JP6960889B2 - Optical scanning device and its driving method - Google Patents

Description

The present invention relates to an optical scanning device and a method for driving the optical scanning device, and more particularly to an optical scanning device provided with a diaphragm and a method for driving the optical scanning device.

Conventionally, an optical scanning device in which a reflector is connected to a diaphragm with an elastic body interposed therebetween is known. In this optical scanning device, by vibrating the diaphragm, the reflector rotates, and the light emitted to the reflector is scanned. In order to vibrate the diaphragm, a piezoelectric element is arranged on the diaphragm. In the piezoelectric element, the piezoelectric body is sandwiched between one electrode and the other electrode.

Patent Document 1 and Patent Document 2 are 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 AC voltage having a 180 ° phase difference to a piezoelectric element arranged on a diaphragm. Patent Document 2 proposes an optical scanning device that rotates a reflector by applying a unipolar constant frequency voltage to a piezoelectric element arranged on the diaphragm.

It is known that when a bipolar voltage is applied to a piezoelectric element, polarization fatigue occurs and the characteristics deteriorate, so it is not suitable for applications in optical scanning devices that require a long life (). Non-patent document 1). On the other hand, it is known that when a unipolar voltage is applied to the piezoelectric element, the polarization fatigue of the piezoelectric element is significantly reduced as compared with the case where a bipolar voltage is applied (Non-Patent Document 2). ..

Japanese Unexamined Patent Publication No. 2005-128147 Japanese Unexamined Patent Publication No. 2014-103360

Lou, X. J. “Polarization fatigue in recently 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 recently lead zirconate titanate thin films: An experimental comparison study.” Journal of Applied Physics 108.3 (2010): 034104.

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

The present invention has been made to solve the above problems, and one object of the present invention is to provide an optical scanning device capable of vibrating a diaphragm in both vertical and vertical directions by applying a unipolar voltage. And another purpose is to provide a method of driving such an optical scanning device.

The optical scanning device according to the present invention includes a support, a diaphragm, a first piezoelectric element, a second piezoelectric element, and a reflector. The diaphragm has a first end portion and a second end portion located at a distance from each other, and the first end portion 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 with an elastic body interposed therebetween, and has a reflecting 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. The first mode is d ₃₁ mode and the second mode is d ₃₃ mode. By applying the first voltage and the second voltage out of phase with each other, the first piezoelectric element and the second piezoelectric element are driven at different times, so that the diaphragm is bent and the reflector is tilted. ..

The driving method of the optical scanning device according to the present invention has a first end portion and a second end portion facing each other at a distance, the first end portion is supported by a support, and the second end portion is an elastic body. The diaphragm connected to the reflector with the interposition, and the first piezoelectric element driven in the first mode and the second piezoelectric element driven in the second mode different from the first mode arranged on the diaphragm This is a method of driving an optical scanning device. By applying a unipolar first voltage to the first piezoelectric element, the first piezoelectric element is driven in the first mode. 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. The first mode is d ₃₁ mode and the second mode is d ₃₃ 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 out of phase with each other, the first piezoelectric element and the second piezoelectric element are driven with a time lag.

According to the optical scanning apparatus according to the present invention, a first piezoelectric element driven in the first mode and a second piezoelectric element driven in a 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 apparatus 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 reflector is tilted by applying the first voltage and the second voltage out of phase and bending the diaphragm. As a result, the diaphragm of the optical scanning device can be vibrated in both directions to tilt the reflector.

It is a perspective view of the optical scanning apparatus which concerns on Embodiment 1 of this invention. It is a top view of the optical scanning apparatus in the same embodiment. In the same embodiment, it is a partial cross-sectional view of the first piezoelectric element. It is a partial cross-sectional view for demonstrating an example of the drive mechanism of the 1st piezoelectric element in the same embodiment. It is a partial cross-sectional view of the 2nd piezoelectric element in the same embodiment. It is a partial cross-sectional view for demonstrating an example of the drive mechanism of the 2nd piezoelectric element in the same embodiment. It is a perspective view which shows an example of the arrangement pattern of the electrode of the 2nd piezoelectric element in the same embodiment. It is a top view which shows an example of the arrangement pattern of the electrode of the 2nd piezoelectric element in the same embodiment. It is sectional drawing which shows one step of the manufacturing method of the optical scanning apparatus in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 9 in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 10 in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 11 in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 12 in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 13 in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 14 in the same embodiment. It is sectional drawing which shows the process performed after the process shown in FIG. 15 in the same embodiment. It is a graph which shows an example of the waveform of the unipolar voltage applied to the 1st piezoelectric element and the 2nd piezoelectric element in the same embodiment. FIG. 5 is a cross-sectional view schematically showing an example of a bending mode of a diaphragm in the same embodiment. FIG. 5 is a cross-sectional view schematically showing another example of the bending mode of the diaphragm in the same embodiment. In the same embodiment, it is a perspective view for demonstrating the inclination of a reflector with bending of a diaphragm. It is a perspective view of the optical scanning apparatus which concerns on Embodiment 2 of this invention. It is a top view of the optical scanning apparatus in the same embodiment. It is a perspective view of the optical scanning apparatus which concerns on a comparative example. It is a top view of the optical scanning apparatus which concerns on a comparative example.

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

The optical scanning device 1 includes a support 3, a diaphragm 5a, a diaphragm 5b, and a reflector 9. The diaphragm 5a has a first end portion 5aa and a second end portion 5ab that face each other with a distance in the X-axis direction. The first end portion 5aa is connected to the support 3. The second end portion 5ab is connected to the reflector 9 via the elastic body 7a. The elastic body 7a is connected to the central portion in the Y-axis direction of the second end portion 5ab of the diaphragm 5a.

The diaphragm 5b has a first end portion 5ba and a second end portion 5bb that face each other with a distance in the X-axis direction. The first end portion 5ba is connected to the support 3. The second end portion 5bb is connected to the reflector 9 via the elastic body 7b. The elastic body 7b is connected to the central portion in the Y-axis direction of the second end portion 5bb of the diaphragm 5b. The reflecting plate 9 is provided with a reflecting 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 side of the first end portion 5aa to the side of the second end portion 5ab. The first piezoelectric elements 13c and 13d and the second piezoelectric elements 21c and 21d are arranged on the diaphragm 5b. 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 from the side of the first end portion 5ba to the side of the second end portion 5bb.

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

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 the lower electrode 15, the piezoelectric body 17, and the upper electrode 19. The lower electrode 15, the piezoelectric body 17, and the upper electrode 19 are laminated on the diaphragm 5 (5a, 5b).

The piezoelectric body 17 is polarized in the positive or negative direction in the Z-axis direction by polarization treatment or by applying a unipolar voltage that exceeds the coercive electric field. By applying a unipolar voltage 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 in the positive direction of the Z-axis with respect to the support 3. become. The bending of the first piezoelectric element 13 is referred to _{as the d 31 mode as the first mode.}

As shown in FIG. 4, for example, when the lower electrode 15 side of the piezoelectric body 17 is polarized so as to be positive and the upper electrode 19 side is negative, the lower portion is placed between 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 vibrating plate 5 is shown by an arrow. In addition, it bends so as to be convex in the negative direction of the Z axis.

When the direction of polarization of the piezoelectric body 17 is opposite to the direction shown in FIG. 4, the voltage applied to the lower electrode 15 between the lower electrode 15 and the upper electrode 19 is relative to the voltage applied to the lower electrode 15. By applying a voltage so that the voltage applied to the upper electrode 19 becomes low, the vibrating plate 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 is bent 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 elements 21 (21a to 21d) are formed by the first electrode 23, the second electrode 25, and the 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 intervals. The piezoelectric body 27 is formed on the diaphragm 5.

The piezoelectric body 27 is polarized in the positive or negative direction in the X-axis direction by polarization treatment or by applying a unipolar voltage that exceeds 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. As the piezoelectric body 27 extends in the X-axis direction, the diaphragm 5 bends so as to be convex in the positive direction of the Z-axis. The second piezoelectric element 21 will be driven in _{the d 33 mode as the second mode.}

As shown in FIG. 6, for example, when the piezoelectric body 27 is polarized so that the central portion in the X-axis direction is positive and the end portion in the X-axis direction is negative, the first electrode 23 and the second electrode 23 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 is bent so as to be convex in the positive direction of the Z-axis as shown by the arrow, and the diaphragm 5 is bent in the negative direction of the Z-axis. become.

When the direction of polarization of the piezoelectric body 27 is opposite to the direction shown in FIG. 6, the voltage applied to the second electrode 25 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 low, 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 at intervals of, for example, about 1 μm to 10 μm. By applying a voltage between the first electrode 23 and the second electrode 25, it is possible to apply a voltage in the X-axis direction of the piezoelectric body 27. As shown in FIGS. 7 and 8, such an electrode structure of the first electrode 23 and the second electrode 25 is typically referred to as a comb field type 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 intervals 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 intervals from each other. The portion of the first electrode 23 extending in the Y-axis direction and the 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 reflector 9, the elastic body 7, the diaphragm 5, and the support 3 which are the constituent elements of the optical scanning device 1 is silicon. It is desirable that these components are integrally formed by etching an SOI (Silicon On Insulator) wafer. By using the SOI wafer, the thickness of each component can be changed.

For example, by increasing the thickness of the reflector 9 to reduce the distortion of the reflector 9, and reducing the thickness of the diaphragm 5, it is possible to increase the displacement of the diaphragm 5. By forming each component integrally using a semiconductor process, alignment accuracy is improved and alignment accuracy is improved as compared with a method of combining each component by using a method of joining or bonding each component. It also facilitates miniaturization and weight reduction.

It is desirable that the reflecting surface 11 formed on the surface of the reflecting plate 9 is formed of a metal film having a high reflectance with respect to the wavelength of the scanned light. For example, when the light to be scanned is infrared (IR), a gold (Au) film is suitable 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. The film structure of the reflective surface 11 including the adhesion layer includes, for example, chromium (Cr) film) / nickel (Ni) film / gold (Au) film, or titanium (Ti) film / platinum (Pt) film / gold ( Au) Membrane-like membrane structures are suitable.

Further, when it is considered that the reflective surface 11 is very unlikely to be oxidized, the reflective surface 11 may be formed of an aluminum (Al) film. When the reflective surface 11 is less oxidized, for example, the optical scanning device 1 may be vacuum-sealed. In addition, the optical scanning device 1 may be filled with an inert gas such as nitrogen.

The materials of the piezoelectric bodies 17 and 27 include lead zirconate titanate (PZT: Pb (Zr, Ti) O ₃ ) having a piezoelectric effect, aluminum nitride (AlN), or potassium niobate (KNN: (K, K,). Materials such as Na) NbO ₃ ) are used. Among these materials, lead zirconate titanate (PZT), which is said to have a large piezoelectric constant and can obtain 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 a wet etching process or a dry etching process. Will be 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 the manufacturing method of the optical scanning apparatus 1 will be described. Here, the first piezoelectric element and the second piezoelectric element are simultaneously formed on the SOI wafer. First, the SOI wafer 31 (see FIG. 9) is prepared. In the initial state, the SOI wafer 31 has a three-layer structure of a silicon layer 33, a silicon oxide film 35, and a silicon layer 37 (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 the SOI wafer 31, and a silicon oxide film 39 is formed on the back surface (silicon layer 33) of the SOI wafer 31. There are various methods for forming the silicon oxide films 41 and 39, but the thermal oxidation method, which has good film quality and can be formed on the front surface and the back surface of the SOI wafer 31 at the same time, 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 that serves as a lower electrode of the first piezoelectric element. Next, the piezoelectric film 45 is formed by a sputtering method or a CSD method so as to cover the metal film 43. The piezoelectric film 45 is a film that serves as a piezoelectric material for the first piezoelectric element and the second piezoelectric element. Next, the metal film 47 is formed so as to cover the piezoelectric film 45. The metal film 47 is a film that serves as an upper electrode of the first piezoelectric element. The metal film 47 is a film that serves as a first electrode and a 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 piezoelectric elements is desirable. Another laminated film may be applied as long as it has sufficient conductivity as an electrode and can ensure good adhesion to a substrate or the like. Further, an oxide electrode film such as a strontium oxide (SrO) film, which is said 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. A photolithography technique using a resist film as a protective film is suitable for patterning the metal film 47. Reactive ion etching (RIE) or wet etching using an etchant is used for the etching treatment of the metal film 47.

In any of the etching treatments, 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 a metal film 47 formed on the surface of a PZT film as a piezoelectric film 45 is patterned by a reactive ion etching process, chlorine (Cl ₂ ) / argon is used. (Ar) -based gas is suitable. After patterning the metal film 47, the resist film is removed. _{Oxygen (O 2} ) ashing treatment or the like is used to remove the resist film.

Next, as shown in FIG. 12, the piezoelectric film 45 is patterned by a photolithography technique and an etching process. 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 selection ratio 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 as the metal film 43 and the platinum film is patterned by the reactive ion etching treatment, Cl ₂ / BCl ₂ / CH _{Type 4} gas is suitable. After patterning the piezoelectric film 45, the _{resist film is removed by oxygen (O 2} ) ashing treatment or the like.

Next, as shown in FIG. 13, the metal film 43 is patterned by the photolithography technique and the etching process. 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 selection ratio between the metal film 43 and the underlying film. When patterning a laminated film of a titanium film and a platinum film as a metal film 43 formed on the surface of a silicon oxide film 41 by reactive ion etching treatment, a chlorine (Cl ₂ ) / argon (Ar) system is used. Gas is suitable. After patterning the metal film 43, the _{resist film is removed by an oxygen (O 2} ) ashing treatment or the like.

Next, the reflective surface 11 is formed on the reflector 9, and then the reflector 9, the elastic body 7, the diaphragm 5, and the support 3 are formed.

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

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

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, it is desirable to perform deep reactive etching (DRIE) processing by the Bosch method, which enables etching processing with a high aspect ratio. The etching process is performed until the silicon oxide film 35 is exposed. After the etching treatment, the _{resist film is removed by an oxygen (O 2} ) ashing treatment or the like.

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

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 treatment, deep reactive etching (DRIE) treatment by the Bosch method is desirable. The etching process is performed until the silicon oxide film 35 is exposed.

Subsequently, the exposed silicon oxide film 35 is subjected to an etching treatment to remove the silicon oxide film 35. As the etching treatment of the silicon oxide film 35, a reactive ion etching treatment or a wet etching treatment is used. When the silicon oxide film 39 is patterned by reactive ion etching treatment, a chlorine (Cl ₂ ) -based gas is suitable. Then, the optical scanning device is completed by cutting out a portion of the SOI wafer 31 to be a support to a desired size by dicing.

Next, a method of driving the optical scanning device will be described. A voltage having a unipolar constant 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, in opposite phases or out of phase. Will be done. As an example of such a voltage, a half-wave graph 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 out of phase by 180 degrees.

When the piezoelectric body 17 of the first piezoelectric element 13 is in the polarized state shown in FIG. 4, for example, the upper electrode 19 has a half-wave waveform 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, the piezoelectric body 17 contracts in the X-axis direction in the first piezoelectric element 13. As the piezoelectric body 17 contracts, 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 the 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 the reference potential. A voltage having the waveform of is applied. As shown in FIG. 6, when this voltage is applied, the piezoelectric body 27 extends in the X-axis direction in the second piezoelectric element 21. As the piezoelectric body 27 extends, the diaphragm 5 bends so as to be convex in the positive direction of the Z axis, and the diaphragm 5 bends in the negative direction of the Z axis with respect to the support 3. ..

In this way, when the voltage is applied to the first piezoelectric element 13, the diaphragm 5 bends from the support 3 in the positive direction of the Z axis (d ₃₁ mode). On the other hand, when a voltage is applied to the second piezoelectric element 21, the diaphragm 5 bends from the support 3 in 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 direction and the negative direction of the Z axis.

As an example of the state in which the diaphragm 5 is bent, the state in which the diaphragm 5a is bent from the support 3 to the positive direction side of the Z axis and the diaphragm 5b is bent from the support 3 to the negative direction side of the Z axis is shown in FIG. 18 is shown. In the diaphragm 5a, the first piezoelectric elements 13a and 13b are in the d ₃₁ mode, and no voltage is applied to the second piezoelectric elements 21a and 21b. In the diaphragm 5b, the second piezoelectric elements 21c and 21d are in the d ₃₃ mode, and no voltage is applied to the first piezoelectric elements 13c and 13d.

In this case, the second end portion 5ab of the diaphragm 5a is bent upward, and the second end portion 5bb of the diaphragm 5b is bent downward. The reflector 9 connected to the diaphragms 5a and 5b with the elastic bodies 7a and 7b interposed therebetween is tilted with respect to the support 3 (XY plane) by bending the diaphragms 5a and 5b.

Next, as another example of the state in which the diaphragm 5 is bent, the diaphragm 5a is bent from the support 3 to the negative side of the Z axis, and the diaphragm 5b is bent from the support 3 to the positive side of the Z axis. The state is shown in FIG. The states of the diaphragms 5a and 5b shown in FIG. 19 correspond to the states after half the time of the period of the sine wave has elapsed from the states of the diaphragms 5a and 5b shown in FIG. In the diaphragm 5a, the second piezoelectric elements 21a and 21b are in the d ₃₃ mode, and no voltage is applied to the first piezoelectric elements 13a and 13b. In the diaphragm 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 second end portion 5ab of the diaphragm 5a is bent downward, and the second end portion 5bb of the diaphragm 5b is bent upward. The reflector 9 connected to the diaphragms 5a and 5b with the elastic bodies 7a and 7b interposed therebetween is tilted with respect to the support 3 (XY plane) by bending the diaphragms 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 reflector 9 is parallel to the Y axis and the X axis of the reflector 9. The axis C2 (virtual line) passing through the central portion of the direction is used as the rotation axis for rotation. The light applied to the reflecting surface 11 of the reflecting plate 9 is reflected by the reflecting surface 11. The reflecting plate 9 on which the reflecting surface 11 is formed rotates, so that the reflected light is scanned as the reflecting surface 11 rotates.

In the optical scanning device 1 described above, the first piezoelectric elements 13a, 13b (13c, 13d) and the second piezoelectric elements 21a, 21b (21c, 21d) are arranged on the diaphragm 5a (5b). The first piezoelectric elements 13a, 13b (13c, 13d) and the second piezoelectric elements 21a, 21b (21c, 21d) are bent in opposite directions (d ₃₃ mode, d ₃₁ mode). By alternately applying unipolar voltages to the first piezoelectric elements 13a and 13b (13c, 13d) and the second piezoelectric elements 21a and 21b (21c, 21d), the diaphragm 5a (5b) is formed. The diaphragm 9 can be rotated by bending the support 3 in both vertical and vertical directions (Z-axis direction).

Further, by applying a unipolar voltage, it is possible to reduce the polarization fatigue of the piezoelectric body as compared with the case where the diaphragm is bent in both the upper and lower directions by applying a bipolar voltage. It can contribute to extending the service life.

Further, the diaphragms 5a and 5b, the elastic bodies 7a and 7b, and the reflector 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). As a result, 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 twisting of the elastic bodies 7a, 7b, the reflector 9, and the like.

Embodiment 2.
The optical scanning apparatus 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 body 7a, the reflector 9, the elastic body 7b, and the diaphragm 5b are arranged with respect to the axis C1 (virtual line) parallel to the X axis. It is 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 line-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 line-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 diaphragm 5b. The second piezoelectric element 21b is arranged line-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 line-symmetrically with respect to the axis C1 so as to sandwich the second piezoelectric element 21b. Since the other configurations are the same as those of the optical scanning apparatus 1 shown in FIGS. 1 and 2, the same members are designated by the same reference numerals, and the description thereof will not be repeated unless necessary.

Next, the manufacturing method of the optical scanning apparatus 1 described above will be described. In the above-mentioned optical scanning device 1, the patterns of the first piezoelectric element 13 and the second piezoelectric element 21 arranged on the vibrating plate 5 are arranged on the vibrating plate 5 of the above-mentioned optical scanning device 1 (see FIGS. 1 and 2). It is different from the pattern of the first piezoelectric element 13 and the second piezoelectric element 21. Therefore, in the process shown in FIG. 11, only by changing the patterns of the first piezoelectric element 13 and the second piezoelectric element 21, the production can be performed by substantially the same manufacturing process as the above-mentioned manufacturing process.

Next, a method of driving the optical scanning device will be described. When a voltage is applied to the first piezoelectric elements 13a and 13b (13c, 13d), the diaphragm 5a (5b) bends from the support 3 in the positive direction of the Z axis (d _31). mode). On the other hand, when a voltage is applied to the second piezoelectric element 21a (21b), the diaphragm 5a (5b) bends from the support 3 in 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 direction and the negative direction of the Z axis.

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

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

When a voltage is applied to the first piezoelectric element 13a (13b), the diaphragm 5a (5b) bends from the support 3 in the positive direction of the Z axis (d ₃₁ mode). On the other hand, when a voltage is applied to the second piezoelectric element 21a (21b), the diaphragm 5a (5b) bends from the support 3 in 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 direction and the negative direction 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 the Y-axis positive direction side with respect to the axis C1 and Y. The portion of the diaphragm located on either side of the negative axis tends to bend. Therefore, the elastic body 7 and the reflector 9 are twisted. Twisting of the reflector 9 may distort the reflecting surface 11 and prevent desired optical scanning.

In the optical scanning apparatus 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 line-symmetrically with respect to the axis C1 on the diaphragm 5a. Has been done. Further, on the diaphragm 5b, the first piezoelectric element 13c, the first piezoelectric element 13d, and the second piezoelectric element 21b are arranged line-symmetrically with respect to the axis C1. Therefore, it is possible to prevent the elastic body 7 and the reflector 9 from being twisted with respect to the bending of the diaphragms 5a and 5b, and to reduce the distortion of the reflecting surface 11.

The optical scanning devices described in each embodiment can be combined in various ways as needed.

The embodiments disclosed this time are examples and are not limited thereto. The present invention is shown by the scope of claims, not the scope described above, and is intended to include all modifications in the sense and scope equivalent to the scope of claims.

The present invention is effectively used in an optical scanning device provided with a diaphragm.

1 Optical scanning device, 3 Support, 5 Vibrating plate, 5a Vibrating plate, 5aa 1st end, 5ab 2nd end, 5b Vibrating plate, 5ba 1st end, 5bb 2nd end, 7 Elastic body, 7a Elastic body, 7b Elastic body, 9 Reflector, 11 Reflective surface, 13 First piezoelectric element, 13a, 13b First piezoelectric element, 13c, 13d First piezoelectric element, 15 Lower electrode, 17 Piezoelectric, 19 Upper electrode, 21 2nd piezo element, 21a, 21b 2nd piezo element, 21c, 21d 2nd piezo element, 23 1st electrode, 25 2nd electrode, 27 piezoelectric body, 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 axes.

Claims (7)

With the support
A diaphragm having a first end portion and a second end portion located at a distance from each other and the first end portion being supported by the support body.
The first piezoelectric element and the second piezoelectric element arranged on the diaphragm,
It is provided with a reflector which is connected to the second end of the diaphragm with an elastic body interposed therebetween and has a reflecting surface for reflecting 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.
The first mode is d ₃₁ mode.
The second mode is the d ₃₃ mode.
By applying the first voltage and the second voltage out of phase with each other, the first piezoelectric element and the second piezoelectric element are driven with different times, so that the vibrating plate is bent. An optical scanning device in which the reflector is tilted. The optical scanning apparatus according to claim 1, wherein the diaphragm, the first piezoelectric element, the second piezoelectric element, and the elastic body are arranged line-symmetrically with respect to a virtual line extending in the first direction. Each of the first piezoelectric element and the second piezoelectric element extends in a second direction intersecting the first direction.
The optical scanning apparatus according to claim 2 , wherein the first piezoelectric element and the second piezoelectric element are arranged at intervals in the first direction. The second piezoelectric element is arranged so as to straddle the virtual line.
The optical scanning apparatus according to claim 2 , wherein the first piezoelectric element is arranged line-symmetrically with respect to the virtual line with the second piezoelectric element interposed therebetween. The optical scanning apparatus according to claim 1, wherein the support, the diaphragm, the elastic body, and the reflector are formed of 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 with an elastic body interposed therebetween. With the diaphragm,
A method for driving an optical scanning device having a first piezoelectric element and a second piezoelectric element arranged on the diaphragm.
By applying a unipolar first voltage to the first piezoelectric element, the first piezoelectric element is driven in the first mode.
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.
The first mode is d ₃₁ mode.
The second mode is the d ₃₃ 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, in which the first piezoelectric element and the second piezoelectric element are driven by shifting the phases of the first voltage and the second voltage. The method for driving an optical scanning apparatus according to claim 6 , wherein the first voltage and the second voltage each have a periodic waveform.

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