Optical device and imaging unit provided with optical device

Abstract

The present disclosure provides an optical device in which foreign substances adhering to the surface of a light-transmitting body can be sufficiently removed without complicating the configuration, and an imaging unit provided with the optical device. An optical device (10) is provided with an outermost layer lens (1) (light-transmitting body), a housing (2), a vibrating body (3), a piezoelectric element (5), and a drive circuit (6). The drive circuit (6) causes a voltage (Vp-p_1) of a drive signal that drives the piezoelectric element (5) in an atomization mode (first vibration mode) among a plurality of vibration modes that vibrate the outermost layer lens (1), and a voltage (Vp-p_(underbar)2) of a drive signal that drives the piezoelectric element (5) in a heating mode (second vibration mode), to be the same. The drive circuit (6) drives the piezoelectric element (5) such that an effective voltage (Veff_1) applied to the piezoelectric element (5) within a predetermined period of the atomization mode, and an effective voltage (Veff_2) applied to the piezoelectric element (5) within a predetermined period of the heating mode, are different.

Description

Optical device and imaging unit including optical device

[0001] The present disclosure relates to an optical device and an imaging unit including the optical device.

[0002] Imaging units are installed in the front or rear of a vehicle, and images obtained by the imaging units are used to control safety devices and drive assistance controls. Since such imaging units are often installed outside the vehicle, foreign matter such as raindrops (water droplets), mud, and dust may adhere to the transparent body (protective cover or lens) that covers the exterior. Furthermore, in cold weather, ice or frost may adhere to the surface of the transparent body of an imaging unit installed outside the vehicle, making it difficult to obtain clear images.

[0003] Therefore, in the lens cleaning system described in Patent Document 1, the light-transmitting body is vibrated in a plurality of drive sequences, such as a dehydration sequence and a heating sequence, to remove foreign matter adhering to the surface of the light-transmitting body. In this lens cleaning system, the voltage applied to the transducer, the period and frequency for vibrating the light-transmitting body, etc. are changed depending on the type of drive sequence.

[0004] US Patent Application Publication No. 2020 / 0282435

[0005] However, in the system disclosed in Patent Document 1, a boost circuit for changing the voltage applied to the transducer needs to be provided in the drive circuit, which increases the manufacturing cost of the drive circuit. Also, in the system disclosed in Patent Document 1, the light-transmitting body is driven at maximum power during the period in which it is vibrated, which requires circuits and wiring that can withstand this maximum power, which may lead to a complex system.

[0006] Therefore, an object of the present disclosure is to provide an optical device that can remove foreign matter adhering to the surface of a light-transmitting body without complicating the configuration, and an imaging unit that includes the optical device.

[0007] An optical device according to one aspect of the present disclosure includes a translucent body that transmits light of a predetermined wavelength, a housing that holds the translucent body, a vibrator that contacts the translucent body held in the housing, a piezoelectric element that is provided on the vibrator and vibrates the vibrator, and a drive circuit that drives the piezoelectric element. The vibrator is a cylindrical body that contacts the translucent body at a first end and has the piezoelectric element provided at a second end opposite the first end. The drive circuit drives the piezoelectric element by setting a voltage Vp-p_1 of an AC signal that drives the piezoelectric element in a first vibration mode among a plurality of vibration modes that vibrate the translucent body to be the same as a voltage Vp-p_2 of an AC signal that drives the piezoelectric element in a second vibration mode, and by setting an effective voltage Veff_1 applied to the piezoelectric element within a predetermined period in the first vibration mode to be different from an effective voltage Veff_2 applied to the piezoelectric element within a predetermined period in the second vibration mode.

[0008] An imaging unit according to one embodiment of the present disclosure includes the optical device described above and an imaging element arranged so that the light-transmitting body is in the field of view.

[0009] According to the present disclosure, the voltage of the AC signal that drives the piezoelectric element is the same in the first vibration mode and the second vibration mode, and the piezoelectric element is driven so that the effective voltage Veff_1 in the first vibration mode and the effective voltage Veff_2 in the second vibration mode are different. Therefore, the translucent body can be vibrated at different frequencies to remove foreign matter that adheres to the surface of the translucent body without complicating the configuration.

[0010] 1 is a half cross-sectional view of an imaging unit according to embodiment 1. FIG. 2 is a block diagram for explaining the configuration of a drive circuit according to embodiment 1. FIG. 3 is a graph showing the relationship between frequency and impedance when the optical device according to embodiment 1 is vibrated. FIG. 4 is a diagram for explaining a drive signal for driving a piezoelectric element in the drive circuit according to embodiment 1. FIG. 5 is a graph for explaining the relationship between the displacement amount of a light-transmitting body and the duty ratio of a drive signal. FIG. 6 is a graph for explaining a change in the maximum displacement amount of a light-transmitting body due to a change in the duty ratio of a drive signal. FIG. 7 is a graph for explaining a transient response of vibration when a light-transmitting body is excited by a drive signal. FIG. 8 is a circuit diagram for explaining the configuration of a drive circuit according to embodiment 2. FIG. 9 is a diagram for explaining a drive signal for driving a piezoelectric element in a drive circuit according to embodiment 3. FIG. 10 is a circuit diagram for explaining the configuration of a drive circuit according to embodiment 4. FIG. 11 is a graph for explaining the characteristics of a filter circuit provided in the drive circuit according to embodiment 4.

[0011] An optical device according to an embodiment and an imaging unit including the optical device will be described in detail below with reference to the drawings. Note that the same reference numerals in the drawings indicate the same or corresponding parts. The optical device described below is applied to, for example, an in-vehicle imaging unit, and can vibrate a transparent body (e.g., the outermost lens) to remove foreign matter adhering to the surface of the transparent body. The optical device is not limited to applications in in-vehicle imaging units. For example, the optical device can also be applied to security surveillance cameras, imaging units for drones, and the like.

[0012] (Embodiment 1) Fig. 1 is a half cross-sectional view of an imaging unit 100 according to embodiment 1. The X and Z directions in the figure indicate the horizontal and vertical directions of the imaging unit 100, respectively. The dashed-dotted line in Fig. 1 indicates the portion passing through the central axis of the imaging unit 100. The imaging unit 100 has an optical device 10 and an imaging element 20 arranged so that the outermost lens 1 and the inner lens 4 are in the field of view. The imaging element 20 is an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and is mounted on a circuit board (not shown).

[0013] The optical device 10 has an outermost lens 1, a housing 2, a vibrating body 3, an inner lens 4, a piezoelectric element 5, and a drive circuit 6. In the present disclosure, the optical device 10 is required to include at least the outermost lens 1, the housing 2, the vibrating body 3, the piezoelectric element 5, and the drive circuit 6, and may be configured such that the inner lens 4 is included in the imaging unit 100. After adjusting the alignment between the outermost lens 1 and the inner lens 4, the optical device 10 becomes the imaging unit 100 by attaching a case including an imaging element 20.

[0014] The outermost lens 1 is a translucent body that transmits light of a predetermined wavelength (e.g., a wavelength of visible light or a wavelength that can be captured by an imaging element), and is, for example, a convex meniscus lens. Note that the optical device 10 may use a transparent member such as a protective cover instead of the outermost lens 1. The protective cover may be made of glass or a resin such as transparent plastic.

[0015] An end of the outermost lens 1 is held by an end of a leaf spring 2a extending from the housing 2. An adhesive 2c is filled between the outermost lens 1 and a retainer 2b, which is the end of the leaf spring 2a. Although the outermost lens 1 is held by the end of the leaf spring 2a, the housing 2 may hold the outermost lens 1 directly or indirectly. Furthermore, the optical device 10 has a vibrating body 3 provided at a position in contact with the outermost lens 1 to vibrate the outermost lens 1 held in the housing 2.

[0016] The vibrating body 3 is a cylindrical body, and is in contact with the outermost lens 1 at one end 31 (first end), and has a piezoelectric element 5 provided at the other end 32 (second end) opposite the one end. The vibrating body 3 is configured such that one end 31 and the other end 32 are connected by a support part 33. The cross section of the support part 33 is S-shaped. An inner lens 4 is arranged inside the cylinder of the vibrating body 3, as shown in FIG. 1.

[0017] One end 31 has a shape that extends in the radial direction (X and Y directions) of the cylindrical body, allowing it to be stably connected to the peripheral edge of the outermost lens 1. The other end 32 is a portion that vibrates along with the vibration of the piezoelectric element 5 and has a thickness greater than other portions. This makes it easier to transmit the vibration of the piezoelectric element 5 to the outermost lens 1 more efficiently. The support portion 33 supports the one end 31 and transmits the vibration of the other end 32 to the one end 31. Note that the one end 31, the other end 32, and the support portion 33 may be formed integrally or separately. Furthermore, as shown in FIG. 1 , the maximum outer dimension of the support portion 33 is larger than the maximum outer dimension of the one end 31, and the maximum outer dimension of the other end 32 is larger than the maximum outer dimension of the support portion 33. This allows the vibration of the other end 32 (i.e., the vibration of the piezoelectric element 5) to be efficiently transmitted to the outermost lens 1 (translucent body).

[0018] The piezoelectric element 5 is provided at the other end 32. The piezoelectric element 5 has a hollow circular shape and vibrates by being polarized in the thickness direction, for example. The piezoelectric element 5 is made of lead zirconate titanate piezoelectric ceramics. However, (K,Na)NbO ３ Other piezoelectric ceramics such as LiTaO may also be used. ３ Alternatively, a piezoelectric single crystal such as the above may be used. The piezoelectric element 5 is connected to a drive circuit 6, and vibrates the outermost lens 1 based on a signal from the circuit.

[0019] The drive circuit 6 can drive the piezoelectric element 5 in an atomization mode in which the outermost lens 1 is vibrated at the resonance frequency of the vibrating body 3 in order to remove foreign matter such as raindrops, mud, and dust adhering to the outermost lens 1. The drive circuit 6 can also drive the piezoelectric element 5 in a heating mode in which the outermost lens 1 is vibrated at the natural vibration frequency of the outermost lens 1 in order to remove foreign matter such as ice and frost adhering to the outermost lens 1. The drive circuit 6 can drive the piezoelectric element 5 by switching between a plurality of vibration modes, including the atomization mode and the heating mode. The drive circuit 6 also serves as a switching unit that switches between the mode in which the outermost lens 1 is vibrated from a plurality of vibration modes.

[0020] The drive circuit 6 will now be described in detail with reference to the drawings. Fig. 2 is a block diagram for explaining the configuration of the drive circuit 6 according to the first embodiment. Fig. 2 illustrates an example in which the piezoelectric element 5 is connected to the drive circuit 6 in a single-ended manner, but this connection method is merely an example and is not limited to this. The reference potential of the piezoelectric element 5 may be, for example, ground or a body earth connected to the negative terminal of the battery.

[0021] The drive circuit 6 includes a control circuit 61 and an output circuit 62. The control circuit 61 controls the output circuit 62 to convert the voltage Vout supplied from the drive power supply circuit 7 into a drive voltage Vdrv and output it to the piezoelectric element 5. The drive circuit 6 adjusts the drive voltage Vdrv output to the piezoelectric element 5 to switch between a plurality of vibration modes including an atomization mode and a heating mode to drive the piezoelectric element 5. Although the drive power supply circuit 7 has been described as not being included in the drive circuit 6, the drive circuit 6 may include the drive power supply circuit 7.

[0022] The control circuit 61 adjusts the frequency of the drive signal by controlling the switching frequencies of multiple switches included in the output circuit 62. The control circuit 61 includes a general-purpose processor such as a CPU or MPU that executes programs to achieve predetermined functions. The control circuit 61 is configured to be able to communicate with a storage device and performs various processes in the control circuit 61, such as switching the multiple switches, by calling and executing arithmetic programs stored in the storage device. The control circuit 61 is not limited to a configuration in which hardware resources and software work together to achieve predetermined functions, but may also be a hardware circuit designed specifically to achieve the predetermined functions. In other words, the control circuit 61 can be realized by various processors such as a CPU, an MPU, a GPU, an FPGA, a DSP, an ASIC, etc. In addition to a CPU or an MPU, such a control circuit 61 can be configured, for example, as a signal processing circuit that is a semiconductor integrated circuit.

[0023] When a drive signal is applied to the piezoelectric element 5, the impedance of the piezoelectric element 5 changes depending on the frequency of the drive signal. Fig. 3 is a graph showing the relationship between frequency and impedance when the optical device 10 according to the first embodiment is vibrated. As shown in Fig. 3, the piezoelectric element 5 has a plurality of frequencies at which the impedance locally decreases. These frequencies correspond to the resonant frequencies of the vibrating body 3. In the optical device 10 according to this embodiment, the resonant frequencies are, for example, approximately 30 kHz (arrow I) and approximately 550 kHz (arrow II).

[0024] When a drive signal corresponding to one of these resonant frequencies is input, the piezoelectric element 5 vibrates the outermost lens 1 in a vibration mode that differs for each frequency. For example, when a drive signal having a frequency of approximately 30 kHz is input, the piezoelectric element 5 vibrates the outermost lens 1 via the vibrating body 3 in a first vibration mode, which is a vibration mode that vibrates the outermost lens 1 as a whole. The first vibration mode is an atomization mode that can atomize and remove foreign matter such as droplets adhering to the outermost lens 1.

[0025] Furthermore, when a drive signal having a frequency of approximately 550 kHz is input, the piezoelectric element 5 vibrates the outermost lens 1 via the vibrating body 3 in a second vibration mode (heating mode) in which the temperature of the outermost lens 1 is easily increased. Vibrations around approximately 550 kHz vibrate the outermost lens 1 in a higher-order vibration mode with a greater number of nodes than vibrations at approximately 30 kHz. In the heating mode, the impedance of the piezoelectric element 5 is small, so a large amount of power is applied to the piezoelectric element 5, allowing the temperature of the outermost lens 1 to be increased quickly.

[0026] Between the first and second vibration modes, at a frequency of approximately 110 kHz, there exists a frequency that resonates with the natural vibration of the outermost lens 1. When a drive signal having this frequency is input, the piezoelectric element 5 vibrates the center of the outermost lens 1 more strongly than the peripheral portion via the vibrating body 3. The piezoelectric element 5 may be configured to apply vibrations other than the vibration modes described above to the outermost lens 1. The above-described resonant frequency is an example and can be changed depending on the shape and material of the optical device 10, etc.

[0027] As shown in FIG. 3, when a drive signal having a frequency corresponding to the resonant frequency is input to the piezoelectric element 5, the impedance of the piezoelectric element 5 becomes locally minimum.

[0028] Until now, when the drive circuit 6 drives the piezoelectric element 5 by switching between the above-mentioned multiple vibration modes, the voltage applied to the piezoelectric element 5 has been adjusted according to the switched vibration mode. However, in order to adjust the voltage applied to the piezoelectric element 5 in the drive circuit 6, a boost circuit must be provided in the drive circuit 6, which increases the manufacturing cost of the drive circuit 6. In addition, the atomization mode and the heating mode have different conditions, such as the vibration acceleration required for the vibration to be excited. For example, in the atomization mode, the frequency of the vibration to be excited is several tens of kHz, and the vibration acceleration is 8.0 x 10 ５ m / s ２ On the other hand, in the heating mode, the frequency of the vibration to be excited is several hundred kHz, and it is necessary to supply to the piezoelectric element 5 an electric power sufficient to melt the ice and prevent overheating.

[0029] Furthermore, the optimal vibration magnitude differs between the atomization mode and the heating mode, and the voltage applied to the piezoelectric element 5 to achieve this also differs. Generally, the resonant resistance in the heating mode is significantly smaller than the resonant resistance in the atomization mode, and applying the same voltage to the piezoelectric element 5 will result in damage due to overheating and increased power consumption. Therefore, a drive circuit that supplies a rectangular wave using a half-bridge circuit or the like requires a boost circuit to adjust the voltage applied to the piezoelectric element 5, which increases the manufacturing cost of the drive circuit.

[0030] Therefore, in the optical device 10 according to the present embodiment, by adjusting the waveform of the input drive signal itself, it is possible to switch the vibration mode without changing the voltage applied from the drive circuit 6 to the piezoelectric element 5. Fig. 4 is a diagram for explaining the drive signal used to drive the piezoelectric element 5 by the drive circuit 6 according to the first embodiment. The drive circuit 6 outputs to the piezoelectric element 5 as a drive signal a rectangular wave, one cycle of which consists of a high period th where the voltage is a positive value and a low period tl where the voltage is a negative value, as shown by waveform a in Fig. 4 .

[0031] The drive circuit 6 adjusts the length of the high period th and the length of the low period tl according to the vibration mode without changing the voltage value of the high period th or the voltage value of the low period tl. In other words, the drive circuit 6 sets the voltage Vp-p_1 of the drive signal (AC signal) that drives the piezoelectric element 5 in the atomization mode, which vibrates the outermost lens 1, to the same voltage Vp-p_(underscore)2 of the drive signal that drives the piezoelectric element 5 in the heating mode (Vp-p_1 = Vp-p_2). Note that if the drive circuit 6 is considered to include a drive power supply circuit and an output circuit that converts the DC voltage output from the drive power supply circuit into an AC signal, it may be defined that the DC voltage output from the drive power supply circuit is the same in multiple vibration modes. In other words, the drive circuit 6 sets the DC voltage Vout_1 for generating a drive signal (AC signal) that drives the piezoelectric element 5 in the atomization mode, which vibrates the outermost lens 1, and the DC voltage Vout_(underscore)2 for generating a drive signal that drives the piezoelectric element 5 in the heating mode to the same voltage (Vout_1 = Vout_2).

[0032] Furthermore, the drive circuit 6 drives the piezoelectric element 5 so that the effective voltage Veff_1 applied to the piezoelectric element 5 during a specified period in the atomization mode is different from the effective voltage Veff_2 applied to the piezoelectric element 5 during a specified period in the heating mode (Veff_1≠Veff_2).

[0033] Here, voltage Vpp refers to the difference (peak-to-peak value) between the maximum value (+Vpp) and the minimum value (-Vpp) of the drive signal (AC signal). Effective voltage Veff refers to the voltage value supplied as vibration to outermost lens 1 when piezoelectric element 5 is driven by a drive signal of voltage Vpp. Drive circuit 6 changes effective voltage Veff by adjusting the length of high period th and the length of low period tl, thereby switching between atomization mode and heating mode. In the heating mode, from the viewpoint of preventing overheating of outermost lens 1, it is preferable that effective voltage Veff_1 applied to piezoelectric element 5 during a predetermined period in atomization mode be greater than effective voltage Veff_2 applied to piezoelectric element 5 during a predetermined period in heating mode (Veff_1>Veff_2).

[0034] Furthermore, the magnitude of displacement when outermost lens 1 is vibrated is defined as vibration amplitude Av, and the power input to excite outermost lens 1 is defined as power Pv. When drive circuit 6 drives piezoelectric element 5 in atomization mode, it is necessary to make the vibration amplitude Av of outermost lens 1 larger than when piezoelectric element 5 is driven in heating mode, so that foreign matter such as droplets adhering to outermost lens 1 can be atomized and removed. In other words, drive circuit 6 preferably sets the vibration amplitude Av_1 of outermost lens 1 in atomization mode to be larger than the vibration amplitude Av_2 of outermost lens 1 in heating mode (Av_1>Av_2).

[0035] Furthermore, compared to when driving the piezoelectric element 5 in the atomization mode, when driving the piezoelectric element 5 in the heating mode, the resonance resistance is lower, as shown in Figure 3, and therefore the power Pv input is greater. In other words, it is preferable that the power Pv_1 input by the drive circuit 6 in the atomization mode is smaller than the power Pv_2 input in the heating mode (Pv_1 < Pv_2). This allows the drive circuit 6 to efficiently drive the piezoelectric element 5 in each vibration mode, the atomization mode and the heating mode.

[0036] If the shorter of the high period th and the low period tl, min(th, tl), is the active period ta, the duty ratio of the drive signal can be expressed as min(th, tl) / (th + tl) = ta / (th + tl). Adjusting the length of the high period th and the length of the low period tl also adjusts the duty ratio of the drive signal. Therefore, the drive circuit 6 can change the effective voltage Veff by adjusting the duty ratio of the drive signal, making it possible to switch between atomization mode and heating mode without changing the voltage Vp-p applied to the piezoelectric element 5.

[0037] When the relationship between the drive signal in the atomization mode and the drive signal in the heating mode is generalized using the duty ratio of the drive signal, the relationship becomes as shown in Equation 1.

[0038]

[0039] Here, the high period th_1, low period tl_1, and active period ta_1 in the atomization mode, and the high period th_2, low period tl_2, and active period ta_2 in the heating mode are defined as follows. In other words, when the drive circuit 6 drives the piezoelectric element 5 for a predetermined period dt, it is preferable that the first integral value obtained by integrating the duty ratio of the drive signal that drives the piezoelectric element 5 in the atomization mode over the predetermined period dt is greater than the second integral value obtained by integrating the duty ratio of the drive signal that drives the piezoelectric element 5 in the heating mode over the predetermined period dt. This allows the drive circuit 6 to arbitrarily adjust the effective voltage Veff by changing the duty ratio of the drive signal.

[0040] 4, when the duty ratio of the drive signal is changed and the low period tl becomes longer as shown in waveform b of Fig. 4, the average value of the voltage over multiple cycles does not become 0 (zero) V but becomes a negative value. If the average value of the voltage of the drive signal is not 0 (zero) V, an offset DC voltage is applied to the piezoelectric element 5, and migration may occur between the two electrodes of the piezoelectric element 5.

[0041] Therefore, the drive circuit 6 generates a drive signal by alternating between periods in which the low period tl is long and periods in which the high period th is long, as shown in waveform c in Figure 4, so that the number of periods in which the low period tl is long and the number of periods in which the high period th are long are the same within the predetermined period dt. Specifically, in waveform c in Figure 4, the drive signal is configured so that the first high period th1 and the second low period tl2 are the same length, and the first low period tl1 and the second high period th2 are the same length. This allows the drive circuit 6 to drive the piezoelectric element 5 so that the average value of the voltage applied to the piezoelectric element 5 during the predetermined period dt is 0 (zero) V, thereby preventing migration from occurring between the electrodes of the piezoelectric element 5.

[0042] Next, it will be explained that the vibration level of the outermost lens 1 can be adjusted by changing the duty ratio of the drive signal. Fig. 5 is a graph illustrating the relationship between the displacement amount of the light-transmitting body (outermost lens 1) and the duty ratio of the drive signal. Fig. 6 is a graph illustrating the change in the maximum displacement amount of the light-transmitting body (outermost lens 1) due to a change in the duty ratio of the drive signal.

[0043] In Fig. 5, the horizontal axis represents frequency (kHz) and the vertical axis represents the displacement (μm) of the outermost lens 1, and the displacement of the outermost lens 1 is plotted when the duty ratio of the drive signal is changed from 10% to 50%. In Fig. 6, the horizontal axis represents the duty ratio (%) of the drive signal and the vertical axis represents the maximum displacement (μm) of the outermost lens 1, and the maximum displacement of the outermost lens 1 is plotted when the voltage Vp-p is 30 V and 50 V. The displacement of the outermost lens 1 can be measured using, for example, a laser Doppler displacement meter.

[0044] As shown in Figures 5 and 6, when driving the piezoelectric element 5 in atomization mode, the drive circuit 6 can increase the maximum displacement of the outermost lens 1 by changing the duty ratio of the drive signal from 10% to 50%. Therefore, the drive circuit 6 can adjust the maximum displacement (vibration level) of the outermost lens 1 by adjusting the duty ratio of the drive signal in atomization mode. Similarly, the drive circuit 6 can change the maximum displacement of the outermost lens 1 by adjusting the duty ratio of the drive signal in heating mode, thereby accurately adjusting the amount of heat generated by the outermost lens 1. In particular, when driving the piezoelectric element 5 in heating mode, the drive circuit 6 can prevent overheating of the outermost lens 1 and insufficient de-icing performance by adjusting the amount of heat generated by the drive signal.

[0045] Furthermore, adjusting the vibration level of the outermost lens 1 by changing the duty ratio of the drive signal can also be explained from the perspective of mechanical resonance. Fig. 7 is a graph for explaining the transient response of vibration when the light-transmitting body (outermost lens 1) is excited by a drive signal. In Fig. 7, the horizontal axis represents time and the vertical axis represents the displacement of the outermost lens 1.

[0046] When vibrating the outermost lens 1, the maximum displacement amount is not reached the instant a voltage is applied to the piezoelectric element 5, but rather the vibration of the outermost lens 1 is accelerated over several cycles of vibration depending on the Q value of the vibrating body 3, and reaches the maximum displacement amount. Therefore, as shown in Figure 7, when the duty ratio of the drive signal is small, the vibration is switched to the OFF state before the vibration of the outermost lens 1 has fully risen, so the displacement amount of the outermost lens 1 plateaus without reaching the maximum displacement amount and remains at a small displacement amount. On the other hand, when the duty ratio of the drive signal is large, the vibration is switched to the OFF state after the vibration of the outermost lens 1 has fully risen, so the displacement amount of the outermost lens 1 reaches the maximum displacement amount.

[0047] (Embodiment 2) In the first embodiment, the optical device 10 was described, which can change the effective voltage Veff by adjusting the duty ratio of the drive signal, and can switch between the atomization mode and the heating mode without changing the voltage Vp-p. Whether the frequency of the voltage applied to the piezoelectric element 5 is the resonant frequency can be determined by detecting the value of the current flowing through the piezoelectric element 5. Therefore, in the second embodiment, an optical device will be described which adjusts the vibration level according to the value of the current flowing through the piezoelectric element.

[0048] The optical device according to the second embodiment has the same configuration as the optical device 10 according to the first embodiment, and therefore the same components will be described using the same reference numerals and detailed description will not be repeated. Fig. 8 is a circuit diagram illustrating the configuration of a drive circuit 6A according to the second embodiment. The drive circuit 6A includes a control circuit 61, an output circuit 62, a current detection circuit 63, a capacitor 64, and a resistor 65.

[0049] The output circuit 62 is connected to the drive power supply circuit. The output circuit 62 includes a series circuit of a first switch 62a and a second switch 62b, to which a voltage Vout from the drive power supply circuit is input. A connection point C1 between the first switch 62a and the second switch 62b is connected to the piezoelectric element 5 via a capacitor 64. The first switch 62a and the second switch 62b are, for example, but not limited to, metal oxide semiconductor field effect transistors (MOSFETs).

[0050] The current detection circuit 63 detects at least one of the current flowing through the first switch 62 a and the current flowing through the second switch 62 b, and outputs a detection signal indicating the magnitude of the detected current to the control circuit 61. The current detection circuit 63 has a current-voltage conversion element 63 a, a low-pass filter 63 b, and an analog-to-digital conversion circuit (AD conversion circuit) 63 c.

[0051] The current-voltage conversion element 63a can convert the current flowing through the current-voltage conversion element 63a into a voltage corresponding to the magnitude of the current flowing through the current-voltage conversion element 63a. The current-voltage conversion element 63a is a resistor (shunt resistor) having a predetermined resistance value. The current-voltage conversion element 63a is not limited to a shunt resistor and may be a Hall element.

[0052] The low-pass filter 63b is a filter circuit that removes signals having frequency components higher than the cutoff frequency. In this embodiment, the low-pass filter 63b is connected to the connection point between the current-voltage conversion element 63a and the second switch 62b. The low-pass filter 63b smoothes the voltage input from the current-voltage conversion element 63a and outputs the smoothed voltage to the AD conversion circuit 45.

[0053] The AD conversion circuit 63c is a circuit that converts the voltage (analog signal) smoothed by the low-pass filter 63b into a digital signal that can be input to the control circuit 61. The AD conversion circuit 63c outputs the digital signal as a detection signal to the control circuit 61. The current detection circuit 63 may be configured not to include the AD conversion circuit 63c, but to output the voltage smoothed by the low-pass filter 63b as a detection signal to the control circuit 61.

[0054] The current detection circuit 63 outputs a detection signal, which is a digital signal generated based on the magnitude of the current flowing through the second switch 62b, to the control circuit 61. However, the current detection circuit 63 is not limited to this. For example, the current detection circuit 63 may be configured to include only the current-voltage conversion element 63a and the low-pass filter 63b, and to output a detection signal, which is an analog signal rather than a digital signal, to the control circuit 61.

[0055] In a first state (to be described later), the capacitor 64 can store charge based on the voltage Vout applied by the drive power supply circuit. In a second state (to be described later), the capacitor 64 can release the stored charge to the ground potential via the second switch 62b. This allows the drive circuit 6A to pass the currents I1 and I2 through the piezoelectric element 5 by the control circuit 61 controlling the switching processes of the first switch 62a and the second switch 62b.

[0056] The resistor 65 is connected between the connection point between the piezoelectric element 5 and the capacitor 64 and the ground potential. When the switching process by the control circuit 61 is completed, one end of the piezoelectric element 5 is connected to the ground potential via the resistor 65, so that the one end and the other end are at the same potential.

[0057] The control circuit 61 of the drive circuit 6A performs switching processing to complementarily switch the first switch 62a and the second switch 62b at a switching frequency. That is, the control circuit 61 controls the first switch 62a and the second switch 62b so that the second switch 62b is off (first state) when the first switch 62a is on. The control circuit 61 also controls the first switch 62a and the second switch 62b so that the second switch 62b is on (second state) when the first switch 62a is off. By complementarily switching the first switch 62a and the second switch 62b, the control circuit 61 applies a drive voltage Vdrv having a frequency corresponding to the switching frequency as a drive signal to the piezoelectric element 5 based on the voltage Vout from the drive power supply circuit.

[0058] In the first state, a current I1 flows through the drive circuit 6A via the first switch 62a. The current I1 is indicated by a dashed arrow in Fig. 8. As shown in Fig. 8, the current I1 flows from the drive power supply circuit to the piezoelectric element 5 via the first switch 62a. Therefore, a voltage that makes the drive circuit 6A side a high potential is applied to the piezoelectric element 5.

[0059] In the drive circuit 6A, when a voltage is applied to the piezoelectric element 5 in the first state, a positive charge accumulates on the output circuit 62 side and a negative charge accumulates on the ground side of the capacitor 64 located between the output circuit 62 and the piezoelectric element 5. When the control circuit 61 changes the output circuit 62 from the first state to the second state, the capacitor 64 and the piezoelectric element 5 release the charge. In the second state, the released charge flows as a current I2 within the drive circuit 6A via the second switch 62b. The current I2 is indicated by a dashed arrow in FIG. 8. As shown in FIG. 8, the current I2 flows from the piezoelectric element 5 to the ground potential via the second switch 62b. Furthermore, a negative charge accumulates on the output circuit 62 side of the capacitor 64 and a positive charge accumulates on the piezoelectric element 5 side. Therefore, a voltage that makes the drive circuit 6A side low potential is applied to the piezoelectric element 5.

[0060] In this way, the drive circuit 6A switches on and off the first switch 62a and the second switch 62b, thereby outputting a drive signal with inverted polarity at a predetermined frequency to the piezoelectric element 5. Therefore, the drive circuit 6A can adjust the frequency of the drive signal by controlling the switching frequency at which the first switch 62a and the second switch 62b are switched.

[0061] Furthermore, the drive circuit 6A can determine the resonant frequency of the vibrating body 3 by changing the switching frequency within a predetermined frequency range. Specifically, the drive circuit 6A changes the switching frequency by a predetermined increment (or decrement) within the predetermined frequency range, and determines the switching frequency at which the current value detected by the current detection circuit 63 is the largest as the resonant frequency. Therefore, the drive circuit 6A can determine the vibration level from the current value detected by the current detection circuit 63, and can change the duty ratio of the drive signal according to the determined vibration level. In other words, the drive circuit 6A can change the duty ratio of the drive signal according to the current value detected by the current detection circuit 63, and therefore can adjust for performance differences due to individual differences and temperature characteristics of devices.

[0062] (Embodiment 3) In the first embodiment, the optical device 10 was described, which can change the effective voltage Veff by adjusting the duty ratio of the drive signal. However, the method of changing the effective voltage Veff is not limited to this, and there is also a method of thinning out some pulse signals from the drive signal, which is a pulse signal that alternates between high and low periods. In the third embodiment, an optical device will be described, which can reduce the effective voltage by thinning out pulse signals from the drive signal at regular intervals. Note that the optical device according to the third embodiment has the same configuration as the optical device 10 according to the first embodiment, and therefore the same components will be described using the same reference numerals, and detailed description will not be repeated.

[0063] 9 is a diagram for explaining a drive signal for driving the piezoelectric element 5 by the drive circuit 6 according to embodiment 3. The drive circuit 6 outputs a rectangular wave, one cycle of which consists of a high period th where the voltage is a positive value and a low period tl where the voltage is a negative value, to the piezoelectric element 5 as a drive signal, as shown by waveform a in FIG.

[0064] In order to change the effective voltage Veff, the drive circuit 6 fixes the voltage during the thinning period tz to a low level (-Vpp) as shown in waveform b of Fig. 9. In waveform b of Fig. 9, the thinning period tz is set to two cycles, and the pulse signal is thinned out every two cycles. Note that although it has been described that the voltage during the thinning period tz is fixed to a low level (-Vpp) in waveform b of Fig. 9, the voltage during the thinning period tz may also be fixed to a high level (+Vpp).

[0065] If the voltage during the thinning period tz is fixed to a low level (-Vpp) or a high level (+Vpp), the average value of the voltage over multiple cycles will not be 0 (zero) V but will be a negative value (if fixed to a high level (+Vpp), the average voltage will be a positive value), as shown by waveform b in Figure 9. If the average value of the voltage of the drive signal is not 0 (zero) V, an offset DC voltage will be applied to the piezoelectric element 5, and migration may occur between the two electrodes of the piezoelectric element 5.

[0066] Therefore, the drive circuit 6 fixes the voltage during the thinning-out period tz to 0 (zero) V (GND) instead of fixing it to a low level (−Vpp) or a high level (+Vpp) as shown in waveform c in Fig. 9. Specifically, if the output circuit 62 is a half-bridge circuit of a first switch 62a and a second switch 62b as shown in Fig. 8, the voltage during the thinning-out period tz can be fixed to 0 (zero) V (GND) by turning off the first switch 62a and the second switch 62b.

[0067] In the optical device 10 according to the third embodiment, it has been explained that the effective voltage Veff is changed by providing a thinning period tz in the drive signal, but this may also be combined with the method of changing the effective voltage Veff by adjusting the duty ratio of the drive signal as described in the first embodiment.

[0068] When the relationship between the drive signal in the atomization mode and the drive signal in the heating mode is generalized using the thinning-out period tz and the duty ratio of the drive signal, the relationship becomes as shown in Equation 2.

[0069]

[0070] Here, the atomization mode has a high period th_1, a low period tl_1, and an active period ta_1, and the heating mode has a high period th_2, a low period tl_2, and an active period ta_2. The thinning-out period in both the atomization mode and the heating mode is a thinning-out period tz. Furthermore, for the drive signal shown in Equation 2, it is preferable to adjust the high period th_1 and the low period tl_1 in the atomization mode and the high period th_2 and the low period tl_2 in the heating mode so that the average value of the voltage over the predetermined period dt is 0 (zero) V.

[0071] (Embodiment 4) In the first embodiment, the optical device 10 was described, which can change the effective voltage Veff by adjusting the duty ratio of the drive signal. However, the method for changing the effective voltage Veff is not limited to this, and there is also a method for changing the load of the drive circuit. In the fourth embodiment, an optical device will be described, which can change the load of the drive circuit by inserting a filter circuit between the drive circuit and the piezoelectric element, thereby reducing the effective voltage. Note that the optical device according to the fourth embodiment has the same configuration as the optical device 10 according to the first embodiment, and therefore the same components will be described using the same reference numerals, and detailed description will not be repeated.

[0072] Fig. 10 is a circuit diagram for explaining the configuration of a drive circuit 6B according to embodiment 4. Drive circuit 6B includes a control circuit 61, an output circuit 62, a current detection circuit 63, a capacitor 64, a resistor 65, and a filter circuit 66. The filter circuit 66 may not be included in the drive circuit, but may be inserted between drive circuit 6 and piezoelectric element 5 as shown in Fig. 2, or may be inserted between drive circuit 6A and piezoelectric element 5 as shown in Fig. 8. In drive circuit 6B shown in Fig. 10, the same components as those in drive circuit 6A shown in Fig. 8 are designated by the same reference numerals, and detailed description thereof will not be repeated.

[0073] The filter circuit 66 is a low-pass filter (LPF) including a resistor 66a and a capacitor 66b. The filter circuit 66 can output a rectangular wave drive signal obtained by switching the first switch 62a and the second switch 62b at a switching frequency that is significantly faster (for example, approximately 1 / 10) than the time constant (RC), as a signal close to a triangular wave. Fig. 11 is a graph illustrating the characteristics of the filter circuit 66 provided in the drive circuit 6B according to the fourth embodiment. In Fig. 11, the horizontal axis represents time and the vertical axis represents response.

[0074] The filter circuit 66 can reduce the effective voltage of the drive signal by converting the input rectangular wave drive signal into a signal that resembles a triangular wave, as shown in FIG. 11 . When the voltage difference (peak-to-peak value) between the maximum and minimum values ​​of the signal that resembles a triangular wave is the same as the voltage difference (peak-to-peak value) between the maximum value (+Vpp) and the minimum value (-Vpp) of the drive signal, the effective voltage of the signal that resembles a triangular wave is approximately half the effective voltage of the drive signal. Note that in the case of a signal that resembles a triangular wave, as shown in FIG. 11 , the drive circuit 6B sets the DC voltage Vout_1 for generating the drive signal (AC signal) that drives the piezoelectric element 5 in the atomization mode that vibrates the outermost lens 1 and the DC voltage Vout_(underscore)2 for generating the drive signal that drives the piezoelectric element 5 in the heating mode to the same value (Vout_1 = Vout_2).

[0075] 10 shows a configuration in which one filter circuit 66 is inserted between the output circuit 62 and the piezoelectric element 5, but the configuration is not limited to this and multiple filter circuits 66 may be inserted. By inserting multiple filter circuits 66 between the output circuit 62 and the piezoelectric element 5, the drive circuit 6B can also output a sine wave drive signal.

[0076] 3, the frequency of the drive signal that drives the piezoelectric element 5 in the atomization mode is smaller than the frequency of the drive signal that drives the piezoelectric element 5 in the heating mode. Therefore, in drive circuit 6B, by setting the time constant (RC) to be smaller than the half cycle of the drive signal that drives the piezoelectric element 5 in the atomization mode and larger than the half cycle of the drive signal that drives the piezoelectric element 5 in the heating mode, it is possible to make the effective voltage Veff_1 in the atomization mode larger than the effective voltage Veff_2 in the heating mode (Veff_1>Veff_2).

[0077] Furthermore, the drive circuit 6B may use a variable resistor for the resistor 66a and a variable capacitance for the capacitor 66b included in the filter circuit 66, and may change the resistance value of the resistor 66a and the capacitance value of the capacitor 66b according to the value of the current detected by the current detection circuit 63. By changing the resistance value of the resistor 66a and the capacitance value of the capacitor 66b according to the value of the current detected by the current detection circuit 63, the drive circuit 6B can adjust for performance differences due to individual differences and temperature characteristics of devices.

[0078] The configuration of the drive circuit 6B according to the fourth embodiment can be combined with the optical device according to the other embodiments.

[0079] (Modification) In the optical device 10 according to the embodiment, the cross-sectional shape of the support portion 33 is described as being S-shaped. However, the cross-sectional shape of the support portion is not limited to an S-shape as long as it is a shape that does not cause stress concentration in the vibrating body. For example, the cross-sectional shape of the support portion 33 may be a shape formed by connecting multiple S-shapes. Furthermore, as long as the cross-sectional shape reduces the areas where stress concentrates in the support portion 33, the cross-sectional shape may be a curved shape that is half of an S-shape.

[0080] The imaging unit 100 according to the above-described embodiment may include a camera, LiDAR, radar, etc. Furthermore, a plurality of imaging units 100 may be arranged side by side.

[0081] The imaging unit 100 according to the above-described embodiment is not limited to imaging units installed in vehicles, but can be similarly applied to any imaging unit that includes an optical device and an imaging element arranged so that a light-transmitting body is in the field of view, and that requires removal of foreign matter from the light-transmitting body.

[0082] (Aspects) (1) An optical device according to the present disclosure includes: a translucent body that transmits light of a predetermined wavelength; a housing that holds the translucent body; a vibrator that contacts the translucent body held in the housing; a piezoelectric element that is provided on the vibrator and vibrates the vibrator; and a drive circuit that drives the piezoelectric element, wherein the vibrator is a cylindrical body that contacts the translucent body at a first end and has the piezoelectric element provided at a second end opposite the first end, and the drive circuit drives the piezoelectric element by making the voltage Vp-p_1 of an AC signal that drives the piezoelectric element in a first vibration mode of a plurality of vibration modes that vibrate the translucent body equal to the voltage Vp-p_(underscore)2 of an AC signal that drives the piezoelectric element in a second vibration mode, and by making the effective voltage Veff_1 applied to the piezoelectric element within a predetermined period of the first vibration mode different from the effective voltage Veff_2 applied to the piezoelectric element within a predetermined period of the second vibration mode.

[0083] (2) In the optical device described in (1), the drive circuit drives the piezoelectric element so that the effective voltage Veff_1 applied to the piezoelectric element within a predetermined period of the first vibration mode is greater than the effective voltage Veff_2 applied to the piezoelectric element within a predetermined period of the second vibration mode.

[0084] (3) In the optical device described in (1) or (2), the drive circuit drives the piezoelectric element so that the vibration amplitude Av_1 of the light-transmitting body in the first vibration mode is greater than the vibration amplitude Av_2 of the light-transmitting body in the second vibration mode, and the power Pv_1 input in the first vibration mode is less than the power Pv_2 input in the second vibration mode.

[0085] (4) In the optical device described in any one of (1) to (3), the drive circuit drives the piezoelectric element so that a first integral value obtained by integrating the duty ratio of an AC signal that drives the piezoelectric element in a first vibration mode over a predetermined period is greater than a second integral value obtained by integrating the duty ratio of an AC signal that drives the piezoelectric element in a second vibration mode over a predetermined period.

[0086] (5) In the optical device described in (4), the drive circuit drives the piezoelectric element so that the average value of the voltage applied to the piezoelectric element during a predetermined period becomes 0 (zero) V.

[0087] (6) In the optical device described in (4) or (5), the driving circuit provides a period in which the voltage value of the AC signal that drives the piezoelectric element is 0 (zero), and drives the piezoelectric element so that the first integral value is greater than the second integral value.

[0088] (7) In the optical device described in any one of (1) to (6), the driving circuit includes: a current detection circuit that detects the value of a current flowing through the piezoelectric element; and a control circuit that changes the duty ratio of an AC signal that drives the piezoelectric element according to the current value detected by the current detection circuit, thereby controlling the effective voltage Veff_1 to be greater than the effective voltage Veff_2.

[0089] (8) In the optical device described in any one of (1) to (7), the drive circuit outputs an AC signal to the piezoelectric element via a filter circuit, and the time constant of the filter circuit is smaller than half the period of the AC signal that drives the piezoelectric element in the first vibration mode and larger than half the period of the AC signal that drives the piezoelectric element in the second vibration mode.

[0090] (9) In the optical device described in any one of (1) to (8), the first vibration mode is an atomization mode in which the light-transmitting body is vibrated to atomize foreign matter adhering to the light-transmitting body, and the second vibration mode is a heating mode in which the light-transmitting body is vibrated to heat the light-transmitting body.

[0091] (10) The optical device described in (9) further includes a switching unit that switches the mode in which the transparent body is vibrated from among a plurality of vibration modes, and the switching unit switches between the atomization mode and the heating mode based on an image obtained by the imaging element.

[0092] (11) Another optical device according to the present disclosure includes: a translucent body that transmits light of a predetermined wavelength; a housing that holds the translucent body; a vibrator that contacts the translucent body held in the housing; a piezoelectric element that is provided on the vibrator and vibrates the vibrator; and a drive circuit that drives the piezoelectric element, wherein the vibrator is a cylindrical body that contacts the translucent body at a first end and has the piezoelectric element provided at a second end opposite to the first end, and the drive circuit includes: a drive power supply circuit; and an output circuit that converts a DC voltage output from the drive power supply circuit into an AC signal, wherein the DC voltage Vout_1 for generating an AC signal that drives the piezoelectric element in a first vibration mode out of a plurality of vibration modes that vibrate the translucent body is the same as the DC voltage Vout_(underscore)2 for generating an AC signal that drives the piezoelectric element in a second vibration mode, The piezoelectric element is driven so that an effective voltage Veff_1 applied to the piezoelectric element within a predetermined period in the first vibration mode is different from an effective voltage Veff_2 applied to the piezoelectric element within the predetermined period in the second vibration mode.

[0093] (12) An imaging unit according to the present disclosure includes the optical device according to any one of (1) to (11) and an imaging element arranged so that the light-transmitting body is in the field of view.

[0094] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0095] 1 Outermost lens, 2 Housing, 2a Leaf spring, 2b Retainer, 3 Vibrator, 4 Inner lens, 5 Piezoelectric element, 6, 6A, 6B Drive circuit, 7 Drive power supply circuit, 10 Optical device, 20 Imaging element, 61 Control circuit, 62 Output circuit, 63 Current detection circuit, 64, 66b Capacitor, 65, 66a Resistor, 66 Filter circuit, 100 Imaging unit.

Claims

1. A light-transmitting body that transmits light of a predetermined wavelength; A housing for holding the light-transmitting body; a vibrator in contact with the light-transmitting body held by the housing; a piezoelectric element provided on the vibrating body and vibrating the vibrating body; A drive circuit for driving the piezoelectric element, The vibrator is a cylindrical body, and is in contact with the light-transmitting body at a first end, and the piezoelectric element is provided at a second end opposite to the first end, The drive circuit includes: a voltage Vp-p_1 of an AC signal for driving the piezoelectric element in a first vibration mode among a plurality of vibration modes for vibrating the transparent body is set equal to a voltage Vp-p_2 of an AC signal for driving the piezoelectric element in a second vibration mode; driving the piezoelectric element such that an effective voltage Veff_1 applied to the piezoelectric element within a predetermined period of the first vibration mode is greater than an effective voltage Veff_2 applied to the piezoelectric element within the predetermined period of the second vibration mode; The first vibration mode is an atomization mode in which the transparent body is vibrated to atomize foreign matter attached to the transparent body, The optical device, wherein the second vibration mode is a heating mode in which the light-transmitting body is vibrated to heat the light-transmitting body.

2. 2. The optical device according to claim 1, wherein the drive circuit drives the piezoelectric element such that a vibration amplitude Av_1 of the translucent body in the first vibration mode is greater than a vibration amplitude Av_2 of the translucent body in the second vibration mode, and a power Pv_1 input in the first vibration mode is smaller than a power Pv_2 input in the second vibration mode.

3. 3. The optical device of claim 1, wherein the driving circuit drives the piezoelectric element so that a first integral value obtained by integrating a duty ratio of an AC signal that drives the piezoelectric element in the first vibration mode over the specified period is greater than a second integral value obtained by integrating a duty ratio of an AC signal that drives the piezoelectric element in the second vibration mode over the specified period.

4. 4. The optical device according to claim 3, wherein the drive circuit drives the piezoelectric element so that an average value of the voltage applied to the piezoelectric element during the predetermined period becomes 0 (zero) V.

5. The optical device according to claim 3 , wherein the driving circuit provides a period during which a voltage value of an AC signal that drives the piezoelectric element is 0 (zero), and drives the piezoelectric element so that the first integral value is greater than the second integral value.

6. The drive circuit includes: a current detection circuit for detecting a value of a current flowing through the piezoelectric element; 3. The optical device according to claim 1, further comprising: a control circuit that changes a duty ratio of an AC signal that drives the piezoelectric element in accordance with a current value detected by the current detection circuit so that the effective voltage Veff_1 is greater than the effective voltage Veff_2.

7. The drive circuit outputs an AC signal to the piezoelectric element through a filter circuit, 3. The optical device according to claim 1, wherein a time constant of the filter circuit is smaller than a half period of the AC signal that drives the piezoelectric element in the first vibration mode and is larger than a half period of the AC signal that drives the piezoelectric element in the second vibration mode.

8. A switching unit that switches a mode in which the light-transmitting body is vibrated from among the plurality of vibration modes, The optical device according to claim 1 , wherein the switching unit switches between the atomization mode and the heating mode based on an image obtained by an imaging element.

9. A light-transmitting body that transmits light of a predetermined wavelength; A housing for holding the light-transmitting body; a vibrator in contact with the light-transmitting body held by the housing; a piezoelectric element provided on the vibrating body and vibrating the vibrating body; A drive circuit for driving the piezoelectric element, The vibrator is a cylindrical body, and is in contact with the light-transmitting body at a first end, and the piezoelectric element is provided at a second end opposite to the first end, The drive circuit includes: a driving power supply circuit; and an output circuit that converts a DC voltage output from the driving power supply circuit into an AC signal, the DC voltage Vout_1 for generating an AC signal for driving the piezoelectric element in a first vibration mode among a plurality of vibration modes for vibrating the transparent body is set to be equal to the DC voltage Vout_2 for generating an AC signal for driving the piezoelectric element in a second vibration mode, driving the piezoelectric element such that an effective voltage Veff_1 applied to the piezoelectric element within a predetermined period of the first vibration mode is greater than an effective voltage Veff_2 applied to the piezoelectric element within the predetermined period of the second vibration mode; The first vibration mode is an atomization mode in which the transparent body is vibrated to atomize foreign matter attached to the transparent body, The optical device, wherein the second vibration mode is a heating mode in which the light-transmitting body is vibrated to heat the light-transmitting body.

10. The optical device according to any one of claims 1 to 9, an imaging element disposed so that the light-transmitting body is in a field of view;