KR20030083995A - Actuator for optical pickup - Google Patents

Abstract

PURPOSE: An actuator for an optical pickup is provided to secure high sensitivity by lightening an operating unit and realize high level of second resonant frequency. CONSTITUTION: A bobbin(120) is provided to load an objective lens(100). The bobbin is formed in a structure removing a through-hole for arranging a part of a magnetic circuit. The magnetic circuit includes a focus coil(140) and a tracking coil(150) installed on the same sides(121,123) of the bobbin, and a plurality of magnets(190) installed on a base, facing the focus coil and the tracking coil. The plurality of magnets are installed in a polarization structure corresponding to the focus coil and the tracking coil in common.

Description

Actuator for optical pickup

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator for optical pickup, and more particularly, to an optical pickup actuator suitable for a high speed and high density optical recording / reproducing apparatus.

Referring to FIG. 1, which shows an example of a conventional optical pickup actuator, a holder 30 is fixedly installed on a base 70, and a bobbin 20 on which an objective lens 10 is mounted is wired 61 to 64. It is supported by the holder 30 by the.

A pair of focus coils 40 are provided on the outer surface 21 of the bobbin 20 so as to be symmetrical to both sides, and the focus coils are formed on the inner surface 22 of the through hole 20a formed in the bobbin 20. Like 40, a pair of tracking coils 50 are installed symmetrically. That is, the pair of focus coil 40 and the tracking coil 50 are symmetrically installed on different sidewalls, respectively.

The base 70 is provided with a pair of first magnets 91 and first yokes 81 corresponding to the focus coil 40, and a second magnet 92 corresponding to the tracking coil 50. And a pair of second yoke 82 is also located in the through hole 20a.

In this configuration, the focus operation is performed by the magnetic force generated between the current flowing through the focus coil 40 and the first magnet 91, the current flowing through the tracking coil 50 and the second magnet. The tracking operation is performed by the magnetic force generated between 92.

On the other hand, the focus coil 40 is not wound around the entire bobbin 20, only the necessary portion is disposed to face the first magnet 91, even if a very short length is installed to perform the focus operation It becomes possible. That is, the coil 40 is provided only on the outer side 21 of the bobbin 20 facing the first magnet 91 and the first yoke 81, and the portion surrounding the bobbin 20 is unnecessary. Since the focus operation can be performed even with such a short length, the use efficiency of the coil is improved.

As such, when the unnecessary coil part is removed from the bobbin 20, the weight of the movable part including the bobbin 20 is lighter, and thus, the control speed is increased during focusing and tracking operation, which is advantageous in terms of sensitivity.

However, in the conventional optical pickup actuator as described above, the second magnet 92 and the second yoke 82 corresponding to the tracking coil 50 and the tracking coil 50 corresponding thereto in the bobbin 20. Since the through-hole 20a for installing) is formed, the movable part has a low secondary resonance frequency.

Here, in the optical recording and reproducing apparatus, the cut-off frequency of the optical pickup actuator that determines the disk tracking capability at higher density and higher speed should be higher, and thus the optical pickup actuator has good frequency characteristics up to a high frequency band. You are asked to do it.

However, as described above, the conventional optical pickup actuator having the through-hole 20a in the bobbin 20 does not have a high secondary resonance frequency, and thus is not suitable for the high density and high speed optical recording / reproducing apparatus.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an actuator for optical pickup capable of simultaneously securing high sensitivity and secondary resonant frequency characteristics so as to be suitable for a high speed and high density optical recording / reproducing apparatus. have.

1 is an exploded perspective view schematically showing an example of a conventional optical pickup actuator;

2 is an exploded perspective view schematically showing an actuator for an optical pickup according to an embodiment of the present invention;

3 is a plan view of the actuator for the optical pickup shown in FIG.

4 is a view schematically showing an example of a magnetic circuit applied to an optical pickup actuator according to the present invention;

5A and 5B illustrate a principle of driving a movable part of an optical pickup actuator in a track direction by a magnetic circuit including a magnet having a polarization structure as shown in FIG. 4 and a tracking coil and a focus coil disposed corresponding thereto. drawing,

6A and 6B illustrate a principle of driving a movable part of an optical pickup actuator in a focus direction by a magnetic circuit including a magnet having a polarization structure as shown in FIG. 4 and a tracking coil and a focus coil disposed corresponding thereto. For drawing.

<Description of Symbols for Main Parts of Drawings>

100 ... objective lens 120 ... bobbin

130 ... holder 140 ... focus coil

150 ... Tracking Coil 161 ... 164

180 ... outer yoke 190 ... magnet

191,193 ... first and second magnets 195,197 ... first and second boundary

In order to achieve the above object, the present invention includes: a bobbin mounted with an objective lens; A suspension having one end coupled to the bobbin and the other end fixed to a holder provided on one side on the base to support the bobbin movably; And a magnetic circuit provided at the bobbin and the base; wherein the bobbin is formed in a structure in which a through hole for disposing a part of the magnetic circuit is excluded, and the magnetic circuit is formed of the bobbin. A focus coil and a tracking coil installed on the same side; And a magnet having a polarization structure corresponding to the focus coil and the tracking coil in common, and disposed in the base to face the focus coil and the tracking coil.

Here, the magnet is composed of first and second magnet portions having opposite polarization arrangements, and a first boundary extending from the first boundary and a first boundary that forms a boundary between the first and second magnet portions in a focus driving direction. It is preferable that two boundaries are formed to have a L shape, the focus coil is arranged to span the first boundary, and the track coil is arranged to span the first and second boundaries.

The magnet is preferably a bipolar plane polarization magnet.

It is preferable to further include; the outer yoke for supporting the magnet and guides the magnetic flux generated in the magnet.

Hereinafter, preferred embodiments of an optical pickup actuator according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a perspective view schematically illustrating an optical pickup actuator according to an exemplary embodiment of the present invention, and FIG. 3 is a plan view of the optical pickup actuator illustrated in FIG. 2.

2 and 3, the optical pickup actuator according to the present invention includes a bobbin 120 on which an objective lens 100 is mounted, one end of which is coupled to the bobbin 120, and the other end of which is on the base 170. It is configured to include a suspension (161 ~ 164) fixed to the holder 130 provided on one side to support the bobbin 120 to move, and a magnetic circuit installed on the bobbin 120 and the base 170.

In the optical pickup actuator according to the present invention, the bobbin 120 is formed in a structure in which a through hole for disposing a part of a conventional magnetic circuit is excluded so that the secondary resonance frequency can be high-passed. A magnetic circuit is provided to enable the structure to eliminate the problem. As such, when the bobbin 120 is formed in a structure without a through hole, the inner yoke provided in the normal optical pickup actuator is also excluded.

The suspensions 161 to 164 are preferably coupled to side surfaces 125 and 127 different from the side surfaces 121 and 123 of the bobbin 120 in which the coil of the magnetic circuit is installed. It can be done as one.

The magnetic circuit includes a focus coil 140 and a tracking coil 150, and a magnet 190 having a polarization structure corresponding to the focus coil 140 and the tracking coil 150 in common.

The focus coil 140 and the tracking coil 150 are installed on the same side 121 and 123 of the bobbin 120. At least one of the focus coil 140 and the tracking coil 150 may be a fine pattern coil. Since the fine type coil is manufactured by patterning the coil shape on the film, the thickness is thin and light, which has the advantage that it can greatly contribute to the compactness of the actuator and the reduction of the moving part of the actuator. Alternatively, the focus coil 140 and / or the tracking coil 150 may include a bulk type coil made by winding a copper wire.

2 and 3 show an example in which the focus coil 140 and the tracking coil 150 are provided in a rectangular shape to face the magnet 190. The focus coil 140 and the tracking coil 150 may have a structure wound like the conventional focus coil 40 and the tracking coil 50 shown in FIG. 1. That is, the focus coil 140 may have a structure wound in a horizontal direction and the tracking coil 150 may have a structure wound in a vertical direction.

As described with reference to FIGS. 2 and 3, in the optical pickup actuator according to the present invention, the focus coil 140 does not wind the entire bobbin 120, but rather the bobbin 120 facing the magnet 190. Since it is located only on the side of the), compared to the structure of winding the focus coil around the bobbin in the general optical pickup actuator, there is an advantage that the weight of the movable part including the bobbin 120 is light.

Referring to FIG. 4, the magnet 190 includes first and second magnet parts 191 and 193 having polarization arrangements opposite to each other, and includes the first and second magnet parts in a focus driving direction. A first boundary 195 forming a boundary between 191 and 193 and a second boundary 197 extending from the first boundary 195 form an L-shape. 4 illustrates an example in which the first magnet portion 191 has an N pole and the second magnet portion 193 has a polarization of the S pole on the ground. Bottom surfaces of the first and second magnet parts 191 and 193 have polarization opposite to those shown in the drawing.

As shown in FIG. 4, since the magnet 190 has a rectangular shape and is bi-polarized in a L shape, the magnetic force due to the interaction of the current flowing through the focus coil 140 with the magnetic flux from the magnet 190. The focus coil 140 may be disposed to span the first boundary 195 to perform a focus operation. In addition, the tracking coil 150 may be configured to perform the tracking operation by the magnetic force caused by the interaction of the current flowing in the tracking coil 150 and the magnetic flux from the magnet 190. 195) and 197, preferably disposed.

The magnet 190 is preferably provided with a bipolar plane polarization magnet. When the surface polarization magnet is provided as the magnet 190, there is an advantage in that the pore magnetic flux density can be improved. Alternatively, the magnet 190 may be formed by arranging the processed magnet in a polarization structure as shown in FIG. 4.

Meanwhile, the optical pickup actuator according to the present invention may further include an outer yoke 180 supporting the magnet 190 and guiding the magnetic flux generated by the magnet 190.

The optical pickup actuator according to the present invention as described above drives the objective lens 100 mounted on the bobbin 120 of the movable part in the track direction and the focus direction as follows.

5A and 5B are magnetic circuits including a magnet 190 having a polarization structure as shown in FIG. 4, a tracking coil 150, and a focus coil 140 disposed corresponding thereto, and a movable part of an optical pickup actuator. Demonstrate the principle of driving in the track direction.

As shown in FIG. 5A, when a current flows in the counterclockwise direction in the tracking coil 150, the magnetic force Ft acts in the left direction in the tracking coil 150. On the contrary, as shown in FIG. 5B, when a current flows in the tracking coil 150 in the clockwise direction, the magnetic force Ft acts on the tracking coil 150 in the right direction.

6A and 6B are magnetic circuits having a magnet 190 having a polarization structure as shown in FIG. 4, a tracking coil 150 and a focus coil 140 disposed corresponding thereto, and a movable part of an optical pickup actuator. The principle of driving in the focus direction is shown.

As shown in FIG. 6A, when a current flows in the focus coil 140 in a counterclockwise direction, the magnetic force Ff acts on the focus coil 140 in a downward direction (a direction away from the recording medium and the objective lens 100). do. On the contrary, as shown in FIG. 6B, when a current flows in the clock coil 140 in the clockwise direction, the magnetic force Ff is upward in the focus coil 140 (the direction between the recording medium and the objective lens 100). This works.

According to the optical pickup actuator according to the present invention as described above, the bobbin is formed in a structure in which a through hole for disposing a part of the magnetic circuit is excluded, and the tracking coil and the focus coil are arranged on the same side of the bobbin, Because of its light weight, high sensitivity can be ensured, and the secondary resonance frequency is increased by the structure in which the through-hole of the bobbin is excluded.

Therefore, the optical pickup actuator according to the present invention is suitable for a high speed and high density optical recording / reproducing apparatus.

Claims (4)

A bobbin on which an objective lens is mounted; A suspension having one end coupled to the bobbin and the other end fixed to a holder provided on one side on the base to support the bobbin movably; An optical pickup actuator comprising: a magnetic circuit provided at the bobbin and a base, The bobbin is formed of a structure in which a through hole for disposing a part of the magnetic circuit is excluded, The magnetic circuit, A focus coil and a tracking coil installed on the same side of the bobbin; And a magnet having a polarization structure corresponding to the focus coil and the tracking coil in common, the magnet being installed on the base to face the focus coil and the tracking coil. The first boundary and the first boundary of claim 1, wherein the magnet comprises first and second magnet portions having opposite polarization arrangements and forms a boundary between the first and second magnet portions in a focus driving direction. The second boundary extending from the And the focus coil is arranged to span the first boundary, and the track coil is arranged to span the first and second boundaries. The optical pickup actuator of claim 2, wherein the magnet is a bipolar plane polarization magnet. The optical pickup actuator of claim 1, further comprising an outer yoke for supporting the magnet and guiding a magnetic flux generated by the magnet.