JPH082812Y2 - Focus actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an optical recording / reproducing apparatus for recording or reproducing information by condensing a light beam as a light spot on a disk-shaped recording medium by an objective lens. The present invention relates to a focus actuator that drives an objective lens.

[Outline of device]

The present invention comprises a first pair of piezoelectric plates that are substantially parallel to each other.
Attaching a second piezoelectric drive means composed of a pair of substantially parallel piezoelectric plates to the piezoelectric drive means via a bendable connecting member and a support member, and attaching an objective lens holder to the second piezoelectric drive means. It is possible to correspond to the drive which has a large amplitude and a small amplitude but has a high speed followability.
A focus actuator that prevents mutual interference is also provided.

[Conventional technology]

A conventional actuator found in JP-A-63-64640 will be described with reference to FIGS. 7 and 8.

FIG. 7 is a perspective view of a conventional actuator. The conventional example drives a head 51 for reading data recorded on an optical card as an example of a disk-shaped recording medium in a focus direction perpendicular to the plane of the optical card and in a tracking direction orthogonal to the focus direction. Is. One end of the bimorph 52 that is displaceable in the focus direction has a bimorph that is displaceable in the tracking direction via the relay member 53.
54 is attached, and the other end is attached to the fixing member 55. head
51 is attached to a bimorph 54 which is displaceable in the tracking direction. In this way, the head 51 is supported so as to be displaceable with respect to the fixed member 55 in the focus direction and the tracking direction.

The bimorph 52, which is displaceable in the focus direction, has two piezoelectric elements 52 as shown in the enlarged side view of FIG.
a, 52b are bonded together, the central electrode 56 and one outer electrode 57 are provided over substantially the entire length direction of the piezoelectric elements 52a, 52b, and the other outer electrode is divided in the length direction and has a length. And a long electrode 58b having a long length. In the bimorph 52, the short electrode 58a has a short electrode 58a.
Both ends of the relay member 53 and the fixing member 55 so that they are on the 3 side.
It is attached to and respectively.

The bimorph 54 is also configured in the same manner as the bimorph 52, and the short electrode 59a on one surface is attached to the head 51 side and the long electrode 59b is attached to the relay member 54 side.

In this way, when the head 51 is driven by the bimorph 52 with a large amplitude in the focus direction, the short electrode 58
When both a and the long electrode 58b are selected to drive with a small amplitude, the short electrode 58a is selected. Similarly, when the head 51 is driven by the bimorph 54 with a large amplitude in the tracking direction, both the short electrode 59a and the long electrode 59b are selected,
When driving with a small amplitude, the short electrode 59a is selected.

With this configuration, the head 51 can be driven with a large amplitude in the focus direction and the tracking direction, and at the same time, can be quickly driven with a small amplitude.

[Problems to be solved by the device]

In such a conventional actuator, when the head 51 is driven by the bimorph 52 with a large amplitude in the focus direction, both the short electrode 58a and the long electrode 58b are selected,
When driving with a small amplitude, the short electrode 58a is selected.

On the other hand, in an optical recording / reproducing apparatus that records or reproduces information by condensing it on a disk-shaped recording medium, a large amplitude corresponding to a direct-current change that drives the objective lens in the focus direction and pulls it into a predetermined operating position is used. At the same time, it is necessary to drive at a small amplitude corresponding to an AC change that requires high-speed followability during operation. Since the conventional actuator uses a common bimorph that gives individual drive signals to the short electrode 58a and the long electrode 58b,
There was a problem that they interfere with each other.

The present invention has been made in order to solve such a conventional problem, and it corresponds to a drive having a large amplitude and a small amplitude but a high speed followability, and eliminates mutual interference. The subject is to obtain a focus actuator.

[Means for solving the problem]

The focus actuator of the present invention comprises a first piezoelectric drive means composed of a pair of substantially parallel piezoelectric plates and a second piezoelectric drive means composed of a pair of substantially parallel piezoelectric plates. The second piezoelectric driving means is attached to the means via a bendable first connecting member and a supporting member, and the objective lens holder is attached to the second piezoelectric driving means via a bendable second connecting member. Install.

[Action]

Since the first piezoelectric driving means and the second piezoelectric driving means are provided, it is possible to cope with driving having a large amplitude and a small amplitude but high-speed followability, and at the same time, a connecting member bendable to the first piezoelectric driving means. Since the second piezoelectric driving means is attached via the support member and the first piezoelectric driving means and the second piezoelectric driving means,
Therefore, the piezoelectric driving means and the other piezoelectric driving means are constituted by different piezoelectric plates, for example, different bimorphs, and there is no mutual interference. In addition, since the connecting member and the supporting member that can be bent are used for mounting and the supporting member has rigidity, the connecting member bends in the direction opposite to the bending direction of the first piezoelectric driving means.

〔Example〕

Hereinafter, embodiments of the focus actuator of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a first embodiment of the focus actuator of the present invention. FIG. 2 is a sectional view of the embodiment. In this embodiment, an objective lens holder 2 of an optical recording / reproducing apparatus for recording or reproducing information by condensing a light beam as a light spot on a disc-shaped recording medium by an objective lens 1.
Is driven in the focus direction perpendicular to the surface of the disk-shaped recording medium.

The first piezoelectric driving means 3 is composed of a pair of substantially parallel piezoelectric plates, for example, bimorphs 4 and 5, one end of which is fixed to a fixing member 6 and the other end of which protrudes substantially in parallel from the center of the bimorphs 4 and 5. A pair of bendable first connecting members 7,
It is fixed to a supporting member 9 having rigidity via 8. Second
The piezoelectric driving means 10 comprises a pair of substantially parallel piezoelectric plates, such as bimorphs 11 and 12, one end of which is the support member 9
A pair of bendable second connecting members 13 and 14 which are fixed to each other and whose other ends project from the centers of the bimorphs 11 and 12 substantially in parallel.
It is fixed to the lens holder 2 having rigidity via the.

The bimorphs 4 and 5 of the first piezoelectric drive means 3 are longer and have a larger area than the bimorphs 11 and 12 of the second piezoelectric drive means 10. Therefore, the first piezoelectric drive means 3 can be adapted to drive the objective lens 1 in the focus direction and draw it to a predetermined operating position with a large amplitude that mainly makes a DC change. On the other hand, the second piezoelectric drive means 10 can cope with a drive having a high-speed follow-up property, although the amplitude is a small amplitude that changes mainly in AC during operation.

A bimorph 4 as an example of a piezoelectric plate has two plates 4 composed of piezoelectric elements, as shown in the enlarged sectional view of FIG.
A and 4b are bonded to each other via a central electrode 7a so that their polarization directions are opposite to each other, and external electrodes 15a and 15b are formed on both surfaces. When one end of such a bimorph 4 is fixed and a voltage is applied to the central electrode 7a and the outer electrodes 15a and 15b, the bimorph 4 is curvedly displaced, and the free end of the bimorph 4 moves up and down (shown by an arrow in FIG. 2). Focus direction).

FIG. 4 is an enlarged sectional view of a main part of the first embodiment of the focus actuator of the present invention. In this embodiment, the first connecting members 7 and 8 are connected to the bimorph 4 of the first piezoelectric driving means.
The central electrodes 7a and 8a of FIG. By using them in this way, the number of parts can be reduced. Moreover, since the first connecting members 7 and 8 that can be bent and the supporting member 9 are used for mounting, and the supporting member 9 has rigidity, the first connecting members 7 and 8 are the first piezoelectric driving means. The support member 9 and the second piezoelectric drive means 10 fixed to the support member 9 and bent in the direction opposite to the bending direction are movable in parallel without tilting.

On the other hand, although not shown in FIG.
As shown in the figure, the second piezoelectric driving means 10 has a lens holding body having rigidity through a pair of bendable second connecting members 13 and 14 projecting from the centers of the bimorphs 11 and 12 substantially in parallel. You may support 2. With this configuration, since the second connecting members 13 and 14 which can be bent for mounting support the lens holder 2 having rigidity, the second connecting member is provided.
13 and 14 bend in the direction opposite to the bending direction of the second piezoelectric drive means,
The lens holder 2 can move in parallel without tilting. At this time, the bimorphs 11 and 12 of the second piezoelectric drive means 10
The central electrodes 7a, 8a of the bimorphs 4, 5 of the first piezoelectric drive means 3 are extended as the central electrodes of the
It is also possible to use it together with 13 and 14. In this way, by using the second connecting members 13 and 14 also as the central electrodes 7a and 8a of the bimorphs 4 and 5 of the first piezoelectric drive means 3, the number of parts can be further reduced.

5 and 6 show second and third embodiments of the focus actuator of the present invention. As a pair of substantially parallel piezoelectric plates, the laminated voltage actuators 16, 17, 1
8 and 19 are used, and the laminated piezoelectric actuator 1
The operating principle of 6, 17, 18 and 19 is the same as that of bimorph, by reducing the thickness of one layer and firing it in multiple layers,
It can be driven at a low voltage that is inversely proportional to the number of stacked layers. The connecting members 20, 21, 22, 23 are characteristic, and in the second embodiment of FIG. 5, the connecting members 20, 21 are metallic members, and the curved portions 20a, 21a are provided in the middle to obtain elasticity. I am trying. In the third embodiment of FIG. 6, the connecting members 22 and 23 are members made of plastic, and thin portions 22a and 23a are provided in the middle to facilitate elasticity.

[Effect of device]

As described above, since the focus actuator of the present invention has the first piezoelectric drive means and the second piezoelectric drive means, it is compatible with the drive having a large amplitude and a small amplitude but a high speed followability. By attaching the second piezoelectric driving means to the first piezoelectric driving means via the bendable connecting member and the supporting member, the first piezoelectric driving means and the second piezoelectric driving means are different piezoelectric plates, for example, By constructing different bimorphs, mutual interference is eliminated. Moreover, since the flexible connecting member and the supporting member are used for mounting, the supporting member has rigidity, and the connecting member bends in the direction opposite to the bending direction of the first piezoelectric driving means, so that the objective lens is moved in the focusing direction. The objective lens can move in parallel without being tilted.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the focus actuator of the present invention. FIG. 2 is a sectional view of the first embodiment of the focus actuator of the present invention. FIG. 3 is an enlarged sectional view of the bimorph. FIG. 4 is an enlarged sectional view of a main part of the first embodiment of the focus actuator of the present invention. FIG. 5 is an enlarged sectional view of a main part of the second embodiment of the focus actuator of the present invention. FIG. 6 is an enlarged sectional view of the essential parts of a third embodiment of the focus actuator of the present invention. FIG. 7 is a perspective view of a conventional actuator. FIG. 8 is an enlarged side view of a conventional bimorph. DESCRIPTION OF SYMBOLS 1 ... Objective lens 2 ... Objective lens holder 3 ... 1st piezoelectric drive means 4, 5 ... Bimorph 4a, 4b ... Plate consisting of a piezoelectric element 5 ... Fixing member 7, 8 ... 1st Connecting members 7a, 8a ... Central electrode 9 ... Supporting member 10 ... Second piezoelectric driving means 11, 12 ... Bimorph 13, 14 ... Second connecting member 15a, 15b ... External electrodes 16, 17, 18, 19 ... Multilayer piezoelectric actuator 20, 21, 22, 23 ... Connecting member 20a, 21a ... Curved portion 22a, 23a ... Thin portion

Claims (3)

[Scope of utility model registration request] 1. A first device comprising a pair of substantially parallel piezoelectric plates.
Piezoelectric driving means and a second piezoelectric driving means composed of a pair of substantially parallel piezoelectric plates, and the second piezoelectric driving means via a connecting member and a supporting member bendable to the first piezoelectric driving means. A drive means is attached to the second
A focus actuator in which an objective lens holder is attached to the piezoelectric driving means. 2. The focus actuator according to claim 1, wherein the bendable connecting member is formed of a piezoelectric plate electrode. 3. The focus actuator according to claim 1, wherein the bendable connecting member is a plate-shaped member having elasticity.