JPH0770076B2 - Objective lens drive - Google Patents

Description

The present invention relates to an objective lens driving device used in, for example, an optical disk recording / reproducing device.

[Conventional technology]

FIG. 8 is a perspective view showing a main part of a conventional objective lens driving device, and FIG. 9 is a side view thereof.

In the figure, (1) is an objective lens, (2) is an objective lens holder for holding the objective lens (1), (3) is a support portion, and (4a) and (4b) are one end portions of the objective lens holder (2 ), And the other end of the elastic support member is fixed to the support part (3), and (5) is the objective lens holder (2).
The focus direction control coil is wound around, (6) is a permanent magnet, and (7a) and (7b) are yokes. Above (5),
The focal direction drive means (50) is composed of (6) and (7).

Next, the operation will be described. When a predetermined current according to a focusing control signal obtained by a control circuit including an optical system (not shown) is applied to the focus direction control coil (5), the permanent magnet (6) and the yokes (7a) and (7b) are connected to each other. The objective lens holder (2) and thus the objective lens (1) are driven in the direction of arrow A by electromagnetic interaction with the generated magnetic field so that the focusing spot is always formed on the disk (not shown). Take control.

Since the conventional objective lens driving device is configured as described above, it is necessary to wind the focus control coil (5) around the objective lens holder (2), which increases the weight of the movable part and the coil lead wire (not shown). There is a problem that the processing of (z) becomes complicated. The permanent magnet (6) and the yoke (7
Since it is necessary to construct a magnetic circuit by a) and (7b), there are problems that assembly is complicated and leakage flux from the magnetic circuit to the outside occurs.

An objective lens driving device as shown in FIG. 10 has been proposed to improve the above drawbacks.

In the figure, (8a) and (8b) are bimorph type piezoelectric elements, one end of which is connected to the objective lens holder (2) and the other end of which is connected to the fixed portion (3). The same reference numerals as those in FIGS. 8 and 9 indicate the same or corresponding portions.

Next, the operation will be described. Bimorph type piezoelectric element (8
When a desired voltage is applied to a) and (8b), the bimorph type piezoelectric elements (8a) and (8b) are deformed, and the objective lens holder (2), and thus the objective lens (1) is driven in the direction of arrow A to move the focus direction. Take control.

[Problems to be solved by the invention]

Since the conventional objective lens driving device shown in FIG. 10 is constructed as described above, the above-mentioned drawbacks of the conventional device shown in FIGS. Since only the element is used, its frequency characteristics are as shown in Part B of FIG.
There was a problem that the next resonance occurred and the servo band could not be wide.

The present invention has been made in order to solve the above problems, and an object of the present invention is to obtain an objective lens driving device that does not necessarily need to form a magnetic circuit with a simple structure and can have a wide servo band. To do.

[Means for solving problems]

In the objective lens driving device according to the present invention, at least one of the focus direction driving means and the track direction driving means has a first driving source having a low resonance frequency and capable of large displacement, and a high displacement having a high resonance frequency and small displacement. It has a possible second drive source, and drives the objective lens by using the first and second drive sources at a sharing ratio determined based on the frequency at which the objective lens is driven.

[Work]

The driving means in the present invention can use a wide variety of servo bands by sharing two different types of driving sources.

〔Example〕

FIG. 1, FIG. 2, and FIG. 3 show an embodiment of the present invention, and reference numerals (1), (2), (3), (8a), (8b) in the drawings.
Indicates the same or corresponding part as the above-mentioned conventional one.

(10a) and (10b) are laminated piezoelectric elements, one end of which is fixed to the bimorph type piezoelectric elements (8a) and (8b), and the other end of which is fixed to the objective lens holder (2). In this embodiment, the bimorph type piezoelectric elements (8a) and (8b) form a first drive source, and the laminated piezoelectric elements (10a) and (10b) form a second drive source. Drive source (8a),
The focal point direction driving means (50) is constituted by (8b) and the second driving sources (10a), (10b).

In a relatively low frequency range, a desired voltage is applied to the bimorph type piezoelectric elements (8a) and (8b) serving as the first drive source to generate a flexural deformation, thereby causing the objective lens holder (2) and thus the objective lens (1). ) In the direction of arrow A. In a comparatively high frequency region, a desired voltage is applied to the laminated piezoelectric elements (10a) and (10b) as the second driving source to cause vertical deformation, so that the objective lens holder (2) and thus the objective lens. Drive (1) in the direction of arrow A. The drive amount of the former is relatively large, and the drive amount of the latter is minute, and the drive amount of both is adjusted by circuit means (not shown).
The focus direction control is shared. Therefore, the servo band can be widened and the adjustment accuracy of the objective lens (1) can be improved.

In the above-mentioned embodiment, the configuration in which the focus control is performed has been shown, but the configuration may be such that the tracking control is performed as shown in FIG. In addition, (60) is a track direction driving means including a bimorph type piezoelectric element (8a), (8b) as a first driving source and a laminated piezoelectric element (10a), (10b) as a second driving source. is there. The principle of operation is exactly the same as that described above, except that the driving direction changes in the direction of arrow B.

Further, as shown in FIG. 5, both focus control and track control may be performed. In addition, in the figure (3a),
(3b) is a support part, (8c) and (8d) are bimorph type piezoelectric elements as a first drive source for controlling the track direction, (10
Similarly, c) and (10d) are laminated piezoelectric elements as the second drive source for controlling the track direction.

Further, in the above-described embodiments, the bimorph type piezoelectric element is used as a mechanism for generating a relatively large displacement, but as shown in FIG. 6, an electromagnetic force is used and a minute displacement is shared by the laminated piezoelectric element. May be

Further, as shown in FIG. 7, the laminated piezoelectric elements (10a), (10
Between the b) and the lens holder (2), the displacement magnifying mechanism (20
The displacement magnifying mechanism (20a), (2
According to 0b), it may be configured to generate a larger displacement.

〔The invention's effect〕

As described above, according to the present invention, at least one of the focus direction drive means and the track direction drive means includes the first drive source having a low resonance frequency and capable of large displacement,
A second drive source having a high resonance frequency and capable of minute displacement, and driving the objective lens using the first and second drive sources at a sharing ratio determined based on the frequency at which the objective lens is driven. Therefore, the magnetic circuit can be omitted with a simple structure, and accordingly, the weight is light and the servo band can be widened.

[Brief description of drawings]

1 is a perspective view of an essential part showing an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a front view of FIG. 1, and FIG. 3 is a side view of FIG. 4, 5, 6 and 7 are the second and the third of the present invention.
The third, fourth and fifth embodiments are respectively shown. FIGS. 4 to 6 are perspective views of essential parts and FIG. 7 is a side view of essential parts. FIG. 8 is a perspective view of a main part showing a conventional device, FIG. 9 is a side view of FIG. 8, and FIG. 10 is a perspective view of a main part showing another conventional device.
The figure is a frequency characteristic diagram of the conventional apparatus shown in FIG. In the figure, (1) is an objective lens, (8a) and (8b) are bimorph type piezoelectric elements as a first driving source, (10a),
(10b) is a laminated piezoelectric element as a second drive source,
Reference numeral 0) is a focus direction driving means, and (60) is a track direction driving means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. An objective lens for condensing light emitted from a light source on a disc, a focus direction driving means for driving the objective lens in the focal direction, and a track direction driving means for driving the objective lens in the track direction of the disc. At least one of the driving means, at least one of the focus direction driving means and the track direction driving means has a first driving source having a low resonance frequency and capable of large displacement, and a resonance frequency. And a second drive source capable of minute displacement, and drives the objective lens by using the first and second drive sources at a sharing ratio determined based on a frequency at which the objective lens is driven. An objective lens drive device characterized by the above. 2. The objective lens according to claim 1, wherein the first drive source is composed of a bimorph type piezoelectric element, and the second drive source is composed of a laminated type piezoelectric element. Drive. 3. The objective lens driving device according to claim 2, further comprising means for enlarging a displacement amount of the laminated piezoelectric element.