JPH0458769A - Piezoelectric micro rotation device - Google Patents

Abstract

PURPOSE:To facilitate positioning at the time of fixing of a bimorph piezoelectric displacement element by eliminating bending displacement caused under elongation mode thereby taking out only rotation around one axis based on torsional displacement. CONSTITUTION:A piezoelectric micro rotation device comprises two bimorph piezoelectric displacement elements (hereinafter, referred to bimorph) 111, 112 where two LN stripes 121, 122 are bonded through a thin metallic board 13, or each displacement direction of the piezoelectric displacement element is selected, or the cutting direction of a piezoelectric crystal board is selected. Upon application of a voltage on two bimorphs, torsional displacement of bimorph causes rotation of a mirror 17 around the longitudinal direction of bimorph. When the bending displacement of bimorph is set, in its polarity, such that a driven body is displaced in same direction, rotation only around one axis can be produced through torsional displacement without causing bending displacement at the free end of the bimorph.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a rotary fine movement device used for deflecting a light beam, etc., and particularly relates to a piezoelectric rotational fine movement device using a bimorph type piezoelectric displacement element. Regarding equipment.

(Prior Art) In recent years, lasers have come to be used in various fields, and as a result, the need for devices that deflect light beams has increased. As a device for deflecting a light beam, a configuration using a bimorph type piezoelectric displacement element (hereinafter abbreviated as bimorph) in which two piezoelectric ceramics are bonded together via a thin metal plate is known. In this device, the beam can be deflected by utilizing bending displacement by extending one side of the piezoelectric ceramic and contracting the other.

A light beam deflection device using a bimorph has a simple structure and can be miniaturized. However, since the domain state of piezoelectric ceramics made of ferroelectric microcrystals changes depending on voltage, deflection devices using this essentially have hysteresis in the rotation angle vs. applied voltage characteristics, and linearity is not sufficient. do not have. Furthermore, even if a constant voltage is applied, there is a so-called creep phenomenon in which the rotation angle changes slowly over time. Such characteristics are not suitable for applications in which a light beam is to be controlled with high precision. Furthermore, since bending displacement is utilized, there is a problem in that the position of the mirror becomes blurred as the mirror rotates.

Recently, lithium niobate (L i N b
03) It has been proposed to use a single crystal. LiN
The b0a (hereinafter abbreviated as LN) single crystal has a high Curie point, and changes in domains due to voltage application are difficult to occur at room temperature, so hysteresis and creep do not occur.

As a method of causing rotation by this LN single crystal, it has been proposed to use a bimorph type piezoelectric displacement element with torsional displacement. This proposal describes a method of realizing a bimorph with a single LN plate by forming a layer in which the polarity of the piezoelectric effect is reversed, called a polarization inversion layer, inside the single LN plate. However, if you compare the bimorph created by this method with the bimorph created by the normal method (two LN plates glued together via a thin metal plate), it will take twice as long to obtain the same rotation angle for the same dimensions. voltage is required.

Additionally, since there is no thin metal plate that acts as a reinforcing material, there is a problem that it is mechanically weak. Therefore, in the following, a bimorph created by a conventional method will be described as an example. The operating principle is the same for bimorphs based on polarization inversion layers and bimorphs based on adhesives.

Here, the cutting direction of the LN single crystal will be explained using FIG. 8. As shown in FIG. 8(a), the coordinate system (X, Y.

Let the coordinate system obtained by rotating Z) by 00 around the X axis be (X', Y', Z",). In this coordinate system, Y'
A plate cut out with the axis in the direction of thickness t is called a θ-rotated Y plate. Furthermore, as shown in Fig. 9(b), consider a straight line that makes an angle between the X axis and θ' of the θ-rotated Y plate, and cut out a long and thin plate (width W, length) whose longitudinal direction is parallel to this. shall be.

When electrodes are formed on both sides of this plate and a voltage is applied, a face veri mode in which shear deformation occurs in the plane as shown in Figure 9(a) and longitudinal expansion/contraction deformation as shown in Figure 9(b) occur. A deformation called length elongation mode occurs. In addition, the broken line in the figure shows the state after deformation. Further, in the figure, thick arrows indicate the direction of deformation, and thin arrows indicate the Y' axis.

FIG. 10 shows a torsional displacement bimorph using an LN single crystal. The bimorph is from the 1000 rotation Y plate to the X axis and 45
Two long and thin LN plates 2+22 (
This figure shows the case of θ-140° and θ'-45°, which is a cutting direction in which the facing verimode is large) are bonded together via a thin metal plate 3. On both sides of each LN plate 21.22 are electrodes 4. ．． 42,4. ．． 44 are provided and are bonded together with electrodes 42.4s in between. and,
This bimorph is connected at one end to a base 5, and each electrode 4 is connected to a power source 9 by a lead wire 8 as shown. Note that the thin arrow in the figure indicates the direction of the Y' axis.

Next, the operation of this bimorph will be explained using FIG. 11. When a voltage is applied to the bimorph, two LNs are separated by the facing verimode as shown in Figure 11(a).
Shear deformation occurs in the plates in mutually opposite directions, causing twisting displacement as a whole as shown by the broken line, and an inclination θt is obtained at the tip. This is a torsional displacement bimorph, and if a mirror is provided at the free end of this bimorph, an optical beam deflection device without hysteresis or creep can be realized.

However, this type of device has the following problems. In other words, torsional displacement occurs in the bimorph because the two LN plates undergo shear deformation in opposite directions, but in addition to shear deformation, these two LN plates also undergo expansion and contraction deformation due to the length elongation mode. arise. When expansion/contraction deformation occurs, as shown in Fig. 11(b), when one of the LN plates contracts, the other expands, and similar to the bending displacement bimorph of piezoelectric ceramics, bending displacement and the resulting inclination θb also occur. Put it away. For this reason, the mirror attached to the free end of the bimorph rotates around two axes at the same time, creating a serious problem in positioning when attaching the deflection device.

(Problem to be solved by the invention) As described above, in conventional piezoelectric rotational fine movement devices using a torsional displacement bimorph of LN single crystal, torsional displacement and bending displacement occur simultaneously, and driven objects such as mirrors move around two axes. Because of this, there were problems such as difficulty in positioning this device when attaching it to a part of an optical system or the like. Further, there is a problem in that the position of the driven body shifts as the driven body rotates.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a piezoelectric rotation fine movement device that can obtain only rotation around one axis based on torsional displacement and is easy to position when installed. It's about doing.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to provide a bimorph piezoelectric displacement element using a piezoelectric crystal plate having a facing veri mode and a length elongation mode. The purpose is to eliminate bending displacement.

That is, the present invention (claim 1) is made by bonding two piezoelectric single crystal plates with a cutting orientation that has a facing veri mode and a length elongation mode, and when a voltage is applied, torsional displacement and length elongation due to the facing veri mode occur. A piezoelectric rotation fine movement device that rotates a driven body around one axis using two bimorph type piezoelectric displacement elements that generate bending displacement depending on the mode, and one end of each of the two piezoelectric displacement elements is connected to the driven body. and the other end is connected to the fixed end and arranged in a straight line so that the torsional displacement of the two piezoelectric displacement elements rotates the driven body in the same direction, and the bending displacement displaces the driven body in the same direction. The settings are made so that the

Further, the present invention (claim 2) comprises a bimorph type piezoelectric displacement element made by bonding two piezoelectric single crystal plates with a cutting orientation having a facing veri mode and a length elongation mode, and one end of the element is Connect to the driven body and connect the other end to the fixed end,
In a piezoelectric rotation fine movement device that rotates a driven body around one axis, when voltage is applied to two piezoelectric single crystal plates,
The thickness directions of the two piezoelectric single crystal plates are opposite to each other so that the shear deformation due to the plane slip mode of the two piezoelectric single crystal plates is in opposite directions, and the expansion/contraction deformation due to the length elongation mode is in the same direction. This is so that it can be set in the same direction.

Furthermore, the present invention (claim 3) comprises a bimorph type piezoelectric displacement element made by bonding two piezoelectric single crystal plates having verimode and length elongation mode facing each other depending on the cutting direction,
In a piezoelectric rotating fine movement device that connects one end to a driven body and the other end to a fixed end to rotate the driven body around one axis, the cutting direction of two piezoelectric single crystal plates is The orientation is selected such that the piezoelectric strain constant of expansion/contraction deformation due to the length elongation mode of the plate is approximately zero, and the piezoelectric strain constant of shear deformation due to the face veri mode is greater than or equal to a predetermined value.

(Function) According to the present invention (claim 1), since the torsional displacement of the two bimorph type piezoelectric displacement elements is set so as to rotate the driven body in the same direction, the free ends of the piezoelectric displacement elements are twisted. A displacement occurs.

On the other hand, although a force due to the length extension mode is applied to the two piezoelectric displacement elements, one end of each of the two piezoelectric displacement elements is connected to the fixed end, and each free end is connected to the driven body, so the piezoelectric displacement No bending displacement occurs in the element. Therefore, the driven body supported by the two piezoelectric displacement elements undergoes only rotation due to the torsional displacement of the piezoelectric displacement elements, making it possible to obtain pure rotation only around one axis.

Further, according to the present invention (claim 2), by setting the thickness directions of the two piezoelectric single crystal plates to be opposite to each other, the expansion and contraction deformation due to the length elongation mode of the two piezoelectric crystal plates is prevented. Since they are in the same direction, no bending displacement occurs in these piezoelectric crystal plates bonded together. On the other hand, since the shear deformation due to the plane slip mode is in the opposite direction, torsional displacement occurs.

Therefore, in this case as well, pure rotation around one axis can be obtained.

Further, according to the present invention (claim 3), since the piezoelectric strain constant of the expansion and contraction deformation due to the length elongation mode of the two piezoelectric crystal plates is zero, even if a voltage is applied, the two piezoelectric crystal plates No expansion/contraction deformation occurs, and no bending displacement occurs based on this. on the other hand,
Since shear deformation occurs in the plane slip mode, only torsional displacement occurs in the two piezoelectric crystal plates. Therefore, in this case as well, pure rotation about one axis can be obtained.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a light beam deflection device according to a first embodiment of the present invention. Two bimorph type piezoelectric displacement elements (hereinafter abbreviated as bimorph) 111, 11° are both made of two elongated LN plates 12. ．． 12 □ are bonded together with a thin metal plate 13 interposed therebetween. Each LN board 121
Electrodes 14. ．． 142,143°144
is provided, and LN plate 12+ 12□ is electrode 1
They are attached with 42 and 143 in between. The thin arrow in the figure indicates the direction of the Y' axis. two bimorphs 1
1. ．． 112 are arranged approximately in a straight line, one end of each is connected to the base (fixed end) 15, and the other end is connected to the connecting member 16.
are connected via. A mirror (driven body) 1 for reflecting (deflecting) the beam onto this coupling member 16
7 is installed.

Further, a power source 19 is connected to the electrode 14 by a lead wire 18 as shown in the figure. That is, the negative side of the power source 19 is connected to the electrodes 141 and 14 degrees on both sides of the bimorph 111, and the positive side of the power source 19 is connected to the electrodes 142 and 143 that are in contact with the thin metal plate 13. And, conversely, the positive and negative terminals of a power source 19 are connected to the bimorph 11°.

In such a configuration, two bimorphs 111.1
When a voltage of the polarity shown is applied to bimorph 11.
．． Since the polarity of the 11° torsional displacement is set so as to rotate the mirror 17 in the same direction, the mirror 17 rotates about the longitudinal direction of the bimorph. On the other hand, two bimorphs 11. ．． The polarity of the bending displacement of 11 degrees is set so that the driven body is displaced in the same direction, but since the structure as a whole is fixed at both ends, no bending displacement occurs. As a result, the mirror 17 has a bimorph If, 1
Only rotation due to 12 torsional displacements will occur.

Like this device, bimorph 11. .

It is possible to cause only rotation around one axis by torsional displacement without causing bending displacement in the free end of 112. Therefore, the inconvenience that the position of the mirror 17 shifts as the mirror 17 rotates does not occur. Further, when this device is attached to a part of the optical system, there is no need to take into consideration the positional shift of the mirror 17, so that the positioning at the time of attachment is easy. Further, in this embodiment, the mirror 17
Since both ends of the structure including the bimorphs 111 and 112 centered on are fixed, it has the advantage of high mechanical strength.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention. Bimorph 21 rotates 140° from the Y plate to the X axis and 45
Two long thin LN plates 22 cut out at an angle of . ．． 22
□ are bonded together with a thin metal plate 23 interposed therebetween. Electrodes 24+, 242.
243244 is provided, and the LN plate 221. 22
2 are bonded together with electrodes 24□ and 243 in between. In the figure, thin arrows indicate the direction of the Y' axis, and thick arrows indicate the direction of deformation. The bimorph 21 is connected to the base 25 at one end, and a mirror (not shown) is installed at the other end.

Further, a power source 29 is connected to the electrode 24 by a lead wire 28 as shown in the figure. That is, the negative side of the power source 29 is connected to the electrodes 241 and 244 on both sides of the bimorph 21, and the positive side of the power source 29 is connected to the electrodes 242 and 243 that are in contact with the thin metal plate 23. Note that this device differs from the configuration shown in FIG. 10 only in the orientation of the lower LN plate 22□.

Here, the relationship among the Y' axis of the LN plate, the applied voltage, and the deformation direction is shown in FIG. FIG. 3(a) shows the relationship among the Y' axis, applied voltage, and deformation direction in the facing veri mode of the LN plate, and FIG. 3(b) shows these relationships in the length elongation mode.

As can be seen from this figure, in the length elongation mode, the direction of deformation is reversed even if the orientation of the crystal is reversed or the applied voltage is reversed. In contrast, in plane slip mode, the direction of deformation is reversed only when the applied voltage is reversed; the direction of deformation does not change even if the orientation of the crystal is reversed.

Therefore, the lower LN plate in Figure 2 and the lower LN plate in Figure 10
Comparing the plates, although the direction of expansion and contraction changes, the direction of shear deformation does not change, and deformation occurs in the direction indicated by the thick arrow in FIG. 2. As a result, shear deformation occurs in opposite directions, causing torsional displacement as a whole, but since stretching deformation causes both the upper and lower LN plates to contract, only stretching deformation occurs as a whole, and no bending displacement occurs.

That is, only pure rotation in one axis direction can be obtained, and the same effect as in the first embodiment can be obtained.

FIG. 4 is a schematic configuration diagram showing a third embodiment of the present invention. This example uses two bimorphs in the second example.
Both ends are fixed as in the first embodiment. Torsional displacement bimorph 41 . ．． One end of each of 412 is connected,
Bimorph 41. ．． The other end of 412 is connected to base 45. A power source 49 is connected to these bimorphs 41□, 41□ via a lead wire 48, and a voltage is applied in the same relationship as in FIG.

In the second embodiment, when a voltage is applied, the left bimorph 41,
is shortened in the longitudinal direction, and the right bimorph 412 is made to extend in the longitudinal direction so that no stress is generated in the longitudinal direction inside the bimorph. Therefore, not only the same effects as in the first embodiment can be obtained, but also the effect of reducing the stress generated inside the bimorph.

In this embodiment, the mirror 47 moves slightly in the longitudinal direction, and since this movement is parallel to the rotation axis, there is no problem with beam deflection.

In addition, if movement of the mirror 47 in the longitudinal direction becomes a problem,
If the stress is within an allowable range, the bimorph can be made to expand and contract in the same direction so that the position of the mirror 47 does not move.

Next, a fourth embodiment of the present invention will be described.

Strain of shear deformation occurring in the face veri mode sps
is the product of the piezoelectric strain constant dps and the applied electric field E, and the strain SLE of stretching deformation occurring in the length elongation mode is the piezoelectric strain constant d
It is proportional to the product of LE and the applied electric field E. Furthermore, the torsional displacement of the bimorph is caused by the facing veri mode, the bending displacement is caused by the length elongation mode, and the piezoelectric strain constant depends on the cutting orientation of the crystal. Therefore, if there is a cutting direction in which dFs is sufficiently large and dLE←0, only torsional displacement due to the facing veri mode occurs, and a bimorph is realized in which no bending displacement due to the length elongation mode occurs.

FIG. 5(a) shows the dependence of the piezoelectric strain constant dFs in the veri mode facing the cutting direction, and FIG. 5(b) shows the dependence of the piezoelectric constant dLH in the length elongation mode on the cutting direction. The point indicated by A in the figure is the direction of θ-140° and θ”-45°, and the dps is the maximum of 48.3Xl low 12111/■.
In a), the contour lines of d LE-0 are also shown,
This contour line is 1dpsl≧40×10-” s/V
(approximately 86% of the maximum value). Therefore, this cutting direction, i.e., d ps I≧40X 10-12 m/V, d
If an orientation of LE-0 is used, a bimorph with sufficiently large torsional displacement and no bending displacement will be realized.

FIG. 6 is a schematic configuration diagram showing a fourth embodiment based on this idea. The bimorph 61 is made by bonding two elongated LN plates 621 and 622 cut out in the direction explained in FIG. 5 with a thin metal plate 63 interposed therebetween. There are electrodes 64 on both sides of each LN plate 621 and 622. ．． 642,643
.

644 is provided, and LN board B2+, 62
2 are bonded together with electrodes 642' and 643 in between. In the figure, long thin arrows indicate the direction of the Y' axis, and thick arrows indicate the direction of deformation.

The other configurations and the direction of voltage application are the same as those in the conventional device shown in FIG. 10, and the only difference from the conventional device is the cutting direction of the LN plate described above. However, in a deflector using a bimorph with this cutting orientation, no bending displacement occurs, but only torsional displacement. Therefore, as in the second embodiment, pure rotation about one axis can be obtained with one bimorph.

FIG. 7 is a schematic configuration diagram showing a fifth embodiment of the present invention. This example uses two bimorphs in the fourth example.
Both ends are fixed as in the first embodiment. Torsional displacement bimorph 71 . ．． One end of each of the bimorphs 71.712 is connected. ．． The other end of 712 is connected to base 75 . And these bimorphs 71, . A power supply 79 is connected to 71□ via a lead wire 78, and a voltage is applied in the same relationship as in FIG.

With such a configuration, since both ends are fixed, not only the same effects as the first and third embodiments can be obtained, but also the following advantages. That is, in the first embodiment, the mirror is prevented from moving by generating stress inside the bimorph, and in the third embodiment, the stress inside the bimorph is reduced by moving the mirror in a direction parallel to the rotation axis. ing. On the other hand, in this embodiment, since a bimorph with a sufficiently large twisting displacement and no bending displacement is used, there is no need to move the mirror, and it is possible to reduce the stress inside the bimorph.

Note that the present invention is not limited to the embodiments described above. In the embodiment, LiNbO3 was used as the piezoelectric crystal plate, but LiTaO3 could also be used instead. In short, any piezoelectric single crystal plate can be used as long as it has veri mode and length elongation mode depending on the cutting direction. Further, the present invention is not limited to deflecting a light beam, and can be applied to a device that minutely rotates a driven body. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, in a bimorph type piezoelectric displacement element using a piezoelectric crystal plate having a plane slip mode and a length elongation mode, piezoelectric displacement is achieved by combining two piezoelectric displacement elements. By selecting each displacement direction of the element or the cutting direction of the piezoelectric crystal plate, the bending displacement caused by the length elongation mode is eliminated. It becomes possible to realize a piezoelectric rotation fine movement device that can obtain only pure rotation.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a light beam deflection device according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing a second embodiment of the present invention, and FIG. 3 is a Y'-axis, FIG. 4 is a schematic diagram showing the relationship between the applied voltage and the direction of deformation, FIG. 4 is a schematic configuration diagram showing the third embodiment of the present invention, FIG. 5 is a characteristic diagram showing the dependence of the piezoelectric strain constant on cutting direction, and FIG. The figure is a schematic block diagram showing a fourth embodiment of the present invention, Figure 7 is a schematic block diagram showing a fifth embodiment of the present invention, and Figures 8 to 11 are for explaining the problems of the conventional technology. This is a diagram. 11.21, 41.61.71...bimorph, 12
．． 22.62... LN plate, 13.23.63... Metal thin plate, 14.24.64... Electrode, 15.25, 45, 65.75... Base (fixed end),
16.46.76...Coupling member, 77...Mirror 12g 48. 78...Lead wire, 19.29. 49 79...Power supply.

Claims (3)

[Claims] (1) Created by gluing together two piezoelectric single-crystal plates with cutting orientations that have a face-to-face mode and a length-extension mode, and when voltage is applied, torsional displacement due to the face-to-face mode and bending displacement due to the length-extension mode. A piezoelectric rotation fine movement device that rotates a driven body around one axis using two bimorph type piezoelectric displacement elements that generate The two piezoelectric displacement elements are arranged in a straight line with their ends connected to the fixed end, and the torsional displacement of the two piezoelectric displacement elements rotates the driven body in the same direction, and the bending displacement displaces the driven body in the same direction. A piezoelectric rotation fine movement device characterized by being set. (2) Consists of a bimorph type piezoelectric displacement element made by gluing together two piezoelectric single crystal plates with cutting orientations that have a plane deflection mode and a length elongation mode, and one end of the element is connected to a driven body. In a piezoelectric rotation fine movement device in which the other end is connected to a fixed end to rotate a driven body around one axis, the direction of the thickness direction of the two piezoelectric single crystal plates is set to be opposite to each other, and the two piezoelectric single crystal plates are A voltage is applied to two piezoelectric single crystal plates so that the shear deformation due to the plane shear mode of the piezoelectric single crystal plates is in the opposite direction, and the expansion/contraction deformation due to the length elongation mode is in the same direction. Features a piezoelectric rotating fine movement device. (3) It consists of a bimorph type piezoelectric displacement element made by gluing together two piezoelectric single crystal plates that have a plane deflection mode and a length elongation mode depending on the cutting direction. One end is connected to the driven body and the other end is connected to the driven body. In a piezoelectric rotation fine movement device that is connected to a fixed end and rotates a driven body around one axis, the two piezoelectric single crystal plates have a piezoelectric strain constant of expansion/contraction deformation due to a length elongation mode of the piezoelectric single crystal plates. 1. A piezoelectric rotary fine movement device, characterized in that the cutting direction is selected such that the piezoelectric strain constant of shear deformation due to the plane shearing mode is approximately zero and a piezoelectric strain constant of a predetermined magnitude or more.