Ultrasonic sensor

Abstract

Provided is an ultrasonic sensor capable of transmitting an ultrasonic beam having a small diameter of a point to a close object. The ultrasonic sensor is a sensor that transmits an ultrasonic wave to an object and receives an ultrasonic wave reflected by the object, and includes an ultrasonic array chip in which ultrasonic elements that transmit and receive ultrasonic waves are arranged in an array. The ultrasonic element includes a vibrating portion and a piezoelectric element provided to the vibrating portion, and transmits an ultrasonic wave by vibrating the vibrating portion by applying a voltage to the piezoelectric element, and detects reception of an ultrasonic wave using a signal output from the piezoelectric element by vibration of the vibrating portion, and a resonance frequency of the ultrasonic element is 2000 kHz or less.

Description

Technical Field

[0001] This invention relates to ultrasonic sensors. Background Technology

[0002] In the prior art, ultrasonic sensors are known to measure the distance to an object by transmitting ultrasonic waves and receiving reflected waves reflected by the object (see, for example, Patent Document 1).

[0003] The prior art ultrasonic sensor in Patent Document 1 generates ultrasonic waves by vibrating a piezoelectric vibrator and receives ultrasonic waves reflected from an object via the piezoelectric vibrator. Capacitors are connected in parallel to the piezoelectric vibrator and configured such that the capacitors connected in parallel to the piezoelectric vibrator can be selected by a switching operation. In such an ultrasonic sensor, the reverberation time consumed before the received signal output when the reflected wave is received by the piezoelectric vibrator decays is controlled by changing the combination of capacitors connected to the piezoelectric vibrator.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-343482.

[0007] However, in so-called bulk ultrasonic transducers, such as those described in Patent Document 1 above, which transmit ultrasonic waves through the vibration of the piezoelectric element itself and detect the reception of ultrasonic waves by receiving ultrasonic waves through vibration of the piezoelectric element itself, it is difficult to miniaturize the ultrasonic element in manufacturing. For example, there is a technical problem that it is difficult to perform close-range measurements of less than 10 mm.

[0008] In other words, when using ultrasound to detect objects positioned at close range, high-frequency ultrasound is needed to reduce reverberation time. However, as mentioned above, miniaturization is difficult in bulky ultrasonic transducers, and there are limits to increasing the frequency of ultrasound.

[0009] Furthermore, when measuring objects at close range using ultrasound, it is desirable to detect the object's shape (such as convexity or concavity) and tilt within a narrow range. However, in the bulky ultrasonic transducer described in Patent Document 1, miniaturization is difficult, thus presenting a technical problem of limitations in reducing the point diameter of the ultrasonic wave. Summary of the Invention

[0010] The ultrasonic sensor of the first aspect of this disclosure is an ultrasonic sensor that transmits ultrasonic waves to an object and receives ultrasonic waves reflected by the object. It includes an ultrasonic array chip in which ultrasonic elements for transmitting and receiving ultrasonic waves are arranged in an array. The ultrasonic elements include a vibrating part and a piezoelectric element disposed on the vibrating part. The vibrating part is vibrated by applying a voltage to the piezoelectric element to transmit ultrasonic waves, and the reception of ultrasonic waves is detected by the signal output from the piezoelectric element through the vibration of the vibrating part. The resonant frequency of the ultrasonic element is below 2000 kHz.

[0011] In the ultrasonic sensor of this aspect, when viewed from the direction of ultrasonic wave transmission, the ultrasonic array chip is rectangular, and the length of one side is less than 5 mm.

[0012] In the ultrasonic sensor of this aspect, the resonant frequency of the ultrasonic element is less than 1000 kHz, and the ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to less than 10% of the vibration amplitude of the vibrating part immediately after transmitting the ultrasonic waves, the reverberation time is less than 60 μs.

[0013] In the ultrasonic sensor of this aspect, the resonant frequency of the ultrasonic element is above 1000 kHz and less than 1500 kHz, and the ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to less than 10% of the vibration amplitude of the vibrating part immediately after transmitting ultrasonic waves, the reverberation time is less than 50 μs.

[0014] In the ultrasonic sensor of this aspect, the resonant frequency of the ultrasonic element is above 1500 kHz and below 2000 kHz, and the ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to less than 10% of the vibration amplitude of the vibrating part immediately after transmitting the ultrasonic waves, the reverberation time is less than 25 μs. Attached Figure Description

[0015] Figure 1 A schematic diagram illustrating a simplified configuration of an ultrasonic sensor according to an embodiment of the present invention.

[0016] Figure 2 A cross-sectional view showing the simplified configuration of the ultrasonic array chip in this embodiment.

[0017] Figure 3 This diagram illustrates an example of the connection of an ultrasonic transducer within the ultrasonic array chip of this embodiment.

[0018] Figure 4 This is a graph showing the relationship between the distance from the ultrasonic array chip and the point diameter of the ultrasonic beam when the resonant frequency of the ultrasonic transducer is set to 600 kHz.

[0019] Figure 5 This is a graph showing the relationship between the distance from the ultrasonic array chip and the point diameter of the ultrasonic beam when the resonant frequency of the ultrasonic transducer is set to 900 kHz.

[0020] Figure 6 The graph illustrates the relationship between the distance from the ultrasonic array chip and the point diameter of the ultrasonic beam when the resonant frequency of the ultrasonic transducer is set to 1000kHz, 2000kHz, and 3000kHz.

[0021] Figure 7 This is a diagram showing the change in vibration of the vibrating part after ultrasonic waves are transmitted from the ultrasonic sensor of this embodiment.

[0022] Figure 8 A graph illustrating the changes in the vibration of an ultrasonic transducer after ultrasonic waves are transmitted from a bulk ultrasonic transducer.

[0023] Figure 9 A graph showing the relationship between the resonant frequency and the measurable distance in the ultrasonic sensor of this embodiment and in bulk ultrasonic transducers in the prior art.

[0024] Figure 10 A schematic diagram illustrating the simplified configuration of the ultrasonic sensor involved in Modification 1.

[0025] Symbol Explanation

[0026] 1: Object; 10: Ultrasonic sensor; 20: Ultrasonic array chip; 21: Component substrate; 22: Vibrating plate; 22A: Ultrasonic transceiver surface; 23: Piezoelectric element; 24: Ultrasonic transducer; 30: Control circuit; 31: Adapter circuit; 32: Signal ground; 33: Transmitting circuit section; 34: Receiving and processing section; 35: Microcomputer; 211: Opening; 221: Vibrating section; 231: Lower electrode. Detailed Implementation

[0027] The ultrasonic sensor of one embodiment will be described below.

[0028] Figure 1 This is a schematic diagram illustrating the simplified configuration of the ultrasonic sensor 10 of this embodiment.

[0029] The ultrasonic sensor 10 includes an ultrasonic array chip 20 disposed on a substrate 11, etc., and a control circuit 30 for controlling the ultrasonic array chip 20. The ultrasonic sensor 10 performs ultrasonic transceiver processing, in which ultrasonic waves are transmitted from the ultrasonic array chip 20 toward an object 1 under the control of the control circuit 30, and ultrasonic waves reflected from the object 1 are received by the ultrasonic array chip 20. Then, the control circuit 30 calculates the distance from the ultrasonic array chip 20 to the object 1 based on the time from the timing of transmitting the ultrasonic waves to the timing of receiving the ultrasonic waves reflected from the object 1 during the ultrasonic transceiver processing via the ultrasonic array chip 20.

[0030] In particular, the ultrasonic sensor 10 of this embodiment is advantageous as a measuring device for close-range applications where the placement space is limited and the distance to the object 1 is, for example, less than 10 mm. Such an ultrasonic sensor 10 can be applied to printers, image scanners, etc., and can be appropriately used to measure the distance to the paper surface, detect the unevenness of the paper surface, or the paper's transport status, either with the paper surface as the object 1. Furthermore, it can be used by mounting it on a robot arm, etc., to accurately detect the distance between the object 1 and the robot arm when the robot arm approaches the object 1, and to measure damage caused by collision between the robot arm and the object 1.

[0031] When used with printers or image scanners, it is preferable to simultaneously detect unevenness or creases on the paper surface, such as tilting or wrinkling.

[0032] Furthermore, when the ultrasonic sensor 10 is mounted on a robot arm, etc., if there are protrusions or the like in the object 1 when the robot arm approaches the object 1, there is a possibility that the object 1 may be damaged or broken due to accidental contact between the robot arm and the object 1.

[0033] Therefore, as an ultrasonic sensor 10, it is preferable not only to simply measure the distance to the object 1, but also to appropriately determine the surface shape of the object 1. Thus, in the ultrasonic sensor 10 of this embodiment, the unevenness or other features of the object 1 are detected by measuring a narrow range of the object 1.

[0034] The following is a detailed description of the components of such an ultrasonic sensor 10.

[0035] [Composition of the ultrasonic array chip 20]

[0036] Figure 2 A cross-sectional view showing the simplified configuration of the ultrasonic array chip 20.

[0037] The ultrasonic array chip 20 sends ultrasonic waves to the object 1 and outputs a received signal by receiving the ultrasonic waves reflected by the object 1.

[0038] like Figure 2 As shown, the ultrasonic array chip 20 is configured to include an element substrate 21, a vibrating plate 22, and a piezoelectric element 23. Additionally, although not shown in the figure, the ultrasonic array chip 20 also includes a fixing substrate for fixing the element substrate 21. It should be noted that, in the following description, the direction of transmission and reception of ultrasonic waves from the ultrasonic array chip 20 towards the object 1 is defined as the Z direction.

[0039] The component substrate 21 is a substrate that supports the vibrating plate 22 and is made of a semiconductor substrate such as Si. A plurality of openings 211 extending through the component substrate 21 along the Z direction are provided in the component substrate 21.

[0040] The vibrating plate 22 is constructed, for example, from a laminate of SiO2 and ZrO2, and is disposed on the -Z side of the component substrate 21. The vibrating plate 22 is supported by the component substrate 21, which forms the opening 211, and blocks the -Z side of the opening 211. The portion of the vibrating plate 22 that overlaps with each opening 211 when viewed from the Z direction constitutes a vibrating section 221 in the vibrating plate 22 for transmitting and receiving ultrasonic waves through vibration. Furthermore, the surface of the vibrating plate 22 on the +Z side, that is, the side opposite to the component substrate 21, and composed of a plurality of vibrating sections 221 arranged in an array, constitutes an ultrasonic transceiver surface 22A (see reference). Figure 1 ).

[0041] The piezoelectric element 23 is positioned on the vibrating plate 22, overlapping with each vibrating part 221 when viewed from the Z direction. For example... Figure 2 As shown, the piezoelectric element 23 is formed by sequentially stacking a lower electrode 231, a piezoelectric film 232, and an upper electrode 233 on a vibrating plate 22.

[0042] In such an ultrasonic array chip 20, an ultrasonic transducer 24 (ultrasonic element) is formed by a vibrating part 221 and a piezoelectric element 23 disposed on the vibrating part 221.

[0043] Furthermore, in this ultrasonic array chip 20, if a voltage is applied between the lower electrode 231 and the upper electrode 233, the piezoelectric film 232 will expand and contract, and the vibrating part 221 will vibrate at an oscillation frequency corresponding to the opening width of the opening part 211. As a result, ultrasonic waves are transmitted from the vibrating part 221 toward the +Z side.

[0044] Furthermore, in the ultrasonic array chip 20, if an ultrasonic wave reflected by the object 1 is input to the vibration unit 221, the vibration unit 221 will vibrate with an amplitude corresponding to the sound pressure of the input ultrasonic wave, and a potential difference will occur between the lower electrode 231 side and the upper electrode 233 side of the piezoelectric film 232. Therefore, a received signal corresponding to this potential difference will be output from each piezoelectric element 23.

[0045] Figure 3 This diagram illustrates an example of the connection of the ultrasonic transducer 24 within the ultrasonic array chip 20.

[0046] In this embodiment, multiple ultrasonic transducers 24 are configured in an n x m matrix. The lower electrodes 231 of each ultrasonic array chip 20 are interconnected via a first bypass wiring 231A and connected to a first terminal 251 located on a portion of the element substrate 21. Similarly, the upper electrodes 233 of each ultrasonic array chip 20 are interconnected via a second bypass wiring 233A and connected to a second terminal 252 located on a portion of the element substrate 21. These first terminals 251 and second terminals 252 are respectively connected to a control circuit 30. In this configuration, by applying a voltage between the first terminal 251 and the second terminal 252, all ultrasonic transducers 24 can be driven simultaneously.

[0047] It should be noted that, Figure 3 The example shown is a configuration in which all the lower electrodes 231 of the ultrasonic transducer 24 are connected to the first terminal 251 via wiring. However, it is also possible to configure a predetermined number of ultrasonic transducers 24 as one channel and provide a first terminal 251 for each channel. In this case, by simultaneously inputting a drive signal between all the first terminals 251 and the second terminal 252, it is possible to... Figure 3 Similarly, all ultrasonic transducers 24 can be driven simultaneously. Alternatively, each first terminal 251 can be driven individually. In this case, the transmitted sound pressure can be adjusted by controlling the number of driven channels, and the transmission direction of the ultrasonic waves can be controlled by delaying the driving timing of each channel. Alternatively, the multiple channels can be divided into transmitting channels for transmitting ultrasonic waves and receiving channels for receiving ultrasonic waves.

[0048] In this embodiment, the ultrasonic array chip 20 is rectangular when viewed from above in the Z direction. Specifically, in the ultrasonic array chip 20, the transceiver area for arranging multiple ultrasonic transducers 24, that is, the area constituting the ultrasonic transceiver surface 22A for transmitting and receiving ultrasonic waves, is rectangular, and the length of the long side (array opening width) of this rectangular transceiver area is 5 mm or less. In other words, in this embodiment, the length of one side of the ultrasonic array chip 20 being 5 mm or less means that the long side (array opening width) of the rectangular transceiver area for arranging multiple ultrasonic transducers 24 is 5 mm or less.

[0049] Additionally, in the ultrasonic array chip 20, a vibration suppression layer having a predetermined Young's modulus can be disposed on the vibrating plate 22. As the vibration suppression layer, a resin material can be used, for example. The vibration suppression layer can further suppress the vibration of each vibrating part 221, thereby shortening the reverberation time. Here, the reverberation time in this embodiment refers to the time before the vibration amplitude of the vibrating part 221, which occurs during the transmission of the ultrasonic wave after it has been transmitted from the ultrasonic transducer 24, decays to less than 10%.

[0050] [Frequency and diameter of the ultrasonic beam]

[0051] Next, the frequency of the ultrasonic waves emitted from the ultrasonic array chip 20 and the point diameter of the ultrasonic beam formed by the ultrasonic waves will be explained.

[0052] As described above, the ultrasonic sensor 10 of this embodiment is primarily intended to properly measure the distance between the ultrasonic array chip 20 and the object 1 located close to the ultrasonic transceiver surface 22A of the ultrasonic array chip 20, and to appropriately detect the state of the object 1, such as its unevenness, located close to the ultrasonic transceiver surface 22A of the ultrasonic array chip 20.

[0053] In this case, the ultrasonic array chip 20 is required to transmit a small-diameter ultrasonic beam from the ultrasonic transceiver surface 22A to the target distance range.

[0054] In this embodiment of the ultrasonic sensor 10, when viewed from above in the Z direction, the array opening width of the ultrasonic array chip 20 is less than 5 mm, and the resonant frequency of each ultrasonic transducer 24 is less than 2000 kHz.

[0055] In such an ultrasonic sensor 10, the ultrasonic beam transmitted from the ultrasonic transceiver surface 22A at a close distance of 50 mm or less becomes an ultrasonic beam with a dot diameter of 10 mm or less. It should be noted that the dot diameter is the maximum diameter of the ultrasonic beam in a plane orthogonal to the transmission direction (Z direction) of the ultrasonic wave.

[0056] Figure 4 A graph illustrating the relationship between the distance from the ultrasonic array chip 20 and the point diameter of the ultrasonic beam. Figure 4 The diagram shows the point diameter of the ultrasonic beam when the resonant frequency of the ultrasonic transducer 24 is set to 600 kHz and the array aperture width is set to 10 mm, 5 mm, 3 mm, and 1 mm. Figure 5 The point diameter of the ultrasonic beam is shown when the resonant frequency of the ultrasonic transducer 24 is set to 900 kHz and the array aperture width is set to 10 mm, 5 mm, 3 mm and 1 mm. Figure 6 The dot diameter of the ultrasonic beam is shown when the resonant frequency of the ultrasonic transducer 24 is set to 2000 kHz and the array aperture width is set to 10 mm, 5 mm, 3 mm, and 1 mm. Figures 4 to 6 In the diagram, solid lines indicate data for 5mm, single-dash lines indicate data for 3mm, double-dash lines indicate data for 1mm, and dashed lines indicate data for 10mm.

[0057] like Figures 4 to 6 As shown, when the resonant frequency of the ultrasonic transducer 24 is below 2000 kHz, if the array aperture width is below 5 mm, then the point diameter can be set to below 10 mm within a distance of 10 mm or less from the ultrasonic transceiver surface 22A. In particular, if the resonant frequency exceeds 1 MHz, then an ultrasonic beam with a point diameter of 10 mm or less can be transmitted within a close range of 50 mm or less.

[0058] On the other hand, when the array opening width exceeds 5mm, there are cases where the dot diameter exceeds 10mm even within a range of less than 10mm from the ultrasonic sensor 10. For example, as... Figure 4 and Figure 5 As shown, when the array opening width is set to 10mm, the point diameter exceeds 10mm at a position 10mm away from the ultrasonic sensor 10.

[0059] It should be noted that the higher the resonant frequency of the ultrasonic transducer 24, the greater the attenuation of the ultrasonic waves. In particular, when ultrasonic waves are transmitted from the ultrasonic transducer 24 into the air, the attenuation rate becomes even greater, and it becomes difficult to detect ultrasonic waves reflected by the object 1. Therefore, the frequency of the ultrasonic waves used, that is, the resonant frequency of the ultrasonic transducer 24, is preferably set to 2000 kHz or less.

[0060] In addition, Figures 4-6The graph shows that even when the array aperture width is larger than 5mm but less than 10mm, the dot diameter will still be below 5mm due to frequency band limitations. However, if the array aperture width exceeds 5mm, the sidelobe effect becomes greater, and it may be impossible to achieve a dot diameter below 10mm. To address this, by keeping the array aperture width below 5mm, it is possible to suppress the sidelobe effect while achieving a dot diameter below 10mm in the near-field range. Figures 4-6 The point diameter is less than 10mm, as shown.

[0061] However, when measuring the distance to an object located close to the ultrasonic array chip 20, the so-called Time of Flight (ToF) method is used. In the ToF method, ultrasonic waves are transmitted from the ultrasonic array chip 20 and ultrasonic waves reflected by the object are received, and the time from the timing of transmitting the ultrasonic waves to the timing of receiving the reflected ultrasonic waves is measured.

[0062] In order to properly detect the timing of receiving reflected ultrasonic waves using the Time-of-Flight (ToF) method, it is necessary to ensure that the vibration of the vibrating part 221 generated by receiving reflected ultrasonic waves is not masked by the reverberant vibration of the vibrating part 221 that occurs when transmitting ultrasonic waves. In other words, when receiving reflected ultrasonic waves, the vibration amplitude of the vibrating part 221 that transmits ultrasonic waves needs to be attenuated to less than 10%.

[0063] Here, the reverberation time from the time the ultrasonic wave is transmitted until the vibration amplitude of the vibrating part 221 reaches less than 10% is mainly determined by the frequency of the ultrasonic wave emitted from the ultrasonic transducer 24, that is, the change in the resonant frequency of the ultrasonic transducer 24.

[0064] Figure 7 A graph showing the change in vibration of the vibrating part 221 after ultrasonic waves are transmitted from the ultrasonic sensor 10 of this embodiment. Figure 8 This diagram illustrates the changes in the vibration of an ultrasonic transducer after ultrasonic waves are transmitted from a bulk ultrasonic transducer. It should be noted that... Figure 7 To illustrate the vibration changes when the frequency of the ultrasound was set to 1.7 MHz, Figure 8 The vibration variation is shown when the frequency of the ultrasound is set to 1.5 MHz.

[0065] like Figure 7 As shown, in the ultrasonic sensor 10 of this embodiment, the reverberation time T1 is approximately 20 μs. On the other hand, as... Figure 8 As shown, in a bulk ultrasonic transducer, the reverberation time T2 is approximately 30 μs.

[0066] like Figure 7 and Figure 8As shown, in bulk ultrasonic transducers, compared with thin-film ultrasonic transducers in which the vibrating part 221 is vibrated by the piezoelectric element 23 as in this embodiment, there is a tendency for the reverberation time to be longer.

[0067] Figure 9 A graph illustrating the relationship between the resonant frequency and the measurable distance in the ultrasonic sensor 10 of this embodiment and in bulk ultrasonic transducers in the prior art. Figure 9 In the diagram, the ultrasonic sensor 10 of this embodiment is shown in solid lines, while the bulky ultrasonic transducer of the prior art is shown in dashed lines.

[0068] In existing bulk ultrasonic transducers, the components typically involve applying a voltage to cause a piezoelectric element to vibrate and transmit ultrasonic waves, while the piezoelectric element receives ultrasonic waves reflected from an object. The reception of ultrasonic waves is detected by the vibration of the piezoelectric element itself. However, in such bulk ultrasonic transducers, the piezoelectric element needs to be cut to the desired size, making it very difficult to manufacture in miniaturized form and increasing manufacturing costs.

[0069] For example, in Figure 8 An example of a bulk ultrasonic transducer with a reverberation time T2 of approximately 30 μs is shown. However, in reality, due to differences in ultrasonic transducers, the reverberation time can be further lengthened, making it difficult to form bulk ultrasonic transducers with a reverberation time of less than 30 μs.

[0070] Large-sized ultrasonic transducers are typically formed by cutting piezoelectric materials; however, when cutting using methods such as laser cutting, which do not incur manufacturing costs, only a limited number of large-scale ultrasonic transducers can be achieved. Figure 9 The frequencies shown are below 1000kHz. In such cases, the reverberation time also increases, and the detection distance can exceed 10mm using a large ultrasonic transducer.

[0071] In addition, because large-sized ultrasonic transducers are formed into block-shaped transducers and their thickness increases, the space available for their installation is also limited.

[0072] On the other hand, in the ultrasonic sensor 10 of this embodiment, a thin-film vibrating portion 221 can be formed on a component substrate 21 such as Si through micro-processing such as etching, and the thin-film piezoelectric element 23 can also be easily patterned into a desired pattern through etching. In this configuration, by controlling the opening width of the opening 211, the thickness of the vibrating portion 221, etc., the resonant frequency of the ultrasonic transducer 24 can be set to any value from 500kHz to 2000kHz. Figure 7 As shown, in such an ultrasonic sensor 10, the reverberation time can be significantly shortened compared to a bulky ultrasonic transducer, thus, as Figure 9 It is shown that it is able to properly detect an object 1 configured to be less than 10 mm away from the ultrasonic sensor 10 in the range of 500 kHz to 2000 kHz.

[0073] like Figures 4 to 6 and Figure 9 As shown, in this embodiment, the ultrasonic transducer 24 is configured such that when the resonant frequency (frequency of the transmitted ultrasonic wave) of the ultrasonic transducer 24 is above 600 kHz and below 1000 kHz, the reverberation time is below 60 μs. Therefore, an ultrasonic beam with a point diameter of less than 10 mm can be transmitted to an object 1 at a distance of approximately 10 mm from the ultrasonic sensor 10.

[0074] Furthermore, the ultrasonic transducer 24 is configured such that, when the resonant frequency of the ultrasonic transducer 24 is set to 1000kHz or higher and less than 1500kHz, the reverberation time is less than 50μs. Therefore, it is possible to transmit an ultrasonic beam with a point diameter of less than 10mm to an object 1 located at a distance of 5mm to 10mm from the ultrasonic sensor 10.

[0075] Furthermore, the ultrasonic transducer 24 is configured such that, when the resonant frequency of the ultrasonic transducer 24 is set to 1500kHz or higher and 2000kHz or lower, the reverberation time will be less than 25μs. Therefore, even for an object 1 within 5mm of the ultrasonic sensor 10, an ultrasonic beam with a point diameter of less than 10mm can be transmitted.

[0076] Furthermore, the ultrasonic sensor 10 of this embodiment is configured to place a thin-film piezoelectric element 23 within a thin-film vibrating section 221, and its thickness can be greatly reduced compared to a bulky ultrasonic transducer. Therefore, the degree of freedom in the placement space is increased; for example, the ultrasonic sensor 10 can be placed even in narrow spaces with a gap size of about 5 mm.

[0077] [Composition of control circuit 30]

[0078] Return to Figure 1 The control circuit 30 will be described below. As described above, the control circuit 30 is connected to the first terminal 251 and the second terminal 252 of the ultrasonic array chip 20.

[0079] like Figure 1As shown, the control circuit 30 includes a switching circuit 31, a signal ground terminal 32, a transmitting circuit section 33, a receiving and processing section 34, and a microcomputer 35 (microcontroller). As an example of the control circuit 30, integrated circuits such as SoC (System-On-Chip) and ASSP (Application Specific Standard Product) can be cited.

[0080] The switching circuit 31 is connected to the first terminal 251, the transmitting circuit section 33, and the receiving processing section 34 of the ultrasonic array chip 20. The switching circuit 31 can switch the transmitting connection between the first terminal 251 and the transmitting circuit section 33 and the receiving connection between the first terminal 251 and the receiving processing section 34 based on the control of the microcomputer 35.

[0081] Signal ground terminal 32 is a ground terminal connected to the second terminal 252, and maintains the second terminal 252 at a predetermined reference potential.

[0082] The transmitting circuit 33 is controlled, for example, by a microcomputer 35, and outputs a pulse drive signal of a predetermined voltage to the first terminal 251. This drives each ultrasonic transducer 24, and ultrasonic waves are output from the ultrasonic array chip 20 toward the object 1.

[0083] The receiving processing unit 34 is configured to include, for example, a receiving amplifier, a comparator, etc., and processes the received signal output in the ultrasonic array chip 20 when receiving ultrasonic waves, and outputs the received signal to the microcomputer 35.

[0084] The microcomputer 35 includes a memory for storing various programs and data, and a processor for executing a set of commands described in the programs stored in the memory. Furthermore, the microcomputer 35 transmits ultrasonic waves from the ultrasonic array chip 20 by issuing an output pulse drive signal to the transmitting circuit unit 33. Additionally, the microcomputer 35 measures the time from the timing of transmitting the ultrasonic waves to the output of a received signal from the receiving processing unit 34, and calculates the distance from the ultrasonic array chip 20 to the object 1 based on this time.

[0085] In this embodiment, since ultrasonic waves are transmitted to the object 1 within a narrow range of less than 10 mm and the reflected ultrasonic waves are received, the distance between the object 1 and the ultrasonic array chip 20 is continuously calculated while the relative position of the ultrasonic array chip 20 with respect to the object 1 is moved. This allows the surface condition of the object 1, such as whether there are bumps or depressions, tilt angles, etc., to be determined.

[0086] [Effects of this implementation method]

[0087] The ultrasonic sensor 10 of this embodiment transmits ultrasonic waves to an object and receives ultrasonic waves reflected by the object. The ultrasonic sensor 10 includes an ultrasonic array chip 20 that configures ultrasonic transducers 24 for transmitting and receiving ultrasonic waves in an array. The ultrasonic transducers 24 include a vibrating section 221 and a piezoelectric element 23 disposed on the vibrating section 221. The vibrating section 221 is vibrated by applying a voltage to the piezoelectric element 23 to transmit ultrasonic waves, and the reception of ultrasonic waves is detected based on the signal output from the piezoelectric element due to the vibration of the vibrating section 221. Furthermore, in this embodiment, the resonant frequency of the ultrasonic transducer 24 is below 2000 kHz.

[0088] In this configuration of the ultrasonic sensor 10, the reverberation time of the vibrating section 221 in each ultrasonic transducer 24 before the reverberation vibration decays during ultrasonic wave transmission is sufficiently small compared to that of a bulk ultrasonic transducer. Therefore, even when the object 1 is located at a distance of 10 mm or less from the ultrasonic sensor 10, reverberation vibration can be suppressed when receiving ultrasonic waves reflected from the object 1 through the ultrasonic transducer 24, and the reception of the reflected ultrasonic waves can be properly detected. Furthermore, by setting the resonant frequency to 2000 kHz or less, attenuation of ultrasonic waves in the air can be suppressed, and ultrasonic waves reflected from the object 1 at close range can be properly detected.

[0089] In the ultrasonic sensor 10 of this embodiment, when viewed from the direction of ultrasonic wave transmission, the ultrasonic array chip 20 is rectangular and the array opening width is less than 5 mm.

[0090] In this configuration, ultrasonic beams are formed by ultrasonic waves emitted from each ultrasonic transducer 24 disposed in the ultrasonic sensor 10. Within a distance range of 10 mm from the ultrasonic sensor 10, the dot diameter of this ultrasonic beam is less than 10 mm. Therefore, ultrasonic waves can be emitted to a narrow range of the object 1 with a dot diameter of less than 10 mm, and the distance between this narrow range of the object 1 and the ultrasonic sensor 10 can be measured.

[0091] In this case, for example, by continuously varying the narrow range of transmitted ultrasonic waves relative to the position of the ultrasonic sensor 10 and monitoring the distance change, it is possible to measure the tilt of the object 1 and the surface shape of the object 1.

[0092] In the ultrasonic sensor 10 of this embodiment, the ultrasonic transducer 24 is configured such that when the resonant frequency of the ultrasonic transducer 24 is set to less than 1000 kHz, the reverberation time will be less than 60 μs.

[0093] Therefore, it is possible to send an ultrasonic beam with a point diameter of less than 10 mm to an object 1 at a distance of about 10 mm from the ultrasonic sensor 10.

[0094] In the ultrasonic sensor 10 of this embodiment, the ultrasonic transducer 24 is configured such that when the resonant frequency of the ultrasonic transducer 24 is set to 1000 kHz or more and less than 1500 kHz, the reverberation time will be less than 50 μs.

[0095] Therefore, it is possible to send an ultrasonic beam with a point diameter of less than 10 mm to an object 1 that is 5 mm to 10 mm away from the ultrasonic sensor 10.

[0096] In the ultrasonic sensor 10 of this embodiment, the ultrasonic transducer 24 is configured such that when the resonant frequency of the ultrasonic transducer 24 is set to 1500 kHz or more and 2000 kHz or less, the reverberation time will be less than 25 μs.

[0097] Therefore, it is possible to send an ultrasonic beam with a point diameter of less than 10 mm to an object 1 within 5 mm of the ultrasonic sensor 10.

[0098] [Variation Example]

[0099] It should be noted that the present invention is not limited to the embodiments described above. The configurations obtained by modifying, improving and appropriately combining the embodiments within the scope of achieving the purpose of the present invention are included in the present invention.

[0100] [Variation Example 1]

[0101] In the above embodiments, Figure 1 In this context, the space between the ultrasonic array chip 20 disposed on the substrate 11 and the object 1 becomes a space for other configurations, but it is not limited to this.

[0102] Figure 10 This is a schematic diagram illustrating other configuration examples of the ultrasonic sensor 10. For example, such as... Figure 10 As shown, it can also be configured as follows: a spacer plate 12 is provided between the ultrasonic sensor 10 and the object 1 to cover the ultrasonic array chip 20, and a through hole 121 is provided in the spacer plate 12 to allow the ultrasonic beam to pass through.

[0103] [Variation Example 2]

[0104] As described above, in this disclosure, the length of one side of the ultrasonic array chip 20 being 5 mm or less refers to the length of one side of a rectangular transceiver area obtained by arranging the ultrasonic transducers 24 that transmit and receive ultrasonic waves in an array within the ultrasonic array chip 20. Therefore, when there is a wiring area, for example, forming wiring, outside the transceiver area, there is no particular limitation on the size of the wiring area.

[0105] Here, in the above embodiment, an example is shown where the ultrasonic array chip 20 is rectangular and the shape of the transceiver area of ​​the ultrasonic transceiver surface 22A is also rectangular, but it is not limited to this. For example, a square transceiver area with one side length of less than 5 mm can also be provided, a circular transceiver area with a diameter of less than 5 mm can also be provided, or an elliptical transceiver area with a major axis length of less than 5 mm can also be provided.

[0106] [Summary of this disclosure]

[0107] The ultrasonic sensor of the first aspect of this disclosure is an ultrasonic sensor that transmits ultrasonic waves to an object and receives ultrasonic waves reflected by the object. It includes an ultrasonic array chip in which ultrasonic elements for transmitting and receiving ultrasonic waves are arranged in an array. The ultrasonic elements include a vibrating part and a piezoelectric element disposed on the vibrating part. The vibrating part is vibrated by applying a voltage to the piezoelectric element to transmit ultrasonic waves, and the reception of ultrasonic waves is detected by the signal output from the piezoelectric element through the vibration of the vibrating part. The resonant frequency of the ultrasonic element is below 2000 kHz.

[0108] Therefore, compared to bulk ultrasonic transducers, the reverberation time before the decay of reverberation vibration when ultrasonic waves are transmitted in the ultrasonic element of the ultrasonic sensor can be significantly reduced. Thus, even when the object is located at a distance of, for example, less than 10 mm from the ultrasonic sensor, reverberation vibration can be suppressed when receiving ultrasonic waves reflected from the object through the ultrasonic element, and the reception of reflected ultrasonic waves can be properly detected.

[0109] In the ultrasonic sensor of this aspect, when viewed from the direction of ultrasonic wave transmission, the ultrasonic array chip is rectangular, and the length of one side is less than 5 mm.

[0110] Therefore, it is possible to reduce the point diameter of the ultrasonic beam formed within a distance range of 10 mm from the ultrasonic sensor to less than 10 mm, and to measure the tilt and surface shape of the object.

[0111] In the ultrasonic sensor of this aspect, the resonant frequency of the ultrasonic element is less than 1000 kHz, and the ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to less than 10% of the vibration amplitude of the vibrating part immediately after transmitting the ultrasonic waves, the reverberation time is less than 60 μs.

[0112] Therefore, it is possible to send an ultrasonic beam with a point diameter of less than 10 mm to objects at close range, within about 10 mm of the ultrasonic sensor.

[0113] In the ultrasonic sensor of this aspect, the resonant frequency of the ultrasonic element is 1000 kHz or more and less than 1500 kHz, and the ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to less than 10% of the vibration amplitude of the vibrating part immediately after transmitting the ultrasonic waves, the reverberation time is less than 50 μs.

[0114] Therefore, it is possible to send an ultrasonic beam with a point diameter of less than 10 mm to an object that is 5 mm to 10 mm away from the ultrasonic sensor.

[0115] In the ultrasonic sensor of this aspect, the resonant frequency of the ultrasonic element is 1500 kHz or higher and 2000 kHz or lower, and the ultrasonic element is configured such that when the resonant time is defined as the time from the vibration amplitude of the vibrating part generated by transmitting ultrasonic waves from the ultrasonic element to less than 10% of the vibration amplitude of the vibrating part immediately after transmitting ultrasonic waves, the resonant time is less than 25 μs.

[0116] Therefore, it is possible to send an ultrasonic beam with a point diameter of less than 10 mm to an object within 5 mm of the ultrasonic sensor.

Claims

1. An ultrasonic sensor, characterized in that, The ultrasonic sensor transmits ultrasonic waves to an object and receives ultrasonic waves reflected by the object, the ultrasonic sensor comprising: An ultrasonic array chip is obtained by configuring ultrasonic elements that transmit and receive ultrasonic waves in an array. The ultrasonic element includes an element substrate, a thin-film vibrating plate that blocks an opening formed in the element substrate, and a thin-film piezoelectric element disposed on the vibrating plate as part of the vibrating portion that blocks the opening. The vibrating portion is vibrated by applying a voltage to the piezoelectric element to transmit ultrasonic waves, and the reception of ultrasonic waves is detected by the signal output from the piezoelectric element due to the vibration of the vibrating portion. The component substrate is made of a semiconductor substrate. The vibrating plate is composed of a laminate containing SiO2 and ZrO2. The resonant frequency of the ultrasonic element is above 500kHz and below 2000kHz. When viewed from the direction of ultrasonic wave transmission, the ultrasonic array chip is rectangular, with one side length less than 5mm. The ultrasonic array chip transmits an ultrasonic beam with a point diameter of less than 10 mm to an object positioned at a predetermined distance from the vibrating part. When the predetermined distance is y and the resonant frequency of the ultrasonic element is x, -0.0076x+15.745≦y﹤-0.0076x+20.241, Where y is measured in mm and x in kHz.

2. The ultrasonic sensor according to claim 1, wherein, The resonant frequency of the ultrasonic element is above 500kHz and below 1000kHz. The ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to the time before the vibration amplitude of the vibrating part immediately after transmitting ultrasonic waves is less than 10%, the reverberation time will be less than 60 μs.

3. The ultrasonic sensor according to claim 1, wherein, The resonant frequency of the ultrasonic element is above 1000kHz and below 1500kHz. The ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to the time before the vibration amplitude of the vibrating part immediately after transmitting ultrasonic waves is less than 10%, the reverberation time will be less than 50 μs.

4. The ultrasonic sensor according to claim 1, wherein, The resonant frequency of the ultrasonic element is above 1500kHz and below 2000kHz. The ultrasonic element is configured such that when the reverberation time is defined as the time from the vibration amplitude of the vibrating part caused by transmitting ultrasonic waves from the ultrasonic element to the time before the vibration amplitude of the vibrating part immediately after transmitting ultrasonic waves is less than 10%, the reverberation time will be less than 25 μs.

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