KR20010109532A - Actuator for optical pickup - Google Patents

Abstract

The present invention relates to an optical pickup actuator that enables thinning of an actuator that performs two-axis linear motion.

The optical pickup actuator of the present invention comprises a lens holder in which a lens for focusing light is mounted at a central portion, permanent magnet means disposed at both sides of the lens holder in a direction orthogonal to the path of the light, and a magnetic circuit together with the permanent magnet means. And a coil wound around the lens holder to generate a driving force for two-axis driving of the lens holder.

According to the present invention, the optical pickup can be made thin by avoiding the optical path by mounting the magnetic circuit part for biaxial driving in the focusing and tracking directions using the magnetic flux in different directions.

Description

Actuator Of Optical Pick-up

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup actuator, and more particularly, to an optical pickup actuator that enables thinning of an actuator that performs two-axis linear motion.

Recently, due to the rapid development of optical-related disk media, various product developments of optical pickup for reading information recorded on the disk have been made. The optical pickup includes an actuator for driving the objective lens so that the optical spot tracks the track against the surface vibration and the eccentricity of the disk together with the optical system so that the objective lens performs the focusing and tracking operation. Such optical pickup actuators have less mechanical tolerances and less objective lens tolerances due to the higher density of disks. In order to reduce the height of the actuator for thinning the actuator, the optical path and the actuator through which the light beam travels from the light source must be disposed on the same plane. In this case, since the magnetic circuit part for focusing and tracking driving of the actuator is located on the optical path, there is a limit in reducing the height of the actuator, which makes it impossible to reduce the thickness. Hereinafter, the above-described problems will be described in detail with reference to the accompanying drawings.

1A to 1C are cross-sectional views showing the structure and operation principle of a conventional optical pickup actuator. The optical pickup actuator shown in FIG. 1A includes an objective lens 92, a lens holder 4, a permanent magnet 6, and a yoke ( Yoke (8), tracking coil (10), focusing coil (12) and wire spring (14).

In FIG. 1A, the objective lens 2 focuses a light beam generated by a light source and incident on the recording surface of the disc in a spot shape. The lens holder 4 has a cylindrical hole in the center thereof, and the objective lens 2 is seated in the hole. The focusing coil 12 is wound around the side wall of the lens holder 4. The tracking coil 10 is wound to form a closed loop orthogonal to the focusing coil 12 and bonded to the focusing coil 12. The permanent magnet 6 is bonded to the yoke 8 located on the upper and lower sides of the lens holder 4 so as to face the tracking coil 10. The current is applied to the tracking coil 10 and the focusing coil 12 so as to link with the magnetic flux of the permanent magnet 6 so that the lens holder 4 is driven by the Lorentz force according to the Fleming's left hand law. (2) is driven. The yoke 8 located at the rear of the permanent magnet 6 serves to prevent the magnetic flux from leaking out of the rear of the permanent magnet 6. The wire spring 14 supplies a current to the tracking coil 10 and the focusing coil 12, and the lens holder 4 has a hinge role and an elastic force when the lens holder 4 is driven in a pivoting motion, that is, a focusing direction or a tracking direction. 4) to support the role.

FIG. 1B is a view for explaining the focusing operation principle of the above-described actuator. The magnetic circuit for the focusing operation includes a focusing coil 12, a permanent magnet 6 magnetized with an N pole and an S pole, and a permanent magnet 6. It consists of a yoke (8) located on the back of the. In FIG. 1B, the magnetic flux generated by the permanent magnet 6 passes through the permanent magnet 6 magnetized by N and S, and then passes through the yoke 8 to bridge the focusing coil 12. The direction of the force driving the lens holder 4 in accordance with the direction of the current applied to the focusing coil 12 so as to bridge with the magnetic flux of the permanent magnet 6 generated in the horizontal direction to drive the focusing operation in the vertical direction do.

FIG. 1C is a view for explaining the principle of the tracking operation of the actuator. The magnetic circuit for the tracking operation includes a tracking coil facing the magnetic screen of the permanent magnet 6 and the permanent magnet 6 magnetized to the N pole and the S pole ( 10). In FIG. 1C, the magnetic flux generated by the permanent magnet 6 is generated in a vertical direction in the drawing, and the direction of the force driving the lens holder 4 in the horizontal direction is in the horizontal direction in the direction of the current applied to the tracking coil 10. It will act as a tracking operation.

However, the conventional actuator shown in FIG. 1A has a limitation in reducing the height of the actuator because the magnetic circuit part, that is, the permanent magnet 6, the focusing coil 12, and the tracking coil 10, are positioned on the optical path. There is a difficult problem. In order to solve this problem, as shown in FIGS. 2 and 3, an optical path avoiding actuator and a lens protruding actuator in which a magnetic circuit unit is disposed to avoid an optical path have been proposed.

Figure 2 shows a plan view of the optical path avoiding actuator for thinning viewed from the disk side.

The optical path avoiding actuator shown in FIG. 2 is separated into upper and lower sides of the lens holder 22 to avoid the optical path by the objective lens 20 for collecting the light beam, the lens holder 22 on which the objective lens 20 is seated, and the optical path. And a yoke 26 attached to the rear surface of the permanent magnet 24 and the permanent magnet 24 and inserted into a hole provided at four corner portions of the lens holder 22, and an outer periphery of the lens holder 22. The focusing coil 30 wound around the tracking coil, the tracking coil 28 attached to the focusing coil 30 so as to face the permanent magnet 24, and the focusing coil 30 and the tracking coil 28. It is provided with a wire spring 32 for supporting the holder 20 with an elastic force. However, the actuator of the above-described structure is complicated to separate the magnetic circuit configuration in order to avoid the optical path, and as the permanent magnet 24 and the yoke 26 are required by four, the volume of the actuator is increased to inhibit the thinning. In addition, cost increases due to rising material costs and increasing number of manufacturing processes. In addition, the actuator has a structure in which holes for inserting the yoke 26 in the lens holder 22 are dispersed so that the rigidity is weakened, so that the resonance point is lowered in the high frequency characteristic, thereby failing to satisfy the high accuracy characteristic.

Figure 3 shows a plan view of a conventional lens projection actuator from the disc side.

The lens projection actuator shown in FIG. 3 is wound around an objective lens 34 for condensing a light beam, a lens holder 36 provided with a projection on which the objective lens 34 is seated, and an inner hole of the lens holder 36. The jean focusing coil 44, a permanent magnet 38 disposed opposite to each other inside and outside the focusing coil 44 in the inner hole of the lens holder 36, and a yoke attached to the rear surface of the permanent magnet 38 40, a tracking coil 42 disposed on the outer wall of the porting coil 44 to face the permanent magnet 38, and a focusing coil 44 and the tracking coil 42 to supply current to the lens holder. And a wire spring 46 for supporting 36 with an elastic force. The actuator has a lens 34 protruding from the optical path to avoid the configuration of the magnetic circuit portion, but a large square hole in the center of the lens holder 36 for the configuration of the magnetic circuit portion, the focusing coil 44 and the tracking coil 42. Since it should be formed, there is a problem that the resonance point of the lens holder 36 is lowered in the high frequency characteristics. In addition, the actuator has a problem in that the vibration point is poor because the fixing point of the wire 46 is far from the lens 34 and the excitation centers of the focusing and the tracking are different from each other.

Accordingly, it is an object of the present invention to provide an optical pickup actuator capable of forming a thinner magnetic circuit portion to avoid a light path.

Another object of the present invention is to provide an optical pick-up actuator in which the lens is positioned at the wire spring support fixing point to increase the resonance point of the lens holder so that there is no influence of secondary vibration.

It is still another object of the present invention to provide an optical pickup actuator capable of separating focusing and tracking magnetic circuits to improve magnetic circuit efficiency, high sensitivity, and linear characteristics.

1A to 1C are cross-sectional views showing the configuration and operation principle of a conventional optical pickup actuator.

Figure 2 is a plan view showing a conventional optical path avoiding actuator.

Figure 3 is a plan view showing a conventional lens projection actuator.

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

5 is a view illustrating an operation principle of the focusing magnetic circuit unit shown in FIG. 4;

6 is a view showing the operation principle of the tracking magnetic circuit unit shown in FIG.

FIG. 7 is a plan view of the actuator shown in FIG. 4 seen from the disc side; FIG.

8A and 8B are cross-sectional views comparing the optical path of the actuator shown in FIG. 1A with the optical path of the actuator shown in FIG. 4.

9 is an exploded perspective view showing the actuator shown in FIG. 4.

<Brief description of symbols for the main parts of the drawings>

2, 50: objective lens 4, 52: lens holder

6, 58: permanent magnet 8, 60: yoke

10, 56: tracking coil 12, 54: focusing coil

14: wire spring 22, 64: frame

66: magnetic flux line 68: light source

70: reflector 62: leaf spring

In order to achieve the above objects, the optical pickup actuator according to the present invention comprises a lens holder in which a lens for focusing light is seated at the center portion, permanent magnet means disposed on both sides of the lens holder in a direction orthogonal to the path of light, and permanently. The magnetic circuit may be configured together with the magnetic means to provide a coil mounted on the lens holder to generate a driving force for driving the two axes of the lens holder.

Other objects and advantages of the present invention in addition to the above object will become apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4 to 9.

FIG. 4 illustrates an overall stereoscopic view of an optical pickup actuator according to a first embodiment of the present invention. In the optical pickup actuator of FIG. 4, an objective lens 50 and an objective lens 50 for condensing a light beam are mounted. The lens holder 52, the focusing coil 54 wound around the guide frame provided on the left and right side walls of the lens holder 52, and the tracking coil 56 wound around the upper and lower walls of the lens holder 52. And a permanent magnet 58 disposed to face the focusing coil 54, a yoke 60 attached to the rear surface of the permanent magnet 58 and inserted into an inner hole of the focusing coil 54, and a lens holder 52. ) And a leaf spring 62 to which the leaf spring 62 is fixed.

In the actuator shown in FIG. 4, the objective lens 50 is seated in an inner hole provided in the center of the lens holder 52. Permanent magnets 58 and yoke 60 of the magnetic circuit portion for operating the lens holder 52 are disposed on the left and right sides of the lens holder 52 to avoid the optical path, and correspondingly focusing to generate a force for biaxial driving. The coil 54 and the tracking coil 56 are disposed on the left and right side walls and the upper and lower side walls of the lens holder 52, respectively. Focusing and tracking operations of the actuator by the Lorentz force generated in the magnetic circuit of this configuration are as shown in FIGS. 5 and 6.

FIG. 5 is a cross-sectional view illustrating only a magnetic circuit unit for a focusing operation in the actuator shown in FIG. 4.

In FIG. 5, each of the permanent magnets 58 is magnetized in multiple poles, that is, S / N / S and N / S / N, and the focusing coil 54 utilizes the yoke 60 and the center pole of the permanent magnet 58. In addition, it is wound to form a magnetic circuit path and to generate a force in the vertical direction by linking with the flux line 66 in the Bx direction. In addition, the focusing coil 54 is constituted by a magnetic circuit so as to keep the magnetic flux density of the permanent magnets 58 which are surrounded by the yoke 60 at the coil 54 portion high. In addition, the magnetic circuit portion for such a focusing operation is configured on the left and right of the lens portion so as not to block the optical path. Here, the multi-pole magnetized permanent magnet 58 may be configured by forming a magnetic pole on both sides of the mono-pole magnetized permanent magnet.

6 is a cross-sectional view illustrating only a magnetic circuit unit for a tracking operation in the actuator shown in FIG. 4.

The tracking magnetic circuit shown in FIG. 6 is a structure separate from the focusing magnetic circuit, and the permanent magnets 58 generate the magnetic flux lines 66 as shown in FIG. 6 by different polarities. The tracking coil 56 is located at the poles of the multi-pole magnetized permanent magnets 58 so as to generate a force in the tracking direction by linking the current flowing in the tracking coil 56 with the magnetic flux density in the By-direction of the magnetic flux lines 66. It is wound and attached to the lens holder 52. In this case, since the magnetic circuit formed on the left and right sides of the lens unit 50 is used, it is configured to avoid the path of light incident on the lens 50.

Here, the multi-pole magnetized permanent magnet 58 may be configured by forming a magnetic pole on both sides of the mono-pole magnetized permanent magnet. In addition, since the center of the lens unit 50 becomes the driving point during both the focusing and tracking operation of the actuator, the influence of secondary resonance, etc. can be eliminated, and the focusing coil 54 and the tracking coil 56 of the lens holder 52 Since the structure is wrapped around the central portion, the size of the magnetic circuit configuration can be reduced and the size of the through hole formed in the lens holder 54 can be reduced, thereby increasing the rigidity of the lens holder 54 to increase the resonance point in high frequency operation. It becomes possible. In addition, the effective magnetic flux is increased by separating the focusing and tracking magnetic circuits and opposing the permanent magnet plane, and the effective length of the coil is effectively opposed to the permanent magnet plane, thereby increasing the efficiency of the magnetic circuit.

FIG. 7 shows a plan view of the actuator shown in FIG. 4 seen from the disc side.

In FIG. 7, the objective lens 50 is positioned at the center of the movable part, and the tracking coil 56 and the focusing coil 54 are configured to surround the objective lens 50 in the lens holder 52 to have stable characteristics. Able to know. Further, it can be seen that the thinning of the actuator can be achieved since the yoke 60 and the permanent magnet 58 do not interfere at all with the path of the light beam traveling from the light source 68.

8A and 8B are cross-sectional views of a conventional actuator located on an optical path and an actuator located on an optical path of the present invention.

In the conventional actuator shown in FIG. 8A, since the permanent magnet 6 and the yoke 8 that block the magnetic circuit block the optical path, the reflector 70 positioned on the optical path avoids the interference portion of the actuator. The height of the optical pickup is increased by being disposed on the optical pickup.

On the other hand, in the actuator of the present invention shown in FIG. 8B, the yoke 60 and the permanent magnet 58 may be disposed to avoid the optical path, so that a part of the magnetic circuit and the prism 70 may be arranged to overlap each other, so that the entire pickup By lowering the height of the thinner can be used for notebooks, etc.

9 is an exploded perspective view showing the actuator shown in FIG. 4.

The leaf spring 62 for supporting the above-mentioned movable part in FIG. 9 is assembled across both sides of the lens holder 52 and the end is fixed to the frame 64 so that the actuator can be biaxially operated. In addition, the tracking coil 56 and the focusing coil 54 assembled to the lens holder 52 can be easily assembled by the guide structure of the lens holder 52, so that the assembly cost and productivity can be improved.

As described above, according to the optical pickup actuator according to the present invention, the optical pickup can be made thin by avoiding the optical path by mounting a magnetic circuit part for biaxial driving in the focusing and tracking directions using the magnetic flux in different directions. . In addition, according to the optical pickup actuator according to the present invention, since the movable portion can be moved to the center of the lens, the resonance point can be increased and the influence of the secondary vibration can be avoided. In addition, according to the optical pickup actuator according to the present invention, the effective magnetic flux is increased by separating the focusing and tracking magnetic circuits to face the permanent magnets, and the effective length of the coil can be effectively opposed to the permanent magnets to improve the magnetic circuit efficiency. Will be.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

A lens holder in which a lens for focusing light is seated at the center portion, Permanent magnet means disposed at both sides of the lens holder in a direction orthogonal to the path of the light; And a coil wound on the lens holder to form a magnetic circuit together with the permanent magnet means to generate a driving force for driving the lens holder biaxially. The method of claim 1, Yoke for guiding the magnetic flux generated from the permanent magnet means toward the coil, An elastic body mounted on the lens holder to support with elastic force and supply current to the coil; And a frame for supporting the elastic body. The method of claim 1, The coil is A focusing coil mounted on the lens holder so as to face the permanent magnet means and configured to drive the lens holder in a vertical direction; And a tracking coil mounted on the left and right side walls of the lens holder to drive the lens holder in the left and right directions, respectively. The method of claim 2 or 3, The permanent magnet is multipolar magnetized, The focusing coil is wound so as to link with the magnetic flux that proceeds through the central pole of the permanent magnet and the yoke, The tracking coil is located in the pole interval of the permanent magnet and the optical pickup actuator, characterized in that the winding so as to link with the magnetic flux due to the different polarity. The method of claim 4, wherein The permanent magnet is a monopole magnetized and the optical pickup actuator, characterized in that the magnetic pole on both sides to form a multi-pole.