is, the magnet 451 has a 2×2 format and is sectioned in a cross type along a first polarization line L 1 parallel to the focus driving direction (Y direction) of the blade 35 and a second polarization line L 2 parallel to a track driving direction (X direction) of the blade 35 . The magnet 451 comprises first through fourth magnet portions 451 a , 451 b , 451 c , and 451 d respectively arranged in the first through fourth quadrants. The neighboring magnet portions are polarized to have the opposite poles. For example, in the first and third magnet portions 451 a and 451 c , N poles face the fine pattern coil 41 while, in the second and fourth magnet portions 451 b and 451 d , S poles face the fine pattern coil 41 . The present invention is not limited hereto, and may vary as necessary.

The above arrangement of the magnet 451 is an example of one of two magnets arranged to face each other. Accordingly, the other magnet has the same sectional structure but the opposite magnetic pole arrangement. For example, when the magnetic pole arrangement of the magnet 451 is that of a portion of the first magnet 45 a of FIG. 6 facing the fine pattern coil 41 , in the magnetic pole arrangement of a portion of the second magnet 45 b of FIG. 6 facing the fine pattern coil 41 , the magnet portions facing the first and third magnet portions 451 a and 451 c are S poles while the magnet portions facing the second and fourth magnet portions 451 b and 451 d are N poles.

When the first through fourth magnet portions 451 a , 451 b , 451 c , and 451 d are arranged as above, since an interval space between the respective magnet portions is not formed, the base 31 is easily assembled.

FIG. 8 is a view illustrating the arrangement of magnetic poles of a magnet according to another embodiment of the present invention. As shown in FIG. 8 , a magnet 453 according to an embodiment of the present invention is two magnets, each of which is 2-pole magnetized and surface divided, for example. The magnet 453 comprises first through fourth magnet portions 453 a , 453 b , 453 c , and 453 d . The first and second magnet portions 453 a and 453 b are arranged close to each other and the magnetic poles thereof are polarized to be opposite to each other with respect to the first polarization line L 1 that is parallel to the focus driving direction (Y direction) of the blade 35 . The third and fourth magnet portions 453 c and 453 d are arranged close to each other and the magnetic poles thereof are polarized to be opposite to each other with respect to the first polarization line L 1 . The third and fourth magnet portions 453 c and 453 d are respectively separated a predetermined distance from the second and first magnet portions 453 b and 453 a in the focus direction (Y) of the blade 35 . Also, the first and fourth magnet portions 453 a and 453 d have the opposite magnetic poles while the second and third magnetic portions 453 b and 453 c have the opposite magnetic poles. For example, the first and third magnetic portions 453 a and 453 c have N poles to face the fine pattern coil 41 while the second and fourth magnetic portions 453 b and 453 d have S poles to face the fine pattern coil 41 .

The above arrangement of the magnet 453 is an example of one of two magnets arranged to face each other. Accordingly, the other magnet has the same sectional structure but the opposite magnetic pole arrangement. In this embodiment of the present invention, since the gap between the magnetic portions in the focus direction is larger than that FIG. 7 , the driving force in the focus direction can be improved.

FIG. 9 is a view illustrating the arrangement of the magnetic poles of a magnet according to yet another embodiment of the present invention. As shown in FIG. 9 , a magnet 455 according to yet another embodiment of the present invention comprises two magnets, each of which is 2-pole magnetized and surface divided, for example. The magnet 455 comprises first through fourth magnet portions 455 a , 455 b , 455 c , and 455 d . The first and fourth magnet portions 455 a and 455 d are arranged close to each other and the magnetic poles thereof are polarized to be opposite to each other with respect to the second polarization line L 2 that is parallel to the track driving direction (X direction) of the blade 35 . The second and third magnet portions 455 b and 455 c are arranged close to each other and the magnetic poles thereof are polarized to be opposite to each other with respect to the second polarization line L 2 . The second and third magnet portions 455 b and 455 c are respectively separated a predetermined distance from the first and fourth magnet portions 455 a and 455 d in the track direction (X) of the blade 35 . Also, the first and second magnet portions 455 a and 455 b have the opposite magnetic poles while the third and fourth magnetic portions 455 c and 455 d have the opposite magnetic poles. For example, the first and third magnetic portions 455 a and 455 c have N poles to face the fine pattern coil 41 while the second and fourth magnetic portions 455 b and 455 d have S poles to face the fine pattern coil 41 .

The above arrangement of the magnet 455 is an example of one of two magnets arranged to face each other. Accordingly, the other magnet has the same sectional structure but the opposite magnetic pole arrangement. In this case, since the gap between the magnet portions in the track direction is larger than that of FIG. 7 , the driving force in the focus direction can be improved.

FIG. 10 is a view illustrating the arrangement of the fine pattern coil 41 and the magnet 451 of FIG. 7 and a driving direction according to the direction of current. FIGS. 11A and 11B are view illustrating the arrangements of coils and electrodes on different layers of the fine pattern coil. As shown in FIGS. 10 , 11 a and 11 B, the structure of the fine pattern coil 41 and the interaction between the magnets and the fine pattern coil 41 will be described in detail.

As shown in FIGS. 10 , 11 A, and 11 B, the fine pattern coil 41 is independently driven by current applied through the suspensions 33 and comprises a track pattern coil 431 , a focus pattern coil 433 , and a tilt pattern coil 435 respectively providing driving force in the track direction (X axis), the focus direction (Y axis), and the tilt direction of the blade 35 .

The fine pattern coil 41 comprises a stacked structure of at least two pattern coil layers that are electrically insulated. A plurality of electrodes 410 electrically connected with the respective suspensions 33 of FIG. 4 are formed at positions corresponding to the respective fine pattern coil layers. As shown in FIG. 10 , the electrode 410 comprises first through sixth electrodes 411 - 416 which are electrically connected with both of the respective suspensions 33 and the fine pattern coil 41 . That is, the first and second electrodes 411 and 412 are electrically connected with the track pattern coil 431 , the third and fourth electrodes 413 and 414 are electrically connected with the focus pattern coil 433 , and the fifth and sixth electrodes 415 and 416 are electrically connected with the tilt pattern coil 435 . Thus, by applying current independently to each of the first through sixth electrodes 411 - 416 , the track pattern coil 431 , the focus pattern coil 433 , and the tilt pattern coil 435 can be selectively and independently driven.

FIGS. 11A and 11B illustrate an example in which the fine pattern coil 41 includes first and second pattern coil layers 41 a and 41 b . As shown in FIG. 11A , the first through sixth electrodes 411 - 416 connected with the suspensions 33 of FIG. 4 , the track pattern coil 431 electrically connected with the first and second electrodes 411 and 412 , and the focus pattern coil 433 electrically connected with the third and fourth electrodes 413 and 414 are formed on the first pattern coil layer 41 a . As shown in FIG. 11B , the first through sixth electrodes 411 - 416 connected with the suspensions 33 of FIG. 4 , the track pattern coil 431 electrically connected with the first and second electrodes 411 and 412 , and the tilt pattern coil 435 electrically connected with the fifth and sixth electrodes 415 and 416 are formed on the second pattern coil layer 41 b.

Since the first through sixth electrodes 411 - 416 and the track pattern coil 431 formed on the first and second pattern coil layers 41 a and 41 b have substantially the same structure and perform the same function, thus, the same reference numerals are used. That is, since the first through sixth electrodes 411 - 416 of the first pattern coil layer 41 a are electrically connected with the first through sixth electrodes 411 - 416 of the second pattern coil layer 41 b , respectively, when current is applied through the suspensions 33 of FIG. 4 , a driving force is generated by an interactive electromagnetic force between the track, focus, and tilt pattern coils 431 , 433 , and 435 and the magnet 45 .

Also, the track pattern coils 431 formed on the first and second pattern coil layers 41 a and 41 b are arranged to face each other when the fine pattern coil 41 is formed by depositing the first and second pattern coil layers 41 a and 41 b , and the portions facing each other are wound in a same rotation direction.

The track pattern coil 431 comprises first and second track pattern coil portions 431 a and 431 b . The first track pattern coil portion 431 a is electrically connected with the first electrode 411 through a first port 431 c . When the magnet 451 configured as shown in FIG. 7 is provided, the first track pattern coil portion 431 a is arranged to face each of the first and second magnet portions 451 a and 451 b . That is, each of two parts of the first track pattern coil portion 431 a parallel to the Y axis is arranged at a different position with respect to the first polarization line L 1 .

The second track pattern coil portion 431 b is electrically connected with the second electrode 412 through a second port 431 d . Also, the first port 431 c and the second port 431 d are electrically connected with each other. When the magnet 451 configured as shown in FIG. 7 is provided, the second track pattern coil portion 431 b is arranged to face each of the third and fourth magnet portions 451 c and 451 d . That is, each of two parts of the second track pattern coil portion 431 b parallel to the Y axis is arranged at a different position with respect to the first polarization line L 1 .

Also, the second track pattern coil portion 431 b is wound in a direction opposite to a direction in which a coil of the first track pattern coil portion 431 a is wound. Thus, as shown in FIG. 10 , when current is applied clockwise to the first track pattern coil portion 431 a , the current is applied counterclockwise to the second track pattern coil portion 431 b . The magnetic poles of the magnet 451 respectively facing the first and second track pattern coil portions 431 a and 431 b are provided opposite to each other. Thus, the current is applied to the first track pattern coil portion 431 a in a direction indicated by an arrow “↑” and to the second track pattern coil portion 431 b in a direction indicated by an arrow “↓”, the blade 35 of FIG. 4 is driven in a track direction indicated by an arrow “←”, that is, in a direction −X axis. Reversely, when the current is applied in a direction opposite to the direction shown in FIG. 10 , the blade 35 is driven in the +X axis direction according to the above-described principle.

Thus, the driving of the blade 35 and the objective lens 37 mounted thereon in the track direction can be performed by the direction of the current applied to the first and second track pattern coil portions 431 a and 431 b and an interactive electromagnetic force between the first through fourth magnet portions 451 a , 451 b , 451 c , and 451 d.

The focus pattern coil 433 and the tilt pattern coil 435 formed on each of the first and second pattern coil layers 41 a and 41 b are arranged to face to each other by depositing the first and second pattern coil layers 41 a and 41 b when the fine pattern coil 41 is formed. At least part of the portions facing each other is wound in a different rotation direction.

As shown in FIG. 11A , the focus pattern coil 433 comprises first and second focus pattern coil portions 433 a and 433 b which are arranged at both side positions with respect to the track pattern coil 431 interposed therebetween. The first focus pattern coil portion 433 a is electrically connected with the third electrode 413 through a third port 433 c . As shown in FIG. 10 , when the magnet 451 configured as shown in FIG. 7 is provided, at least part of the first focus pattern coil portion 433 a is arranged to face each of the second and third magnet portions 451 b and 451 c . That is, each of two portions of the first focus pattern coil portion 433 a parallel to the X axis is arranged at a different position with respect to the second polarization line L 2 .

The second focus pattern coil portion 433 b is electrically connected with the fourth electrode 414 through a fourth port 433 d . The third port 433 c and the fourth port 433 d are electrically connected with each other. When the magnet 451 configured as shown in FIG. 7 is provided, at least part of the second focus pattern coil portion 433 b is arranged to face each of the first and fourth magnet portions 451 a and 451 d . That is, each of the two portions of the second focus pattern coil portion 433 b parallel to the X axis is arranged at a different position with respect to the second polarization line L 2 .

Also, the second focus pattern coil portion 433 b is wound in a direction opposite to a direction in which a coil of the first focus pattern coil portion 433 a is wound. Thus, as shown in FIG. 10 , when current is applied clockwise to the first focus pattern coil portion 433 a , the current is applied counterclockwise to the second focus pattern coil portion 433 b . The magnetic poles of the magnet 451 respectively facing the first and second focus pattern coil portions 433 a and 433 b are provided opposite to each other. Thus, the current is applied to the first focus pattern coil portion 433 a in a direction indicated by an arrow “→” and to the second focus pattern coil portion 433 b in a direction indicated by an arrow “←”, the blade 35 of FIG. 4 is driven in a focus direction indicated by an arrow “↑”, that is, in a direction +Y axis. Reversely, when the current is applied in the opposite direction, the blade 35 is driven in the −Y axis direction according to the same principle.

Thus, the driving of the blade 35 and the objective lens 37 mounted thereon in the focus direction can be performed by the direction of the current applied to the first and second focus pattern coil portions 433 a and 433 b and the interactive electromagnetic force between the first through fourth magnet portions 451 a , 451 b , 451 c , and 451 d.

As shown in FIG. 11B , the tilt pattern coil 435 comprises first and second tilt pattern coil portions 435 a and 435 b which are arranged at both side positions with respect to the track pattern coil 431 interposed therebetween. The first tilt pattern coil portion 435 a is electrically connected with the fifth electrode 415 through a fifth port 435 c . When the magnet 451 configured as shown in FIG. 7 is provided, at least part of the first tilt pattern coil portion 435 a is arranged to face each of the second and third magnet portions 451 b and 451 c . That is, each of two portions of the first tilt pattern coil portion 435 a parallel to the X axis is arranged at a different position with respect to the second polarization line L 2 .

The second tilt pattern coil portion 435 b is electrically connected with the sixth electrode 416 through a sixth port 435 d . The fifth port 435 c and the sixth port 435 d are electrically connected with each other. When the magnet 451 configured as shown in FIG. 7 is provided, at least part of the second tilt pattern coil portion 435 b is arranged to face each of the first and fourth magnet portions 451 a and 451 d . That is, each of the two portions of the second tilt pattern coil portion 435 b parallel to the X axis is arranged at a different position with respect to the second polarization line L 2 .

Also, the second tilt pattern coil portion 435 b is wound in a direction in which a coil of the first tilt pattern coil portion 435 a is wound. Thus, as shown in FIG. 10 , when current is applied clockwise to the first tilt pattern coil portion 435 a , the current is also applied clockwise to the second tilt pattern coil portion 435 b unlike the focus pattern coil 433 . The magnetic poles of the magnet 451 respectively facing the first and second tilt pattern coil portions 435 a and 435 b are provided opposite to each other. Thus, when the current is applied to the first tilt pattern coil portion 435 a in a direction indicated by an arrow “→”, the blade 35 of FIG. 4 is driven in a direction indicated by an arrow “↑”, that is, in a direction +Y axis, in a portion corresponding thereto. Meanwhile, the current is applied to the second tilt pattern coil portion 435 b in the same direction indicated by the arrow “→”. Thus, since in this case the poles of the magnet 45 are arranged to be opposite to each other, the blade 35 of FIG. 4 is driven in a direction indicated by an arrow “↓” (not shown), that is, in the −Y axis direction, in a portion corresponding thereto. Accordingly, the blade 35 is tilt driven in the clockwise direction. Meanwhile, when the current is applied in the opposite direction, the blade 35 is tilt driven in the counterclockwise direction according to the same principle.

Thus, the driving of the blade 35 and the objective lens 37 mounted thereon in the tilt direction can be performed by the direction of the current applied to the first and second tilt pattern coil portions 435 a and 435 b and the interactive electromagnetic force between the first through fourth magnet portions 451 a , 451 b , 451 c , and 451 d.

The fine pattern coil 41 according to the present invention is not limited to the above-described 2-layer deposition structure having the first and second pattern coil layers 41 a and 41 b , and can have a variety of layer structures, for example, four layers or six layers considering a desired intensity of the magnetic driving force.

As described above, since the optical pickup actuator according to an embodiment of the present invention uses the fine pattern coil, a slim-type optical pickup actuator having a height which is greatly reduced can be provided. Also, since the fine pattern coil is formed in the blade in insert molding or directly assembly, and the suspensions and the fine pattern coil are directly connected without using an additional part such as a print circuit board, mass production and assembly accuracy can be secured.

Furthermore, the structure and arrangement of the magnet are improved so that both the upper and lower portions of the focus pattern coil are involved in the focus driving. Thus, the magnetic driving force in the focus direction can be increased. In addition, since the track pattern coil is formed in the upper and lower portions of the magnet with respect to the second polarization line, an effective coil area contributing to the magnetic driving force in the track driving direction can be extended so that the deterioration of sensitivity performance is prevented and negative oscillation due to a leakage magnetic flux is greatly reduced. In forming the fine pattern coil in a multilayer structure, since an independent fine pattern coil is provided, the tilt driving can be performed, without being affected by the focus driving so that driving error can be reduced.

Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.