KR100316230B1 - Piezoelectric Actuator for optical Pick-up Device - Google Patents

Abstract

The present invention relates to an objective lens driving apparatus for an optical pickup, and by applying a driving method having a sufficient driving force for the objective lens and a stable frequency response band, it is possible to advantageously cope with high-speed reproduction and recording.

The objective lens driving apparatus of the present invention is made of a tracking driver by installing a piezo 21 displaced by a potential difference in the tracking direction according to the objective direction of the objective lens 20, and is installed in parallel with the tracking driver to react to the potential difference. Several movable members 22 installed in the focusing direction to cause displacement and drive the objective lens therefrom, and coils 23 and yokes 24 and magnets 25 installed inside the movable members to displace the movable members. It consists of a connecting member 26 for connecting a focusing drive system for driving a movable member, a tracking drive unit and a focusing drive unit.

Accordingly, high-speed driving of the objective lens required for increasing the speed of reproduction and recording is realized, and stability and reliability of the reproduction and recording operations are improved.

Description

Objective pick-up device for optical pickup {Piezoelectric Actuator for optical Pick-up Device}

The present invention relates to an objective lens driving apparatus of an optical pickup, and more particularly, by applying a driving method having a sufficient driving force for a objective lens and a stable frequency response band, so as to advantageously cope with high-speed reproduction and recording.

In general, an optical recording / reproducing apparatus using an optical recording medium (optical disk) such as an LDP (Laser Disk Player) or a CDP (Compact Disk Player) scans a beam of light 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 to the disk surface and reads the beam reflected therefrom 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 focusing of the objective lens according to the operation of driving the objective lens is called focusing, and the movement of the objective lens along the disc track is called tracking. Therefore, in the optical pickup unit, focusing is performed while driving the objective lens. There is an objective lens driving device for performing a tracking operation.

1 shows a typical wire spring-supported two-dimensional optical pickup actuator. The main part is a base (1) on which a magnet (2) and a yoke (3) are formed to form a magnetic field, a holder (4) fixed to the base (1), and one end is fixed to the holder (4) to be connected to a power source. A plurality of wires 5, which are coupled to the other end of the wires 5, are supported in a horizontal / vertically movable manner and wound around a coil holder 7 and a coil holder 7 on which an objective lens 6 is placed on one side of the magnet. (2) and focusing coil (8) and tracking coil (9) for generating electromagnetic force in interaction with the magnetic field formed by yoke (3), focusing coil (8) and tracking coil (9) through current (5) Is provided with a substrate 10 for delivery.

Therefore, the objective lens 6 and the focusing coil 8 / tracking coil 9 attached to the coil holder 7 are supported by several wires 5, and a magnet 2 at the lower part of the yoke 3 is supported. 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, and according to the left-hand law of flaming, focusing direction and tracking are performed. Drive the objective lens 6 in the vertical direction. 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 range in which the objective lens 6 is driven in the focusing direction is ± 1 to 2 mm, and the tracking direction is about ± 0.3 to 0.5 mm.

When the CD is reproduced with such a driving range, it is designed to follow ± 1 μm in the focusing direction and ± 0.1 μm in the tracking direction.

However, as the speed of reproduction and recording increases, in particular, in order to reproduce up to 40 times the speed, it is required to drive the objective lens 6 faster. Furthermore, it is necessary to drive in the tracking direction while maintaining 10 times the accuracy of focusing.

However, in the same manner as the wire spring-supported two-dimensional actuator (objective driving device), it is difficult and limited to drive the objective lens quickly and properly in the focusing / tracking direction.

It is also driven by coils that are only in the magnetic field, which leads to low efficiency, which is not more than about 50% numerically.

The spring-supported two-dimensional actuator is structurally integrated with a tracking / focusing drive unit, so that interference and crosstalk between each other occur, so that the separation of the drive is not complete. This generates a series of unnecessary vibration modes, which degrades the stability of the playback and recording operations.

Accordingly, an object of the present invention is to realize a high speed driving of the optical pickup actuator objective required for increasing the speed of reproduction and recording.

Another object of the present invention is to provide an optical pickup actuator which has a stable frequency response while maintaining a sufficient driving force of the objective lens.

Optical pickup objective lens driving apparatus for achieving the object of the present invention,

(1) It is made of tracking driving part by installing piezo which is displaced by potential difference in tracking direction according to the objective lens driving direction,

(2) several movable members installed in parallel with the tracking drive unit to be displaced in response to the potential difference and to drive the objective lens therefrom;

(3) a focusing drive system for driving a movable member comprising a coil, a yoke and a magnet installed inside the movable member to displace the movable member;

(4) It is characterized by consisting of a connecting member for connecting the tracking drive unit and the focusing drive unit.

Optionally, the movable member provided in the focusing direction is a leaf spring supported by the connecting member and the frame.

Optionally, in a focusing drive system for driving a movable member consisting of a coil, a yoke and a magnet, a heavier magnet and a yoke than the coil are placed on the fixed side, and a relatively light coil is placed on the driving side.

Optionally, the magnets are arranged with the poles in the order of NS so that the direction of the magnetic flux is to the left, the direction of the current is installed while maintaining the direction of exiting or entering the ground, and the coil is mounted on the corresponding vertical ground. It is characterized by one.

1 is a conventional wire spring-supported two-dimensional actuator

FIG. 2 is a diagram illustrating the focusing actuator structure of FIG. 1. FIG.

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

4 illustrates an example tracking operation in accordance with the present invention;

5 illustrates an example of a focusing operation according to the present invention.

6 is for explaining the principle of focusing driving by the potential difference according to the present invention (A) before the displacement (B) is a state of occurrence of displacement

Figure 7 is for explaining the focusing driving principle according to the present invention (A) before displacement (B) is a state of occurrence of displacement

8A and 8B show the determination direction of the focusing drive along the current flow direction.

* Description of the symbols for the main parts of the drawings *

20: objective lens 21: piezo

22: movable member 23: coil

24: York 25: Magnet

26: connecting member 27: leaf spring

28: bobbin 29: frame

30: ceramic layer 31: intermediate core material

In the optical pickup objective lens drive, when the tracking drive unit is a piezo as a driving source, and the focusing drive unit is a movable member that is elastically displaced as a driving source, the target in the desired focusing direction and tracking direction for the information string recorded in the form of a pit on the optical disk. The lens can be driven efficiently and quickly.

Hereinafter, an optical pickup objective driving device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

3 shows an objective lens driving apparatus for an optical pickup, which is an exemplary configuration of the present invention. 4 is an example of an objective tracking operation according to the present invention, and FIG. 5 is an example of a focusing operation. 6 and 7 diagrammatically show the driving principle in the tracking / focusing direction shown by the present invention, respectively.

Referring to FIG. 3, the piezo 21 is displaced by a potential difference in the tracking direction according to the driving direction of the objective lens 20 to form a tracking driver, and in the focusing direction, the potential difference is located in parallel with the tracking driver. In response to this, several movable members 22 for causing displacement and driving the objective lens 20 are installed.

The movable member 22 is provided with a coil 23, a yoke 24, and a magnet 25 inward to provide a focusing unit for driving the movable member 22, and a connecting member 26 between the tracking driver and the focusing driver. ), And the movable members 22 have a leaf spring 27 with a length in the longitudinal direction.

The objective lens 20 is fixed to the bobbin 28, the piezo 21 is coupled to the bobbin 28, the end of the piezo 21 is connected through the movable member 22 and the connecting member 26 do.

The arrangement of the coils 23, the yokes 24, and the magnets 25, which are focused in the movable member 22, has a magnet 25 that is heavier than the coils 23 and the yoke 24 on the fixed side, and a relatively light coil ( 23) is placed on the drive side to take into account the responsiveness to the current flow.

In the arrangement structure in which the magnet 25 has the tracking piezo 21 on the right side as the focusing driving unit on the left side as shown in FIG. 3, the magnets are arranged in the order of NS as shown in FIG. 7 in order to put the magnetic flux to the left side. As shown in Figure 8, the direction of the current is installed by maintaining the direction of exiting or entering the ground, it is configured by mounting a coil on the ground in the corresponding vertical direction.

The objective lens 20 is fixed to the bobbin 28 and fixed, and the bobbin 28 is connected to the piezo 21 to serve as a tracking drive, and the movable member 22 such as the leaf spring 27 is continuously provided. To support the frame 29 to make a focusing drive to give a potential difference, the tracking / focusing drive structurally generates expansion of a certain range of displacement from an arbitrary reference position by repeating expansion and contraction or displacement of the movable member 22. Do this.

The displacement state of the tracking / focusing drive can be expressed as shown in FIGS. 4 and 5, and a more detailed driving principle is described in FIGS. 6 and 7.

Driving the objective lens 20 in the tracking direction is obtained through displacement of the piezo 21. Both sides of the piezo 21 are made of an amorphous ceramic layer 30 and the inner core 31 is contained. When a potential difference is given to both sides of the piezo 21, one side expands and the other side contracts to a predetermined range from a reference position. Generate displacement. Through this, the objective lens 20 is driven in the tracking direction.

That is, the driving in the tracking direction remains undeformed when the potential difference does not exist on the upper and lower surfaces as shown in FIG. 6A. When the potential difference occurs, one side expands and the other side contracts as shown in (B). Obtained by forming a range of displacement from the reference position. The driving force and frequency response required for driving are sufficient in the characteristics of the piezo 21 in response to the potential difference. In addition, the tracking operation is performed separately from the focusing operation so that the tracking operation does not crosstalk each other and easily corresponds to the tracking operation requiring faster operation.

The objective lens 20 driving in the focusing direction is driven by the magnet 25, the yoke 24, and the focusing coil 23 in the vertical direction by combining several thin leaf springs 27 in parallel with each other as shown in FIG. 7. do. In addition, the magnet 25 and the yoke 24, which are heavier than the coil, are placed on the fixed side, and the relatively light coil 23 is placed on the driving side, so that the focusing operation does not occur due to weighting. The magnets 25, yoke 24, and coil 23 are arranged in this way, and the direction of the magnetic flux is arranged from right to left, and the coil 23 is arranged perpendicularly to the ground, changing the direction in which current flows, according to the left-hand rule of framing. The driving force is generated in the direction to form a displacement accordingly, and the driving force in the focusing direction is obtained by using the displacement.

As shown in FIG. 8, the direction of up and down driving is D1, D2, the direction of magnetic flux flowing from right to left is P1, the direction of current is I1, I2, respectively, and the direction of current comes out of the ground (I1) in FIG. 8. (A) In the case where the direction of the current has entered (I2) as shown in FIG. 8B, in the case of (A), the driving direction is the downward direction D1 and the current flows into the ground. In case of (B), it is driven in the direction of D2 above, and focusing driving is performed using this property.

In the driving method in which the piezo 21 is displaced through the potential difference and the tracking / focusing operation of the objective lens 20 is performed through the movable member 22 which reacts up and down according to the direction of magnetic flux and current, The tracking / focusing coil is supported on several wires, and a magnet is attached to the yoke at the bottom to form the magnetic field and magnetic circuit generated by the magnet, so that the tracking lens and the focusing coil are in the focusing direction and the tracking direction. The driving method is completely different from the wire spring-supported two-dimensional actuators that drive up, down, left, and right. That is, the magnitude of the force represented by the driving force in the wire spring-supported two-dimensional actuator is determined in proportion to the relationship between the magnetic flux density of the magnet, the effective length and the number of turns of the coil, and the strength of the current, but is driven by the coil only in the magnetic field. As a result, the efficiency is lowered and the numerical value is not more than about 50%.

When the piezo 21 is displaced to obtain the tracking driving force and the driving force necessary for focusing in response to the direction of the magnetic flux and the current, these variables are reduced and at the same time the driving force is directly generated by the potential difference and the magnetic flux, so The century is great.

Therefore, set the driving range of the objective lens in the focusing direction to ± 1 to 2mm and the tracking direction to ± 0.3 to 0.5mm as the driving area.In the playback stage, ± 1µm in the focusing direction and ± 0.1µm in the tracking direction. The area can be larger than that of general actuators designed to follow. This results in an increase in the double speed of the objective lens for playback and recording, resulting in adaptation to high double speed.

In addition, the wire spring-supported two-dimensional actuator is structurally integrated with a tracking / focusing drive unit, so that the separation of the drive is not complete due to interference and crosstalk between each other. However, the tracking / focusing drive unit has a piezo and leaf spring-type movable member. By replacing it, it is possible to separate the drive. This suppresses the occurrence of unnecessary vibration modes, which helps to ensure the stability of playback and recording operations.

As described above, the present invention enables the high-speed driving of the objective lens required for the double speed increase for the reproduction and recording of the optical pickup head, which is effective in increasing the double speed, and maintains the driving force of the objective lens while maintaining a stable frequency response. In addition, since the driving source in the focusing / tracking direction can be completely separated, unnecessary vibration mode formation can be suppressed, thereby improving the stability and reliability of the playback and recording operations.

Claims (4)

A tracking driver having a piezo displaced by a potential difference in the tracking direction according to the objective lens driving direction; Several movable members which are installed in parallel with the tracking driving unit and arranged in the focusing direction to cause displacement in response to the potential difference and drive the objective lens therefrom; A focusing drive system for driving a movable member comprising a coil, a yoke and a magnet installed inside the movable member to displace the movable member; The objective lens driving apparatus of the optical pickup, characterized in that consisting of a connecting member for connecting the tracking driver and the focusing driver. The objective lens driving apparatus of claim 1, wherein the movable member provided in the focusing direction is a leaf spring supported by the connecting member and the frame. The objective lens of claim 1, wherein in the focusing drive system for driving the movable member consisting of the coil, the yoke, and the magnet, a relatively light coil is placed on the driving side with a magnet and a yoke on the fixed side. Drive system. According to claim 1, The magnet is arranged in the order of the NS in order to leave the direction of the magnetic flux to the left under the condition that there is a tracking drive on the left side, and the direction of the current is installed to maintain the direction going through or entering the ground And a coil mounted to the ground in the vertical direction.