Patent Publication Number: US-2023159323-A1

Title: Mems mirror and mems mirror array system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority benefit of Japanese Patent Application No. 2021-190008 filed in the Japan Patent Office on Nov. 24, 2021. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety. 
     BACKGROUND 
     Embodiments of the present disclosure relate to a microelectromechanical systems (MEMS) mirror and a MEMS mirror array system. 
     In a device such as a MEMS mirror having a movable flat plate, the flat plate is displaced in the film thickness direction by Coulomb force (electrostatic), Lorentz force (electromagnetic), or piezoelectric stress (piezoelectric), for example. The displacement of the flat plate puts stress on a support part that supports the flat plate, and twisting force or other force is applied to the support part by the stress, resulting in generation of vibration in the flat plate. The generated vibration inclines the flat plate. The inclination of the flat plate becomes the most efficient state when being driven at the resonance frequency (natural frequency) of the flat plate. 
     An example of the related art is disclosed in Japanese Patent Laid-open No. 2017-22576. 
     SUMMARY 
     However, the movable flat plate has structural variations in size and thickness, for example, in the manufacturing process, and the variations of the movable flat cause variations in the spring constant of a part that functions as a spring for moving the flat plate. As a result, the natural frequency which is the optimum driving frequency of the device varies in each device. Therefore, it is important to grasp the natural frequency of each device when using the device. Further, in the case where the driving frequency of the device is preliminarily set, if the natural frequency deviates from the driving frequency, the efficiency is deteriorated. In addition, it is difficult to inspect the natural frequency every time it deviates from the driving frequency and adjust the driving frequency. 
     It is desirable to provide a MEMS mirror capable of adjusting a natural frequency, and a MEMS mirror array system including a MEMS mirror array having a plurality of the MEMS mirrors. 
     According to an embodiment of the present disclosure, there is provided a MEMS mirror including a flat plate that is displaceable in a film thickness direction, a frame part that is separated from the flat plate and surrounds the flat plate, a support part that connects the flat plate and the frame part and is smaller in film thickness than the frame part, and a piezoelectric body for control that is arranged on the support part. A control voltage is applied to the piezoelectric body for control to deform the piezoelectric body for control and deform the support part together with the deformation of the piezoelectric body for control, to thereby adjust a spring constant of the support part. 
     In addition, according to another embodiment of the present disclosure, there is provided a MEMS mirror array system including a MEMS mirror array that has a plurality of the above-described MEMS mirrors on a base mount, and a driving control unit that controls a control voltage applied to each of piezoelectric bodies for control included in the plurality of MEMS mirrors. 
     According to the embodiments of the present disclosure, it is possible to provide a MEMS mirror capable of adjusting a natural frequency, and a MEMS mirror array system including a MEMS mirror array having a plurality of the MEMS mirrors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view for illustrating a MEMS mirror according to an embodiment of the present disclosure; 
         FIG.  2    is a cross-sectional view taken along the line II-II of  FIG.  1   ; 
         FIG.  3    is a cross-sectional view taken along the line III-III of  FIG.  1   ; 
         FIG.  4    is a plan view for illustrating a MEMS mirror according to a first modified example of the embodiment; 
         FIG.  5    is a cross-sectional view taken along the line V-V of  FIG.  4   ; 
         FIG.  6    is a cross-sectional view taken along the line VI-VI of  FIG.  4   ; 
         FIG.  7    is a plan view for illustrating a MEMS mirror according to a second modified example of the embodiment; 
         FIG.  8    is a cross-sectional view taken along the line VIII-VIII of  FIG.  7   ; 
         FIG.  9    is a cross-sectional view taken along the line IX-IX of  FIG.  7   ; 
         FIG.  10    is a plan view for illustrating a MEMS mirror according to a third modified example of the embodiment; 
         FIG.  11    is a cross-sectional view taken along the line XI-XI of  FIG.  10   ; 
         FIG.  12    is a cross-sectional view taken along the line XII-XII of  FIG.  10   ; 
         FIG.  13    is a plan view for illustrating a MEMS mirror according to a fourth modified example of the embodiment; and 
         FIG.  14    is a block diagram for illustrating a MEMS mirror array system according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings to be described below, the same or similar parts are denoted by the same or similar reference signs. However, it is important to note that the drawings are schematic, and the relation between the thickness and the plane dimension of each constitutional component or other relation is different from the actual one. Therefore, the specific thickness and dimension should be determined in consideration of the following description. In addition, it is obvious that the dimensional relation or the ratio of constitutional components may differ between the drawings. 
     In addition, the embodiments described below exemplify devices and methods for embodying the technical ideas, and do not specify the material, shape, structure, arrangement, and other configuration of each constitutional component. Various changes can be made to the embodiments in the claims. 
     One example of the specific embodiment is as follows. 
     &lt;1&gt; A MEMS mirror including a flat plate that is displaceable in a film thickness direction, a frame part that is separated from the flat plate and surrounds the flat plate, a support part that connects the flat plate and the frame part and is smaller in film thickness than the frame part, and a piezoelectric body for control that is arranged on the support part, in which a control voltage is applied to the piezoelectric body for control to deform the piezoelectric body for control and deform the support part together with the deformation of the piezoelectric body for control, to thereby adjust a spring constant of the support part. 
     &lt;2&gt; The MEMS mirror according to &lt;1&gt;, in which the support part includes a shaft part with a double-supported beam shape that has one end connected to the flat plate and another end connected to the frame part and that is arranged between the flat plate and the frame part. 
     &lt;3&gt; The MEMS mirror according to claim &lt;1&gt;, in which the support part includes a beam part with a double-supported beam shape that has opposite ends connected to the frame part, and a shaft part with a double-supported beam shape that has one end connected to the flat plate and another end connected to the beam part. 
     According to &lt;1&gt; to &lt;3&gt;, the control voltage is applied to the piezoelectric body for control to deform the piezoelectric body for control, and the support part including the shaft part and/or the beam part is also deformed together with the deformation of the piezoelectric body for control. The deformation of the support part changes the spring constant of the support part itself. Accordingly, the natural frequencies of the flat plate and the MEMS mirror can be adjusted by adjusting the control voltage applied to the piezoelectric body for control. 
     &lt;4&gt; The MEMS mirror according to any one of &lt;1&gt; to &lt;3&gt;, in which the support part is made of the same material as the flat plate. 
     &lt;5&gt; The MEMS mirror according to any one of &lt;1&gt; to &lt;4&gt;, in which the support part is made of the same material as the frame part. 
     &lt;6&gt; The MEMS mirror according to any one of &lt;1&gt; to &lt;5&gt;, in which materials of the flat plate and the support part contain silicon. 
     According to &lt;4&gt; to &lt;6&gt;, since the frame part, the flat plate, and the support part including the shaft part and/or the beam part are made of the same material, they can be formed as one body, and the manufacturing process can thus be further simplified. 
     &lt;7&gt; A MEMS mirror array system including a MEMS mirror array that has a plurality of the MEMS mirrors according to any one of &lt;1&gt; to &lt;6&gt; on a base mount, and a driving control unit that controls a control voltage applied to each of piezoelectric bodies for control included in the plurality of MEMS mirrors. 
     According to &lt;7&gt;, the natural frequencies of the plurality of MEMS mirrors included in the MEMS mirror array can be aligned, or the natural frequencies of some of the MEMS mirrors can be adjusted. Thus, each of the MEMS mirrors can efficiently be driven when the plurality of MEMS mirrors is synchronously driven. 
     &lt;MEMS Mirror&gt; 
     A MEMS mirror according to an embodiment of the present disclosure will be described by using the drawings. 
       FIG.  1    is a plan view for illustrating a MEMS mirror according to the present embodiment.  FIG.  2    is a cross-sectional view taken along the line II-II of  FIG.  1   .  FIG.  3    is a cross-sectional view taken along the line III-III of  FIG.  1   . A MEMS mirror  100  of the present embodiment includes a flat plate  10 A that is displaceable in the film thickness direction, a frame part  10  that is separated from the flat plate  10 A and that surrounds the flat plate  10 A, shaft parts  10 B that connect the flat plate  10 A and the frame part  10  and that are smaller in film thickness than the frame part  10 , piezoelectric bodies for control  14  that are arranged on the shaft parts  10 B, wirings  16  that are electrically connected to the piezoelectric bodies for control  14  and that control the piezoelectric bodies for control  14 , and a wiring  12  that is arranged on the outer edge of the flat plate  10 A and on the shaft part  10 B and the frame part  10 . It should be noted that, although not illustrated in the drawing, the wiring  12  and the wirings  16  are electrically connected to a driving control unit to be described later. The piezoelectric bodies for control  14  are arranged on the respective two shaft parts  10 B disposed to sandwich the flat plate  10 A. 
     In addition, in the present specification, a case where parts are “electrically connected” includes a case where the connection is made through “a part having some electrical action.” Here, “a part having some electrical action” is not limited to a particular one as long as it enables transmission and reception of electrical signals between the objects to be connected to each other. For example, “a part having some electrical action” includes an electrode, a wiring, a switching element, a resistive element, an inductor, a capacitive element, or other elements having various functions. 
     In the present embodiment, the longitudinal direction in which the shaft parts  10 B linearly extend is defined as a Y direction, the direction perpendicular to the Y direction and parallel to an upper surface of the flat plate  10 A is defined as an X direction, and the direction corresponding to the thickness of the flat plate  10 A and other parts is defined as a Z direction. In other words, the Z direction is perpendicular to each of the X direction and the Y direction. In addition, the direction in which the piezoelectric bodies for control  14  are located when viewed from the frame part  10  is defined as an upper direction, and the direction in which the frame part  10  is located when viewed from the piezoelectric bodies for control  14  is defined as a lower direction. In the following description, the vertical direction is defined on the basis of the state of the MEMS mirror  100  illustrated in  FIG.  2   , but the direction in which the MEMS mirror  100  is used is not limited to the defined direction. 
     Each of the frame part  10 , the flat plate  10 A, and the shaft parts  10 B is formed by processing a base mount (a base mount  110  illustrated in  FIG.  14    to be described later) made of, for example, silicon. That is, the frame part  10 , the flat plate  10 A, and the shaft parts  10 B are made of the same material, and the manufacturing process can be further simplified by forming them as one body. 
     Each of the shaft parts  10 B has a double-supported beam shape with the opposite ends fixed. One end of the shaft part  10 B is connected to the flat plate  10 A, and the other end is connected to the frame part  10 . The shaft part  10 B is arranged between the flat plate  10 A and the frame part  10 . Each of the shaft parts  10 B functions as a spring for assisting the movement of the flat plate  10 A when the flat plate  10 A is moved. When the shaft part  10 B functions as the spring, the shaft part  10 B adjusts the spring constant by its own deformation. The shaft part  10 B also functions as a support part for supporting the flat plate  10 A. Each of the shaft parts  10 B can be formed by being etched such that the film thickness thereof becomes smaller than that of the frame part  10  when the base mount is processed. 
     The piezoelectric bodies for control  14  are arranged on the respective shaft parts  10 B, which are support parts, and a control voltage is applied to the piezoelectric bodies for control  14  via the wirings  16  to deform the piezoelectric bodies for control  14 . As the piezoelectric bodies for control  14  deform, opposite ends of each shaft part  10 B are deformed to pull each other, so that the shaft parts  10 B become hardened and the spring constant of the shaft parts  10 B increases. If the control voltage is adjusted, the piezoelectric bodies for control  14  are deformed by application of the adjusted control voltage, and the shaft parts  10 B are also deformed together with the deformation of the piezoelectric bodies for control  14 . As a result, the spring constant of the shaft parts  10 B can be adjusted, and the natural frequency of the flat plate  10 A connected to the shaft parts  10 B can also be adjusted. In addition, since the piezoelectric bodies for control  14  are arranged on the respective two shaft parts  10 B, the twisting of the respective shaft parts  10 B can be made uniform by reducing the difference between the functions of the two shaft parts  10 B as springs, and the loads on the respective shaft parts  10 B can also be made uniform. With the above uniformity, rotational vibration in a constant cycle in an X-Z plane can be achieved. 
     The control voltage may be, for example, 0 V or any fixed voltage, a sine wave of 0 to 5 V, a unipolar pulse, a bipolar pulse, a burst wave, or a continuous wave. In addition, the voltage to be applied to the piezoelectric bodies for control  14  can be a voltage modulated by a filter or other processing. For example, a voltage to be applied to one electrode (an electrode  14   a  to be described later, for example) is modulated, and the modulated voltage can be applied to another electrode (an electrode  14   c  to be described later, for example). Accordingly, the number of electrode pads and the types of driving voltages to be applied can be reduced, and the manufacturing process can be further simplified. 
     The wiring  12  functions as a metal coil. When a current flows through the wiring  12  arranged on the outer edge of the flat plate  10 A, the Lorentz force is generated according to the Fleming&#39;s rule, and the flat plate  10 A inclines. Specifically, when the wiring  12  functioning as a metal coil is arranged in the direction perpendicular to the magnetic field (the direction of the magnetic force is the X direction) and a current is allowed to flow in the direction of arrows  20  illustrated in  FIG.  1   , the Lorentz force is applied to the wiring  12  in the Z direction. The magnitude of the Lorentz force is proportional to the strength of the current and the magnetic field. 
     As illustrated in  FIG.  3   , the flat plate  10 A is configured to be displaceable in the film thickness direction (Z direction). Specifically, the displacement of the flat plate  10 A in the film thickness direction by the Lorentz force becomes possible by making the shaft parts  10 B function as rotary shafts and separating the flat plate  10 A from the frame part  10 . 
     In addition, a mirror  10   a  is provided on the flat plate  10 A, and the mirror  10   a  inclines with the inclination of the flat plate  10 A. By adjusting the spring constant of the shaft parts  10 B and the above-described Lorentz force, the mirror  10   a  can rotate around a rotation axis extending in the Y direction and can rotate and vibrate in the X-Z plane. Accordingly, the optical path of laser light incident on a mirror surface can be changed, and the MEMS mirror  100  can be driven at the natural frequency in the most efficient state. 
     The mirror  10   a  is not limited to a particular one as long as it has a mirror surface that reflects laser light or other light, and may be a metal layer having a reflectance of 90% or more and formed by, for example, vapor deposition or printing. 
     For the wiring  12  and the wirings  16 , for example, copper wires, aluminum wires, and copper-clad aluminum wires (CCAW) can be used. In addition, the wiring  12  and the wirings  16  may be covered with an insulating film, and the insulating film is made of, for example, enamel or resin. 
     Each of the piezoelectric bodies for control  14  is a piezoelectric element, and includes a pair of electrodes  14   a  and  14   c  and a piezoelectric film  14   b  sandwiched between the pair of electrodes  14   a  and  14   c.  The pair of electrodes  14   a  and  14   c  and the piezoelectric film  14   b  are, for example, rectangular. 
     Each of the pair of electrodes  14   a  and  14   c  includes a thin film of metal having conductivity, such as platinum, molybdenum, iridium, or titanium. One electrode  14   c  is located on top of the piezoelectric film  14   b  and is connected to the wiring  16  for applying the control voltage to the electrode  14   c.  The other electrode  14   a  is located under the piezoelectric film  14   b  and is connected to the wiring  16  for applying the control voltage to the electrode  14   a.    
     The piezoelectric film  14   b  is made of, for example, lead zirconate titanate (PZT). In addition to lead zirconate titanate, aluminum nitride (AlN), zinc oxide (ZnO), lead titanate (PbTiO 3 ), or other materials can be used for the piezoelectric film  14   b.    
     When the control voltage is applied to each of the electrode  14   a  and the electrode  14   c,  a potential difference occurs between the electrode  14   a  and the electrode  14   c.  The potential difference deforms the piezoelectric bodies for control  14 . As described above, as the piezoelectric bodies for control  14  deform, the shaft parts  10 B deform, resulting in a change in the natural frequency of the flat plate  10 A. In the present embodiment, the control voltage to be applied to the piezoelectric bodies for control  14  is adjusted, and accordingly, the natural frequency of the MEMS mirror  100  can be adjusted. 
     FIRST MODIFIED EXAMPLE 
     A configuration of a MEMS mirror  100 A according to a modified example of the present embodiment will be described by using  FIG.  4    to  FIG.  6   .  FIG.  4    is a plan view for illustrating the MEMS mirror  100 A.  FIG.  5    is a cross-sectional view taken along the line V-V of  FIG.  4   .  FIG.  6    is a cross-sectional view taken along the line VI-VI of  FIG.  4   . The MEMS mirror  100 A of the present modified example includes a flat plate  10 A that is displaceable in the film thickness direction, a frame part  10  that is separated from the flat plate  10 A and that surrounds the flat plate  10 A, beam parts  10 C that each have opposite ends connected to the frame part  10  and that are smaller in film thickness than the frame part  10 , shaft parts  10 B that connect the flat plate  10 A and the beam parts  10 C and that are smaller in film thickness than the frame part  10 , piezoelectric bodies for control  14  that are arranged on the beam parts  10 C, wirings  16  that are electrically connected to the piezoelectric bodies for control  14  and that control the piezoelectric bodies for control  14 , and a wiring  12  that is arranged on the outer edge of the flat plate  10 A and on the beam part  10 C, the shaft part  10 B, and the frame part  10 . The MEMS mirror  100 A in the present modified example is different from the above-described MEMS mirror  100  illustrated in  FIG.  1    to  FIG.  3    in that the piezoelectric bodies for control  14  are arranged on the beam parts  10 C in place of the piezoelectric bodies for control  14  arranged on the shaft parts  10 B. In the present modified example, the above description will be applied to parts common to the MEMS mirror  100 A and the MEMS mirror  100  illustrated in  FIG.  1    to  FIG.  3   , and different parts will be described below. 
     Each of the beam parts  10 C is arranged between a groove part  18  provided in the frame part  10  and a region (space) defined between the frame part  10  and the flat plate  10 A, and has a double-supported beam shape with the opposite ends fixed to the frame part  10 . Each of the beam parts  10 C functions as a spring for assisting the movement of the flat plate  10 A when the flat plate  10 A is moved. When the beam part  10 C functions as the spring, the beam part  10 C adjusts the spring constant by its own deformation. The beam part  10 C also functions as a support part for supporting the flat plate  10 A. Each of the beam parts  10 C can be formed by being etched such that the film thickness thereof becomes smaller than that of the frame part  10  when the base mount is processed. 
     The piezoelectric bodies for control  14  are arranged on the respective beam parts  10 C, which are support parts, and a control voltage is applied to the piezoelectric bodies for control  14  via the wirings  16  to deform the piezoelectric bodies for control  14 . As the piezoelectric bodies for control  14  deform, opposite ends of each beam part  10 C are deformed to pull each other, so that the beam parts  10 C become hardened and the spring constant of the beam parts  10 C increases. If the control voltage is adjusted, the piezoelectric bodies for control  14  are deformed by application of the adjusted control voltage, and the beam parts  10 C are also deformed together with the deformation of the piezoelectric bodies for control  14 . As a result, the spring constant of the beam parts  10 C can be adjusted, and the natural frequency of the flat plate  10 A connected to the support parts including the shaft parts  10 B and the beam parts  10 C can also be adjusted. 
     As described above, when the control voltage is applied to each of the electrode  14   a  and the electrode  14   c  of the piezoelectric bodies for control  14 , a potential difference occurs between the electrode  14   a  and the electrode  14   c.  The piezoelectric bodies for control  14  are deformed by the potential difference, and as the piezoelectric bodies for control  14  deform, the beam parts  10 C deform, resulting in a change in the natural frequency of the flat plate  10 A. In the present modified example, the control voltage to be applied to the piezoelectric bodies for control  14  is adjusted, and accordingly, the natural frequency of the MEMS mirror  100 A can be adjusted. 
     SECOND MODIFIED EXAMPLE 
     A configuration of a MEMS mirror  100 B according a modified example of the present embodiment will be described by using  FIG.  7    to  FIG.  9   .  FIG.  7    is a plan view for illustrating the MEMS mirror  100 B.  FIG.  8    is a cross-sectional view taken along the line VIII-VIII of  FIG.  7   .  FIG.  9    is a cross-sectional view taken along the line IX-IX of  FIG.  7   . The MEMS mirror  100 B of the present modified example includes a flat plate  10 A that is displaceable in the film thickness direction, a frame part  10  that is separated from the flat plate  10 A and that surrounds the flat plate  10 A, beam parts  10 C that each have opposite ends connected to the frame part  10  and that are smaller in film thickness than the frame part  10 , shaft parts  10 B that connect the flat plate  10 A and the beam parts  10 C and that are smaller in film thickness than the frame part  10 , piezoelectric bodies for control  14  that are continuously arranged on the shaft parts  10 B and the beam parts  10 C, wirings  16  that are electrically connected to the piezoelectric bodies for control  14  and that control the piezoelectric bodies for control  14 , and a wiring  12  that is arranged on the outer edge of the flat plate  10 A and on the beam part  10 C, the shaft part  10 B, and the frame part  10 . The MEMS mirror  100 B in the present modified example is different from the above-described MEMS mirror  100 A illustrated in  FIG.  4    to  FIG.  6    in that the piezoelectric bodies for control  14  are arranged on the shaft parts  10 B and the beam parts  10 C. In the present modified example, the above description will be applied to parts common to MEMS mirror  100 B and the MEMS mirror  100 A illustrated in  FIG.  4    to  FIG.  6   , and different parts will be described below. 
     Since the piezoelectric bodies for control  14  are arranged on the shaft parts  10 B and the beam parts  10 C, the shaft parts  10 B and the beam parts  10 C are deformed as the piezoelectric bodies for control  14  are deformed by application of the control voltage. In the case where the spring constant of the shaft parts  10 B and the spring constant of the beam parts  10 C are different from each other, the natural frequency of the flat plate  10 A connected to the support parts including the shaft parts  10 B and the beam parts  10 C can be adjusted more finely by adjusting the positional relation between the piezoelectric bodies for control  14  and the shaft parts  10 B and between the piezoelectric bodies for control  14  and the beam parts  10 C. 
     As described above, when the control voltage is applied to each of the electrode  14   a  and the electrode  14   c  of the piezoelectric bodies for control  14 , a potential difference occurs between the electrode  14   a  and the electrode  14   c.  The piezoelectric bodies for control  14  are deformed by the potential difference, and as the piezoelectric bodies for control  14  deform, the shaft parts  10 B and the beam parts  10 C deform, resulting in a change in the natural frequency of the flat plate  10 A. In the present modified example, since the force required to deform the support parts is smaller than the case where the piezoelectric bodies for control  14  are arranged on either the shaft parts  10 B or the beam parts  10 C, the potential difference between the electrode  14   a  and the electrode  14   c  can be reduced, and the natural frequency of the flat plate  10 A can be adjusted with a small control voltage. In the present modified example, the control voltage to be applied to the piezoelectric bodies for control  14  is adjusted, and accordingly, the natural frequency of the MEMS mirror  100 B can be adjusted. 
     THIRD MODIFIED EXAMPLE 
     A configuration of a MEMS mirror  100 C according to a modified example of the present embodiment will be described by using  FIG.  10    to  FIG.  12   .  FIG.  10    is a plan view for illustrating the MEMS mirror  100 C.  FIG.  11    is a cross-sectional view taken along the line XI-XI of  FIG.  10   .  FIG.  12    is a cross-sectional view taken along the line XII-XII of  FIG.  10   . The MEMS mirror  100 C of the present modified example includes a flat plate  10 A that is displaceable in the film thickness direction, a frame part  10  that is separated from the flat plate  10 A and that surrounds the flat plate  10 A, beam parts  10 C that each have opposite ends connected to the frame part  10  and that are smaller in film thickness than the frame part  10 , shaft parts  10 B that connect the flat plate  10 A and the beam parts  10 C and that are smaller in film thickness than the frame part  10 , piezoelectric bodies for control  14 A that are arranged on the shaft parts  10 B, piezoelectric bodies for control  14 B that are arranged on the beam parts  10 C, wirings  16 A that control the piezoelectric bodies for control  14 A, wirings  16 B that control the piezoelectric bodies for control  14 B, and a wiring  12  that is arranged on the outer edge of the flat plate  10 A and on the shaft part  10 B and the frame part  10 . The MEMS mirror  100 C in the present modified example is different from the above-described MEMS mirror  100 A illustrated in  FIG.  4    to  FIG.  6    in that the piezoelectric bodies for control  14 A and the piezoelectric bodies for control  14 B are provided in place of the piezoelectric bodies for control  14  continuously arranged on the shaft parts  10 B and the beam parts  10 C. In the present modified example, the above description will be applied to parts common to MEMS mirror  100 C and the MEMS mirror  100 A illustrated in  FIG.  4    to  FIG.  6   , and different parts will be described below. 
     The above description of the piezoelectric bodies for control  14  can be applied to the description of the piezoelectric bodies for control  14 A and the piezoelectric bodies for control  14 B. The above description of the wirings  16  can be applied to the description of the wirings  16 A and the wirings  16 B. 
     Since the piezoelectric bodies for control  14 A are arranged on the shaft parts  10 B and the piezoelectric bodies for control  14 B are arranged on the beam parts  10 C, the shaft parts  10 B and the beam parts  10 C are deformed as the piezoelectric bodies for control  14 A and the piezoelectric bodies for control  14 B are deformed by application of the control voltage. In the case where the shaft parts  10 B on which the piezoelectric bodies for control  14 A are arranged and the beam parts  10 C on which the piezoelectric bodies for control  14 B are arranged are coupled to each other and are regarded as one support part, the force required to deform the support part is smaller than the case where the piezoelectric bodies for control  14  are arranged on either the shaft parts  10 B or the beam parts  10 C. Thus, the potential difference between the electrode  14   a  and the electrode  14   c  can be reduced, and the natural frequency of the flat plate  10 A can be adjusted with a small control voltage. In the present modified example, the control voltage to be applied to the piezoelectric bodies for control  14 A and the piezoelectric bodies for control  14 B is adjusted, and accordingly, the natural frequency of the MEMS mirror  100 C can be adjusted. 
     (Other embodiments) 
     One embodiment has been described above. It should be understood that the statements and drawings incorporated in the disclosure are exemplary and are not limited to particular ones. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure. Thus, the embodiment of the present disclosure includes various embodiments not described herein. 
     For example,  FIG.  13    is a plan view for illustrating a MEMS mirror  100 D, and a configuration in which a piezoelectric body for control  14  is arranged on only one of two shaft parts  10 B that are disposed to sandwich a flat plate  10 A may be employed. 
     &lt;MEMS Mirror Array System&gt; 
     A MEMS mirror array system according to an embodiment of the present disclosure will be described by using the drawing. 
       FIG.  14    is a block diagram for illustrating a MEMS mirror array system according to the present embodiment. A MEMS mirror array system  200  of the present embodiment includes a MEMS mirror array  150  and a driving control unit  120 . The MEMS mirror array  150  has a plurality of MEMS mirrors (for example, the MEMS mirrors  100 ) described above, on a base mount  110 . The driving control unit  120  controls a control voltage to be applied to each of the piezoelectric bodies for control  14  of the plurality of MEMS mirrors  100 . 
     Although the characteristics of the piezoelectric body for control  14 , which is a piezoelectric element, fluctuate due to the finished size such as the film thickness of the piezoelectric film, crystal characteristics of the piezoelectric film, manufacturing quality including minute defects or other defects, environmental factors such as temperature, aging degradation, or other factors, the MEMS mirror array system  200  of the present embodiment can adjust the natural frequency, which fluctuates depending on the environment and the state, for each MEMS mirror  100  that is changed due to such characteristic fluctuations and the flat plate  10 A of the MEMS mirror  100  described above. 
     The base mount  110  is not limited to a particular one as long as the MEMS mirror array  150  can be arranged thereon, and may be, for example, a silicon substrate. If the base mount  110  is a silicon substrate, the frame part  10 , the flat plate  10 A, the shaft parts  10 B, and other parts of the MEMS mirror  100  can be formed by processing the base mount  110 . That is, the base mount  110 , the frame part  10 , the flat plate  10 A, and the shaft parts  10 B are made of the same material and can be formed as one body, so that the manufacturing process can be further simplified. 
     The driving control unit  120  includes a general-purpose microcomputer including, for example, a storage unit, a control unit, and an input/output unit, which are not illustrated. In this case, a computer program that functions as the MEMS mirror array system  200  may be installed in the microcomputer. By executing the computer program, the microcomputer controls the plurality of MEMS mirrors  100  included in the MEMS mirror array system  200 . The control of the plurality of MEMS mirrors  100  may be executed by software or by dedicated hardware. In addition, the plurality of MEMS mirrors  100  may be controlled by individual hardware. 
     The storage unit includes a read only memory (ROM), a random access memory (RAM), or a hard disk, for example. The storage unit stores, as data, information such as the driving voltage and the natural frequency of each MEMS mirror  100 . The storage unit storing these various pieces of data may be provided in one storage device and configured as a region physically or logically separated, or the storage units each storing data may be provided in a plurality of storage devices physically different from one another. 
     The control unit includes, as functions, a selection driving control unit and a voltage control unit. The selection driving control unit controls a current to be supplied to the above-described wiring  12  functioning as a metal coil, and controls the MEMS mirror  100  to be driven. The voltage control unit adjusts a control voltage to be applied to the piezoelectric body for control  14  in the driven MEMS mirror  100 . 
     On the basis of the information such as the driving voltage and the natural frequency of each MEMS mirror  100  stored in the storage unit, the control unit decides which MEMS mirror  100  included in the MEMS mirror array  150  is driven and how the control voltage, which is to be applied to the piezoelectric body for control  14  in the MEMS mirror  100  to be driven, is applied. Then, the control unit controls the plurality of MEMS mirrors  100  on the basis of the decision. 
     Such a configuration makes it possible to align the natural frequencies of the plurality of MEMS mirrors included in the MEMS mirror array or adjust the natural frequencies of some of the MEMS mirrors, and each of the MEMS mirrors can efficiently be driven when the plurality of MEMS mirrors is synchronously driven.