JP2012058152A - State determination device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly determine presence/absence of a defect and a state of the defect of an analyte.SOLUTION: This state determination device includes: a transmitting part; a receiving part; a detection part; and a determination part. The transmitting part generates ultrasonic waves and transmits a ultrasonic signal. The receiving part receives the ultrasonic signal which penetrates the analyte to acquire first reception signals, respectively. The detection part measures crest values of the first reception signals for every receiving part to detect whether or not there is a first reception signal whose crest value is more than a threshold. When there is the first reception signal whose crest value is more than the threshold, the determination part determines the first reception signal as a defect candidate signal. When there is the defect candidate signal, the detection part measures crest values of received second reception signals when time elapses for one or more integral multiples of a predetermined period of time from the time when the defect candidate signal is received in the receiving part which receives the defect candidate signal to detect whether or not there is a second reception signal whose crest value is more than the threshold. When there is the second reception signal whose crest value is more than the threshold, the determination part determines the defect candidate signal as a defect signal.

Description

  Embodiments described herein relate generally to a state determination apparatus and method for determining the state of an object.

  In recent years, banknote inspection machines and sorting and counting machines are not suitable for circulation because tapes are affixed to repair damage. A method of sorting has been proposed. Here, as a method of detecting the presence or absence of this defect, there is a method of detecting using ultrasonic waves.

  In such a detection method using sound waves, when trying to detect a hole in a subject, since the ultrasonic wave directly transmitted through the hole has high intensity and is easily diffracted, it is transmitted by the receiving sensor at the hole position. Not only is the wave detected, but the adjacent receiving sensor receives a wave having a relatively high intensity among the diffracted waves, thereby misidentifying the size of the hole.

JP 2008-207885 A European Patent Application Publication No. 2008-081183

  The problem to be solved by the present invention is to provide a state determination apparatus and method capable of determining the presence or absence of a defect and the state of the defect with high accuracy.

  The state determination apparatus according to the present embodiment includes a transmission unit, one or more reception units, a detection unit, and a determination unit. The transmission unit generates an ultrasonic wave and transmits an ultrasonic signal. One or more receiving units receive the ultrasonic signals that have passed through the subject and acquire first received signals. The detection unit measures a first peak value of the first reception signal for each reception unit, and detects whether or not there is a first reception signal having the first peak value equal to or greater than a first threshold value. When there is a first reception signal having the first peak value equal to or greater than the first threshold, the determination unit determines the first reception signal as a defect candidate signal that may have transmitted through the defect portion of the subject. . When there is the missing candidate signal, the detecting unit receives the second candidate received when the receiving unit that has received the missing candidate signal has passed an integer multiple of one or more of a predetermined period from the time when the missing candidate signal was received. The second peak value of the signal is measured, and it is detected whether there is a second received signal having the second peak value equal to or greater than a second threshold value. When there is a second received signal having the second peak value equal to or greater than a second threshold, the determination unit determines the defect candidate signal as a defect signal transmitted through the defect portion of the subject.

  The state determination device includes a transmission unit, one or more reception units, a detection unit, a determination unit, and a calculation unit. The transmission unit generates an ultrasonic wave and transmits an ultrasonic signal. One or more receiving units receive the ultrasonic signals that have passed through the subject and acquire first received signals. The detection unit measures a peak value of the first reception signal for each reception unit, and detects whether there is a first reception signal having the peak value equal to or greater than a first threshold value. When there is a first reception signal having a peak value equal to or greater than the first threshold, the determination unit determines the first reception signal as a defect candidate signal that may have passed through the defect portion of the subject. The calculation unit calculates an attenuation rate of the envelope of the peak value of the missing candidate signal for each of the missing candidate signals, and measures an attenuation time until the attenuation rate reaches a predetermined attenuation rate. When the decay time is within the second threshold, the determination unit determines the defect candidate signal as a defect signal that has passed through the defect portion of the subject.

  The state determination device includes a transmission unit, a reception unit, a detection unit, a determination unit, and a calculation unit. The transmission unit generates an ultrasonic wave and transmits an ultrasonic signal. The receiving unit receives the ultrasonic signal that has passed through the subject and acquires a first received signal. The detection unit measures a peak value of the first reception signal for each reception unit, and detects whether or not there is a first reception signal having the peak value equal to or greater than a first threshold. When the peak value of the first reception signal is greater than or equal to a first threshold, the determination unit determines the first reception signal as a defect candidate signal that may have transmitted through the defect portion of the subject. The calculation unit calculates, for each defect candidate signal, a first characteristic indicating a frequency characteristic of the defect candidate signal and a second characteristic indicating a frequency characteristic before passing through the subject. If the difference between the first characteristic and the second characteristic is within a second threshold, the determination unit determines the defect candidate signal as a defect signal that has passed through the defect portion of the subject.

The block diagram which shows the state determination apparatus of embodiment. The figure which shows an example of arrangement | positioning with the transmission part of the state apparatus of embodiment, a receiving part, and a subject. The flowchart which shows the determination process of the state determination apparatus of embodiment. The figure which shows an example of the received signal detected by the state determination apparatus of embodiment. The figure which shows another example of the received signal detected by the state determination apparatus of embodiment. The block diagram which shows the state determination apparatus of the 1st modification of embodiment. The flowchart which shows operation | movement of the state determination apparatus of the 1st modification of embodiment. The block diagram which shows the state determination apparatus of the 2nd modification of embodiment. The flowchart which shows operation | movement of the state determination apparatus of the 2nd modification of embodiment.

Hereinafter, the state determination apparatus and method according to the present embodiment will be described in detail with reference to the drawings. Note that, in the following embodiments, the same reference numerals are assigned to the same operations, and duplicate descriptions are omitted as appropriate.
A state determination apparatus according to an embodiment will be described with reference to FIG.
The state determination apparatus 100 according to the embodiment includes a transmission control unit 101, a transmission unit 102, a reception unit 103, an amplification unit 104, an A / D conversion unit 105, a detection unit 106, and a missing position determination unit 107.
The transmission control unit 101 generates a control signal for controlling the transmission timing of the ultrasonic signal.
The transmission unit 102 receives a control signal from the transmission control unit 101 and transmits an ultrasonic signal. For the ultrasonic wave, a piezoelectric transducer, a vibration generator using MEMS, or the like may be used. In this embodiment, the thickness vibration of a 1-3 type composite piezoelectric material of a piezoelectric material and a resin is used as the piezoelectric transducer. By using the thickness vibration, it is possible to irradiate the subject with an ultrasonic signal having a plane wave of the same phase from the entire transmitter 102. The transmission interval of the ultrasonic signal may be a fixed interval or may be transmitted only once for each measurement location of the subject 150 to be described later.

One or more receiving units 103 are installed, receive an ultrasonic signal transmitted through the subject 150, and obtain a received signal. The receiving unit 103 may be the same transducer as the transmitting unit 102 or a displacement meter using interference light that measures vibration as displacement.
The amplification unit 104 is, for example, an operational amplifier, receives a reception signal from the reception unit 103, and amplifies the reception signal.
The A / D conversion unit 105 receives the amplified reception signal from the amplification unit 104 and performs analog-digital conversion for each reception signal to generate a digitized reception signal.
The detection unit 106 receives the digitized reception signal from the A / D conversion unit 105, measures the peak value of the digitized reception signal, and detects whether there is a reception signal having a peak value equal to or greater than a threshold value. . In addition, what is necessary is just to measure any peak value, such as a signal strength, an electric current value, a voltage value, and an electric power value, as a peak value.

The missing position determination unit 107 receives a reception signal having a peak value equal to or greater than the threshold value from the detection unit 106, and determines that this reception signal is a defect candidate signal. The defect candidate signal is a signal indicating that there is a possibility of a defect such as a hole or a tear at a position where the reception signal received by the reception unit 103 has passed through the subject. The defect position determination unit 107 determines that the signal is a defect signal when the defect candidate signal after the elapse of a predetermined period is equal to or greater than a threshold value. The defect signal is a signal indicating that there is a defect at a position where the defect candidate signal passes through the subject. Further, the defect position determination unit 107 determines the position where the defect signal has passed through the subject as the defect position.
The subject 150 is a paper sheet such as a banknote or a card, for example, is installed between the transmission unit 102 and the reception unit 103 and is conveyed in the same direction by a conveyance roller, a belt, or the like.

Next, an example of the arrangement of the transmission unit 102, the reception unit 103, and the subject 150 will be described with reference to FIG.
As shown in FIG. 2, in the state determination apparatus according to the embodiment, one transmission unit 102 and a reception unit array 201 in which one or more reception units 103 smaller than the transmission unit 102 are arranged in series are arranged to face each other. . In addition, the subject 150 is installed between the transmission unit 102 and the reception unit array 201. The examination of the subject 150 is performed by irradiating an ultrasonic signal from the transmission unit 102 and receiving a transmitted wave that has passed through the subject 150 by each reception unit 103 of the reception unit array 201. Note that the distance between the transmission unit 102 and the reception unit 103 may be a distance that allows the reception unit 103 to receive an ultrasonic signal from the transmission unit 102 and can receive a multiple-reflection reception signal. Multiple reflection indicates that in a normal measurement, a received signal is reflected by the receiving unit 103, further reflected by the transmitting unit 102, and received again by the receiving unit 103. Here, the frequency or signal intensity of the ultrasonic signal, the distance between the transmission unit 102 and the reception unit 103, and the size of the transmission unit 102 and the reception unit 103 so that the reception signal that is multiple-reflected by other objects is not affected. It is desirable to set

  An ultrasonic signal directly received through a hole or the like has a high signal intensity, and an ultrasonic signal transmitted through the subject has a low signal intensity. Therefore, if the signal intensity is higher than other signals among a plurality of received ultrasonic signals, it is an ultrasonic signal transmitted through a defect portion such as a hole, and it can be detected that the subject is defective. . The receiving unit 103 is assigned an ID, and can determine which receiving unit 103 receives the signal. Furthermore, if the respective positions of the receiving unit 103 are known, the received signal and the position at which the ultrasonic signal has transmitted through the subject are associated with each other, so it is determined which position on the subject 150 is defective. be able to.

Next, the determination process of the state determination apparatus of the embodiment will be described with reference to the flowchart of FIG.
In step S301, an ultrasonic signal is transmitted from the transmission unit 103. Thereafter, the detection unit 106 receives the ultrasonic signal at each reception unit 103 and measures the peak value of the reception signal received through the amplification unit 104 and the A / D conversion unit 105. For the measurement of the peak value, the peak values of the reception signals of all the reception units 103 of the reception unit array 201 may be read in parallel with a multi-channel logger or the like via an amplifier.
In step S302, the detection unit 106 detects whether or not there is a received signal whose peak value is equal to or greater than a threshold value for each received signal. If there are one or more received signals whose peak values are not less than the threshold among the received signals, the process proceeds to step S303. If there is no received signal whose peak value is not less than the threshold, the same processing is performed for the next sampled received signal. Repeat the detection process.

In step S303, the missing position determination unit 107 determines a received signal whose peak value is equal to or greater than a threshold value as a missing candidate signal. If the peak value is equal to or greater than the threshold value, it is highly likely that the received signal is directly received through the hole without passing through the subject 150, so the position where the received signal has passed through the subject 150 is This is because it is considered that a defect has occurred. Note that the threshold value may be, for example, a measurement of a transmitted wave that has passed through a subject without a defect in advance, and an average value of peak values of received signals that have received the transmitted wave as a threshold value.
In step S <b> 304, the peak value of the received signal subjected to multiple reflection when the detection unit 106 receives a missing candidate signal and the time for the signal to reciprocate the distance between the transmission unit 102 and the reception unit 103 has elapsed. Measure.

In step S305, the detecting unit 106 detects, for each received signal, whether or not there is a multiple-reflected received signal having a peak value equal to or greater than a threshold value in the receiving unit 103 that has received the missing candidate signal. Note that the period in which multiple reflections occur is constant, and the distance between the transmission unit 102 and the reception unit 103 occurs at an integral multiple of the time for which the ultrasonic signal reciprocates. Therefore, when detecting multiple reflected signals, not only the received signal reflected once, but the timing that is an integral multiple of the time that the ultrasonic signal reciprocates the distance between the transmitting unit 102 and the receiving unit 103. Any timing may be used as long as the peak value of the missing candidate signal can be distinguished from the peak value of the received signal other than the missing candidate signal. Further, it is assumed that the threshold value in step S305 is set to a value smaller than the threshold value in step S302. If the peak value of the multiple reflected reception signal is smaller than the threshold value, the process proceeds to step S306, and if the peak value of the multiple reflected reception signal is equal to or greater than the threshold value, the process proceeds to step S307.
In step S306, the defect position determination unit 107 determines the received signal as a diffracted wave.
In step S307, the missing position determination unit 107 determines the received signal as a missing signal.
In step S308, the missing position determination unit 107 identifies the position of the receiving unit 103 that has received the missing signal. Thereby, since the position of the receiving unit 103 corresponds to the position of the defect in the subject 150, the position and size of the defect can be determined. Note that the coordinates of the missing position may be output to the outside. Above, the determination process of the state determination apparatus 100 is complete | finished.

Next, an example of a reception signal detected by the state determination device 100 according to the embodiment will be described with reference to FIGS. 4 and 5. Here, it is assumed that there is a defect at a position where the ultrasonic signals received by the receiving units 103 with IDs “2” and “3” pass through the subject 150.
As shown in FIG. 4, each receiving unit 103 is given an ID, and here, received signals received by the four receiving units 103 are shown. A large vibration is seen in the signal 401, and the peak value is high. Further, the signal 402 received by the receiving unit 103 of ID “1” and ID “4” adjacent to the receiving unit 103 of ID “2” and ID “3” also has a higher peak value than a normal transmitted wave. Yes. This is because the diffracted wave of the ultrasonic signal received by the receiving unit 103 with ID “2” and ID “3” is also received by the adjacent receiving unit 103. That is, an ultrasonic signal as if the other receiving unit 103 has transmitted through the defect portion is received by a diffracted wave having a high signal intensity.

Therefore, FIG. 5 shows a case where determination processing is performed including multiple reflection of signals.
First, there is a part where the peak value of the received signal is large in all the receiving units 103, which is a signal detected when an applied voltage is applied to generate an ultrasonic signal in the transmitting unit 102. It is. After detecting the applied voltage in all receiving units 103, the receiving unit 103 with ID “2” and ID “3” passes through the missing portion of the subject 150 when the peak value 501 is the next highest peak value of the received signal. The case where the ultrasonic signal with high signal intensity is received and the adjacent receiving unit 103 receives the diffracted wave of the ultrasonic signal is shown.
Further, the peak value 502 indicates a multiple-reflected ultrasonic signal, and is received again by the receiving unit 103 after a period 503 in which the ultrasonic signal reciprocates through the distance between the transmitting unit 102 and the receiving unit 103. Signal. In addition, the diffracted wave in the case of multiple reflection becomes small to the extent that it does not affect the transmitted wave. As a result, it is possible to distinguish the received signal transmitted through the hole and the diffracted wave. That is, in the example of FIG. 5, it can be said that the received signal whose peak value 502 is equal to or greater than the threshold value is a missing signal that has passed through the missing portion of the subject. It can be determined that there is a defect at the position where the reception signal received by the reception unit 103 of “3” passes through the subject.

  According to the state determination apparatus of the first embodiment described above, the presence or absence of a subject is determined by determining the state of the subject using a multiple reflected reception signal that is less affected by diffracted waves. In addition, the position and size of the defect can be determined with high accuracy.

(First modification of this embodiment)
In the state determination apparatus according to the embodiment, the missing signal is determined based on the peak value of the multiple reflected reception signal. In the first modification, the missing signal is calculated by calculating the attenuation factor of the envelope of the peak value of the reception signal. The point to judge is different. Since the received signal that has passed directly through the hole is not affected by the diffracted wave from other received signals, the attenuation rate becomes constant in a short time. Due to the influence, it takes time until the attenuation rate becomes constant. Therefore, it is possible to determine the defective portion of the subject by measuring this time.
A state determination apparatus according to a first modification of the embodiment will be described with reference to the block diagram of FIG.
A state determination device 600 according to the first modification of the embodiment includes a transmission control unit 101, a transmission unit 102, a reception unit 103, an amplification unit 104, an A / D conversion unit 105, a detection unit 106, an attenuation factor calculation unit 601, and A defect position determination unit 602 is included. The transmission control unit 101, the transmission unit 102, the reception unit 103, the amplification unit 104, the A / D conversion unit 105, and the detection unit 106 perform the same operation as the state determination device 100 according to the present embodiment. The description here is omitted.

The attenuation factor calculation unit 601 receives the defect candidate signal from the detection unit 106, calculates the attenuation factor of the peak value envelope of the defect candidate signal, and until the attenuation factor of the peak value envelope reaches a predetermined attenuation factor. Is measured for each missing candidate signal.
The missing position determination unit 602 receives the attenuation time from the attenuation rate calculation unit 601, and determines whether the attenuation time is within a threshold value. If the decay time is within the threshold, it is determined as a missing signal, and the position where the missing signal has passed through the subject is determined as the missing position.

Next, the operation of the state determination device 600 of the first modification will be described with reference to the flowchart of FIG. Note that steps S301 to S303 and steps S306 to S308 are the same as those of the state determination apparatus 100 according to the present embodiment shown in FIG.
In step S701, the attenuation rate calculation unit 601 calculates the attenuation rate of the peak value envelope in the missing candidate signal, and measures the attenuation time until a predetermined attenuation rate is reached.
In step S702, the missing position determination unit 601 determines whether the decay time is within a threshold. If the decay time is longer than the threshold value, the process proceeds to step S306, where it is determined as a diffracted wave. If the decay time is within the threshold, the process proceeds to step S307, and is determined as a missing signal.

  According to the state determination device of the first modification example of the embodiment described above, by determining the missing signal based on the attenuation factor of the peak value envelope in the missing candidate signal, The presence / absence of a defect in the subject can be determined, and the position and size of the defect can be determined with high accuracy.

(Second modification of this embodiment)
In the state determination apparatus according to the second modification of the embodiment, the frequency characteristic of the reception signal that has passed through the defect portion of the subject is compared with the frequency characteristic of the reception signal that has passed through a position other than the defect portion of the subject. The difference is that the missing signal is determined.

A state determination apparatus according to a second modification of the embodiment will be described with reference to the block diagram of FIG.
A state determination apparatus 800 according to the second modification of the embodiment includes a transmission control unit 101, a transmission unit 102, a reception unit 103, an amplification unit 104, an A / D conversion unit 105, a detection unit 106, a frequency conversion unit 801, and a defect. A position determination unit 802 is included. The transmission control unit 101, the transmission unit 102, the reception unit 103, the amplification unit 104, the A / D conversion unit 105, and the detection unit 106 perform the same operation as the state determination device 100 according to the present embodiment. The description here is omitted.

The frequency conversion unit 801 receives the defect candidate signal from the detection unit 106 and calculates a frequency characteristic for each defect candidate signal. For example, the frequency characteristic may be calculated by performing a fast Fourier transform (FFT). Further, the frequency characteristic of the ultrasonic signal when not passing through the subject 150 is calculated as the reference frequency characteristic.
The missing position determination unit 802 receives the frequency characteristic and the reference frequency characteristic from the frequency conversion unit 801, and determines whether or not the difference between the frequency characteristic and the reference frequency characteristic is within a threshold value. If the difference is within the threshold, it is determined as a missing signal, and the position where the missing signal has passed through the subject is determined as the missing position. Note that the reference frequency characteristic may be included in the defect position determination unit 802 in advance.

Next, the operation of the state determination device 800 according to the second modification of the embodiment will be described with reference to the flowchart of FIG. Note that steps S301 to S303 and steps S306 to S308 are the same as those of the state determination apparatus 100 of the embodiment shown in FIG.
In step S901, the frequency conversion unit 801 performs FFT processing on the missing candidate signal, and calculates a frequency characteristic and a reference frequency characteristic.
In step S902, the missing position determination unit 802 calculates a difference between the frequency characteristic and the reference frequency characteristic.
In step S903, the missing position determination unit 802 determines whether the difference is within a threshold. When the difference is larger than the threshold value, the process proceeds to step S306 and is determined to be a diffracted wave. When the difference is within the threshold value, it is considered that the received signal is directly received without passing through the subject 150, and thus the process proceeds to step S307, and the missing candidate signal is determined as the missing signal.

  According to the state determination apparatus of the second modification example of the embodiment described above, the presence / absence of the defect of the subject is determined by the determination based on the frequency characteristics of the ultrasonic signal as in the present embodiment. In addition, the position and size of the defect can be determined with high accuracy.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100,600,800 ... State determination apparatus, 101 ... Transmission control part, 102 ... Transmission part, 103 ... Reception part, 104 ... Amplification part, 105 ... A / D conversion part 106 ... detection unit 107,602,802 ... defect position determination unit, 150 ... subject, 201 ... receiver array, 401,402 ... signal, 501,502 ... Crest value, 503... Time, 601... Attenuation rate calculation section, 801... Frequency conversion section, 802.

Claims (9)

A transmitter that generates ultrasonic waves and transmits ultrasonic signals;
One or more receiving units for receiving the ultrasonic signals transmitted through the subject and acquiring the first received signals,
A first detecting unit for measuring a first peak value of the first received signal for each receiving unit, and detecting whether or not there is a first received signal having the first peak value equal to or higher than a first threshold;
A determination unit that determines, when there is a first reception signal whose first peak value is equal to or greater than the first threshold, the first reception signal as a defect candidate signal that may have transmitted the defect portion of the subject; Comprising
When there is the missing candidate signal, the detecting unit receives the second candidate received when the receiving unit that received the missing candidate signal has passed an integer multiple of one or more of a predetermined period from the time when the missing candidate signal was received. Measuring a second peak value of the received signal and detecting whether there is a second received signal having the second peak value equal to or greater than a second threshold;
The determination unit determines the defect candidate signal as a defect signal transmitted through the defect portion of the subject when the second received signal having the second peak value equal to or greater than a second threshold is present. Judgment device.   The state determination apparatus according to claim 1, wherein the predetermined period is a time during which the ultrasonic signal reciprocates a distance between the transmission unit and the reception unit.   The state determination apparatus according to claim 1, wherein the determination unit determines that there is a defect at a position where the defect signal has passed through the subject.   The transmission unit and the reception unit are intervals at which the subject can be inserted between the transmission unit and the reception unit, and the reception unit reflects the reception signal reflected by the transmission unit. The state determination apparatus according to claim 1, wherein the state determination apparatus is disposed to face a position where waves can be received. A transmitter that generates ultrasonic waves and transmits ultrasonic signals;
One or more receiving units for receiving the ultrasonic signals transmitted through the subject and acquiring the first received signals,
A detector that measures a peak value of the first received signal for each of the receivers and detects whether there is a first received signal having a peak value equal to or greater than a first threshold;
A determination unit that determines, when there is a first reception signal whose peak value is equal to or greater than the first threshold, the first reception signal as a defect candidate signal that may have transmitted the defect portion of the subject;
Calculating a decay rate of an envelope of a peak value of the missing candidate signal for each of the missing candidate signals, and a calculating unit that measures the decay time until the decay rate reaches a predetermined decay rate, and
The determination unit, when the decay time is within a second threshold, determines the defect candidate signal as a defect signal that has passed through the defect portion of the subject. A transmitter that generates ultrasonic waves and transmits ultrasonic signals;
One or more receiving units for receiving the ultrasonic signals transmitted through the subject and acquiring the first received signals,
A detector for measuring a peak value of the first received signal for each of the receivers and detecting whether there is a first received signal having the peak value equal to or higher than a first threshold;
A determination unit that, when the peak value of the first received signal is equal to or greater than a first threshold, determines the first received signal as a missing candidate signal that may have passed through the missing portion of the subject;
A calculation unit that calculates a first characteristic indicating a frequency characteristic of the defect candidate signal and a second characteristic indicating a frequency characteristic before passing through the subject for each of the defect candidate signals;
If the difference between the first characteristic and the second characteristic is within a second threshold, the determination unit determines the defect candidate signal as a defect signal that has passed through the defect portion of the subject. A state determination device. Generate ultrasonic waves and send ultrasonic signals,
Receiving the ultrasonic signal transmitted through the subject by one or more receiving units to obtain first received signals, respectively;
Measuring the first peak value of the first received signal for each of the receivers, detecting whether there is a first received signal having the first peak value equal to or greater than a first threshold;
If there is a first received signal whose first peak value is greater than or equal to the first threshold value, the first received signal is determined as a missing candidate signal that may have passed through the missing portion of the subject;
When there is the missing candidate signal, the second receiving signal received when the receiving unit that has received the missing candidate signal has passed an integer multiple of one or more of a predetermined period from the time when the missing candidate signal was received. Measuring a peak value, detecting whether there is a second received signal having the second peak value equal to or greater than a second threshold;
When there is a second received signal whose second peak value is equal to or greater than a second threshold value, the defect candidate signal is determined as a defect signal that has passed through the defect portion of the subject. Method. Generate ultrasonic waves and send ultrasonic signals,
Receiving the ultrasonic signal transmitted through the subject by one or more receiving units to obtain first received signals, respectively;
Measuring the peak value of the first received signal for each of the receivers, detecting whether there is a first received signal whose peak value is greater than or equal to a first threshold;
If there is a first received signal whose peak value is greater than or equal to the first threshold value, the first received signal is determined as a missing candidate signal that may have passed through the missing portion of the subject;
For each missing candidate signal, calculate the decay rate of the envelope of the peak value of the missing candidate signal, measure the decay time until the decay rate reaches a predetermined decay rate,
A state determination method comprising: determining the defect candidate signal as a defect signal transmitted through a defect portion of the subject when the decay time is within a second threshold. Generate ultrasonic waves and send ultrasonic signals,
Receiving the ultrasonic signal transmitted through the subject by one or more receiving units to obtain first received signals, respectively;
Measuring the peak value of the first received signal for each of the receivers, detecting whether there is a first received signal whose peak value is equal to or greater than a first threshold;
If the peak value of the first received signal is greater than or equal to a first threshold, the first received signal is determined as a missing candidate signal that may have passed through the missing portion of the subject;
For each of the defect candidate signals, calculate a first characteristic indicating the frequency characteristic of the defect candidate signal and a second characteristic indicating the frequency characteristic before passing through the subject,
If the difference between the first characteristic and the second characteristic is within a second threshold value, the defect candidate signal is determined as a defect signal that has passed through the defect portion of the subject. State determination method.

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