JP7324989B2 - Deformable mirror - Google Patents

Description

The present invention relates to a deformable mirror, and more particularly to a deformable mirror used in a reflecting optical system.

By correcting the X-ray wavefront with a bimorph mirror in which a piezoelectric element and an X-ray mirror are bonded with resin, we have succeeded in reducing the size of the focused beam to about 7 nm (Patent Documents 1 and 2, Patent document 1). The deformable mirror capable of wavefront compensation includes an X-ray mirror formed with an X-ray reflecting surface extending in the longitudinal direction at the center of the plane of the silicon substrate in the lateral direction, as also shown in Patent Document 2, and It is composed of piezoelectric elements attached to the surfaces of both ends. A plurality of electrodes can be connected to this piezoelectric element, and the amount of deformation of the piezoelectric element can be changed by the applied voltage. The deformed piezoelectric element also transmits the changed shape to the X-ray reflecting surface formed on the silicon substrate to which it is adhered. As a result, the X-ray mirror can be changed into any shape. This property can be used to produce a high quality X-ray beam with the desired wavefront desired by the user.

JP 2008-164553 A Japanese Patent Application Laid-Open No. 2011-137710

H. Mimura, et. al, Nature Physics 6, 122-125 (2010). H. Nakamori, et. al, Review of Scientific Instruments, 83, 053701 (2012).

However, the piezoelectric element in the X-ray bimorph mirror used for the wavefront correction is a bar type with a length of 150 mm to 200 mm, or a large number of relatively small rectangular piezoelectric elements with a side of several cm or less. limited to type. The reason for this is the manufacturing method of the piezoelectric element. The piezoelectric element is mainly made of lead zirconate titanate (PZT) and is manufactured by a sintering method, and the size in manufacturing is limited to the size of the mold. For this reason, when it comes to mirrors larger than 200 mm in length, there are only two options: connecting a plurality of bar-type mirrors or arranging a large number of relatively small rectangular mirrors. In the case of these methods, projection-like bending unevenness occurs on the reflecting surface corresponding to the joint of the piezoelectric element, leading to a decrease in the accuracy of the experiment (Non-Patent Document 2).

Therefore, in view of the above-mentioned situation, the present invention aims to solve the problem by eliminating bending unevenness caused by the joints between piezoelectric elements, so that X-rays can be emitted when a mirror of any length is bent. To prevent projections that affect coherence from being formed on a reflecting surface.

In order to solve the above-described problems, the present invention has constructed a deformable mirror shown below.

(1)
a mirror base which is composed of a rectangular parallelepiped and has a pair of opposing surfaces of the four surfaces extending in the longitudinal direction, the front surface and the back surface, and the other pair of side surfaces, and a reflecting surface formed along the longitudinal direction of the surface;
a plurality of piezoelectric elements attached to at least one of the front surface, back surface, and both side surfaces of the mirror substrate at predetermined intervals in the longitudinal direction;
A deformable mirror characterized in that adjacent piezoelectric elements partially overlap each other in the longitudinal direction.

(2)
The deformable mirror according to (1), wherein part of the piezoelectric element has an acute-angled portion in plan view.

(3)
Piezoelectric elements having a triangular shape in a plan view are arranged on at least one of the front surface, the back surface and both side surfaces of the mirror substrate, alternately reversing their directions, on both sides of the surface except for the central line portion. The deformable mirror according to (1) or (2), comprising:

(4)
The piezoelectric elements arranged on both sides of the center line of at least one of the front surface, back surface and both side surfaces of the mirror substrate are attached so that the triangular bases face each other and are arranged symmetrically with respect to the center line. (3) The deformable mirror according to (3).

(5)
The variable shape mirror according to any one of (1) to (4), wherein a strip-shaped reflecting surface is formed along the center line of the surface of the mirror base.

(6)
The deformable mirror according to (5), wherein piezoelectric elements are respectively attached to the front and back surfaces of the mirror substrate provided with the reflecting surface, and the triangles of the piezoelectric elements on the front and back surfaces are arranged in opposite phases.

(7)
The voltage applied to each piezoelectric element is set to the same voltage for the piezoelectric elements arranged on both sides of the center line on the front and back sides of the mirror substrate, and is set to a different voltage for the piezoelectric elements arranged on both the front and back sides. The deformable mirror according to any one of (1) to (6).

(8)
The deformable mirror according to (7), wherein voltages applied to the piezoelectric elements arranged on the front surface and the back surface of the mirror base are set at a constant rate for the electrodes located at the same distance from the end of the mirror.

(9)
The deformable mirror according to (5), wherein piezoelectric elements are attached to both side surfaces of the mirror substrate, and the triangles of the piezoelectric elements on both side surfaces are arranged in the same phase.

(10)
Piezoelectric elements are attached to both side surfaces of the mirror base, and different voltages are set for the piezoelectric elements arranged across the center line of each side surface, and the same voltage is set for the opposing piezoelectric elements on both side surfaces. , (9).

(11)
The deformable mirror according to any one of (1) to (10), wherein the piezoelectric element and the mirror substrate are bonded by a metal bonded body formed of a bonding material containing metal nanoparticles as a main component.

According to the deformable mirror of the present invention, it is possible to eliminate bending unevenness caused by joints between piezoelectric elements, and it is possible to produce a high-quality X-ray beam having a desired wavefront even with a mirror of any length. can.

1 is a plan view showing the structure of a deformable mirror according to a first embodiment of the present invention; FIG. It is a partial vertical cross-sectional view of the same first embodiment. FIG. 10 is a bottom view showing the structure of the second embodiment of the deformable mirror of the invention; It is also a partial vertical cross-sectional view of the second embodiment. FIG. 10 is a plan view showing the structure of a deformable mirror according to a third embodiment of the present invention; FIG. 11 is a perspective view showing the structure of a deformable mirror according to a fourth embodiment of the present invention; FIG. 3 is a graph showing shape change on the mirror center line of the reflecting surface when the same voltage is applied to all the piezoelectric elements in the deformable mirror of the first embodiment (FIGS. 1 and 2). FIG. 7 is a graph obtained by subtracting a fourth-order polynomial from the shape change amount on the mirror center line of the reflecting surface when the same voltage is applied to all the piezoelectric elements in the deformable mirror of the first embodiment. FIG. 5 is a graph showing shape change on the mirror center line of the reflecting surface when the same voltage is applied to all piezoelectric elements in the deformable mirror of the second embodiment (FIGS. 3 and 4). FIG. 10 is a graph after subtracting a fourth-order polynomial from the amount of shape change on the mirror center line of the reflecting surface when the same voltage is applied to all the piezoelectric elements in the deformable mirror of the second embodiment; 10 is a graph showing the shape change on the mirror center line of the reflecting surface when 500 V is applied to all the piezoelectric elements on the front side and 400 V is applied to all the piezoelectric elements on the back side in the deformable mirror of the second embodiment. After subtracting a fourth-order polynomial from the shape change amount on the mirror center line of the reflecting surface when 500 V is applied to all the piezoelectric elements on the front side and 400 V is applied to all the piezoelectric elements on the back side in the deformable mirror of the second embodiment, is a graph of

The shape-deformable mirror of the present invention is a rectangular parallelepiped, and has a pair of opposing surfaces of the four surfaces extending in the longitudinal direction, the front surface and the back surface, and the other pair of side surfaces. a mirror substrate; and a plurality of piezoelectric elements attached to at least one of a front surface, a back surface, and both side surfaces of the mirror substrate at predetermined intervals in the longitudinal direction, wherein some of the adjacent piezoelectric elements It is preferred that they overlap in the longitudinal direction. Here, "a portion of the adjacent piezoelectric elements overlap each other in the longitudinal direction" means a portion where the adjacent piezoelectric elements intersect the plane perpendicular to the center line of each surface of the mirror substrate. means that there is

It is preferable that a plurality of the piezoelectric elements are attached, and that part of the piezoelectric elements has an acute-angled portion. Specifically, the piezoelectric element preferably has a triangular or trapezoidal shape in plan view. Also, a strip-shaped reflecting surface is formed along the center line of the surface of the mirror substrate. The reflecting surface is processed to have high shape accuracy and surface roughness in order to reflect the wavefront of obliquely incident X-rays without disturbing them. A multilayer film may be formed on the reflecting surface in order to increase the reflectance of X-rays.

In the shape-deformable mirror of the present invention, piezoelectric elements having a triangular shape in a plan view are provided on at least one of the front surface, the back surface, and both side surfaces of the mirror substrate, and the piezoelectric elements are alternately arranged on both sides of the surface except for the center line portion. It is preferable that they are arranged side by side with their directions reversed. Further, the piezoelectric elements arranged on both sides of the center line of at least one of the front surface, back surface and both side surfaces of the mirror substrate are attached in such a manner that the triangular bases face each other and are symmetrical with respect to the center line. It is more preferable that the If the vertices and bases of the triangular piezoelectric element face each other, there is an advantage in that the undulations in the center can be eliminated, but if the element is slightly away from the center, a twist phenomenon will occur. Therefore, by facing the bases of the triangular piezoelectric elements, the undulation can be easily controlled. Note that the amount of bending is reduced when the vertex portions face each other. Therefore, it is possible to eliminate the undulation by controlling the voltage.

The piezoelectric elements may be attached to the front surface, back surface, or both side surfaces of the mirror substrate, but it is preferable that the piezoelectric elements are attached to both side regions of the surface except for the central line portion. Since the reflective surface is provided along the center line of the surface of the mirror substrate, by attaching the piezoelectric elements to both sides of the reflective surface on the surface, the bending amount of the piezoelectric element can be reflected on the reflective surface, This makes it easier to improve wavefront aberration and handle large bends. There is also an advantage in sticking to the side surface of the mirror substrate. If there is no piezoelectric element on the surface provided with the reflective surface, it is easy to shape and coat. In addition, by attaching the piezoelectric element to the side surface of the mirror base, strain during attachment does not easily enter the reflecting surface, so there are cases where additional processing is not required after attachment. Even if the piezoelectric element exists on the surface provided with the reflective surface, if additional processing is performed after bonding, the effect of distortion during bonding can be eliminated, so there is no practical problem, but one process is added.

Moreover, it is particularly preferable that the piezoelectric elements are attached to the front surface and the back surface of the mirror substrate, respectively. Further, it is more preferable that the triangular piezoelectric elements attached to the front surface and back surface of the mirror substrate are arranged in opposite phases. Here, "opposite phase" means that the directions of the vertex and the base of the triangle are opposite directions. When piezoelectric elements are attached only to one side of the mirror substrate, the amount of bending is small where the apexes face each other. becomes possible.

As for the voltage applied to each piezoelectric element, it is preferable that the same voltage is applied to the left and right sides of the center line between the front surface and the rear surface of the mirror substrate, and that different voltages are applied to the front surface and the rear surface. It is more preferable that the voltage applied is set at a constant rate in the electrodes at the same distance from each mirror end. When the piezoelectric elements are attached to both sides of the mirror substrate, it is preferable that the triangles of the piezoelectric elements on both sides are arranged in the same phase. In addition to setting the voltage, it is preferable to set the piezoelectric elements facing each other on both sides to be the same.

As a binder material for attaching the piezoelectric element to the mirror substrate, it is preferable to use a conductive epoxy resin material or a metal bonded body formed of a bonding material containing metal nanoparticles as a main component. In particular, in the case of a metal bonded body, a pressing process is included at the time of attachment. In this case, if the piezoelectric element is large enough to cover the entire area of the mirror, the piezoelectric element is likely to undergo a large amount of strain. The load applied to the piezoelectric element is also reduced.

The bonding material is a paste containing metal nanoparticles with a particle size of 100 nm or less and a resin component, and has a bonding temperature of 150°C to 300°C. This bonding material is used to bond the piezoelectric element and a mirror base mainly composed of silicon or SiO ₂ . At the time of bonding, pressure and heat are applied to fuse the metal nanoparticles, and the resin segments are evaporated. In the bonded state, the content of the resin component at the bonded portion is preferably 10% by weight or less. Here, the smaller the particle size of the metal nanoparticles, the lower the temperature at which bonding is initiated. In addition, the metal nanoparticles must have a melting point higher than the Curie temperature of the piezoelectric element in the bulk state of the metal.

If the bonding temperature of the bonding material is lower than 150° C., bonding does not start. If the temperature is 300° C. or higher, the temperature approaches the Curie temperature of the piezoelectric element, or exceeds the Curie temperature, causing the orientation of the piezoelectric element to change.

The content of the resin component or volatile component in the bonding material is preferably as low as possible, and the content in the metal bonded body in the bonded state is preferably 10% by weight or less.

Although the material of the mirror substrate itself is not particularly limited, it is preferably composed mainly of silicon or SiO ₂ . Since these materials are available as single crystals, they are suitable mirrors for processing into arbitrary shapes with a PV (Peak to Valley) value of about 2 nm, which is a specification required in the X-ray field. It becomes the base.

Further, in the deformable mirror of the present invention, it is preferable that the metal bonded body at the joint between the mirror base and the piezoelectric element has a porosity of 30% or less. If the porosity is high, the bonding strength will decrease, and fatigue will easily occur due to deformation. In addition, since water and the like enter the gap, they are released when the air is vacuumed. Therefore, the porosity is preferably 30% or less.

Next, embodiments according to the present invention will be described based on the drawings.

A deformable mirror according to a first embodiment of the present invention is shown in FIGS. 1 and 2. FIG. FIG. 1 is a plan view of a deformable mirror, and FIG. 2 is a partial longitudinal sectional view thereof. As shown, the deformable mirror of the first embodiment has a structure in which a plurality of piezoelectric elements 2 are attached only to the surface of a slightly flattened rectangular parallelepiped mirror substrate 1 . Each piezoelectric element 2 has a surface electrode 3 and a back electrode 4. A common electrode 5 is formed on the surface of the mirror substrate 1 by an appropriate means such as vapor deposition. Fixed. Here, the binder material 6 is the aforementioned conductive epoxy resin material or a bonding material containing metal nanoparticles as a main component. In the center of the surface of the mirror base 1, a reflecting surface 7 extending in the longitudinal direction is formed with a predetermined shape accuracy. The common electrodes 5, 5 are provided in strips along both sides of the reflecting surface 7, and the plurality of piezoelectric elements 2, . . . The deformable mirror shown in FIG. 1 has 17 piezoelectric elements 2 on each side of the reflecting surface 7 . Here, the back electrode 4, the common electrode 5 and the binder material 6 constitute an intermediate electrode.

The piezoelectric element 2 is most preferably lead zirconate titanate (commonly called PZT). A front electrode 3 and a back electrode 4 are provided on the front and back surfaces of the plate-like PZT oriented in the thickness direction, and when a voltage is applied between the electrodes, the PZT deforms.

The shape of the piezoelectric element 2 preferably has an acute angle in a plan view. Specifically, it is preferably triangular, more preferably an isosceles triangle, or an equilateral triangle. In addition, by alternately changing the orientation of the triangular piezoelectric elements 2 by 180 degrees and adhering them closer to each other, the adjacent piezoelectric elements 2 and 2 partly overlap each other in the longitudinal direction, and the piezoelectric elements 2 and 2 are spaced apart. The area of the gap can be made uniform in the longitudinal direction of the mirror (the shape change direction of the reflecting surface 7). Therefore, compared with the case where a conventional rectangular piezoelectric element is used and a discontinuous portion occurs in the longitudinal direction, the effect of the gap can be moderated.

It is preferable that the material of the mirror substrate 1 is mainly composed of silicon or SiO ₂ . A material containing silicon or SiO ₂ as a main component is a crystalline material, and since it has no grain boundaries, it is an optimum material for ultra-precision processing that achieves processing accuracy within a few atoms.

A surface electrode 3 is provided on the surface of the piezoelectric element 2, and a back surface electrode 4 is provided on the back surface. are joined with a binder material 6 of The back electrode 4, the binder material 6 and the common electrode 5 are electrically integrated to form an intermediate electrode. Normally, the intermediate electrode is grounded, and voltage is applied to the surface electrode 3 of each piezoelectric element 2 by a suitable voltage applying means that does not affect the deformation of the mirror substrate 1, thereby changing the shape of the reflecting surface 7. It can be changed into any shape.

The reflective surface 7 is formed by directly precision-machining the surface of the mirror substrate 1 during use, and the reflective surface 7 remains convex (defocused) even before the mirror shape is deformed by voltage application. ) or concave (focusing). The effective area of the mirror is formed in a belt shape with a width of about 5 to 8 mm in an area near the center line of the mirror substrate 1 in the lateral direction.

Light such as X-rays can be reflected by the reflecting surface 7, and the X-ray beam is incident from the left-hand side to the right-hand side in FIG. 1, for example. When the beam is incident at a shallow angle of several mrad to several tens of mrad, the X-rays can be totally reflected or reflected by multiple layers. Of course, the incident angle for reflection is appropriately set according to the wavelength of the beam.

By changing the shape of the reflecting surface 7 from its initial setting, the size of the X-ray beam can be changed and the wavefront can be corrected, thereby improving the accuracy of various analyzes, shortening the analysis time, and increasing the intensity of the X-rays. It will be possible to contribute to the enhancement of

A deformable mirror according to a second embodiment of the present invention is shown in FIGS. 3 and 4. FIG. FIG. 3 is a bottom view of the deformable mirror, and FIG. 4 is a partial longitudinal sectional view thereof. The deformable mirror of this embodiment has a structure in which piezoelectric elements 2 are attached to both the front and back surfaces of a mirror substrate 1 . The plan view of the deformable mirror of this embodiment is the same as FIG.

The deformable mirror according to the second embodiment differs from the first embodiment only in that piezoelectric elements are attached to the rear surface of the mirror substrate 1 as well. In the variable shape mirror of this embodiment, the strip-shaped reflecting surface 7 is formed along the center line of the surface of the mirror substrate 1 in the same manner as described above. Elements 2 and 8 are attached to each other, and the triangular arrangement of the piezoelectric elements 2 and 8 on the front surface and the rear surface are in opposite phases.

As shown in FIGS. 3 and 4, each piezoelectric element 8 attached to the rear surface of the mirror substrate 1 has a surface electrode 9 and a rear surface electrode 10, and is formed on the rear surface of the mirror substrate 1 by suitable means such as vapor deposition. It is fixed on the common electrode 11 formed as a film using a binder material 12 in a predetermined pattern. Here, the piezoelectric element 8 is the same as the piezoelectric element 2 and the binder material 12 is the same as the binder material 6 . The common electrodes 11, 11 are provided in strips along both sides of the center line of the back surface of the mirror base 1, and the plurality of piezoelectric elements 8, . . . Here, the back electrode 10, the common electrode 11 and the binder material 12 constitute an intermediate electrode. As shown in FIG. 3, the arrangement of the piezoelectric elements 8, . That is, the vertex of the triangle of the piezoelectric element 8 on the back side is positioned at the center of the base of the piezoelectric element 2 on the front side, and conversely, the center of the base of the triangle of the piezoelectric element 8 on the back side is positioned at the center of the bottom side of the triangle on the front side. The vertex of the piezoelectric element 2 is located.

The binder material 6 and binder material 12 are of two types. One is a case where a conductive epoxy resin is used as a main component. In this case, the back electrodes 4 and 10 and the common electrodes 5 and 11 are made of nickel, gold, chromium, or the like, and the mirror substrate 1 and the piezoelectric elements 2 and 8 are made of metal. It is formed by a method such as vapor deposition or plating through a material that enhances adhesion. Also, when using a conductive epoxy resin, the common electrodes 5 and 11 on the side of the mirror substrate 1 may not be present.

The other of the binder material 6 and the binder material 12 is formed of a metal bonded body bonded with a bonding material containing metal nanoparticles as a main component. Metal nanoparticles are preferably materials such as silver nanoparticles, gold nanoparticles, and copper nanoparticles. Metal nanoparticles have the property of starting to melt at a temperature lower than the original melting point of the metal. For this reason, for example, in the case of silver, although the melting point is 962° C., the silver nanoparticles melt together even at 300° C. or less to form a metal bonded body. For this reason, once bonded, it will not melt unless it is heated to, for example, 962° C., which is the melting point of silver. Even if the temperature rises to about 200 to 300°C, the joint does not denature.

When using a bonding material containing metal nanoparticles as a main component, the back electrodes 4, 10 and the common electrodes 5, 11 include gold, silver, and copper, and are formed via a material that enhances adhesion. It is desirable to be More specifically, gold with a thickness of about 30 nm to 100 nm is most ideally formed by sputtering vapor deposition on the joint surface side of the mirror substrate 1 and the piezoelectric elements 2 and 8 via chromium or titanium with a thickness of several nm. is.

In the deformable mirror according to the second embodiment, as shown in FIG. 3, the piezoelectric element 8 on the back side is attached so that the phase of the piezoelectric element 2 on the front side is opposite to that of the piezoelectric element 8 on the front side. In this way, by attaching the front and back piezoelectric elements in opposite phases, it is possible to eliminate the undulations that are formed depending on the triangular shape.

FIG. 5 shows a deformable mirror according to a third embodiment of the invention. In this embodiment, the planar view shape of the piezoelectric element 2 is rectangular. A plurality of rectangular piezoelectric elements 2 are arranged in at least two rows along the longitudinal direction of the mirror base 1 in a brick structure. As a result, adjacent piezoelectric elements can be partially overlapped with each other in the longitudinal direction.

FIG. 6 shows a deformable mirror according to a fourth embodiment of the invention. The shape-deformable mirror of this embodiment uses a parallelepiped mirror base 13 having four faces extending in the longitudinal direction, one pair of which faces the front and the back, and the other pair of which faces the two sides. A reflective surface 14 is formed along the longitudinal direction of the mirror base 13, and a plurality of piezoelectric elements 15, . . . Alignment is in phase.

<Numerical analysis result>
Next, FIG. 7 shows the results of actual analysis by the finite element method (FEM). The FEM was performed with a thickness of 12.5 mm, a width of 50 mm, and a length of 155 mm using a single crystal of Si as the material of the mirror substrate 1 . The results of FIG. 7 are the results of the first embodiment in which the piezoelectric element is attached only to the front surface as shown in FIGS. is not pasted. Under these conditions, there is a shape change of about 2.5 μm, and when a fourth-order polynomial (approximation) is subtracted from the shape change amount, as shown in FIG. was occurring. In the deformable mirror, the low-order (fourth-order in this embodiment) polynomial component is easily deformed by voltage control and is a frequency component that can be corrected. A 4th-order polynomial was subtracted from the amount and evaluated by higher-order waviness.

On the other hand, in the configuration of the second embodiment as shown in FIGS. 3 and 4, piezoelectric elements are attached to each of the front and back sides, and arranged so that the back and front sides are in opposite phases, and 500 V is applied to all the piezoelectric elements. 9, there is a change in shape of about 4.8 μm. Subtracting a fourth-order polynomial from the amount of change in shape yields a PV value of 0.8 μm as shown in FIG. The waviness was reduced to 2 nm. In other words, by attaching a piezoelectric element to each of the front and back surfaces and making the front and back surfaces in opposite phases, it is possible to reduce the magnitude of the undulation to about 1/4, even though the amount of change in shape is about doubled. showing.

Furthermore, in the configuration of the second embodiment as shown in FIGS. 3 and 4, piezoelectric elements are attached to the front and back respectively, and arranged so that the back and front sides are in opposite phases, and all the piezoelectric elements on the front side When 500 V was applied and 400 V was applied to all of the piezoelectric elements on the back side and bent, there was a shape change of about 4.3 μm as shown in FIG. Subtracting a fourth-order polynomial from the amount of change in shape, the undulation was reduced to a PV value of about 0.01 nm as shown in FIG.

INDUSTRIAL APPLICABILITY The shape-deformable mirror of the present invention can be used for various analyzes by nano-focusing of hard X-rays, and in-situ analysis of various reaction phenomena by ptychography XAFS (for example, analysis of reaction phenomena at electrode portions of secondary batteries, etc.). It can also be used in the field of laser acceleration using high-intensity lasers and laser fusion. INDUSTRIAL APPLICABILITY The variable shape mirror of the present invention can be widely used in optical systems that reflect visible light, EUV region or X-ray region electromagnetic waves.

REFERENCE SIGNS LIST 1 mirror base 2 binder material 3 intermediate electrode 4 piezoelectric element 5 surface electrode 6 reflective surface 7 piezoelectric element on the back side

Claims (9)

a mirror base which is composed of a rectangular parallelepiped and has a pair of opposing surfaces of the four surfaces extending in the longitudinal direction, the front surface and the back surface, and the other pair of side surfaces, and a reflecting surface formed along the longitudinal direction of the surface;
a plurality of piezoelectric elements attached to at least one of the front surface, the back surface, and both side surfaces of the mirror substrate at predetermined intervals in the longitudinal direction;
The piezoelectric elements have a triangular shape in a plan view, and are arranged side by side in opposite directions alternately on both sides of the surface except for the center line portion, and the adjacent piezoelectric elements partially overlap each other in the longitudinal direction. A deformable mirror characterized by being wrapped. 2. The deformable mirror according to claim 1 , wherein the piezoelectric elements arranged on both sides of the surface with respect to the center line thereof are attached so that their triangular bases face each other and are arranged symmetrically with respect to the center line. 3. The deformable mirror according to claim 1 , wherein a strip-shaped reflecting surface is formed along the center line of the surface of said mirror substrate. 4. The deformable mirror according to claim 3 , wherein piezoelectric elements are respectively attached to the front and back surfaces of said mirror substrate provided with the reflecting surface, and the triangular arrangement of the piezoelectric elements on the front and back surfaces are in opposite phases. The voltage applied to each piezoelectric element is set to the same voltage for the piezoelectric elements arranged on both sides of the center line on the front and back sides of the mirror substrate, and is set to a different voltage for the piezoelectric elements arranged on both the front and back sides. The variable shape mirror according to any one of claims 1 to 4 , which is set. 6. The deformable mirror according to claim 5 , wherein voltages applied to the piezoelectric elements arranged on the front surface and the back surface of the mirror base are set at a constant ratio for the electrodes located at the same distance from the mirror edge. 4. The deformable mirror according to claim 3 , wherein piezoelectric elements are attached to both side surfaces of said mirror substrate, and the triangles of the piezoelectric elements on both side surfaces are arranged in the same phase. Piezoelectric elements are attached to both side surfaces of the mirror base, and different voltages are set for the piezoelectric elements arranged across the center line of each side surface, and the same voltage is set for the opposing piezoelectric elements on both side surfaces. 8. A deformable mirror according to claim 7 . The deformable mirror according to any one of claims 1 to 8 , wherein the piezoelectric element and the mirror substrate are bonded by a metal bonding body formed of a bonding material containing metal nanoparticles as a main component.

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