JP2000057598A - Biaxial actuator and optical device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxial actuator capable of providing a good-quality optical disk reproducing signal by regulating the frequency of very small vibration given during the operation of the biaxial actuator of a shaft sliding type so as to perform very small vibration by a voltage as small as possible and with good efficiency, and with reduced power consumption, and an optical device using the same. SOLUTION: This biaxial actuator 1 is provided with an objective lens 4 facing an optical recording medium, a movable part 2 having coil members 6 and 7 for driving the objective lens 4 in at least one of focusing and tracking directions, and a fixed part 3 having a rotary shaft 11 formed therein. The rotary shaft is inserted into a guide hole 8A formed in the movable part 2, driving is performed by the sliding movements of the rotary shaft 11 and the movable part 2, vibration is conducted from relative motion between the movable part 2 and the fixed part 3 during driving, and the frequency of the vibration is set equal to that in the vicinity of a primary resonance frequency f0 in the frequency characteristic of a vibration direction. Also, an optical device using this biaxial actuator is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-axis actuator used in an optical pickup device for recording and / or reproducing information signals using an optical recording medium such as an optical disk or a magneto-optical disk, and an optical device using the same. Related to

[0002]

2. Description of the Related Art As one type of a two-axis actuator used in an optical pickup device and capable of independently moving an objective lens in a focus direction and a tracking direction, a type having a movable part having an objective lens attached to a fixed part is provided. There is a shaft sliding type two-axis actuator which can move the objective lens in the horizontal direction by rotating the movable part about an axis by giving a degree of freedom in the vertical direction by sliding.

In this two-axis actuator of the shaft sliding type, a movable part, that is, a bobbin performs an up-and-down motion in the axial direction or a rotational motion about the axis with respect to the axis to cope with various servos. If there is a portion in contact with the movable portion, the sliding characteristics may be impaired due to friction caused by the relative motion.

[0004] In such a two-axis actuator of the shaft sliding type, a magnetic balance or an elastic balance of rubber or the like is used, so that the sleeve portion of the movable portion side bobbin at the mechanical neutral point in an ideal (natural) state. The center of the guide hole coincides with the center of the fixed portion side guide shaft. Therefore, there is no place where the guide shaft and the guide hole are in contact with each other during the vertical and rotational operations.

[0005] However, if there is a place where the movable part and the shaft come into contact with each other due to the above-mentioned imbalance or the like, friction or interference at that place causes a problem.
The operation may have non-linear rather than non-linear elements. That is, there is a case where a phenomenon such as catching is observed and smooth operation becomes impossible. FIG. 4 shows a cross-sectional view of this state. 4, reference numeral 51 denotes a fixed part, 52 denotes a movable part, 53 denotes a guide shaft, 54 denotes a bobbin, 54A denotes a guide hole provided in the bobbin 54, 55 denotes an objective lens, and 56 denotes a balancer. Note that a focus coil, a tracking coil, and a magnet are omitted.

The guide hole 54A of the bobbin 54 of the movable portion 52
Corners are caught on the guide shaft 53, which causes friction.

Further, in order to eliminate rattling during operation due to the clearance between the guide shaft and the guide hole, or for other reasons, the side surface of the guide hole may be intentionally pressed against the guide shaft. FIG. 5 is a sectional view showing the state in this case.
Shown in The reference numerals are the same as those in FIG.

In this case, by pressing the side surface of the guide hole 54A of the bobbin 54 of the movable portion 52 in the direction shown by the arrow in the figure, the mutual movement between the guide shaft 53 and the guide hole 54A is performed as in the case of FIG. Friction occurs at the position surrounded by the dotted line in the figure, resulting in malfunction.

Therefore, in order to solve these problems,
There has been proposed a method of improving slidability by injecting a small vibration when the movable part performs relative movement. That is, the following minute vibration is applied. 1) At the time of the vertical operation, that is, the focus adjustment operation, a minute vibration is applied in the vertical direction or the rotation direction. 2) At the time of a rotation operation, that is, a tracking adjustment operation, a minute vibration is applied in a vertical direction or a rotation direction.

[0010]

Further, the frequency of the above-mentioned minute vibration and the voltage applied to the focus coil or the tracking coil have not been specified so far, and any value has been adopted. However, in such a case, an excessive current may flow through the two-axis actuator, which may cause a problem such as deterioration of the quality of a reproduction signal of the optical disc (so-called jitter) due to disconnection of the coil or heat generation. Further, depending on the frequency, a large applied voltage is required, and as a result, the load on the two-axis actuator may be increased.

In order to solve the above-mentioned problem, in the present invention, the frequency of the minute vibration to be given during the operation of the shaft sliding type two-axis actuator is defined so that the minute vibration can be made with a small and efficient voltage as small as possible. Another object of the present invention is to provide a two-axis actuator which consumes less power and obtains a reproduced signal of an optical disc with good quality, and an optical device using the same.

[0012]

According to the present invention, there is provided a biaxial actuator comprising: a movable portion having an objective lens facing an optical recording medium; a coil member for driving the objective lens in at least one of a focus direction and a tracking direction; A rotary shaft is inserted into a guide hole formed in the movable portion, and the rotary shaft and the movable portion are driven to slide.
At the time of driving, a minute vibration is given to the movable portion, and the frequency of the minute vibration is a frequency near the primary resonance frequency in the frequency characteristics of the focus servo or the tracking servo.

The optical device of the present invention irradiates a laser beam onto an optical recording medium through an objective lens of a biaxial actuator,
In an optical device that records an information signal on the information recording surface of the optical recording medium or reproduces the information signal recorded on the information recording surface, the biaxial actuator includes an objective lens facing the information recording surface and an objective lens facing the information recording surface. A movable part having a coil member for driving the objective lens in at least one of the focus direction and the tracking direction, and a fixed part having a rotating shaft are provided. The rotating shaft is inserted into a guide hole formed in the movable part, and the rotating part is rotated. Driving is performed by sliding the shaft and the movable part. At the time of driving, a minute vibration is given to the movable part, and the frequency of the minute vibration is set to a frequency near the primary resonance frequency in the frequency characteristic of the focus servo or the tracking servo. It was done.

According to the above-described structure of the biaxial actuator of the present invention, by setting the frequency of vibration to a frequency near the primary resonance frequency in the frequency characteristic of the direction of vibration, a larger vibration displacement can be obtained for the same applied voltage. Therefore, the same minute vibration amplitude can be obtained with a low applied voltage.

According to the configuration of the optical device of the present invention described above,
By setting the vibration frequency to a frequency near the primary resonance frequency in the frequency characteristic of the vibration direction, a larger vibration displacement can be obtained for the same applied voltage.
The applied voltage for generating vibration can be reduced.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a movable part having an objective lens facing an optical recording medium, a coil member for driving the objective lens in at least one of a focus direction and a tracking direction, and a fixed part having a rotating shaft formed thereon. With
A two-axis actuator in which a rotary shaft is inserted into a guide hole formed in the movable part, and the rotary shaft and the movable part slide, and the drive is performed. This is a two-axis actuator in which the frequency of the minute vibration is a frequency near the primary resonance frequency in the frequency characteristics of the focus servo or tracking servo.

According to the present invention, an optical recording medium is irradiated with a laser beam through an objective lens of a biaxial actuator, an information signal is recorded on an information recording surface of the optical recording medium, or information recorded on the information recording surface is recorded. In the optical device configured to reproduce a signal, the biaxial actuator includes an objective lens facing the information recording surface, a movable unit having a coil member that drives the objective lens in at least one of the focus direction and the tracking direction, and a rotation axis. A rotating shaft is inserted into a guide hole formed in the movable portion,
Driving is performed by sliding the rotating shaft and the movable part, and a small vibration is given to the movable part at the time of driving, and the frequency of the minute vibration is set to a frequency near the primary resonance frequency in the frequency characteristic of the focus servo or the tracking servo. Optical device.

FIG. 1 is a schematic configuration diagram of an embodiment of a biaxial actuator according to the present invention. The biaxial actuator 1 is roughly divided into two parts, a movable part 2 and a fixed part 3. The movable portion 2 is provided with a bobbin 8 having a substantially T-shaped cross section composed of a flange portion 8F and a sleeve portion 8S, and a laser beam on an optical recording medium, for example, an optical disk surface attached to one end of the flange portion 8F with the sleeve portion 8S interposed therebetween. An objective lens 4 for forming an image and a balancer 5 for balancing the mass of the movable section 2 attached to the other end of the flange section 8F.
And a focus coil 6 attached to the outside of the sleeve 8S and driven in the focus direction, and a tracking coil 7 driven in the tracking direction. At the center of the bobbin 8, there is provided a guide hole 8A through which a guide shaft 11 of the later-described solid portion 3 is inserted so as to penetrate the sleeve portion 8S. The focus coil 6 is wound around the outer periphery of the sleeve portion 8S so that the coil center is directed in the vertical direction (vertical direction).
A pair is provided outside the focus coil 6 so that the coil center is oriented in the horizontal direction.

The fixed part 3 includes a substantially U-shaped yoke 10, a guide shaft 11 for rotating and sliding which is integrally mounted so as to stand upright at the center of the bottom plate of the yoke 10, and a guide shaft 11.
And a pair of coil driving magnets 9 attached to the inside of both vertical side plates of the yoke 10 with the. The magnet 9 is divided and magnetized in the vertical direction to form an N pole and an S pole.

In the two-axis actuator 1, the guide shaft 11 attached to the fixed portion and the sleeve portion (guide hole 8A) of the bobbin 8 slide, so that the bobbin 8 has a degree of freedom in the vertical direction. By rotating about the guide shaft 11, the objective lens 4 at a position eccentric with respect to the guide shaft 11 can be operated. That is, a so-called shaft sliding type two-axis actuator is formed.

Next, the operation of the biaxial actuator 1 will be described. 2A shows an exploded side view of the movable part 2 and the fixed part 3 of the biaxial actuator 1, and FIG. 2B shows a plan view of the movable part 2 of the biaxial actuator 1.

First, attention is paid to the operation in the focus direction F (vertical direction). Although not shown, the magnetic field generated from the magnet 9 passes through the focus coil 6 to form a closed magnetic path.

At the time of focus driving, the current flowing in the focus coil 6 in the horizontal direction and the magnetic field from the magnet 9 cause the bobbin 8 and the objective lens 4 to move in the vertical focus direction F as shown in FIG. The movable part 2 integrally having the above moves with the guide shaft 11 as a guide. Thereby, focusing is performed.

Next, attention is paid to the operation in the tracking direction T (horizontal direction). Although not shown, the magnetic field generated from the magnet 9 passes through the tracking coil 7 and forms a closed magnetic path with the guide shaft 11 interposed therebetween.

At the time of tracking driving, a horizontal force is applied to the bobbin as shown in FIG. 2B by the current of the component in the vertical direction (the same direction as the focus direction F) of the tracking coil 7 and the magnetic field from the magnet 9. As a result, the movable part 2 integrally having the bobbin 8 and the objective lens 4 rotates about the guide shaft 11, and the objective lens 4 moves in the tracking direction T. Thereby, tracking matching is performed.

In the two-axis actuator 1 of this embodiment, a minute vibration is applied in the focus direction F or the tracking direction T during the focus driving or the tracking drive.

That is, for example, the following minute vibration is applied. 1. At the time of focus drive in which the objective lens 4 moves in the focus direction F, which is the vertical direction (at the time of focus adjustment operation)
Then, a minute vibration is applied in the vertical direction (focus direction F). 2. At the time of focus drive in which the objective lens 4 moves in the focus direction F, which is the vertical direction (at the time of focus adjustment operation)
Then, a minute vibration is applied in the rotation direction (tracking direction T). 3. A tracking direction T in which the objective lens 4 is rotated
During the tracking drive (at the time of the tracking adjustment operation), the minute vibration is applied in the vertical direction (focus direction F). 4. A tracking direction T in which the objective lens 4 is rotated
At the time of tracking drive (at the time of tracking adjustment operation), the micro vibration is applied in the rotation direction (tracking direction T).

In practice, a waveform voltage having a predetermined frequency, which will be described later, is applied to the focus coil 6 in the case of minute vibration in the vertical direction and to the tracking coil 7 in the case of minute vibration in the rotation direction. The mechanical vibration is generated by the action of the alternating current flowing through the coil 6 or 7 based on the waveform voltage and the magnetic field from the magnet 9. As this waveform voltage, a continuous waveform, a waveform generated intermittently in a pulse shape, or the like can be used, and is repeatedly applied at a constant frequency.

That is, when the driving direction is the same as the direction of the minute vibration, a voltage in which the driving waveform voltage and the minute vibration waveform voltage are superimposed is applied to the driving coil 6 or 7 in that direction. Will be. When the driving direction is different from the direction of the minute vibration, a driving waveform voltage is applied to one of the driving coils 6 and 7 in each direction, and a minute vibration waveform voltage is applied to the other. Will be.

In the two-axis actuator 1 according to the present embodiment, the frequency of the minute vibration is further defined as described later.

FIG. 3 is a Bode diagram showing gain characteristics of a general servo transfer function of an optical pickup.
This gain characteristic shows the same characteristic for both the focus servo and the tracking servo.

As shown in FIG. 3, the gain (low frequency gain) G _L is constant in the low frequency band, but the ratio of the gain G to the low frequency band gain G _L increases near the primary resonance frequency f ₀ , When G is lifted like a mountain and compared with other high frequency bands or low frequency bands, a larger gain G, that is, a vibration displacement is obtained when vibration of the same applied voltage is applied.

In the two-axis actuator 1 of the present embodiment, by utilizing this, the frequency of the minute vibration is within the frequency range in which the gain G _{equal to} or higher than the low-frequency gain _GL is obtained in the minute vibration (the range f in the figure). ), That is, a frequency within a range utilizing the lifting around the primary resonance frequency f ₀ is selected.
By defining the frequency in this manner, it is possible to efficiently obtain minute vibration with a small voltage.

The value of the primary resonance frequency f ₀ is
The value of the primary resonance frequency f ₀ can be calculated based on the design value and the like of the movable portion 2 and the design value and the like.
Focusing direction F (vertical direction) and tracking direction T
(Rotational direction) and have respective primary resonance frequencies f ₀ . When defining the frequency of the above-mentioned minute vibration, the value of the primary resonance frequency f ₀ in the direction of vibration (focus direction F or tracking direction T) is adopted.

As described above, the efficiency of the voltage is improved, so that the current flowing through the biaxial actuator 1 can be reduced, and the disconnection of the biaxial coil (that is, the focus coil 6 and the tracking coil 7) and the biaxial coil 6 and 7 can be prevented from generating heat. As a result, in an optical device such as an optical pickup using the biaxial actuator 1, it is possible to avoid problems such as disconnection of the biaxial coil and deterioration (jitter) of an optical disk reproduction signal due to heat generation of the biaxial coil.

The two-axis actuator of the present invention and the optical device using the same are not limited to the above-described embodiments, but may have various other configurations without departing from the gist of the present invention.

[0037]

According to the present invention described above, the efficiency of the voltage applied to the biaxial actuator can be increased, and the current flowing through the biaxial actuator can be reduced.
As a result, in the optical device using the biaxial actuator, problems such as disconnection of the biaxial coil and deterioration (jitter) of the optical disk reproduction signal due to heat generated by the biaxial coil can be avoided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a movable part and a fixed part of a two-axis actuator according to the present invention.

FIG. 2A is an exploded side view of a movable part and a fixed part of the biaxial actuator of FIG. 1; B is a plan view of a movable portion of the biaxial actuator of FIG. 1.

FIG. 3 is a Bode diagram showing gain characteristics of a general servo transfer function of an optical pickup.

FIG. 4 is a sectional view showing a state where a guide shaft and a guide hole are caught.

FIG. 5 is a cross-sectional view showing a state where a side surface of a guide hole is pressed against a guide shaft.

[Explanation of symbols]

1 2-axis actuator, 2 movable part, 3 fixed part, 4
Objective lens, 5 balancer, 6 focus coil, 7 tracking coil, 8 bobbin, 9 magnet, 10 yoke, 11 guide shaft, 51 movable part, 5
2 fixed part, 53 guide shaft, 54 bobbin, 55 objective lens, 56 balancer, F focus direction, T
Tracking direction

Claims (2)

[Claims] A movable section having an objective lens facing the optical recording medium and a coil member for driving the objective lens in at least one of a focus direction and a tracking direction;
A two-axis actuator including a fixed part having a rotating shaft formed therein, wherein the rotating shaft is inserted into a guide hole formed in the movable part, and the rotating shaft and the movable part slide to be driven. And a micro-vibration is applied to the movable portion during the driving, and the frequency of the micro-vibration is a frequency near a primary resonance frequency in a frequency characteristic of a focus servo or a tracking servo. . 2. An optical recording medium is irradiated with a laser beam through an objective lens of a two-axis actuator, and an information signal is recorded on an information recording surface of the optical recording medium. In the optical device configured to reproduce, the biaxial actuator includes a movable part having an objective lens facing the information recording surface, a coil member that drives the objective lens in at least one of a focus direction and a tracking direction, and a rotation axis. The movable shaft is inserted into a guide hole formed in the movable portion, and the rotating shaft and the movable portion slide to perform driving. The micro-vibration is applied to the portion, and the frequency of the micro-vibration is a frequency near the primary resonance frequency in the frequency characteristics of the focus servo or the tracking servo. An optical device, comprising: