JPH0625969Y2 - Piezoelectric actuator structure for optical path length control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" This invention is used, for example, to control a laser optical path length of a laser resonator in a ring laser gyro that detects an angular velocity, and a piezoelectric actuator displaces an optical path length control movable mirror. The present invention relates to a piezoelectric actuator structure for controlling an optical path length.

"Prior Art" First, a structure of a ring laser gyro which is considered to be the most effective application field of the present invention will be briefly described, and an applied state of a piezoelectric actuator structure for controlling an optical path length will be described. Fourth
As shown in the figure, an equilateral triangular passage 12 is formed in a glass block 11, and an output mirror 13 and high-reflecting mirrors 14 and 15 are arranged at respective vertices of the equilateral triangle of the passage 12, and these mirrors 13, 14, 15 forms a triangular ring-shaped optical path. The laser medium is enclosed in this passage 12. The anode 1 for communicating with each side of the triangle of the passage 12 to oscillate laser light
6, 17 and a cathode 18 are provided.

When two laser beams traveling in mutually opposite directions are oscillated in the ring-shaped optical path formed by the mirrors 13, 14, and 15 and an angular velocity about the axis of the optical path is applied to the glass block 11, the above two Optical path difference occurs in laser light,
The optical path difference causes an oscillation frequency difference between two laser beams traveling in opposite directions, and an interference fringe is formed by superposing the two laser beams, and the interference fringe is detected to measure the input angular velocity. .

The material of the glass block 11 of this ring laser gyro is usually selected by considering a material having a small coefficient of thermal expansion. In addition to the thermal expansion of the material itself, the attached anodes 16, 17 and cathode 18 are The thermal expansion of the glass block causes a dimensional change as the glass block assembly. The high-reflecting mirror 14 is a movable mirror and is held by the optical path length controlling piezoelectric actuator structure 19 in order to compensate for and maintain a constant change in the optical path length of the ring-shaped optical path due to this dimensional change. There is.

The conventional piezoelectric actuator structure 19 for controlling the optical path is constructed as shown in FIG. That is, the piezoelectric actuator 21 and the mirror holder 22 are integrally connected with the screw 24 via the disk 23. The mirror holder 22 includes a cylindrical fixed portion 22a and a columnar movable portion 22b at the axial center position thereof.
Are connected by a diaphragm 22c, the movable mirror 14 is formed on the movable portion 22b, and the mirror holder 22 is made of, for example, glass. As shown in the exploded view of FIG. 6, the piezoelectric actuator 24 includes two disk-shaped piezoelectric elements 25 and 26 made of ceramic and having different polarities.
7, the disk-shaped electrode 28 is contacted with the piezoelectric element 26 on the disk 23 side, the ring-shaped electrode 29 is contacted with the piezoelectric element 25, and the piezoelectric elements 25 and 26 are sandwiched between these electrodes 28 and 29. The electrodes 28 and 29 are connected to each other, and the piezoelectric elements 25 and 26 and the electrodes 27, 28 and 29 are firmly adhered with a conductive adhesive to form a bimorph piezoelectric actuator 21. Here, the electrode 27 is formed in a disk shape in order to sufficiently transmit the stress generated in the piezoelectric elements 25 and 26 to each other.

It is not possible to obtain piezoelectric elements 25 and 26 whose flatness is precisely controlled. Therefore, the piezoelectric actuator 21
When the piezoelectric actuator 21 is directly contacted with the mirror holder 22, the piezoelectric actuator 21 is locally lifted.
Cannot be transmitted to the movable portion 22b of the mirror holder 22. Moreover, the movable mirror 14 cannot be correctly displaced in the normal direction. For this reason, in the past, the disc 23 having the accurate flatness was firmly adhered to the piezoelectric actuator 21, and the disc 23 was brought into contact with the mirror holder 22. At this time, the piezoelectric actuator 2
The stress of 1 is efficiently transmitted to the disk 23 and the piezoelectric element 25,
In order to move the disc 26 and the disc 23 integrally, the electrode 28 in contact with the disc 23 has a disc shape. Electrodes 27, 28, 2
9 and the disk 23 are both made of a low thermal expansion alloy.

The screw 24 is inserted through the spacer 31 into the hole formed in the central portion of the structure of the piezoelectric actuator 21 and the disk 23.
And the protruding screw 24 is inserted into the mirror holder 2
The piezoelectric actuator 21 and the disk 23 are fixed to the mirror holder 22 by being screwed into the nut 32 held in the second movable portion 22b. Screw 24, spacer 31, nut 3
Similarly, 2 is made of a low thermal expansion alloy.

When a DC voltage is applied between the electrode 27 and the electrodes 28 and 29, the central portions of the piezoelectric elements 25 and 26 are displaced in the normal direction in the direction according to the polarity thereof according to the magnitude of the voltage, and the movable portion is moved. 22b, that is, the movable mirror 14 is displaced in the normal direction,
The optical path length of the ring-shaped optical path in FIG. 4 is adjusted.

[Problems to be Solved by the Invention] As described above, in the conventional optical path length controlling piezoelectric actuator structure, the disk 23 is adhered to one surface of the piezoelectric actuator 21 over the entire surface with an adhesive. Therefore, due to the difference in thermal expansion coefficient between the piezoelectric elements 25 and 26 and the disk 23, a stress is generated in the disk 23 due to the temperature change, and the optical path length cannot be controlled correctly.

[Means for Solving the Problem] According to the present invention, the electrode on the mirror holder side of the piezoelectric actuator is formed in a ring shape, and the ring of the low thermal expansion alloy has the adhesive between the ring-shaped electrode and the mirror holder. Without being intervened.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. In this invention, as shown in FIG. 2, the electrode on the mirror holder 22 side of the piezoelectric actuator 21 is a ring-shaped electrode 35. The outer diameter of the electrode 35 is made equal to the outer diameter of the piezoelectric element 26 in contact therewith. The ring-shaped electrode 35 is firmly adhered to the piezoelectric element 26. After the piezoelectric elements 25, 26 and the electrodes 27, 29, 35 are bonded and fixed to each other, lapping is performed so that the ring-shaped electrode 35 has a predetermined flat surface. In this case, since the electrode 35 has a ring shape, flattening can be easily performed as compared with a disc-shaped electrode. In addition, the piezoelectric elements 25, 2
6 has poor flatness, but generally does not have unevenness over the entire surface, and the thickness of the central portion and the peripheral portion is often different. If you look at it, it is relatively flat. From this point as well, it is easy to flatten the electrode 35.

The ring-shaped electrode 35 having this flat surface is referred to as the electrode 35.
The mirror holder 2 is attached via a ring 36 of substantially the same size as
2, the screw 24 is screwed into the nut 32, and the piezoelectric actuator 21, the ring 36, and the mirror holder 22 are integrated. At this time, with the screw 24 tightened to some extent, the deviation of the outer circumferences of these three members is eliminated, and the screw 24 is tightened sufficiently. The ring 36 is made of a low thermal expansion alloy, is made by cutting, and has sufficient flatness. No adhesive is interposed between the ring 36, the electrode 35, and the mirror holder 22.

With this configuration, the piezoelectric actuator 2
It can be easily understood that when the voltage is applied to the first mirror 1, the movable mirror 14 is also displaced according to the displacement caused by the voltage. Since the piezoelectric actuator 21 and the ring 36 are not bonded, even if there is a difference in the coefficient of thermal expansion between them,
As the temperature changes, the piezoelectric actuator 21 moves the ring 3
The piezoelectric actuator 21 can always make a correct displacement according to the input voltage thereof without receiving unnecessary stress from 6. In addition, since the surface of the electrode 35 of the piezoelectric actuator 21 is a plane with sufficiently high accuracy and the flatness of the ring 36 is also high, there is no small lift between the electrode 35, the ring 36, and the mirror holding body 22, and each part is in close contact. Therefore, the movable mirror 14 is correctly displaced in the normal direction, and even a small displacement of the piezoelectric actuator 21 is correctly corrected.
Be transmitted to. Further, in the related art, the displacement of the piezoelectric actuator 21 deforms the disk 23 and the disk-shaped electrode 28 and transmits the deformation to the movable mirror 14. Therefore, a force for deforming the disk 23 and the electrode 28 is required. In the invention, the displacement of the piezoelectric actuator 21 is directly transmitted to the mirror holding body 22, so that the voltage applied to the piezoelectric actuator can be reduced accordingly, and the displacement of the movable mirror can be correctly performed.

It is also possible to directly contact the mirror-holding body 22 with the electrode 35 having a flat surface, but the electrode 35 is made by press working or chemical etching, and it is difficult to obtain a electrode having a good inner peripheral edge shape accuracy. Moreover, the adhesive when the electrode 35 is bonded to the piezoelectric element 26 often protrudes inside the electrode 35, and the inside of the electrode 35 often does not form a correct circle. Since the piezoelectric actuator 21 is fastened to the mirror holder 22 with the screw 24, a strong force is applied to the inner peripheral edge of the electrode 35, and the displacement of the piezoelectric actuator 21 is transmitted to the mirror holder 22 with reference to the inner peripheral edge. Therefore, if the inner peripheral edge of the electrode 35 is not a correct circle, the displacement of the piezoelectric actuator 21 may not be accurately transmitted in the normal direction. If the protruding adhesive defines a part of the inner peripheral edge, use it. The adhesive that squeezed out in the inside fell, the shape of the inner peripheral edge changed,
The characteristics change, and it becomes unreliable. However, in this invention, the reference position of the piezoelectric actuator 21 is determined by the ring 36 at the inner peripheral edge of the correct circle, and the piezoelectric actuator 21 always operates correctly, has the same characteristics, and does not change with time.

Since the ring 36 does not transmit the force at this portion, but only needs to hold the surface and make a stable contact,
For example, as shown in FIG. 3, seats 3 are formed at three or more same points on each surface of the ring 36 on the electrode 35 side and the mirror holder 22 side.
The seats 37 and 38 may be raised so that the seats 37 and 38 are in the same plane.

[Advantage of Invention] As described above, according to this invention, since the electrode 35 on the side of the mirror holder 22 has a ring shape, it is easy to obtain flatness,
Since the electrode 35 having the flatness is brought into contact with the mirror holding body 22 via the ring 36 without using an adhesive, the reference position and the reference surface of the piezoelectric actuator 21 become correct, and the piezoelectric actuator 21 The displacement is correctly transmitted to the movable mirror 14 in its normal direction. Moreover, since the ring 36 and the piezoelectric actuator 21 are not bonded, even if there is a difference in the coefficient of thermal expansion between them,
The piezoelectric actuator 21 operates properly without being affected by the thermal expansion and contraction of the ring 36. Also, the piezoelectric actuator 21 is used to
Also, it is not necessary to deform the disk-shaped electrode to transmit the displacement to the movable mirror, and the displacement of the piezoelectric actuator 21 can be accurately transmitted to the movable mirror with a weaker force.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an exploded perspective view thereof, FIG. 3 is a perspective view showing a modified example of a ring 36, and FIG. 4 shows a general structure of a ring laser gyro. A plan view, FIG. 5 is a cross-sectional view showing a conventional piezoelectric actuator structure for controlling an optical path length, and FIG. 6 is an exploded perspective view of the piezoelectric actuator 21.

Claims (1)

[Scope of utility model registration request] 1. A piezoelectric actuator in which two disk-shaped piezoelectric elements are bonded together and a mirror holder for holding a movable mirror for controlling an optical path length are connected, and the piezoelectric actuator is driven to move the movable mirror. In the piezoelectric actuator structure for optical path length control that is displaced, the electrode on the mirror holder side of the piezoelectric actuator is ring-shaped, and a ring of low thermal expansion alloy is provided between the ring-shaped electrode and the mirror holder. The piezoelectric actuator is interposed without an adhesive, and the central portion of the piezoelectric actuator is fastened to the central portion of the mirror holder with a screw.
A piezoelectric actuator structure for optical path length control, characterized in that the ring and the mirror holder are integrated.