KR20020062038A - Stack-Type Piezoelectric Actuator For Optical Pick-up Device - Google Patents

Abstract

PURPOSE: A device for driving an objective lens of an optical pickup is provided to drive the objective lens in radial and tangential directions, as well as in existing focusing and tracking directions, to correctly adjust a focus of the objective lens to a pit. Accordingly a tilt angle between the objective lens and a disk is promptly handled and corrected. CONSTITUTION: A base plate(101) forms a magnet(102) and a yoke(103) thereon to form a magnetic field. A fixing block(104) installed on an upper part of the base plate fixes and supports a plurality of wires(105). The wires are fixed at a sidewall of the fixing block to provide elasticity according to the driving of an objective lens(107). A piezoactuator(109) installed on a lower part of the fixing block drives the objective lens in radial and tangential directions, namely, a tilting direction. The piezoactuator is composed of a stack-type piezoactuator(200) displaced by a potential difference. In the piezoactuator, a first piezoactuator(109a) is composed of the triangle-shaped stack-type piezoactuator that becomes wider as going from an upper part to a lower part, and a second piezoactuator(109b) is composed of the triangle-shaped stack-type piezoactuator that becomes wider as going from a lower part to a higher part based on one random oblique plane of the first piezoactuator.

Description

Stack-type Piezoelectric Actuator For Optical Pick-up Device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving apparatus for an optical pickup, and in particular, by driving in a tilting direction while maintaining various driving directions of the optical pickup objective lens, thereby rapidly responding and correcting an inclination angle between the objective lens and the disc. The present invention relates to an objective lens driving device for optical pickup.

In general, an optical recording player using an optical recording medium (optical disk) such as a laser disk player (LDP) and a compact disk player (CDP) scans a light beam such as a laser onto a disk surface and detects the light beam reflected from the disk. Optical pickup unit is installed.

The optical pickup unit scans the light beam through the objective lens onto the disk surface and reads the reflected beam as a binary signal. In order for the optical pickup unit to read the signal correctly, a certain distance, i.e., the focus, between the objective lens to which the light beam is scanned and the disc must be precisely focused, while the scanned light beam must follow the track formed on the disc precisely. It is possible.

The focal length maintenance of the objective lens according to the operation of driving the objective lens is referred to as tracking (horizontal direction) and the movement of the objective lens along the disc track is called tracking (horizontal direction). There is an objective lens driving apparatus for performing focusing and tracking operations while driving an objective lens.

1 is an exploded perspective view showing a conventional wire spring-supported two-dimensional actuator, Figure 2 is a side cross-sectional view showing a driving state of the focusing actuator structure of FIG.

1 shows a typical wire spring-supported two-dimensional optical pickup actuator, the main part of which is provided with a base plate 1 on which a magnet 2 and a yoke 3 for forming a magnetic field are installed, and the base plate 1 A fixed block (4) fixedly installed on the), a 4-wire (5) fixed to one end of the fixed block (4) and connected to a power source, and coupled to the other end of the 4-wire (5) to move horizontally and vertically And the coil holder 7 on which the objective lens 6 is placed on one side thereof, and the magnetic field formed by the magnets 2 and the yoke 3 and wound around the coil holder 7. The focusing 8 and the tracking coil 9 to generate an electromagnetic force, and to transmit the current to the focusing 8 and the tracking coil 9 through the wire (5).

Accordingly, the coil holder 7 is supported by the 4-wire 5 fixed to the fixed holder 7, and the focusing 8 and the tracking coil 9 provided in the coil holder 7 are As shown in FIG. 2, the focusing coil 8 and the tracking coil 9 form a magnetic field and a magnetic circuit generated by the magnet 2. In accordance with the left-hand law of flaming, the objective lens 6 is driven vertically and horizontally, ie up, down, left and right in the focusing (vertical) direction and the tracking (horizontal) direction.

In this way, the 4-wire is fixed to the fixed block and at the same time provides the elastic force to drive the objective lens in the focusing and tracking direction fine.

At this time, the magnitude of the force is determined in proportion to the relationship between the magnetic flux density of the magnet, the effective length of the coil, the number of turns, and the strength of the current.

The fine driving range for driving the objective lens 6 in the focusing (vertical) direction is ± 1 to 2 mm, and about 0.3 to 0.5 mm in the tracking (horizontal) direction.

When a CD having such a fine driving range is reproduced, it is designed to follow ± 1 μm in the focusing (vertical) direction and ± 0.1 μm in the tracking (horizontal) direction.

As the speed of reproduction and recording of the disc 10 increases as described above, in order to reproduce up to 40 times the speed of the disc 10, it is required to drive the objective lens 6 faster, and further, in the tracking (horizontal) direction. It is necessary to drive with 10 times the accuracy of the focusing (vertical) direction.

Therefore, in the same manner as the 4-wire spring-supported two-dimensional actuator (objective driving device), the objective lens is driven only in the focusing and tracking direction, so that the objective lens is moved in a tilting direction other than the focusing and tracking direction. In the case of driving in tangent direction, it is made of 6-wire structure by installing additional wire in addition to the 4-wire spring, and 8-wire structure to compensate for another tilting direction, that is, radial direction. Becomes In this way, in order to drive the objective lens in various tilting directions, the number of wires must be increased, and thus, a driving coil, a magnet, and a yoke are required. Accordingly, the weight of the optical pickup driving device is increased, thereby precisely and minutely driving together with the objective lens. Not only is this difficult, but the efficiency is lowered by using coils, magnets, and yokes that are only in the magnetic field, so that the efficiency is not exceeded by about 50%, and the number of parts increases, making production difficult and increasing the production cost. There was a problem.

In addition, as described above, the two-dimensional actuator having a plurality of wire springs structurally interferes with each other and crosstalk (crosstalk) occurs during driving, so that the separation of the driving is not complete. This has the disadvantage of degrading the stability of the playback and recording operations by generating a series of unnecessary vibration modes.

Accordingly, the present invention is to solve the conventional problems as described above, the object of the present invention is to drive the lens in the conventional focusing and tracking direction to accurately focus the optical pickup objective lens to the Pit (Pit). In addition, by driving fast and finely and precisely in the radial and tangential directions of the tilting direction, it responds and corrects quickly to the inclination angle between the objective lens and the disc to perform precise and accurate driving force so that the disc is reproduced and recorded more stably. It is to provide an objective lens driving apparatus of an optical pickup to be able to perform.

In order to achieve the above object, the objective lens driving device of the optical pickup according to the present invention includes a base plate on which magnets and yokes are installed, a fixed block installed on the base plate, and fixed to the fixed block to focus and track. In the objective lens driving apparatus of the optical pickup consisting of a plurality of wires to provide an elastic force to the objective lens driven by the optical lens, the stacked type is displaced by the potential difference so that the objective lens is driven in the radial and tangential directions of the tilting direction below the fixed block A piezoelectric actuator having a piezo is installed.

1 is a perspective view showing the configuration of a conventional wire spring-supported two-dimensional actuator,

2 is a side cross-sectional view showing a driving state of the focusing actuator structure of FIG. 1;

3 is a perspective view showing the configuration of an objective lens driving device for an optical pickup according to the present invention;

4 is a view showing a driving state of a piezoelectric actuator installed in the objective lens driving device of the optical pickup of FIG.

4A is a diagram in which a piezoelectric driver is driven in a tilting direction to drive an objective lens counterclockwise;

4B is a diagram in which the piezoelectric actuator is driven in the tilting direction to drive the objective lens clockwise.

<Explanation of symbols for the main parts of the drawings>

100: main body 101: base plate

102: magnet 103: yoke

104: fixed block 105: wire

106: focusing coil 107: objective lens

108: tracking coil 109: piezoelectric actuator

109a: first piezoelectric driver 109b: second piezoelectric driver

200: stacked piezo

Hereinafter, an objective lens driving apparatus for an optical pickup according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a perspective view showing the configuration of the objective lens driving apparatus of the optical pickup according to the present invention, Figure 4 is a view showing a driving state of the piezoelectric actuator installed in the objective lens driving apparatus of the optical pickup of Figure 3, Figure 4a is a piezoelectric The driver is driven in the tilting direction to drive the objective lens counterclockwise, and FIG. 4B is a diagram of the piezoelectric actuator driven in the tilting direction to drive the objective lens clockwise.

3 and 4a, b, the main body 100 of the objective lens driving apparatus of the optical pickup is a base plate 101, a fixed block 104, a plurality of wires 105, coil holder, objective lens 107, a focusing coil 106, a tracking coil 108, and a piezoelectric actuator 109 having a stacked piezo 200, which is driven in the direction of focusing and tracking of a disc as an optical recording medium, While driving in the tangential direction, a desired track position is detected on the disk. At the detected track position, a laser beam is incident on a pit recorded on the disk surface, and then the reflected light is detected through an optical system. It is a device for changing and reproducing the recorded contents on the disk surface.

The base plate 101 is provided with a magnet 102 and a yoke 103 on the top surface of the base plate 101 to form a magnetic field.

The fixing block 104 is installed on the base plate 101 to fix and support the plurality of wires 105.

The plurality of wires 105 are fixedly installed on the side wall surface of the fixing block 104 to provide an elastic force according to the driving of the objective lens 107.

The coil holder has an objective lens 107 on its upper surface and is coupled to a plurality of wire 105 tile ends so as to drive the objective lens 107 in the focusing and tracking directions.

The coil holder is wound with a focusing and tracking coil that generates an electromagnetic force by interacting with a magnetic field formed by the magnet 102 and the yoke 103 of the base plate 101.

The current of the magnetic field is intended to be delivered to the focusing and tracking coils via wire 105.

The piezoelectric driver 109 is installed under the fixed block 104 to drive the objective lens 107 in the radial and tangential directions in the tilting direction.

The piezoelectric driver 109 is composed of a stack-type piezoactuator 200 which is displaced by a potential difference.

In addition, the piezoelectric driver 109 is composed of triangular first and second piezoelectric drivers 109a and 109b.

The first piezoelectric driver 109a is formed of a triangular stacked piezo 200 which is widened from top to bottom.

The second piezoelectric driver 109b includes a triangular stacked piezo 200 that narrows from the lower part of the comb angle toward the upper part of the first one of the first piezoelectric actuators 109a.

Next, an operation process of the objective lens driving apparatus for the optical pickup according to the exemplary embodiment of the present invention having the above configuration will be described in more detail with reference to FIGS. 3 and 4A and B.

First, as shown in FIG. 3, the driving body 100 of the objective lens of the optical pickup drives the objective lens 107 in the focusing and tracking directions by the focusing 106 and the tracking coil 108. At the same time, the plurality of wires 105 fixed to the fixed block 104 provide elastic force according to the driving of the objective lens 107.

At this time, in order to drive the objective lens 107 in the radial and tangential directions, which are the tilting direction, in addition to the focusing and tracking directions, the objective lens 107 is displaced by a potential difference to drive the objective lens 107 in the tilting direction under the fixed block 104. Since the piezoelectric driver 109 having the stacked piezoelectric element 200 is provided, the objective lens 107 is driven in the radial and tangential directions in the tilting direction by driving the piezoelectric driver 109.

The stacked piezo 200 has different electrodes on both sides of the piezo 200 (voltage of 180 degrees out of phase in AC), and at the same time, when the potential difference is applied to the different electrodes, one side is stretched and the other side is contracted. Therefore, a certain range of displacement occurs from the reference position so that both ends have a displacement without an angle difference.

As shown in FIG. 4A, since the piezoelectric driver 109 including the stacked piezoelectric member 200 includes triangular first and second piezoelectric actuators 109a and 109b, the first piezoelectric driver 109a may be used. If the displacement is caused by the potential difference, the tension is expanded in the transverse direction and contraction occurs in the longitudinal direction.

At this time, the second piezoelectric driver 109b installed on any one bevel surface of the first piezoelectric driver 109a is compressed with respect to the bevel surface, and the second piezoelectric driver 109b is tensioned in the direction perpendicular to the bevel surface.

Here, the second piezoelectric driver 109b is driven in an acute triangular shape to drive the fixed block 104 counterclockwise to drive the objective lens 107 by a tilting angle θ.

On the contrary, as shown in FIG. 4B, when the displacement occurs due to the potential difference in the first piezoelectric actuator 109a, contraction occurs in the transverse direction and tensile expansion in the longitudinal direction.

At this time, the second piezoelectric driver 109b is tensioned outward with respect to the inclined surface and at the same time, the second piezoelectric driver 109b contracts in a direction perpendicular to the inclined surface.

The second piezoelectric driver 109b is driven in the form of an obtuse triangle to drive the fixed block 104 clockwise to drive the objective lens 107 by a tilting angle θ.

As described above, the driving of the objective lens 107 can be precisely and finely driven by being driven in the radial and tangential directions of the tilting direction in addition to the focusing and tracking directions, which are the existing driving directions of the optical pickup objective lens 107.

On the other hand, as described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit and scope of the present invention.

As described above, according to the objective lens driving apparatus of the optical pickup according to the present invention,

By driving in the tilting direction while maintaining the various driving directions of the optical pickup objective lens, the camera accurately responds and corrects the inclination angle between the objective lens and the disc to perform precise and accurate reproducing and recording operation, thereby making the product stable and reliable. There is an effect that can improve.

Claims (2)

The object of the optical pickup consisting of a base plate on which magnets and yokes are installed, a fixed block installed on the base plate, and a plurality of wires fixed to the fixed block to provide an elastic force to an objective lens driven in a focusing and tracking direction. In the lens drive device, And a piezoelectric actuator having a stacked piezo that is displaced by a potential difference so that the objective lens is driven in the radial and tangential directions in the tilting direction under the fixed block. The method of claim 1, The piezoelectric driver may include a triangular first piezoelectric driver having a stacked piezo, which is widened from the upper part to the lower part, The object of the optical pickup comprising a triangular second piezoelectric actuator having a laminated piezo installed on any one side of the first piezoelectric actuator and narrowed from the lower side to the upper side with respect to the oblique angle of the one side. Lens drive.