JPH01300433A - Lens actuator - Google Patents

Abstract

PURPOSE:To obtain the sufficient quantity of displacement of a lens with constitution of miniaturization, light weight, and thin type by controlling the quantity of deformation of a piezoelectric unimorph by adjusting a voltage to be impressed between the electrodes of the piezoelectric unimorph. CONSTITUTION:The base parts of two arms setting flat springs 2 as their bases are fixed on a pedestal 1, and the lens 3 is supported at the tip part of the two arms so as to be sandwiched from both sides, and the lens 3 can be displaced in the direction of an optical axis and the direction intersecting orthogonally to the optical axis by the flexibility of the arm. Furthermore, those arms are provided with curved parts 2a and 2b, and the piezoelectric unimorphs 4 and 5 which set the flat springs as the electrodes on one side are jpined to the curved parts 2a and 2b, and the lens 3 can be displaced by deforming the curved parts 2a and 2b by the piezoelectric distortion of the piezoelectric unimorphs 4 and 5. In such a way, it is possible to fit the constitution in forming a device making into the miniaturization, the light weight, and the thin type and to take the quantity of displacement of the lens sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvement of a lens actuator incorporated in an optical head in a CD player, an optical disk device, or the like.

(Prior art) As is well known, there are strong demands for optical heads such as CD players to be smaller, lighter, thinner, and lower in price while still satisfying basic performance. Technological developments are being made. Conventional optical heads are configured to displace the objective lens in the direction of the optical axis and in the direction orthogonal to the optical axis using a moving coil type actuator using magnets and coils to perform precise focusing servo and tracking servo. ing.

(Problem to be solved by the invention) Moving coil type lens actuators are difficult to make smaller and thinner than they currently are, and their complicated structure poses problems in assembly and productivity. It is becoming difficult to lower prices even further.

As a lens actuator other than the moving coil type, a piezoelectric lens actuator that uses distortion of a piezoelectric material to displace a lens is known, for example, as disclosed in Japanese Patent Laid-Open No. 150134/1983. There is. However, conventional piezoelectric actuators use a laminated piezoelectric material to obtain the necessary displacement of the lens, and although they have a simple structure and are suitable for mass production, they are inferior to moving coil type actuators in terms of miniaturization and thinning. ing.

This invention was made in view of the conventional problems mentioned above.
The purpose is to provide a lens actuator using a piezoelectric material that can achieve a sufficient amount of lens displacement with a compact, lightweight, and thin configuration.

(Means for Solving the Problems) In the lens actuator according to the present invention, the base ends of two arms based on leaf springs are fixed to a base, and the lens actuator is inserted between the ends of the two arms from both sides. The lens is supported in such a manner that the lens is displaceable in the optical axis direction and in the direction perpendicular to the optical axis by the flexibility of the arm, and each of the arms has a U-shaped curved part, and the lens is supported by the arm. A piezoelectric unimorph having the plate spring as one electrode is bonded to the lens, and the lens is configured to be displaced by deforming the curved portion by piezoelectric distortion of the piezoelectric unimorph. Further, in the second invention, piezoelectric unimorphs are joined to the front and back surfaces of the leaf spring at positions shifted in the longitudinal direction in a substantially flat portion of the arm, and piezoelectric strain of the pair of piezoelectric unimorphs causes the distal end of the arm to is configured to be displaced in the thickness direction of the leaf spring.

(Function) The amount of deformation of the piezoelectric unimorph is controlled by adjusting the voltage applied between the electrodes of the piezoelectric unimorph (the leaf spring is one electrode, and there is another electrode on the opposite side). This makes it possible to change the position of the lens in the direction of the optical axis and in the direction perpendicular to the optical axis, allowing precise focusing servo and tracking servo as in the conventional art.

(Embodiment) FIGS. 1 and 2 show the structure of a lens actuator according to a first embodiment of the present invention. There is a base 1 in the form of a plate with both ends raised, and two symmetrical arms based on leaf springs 2 are attached to the inside of the raised parts at both ends.

The leaf spring 2 that forms the base of the arm has an inverted U-shaped curved portion 2.
a, a horizontal U-shaped curved part 2b, and a flat part 2C are continuous, and one side of the inverted U-shaped curved part 2a (this is the base of the leaf spring 2) is fixed to the base 1. There is. A square cylindrical holder 3a is placed between the tip of the flat part 2C of the leaf spring 2.
A lens 3 attached to the lens 3 is held between the lenses.

A tracking piezoelectric unimorph 4 is bonded to the outer surface of the inverted U-shaped curved portion 2a of the leaf spring 2, and a focusing piezoelectric unimorph 5 is bonded to the inner surface of the horizontal U-shaped curved portion 2b.
are joined. The piezoelectric unimorph 4 uses the leaf spring 2 as one electrode, and has another electrode 4a bonded to the opposite surface. Similarly, the piezoelectric unimorph 5 also uses the leaf spring 2 as the other electrode, and has another electrode 5a bonded to the opposite surface. These electrodes 4a, 5a are wired to electrode leads 6.

When the voltage applied to the tracking piezoelectric unimorph 4 is changed, the opening width of the inverted U-shape changes as shown by the arrow, as shown in FIG. To perform tracking servo, the left and right tracking piezoelectric unimorphs 4 shown in FIG. 1 are driven complementary to each other. In other words, in FIG. 1, when the lens 3 is displaced to the right, the voltage is adjusted so as to reduce the width of the U-shaped opening of the tracking piezoelectric unimorph 4 on the right, and the U-shaped opening of the tracking piezoelectric unimorph 4 on the left is adjusted. Adjust the applied voltage to increase the width. As a result, the tip of the left leaf spring 2 moves to the right and pushes the lens 3, and the tip of the right leaf spring 2 moves to the right and pulls the lens 3. In this way, the lens 3 can be displaced in a direction perpendicular to the optical axis.

Similarly, when the voltage applied to the focusing piezoelectric unimorph 5 is changed, the opening angle of the horizontal U-shape changes as shown by the arrow, as shown in FIG. The focusing servo is controlled by driving two focusing piezoelectric unimorphs 5 on the left and right in the same phase. If the width of the U-shape of the left and right piezoelectric unimorphs 5 is increased, the lens 3 will rise in the optical axis direction, and on the other hand, if the width of the U-shape is decreased, the lens 3 will be lowered in the optical axis direction.

FIG. 4 shows a second embodiment of the invention. The difference from the first embodiment is that a horizontal U-shaped curved portion 2b is provided on the base end side of the leaf spring 2 (a piezoelectric unimorph for focusing 5 is provided here), and a U-shaped curved portion 2a is formed following this. (The tracking piezoelectric unimorph 5 is provided here). In other words, the order of installation of the tracking piezoelectric unimorph 4 and the focusing piezoelectric unimorph 5 is reversed.

As shown in FIG. 5, if the curved portions 2a of the plate spring 2 provided with the piezoelectric unimorph 4 are connected in multiple stages, the amount of displacement of the lens 3 can be increased.

6 and 7 show other embodiments of the invention. The leaf spring 2 here consists of a U-shaped curved section 2a on the proximal end side and a flat section 2c connected from there to the distal end side, and does not have the horizontal U-shaped curved section in the previous embodiment. A tracking piezoelectric unimorph 4 is attached to the U-shaped curved portion 2a as in the previous embodiment.

In the embodiments shown in FIGS. 6 and 7, two focusing piezoelectric unimorphs 7 and 8 are bonded to the flat part 2C of the leaf spring 2 on the front and back sides in order to displace the lens 3 in the optical axis direction. . The two piezoelectric unimorphs 7 and 8 are connected to the leaf spring 2 as shown in the figure.
c are joined at different positions in the longitudinal direction. These piezoelectric unimorphs 7 and 8 also have the leaf spring 2 as one electrode, and the other electrodes 7a and 8a are formed on the opposite side, respectively, in the same manner as described above.

As shown in FIG. 8, by adjusting the voltage applied to the piezoelectric unimorph 7, the tip side of the leaf spring 2 is displaced in the downward direction, and the piezoelectric unimorph 8 similarly connects the tip of the leaf spring 2 and the lens holder 3a. The leaf spring 2 is bent in a direction that does not apply extreme bending stress to the joint portion. The lens 3 is displaced in the optical axis direction by driving the tracking piezoelectric unimorphs 7 and 8 in the same phase with respect to the two leaf springs 2 that sandwich the lens 3.

(Effects of the Invention) As described above in detail, the lens actuator according to the present invention moves the lens in the optical axis direction and in the orthogonal direction to the optical axis using the plate spring that supports the lens in a sandwiching manner and the piezoelectric unimorph bonded to the plate spring. Since the structure is simple and suitable for miniaturization, thinning, and weight reduction, the amount of lens displacement can be sufficiently large, and the number of parts is small and assembly is easy. This allows mass production at low cost.

[Brief explanation of the drawing]

1 is a front view of the first embodiment of the present invention, FIG. 2 is a partial perspective view of the first embodiment, FIG. 3 is a diagram showing the displacement form of the piezoelectric unimorph of the first embodiment, and FIG. 4 is a diagram showing the displacement form of the piezoelectric unimorph of the first embodiment. 5 is a partial front view of the third embodiment, FIG. 6 is a front view of the fourth embodiment, FIG. 7 is a partial perspective view of the fourth embodiment, and FIG.
The figure is a diagram showing a modified form of the piezoelectric unimorph in the fourth embodiment. 1... Base 2... Leaf spring 2a... Curved part 2b... Curved part 2C...
・Flat part 3...Lens 3a...Lens holder 4...Piezoelectric unimorph for tracking 5...
...Focusing piezoelectric unimorph 6...
electrode lead

Claims (2)

[Claims] (1) The proximal ends of two arms based on leaf springs are fixed to the base, and the lens is supported by being sandwiched between the tips of these two arms from both sides, and the flexibility of these arms The lens is displaceable in the optical axis direction and the direction perpendicular to the optical axis depending on the nature of the lens; each arm has a U-shaped curved portion, and this curved portion includes a piezoelectric unimorph having the leaf spring as one electrode. A lens actuator that is bonded to the piezoelectric unimorph and is configured to deform the curved portion and displace the lens by piezoelectric distortion of the piezoelectric unimorph. (2) Piezoelectric unimorphs are joined to the front and back sides of the leaf spring at positions shifted in the longitudinal direction in a substantially flat part of the arm, and piezoelectric strain of the pair of piezoelectric unimorphs causes the tip of the arm to be attached to the leaf spring. 2. The lens actuator according to claim 1, wherein the lens actuator is adapted to be displaced in the thickness direction.