JP2020020865A - Optical scanning device and driving method thereof - Google Patents

Abstract

To provide an optical scanning device capable of vibrating a diaphragm vertically in both directions by applying unipolar voltage, and a driving method thereof.SOLUTION: An optical scanning device 1 includes a support 3, a diaphragm 5a, a diaphragm 5b and a reflector 9. The diaphragm 5a includes first piezoelectric element 13a, 13b and second piezoelectric element 21a, 21b arranged thereon. The diaphragm 5b includes first piezoelectric elements 13c and 13d and the second piezoelectric elements 21c and 21d arranged thereon. The first voltage applied to the first piezoelectric elements 13a and 13b and the second voltage applied to the second piezoelectric elements 21a and 21b are applied with their phases shifted from each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical scanning device and a driving method thereof, and more particularly to an optical scanning device having a diaphragm and a driving method of the optical scanning device.

  2. Description of the Related Art Conventionally, there has been known an optical scanning device in which a reflection plate is connected to a vibration plate via an elastic body. In this optical scanning device, by vibrating the vibrating plate, the reflecting plate rotates and scans the light applied to the reflecting plate. In order to vibrate the diaphragm, a piezoelectric element is arranged on the diaphragm. In a piezoelectric element, a piezoelectric body is sandwiched between one electrode and another electrode.

  Patent Documents 1 and 2 disclose examples of patent documents that disclose this type of optical scanning device. Patent Document 1 proposes an optical scanning device that rotates a reflecting plate by applying a bipolar alternating voltage having a phase difference of 180 ° to a piezoelectric element disposed on a diaphragm. Patent Literature 2 proposes an optical scanning device that rotates a reflecting plate by applying a voltage having a fixed frequency of a single polarity to a piezoelectric element disposed on a diaphragm.

  It is known that when a bipolar voltage is applied to a piezoelectric element, polarization fatigue is caused and its characteristics are deteriorated, and it is not suitable for use in an optical scanning device requiring a long life ( Non-patent document 1). On the other hand, it is known that when a unipolar voltage is applied to a piezoelectric element, polarization fatigue of the piezoelectric element is significantly reduced as compared with a case where a bipolar voltage is applied (Non-Patent Document 2). .

JP 2005-128147 A JP 2014-103360 A

Lou, X. J. “Polarization fatigue in ferroelectric thin films and related materials.” Journal of Applied Physics 105.2 (2009): 024101. Lou, X. J., and J. Wang. “Bipolar and unipolar electrical fatigue in ferroelectric lead zirconate titanate thin films: An experimental comparison study.” Journal of Applied Physics 108.3 (2010): 034104.

  When applying a voltage exceeding a coercive voltage in which the direction of polarization of the piezoelectric body is reversed when applying a unipolar voltage to the piezoelectric element, the polarization direction of the piezoelectric body is applied by applying a voltage exceeding the coercive voltage. Inverts in the direction of voltage application. Therefore, regardless of the polarity of the input voltage, the vibration direction of the diaphragm becomes constant, and there has been a problem that the diaphragm can be bent only in one direction, upward or downward.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical scanning device capable of applying a unipolar voltage to vibrate a diaphragm in both up and down directions. Another object is to provide a method for driving such an optical scanning device.

  An optical scanning device according to the present invention includes a support, a diaphragm, a first piezoelectric element and a second piezoelectric element, and a reflector. The diaphragm has a first end and a second end located at a distance, and the first end is supported by a support. The first piezoelectric element and the second piezoelectric element are arranged on the diaphragm. The reflector is connected to the second end of the diaphragm via an elastic body, and has a reflective surface that reflects light. The first piezoelectric element is driven in the first mode by applying a unipolar first voltage. The second piezoelectric element is driven in a second mode different from the first mode by applying a unipolar second voltage. When the first piezoelectric element or the second piezoelectric element is driven, the diaphragm is bent and the reflector is tilted.

  A driving method of an optical scanning device according to the present invention has a first end and a second end facing each other at a distance, the first end is supported by a support, and the second end is an elastic body. A vibration plate connected to the reflection plate via the first and second piezoelectric elements disposed on the vibration plate, the first piezoelectric element being driven in the first mode, and the second piezoelectric element being driven in a second mode different from the first mode. It is a driving method of the optical scanning device having the above. The first piezoelectric element is driven in the first mode by applying a unipolar first voltage to the first piezoelectric element. By applying a unipolar second voltage to the second piezoelectric element, the second piezoelectric element is driven in a second mode different from the first mode. By driving the first piezoelectric element and the second piezoelectric element, the diaphragm is bent and the reflector is tilted. By applying the first voltage and the second voltage with their phases shifted from each other, the first piezoelectric element and the second piezoelectric element are driven with a time shift.

  According to the optical scanning device of the present invention, the first piezoelectric element driven in the first mode and the second piezoelectric element driven in the second mode different from the first mode are arranged on the diaphragm. By driving the first piezoelectric element or the second piezoelectric element, the diaphragm can be vibrated in both directions, and the reflector can be tilted in both directions.

  According to the driving method of the optical scanning device according to the present invention, the first piezoelectric element is driven by the unipolar first voltage, and the second piezoelectric element is driven by the unipolar second voltage. The first voltage and the second voltage are applied with their phases shifted from each other, and the reflecting plate is inclined by bending the diaphragm. Thus, the reflecting plate can be tilted by vibrating the diaphragm of the optical scanning device in both directions.

FIG. 2 is a perspective view of the optical scanning device according to the first embodiment of the present invention. FIG. 3 is a plan view of the optical scanning device in the embodiment. FIG. 3 is a partial cross-sectional view of a first piezoelectric element in the embodiment. FIG. 3 is a partial cross-sectional view for explaining an example of a driving mechanism of a first piezoelectric element in the embodiment. FIG. 3 is a partial cross-sectional view of a second piezoelectric element in the embodiment. FIG. 3 is a partial cross-sectional view for explaining an example of a driving mechanism of a second piezoelectric element in the embodiment. FIG. 3 is a perspective view showing an example of an arrangement pattern of electrodes of a second piezoelectric element in the embodiment. FIG. 3 is a plan view showing an example of an arrangement pattern of electrodes of a second piezoelectric element in the embodiment. FIG. 6 is a cross-sectional view showing one step of a method of manufacturing the optical scanning device in the embodiment. FIG. 10 is a cross-sectional view showing a step performed after the step shown in FIG. 9 in the embodiment. FIG. 11 is a cross-sectional view showing a step performed after the step shown in FIG. 10 in the embodiment. FIG. 12 is a cross-sectional view showing a step performed after the step shown in FIG. 11 in the embodiment. FIG. 13 is a cross-sectional view showing a step performed after the step shown in FIG. 12 in the embodiment. FIG. 14 is a cross-sectional view showing a step performed after the step shown in FIG. 13 in the embodiment. FIG. 15 is a cross-sectional view showing a step performed after the step shown in FIG. 14 in the embodiment. FIG. 16 is a cross-sectional view showing a step performed after the step shown in FIG. 15 in the embodiment. 3 is a graph illustrating an example of a waveform of a unipolar voltage applied to a first piezoelectric element and a second piezoelectric element in the embodiment. FIG. 4 is a cross-sectional view schematically illustrating an example of a bending mode of the diaphragm in the embodiment. FIG. 9 is a cross-sectional view schematically showing another example of the bending mode of the diaphragm in the embodiment. FIG. 4 is a perspective view for explaining the inclination of the reflector due to the bending of the diaphragm in the embodiment. FIG. 9 is a perspective view of an optical scanning device according to Embodiment 2 of the present invention. FIG. 3 is a plan view of the optical scanning device in the embodiment. FIG. 9 is a perspective view of an optical scanning device according to a comparative example. FIG. 9 is a plan view of an optical scanning device according to a comparative example.

Embodiment 1 FIG.
The optical scanning device according to the first embodiment will be described. Here, the structure and the like will be described by showing the X-axis, the Y-axis, and the Z-axis for convenience of explanation. As shown in FIGS. 1 and 2, the X axis and the Y axis are orthogonal to each other, and the surface on which the optical scanning device 1 (support 3) is disposed is an XY plane. The Z axis is orthogonal to the XY plane.

  The optical scanning device 1 includes a support 3, a vibration plate 5a, a vibration plate 5b, and a reflection plate 9. The diaphragm 5a has a first end 5aa and a second end 5ab facing each other at a distance in the X-axis direction. The first end 5aa is connected to the support 3. The second end 5ab is connected to the reflection plate 9 via the elastic body 7a. The elastic body 7a is connected to the center of the second end 5ab of the diaphragm 5a in the Y-axis direction.

  The diaphragm 5b has a first end 5ba and a second end 5bb facing each other at a distance in the X-axis direction. The first end 5ba is connected to the support 3. The second end 5bb is connected to the reflector 9 via the elastic body 7b. The elastic body 7b is connected to the center of the second end 5bb of the diaphragm 5b in the Y-axis direction. The reflection plate 9 is provided with a reflection surface 11.

  The first piezoelectric elements 13a and 13b and the second piezoelectric elements 21a and 21b are arranged on the diaphragm 5a. The first piezoelectric element 13a, the second piezoelectric element 21a, the first piezoelectric element 13b, and the second piezoelectric element 21b are arranged in this order from the first end 5aa to the second end 5ab. The first piezoelectric elements 13c and 13d and the second piezoelectric elements 21c and 21d are arranged on the diaphragm 5b. From the side of the first end 5ba to the side of the second end 5bb, the second piezoelectric element 21d, the first piezoelectric element 13d, the second piezoelectric element 21c, and the first piezoelectric element 13c are arranged in this order.

  As shown in FIG. 2, the diaphragm 5a (first piezoelectric elements 13a and 13b, second piezoelectric elements 21a and 21b), the elastic body 7a, the reflector 9, the elastic body 7b, and the diaphragm 5b (first piezoelectric element 13c, 13d and the second piezoelectric elements 21c and 21d) are arranged substantially line-symmetrically with respect to an axis C1 parallel to the X axis as a virtual line. The plane shape of the reflecting plate 9 is formed in a rectangular shape so as to be line-symmetric with respect to the axis C1, but if the reflecting plate 9 is not distorted due to the inclination of the reflecting plate 9, the reflecting plate 9 is The planar shape need not be a line-symmetric shape.

  Next, the first piezoelectric elements 13a to 13d and the second piezoelectric elements 21a to 21d will be described. First, the first piezoelectric elements 13a to 13d will be described. As shown in FIG. 3, the first piezoelectric element 13 (13a to 13d) is formed by a lower electrode 15, a piezoelectric body 17, and an upper electrode 19. The lower electrode 15, the piezoelectric body 17, and the upper electrode 19 are stacked on the diaphragm 5 (5a, 5b).

The piezoelectric body 17 is polarized in the positive direction or the negative direction in the Z-axis direction by a polarization process or by applying a unipolar voltage exceeding the coercive electric field. When a unipolar voltage is applied between the lower electrode 15 and the upper electrode 19 of the piezoelectric body 17 in the same direction as the polarization direction, the piezoelectric body 17 contracts in the X-axis direction. Due to the contraction of the piezoelectric body 17 in the X-axis direction, the diaphragm 5 is bent so as to be convex in the negative direction of the Z-axis, and the diaphragm 5 is bent relative to the support 3 in the positive direction of the Z-axis. become. Bending of the first piezoelectric element 13 is referred to as a d ₃₁ mode as the first mode.

  As shown in FIG. 4, for example, when the piezoelectric body 17 is polarized so that the lower electrode 15 side is positive and the upper electrode 19 side is negative, the lower electrode 15 and the upper electrode 19 By applying a voltage so that the voltage applied to the upper electrode 19 becomes higher than the voltage applied to the electrode 15, the piezoelectric body 17 contracts in the X-axis direction, and the diaphragm 5 moves as shown by the arrow. Then, it is bent so as to be convex in the negative direction of the Z axis.

  When the polarization direction of the piezoelectric body 17 is opposite to the direction shown in FIG. 4, the voltage applied between the lower electrode 15 and the upper electrode 19 with respect to the voltage applied to the lower electrode 15 is increased. By applying a voltage so that the voltage applied to the upper electrode 19 decreases, the diaphragm 5 bends so as to be convex in the negative direction of the Z axis. Therefore, regardless of the polarity of the voltage, by applying a unipolar voltage exceeding the coercive voltage, the diaphragm 5 bends so as to be convex in the negative direction of the Z axis.

  Next, the second piezoelectric elements 21a to 21d will be described. As shown in FIG. 5, the second piezoelectric element 21 (21a to 21d) is formed by a first electrode 23, a second electrode 25, and a piezoelectric body 27. The first electrode 23 and the second electrode 25 are formed on the surface of the piezoelectric body 27. The first electrode 23 and the second electrode 25 are arranged at an interval. The piezoelectric body 27 is formed on the vibration plate 5.

The piezoelectric body 27 is polarized in the positive direction or the negative direction in the X-axis direction by a polarization process or by applying a unipolar voltage exceeding the coercive electric field. By applying a unipolar voltage between the first electrode 23 and the second electrode 25 of the piezoelectric body 27 in the same direction as the polarization direction, the piezoelectric body 27 extends in the X-axis direction. When the piezoelectric body 27 extends in the X-axis direction, the diaphragm 5 is bent so as to be convex in the positive direction of the Z-axis. The second piezoelectric element 21 will be driven at d ₃₃ mode as the second mode.

  As shown in FIG. 6, for example, when the piezoelectric body 27 is polarized such that the center in the X-axis direction is positive and the end in the X-axis direction is negative, the first electrode 23 and the second electrode By applying a voltage between the electrode 25 and the second electrode 25 so that the voltage applied to the first electrode 23 is higher than the voltage applied to the second electrode 25, the piezoelectric body 27 extends in the X-axis direction. . Due to the extension of the piezoelectric body 27 in the X-axis direction, the diaphragm 5 bends so as to be convex in the positive direction of the Z-axis as shown by the arrow, and the diaphragm 5 bends in the negative direction of the Z-axis. become.

  When the polarization direction of the piezoelectric body 27 is opposite to the direction shown in FIG. 6, the voltage applied to the second electrode 25 is applied between the first electrode 23 and the second electrode 25. On the other hand, by applying a voltage so that the voltage applied to the first electrode 23 becomes lower, the piezoelectric body 27 extends in the X-axis direction. Therefore, regardless of the polarity of the voltage, by applying a unipolar voltage exceeding the coercive voltage, the diaphragm 5 is bent so as to be convex in the positive direction of the Z axis.

  The first electrode 23 and the second electrode 25 in the second piezoelectric element 21 are arranged on the surface of the piezoelectric body 27 with an interval of about 1 μm to 10 μm, for example. By applying a voltage between the first electrode 23 and the second electrode 25, a voltage can be applied to the piezoelectric body 27 in the X-axis direction. As shown in FIGS. 7 and 8, such an electrode structure of the first electrode 23 and the second electrode 25 is typically called a comb field electrode structure. The first electrode 23 has a portion extending in the X-axis direction and a portion extending in the Y-axis direction at an interval from each other. The second electrode 25 has a portion extending in the X-axis direction and a portion extending in the Y-axis direction at an interval from each other. A portion of the first electrode 23 extending in the Y-axis direction and a portion of the second electrode 25 extending in the Y-axis direction are alternately arranged at intervals in the X-axis direction.

  The main material of the reflection plate 9, the elastic body 7, the vibration plate 5, and the support 3, which are constituent elements of the optical scanning device 1, is silicon. These components are desirably formed integrally by etching an SOI (Silicon On Insulator) wafer. By using an SOI wafer, the thickness of each component can be changed.

  For example, by increasing the thickness of the reflection plate 9 to reduce the distortion of the reflection plate 9, while reducing the thickness of the vibration plate 5, the displacement of the vibration plate 5 can be increased. By using a semiconductor process to form each component integrally, using a method of joining or bonding each component, compared with a method of combining each component, alignment accuracy is improved, and, It is easy to reduce the size and weight.

  The reflection surface 11 formed on the surface of the reflection plate 9 is desirably formed of a metal film having a high reflectance with respect to the wavelength of light to be scanned. For example, when the light to be scanned is infrared (IR), a gold (Au) film is preferable as the metal film. When a gold film is used, it is desirable to interpose an adhesion layer between the gold film and the silicon layer in order to improve the adhesion between the gold film and the silicon layer. As a film structure of the reflection surface 11 including the adhesion layer, for example, a chromium (Cr) film / nickel (Ni) film / gold (Au) film, or a titanium (Ti) film / platinum (Pt) film / gold ( A film structure such as an Au) film is suitable.

  When it is considered that the reflection surface 11 is very unlikely to be oxidized, the reflection surface 11 may be formed of an aluminum (Al) film. The case where the reflection surface 11 is less oxidized is, for example, the case where the optical scanning device 1 is vacuum-sealed. In some cases, the optical scanning device 1 is provided with measures such as filling with an inert gas such as nitrogen.

As a material of the piezoelectric bodies 17 and 27, lead zirconate titanate (PZT: Pb (Zr, Ti) O ₃ ), aluminum nitride (AlN), or sodium potassium niobate (KNN: (K, Na) A material such as NbO ₃ ) is used. Among these materials, lead zirconate titanate (PZT), which has a large piezoelectric constant and can provide a large driving force at a relatively low voltage, is preferable.

  The first piezoelectric element 13 and the second piezoelectric element 21 are formed by patterning each film to be the first piezoelectric element 13 or the second piezoelectric element 21 formed on the SOI wafer by wet etching or dry etching. Is done. Each film to be the first piezoelectric element 13 or the second piezoelectric element 21 is formed by a CVD (Chemical Vapor Deposition) method, a sputtering method, a CSD (Chemical Solution Deposition) method, or the like.

  Next, an example of a method for manufacturing the optical scanning device 1 will be described. Here, the first piezoelectric element and the second piezoelectric element are simultaneously formed on the SOI wafer. First, an SOI wafer 31 (see FIG. 9) is prepared. The SOI wafer 31 has a three-layer structure of a silicon layer 33, a silicon oxide film 35, and a silicon layer 37 in an initial state (see FIG. 9). The thickness of the silicon layer 37 is, for example, about 2 to 200 μm. The thickness of the silicon layer 33 is, for example, about 100 to 1000 μm.

  As shown in FIG. 9, a silicon oxide film 41 is formed on the front surface (silicon layer 37) of SOI wafer 31, and a silicon oxide film 39 is formed on the back surface (silicon layer 33) of SOI wafer 31. There are various methods for forming the silicon oxide films 41 and 39, but a thermal oxidation method that has good film quality and can be simultaneously formed on the front surface and the back surface of the SOI wafer 31 is preferable.

  Next, as shown in FIG. 10, a metal film 43 is formed on the surface of the silicon oxide film 41. The metal film 43 is a film serving as a lower electrode of the first piezoelectric element. Next, a piezoelectric film 45 is formed by sputtering or CSD so as to cover the metal film 43. The piezoelectric film 45 is a film that becomes a piezoelectric body of the first piezoelectric element and the second piezoelectric element. Next, a metal film 47 is formed so as to cover the piezoelectric film 45. The metal film 47 is a film serving as an upper electrode of the first piezoelectric element. The metal film 47 is a film that becomes the first electrode and the second electrode of the second piezoelectric element.

  As the metal films 43 and 47, a laminated film of a titanium (Ti) film and a platinum (Pt) film generally used for a piezoelectric element is desirable. Other stacked films may be used as long as they have sufficient conductivity as electrodes and can ensure good adhesion to a base or the like. Further, an oxide electrode film such as a strontium oxide (SrO) film, which is considered to have an effect of reducing polarization fatigue, may be interposed between the metal films 43 and 47 and the piezoelectric film 45.

  Next, as shown in FIG. 11, the metal film 47 is patterned. The metal film 47 is patterned so as to leave a region where the upper electrode of the first piezoelectric element is formed and a region where the first electrode and the second electrode of the second piezoelectric element are formed. For patterning the metal film 47, a photolithography technique using a resist film as a protective film is suitable. Reactive ion etching (RIE: Reactive Ion Etching) or wet etching using an etchant is used for the etching of the metal film 47.

In any of the etching processes, it is necessary to set conditions for obtaining a sufficient etching selectivity between the metal film 47 and the underlying film. For example, when a laminated film of a titanium film and a platinum film as the metal film 47 formed on the surface of the PZT film as the piezoelectric film 45 is patterned by reactive ion etching, chlorine (Cl ₂ ) / argon is used. (Ar) -based gases are preferred. After the patterning of the metal film 47, the resist film is removed. An oxygen (O ₂ ) ashing process or the like is used for removing the resist film.

  Next, as shown in FIG. 12, the piezoelectric film 45 is patterned by photolithography and etching. The piezoelectric film 45 is formed so as to leave a region where the piezoelectric body of the first piezoelectric element is formed and a region where the piezoelectric body of the second piezoelectric element is formed. As the etching process, a reactive ion etching process or a wet etching process is used.

In the etching process, it is necessary to set conditions for obtaining a sufficient etching selectivity between the piezoelectric film 45 and the underlying film. For example, when the PZT film as the piezoelectric film 45 formed on the surface of the laminated film of the titanium film and the platinum film as the metal film 43 is patterned by the reactive ion etching, Cl ₂ / BCl ₂ / CH _Four- system gases are preferred. After the patterning of the piezoelectric film 45, the resist film is removed by an oxygen (O ₂ ) ashing process or the like.

  Next, as shown in FIG. 13, the metal film 43 is patterned by photolithography and etching. The metal film 43 is patterned so as to leave a region where the lower electrode of the first piezoelectric element is formed and a region where the second piezoelectric element is formed. As the etching process, a reactive ion etching process or a wet etching process is used.

In the etching process, it is necessary to set conditions for obtaining a sufficient etching selectivity between the metal film 43 and the underlying film. When a laminated film of a titanium film and a platinum film as the metal film 43 formed on the surface of the silicon oxide film 41 is patterned by reactive ion etching, a chlorine (Cl ₂ ) / argon (Ar) system is used. Gas is preferred. After the patterning of the metal film 43, the resist film is removed by an oxygen (O ₂ ) ashing process or the like.

  Next, the reflection surface 11 is formed on the reflection plate 9, and thereafter, the reflection plate 9, the elastic body 7, the vibration plate 5, and the support 3 are formed.

As shown in FIG. 14, a metal film 49 serving as a reflection surface is patterned in a region where the reflection plate is formed. First, a metal film 49 is formed to cover the SOI wafer by, for example, a sputtering method or a vacuum evaporation method. At this time, an adhesion layer such as a chromium (Cr) film or a nickel (Ni) film may be interposed between the metal film 49 and the underlying film in order to achieve adhesion with the underlying film. Next, the metal film 49 is patterned by photolithography and etching. As the etching process, a reactive ion etching process or a wet etching process is used. After the patterning of the metal film 49, the resist film is removed by an oxygen (O ₂ ) ashing process or the like.

Next, the silicon oxide film 41 formed on the surface of the silicon layer 37 is patterned by photolithography and etching. As the etching process, a reactive ion etching process or a wet etching process is used. In the next step, a portion of the silicon oxide film 41 located in a region where the silicon layer 37 is etched is removed. When patterning the silicon oxide film 41 by reactive ion etching, a chlorine (Cl ₂ ) -based gas is preferable.

Next, as shown in FIG. 15, the silicon layer 37 is etched using the resist film for patterning the silicon oxide film 41 and the remaining silicon oxide film 41 as an etching mask (protective film). As the etching process, a deep etching (DRIE: Deep Reactive Ion Etching) process by the Bosch method which can perform an etching process with a high aspect ratio is preferable. The etching process is performed until the silicon oxide film 35 is exposed. After the etching process, the resist film is removed by an oxygen (O ₂ ) ashing process or the like.

Next, processing is performed on a portion on the rear surface side of the optical scanning device. The silicon oxide film 39 formed on the surface of the silicon layer 33 is patterned by photolithography and etching. As the etching process, a reactive ion etching process or a wet etching process is used. In the next step, a portion of the silicon oxide film 39 located in a region where the silicon layer 33 is etched is removed. When patterning the silicon oxide film 39 by reactive ion etching, a chlorine (Cl ₂ ) -based gas is preferable.

  Next, as shown in FIG. 16, the silicon layer 33 is etched using the resist film for patterning the silicon oxide film 39 and the remaining silicon oxide film 39 as an etching mask (protective film). As the etching process, a deep trench etching (DRIE) process by the Bosch method is preferable. The etching process is performed until the silicon oxide film 35 is exposed.

Subsequently, the silicon oxide film 35 is removed by performing an etching process on the exposed silicon oxide film 35. As an etching process of the silicon oxide film 35, a reactive ion etching process or a wet etching process is used. When patterning the silicon oxide film 39 by reactive ion etching, a chlorine (Cl ₂ ) -based gas is preferable. Thereafter, the portion of the SOI wafer 31 serving as a support is cut out to a desired size by dicing, whereby the optical scanning device is completed.

  Next, a driving method of the optical scanning device will be described. A voltage having a unipolar fixed period in the same direction as the polarization direction is applied to the first piezoelectric element 13 and the second piezoelectric element 21 in, for example, an opposite phase or a phase shift. Is done. As an example of such a voltage, a graph of a half wave of a sine wave is shown in FIG. The horizontal axis of the graph is the phase, and the vertical axis is the voltage. As shown in FIG. 17, the voltage applied to the first piezoelectric element 13 is shown by a solid line. The voltage applied to the second piezoelectric element 21 is shown by a dotted line. That is, the voltage applied to the first piezoelectric element 13 and the voltage applied to the second piezoelectric element 21 have the same polarity and are 180 degrees out of phase.

  When the piezoelectric body 17 of the first piezoelectric element 13 is, for example, in the polarized state shown in FIG. 4, the upper electrode 19 has a half-wave of a positive sine wave with the lower electrode 15 as a reference potential. A voltage will be applied. As shown in FIG. 4, when this voltage is applied, in the first piezoelectric element 13, the piezoelectric body 17 contracts in the X-axis direction. Due to the contraction of the piezoelectric body 17, the diaphragm 5 bends so as to be convex in the negative direction of the Z axis, and the diaphragm 5 bends in the positive direction of the Z axis with respect to the support 3. .

  On the other hand, when the piezoelectric body 27 of the second piezoelectric element 21 is in a polarized state shown in FIG. 6, for example, a half-wave of a positive sine wave is applied to the first electrode 23 with the second electrode 25 as a reference potential. Will be applied. As shown in FIG. 6, by applying this voltage, in the second piezoelectric element 21, the piezoelectric body 27 extends in the X-axis direction. Due to the extension of the piezoelectric body 27, the diaphragm 5 is bent so as to be convex in the positive direction of the Z axis, and the diaphragm 5 is bent relative to the support 3 in the negative direction of the Z axis. .

Thus, in the state where a voltage is applied to the first piezoelectric element 13, the vibrating plate 5, the support 3 will be bent toward the positive direction of the Z-axis (d ₃₁ mode). Meanwhile, in the state where a voltage is applied to the second piezoelectric element 21, the vibrating plate 5, the support 3 will be bent toward the negative direction of the Z-axis (d ₃₃ mode). By alternately applying the voltage applied to the first piezoelectric element 13 and the voltage applied to the second piezoelectric element 21, the diaphragm 5 can be bent in the positive and negative directions of the Z axis.

As an example of a state in which the diaphragm 5 is bent, a state in which the diaphragm 5a is bent from the support 3 in the positive direction of the Z-axis, and the diaphragm 5b is bent from the support 3 in the negative direction of the Z-axis. 18. In the vibrating plate 5a, the first piezoelectric element 13a, 13b is _{d 31} mode, a second piezoelectric element 21a, the 21b is a state where no voltage is applied. In the vibrating plate 5b, the second piezoelectric element 21c, 21d is _{d 33} mode, the first piezoelectric element 13c, the 13d is a state where no voltage is applied.

  In this case, the diaphragm 5a is bent so that the second end 5ab of the diaphragm 5a faces upward and the second end 5bb of the diaphragm 5b faces downward. The reflection plate 9 connected to the vibration plates 5a and 5b with the elastic members 7a and 7b interposed therebetween is inclined with respect to the support 3 (XY plane) by the bending of the vibration plates 5a and 5b.

Next, as another example of the state where the diaphragm 5 is bent, the diaphragm 5a is bent from the support 3 in the negative direction of the Z axis, and the diaphragm 5b is bent from the support 3 in the positive direction of the Z axis. FIG. 19 shows this state. The state of the diaphragms 5a and 5b shown in FIG. 19 corresponds to the state after a lapse of half the period of the sine wave from the state of the diaphragms 5a and 5b shown in FIG. In the vibrating plate 5a, the second piezoelectric element 21a, 21b is _{d 33} mode, the first piezoelectric element 13a, the 13b is a state where no voltage is applied. In the vibration plate 5b, the first piezoelectric elements 13c and 13d are in the d31 mode, and no voltage is applied to the second piezoelectric elements 21c and 21d.

  In this case, the diaphragm 5a is bent such that the second end 5ab of the diaphragm 5a faces downward and the second end 5bb of the diaphragm 5b faces upward. The reflection plate 9 connected to the vibration plates 5a and 5b with the elastic members 7a and 7b interposed therebetween is inclined with respect to the support 3 (XY plane) by the bending of the vibration plates 5a and 5b.

  As shown in FIG. 20, by periodically applying a voltage to the first piezoelectric element 13 and the second piezoelectric element 21 (see FIG. 17), the reflecting plate 9 is parallel to the Y axis and the X axis of the reflecting plate 9. The rotation is performed with the axis C2 (virtual line) passing through the center in the direction as the rotation axis. The light applied to the reflection surface 11 of the reflection plate 9 is reflected on the reflection surface 11. When the reflecting plate 9 on which the reflecting surface 11 is formed rotates, the reflected light is scanned with the rotation of the reflecting surface 11.

In the optical scanning device 1 described above, the first piezoelectric elements 13a and 13b (13c and 13d) and the second piezoelectric elements 21a and 21b (21c and 21d) are arranged on the diaphragm 5a (5b). The first piezoelectric element 13a, 13b (13c, 13d) and the second piezoelectric element 21a, and the 21b (21c, 21d), bent in opposite directions to each other _{(d 33 mode, d 31} mode). By alternately applying a unipolar voltage to the first piezoelectric elements 13a, 13b (13c, 13d) and the second piezoelectric elements 21a, 21b (21c, 21d), the diaphragm 5a (5b) is moved. The reflecting plate 9 can be rotated by bending the support 3 vertically in both directions (Z-axis direction).

  Further, by applying a unipolar voltage, polarization fatigue of the piezoelectric body can be reduced as compared with the case where a bipolar voltage is applied to bend the diaphragm vertically in both directions. This can contribute to a longer life.

  Further, the vibration plates 5a and 5b, the elastic bodies 7a and 7b, and the reflection plate 9 are arranged substantially line-symmetrically with respect to the axis C1, including the first piezoelectric elements 13a to 13d and the second piezoelectric elements 21a to 21d. (See FIG. 2). Accordingly, when driving the first piezoelectric elements 13a to 13d and the second piezoelectric elements 21a to 21d, the reflector 9 can be rotated without causing the elastic bodies 7a and 7b and the reflector 9 to be twisted.

Embodiment 2 FIG.
An optical scanning device according to the second embodiment will be described.

  As shown in FIGS. 21 and 22, in the optical scanning device 1, the diaphragm 5a, the elastic member 7a, the reflecting plate 9, the elastic member 7b, and the diaphragm 5b move with respect to an axis C1 (virtual line) parallel to the X axis. And are arranged almost line-symmetrically. The first piezoelectric elements 13a and 13b and the second piezoelectric element 21a are arranged on the diaphragm 5a. The second piezoelectric element 21a is arranged symmetrically with respect to the axis C1 so as to straddle the axis C1. The first piezoelectric element 13a and the first piezoelectric element 13b are arranged symmetrically with respect to the axis C1 so as to sandwich the second piezoelectric element 21a.

  The first piezoelectric elements 13c and 13d and the second piezoelectric element 21b are arranged on the vibration plate 5b. The second piezoelectric element 21b is arranged symmetrically with respect to the axis C1 so as to straddle the axis C1. The first piezoelectric element 13c and the first piezoelectric element 13d are arranged symmetrically with respect to the axis C1 so as to sandwich the second piezoelectric element 21b. Since the other configuration is the same as that of the optical scanning device 1 shown in FIGS. 1 and 2, the same members are denoted by the same reference numerals, and description thereof will not be repeated unless necessary.

  Next, a method for manufacturing the above-described optical scanning device 1 will be described. In the optical scanning device 1 described above, the patterns of the first piezoelectric element 13 and the second piezoelectric element 21 arranged on the diaphragm 5 are arranged on the diaphragm 5 of the optical scanning device 1 (see FIGS. 1 and 2). This is different from the patterns of the first piezoelectric element 13 and the second piezoelectric element 21 that are performed. For this reason, in the process shown in FIG. 11, it is possible to manufacture by substantially the same manufacturing process as the above-described manufacturing process only by changing the patterns of the first piezoelectric element 13 and the second piezoelectric element 21.

Next, a driving method of the optical scanning device will be described. The first piezoelectric element 13a, in the state where the 13b (13c, 13d) a voltage is applied to the diaphragm 5a (5b) will be bent toward the positive direction of the Z axis from the support 3 _{(d 31} mode). Meanwhile, in the state where a voltage is applied to the second piezoelectric element 21a (21b), the vibration plate 5a (5b) from the support 3 will be bent toward the negative direction of the Z-axis _{(d 33} mode) . By alternately applying the voltage applied to the first piezoelectric element 13 and the voltage applied to the second piezoelectric element 21, the diaphragm 5 can be bent in the positive and negative directions of the Z axis.

  In the optical scanning device 1 described above, the distortion of the reflection plate 9 and the like can be reduced with respect to the bending of the diaphragm 5. This will be described in comparison with the optical scanning device according to the comparative example. For convenience of description, the same members as those of the optical scanning device 1 according to the embodiment will be described with the same reference numerals.

  As shown in FIGS. 23 and 24, in the optical scanning device 1 according to the comparative example, the first piezoelectric element 13a and the second piezoelectric element 21a are arranged on the vibration plate 5a asymmetrically with respect to the axis C1. . Further, the first piezoelectric element 13b and the second piezoelectric element 21b are arranged on the diaphragm 5b asymmetrically with respect to the axis C1.

In a state where a voltage is applied to the first piezoelectric element 13a (13b), the vibration plate 5a (5b) from the support 3 will be bent toward the positive direction of the Z-axis _{(d 31} mode). Meanwhile, in the state where a voltage is applied to the second piezoelectric element 21a (21b), the vibration plate 5a (5b) from the support 3 will be bent toward the negative direction of the Z-axis _{(d 33} mode) . By alternately applying the voltage applied to the first piezoelectric element 13 and the voltage applied to the second piezoelectric element 21, the diaphragm 5 bends in the positive and negative directions of the Z axis.

  Since the first piezoelectric element 13a (13b) and the second piezoelectric element 21a (21b) are arranged asymmetrically with respect to the axis C1, the diaphragm 5 has a positive Y-axis direction with respect to the axis C1 and Y The portion of the diaphragm located on either side of the negative axis direction is about to bend. Therefore, the elastic body 7 and the reflection plate 9 are twisted. When the reflecting plate 9 is twisted, the reflecting surface 11 may be distorted, so that desired optical scanning may not be performed.

  In the optical scanning device 1 according to the second embodiment with respect to the comparative example, the first piezoelectric element 13a, the first piezoelectric element 13b, and the second piezoelectric element 21a are arranged on the diaphragm 5a symmetrically with respect to the axis C1. Have been. Further, the first piezoelectric element 13c, the first piezoelectric element 13d, and the second piezoelectric element 21b are arranged on the vibration plate 5b symmetrically with respect to the axis C1. For this reason, twisting of the elastic body 7 and the reflecting plate 9 due to the bending of the vibration plates 5a and 5b is suppressed, and the distortion of the reflecting surface 11 can be reduced.

  Note that the optical scanning devices described in the embodiments can be variously combined as needed.

  The embodiment disclosed this time is an example, and the present invention is not limited to this. The present invention is defined by the terms of the claims, rather than the range described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  INDUSTRIAL APPLICABILITY The present invention is effectively used for an optical scanning device having a diaphragm.

  Reference Signs List 1 optical scanning device, 3 support, 5 diaphragm, 5a diaphragm, 5aa first end, 5ab second end, 5b diaphragm, 5ba first end, 5bb second end, 7 elastic body, 7a Elastic body, 7b Elastic body, 9 reflector, 11 reflection surface, 13 first piezoelectric element, 13a, 13b first piezoelectric element, 13c, 13d first piezoelectric element, 15 lower electrode, 17 piezoelectric body, 19 upper electrode, 21 2nd piezoelectric element, 21a, 21b 2nd piezoelectric element, 21c, 21d 2nd piezoelectric element, 23 1st electrode, 25 2nd electrode, 27 piezoelectric, 31 SOI wafer, 33 silicon layer, 35 silicon oxide film, 37 silicon Layers, 39, 41 silicon oxide film, 43 metal film, 45 piezoelectric film, 47, 49 metal film, C1, C2 axis.

Claims (8)

A support,
A diaphragm having a first end and a second end located at a distance, wherein the first end is supported by the support;
A first piezoelectric element and a second piezoelectric element disposed on the diaphragm,
A reflector having a reflective surface that reflects light and is connected to the second end of the diaphragm with an elastic body interposed therebetween;
The first piezoelectric element is driven in a first mode by applying a unipolar first voltage,
The second piezoelectric element is driven in a second mode different from the first mode by applying a unipolar second voltage,
The optical scanning device, wherein the diaphragm is bent and the reflector is tilted by driving the first piezoelectric element or the second piezoelectric element.   2. The optical scanning device according to claim 1, wherein the first piezoelectric element and the second piezoelectric element are driven with a time lag by applying the first voltage and the second voltage with a phase shifted from each other. 3.   The optical scanning device according to claim 1, wherein the diaphragm, the first piezoelectric element, the second piezoelectric element, and the elastic body are arranged symmetrically with respect to a virtual line extending in a first direction. Each of the first piezoelectric element and the second piezoelectric element extends in a second direction that intersects the first direction,
The optical scanning device according to claim 3, wherein the first piezoelectric element and the second piezoelectric element are arranged at an interval in the first direction. The first piezoelectric element is disposed so as to straddle the virtual line,
The optical scanning device according to claim 3, wherein the second piezoelectric element is arranged symmetrically with respect to the virtual line with the first piezoelectric element interposed therebetween.   The optical scanning device according to claim 1, wherein the support, the vibration plate, the elastic body, and the reflection plate are formed from a silicon layer. It has a first end and a second end located at a distance, the first end is supported by a support, and the second end is connected to a reflector via an elastic body. A diaphragm,
A method for driving an optical scanning device having a first piezoelectric element and a second piezoelectric element disposed on the diaphragm,
Driving the first piezoelectric element in a first mode by applying a unipolar first voltage to the first piezoelectric element;
By applying a unipolar second voltage to the second piezoelectric element, the second piezoelectric element is driven in a second mode different from the first mode,
By driving the first piezoelectric element and the second piezoelectric element, the diaphragm is bent and the reflector is tilted,
A method for driving an optical scanning device, wherein the first voltage and the second voltage are applied with their phases shifted from each other to thereby drive the first piezoelectric element and the second piezoelectric element with a time shift. The driving method of the optical scanning device according to claim 7, wherein the first voltage and the second voltage each have a periodic waveform.

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