Inspection apparatus, inspection method, inspection program, and recording medium

Abstract

To solve the problem in which conventional inspection devices perform fast Fourier transform on a received signal to obtain a frequency spectrum, and suppress grating lobes in the frequency domain, and their device configuration are complicated.SOLUTION: Each of a plurality of receiving elements 111 to 1 mn in an array sensor 1 receives a reflected wave, converts the received reflected wave into an electrical signal, and outputs a reception signal composed of temporally short pulses. A synthetic signal calculation unit 205 adds, in the time domain, received signals, which are temporally short pulses, output from the plurality of receiving elements 111 to 1 mn, and obtains a synthesized signal. A threshold calculation unit 206 calculates a threshold value from the received signals, which are temporally short pulses, output from the plurality of receiving elements 111 to 1 mn. A comparison unit 207 compares a value of amplitude of the synthesized signal obtained by the synthetic signal calculation unit 205 with the threshold value obtained by the threshold calculation unit 206 and outputs a comparison result.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an inspection apparatus that uses an array sensor having a plurality of receiving elements that convert reflected waves into electrical signals and output them as received signals, and obtains the position and shape of a reflection source.

Background Art

[0002] As a type of inspection apparatus using an array sensor, an underwater detection apparatus is disclosed in Patent Document 1. The underwater detection apparatus disclosed in Patent Document 1, regardless of the element arrangement, in order to reduce the grating lobe at low cost, in a two-dimensional region specified by the azimuth direction in which the received signal arrives and the frequency included in the received signal, an intensity spectrum calculation unit that calculates the intensity spectrum of the received signal, a target signal based on the frequency domain intensity spectrum that is the intensity spectrum in each azimuth direction among the intensity spectra calculated by the intensity spectrum calculation unit, a comparison unit that compares the target signal with reference information that is a comparison target of the target signal, and an echo intensity reduction unit that reduces the echo intensity of the frequency domain intensity spectrum according to the comparison result in the comparison unit.

[0003] The signal in the two-dimensional region calculated by the intensity spectrum calculation unit is a signal specified by performing beamforming on the frequency domain signal generated by performing fast Fourier transform processing on the received signal and the azimuth direction in which the signal arrives and the frequency included in the received signal.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Thus, the underwater detection device disclosed in Patent Document 1 obtains a frequency spectrum by performing a fast Fourier transform on a received signal and suppresses grating lobes in the frequency domain, but there is a problem that the device configuration becomes complicated.

[0006] The present disclosure has been made in view of the above points, and an object thereof is to obtain an inspection device that suppresses grating lobes by signal processing only in the time domain.

Means for Solving the Problems

[0007] The inspection device according to the present disclosure includes an array sensor having a plurality of receiving elements that each receive a reflected wave, convert the received reflected wave into an electrical signal, and output a received signal composed of temporally short pulses, and a composite signal calculation unit that adds the received signals, which are temporally short pulses output from the plurality of receiving elements, in the time domain to obtain a composite signal, and a threshold calculation unit that calculates a threshold from the received signals, which are temporally short pulses output from the plurality of receiving elements, and a comparison unit that compares the amplitude value of the composite signal obtained by the composite signal calculation unit with the threshold obtained by the threshold calculation unit and outputs a comparison result. The value of each amplitude shown from the received signals, which are temporally short pulses output from the plurality of receiving elements, and a comparison unit that compares the amplitude value of the composite signal obtained by the composite signal calculation unit with the threshold obtained by the threshold calculation unit and outputs a comparison result.

Advantages of the Invention

[0008] According to the present disclosure, suppression of grating lobes can be performed by signal processing only in the time domain of the received signal, which is a temporally short pulse.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] Embodiment 1. The inspection apparatus according to Embodiment 1 will be described with reference to the drawings. The inspection apparatus according to Embodiment 1 uses an array sensor having a plurality of receiving elements that each convert a reflected wave from a reflection source into an electrical signal and output it as a received signal consisting of temporally short pulses, and is an inspection apparatus for obtaining at least one of the position or shape of the reflection source. In particular, it is an inspection apparatus that performs mapping by synthesizing received signals, which are temporally short pulses, from a plurality of receiving elements.

[0011] Here, mapping means an operation of obtaining a composite signal by signal processing based on the received signals of each channel output from each of the plurality of receiving elements of the array sensor, obtaining a value (hereinafter referred to as a mapping value) that reflects reflection source information such as the position, material, and shape of the reflection source from the composite signal, and expanding the mapping value in space.

[0012] As shown in FIG. 1, the inspection apparatus according to Embodiment 1 includes an array sensor 1, a transceiver 2, and a display 3. The transceiver 2 includes a transmission unit 21, a reception unit 22, and a signal processing unit 23. The signal processing unit 23 includes a transmission-side signal processing unit 100, a reception-side signal processing unit 200, and a control unit 300.

[0013] The inspection apparatus according to Embodiment 1 uses the array sensor 1 and the transceiver 2 such that the reception signal of the array sensor 1 becomes a temporally short pulse as shown in FIG. 3. As shown in FIG. 3, the temporally short pulse means a waveform in which the difference between the maximum value of the absolute value of the amplitude and the values of the absolute values of the subsequent amplitudes is significant. In FIG. 3, arrows are attached to the amplitudes from the maximum value to the fourth one, and there is a significant difference between the maximum value of the amplitude and the values of the second to fourth amplitudes in terms of the absolute value.

[0014] Note that FIG. 3 shows an example of the waveform of the reception signal, and the reception signal is not limited to the waveform shown in FIG. 3. In short, the reception signal may be a temporally short pulse having a plurality of different amplitudes and having a significant difference between the amplitude with the maximum absolute value and the other amplitudes. In the following description, in order to avoid complexity of the description, a short pulse having a significant difference in the absolute value of the amplitude is simply described as a temporally short pulse.

[0015] The array sensor 1 includes a plurality (m) of reception elements 1 arranged in a matrix in a plurality (n) of rows and a plurality (n) of columns. 11 ~1 mn and transmission elements 1. S It has. In Embodiment 1, as shown in FIG. 2, for example, it is composed of 128 reception elements in 8 rows × 16 columns and one transmission element arranged in the center. Hereinafter, when it is not necessary to separately describe the reception elements 1 11 ~1 mn for the sake of simplicity of description, they are described as the reception element 1 R for the sake of simplicity of description.

[0016] Also, the transmitting element 1 S is not limited to one and may be plural, or a transmitting and receiving element that also serves as a receiving element may be used. That is, a transmitting and receiving element may be arranged in a plurality of rows and columns. By using a plurality of transmitting elements and emitting transmission waves from each of the plurality of transmitting elements, the SN ratio of the received signal at each receiving element 1 R is improved.

[0017] The transmitting element 1 S is excited by the transmission signal from the transmission unit 21 and converted into a transmission wave, and the transmission wave is emitted to the outside toward the reflection source. The transmission signal is, as an example, a short pulse in terms of time having the same waveform as the waveform of the received signal shown in FIG. 3, and the waveform of the transmission wave is also the same waveform based on the transmission signal. The transmission wave uses ultrasonic waves in the first embodiment, but may be sound waves or electromagnetic waves.

[0018] The transmission unit 21 is excited by the control signal from the signal processing unit 23 and outputs the transmission signal to the transmitting element 1 S . The transmission wave radiated from the transmitting element 1 S is determined by the timing of the transmission signal output from the transmission unit 21, and what kind of transmission wave is formed is determined by the control signal from the signal processing unit 23. The transmission wave radiated from the transmitting element 1 S is determined by the transmission signal, which is a short pulse in terms of time, output from the transmission unit 21.

[0019] Each of the plurality of receiving elements 1 R receives the reflected wave obtained by reflecting the transmission wave radiated from the transmitting element 1 S by the reflection source, converts the received reflected wave into an electrical signal, and outputs it as a received signal. The reflected wave is a short pulse in terms of time, similar to the transmission wave, and each of the plurality of receiving elements 1 R outputs a received signal composed of short pulses in terms of time, shown as an example in FIG. 3.

[0020] The receiving unit 22 amplifies the received signal if necessary, converts the received signal into digital data, and sends it to the signal processing unit 23. In the following description, the transmission path in the transceiver 2 that transmits the received signals from the receiving elements 1 11 ~1 mn is referred to as channel ch 11 ~ch mn as such. Channel ch 11 ~ch mn exists corresponding to each of the plurality of receiving elements 1 11 ~1 mn respectively. Incidentally, hereinafter, when it is not necessary to separately describe channels ch 11 ~ch mn for the sake of simplicity of explanation, they will be described as channel ch.

[0021] The transmission-side signal processing unit 100 in the signal processing unit 23 outputs a control signal to the transmission unit 21 under the control of the control unit 300. The reception-side signal processing unit 200 in the signal processing unit 23 uses the received signals of the plurality of receiving elements 1 output from the receiving unit 22 under the control of the control unit 300 R respectively, calculates a composite signal in the time domain, suppresses the composite signal of the grating lobe by the calculated composite signal, then performs mapping, and outputs the mapping value to the display 3.

[0022] The reception-side signal processing unit 200 includes an input interface 201, a storage unit 202, a mapping point determination unit 203, a time domain determination unit 204, a composite signal calculation unit 205, a threshold calculation unit 206, a comparison unit 207, a mapping value generation unit 208, and an output interface 209.

[0023] The storage unit 202 stores the received signals of the plurality of receiving elements output from the receiving unit 22 via the input interface 201 1 R respectively.

[0024] The mapping point determination unit 203 determines the mapping point O with respect to the reflection source. The mapping point is the coordinate at which the mapping value is obtained. In the case of a three-dimensional space, for example, it is represented by a value such as O(x O , y O , z O ). The mapping points are a plurality of points arranged in a matrix in a plurality of rows and columns with respect to the reflection source.

[0025] The time region determination unit 204 determines a time region T to T + ΔT based on the time T from when the transmission wave emitted from the transmission element 1 s is reflected by the mapping point O at the reflection source until the reflected wave is received by the reception element 1 R . The determination of the time region T to T + ΔT in the time region determination unit 204 is performed for each of the plurality of reception elements 1 R with respect to each mapping point O. For each of the plurality of reception elements 1 R , and moreover, for each mapping point O, at least the time T is different, but for the sake of simplicity of explanation, it will be explained as the time T.

[0026] The determination of the time region T to T + ΔT in the time region determination unit 204 is performed as follows. First, the distance r1 from the transmission point S where the transmission element 1 S is located to the mapping point O is obtained, for example, by the following equation (1). The distance r1 is a value that varies depending on the position of the mapping point O, but is shown as r1 to avoid complexity.

[0027] r1 = √{(x O - x s ) 2 + (y O - y s ) 2 + (z O - z s ) 2} ···(1) However, in equation (1), x O , yO , z O is the value of the x - coordinate, y - coordinate, and z - coordinate of the mapping point O(x O , y O , z O ). x s , y s , z s is the value of the x - coordinate, y - coordinate, and z - coordinate of the transmission point S(x s , y s , z s ) which is treated as the origin of the transmitted wave.

[0028] Receiving element 1 R The distance r2 from the receiving point R where each is located to the mapping point O is obtained, for example, by the following formula (2). The distance r2 has different values depending on the positions of the receiving elements 1 R but is denoted as r2 to avoid complexity.

[0029] r2 = √{(x O - x R ) 2 +(y O - y R ) 2 +(z O - z R ) 2} ···(2) However, in formula (2), x R , y R , z R are the values of the x - coordinate, y - coordinate, and z - coordinate of the receiving point R(x R , y R , z R ) of the reflected wave.

[0030] The time T from when the transmitted wave from the transmission point S is reflected by the mapping point O until the reflected wave is received by the receiving point R is obtained by the following formula (3). The time T obtained by the following formula (3) is hereinafter referred to as the arrival time T of the transmitted wave.

[0031] T=(r1 + r2) / V ···(3) However, in the formula (3)In this case, V uses ultrasonic waves as the transmission wave and represents the speed when the ultrasonic waves propagate through the propagation medium.

[0032] And the time from T to T + ΔT is the time obtained by adding ΔT to the arrival time T obtained by the above formula (3), and is in the time domain. ΔT is related to the receiving element 1 R and is a value determined in advance by factors such as the duration of the received signal from the receiving element 1 and the interval between adjacent mapping points O.

[0033] That is, ΔT is the time after the transmission wave is emitted from the transmitting element 1 S (transmission point S), reflected by the reflection source, and then the received reflected wave is received by the receiving element 1 R (reception point R), and corresponds to the time when the received signal is captured as a temporally short pulse in the channel ch. ΔT is a time that includes the time when a temporally short pulse as shown in FIG. 3 occurs.

[0034] Under the control of the control unit 300, the composite signal calculation unit 205 reads all the received signals output from a plurality of receiving elements 1 R selected from the receiving elements 1 R in the time domain T to T + ΔT, which is the reception time for the selected receiving element 1, reads all the received signals output from the plurality of receiving elements 1 R stored in the storage unit 202 in the time domain T to T + ΔT, and adds all the received signals output from the read plurality of receiving elements 1 R to obtain a composite signal at the mapping point O.

[0035] The reason why it is possible to distinguish between the composite signal of the main lobe and the composite signal of the grating lobe based on the composite signal obtained by the composite signal calculation unit 205 is as follows. When a transmission wave is emitted from the transmitting element 1 S and sensing is performed using a wall perpendicular to the transmission wave as a reflection source, the received signals in each channel ch output from a plurality of receiving elements 1 R that received the received wave reflected from the wall are, as shown in FIG. 4, almost the same waveform, and the reception times are also almost the same.

[0036] Therefore, when the composite signal calculation unit 205 maps the front direction, that is, when obtaining the mapping value in the front direction using the composite signal, all of the reception signals for each channel ch output from the reception element 1 R are combined without applying a delay. The composite signal by the composite signal calculation unit 205 has the phases of the reception signals for each channel ch coinciding and the maximum amplitude values overlapping. Therefore, as shown in FIG. 5, the signal has a large amplitude.

[0037] FIG. 5 shows the composite signal for the reception signals for each channel ch of one column of the reception element 1 11 ~1 m1 for channels ch 11 ~ch m1 However, the same applies to other columns, and the composite signal obtained by adding all of the reception signals for each channel ch also becomes a signal with a large amplitude, similar to the waveform shown in FIG. 5. This becomes the composite signal of the main lobe.

[0038] On the other hand, when the composite signal calculation unit 205 maps an oblique direction instead of the front direction, that is, when obtaining the mapping value in the oblique direction using the composite signal for the reception signal in the selected channel ch, the reception signals for each channel ch are combined after applying a delay. That is, the reception signals for each channel ch are given a delay as follows, and all of the reception signals for each channel ch given the delay are combined.

[0039] The delay amount τ between adjacent reception elements 1 R is a function of the interval d between adjacent reception elements 1 R and the angle φ of the oblique direction with respect to the front direction. The adjacent reception elements 1 R are in the relationship shown in FIG. 6, and the delay amount τ can be obtained by the following equation (4). The interval between reception elements 1 R adjacent in the row direction and the interval between reception elements 1 R adjacent in the column direction are both equally spaced.

[0040] τ = D ÷ V = d × sinφ ÷ V ···(4) D is the distance difference from a sufficiently far distance between adjacent receiving elements 1 R That is, it is the distance difference between the transmission path from the transmission point S to the receiving point R and the reflected wave of the transmitted wave. The distance difference D becomes d × sinφ.

[0041] Adjacent receiving elements 1 R When the delay amount τ between them matches the period τ0 of the received signal in each channel ch, for example, in the case of a short pulse in terms of time shown in FIG. 3, as shown in FIG. 7, for the composite signal obtained by adding all the received signals in each channel ch, although the phases of the received signals in each channel ch are the same, the maximum amplitude values of the received signals in each channel ch do not overlap. In this example, the maximum amplitude value overlaps with the amplitudes from the third one onwards, but the maximum value of the amplitude of the composite signal is smaller than the maximum value of the amplitude of the composite signal where the maximum amplitude values overlap.

[0042] Therefore, when the composite signal calculation unit 205 maps the angle φ direction, which is the diagonal direction, in the received signal of the selected channel ch, for adjacent receiving elements 1 R It gives a delay of the period τ0 of the received signal between them, and adds all the received signals in each channel ch in the time domain T to T + ΔT to obtain a composite signal.

[0043] FIG. 7 shows the composite signal for the received signals in channels ch 11 ~ 1 m1 for one column of receiving elements 1 11 ~ ch m1 However, the same applies to other columns, and for the composite signal obtained by adding all the received signals in each channel ch, similar to the waveform shown in FIG. 7, the maximum value of the amplitude of the composite signal is smaller than the maximum value of the amplitude of the composite signal where the maximum amplitude values overlap. This becomes the composite signal of the grating lobe.

[0044] In short, the composite signal calculation unit 205 obtains the composite signal of the main lobe by adding all the received signals in each channel ch in the time domain T to T + ΔT without delay in the received signal of the selected channel ch, delays the received signals in each channel ch by the period τ0 of the received signal one by one, and obtains the composite signal of the grating lobe by adding all the delayed received signals in each channel ch.

[0045] That is, the composite signal calculation unit 205 obtains a composite signal by adding all the received signals in each channel ch in the time domain T to T + ΔT in the received signal of the selected channel ch after delaying them by an integer multiple of the period τ0. When the integer multiple is zero, it becomes the composite signal of the main lobe, and when the integer multiple is a natural number such as 1, 2, ···, it becomes the composite signal of the grating lobe.

[0046] The composite signal of the main lobe and the composite signal of the grating lobe obtained in the selected channel ch in this way are shown in FIG. 8 as an example. In FIG. 8, the composite signal of the main lobe is the case where the front direction is mapped, and the composite signal of the grating lobe is the case where the diagonal direction of the angle φ (= sin -1 (λ / d)) is mapped. As shown in FIG. 8, the mapping value, which is a value obtained from the amplitude of the composite signal, shows a larger value although the mapping value in the composite signal of the grating lobe is smaller than the mapping value in the composite signal of the main lobe.

[0047] The reason why a difference can be obtained between the mapping value in the composite signal of the main lobe and the mapping value of the composite signal of the grating lobe obtained in this way is that a temporally short pulse is used as the received signal in the channel ch.

[0048] For example, when a long waveform over time such as a continuous wave is used as the received signal on channel ch instead of a short pulse over time, even if the received signals on each channel ch are added together to obtain a composite signal, it is impossible to distinguish between the composite signal of the main lobe and the composite signal of the grating lobe.

[0049] When mapping the front direction using the received signal that is a continuous wave on channel ch, if all of the received signals on each channel are added without applying a delay, as shown in FIG. 9, the phases of all of the received signals on each channel match, and the maximum values of the amplitudes of the received signals on each channel ch overlap, so the composite signal has a large amplitude.

[0050] Also, when mapping an oblique direction using the received signal that is a continuous wave on channel ch, if a delay is applied to the received signal on each channel ch and then added together, as shown in FIG. 10, the phases of the received signals on each channel ch overlap, and the maximum values of the amplitudes of the received signals on each channel ch overlap, so the composite signal has a large amplitude.

[0051] The amplitude of the composite signal when mapping the oblique direction is approximately the same as the amplitude of the composite signal when mapping the front direction, and it is difficult to distinguish between the composite signal of the main lobe and the composite signal of the grating lobe.

[0052] By the way, as shown in FIG. 8, for the composite signal of the grating lobe and the composite signal of the main lobe in the received signal on the selected channel ch obtained by the composite signal calculation unit 205, the mapping value of the composite signal of the grating lobe is a small value compared to the mapping value of the main lobe, but because the phases match when synthesizing, it has a magnitude that cannot be ignored.

[0053] If there is a composite signal of the grating lobe with a large mapping value, it will seem as if there is a reflection source even though there is none, so it is necessary to suppress the grating lobe. In the receiving - side signal processing unit 200 in the inspection apparatus according to Embodiment 1, there is further a threshold - value calculation unit 206 that calculates a threshold value for comparison with the amplitude value of the composite signal obtained by the composite - signal calculation unit 205.

[0054] The threshold value is set to be smaller than the maximum value of the composite signal of the main lobe obtained by the composite - signal calculation unit 205 and larger than the maximum value of the composite signal of the grating lobe. Under the control of the control unit 300, the threshold - value calculation unit 206 calculates a threshold value from the reception signals output from a plurality of receiving elements 1 R selected from among the plurality of receiving elements 1 R in the time domain T to T + ΔT, which is the reception time for the selected receiving element 1 R and stored in the storage unit 202 in the time domain T to T + ΔT.

[0055] The calculation of the threshold value is, for example, a value that is a multiple larger than 1 of the maximum value of the amplitudes indicated by the reception signals from a plurality of receiving elements 1 R or a value that is a multiple larger than 1 of the average value of the amplitudes indicated by the reception signals from a plurality of receiving elements 1 R respectively.

[0056] The threshold value determined in this way is smaller than the maximum value of the composite signal of the main lobe obtained by the composite - signal calculation unit 205 and larger than the maximum value of the composite signal of the grating lobe. Also, since the time domain T to T + ΔT, which is the reception time, is different for each of the plurality of receiving elements 1 R the threshold value determined in this way becomes different for each of the plurality of receiving elements 1 R and also becomes different depending on the mapping point O.

[0057] The comparison unit 207 compares the amplitude value of the composite signal obtained by the composite - signal calculation unit 205 with the threshold value obtained by the threshold - value calculation unit 206 and outputs the comparison result. When the value of the amplitude of the composite signal obtained by the composite signal calculation unit 205 is greater than or equal to the threshold value obtained by the threshold value calculation unit 206, the comparison unit 207 sets the comparison result as the composite signal obtained by the composite signal calculation unit 205. This composite signal becomes the composite signal of the main lobe.

[0058] On the other hand, when the value of the amplitude of the composite signal obtained by the composite signal calculation unit 205 is less than the threshold value obtained by the threshold value calculation unit 206, the comparison unit 207 sets the comparison result to zero. In this case, it is not limited to setting the comparison result to zero, and it may be a composite signal with the amplitude of the composite signal obtained by the composite signal calculation unit 205 reduced.

[0059] The mapping value generation unit 208 generates a mapping value based on the comparison result from the comparison unit 207, and outputs the generated mapping value to the display 3 via the output interface 209. When the comparison result is the composite signal obtained by the composite signal calculation unit 205, it is recognized as the composite signal of the main lobe, and as shown in FIG. 11, the maximum value of the amplitude of the composite signal is set as the mapping value.

[0060] When the comparison result is zero, it is recognized as the composite signal of the grating lobe, and as shown in FIG. 11, the mapping value generation unit 208 sets the mapping value to zero. As a result, the grating lobes in the received signals of each channel ch are suppressed.

[0061] Also, when the comparison result is a composite signal with the amplitude of the composite signal obtained by the composite signal calculation unit 205 reduced, the mapping value generation unit 208 sets the maximum value of the amplitude of the reduced composite signal as the mapping value. Even in this case, the grating lobes in the received signals of each channel ch are suppressed.

[0062] The display 3 receives the mapping value from the mapping value generation unit 208 via the output interface 209 and displays the inspection result. The inspection result may be displayed as numbers or by the brightness of an LED lamp. The display method is not limited to these and is not restricted to these.

[0063] The signal processing unit 23 is constituted by, for example, a computer with a built-in CPU (Central Processing Unit) such as a personal computer or a workstation, or 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).

[0064] As shown in FIG. 12, the signal processing unit 23 has a processor 231 including a CPU, a ROM (Read Only Memory) 232, a RAM (Random Access Memory) 233, a transmission / reception interface circuit 234, a display interface circuit 235, and a recording medium 236. The processor 231, the ROM 232, the RAM 233, the transmission / reception interface circuit 234, the display interface circuit 235, and the recording medium 236 are mutually connected via a signal path 237 such as a bus circuit.

[0065] The processor 231 uses the RAM 233 as a working memory and executes the inspection computer program read from the ROM 232. The processor 231, the ROM 232, and the RAM 233 perform the functions of the control unit 300, the transmission-side signal processing unit 100, the mapping point determination unit 203, the time domain determination unit 204, the composite signal calculation unit 205, the threshold calculation unit 206, the comparison unit 207, and the mapping value generation unit 208. The RAM 233 functions as the storage unit 202.

[0066] The transmission / reception interface circuit 234 is a circuit used for signal transmission between the transmission unit 21 and signal transmission between the reception unit 22, and functions as an output interface (not shown) and an input interface 201 of the transmission-side signal processing unit 100. The display interface circuit 235 is a circuit used for signal transmission between the display 3, and functions as an output interface 209.

[0067] The recording medium 236 is configured using, for example, a volatile memory such as SDRAM (Synchronous DRAM), or an HDD (hard disk drive) or an SSD (solid state drive).

[0068] Next, the operation of the inspection apparatus according to Embodiment 1 will be described. First, under the control of the control unit 300, a control signal is output from the transmission-side signal processing unit 100 to the transmission unit 21. The transmission unit 21 is excited by the control signal from the signal processing unit 23 and outputs a transmission signal to the transmission element 1 S The transmission element 1 S is excited by the transmission signal from the transmission unit 21, converted into a transmission wave, and emitted to the outside toward the reflection source.

[0069] The transmission signal from the transmission unit 21 is, for example, a signal obtained by intermittently repeating short pulses in time as shown in FIG. 3. The transmission element 1 S The transmission wave radiated from is determined by the transmission signal which is a short pulse in time output from the transmission unit 21.

[0070] The transmission wave radiated from the transmission element 1 S is reflected by the reflection source, and the reflected wave is received by a plurality of receiving elements 1 R . A plurality of receiving elements 1 R each convert the received reflected wave into an electrical signal and output it as a received signal. A plurality of receiving elements 1 RThe received signal output from is converted from an analog signal to digital data via the receiving unit 22 and the input interface 201, and stored in the storage unit 202. In the receiving unit 22, the received signal is amplified if necessary.

[0071] The received signal stored in the storage unit 202 is associated with the received receiving element 1 R and the received time. The received signals output from the plurality of receiving elements 1 R are, for example, signals obtained by intermittently repeating short pulses in time as shown in FIG. 3.

[0072] The receiving-side signal processing unit 200 adds the received signals output from the plurality of receiving elements 1 R input via the receiving unit 22 and the input interface 201 for each channel ch to obtain a composite signal, performs mapping from the composite signal, and outputs the mapping value to the display 3.

[0073] Hereinafter, the processing in the receiving-side signal processing unit 200 will be described using the flowchart shown in FIG. 13. The following steps are executed under the control of the control unit 300. That is, it is performed by the processor 231 executing the inspection program stored in the ROM 232.

[0074] First, in step ST1, the mapping point determination unit 203 obtains the coordinates (x O , y O , z O ) of each of the plurality of set mapping points O for the reflection source, and determines one mapping point O among the plurality of mapping points O.

[0075] Next, in step ST2, the time domain determination unit 204 selects one channel ch out of the plurality of channels ch, and obtains the time T in the selected channel ch for the determined mapping point O using the above equations (1) to (3). Based on the obtained time T, the time from T to T+ΔT, which is the time domain representing the reception time, is determined.

[0076] In step ST3, the received signals of all channels ch in the time region T to T+ΔT determined by the time region determining unit 204 are read from the storage unit 202. In step ST4, the composite signal calculation unit 205 calculates the composite signal of the adjacent receiving elements 111 for the received signals of all the channels ch read out from the storage unit 202. R The received signals are delayed by a period τ0 that is an integer multiple of the received signal between the first and second channels, and the delayed received signals are added together to obtain a composite signal.

[0077] For example, as shown in FIG. 2, 128 receiving elements 1 are arranged in 8 rows and 16 columns. R When a received signal according to the above formula is input to the receiving side signal processing unit 200, the received signals on 128 channels are read from the memory unit 202 for the determined mapping point O, and the received signals on the 128 channels are added together to obtain a composite signal.

[0078] The integer multiples are 0, 1, etc., and the delay amount of the 0-times period τ0 is 0, meaning that there is no delay. At mapping point O, for the selected channel ch, the combined signal forms a main lobe when the delay amount is 0 times the period τ0, and forms a grating lobe when the delay amount is 1 time or more the period τ0.

[0079] In step ST5, the control unit 300 determines whether all of the multiple channels have been selected, and if it determines that a combined signal has not been obtained for the mapping point O determined for all of the channels, the process returns to step ST2.

[0080] Returning to step ST2, one channel ch is newly selected from the plurality of channels ch, and the processes from step ST3 to step ST5 are executed. For example, 128 receiving elements RWhen obtaining the received signal according to , steps ST2 to ST5 are repeated 128 times.

[0081] In step ST5, when the control unit 300 determines whether all channels ch have been selected for a plurality of channels ch, the process proceeds to step ST6. In step ST6, the threshold value for the determined mapping point O determined in step ST1 is calculated by the threshold value calculation unit.

[0082] The threshold value is calculated from the received signals of all channels ch in the time domain T to T + ΔT read from the storage unit 202 in step ST3.

[0083] In step ST7, the value of the amplitude of the composite signal calculated in step ST4 and the threshold value calculated in step ST6 are compared by the comparison unit 207 to obtain a comparison result. Also, based on the comparison result obtained by the comparison unit 207, the mapping value generation unit 208 obtains a mapping value.

[0084] When the comparison result by the comparison unit 207 is that the value of the amplitude of the composite signal is greater than or equal to the threshold value, the mapping value generation unit 208 sets the value based on the value of the amplitude of the composite signal as the mapping value. When the comparison result by the comparison unit 207 is that the value of the amplitude of the composite signal is less than the threshold value, the mapping value generation unit 208 sets 0 or a value based on the amplitude value obtained by reducing the value of the amplitude of the composite signal as the mapping value.

[0085] In step ST8, the control unit 300 determines whether all the set mapping points O have been selected for a plurality of mapping points O. If it is determined that the composite signal has not been obtained for all the mapping points O, the process returns to step ST1.

[0086] When returning to step ST1, a new mapping point O among the plurality of mapping points O is determined, and the processes of steps ST2 to ST7 are executed. In step ST8, when the control unit 300 determines that the processing has been executed for all of the plurality of set mapping points O, the processing ends.

[0087] As described above, the process of "the number of receiving elements 1 R × the number of mapping points O" is performed. The reception signals, which are pulses having a short time, output from the plurality of receiving elements are added in the time domain by the composite signal calculation unit 205. When the value of the amplitude of the composite signal is equal to or greater than the threshold value, the mapping value generation unit 208 sets a value based on the value of the amplitude of the composite signal as the mapping value. When the value of the amplitude of the composite signal is less than the threshold value, the mapping value is set to 0 or a value based on an amplitude value obtained by reducing the value of the amplitude of the composite signal. Therefore, at all of the set mapping points O, the mapping value of the grating lobe can be set to 0 or a small value, the grating lobe can be suppressed, and the mapping value based on the main lobe can be obtained.

[0088] In step ST8, the mapping value obtained by the mapping value generation unit 208 is output to the display 3, and a display corresponding to the mapping value is made on the display 3.

[0089] The processing steps shown in FIG. 13 may be stored as a program in the ROM 232 shown in FIG. 12. That is, the program stored in the ROM causes the processor (computer) to execute a procedure of adding reception signals, which are pulses having a short time, output from a plurality of receiving elements in the time domain to obtain a composite signal, a procedure of calculating a threshold value from reception signals, which are pulses having a short time, output from the plurality of receiving elements, and a procedure of comparing the value of the amplitude of the composite signal with the threshold value and outputting the comparison result, and is an inspection program.

[0090] Next, in the inspection apparatus according to the first embodiment, a simulation was performed to confirm that the grating lobe is suppressed. In the simulation, the reception signal shown in FIG. 14 was used, and the receiving element 1 of the array sensor 1 shown in FIG. 2 11 ~1 mnThe arrangement was set as such, and the positional relationship between the wall perpendicular to the transmitted wave assumed as the reflection source shown in Fig. 15 and the array sensor 1 was determined. Also,

[0091] The characteristics of the received signal shown in Fig. 14 were the received signal from a flat wall perpendicular to the array sensor 1, and a temporally short pulse with a center frequency of 0.5 MHz was used. In Fig. 14, the left figure shows the time waveform, and the right figure shows the frequency spectrum of the time waveform. 128 receiving elements 1 of 8 rows × 16 columns 11 ~1 mn were arranged at equal intervals, and the interval between adjacent receiving elements was set to 10 mm.

[0092] Since the sound speed V of the transmitted wave was set to 1,500 m / s, it was a temporally short pulse with a center frequency of 0.5 MHz, and the wavelength at the center frequency was 3 mm. Therefore, the interval of 10 mm between adjacent receiving elements was set to be three times or more the wavelength of 3 mm at the center frequency of the temporally short pulse.

[0093] That is, it was assumed that the interval between adjacent receiving elements was increased to realize a large aperture area with a small number of receiving elements and improve the resolution. On the other hand, since the interval between adjacent receiving elements is equal to or greater than the wavelength at the center frequency, it is assumed that grating lobes will occur.

[0094] Also, as shown in Fig. 15, the array sensor 1 was installed at a position with a depth of 0.5 m, and the distance from the wall was 4 m. The size of the wall was 1 m in length and 3 m in width. The propagation medium was water. The wall was assumed to be not flat but have irregularities. The threshold value in the threshold calculation unit 206 was set to 16 times the maximum value of the amplitude of the received signal in each channel ch in the time domain T to T + ΔT which was the reception time. In the comparison unit 207, when the amplitude value of the composite signal obtained by the composite signal calculation unit 205 was smaller than the threshold value obtained by the threshold calculation unit 206, the comparison result was set to zero, and the mapping value by the mapping value generation unit 208 was set to zero.

[0095] In the inspection apparatus according to Embodiment 1, as a result of mapping a vertical wall under the above-described simulation conditions, the result shown in FIG. 16 was obtained. As is apparent from FIG. 16, the grating lobes are suppressed, and in particular, it can be seen that the wall is clearly mapped from the top view.

[0096] For comparison, FIG. 17 shows the result of mapping without performing threshold processing. That is, FIG. 17 is a diagram showing the result of obtaining mapping values by the mapping value generation unit 208 from the composite signal obtained by the composite signal calculation unit 205 as it is.

[0097] In FIG. 17, in the region facing the array sensor 1, the mapping value is large, and this is the main lobe (ML). Also, there are regions with large mapping values on both sides of the main lobe, and this is the grating lobe (GL). As shown in FIG. 17, due to the grating lobes, the wall is not clearly mapped.

[0098] It can be seen that the simulation result in the inspection apparatus according to Embodiment 1 clearly maps the vertical wall and shows a very superior result compared to the comparative example.

[0099] Next, as shown in FIG. 18, the wall as the reflection source was a wall inclined 30° with respect to the vertical wall. Simulation was performed with other conditions the same as those for the vertical wall. In the inspection apparatus according to Embodiment 1, as a result of mapping the 30°-inclined wall under the above-described simulation conditions, the result shown in FIG. 19 was obtained. As is apparent from FIG. 19, the grating lobes are not completely eliminated but are considerably suppressed, and in particular, it can be seen that the wall is clearly mapped from the top view.

[0100] For comparison, FIG. 20 shows the result of mapping without performing threshold processing. That is, FIG. 20 shows the result of obtaining the mapping value from the composite signal obtained by the composite signal calculation unit 205 as it is by the mapping value generation unit 208.

[0101] In FIG. 20, the mapping value is large at the position where there is a wall, and this is the main lobe (ML). Also, as is clear from the top view, there is a region where the mapping value is large in addition to the main lobe, and this is the grating lobe. As shown in FIG. 20, because there is a grating lobe, the wall is not clearly mapped.

[0102] It can be seen that the simulation result in the inspection apparatus according to the first embodiment clearly maps a wall inclined at 30°, and a very superior result is obtained compared to the comparative example.

[0103] As described above, the inspection apparatus according to the first embodiment includes a composite signal calculation unit that adds reception signals, which are short pulses in time output from a plurality of reception elements in an array sensor, in the time domain to obtain a composite signal, a threshold calculation unit that calculates a threshold from the reception signals, which are short pulses in time output from the plurality of reception elements, and a comparison unit that compares the amplitude value of the composite signal obtained by the composite signal calculation unit with the threshold obtained by the threshold calculation unit and outputs a comparison result. Therefore, the grating lobe can be suppressed.

[0104] Moreover, since the grating lobe can be suppressed by performing signal processing on the reception signal, which is a short pulse in time, in the time domain, the device configuration is simple. Furthermore, after suppressing the grating lobe, the element interval between the plurality of reception elements in the array sensor can be increased to realize a large aperture area with a small number of reception elements, and the resolution can be improved.

[0105] Note that any component of the embodiment can be modified or any component of the embodiment can be omitted.

Industrial Applicability

[0106] The inspection apparatus according to Embodiment 1 can be applied to an inspection apparatus including an array sensor that determines the position and shape of a reflection source that can reflect ultrasonic waves, sound waves, electromagnetic waves, or the like. For example, it can be applied to an underwater detection apparatus.

Description of Reference Numerals

[0107] 1 array sensor, 1 11 ~1mn receiving element, 1 S transmitting element, 2 transceivers, 21 transmitting unit, 22 receiving unit, 23 signal processing unit, 100 transmitting-side signal processing unit, 200 receiving-side signal processing unit, 201 input interface, 202 storage unit, 203 mapping point determination unit, 204 time domain determination unit, 205 composite signal calculation unit, 206 threshold calculation unit, 207 comparison unit, 208 mapping value generation unit, 209 output interface, 300 control unit, 3 display

Claims

1. An array sensor having a plurality of receiving elements, each of which receives a reflected wave, converts the received reflected wave into an electrical signal, and outputs a received signal composed of temporally short pulses; A composite signal calculation unit that adds the received signals, which are temporally short pulses output from the plurality of receiving elements, in the time domain to obtain a composite signal; A threshold calculation unit that calculates a threshold from the values of the amplitudes indicated by the received signals, which are temporally short pulses output from the plurality of receiving elements; A comparison unit that compares the value of the amplitude of the composite signal obtained by the composite signal calculation unit with the threshold obtained by the threshold calculation unit and outputs the comparison result; An inspection device comprising the above.

2. An array sensor having a plurality of receiving elements, each of which receives a reflected wave, converts the received reflected wave into an electrical signal, and outputs a received signal composed of temporally short pulses; A composite signal calculation unit that adds the received signals, which are temporally short pulses output from the plurality of receiving elements, in the time domain to obtain a composite signal; A threshold calculation unit that calculates a threshold from the received signals, which are temporally short pulses output from the plurality of receiving elements; A comparison unit that compares the value of the amplitude of the composite signal obtained by the composite signal calculation unit with the threshold obtained by the threshold calculation unit and outputs the comparison result, wherein the threshold is a value that is a multiple greater than 1 of the maximum value among the values of the amplitudes indicated by the received signals output from the plurality of receiving elements. An inspection device.

3. An array sensor having a plurality of receiving elements, each of which receives a reflected wave, converts the received reflected wave into an electrical signal, and outputs a received signal composed of temporally short pulses; A composite signal calculation unit that adds the received signals, which are temporally short pulses output from the plurality of receiving elements, in the time domain to obtain a composite signal; A threshold calculation unit that calculates a threshold from the received signals, which are temporally short pulses output from the plurality of receiving elements; A comparison unit that compares the value of the amplitude of the composite signal obtained by the composite signal calculation unit with the threshold obtained by the threshold calculation unit and outputs the comparison result, wherein the threshold is a value that is a multiple greater than 1 of the average value of the amplitudes indicated by the received signals output from the plurality of receiving elements. An inspection device.

4. The inspection device according to any one of Claims 1 to 3, wherein when the value of the amplitude of the composite signal is smaller than the threshold, the comparison unit sets the comparison result as a composite signal with the value of the amplitude of the composite signal made smaller.

5. The inspection apparatus according to any one of claims 1 to 3, wherein the comparison unit sets the comparison result to zero when the value of the amplitude of the combined signal is smaller than the threshold value.

6. A step in which a combined signal calculation unit adds reception signals, which are short pulses in time output from a plurality of reception elements, in the time domain to obtain a combined signal; A step in which a threshold value calculation unit calculates a threshold value from the value of each amplitude indicated by the reception signals, which are short pulses in time output from the plurality of reception elements; A step in which a comparison unit compares the value of the amplitude of the combined signal with the threshold value and outputs a comparison result; An inspection method comprising the steps.

7. A procedure for adding reception signals, which are short pulses in time output from a plurality of reception elements, in the time domain to obtain a combined signal; A procedure for calculating a threshold value from the value of each amplitude indicated by the reception signals, which are short pulses in time output from the plurality of reception elements; A procedure for comparing the value of the amplitude of the combined signal with the threshold value and outputting a comparison result; An inspection program that causes a computer to execute the procedures.

8. A procedure for adding reception signals, which are short pulses in time output from a plurality of reception elements, to obtain a combined signal; A procedure for calculating a threshold value from the value of each amplitude indicated by the reception signals, which are short pulses in time output from the plurality of reception elements; A procedure for comparing the value of the amplitude of the combined signal with the threshold value and outputting a comparison result; A recording medium storing a program that causes a computer to execute the procedures.

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