KR20060025756A - High thrust magnetic circuit and optical pickup actuator employing the same - Google Patents

Abstract

The present invention discloses a high thrust magnetic circuit that provides an appropriate AC sensitivity to an optical pickup actuator for a Blu-ray disc and an optical pickup actuator using the magnetic circuit. According to one type of the present invention, in a magnetic circuit for an optical pickup actuator in which a plurality of coils are arranged between two opposing magnet portions, the two opposing magnetic portions each have a plurality of closed loops on respective opposing surfaces. Each comprising two magnets polarized in opposite directions to form a magnetic field, wherein the coils between the two magnet portions are arranged to pass through the plurality of closed loop magnetic fields respectively formed on respective opposite surfaces of the two magnet portions; It is characterized by.

Optical Pickup, Actuator, Blu-ray Disc, Focusing Coil, Tracking Coil, Optical Recording / Reproduction Device, Objective Lens, Bobbin, Magnetic Circuit

Description

High thrust magnetic circuit and optical pickup actuator employing the same

1 is a perspective view schematically showing the structure of a general actuator.

2A is a perspective view showing a schematic structure of a magnetic circuit for an optical pickup actuator according to the present invention.

2B and 2C are a plan view and a side view, respectively, showing a schematic structure of a magnetic circuit for an optical pickup actuator according to the present invention.

Figure 2d shows the positional relationship of the magnet and the coil in the magnetic circuit for the optical pickup actuator according to the present invention.

2E is a diagram illustrating the principle of a magnetic circuit according to the present invention.

3 is an exploded perspective view of the optical pickup actuator according to the present invention.

4 schematically shows the structure of an optical recording / reproducing apparatus employing an optical pickup actuator according to the present invention.

5 and 6 are perspective views schematically showing a conventional magnetic circuit.

※ Explanation of code about main part of drawing ※

10 ........ Magnetic circuit 11,18 ..... First magnet

12,19 ..... Second magnet 14,21 ..... Magnetic part

15,16 ..... Tracking Coil 17 ........ Focusing Coil

30 ........ Optical Pickup Actuator 31 ........ Bobbin

32 ........ Objective lens 40 ........ Optical recording / playback device

The present invention relates to a high-pump magnetic circuit and an optical pickup actuator using the magnetic circuit. More particularly, the present invention relates to an alternating current sensitivity suitable for an optical pickup actuator for a Blu-ray Disc (BD). The present invention relates to a high force magnetic circuit providing an optical pickup actuator using the magnetic circuit.

In general, an optical pickup is an apparatus that is employed in an optical recording / reproducing apparatus and records and / or reproduces information on a disk mounted on a turntable in a non-contact manner while moving in a radial direction of a disk which is a recording medium. The optical pickup focuses the light emitted from the light source to form an optical spot on the optical disk, and the optical lens is arranged in a tracking direction, focusing direction, and tilt direction so that the optical spot formed by the objective lens is positioned at the correct position of the optical disk. It includes an actuator to control. Here, the tracking direction drive refers to adjusting the objective lens in the radial direction of the optical disc so that an optical spot can be formed at the center of the track. Typically, the optical pickup actuator is based on tracking direction and focus direction driving, that is, two-axis driving.

1 is a perspective view schematically showing the structure of such an optical pickup actuator. As shown in FIG. 1, a conventional optical pickup actuator includes a base 100, a holder 103 fixed to the base 100, a bobbin 107 fixing the objective lens 105, and the bobbin 107. And a plurality of suspension wires 130 connected between the holder 103 and the holder 103 to movably support the bobbin 107 with respect to the holder 103, and the bobbin 107 in a tracking direction, focus direction, or tilt. And a magnetic drive unit for moving in the direction. The magnetic driving unit includes a magnet 110 provided in the base 100 and a plurality of coils 120, 122, and 125 provided in the bobbin 107, and applies current to the coils 120, 122, and 125 in the magnetic field generated by the magnet 110. When the bobbin 107 is driven by the electromagnetic force generated.

Meanwhile, in accordance with the trend of increasing the capacity of optical recording media, Blu-ray discs capable of storing information up to several tens of gigabytes (giga bytes) have been developed and commercialized. As the recording capacity of optical recording media increases, there is a demand for optical pickup actuators that are much more sensitive than optical pickup actuators for compact discs (CDs) or digital versatile discs (DVDs). For example, in the case of BD, the numerical aperture NA is increased from 0.65 to 0.85, and the wavelength is decreased from 680 nm to 405 nm as compared to the DVD. As a result, the tolerance of each servo system is inevitably reduced. For example, in the case of a focus servo, the tolerance of ± 0.15 μm in DVD is estimated to be ± 0.046 μm in BD, which is only about 1/3 to 1/4 of DVD. In the case of a track servo, the tolerance of the DVD was ± 0.031 μm, which is estimated to be ± 0.009 μm in the BD, which is only 1/3 to 1/4 of the DVD.

In Blu-ray discs requiring such a small tolerance, in order to implement a high-speed recording / reproducing apparatus, it is necessary to increase the AC sensitivity of the optical pickup actuator. As a method for increasing the AC sensitivity of the optical pickup actuator, for example, a method of reducing the weight of the actuator, a method of increasing the thrust of the actuator, or a method of increasing the primary resonance frequency of the actuator, and the like. However, in the case of BD, since a large number of optical parts must be added to the actuator compared to a CD or a DVD, weight reduction cannot be expected. In addition, when the primary resonant frequency is increased, a problem arises in that the direct current sensitivity of the actuator is excessively reduced. If the DC sensitivity is excessively reduced, it may result in a weakening of the response of the optical pickup actuator to the deflection / eccentric disk. As a result, in order to realize a high speed of 4 times or more in the optical pickup actuator for BD, an increase in thrust is necessary, and the design of a magnetic circuit for this is necessary.

It is therefore an object of the present invention to provide a magnetic circuit for an optical pickup actuator of high force.

Another object of the present invention is to provide an optical pickup actuator having a high AC sensitivity suitable for an optical pickup actuator for a high speed Blu-ray disc by increasing the thrust of the magnetic circuit.

Still another object of the present invention is to provide an optical recording / reproducing apparatus for a high speed Blu-ray disc.

According to one type of the present invention, in a magnetic circuit for an optical pickup actuator in which a plurality of coils are arranged between two opposing magnet portions, the two opposing magnetic portions each have a plurality of closed loops on respective opposing surfaces. Each comprising two magnets polarized in opposite directions to form a magnetic field, wherein the coils between the two magnet portions are arranged to pass through the plurality of closed loop magnetic fields respectively formed on respective opposite surfaces of the two magnet portions; It is characterized by.

In this case, each of the magnet portion, the first magnet polarized in a predetermined direction; And a second magnet polarized in a direction opposite to the first magnet and surrounding at least three sides of the circumference of the first magnet. The plurality of coils may be disposed in a space between the second magnets facing each other, and may be wound in a direction perpendicular to the second magnet surface.

In addition, the optical pickup actuator according to another type of the present invention, the base; Bobbin for fixing the objective lens; A support member having one end coupled to the bobbin and the other end fixed to a holder provided on the base such that the bobbin can move relative to the base; And a pair of magnets installed in the base and a plurality of coils coupled to the bobbins, respectively, adjacent to front and rear sides of the bobbins, and a driving unit driving the bobbins, wherein the magnets face the bobbins. It has two magnets polarized in opposite directions to form a plurality of closed loop magnetic field on the surface, characterized in that the plurality of coils coupled to the bobbin are each disposed to pass through the plurality of closed loop magnetic field .

In this case, the magnet unit: a first magnet polarized in a predetermined direction; And a second magnet that is polarized in a direction opposite to the first magnet and surrounds the circumference of the first magnet on at least three surfaces, wherein the second magnet has a lower surface of the first magnet and left and right side surfaces of the first magnet. It is characterized by surrounding.

In addition, the optical pickup actuator according to the present invention, the focusing coil wound around the lower end of the bobbin to correspond to the second magnet portion surrounding the lower surface of the first magnet; And first and second tracking coils respectively wound on both sides of the bobbin so as to correspond to second magnet portions surrounding the left and right sides of the first magnet, wherein the focusing coil and the first and second tracking coils It is characterized in that the winding in the direction perpendicular to the second magnet surface.

On the other hand, according to another type of the present invention, comprising an objective lens for focusing the light emitted from the light source to the optical disk and an optical pickup actuator for driving the objective lens, the object is installed to be movable in the radial direction of the optical disk An optical recording / reproducing apparatus, comprising: an optical pickup for irradiating light to a desired position of the optical disc through a lens to record or reproduce information, wherein the optical pickup actuator comprises: a base; A bobbin for fixing the objective lens; A support member having one end coupled to the bobbin and the other end fixed to a holder provided on the base such that the bobbin can move relative to the base; And a pair of magnets installed in the base and a plurality of coils coupled to the bobbins, respectively, adjacent to front and rear sides of the bobbins, and a driving unit driving the bobbins, wherein the magnets face the bobbins. It characterized by having two magnets polarized in opposite directions to form a plurality of closed loop magnetic fields on the surface, the plurality of coils coupled to the bobbin are each arranged to pass through the plurality of closed loop magnetic fields .

According to the present invention, the optical pickup actuator further comprises an aberration correction plate for correcting spherical aberration mounted to the lower portion of the bobbin.

Hereinafter, a structure and an operation of a magnetic circuit, an optical pickup actuator, and an optical recording / reproducing apparatus employing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2A shows a perspective view of a magnetic circuit for an optical pickup actuator according to the present invention. As shown in FIG. 2A, the magnetic circuit 10 according to the present invention has a structure in which a plurality of coils 15, 16, and 17 are disposed between two opposing magnet parts 14 and 21 facing each other. Have

In this case, each of the magnet parts 14 and 21 includes a bipolar polarization including first magnets 11 and 18 and second magnets 12 and 19 surrounding the circumference of the first magnets 11 and 18, respectively. In the form of a magnet. In FIG. 2A, the second magnets 12, 19 are shown in a 凹 shape that surrounds three surfaces (ie, bottom and left and right sides) of the first magnets 11 and 18, but the first magnets 11 and 18 are not shown. It may be configured to surround all four sides of the. The first magnets 11 and 18 and the second magnets 12 and 19 are mutually formed so as to form a plurality of closed loop magnetic fields on opposite surfaces of the two magnet portions 14 and 21 facing each other. It is polarized in the opposite direction. For example, the first magnets 11 and 18 may be N poles, and the second magnets 12 and 19 may be S poles. In contrast, the first magnets 11 and 18 may be formed as S poles, and the second magnets 12 and 19 may be formed as N poles. Yokes 13 and 20 coupled to the rear surfaces of the first magnets 11 and 18 are used to support the first magnets 11 and 18, and the first magnets 11 and 18 are the yoke 13. 20 is mounted to and supported by a base (not shown) of the optical pickup actuator.

Meanwhile, the plurality of coils 15, 16 and 17 are disposed in a space formed between the second magnets 12 and 19 of the two magnet parts 14 and 21 facing each other. That is, as shown in FIG. 2A, the coils are disposed in a space where the second magnet 12 of the first magnet part 14 and the second magnet 19 of the second magnet part 21 face each other. do. For example, the first and second coils 15 and 16 are disposed perpendicularly to the bottom surface at portions of the second magnets 12 and 19 surrounding the left and right sides of the first magnets 11 and 18, respectively. 2 magnets 12 and 19 are wound in a direction perpendicular to the plane (i.e., x-axis direction). In addition, the third coil 17 is disposed horizontally with the bottom surface at the center of the second magnets 12 and 19 surrounding the lower surfaces of the first magnets 11 and 18, and the second magnets 12 19 is wound in a direction perpendicular to the plane (ie, in the x-axis direction).

In this structure, when a current is applied to each coil, the first and second coils 15, 16 are forced to the left and right sides (i.e., + y-axis or -y-axis direction) according to the direction of the current, and the third The coil 17 is forced up and down (ie, in the + z axis or -z axis direction). Thus, when used in an optical pickup actuator, the first and second coils 15 and 16 serve as tracking coils and the third coil 17 serves as a focusing coil.

2B and 2C are a plan view and a side view, respectively, showing a schematic structure of a magnetic circuit 10 for an optical pickup actuator according to the present invention. As can be seen from the plan view of FIG. 2B, the second magnets 12 and 19 surround the left and right sides of the first magnets 11 and 18, respectively, and the first and second coils 15 and 16 have two agents. It is arranged in the space connecting the left and the space connecting the right between the two magnets (12, 19), respectively. Also, as can be seen from the right side view of FIG. 2C, the first and second coils 15 and 16 are disposed perpendicularly to the bottom surface, and a third under the first and second coils 15 and 16. The coil 17 is installed horizontally with the bottom surface. At this time, a predetermined gap (that is, an air gap) exists between each of the coils 15, 16, 17 and the second magnets 12, 19 so that the coils may move relative to the magnets.

Figure 2d also shows the positional relationship between the magnet and the coil in the magnetic circuit 10 for the optical pickup actuator according to the present invention, the first and second coils (15, 16) of the second magnets (12, 19) It can be seen that the left and right sides are disposed vertically on the ground and are horizontally disposed on the lower portions 12 and 19 of the second magnet of the third coil 17. Also, as shown in FIG. 2D, a predetermined gap 23 may exist between the first magnets 11 and 18 and the second magnets 12 and 19.

According to the present invention having such a structure, it is possible to obtain a magnetic circuit having an increased thrust as compared with the prior art. The reason why the magnetic circuit 10 according to the present invention has a larger thrust than the conventional magnetic circuit can be understood by comparing the structure of the magnetic circuit 10 according to the present invention with the structure of the magnetic circuit used in the related art.

5 and 6 are perspective views exemplarily showing a conventional magnetic circuit compared with the magnetic circuit according to the present invention. First, the magnetic circuit 50 shown in FIG. 5 is a conventional structure in which two monopolar magnets 51 are disposed to face each other. Here, the focusing coil 52 is disposed horizontally with the ground at the bottom between the two magnets 51, and the two tracking coils 53, 54 are disposed perpendicularly to the ground on the left and right sides of the magnet 51. The tracking coils 53, 54 are parallel to the opposing surfaces of two magnets 51 facing each other, and a part of the coils 53, 54 protrudes out of the magnet 51.

In this case, as shown in FIG. 5, since the magnetic field B formed by the magnet 51 does not form a closed loop in the magnet surface, the magnetic flux passes through two surfaces of the coils 52, 53, and 54. I will go. In this structure, when the current flows in the clockwise direction, the force acts downward in the focusing coil 52 portion parallel to the magnet 51 in accordance with Fleming's left hand law. On the other hand, a force acts upward at the portion of the focusing coil 52 perpendicular to the magnet 51. Thus, the force acting on the focusing coil 52 cancels out substantially. Similarly, in the case of the tracking coils 53 and 54, since a force acts in one direction toward the magnet 51 and the other in the opposite direction, a substantial portion of the force acting on the tracking coils 53 and 54 Offset. Thrust obtained from such a conventional magnetic circuit 50 is only about 30mN / V.

Fig. 6 shows a conventional magnetic circuit 60 normally used for DVD 16x recording. As shown in FIG. 6, the conventional magnetic circuit 60 includes first and second magnets 61 and 62 adjacent to each other and polarized in opposite directions, and at one corner portion of the first magnet 61. A third magnet 63 in contact with and polarized in the opposite direction to the first magnet 61, and a fourth in contact with one corner portion of the second magnet 62 and polarized in the opposite direction to the second magnet 62. And a magnet 64. That is, the magnet used in the conventional magnetic circuit 60 is a quadrupole magnet formed by simultaneously magnetizing quadrupoles on one surface. At this time, the tracking coil 65 is located between the first magnet 61 and the second magnet 62, the first focusing coil 66 is between the first magnet 61 and the third magnet 63, The two focusing coils 67 are located between the second magnet 62 and the fourth magnet 64, respectively. In this structure, since there is a neutral zone where no magnetic flux exists in the central portion of each coil 65, 66, 67, there is a limit to increasing the electromagnetic force acting on each coil 65, 66, 67. There is. In the case of the conventional magnetic circuit 60 shown in Figure 6, it can exert a thrust up to about 50mN / V.

On the other hand, in the case of the magnetic circuit 10 according to the present invention, as shown in FIG. 2E, a plurality of magnets formed by at least three locations of the magnet part 14 by the first magnet 11 and the second magnet 12 are shown. Since each of the coils 15, 16, and 17 completely passes through the closed loop magnetic field, the leakage flux is not lost. In addition, in the magnetic circuit 10 according to the present invention, there is no neutral region in the loop formed by each of the coils 15, 16, and 17. Therefore, according to the present invention, a thrust of about 70 mN / V, which is 40% or more larger than that of a conventional magnetic circuit, can be obtained. This is a figure that can be utilized at the BD 4x to 6x speed, and it is possible to provide a high AC sensitivity in both the focusing direction and the tracking direction as compared to the conventional.

3 is an exploded perspective view of the optical pickup actuator 30 according to the present invention employing the magnetic circuit 10 of the above-described structure. As shown in FIG. 3, the optical pickup actuator 30 according to the present invention includes a bobbin 31 for fixing the objective lens 32 and a bobbin 31 on a base (not shown, see FIG. 1). Support members 34 and 35 movably supported relative to each other, a pair of magnet portions 14 and 21 adjacent to the front and rear of the bobbin 31, and a tracking coil 15 coupled to the bobbin 31, respectively. 16 and a focusing coil 17.

Support members (34, 35) is a casing (34) surrounding the side of the bobbin 31 and one end is coupled to the left and right sides of the casing 34 and the other end is provided in the base holder (not shown, Fig. 1 A plurality of suspensions 35 fixed thereto. However, it is also possible to couple the suspension 35 directly to the side of the bobbin 31 without the casing 34. On the other hand, magnet portions 14 and 21 adjacent to the front and rear of the bobbin 31 are provided in the base. Here, the magnets 14, 21 and the coils 15, 16, and 17 are driving units for driving the bobbin 31 and have the same structure as the magnetic circuit 10 described above. In addition, the optical pickup actuator 30 according to the present invention further includes an aberration correction plate 33 mounted to the lower portion of the bobbin 31 for spherical aberration correction.

As described above, the magnet portions 14 and 21 adjacent to the front and rear of the bobbin 31 respectively surround the circumferences of the first magnets 11 and 18 and the first magnets 11 and 18 on at least three surfaces. Is a bipolar magnet comprising second magnets 12 and 19, respectively. The first magnets 11 and 18 and the second magnets 12 and 19 are polarized in opposite directions so as to form a plurality of closed loop magnetic fields on the opposite surface of the bobbin 31.

On the other hand, the focusing coil 17 is wound around the lower end of the bobbin 31 so as to correspond to the portion of the second magnets 12 and 19 surrounding the lower surfaces of the first magnets 11 and 18. The bobbins 31 are provided so that the first and second tracking coils 15 and 16 correspond to portions of the second magnets 12 and 19 surrounding the left and right sides of the first magnets 11 and 18, respectively. It is wound on both sides of each. Accordingly, the focusing coil 17 and the first and second tracking coils 15 and 16 have winding directions perpendicular to the surfaces of the second magnets 12 and 19 and a plurality of closed holes formed in the magnet parts 14 and 21. Pass through the loop magnetic field.

Since the optical pickup actuator 30 of the present invention having such a structure is driven with a large thrust of about 70 mN / V, it has high AC sensitivity. Thus, the optical pickup actuator 30 according to the present invention is sufficiently capable of operating within the tolerances required in the Blu-ray Disc BD.

4 schematically shows the configuration of an optical recording / reproducing apparatus employing the optical pickup actuator 30 according to the present invention. As shown in Fig. 4, the optical recording / reproducing apparatus 40 according to the present invention comprises a spindle motor 45 for rotating an optical disc D such as an optical information storage medium, for example, CD, DVD or BD. An optical pickup 41 which is installed to be movable in the radial direction of the optical disk D and reproduces the information recorded on the optical disk or records the information on the optical disk, a drive unit for driving the spindle motor 45 and the optical pickup 41 ( 47), a control unit 49 for controlling the focusing, tracking and / or tilt servo of the optical pickup 41. Herein, reference numeral 42 denotes a turntable, and 43 denotes a clamp for chucking the optical disk D. FIG.

The optical pickup 41 includes an optical pickup optical system including an objective lens 32 for focusing light emitted from a light source onto the optical disc D, and an optical pickup actuator for driving the objective lens 32. As the optical pickup actuator, the optical pickup actuator 30 having the magnetic circuit 10 according to the present invention described above is used.

The light reflected from the optical disc D is detected by a photodetector provided in the optical pickup 41 and photoelectrically converted into an electrical signal, which is input to the controller 49 through the driver 47. The driver 47 controls the rotational speed of the spindle motor 45, amplifies the input signal, and drives the optical pickup 41. The controller 49 sends the focusing servo, tracking servo, and / or tilt servo command adjusted based on the signal input from the driving unit 47 back to the driving unit 47, thereby focusing, tracking, and / or Or allow the tilt servo operation to be implemented.

The optical recording / reproducing apparatus according to the present invention as described above can be controlled very finely in focusing, tracking and / or tilt servo operation, and when used for a recordable DVD, it is possible to realize a high speed of 16 times or more sufficiently for BD. Even when used as a high speed can be achieved 4 times faster than 6 times.

The structure and operation of the magnetic circuit, the optical pickup actuator and the optical recording / reproducing apparatus according to the present invention have been described in detail so far. However, the present invention is not limited only to the above structure. For example, in the above description, although the second magnet surrounds only both side surfaces and the bottom surface of the first magnet, the second magnet may surround both side surfaces and the top surface of the first magnet, and may further surround all four surfaces of the first magnet. Therefore, the focusing coil can also be wound around the upper end of the bobbin, and it is also possible to install the focusing coil around the upper and lower ends of the bobbin.

As described so far, according to the present invention, it is possible to provide a magnetic circuit for an optical pickup actuator having a high thrust which cannot be conventionally obtained. Since the optical pickup actuator according to the present invention employing the magnetic circuit having such a high thrust has excellent AC sensitivity, it is possible to sufficiently realize high sensitivity in focusing, tracking and / or tilt driving required at high speed. Therefore, it is possible to apply to the optical recording / reproducing apparatus of the high speed BD which requires very small tolerance.

Claims (20)

In a magnetic circuit in which a plurality of coils are disposed between two magnet portions facing each other, The two opposing magnets each include two magnets polarized in opposite directions to form a plurality of closed loop magnetic fields on respective opposing surfaces, And the coils between the two magnet portions are arranged to pass through the plurality of closed loop magnetic fields respectively formed on opposite surfaces of the two magnet portions. The method of claim 1, And the two opposing magnets form a closed loop magnetic field at at least three locations on each opposing surface. The method of claim 2, Each of the magnet parts: A first magnet polarized in a predetermined direction; And And a second magnet polarized in a direction opposite to the first magnet and surrounding at least three sides of the circumference of the first magnet. The method of claim 3, wherein The plurality of coils are disposed in the space between the second magnet of the two magnet portions facing each other, the magnetic circuit characterized in that the winding in the direction perpendicular to the second magnet surface. The method of claim 4, wherein And a predetermined distance is present between the plurality of coils and the second magnet so that the plurality of coils can move relative to the second magnet. The method of claim 3, wherein And the second magnet is formed to surround the bottom surface of the first magnet and the left and right side surfaces of the first magnet. The method of claim 6, First and second coils disposed respectively on second magnet portions surrounding left and right sides of the first magnet; And And a third coil disposed in a second magnet portion surrounding the lower surface of the first magnet, And the first to third coils are wound in a direction perpendicular to the second magnet surface. Base; Bobbin for fixing the objective lens; A support member having one end coupled to the bobbin and the other end fixed to a holder provided on the base such that the bobbin can move relative to the base; And In the optical pickup actuator comprising a; a pair of magnets provided on the base and a plurality of coils coupled to the bobbin so as to be adjacent to the front and rear of the bobbin, respectively, and to drive the bobbin. The magnet part has two magnets polarized in opposite directions to form a plurality of closed loop magnetic fields on the opposite surface to the bobbin, And a plurality of coils coupled to the bobbin are arranged to pass through the plurality of closed loop magnetic fields, respectively. The method of claim 8, The magnet part: A first magnet polarized in a predetermined direction; And And a second magnet that is polarized in a direction opposite to the first magnet and surrounds the circumference of the first magnet in at least three planes. The method of claim 9, The plurality of coils coupled to the bobbin are disposed in the space between two second magnets adjacent to the front and rear of the bobbin, and are wound in a direction perpendicular to the second magnet surface. The method of claim 10, And a predetermined distance is present between the plurality of coils and the second magnet so that the plurality of coils can move relative to the second magnet. The method of claim 9, And the second magnet is formed to surround the bottom surface of the first magnet and the left and right side surfaces of the first magnet. The method of claim 12, A focusing coil wound around a lower end of the bobbin so as to correspond to a second magnet portion surrounding a lower surface of the first magnet; And first and second tracking coils respectively wound on both sides of the bobbin so as to correspond to second magnet portions surrounding the left and right sides of the first magnet, respectively. And the focusing coil and the first and second tracking coils are wound in a direction perpendicular to the second magnet surface. An objective lens for focusing the light emitted from the light source to the optical disc and an optical pickup actuator for driving the objective lens, the optical lens being movable in a radial direction of the optical disc to provide light to a desired position of the optical disc through the objective lens; An optical recording / reproducing apparatus comprising: an optical pickup for irradiating and recording or reproducing information, wherein the optical pickup actuator comprises: Base; A bobbin for fixing the objective lens; A support member having one end coupled to the bobbin and the other end fixed to a holder provided on the base such that the bobbin can move relative to the base; And And a driving unit having a pair of magnets installed in the base and a plurality of coils coupled to the bobbin so as to be adjacent to front and rear of the bobbin, respectively, and driving the bobbin. The magnet part has two magnets polarized in opposite directions to form a plurality of closed loop magnetic fields on the opposite surface to the bobbin, And the plurality of coils coupled to the bobbin are arranged to pass through the plurality of closed loop magnetic fields, respectively. The method of claim 14, The magnet part: A first magnet polarized in a predetermined direction; And And a second magnet that is polarized in a direction opposite to the first magnet and surrounds the circumference of the first magnet in at least three planes. The method of claim 15, And a plurality of coils coupled to the bobbin are disposed in a space between two second magnets adjacent to the front and rear sides of the bobbin and are wound in a direction perpendicular to the second magnet surface. The method of claim 16, And a predetermined distance exists between the plurality of coils and the second magnet so that the plurality of coils can move relative to the second magnet. The method of claim 15, And the second magnet is formed to surround the bottom surface of the first magnet and the left and right side surfaces of the first magnet. The method of claim 18, A focusing coil wound around a lower end of the bobbin so as to correspond to a second magnet portion surrounding a lower surface of the first magnet; And first and second tracking coils respectively wound on both sides of the bobbin so as to correspond to second magnet portions surrounding the left and right sides of the first magnet, respectively. And the focusing coil and the first and second tracking coils are wound in a direction perpendicular to the second magnet surface. The method of claim 14, The optical pickup actuator further comprises an aberration correction plate for correcting spherical aberration mounted to the lower portion of the bobbin.

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