Vibration device and vibration method

Abstract

This vibration device comprises a light transmissive body, a vibration body that vibrates the light transmissive body, a drive unit that drives the vibration body, and a control unit that controls the drive unit. The control unit determines a high-frequency-band resonance frequency of the vibration body on the basis of a state of the drive unit obtained by varying the drive frequency of the drive unit in a high-frequency band of 100 kHz or more, and estimates the temperature of the light transmissive body on the basis of the high-frequency-band resonance frequency that has been determined of the vibration body.

Description

[Technical Field]

[0001] The present disclosure relates to a vibration device and a vibration method. [Background technology]

[0002] There is known a technology in which an imaging device is installed outside a vehicle and the captured image is used to control safety devices, automatic driving, etc. In such imaging devices, foreign matter such as mud, dust, raindrops, snow, ice, frost, etc. may adhere to the transparent body, such as the lens or protective cover, that covers the exterior of the imaging device. When foreign matter adheres to the transparent body, the foreign matter is reflected in the captured image, making it difficult to obtain a clear image.

[0003] Patent Document 1 discloses a technique for vibrating a lens at a first frequency (cleaning mode) to remove foreign matter adhering to the lens, and a technique for vibrating the lens at a second frequency (heating mode) to heat the lens in cold weather. The technique described in Patent Document 1 estimates the lens temperature by measuring the impedance response of a lens cover system to determine whether to heat the lens. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2011-517417 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the impedance related to the vibration of the transparent body depends not only on the temperature of the transparent body but also on the amount of foreign matter attached to the transparent body, it may not be possible to accurately estimate the temperature of the transparent body based on measuring the impedance response.

[0006] An object of the present disclosure is to provide a vibration device and a vibration method that can estimate the temperature of a light-transmitting body more accurately than conventional techniques. [Means for solving the problem]

[0007] A vibration device according to one aspect of the present disclosure includes: A transparent body; a vibrator that vibrates the transparent body; a drive unit that drives the vibrator; a control unit that controls the drive unit, The control unit determining a high frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a high frequency band of 100 kHz or more; The temperature of the transparent body is estimated based on the determined high frequency band resonance frequency.

[0008] A vibration method according to one aspect of the present disclosure includes: A transparent body; a vibrator that vibrates the transparent body; a drive unit that drives the vibrator; A vibration method performed by a vibration device including a control unit that controls the drive unit, a step in which the control unit determines a high-frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a high-frequency band of 100 kHz or more; The control unit estimates a temperature of the transparent body based on the determined high frequency band resonance frequency; Includes: [Effects of the Invention]

[0009] According to the vibration device and vibration method of the present disclosure, it is possible to estimate the temperature of a light-transmitting body more accurately than with conventional techniques. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view showing a configuration example of an imaging unit according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the imaging unit of FIG. [Figure 3] FIG. 2 is a block diagram illustrating a hardware configuration of an imaging unit according to an embodiment. [Figure 4] 10 is a flowchart illustrating an example of the operation of the imaging unit according to the embodiment. [Figure 5] 10 is a graph showing the relationship between the resonance frequency, impedance, and temperature of the vibrating section in the low frequency band. [Figure 6A] 10 is a graph showing the relationship between the resonance frequency and temperature in the low frequency band of the vibrating section. [Figure 6B] 10 is a graph showing the relationship between the minimum impedance value and temperature in the low frequency band of a piezoelectric vibrator. [Figure 7A] 10 is a graph showing the relationship between the amount of attached water, which is an example of foreign matter, and the resonance frequency of the vibrating section in a low frequency band. [Figure 7B] 10 is a graph showing the relationship between the amount of attached water, which is an example of foreign matter, and the impedance of a piezoelectric vibrator in a low frequency band. [Figure 8A] 10 is a graph showing the relationship between the resonance frequency and temperature in the high frequency band of the vibrating section. [Figure 8B] 10 is a graph showing the relationship between the minimum impedance value and temperature in the high frequency band of a piezoelectric vibrator. [Figure 9A] 10 is a graph showing the relationship between the amount of attached water, which is an example of foreign matter, and the resonance frequency of the vibrating section in a high frequency band. [Figure 9B] 10 is a graph showing the relationship between the amount of attached water, which is an example of foreign matter, and the impedance of a piezoelectric vibrator in a high frequency band. [Figure 10] 5 is a flowchart illustrating an example of the temperature estimation operation of FIG. 4. [Figure 11] 10 is a schematic timing chart for explaining a heating operation in the imaging unit according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A vibration device according to one aspect of the present disclosure includes: A transparent body; a vibrator that vibrates the transparent body; a drive unit that drives the vibrator; a control unit that controls the drive unit, The control unit determining a high frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a high frequency band of 100 kHz or more; The temperature of the transparent body is estimated based on the determined high frequency band resonance frequency.

[0012] According to this configuration, the temperature of the light-transmitting body can be estimated more accurately than with conventional techniques.

[0013] In the vibration device, the control unit When the estimated temperature of the light-transmitting body is lower than a predetermined value, the driving unit is controlled to vibrate the vibrating body at a high frequency of 100 kHz or more; When the estimated temperature of the translucent body is equal to or higher than the predetermined value, the low-frequency band resonant frequency of the vibrator may be determined based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band of less than 100 kHz, and the drive unit may be controlled to vibrate the vibrator at the determined low-frequency band resonant frequency.

[0014] According to this configuration, the temperature of the light-transmitting body can be increased as needed, and foreign matter adhering to the light-transmitting body can be easily removed.

[0015] In the vibration device, the control unit If the estimated temperature of the transparent body is less than a predetermined value, determining again the high frequency band resonance frequency of the vibrator based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a high frequency band; re-estimating the temperature of the transparent body based on the re-determined high frequency band resonance frequency; If the re-estimated temperature of the light-transmitting body is less than the predetermined value, the re-estimated temperature of the light-transmitting body is measured until the re-estimated temperature of the light-transmitting body becomes equal to or greater than the predetermined value. controlling the driving unit to vibrate the vibrating body for a predetermined period at a frequency in a high frequency band; After the predetermined period has elapsed, determining again the high frequency band resonance frequency of the vibrator based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a high frequency band; The temperature of the transparent body may be estimated again based on the re-determined high frequency band resonance frequency.

[0016] According to this configuration, the temperature of the light-transmitting body can be increased as needed, and foreign matter adhering to the light-transmitting body can be easily removed.

[0017] In the vibration device, when the re-estimated temperature of the translucent body becomes equal to or higher than the predetermined value, or when the estimated temperature of the translucent body is equal to or higher than the predetermined value, the control unit may determine a low-frequency band resonant frequency of the vibrator based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band of less than 100 kHz, and control the drive unit to vibrate the vibrator at the determined low-frequency band resonant frequency.

[0018] According to this configuration, when the temperature of the light-transmitting body reaches or exceeds the predetermined value, foreign matter adhering to the light-transmitting body can be easily removed.

[0019] The vibration device may further include a temperature sensor that measures a temperature of the transparent body. When the temperature of the translucent body measured by the temperature sensor is equal to or higher than the predetermined value, the control unit may determine a low-frequency band resonant frequency of the vibrator based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band of less than 100 kHz, and control the drive unit to vibrate the vibrator at the determined low-frequency band resonant frequency.

[0020] According to this configuration, the temperature of the light-transmitting body can be controlled more accurately, and foreign matter adhering to the light-transmitting body can be more easily removed.

[0021] In the vibration device, the optically transparent body is disposed in a field of view of an imaging device; The control unit may acquire an image from the imaging device and perform image processing on the image, and if the result of the image processing indicates that no foreign matter is attached to the surface of the translucent body, may determine a low-frequency band resonant frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band of less than 100 kHz, and control the drive unit to vibrate the vibrator at the determined low-frequency band resonant frequency.

[0022] According to this configuration, it is possible to more accurately determine whether or not foreign matter is attached to the light-transmitting body, and it becomes easier to remove foreign matter attached to the light-transmitting body.

[0023] In the vibration device, the control unit determines the low frequency band resonance frequency based on the state of the drive unit, the control unit changes the drive frequency of the drive unit within a low frequency band and measures the drive current of the drive unit; the control unit determines the low frequency band resonant frequency based on the measured value of the drive current; may include:

[0024] According to this configuration, the low frequency band resonance frequency can be determined with high accuracy, and foreign matter adhering to the transparent body can be more easily removed.

[0025] In the vibration device, the control unit determines the high frequency band resonance frequency based on the state of the drive unit, the control unit changes the drive frequency of the drive unit within a high frequency band and measures the drive current of the drive unit; the control unit determines the high frequency band resonant frequency based on the measured value of the drive current; may include:

[0026] According to this configuration, the high frequency band resonant frequency can be determined with high accuracy, and the temperature of the light-transmitting body can be estimated more accurately than with conventional techniques.

[0027] In the vibration device, the control unit may estimate the temperature T of the light-transmitting body based on equation (1). T=A·fr+B ···(1) Here, A is a constant smaller than 0, B is a constant larger than 0, and fr is the resonant frequency of the vibrating body.

[0028] According to this configuration, the temperature of the light-transmitting body can be estimated more accurately.

[0029] A vibration method according to one aspect of the present disclosure includes: A transparent body; a vibrator that vibrates the transparent body; a drive unit that drives the vibrator; A vibration method performed by a vibration device including a control unit that controls the drive unit, a step in which the control unit determines a high-frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a high-frequency band of 100 kHz or more; The control unit estimates a temperature of the transparent body based on the determined high frequency band resonance frequency; Includes:

[0030] According to the vibration method, the temperature of the light-transmitting body can be estimated more accurately than with the prior art.

[0031] Hereinafter, an embodiment of a vibration device according to the present disclosure will be described with reference to the accompanying drawings. Note that in the following embodiments, identical or similar components are designated by the same reference numerals. Furthermore, in the accompanying drawings, the shape, size, positional relationship, etc. of each component may be exaggerated to facilitate understanding of the description.

[0032] 1. Configuration 1-1. Overall structure FIG. 1 is a perspective view showing an example configuration of an imaging unit 100 according to an embodiment of the present disclosure.

[0033] For ease of explanation, a virtual axis C is shown in FIG. 1. In this specification, the direction parallel to the axis C is called the axial direction, the direction perpendicular to the axis C is called the radial direction, and the circumferential direction centered on the axis C is called the circumferential direction. With respect to the axial direction, the direction toward the left as you face the paper surface of FIG. 1 is considered positive. The positive axial direction is also called the tip side, and the negative axial direction is also called the base side. With respect to the radial direction, the direction away from the axis C is sometimes called the outward direction, and the direction toward the axis C is sometimes called the inward direction.

[0034] The imaging unit 100 includes a housing 1, a transparent protective cover 2 provided on one surface of the housing 1, and a cleaning nozzle 3. The cleaning nozzle 3 has an opening 31 for discharging a cleaning liquid (cleaning agent) toward the protective cover 2.

[0035] Fig. 2 is a cross-sectional view of the imaging unit 100 of Fig. 1. The imaging unit 100 further includes a vibration section 12 that vibrates the protective cover 2, and an imaging device 5.

[0036] The imaging unit 100 has a configuration for capturing images (imaging device 5), a configuration for vibrating the protective cover 2 to remove foreign matter adhering to the protective cover 2 (vibration device), and a configuration for ejecting a cleaning liquid onto the protective cover 2 to remove foreign matter adhering to the protective cover 2 (cleaning device). The cleaning nozzle 3 is an example of the cleaning device.

[0037] 2, a base plate 4a is fixed to one end of the housing 1, and a protective cover 2 and a vibrating section 12 are provided on the other end of the housing 1. An imaging device 5 is supported by a cylindrical main body member 4 and fixed to the base plate 4a.

[0038] A circuit 6 including an imaging element is built into the imaging device 5. A lens module 7 is fixed in the imaging direction of the imaging device 5. The lens module 7 is made of a cylindrical body and has a plurality of lenses 9 arranged axially inside. However, the structure of the imaging device 5 is not limited to this, and it may be any structure that can capture an image of a subject located in front of the lenses 9 (toward the tip end).

[0039] The vibrating section 12 has a cylindrical first tubular member 13 centered on the axis C, a cylindrical second tubular member 14 centered on the axis C, and a cylindrical piezoelectric vibrator 15 centered on the axis C. The vibrating section 12 is an example of a vibrating body. The piezoelectric vibrator 15 is sandwiched between the first tubular member 13 and the second tubular member 14.

[0040] The piezoelectric vibrator 15 has cylindrical piezoelectric plates 16 and 17. The piezoelectric plates 16 and 17 are each polarizable in the axial direction. The polarization direction of the piezoelectric plate 16 is configured to be opposite to the polarization direction of the piezoelectric plate 17.

[0041] The piezoelectric plates 16 and 17 include, for example, lead zirconate titanate piezoelectric ceramics, (K,Na)NbO3 piezoelectric ceramics, or LiTaO3 piezoelectric single crystal. Electrodes (not shown) are formed on each of the piezoelectric plates 16 and 17. The electrodes have, for example, a layered structure of Ag / NiCu / NiCr.

[0042] The first cylindrical member 13 and the second cylindrical member 14 are made of, for example, a metal such as duralumin, stainless steel, or Kovar, or a semiconductor such as Si having electrical conductivity.

[0043] By applying an AC electric field to the electrodes of each of the piezoelectric plates 16 and 17, the piezoelectric vibrator 15 can be vibrated in the vertical or horizontal direction. The first cylindrical member 13 has a male thread portion on at least a portion of its outer surface, and the second cylindrical member 14 has a female thread portion on at least a portion of its inner surface. These threads allow the first cylindrical member 13 to be screwed into the second cylindrical member 14, and the first cylindrical member 13 is fixed to the second cylindrical member 14. This screwing brings a portion of the first cylindrical member 13 and a portion of the second cylindrical member 14 into pressure contact with one side and the other side of the piezoelectric vibrator 15, respectively.

[0044] Therefore, the entire vibrating portion 12 vibrates efficiently due to the vibration generated in the piezoelectric vibrator 15. In this embodiment, the vibrating portion 12 is excited efficiently by the longitudinal effect or the lateral effect.

[0045] The second cylindrical member 14 has a cylindrical thin-walled portion 14a and flange portions 14b and 14c. The flange portion 14c protrudes outward from the thin-walled portion 14a at the tip of the second cylindrical member 14. The flange portion 14b protrudes outward from the thin-walled portion 14a on the base end side of the second cylindrical member 14 from the flange portion 14c. The thickness of the thin-walled portion 14a is thinner than the thickness of the first cylindrical member 13. Therefore, the cylindrical thin-walled portion 14a is largely displaced by the vibration of the vibrating portion 12, and the vibration, particularly the amplitude, can be increased.

[0046] The protective cover 2 is fixed to the flange portion 14c. In the illustrated example, the protective cover 2 has a hemispherical shape. The protective cover 2 is an example of a translucent body that transmits light from the subject. The material of the protective cover 2 is, for example, soda glass, borosilicate glass, aluminosilicate glass, or a combination thereof. The protective cover 2 may be tempered glass whose strength has been increased by chemical strengthening or the like. The surface of the protective cover 2 may be coated with an anti-reflective film, a water-repellent material, an impact-resistant material, or the like.

[0047] The cleaning nozzle 3 receives a supply of cleaning liquid from the base end side, and discharges the cleaning liquid onto the protective cover 2 through an internal tube extending in the axial direction and an opening 31. The tip of the cleaning nozzle 3 is outside the imaging range (field of view) of the imaging device 5, and is not in a position where it will appear in an image captured by the imaging device 5. In this embodiment, a configuration is shown in which the imaging unit 100 is equipped with one cleaning nozzle 3, but the imaging unit 100 may be equipped with multiple cleaning nozzles 3.

[0048] 1-2.Hardware configuration 3 is a block diagram illustrating an example of the hardware configuration of the imaging unit 100. The imaging unit 100 further includes a signal processing circuit 20, a piezoelectric driving unit 30, a cleaning liquid discharging unit 50, a cleaning driving unit 60, an impedance detection unit 70, and a power supply circuit 80.

[0049] The signal processing circuit 20 is a control unit that processes signals from the imaging device 5 and supplies control signals to the imaging device 5, the piezoelectric driving unit 30, and the cleaning driving unit 60. Such information processing is realized, for example, by the signal processing circuit 20 operating in accordance with instructions from a program.

[0050] The signal processing circuit 20 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), an input / output interface for maintaining signal consistency with peripheral devices, etc. The ROM stores, for example, programs and control data for the CPU to operate. The RAM functions as a work area for the CPU.

[0051] The piezoelectric driver 30 generates an AC output signal in response to a control signal from the signal processing circuit 20 and transmits it to the piezoelectric vibrator 15. The AC output signal includes, for example, information regarding frequency and voltage. The piezoelectric vibrator 15 vibrates based on the received AC output signal, causing the vibrating part 12 and the protective cover 2 to vibrate.

[0052] The cleaning drive unit 60 causes the cleaning liquid discharge unit 50 to supply the cleaning liquid based on a control signal from the signal processing circuit 20. The supplied cleaning liquid is discharged onto the protective cover 2 through the opening 31 of the cleaning nozzle 3.

[0053] The impedance detection unit 70 monitors electrical characteristics such as the drive current and impedance of the piezoelectric drive unit 30 when the piezoelectric drive unit 30 applies an AC output signal to the piezoelectric vibrator 15 to operate the piezoelectric vibrator 15. The impedance detection unit 70 is an example of a control unit, and may be provided separately from the signal processing circuit 20 as shown in FIG.

[0054] 2.Operation 2-1. Overall operation 4 is a flowchart for explaining an example of the operation of the imaging unit 100. The operation of FIG.

[0055] First, the signal processing circuit 20 estimates the temperature of the protective cover 2 based on the drive current of the piezoelectric drive unit 30 (S1). The temperature estimation step S1 will be described in detail later.

[0056] Next, the signal processing circuit 20 determines whether the temperature estimated in step S1 is less than the lower threshold value of 0°C (S2). The lower threshold value is not limited to 0°C, and may be set to a temperature selected in advance from, for example, -4°C to +4°C.

[0057] If the temperature estimated in step S1 is below 0°C (Yes in S2), the signal processing circuit 20 causes the piezoelectric driving unit 30 to operate the piezoelectric vibrator 15 in heating mode for a predetermined time (S3). The heating mode is a mode in which the piezoelectric vibrator 15 vibrates at a frequency in the high frequency band, and the vibration can increase the temperature of the protective cover 2. After completing step S3, the signal processing circuit 20 returns to step S1.

[0058] If the temperature estimated in step S1 is not below 0° C. (No in S2), that is, if it is 0° C. or higher, the signal processing circuit 20 operates the piezoelectric vibrator 15 in a low frequency band search mode (S4).

[0059] The low frequency band search mode in step S4 is a mode for searching for a resonance frequency in the low frequency band of the vibration unit 12 (hereinafter referred to as "low frequency band resonance frequency"). In this specification, low frequency means a frequency less than 100 kHz, and high frequency means a frequency equal to or greater than 100 kHz. In the low frequency band search mode, the piezoelectric driving unit 30 sets the drive voltage Vdr of the piezoelectric vibrator 15 to V1, sweeps the drive frequency f, and applies an AC output signal to the piezoelectric vibrator 15.

[0060] During the low frequency band search mode in step S4, the impedance detection unit 70 monitors the current value or impedance of the piezoelectric driver 30. Specifically, the impedance detection unit 70 measures the current value or the impedance, which is the reciprocal of the current value, flowing through the piezoelectric driver 30. The signal processing circuit 20 acquires the drive frequency f and the current value or impedance, and determines the drive frequency f at which the current value is maximum I_low0 or the drive frequency f at which the impedance is minimum as the initial resonance frequency fr_low0. In this way, the signal processing circuit 20 measures the maximum current value I_low0 and the corresponding initial resonance frequency fr_low0.

[0061] The signal processing circuit 20 updates the memory with the initial resonance frequency fr_low0 and current value I_low0 measured in step S4 as the reference frequency fr and reference current value I, respectively (step S5).

[0062] Next, the signal processing circuit 20 operates the piezoelectric vibrator 15 in a low frequency band search mode and measures the maximum current value I_low1 and the corresponding resonance frequency fr_low1 by the same means as in step S4 (S6). Step S6 is executed after a certain time, for example, one second, has elapsed since step S4.

[0063] The signal processing circuit 20 calculates a difference value Δfr between the reference frequency fr and the resonant frequency fr_low1, and a difference value ΔI (=I_low1-I) between the reference current value I and the maximum current value I_low1, and determines whether the difference values Δf and ΔI are equal to or less than a first threshold value (S7). Specifically, the signal processing circuit 20 determines whether the difference values Δf (=fr_low1-fr)≦-fth and ΔI (=I_low1-I)≦-Ith.

[0064] Here, the relationship between the low-frequency band resonant frequency and temperature will be explained. FIG. 5 is a graph showing the relationship between the low-frequency band resonant frequency, impedance, and temperature of the vibrating portion 12. The horizontal axis of the graph in FIG. 5 represents frequency [kHz], and the vertical axis represents impedance [Ω]. The graph in FIG. 5 shows how the low-frequency band resonant frequency changes when the temperature is changed from -40°C to 85°C. In the graph in FIG. 5, the frequency at which the impedance changes suddenly is the low-frequency band resonant frequency. As can be seen from the graph in FIG. 5, the low-frequency band resonant frequency decreases as the temperature increases.

[0065] Furthermore, the low-frequency band resonant frequency decreases as the amount or weight of foreign matter attached to the surface of the protective cover 2 increases. That is, a decrease in the low-frequency band resonant frequency occurs not only due to an increase in temperature but also due to the attachment of foreign matter. Therefore, simply measuring the change in the low-frequency band resonant frequency using the impedance detection unit 70 does not allow for distinguishing between the attachment of foreign matter to the surface of the protective cover 2 and a temperature change.

[0066] In particular, if the signal processing circuit 20 makes a judgment based only on the low-frequency band resonant frequency, there is a risk that the decrease in the low-frequency band resonant frequency may be mistakenly determined to be due to foreign matter adhering to the surface of the protective cover 2, even though the decrease is actually due to a temperature rise. If the signal processing circuit 20 mistakenly determines that the decrease in the low-frequency band resonant frequency is due to foreign matter adhering to the surface of the protective cover 2, it will perform control to increase the vibration amplitude of the piezoelectric vibrator 15 in order to remove the foreign matter. Increasing the vibration amplitude of the piezoelectric vibrator 15 further increases the temperature of the surface of the protective cover 2. If foreign matter is adhering to the surface of the protective cover 2, the signal processing circuit 20 becomes even more unstable, making it difficult to make an accurate judgment.

[0067] Changes in the low-frequency band resonant frequency occur not only due to temperature changes but also due to aging of the joint between the protective cover 2 and the vibrating part 12, moisture absorption of the resin part, etc. The signal processing circuit 20 may determine that a foreign object has adhered to the surface of the protective cover 2 based on information other than the change in the low-frequency band resonant frequency.

[0068] 5, the low frequency band resonant frequency and the minimum value of impedance decrease as the temperature changes from -40° C. to 85° C. To easily explain this relationship, the graph will be divided into two graphs: one showing the change in the low frequency band resonant frequency with respect to temperature, and the other showing the change in the minimum value of impedance with respect to temperature.

[0069] Figure 6A is a graph showing the relationship between the low-frequency band resonant frequency and temperature. The horizontal axis of Figure 6A represents temperature [°C], and the vertical axis represents the low-frequency band resonant frequency [kHz]. As can be seen from the graph of Figure 6A, the low-frequency band resonant frequency decreases as the temperature increases.

[0070] Fig. 6B is a graph showing the relationship between the minimum impedance (minimum value of impedance) and temperature in the low frequency band of piezoelectric vibrator 15. The horizontal axis of Fig. 6B represents temperature [°C], and the vertical axis represents minimum impedance [Ω]. As can be seen from the graph of Fig. 6B, the minimum impedance in the low frequency band of piezoelectric vibrator 15 decreases as the temperature increases.

[0071] Next, changes in the low frequency band resonance frequency and the minimum value of the impedance when a foreign object adheres to the surface of the protective cover 2 will be described with reference to FIGS. 7A and 7B.

[0072] Fig. 7A is a graph showing the relationship between the amount of water attached, which is an example of foreign matter, and the low-frequency band resonance frequency. The horizontal axis of Fig. 7A shows the volume [µl] of water attached to the surface of the protective cover 2 (hereinafter referred to as "water attachment amount"), and the vertical axis shows the low-frequency band resonance frequency [kHz]. As can be seen from the graph shown in Fig. 7A, the low-frequency band resonance frequency decreases as the amount of water attachment increases.

[0073] 7B is a graph showing the relationship between the amount of attached water, an example of foreign matter, and the minimum impedance of piezoelectric vibrator 15 in the low frequency band. The horizontal axis of FIG. 7B represents the amount of attached water [μl], and the vertical axis represents the rate of change in impedance. As can be seen from the graph shown in FIG. 7B, the rate of change in the minimum impedance of piezoelectric vibrator 15 increases as the amount of attached water increases. Conversely, the rate of change in current value I corresponding to the minimum impedance of piezoelectric vibrator 15 decreases as the amount of attached water increases.

[0074] 6A, 6B, 7A, and 7B, the signal processing circuit 20 combines the change in the low-frequency band resonant frequency with the change in the minimum impedance of the piezoelectric vibrator 15 to make a judgment. This makes it possible to accurately determine whether these changes are due to foreign matter adhering to the surface of the protective cover 2 or to a temperature change. Note that the minimum impedance of the piezoelectric vibrator 15 also changes due to aging of the joint between the protective cover 2 and the vibrating part 12, moisture absorption by the resin part, and the like. However, these changes are different from the changes caused by foreign matter adhering to the surface of the protective cover 2, and therefore it is possible to distinguish between the two and make a judgment.

[0075] As described above, the low-frequency band resonant frequency and the minimum impedance decrease as the temperature increases. Furthermore, as the amount of foreign matter adhering to the surface of the protective cover 2 increases, the low-frequency band resonant frequency decreases, while the rate of change in the minimum impedance increases.

[0076] Therefore, by combining the change in the low frequency band resonance frequency with the change in the minimum impedance or current of the piezoelectric vibrator 15, it is possible to distinguish between the adhesion of a foreign object to the surface of the protective cover 2 and the occurrence of a temperature change. The signal processing circuit 20 executes the process corresponding to this determination in step S7 described above.

[0077] That is, when the amount of change (Δfr) in the decrease in the resonant frequency is equal to or less than the first frequency threshold fth and the amount of change (ΔI) in the current value is equal to or less than the first current threshold Ith, the signal processing circuit 20 determines that a foreign object has adhered to the surface of the protective cover 2. In this way, the signal processing circuit 20 can determine the presence or absence of a foreign object on the surface of the protective cover 2 not only from the amount of change (time change) in the resonant frequency, but also from the amount of change (time change) in the current value, which is a value related to impedance.

[0078] 4, if it is determined that the difference values Δf and ΔI are greater than the first threshold value (No in S7), the signal processing circuit 20 returns the process to step S5. In this case, it is assumed that no foreign matter is attached to the surface of the protective cover 2. In step S5, which is executed again, the signal processing circuit 20 updates its memory by setting the resonant frequency fr_low1 and the current value I_low1 measured in step S6 as the reference frequency fr and the reference current value I, respectively.

[0079] If it is determined in step S7 that the difference values Δf and ΔI are equal to or less than the first threshold (Yes in S7), the signal processing circuit 20 determines whether the difference values Δf and ΔI are equal to or less than a second threshold different from the first threshold (S8). Specifically, the signal processing circuit 20 determines whether the difference values Δf≦−fth1 and ΔI≦−Ith1. Here, the absolute value of the second frequency threshold fth1 is greater than the absolute value of the first frequency threshold fth (fth1>fth), and the second current threshold Ith1 is greater than the first current threshold Ith (Ith1>Ith).

[0080] The signal processing circuit 20 performs specific processing when the difference values Δf, ΔI are equal to or less than the second threshold value, thereby performing processing corresponding to the case where the amount of foreign matter attached to the surface of the protective cover 2 is large or heavy (severely dirty).

[0081] The signal processing circuit 20 determines whether or not there is foreign matter adhering to the surface of the protective cover 2 using the first threshold values fth and Ith, and determines the degree of foreign matter adhering to the surface of the protective cover 2 using the second threshold values fth1 and Ith1.

[0082] In step S8, if it is determined that the difference values Δf and ΔI are greater than the second threshold value (No in S8), the signal processing circuit 20 sets the drive voltage Vdr of the piezoelectric drive unit 30 to V2 and sets the drive frequency fdr to the resonance frequency fmax (S9), where V2 is greater than V1.

[0083] Next, the signal processing circuit 20 executes drive mode A (S10) in which only the piezoelectric drive unit 30 is driven at the drive voltage and resonance frequency set in step S9. In drive mode A in step S10, the signal processing circuit 20 drives only the piezoelectric drive unit 30 without driving the cleaning drive unit 60.

[0084] On the other hand, if it is determined in step S8 that the difference values Δf and ΔI are equal to or less than the second threshold value (Yes in S8), the signal processing circuit 20 sets the drive voltage Vdr of the piezoelectric drive unit 30 to V3 and sets the drive frequency fdr to the resonance frequency fmax (S11), where V3 is smaller than V2.

[0085] Next, the signal processing circuit 20 drives the piezoelectric driver 30 at the drive voltage and resonance frequency set in step S11, and also executes drive mode B, which drives the cleaning driver 60 (S12). Since the drive voltage V3 in drive mode B is smaller than the drive voltage V2 in drive mode A, in drive mode B the piezoelectric driver 30 vibrates the piezoelectric vibrator 15 with weaker vibration than in drive mode A.

[0086] By executing drive mode B, the signal processing circuit 20 can more powerfully clean foreign matter adhering to the protective cover 2. Note that the signal processing circuit 20 may control the cleaning drive unit 60 to use a cleaning power stronger than that of the cleaning liquid ejected in drive mode B, based on at least one of the resonance frequency, the value related to impedance (current value), and the image captured by the imaging device 5.

[0087] After the cleaning in step S10 or step S12, the signal processing circuit 20 determines whether the current value Idr measured by the impedance detection unit 70 has increased to or above a predetermined value (S13). When the foreign matter adhering to the surface of the protective cover 2 is removed, the current value Idr measured by the impedance detection unit 70 increases to or above a predetermined value. In other words, the current value Idr measured by the impedance detection unit 70 returns to approximately the value of the current value Idr when no foreign matter is adhering to the surface of the protective cover 2. Therefore, by having the signal processing circuit 20 determine whether the current value Idr measured by the impedance detection unit 70 has increased to or above a predetermined value, information as to whether the foreign matter adhering to the surface of the protective cover 2 has been removed can be obtained.

[0088] If it is determined in step S13 that the current value Idr has increased to or above a predetermined value (Yes in S13), the signal processing circuit 20 ends the processing in Fig. 4. Alternatively, the signal processing circuit 20 may determine whether or not an operation to end the cleaning process has been accepted, and if accepted, end the processing in Fig. 4, or if not accepted, return the processing to step S1 or S4.

[0089] If it is determined in step S13 that the current value Idr has not increased to or above a predetermined value (No in S13), the signal processing circuit 20 determines whether the operation time in drive mode A or B exceeds a threshold value (e.g., 1 minute) (S14). In step S14, for example, if the sum of the operation time in drive mode A and the operation time in drive mode B exceeds the threshold value, the signal processing circuit 20 determines that the operation time in drive mode A or B exceeds the threshold value.

[0090] If it is determined that the operating time in drive mode A or B exceeds the threshold (Yes in S14), the signal processing circuit 20 terminates the processing in FIG. 4 due to an abnormality (abnormal termination). If the piezoelectric vibrator 15 is driven for a long time in the cleaning drive mode, there is a possibility that a malfunction such as heat generation in the protective cover 2 may occur. By having the signal processing circuit 20 normally terminate the processing in a predetermined case, it is possible to prevent such a malfunction from occurring.

[0091] If it is determined in step S13 that the current value Idr has not increased above a predetermined value (No in S13) and that the operating time in drive mode A or B has not exceeded the threshold (No in S14), the signal processing circuit 20 returns the processing to step S8.

[0092] 2-2. Temperature estimation 2-2-1. Knowledge about temperature estimation Below, the temperature estimation step S1 in Fig. 4 will be explained, but as a prerequisite, findings regarding temperature estimation will be explained using Figs. 8A, 8B, 9A, and 9B. The inventors have conducted extensive research into the relationship between the vibration and temperature of the protective cover 2, and have obtained the findings regarding temperature estimation as described below. Furthermore, based on the findings obtained, they have come to create a technical idea for estimating the temperature of the protective cover 2.

[0093] Fig. 8A is a graph showing the relationship between the temperature and the resonance frequency in the high frequency band of vibrating section 12 (hereinafter referred to as "high frequency band resonance frequency"). Fig. 8B is a graph showing the relationship between the temperature and the minimum impedance in the high frequency band of piezoelectric vibrator 15. In the graphs of Fig. 8A and Fig. 8B, each black circle indicates an actual measurement value.

[0094] The graph shown in Fig. 8A shows that the high-frequency band resonant frequency decreases as the temperature increases. In contrast, the graph shown in Fig. 8B shows that there is no correlation between the minimum impedance and temperature in the high-frequency band of piezoelectric vibrator 15. At least, there is no correlation between the minimum impedance and temperature in the high-frequency band of piezoelectric vibrator 15 in Fig. 8B, where the minimum impedance decreases as the temperature increases, as in Fig. 8A.

[0095] Fig. 9A is a graph showing the relationship between the amount of adhering water and the high-frequency resonant frequency. Fig. 9B is a graph showing the relationship between the amount of adhering water and the minimum impedance of piezoelectric vibrator 15 in the high-frequency band. In the graphs of Fig. 9A and Fig. 9B, each black circle indicates an actual measurement value. From the graphs shown in Fig. 9A and Fig. 9B, it can be seen that there is no correlation between the amount of adhering water and the high-frequency resonant frequency, or between the amount of adhering water and the minimum impedance of piezoelectric vibrator 15 in the high-frequency band.

[0096] 8A is the only frequency that decreases as the temperature increases, the temperature of the protective cover 2 in this embodiment can be estimated based on the high frequency band resonance frequency. Specifically, in the high frequency band, the temperature T of the protective cover 2 can be estimated based on the following equation (1) that uses the resonance frequency fr of the vibrating part 12.

[0097] T=A·fr+B ···(1) Here, A is a constant less than 0, and B is a constant greater than 0.

[0098] In the measured values shown in the graph of FIG. 8A, A=-17 and B=9300. The correlation coefficient R between T and fr in equation (1) is R 2 =0.9973.

[0099] For example, the relationship (1) holds when the spring constant of a vibrating component is temperature dependent. The spring constant represents the ease with which a component stretches. Generally, for components that stretch more easily with increasing temperature, the spring constant decreases as the temperature increases. In other words, for components that stretch more easily with increasing temperature, the frequency of the component's vibration decreases as the temperature increases.

[0100] 9A and 9B, the amount of foreign matter attached is not correlated with either the high frequency band resonance frequency or the minimum impedance in the high frequency band of the piezoelectric vibrator 15, so equation (1) holds even if foreign matter is attached to the transparent body. Therefore, regardless of whether or not foreign matter is attached, equation (1) can estimate the temperatures of the vibrating vibrating part 12 and the protective cover 2 more accurately than before.

[0101] 2-2-2. Temperature estimation operation FIG. 10 is a flowchart illustrating an example of the temperature estimation step S1 in FIG.

[0102] First, the signal processing circuit 20 causes the piezoelectric driver 30 to operate the piezoelectric vibrator 15 in a high frequency band search mode (S101). The high frequency band search mode in step S101 is a mode for searching for a resonance frequency in the high frequency band of the vibrating unit 12. In the high frequency band search mode, the piezoelectric driver 30 sets the drive voltage Vdr of the piezoelectric vibrator 15 to V4 and sweeps the drive frequency f within the high frequency band to apply an AC output signal to the piezoelectric vibrator 15.

[0103] During the high frequency band search mode in step S101, the impedance detection unit 70 monitors the current value or impedance of the piezoelectric driver 30. Specifically, the impedance detection unit 70 measures the current value flowing through the piezoelectric driver 30 or the impedance, which is the reciprocal of the current value.

[0104] After step S101, the signal processing circuit 20 acquires the drive frequency f and the current value or impedance, and determines the drive frequency f at which the current value I0_high is the maximum value or the drive frequency f at which the impedance is the minimum value as the high frequency band resonant frequency f0_high (S102). In this way, the signal processing circuit 20 measures the maximum current value I0_high and the corresponding high frequency band resonant frequency f0_high.

[0105] Next, the signal processing circuit 20 calculates the estimated temperatures of the vibrating part 12 and the protective cover 2 based on the high frequency band resonance frequency f0_high determined in step S102 (S103). Specifically, the signal processing circuit 20 calculates the estimated temperature T by substituting the high frequency band resonance frequency f0_high measured in step S102 for fr in equation (1).

[0106] 2-2-3. Heating operation based on the temperature estimation results 4, the temperature estimation step S1 and the heating step S3 are repeated until the estimated temperature becomes 0° C. or higher (No in S2). FIG. 11 is a schematic graph for explaining such a heating operation in the imaging unit 100.

[0107] 11, the horizontal axis represents time [s], and the vertical axis represents the high frequency band resonance frequency f0_high [kHz]. The signal processing circuit 20 operates in a high frequency band search mode (S101), determines the high frequency band resonance frequency f0_high (S102), and calculates the estimated temperature (S103). When the estimated temperature is 0°C, less than If so, the signal processing circuit 20 operates in the heating mode (S3) and increases the temperature of the protective cover 2. When the temperature of the protective cover 2 increases, the high frequency band resonance frequency f0_high decreases.

[0108] The operation time of the heating mode is, for example, 30 seconds the first time and 10 seconds from the second time onwards, but is not limited to this. The high frequency band search mode is executed for, for example, 1 second each time.

[0109] The signal processing circuit 20 repeats the above operation until the estimated temperature becomes 0°C or higher (No in S2), that is, until the high frequency band resonance frequency f0_high becomes equal to or lower than the frequency fr (T=0°C) corresponding to 0°C. In the graph of Fig. 11, f0_high=fr (T=0°C) at time t0. Therefore, the signal processing circuit 20 transitions to the low frequency band search mode (S4) after time t0.

[0110] 3. Summary As described above, the vibration device according to one embodiment of the present disclosure includes the protective cover 2, which is an example of a light-transmitting body, the vibration unit 12, which is an example of a vibrating body that vibrates the protective cover 2, the piezoelectric driving unit 30 that drives the vibration unit 12, and the signal processing circuit 20, which is an example of a control unit that controls the piezoelectric driving unit 30. The signal processing circuit 20 determines the high-frequency band resonant frequency of the vibration unit 12 based on the state of the piezoelectric driving unit 30 obtained by changing the drive frequency of the piezoelectric driving unit 30 within a high-frequency band of 100 kHz or more (S101) and estimates the temperature of the protective cover 2 based on the determined high-frequency band resonant frequency (S103).

[0111] According to this configuration, the temperature of the protective cover 2 can be estimated more accurately than with conventional techniques.

[0112] In the vibration device, if the estimated temperature of the protective cover 2 is below a predetermined value (Yes in S2), the signal processing circuit 20 may control the piezoelectric driving unit 30 to vibrate the vibration unit 12 at a high frequency of 100 kHz or more (S3). If the estimated temperature of the protective cover 2 is above a predetermined value (No in S2), the signal processing circuit 20 may determine a low-frequency band resonant frequency of the vibration unit 12 based on the state of the piezoelectric driving unit 30 obtained by changing the drive frequency of the piezoelectric driving unit 30 within a low-frequency band below 100 kHz (S4, S6), and control the piezoelectric driving unit 30 to vibrate the vibration unit 12 at the low-frequency band resonant frequency (S9, S11).

[0113] According to this configuration, when the temperature of the protective cover 2 is below a predetermined value, the temperature of the protective cover 2 can be increased. This makes it easier to melt foreign matter such as ice or snow adhering to the protective cover 2 and remove the foreign matter.

[0114] If the estimated temperature of the protective cover 2 is still below a predetermined value after vibrating the vibrating unit 12 at a high frequency (S3), the signal processing circuit 20 may again determine the high frequency band resonance frequency of the vibrating unit 12 based on the state of the piezoelectric driving unit 30 obtained by changing the driving frequency of the piezoelectric driving unit 30 within the high frequency band. The signal processing circuit 20 may again estimate the temperature of the protective cover 2 based on the re-determined high frequency band resonance frequency. If the re-estimated temperature of the protective cover 2 is below a predetermined value, the signal processing circuit 20 continues to Controlling the piezoelectric driving unit 30 so as to vibrate the vibration unit 12 for a predetermined period at a frequency in the high frequency band; After a predetermined period of time has elapsed, the high frequency band resonance frequency of the vibration unit 12 is determined again based on the state of the piezoelectric driving unit 30 obtained by changing the driving frequency of the piezoelectric driving unit 30 within the high frequency band; The temperature of the protective cover 2 may be estimated again based on the re-determined high frequency band resonant frequency, and this process may be repeated.

[0115] According to this configuration, the temperature of the protective cover 2 can be increased until it reaches a predetermined value or higher, which makes it easier to melt foreign matter such as ice or snow adhering to the protective cover 2 and remove the foreign matter.

[0116] When the re-estimated temperature of the protective cover 2 becomes equal to or higher than a predetermined value, or when the re-estimated temperature of the protective cover 2 is equal to or higher than a predetermined value, the signal processing circuit 20 may determine the low frequency band resonant frequency of the vibration unit 12 based on the state of the piezoelectric drive unit 30 obtained by changing the drive frequency of the piezoelectric drive unit 30 within a low frequency band of less than 100 kHz, and control the piezoelectric drive unit 30 to vibrate the vibration unit 12 at the low frequency band resonant frequency.

[0117] According to this configuration, by vibrating the protective cover 2 when the temperature reaches or exceeds a predetermined value, foreign matter such as ice or snow can be melted, making it easier to remove foreign matter adhering to the protective cover 2.

[0118] In the vibration device, the signal processing circuit 20 may estimate the temperature T of the protective cover 2 based on the formula (1). T=A·fr+B ···(1) Here, A is a constant smaller than 0, B is a constant larger than 0, and fr is the resonance frequency of the vibrating portion 12.

[0119] According to this configuration, the temperature of the protective cover 2 can be estimated more accurately.

[0120] (Variation) Although the embodiments of the present disclosure have been described in detail above, the above description is merely an example of the present disclosure in every respect. Various improvements and modifications can be made without departing from the scope of the present disclosure. For example, the following modifications are possible. Note that, in the following, the same reference numerals are used for components similar to those in the above embodiment, and descriptions of the same points as those in the above embodiment will be omitted as appropriate. The following modifications can be combined as appropriate.

[0121] (First Modification) In the above embodiment, an example has been described in which the temperature of the protective cover 2 is estimated based on the high-frequency band resonant frequency, but the present disclosure is not limited to this. For example, the vibration device may be provided with a temperature sensor that measures the temperature of the protective cover 2, and the temperature sensor may measure the temperature of the protective cover 2 in addition to or instead of the temperature estimation step S1. With this configuration, the temperature of the protective cover 2 can be measured more accurately.

[0122] (Second Modification) In the above embodiment, an example has been described in which the signal processing circuit 20 determines the presence and extent of foreign matter on the surface of the protective cover 2 based on the measurement results of the resonant frequency and the current value, but the present disclosure is not limited to this. For example, the signal processing circuit 20 may acquire a captured image from the imaging device 5, perform image processing, and use the results of the image processing to determine the presence and extent of foreign matter on the surface of the protective cover 2.

[0123] For example, in order to determine whether a foreign object has adhered to the surface of the protective cover 2, the signal processing circuit 20 may take into consideration information on the change over time of the image captured by the imaging device 5, in addition to the change over time of the resonance frequency fr and the change over time of the current value I. Furthermore, in order to determine whether a foreign object has adhered to the surface of the protective cover 2, the signal processing circuit 20 may combine the change over time of the resonance frequency fr and the change over time of the image captured by the imaging device 5. Furthermore, in order to determine whether a foreign object has adhered to the surface of the protective cover 2, the signal processing circuit 20 may combine the change over time of the current value Ir and the change over time of the image captured by the imaging device 5.

[0124] For example, if the amount of change in the resonance frequency fr is greater than the absolute value of the threshold value fth and the integrated brightness value of the image captured by the imaging device 5 has decreased, the signal processing circuit 20 may determine that a foreign object has adhered to the surface of the protective cover 2. In this way, by taking into account the amount of change in the resonance frequency fr, the signal processing circuit 20 can distinguish between a decrease in the integrated brightness value that occurs when the vehicle equipped with the imaging unit 100 enters, for example, a tunnel, and a decrease in the integrated brightness value that occurs when a foreign object has adhered to the surface of the protective cover 2.

[0125] Furthermore, the signal processing circuit 20 may determine that the foreign matter adhering to the surface of the protective cover 2 is an opaque substance such as mud when the amount of change in the resonance frequency fr and the amount of change in the current value I are greater than the absolute values of the thresholds fth and Ith, respectively, and the integrated brightness value of the image captured by the imaging device 5 has dropped significantly. The signal processing circuit 20 may determine that the foreign matter adhering to the surface of the protective cover 2 is a transparent substance such as water when the drop in the integrated brightness value of the image captured by the imaging device 5 is small. In this way, the signal processing circuit 20 can more accurately determine the type of foreign matter adhering to the surface of the protective cover 2 by taking into account information on the time change in the image captured by the imaging device 5.

[0126] (Third Modification) In the above embodiment, an example has been described in which the device operates in the heating mode when it is determined that the temperature of the protective cover 2 is below a predetermined lower threshold (0°C) (Yes in S2), but the present disclosure is not limited to this. For example, when it is determined that the temperature of the protective cover 2 is equal to or higher than a predetermined upper threshold, the signal processing circuit 20 may execute a process to prevent a temperature rise of the protective cover 2 or a process to cool the protective cover 2. An example of a process to prevent a temperature rise of the protective cover 2 is to stop driving the piezoelectric driving unit 30, thereby stopping the vibration of the piezoelectric vibrator 15, the vibrating unit 12, and the protective cover 2. An example of a process to cool the protective cover 2 is to use the cleaning nozzle 3 to eject a cleaning liquid, a cooling liquid, or another liquid onto the protective cover 2.

[0127] According to this modification, the protective cover 2 or the entire imaging unit 100 can be prevented from becoming excessively hot, and the safety of the imaging unit 100, the vehicle in which it is mounted, and objects and people around them can be ensured. [Explanation of symbols]

[0128] 1 chassis 2 Protective Cover 3 Cleaning nozzle 4 Main body parts 4a Base Plate 5. Imaging device 6 circuits 7 Lens Module 9 Lenses 12 Vibration unit 13 First cylindrical member 14 Second cylindrical member 14a Thin section 14b Flange part 14c Flange 15 Piezoelectric vibrator 16,17 Piezoelectric plate 20 Signal processing circuit 30 Piezoelectric drive unit 31 Opening 50 Cleaning liquid discharge part 60 Cleaning drive unit 70 Impedance detection unit 80 Power circuit 100 Imaging unit

Claims

1. A transparent body; a vibrator that vibrates the transparent body; a drive unit that drives the vibrator; a control unit that controls the drive unit, The control unit determining a high-frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a high-frequency band of 100 kHz or more; estimating a temperature of the transparent body based on the determined high frequency band resonance frequency; Vibration device.

2. The control unit When the estimated temperature of the light-transmitting body is lower than a predetermined value, the driving unit is controlled to vibrate the vibrating body at a high frequency of 100 kHz or more; When the estimated temperature of the light-transmitting body is equal to or higher than the predetermined value, a low-frequency band resonance frequency of the vibrator is determined based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band less than 100 kHz, and the drive unit is controlled so as to vibrate the vibrator at the determined low-frequency band resonance frequency. The vibration device according to claim 1 .

3. The control unit If the estimated temperature of the transparent body is less than a predetermined value, determining again the high frequency band resonance frequency of the vibrator based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a high frequency band; re-estimating the temperature of the transparent body based on the re-determined high frequency band resonance frequency; If the re-estimated temperature of the light-transmitting body is less than the predetermined value, the re-estimated temperature of the light-transmitting body is measured until the re-estimated temperature of the light-transmitting body becomes equal to or greater than the predetermined value. controlling the driving unit to vibrate the vibrating body for a predetermined period at a frequency in a high frequency band; After the predetermined period has elapsed, determining again the high frequency band resonance frequency of the vibrator based on the state of the drive unit obtained by changing the drive frequency of the drive unit within a high frequency band; and re-estimating the temperature of the transparent body based on the re-determined high frequency band resonance frequency. The vibration device according to claim 1 .

4. When the re-estimated temperature of the light-transmitting body becomes equal to or higher than the predetermined value, or when the re-estimated temperature of the light-transmitting body is equal to or higher than the predetermined value, the control unit determines a low-frequency band resonance frequency of the vibrating body based on a state of the driving unit obtained by changing the driving frequency of the driving unit within a low-frequency band of less than 100 kHz, and controls the driving unit to vibrate the vibrating body at the determined low-frequency band resonance frequency. The vibration device according to claim 3 .

5. Further provided is a temperature sensor for measuring the temperature of the transparent body; When the temperature of the light-transmitting body measured by the temperature sensor is equal to or higher than the predetermined value, the control unit determines a low-frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band less than 100 kHz, and controls the drive unit to vibrate the vibrator at the determined low-frequency band resonance frequency. The vibration device according to claim 2 .

6. the optically transparent body is disposed in a field of view of an imaging device; the control unit acquires a captured image from the imaging device and performs image processing on the captured image, and when a result of the image processing indicates that no foreign matter is attached to the surface of the light-transmitting body, determines a low-frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a low-frequency band less than 100 kHz, and controls the drive unit to vibrate the vibrator at the determined low-frequency band resonance frequency. The vibration device according to claim 2 .

7. The control unit determines the low frequency band resonance frequency based on the state of the drive unit, the control unit changes the drive frequency of the drive unit within a low frequency band and measures the drive current of the drive unit; the control unit determines the low frequency band resonant frequency based on the measured value of the drive current; The vibration device of claim 2 , comprising:

8. The control unit determines the high frequency band resonance frequency based on the state of the drive unit, the control unit changes the drive frequency of the drive unit within a high frequency band and measures the drive current of the drive unit; the control unit determines the high frequency band resonant frequency based on the measured value of the drive current; The vibration device of claim 1 , comprising:

9. The vibration device according to any one of claims 1 to 8, wherein the control unit estimates the temperature T of the light-transmitting body based on equation (1). T=A・fr+B...(1) Here, A is a constant smaller than 0, B is a constant larger than 0, and fr is the resonant frequency of the vibrating body.

10. A transparent body; a vibrator that vibrates the transparent body; a drive unit that drives the vibrator; A vibration method performed by a vibration device including a control unit that controls the drive unit, a step in which the control unit determines a high-frequency band resonance frequency of the vibrator based on a state of the drive unit obtained by changing the drive frequency of the drive unit within a high-frequency band of 100 kHz or more; The control unit estimates a temperature of the transparent body based on the determined high frequency band resonance frequency; A vibration method including:

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