Ultrasonic inspection apparatus and ultrasonic inspection method

Abstract

To provide an ultrasonic inspection device having detection performance of a defective part, for example, a small detectable defect size, and capable of detecting even a minute defect.SOLUTION: The scanning measurement device 1 of the ultrasonic inspection device Z includes the transmission probe 110 and the reception probe 121 installed on the opposite side of the transmission probe 110 with respect to the inspection object, the transmission probe 110 has a plurality of wave packets having two or more wave numbers and emits an ultrasonic beam by applying a voltage waveform repeating a wave packet group in which a wave packet delay time between a first wave packet and a second wave packet is arbitrarily set, the control device 2 includes the signal processing unit 250, and the signal processing unit 250 includes the frequency conversion unit 230 that converts the reception signal of the reception probe 121 into a frequency component.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to an ultrasonic inspection device and an ultrasonic inspection method. [Background technology]

[0002] There is a known method for inspecting defects in an object using an ultrasonic beam. For example, if the object contains a defect (cavity, etc.) with a low acoustic impedance, such as air, a gap in acoustic impedance occurs inside the object, reducing the amount of transmitted ultrasonic beam. Therefore, by measuring the amount of transmitted ultrasonic beam, defects inside the object can be detected.

[0003] A known technology for an ultrasonic inspection device is described in Patent Document 1. Patent Document 1 describes "an ultrasonic inspection device that inspects an object under inspection by irradiating the object under inspection with an ultrasonic beam via a fluid, the ultrasonic inspection device comprising: a scanning measurement device that scans and measures the object under inspection with the ultrasonic beam; and a control device that controls the driving of the scanning measurement device; the scanning measurement device comprising a transmitting probe that emits the ultrasonic beam and a receiving probe that receives the ultrasonic beam; the control device comprising a signal processing unit; the signal processing unit comprising a filter unit that reduces at least a maximum intensity frequency component of a signal received by the receiving probe; and the filter unit that detects base components other than the maximum intensity frequency component of a fundamental wave band that includes the maximum intensity frequency component." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-54642 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, defects are detected using frequency components other than the frequency component with the greatest intensity in the received signal (paragraph 0049). However, because frequency components other than the greatest intensity are used, the signal intensity of the frequency components used for detection may be low. Therefore, if the signal intensity of the frequency components used for detection can be increased, the defect detection performance can be further improved. The problem to be solved by the present disclosure is to provide an ultrasonic inspection device and an ultrasonic inspection method that have high defect detection performance, for example, that have a small detectable defect size and are capable of detecting even minute defects. [Means for solving the problem]

[0006] The ultrasonic inspection device disclosed herein inspects an object under inspection by irradiating the object under inspection with an ultrasonic beam via a fluid, and includes a scanning and measuring device that scans and measures the object under inspection with the ultrasonic beam, and a control device that controls the operation of the scanning and measuring device, the scanning and measuring device including a transmitting probe that emits the ultrasonic beam, and a receiving probe that is disposed on the opposite side of the transmitting probe with respect to the object under inspection and receives the ultrasonic beam, the transmitting probe has a plurality of wave packets including a first wave packet with a wave number of two or more and a second wave packet with a wave number of two or more at a fundamental frequency that is an excitation frequency of the transmitting probe, and emits an ultrasonic beam in response to application of a voltage waveform that repeats a wave packet group in which a wave packet delay time between the first wave packet and the second wave packet is arbitrarily set, the control device includes a signal processing unit, and the signal processing unit includes a frequency conversion unit that converts a signal received by the receiving probe into frequency components. Other solutions will be described later in the description of the embodiment. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an ultrasonic inspection device and an ultrasonic inspection method that can adjust the signal strength caused by defects and improve the detection performance of defects, for example, by making it possible to detect even minute defects with a small detectable size. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the configuration of an ultrasonic inspection device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of a transmission probe. [Figure 3A] FIG. 1 is a diagram showing the propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the beam incident on a healthy part. [Figure 3B] FIG. 1 is a diagram showing the propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the beam entering a defect. [Figure 4] FIG. 10 is a diagram showing the interaction between a defect in an object to be inspected and an ultrasonic beam, showing how a direct ultrasonic beam is received. [Figure 5] FIG. 1 is a diagram schematically illustrating a scattered wave, which is an ultrasonic beam that has interacted with a defect. [Figure 6] FIG. 2 is a functional block diagram of a control device. [Figure 7] 1 shows a conventional voltage waveform of a burst wave applied to a transmitting probe. [Figure 8] 10 shows a voltage waveform of a burst wave applied to a transmitting probe in this embodiment. [Figure 9] FIG. 2 is a diagram schematically illustrating the distribution of frequency components of a received signal. [Figure 10] 1 is a diagram showing a spectrum of the fundamental wave band of a received signal of an ultrasonic beam that has passed through an object under test. [Figure 11] FIG. 2 is a diagram schematically illustrating a spectrum of a fundamental wave band. [Figure 12] FIG. 10 is a diagram illustrating the meaning of bandwidth. [Figure 13] FIG. 10 is a diagram illustrating the relationship between the wave number and the bandwidth of the fundamental wave band. [Figure 14] FIG. 10 is a diagram schematically illustrating the spectrum of a received signal when a burst wave composed of a wave packet group having a plurality of wave packets is used. [Figure 15] This is a plot of the magnitude of the frequency component at the detection frequency when the wavenumber between wave packets is changed. [Figure 16] This is a diagram showing a wave packet group composed of two wave packets. [Figure 17A] FIG. 10 is a diagram showing an example of a burst wave of a single wave packet, which is a conventional example, in the case where the wave packet delay amount αd=5. [Figure 17B] FIG. 10 is a diagram showing an example of a burst wave composed of multiple wave packets according to this embodiment, in which the wave packet delay amount αd=5.5. [Figure 18A] The spectrum and interference function are shown for a wave packet delay of αd=5.25. [Figure 18B] The spectrum and interference function are shown when the wave packet delay amount αd=5.75. [Figure 19A] 10 is a graph plotting the magnitude of frequency components at a detection frequency of 0.74 MHz relative to the inter-wave packet wavenumber. [Figure 19B] 10 is a graph plotting the magnitude of frequency components at a detection frequency of 0.76 MHz relative to the inter-wave packet wavenumber. [Figure 19C] 10 is a graph plotting the magnitude of frequency components at a detection frequency of 0.82 MHz relative to the inter-wave packet wavenumber. [Figure 19D] 10 is a graph plotting the magnitude of frequency components at a detection frequency of 0.90 MHz relative to the inter-wave packet wavenumber. [Figure 20A] FIG. 10 is a diagram showing a burst wave signal made up of two wave packets in the second embodiment. [Figure 20B] FIG. 20B is a diagram showing the spectrum (solid line) and interference function K (dashed line) for the burst wave shown in FIG. 20A. [Figure 21A] FIG. 11 is a diagram showing a burst wave signal made up of two wave packets in the third embodiment. [Figure 21B] FIG. 21B is a diagram showing the spectrum (solid line) and interference function K (dashed line) for the burst wave shown in FIG. 21A. [Figure 22A] FIG. 11 is a diagram showing a burst wave signal made up of two wave packets in the fourth embodiment. [Figure 22B] FIG. 22B is a diagram showing the spectrum (solid line) and interference function K (dashed line) for the burst wave shown in FIG. 22A. [Figure 23A]FIG. 13 is a diagram showing a burst wave signal made up of two wave packets in the fifth embodiment. [Figure 23B] FIG. 23B is a diagram showing a spectrum of the burst wave shown in FIG. 23A. [Figure 24] FIG. 10 is a block diagram showing the configuration of an ultrasonic inspection device according to a sixth embodiment. [Figure 25] FIG. 13 is a diagram showing an example of a display screen of a display device according to a sixth embodiment. [Figure 26] FIG. 13 is a diagram showing an example of a display screen of a display device according to a seventh embodiment. [Figure 27A] FIG. 13 is a diagram schematically illustrating a propagation path of an ultrasonic beam when the focal length of a transmitting probe and the focal length of a receiving probe are set equal in the eighth embodiment. [Figure 27B] FIG. 13 is a diagram schematically illustrating a propagation path of an ultrasonic beam when the focal length of a receiving probe is set longer than the focal length of a transmitting probe in the eighth embodiment. [Figure 28] 10A and 10B are diagrams illustrating the relationship between the beam incident area in a transmitting probe and the beam incident area in a receiving probe. [Figure 29] FIG. 13 is a diagram schematically illustrating an arrangement of a transmitting probe, a device under test, and a receiving probe in the ninth embodiment. [Figure 30] FIG. 23 is a diagram showing the configuration of an ultrasonic inspection device according to a tenth embodiment. [Figure 31A] 1 is a diagram illustrating the transmission sound axis, the reception sound axis, and the eccentricity distance, in the case where the transmission sound axis and the reception sound axis extend in the vertical direction. FIG. [Figure 31B] 1 is a diagram illustrating a transmission sound axis, a reception sound axis, and an eccentricity distance, in which the transmission sound axis and the reception sound axis extend at an angle. FIG. [Figure 32] FIG. 23 is a diagram showing the configuration of an ultrasonic inspection device according to an eleventh embodiment. [Figure 33] FIG. 22 is a diagram for explaining why the eleventh embodiment produces an effect. [Figure 34] FIG. 23 is a diagram showing the configuration of an ultrasonic inspection device according to a twelfth embodiment. [Figure 35]10 is a graph showing voltages obtained by delaying the phase of the second wave packet by 180° and setting the wave packet delay time. [Figure 36] FIG. 2 is a diagram illustrating a hardware configuration of a control device 2. [Figure 37] 1 is a flowchart illustrating an ultrasonic inspection method according to each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, modes for carrying out the present disclosure (hereinafter referred to as "embodiments") will be described with reference to the drawings. In the following description of one embodiment, other embodiments applicable to the one embodiment will also be described as appropriate. The present disclosure is not limited to the one embodiment described below, and different embodiments can be combined with each other or modified as desired without significantly impairing the effects of the present disclosure. Furthermore, the same components will be given the same reference numerals, and redundant descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for convenience of illustration, changes may be made from the actual configuration within the scope of not significantly impairing the effects of the present disclosure, and some components may be omitted or modified between drawings. Furthermore, the same embodiment does not necessarily have to include all of the configurations.

[0010] (First embodiment) Fig. 1 is a diagram showing the configuration of an ultrasonic inspection device Z according to a first embodiment. In Fig. 1, a scanning measurement device 1 is shown in a schematic cross-sectional view. Fig. 1 shows a coordinate system of three orthogonal axes, including an x-axis as the left-right direction on the paper, a y-axis as the direction perpendicular to the paper, and a z-axis as the up-down direction on the paper.

[0011] The ultrasonic inspection device Z inspects the object E under inspection by irradiating an ultrasonic beam U (described later) onto the object E under inspection via a fluid F. The fluid F is, for example, a liquid W (described later) such as water, or a gas G such as air, and the object E under inspection exists in the fluid F. In the first embodiment, the fluid F is air (an example of the gas G). Therefore, the inside of the housing 101 of the scanning measurement device 1 is a cavity filled with air. As shown in FIG. 1, the ultrasonic inspection device Z includes the scanning measurement device 1, a control device 2, and a display device 3. The display device 3 is connected to the control device 2.

[0012] The scanning measurement device 1 scans and measures an object under test E with an ultrasonic beam U. The scanning measurement device 1 includes a sample stage 102 fixed to a housing 101, and the object under test E is placed on the sample stage 102. Preferably, the object under test E is fixed to the sample stage 102 with a fixture (not shown) to prevent it from moving. A fixture may be unnecessary if the object under test E is sufficiently heavy and does not move unintentionally. The object under test E is made of any material. The object under test E may be, for example, a solid material, more specifically, metal, glass, a resin material, or a composite material such as CFRP (carbon fiber reinforced plastics). In the example of FIG. 1 , the object under test E has a defect D therein. The defect D (defect) may be a cavity or the like. Examples of the defect D include a cavity, a foreign material that is different from the original material, and the like. In the object under test E, the portion other than the defect D is referred to as a healthy portion N.

[0013] The defective part D and the healthy part N are made of different materials, so the acoustic impedance differs between them, and the propagation characteristics of the ultrasonic beam U change. The ultrasonic inspection device Z observes this change and detects the defective part D.

[0014] The scanning measurement device 1 has a transmitting probe 110 that emits an ultrasonic beam U and a receiving probe 121 that receives the ultrasonic beam U. The transmitting probe 110 is installed in the housing 101 via a transmitting probe scanning unit 103 and emits the ultrasonic beam U. The receiving probe 121 is installed on the opposite side of the transmitting probe 110 with respect to the object under test E to receive the ultrasonic beam U, and is a receiving probe 140 (coaxially arranged receiving probe) that is arranged coaxially with the transmitting probe 110 (the eccentricity distance L described below is zero). Therefore, in the present disclosure, the eccentricity distance L (distance described below) between the transmitting sound axis AX1 (sound axis) of the transmitting probe 110 and the receiving sound axis AX2 (sound axis) of the receiving probe 140 is zero. This allows the transmitting probe 110 and the receiving probe 140 to be easily installed.

[0015] Here, "the opposite side of the transmitting probe 110" means the space opposite (opposite side in the z-axis direction) from the space in which the transmitting probe 110 is located, out of the two spaces separated by the subject E, and is not limited to the opposite side with the same x and y coordinates (i.e., a position that is symmetrical with respect to the xy plane).

[0016] In the example of the present disclosure, the transmitting probe 110 is installed so that the transmission acoustic axis AX1 of the transmitting probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102. That is, the transmitting probe 110 is installed so that the transmission acoustic axis AX1 is normal to the mounting surface 1021 of the sample stage 102 for the object under test E. In this way, for a plate-shaped object under test E, the transmission acoustic axis AX1 is arranged perpendicular to the surface of the object under test E, which has the effect of making it easier to understand the correspondence relationship between the scanning position and the position of the defect portion D.

[0017] However, the present disclosure is not limited to installing the transmitting probe 110 so that the transmission sound axis AX1 is perpendicular to the mounting surface 1021 of the sample stage 102 for the object under test E. The present disclosure is effective even when the transmission sound axis AX1 is not perpendicular to the mounting surface 1021 of the sample stage 102 for the object under test E. In the latter case, to accurately determine the position of the defect D, the path of the transmission sound axis AX1 can be calculated according to the inclination of the transmission sound axis AX1 from the vertical direction.

[0018] Here, the positional relationship between the transmitting probe 110 and the receiving probe 121 will be described. The distance between the transmitting sound axis AX1 of the transmitting probe 110 and the receiving sound axis AX2 of the receiving probe 121 is defined as the eccentricity distance L, as described above. In this disclosure, the eccentricity distance L is set to zero, as described above. That is, the receiving probe 121 is arranged so that the transmitting sound axis AX1 and the receiving sound axis AX2 are coaxial. This is called a coaxial arrangement. Note that in this disclosure, the eccentricity distance L is not limited to zero.

[0019] In this disclosure, the arrangement of the receiving probe 121 in which the transmission sound axis AX1 and the reception sound axis AX2 are coaxially arranged is called a coaxial arrangement, and the arrangement in which the two sound axes (transmission sound axis AX1 and reception sound axis AX2) are shifted (i.e., eccentric arrangement) is called an eccentric arrangement. The present disclosure is effective in both cases where the receiving probe 121 is coaxially arranged and where it is eccentrically arranged. Therefore, the present disclosure includes both a coaxial arrangement and an eccentric arrangement as the arrangement of the receiving probe 121. Specific illustrations of an eccentric arrangement will be provided later.

[0020] In this disclosure, when specifying the receiving arrangement position, the coaxially arranged receiving probe 121 will be referred to as the receiving probe 140 (coaxially arranged receiving probe), and the eccentrically arranged receiving probe 121 will be referred to as the receiving probe 120 (eccentrically arranged receiving probe, described below). When referring to the receiving probe 121, there is no particular specification as to whether it is coaxially arranged or eccentrically arranged.

[0021] The sound axis is defined as the central axis of the ultrasonic beam U. Here, the transmission sound axis AX1 is defined as the sound axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110. In other words, the transmission sound axis AX1 is the central axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110. As will be described later, the transmission sound axis AX1 is intended to include refraction due to the interface of the object E to be inspected. In other words, when the ultrasonic beam U emitted from the transmitting probe 110 is refracted at the interface of the object E to be inspected, the center (sound axis) of the propagation path of the ultrasonic beam U becomes the transmission sound axis AX1.

[0022] The reception sound axis AX2 is defined as the sound axis of the propagation path of the virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U. In other words, the reception sound axis AX2 is the central axis of the virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.

[0023] As a specific example, we will consider a non-focusing receiving probe with a flat probe surface. In this case, the direction of the receiving sound axis AX2 is the normal direction to the probe surface, and the axis passing through the center point of the probe surface is the receiving sound axis AX2. If the probe surface is rectangular, the center point is defined as the intersection of the diagonals of the rectangle.

[0024] A control device 2 is connected to the scanning measurement device 1. The control device 2 controls the driving of the scanning measurement device 1, and controls the movement (scanning) of the transmitting probe 110 and the receiving probe 121 by issuing instructions to the transmitting probe scanning unit 103 and the receiving probe scanning unit 104. The transmitting probe scanning unit 103 and the receiving probe scanning unit 104 move in the x-axis and y-axis directions in synchronization, causing the transmitting probe 110 and the receiving probe 121 to scan the object under test E in the x-axis and y-axis directions. Furthermore, the control device 2 emits an ultrasonic beam U from the transmitting probe 110 and performs waveform analysis based on the signal acquired from the receiving probe 121. Note that the plane formed by the two axes, the x-axis and y-axis directions, which are the scanning directions of the transmitting probe 110, is referred to as the scanning plane.

[0025] In this disclosure, an example is shown in which the transmitting probe 110 and the receiving probe 121 are scanned in a state in which the object under test E is fixed to the housing 101 via the sample stage 102, that is, in a state in which the object under test E is fixed to the housing 101. Conversely, a configuration may be used in which the transmitting probe 110 and the receiving probe 121 are fixed to the housing 101, and the position of the sample stage 102 is scanned in the x-axis and y-axis directions. In this configuration, the object under test E placed on the sample stage 102 also moves, so that the relative position with respect to the transmitting probe 110 is scanned in the x-axis and y-axis directions.

[0026] In the illustrated example, gas G (an example of fluid F; liquid W (described later) may also be used) is interposed between the transmitting probe 110 and the test subject E, and between the receiving probe 121 and the test subject E. This allows the transmitting probe 110 and the receiving probe 121 to test the test subject E without contact, making it possible to change the relative positions in the xy plane smoothly and quickly. In other words, by interposing fluid F (gas G) between the transmitting probe 110 and the receiving probe 121 and the test subject E, smooth scanning becomes possible.

[0027] When a local ultrasonic beam U is emitted from the transmitting probe 110, the emitted ultrasonic beam U is locally irradiated onto the object under test E. The position to which the local ultrasonic beam U is irradiated is changed by scanning. As described above, the ultrasonic beam U that reaches the receiving probe 121 varies depending on whether it is a defective part D or a healthy part N of the object under test E, so this configuration makes it possible to detect the defective part D.

[0028] In this embodiment, a convergent transmitting probe 110 is used to generate a localized ultrasonic beam U. A specific configuration of the convergent transmitting probe 110 will be described later. A configuration for generating a localized ultrasonic beam U may be used in which the beam diameter is reduced by reducing the area of ​​a piezoelectric element (a transducer 111 described later; the same applies hereinafter) that generates the ultrasonic beam U. The convergent transmitting probe 110 is more preferable because it can reduce the beam diameter while increasing the area of ​​the piezoelectric element, thereby generating a localized ultrasonic beam U with high beam intensity and a small beam diameter.

[0029] The transmitting probe 110 is a convergent type transmitting probe 110. On the other hand, the receiving probe 121 is a probe with weaker convergence than the transmitting probe 110. In the present disclosure, a non-convergent type probe with a flat probe face is used as the receiving probe 121. Therefore, the receiving probe 121 is a non-convergent type receiving probe. By using such a non-convergent type receiving probe 121, information on the defect D can be collected over a wide range.

[0030] Fig. 2 is a cross-sectional schematic diagram showing the structure of the transmitting probe 110. For simplicity, Fig. 2 shows only the outer contour of the emitted ultrasonic beam U, but in reality, a large number of ultrasonic beams U are emitted in the normal vector direction of the probe surface 114 over the entire area of ​​the probe surface 114.

[0031] The transmitting probe 110 is configured to focus the ultrasonic beam U. This allows for highly accurate detection of minute defects D in the object E to be inspected. The reason why minute defects D can be detected will be described later. The transmitting probe 110 includes a transmitting probe housing 115, which includes a backing 112, a vibrator 111, and a matching layer 113 inside the transmitting probe housing 115. An electrode (not shown) is attached to the vibrator 111, and the electrode is connected to a connector 116 by a lead wire 118. Furthermore, the connector 116 is connected to a power supply unit (not shown) and a control unit 2 by a lead wire 117.

[0032] In the present disclosure, the probe surface 114 of the transmitting probe 110 or the receiving probe 121 is defined as the surface of the matching layer 113 if the matching layer 113 is provided, and as the surface of the transducer 111 if the matching layer 113 is not provided. That is, the probe surface 114 is the surface that emits the ultrasonic beam U in the case of the transmitting probe 110, and is the surface that receives the ultrasonic beam U in the case of the receiving probe 121.

[0033] Here, a conventional ultrasonic inspection method will be described as a comparative example.

[0034] 3A is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the beam being incident on a healthy part N. FIG. 3B is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the beam being incident on a defective part D. In the conventional ultrasonic inspection method, as described in Patent Document 1, for example, a transmitting probe 110 and a receiving probe 140 serving as a receiving probe 121 are arranged so that a transmitting sound axis AX1 and a receiving sound axis AX2 coincide with each other.

[0035] As shown in FIG. 3A, when an ultrasonic beam U is incident on a healthy portion N of an object E to be inspected, the ultrasonic beam U passes through the object E to reach the receiving probe 140. Therefore, the received signal becomes large. On the other hand, as shown in FIG. 3B, when the ultrasonic beam U is incident on a defective portion D, the defective portion D prevents the ultrasonic beam U from passing through, and the received signal decreases. In this way, the defective portion D is detected by the decrease in the received signal. This is as shown in Patent Document 1.

[0036] Here, as shown in Figures 3A and 3B, the method of detecting a defect D by blocking the transmission of an ultrasonic beam U at the defect D, thereby reducing the received signal, will be referred to as the "blocking method."

[0037] Here, if the size of the defect D becomes smaller than the beam size, it becomes difficult to detect. This point will be explained with reference to FIG.

[0038] FIG. 4 is a diagram showing the interaction between a defect D in an object E and an ultrasonic beam U, and illustrates the reception of a direct ultrasonic beam U (hereinafter referred to as a "direct wave U3"). The direct wave U3 will be described later. Here, we consider a case where the size of the defect D is smaller than the width of the ultrasonic beam U (hereinafter referred to as the beam width BW). The beam width BW here is the width of the ultrasonic beam U when it reaches the defect D.

[0039] 4 shows the shape of the ultrasonic beam U in a minute area near the defect D, and therefore the ultrasonic beam U is drawn parallel, but in reality it is a converged ultrasonic beam U. Furthermore, the position of the receiving probe 121 in FIG. 4 is a conceptual position drawn for easy understanding, and the position and shape of the receiving probe 121 are not accurately scaled. In other words, when considering the shapes of the defect D and the ultrasonic beam U on an enlarged scale, the receiving probe 121 is located at a position farther away in the vertical direction of the drawing than the position shown in FIG. 4.

[0040] Figure 4 shows the case of the blocking method in which the transmitting acoustic axis AX1 and the receiving acoustic axis AX2 are aligned. If the defect D is smaller than the beam width BW, part of the ultrasonic beam U is blocked, so the received signal decreases, but does not become zero. For example, if the cross-sectional area of ​​the defect D is 5% of the beam cross-sectional area defined by the beam width BW, the received signal decreases by only about 5%, making it difficult to detect the defect D. In other words, in the case shown in Figure 4, the received signal decreases by only 5% where the defect D exists. In this way, if the defect D is smaller than the beam width BW, many beams pass through without interacting with the defect D, reducing the detection accuracy of the defect D.

[0041] FIG. 5 is a schematic diagram showing a scattered wave U1, which is an ultrasonic beam U that has interacted with a defect D. In this disclosure, the ultrasonic beam U that has interacted with the defect D is referred to as the scattered wave U1. Therefore, in this disclosure, the "scattered wave U1" refers to an ultrasonic wave that has interacted with the defect D. Some scattered waves U1 change direction, as shown in FIG. 5. Other scattered waves U1 change at least one of their phase or frequency upon interaction with the defect D, but their direction of travel remains unchanged. Ultrasonic waves that pass through the defect D without interacting with it are referred to as direct waves U3. If only the scattered waves U1 can be detected, distinguishing them from the direct waves U3, it becomes easier to detect small defects D. In this disclosure, the scattered waves U1 are efficiently detected by focusing on the difference in frequency.

[0042] In this embodiment, a gas G such as air is used as the fluid F between the transmitting probe 110 and the object under test E. In this case, for the reasons described below, it becomes particularly difficult to detect minute defects D using the above-mentioned blocking method. For this reason, the effect of the present disclosure in detecting the scattered wave U1 is significant.

[0043] Compared to liquid W, ultrasonic waves are attenuated more in gas G. It is known that the attenuation of ultrasonic waves in gas G is proportional to the square of the frequency. For this reason, the upper limit for ultrasonic waves propagating in gas G is about 1 MHz. In liquid W, ultrasonic waves of 5 MHz to several tens of MHz can also propagate, so the frequencies that can be used in gas G are lower than those in liquid W.

[0044] Generally, as the frequency of the ultrasonic beam U decreases, it becomes more difficult to focus the ultrasonic beam U. Therefore, the beam diameter that can be focused for a 1 MHz ultrasonic beam U propagating through a gas G is larger than that of an ultrasonic beam U in a liquid W. On the other hand, as shown in FIG. 4 above, it is difficult to detect a defect D smaller than the beam size with the above-mentioned blocking method. However, according to the present disclosure, as shown in FIG. 5 above, the proportion of the scattered wave U1 component is increased for detection, making it possible to detect a defect D smaller than the beam size.

[0045] FIG. 6 is a functional block diagram of the control device 2. The control device 2 controls the driving of the scanning measurement device 1. The control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250. The driving unit 202 drives the transmitting probe 110 and the receiving probe 121, for example, to change the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the object under test E. The position measurement unit 203 measures the scanning position. The scan controller 204 drives the transmitting probe 110 and the receiving probe 121 via the driving unit 202. The scanning positions of the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 via the position measurement unit 203.

[0046] The receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250. That is, the signal processing unit 250 includes the receiving system 220 and the data processing unit 201, and performs signal processing such as amplification and filtering of the signal from the receiving probe 121 to extract significant information.

[0047] (The natural frequency (fres) of the transmitting probe 110 and the excitation frequency (fex)) The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a delay time setting unit 213. A burst wave signal is generated by the waveform generator 211. The generated burst wave signal is then amplified by the signal amplifier 212. The voltage output from the signal amplifier 212 is applied to the transmission probe 110. Therefore, the transmission probe 110 is driven by the burst wave.

[0048] The burst wave signal will now be described. The configuration of the burst wave signal is a feature of the present disclosure. FIG. 7 is a diagram showing a conventional burst wave signal, and FIG. 8 is a diagram showing a burst wave signal in this embodiment.

[0049] FIG. 7 shows the voltage waveform of a conventional burst wave applied to the transmitting probe 110. A conventional burst wave is a burst wave consisting of only one type of wave packet. The horizontal axis represents time, and the vertical axis represents voltage. In the example of FIG. 7, ten sine waves with a fundamental frequency f0 of 0.78 MHz are applied. These ten waves are called a wave packet. The fundamental frequency f0 is the excitation frequency fex (the frequency that excites the transmitting probe 110) of the transmitting probe 110. The reciprocal of the fundamental frequency f0 is called the fundamental period T0. As shown in the figure, the fundamental period T0 is the period of the waves that make up one wave packet. The number of waves of fundamental frequency f0 that make up one wave packet is called the wave number N0. The wave packet is applied with a repetition period Tr = 5 ms. Therefore, the transmitting probe 110 emits an ultrasonic beam U when a voltage waveform of a repetitive wave packet consisting of wave packets with a wave number N0 of 2 or more is applied.

[0050] 8 shows the voltage waveform of the burst wave of this embodiment applied to the transmitting probe 110. A feature of this burst wave is that the wave for each repetition period Tr is made up of multiple (multiple types of) wave packets (wave packet 10, wave packet 11). In other words, a group of wave packets made up of multiple wave packets is repeated in the repetition period Tr.

[0051] FIG. 8 shows an example consisting of two wave packets, namely, wave packet 10 and wave packet 11. The time from the start time of wave packet 10 to the start time of wave packet 11 is called the wave packet delay time Δtd. The wave packet delay time Δtd is the time that indicates how much the start time of wave packet 11 is delayed from the start time of wave packet 10. In addition, the time from the end time of wave packet 10 to the start time of wave packet 11 is called the wave packet inter-time ΔtI. The wave packet inter-time ΔtI is the time between adjacent wave packets 10 and 11.

[0052] Although FIG. 8 shows an example in which the wave packet group is composed of two wave packets, it may be composed of three or more wave packets. Furthermore, the wave number N0 of wave packet 10 may be different from the wave number N0 of wave packet 11. The voltage amplitude of wave packet 10 may also be different from the voltage amplitude of wave packet 11. Furthermore, in the example of the present disclosure, the fundamental frequency f0 of each of the multiple wave packets is different. That is, the fundamental frequency f0 of the wave packet 11 is different from the fundamental frequency f0 of the wave packet 10. This can improve the performance of detecting the defect D.

[0053] 8, the use of a burst wave in which a group of wave packets is repeated with a repetition period Tr is a feature of the present disclosure. As described above, the group of wave packets has a plurality of wave packets including a wave packet 10 (first wave packet) having a wave number of 2 or more at the fundamental frequency which is the excitation frequency of the transmitting probe 110, and a wave packet 11 (second wave packet) having a wave number of 2 or more. The effects brought about by this feature will be described later.

[0054] 7 shows a typical example of the time width and repetition period Tr of a wave packet. The fundamental period T0 of the wave packet is 1.2 μs, and the wave number N0=10, so the time width of the wave packet is 12 μs, while the repetition period Tr is 5 ms.

[0055] On the other hand, Figure 8 shows a typical example of the time width of a wave packet group. The fundamental period T0 of the wave packet is 1.2 μs, and the wave number N0 = 5, so when the inter-wave packet time ΔtI is 10 μs, the time width of the wave packet group is 22 μs. On the other hand, the repetition period Tr is 5 ms. The time width of the wave packet group is small, about 0.4% of Tr.

[0056] In this way, the time width of the wave packet group is typically 30% or less, more preferably 20% or less, of the repetition period Tr. In this way, a wave packet group made up of multiple wave packets can be clearly distinguished even from the time waveform.

[0057] It goes without saying that the time examples shown here are typical examples, and the present disclosure is not limited to these.

[0058] Returning to the configuration diagram of FIG. 6 , the burst wave signal composed of multiple wave packets shown in FIG. 8 is input to the signal amplifier 212, amplified, and applied to the transmitting probe 110. This causes the transmitting probe 110 to emit an ultrasonic beam U of a burst wave composed of multiple wave packets. That is, the transmitting probe 110 emits the ultrasonic beam U by applying a voltage waveform having multiple wave packets and repeating a wave packet group in which the wave packet delay time Δtd between the first wave packet and the second wave packet is arbitrarily set. In another embodiment, the transmitting probe 110 emits the ultrasonic beam U by applying a voltage waveform having a wave packet delay time Δtd with frequency components greater than the frequency components when the wave packet inter-time ΔtI, which is the time between multiple wave packets, is zero. In yet another embodiment, the transmitting probe 110 emits the ultrasonic beam U by applying a voltage waveform having a wave packet delay time Δtd with frequency components greater than the frequency components when the wave packet inter-time ΔtI, which is the time between multiple wave packets, is zero. These multiple wave packets include a first wave packet having a fundamental frequency f0, which is the excitation frequency fex of the transmitting probe 110, and a wave number of 2 or more, and a second wave packet having a wave number of 2 or more.

[0059] As described above, the transmission system 210 includes the delay time setting unit 213. The delay time setting unit 213 is provided in the scanning measurement device 1 and sets the wave packet delay time Δtd of multiple wave packets. The delay time setting unit 213 can set the wave packet delay time Δtd between multiple wave packets to an appropriate value. The appropriate value here is a value that can generate a foot component W3 (described below) having an intensity sufficient to enable detection of the defect D using the foot component W3.

[0060] The delay time setting unit 213 sets the wave packet delay time Δtd by making the inter-wave packet time ΔtI of the multiple wave packets greater than zero so that the magnitude of the frequency components different from the fundamental frequency f0 becomes greater than the magnitude of the frequency components when the inter-wave packet time ΔtI is zero. This makes it possible to detect the defect D using the frequency components different from the fundamental frequency f0.

[0061] As will be described later, by setting the excitation frequency fex to an appropriate value, the performance of the ultrasonic inspection device Z of this embodiment can be improved.

[0062] Generally, when the transmitting probe 110 is operated at a specific frequency determined for each probe, the amplitude intensity (sound pressure) of the generated ultrasonic beam U is maximized. This maximum frequency is called the natural frequency fres (resonance frequency) of the transmitting probe 110. The reason that the sound pressure is maximized at the natural frequency fres is because the vibration of the built-in piezoelectric element (vibrator 111) resonates at the natural frequency fres. For this reason, the transmitting probe 100 is usually used with the excitation frequency fex set equal to the natural frequency fres.

[0063] The excitation frequency fex corresponds to the fundamental frequency f0 in FIG.

[0064] In this embodiment, the excitation frequency fex may be equal to or different from the natural frequency fres of the transmitting probe 110. It is more preferable to set the excitation frequency fex so as to be shifted from the natural frequency fres, since this makes it easier to receive the scattered wave U1 at the defect D, which will be described later. The natural frequency fres of the transmitting probe 110 used in this embodiment is 0.82 MHz. The excitation frequency fex may be set to 0.82 MHz, which is equal to the natural frequency fres. Alternatively, the excitation frequency fres may be set to 0.78 MHz or 0.86 MHz, which is a deviation of about 5% from the natural frequency fres. By deviating the excitation frequency fres from the natural frequency fres in this way, the defect D becomes easier to detect.

[0065] The ultrasonic beam U of a burst wave emitted from the transmitting probe 110 passes through the subject E and is then received by the receiving probe 140. The receiving probe 140 converts the ultrasonic beam U into an electrical signal. The converted electrical signal is input to the receiving system 220. The receiving system 220 amplifies the electrical signal output by the receiving probe 140 using a signal amplifier 222.

[0066] The electrical signal output from the signal amplifier 222 is a time-domain waveform. The time-domain waveform is a waveform in which the horizontal axis represents time and the vertical axis represents signal voltage. The output of the signal amplifier 222 is input to the frequency conversion unit 230.

[0067] The frequency conversion unit 230 is provided in the signal processing unit 250 and converts the received signal of the receiving probe 140 into frequency components. Specifically, the frequency conversion unit 230 converts a time domain waveform into a frequency domain signal. A frequency domain signal is a signal that represents the magnitude of a signal component for each frequency, and typically, the horizontal axis represents frequency and the vertical axis represents the magnitude of the frequency component. The frequency domain signal includes a spectrum. The frequency components of a frequency domain signal may have phase information in addition to magnitude. Also, the frequency components may be complex numbers. The fact that the frequency components are complex numbers is equivalent to the fact that the frequency components have both magnitude and phase information. When the frequency components of the frequency domain signal are complex numbers, the phase information of the frequency components can also be used to detect the defect D, which is advantageous in that it makes it easier to detect the defect D. The frequency conversion unit 230 may be provided in the signal processing unit 250, or may be provided in the data processing unit 201 described later. The frequency transform unit 230 may also be called a frequency component transform unit. In this specification, the terms frequency transform unit and frequency component transform unit are synonymous and have the same meaning as defined above.

[0068] The conversion in the frequency conversion unit 230 can be performed by, for example, a Fourier transform. The conversion may also be performed while extracting only frequency components in a pre-specified frequency range (frequency parameters). The signal converted into frequency components by the frequency conversion unit 230 is input to the data processing unit 201. The frequency conversion unit 230 may be provided inside the data processing unit 201. That is, the signal may be converted into frequency components within the data processing unit.

[0069] The frequency conversion unit 230 converts the received signal in a time range including at least two of the multiple wave packets into frequency components, thereby improving the detection performance of the defect D, which is an effect of the present disclosure obtained by using two wave packets.

[0070] (Storage of frequency component data) The data processing unit 201 includes a storage unit 261, a frequency selection unit 242, an imaging unit 262, and a display unit 263. Therefore, the signal processing unit 250 includes a frequency conversion unit 230, an imaging unit 262, a frequency selection unit 242, and a display unit 263.

[0071] In the example of the present disclosure, the frequency conversion unit 230 converts the time-domain waveform into frequency component data and stores the data together with position information in the storage unit 261. Then, the imaging unit 262, as will be described in detail later, generates an image 273 (described later) indicating the defect position using a portion of the converted frequency components that is specified by the frequency parameters. That is, the imaging unit 262 visualizes the signal feature amount based on the input frequency parameters. That is, when the inspected object E is measured once, the conversion to frequency component data is performed only once, and the extraction of the signal feature amount from the frequency component data is performed multiple times.

[0072] This configuration is preferable for the following two reasons. The first is the time required for calculation. The conversion process into frequency component data in the frequency conversion unit 230 takes time. Typically, a Fourier transform is used as described above, but even if a fast Fourier transform (FFT), known as a high-speed algorithm, is used, the processing time for this conversion is long. On the other hand, the signal feature amount is calculated using equation (1) described below, and the calculation time required for this is short. As a typical example, even for measurement points of 100 rows x 100 columns, processing is completed in 0.2 seconds or less.

[0073] Therefore, according to the example of the present disclosure, as will be described in detail later, when the frequency parameters are "updated," it is possible to instantly obtain an updated image 273 (described later). In this way, by storing the frequency component data in the storage unit 261, it is possible to select a frequency set suitable for improving the detection performance of the defect portion D in a short time.

[0074] Second, the amount of data can be reduced. The signal waveform of the receiving probe 140 has about 100,000 points in the time domain waveform for one measurement position, whereas the frequency component data only requires complex numbers for 20 to 100 different frequencies. In other words, the amount of data for the test subject E can be reduced to about 1 / 1000. This also has the advantage of significantly reducing the amount of data stored in the storage unit 261.

[0075] The data processing unit 201 also receives information about the scanning position from the scan controller 204. In this way, data related to the frequency components of the received signal at the current two-dimensional scanning position (x, y) (hereinafter referred to as frequency component data) is obtained. The data processing unit 201 associates the scanning position (x, y) with the frequency component data at that position and stores them in the storage unit 261. Note that an image 273 related to the defect D is created by determining a signal feature amount determined from the frequency component data for each scanning position.

[0076] The frequency component data is a frequency component corresponding to a plurality of frequencies. In a typical example, the frequency component data is a frequency spectrum obtained by Fourier transform of the received signal. As mentioned above, it is more preferable that the frequency components include phase information in addition to amplitude (absolute value). This is equivalent to treating the frequency components as complex numbers. As will be described later, including phase information enables the calculation of signal features with higher performance.

[0077] 6, the data processing unit 201 includes an imaging unit 262. The imaging unit 262 is included in the signal processing unit 250, and generates an image 273 (described below) indicating the position (defect position) of a defect D using a portion of the converted frequency components that is specified by the frequency parameters. Specifically, the imaging unit 262 creates the image 273 based on a change (amount of change) in a signal caused by the defect D of the object E in a frequency spectrum of a portion that corresponds to an appropriate frequency parameter out of the frequency spectrum corresponding to the frequency components converted by the frequency conversion unit 230. In this way, the image 273 can be generated.

[0078] In the example of the present disclosure, the signal change (change in the received signal) referred to here is a signal feature. Therefore, the imaging unit 262 first calculates the signal feature from the input frequency parameter portion of the frequency spectrum corresponding to the converted frequency component. The calculation method of the signal feature will be described later, but as described above, it is, for example, a value that represents the signal change, and is a value calculated from frequency component data so as to appropriately include defect information (e.g., the position of the defect D). A specific example of the calculation method of the signal feature will be described later. By plotting the signal feature thus obtained against the scanning position (x, y), a two-dimensional image (defect image) of the defect D present inside the object E to be inspected is generated.

[0079] The desired range is scanned by repeating the above procedure while changing the scanning position (x, y). When the scanning is completed, the frequency component data and signal feature amounts corresponding to the scanning position (x, y) are stored in the storage unit 261 in the data processing unit 201. In the present disclosure, the signal feature amounts are calculated each time a signal is acquired at a scanning position. However, the frequency component data may be stored in the storage unit 261 during measurement, and the signal feature amounts may be calculated all at once after the measurement to generate a defect image.

[0080] (Calculation of signal features) The method of calculating signal features from frequency component data used in the examples of the present disclosure will be described. To make the formula easier to understand, we will express frequency f as angular frequency ω, which is frequency f multiplied by 2π. Also, j represents the imaginary unit.

[0081] This shows a process for calculating frequency components H(ω) from the measured signal waveform h1(t) in the time domain. This is an example of a method for processing the output signal of the signal amplifier 222 in FIG. 6 by the frequency conversion unit 230.

[0082]

number

[0083] Here, tk is a time sequence spaced at an appropriate sampling frequency. k is zero or a finite positive integer (k=0, 1, 2, ...). Equation (1) performs a process roughly equivalent to integrating over the time range to obtain the sum. Equation (1) gives the frequency component H(ω).

[0084] An appropriate sampling frequency is one that satisfies the commonly known sampling theorem. In other words, the sampling frequency is set to a frequency at least twice the frequency band of the signal to be observed. Furthermore, it is preferable to set the sampling frequency to at least 10 times the fundamental frequency f0 of the transmitted ultrasonic beam U, since this allows distortion of the signal waveform to be reproduced. In this embodiment, the sampling frequency was set to 50 MHz for a signal waveform with a fundamental frequency f0 = 0.86 MHz.

[0085] The frequency component H(ω) obtained by equation (1) is a complex number. That is, the frequency component H(ω) has a phase in addition to an absolute value. The frequency spectrum shown in Figure 12 above is a plot of the absolute value |H(ω)| of the complex number H(ω) against the frequency ω.

[0086] Next, we will show how to calculate signal features from the frequency components H(ω) expressed as complex numbers. First, h(t) is calculated according to the following equation (2).

[0087]

number

[0088]

number

[0089] Here, in equation (2), j is the imaginary unit, and in equation (3), Re[ ] is the process of extracting the real part of a complex number. In equation (2), the subscript ω of the Σ symbol indicates the frequency set of the angular frequency components to be integrated. In equation (2), the angular frequency components to be integrated are calculated for an appropriately set frequency set {ω}, as described below.

[0090] In equation (2), the set of frequencies {ω} to be included in the integration is called a frequency parameter. The frequency parameter may be specified in the form of a frequency set {ω} or a frequency range. The frequency parameter may also be set in advance. The frequency parameter may also be input by the user.

[0091] h(t) obtained by Equation (3) is a time domain signal waveform synthesized from a frequency set set by frequency parameters. In the example of the present disclosure, the difference between the maximum and minimum values ​​of this h(t) (Peak-to-Peak value) is used as the signal feature. In the example of the present disclosure, the difference between the maximum and minimum values ​​(Peak-to-Peak value) is abbreviated as the PP value.

[0092] In equation (2), H(ω) and exp(jωt) are both complex numbers, and are calculated as complex numbers. That is, the signal feature quantity is calculated taking into consideration the phase information of the frequency component H(ω). This is more preferable because it allows for the acquisition of a signal feature quantity that accurately reflects the position information of the defect D.

[0093] The selection of the frequency parameter, i.e., the set of frequencies {ω} to be included in the summation in equation (2), is important. The fundamental frequency f0 is excluded from the set of frequencies {ω} to be included in the summation. In this way, a filter section (not shown) that reduces the maximum intensity frequency component can be configured. Furthermore, the frequencies to be included in the summation include the frequency of the skirt component W3 of the fundamental wave band W1. This improves the detection performance of the defect D in the object E to be inspected. Furthermore, it is even more effective to also exclude frequency components near the fundamental frequency f0.

[0094] Since the angular frequency ω can be converted to the frequency f using the relationship ω = 2πf, we will make appropriate conversions and interpret the results accordingly. For example, when we write "excluding the fundamental frequency f0 from the frequency set {ω}," it means "excluding ω0 = 2πf0."

[0095] The fundamental frequency f0 is the frequency of the waves that make up the wave packet 10, as shown in Figure 8. Since Figure 8 shows the applied voltage to the transmitting probe 110, the fundamental frequency f0 is equal to the excitation frequency fex.

[0096] Furthermore, in equation (2), the set of frequencies {ω} to be included in the summation may include only frequencies lower than the fundamental frequency f0. This allows for the configuration of a filter section (not shown) with low-pass filter characteristics. Similarly, only frequencies lower than the fundamental frequency f0 may be included.

[0097] The frequency parameters are appropriately set in the frequency selection section 242. In this way, the frequency conversion section 230 and the frequency selection section 242 form a filter section (not shown).

[0098] The frequency parameters may be set appropriately before the test, may be changed after the measurement, or may be set by the user.

[0099] Note that the signal feature quantity is not limited to the above calculation method, as long as it is a value calculated from frequency component data so as to appropriately include the position information of the defect portion D. In the above example, the P-P value of the time-domain signal waveform h(t) is used as the signal feature quantity. However, the absolute value of h(t) may be calculated, and the area of ​​h(t) may be calculated as the signal feature quantity. Here, the area may be calculated by sampling h(t) at appropriate time intervals and calculating the sum of h(t) at the sampling points. Furthermore, the squared value of h(t) may be used instead of the absolute value of h(t). Furthermore, instead of using Equations (2) and (3), the sum of the absolute values ​​of the frequency component H(ω) for the input frequency set {ω} may be used as the signal feature quantity.

[0100] Figure 9 is a diagram showing a typical distribution of frequency components (frequency spectrum) of a received signal. In Figure 9, the horizontal axis represents frequency and the vertical axis represents component strength (intensity). The vertical axis is shown on a logarithmic scale, showing a typical wide range of intensity.

[0101] Strong frequency components appear near the fundamental frequency f0 of the wave packet 10 that constitutes the burst wave. The frequency components of the signal have a spread around the fundamental frequency f0, which is called the fundamental wave band W1. Therefore, the fundamental wave band W1 is a range of frequency components that have a spread around the fundamental frequency f0. The fundamental frequency f0 is equal to the excitation frequency fex.

[0102] A component with a frequency N times the fundamental frequency f0 (N×f0) is a harmonic. A component with a frequency 1 / N times the maximum component frequency f0 (f0 / N) is a sub-harmonic. Here, N is an integer N≧2. Harmonics and sub-harmonics also have a spread. In this disclosure, when it is particularly emphasized that harmonics and sub-harmonics have a frequency spread, they are called harmonic bands and sub-harmonic bands, respectively. Therefore, even when simply referred to as "harmonics," they have a frequency spread. Harmonic bands and sub-harmonic bands are generated by nonlinear phenomena, and occur when the sound pressure of the ultrasonic beam U input to the object E to be inspected is extremely strong.

[0103] When gas G is interposed between the transmitting probe 110 and the object under test E as in the first embodiment, it is generally difficult to introduce an ultrasonic beam U with a strong sound pressure into the object under test E, and therefore at least one of the harmonic bands or sub-harmonic bands is often not observed. Even under the conditions of the first embodiment, the harmonic bands and sub-harmonic bands were below the detection limit.

[0104] As shown in Figure 9, the fundamental wave band W1 has a wide frequency range. Within the fundamental wave band W1, frequency components other than the component of the fundamental frequency f0 will be referred to as "skirt components W3." Although not shown in Figure 9, side lobes (peaks) of the fundamental wave band W1 may appear at frequencies slightly shifted from the fundamental frequency f0. Since the side lobes are included in the fundamental wave band W1 and are frequency components shifted from the fundamental frequency f0, the skirt components W3 also include the side lobes of the fundamental wave band W1.

[0105] In Figure 9, the frequency range on the horizontal axis is a wide range from 0 Hz to 2 x f0 or more. Looking at this wide frequency range, it can be seen that the fundamental wave band W1 of the signal in this embodiment is contained within a relatively narrow range centered on the fundamental frequency f0. This is because a burst wave with a wave number N0 of 2 or more is used. In contrast, if a pulse voltage consisting of a wave number N0 of 1 is applied, the result will be a high-bandwidth signal that spans a wide frequency range.

[0106] 10 is a diagram showing the spectrum of the fundamental wave band W1 of the received signal of the ultrasonic beam U that has passed through the object under test E. The fundamental frequency f0 is 0.82 MHz, and the horizontal axis indicates a relatively narrow range of 0.70 to 0.90 MHz.

[0107] In FIG. 10, the solid line represents the spectrum observed when a healthy portion N of the object E is observed, and the dashed line represents the spectrum observed when a defective portion D is observed. The spectra of the healthy portion N and the defective portion D are compared. The difference between the spectra is greater in a frequency range of, for example, 0.75 to 0.80 MHz, which is shifted from the fundamental frequency f0, than in the spectrum at the fundamental frequency f0 = 0.82 MHz. In this embodiment, the defective portion D in the object E is detected by detecting changes in the signal intensity of the healthy portion N and the defective portion D. Therefore, the greater the difference between the two (the difference between the spectra), the easier it is to detect a defect. In other words, detecting frequency components at frequencies shifted from the fundamental frequency f0 improves the detection performance of the defective portion D. As described above, the frequency components of the fundamental wave band W1 other than the fundamental frequency f0 are the skirt components W3.

[0108] In this way, shifting the detection frequency fdet from the excitation frequency fex (fundamental frequency f0) is effective in improving the detection performance of the defect D. However, at a frequency shifted from the excitation frequency fex, the component strength (signal strength) is not maximum, and therefore there is a problem that the frequency component may become small as described above.

[0109] FIG. 11 is a diagram schematically showing the spectrum of the fundamental wave band W1. The vertical axis represents the intensity of the frequency component (component intensity), and the horizontal axis represents frequency. The solid line represents the case where wave number N0 is 10, and the dashed line represents the case where wave number N0 is 30. The spectrum of the fundamental wave band W1, whether shown as a solid line or a dashed line, is maximum at the fundamental frequency f0, as shown in FIG. 11. Therefore, as described above, at frequencies shifted from the fundamental frequency f0 (detection frequency fdet in FIG. 11), the frequency components become relatively small.

[0110] Increasing the wave number N0 of the burst wave increases the frequency components of the excitation frequency fex. However, because the bandwidth of the fundamental wave band W1 narrows, the frequency components of frequencies shifted from the excitation frequency fex do not increase, or rather decrease.

[0111] Figure 12 is a diagram explaining the meaning of bandwidth. The vertical axis represents spectral intensity (component intensity), and the horizontal axis represents frequency. Bandwidth (FWHM) refers to the full width at half maximum, which is the width of the frequency at which the spectral intensity is half the peak intensity at frequency fm where the spectral intensity is maximum. Note that the frequency fm where the spectral intensity is maximum is equal to the fundamental frequency f0 for a single burst wave. The full width at half maximum (FWHM) ratio is defined as the value normalized by the fundamental frequency f0. That is, the full width at half maximum (FWHM) ratio is expressed by the following equation: FWHM ratio = full width at half maximum / f0 The FWHM ratio is a measure of the bandwidth.

[0112] FIG. 13 is a diagram showing the relationship between the wave number N0 and the bandwidth (FWHM) of the fundamental wave band W1. The horizontal axis represents the wave number N0, and the vertical axis represents the FWHM ratio. As shown in FIG. 13, as the wave number N0 increases, the FWHM ratio decreases. For this reason, as schematically shown in FIG. 11 above, as the wave number N0 increases, the peak becomes steeper, and the signal component at the detection frequency fdet actually decreases.

[0113] As described above, when using a conventional burst waveform such as that shown in Fig. 7, it is difficult to increase the frequency component of a frequency shifted from the excitation frequency fex. Therefore, in this embodiment, this problem is solved by using a burst wave composed of a wave packet group having multiple wave packets, as shown in Fig. 8.

[0114] If the fundamental frequency of a wave packet (for example, wave packet 10 (first wave packet)) is f0, the frequencies detected by the signal processing unit 250 (FIG. 6) preferably include frequencies in the range of (f0±0.25f0). This is because signal components containing information about the defect D appear in the frequency range of f0±0.25f0. Therefore, by including frequencies in this range, the detection accuracy of the defect D can be improved.

[0115] Furthermore, it is preferable that the full width at half maximum of the frequency spectrum of the fundamental wave band W1 is 50% or less of the fundamental frequency f0 of the wave packet. In other words, it is preferable that the FWHM ratio is 50% or less. This improves the detection accuracy of the defect D. As described above, the fundamental wave band W1 is a range of frequency components that has a spread before and after the fundamental frequency f0.

[0116] Furthermore, it is preferable that the wave number of the wave packet (for example, wave packet 10 (first wave packet)) is equal to or less than 30. This makes it possible to widen the full width at half maximum.

[0117] FIG. 14 is a diagram showing a typical spectrum of a received signal when a burst wave composed of a wave packet group having multiple wave packets is used. FIG. 14 shows the case where the wave number N0 of wave packets 10 and 11 is 5. When the inter-wave packet time ΔtI is zero (ΔtI = 0, i.e., αI = 0), the two wave packets are continuously connected, resulting in the same configuration as a single wave packet with wave number N0 = 10 (see FIG. 13 above; however, the shape in FIG. 14 is slightly modified from that in FIG. 13). Note that αI here is the inter-wave packet wave number, the definition of which will be described later. The spectrum in this case has a shape with a peak at the fundamental frequency f0, as shown by the dotted line in FIG. 14. In contrast, when the inter-wave packet time ΔtI is 0.5 waves (ΔtI = 0.5 waves, i.e., αI = 0.5), the spectrum includes two peaks sandwiching the fundamental frequency f0, as shown by the solid line in FIG. 14. Therefore, the frequency component becomes stronger at the detection frequency fdet, which is a frequency shifted from the fundamental frequency f0.

[0118] As will be described in detail later, it is theoretically easier to handle the inter-wave packet time ΔtI using the inter-wave packet wave number αI. The inter-wave packet wave number αI is a value normalized by the fundamental period T0 of wave packet 10. In other words, αI = ΔtI / T0. Therefore, the above "ΔtI = 0.5 waves" has the same meaning as "αI = 0.5" as above.

[0119] FIG. 15 shows the plot of the magnitude of frequency components at the detection frequency fdet when the inter-wave packet wave number αI is changed. The horizontal axis represents the inter-wave packet wave number αI, and the vertical axis represents the magnitude of frequency components at the detection frequency fdet. FIG. 15 shows an example where the fundamental frequency f0 = 0.82 MHz and the detection frequency fdet = 0.74 MHz. Therefore, the fundamental frequency f0 is different from the detection frequency fdet of the ultrasonic beam U by the receiving probe 140. In other words, the detection frequency fdet of the ultrasonic beam U by the receiving probe 140 is different from the fundamental frequency f0. αI = 0 represents a single wave packet burst wave, i.e., a conventional configuration. If the magnitude of the frequency component when αI = 0 is 1, then when αI = 0.5 waves, the magnitude of the frequency component at the detection frequency fdet increases by 21 times.

[0120] In this way, by making the burst wave signal applied to the transmitting probe 110 a signal that repeats a wave packet group having multiple wave packets, it is possible to increase the frequency components at frequencies shifted from the fundamental frequency f0. As described above, the components of the scattered wave U1 at the defect D in the object under test E are largely contained in the skirt component W3 of the fundamental wave band W1, which is shifted from the fundamental frequency f0. Therefore, according to this embodiment, by appropriately setting the inter-wave packet time tI (inter-wave packet wave number αI), it is possible to obtain the effect that the defect D becomes easier to detect.

[0121] The signal processing unit 250 (FIG. 6) detects a skirt component W3 that is different from the fundamental frequency f0 of the wave packet within the range of the fundamental wave band W1 from the frequency domain signal output from the frequency conversion unit 230. This improves the detection performance of the defect D. As described above, the fundamental wave band W1 is a range of frequency components that has a spread before and after the fundamental frequency f0.

[0122] (Frequency components of multiple wave packet burst waves) The operation of this embodiment will be described below: The spectrum of a burst wave composed of a plurality of wave packets is theoretically obtained.

[0123] FIG. 16 is a diagram showing a wave packet group consisting of two wave packets. This wave packet group becomes a burst wave that repeats with a repetition period Tr. The waveform of wave packet 10 is generally represented by f1(t). The waveform of wave packet 11 is f1(t-Δtd). Therefore, the waveform of the wave packet group is expressed by the following equation.

[0124]

number

[0125] Using the Fourier transform shift theorem, we can find the Fourier transform F1(ω) of f(t) as follows:

[0126]

number

[0127] Equation (5) is a complex number. The magnitude of the frequency component is the absolute value of F(t) in equation (5), so it is the square root of the product of F(t) and its complex conjugate. This can be calculated as follows:

[0128]

number

[0129] Here, the wave packet delay amount αd is an amount that expresses the wave packet delay time Δtd in units of the fundamental period T0, as shown in equation (7).

[0130]

number

[0131] Furthermore, in the above equation (6), the frequency is expressed as frequency f, not as angular frequency ω. As shown in equation (8), equation (6) can be expressed using an interference function K(f, f0, αd).

[0132]

number

[0133] The function form of the interference function K(f, f0, αd) is expressed by equation (9).

[0134]

number

[0135] In the above equation (8), |F1(f)| on the right side represents the spectrum of the wave packet 10 alone. That is, the spectrum of the burst wave composed of multiple wave packets shown in Fig. 16 is obtained by multiplying the spectrum of the wave packet 10 alone by the interference function K(f, f0, αd).

[0136] (Frequency characteristics of interference function) Next, the spectrum of equation (8) and the interference function of equation (9) will be shown using a specific example.

[0137] 17A is a diagram showing an example of a burst wave of a single wave packet, which is a conventional example, when the wave packet delay amount αd=5 (wave number between wave packets αI=0). FIG. 17B is a diagram showing an example of a burst wave composed of multiple wave packets of this embodiment, when the wave packet delay amount αd=5.5 (wave number between wave packets αI=0.5). In FIGS. 17A and 17B, the fundamental frequency f0 of the wave packet 10 is 0.82 MHz, and the wave number N0 is 5.

[0138] Here, the relationship between the wave packet delay time Δtd, i.e., the delay time between the leading times of wave packet 10 and wave packet 11, and the inter-wave packet time ΔtI will be summarized. As can be seen from FIG. 8 above, the following relationship, Equation (10), holds between the wave packet delay time Δtd and the inter-wave packet time ΔtI. Here, N0 is the wave number of wave packet 10, and T0 is the fundamental period of wave packet 10.

[0139]

number

[0140] Therefore, the following equation (11) holds between the wave packet delay amount αd and the inter-wave packet wave number αI.

[0141]

number

[0142] (Definition and terminology of wave packet delay time Δtd and inter-wave packet time ΔtI) Here, the quantities representing the delay times of wave packets 10 and 11 will be organized. As described above, the wave packet delay time Δtd is the time from the start time of wave packet 10 to the start time of wave packet 11. In contrast, the wave packet inter-time ΔtI is the time from the end time of wave packet 10 to the start time of wave packet 11, as described above.

[0143] Comparing the wave packet delay time Δtd and the wave packet inter-time ΔtI, the wave packet delay time Δtd is a quantity that is easier to express the interference function K. On the other hand, using the wave packet inter-time tI has the advantage of making the difference from the conventional single wave packet burst wave clear. In other words, ΔtI = 0 corresponds to the conventional single wave packet burst wave. For this reason, in this specification, the wave packet delay time Δtd and the wave packet inter-time ΔtI are used together.

[0144] As can be seen from the above equations (6) and (9), it is easier to understand the wave packet delay time Δtd when expressed as a wave packet delay amount αd divided by the fundamental period T0 of the wave packet 10. For this reason, the wave packet delay amount αd is also used. Similarly, the inter-wave packet wave number αI obtained by dividing the inter-wave packet time ΔtI by the fundamental period T0 of the wave packet 10 is also used.

[0145] 17A and 17B, the solid line is the spectrum expressed by equation (8), and the dashed line is the interference function K(f, f0, αd) expressed by equation (9). In either case, it can be seen that the spectrum shown by the solid line is strongly influenced by the frequency characteristics of the interference function K(f, f0, αd) shown by the dashed line. Hereinafter, the interference function K(f, f0, αd) will be abbreviated as the interference function K, etc.

[0146] The interference function K is a periodic function of frequency f, and acts like a comb filter. The frequency position where the value of the interference function K (value of the frequency component) is minimum is called a "node," and the frequency position where the value of the interference function K is maximum is called an "antinode." Because the interference function K is a periodic function, nodes and antinodes alternate.

[0147] In Figure 17A, the interference function K reaches its maximum position, i.e., its antinode, at the position of the fundamental frequency f0. Therefore, the frequency component at the fundamental frequency f0 = 0.82 MHz is the largest. On the other hand, the detection frequency fdet = 0.74 MHz is close to the node of the interference function K, so the frequency component is small.

[0148] In the case of FIG. 17B, which is an example of this embodiment, the value of the interference function K indicated by the dashed line reaches a maximum value near the detection frequency fdet. That is, the frequency position near the detection frequency fdet is the position of the antinode. Therefore, the frequency component of the burst wave also becomes large. Therefore, the signal at the detection frequency can be efficiently acquired.

[0149] Similarly, by setting the wave packet delay amount αd to an appropriate value and setting the position of the loop of the interference function K, it is possible to increase the desired frequency component.

[0150] Figure 18A shows the spectrum (solid line) and interference function (dashed line) when the wave packet delay amount αd = 5.25 (wave number between wave packets αI = 0.25). The frequency components of approximately 0.7 MHz to 0.8 MHz (especially around 0.77 MHz), which is shifted from the fundamental frequency f0 = 0.82 MHz, are large. Therefore, the wave packet delay amount αd = 5.25 used in the calculation of Figure 18A is an αd value suitable when using a detection frequency fdet of approximately 0.77 MHz.

[0151] Figure 18B shows the spectrum (solid line) and interference function (dashed line) for a wave packet delay of αd = 5.75 (wave packet wave number αI = 0.75). The frequency component of approximately 0.86 MHz, which is shifted from the fundamental frequency f0 = 0.82 MHz, is large. Therefore, a wave packet delay of αd = 5.75 is an appropriate αd value when using a detection frequency fdet of approximately 0.86 MHz.

[0152] 18A and 18B, how the peak indicated by the solid line deviates from the fundamental frequency f0, specifically, whether it deviates to a frequency lower than the fundamental frequency f0 or a frequency higher than the fundamental frequency f0, varies depending on the magnitude of the wave packet delay amount αd. Therefore, it is preferable to compare the magnitude of the peak occurring on the frequency lower than the fundamental frequency f0 with the magnitude of the peak occurring on the frequency higher than the fundamental frequency f0, and use the relatively larger peak for detection. Specifically, it is preferable to set the detection frequency fdet on the side where the relatively larger peak exists.

[0153] (Why it is periodic with respect to the wavenumber αI between wave packets) The reason why the relationship between the magnitude of the frequency component and the inter-wave packet wave number αI has the dependency shown in FIG. 15 will be explained below.

[0154] FIG. 19A is a graph plotting the magnitude of frequency components with respect to the inter-wave packet wavenumber when the detection frequency fdet is 0.74 MHz. FIG. 19B is a graph plotting the magnitude of frequency components with respect to the inter-wave packet wavenumber when the detection frequency fdet is 0.76 MHz. FIG. 19C is a graph plotting the magnitude of frequency components with respect to the inter-wave packet wavenumber when the detection frequency fdet is 0.82 MHz. FIG. 19D is a graph plotting the magnitude of frequency components with respect to the inter-wave packet wavenumber when the detection frequency fdet is 0.90 MHz. In all cases, the fundamental frequency f0 of wave packet 10 is 0.82 MHz, and the wave number of wave packet 10 is 5 waves.

[0155] In each figure, the solid line represents the magnitude of the frequency component calculated from a waveform composed of two wave packets. The dashed line represents a plot of the interference function K of equation (9). The dashed line represents a conventional example (a conventional example in which a burst wave composed of only one wave packet is applied). Therefore, the greater the difference between this embodiment shown by the solid line and the graph shown by the dashed line (straight line), the greater the value of the detected frequency component (vertical axis).

[0156] Comparing the solid line and the dashed line, the shapes of the two correspond well, and it can be seen that the dependence of the frequency component shown by the solid line on αI mainly corresponds to the interference function K. In equation (9), when the frequency f is fixed, it becomes a periodic function of the wave packet delay amount αd, and this periodicity appears in Figures 19A to 19D.

[0157] Under the condition of detection frequency fdet=0.74 MHz shown in FIG. 19A, the value of the interference function K is small when αI=0, which corresponds to a single wave packet burst wave (dash-dotted line). The frequency component reaches a maximum near αI=0.5. The frequency component becomes zero near αI=1.1. Therefore, in FIG. 19A, by setting αI so that the magnitude of the frequency component (solid line) exceeds the value (dash-dotted line) at αI=0, the detected frequency component can be increased, thereby improving the detection performance of the defect D. That is, αI can be set within a range in FIG. 19A where the solid line is above the dash-dotted line. In other words, it is preferable that the inter-wave packet wavenumber αI be an inter-wave packet wavenumber αI that results in a frequency component that is greater than the frequency component when the inter-wave packet wavenumber αI, which is the wavenumber between multiple wave packets, is zero (αI=0). That is, it is preferable that the transmitting probe 110 emits the ultrasonic beam U by applying a voltage waveform having an inter-wave packet wave number αI with a frequency component greater than the frequency component when the inter-wave packet wave number αI is zero. This can improve the detection performance of the defect D.

[0158] 19B, the magnitude of the frequency component becomes large when αI=0. Specifically, the magnitude of the frequency component is located at the position of the dashed-dotted line in FIG. 19B. Even in this case, the detection performance of the defect D can be improved by setting the inter-wavepacket wavenumber αI within a range where the inter-wavepacket wavenumber αI is such that the magnitude of the frequency component (solid line) becomes larger than the value (dashed-dotted line) when αI=0.

[0159] In the case shown in Figure 19C, the fundamental frequency f0 is the detection frequency fdet, and this is the conventional method of detecting by making the fundamental frequency f0 (= excitation frequency fex) equal to the detection frequency fdet. In this case, the frequency component reaches a maximum when αI = 0. This shows that it is better to use a single wave packet burst wave as usual.

[0160] 19C shows that setting the inter-wavepacket wavenumber αI to a value other than zero, as in the present disclosure, is effective when the detection frequency fdet is shifted from the fundamental frequency f0. Therefore, the inter-wavepacket wavenumber αI that has a frequency component larger than the frequency component when the inter-wavepacket wavenumber αI is zero (αI = 0) can be set by making the fundamental frequency f0 and the detection frequency fdet different (i.e., making them different).

[0161] In the case of FIG. 19D, similarly to the above-described FIGS. 19A and 19B, the inter-wave packet wave number αI is set to a value other than zero to increase the magnitude of the detected frequency component, thereby improving the detection performance of the defect D.

[0162] As described above, by setting the inter-wavenumber αI within a range in which the magnitude of the frequency component at the detection frequency fdet is larger than the value at αI=0, the frequency component can be increased, thereby improving the detection performance of the defect D.

[0163] 19A to 19D, the intensity of the frequency component at the detection frequency fdet corresponds to the magnitude of the interference function K. Therefore, by setting the inter-wavenumber αI within a range in which the value of the interference function K is larger than when αI=0, the detection performance of the defect D can be improved.

[0164] More preferably, in the relationship between the interference function K and the wave packet delay amount αd, the wave packet delay amount αd is set in a range such that the value of the interference function K is greater than half the maximum value of the interference function K. This increases the frequency component at the detection frequency fdet, thereby improving the detection performance of the defect portion D, which is even more preferable.

[0165] Therefore, in the example of the present disclosure, the signal processing unit 250 (FIG. 6) detects a frequency component at which the value of the interference function K is equal to or greater than half the maximum value of the interference function K. This improves the performance of detecting the defect D. Note that the interference function K is a function whose parameters are the wave packet delay time Δtd between wave packet 10 (first wave packet) and wave packet 11 (second wave packet) among the multiple wave packets, and the fundamental frequency f0 of wave packet 10.

[0166] The wave packet delay amount αd and the inter-wave packet wave number αI are related by the above formula (11). Therefore, it goes without saying that setting the wave packet delay amount αd is equivalent to setting the optimum range of the inter-wave packet wave number αI.

[0167] As expressed in the above formula (7), the wave packet delay amount αd is the wave packet delay time Δtd expressed in wave number units. Therefore, it goes without saying that setting the wave packet delay amount αd to an appropriate value is equivalent to setting the wave packet delay time Δtd to the corresponding appropriate value. Similarly, it is also clear that setting the inter-wave packet wave number αI to an appropriate value is equivalent to setting the wave packet delay time Δtd to an appropriate value.

[0168] (Second embodiment) A second embodiment of the present disclosure will be described with reference to Figures 20A and 20B. This embodiment is an example in which the wave packet delay time Δtd is made longer than that of the first embodiment.

[0169] 20A is a diagram showing a burst wave signal composed of two wave packets in the second embodiment. A wave packet group including these two wave packets is repeated with a repetition period Tr=5 ms. The horizontal axis represents time and the vertical axis represents signal voltage. The conditions are that the fundamental frequency of the wave packet f0=0.82 MHz, the wave number N0 of wave packets 10 and 11=5, and the wave packet delay amount αd=10.5. The frequency conversion period will be described later.

[0170] FIG. 20B is a diagram showing the spectrum (solid line) and interference function K (dashed line) for the burst wave shown in FIG. 20A. The horizontal axis represents frequency, and the vertical axis represents the magnitude of the frequency component. In this case, too, due to the influence of the interference function K, the frequency component at the fundamental frequency (center frequency) f0=0.82 MHz decreases, and the signal components at 0.78 MHz and 0.86 MHz that deviate from the fundamental frequency f0 increase. In this way, of the fundamental wave band W1 around the fundamental frequency f0, the skirt component W3, which is the component that deviates from the fundamental frequency f0, increases. This has the effect of making it easier to detect the defect D.

[0171] One of the important points in this disclosure is the selection of the frequency conversion period (FIG. 20A) when converting a time domain waveform into a frequency domain signal (spectrum) in frequency conversion section 230 (FIG. 6). The frequency conversion period may be set to a range that includes wave packets 10 and 11, as shown in FIG. 20A.

[0172] The frequency conversion period corresponds to the range for taking the sum of the above formula (1). By converting into frequency components in this manner within the range of the frequency conversion period spanning two wave packets (i.e., a range including at least two wave packets), the two wave packets interfere in the frequency domain, generating an interference function K. As described above, the effects of the present disclosure are obtained by the action of this interference function K.

[0173] Therefore, even if a method such as inverting the phase of the wave packet for each repetition period Tr of the burst wave is used, or if frequency conversion is performed for each wave packet, the effect of the present disclosure cannot be obtained. The effect of the present disclosure can be obtained by applying multiple wave packets for each repetition period Tr.

[0174] Next, when the wave packet delay amount αd is made larger than the wave number N0, the inter-wave packet wave number αI becomes larger. In this way, even when damped vibration of the oscillator 111 (piezoelectric oscillator) of the transmitting probe 110 occurs, the effect on the wave packet 11 is reduced. That is, this effect can be obtained by setting the inter-wave packet wave number αI larger than the wave number of the damped vibration of the transmitting probe 110. The wave number of the damped vibration of the transmitting probe 110 is typically about 2 to 3 waves.

[0175] The damped vibration of the vibrator 111 of the transmitting probe 110 refers to a phenomenon in which the vibration of the vibrator 111 does not immediately stop even after the voltage applied to the transmitting probe 110 is reduced to zero, but the vibration amplitude gradually attenuates and stops.

[0176] (Third embodiment) 21A and 21B, a third embodiment of the present disclosure will be described. This embodiment is an example in which the wave packet delay time Δtd is made longer than that of the first embodiment.

[0177] 21A is a diagram showing a burst wave signal composed of two wave packets in the third embodiment. A wave packet group including these two wave packets is repeated with a repetition period Tr=5 ms. The horizontal axis represents time and the vertical axis represents signal voltage. The conditions are that the fundamental frequency of the wave packet f0=0.82 MHz, the wave number N0 of wave packet 10 and wave packet 11=5, and the wave packet delay amount αd=20.5.

[0178] FIG. 21B shows the spectrum (solid line) and interference function K (dashed line) for the burst wave shown in FIG. 21A. As the wave packet delay amount αd increases, the period of the interference function K becomes shorter. This can also be seen from the equation for the interference function K in equation (9) above. For this reason, the spectrum (solid line) becomes more fragmented, but the frequency components at frequencies deviating from the fundamental frequency f0 still become larger. In the case of FIG. 21B, the frequencies of the second largest frequency components are 0.76 MHz and 0.88 MHz. In this way, frequency components deviating from the fundamental frequency f0 by approximately ±5% can be efficiently acquired.

[0179] In this embodiment, the frequency conversion period of the frequency conversion unit 230 is also set to include two wave packets (wave packet 10 and wave packet 11). By setting it in this way, the two wave packets interfere in the frequency domain, and an interference function K is generated.

[0180] (Fourth embodiment) A fourth embodiment of the present disclosure will be described with reference to Figures 22A and 22B. In this embodiment, the amplitudes of wave packets 10 and 11 are set to be different from each other.

[0181] 22A is a diagram showing a burst wave signal composed of two wave packets in the fourth embodiment. A wave packet group including these two wave packets is repeated with a repetition period Tr=5 ms. The horizontal axis represents time and the vertical axis represents voltage (signal voltage). The conditions are that the fundamental frequency of the wave packet f0=0.82 MHz, the wave number N0 of wave packet 10 and wave packet 11=5, and the wave packet delay amount αd=5.5. The amplitude of wave packet 11 is 1 / 2 of the amplitude of wave packet 10.

[0182] 22B is a diagram showing the spectrum (solid line) and interference function K (dashed line) for the burst wave shown in FIG. 22A. As shown in FIG. 22B, even if the amplitudes of wave packet 10 and wave packet 11 are set to be different, the frequency components at frequencies shifted from the fundamental frequency f0 become larger, and the effects of the present disclosure are obtained. In this case, the function form of interference function K is different from that of equation (9) above, but the function form of interference function K is the same as in the first embodiment in that it is a periodic function with periodic antinodes and nodes. Therefore, the effects of the present invention are obtained.

[0183] If the amplitudes of the wave packets 10 and 11 are b1 and b2, respectively, the function form of the interference function K(f, f0, αd) is expressed by the following equation.

[0184]

number

[0185] When b1 = b2 = 1, the interference function K is the same as the above equation (9). In this way, even if the function form is different from equation (9), the effect of the present disclosure can be obtained because the function that has a maximum (antinode) with respect to frequency f is the interference function K. Specifically, the wave packet delay amount αd can be determined so that the frequency to be detected is near the maximum value of the interference function K. The dashed line in FIG. 22B indicates the interference function K of equation (12).

[0186] (Fifth embodiment) 23A and 23B, a fifth embodiment of the present disclosure will be described. In this embodiment, wave packets 10 and 11 are set so that their fundamental frequencies f0 are different. That is, the fundamental frequencies f0 of the multiple wave packets are different.

[0187] 23A is a diagram showing a burst wave signal composed of two wave packets in the fifth embodiment. A wave packet group including these two wave packets is repeated with a repetition period Tr=5 ms. The horizontal axis represents time, and the vertical axis represents voltage (signal voltage). The conditions are as follows: fundamental frequency f0 of wave packet 10=0.82 MHz, wave number N0 of wave packets 10 and 11=5, and wave packet delay amount αd=5.5. The fundamental frequency f0 of wave packet 10 was set to f0=0.82 MHz, and the fundamental frequency f0 of wave packet 11 (fundamental frequency f02)=0.86 MHz (period is T02).

[0188] Fig. 23B is a diagram showing the spectrum of the burst wave shown in Fig. 23A. The spectrum has a maximum value at a frequency of 0.78 MHz, which is 40 kHz shifted from the fundamental frequency f0, and the frequency components shifted from the fundamental frequency f0 (the skirt components of the fundamental wave band) are large. This improves the detection of defect D. In this way, the effects of the present invention can be obtained even when the fundamental frequencies f0 of wave packet 10 and wave packet 11 are set to be different (the fundamental frequencies f0 of the multiple wave packets are different).

[0189] (Sixth embodiment) FIG. 24 is a block diagram showing the configuration of an ultrasonic inspection device Z according to a sixth embodiment. The ultrasonic inspection device Z according to the sixth embodiment includes a display device 3 that displays an interference function K, and an input device 4 that inputs an appropriate wave packet delay amount Δαd. In this embodiment, the display device 3 and the input device 4 are integrated and are a common device. A user can input the wave packet delay amount Δαd from the input device 4. The interference function K is calculated from the input wave packet delay amount Δαd, and the calculated interference function K is displayed on the display device 3. A specific method of calculation will be described later.

[0190] 25 is a diagram showing an example of a display screen of the display device 3 of the sixth embodiment. The display screen 270 has a defect image display section 276, on which an image 273 showing a defect portion D obtained as a result of measurement is displayed. The display screen 270 has a spectrum display section 271, on which a frequency spectrum is displayed. The display screen 270 is provided with a wave packet delay amount input section 275, into which a wave packet delay amount Δαd can be input.

[0191] When the wave packet delay amount Δαd is input from the input device 4 shown in FIGS. 24 and 25, the spectrum calculation unit 223 calculates the interference function K using this wave packet delay amount Δαd. The spectrum calculation unit 223 displays the calculated interference function K on the spectrum display unit 271. A good display method is to superimpose the interference function K on the spectrum, for example. Displaying it in this manner allows the user to visually select a region where the difference between the spectrum and the interference function K is large, making it possible to determine an appropriate wave packet delay amount Δαd that matches the frequency region to be detected. The above equation (9) can be used, for example, to calculate the interference function K.

[0192] Furthermore, instead of displaying the interference function K, the spectrum calculation unit 223 may calculate a predicted frequency spectrum using the wave packet delay amount Δαd and superimpose and display it on the spectrum display unit 271. If the wave packet delay amount Δαd is given, the time waveform can be calculated, and the frequency spectrum can be calculated using a Fourier transform or the like.

[0193] Alternatively, instead of inputting the wave packet delay amount Δαd, a detection frequency to be detected may be designated, and the spectrum calculation unit 223 may calculate a wave packet delay amount Δαd appropriate for that frequency and display the predicted spectrum of the calculation result. This is preferable because it allows the operator (user of the ultrasonic inspection device Z) to set the measurement conditions more easily.

[0194] As shown in Fig. 25, a detection frequency designation unit 272 may be provided to designate a detection frequency. An example of an interface for the detection frequency designation unit 272 is a slider button for designating the position of the detection frequency fdet. Alternatively, the slider button may be given a range so that a frequency range can be designated. After the user has designated a frequency, the user can press an update button 274 to update the display content of the display device 3.

[0195] 24, when there are three or more wave packets, the delay time setting unit 213 sets a plurality of wave packet delay times Δtd for each wave packet. The set wave packet delay times Δtd are output to the waveform generator 211. Furthermore, information input by a user via the input device 4, for example, is input to the delay time setting unit 213 via the reception unit 224. Then, the delay time setting unit 213 sets the wave packet delay time Δtd based on the input information.

[0196] Furthermore, the delay time setting unit 213 sets the wave packet delay time Δtd such that the value of the interference function K is equal to or greater than half the maximum value of the interference function K. This makes it possible to detect the defect D using a frequency component different from the fundamental frequency f0. Note that the interference function K is a function whose parameters are the wave packet delay time Δtd between the wave packet 10 (first wave packet) and the wave packet 11 (second wave packet) among the multiple wave packets, and the fundamental frequency f0 of the wave packet 10.

[0197] Seventh embodiment 26 is a diagram showing an example of a display screen of the display device 3 of the seventh embodiment. The display screen 270 includes an interference function display section 277, which displays an interference function K with the wave packet delay amount αd on the horizontal axis.

[0198] A desired detection frequency fdet is determined in advance, and the magnitude of the interference function K versus the wave packet delay amount αd is plotted in the interference function display unit 277 using, for example, the interference function K of the above equation (9). A user (measurer) of the ultrasonic inspection device Z can refer to the value of the interference function K displayed in the interference function display unit 277, input an appropriate value for the wave packet delay amount αd into the wave packet delay amount input unit 275, and set the wave packet delay amount αd.

[0199] In the above explanation, an example was given in which the wave packet delay amount αd was used as a parameter, but the inter-wave packet wave number αI may also be used as a parameter. As mentioned above, the inter-wave packet wave number αI and the wave packet delay amount αd are quantities that can be associated by the above equation (11), so the parameter value of either one can be easily calculated from the other. In FIG. 26, the horizontal axis of the interference function display unit 277 may represent the inter-wave packet wave number αI. Also, the wave packet delay amount input unit 275 may be a user interface for inputting the inter-wave packet wave number αI. If necessary, it can be converted to the wave packet delay amount αd internally using equation (11).

[0200] When the inter-wave packet wave number αI is used, αI=0 corresponds to the continuous waveform of the conventional example, and therefore has the advantage of being intuitively easy to understand.

[0201] Furthermore, the wave packet delay time Δtd may be used instead of the wave packet delay amount αd. The two can be converted to each other using equation (7). Furthermore, the wave packet inter-wave number αI may be replaced by the wave packet inter-time ΔtI. The two can be converted to each other using an equation corresponding to equation (7). That is, the conversion can be performed using ΔtI = αI × T0.

[0202] When the inter-wave packet wave number αI is used, it is possible to intuitively understand how many periods of the fundamental period T0 the time interval is, which has the advantage of being easier to understand than the inter-wave packet time ΔtI.

[0203] 26, a spectrum display section 271 may be added. By referring to both the spectrum display section 271 and the interference function display section 277, the user can easily select an appropriate detection frequency fdet and wave packet delay amount αd. The spectrum display section 271 and the interference function display section 277 may be individually arranged and displayed on the screen. Alternatively, the interference function display section 277 may be switched to display the spectrum.

[0204] (Eighth embodiment. Focal length of receiving probe 121) In the eighth embodiment, the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. This is more preferable because, as will be described later, it becomes possible to detect more of the scattered wave U1 component. As described above, the scattered wave U1 is an ultrasonic beam U that has interacted with the defect D, so the greater the proportion of the scattered wave U1 component, the easier it becomes to detect the defect D.

[0205] 27A is a diagram schematically showing the propagation path of an ultrasonic beam U in the eighth embodiment when the focal length R1 of the transmitting probe 110 and the focal length R2 of the receiving probe 121 are equal. The receiving probe 121 can detect the ultrasonic beam U within the range of the cone (shape) C2 of the virtual beam virtually emitted from the receiving probe 121. In the example shown in FIG. 27A, the convergence point of the ultrasonic beam U transmitted from the transmitting probe 110 and the convergence point of the virtual beam virtually emitted from the receiving probe 121 are the same. Therefore, the ultrasonic beam U whose propagation direction does not change at the defect D can be efficiently received. On the other hand, the ultrasonic beam U whose propagation direction changes at the defect D is difficult to detect.

[0206] FIG. 27B is a diagram schematically illustrating the propagation path of an ultrasonic beam U when the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110 in the eighth embodiment. The receiving probe 121 can detect an ultrasonic beam U within the range of a cone (shape) C3 of a virtual beam virtually emitted from the receiving probe 121. Therefore, even a scattered wave U1 (not shown in FIG. 27B) whose propagation direction has changed slightly at a defect D can be detected as long as it is within the range of the cone C3. In this way, by making the focal length R2 of the receiving probe 121 longer than the focal length R1 of the transmitting probe 110, the detectable scattered wave U1 can be increased. As described above, the scattered wave U1 is a wave that has interacted with the defect D, and this can further improve the detection performance of the defect D.

[0207] The magnitude relationship of the convergence is also defined by the magnitude relationship between the beam incident areas T1 and T2 on the surface of the inspection object E. The beam incident areas T1 and T2 will be explained below.

[0208] 28 is a diagram illustrating the relationship between the beam incident area T1 of the transmitting probe 110 and the beam incident area T2 of the receiving probe 121. The beam incident area T1 of the transmitting probe 110 at the object E under test is the area of ​​intersection of the ultrasonic beam U emitted from the transmitting probe 110 on the surface of the object E under test. The beam incident area T2 of the receiving probe 121 is the area of ​​intersection of the ultrasonic beam U2, which is a virtual ultrasonic beam U2 assuming that the ultrasonic beam U is emitted from the receiving probe 121, on the surface of the object E under test.

[0209] 28, the path of the ultrasonic beam U is shown as the path when there is no object under test E. When there is an object under test E, the ultrasonic beam U is refracted at the surface of the object under test E, and so the ultrasonic beam U propagates along a path different from the path shown by the dashed line. Here, as shown in FIG. 28, the beam incident area T2 of the receiving probe 121 at the object under test E is larger than the beam incident area T1 of the transmitting probe 110 at the object under test E. In this way, the convergence of the receiving probe 121 can be made looser than the convergence of the transmitting probe 110.

[0210] Furthermore, the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. In this way, the convergence of the receiving probe 121 can be made looser than the convergence of the transmitting probe 110. In this case, the distances from the test subject E to the transmitting probe 110 and the receiving probe 121 are, for example, the same, but they do not have to be the same.

[0211] In the example of the present disclosure, the convergence of the receiving probe 121 is set looser than the convergence of the transmitting probe 110. That is, the focal length R2 of the receiving probe 121 is set longer than the focal length R1 of the transmitting probe 110. As a result, the beam incident area T2 of the receiving probe 121 is widened, and the scattered wave U1 can be detected over a wide range. This makes it possible for the receiving probe 121 to detect the scattered wave U1 even if the propagation path of the scattered wave U1 changes slightly. As a result, the defective portion D can be detected over a wide range.

[0212] Furthermore, the focal point P1 of the receiving probe 121 is located closer to the transmitting probe 110 (above in the illustrated example) than the focal point P2 of the transmitting probe 110. By shifting the focal points P1 and P2 in this way, the receiving probe 121 can more easily receive the scattered wave U1, and the scattered wave U1 can be more easily detected.

[0213] Note that a non-converging probe (not shown) may be used as the receiving probe 121, in order to configure the focal length R2 of the receiving probe 121 to be longer than the focal length R1 of the transmitting probe 110. In the non-converging probe, the focal length R2 is infinite, so it is longer than the focal length R1 of the transmitting probe 110. In other words, even in the case of the non-converging receiving probe 121, the convergence of the receiving probe 121 is weaker than the convergence of the transmitting probe 110.

[0214] (Ninth embodiment) 28, the ninth embodiment is configured such that the beam incident area T2 of the receiving probe 121 is set larger than the beam incident area T1 of the transmitting probe. This is more preferable because it makes it possible to detect more of the scattered wave U1 components, as will be described later. As described above, the scattered wave U1 is the ultrasonic beam U that has interacted with the defect D, so the greater the proportion of the scattered wave U1 components, the easier it is to detect the defect D.

[0215] FIG. 29 is a diagram schematically illustrating the arrangement of the transmitting probe 110, the object under test E, and the receiving probe 121 in the ninth embodiment. In this embodiment, the transmitting probe 110 and the receiving probe 121 have the same focal length. However, the transmitting probe 110, the object under test E, and the receiving probe 121 are arranged so that the distance d2 between the receiving probe 121 and the surface of the object under test E is shorter than the distance d1 between the transmitting probe 110 and the surface of the object under test E. Therefore, the beam incident area T2 of the receiving probe 121 is larger than the beam incident area T1 of the transmitting probe. As a result, the scattered wave U1 can be detected over a wide range. This makes it possible for the receiving probe 121 to detect the scattered wave U1 even if the propagation path of the scattered wave U1 changes slightly. As a result, the defective portion D can be detected over a wide range.

[0216] In this embodiment, the focal lengths of the transmitting probe 110 and the receiving probe 121 are the same, but the focal lengths do not have to be the same. By appropriately setting the distance d2 between the receiving probe 121 and the surface of the object under test E, the effect of this embodiment can be obtained if the beam incident area T2 of the receiving probe 121 is wider than the beam incident area T1 of the transmitting probe 110.

[0217] (Tenth embodiment) 30 is a diagram showing the configuration of an ultrasonic inspection device Z in a tenth embodiment. In the tenth embodiment, the transmission sound axis AX1 of the transmitting probe 110 and the reception sound axis AX2 of the receiving probe 121 are arranged so as to be offset from each other. That is, the receiving probe 121 in the tenth embodiment is a receiving probe 120 (eccentrically arranged receiving probe) having a reception sound axis AX2 arranged at a position different from the transmission sound axis AX1 of the transmitting probe 110. Therefore, the eccentricity distance L (distance) between the transmission sound axis AX1 (sound axis) of the transmitting probe 110 and the reception sound axis AX (sound axis) of the receiving probe 120 is greater than zero.

[0218] This arrangement makes it possible to detect scattered waves U1 whose spatial direction has changed. By combining the principle of extracting frequency-specific scattered waves U1 based on the frequency spectrum of the received signal (Fig. 10) with the principle of extracting spatially scattered waves U1 due to eccentric arrangement, the detection performance of the defect D can be further improved.

[0219] In the tenth embodiment, the receiving probe 120 is arranged to be offset by an eccentric distance L in the x-axis direction of Fig. 30 with respect to the transmitting probe 110, but the receiving probe 120 may be arranged to be offset in the y-axis direction of Fig. 30. Alternatively, the receiving probe 120 may be arranged at L1 in the x-axis direction and L2 in the y-axis direction (i.e., if the position of the transmitting probe 110 on the xy plane is taken as the origin, then the position is (L1, L2)).

[0220] Fig. 31A is a diagram illustrating the transmission sound axis AX1, the reception sound axis AX2, and the eccentricity distance L when the transmission sound axis AX1 and the reception sound axis AX2 extend vertically. Fig. 31B is a diagram illustrating the transmission sound axis AX1, the reception sound axis AX2, and the eccentricity distance L when the transmission sound axis AX1 and the reception sound axis AX2 extend at an angle. For reference, Figs. 31A and 31B also illustrate the receiving probe 140 (coaxially arranged receiving probe) with dashed lines.

[0221] The direction of the receiving sound axis AX2 is the normal direction of the probe surface 114 (FIG. 2). The reason is that the virtual ultrasonic beam U radiated from the receiving probe 121 is emitted in the normal direction of the probe surface 114. When receiving the ultrasonic beam U, the ultrasonic beam U incident in the normal direction of the probe surface 114 can also be received with good sensitivity.

[0222] The eccentricity distance L is defined as the distance offset between the transmission sound axis AX1 and the reception sound axis AX2. Therefore, as shown in Fig. 31B, when an ultrasonic beam U emitted from the transmission probe 110 is refracted, the eccentricity distance L is defined as the distance offset between the refracted transmission sound axis AX1 and the reception sound axis AX2. In the ultrasonic inspection device Z of the tenth embodiment, the transmission probe 110 and the reception probe 120 are adjusted by an eccentricity distance adjustment unit 105 (Fig. 30) that adjusts the eccentricity distance L so that the eccentricity distance L defined in this way becomes a distance greater than zero.

[0223] FIG. 31A shows a case where the transmitting probe 110 is arranged in the normal direction to the surface of the object under test E. In FIGS. 31A and 31B, the transmitting sound axis AX1 is shown by a solid line. The receiving sound axis AX2 is shown by a dashed line. In FIGS. 31A and 31B, the position of the receiving probe 121 shown by the dashed line is a position where the eccentricity distance L is zero, and the receiving probe 121 where the transmitting sound axis AX1 and the receiving sound axis AX2 coincide is the receiving probe 140 as a coaxially arranged receiving probe. In addition, the receiving probe 121 shown by the solid line is the receiving probe 120 (eccentrically arranged receiving probe) that is arranged at a position where the eccentricity distance L is greater than zero. When the transmitting probe 110 is installed so that the transmitting sound axis AX1 is perpendicular to the horizontal plane (the xy plane in FIG. 30), the propagation path of the ultrasonic beam U is not refracted. In other words, the transmitting sound axis AX1 is not refracted. This corresponds to the case where the transmission probe 110 is installed so that the transmission sound axis AX1 of the transmission probe 110 is perpendicular to the mounting surface 1021 of the sample stage .

[0224] In this embodiment, the transmitting probe 110 is installed so that the transmission acoustic axis AX1 is normal to the mounting surface 1021 of the specimen stage 102 for the object under test E. As described above, this arrangement has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D, since the transmission acoustic axis AX1 is arranged perpendicular to the surface of the object under test E in the case of a plate-like object under test E.

[0225] FIG. 31B shows a case where the transmitting probe 110 is arranged at an angle α from the normal direction to the surface of the object under test E. As in FIG. 31A, in FIG. 31B, the transmitting sound axis AX1 is indicated by a solid line and the receiving sound axis AX2 is indicated by a dashed line. In the example shown in FIG. 31B, the propagation path of the ultrasonic beam U is refracted at a refraction angle β at the interface between the object under test E and the fluid F. Therefore, the transmitting sound axis AX1 is bent (refracted) as shown by the solid arrow in FIG. 31B. In this case, the position of the receiving probe 140 shown by the dashed line is located on the transmitting sound axis AX1, and therefore the eccentricity distance L is zero. As described above, even when the ultrasonic beam U is refracted, the receiving probe 120 is arranged so that the distance between the transmitting sound axis AX1 and the receiving sound axis AX2 is L. In the example shown in FIG. 30, the transmitting probe 110 is installed in the normal direction to the surface of the object under test E, and therefore the eccentricity distance L is as shown in FIG. 31A.

[0226] It is more preferable to set the eccentric distance L at a position where the signal strength at the defective portion D is greater than the signal strength at the healthy portion N of the object E to be inspected.

[0227] (Eleventh embodiment) 32 is a diagram showing the configuration of an ultrasonic inspection device Z in the eleventh embodiment. In the eleventh embodiment, the scanning measurement device 1 includes an installation angle adjustment unit 106 that adjusts the tilt of the receiving probe 120. This increases the strength of the received signal and the signal-to-noise ratio (SNR) of the signal. The installation angle adjustment unit 106 is configured, for example, by an actuator, a motor, etc., neither of which are shown.

[0228] Here, the angle θ formed by the transmission sound axis AX1 and the reception sound axis AX2 is defined as the receiving probe installation angle. In the case of FIG. 32, the transmitting probe 110 is installed in the vertical direction, and therefore the transmission sound axis AX1 is in the vertical direction. Therefore, the angle θ, which is the receiving probe installation angle, is the angle formed between the transmission sound axis AX1 (i.e., the vertical direction) and the normal to the probe surface of the receiving probe 120. Then, the installation angle adjustment unit 106 tilts the angle θ toward the side where the transmission sound axis AX1 exists, and sets the angle θ to a value greater than zero. In other words, the receiving probe 120 is tilted. Specifically, the receiving probe 120 is tilted so as to satisfy 0°<θ<90°, and the angle θ is, for example, 10°, but is not limited to this.

[0229] When the present inventors actually performed detection of the defect D with the receiving probe 120 inclined in this manner, the signal strength of the received signal increased three times compared to when θ=0.

[0230] Furthermore, the eccentricity distance L when the receiving probe 120 is disposed at an angle is defined as follows: An intersection point P12 between the receiving sound axis AX2 and the probe surface of the receiving probe 120 is defined. Also, an intersection point P11 between the transmitting sound axis AX1 and the probe surface of the transmitting probe 110 is defined. The eccentricity distance L is defined as the distance between the coordinate position (x4, y4) (not shown) when the position of intersection point P11 is projected onto the xy plane, and the coordinate position (x5, y5) (not shown) when the position of intersection point P12 is projected onto the xy plane.

[0231] FIG. 33 is a diagram illustrating why the eleventh embodiment provides an effect. The scattered wave U1 propagates in a direction away from the acoustic transmission axis AX1. Therefore, as shown in FIG. 33, when the scattered wave U1 reaches the outside of the object under test E, it is incident on the interface between the object under test E and the outside at a non-zero angle α2 with respect to the normal vector of the surface of the object under test E. The angle of the scattered wave U1 emitted from the surface of the object under test E is a non-zero exit angle β2 with respect to the normal direction of the surface of the object under test E. The scattered wave U1 can be received most efficiently when the normal vector of the probe surface of the receiving probe 120 is aligned with the propagation direction of the scattered wave U1. In other words, the strength of the received signal can be increased by tilting the receiving probe 120.

[0232] The reception effect is highest when the angle β2 of the ultrasonic beam U emitted from the object E matches the angle θ formed by the transmission sound axis AX1 and the reception sound axis AX2. However, even if the angle β2 and the angle θ do not match perfectly, the effect of increasing the received signal can be obtained, so as shown in Figure 33, the angle β2 and the angle θ do not have to match perfectly.

[0233] (Twelfth embodiment) 34 is a diagram showing the configuration of an ultrasonic inspection device Z according to the twelfth embodiment. In the twelfth embodiment, the fluid F is a liquid W, which is water in the illustrated example. The ultrasonic inspection device Z inspects the object E to be inspected by irradiating an ultrasonic beam U onto the object E to be inspected through the liquid W, which is the fluid F. The object E to be inspected is placed below the liquid surface L0 of the liquid W and is immersed in the liquid W.

[0234] As in the first embodiment, in this embodiment, the excitation frequency fex is set to a frequency that is shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex that is shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. Setting the excitation frequency fex to an appropriate value can improve the performance of the ultrasonic inspection device Z of this embodiment.

[0235] The fluid F may be the gas G (FIG. 1) as described above, or the liquid W (FIG. 47) as in this embodiment. However, when the gas G such as air is used as the fluid F, more preferable effects are obtained as described above.

[0236] Furthermore, as described above, when gas G is used as the fluid F, it is more difficult to reduce the beam size of the ultrasonic beam U, and therefore the effects of the present disclosure are even greater. Thus, when gas G is used as the fluid F, the present disclosure can achieve more preferable effects.

[0237] (Thirteenth embodiment) In the above explanation, sine waves have been used as examples of waves constituting a wave packet. However, the present disclosure is not limited to sine waves. In the burst wave configuration shown in FIG. 8, wave packets 10 and 11 may be composed of rectangular waves. In this case, the effects of the present disclosure can also be obtained. It is clear from the above formulas (4) to (9) that the present disclosure is not limited to a sine wave, because these formulas are valid for any waveform, without limiting the waveform of wave packet 10 to a sine wave. That is, the interference function K shown in equation (9) holds even if each wave packet is not a sine wave.

[0238] (Fourteenth embodiment) In a variation of the present disclosure, the phase of the second wave packet (wave packet 11) may be changed. 35 is a graph showing voltages when the phase of the second wave packet 11 is delayed by 180° and a wave packet delay time Δtd is set. The interference function K in this case is expressed by equation (13).

[0239]

number

[0240] When the phase is changed by an arbitrary angle other than 180°, the frequency spectrum can be calculated from the time waveform using a method such as Fourier transform.

[0241] In this specification, the case where the inter-wave packet time ΔtI is positive has been mainly described as shown in Fig. 8. However, the inter-wave packet time ΔtI is not limited to being positive, and may be negative. However, if ΔtI is negative, the two wave packets will also interfere in the time domain. For example, if the inter-wave packet time ΔtI is set to -4.5 waves, approximately four waves will overlap in antiphase, resulting in cancellation in this time domain. For this reason, it is preferable to set the inter-wave packet time ΔtI to a positive value.

[0242] FIG. 36 is a diagram showing the hardware configuration of the control device 2. Some or all of the above-described components, functions, and components constituting the block diagram may be implemented in hardware, for example, by designing them as integrated circuits. As shown in FIG. 36, the above-described components, functions, and components may be implemented in software by a processor, such as a CPU 252, interpreting and executing a program that implements each function. The control device 2 includes, for example, a memory 251, a CPU 252, a storage device 253 (such as an SSD or HDD), a communication device 254, and an I / F 255. Information such as programs, tables, and files that implement each function can be stored in a storage device, such as a memory or SSD (Solid State Drive), or a storage medium, such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).

[0243] Figure 37 is a flowchart showing the ultrasonic inspection method of each of the above-mentioned embodiments. The ultrasonic inspection method of the present disclosure can be executed by the control device 2 of the above-mentioned ultrasonic inspection device Z, and will be described as an example with reference to Figures 1 and 6 as appropriate. The ultrasonic inspection method of the present disclosure inspects the object E to be inspected (Figure 1) by irradiating an ultrasonic beam U onto the object E to be inspected (Figure 1) via a gas G (Figure 1; an example of a fluid F). Note that this ultrasonic inspection method will be described in an embodiment using gas G as the fluid F, but it goes without saying that this ultrasonic inspection method is also effective in an embodiment using liquid W as the fluid F.

[0244] The ultrasonic inspection method of the present disclosure includes steps S100 to S105, S111, and S112. First, a user inputs wave packet delay times Δtd of a plurality of wave packets to the delay time setting unit 213, for example, via the input device 4. In response to this, the delay time setting unit 213 sets the wave packet delay times Δtd (step S100, delay time setting step).

[0245] Next, in response to a command from the control device 2, the transmitting probe 110 performs step S101 (emission step) of emitting an ultrasonic beam U from the transmitting probe 110. In step S101, the transmitting probe 110 has a plurality of wave packets including a first wave packet and a second wave packet, and emits the ultrasonic beam U by applying a voltage waveform that repeats a wave packet group in which the wave packet delay time Δtd between wave packet 10 (first wave packet) and wave packet 11 (second wave packet) is arbitrarily set. Wave packet 10 (first wave packet) is a wave packet with a wave number of 2 or more at a fundamental frequency f0 that is the excitation frequency fex of the transmitting probe 110 that emits the ultrasonic beam U. Wave packet 11 (second wave packet) is a wave packet with a wave number of 2 or more.

[0246] Subsequently, in step S102 (reception step), the receiving probe 121 receives the ultrasonic beam U.

[0247] Thereafter, the frequency conversion unit 230 converts the signal of the ultrasonic beam U received by the receiving probe 121 into frequency components based on the signal (e.g., waveform signal) of the ultrasonic beam U received by the receiving probe 121 (step S103, frequency component conversion step).

[0248] Then, the data processing unit 201 performs step S104 (signal intensity calculation step) of detecting the base component W3 of the fundamental wave band W1 from the converted frequency components and generating signal intensity data. Therefore, in step S104, the base component W3 of the fundamental wave band W1 in the signal of the ultrasound beam U is detected. As a method of generating signal intensity data, in this embodiment, a time domain waveform h(t) is reconstructed from the converted frequency components for an appropriate frequency range using the above equations (2) and (3), and the peak-to-peak signal of this h(t) is used. This is the difference between the maximum and minimum values ​​of the signal.

[0249] Next, step S105 (shape display step) is performed. Scanning position information of the transmitting probe 110 and the receiving probe 121 is transmitted from the position measurement unit 203 to the scan controller 204. The data processing unit 201 plots signal intensity data at each scanning position against the scanning position information of the transmitting probe 110 acquired from the scan controller 204. In this way, the signal intensity data is visualized. This is step S105.

[0250] Note that Figure 25 above shows the case where the scanning position information is one-dimensional (one direction), and when the scanning position information is two-dimensional in x and y, the signal intensity data is plotted to show the defect D as a two-dimensional image, which is then displayed on the display device 3.

[0251] The data processing unit 201 determines whether the scanning is complete (step S111). If the scanning is complete (Yes), the control device 2 ends the processing. If the scanning is not complete (No), the data processing unit 201 outputs a command to the driving unit 202 to move the transmitting probe 110 and the receiving probe 121 to the next scanning position (step S112), and the processing returns to step S101.

[0252] According to the ultrasonic inspection device Z and ultrasonic inspection method described above, the performance of detecting the defect portion D, for example, the performance of detecting minute defects, can be improved.

[0253] In each of the above embodiments, an example is described in which the defect D is a cavity, but the defect D may also be a foreign object containing a material different from the material of the object E to be inspected. In this case, too, a difference in acoustic impedance (Gap) occurs at the interface where the different materials come into contact, generating a scattered wave U1, so the configurations of the above embodiments are effective. The ultrasonic inspection device Z according to each of the above embodiments is premised on being an ultrasonic defect imaging device, but may also be applied to a non-contact in-line internal defect inspection device.

[0254] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those having all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0255] In each embodiment, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are interconnected. [Explanation of symbols]

[0256] 1. Scanning measurement device 10 wave packet 100 sent probes 101 Case 102 Sample stage 1021 Placement surface 103 Transmission probe scanning unit 104 Receiving probe scanning unit 105 Eccentric distance adjustment section 106 Installation angle adjustment section 11 wave packet 110 Send Probe 111 Oscillator 112 Backing 113 Matching layer 114 Probe surface 115 Transmitting probe housing 116 Connector 117 Lead Wire 118 Lead Wire 120 Received Probes 121 Incoming Probes 140 Incoming Probes 2. Control device 201 Data Processing Unit 202 Drive unit 203 Position measurement unit 204 Scan Controller 210 Transmission System 211 Waveform Generator 212 Signal Amplifier 213 Delay time setting section 220 Receiving System 222 Signal Amplifier 223 Spectral Calculation Unit 224 Reception Department 230 Frequency conversion unit 242 Frequency Selector 250 Signal Processing Unit 251 memory 252 CPU 253 Storage device 254 Communication equipment 255 I / F 261 Storage section 262 Imaging Department 263 Display section 270 display screen 271 Spectral display 272 Detection frequency designation section 273 images 274 Update button 275 Wave packet delay input section 276 Defect image display section 277 Interference function display 3 Display device 4 Input Devices D Defective part E. Test object F fluid G gas L Eccentric distance N Healthy part R1 focal length R2 focal length T0 fundamental period T1 Beam entrance area T2 Beam entrance area tI Interwavelet time Tr repeat period U ultrasonic beam U1 scattered wave U2 ultrasonic beam U3 direct wave W liquid W1 basic wave band W3 Susono ingredients Z-mode ultrasound examination device Δtd Beam delay time ΔtI inter-beam time αd Beam Delay αI inter-beam wavenumber

Claims

1. An ultrasonic inspection apparatus for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a fluid, a scanning and measuring device that scans and measures the object under test with the ultrasonic beam; and a control device that controls driving of the scanning and measuring device, The scanning measurement device a transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is installed on the opposite side of the transmitting probe with respect to the object under test, The transmitting probe has a plurality of wave packets including a first wave packet having a wave number of 2 or more and a second wave packet having a wave number of 2 or more at a fundamental frequency that is an excitation frequency of the transmitting probe, and emits an ultrasonic beam by applying a voltage waveform that repeats a wave packet group in which a wave packet delay time between the first wave packet and the second wave packet is arbitrarily set; the control device includes a signal processing unit; The signal processing unit includes a frequency conversion unit that converts the received signal of the receiving probe into frequency components. Ultrasound testing equipment.

2. The ultrasonic inspection apparatus according to claim 1, wherein the scanning measurement device includes a delay time setting unit that sets a wave packet delay time of the plurality of wave packets.

3. 2. The ultrasonic inspection device according to claim 1, further comprising a delay time setting unit that sets the wave packet delay time by making the inter-wave packet time of the plurality of wave packets greater than zero so that the magnitude of a frequency component different from the fundamental frequency becomes greater than the magnitude of the frequency component when the inter-wave packet time is zero.

4. 2. The ultrasonic inspection device according to claim 1, wherein the frequency conversion unit converts a received signal in a time range including at least two wave packets out of the plurality of wave packets into the frequency components.

5. 2. The ultrasonic inspection device according to claim 1, wherein the signal processing unit detects, from the frequency domain signal output from the frequency conversion unit, a skirt component different from the fundamental frequency of the wave packet within a fundamental wave band, which is a range of frequency components that have a spread before and after the fundamental frequency.

6. 2. The ultrasonic inspection device according to claim 1, wherein the signal processing unit detects a frequency component at which a value of an interference function having parameters of a wave packet delay time between a first wave packet and a second wave packet among the plurality of wave packets and a fundamental frequency of the first wave packet is equal to or greater than half of a maximum value of the interference function.

7. 2. The ultrasonic inspection device according to claim 1, further comprising a delay time setting unit that sets a wave packet delay time such that a value of an interference function having a wave packet delay time between a first wave packet and a second wave packet among the plurality of wave packets and a fundamental frequency of the first wave packet as parameters is equal to or greater than half of a maximum value of the interference function.

8. 2. The ultrasonic inspection apparatus according to claim 1, wherein the focal length of the receiving probe is longer than the focal length of the transmitting probe.

9. 2. The ultrasonic inspection apparatus according to claim 1, wherein the beam incident area of ​​the receiving probe is larger than the beam incident area of ​​the transmitting probe.

10. 2. The ultrasonic inspection apparatus according to claim 1, wherein the receiving probe is a non-focusing type receiving probe.

11. 2. The ultrasonic inspection device according to claim 1, wherein the full width at half maximum of the frequency spectrum of the fundamental wave band, which is a range of frequency components having a spread before and after the fundamental frequency, is 50% or less of the fundamental frequency of the wave packet.

12. 2. The ultrasonic inspection device according to claim 1, wherein the wave number of the first wave packet is 30 or less.

13. 2. The ultrasonic inspection device according to claim 1, wherein the frequencies detected by the signal processing unit include frequencies in a range of (f0±0.25f0), where f0 is the fundamental frequency of the first wave packet.

14. 2. The ultrasonic inspection apparatus according to claim 1, wherein the fundamental frequencies of the plurality of wave packets are different from each other.

15. 2. The ultrasonic inspection device according to claim 1, wherein the distance between the acoustic axis of the transmitting probe and the acoustic axis of the receiving probe is greater than zero.

16. 2. The ultrasonic inspection apparatus according to claim 1, wherein the fluid is a gas.

17. 2. The ultrasonic inspection device according to claim 1, wherein the transmitting probe is applied with the voltage waveform having a wave packet delay time that results in a frequency component greater than a frequency component when an inter-wave packet time, which is the time between the plurality of wave packets, is zero, and emits the ultrasonic beam.

18. 2. The ultrasonic inspection apparatus according to claim 1, wherein a frequency at which the ultrasonic beam is detected by the receiving probe is different from the fundamental frequency.

19. An ultrasonic inspection apparatus for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a fluid, a scanning and measuring device that scans and measures the object under test with the ultrasonic beam; and a control device that controls driving of the scanning and measuring device, The scanning measurement device a transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is installed on the opposite side of the transmitting probe with respect to the object under test, the transmitting probe emits an ultrasonic beam when a voltage waveform is applied to the transmitting probe, the voltage waveform repeating a wave packet group having a plurality of wave packets including a first wave packet having a wave number of 2 or more and a second wave packet having a wave number of 2 or more at a fundamental frequency that is an excitation frequency of the transmitting probe; the control device includes a signal processing unit; the signal processing unit includes a frequency conversion unit that converts the received signal of the receiving probe into frequency components; a delay time setting unit that sets a wave packet delay time such that the magnitude of a frequency component different from the fundamental frequency becomes larger than the magnitude of the frequency component when the wave packet inter-time is zero by making the wave packet inter-time of the plurality of wave packets larger than zero; Ultrasound testing equipment.

20. 1. An ultrasonic inspection method for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a fluid, comprising: an emission step of emitting the ultrasonic beam by applying a voltage waveform that repeats a wave packet group having a first wave packet with a wave number of 2 or more and a second wave packet with a wave number of 2 or more at a fundamental frequency that is an excitation frequency of a transmitting probe that emits an ultrasonic beam, and a wave packet delay time between the first wave packet and the second wave packet is arbitrarily set; a receiving step of receiving the ultrasonic beam; a frequency component conversion step of converting the ultrasonic beam signal received in the receiving step into frequency components. An ultrasonic inspection method characterized by:

Images