JP2955703B2 - Piezoelectric actuator structure for optical path length control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, for controlling a laser optical path length of a laser resonator in a ring laser gyro for detecting an angular velocity, wherein a piezoelectric actuator controls the displacement of an optical path length controlling movable mirror. The present invention relates to a control piezoelectric actuator structure.

[0002]

2. Description of the Related Art First, the structure of a ring laser gyro, which is considered to be the most effective field of application of the present invention, will be briefly described, and the application state of a piezoelectric actuator structure for controlling an optical path length will be described. As shown in FIG.
A passage 12 having an equilateral triangle is formed in each of the output mirrors 13, an output mirror 13, a high reflection mirror 14,
15 are arranged respectively, and these mirrors 13, 14, 15
Form a triangular ring-shaped optical path. A laser medium is sealed in the passage 12. Anodes 16 and 17 and a cathode 18 for oscillating laser light are provided in communication with the respective sides of the triangle of the passage 12.

Two laser beams traveling in opposite directions are oscillated in a ring-shaped optical path composed of mirrors 13, 14 and 15, and in this state an angular velocity about the axis of the optical path is applied to the glass block 11. Then, an optical path difference occurs between the two laser lights, and the optical path difference causes an oscillation frequency difference between the two laser lights traveling in opposite directions. Accordingly, interference fringes are formed by superimposing these two laser beams, and the input angular velocity is measured by detecting the interference fringes.

As the material of the glass block 11 of this ring laser gyro, one having a small coefficient of thermal expansion is selected. In addition to the thermal expansion of the material itself, the attached anodes 16, 17 and cathode 18 and the like are used. Due to the thermal expansion of the glass block, a dimensional change occurs as a glass block assembly. In order to compensate for the change in the optical path length of the ring-shaped optical path caused by this dimensional change and to keep it constant, the high reflection mirror 14 is used.
Is a movable mirror, which is held by a piezoelectric actuator structure 19 for controlling the optical path length.

[0005] A conventional piezoelectric actuator structure 19 for controlling the optical path length was configured as shown in FIG. That is, the piezoelectric actuator 21 and the mirror holder 22 are configured to be in contact with each other and integrally connected by the screw 23.
The mirror holder 22 is configured such that a cylindrical fixed portion 22a and a columnar movable portion 22b at the axial center thereof are connected by a diaphragm 22c, and the movable mirror 14 is formed on the movable portion 22b. The mirror holder 22 is made of, for example, glass,
The movable mirror 14 is formed by forming a multilayer film made of, for example, SiO ₂ and TiO ₂ on the mirror-finished movable portion 22b.

As shown in an exploded view in FIG. 5, the piezoelectric actuator 21 has two disk-shaped piezoelectric elements 24, 25 stacked on each other via a disk-shaped electrode 26, and furthermore, these piezoelectric elements 24, 2
5, ring-shaped electrodes 27 and 28 are superimposed on each other,
The piezoelectric elements 24 and 25 are sandwiched between the electrodes 27 and 28, and the electrodes 27 and 28 are connected to each other.
5. The electrodes 26, 27, and 28 are firmly bonded with a conductive adhesive. The electrodes 26, 27, 2
8 is made of a low thermal expansion alloy.

A screw 23 is inserted into a hole formed at the center of the piezoelectric actuator 21 via a spacer 31, and its tip is screwed into a nut 32 held in the movable portion 22 b of the mirror holder 22. , Mirror holder 22
Is fixed to the piezoelectric actuator 21. The screw 23, the spacer 31, and the nut 32 are similarly made of a low thermal expansion alloy.

When a DC voltage is applied between the electrode 26 and the electrodes 27 and 28, the center portions of the piezoelectric elements 24 and 25 are displaced in the normal direction according to the magnitude of the voltage in the direction corresponding to the polarity. Thereby, the movable mirror 14 formed on the movable portion 22b is displaced in the normal direction, and the optical path length of the ring-shaped optical path in FIG. 3 is adjusted.

[0009]

As described above, the center of the piezoelectric actuator 21 is assembled to the movable portion 22b, which is located at the center of the mirror holder 22, with the screw 23, and the piezoelectric actuator 21 is assembled. In this state, the piezoelectric actuator 21 and the mirror holder 22 are slightly warped in a direction in which their central parts are close to each other. FIG. 6 shows this state in an enlarged manner, and the warpage causes the inner peripheral edge of the ring-shaped electrode 28 of the piezoelectric actuator 21 to be pressed against the mirror holder 22 so as to be in contact with the mirror holder 22. Accordingly, the displacement of the piezoelectric actuator 21 is transmitted to the mirror holder 22 with reference to the inner peripheral edge of the electrode 28.

However, the electrode 28 has a thickness of 0.1 to 0.1 mm.
It is as thin as about 2 mm, and it is difficult to obtain a good flatness itself. Also, due to a variation in the thickness of the adhesive layer in bonding with the piezoelectric element 25, a high flatness over the entire circumference in the assembled state as the piezoelectric actuator 21 is obtained. It was difficult to obtain. For this reason, in the conventional piezoelectric actuator structure 19 for controlling the optical path length, a local lift occurs between the inner peripheral edge of the electrode 28 and the mirror holder 22, and the presence of the lift causes a small movement of the piezoelectric actuator 21 to move the mirror holder 22. And that the movable mirror 14 of the mirror holder 22 cannot be displaced stably and with good reproducibility.

On the other hand, FIG. 7A is an exploded view of the structure of a piezoelectric actuator 41 of a conventionally proposed piezoelectric actuator structure for controlling an optical path length in order to solve the above-mentioned problem, and FIG. 3 shows the shape of the three-point seat plate 42. Parts corresponding to those in FIG. 5 are denoted by the same reference numerals. In this example, a conductive three-point seat plate 42 is formed by integrally protruding three seats 42a at substantially equal angular intervals on the outer peripheral edge of one plate surface of a disk-shaped plate, and the seat 42a is a mirror holder. On the side of the piezoelectric element 25 and the electrode 26, the three seats 42a are held by the electrode 43 opposed to the mirror holding member 22 in a state where the piezoelectric actuator 41 is bonded and assembled. It is configured to protrude toward the body 22 side.

For this reason, the piezoelectric element 25 is provided with three notches 25a at the outer periphery thereof as escapes of the seat 42a, and the electrode 43 has a portion corresponding to the inner periphery as shown in FIG. 7A. It has a ring shape that escapes to the side.
In this example, the piezoelectric actuator 41 has its three seats 4.
2a is in contact with the mirror holder 22, that is, in a three-point contact state, so that each seat 42a is stably contacted with the mirror holder 22 without being lifted, and thus the piezoelectric actuator 41 and the mirror holder 22 are in contact with each other. A good connection state is obtained, and the displacement of the piezoelectric actuator 41 can be transmitted to the mirror holder 22 accurately.

However, in the conventional piezoelectric actuator structure for controlling the optical path length, the three-point seat plate 42 is required as a new part, and the three-point seat plate 42 is cut by using a low thermal expansion alloy. However, there is a drawback in that it is expensive as a whole because it is made and expensive to manufacture. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described various problems, and to accurately transmit the displacement of a piezoelectric actuator to a mirror holder, that is, to perform displacement control of a movable mirror with high accuracy and to configure at low cost. It is an object of the present invention to provide a piezoelectric actuator structure for controlling an optical path length that can be used.

[0014]

According to the present invention, a piezoelectric actuator is brought into contact with a mirror holder for holding a movable mirror for controlling an optical path length, and the movable mirror is displaced by driving the piezoelectric actuator. In the piezoelectric actuator structure, three projections are integrally formed at substantially equiangular intervals on the electrode forming surface from the inner periphery of the ring-shaped electrode facing the mirror holder of the piezoelectric actuator, and the tips of the three projections are formed. Are brought into point contact with the mirror holder.

[0015]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a piezoelectric actuator structure for controlling an optical path length according to the present invention, and FIG. 2 is an exploded view thereof. Parts corresponding to those in FIGS. 4 and 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this example, the ring-shaped electrode 52 facing the mirror holder 22 of the piezoelectric actuator 51 has three projections 52a on its inner periphery at substantially equal angular intervals. These protrusions 52a are located in the electrode forming surface, that is, protrude from the inner periphery of the electrode 52 toward the center thereof.
2 and are formed integrally. The projection 52a is substantially semicircular in this example, but may be, for example, triangular. The tips of the three projections 52a are located on the same circumference concentric with the electrode 52.

The electrode 52 is made of a low thermal expansion alloy like the other electrodes 26 and 27, and is formed by etching or pressing. Piezoelectric elements 24 and 25 and electrode 2
The outer diameters of 6, 27, and 52 are equal to each other, and they are firmly bonded and fixed to each other with a conductive adhesive to form a bimorph piezoelectric actuator 51.

The electrode 52 is brought into contact with the mirror holder 22,
The screw 23 is screwed into the nut 32 to integrate the piezoelectric actuator 51 with the mirror holder 22. At this time, the piezoelectric actuator 51 and the mirror holder 22 are warped by the tightening force of the screw 23 in a direction in which their central parts are close to each other.
Reference numeral 1 denotes a state in which the tips of the three projections 52 a formed on the electrode 52 are pressed against the mirror holder 22.

Therefore, the piezoelectric actuator 51 is brought into a state of three-point contact with the mirror holder 22 by the projection 52a, so that the piezoelectric actuator 51 is connected to the mirror holder 22 satisfactorily and stably.

[0020]

As described above, according to the present invention, the three projections 52 formed on the inner peripheral portion of the ring-shaped electrode 52 are provided.
a, the piezoelectric actuator 51 and the mirror holder 22
Are connected in three-point contact with each other, so that a good and stable connection state can be obtained without the occurrence of lifting at the contact portion.

Therefore, even if the displacement of the piezoelectric actuator 51 is a minute displacement, it is accurately transmitted to the mirror holder 22, and the displacement of the movable mirror 14 can be controlled with extremely high precision. Note that the projection 52 is
a is formed and is also used as an electrode and a three-point seat, so that the number of components does not increase unlike the piezoelectric actuator 41 shown in FIG. 7, and the ring-shaped electrode 52 is connected to the other electrodes 26 and 27. Since the same material can be easily manufactured by etching or the like, it can be configured at a low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is an exploded perspective view of FIG.

FIG. 3 is a plan view showing a general configuration of a ring laser gyro.

FIG. 4 is a sectional view showing a conventional piezoelectric actuator structure for controlling an optical path length.

FIG. 5 is an exploded perspective view of the piezoelectric actuator used in FIG.

FIG. 6 is a partially enlarged cross-sectional view for explaining warpage of the piezoelectric actuator and the mirror holder.

FIG. 7A is an exploded perspective view of a piezoelectric actuator of a conventionally proposed piezoelectric actuator structure for controlling an optical path length,
B is a perspective view of a three-point seat plate used therein.

[Explanation of symbols]

 14 Movable mirror 22 Mirror holder 51 Piezoelectric actuator 52a Projection

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01S 3/083 G01C 19/66

Claims (1)

(57) [Claims] 1. A piezoelectric actuator structure for optical path length control, wherein a piezoelectric actuator is brought into contact with a mirror holder holding an optical path length controlling movable mirror, and the piezoelectric actuator is driven to displace the movable mirror. From the inner periphery of the ring-shaped electrode of the piezoelectric actuator facing the mirror holder, three projections are integrally formed at substantially equiangular intervals in the electrode forming surface, and the tips of the three projections are the mirrors. A piezoelectric actuator structure for controlling an optical path length, wherein said piezoelectric actuator structure is in point contact with each of said holding members.