Signal-processing device, ultrasonic measurement device, signal-processing program, and signal-processing method

Abstract

This signal-processing device comprises: a transmission control unit (141) that transmits a control signal for causing a transmission unit (11) to transmit a plurality of transmission signals having different characteristics; a reception signal acquisition unit (142) that acquires a plurality of reception signals from a reception sensor (13); a non-linear component extraction unit (143) that extracts a non-linear component by performing calculation according to the characteristics of the transmission signals transmitted by the transmission unit (11), on the basis of the plurality of reception signals acquired by the reception signal acquisition unit (142); and a property estimation unit (144) that estimates a property of a measurement target (2) on the basis of the non-linear component extracted by the non-linear component extraction unit (143). The plurality of transmission signals each have an amplitude that allows a plurality of transmission pulses to exhibit non-linear effects in air. The plurality of reception signals include low-frequency components generated by the non-linear effects in air.

Description

Signal processing device, ultrasonic measurement device, signal processing program, and signal processing method

[0001] The present disclosure relates to a signal processing device, an ultrasonic measurement device, a signal processing program, and a signal processing method.

[0002] In recent years, labor shortages caused by the declining birthrate and aging population, as well as reductions in work hours due to work style reforms, have led to labor-saving efforts in various industries. For example, robots are used in manufacturing, nursing care, ports, and shipping, and automated guided vehicles (AGVs) or autonomous mobile robots (AMRs) are used in the logistics industry. This trend is expected to continue in the future.

[0003] When AGVs and AMRs detect an object that obstructs their movement, they stop or avoid it. Ultrasonic sensors are used to detect objects, but one challenge with these sensors is the detection of objects in areas that are hidden by the obstacle. One possible solution to this challenge is to use diffracted waves generated at the edge of the obstacle.

[0004] The diffracted waves generated at the edge are weak, but are generated relatively efficiently if the frequency is low. For example, when sensing with 40 kHz ultrasound, the diffracted waves are weak at 40 kHz, but the low-frequency components generated by the nonlinear effect of air generate diffracted waves relatively efficiently, so it is thought that these low-frequency components can be used to detect objects in areas beyond the line of sight.

[0005] However, sensing using the nonlinear effect of air also has its challenges. These challenges will be explained with reference to FIGS. 12 to 19. FIG. 12 is a diagram illustrating the situation of non-line-of-sight groove depth measurement using ultrasonic waves. As shown in FIG. 12, the transmitting sensor 12 transmits a transmission pulse, and the receiving sensor 13 receives the reflected wave of the transmission pulse from the groove to obtain a received signal. FIG. 13 is a diagram illustrating the concept of the reflected wave from the groove in the groove depth measurement shown in FIG. 12. FIG. 14 is a diagram illustrating the positional relationship between the transmitting sensor 12, the receiving sensor 13, and the groove in a simulation of the groove depth measurement shown in FIG. 12. FIG. 15 is a diagram illustrating the waveform of the transmission pulse transmitted by the transmitting sensor 12 in the simulation. FIG. 16 is a diagram illustrating the frequency spectrum of the transmission pulse transmitted by the transmitting sensor 12 in the simulation. FIG. 17 is a diagram illustrating the waveform of the received signal obtained by the receiving sensor 13 in the simulation. FIG. 18 is a diagram illustrating the frequency spectrum of the received signal obtained by the receiving sensor 13 in the simulation. FIG. 19 is a diagram showing a waveform in which only the low frequency components of the received signal obtained by the receiving sensor 13 in the simulation are extracted.

[0006] In Figure 12, a groove is assumed as the out-of-line-of-sight object to be measured. For the sake of explanation, among the corners at the top of the groove, those closest to the transmitting sensor 12 and the receiving sensor 13 are referred to as edge parts, and those farther from the transmitting sensor 12 and the receiving sensor 13 are referred to as upper corners. Furthermore, among the corners at the bottom of the groove, those farther from the transmitting sensor 12 and the receiving sensor 13 are referred to as lower corners. As shown in Figure 12, the lower corner is out of line of sight from the transmitting sensor 12 and the receiving sensor 13. For this reason, the transmission pulse transmitted by the transmitting sensor 12 does not reach the lower corner directly, but a diffracted wave generated at the edge part reaches the lower corner and becomes a reflected wave.

[0007] In this case, the received signal obtained by the receiving sensor 13 is a reflected wave from the end, the upper corner, and the lower corner, as shown in Figure 13. The depth (d) of the groove is determined by the distance from the end to the upper corner. １The distance from the edge to the bottom corner is l ２ Then, it can be roughly estimated using the following equation (1).

[0008] In this way, if the reflected waves from the edge, upper corner, and lower corner can be clearly received, it is possible to estimate the depth of the groove. However, since the lower corner is out of line of sight, it is unclear whether the reflected waves can be clearly received.

[0009] Therefore, the reception status of the reflected wave is examined by simulation. In the simulation, as shown in FIG. 14, the distance from the transmitting sensor 12 and the receiving sensor 13 to the end is set to 880 mm, the groove width is 332 mm, and the depth is 260 mm. The nonlinear effect of air is also taken into consideration. In the simulation, the transmission pulse shown in FIG. 15 is transmitted from the transmitting sensor 12. In the simulation, the center frequency of the transmission pulse is set to 40 kHz, as shown in FIG. 16.

[0010] FIG. 17 shows the received signal obtained by the receiving sensor 13 in the simulation. As shown in FIG. 17, the reflected waves from the edge and the upper corner are clearly received. In particular, the upper corner is directly irradiated with the transmitted pulse, so the reflected waves are very large. On the other hand, the reflected waves from the lower corner are much smaller than the reflected waves from the upper corner. In such a situation, there is a possibility that the reflected waves from the lower corner will be overlooked. However, if the difference in amplitude between the reflected waves from the upper and lower corners is reduced, the possibility of overlooking the reflected waves from the lower corner will be significantly reduced.

[0011] Furthermore, due to the nonlinear effect of air, low-frequency and high-frequency components are generated in the frequency spectrum of the received signal, as shown in Figure 18. Since the transmitted pulse is directly irradiated onto the upper corner, the original 40 kHz component of the reflected wave is very large, while the diffracted wave generated at the edge propagates to the lower corner, resulting in a relatively large low-frequency component.

[0012] Figure 19 shows a waveform in which only low-frequency components below 20 kHz are extracted from the received signal. In the waveform shown in Figure 19, the difference in amplitude between the reflected waves from the upper and lower corners is small. With this waveform, there is little chance of overlooking the reflected wave from the lower corner. However, to obtain a waveform by extracting only the low-frequency components from the frequency spectrum shown in Figure 18, sophisticated filtering is required.

[0013] An example of a conventional ultrasonic measurement device using diffracted waves is the device disclosed in Patent Document 1. The device disclosed in Patent Document 1 detects cracks using high-frequency components and low-frequency components generated by nonlinear effects. However, the device disclosed in Patent Document 1 does not solve the above-mentioned problems.

[0014] JP 2014-186029 A

[0015] As mentioned above, it is thought that by extracting only the low-frequency components from the frequency spectrum of the received signal, it is possible to receive reflected waves from beyond the line of sight without missing them. However, extracting only the low-frequency components from the frequency spectrum of the received signal to obtain a waveform requires sophisticated filtering.

[0016] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a signal processing device that can estimate the properties of an object to be measured with greater accuracy than conventional devices without performing high-performance filter processing.

[0017] The signal processing device according to the present disclosure comprises a transmission control unit that transmits a control signal to a transmission unit that transmits a transmission signal, causing the transmission unit to transmit a plurality of transmission signals with different characteristics; a reception signal acquisition unit that acquires a plurality of reception signals from a reception sensor that obtains a plurality of reception signals by receiving reflected waves of a plurality of ultrasonic transmission pulses transmitted by a transmission sensor in response to the plurality of transmission signals transmitted by the transmission unit, the plurality of reception signals being reflected by the object to be measured; a nonlinear component extraction unit that extracts nonlinear components by performing calculations according to the characteristics of the transmission signals transmitted by the transmission unit based on the plurality of reception signals acquired by the reception signal acquisition unit; and a property estimation unit that estimates the properties of the object to be measured based on the nonlinear components extracted by the nonlinear component extraction unit, wherein the amplitudes of the plurality of transmission signals transmitted by the transmission unit are amplitudes at which the plurality of transmission pulses transmitted by the transmission sensor can obtain the nonlinear effect of air, and the plurality of reception signals obtained by the reception sensor include low-frequency components generated by the nonlinear effect of air.

[0018] According to the present disclosure, with the above-described configuration, it is possible to estimate the properties of an object to be measured with higher accuracy than in the past without performing sophisticated filtering processing.

[0019] 1A and 1B are conceptual diagrams for explaining the relationship between transmitted sound pressure and the amplitude of a received signal, with FIG. 1A showing the case of a linear signal and FIG. 1B showing the case of a nonlinear signal.

[0033] FIG. 1A shows an example of the configuration and operation of an ultrasonic measurement device including a signal processing device according to embodiment 1. and

[0034] FIG. 1B shows an example of the hardware configuration of the signal processing device according to embodiment 1. and

[0035] FIG. 1C is a flowchart showing an example of the operation of the signal processing device according to embodiment 1.

[0036] FIG. 1D is a diagram showing the waveform of a received signal obtained by a receiving sensor when the amplitude of the transmitted signal is halved in the simulation of groove depth measurement shown in FIG. 12.

[0037] FIG. 1F is a diagram showing the waveform of a received signal resulting from subtraction processing by the signal processing device according to embodiment 1 using the received signal shown in FIG. 5 and the received signal shown in FIG. 17.

[0038] FIG. 1F is a conceptual diagram for explaining the relationship between the polarity of a transmitted signal and the phase of a received signal.

[0039] FIG. 1D is a diagram showing an example of the configuration and operation of an ultrasonic measurement device including a signal processing device according to embodiment 2. and

[0039] FIG. 1F is a flowchart showing an example of the operation of the signal processing device according to embodiment 2.

[0039] FIG. 1F is a diagram showing the waveform of a received signal obtained by a receiving sensor when the polarity of the transmitted signal is inverted in the simulation of groove depth measurement shown in FIG. 12. and

[0039] FIG. 1C is a diagram showing the waveform of a received signal resulting from subtraction processing by the signal processing device according to embodiment 2 using the received signal shown in FIG. 10 and the received signal shown in FIG. 17. 12. A diagram for explaining the situation of non-line-of-sight groove depth measurement using ultrasonic waves. A diagram for explaining the concept of reflected waves from the groove in the groove depth measurement shown in FIG. 12. A diagram showing the positional relationship between the transmitting sensor, receiving sensor, and groove in the groove depth measurement simulation shown in FIG. 12. A diagram showing the waveform of a transmission pulse transmitted by the transmitting sensor in the groove depth measurement simulation shown in FIG. 12. A diagram showing the frequency spectrum of the transmission pulse transmitted by the transmitting sensor in the groove depth measurement simulation shown in FIG. 12. A diagram showing the waveform of a reception signal obtained by the receiving sensor in the groove depth measurement simulation shown in FIG. 12. A diagram showing the frequency spectrum of the reception signal obtained by the receiving sensor in the groove depth measurement simulation shown in FIG. 12. A diagram showing a waveform in which only the low frequency component of the reception signal obtained by the receiving sensor is extracted in the groove depth measurement simulation shown in FIG.

[0020] Hereinafter, embodiments will be described in detail with reference to the drawings. Embodiment 1. An ultrasonic measurement device 1 according to embodiment 1 will be described using FIGS. 1 to 6. The ultrasonic measurement device 1 is a device that uses ultrasonic waves to estimate the properties of an object to be measured 2. In particular, this ultrasonic measurement device 1 is assumed to be a device that estimates the properties of an object to be measured 2 in a situation where an object exists between the transmitting sensor 12 and receiving sensor 13 and the reflection source of the object to be measured 2, making it impossible to use direct waves. Note that the following description will be given taking as an example a case where the property of the object to be measured 2 is the depth of a groove.

[0021] FIG. 1 is a conceptual diagram for explaining the relationship between transmitted sound pressure and the amplitude of a received signal. FIG. 2 is a diagram showing an example of the configuration and operation of an ultrasonic measurement device 1 including a signal processing device 14 according to embodiment 1. FIG. 3 is a diagram showing an example of the hardware configuration of the signal processing device 14 according to embodiment 1. FIG. 4 is a flowchart showing an example of the operation of the signal processing device 14 according to embodiment 1. FIG. 5 is a diagram showing the waveform of a received signal obtained by the receiving sensor 13 when the amplitude of the transmitted signal is halved in the groove depth measurement simulation shown in FIG. 12. FIG. 6 is a diagram showing the waveform of a received signal resulting from subtraction processing performed by the signal processing device 14 according to embodiment 1 using the received signal shown in FIG. 5 and the received signal shown in FIG. 17.

[0022] First, we will explain the change in the amplitude of the received signal relative to the change in the transmitted sound pressure (amplitude of the transmitted signal) using Figure 1. In Figure 1, the horizontal axis represents the transmitted sound pressure, and the vertical axis represents the amplitude of the received signal. Figure 1A shows the case of a linear signal, and Figure 1B shows the case of a nonlinear signal.

[0023] As shown in FIG. 1A, in the case of a linear signal, the transmitted sound pressure is expressed as p ０ Half of that, 0.5p ０If the amplitude of the received signal is halved, the amplitude of the received signal will also be halved. In other words, in the case of a linear signal, for example, if the transmission sound pressure of one of two transmission pulses is halved and the amplitude of the received signal corresponding to the one transmission pulse of two reception signals is doubled, the amplitudes of the two reception signals will be the same. Therefore, if these two reception signals are subtracted, the reception signal will disappear.

[0024] On the other hand, in the case of a nonlinear signal, as shown in FIG. 1B, the transmitted sound pressure is p ０ Half of that, 0.5p ０ Even if the amplitude of the received signal is halved, the amplitude of the received signal will not be halved. In other words, in the case of a nonlinear signal, for example, even if the transmission sound pressure of one of the two transmission pulses is halved and the amplitude of the received signal corresponding to the one of the two transmission pulses is doubled, the amplitudes of the two received signals will not be the same. Therefore, even if these two received signals are subtracted, the received signal remains.

[0025] From the above, by utilizing the above characteristics, it is possible to remove linear components from the received signal and extract nonlinear components (low-frequency components generated by nonlinear effects). Therefore, in the ultrasonic measurement device 1 according to the first embodiment, this characteristic is utilized to extract the nonlinear components and then estimate the properties of the object to be measured 2.

[0026] Next, an example of the configuration of the ultrasonic measurement device 1 will be described with reference to Fig. 2. For example, as shown in Fig. 2, the ultrasonic measurement device 1 includes a transmitter 11, a transmitting sensor 12, a receiving sensor 13, and a signal processing device 14. As shown in Fig. 2, the transmitter 11 is connected to the transmitting sensor 12, and the signal processing device 14 is connected to the transmitter 11 and the receiving sensor 13.

[0027] The transmitter 11 transmits a plurality of transmission signals with different characteristics to the transmitting sensor 12 in response to a control signal from the signal processing device 14. The amplitudes of the plurality of transmission signals transmitted by the transmitter 11 are such that the plurality of transmission pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air.

[0028] The transmitter 11 in the first embodiment transmits a plurality of transmission signals with different amplitudes as a plurality of transmission signals with different characteristics to the transmitting sensor 12. In this case, for example, the transmitter 11 first generates a plurality of transmission signals with the same amplitude. Then, the transmitter 11 generates a plurality of transmission signals with different amplitudes by setting the amplitudes of the remaining transmission signals, excluding one transmission signal, to amplitudes that are divided by different coefficients. Then, the transmitter 11 transmits the generated plurality of transmission signals with different amplitudes to the transmitting sensor 12.

[0029] 2, the transmitter 11 transmits two transmission signals with different amplitudes to the transmission sensor 12. The difference in amplitude between the two transmission signals transmitted by the transmitter 11 is, for example, two times. The amplitudes of the two transmission signals transmitted by the transmitter 11 are each large enough to clearly obtain the nonlinear effect of air.

[0030] The transmitting sensor 12 transmits a plurality of ultrasonic transmission pulses in response to the plurality of transmission signals transmitted by the transmitting unit 11. The plurality of transmission pulses transmitted by the transmitting sensor 12 are reflected by the object 2 to be measured.

[0031] For example, as shown in FIG. 2, when two transmission signals are transmitted by the transmitter 11, the transmitting sensor 12 transmits two transmission pulses corresponding to the two transmission signals.

[0032] The receiving sensor 13 obtains a plurality of received signals by receiving the reflected waves of the plurality of transmission pulses transmitted by the transmitting sensor 12 from the object under test 2. The plurality of received signals obtained by the receiving sensor 13 include low-frequency components generated by nonlinear effects. The receiving frequency bandwidth of the receiving sensor 13 is a bandwidth that can receive the low-frequency components generated by the nonlinear effects of air.

[0033] For example, as shown in Fig. 2, when two transmission pulses are transmitted by the transmitting sensor 12, the receiving sensor 13 obtains two reception signals by receiving the waves reflected by the object under test 2. In Fig. 2, these two reception signals are referred to as reception signal A and reception signal B, respectively.

[0034] The signal processing device 14 transmits a control signal for controlling the transmission process to the transmitting unit 11. The signal processing device 14 also estimates the properties of the object to be measured 2 based on a plurality of received signals obtained by the receiving sensor 13. As shown in FIG. 2 , the signal processing device 14 includes a transmission control unit 141, a received signal acquisition unit 142, a nonlinear component extraction unit 143, and a property estimation unit 144.

[0035] The transmission control unit 141 transmits a control signal to the transmitter 11 to cause the transmitter 11 to transmit a plurality of transmission signals with different characteristics. The transmission control unit 141 in the first embodiment transmits a control signal to the transmitter 11 to cause the transmitter 11 to transmit a plurality of transmission signals with different amplitudes as a plurality of transmission signals with different characteristics.

[0036] The received signal acquisition unit 142 acquires a plurality of received signals from the receiving sensor 13 .

[0037] The nonlinear component extraction unit 143 extracts nonlinear components (low frequency components) by performing calculations according to the characteristics of the transmission signal transmitted by the transmitter 11 based on the multiple received signals acquired by the received signal acquisition unit 142.

[0038] The nonlinear component extraction unit 143 in the first embodiment extracts nonlinear components by performing subtraction processing based on the multiple received signals acquired by the received signal acquisition unit 142. In this case, for example, first, the nonlinear component extraction unit 143 multiplies the amplitude of each received signal, among the multiple received signals acquired by the received signal acquisition unit 142, by the coefficient, corresponding to the transmitted signal whose amplitude has been reduced to one divided by the coefficient. Then, the nonlinear component extraction unit 143 subtracts the multiple received signals from each other. In this way, the nonlinear component extraction unit 143 can extract nonlinear components generated by the nonlinear effect of air from the multiple received signals acquired by the received signal acquisition unit 142.

[0039] For example, as shown in Fig. 2, if the transmitter 11 transmits two transmission signals, one of which has half the amplitude of the other, the nonlinear component extractor 143 doubles the amplitude of the reception signal corresponding to one of the transmission signals (reception signal B in the example of Fig. 2).The nonlinear component extractor 143 then subtracts reception signal B, with its amplitude doubled, from reception signal A.As a result, linear components are removed by the subtraction process because their amplitudes match, but nonlinear components remain without being removed by the subtraction process because their amplitudes do not match.

[0040] The property estimation unit 144 estimates the property of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extraction unit 143. Note that the method of estimating the property by the property estimation unit 144 itself can be a conventional estimation method.

[0041] For example, if the property of the object to be measured 2 is a groove depth as shown in FIG. 12 , extracting the nonlinear component reduces the amplitude difference between the reflected waves from the upper corner and the lower corner. Therefore, the property estimation unit 144 can easily and accurately determine the distance from the end to the upper corner and the distance from the end to the lower corner. As a result, the property estimation unit 144 can accurately estimate the groove depth from equation (1).

[0042] The hardware configuration of the signal processing device 14 can be realized using a computer with a built-in CPU (Central Processing Unit), such as a personal computer or a workstation, or may be realized using an LSI (Large Scale Integrated Circuit), such as a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array).

[0043] Fig. 3 is a block diagram showing a schematic example of the hardware configuration of the signal processing device 14. The example shown in Fig. 3 includes a processor 51 including a CPU, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a recording medium 54, a transmission / reception interface circuit 55, a display interface circuit 56, and a display 57. The processor 51, ROM 52, RAM 53, recording medium 54, transmission / reception interface circuit 55, and display interface circuit 56 are connected to each other via a signal path 58 such as a bus circuit.

[0044] The processor 51 uses the RAM 53 as a working memory and executes a control computer program read from the ROM 52. The recording medium 54 is configured using, for example, a volatile memory such as an SDRAM (Synchronous DRAM), or an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The transmission / reception interface circuit 55 is a circuit used for signal transmission with the transmitter 11 and with the receiving sensor 13. The display interface circuit 56 is a circuit used for signal transmission with a display 57.

[0045] The display 57 displays the results. The results may be displayed as numbers or by an LED lamp or the like. The display method is not limited.

[0046] Next, an example of operation of the signal processing device 14 shown in Fig. 2 will be described with reference to Fig. 4. In the example of operation of the signal processing device 14 shown in Fig. 2, as shown in Fig. 4, for example, first, the transmission control unit 141 transmits a control signal to the transmitting unit 11 to cause the transmitting unit 11 to transmit a plurality of transmission signals with different characteristics (step ST101). The transmission control unit 141 in the first embodiment transmits a control signal to the transmitting unit 11 to cause the transmitting unit 11 to transmit a plurality of transmission signals with different amplitudes as a plurality of transmission signals with different characteristics.

[0047] The transmitting unit 11 then transmits a plurality of transmission signals with different amplitudes to the transmitting sensor 12 in response to a control signal from the transmission control unit 141. The amplitudes of the plurality of transmission signals transmitted by the transmitting unit 11 are such that the plurality of transmission pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air. The transmitting sensor 12 then transmits a plurality of ultrasonic transmission pulses in response to the plurality of transmission signals transmitted by the transmitting unit 11. The plurality of transmission pulses transmitted by the transmitting sensor 12 are reflected by the object to be measured 2. The receiving sensor 13 then obtains a plurality of reception signals by receiving the reflected waves of the plurality of transmission pulses transmitted by the transmitting sensor 12 from the object to be measured 2. The plurality of reception signals obtained by the receiving sensor 13 include low-frequency components generated by the nonlinear effect.

[0048] Next, the received signal acquiring unit 142 acquires a plurality of received signals from the receiving sensor 13 (step ST102).

[0049] Next, the nonlinear component extraction unit 143 extracts nonlinear components (low frequency components) by performing calculations according to the characteristics of the transmission signal transmitted by the transmitter 11 based on the multiple received signals acquired by the received signal acquisition unit 142 (step ST103).

[0050] The nonlinear component extraction unit 143 in the first embodiment extracts nonlinear components by performing subtraction processing based on the multiple received signals acquired by the received signal acquisition unit 142. In this case, for example, first, the nonlinear component extraction unit 143 sets the amplitude of each received signal, among the multiple received signals acquired by the received signal acquisition unit 142, corresponding to the transmitted signal whose amplitude has been divided by the coefficient, to an amplitude that is multiplied by the coefficient. Then, the nonlinear component extraction unit 143 subtracts the multiple received signals from each other.

[0051] Next, the property estimation section 144 estimates the property of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extraction section 143 (step ST104).

[0052] Next, a simulation for confirming the effect of the operation of the ultrasonic measurement device 1 according to embodiment 1 shown in Fig. 2 will be described. Fig. 5 shows a received signal obtained by performing a similar simulation, assuming the same situation as Fig. 14 used to explain the problem, but with the amplitude of the transmitted signal reduced to half that of Fig. 15. As shown in Fig. 5, the edge and the upper corner can be clearly distinguished, but the reflected wave from the lower corner is very small.

[0053] Here, the received signal shown in FIG. 17 is referred to as received signal A. The received signal shown in FIG. 5 is referred to as received signal B. The results of performing a subtraction process of (A-2×B) using these received signals are shown in FIG. 6. As shown in FIG. 6, by performing the subtraction process described above, the difference in amplitude between the reflected waves from the upper corner and the lower corner is reduced, making it possible to clearly distinguish between them. Therefore, the effect of embodiment 1 was confirmed.

[0054] In the received signal shown in Fig. 6, there is a high-frequency component between the upper corner component and the lower corner component. This is because the component around 80 kHz generated by the nonlinear effect remains after the subtraction process, as shown in Fig. 18.

[0055] The above description has been given on the assumption that the transmitting sensor 12 and the receiving sensor 13 are stationary. However, when the transmitting sensor 12 and the receiving sensor 13 are mounted on an AGV or an AMR, sensing may be performed while the transmitting sensor 12 and the receiving sensor 13 are moving. In such cases, the property estimation unit 144 performs correction using (the time difference between) the transmission timings of multiple transmission signals from the transmitting sensor 12 and the moving speeds of the transmitting sensor 12 and the receiving sensor 13. Specifically, the property estimation unit 144 calculates the distance traveled while multiple transmission signals are being transmitted from the time difference between the transmission timings and the moving speed, and uses this distance as a correction amount to correct the horizontal axis (distance) of the received signal.

[0056] In the above description, the amplitude difference between the plurality of transmission signals is two times. However, in the first embodiment, the amplitude difference between the plurality of transmission signals does not have to be two times. For example, if the amplitude difference between the plurality of transmission signals is three times, the nonlinear component extraction unit 143 may triple the amplitude of the received signal and then perform the subtraction process. In this way, the amplitude difference between the transmission signals is not limited.

[0057] In the above description, the number of transmission signals is two. However, the number of transmission signals does not need to be two, and any number of transmission signals may be used. For example, the same processing as described above may be performed using three transmission signals.

[0058] In this way, the ultrasonic measurement device 1 according to embodiment 1 uses multiple transmission signals with different amplitudes and performs subtraction processing on the corresponding reception signals, thereby clearly distinguishing between the upper corner components and the lower corner components in the reception signals and estimating the properties of the object to be measured 2.

[0059] As described above, according to this embodiment 1, the signal processing device 14 includes a transmission control unit 141 that transmits a control signal to the transmitting unit 11, which transmits the transmission signal, to cause the transmitting unit 11 to transmit a plurality of transmission signals with different characteristics; a received signal acquisition unit 142 that acquires a plurality of received signals from the receiving sensor 13 that obtains a plurality of received signals by receiving reflected waves of a plurality of ultrasonic transmission pulses transmitted by the transmitting sensor 12 in response to the plurality of transmission signals transmitted by the transmitting unit 11 from the object to be measured 2; a nonlinear component extraction unit 143 that extracts nonlinear components by performing calculations according to the characteristics of the transmission signals transmitted by the transmitting unit 11 based on the plurality of received signals acquired by the received signal acquisition unit 142; and a property estimation unit 144 that estimates the properties of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extraction unit 143. The amplitudes of the plurality of transmission signals transmitted by the transmitting unit 11 are amplitudes at which the plurality of transmission pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air, and the plurality of received signals acquired by the receiving sensor 13 include low-frequency components generated by the nonlinear effect of air. According to the first embodiment, the receiving frequency bandwidth of the receiving sensor 13 is a bandwidth capable of receiving low-frequency components caused by the nonlinear effect of air. According to the first embodiment, the transmission control unit 141 causes the transmitting unit 11 to transmit a plurality of transmission signals having different amplitudes, and the nonlinear component extraction unit 143 extracts nonlinear components by performing subtraction processing based on the plurality of reception signals acquired by the reception signal acquisition unit 142. As a result, the signal processing device 14 according to the first embodiment can extract low-frequency components caused by nonlinear effects, and can estimate the properties of the object to be measured 2 more accurately than in the past without performing sophisticated filtering processing.

[0060] Furthermore, according to the first embodiment, the property estimation unit 144 estimates the property of the object to be measured 2 after correcting the nonlinear components extracted by the nonlinear component extraction unit 143 using a correction amount based on the transmission timing of the multiple transmission signals from the transmitting sensor 12 and the movement speeds of the transmitting sensor 12 and the receiving sensor 13. As a result, the signal processing device 14 according to the first embodiment can accurately estimate the property of the object to be measured 2 even when the transmitting sensor 12 and the receiving sensor 13 are moving.

[0061] According to the first embodiment, the ultrasonic measurement device 1 includes a transmission unit 11 that transmits a plurality of transmission signals having different characteristics, a transmission sensor 12 that transmits a plurality of ultrasonic transmission pulses in response to the plurality of transmission signals transmitted by the transmission unit 11, a reception sensor 13 that obtains a plurality of reception signals by receiving the plurality of transmission pulses transmitted by the transmission sensor 12 reflected by the object 2 to be measured, and a signal processing device 14 that estimates the properties of the object 2 to be measured based on the plurality of reception signals obtained by the reception sensor 13. The signal processing device 14 includes a transmission control unit 141 that transmits a control signal to the transmission unit 11 to cause the transmission unit 11 to transmit a plurality of transmission signals having different characteristics, and a reception sensor 13 that receives a plurality of reception signals from the reception sensor 13. The ultrasonic measuring device 1 according to the first embodiment includes a received signal acquiring unit 142 that acquires a plurality of received signals, a nonlinear component extracting unit 143 that extracts nonlinear components by performing a calculation according to the characteristics of a transmitted signal transmitted by a transmitting unit 11 based on the plurality of received signals acquired by the received signal acquiring unit 142, and a property estimating unit 144 that estimates the property of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extracting unit 143, wherein the amplitudes of the plurality of transmitted signals transmitted by the transmitting sensor 12 are such that the plurality of transmitted pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air, and the plurality of received signals obtained by the receiving sensor 13 include low-frequency components generated by the nonlinear effect of air. As a result, the ultrasonic measuring device 1 according to the first embodiment can extract the low-frequency components generated by the nonlinear effect, and can estimate the property of the object to be measured 2 more accurately than in the past without performing sophisticated filtering.

[0062] Furthermore, according to the first embodiment, the signal processing program causes a computer to function as a signal processing device 14. As a result, the signal processing program according to the first embodiment makes it possible to extract low-frequency components generated by nonlinear effects, and to estimate the properties of the object to be measured 2 more accurately than in the past without performing sophisticated filtering.

[0063] Furthermore, according to this embodiment 1, the signal processing method includes the steps of: a transmission control unit 141 transmitting a control signal to the transmitting unit 11, which transmits the transmission signal, to cause the transmitting unit 11 to transmit a plurality of transmission signals having different characteristics; a reception signal acquiring unit 142 acquiring a plurality of reception signals from the receiving sensor 13, which obtains a plurality of reception signals by receiving reflected waves from the object to be measured 2 of a plurality of ultrasonic transmission pulses transmitted by the transmitting sensor 12 in response to the plurality of transmission signals transmitted by the transmitting unit 11; a nonlinear component extracting unit 143 extracting nonlinear components by performing a calculation according to the characteristics of the transmission signals transmitted by the transmitting unit 11 based on the plurality of reception signals acquired by the reception signal acquiring unit 142; and a property estimating unit 144 estimating the properties of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extracting unit 143, wherein the amplitudes of the plurality of transmission signals transmitted by the transmitting unit 11 are amplitudes at which the plurality of transmission pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air, and the plurality of reception signals acquired by the receiving sensor 13 include low-frequency components generated by the nonlinear effect of air. As a result, the signal processing method according to embodiment 1 makes it possible to extract low-frequency components generated by nonlinear effects, and to estimate the properties of the object to be measured 2 more accurately than in the past without performing sophisticated filtering.

[0064] Embodiment 2. The ultrasonic measurement device 1 according to embodiment 1 shows a case where a plurality of transmission signals with different amplitudes are used as a plurality of transmission signals with different characteristics, and a subtraction process is performed on the corresponding reception signals to extract nonlinear components (low frequency components). In contrast, the ultrasonic measurement device 1 according to embodiment 2 shows a case where a plurality of transmission signals with different polarities are used as a plurality of transmission signals with different characteristics, and a subtraction process is performed on the corresponding reception signals to extract nonlinear components (low frequency components).

[0065] An ultrasonic measurement device 1 according to a second embodiment will be described with reference to FIGS. 7 to 11. FIG. 7 is a conceptual diagram illustrating the relationship between the polarity of a transmission signal and the phase of a reception signal. FIG. 8 is a diagram illustrating an example of the configuration and operation of an ultrasonic measurement device 1 including a signal processing device 14b according to the second embodiment. FIG. 9 is a flowchart illustrating an example of the operation of the signal processing device 14b according to the second embodiment. FIG. 10 is a diagram illustrating the waveform of a reception signal obtained by the receiving sensor 13 when the polarity of the transmission signal is inverted in the groove depth measurement simulation shown in FIG. 12. FIG. 11 is a diagram illustrating the waveform of a reception signal resulting from subtraction processing performed by the signal processing device 14b according to the second embodiment using the reception signal shown in FIG. 10 and the reception signal shown in FIG. 17.

[0066] First, the difference in phase of the received signal relative to the difference in polarity of the transmitted signal will be described with reference to FIG.

[0067] As shown in the center of Figure 7, in the case of a linear signal, if the polarity of the transmitted signal is inverted, the phase of the received signal is also inverted. That is, in the case of a linear signal, for example, if the polarity of one of the two transmitted signals is inverted and the two received signals are added, the received signal will disappear.

[0068] In contrast, in the case of a nonlinear signal, reversing the polarity of the transmitted signal does not reverse the phase of the received signal, as shown on the right side of Figure 7. In other words, in the case of a nonlinear signal, for example, if the polarity of one of two transmitted signals is reversed and the two received signals are added, the received signal will be doubled and the received signal will remain.

[0069] From the above, by utilizing the above characteristics, it is possible to remove linear components from the received signal and extract nonlinear components (low-frequency components generated by nonlinear effects). Therefore, in the ultrasonic measurement device 1 according to the second embodiment, this characteristic is utilized to extract the nonlinear components and then estimate the properties of the object to be measured 2.

[0070] Next, an example of the configuration of the ultrasonic measurement device 1 will be described with reference to Fig. 8. The ultrasonic measurement device 1 includes, for example, a transmitter 11, a transmitting sensor 12, a receiving sensor 13, and a signal processing device 14b, as shown in Fig. 8. Note that, as shown in Fig. 8, the transmitter 11 is connected to the transmitting sensor 12, and the signal processing device 14b is connected to the transmitter 11 and the receiving sensor 13.

[0071] In response to a control signal from the signal processing device 14b, the transmitter 11 transmits a plurality of transmission signals with different characteristics to the transmitting sensor 12. The amplitudes of the plurality of transmission signals transmitted by the transmitter 11 are such that the plurality of transmission pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air.

[0072] The transmitter 11 in the second embodiment transmits a plurality of transmission signals with different polarities to the transmitting sensor 12 as a plurality of transmission signals with different characteristics. In this case, for example, the transmitter 11 first generates a plurality of transmission signals with the same amplitude. Then, the transmitter 11 generates a plurality of transmission signals with different polarities by excluding one set of transmission signals from the plurality of transmission signals and inverting the polarities of the other set of transmission signals. Then, the transmitter 11 transmits the generated plurality of transmission signals with different polarities to the transmitting sensor 12.

[0073] 8, the transmitter 11 transmits two transmission signals with different polarities to the transmission sensor 12. The amplitudes of the two transmission signals transmitted by the transmitter 11 are each large enough to clearly obtain the nonlinear effect of air.

[0074] The transmitting sensor 12 transmits a plurality of ultrasonic transmission pulses in response to the plurality of transmission signals transmitted by the transmitting unit 11. The plurality of transmission pulses transmitted by the transmitting sensor 12 are reflected by the object 2 to be measured.

[0075] For example, as shown in FIG. 8, when two transmission signals are transmitted by the transmitter 11, the transmitting sensor 12 transmits two transmission pulses corresponding to the two transmission signals.

[0076] The receiving sensor 13 obtains a plurality of received signals by receiving the reflected waves of the plurality of transmission pulses transmitted by the transmitting sensor 12 from the object under test 2. The plurality of received signals obtained by the receiving sensor 13 include low-frequency components generated by nonlinear effects. The receiving frequency bandwidth of the receiving sensor 13 is a bandwidth that can receive the low-frequency components generated by the nonlinear effects of air.

[0077] For example, as shown in Fig. 8, when two transmission pulses are transmitted by the transmitting sensor 12, the receiving sensor 13 obtains two reception signals by receiving the waves reflected by the object under test 2. In Fig. 8, these two reception signals are referred to as reception signal A and reception signal C, respectively.

[0078] The signal processing device 14b transmits a control signal for controlling the transmission process to the transmitting unit 11. The signal processing device 14b also estimates the properties of the object to be measured 2 based on a plurality of received signals obtained by the receiving sensor 13. As shown in Fig. 8, for example, the signal processing device 14b includes a transmission control unit 141b, a received signal acquiring unit 142b, a nonlinear component extracting unit 143b, and a property estimating unit 144b.

[0079] The transmission control unit 141b transmits a control signal to the transmitter 11 to cause the transmitter 11 to transmit a plurality of transmission signals with different characteristics. The transmission control unit 141b in the second embodiment transmits a control signal to the transmitter 11 to cause the transmitter 11 to transmit a plurality of transmission signals with different polarities as a plurality of transmission signals with different characteristics.

[0080] The reception signal acquisition unit 142 b acquires a plurality of reception signals from the reception sensor 13 .

[0081] The nonlinear component extraction unit 143b extracts nonlinear components (low frequency components) by performing calculations according to the characteristics of the transmission signal transmitted by the transmitter 11 based on the multiple received signals acquired by the received signal acquisition unit 142b.

[0082] The nonlinear component extracting unit 143b in the second embodiment extracts nonlinear components by performing an addition process based on the multiple received signals acquired by the received signal acquiring unit 142b. At this time, for example, the nonlinear component extracting unit 143b adds the multiple received signals acquired by the received signal acquiring unit 142b. This allows the nonlinear component extracting unit 143b to extract nonlinear components generated by the nonlinear effect of air from the multiple received signals acquired by the received signal acquiring unit 142b.

[0083] For example, as shown in Fig. 8, when the transmitter 11 transmits two transmission signals in which the polarity of one of the transmission signals is inverted, the nonlinear component extractor 143b adds together the two reception signals corresponding to the two transmission signals (reception signal A and reception signal C in the example of Fig. 8). As a result, the linear components are removed by the addition process because their phases are inverted, but the nonlinear components are not inverted in phase and remain without being removed by the addition process.

[0084] The property estimation unit 144b estimates the property of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extraction unit 143b. Note that the method of property estimation itself by the property estimation unit 144b can be a conventional estimation method.

[0085] For example, if the property of the object to be measured 2 is a groove depth as shown in FIG. 12 , extracting the nonlinear component reduces the amplitude difference between the reflected waves from the upper corner and the lower corner. Therefore, the property estimation unit 144b can easily and accurately determine the distance from the end to the upper corner and the distance from the end to the lower corner. As a result, the property estimation unit 144b can accurately estimate the groove depth from equation (1).

[0086] Next, an example of operation of the signal processing device 14b shown in Fig. 8 will be described with reference to Fig. 9. In the example of operation of the signal processing device 14b shown in Fig. 8, as shown in Fig. 9, for example, the transmission control unit 141b first transmits a control signal to the transmitting unit 11 to cause it to transmit a plurality of transmission signals with different characteristics (step ST201). The transmission control unit 141b in the second embodiment transmits a control signal to the transmitting unit 11 to cause it to transmit a plurality of transmission signals with different polarities as a plurality of transmission signals with different characteristics.

[0087] The transmitting unit 11 then transmits multiple transmission signals of different polarities to the transmitting sensor 12 in response to a control signal from the transmission control unit 141b. The amplitude of the multiple transmission signals transmitted by the transmitting unit 11 is such that the multiple transmission pulses transmitted by the transmitting sensor 12 can obtain the nonlinear effect of air. The transmitting sensor 12 then transmits multiple ultrasonic transmission pulses in response to the multiple transmission signals transmitted by the transmitting unit 11. The multiple transmission pulses transmitted by the transmitting sensor 12 are reflected by the object to be measured 2. The receiving sensor 13 then obtains multiple reception signals by receiving the waves of the multiple transmission pulses transmitted by the transmitting sensor 12 reflected by the object to be measured 2. The multiple reception signals obtained by the receiving sensor 13 include low-frequency components generated by the nonlinear effect.

[0088] Next, the received signal acquiring unit 142b acquires a plurality of received signals from the receiving sensor 13 (step ST202).

[0089] Next, the nonlinear component extraction unit 143b extracts nonlinear components by performing calculations according to the characteristics of the transmission signal transmitted by the transmission unit 11 based on the multiple received signals acquired by the received signal acquisition unit 142b (step ST203).

[0090] The nonlinear component extracting unit 143b in the second embodiment extracts nonlinear components (low frequency components) by performing an addition process based on the multiple received signals acquired by the received signal acquiring unit 142b. In this case, for example, the nonlinear component extracting unit 143b adds the multiple received signals acquired by the received signal acquiring unit 142b.

[0091] Next, the property estimating section 144b estimates the property of the object to be measured 2 based on the nonlinear components extracted by the nonlinear component extracting section 143b (step ST104).

[0092] Next, a simulation for confirming the effect of the operation of the ultrasonic measurement device 1 according to the second embodiment shown in Fig. 8 will be described. Fig. 10 shows the received signal obtained by performing a similar simulation, assuming the same situation as Fig. 14 used to explain the problem, but with the polarity of the transmitted signal reversed compared to Fig. 15. As shown in Fig. 10, the end and the upper corner can be clearly distinguished, but the reflected wave from the lower corner is very small.

[0093] Here, the received signal shown in FIG. 17 is referred to as received signal A. The received signal shown in FIG. 10 is referred to as received signal C. The result of performing an addition process (A+C) using these received signals is shown in FIG. 11. As shown in FIG. 11, by performing the above-described addition process, the amplitude difference between the reflected waves from the upper corner and the lower corner is reduced, allowing them to be clearly distinguished. Therefore, the effect of embodiment 2 was confirmed.

[0094] In the received signal shown in Fig. 11, there is a high-frequency component between the upper corner component and the lower corner component. This is because the component around 80 kHz generated by the nonlinear effect remains after the subtraction process, as shown in Fig. 18.

[0095] The above description has been given on the assumption that the transmitting sensor 12 and the receiving sensor 13 are stationary. However, when the transmitting sensor 12 and the receiving sensor 13 are mounted on an AGV or an AMR, sensing may be performed while the transmitting sensor 12 and the receiving sensor 13 are moving. In such cases, the property estimation unit 144b performs correction using (the time difference between) the transmission timings of multiple transmission signals from the transmitting sensor 12 and the moving speeds of the transmitting sensor 12 and the receiving sensor 13. Specifically, the property estimation unit 144b calculates the distance traveled while multiple transmission signals are being transmitted from the time difference between the transmission timings and the moving speed, and uses this distance as a correction amount to correct the horizontal axis (distance) of the received signal.

[0096] In the above description, the number of transmission signals is two. However, the number of transmission signals does not need to be two, and any number of transmission signals may be used. For example, four transmission signals may be used, and the polarities of two of the transmission signals may be inverted to perform the same processing as described above.

[0097] In this way, the ultrasonic measurement device 1 according to embodiment 2 uses multiple transmission signals of different polarities and performs addition processing of the corresponding reception signals, thereby being able to clearly distinguish between the upper corner components and the lower corner components in the reception signals and to estimate the properties of the object 2 to be measured.

[0098] As described above, according to the second embodiment, the transmission control unit 141b causes the transmitter 11 to transmit a plurality of transmission signals with different polarities, and the nonlinear component extraction unit 143b extracts nonlinear components by performing addition processing based on the plurality of reception signals acquired by the reception signal acquisition unit 142b. As a result, the signal processing device 14b according to the second embodiment can extract low-frequency components generated by nonlinear effects, and can estimate the properties of the device under test 2 with higher accuracy than conventional methods without performing sophisticated filtering processing.

[0099] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted.

[0100] The signal processing device according to the present disclosure is capable of estimating the properties of an object to be measured with higher accuracy than conventional methods without performing sophisticated filtering, and is suitable for use in signal processing devices and the like.

[0101] 1 ultrasonic measuring device, 2 object to be measured, 11 transmitting unit, 12 transmitting sensor, 13 receiving sensor, 14, 14b signal processing device, 51 processor, 52 ROM, 53 RAM, 54 recording medium, 55 transmitting / receiving interface circuit, 56 display interface circuit, 57 display, 58 signal path, 141, 141b transmission control unit, 142, 142b received signal acquisition unit, 143, 143b nonlinear component extraction unit, 144, 144b property estimation unit.

Claims

1. A signal processing device comprising: a transmission control unit that transmits a control signal to a transmission unit that transmits a transmission signal, causing the transmission unit to transmit a plurality of transmission signals with different characteristics; a reception signal acquisition unit that acquires a plurality of reception signals from a reception sensor that obtains a plurality of reception signals by receiving reflected waves of a plurality of ultrasonic transmission pulses transmitted by a transmission sensor in response to the plurality of transmission signals transmitted by the transmission unit, the plurality of reception signals being reflected by the object to be measured; a nonlinear component extraction unit that extracts nonlinear components by performing calculations according to the characteristics of the transmission signals transmitted by the transmission unit based on the plurality of reception signals acquired by the reception signal acquisition unit; and a property estimation unit that estimates the properties of the object to be measured based on the nonlinear components extracted by the nonlinear component extraction unit, wherein the amplitudes of the plurality of transmission signals transmitted by the transmission unit are such that the plurality of transmission pulses transmitted by the transmission sensor can obtain the nonlinear effect of air, and the plurality of reception signals obtained by the reception sensor include low-frequency components generated by the nonlinear effect of air.

2. A signal processing device according to claim 1, wherein the receiving frequency bandwidth of said receiving sensor is a bandwidth capable of receiving low frequency components generated by the nonlinear effect of air.

3. A signal processing device as described in claim 1 or claim 2, characterized in that the transmission control unit causes the transmission unit to transmit multiple transmission signals with different amplitudes, and the nonlinear component extraction unit extracts nonlinear components by performing subtraction processing based on the multiple received signals acquired by the received signal acquisition unit.

4. A signal processing device as described in claim 1 or claim 2, characterized in that the transmission control unit causes the transmission unit to transmit multiple transmission signals of different polarities, and the nonlinear component extraction unit extracts nonlinear components by performing an addition process based on the multiple received signals acquired by the received signal acquisition unit.

5. A signal processing device as described in claim 3 or 4, characterized in that the property estimation unit estimates the property of the object to be measured after correcting the nonlinear components extracted by the nonlinear component extraction unit using a correction amount based on the transmission timing of multiple transmission signals from the transmitting sensor and the movement speed of the transmitting sensor and the receiving sensor.

6. An ultrasonic measuring device comprising: a transmitting unit that transmits a plurality of transmission signals with different characteristics; a transmitting sensor that transmits a plurality of ultrasonic transmission pulses in response to the plurality of transmission signals transmitted by the transmitting unit; a receiving sensor that obtains a plurality of reception signals by receiving waves of the plurality of transmission pulses transmitted by the transmitting sensor reflected by an object to be measured; and a signal processing device that estimates the properties of the object to be measured based on the plurality of reception signals obtained by the receiving sensor, wherein the signal processing device comprises: a transmission control unit that transmits a control signal to the transmitting unit to cause the transmitting unit to transmit the plurality of transmission signals with different characteristics; a reception signal acquisition unit that acquires the plurality of reception signals from the receiving sensor; a nonlinear component extraction unit that extracts nonlinear components by performing an operation according to the properties of the transmission signals transmitted by the transmitting unit based on the plurality of reception signals acquired by the reception signal acquisition unit; and a property estimation unit that estimates the properties of the object to be measured based on the nonlinear components extracted by the nonlinear component extraction unit, wherein the amplitudes of the plurality of transmission signals transmitted by the transmitting unit are such that the plurality of transmission pulses transmitted by the transmitting sensor can obtain the nonlinear effect of air, and the plurality of reception signals obtained by the receiving sensor include low-frequency components generated by the nonlinear effect of air.

7. A signal processing program for causing a computer to function as a signal processing device according to any one of claims 1 to 5.

8. A signal processing method comprising the steps of: a transmission control unit transmitting a control signal to a transmission unit that transmits a transmission signal, causing the transmission unit to transmit a plurality of transmission signals with different characteristics; a reception signal acquisition unit acquiring a plurality of reception signals from a reception sensor that obtains a plurality of reception signals by receiving reflected waves from an object to be measured of a plurality of ultrasonic transmission pulses transmitted by a transmission sensor in response to the plurality of transmission signals transmitted by the transmission unit; a nonlinear component extraction unit extracting a nonlinear component by performing a calculation according to the characteristics of the transmission signal transmitted by the transmission unit based on the plurality of reception signals acquired by the reception signal acquisition unit; and a property estimation unit estimating the property of the object to be measured based on the nonlinear component extracted by the nonlinear component extraction unit, wherein the amplitudes of the plurality of transmission signals transmitted by the transmission unit are amplitudes at which the plurality of transmission pulses transmitted by the transmission sensor can obtain the nonlinear effect of air, and the plurality of reception signals obtained by the reception sensor include low-frequency components generated by the nonlinear effect of air.

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