Optical reflection element

Abstract

This optical reflection element comprises a movable part in which a mirror (11a) is formed, and a drive part that drives the movable part. The mirror (11a) is provided with a metal reflective film (130), a first dielectric film (141), and a second dielectric film (142) having a higher refractive index than the first dielectric film (141). The drive part is provided with a piezoelectric body (110), a first protective film (121) made of the same material as the first dielectric film (141), and a second protective film (122) made of the same material as the second dielectric film (142). The total value (T1 + T2) of the thicknesses of the first dielectric film (141) and the second dielectric film (142) is included in the range of the total thickness of the first dielectric film (141) and the second dielectric film (142) in which the variation in the reflectance of the mirror (11a) is smaller than the variation in the reflectance of the metal reflective film (130) alone.

Description

Optical Reflective Elements

[0001] The present invention relates to an optical reflecting element that drives a movable part on which a mirror for reflecting light is formed.

[0002] In recent years, optical reflecting elements that rotate a movable part having a mirror using MEMS (Micro Electro Mechanical System) technology have been developed. This type of optical reflecting element is mounted on image display devices such as head-up displays and head-mounted displays. In addition, this type of optical reflecting element can also be used in laser radars that detect objects using laser light.

[0003] In the following Patent Document 1, Ag film, Al ２ O ３ Film and TiO ２ In a reflective mirror having a multilayer film formed thereon, Al ２ O ３ Film and TiO ２ It is described that the films are each formed at λ / 4. Patent Document 2 listed below describes an optical scanning device having a mirror that reflects laser light and an actuator that oscillates the mirror to scan the laser light. In this device, a low-refractive-index film with a film thickness of 0.51×λ / 4 is laminated on a metal film, and a high-refractive-index film with a film thickness of 0.82×λ / 4 is laminated on the low-refractive-index film.

[0004] JP 2003-4919 A ​​Japanese Patent No. 6236987 A

[0005] In the optical reflecting element described above, for example, a piezoelectric body may be provided as a driving unit for driving the movable part. In this case, a protective film is formed on the upper side of the piezoelectric body to protect the upper surface of the piezoelectric body. Furthermore, as described in Patent Documents 1 and 2, a mirror consisting of a metal reflective film and multiple dielectric films stacked on its upper surface may be formed on the movable part. In this case, when forming the optical reflecting element, various films are formed on the metal reflective film and the piezoelectric body. Forming these films separately would result in a problem of complicated film formation processes. On the other hand, it is preferable that the mirror formed on the movable part has as uniform a reflectivity as possible in the wavelength band of the incident light.

[0006] In view of these problems, the present invention aims to provide an optical reflecting element that can suppress fluctuations in the reflectivity of a mirror on a movable part in the wavelength band of light incident on the mirror, while allowing the formation of multiple dielectric films that constitute the mirror and a protective film for a piezoelectric body that serves as a driving source using a simple process.

[0007] A main aspect of the present invention relates to an optical reflecting element in which a movable part having a mirror formed thereon is driven by a driving unit. In the optical reflecting element according to this aspect, the mirror includes a metal reflective film, a first dielectric film formed on the upper surface of the metal reflective film, and a second dielectric film formed on the upper surface of the first dielectric film and having a refractive index higher than that of the first dielectric film. The driving unit includes a piezoelectric body, a first protective film formed on the upper side of the piezoelectric body and made of the same material as the first dielectric film, and a second protective film formed on the upper side of the first protective film and made of the same material as the second dielectric film. Here, the sum of the thicknesses of the first and second dielectric films falls within a range in which the variation in reflectivity of the mirror over a wavelength band of light incident on the mirror is smaller than the variation in reflectivity of the metal reflective film alone over the wavelength band.

[0008] As a result of extensive research, the inventors have found that, if the total thickness of the first dielectric film and the second dielectric film is within a predetermined range, the fluctuation in the reflectance of the mirror in the wavelength band of the incident light can be suppressed more than the fluctuation in the reflectance of the metal reflective film alone. Based on this finding, by adjusting the thicknesses of the first dielectric film and the second dielectric film so that the total thickness of the first dielectric film and the second dielectric film is within this range, the fluctuation in the reflectance of the mirror in the wavelength band of the incident light can be effectively suppressed.

[0009] Furthermore, by forming the first dielectric film and the first protective film from the same material that can provide the required characteristics for each, these films can be formed in a common process, and by forming the second dielectric film and the second protective film from the same material that can provide the required characteristics for each, these films can be formed in a common process, thereby allowing these films to be formed in a simple process.

[0010] Here, the thicknesses of the first and second dielectric films can be set arbitrarily under relatively loose constraints as long as the total thickness of these films falls within the above range. Therefore, the thicknesses of the first and second dielectric films can be set flexibly while taking into consideration the thicknesses required for the first and second protective films. Therefore, the first and second dielectric films and the first and second protective films can be stably formed using a common process.

[0011] As described above, according to the present invention, an optical reflecting element can be provided that can suppress fluctuations in the reflectivity of the mirror on the movable part in the wavelength band of light incident on the mirror, while allowing the formation of multiple dielectric films that make up the mirror and a protective film for the piezoelectric body that serves as the driving source using a simple process.

[0012] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below.

[0013] FIG. 1 is a perspective view showing the configuration of an optical reflecting element according to an embodiment. FIG. 2 is a perspective view of an optical reflecting element according to an embodiment when viewed from the bottom side. FIG. 3 is a cross-sectional view schematically showing the layered structure of an optical reflecting element according to an embodiment. FIG. 4(a) is a cross-sectional view schematically showing the layered structure according to a simulation of an embodiment. FIGS. 4(b) and 4(c) are exemplary diagrams of numerical settings according to a simulation of an embodiment. FIG. 5 is a graph showing the reflectance obtained when the total film thickness is 90 nm according to a simulation of an embodiment. FIGS. 6(a) and 6(b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness according to a simulation of an embodiment. FIG. 7 is a graph showing the fluctuation ranges obtained when the total film thickness is 95 nm according to a simulation of an embodiment. FIGS. 8(a) and 8(b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness according to a simulation of a first modification. FIGS. 9(a) and 9(b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness according to a simulation of a second modification. 10(a) and (b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness in a simulation of Modification Example 3. FIGS. 11(a) and (b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness in a simulation of Modification Example 4. FIGS. 12(a) and (b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness in a simulation of Modification Example 5. FIGS. 13(a) and (b) are graphs showing the maximum and average fluctuation ranges obtained for each total film thickness in a simulation of Modification Example 6. FIG. 14 is a cross-sectional view schematically showing a layered structure of an optical reflecting element according to another modification.

[0014] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with X, Y, and Z axes that are orthogonal to each other. The Y axis direction is parallel to the rotation axis of the optical reflecting element, and the Z axis direction is the thickness direction of the optical reflecting element.

[0016] FIG. 1 is a perspective view showing the configuration of an optical reflecting element 1, and FIG. 2 is a perspective view of the optical reflecting element 1 as viewed from the bottom side (Z-axis negative side).

[0017] The optical reflecting element 1 includes a movable portion 11, two drive portions 12, two torsion portions 13, two connecting portions 14, and a fixed portion 15. The optical reflecting element 1 has a rectangular outline in a plan view. The optical reflecting element 1 has a shape that is symmetrical in the Y-axis direction and in the X-axis direction about the center of the movable portion 11.

[0018] Movable portion 11 is supported by fixed portion 15 via two torsion portions 13 and two connecting portions 14 so as to be rotatable about rotation axis R0. Rotation axis R0 extends parallel to the length direction (Y axis direction) of optical reflecting element 1 at the midpoint in the width direction (X axis direction) of optical reflecting element 1. A mirror 11a is formed on the upper surface (surface on the positive side of the Z axis) of movable portion 11. The configuration of mirror 11a will be described later with reference to FIG. 3.

[0019] The two torsion sections 13 have a beam-like shape extending along the rotation axis R0 and are arranged to sandwich the movable section 11 in the Y-axis direction. One end of the torsion section 13 on the Y-axis positive side is connected to the side surface of the movable section 11 on the Y-axis positive side, and the other end is connected to the connecting section 14 on the Y-axis positive side. One end of the torsion section 13 on the Y-axis negative side is connected to the side surface of the movable section 11 on the Y-axis negative side, and the other end is connected to the connecting section 14 on the Y-axis negative side.

[0020] The two connecting portions 14 have a plate-like shape extending along the rotation axis R0. The connecting portions 14 connect the drive portion 12 and the torsion portion 13 to the fixed portion 15.

[0021] The two driving units 12 each include a piezoelectric actuator 12b as a driving source and rotate the movable unit 11 about a rotation axis R0. Each of the two driving units 12 is formed by a tuning fork vibrator. That is, the two driving units 12 are formed by arranging the two tuning fork vibrators in opposite directions along the rotation axis R0.

[0022] Each drive unit 12 includes a pair of arm units 12a extending in an L-shape from the connecting unit 14. A piezoelectric actuator 12b for driving the movable unit 11 is disposed on the upper surface of the portion of each arm unit 12a extending in the Y-axis direction. In addition, a piezoelectric actuator 12c for detecting the vibration state of the arm unit 12a is disposed near the base of each arm unit 12a.

[0023] The piezoelectric actuators 12b and 12c have a laminated structure in which an upper electrode layer and a lower electrode layer are respectively disposed above and below a piezoelectric layer. The laminated structure of the piezoelectric actuators 12b and 12c will be described later with reference to FIG.

[0024] Fixed portion 15 has a frame shape with a rectangular outline in a plan view. The outer contour of fixed portion 15 forms the outer contour of optical reflecting element 1. Fixed portion 15 supports movable portion 11, drive portion 12, and torsion portion 13 via two connecting portions 14.

[0025] Two terminals 16 are arranged on the upper surface of fixed portion 15. Terminal 16 on the Y-axis positive side is connected to two piezoelectric actuators 12b and two piezoelectric actuators 12c on the Y-axis positive side via wiring 17. Terminal 16 on the Y-axis negative side is connected to two piezoelectric actuators 12b and two piezoelectric actuators 12c on the Y-axis negative side via wiring 17. Similar to piezoelectric actuators 12b and 12c, wiring 17 has a layered structure in which an upper electrode layer and a lower electrode layer are arranged above and below a piezoelectric layer.

[0026] Four first electrode pads 16a connected to the upper electrode layers of the corresponding piezoelectric actuators 12b, 12c and two second electrode pads 16b connected to the lower electrode layers of the corresponding piezoelectric actuators 12b, 12c for connecting these lower electrode layers to ground are arranged on the upper surface of the terminal portion 16. The first electrode pads 16a and the second electrode pads 16b are exposed upward.

[0027] The base portion of optical reflecting element 1 is formed by processing an SOI wafer consisting of substrate 101 and material layer 102. Substrate 101 and material layer 102 each have a certain thickness. Substrate 101 and material layer 102 are made of, for example, silicon (Si). Note that substrate 101 and material layer 102 may be made of different materials, or may be made of a material other than silicon (Si).

[0028] When optical reflecting element 1 is fabricated, mirror 11a, piezoelectric actuators 12b and 12c, terminal portion 16, first electrode pad 16a, second electrode pad 16b, and wiring 17 are formed in corresponding regions on substrate 101 of an SOI wafer. Next, substrate 101 and material layer 102 are removed by etching or the like so as to leave movable portion 11, drive portion 12, torsion portion 13, connecting portion 14, and fixed portion 15. As a result, substrate 101 becomes a common substrate for the entire optical reflecting element 1, and an opening 15a penetrating vertically is formed around movable portion 11. Furthermore, as shown in FIG. 2 , material layer 102 is removed from the SOI wafer by etching or the like so as to leave a region corresponding to fixed portion 15. As a result, the mechanical strength of fixed portion 15 is increased compared to the portions other than fixed portion 15.

[0029] The optical reflecting element 1 is used by being electrically connected to an external circuit board or the like via the first electrode pads 16 a and the second electrode pads 16 b. The first electrode pads 16 a and the second electrode pads 16 b are connected to the external circuit board or the like by wiring means such as wire bonding. The first electrode pads 16 a and the second electrode pads 16 b may also be connected to the external circuit board or the like via a support substrate. In this case, the support substrate has a plurality of electrode pads arranged in positions facing the plurality of electrode pads on the optical reflecting element 1 side, and the first electrode pads 16 a and the second electrode pads 16 b are connected to the external circuit board or the like by adhering the optical reflecting element 1 to the support substrate.

[0030] When the optical reflecting element 1 is driven, an AC voltage is applied to the four piezoelectric actuators 12b to resonantly drive the movable portion 11 at the natural frequency (resonance frequency) of the optical reflecting element 1. As a result, each of the four piezoelectric actuators 12b deforms due to the inverse piezoelectric effect. At this time, the AC voltages applied to two piezoelectric actuators 12b aligned in the Y-axis direction are set to the same phase, and the AC voltages applied to two piezoelectric actuators 12b aligned in the X-axis direction are set to opposite phases. As a result, the deformation direction (amplitude direction) of the two piezoelectric actuators 12b on the positive side of the X-axis is opposite to the deformation direction (amplitude direction) of the piezoelectric actuator 12b on the negative side of the X-axis. In this way, the deformation of the four piezoelectric actuators 12b deforms the arm portion 12a, and the movable portion 11 is resonantly driven around the rotation axis R0 at a predetermined resonant frequency via the two torsion portions 13.

[0031] The four piezoelectric actuators 12c for vibration detection generate currents due to the piezoelectric effect in response to the deformation of the corresponding arms 12a. Therefore, the vibration state of the arms 12a can be monitored from these currents. An external drive circuit uses these currents to control the AC voltages applied to the piezoelectric actuators 12b so that the amplitude, frequency, and phase of each arm 12a converge to their respective target values. This causes the movable part 11 and mirror 11a to rotate at the target resonant frequency and deflection angle. Light of a predetermined wavelength band incident on the movable part 11 from above is reflected by the mirror 11a of the movable part 11 and irradiated onto the target area.

[0032] FIG. 3 is a cross-sectional view showing a schematic layer structure of the optical reflecting element 1. As shown in FIG.

[0033] FIG. 3 shows a schematic cross section of the laminated structure in the "piezoelectric region" and the "movable portion region." The piezoelectric region is the region where the piezoelectric actuators 12b and 12c, the portion of the terminal portion 16 excluding the first electrode pad 16a and the second electrode pad 16b, and the wiring 17 are arranged. The movable portion region is the region where the movable portion 11 is located. For convenience, FIG. 3 shows the vicinity of the upper end of the substrate 101 of the SOI wafer consisting of the substrate 101 and the material layer 102. Each layer of the laminated structure is formed by a PVD (physical vapor deposition) method, such as sputtering or evaporation, a CVD (chemical vapor deposition) method, or a liquid phase deposition method, such as a sol-gel method. Each layer of the laminated structure is removed by applying a resist, dry etching, wet etching, or the like.

[0034] In the piezoelectric region, a piezoelectric body 110, a first protective film 121, and a second protective film 122 are stacked in this order upward on the upper surface of the substrate 101. The piezoelectric body 110 includes a lower electrode layer 111, a piezoelectric body layer 112, and an upper electrode layer 113, and the lower electrode layer 111, the piezoelectric body layer 112, and the upper electrode layer 113 are stacked in this order upward.

[0035] The lower electrode layer 111 is made of a material with low electrical resistance and high heat resistance, such as platinum (Pt). The piezoelectric layer 112 is made of a material with low electrical resistance and high heat resistance, such as PZT (lead zirconate titanate: Pb(Zr,Ti)O ３ The upper electrode layer 113 is made of a material having low electrical resistance and high heat resistance, such as gold (Au).

[0036] First protective film 121 and second protective film 122 protect the upper surface of piezoelectric body 110. First protective film 121 is intended to prevent the intrusion of moisture, and second protective film 122 is intended to prevent the intrusion of moisture and hot water. For this reason, first protective film 121 is made of a material that has excellent moisture resistance, and second protective film 122 is made of a material that has excellent moisture resistance and hot water resistance. This allows optical reflecting element 1 to operate reliably and stably even when used in a high-temperature, high-humidity environment.

[0037] In this embodiment, the first protective film 121 is made of aluminum oxide (Al ２ O ３ , alumina), and the second protective film 122 is made of zirconium dioxide (ZrO ２ It is composed of titanium dioxide (zirconia).

[0038] In order to improve the adhesion between the substrate 101 and the lower electrode layer 111, an adhesion layer may be disposed between the substrate 101 and the lower electrode layer 111, and in order to improve the adhesion between the piezoelectric layer 112 and the upper electrode layer 113, an adhesion layer may be disposed between the piezoelectric layer 112 and the upper electrode layer 113. In this case, the adhesion layer is made of, for example, titanium (Ti).

[0039] In the movable portion region, a metal reflective film 130, a first dielectric film 141, and a second dielectric film 142 are stacked in this order from top to bottom on the upper surface of the substrate 101. The first dielectric film 141 and the second dielectric film 142 form a mirror 11a.

[0040] The metal reflective film 130 is made of a material that can increase the reflectance of light incident on the movable portion 11. In this embodiment, the metal reflective film 130 is made of silver (Ag) or a silver (Ag) alloy. The silver alloy is, for example, an alloy made of silver (Ag), palladium (Pd), and copper (Cu), and APC (registered trademark) alloy can be used as the silver alloy. The metal reflective film 130 may be made of two layers with a metal film such as titanium (Ti) as a base.

[0041] The second dielectric film 142 is made of a material having a higher refractive index than the first dielectric film 141. This forms a dielectric multilayer film based on the first dielectric film 141 and the second dielectric film 142, which can increase the reflectance of light incident on the mirror 11a. The first dielectric film 141 and the second dielectric film 142 also protect the upper surface of the metal reflective film 130. In this embodiment, the first dielectric film 141 is made of Al ２ O ３ The second dielectric film 142 is made of ZrO ２ It is composed of:

[0042] 3 is formed on the metal reflective film 130 and the piezoelectric body 110. If these films are formed separately, the process for forming the films becomes complicated. On the other hand, it is preferable that the mirror 11a formed on the movable part 11 has a reflectance that is as uniform as possible in the wavelength band of the incident light.

[0043] In contrast, in this embodiment, as shown in Figure 3, the first protective film 121 and the first dielectric film 141 are made of the same material and have the same thickness T1. Furthermore, the second protective film 122 and the second dielectric film 142 are made of the same material and have the same thickness T2. As a result, in the process of forming the first dielectric film 141 and the second dielectric film 142 on the upper surface of the metal reflective film 130, the first protective film 121 and the second protective film 122 can also be formed on the upper side of the piezoelectric body 110 at the same time. Therefore, these films can be formed by a simple process.

[0044] On the other hand, after extensive research, the inventors have found that, as long as the sum of the thicknesses of the first dielectric film 141 and the second dielectric film 142 falls within a predetermined range, fluctuations in the reflectance of the mirror 11a in the wavelength band of the incident light can be suppressed more effectively than fluctuations in the reflectance of the metal reflective film 130 alone. Based on this finding, by adjusting the thicknesses of the first dielectric film 141 and the second dielectric film 142 so that the sum of the thicknesses of the first dielectric film 141 and the second dielectric film 142 falls within this range, fluctuations in the reflectance of the mirror 11a in the wavelength band of the incident light can be effectively suppressed. Below, a simulation performed by the inventors to examine such suppression of fluctuations in reflectance will be described.

[0045] <Simulation of Fluctuation Rate> As shown in Fig. 4(a), the inventors assumed a laminated structure ST similar to that of the movable portion region in Fig. 3. In this simulation, the metal reflective film 130 was made of a silver (Ag) alloy, and the first dielectric film 141 was made of aluminum oxide (Al ２ O ３ ), and the second dielectric film 142 is made of zirconium dioxide (ZrO ２ ) was composed of:

[0046] The refractive index of the silver alloy for light having a wavelength of about 440 nm to 650 nm is set to 0.1617 to 0.16, and the refractive index of the Al alloy for light having a wavelength of about 450 nm to 650 nm is set to 0.1617 to 0.16. ２ O ３ The refractive index of ZrO is set to 1.677 to 1.668, and the refractive index of ZrO is set to 1.677 to 1.668 for light having a wavelength of about 441.14 nm to 674.67 nm. ２ The refractive index was set to 2.085 to 2.039.

[0047] 4(b), the inventors assumed combinations in which the total thickness (T1+T2) of the first dielectric film 141 and the second dielectric film 142 in the stacked structure ST was varied by 1 nm, and the thickness T1 of the first dielectric film 141 and the thickness T2 of the second dielectric film 142 were varied by 1 nm for each total thickness. Then, for each stacked structure ST having a different combination of the total thickness (T1+T2) and the thicknesses T1 and T2, the inventors varied the wavelength λ by 1 nm, as shown in FIG. 4(c), and obtained the reflectance of the stacked structure ST for light of each wavelength by simulation.

[0048] FIG. 5 is a graph showing the reflectance obtained when the total film thickness is 90 nm according to the simulation of this embodiment.

[0049] In Fig. 5, the horizontal axis represents wavelength λ (nm), and the vertical axis represents reflectance (%). For convenience, Fig. 5 shows only some combinations of film thicknesses T1 and T2 that result in a total film thickness of 90 nm. Fig. 5 also shows the reflectance when the stacked structure ST is composed only of the metal reflective film 130 (silver alloy).

[0050] Here, since the light reflected by the mirror 11a of the optical reflecting element 1 is generally visible light, the inventors reflected light having a wavelength λ in the range of 450 nm or more and 640 nm or less (hereinafter referred to as the "wavelength band WB") and investigated the degree of flatness of the reflectivity of each laminate structure ST in the wavelength band WB.

[0051] That is, the inventors first obtained the fluctuation range (%) of the reflectance at wavelengths λ of 450 nm, 520 nm, and 640 nm for all stacked structures ST consisting of combinations of total thickness and thicknesses T1 and T2, calculated by subtracting the minimum reflectance (%) from the maximum reflectance (%). The fluctuation range roughly indicates the flatness of the reflectance of the stacked structure ST in the wavelength band WB, and the smaller the fluctuation range, the higher the flatness. For example, when the total thickness is 90 nm, thickness T1 is 80 nm, and thickness T2 is 10 nm (thick curve in Figure 5), the fluctuation range is 0.54%. On the other hand, when the stacked structure ST is composed only of the metal reflective film 130 (silver alloy), the fluctuation range is 4.28%.

[0052] Next, the inventors selected the maximum fluctuation range among the combinations of film thicknesses T1 and T2 included in each total film thickness, and calculated the average fluctuation range of all combinations included in the total film thickness. In this way, the inventors obtained the maximum and average fluctuation ranges for each total film thickness.

[0053] FIG. 6A is a graph showing the maximum and average fluctuation ranges obtained for each total film thickness in the simulation of this embodiment.

[0054] In FIG. 6A, the horizontal axis represents the total film thickness (T1+T2) (nm), and the vertical axis represents the fluctuation range (%).

[0055] As shown in FIG. 6A, when the total film thickness is changed, the maximum and average fluctuation ranges corresponding to the total film thickness also change. On the other hand, when the stacked structure ST is composed only of the metal reflective film 130 (silver alloy), the fluctuation range V0 is constant at 4.28%, as shown by the dashed line. Furthermore, when the total film thickness of the stacked structure ST is changed, the graphs of the maximum and average fluctuation ranges generally form a downwardly protruding shape, with the lower end of this shape falling below the fluctuation range V0 corresponding to the metal reflective film 130 (silver alloy). Therefore, if the total film thickness is set so that the maximum fluctuation range (see the bold line) is less than the fluctuation range V0 in the wavelength band WB, it can be said that the flatness of the reflectivity of the stacked structure ST formed with that total film thickness is higher than that of the metal reflective film 130 (silver alloy).

[0056] 6A, the maximum fluctuation ranges for total film thicknesses of 64 nm and 108 nm are 3.95% and 4.07%, respectively, which are lower than the fluctuation range V0 (4.28%) of the metal reflective film 130 (silver alloy). Therefore, it can be said that when the total film thickness is set to 64 nm or more and 108 nm or less in wavelength band WB, fluctuations in the reflectance of the stacked structure ST can be more effectively suppressed than with the metal reflective film 130 (silver alloy).

[0057] When actually determining the film thicknesses T1 and T2 based on the graph of FIG. 6A, the total film thickness in the range where the fluctuation range is small (in other words, where the flatness is high) is referenced. For example, the total film thickness is determined between the total film thickness corresponding to the point (bottom P1) where the maximum fluctuation range is smallest and the total film thickness corresponding to the point (bottom P2) where the average fluctuation range is smallest. Then, within the determined range of total film thickness, the film thicknesses T1 and T2 are determined taking into consideration the reflectivity of the mirror 11a and the protective performance for the metal reflective film 130 and the piezoelectric body 110. However, when the bottoms P1 and P2 are far from each other, as in FIG. 6A, the reference range becomes wider, making it difficult to determine which bottom should be prioritized, making it difficult to determine the total film thickness.

[0058] In response to this, the inventors, after further investigation, discovered that by limiting at least one of the film thicknesses T1 and T2 to a predetermined value or greater, it is possible to bring the bottom P1 of the graph showing the maximum fluctuation range and the bottom P2 of the graph showing the average fluctuation range closer to each other.

[0059] For example, by limiting the thickness T1 of the first dielectric film 141 to 40 nm or more, the graph shown in FIG. 6( a) changes to the graph shown in FIG. 6( b). The graph in FIG. 6( b) shows that setting the total thickness between 64 nm and 123 nm can suppress fluctuations in the reflectance of the stacked structure ST to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 6( b), the bottom P1 of the graph showing the maximum fluctuation range and the bottom P2 of the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total thickness can be smoothly determined to be, for example, around 97 nm.

[0060] The reason why the bottoms P1 and P2 can be brought closer to each other by limiting the film thickness T1 to 40 nm or more in the graph shown in FIG. 6A is as follows.

[0061] FIG. 7 is a graph showing the fluctuation range obtained when the total film thickness (T1+T2) is 95 nm in the simulation of this embodiment.

[0062] In FIG. 7, the horizontal axis represents the film thickness T1 (nm), and the vertical axis represents the fluctuation range (%).

[0063] 7, when the film thickness T1 is less than 30 nm, the fluctuation range increases as the film thickness T1 decreases, resulting in a larger maximum value of the fluctuation range in the total film thickness. Therefore, from the viewpoint of suppressing the fluctuation range, i.e., from the viewpoint of improving flatness, it is preferable not to use the range where the film thickness T1 is less than 30 nm for film thickness setting. Therefore, in this case, by targeting the range where the film thickness T1 is 30 nm or more, the maximum value of the fluctuation range can be suppressed and the maximum value and the average value of the fluctuation range can be made closer to each other.

[0064] The inventors varied the film thicknesses T1 and T2 for each total film thickness, and by referring to the correspondingly changing fluctuation range, investigated the range of film thicknesses T1 and T2 in which the maximum value of the fluctuation range is suppressed as described above. As a result, in the configuration of this simulation, it was found that by limiting the film thickness T1 to 40 nm or more, the bottom P1 of the graph of the maximum fluctuation range and the bottom P2 of the graph of the average fluctuation range approach each other, as shown in Figure 6(b).

[0065] Based on the above simulations, in this embodiment, as shown in FIG. 6A, the total film thickness is set to 64 nm or more and 108 nm or less in the wavelength band WB. This effectively suppresses fluctuations in the reflectivity of the mirror 11a. Furthermore, in this embodiment, as shown in FIG. 6B, the total film thickness may be set to 64 nm or more and 123 nm or less in the wavelength band WB, and the film thickness T1 may be set to 40 nm or more. This allows the bottom P1 of the graph showing the maximum fluctuation range and the bottom P2 of the graph showing the average fluctuation range to be closer to each other. As a result, it becomes easier to determine the total film thickness near these two bottoms P1 and P2. This determined total film thickness prevents the fluctuation range from becoming unintentionally large even if an error in the film thickness occurs during manufacturing.

[0066] In the above simulation, the metal reflective film 130 was made of a silver (Ag) alloy, but it may be made of silver (Ag). In this case, the same results as those in the simulations shown in Figures 6(a) and 6(b) are obtained, and similar effects can be obtained by setting the various film thicknesses as described above. Therefore, in the embodiment, the metal reflective film 130 may be made of silver (Ag) or a silver (Ag) alloy.

[0067] <Effects of the embodiment> According to the embodiment, the following effects are achieved.

[0068] 1, optical reflecting element 1 has movable section 11 on which mirror 11a is formed, driven by driver 12. As shown in Fig. 3, mirror 11a includes metal reflective film 130, first dielectric film 141 formed on the upper surface of metal reflective film 130, and second dielectric film 142 formed on the upper surface of first dielectric film 141 and having a higher refractive index than first dielectric film 141. Driver 12 includes piezoelectric body 110, first protective film 121 formed on the upper side of piezoelectric body 110 and made of the same material as first dielectric film 141, and second protective film 122 formed on the upper side of first protective film 121 and made of the same material as second dielectric film 142. Here, the total thickness of the first dielectric film 141 and the second dielectric film 142 (T1 + T2) is included in the range of the total thickness of the first dielectric film 141 and the second dielectric film 142 in which the variation in the reflectivity of the mirror 11a in the wavelength band WB of light incident on the mirror 11a is smaller than the variation in the reflectivity of the metal reflective film 130 alone in the wavelength band WB.

[0069] As described above, the inventors have found, as a result of extensive research, that as long as the total value (T1 + T2) of the thickness of the first dielectric film 141 and the thickness of the second dielectric film 142 falls within a predetermined range, fluctuations in the reflectance of the mirror 11a in the wavelength band WB of the incident light can be suppressed more effectively than fluctuations in the reflectance of the metal reflective film 130 alone. Based on this finding, by adjusting the thicknesses of the first dielectric film 141 and the second dielectric film 142 so that the total value (T1 + T2) of the thickness T1 of the first dielectric film 141 and the thickness T2 of the second dielectric film 142 falls within this range, fluctuations in the reflectance of the mirror 11a in the wavelength band WB of the incident light can be effectively suppressed.

[0070] Furthermore, by forming the first dielectric film 141 and the first protective film 121 from the same material that can achieve the properties required for each, these films can be formed in a common process, and by forming the second dielectric film 142 and the second protective film 122 from the same material that can achieve the properties required for each, these films can be formed in a common process, thereby allowing these films to be formed in a simple process.

[0071] Here, the thicknesses T1 and T2 of the first dielectric film 141 and the second dielectric film 142 can be set arbitrarily under relatively loose constraints as long as the sum of their thicknesses T1 and T2 (T1 + T2) falls within the above range. Therefore, the thicknesses of the first dielectric film 141 and the second dielectric film 142 can be set flexibly while taking into consideration the thicknesses T1 and T2 required for the first protective film 121 and the second protective film 122. Therefore, the first dielectric film 141 and the second dielectric film 142 and the first protective film 121 and the second protective film 122 can be stably formed using a common process.

[0072] The metal reflective film 130 is made of silver (Ag) or a silver (Ag) alloy.

[0073] This configuration can increase the reflectance of the mirror 11a.

[0074] The first dielectric film 141 and the first protective film 121 are Al ２ O ３ The second dielectric film 142 and the second protective film 122 are made of ZrO ２ The total value (T1+T2) is set to 64 nm or more and 108 nm or less.

[0075] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ By including ZrO, moisture resistance can be achieved on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110. ２ By including Al, it is possible to realize moisture resistance and warm water resistance on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110. ２ O ３ By including ZrO, the insulating properties and thermal conductivity of the first protective film 121 are increased, so that the insulating properties with respect to the piezoelectric body 110 can be ensured, heat dissipation of the piezoelectric body 110 can be promoted, and the performance and life of the piezoelectric body 110 can be improved. ２ By including the above, the toughness (mechanical strength) of the second dielectric film 142 and the second protective film 122 increases, so that the upper surfaces of the metal reflective film 130 and the piezoelectric body 110 can be effectively protected.

[0076] The first dielectric film 141 and the first protective film 121 are Al ２ O ３ The thickness T1 of the first dielectric film 141 is set to 40 nm or more, and the second dielectric film 142 and the second protective film 122 are made of ZrO ２ The total value (T1+T2) is set to be equal to or greater than 64 nm and equal to or less than 123 nm.

[0077] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0078] In the embodiment, the first dielectric film 141 is made of Al ２ O ３ However, it is substantially composed of Al ２ O ３ For example, the first dielectric film 141 may be made of Al ２ O ３ Similarly, in the embodiment, the second dielectric film 142 may be made of ZrO ２ However, the composition is substantially ZrO ２ For example, the second dielectric film 142 may be made of ZrO ２ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with Al. ２ O ３ The second dielectric film 142 is substantially composed of ZrO ２ In the case of the above configuration, the same results as those in the simulations shown in FIGS. 6A and 6B are obtained, and therefore, if the various film thicknesses are set as described above, the same effects can be obtained.

[0079] <Modification 1> In this modification, the first protective film 121 is also for preventing moisture from entering, and the second protective film 122 is for preventing moisture and hot water from entering. For this reason, the first protective film 121 is made of a material that has excellent moisture resistance, and the second protective film 122 is made of a material that has excellent moisture resistance and hot water resistance.

[0080] In this modification, the first dielectric film 141 and the first protective film 121 are made of aluminum oxide (Al ２ O ３ ), and the second dielectric film 142 and the second protective film 122 are made of tantalum pentoxide (Ta ２ O ５ The other configurations of this modified example are the same as those of the above embodiment.

[0081] The inventors also performed a simulation similar to that of the above embodiment for the configuration of this modified example. ２ O ３ The refractive index of Ta is set to 1.677 to 1.668, and the refractive index of Ta is set to 1.677 to 1.668 for light having a wavelength of about 450 nm to 1000 nm. ２ O ５ The refractive index of the thin film was set to 2.15 to 2.1. The inventors obtained the simulation results of this modified example shown in FIGS. 8( a) and 8(b), similar to the simulation of the embodiment shown in FIGS.

[0082] As shown in Figure 8 (a), according to the graph showing the maximum fluctuation range, when the total film thickness is set to 63 nm or more and 105 nm or less in the wavelength band WB, the fluctuation in the reflectivity of the stacked structure ST can be effectively suppressed compared to the metal reflective film 130 (silver alloy).

[0083] Furthermore, in this modified example, as a result of the inventors' investigations, by limiting the thickness of the first dielectric film 141 to 50 nm or more, the graph shown in FIG. 8( a) changes to the graph shown in FIG. 8( b). As shown in FIG. 8( b), the graph showing the maximum fluctuation range indicates that when the total film thickness is set to 63 nm or more and 124 nm or less in the wavelength band WB, fluctuations in the reflectance of the stacked structure ST can be suppressed to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 8( b), the bottoms of the graph showing the maximum fluctuation range and the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total film thickness can be smoothly determined to be, for example, approximately 95 nm.

[0084] <Effects of Modified Example 1> According to this modified example, the following effects are achieved.

[0085] As described with reference to FIG. 8A, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ The second dielectric film 142 and the second protective film 122 are made of Ta. ２ O ５ The total value (T1+T2) is set to 63 nm or more and 105 nm or less.

[0086] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ By including Ta, moisture resistance can be achieved on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110, and the second dielectric film 142 and the second protective film 122 can be made to contain Ta. ２ O ５ By including Al, it is possible to realize moisture resistance and warm water resistance on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110. ２ O ３ By including Ta, the insulating properties and thermal conductivity of the first protective film 121 are increased, so that the insulating properties for the piezoelectric body 110 can be ensured, heat dissipation of the piezoelectric body 110 can be promoted, and the performance and life of the piezoelectric body 110 can be improved. ２ O ５ By including the element, the refractive index of the second dielectric film 142 can be increased.

[0087] As described with reference to FIG. 8B, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ The thickness T1 of the first dielectric film 141 is set to 50 nm or more, and the second dielectric film 142 and the second protective film 122 are made of Ta. ２ O ５ The total value (T1+T2) is set to be equal to or greater than 63 nm and equal to or less than 124 nm.

[0088] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0089] In this modification, the first dielectric film 141 is made of Al ２ O ３ However, it is substantially composed of Al ２ O ３ For example, the first dielectric film 141 may be made of Al ２ O ３ Similarly, in the embodiment, the second dielectric film 142 may be made of a mixture material in which other materials are slightly mixed with Ta. ２ O ５ However, it is essentially Ta ２ O ５ For example, the second dielectric film 142 may be made of Ta. ２ O ５ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with Al. ２ O ３ The second dielectric film 142 is substantially Ta. ２ O ５ In the case of the configuration as above, the same results as those in the simulation shown in FIGS. 8A and 8B are obtained, and therefore, if the various film thicknesses are set as above, the same effect can be obtained.

[0090] <Modification 2> In this modification, the first protective film 121 is also for preventing moisture from entering, and the second protective film 122 is for preventing moisture and hot water from entering. For this reason, the first protective film 121 is made of a material that has excellent moisture resistance, and the second protective film 122 is made of a material that has excellent moisture resistance and hot water resistance.

[0091] In this modification, the first dielectric film 141 and the first protective film 121 are made of aluminum oxide (Al ２ O ３ ), and the second dielectric film 142 and the second protective film 122 are made of titanium dioxide (TiO ２ The other configurations of this modified example are the same as those of the above embodiment.

[0092] The inventors also performed a simulation similar to that of the above embodiment for the configuration of this modified example. ２ O ３ The refractive index of TiO is set to 1.677 to 1.668, and the refractive index of TiO is set to 1.677 to 1.668 for light having a wavelength of about 449.7 nm to 674.6 nm. ２ The refractive index of the thin film was set to 2.423 to 2.267. The inventors obtained the simulation results of this modified example shown in FIGS. 9(a) and 9(b), similar to the simulation of the embodiment shown in FIGS.

[0093] As shown in Figure 9(a), according to the graph showing the maximum fluctuation range, when the total film thickness is set to 65 nm or more and 93 nm or less in the wavelength band WB, the fluctuation in the reflectivity of the stacked structure ST can be effectively suppressed compared to the metal reflective film 130 (silver alloy).

[0094] Furthermore, in this modified example, as a result of the inventors' investigations, by limiting the thickness of the first dielectric film 141 to 50 nm or more, the graph shown in FIG. 9( a) changes to the graph shown in FIG. 9( b). As shown in FIG. 9( b), the graph showing the maximum fluctuation range indicates that when the total film thickness is set to 63 nm or more and 119 nm or less in the wavelength band WB, fluctuations in the reflectance of the stacked structure ST can be suppressed to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 9( b), the bottoms of the graph showing the maximum fluctuation range and the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total film thickness can be smoothly determined to be, for example, approximately 96 nm.

[0095] <Effects of Modified Example 2> According to this modified example, the following effects are achieved.

[0096] As described with reference to FIG. 9A, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ The second dielectric film 142 and the second protective film 122 are made of TiO ２ The total value (T1+T2) is set to 65 nm or more and 93 nm or less.

[0097] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ By including TiO, moisture resistance can be achieved on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110. ２ By including Al, it is possible to realize moisture resistance and warm water resistance on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110. ２ O ３ By including TiO, the insulating properties and thermal conductivity of the first protective film 121 are increased, so that the insulating properties for the piezoelectric body 110 can be ensured, heat dissipation of the piezoelectric body 110 can be promoted, and the performance and life of the piezoelectric body 110 can be improved. ２ By including the element, the refractive index of the second dielectric film 142 can be increased.

[0098] As described with reference to FIG. 9B, the first dielectric film 141 and the first protective film 121 are made of Al. ２ O ３ The thickness T1 of the first dielectric film 141 is set to 50 nm or more, and the second dielectric film 142 and the second protective film 122 are made of TiO ２ The total value (T1+T2) is set to be equal to or greater than 63 nm and equal to or less than 119 nm.

[0099] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0100] In this modification, the first dielectric film 141 is made of Al ２ O ３ However, it is substantially composed of Al ２ O ３ For example, the first dielectric film 141 may be made of Al ２ O ３ Similarly, in the embodiment, the second dielectric film 142 may be made of a TiO ２ However, the composition is essentially TiO ２ For example, the second dielectric film 142 may be made of TiO ２ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with Al. ２ O ３ The second dielectric film 142 is substantially composed of TiO ２ 9A and 9B, similar results to those of the simulations shown in FIGS. 9A and 9B can be obtained, and similar effects can be obtained by setting the various film thicknesses as described above.

[0101] In this modification, both the first protective film 121 and the second protective film 122 are intended to prevent moisture and hot water from seeping in. Therefore, both the first protective film 121 and the second protective film 122 are made of a material that is highly resistant to moisture and hot water.

[0102] In this modification, the first dielectric film 141 and the first protective film 121 are made of silicon dioxide (SiO ２ ), and the second dielectric film 142 and the second protective film 122 are made of zirconium dioxide (ZrO ２ The other configurations of this modified example are the same as those of the above embodiment.

[0103] The inventors also performed a simulation similar to that of the above embodiment for the configuration of this modified example. In this simulation, the SiO ２ The refractive index of ZrO is set to 1.46669 to 1.45671, and the refractive index of ZrO is set to 1.46669 to 1.45671 for light having a wavelength of about 441.14 nm to 674.67 nm. ２ The refractive index of the thin film was set to 2.085 to 2.039. The inventors obtained the simulation results of this modified example shown in FIGS. 10(a) and 10(b), similar to the simulation of the embodiment shown in FIGS.

[0104] As shown in Figure 10(a), according to the graph showing the maximum fluctuation range, when the total film thickness is set to 78 nm or more and 108 nm or less in the wavelength band WB, the fluctuation in the reflectivity of the stacked structure ST can be effectively suppressed compared to the metal reflective film 130 (silver alloy).

[0105] Furthermore, in this modified example, the inventors' investigations revealed that limiting the thickness T1 of the first dielectric film 141 to 35 nm or more and the thickness T2 of the second dielectric film 142 to 10 nm or more changes the graph shown in FIG. 10(a) to the graph shown in FIG. 10(b). As shown in FIG. 10(b), the graph showing the maximum fluctuation range indicates that when the total film thickness is set to 63 nm or more and 127 nm or less in the wavelength band WB, the fluctuation in the reflectance of the stacked structure ST can be suppressed to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 10(b), the bottoms of the graph showing the maximum fluctuation range and the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total film thickness can be smoothly determined to be, for example, approximately 101 nm.

[0106] <Effects of Modified Example 3> According to this modified example, the following effects are achieved.

[0107] As described with reference to FIG. 10A, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 are made of ZrO ２ The total value (T1+T2) is set to 78 nm or more and 108 nm or less.

[0108] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 include ZrO ２ By including SiO, the upper surfaces of the metal reflective film 130 and the piezoelectric body 110 can be made resistant to moisture and warm water. ２ By including ZrO, the refractive index of the first dielectric film 141 can be reduced, and insulation properties with respect to the piezoelectric body 110 can be ensured. ２ By including the above, the toughness (mechanical strength) of the second dielectric film 142 and the second protective film 122 increases, so that the upper surfaces of the metal reflective film 130 and the piezoelectric body 110 can be effectively protected.

[0109] As described with reference to FIG. 10B, the first dielectric film 141 and the first protective film 121 are made of SiO２ The thickness T1 of the first dielectric film 141 is set to 35 nm or more, and the second dielectric film 142 and the second protective film 122 are made of ZrO ２ The thickness T2 of the second dielectric film 142 is set to 10 nm or more, and the total value (T1+T2) is set to 63 nm or more and 127 nm or less.

[0110] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0111] In this modification, the first dielectric film 141 is made of SiO ２ However, it is substantially composed of SiO ２ For example, the first dielectric film 141 may be made of SiO ２ Similarly, in the embodiment, the second dielectric film 142 may be made of ZrO ２ However, the composition is substantially ZrO ２ For example, the second dielectric film 142 may be made of ZrO ２ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with the first dielectric film 141. ２ The second dielectric film 142 is substantially composed of ZrO ２ In the case of the configuration as above, the same results as those in the simulations shown in FIGS. 10(a) and 10(b) are obtained, and therefore, if the various film thicknesses are set as above, the same effects can be obtained.

[0112] In this modification, both the first protective film 121 and the second protective film 122 are intended to prevent moisture and hot water from seeping in. Therefore, both the first protective film 121 and the second protective film 122 are made of a material that is highly resistant to moisture and hot water.

[0113] In this modification, the first dielectric film 141 and the first protective film 121 are made of silicon dioxide (SiO ２ ), and the second dielectric film 142 and the second protective film 122 are made of tantalum pentoxide (Ta ２ O ５ The other configurations of this modified example are the same as those of the above embodiment.

[0114] The inventors also performed a simulation similar to that of the above embodiment for the configuration of this modified example. In this simulation, the SiO ２ The refractive index of Ta is set to 1.46669 to 1.45671, and the refractive index of Ta is set to 1.46669 to 1.45671 for light having a wavelength of approximately 450 nm to 1000 nm. ２ O ５ The refractive index of the thin film was set to 2.15 to 2.1. The inventors obtained the simulation results of this modified example shown in FIGS. 11(a) and 11(b), similar to the simulation of the embodiment shown in FIGS.

[0115] As shown in Figure 11 (a), according to the graph showing the maximum fluctuation range, when the total film thickness is set to 77 nm or more and 105 nm or less in the wavelength band WB, the fluctuation in the reflectivity of the stacked structure ST can be effectively suppressed compared to the metal reflective film 130 (silver alloy).

[0116] Furthermore, in this modified example, the inventors' investigations revealed that limiting the thickness T1 of the first dielectric film 141 to 35 nm or more and the thickness T2 of the second dielectric film 142 to 10 nm or more changes the graph shown in FIG. 11(a) to the graph shown in FIG. 11(b). As shown in FIG. 11(b), the graph showing the maximum fluctuation range indicates that when the total film thickness is set to 61 nm or more and 125 nm or less in the wavelength band WB, the fluctuation in the reflectance of the stacked structure ST can be suppressed to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 11(b), the bottoms of the graph showing the maximum fluctuation range and the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total film thickness can be smoothly determined to be, for example, approximately 99 nm.

[0117] <Effects of Modified Example 4> According to this modified example, the following effects are achieved.

[0118] As described with reference to FIG. 11A, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 are made of Ta. ２ O ５ The total value (T1+T2) is set to 77 nm or more and 105 nm or less.

[0119] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 include Ta. ２ O ５ By including SiO, the upper surfaces of the metal reflective film 130 and the piezoelectric body 110 can be made resistant to moisture and warm water. ２ By including Ta, the refractive index of the first dielectric film 141 can be reduced, and insulation properties with respect to the piezoelectric body 110 can be ensured. ２ O ５ By including the element, the refractive index of the second dielectric film 142 can be increased.

[0120] As described with reference to FIG. 11B, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The thickness T1 of the first dielectric film 141 is set to 35 nm or more, and the second dielectric film 142 and the second protective film 122 are made of Ta. ２ O ５ The thickness T2 of the second dielectric film 142 is set to 10 nm or more, and the total value (T1+T2) is set to 61 nm or more and 125 nm or less.

[0121] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0122] In this modification, the first dielectric film 141 is made of SiO２ However, it is substantially composed of SiO ２ For example, the first dielectric film 141 may be made of SiO ２ Similarly, in the embodiment, the second dielectric film 142 may be made of a mixture material in which other materials are slightly mixed with Ta. ２ O ５ However, it is essentially Ta ２ O ５ For example, the second dielectric film 142 may be made of Ta. ２ O ５ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with the first dielectric film 141. ２ The second dielectric film 142 is substantially Ta. ２ O ５ In the case of the configuration as above, the same results as those in the simulations shown in FIGS. 11A and 11B are obtained, and therefore, if the various film thicknesses are set as above, the same effects can be obtained.

[0123] <Modification 5> In this modification, both the first protective film 121 and the second protective film 122 are intended to prevent moisture and hot water from seeping in. For this reason, both the first protective film 121 and the second protective film 122 are made of a material that is highly resistant to moisture and hot water.

[0124] In this modification, the first dielectric film 141 and the first protective film 121 are made of silicon dioxide (SiO ２ ), and the second dielectric film 142 and the second protective film 122 are made of titanium dioxide (TiO ２ The other configurations of this modified example are the same as those of the above embodiment.

[0125] The inventors also performed a simulation similar to that of the above embodiment for the configuration of this modified example. In this simulation, the SiO ２ The refractive index of TiO is set to 1.46669 to 1.45671, and the refractive index of TiO is set to 1.46669 to 1.45671 for light having a wavelength of about 449.7 nm to 674.6 nm. ２The refractive index of the thin film was set to 2.423 to 2.267. The inventors obtained the simulation results of this modified example shown in FIGS. 12(a) and 12(b), similar to the simulation of the embodiment shown in FIGS.

[0126] As shown in Figure 12(a), according to the graph showing the maximum fluctuation range, when the total film thickness is set to 76 nm or more and 93 nm or less in the wavelength band WB, fluctuations in the reflectivity of the stacked structure ST can be effectively suppressed compared to the metal reflective film 130 (silver alloy).

[0127] Furthermore, in this modified example, the inventors' investigations revealed that limiting the thickness T1 of the first dielectric film 141 to 45 nm or more and the thickness T2 of the second dielectric film 142 to 5 nm or more changes the graph shown in FIG. 12(a) to the graph shown in FIG. 12(b). As shown in FIG. 12(b), the graph showing the maximum fluctuation range indicates that when the total film thickness is set to 65 nm or more and 122 nm or less in the wavelength band WB, the fluctuation in the reflectance of the stacked structure ST can be suppressed to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 12(b), the bottoms of the graph showing the maximum fluctuation range and the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total film thickness can be smoothly determined to be, for example, approximately 100 nm.

[0128] <Effects of Modified Example 5> According to this modified example, the following effects are achieved.

[0129] As described with reference to FIG. 12A, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 are made of TiO ２ The total value (T1+T2) is set to 76 nm or more and 93 nm or less.

[0130] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of SiO ２ and the second dielectric film 142 and the second protective film 122 include TiO ２By including SiO, the upper surfaces of the metal reflective film 130 and the piezoelectric body 110 can be made resistant to moisture and warm water. ２ By including TiO, the refractive index of the first dielectric film 141 can be reduced, and insulation properties with respect to the piezoelectric body 110 can be ensured. ２ By including the element, the refractive index of the second dielectric film 142 can be increased.

[0131] As described with reference to FIG. 12B, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The thickness T1 of the first dielectric film 141 is set to 45 nm or more, and the second dielectric film 142 and the second protective film 122 are made of TiO ２ The thickness T2 of the second dielectric film 142 is set to 5 nm or more, and the total value (T1+T2) is set to 65 nm or more and 122 nm or less.

[0132] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0133] In this modification, the first dielectric film 141 is made of SiO ２ However, it is substantially composed of SiO ２ For example, the first dielectric film 141 may be made of SiO ２ Similarly, in the embodiment, the second dielectric film 142 may be made of a TiO ２ However, the composition is essentially TiO ２ For example, the second dielectric film 142 may be made of TiO ２ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with the first dielectric film 141. ２ The second dielectric film 142 is substantially composed of TiO ２In the case of the configuration as above, the same results as those in the simulations shown in FIGS. 12(a) and 12(b) are obtained, and therefore, if the various film thicknesses are set as above, the same effects can be obtained.

[0134] <Modification 6> In this modification, the first protective film 121 is for preventing the intrusion of moisture and hot water, and the second protective film 122 is for preventing the intrusion of moisture. Therefore, the first protective film 121 is made of a material that is highly resistant to moisture and hot water, and the second protective film 122 is made of a material that is highly resistant to moisture.

[0135] In this modification, the first dielectric film 141 and the first protective film 121 are made of silicon dioxide (SiO ２ ), and the second dielectric film 142 and the second protective film 122 are made of aluminum oxide (Al ２ O ３ The other configurations of this modified example are the same as those of the above embodiment.

[0136] The inventors also performed a simulation similar to that of the above embodiment for the configuration of this modified example. In this simulation, the SiO ２ The refractive index of Al is set to 1.46669 to 1.45671, and the refractive index of Al is set to 1.46669 to 1.45671 for light having a wavelength of about 450 nm to 650 nm. ２ O ３ The refractive index of the thin film was set to 1.677 to 1.668. The inventors obtained the simulation results of this modified example shown in FIGS. 13(a) and 13(b), similar to the simulation of the embodiment shown in FIGS.

[0137] As shown in Figure 13(a), according to the graph showing the maximum fluctuation range, when the total film thickness is set to 79 nm or more and 136 nm or less in the wavelength band WB, the fluctuation in the reflectivity of the stacked structure ST can be effectively suppressed compared to the metal reflective film 130 (silver alloy).

[0138] Furthermore, in this modified example, as a result of the inventors' investigations, by limiting the thickness T2 of the second dielectric film 142 to 30 nm or more, the graph shown in FIG. 13(a) changes to the graph shown in FIG. 13(b). As shown in FIG. 13(b), the graph showing the maximum fluctuation range indicates that when the total film thickness is set to 66 nm or more and 136 nm or less in the wavelength band WB, fluctuations in the reflectance of the stacked structure ST can be suppressed to a value less than the fluctuation range V0. Furthermore, in the graph shown in FIG. 13(b), the bottoms of the graph showing the maximum fluctuation range and the graph showing the average fluctuation range are close to each other. Therefore, in this case, the total film thickness can be smoothly determined to be, for example, approximately 94 nm.

[0139] <Effects of Modified Example 6> According to this modified example, the following effects are achieved.

[0140] As described with reference to FIG. 13A, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 are made of Al ２ O ３ The total value (T1+T2) is set to 79 nm or more and 136 nm or less.

[0141] According to this configuration, the first dielectric film 141 and the first protective film 121 are made of SiO ２ By including Al, the upper surfaces of the metal reflective film 130 and the piezoelectric body 110 can be made resistant to moisture and warm water. ２ O ３ By including the first dielectric film 141 and the first protective film 121, moisture resistance can be achieved on the upper surfaces of the metal reflective film 130 and the piezoelectric body 110. ２ By including Al, the refractive index of the first dielectric film 141 can be reduced, and insulation properties with respect to the piezoelectric body 110 can be ensured. ２ O ３ By including this, the insulating properties and thermal conductivity of the second protective film 122 are improved, thereby ensuring insulation against the piezoelectric body 110, promoting heat dissipation from the piezoelectric body 110, and improving the performance and lifespan of the piezoelectric body 110.

[0142] As described with reference to FIG. 13B, the first dielectric film 141 and the first protective film 121 are made of SiO ２ The second dielectric film 142 and the second protective film 122 are made of Al ２ O ３ The thickness T2 of the second dielectric film 142 is set to 30 nm or more, and the total value (T1+T2) is set to 66 nm or more and 136 nm or less.

[0143] This configuration can suppress the maximum fluctuation for each sum, making it possible to smoothly determine the sum that can effectively suppress fluctuations in the reflectance of the mirror 11 a. Furthermore, the sum determined in this way can prevent the range of fluctuation from becoming unintentionally large even if errors occur in the thicknesses T1 and T2 during manufacturing.

[0144] In this modification, the first dielectric film 141 is made of SiO ２ However, it is substantially composed of SiO ２ For example, the first dielectric film 141 may be made of SiO ２ Similarly, in the embodiment, the second dielectric film 142 may be made of a mixture material in which other materials are slightly mixed with Al. ２ O ３ However, it is substantially composed of Al ２ O ３ For example, the second dielectric film 142 may be made of Al ２ O ３ The first dielectric film 141 may be made of a mixture material in which other materials are slightly mixed with the first dielectric film 141. ２ The second dielectric film 142 is substantially made of Al. ２ O ３ In the case of the configuration as above, the same results as those in the simulations shown in FIGS. 13A and 13B are obtained, and therefore, if the various film thicknesses are set as above, the same effects can be obtained.

[0145] <Other Modifications> The configuration examples of the present invention are not limited to the above-described embodiment and modifications, and various modifications are possible.

[0146] In the above-described embodiment and modified examples, another film may be formed between the substrate 101 and the metal reflective film 130, and another film may be formed between the upper electrode layer 113 and the first protective film 121. For example, as shown in FIG. 14 , another film 123 having the same thickness T3 and made of the same material may be disposed between the substrate 101 and the metal reflective film 130 and between the piezoelectric body 110 and the first protective film 121. In this case, the other film 123 in the movable portion region and the other film 123 in the piezoelectric body region can be formed in a common process. Therefore, the other film 123 can be formed by a simple process.

[0147] 14 shows a configuration in which the other film 123 is made of the same material as, for example, the first dielectric film 141 and the first protective film 121. For this reason, for convenience, the boundary between the first protective film 121 and the other film 123 is shown by a broken line in FIG. 14. For example, the first dielectric film 141, the first protective film 121, and the other film 123 are made of substantially Al. ２ O ３ In this case, the adhesion between the metal reflective film 130 and the substrate 101 can be improved, and the moisture resistance of the upper surface of the piezoelectric body 110 can be improved compared to the above embodiment.

[0148] In the above embodiment and modified examples, the metal reflective film 130 is made of silver (Ag) or a silver (Ag) alloy, but it may be made of other metals or alloys. Furthermore, in the above embodiment and modified examples, the wavelength band WB is set to a range of 450 nm or more and 640 nm or less, but other wavelength bands may be used. In these cases, too, it is sufficient that the total thickness of the first dielectric film 141 and the second dielectric film 142 is within a range of total thickness in which the variation in the reflectance of the mirror 11a is smaller than the variation in the reflectance of the metal reflective film 130 alone in the wavelength band WB.

[0149] In the above embodiment and modified example, the driving unit 12 is a tuning fork type vibrator, but the driving unit 12 may be a vibrator of another type (for example, a meander type vibrator).

[0150] In the above embodiment and modified examples, the shape of the movable portion 11 is circular, but the shape of the movable portion 11 may be other shapes such as square. The shape of the optical reflecting element 1 in a plan view and the dimensions of each part of the optical reflecting element 1 can also be changed as appropriate.

[0151] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims.

[0152] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0153] (Technology 1) An optical reflecting element in which a movable part on which a mirror is formed is driven by a driving part, wherein the mirror comprises: a metal reflecting film; a first dielectric film formed on an upper surface of the metal reflecting film; and a second dielectric film formed on the upper surface of the first dielectric film and having a refractive index higher than that of the first dielectric film; and the driving part comprises: a piezoelectric body; a first protective film formed on the upper side of the piezoelectric body and made of the same material as the first dielectric film; and a second protective film formed on the upper side of the first protective film and made of the same material as the second dielectric film; and the optical reflecting element is characterized in that the total thickness of the first dielectric film and the second dielectric film is included in a range in which the variation in reflectivity of the mirror in the wavelength band of light incident on the mirror is smaller than the variation in reflectivity of the metal reflecting film alone in the wavelength band.

[0154] As a result of extensive research, the inventors have found that, if the total thickness of the first dielectric film and the second dielectric film is within a predetermined range, the fluctuation in the reflectance of the mirror in the wavelength band of the incident light can be suppressed more than the fluctuation in the reflectance of the metal reflective film alone. Based on this finding, by adjusting the thicknesses of the first dielectric film and the second dielectric film so that the total thickness of the first dielectric film and the second dielectric film is within this range, the fluctuation in the reflectance of the mirror in the wavelength band of the incident light can be effectively suppressed.

[0155] Furthermore, by forming the first dielectric film and the first protective film from the same material that can provide the required characteristics for each, these films can be formed in a common process, and by forming the second dielectric film and the second protective film from the same material that can provide the required characteristics for each, these films can be formed in a common process, thereby allowing these films to be formed in a simple process.

[0156] Here, the thicknesses of the first and second dielectric films can be set arbitrarily under relatively loose constraints as long as the total thickness of these films falls within the above range. Therefore, the thicknesses of the first and second dielectric films can be set flexibly while taking into consideration the thicknesses required for the first and second protective films. Therefore, the first and second dielectric films and the first and second protective films can be stably formed using a common process.

[0157] (Technology 2) The optical reflecting element according to Technology 1, characterized in that the metal reflective film is made of silver (Ag) or a silver (Ag) alloy.

[0158] This technique can increase the reflectivity of the mirror.

[0159] (Technology 3) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of Al. ２ O ３ wherein the second dielectric film and the second protective film are substantially composed of ZrO ２ and the total value is set to be equal to or greater than 64 nm and equal to or less than 108 nm.

[0160] According to this technique, the first dielectric film and the first protective film are made of Al. ２ O ３ By including ZrO, moisture resistance can be realized on the upper surface of the metal reflective film and the piezoelectric body, and the second dielectric film and the second protective film ２ By including Al, it is possible to realize resistance to warm water on the metal reflective film and the upper surface of the piezoelectric body. ２ O ３By including ZrO, the insulating properties and thermal conductivity of the first protective film are improved, so that the insulating properties with respect to the piezoelectric body can be ensured, heat dissipation from the piezoelectric body can be promoted, and the performance and life of the piezoelectric body can be improved. ２ By including the above, the toughness (mechanical strength) of the second dielectric film and the second protective film is increased, and therefore the metal reflective film and the upper surface of the piezoelectric body can be effectively protected.

[0161] (Technology 4) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of Al. ２ O ３ the thickness of the first dielectric film is set to 40 nm or more, and the second dielectric film and the second protective film are substantially made of ZrO ２ and the total value is set to be equal to or greater than 64 nm and equal to or less than 123 nm.

[0162] This technique can reduce the maximum variation in the total thickness of the first and second dielectric films, making it possible to smoothly determine the total thickness that effectively reduces the variation in the reflectivity of the mirror. Furthermore, the total thickness determined in this way can prevent the range of variation from becoming unintentionally large even if an error in thickness occurs during manufacturing.

[0163] (Technology 5) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of Al. ２ O ３ wherein the second dielectric film and the second protective film are substantially composed of Ta. ２ O ５ and the total value is set to be equal to or greater than 63 nm and equal to or less than 105 nm.

[0164] According to this technique, the first dielectric film and the first protective film are made of Al. ２ O ３ By including Ta, moisture resistance can be realized on the upper surface of the metal reflective film and the piezoelectric body, and the second dielectric film and the second protective film ２ O ５By including Al, it is possible to realize moisture resistance and warm water resistance on the upper surface of the metal reflective film and the piezoelectric body. ２ O ３ By including Ta, the insulating properties and thermal conductivity of the first protective film are increased, so that the insulating properties with respect to the piezoelectric body can be ensured, and heat dissipation of the piezoelectric body can be promoted, thereby improving the performance and life of the piezoelectric body. ２ O ５ By including the element, the refractive index of the second dielectric film can be increased.

[0165] (Technology 6) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of Al. ２ O ３ The first dielectric film has a thickness of 50 nm or more, and the second dielectric film and the second protective film are substantially made of Ta. ２ O ５ and the total value is set to be equal to or greater than 63 nm and equal to or less than 124 nm.

[0166] This technique can reduce the maximum variation for each sum, allowing for a smooth determination of the sum that effectively reduces variations in the mirror's reflectivity. Furthermore, the sum determined in this way can prevent unintended large variations even if thickness errors occur during manufacturing.

[0167] (Technology 7) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of Al. ２ O ３ wherein the second dielectric film and the second protective film are substantially composed of TiO ２ and the total value is set to be equal to or greater than 65 nm and equal to or less than 93 nm.

[0168] According to this technique, the first dielectric film and the first protective film are made of Al. ２ O ３ By including TiO, moisture resistance can be realized on the upper surface of the metal reflective film and the piezoelectric body, and the second dielectric film and the second protective film２ By including Al, it is possible to realize moisture resistance and warm water resistance on the upper surface of the metal reflective film and the piezoelectric body. ２ O ３ By including TiO, the insulating properties and thermal conductivity of the first protective film are increased, thereby ensuring insulation from the piezoelectric body and promoting heat dissipation from the piezoelectric body, thereby improving the performance and life of the piezoelectric body. ２ By including the element, the refractive index of the second dielectric film can be increased.

[0169] (Technology 8) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of Al. ２ O ３ the thickness of the first dielectric film is set to 50 nm or more, and the second dielectric film and the second protective film are substantially made of TiO ２ and the total value is set to be equal to or greater than 63 nm and equal to or less than 119 nm.

[0170] This technique can reduce the maximum variation for each sum, allowing for a smooth determination of the sum that effectively reduces variations in the mirror's reflectivity. Furthermore, the sum determined in this way can prevent unintended large variations even if thickness errors occur during manufacturing.

[0171] (Technology 9) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of ZrO ２ and the total value is set to be equal to or greater than 78 nm and equal to or less than 108 nm.

[0172] According to this technique, the first dielectric film and the first protective film are made of SiO ２ and the second dielectric film and the second protective film are made of ZrO ２ By including the first dielectric film and the first protective film, moisture resistance and warm water resistance can be realized on the upper surface of the metal reflective film and the piezoelectric body.２ By including ZrO, the refractive index of the first dielectric film can be reduced, and insulation properties with respect to the piezoelectric body can be ensured. ２ By including the above, the toughness (mechanical strength) of the second dielectric film and the second protective film is increased, and therefore the metal reflective film and the upper surface of the piezoelectric body can be effectively protected.

[0173] (Technology 10) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ the thickness of the first dielectric film is set to 35 nm or more, and the second dielectric film and the second protective film are substantially made of ZrO ２ an optical reflecting element comprising: a first dielectric film having a thickness of 10 nm or more; and a second dielectric film having a thickness of 10 nm or more; and a total thickness of 63 nm or more and 127 nm or less.

[0174] This technique can reduce the maximum variation for each sum, allowing for a smooth determination of the sum that effectively reduces variations in the mirror's reflectivity. Furthermore, the sum determined in this way can prevent unintended large variations even if thickness errors occur during manufacturing.

[0175] (Technology 11) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of Ta. ２ O ５ and the total value is set to be equal to or greater than 77 nm and equal to or less than 105 nm.

[0176] According to this technique, the first dielectric film and the first protective film are made of SiO ２ The second dielectric film and the second protective film are Ta ２ O ５ By including the first dielectric film and the first protective film, moisture resistance and warm water resistance can be realized on the upper surface of the metal reflective film and the piezoelectric body. ２By including Ta, the refractive index of the first dielectric film can be reduced, and insulation properties with respect to the piezoelectric body can be ensured. ２ O ５ By including the element, the refractive index of the second dielectric film can be increased.

[0177] (Technology 12) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ The first dielectric film has a thickness of 35 nm or more, and the second dielectric film and the second protective film are substantially made of Ta. ２ O ５ an optical reflecting element comprising: a first dielectric film having a thickness of 10 nm or more; and a second dielectric film having a thickness of 10 nm or more; and a total thickness of 61 nm or more and 125 nm or less.

[0178] This technique can reduce the maximum variation for each sum, allowing for a smooth determination of the sum that effectively reduces variations in the mirror's reflectivity. Furthermore, the sum determined in this way can prevent unintended large variations even if thickness errors occur during manufacturing.

[0179] (Technology 13) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of TiO ２ and the total value is set to be equal to or greater than 76 nm and equal to or less than 93 nm.

[0180] According to this technique, the first dielectric film and the first protective film are made of SiO ２ and the second dielectric film and the second protective film are TiO ２ By including the first dielectric film and the first protective film, moisture resistance and warm water resistance can be realized on the upper surface of the metal reflective film and the piezoelectric body. ２ By including TiO, the refractive index of the first dielectric film can be reduced, and insulation properties with respect to the piezoelectric body can be ensured. ２By including the element, the refractive index of the second dielectric film can be increased.

[0181] (Technology 14) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ the thickness of the first dielectric film is set to 45 nm or more, and the second dielectric film and the second protective film are substantially made of TiO ２ an optical reflecting element comprising: a first dielectric film having a thickness of 5 nm or more; and a second dielectric film having a thickness of 5 nm or more; and a total thickness of 65 nm or more and 122 nm or less.

[0182] This technique can reduce the maximum variation for each sum, allowing for a smooth determination of the sum that effectively reduces variations in the mirror's reflectivity. Furthermore, the sum determined in this way can prevent unintended large variations even if thickness errors occur during manufacturing.

[0183] (Technology 15) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of Al ２ O ３ and the total value is set to be equal to or greater than 79 nm and equal to or less than 136 nm.

[0184] According to this technique, the first dielectric film and the first protective film are made of SiO ２ By including Al, it is possible to realize moisture resistance and warm water resistance on the upper surface of the metal reflective film and the piezoelectric body, and ２ O ３ By including the first dielectric film and the first protective film, moisture resistance can be achieved on the upper surface of the metal reflective film and the piezoelectric body. ２ By including Al, the refractive index of the first dielectric film can be reduced, and insulation properties with respect to the piezoelectric body can be ensured. ２ O ３By including this, the insulating properties and thermal conductivity of the second protective film are improved, so that insulation against the piezoelectric body can be ensured, heat dissipation from the piezoelectric body can be promoted, and the performance and life of the piezoelectric body can be improved.

[0185] (Technology 16) In the optical reflecting element according to Technology 2, the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of Al ２ O ３ an optical reflecting element comprising: a first dielectric film having a thickness of 30 nm or more; and a second dielectric film having a thickness of 66 nm or more and a total thickness of 136 nm or less.

[0186] This technique can reduce the maximum variation for each sum, allowing for a smooth determination of the sum that effectively reduces variations in the mirror's reflectivity. Furthermore, the sum determined in this way can prevent unintended large variations even if thickness errors occur during manufacturing.

[0187] REFERENCE SIGNS LIST 1 Optical reflecting element 11 Movable part 11a Mirror 12 Driving part 110 Piezoelectric body 121 First protective film 122 Second protective film 130 Metallic reflective film 141 First dielectric film 142 Second dielectric film

Claims

1. An optical reflecting element in which a movable part on which a mirror is formed is driven by a driving part, wherein the mirror comprises: a metal reflective film; a first dielectric film formed on the upper surface of the metal reflective film; and a second dielectric film formed on the upper surface of the first dielectric film and having a higher refractive index than the first dielectric film; and the driving part comprises: a piezoelectric body; a first protective film formed on the upper side of the piezoelectric body and made of the same material as the first dielectric film; and a second protective film formed on the upper side of the first protective film and made of the same material as the second dielectric film; and wherein the total thickness of the first dielectric film and the second dielectric film is within a range in which the fluctuation in reflectivity of the mirror in the wavelength band of light incident on the mirror is smaller than the fluctuation in reflectivity of the metal reflective film alone in the wavelength band.

2. An optical reflecting element according to claim 1, characterized in that the metal reflective film is made of silver (Ag) or a silver (Ag) alloy.

3. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of Al. ２ O ３ wherein the second dielectric film and the second protective film are substantially composed of ZrO ２ and the total value is set to be equal to or greater than 64 nm and equal to or less than 108 nm.

4. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of Al. ２ O ３ the thickness of the first dielectric film is set to 40 nm or more, and the second dielectric film and the second protective film are substantially made of ZrO ２ and the total value is set to be equal to or greater than 64 nm and equal to or less than 123 nm.

5. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of Al. ２ O ３ wherein the second dielectric film and the second protective film are substantially composed of Ta. ２ O ５ and the total value is set to be equal to or greater than 63 nm and equal to or less than 105 nm.

6. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of Al. ２ O ３ The first dielectric film has a thickness of 50 nm or more, and the second dielectric film and the second protective film are substantially made of Ta. ２ O ５ and the total value is set to be equal to or greater than 63 nm and equal to or less than 124 nm.

7. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of Al. ２ O ３ wherein the second dielectric film and the second protective film are substantially composed of TiO ２ and the total value is set to be equal to or greater than 65 nm and equal to or less than 93 nm.

8. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of Al. ２ O ３ the thickness of the first dielectric film is set to 50 nm or more, and the second dielectric film and the second protective film are substantially made of TiO ２ and the total value is set to be equal to or greater than 63 nm and equal to or less than 119 nm.

9. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of ZrO ２ and the total value is set to be equal to or greater than 78 nm and equal to or less than 108 nm.

10. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ the thickness of the first dielectric film is set to 35 nm or more, and the second dielectric film and the second protective film are substantially made of ZrO ２ an optical reflecting element comprising: a first dielectric film having a thickness of 10 nm or more; and a second dielectric film having a thickness of 10 nm or more; and a total thickness of 63 nm or more and 127 nm or less.

11. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of Ta. ２ O ５ and the total value is set to be equal to or greater than 77 nm and equal to or less than 105 nm.

12. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ The first dielectric film has a thickness of 35 nm or more, and the second dielectric film and the second protective film are substantially made of Ta. ２ O ５ an optical reflecting element comprising: a first dielectric film having a thickness of 10 nm or more; and a second dielectric film having a thickness of 10 nm or more; and a total thickness of 61 nm or more and 125 nm or less.

13. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of TiO ２ and the total value is set to be equal to or greater than 76 nm and equal to or less than 93 nm.

14. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ the thickness of the first dielectric film is set to 45 nm or more, and the second dielectric film and the second protective film are substantially made of TiO ２ an optical reflecting element comprising: a first dielectric film having a thickness of 5 nm or more; and a second dielectric film having a thickness of 5 nm or more; and a total thickness of 65 nm or more and 122 nm or less.

15. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of Al ２ O ３ and the total value is set to be equal to or greater than 79 nm and equal to or less than 136 nm.

16. The optical reflecting element according to claim 2, wherein the first dielectric film and the first protective film are substantially made of SiO ２ wherein the second dielectric film and the second protective film are substantially composed of Al ２ O ３ an optical reflecting element comprising: a first dielectric film having a thickness of 30 nm or more; and a second dielectric film having a thickness of 66 nm or more and a total thickness of 136 nm or less.

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